1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2013 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.
51 @c man begin COPYRIGHT
52 Copyright @copyright{} 1988-2013 Free Software Foundation, Inc.
54 Permission is granted to copy, distribute and/or modify this document
55 under the terms of the GNU Free Documentation License, Version 1.3 or
56 any later version published by the Free Software Foundation; with the
57 Invariant Sections being ``Free Software'' and ``Free Software Needs
58 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
59 and with the Back-Cover Texts as in (a) below.
61 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
62 this GNU Manual. Buying copies from GNU Press supports the FSF in
63 developing GNU and promoting software freedom.''
68 This file documents the @sc{gnu} debugger @value{GDBN}.
70 This is the @value{EDITION} Edition, of @cite{Debugging with
71 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
72 @ifset VERSION_PACKAGE
73 @value{VERSION_PACKAGE}
75 Version @value{GDBVN}.
81 @title Debugging with @value{GDBN}
82 @subtitle The @sc{gnu} Source-Level Debugger
84 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
85 @ifset VERSION_PACKAGE
87 @subtitle @value{VERSION_PACKAGE}
89 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
93 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
94 \hfill {\it Debugging with @value{GDBN}}\par
95 \hfill \TeX{}info \texinfoversion\par
99 @vskip 0pt plus 1filll
100 Published by the Free Software Foundation @*
101 51 Franklin Street, Fifth Floor,
102 Boston, MA 02110-1301, USA@*
103 ISBN 978-0-9831592-3-0 @*
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2013 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Process Record and Replay:: Recording inferior's execution and replaying it
138 * Stack:: Examining the stack
139 * Source:: Examining source files
140 * Data:: Examining data
141 * Optimized Code:: Debugging optimized code
142 * Macros:: Preprocessor Macros
143 * Tracepoints:: Debugging remote targets non-intrusively
144 * Overlays:: Debugging programs that use overlays
146 * Languages:: Using @value{GDBN} with different languages
148 * Symbols:: Examining the symbol table
149 * Altering:: Altering execution
150 * GDB Files:: @value{GDBN} files
151 * Targets:: Specifying a debugging target
152 * Remote Debugging:: Debugging remote programs
153 * Configurations:: Configuration-specific information
154 * Controlling GDB:: Controlling @value{GDBN}
155 * Extending GDB:: Extending @value{GDBN}
156 * Interpreters:: Command Interpreters
157 * TUI:: @value{GDBN} Text User Interface
158 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
159 * GDB/MI:: @value{GDBN}'s Machine Interface.
160 * Annotations:: @value{GDBN}'s annotation interface.
161 * JIT Interface:: Using the JIT debugging interface.
162 * In-Process Agent:: In-Process Agent
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 @ifset SYSTEM_READLINE
167 * Command Line Editing: (rluserman). Command Line Editing
168 * Using History Interactively: (history). Using History Interactively
170 @ifclear SYSTEM_READLINE
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
174 * In Memoriam:: In Memoriam
175 * Formatting Documentation:: How to format and print @value{GDBN} documentation
176 * Installing GDB:: Installing GDB
177 * Maintenance Commands:: Maintenance Commands
178 * Remote Protocol:: GDB Remote Serial Protocol
179 * Agent Expressions:: The GDB Agent Expression Mechanism
180 * Target Descriptions:: How targets can describe themselves to
182 * Operating System Information:: Getting additional information from
184 * Trace File Format:: GDB trace file format
185 * Index Section Format:: .gdb_index section format
186 * Man Pages:: Manual pages
187 * Copying:: GNU General Public License says
188 how you can copy and share GDB
189 * GNU Free Documentation License:: The license for this documentation
190 * Concept Index:: Index of @value{GDBN} concepts
191 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
192 functions, and Python data types
200 @unnumbered Summary of @value{GDBN}
202 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
203 going on ``inside'' another program while it executes---or what another
204 program was doing at the moment it crashed.
206 @value{GDBN} can do four main kinds of things (plus other things in support of
207 these) to help you catch bugs in the act:
211 Start your program, specifying anything that might affect its behavior.
214 Make your program stop on specified conditions.
217 Examine what has happened, when your program has stopped.
220 Change things in your program, so you can experiment with correcting the
221 effects of one bug and go on to learn about another.
224 You can use @value{GDBN} to debug programs written in C and C@t{++}.
225 For more information, see @ref{Supported Languages,,Supported Languages}.
226 For more information, see @ref{C,,C and C++}.
228 Support for D is partial. For information on D, see
232 Support for Modula-2 is partial. For information on Modula-2, see
233 @ref{Modula-2,,Modula-2}.
235 Support for OpenCL C is partial. For information on OpenCL C, see
236 @ref{OpenCL C,,OpenCL C}.
239 Debugging Pascal programs which use sets, subranges, file variables, or
240 nested functions does not currently work. @value{GDBN} does not support
241 entering expressions, printing values, or similar features using Pascal
245 @value{GDBN} can be used to debug programs written in Fortran, although
246 it may be necessary to refer to some variables with a trailing
249 @value{GDBN} can be used to debug programs written in Objective-C,
250 using either the Apple/NeXT or the GNU Objective-C runtime.
253 * Free Software:: Freely redistributable software
254 * Free Documentation:: Free Software Needs Free Documentation
255 * Contributors:: Contributors to GDB
259 @unnumberedsec Free Software
261 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
262 General Public License
263 (GPL). The GPL gives you the freedom to copy or adapt a licensed
264 program---but every person getting a copy also gets with it the
265 freedom to modify that copy (which means that they must get access to
266 the source code), and the freedom to distribute further copies.
267 Typical software companies use copyrights to limit your freedoms; the
268 Free Software Foundation uses the GPL to preserve these freedoms.
270 Fundamentally, the General Public License is a license which says that
271 you have these freedoms and that you cannot take these freedoms away
274 @node Free Documentation
275 @unnumberedsec Free Software Needs Free Documentation
277 The biggest deficiency in the free software community today is not in
278 the software---it is the lack of good free documentation that we can
279 include with the free software. Many of our most important
280 programs do not come with free reference manuals and free introductory
281 texts. Documentation is an essential part of any software package;
282 when an important free software package does not come with a free
283 manual and a free tutorial, that is a major gap. We have many such
286 Consider Perl, for instance. The tutorial manuals that people
287 normally use are non-free. How did this come about? Because the
288 authors of those manuals published them with restrictive terms---no
289 copying, no modification, source files not available---which exclude
290 them from the free software world.
292 That wasn't the first time this sort of thing happened, and it was far
293 from the last. Many times we have heard a GNU user eagerly describe a
294 manual that he is writing, his intended contribution to the community,
295 only to learn that he had ruined everything by signing a publication
296 contract to make it non-free.
298 Free documentation, like free software, is a matter of freedom, not
299 price. The problem with the non-free manual is not that publishers
300 charge a price for printed copies---that in itself is fine. (The Free
301 Software Foundation sells printed copies of manuals, too.) The
302 problem is the restrictions on the use of the manual. Free manuals
303 are available in source code form, and give you permission to copy and
304 modify. Non-free manuals do not allow this.
306 The criteria of freedom for a free manual are roughly the same as for
307 free software. Redistribution (including the normal kinds of
308 commercial redistribution) must be permitted, so that the manual can
309 accompany every copy of the program, both on-line and on paper.
311 Permission for modification of the technical content is crucial too.
312 When people modify the software, adding or changing features, if they
313 are conscientious they will change the manual too---so they can
314 provide accurate and clear documentation for the modified program. A
315 manual that leaves you no choice but to write a new manual to document
316 a changed version of the program is not really available to our
319 Some kinds of limits on the way modification is handled are
320 acceptable. For example, requirements to preserve the original
321 author's copyright notice, the distribution terms, or the list of
322 authors, are ok. It is also no problem to require modified versions
323 to include notice that they were modified. Even entire sections that
324 may not be deleted or changed are acceptable, as long as they deal
325 with nontechnical topics (like this one). These kinds of restrictions
326 are acceptable because they don't obstruct the community's normal use
329 However, it must be possible to modify all the @emph{technical}
330 content of the manual, and then distribute the result in all the usual
331 media, through all the usual channels. Otherwise, the restrictions
332 obstruct the use of the manual, it is not free, and we need another
333 manual to replace it.
335 Please spread the word about this issue. Our community continues to
336 lose manuals to proprietary publishing. If we spread the word that
337 free software needs free reference manuals and free tutorials, perhaps
338 the next person who wants to contribute by writing documentation will
339 realize, before it is too late, that only free manuals contribute to
340 the free software community.
342 If you are writing documentation, please insist on publishing it under
343 the GNU Free Documentation License or another free documentation
344 license. Remember that this decision requires your approval---you
345 don't have to let the publisher decide. Some commercial publishers
346 will use a free license if you insist, but they will not propose the
347 option; it is up to you to raise the issue and say firmly that this is
348 what you want. If the publisher you are dealing with refuses, please
349 try other publishers. If you're not sure whether a proposed license
350 is free, write to @email{licensing@@gnu.org}.
352 You can encourage commercial publishers to sell more free, copylefted
353 manuals and tutorials by buying them, and particularly by buying
354 copies from the publishers that paid for their writing or for major
355 improvements. Meanwhile, try to avoid buying non-free documentation
356 at all. Check the distribution terms of a manual before you buy it,
357 and insist that whoever seeks your business must respect your freedom.
358 Check the history of the book, and try to reward the publishers that
359 have paid or pay the authors to work on it.
361 The Free Software Foundation maintains a list of free documentation
362 published by other publishers, at
363 @url{http://www.fsf.org/doc/other-free-books.html}.
366 @unnumberedsec Contributors to @value{GDBN}
368 Richard Stallman was the original author of @value{GDBN}, and of many
369 other @sc{gnu} programs. Many others have contributed to its
370 development. This section attempts to credit major contributors. One
371 of the virtues of free software is that everyone is free to contribute
372 to it; with regret, we cannot actually acknowledge everyone here. The
373 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
374 blow-by-blow account.
376 Changes much prior to version 2.0 are lost in the mists of time.
379 @emph{Plea:} Additions to this section are particularly welcome. If you
380 or your friends (or enemies, to be evenhanded) have been unfairly
381 omitted from this list, we would like to add your names!
384 So that they may not regard their many labors as thankless, we
385 particularly thank those who shepherded @value{GDBN} through major
387 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
388 Jim Blandy (release 4.18);
389 Jason Molenda (release 4.17);
390 Stan Shebs (release 4.14);
391 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
392 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
393 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
394 Jim Kingdon (releases 3.5, 3.4, and 3.3);
395 and Randy Smith (releases 3.2, 3.1, and 3.0).
397 Richard Stallman, assisted at various times by Peter TerMaat, Chris
398 Hanson, and Richard Mlynarik, handled releases through 2.8.
400 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
401 in @value{GDBN}, with significant additional contributions from Per
402 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
403 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
404 much general update work leading to release 3.0).
406 @value{GDBN} uses the BFD subroutine library to examine multiple
407 object-file formats; BFD was a joint project of David V.
408 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
410 David Johnson wrote the original COFF support; Pace Willison did
411 the original support for encapsulated COFF.
413 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
415 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
416 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
418 Jean-Daniel Fekete contributed Sun 386i support.
419 Chris Hanson improved the HP9000 support.
420 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
421 David Johnson contributed Encore Umax support.
422 Jyrki Kuoppala contributed Altos 3068 support.
423 Jeff Law contributed HP PA and SOM support.
424 Keith Packard contributed NS32K support.
425 Doug Rabson contributed Acorn Risc Machine support.
426 Bob Rusk contributed Harris Nighthawk CX-UX support.
427 Chris Smith contributed Convex support (and Fortran debugging).
428 Jonathan Stone contributed Pyramid support.
429 Michael Tiemann contributed SPARC support.
430 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
431 Pace Willison contributed Intel 386 support.
432 Jay Vosburgh contributed Symmetry support.
433 Marko Mlinar contributed OpenRISC 1000 support.
435 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
437 Rich Schaefer and Peter Schauer helped with support of SunOS shared
440 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
441 about several machine instruction sets.
443 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
444 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
445 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
446 and RDI targets, respectively.
448 Brian Fox is the author of the readline libraries providing
449 command-line editing and command history.
451 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
452 Modula-2 support, and contributed the Languages chapter of this manual.
454 Fred Fish wrote most of the support for Unix System Vr4.
455 He also enhanced the command-completion support to cover C@t{++} overloaded
458 Hitachi America (now Renesas America), Ltd. sponsored the support for
459 H8/300, H8/500, and Super-H processors.
461 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
463 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
466 Toshiba sponsored the support for the TX39 Mips processor.
468 Matsushita sponsored the support for the MN10200 and MN10300 processors.
470 Fujitsu sponsored the support for SPARClite and FR30 processors.
472 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
475 Michael Snyder added support for tracepoints.
477 Stu Grossman wrote gdbserver.
479 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
480 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
482 The following people at the Hewlett-Packard Company contributed
483 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
484 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
485 compiler, and the Text User Interface (nee Terminal User Interface):
486 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
487 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
488 provided HP-specific information in this manual.
490 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
491 Robert Hoehne made significant contributions to the DJGPP port.
493 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
494 development since 1991. Cygnus engineers who have worked on @value{GDBN}
495 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
496 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
497 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
498 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
499 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
500 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
501 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
502 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
503 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
504 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
505 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
506 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
507 Zuhn have made contributions both large and small.
509 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
510 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
512 Jim Blandy added support for preprocessor macros, while working for Red
515 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
516 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
517 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
518 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
519 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
520 with the migration of old architectures to this new framework.
522 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
523 unwinder framework, this consisting of a fresh new design featuring
524 frame IDs, independent frame sniffers, and the sentinel frame. Mark
525 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
526 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
527 trad unwinders. The architecture-specific changes, each involving a
528 complete rewrite of the architecture's frame code, were carried out by
529 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
530 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
531 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
532 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
535 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
536 Tensilica, Inc.@: contributed support for Xtensa processors. Others
537 who have worked on the Xtensa port of @value{GDBN} in the past include
538 Steve Tjiang, John Newlin, and Scott Foehner.
540 Michael Eager and staff of Xilinx, Inc., contributed support for the
541 Xilinx MicroBlaze architecture.
544 @chapter A Sample @value{GDBN} Session
546 You can use this manual at your leisure to read all about @value{GDBN}.
547 However, a handful of commands are enough to get started using the
548 debugger. This chapter illustrates those commands.
551 In this sample session, we emphasize user input like this: @b{input},
552 to make it easier to pick out from the surrounding output.
555 @c FIXME: this example may not be appropriate for some configs, where
556 @c FIXME...primary interest is in remote use.
558 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
559 processor) exhibits the following bug: sometimes, when we change its
560 quote strings from the default, the commands used to capture one macro
561 definition within another stop working. In the following short @code{m4}
562 session, we define a macro @code{foo} which expands to @code{0000}; we
563 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
564 same thing. However, when we change the open quote string to
565 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
566 procedure fails to define a new synonym @code{baz}:
575 @b{define(bar,defn(`foo'))}
579 @b{changequote(<QUOTE>,<UNQUOTE>)}
581 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
584 m4: End of input: 0: fatal error: EOF in string
588 Let us use @value{GDBN} to try to see what is going on.
591 $ @b{@value{GDBP} m4}
592 @c FIXME: this falsifies the exact text played out, to permit smallbook
593 @c FIXME... format to come out better.
594 @value{GDBN} is free software and you are welcome to distribute copies
595 of it under certain conditions; type "show copying" to see
597 There is absolutely no warranty for @value{GDBN}; type "show warranty"
600 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
605 @value{GDBN} reads only enough symbol data to know where to find the
606 rest when needed; as a result, the first prompt comes up very quickly.
607 We now tell @value{GDBN} to use a narrower display width than usual, so
608 that examples fit in this manual.
611 (@value{GDBP}) @b{set width 70}
615 We need to see how the @code{m4} built-in @code{changequote} works.
616 Having looked at the source, we know the relevant subroutine is
617 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
618 @code{break} command.
621 (@value{GDBP}) @b{break m4_changequote}
622 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
626 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
627 control; as long as control does not reach the @code{m4_changequote}
628 subroutine, the program runs as usual:
631 (@value{GDBP}) @b{run}
632 Starting program: /work/Editorial/gdb/gnu/m4/m4
640 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
641 suspends execution of @code{m4}, displaying information about the
642 context where it stops.
645 @b{changequote(<QUOTE>,<UNQUOTE>)}
647 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
649 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
653 Now we use the command @code{n} (@code{next}) to advance execution to
654 the next line of the current function.
658 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
663 @code{set_quotes} looks like a promising subroutine. We can go into it
664 by using the command @code{s} (@code{step}) instead of @code{next}.
665 @code{step} goes to the next line to be executed in @emph{any}
666 subroutine, so it steps into @code{set_quotes}.
670 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
672 530 if (lquote != def_lquote)
676 The display that shows the subroutine where @code{m4} is now
677 suspended (and its arguments) is called a stack frame display. It
678 shows a summary of the stack. We can use the @code{backtrace}
679 command (which can also be spelled @code{bt}), to see where we are
680 in the stack as a whole: the @code{backtrace} command displays a
681 stack frame for each active subroutine.
684 (@value{GDBP}) @b{bt}
685 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
687 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
689 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
690 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
692 #4 0x79dc in expand_input () at macro.c:40
693 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
697 We step through a few more lines to see what happens. The first two
698 times, we can use @samp{s}; the next two times we use @code{n} to avoid
699 falling into the @code{xstrdup} subroutine.
703 0x3b5c 532 if (rquote != def_rquote)
705 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
706 def_lquote : xstrdup(lq);
708 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
711 538 len_lquote = strlen(rquote);
715 The last line displayed looks a little odd; we can examine the variables
716 @code{lquote} and @code{rquote} to see if they are in fact the new left
717 and right quotes we specified. We use the command @code{p}
718 (@code{print}) to see their values.
721 (@value{GDBP}) @b{p lquote}
722 $1 = 0x35d40 "<QUOTE>"
723 (@value{GDBP}) @b{p rquote}
724 $2 = 0x35d50 "<UNQUOTE>"
728 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
729 To look at some context, we can display ten lines of source
730 surrounding the current line with the @code{l} (@code{list}) command.
736 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
738 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
741 538 len_lquote = strlen(rquote);
742 539 len_rquote = strlen(lquote);
749 Let us step past the two lines that set @code{len_lquote} and
750 @code{len_rquote}, and then examine the values of those variables.
754 539 len_rquote = strlen(lquote);
757 (@value{GDBP}) @b{p len_lquote}
759 (@value{GDBP}) @b{p len_rquote}
764 That certainly looks wrong, assuming @code{len_lquote} and
765 @code{len_rquote} are meant to be the lengths of @code{lquote} and
766 @code{rquote} respectively. We can set them to better values using
767 the @code{p} command, since it can print the value of
768 any expression---and that expression can include subroutine calls and
772 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
774 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
779 Is that enough to fix the problem of using the new quotes with the
780 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
781 executing with the @code{c} (@code{continue}) command, and then try the
782 example that caused trouble initially:
788 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
795 Success! The new quotes now work just as well as the default ones. The
796 problem seems to have been just the two typos defining the wrong
797 lengths. We allow @code{m4} exit by giving it an EOF as input:
801 Program exited normally.
805 The message @samp{Program exited normally.} is from @value{GDBN}; it
806 indicates @code{m4} has finished executing. We can end our @value{GDBN}
807 session with the @value{GDBN} @code{quit} command.
810 (@value{GDBP}) @b{quit}
814 @chapter Getting In and Out of @value{GDBN}
816 This chapter discusses how to start @value{GDBN}, and how to get out of it.
820 type @samp{@value{GDBP}} to start @value{GDBN}.
822 type @kbd{quit} or @kbd{Ctrl-d} to exit.
826 * Invoking GDB:: How to start @value{GDBN}
827 * Quitting GDB:: How to quit @value{GDBN}
828 * Shell Commands:: How to use shell commands inside @value{GDBN}
829 * Logging Output:: How to log @value{GDBN}'s output to a file
833 @section Invoking @value{GDBN}
835 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
836 @value{GDBN} reads commands from the terminal until you tell it to exit.
838 You can also run @code{@value{GDBP}} with a variety of arguments and options,
839 to specify more of your debugging environment at the outset.
841 The command-line options described here are designed
842 to cover a variety of situations; in some environments, some of these
843 options may effectively be unavailable.
845 The most usual way to start @value{GDBN} is with one argument,
846 specifying an executable program:
849 @value{GDBP} @var{program}
853 You can also start with both an executable program and a core file
857 @value{GDBP} @var{program} @var{core}
860 You can, instead, specify a process ID as a second argument, if you want
861 to debug a running process:
864 @value{GDBP} @var{program} 1234
868 would attach @value{GDBN} to process @code{1234} (unless you also have a file
869 named @file{1234}; @value{GDBN} does check for a core file first).
871 Taking advantage of the second command-line argument requires a fairly
872 complete operating system; when you use @value{GDBN} as a remote
873 debugger attached to a bare board, there may not be any notion of
874 ``process'', and there is often no way to get a core dump. @value{GDBN}
875 will warn you if it is unable to attach or to read core dumps.
877 You can optionally have @code{@value{GDBP}} pass any arguments after the
878 executable file to the inferior using @code{--args}. This option stops
881 @value{GDBP} --args gcc -O2 -c foo.c
883 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
884 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
886 You can run @code{@value{GDBP}} without printing the front material, which describes
887 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
894 You can further control how @value{GDBN} starts up by using command-line
895 options. @value{GDBN} itself can remind you of the options available.
905 to display all available options and briefly describe their use
906 (@samp{@value{GDBP} -h} is a shorter equivalent).
908 All options and command line arguments you give are processed
909 in sequential order. The order makes a difference when the
910 @samp{-x} option is used.
914 * File Options:: Choosing files
915 * Mode Options:: Choosing modes
916 * Startup:: What @value{GDBN} does during startup
920 @subsection Choosing Files
922 When @value{GDBN} starts, it reads any arguments other than options as
923 specifying an executable file and core file (or process ID). This is
924 the same as if the arguments were specified by the @samp{-se} and
925 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
926 first argument that does not have an associated option flag as
927 equivalent to the @samp{-se} option followed by that argument; and the
928 second argument that does not have an associated option flag, if any, as
929 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
930 If the second argument begins with a decimal digit, @value{GDBN} will
931 first attempt to attach to it as a process, and if that fails, attempt
932 to open it as a corefile. If you have a corefile whose name begins with
933 a digit, you can prevent @value{GDBN} from treating it as a pid by
934 prefixing it with @file{./}, e.g.@: @file{./12345}.
936 If @value{GDBN} has not been configured to included core file support,
937 such as for most embedded targets, then it will complain about a second
938 argument and ignore it.
940 Many options have both long and short forms; both are shown in the
941 following list. @value{GDBN} also recognizes the long forms if you truncate
942 them, so long as enough of the option is present to be unambiguous.
943 (If you prefer, you can flag option arguments with @samp{--} rather
944 than @samp{-}, though we illustrate the more usual convention.)
946 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
947 @c way, both those who look for -foo and --foo in the index, will find
951 @item -symbols @var{file}
953 @cindex @code{--symbols}
955 Read symbol table from file @var{file}.
957 @item -exec @var{file}
959 @cindex @code{--exec}
961 Use file @var{file} as the executable file to execute when appropriate,
962 and for examining pure data in conjunction with a core dump.
966 Read symbol table from file @var{file} and use it as the executable
969 @item -core @var{file}
971 @cindex @code{--core}
973 Use file @var{file} as a core dump to examine.
975 @item -pid @var{number}
976 @itemx -p @var{number}
979 Connect to process ID @var{number}, as with the @code{attach} command.
981 @item -command @var{file}
983 @cindex @code{--command}
985 Execute commands from file @var{file}. The contents of this file is
986 evaluated exactly as the @code{source} command would.
987 @xref{Command Files,, Command files}.
989 @item -eval-command @var{command}
990 @itemx -ex @var{command}
991 @cindex @code{--eval-command}
993 Execute a single @value{GDBN} command.
995 This option may be used multiple times to call multiple commands. It may
996 also be interleaved with @samp{-command} as required.
999 @value{GDBP} -ex 'target sim' -ex 'load' \
1000 -x setbreakpoints -ex 'run' a.out
1003 @item -init-command @var{file}
1004 @itemx -ix @var{file}
1005 @cindex @code{--init-command}
1007 Execute commands from file @var{file} before loading the inferior (but
1008 after loading gdbinit files).
1011 @item -init-eval-command @var{command}
1012 @itemx -iex @var{command}
1013 @cindex @code{--init-eval-command}
1015 Execute a single @value{GDBN} command before loading the inferior (but
1016 after loading gdbinit files).
1019 @item -directory @var{directory}
1020 @itemx -d @var{directory}
1021 @cindex @code{--directory}
1023 Add @var{directory} to the path to search for source and script files.
1027 @cindex @code{--readnow}
1029 Read each symbol file's entire symbol table immediately, rather than
1030 the default, which is to read it incrementally as it is needed.
1031 This makes startup slower, but makes future operations faster.
1036 @subsection Choosing Modes
1038 You can run @value{GDBN} in various alternative modes---for example, in
1039 batch mode or quiet mode.
1047 Do not execute commands found in any initialization file.
1048 There are three init files, loaded in the following order:
1051 @item @file{system.gdbinit}
1052 This is the system-wide init file.
1053 Its location is specified with the @code{--with-system-gdbinit}
1054 configure option (@pxref{System-wide configuration}).
1055 It is loaded first when @value{GDBN} starts, before command line options
1056 have been processed.
1057 @item @file{~/.gdbinit}
1058 This is the init file in your home directory.
1059 It is loaded next, after @file{system.gdbinit}, and before
1060 command options have been processed.
1061 @item @file{./.gdbinit}
1062 This is the init file in the current directory.
1063 It is loaded last, after command line options other than @code{-x} and
1064 @code{-ex} have been processed. Command line options @code{-x} and
1065 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1068 For further documentation on startup processing, @xref{Startup}.
1069 For documentation on how to write command files,
1070 @xref{Command Files,,Command Files}.
1075 Do not execute commands found in @file{~/.gdbinit}, the init file
1076 in your home directory.
1082 @cindex @code{--quiet}
1083 @cindex @code{--silent}
1085 ``Quiet''. Do not print the introductory and copyright messages. These
1086 messages are also suppressed in batch mode.
1089 @cindex @code{--batch}
1090 Run in batch mode. Exit with status @code{0} after processing all the
1091 command files specified with @samp{-x} (and all commands from
1092 initialization files, if not inhibited with @samp{-n}). Exit with
1093 nonzero status if an error occurs in executing the @value{GDBN} commands
1094 in the command files. Batch mode also disables pagination, sets unlimited
1095 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1096 off} were in effect (@pxref{Messages/Warnings}).
1098 Batch mode may be useful for running @value{GDBN} as a filter, for
1099 example to download and run a program on another computer; in order to
1100 make this more useful, the message
1103 Program exited normally.
1107 (which is ordinarily issued whenever a program running under
1108 @value{GDBN} control terminates) is not issued when running in batch
1112 @cindex @code{--batch-silent}
1113 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1114 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1115 unaffected). This is much quieter than @samp{-silent} and would be useless
1116 for an interactive session.
1118 This is particularly useful when using targets that give @samp{Loading section}
1119 messages, for example.
1121 Note that targets that give their output via @value{GDBN}, as opposed to
1122 writing directly to @code{stdout}, will also be made silent.
1124 @item -return-child-result
1125 @cindex @code{--return-child-result}
1126 The return code from @value{GDBN} will be the return code from the child
1127 process (the process being debugged), with the following exceptions:
1131 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1132 internal error. In this case the exit code is the same as it would have been
1133 without @samp{-return-child-result}.
1135 The user quits with an explicit value. E.g., @samp{quit 1}.
1137 The child process never runs, or is not allowed to terminate, in which case
1138 the exit code will be -1.
1141 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1142 when @value{GDBN} is being used as a remote program loader or simulator
1147 @cindex @code{--nowindows}
1149 ``No windows''. If @value{GDBN} comes with a graphical user interface
1150 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1151 interface. If no GUI is available, this option has no effect.
1155 @cindex @code{--windows}
1157 If @value{GDBN} includes a GUI, then this option requires it to be
1160 @item -cd @var{directory}
1162 Run @value{GDBN} using @var{directory} as its working directory,
1163 instead of the current directory.
1165 @item -data-directory @var{directory}
1166 @cindex @code{--data-directory}
1167 Run @value{GDBN} using @var{directory} as its data directory.
1168 The data directory is where @value{GDBN} searches for its
1169 auxiliary files. @xref{Data Files}.
1173 @cindex @code{--fullname}
1175 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1176 subprocess. It tells @value{GDBN} to output the full file name and line
1177 number in a standard, recognizable fashion each time a stack frame is
1178 displayed (which includes each time your program stops). This
1179 recognizable format looks like two @samp{\032} characters, followed by
1180 the file name, line number and character position separated by colons,
1181 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1182 @samp{\032} characters as a signal to display the source code for the
1185 @item -annotate @var{level}
1186 @cindex @code{--annotate}
1187 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1188 effect is identical to using @samp{set annotate @var{level}}
1189 (@pxref{Annotations}). The annotation @var{level} controls how much
1190 information @value{GDBN} prints together with its prompt, values of
1191 expressions, source lines, and other types of output. Level 0 is the
1192 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1193 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1194 that control @value{GDBN}, and level 2 has been deprecated.
1196 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1200 @cindex @code{--args}
1201 Change interpretation of command line so that arguments following the
1202 executable file are passed as command line arguments to the inferior.
1203 This option stops option processing.
1205 @item -baud @var{bps}
1207 @cindex @code{--baud}
1209 Set the line speed (baud rate or bits per second) of any serial
1210 interface used by @value{GDBN} for remote debugging.
1212 @item -l @var{timeout}
1214 Set the timeout (in seconds) of any communication used by @value{GDBN}
1215 for remote debugging.
1217 @item -tty @var{device}
1218 @itemx -t @var{device}
1219 @cindex @code{--tty}
1221 Run using @var{device} for your program's standard input and output.
1222 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1224 @c resolve the situation of these eventually
1226 @cindex @code{--tui}
1227 Activate the @dfn{Text User Interface} when starting. The Text User
1228 Interface manages several text windows on the terminal, showing
1229 source, assembly, registers and @value{GDBN} command outputs
1230 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1231 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1232 Using @value{GDBN} under @sc{gnu} Emacs}).
1235 @c @cindex @code{--xdb}
1236 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1237 @c For information, see the file @file{xdb_trans.html}, which is usually
1238 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1241 @item -interpreter @var{interp}
1242 @cindex @code{--interpreter}
1243 Use the interpreter @var{interp} for interface with the controlling
1244 program or device. This option is meant to be set by programs which
1245 communicate with @value{GDBN} using it as a back end.
1246 @xref{Interpreters, , Command Interpreters}.
1248 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1249 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1250 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1251 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1252 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1253 @sc{gdb/mi} interfaces are no longer supported.
1256 @cindex @code{--write}
1257 Open the executable and core files for both reading and writing. This
1258 is equivalent to the @samp{set write on} command inside @value{GDBN}
1262 @cindex @code{--statistics}
1263 This option causes @value{GDBN} to print statistics about time and
1264 memory usage after it completes each command and returns to the prompt.
1267 @cindex @code{--version}
1268 This option causes @value{GDBN} to print its version number and
1269 no-warranty blurb, and exit.
1271 @item -configuration
1272 @cindex @code{--configuration}
1273 This option causes @value{GDBN} to print details about its build-time
1274 configuration parameters, and then exit. These details can be
1275 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1280 @subsection What @value{GDBN} Does During Startup
1281 @cindex @value{GDBN} startup
1283 Here's the description of what @value{GDBN} does during session startup:
1287 Sets up the command interpreter as specified by the command line
1288 (@pxref{Mode Options, interpreter}).
1292 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1293 used when building @value{GDBN}; @pxref{System-wide configuration,
1294 ,System-wide configuration and settings}) and executes all the commands in
1297 @anchor{Home Directory Init File}
1299 Reads the init file (if any) in your home directory@footnote{On
1300 DOS/Windows systems, the home directory is the one pointed to by the
1301 @code{HOME} environment variable.} and executes all the commands in
1304 @anchor{Option -init-eval-command}
1306 Executes commands and command files specified by the @samp{-iex} and
1307 @samp{-ix} options in their specified order. Usually you should use the
1308 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1309 settings before @value{GDBN} init files get executed and before inferior
1313 Processes command line options and operands.
1315 @anchor{Init File in the Current Directory during Startup}
1317 Reads and executes the commands from init file (if any) in the current
1318 working directory as long as @samp{set auto-load local-gdbinit} is set to
1319 @samp{on} (@pxref{Init File in the Current Directory}).
1320 This is only done if the current directory is
1321 different from your home directory. Thus, you can have more than one
1322 init file, one generic in your home directory, and another, specific
1323 to the program you are debugging, in the directory where you invoke
1327 If the command line specified a program to debug, or a process to
1328 attach to, or a core file, @value{GDBN} loads any auto-loaded
1329 scripts provided for the program or for its loaded shared libraries.
1330 @xref{Auto-loading}.
1332 If you wish to disable the auto-loading during startup,
1333 you must do something like the following:
1336 $ gdb -iex "set auto-load python-scripts off" myprogram
1339 Option @samp{-ex} does not work because the auto-loading is then turned
1343 Executes commands and command files specified by the @samp{-ex} and
1344 @samp{-x} options in their specified order. @xref{Command Files}, for
1345 more details about @value{GDBN} command files.
1348 Reads the command history recorded in the @dfn{history file}.
1349 @xref{Command History}, for more details about the command history and the
1350 files where @value{GDBN} records it.
1353 Init files use the same syntax as @dfn{command files} (@pxref{Command
1354 Files}) and are processed by @value{GDBN} in the same way. The init
1355 file in your home directory can set options (such as @samp{set
1356 complaints}) that affect subsequent processing of command line options
1357 and operands. Init files are not executed if you use the @samp{-nx}
1358 option (@pxref{Mode Options, ,Choosing Modes}).
1360 To display the list of init files loaded by gdb at startup, you
1361 can use @kbd{gdb --help}.
1363 @cindex init file name
1364 @cindex @file{.gdbinit}
1365 @cindex @file{gdb.ini}
1366 The @value{GDBN} init files are normally called @file{.gdbinit}.
1367 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1368 the limitations of file names imposed by DOS filesystems. The Windows
1369 port of @value{GDBN} uses the standard name, but if it finds a
1370 @file{gdb.ini} file in your home directory, it warns you about that
1371 and suggests to rename the file to the standard name.
1375 @section Quitting @value{GDBN}
1376 @cindex exiting @value{GDBN}
1377 @cindex leaving @value{GDBN}
1380 @kindex quit @r{[}@var{expression}@r{]}
1381 @kindex q @r{(@code{quit})}
1382 @item quit @r{[}@var{expression}@r{]}
1384 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1385 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1386 do not supply @var{expression}, @value{GDBN} will terminate normally;
1387 otherwise it will terminate using the result of @var{expression} as the
1392 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1393 terminates the action of any @value{GDBN} command that is in progress and
1394 returns to @value{GDBN} command level. It is safe to type the interrupt
1395 character at any time because @value{GDBN} does not allow it to take effect
1396 until a time when it is safe.
1398 If you have been using @value{GDBN} to control an attached process or
1399 device, you can release it with the @code{detach} command
1400 (@pxref{Attach, ,Debugging an Already-running Process}).
1402 @node Shell Commands
1403 @section Shell Commands
1405 If you need to execute occasional shell commands during your
1406 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1407 just use the @code{shell} command.
1412 @cindex shell escape
1413 @item shell @var{command-string}
1414 @itemx !@var{command-string}
1415 Invoke a standard shell to execute @var{command-string}.
1416 Note that no space is needed between @code{!} and @var{command-string}.
1417 If it exists, the environment variable @code{SHELL} determines which
1418 shell to run. Otherwise @value{GDBN} uses the default shell
1419 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1422 The utility @code{make} is often needed in development environments.
1423 You do not have to use the @code{shell} command for this purpose in
1428 @cindex calling make
1429 @item make @var{make-args}
1430 Execute the @code{make} program with the specified
1431 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1434 @node Logging Output
1435 @section Logging Output
1436 @cindex logging @value{GDBN} output
1437 @cindex save @value{GDBN} output to a file
1439 You may want to save the output of @value{GDBN} commands to a file.
1440 There are several commands to control @value{GDBN}'s logging.
1444 @item set logging on
1446 @item set logging off
1448 @cindex logging file name
1449 @item set logging file @var{file}
1450 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1451 @item set logging overwrite [on|off]
1452 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1453 you want @code{set logging on} to overwrite the logfile instead.
1454 @item set logging redirect [on|off]
1455 By default, @value{GDBN} output will go to both the terminal and the logfile.
1456 Set @code{redirect} if you want output to go only to the log file.
1457 @kindex show logging
1459 Show the current values of the logging settings.
1463 @chapter @value{GDBN} Commands
1465 You can abbreviate a @value{GDBN} command to the first few letters of the command
1466 name, if that abbreviation is unambiguous; and you can repeat certain
1467 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1468 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1469 show you the alternatives available, if there is more than one possibility).
1472 * Command Syntax:: How to give commands to @value{GDBN}
1473 * Completion:: Command completion
1474 * Help:: How to ask @value{GDBN} for help
1477 @node Command Syntax
1478 @section Command Syntax
1480 A @value{GDBN} command is a single line of input. There is no limit on
1481 how long it can be. It starts with a command name, which is followed by
1482 arguments whose meaning depends on the command name. For example, the
1483 command @code{step} accepts an argument which is the number of times to
1484 step, as in @samp{step 5}. You can also use the @code{step} command
1485 with no arguments. Some commands do not allow any arguments.
1487 @cindex abbreviation
1488 @value{GDBN} command names may always be truncated if that abbreviation is
1489 unambiguous. Other possible command abbreviations are listed in the
1490 documentation for individual commands. In some cases, even ambiguous
1491 abbreviations are allowed; for example, @code{s} is specially defined as
1492 equivalent to @code{step} even though there are other commands whose
1493 names start with @code{s}. You can test abbreviations by using them as
1494 arguments to the @code{help} command.
1496 @cindex repeating commands
1497 @kindex RET @r{(repeat last command)}
1498 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1499 repeat the previous command. Certain commands (for example, @code{run})
1500 will not repeat this way; these are commands whose unintentional
1501 repetition might cause trouble and which you are unlikely to want to
1502 repeat. User-defined commands can disable this feature; see
1503 @ref{Define, dont-repeat}.
1505 The @code{list} and @code{x} commands, when you repeat them with
1506 @key{RET}, construct new arguments rather than repeating
1507 exactly as typed. This permits easy scanning of source or memory.
1509 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1510 output, in a way similar to the common utility @code{more}
1511 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1512 @key{RET} too many in this situation, @value{GDBN} disables command
1513 repetition after any command that generates this sort of display.
1515 @kindex # @r{(a comment)}
1517 Any text from a @kbd{#} to the end of the line is a comment; it does
1518 nothing. This is useful mainly in command files (@pxref{Command
1519 Files,,Command Files}).
1521 @cindex repeating command sequences
1522 @kindex Ctrl-o @r{(operate-and-get-next)}
1523 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1524 commands. This command accepts the current line, like @key{RET}, and
1525 then fetches the next line relative to the current line from the history
1529 @section Command Completion
1532 @cindex word completion
1533 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1534 only one possibility; it can also show you what the valid possibilities
1535 are for the next word in a command, at any time. This works for @value{GDBN}
1536 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1538 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1539 of a word. If there is only one possibility, @value{GDBN} fills in the
1540 word, and waits for you to finish the command (or press @key{RET} to
1541 enter it). For example, if you type
1543 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1544 @c complete accuracy in these examples; space introduced for clarity.
1545 @c If texinfo enhancements make it unnecessary, it would be nice to
1546 @c replace " @key" by "@key" in the following...
1548 (@value{GDBP}) info bre @key{TAB}
1552 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1553 the only @code{info} subcommand beginning with @samp{bre}:
1556 (@value{GDBP}) info breakpoints
1560 You can either press @key{RET} at this point, to run the @code{info
1561 breakpoints} command, or backspace and enter something else, if
1562 @samp{breakpoints} does not look like the command you expected. (If you
1563 were sure you wanted @code{info breakpoints} in the first place, you
1564 might as well just type @key{RET} immediately after @samp{info bre},
1565 to exploit command abbreviations rather than command completion).
1567 If there is more than one possibility for the next word when you press
1568 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1569 characters and try again, or just press @key{TAB} a second time;
1570 @value{GDBN} displays all the possible completions for that word. For
1571 example, you might want to set a breakpoint on a subroutine whose name
1572 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1573 just sounds the bell. Typing @key{TAB} again displays all the
1574 function names in your program that begin with those characters, for
1578 (@value{GDBP}) b make_ @key{TAB}
1579 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1580 make_a_section_from_file make_environ
1581 make_abs_section make_function_type
1582 make_blockvector make_pointer_type
1583 make_cleanup make_reference_type
1584 make_command make_symbol_completion_list
1585 (@value{GDBP}) b make_
1589 After displaying the available possibilities, @value{GDBN} copies your
1590 partial input (@samp{b make_} in the example) so you can finish the
1593 If you just want to see the list of alternatives in the first place, you
1594 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1595 means @kbd{@key{META} ?}. You can type this either by holding down a
1596 key designated as the @key{META} shift on your keyboard (if there is
1597 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1599 @cindex quotes in commands
1600 @cindex completion of quoted strings
1601 Sometimes the string you need, while logically a ``word'', may contain
1602 parentheses or other characters that @value{GDBN} normally excludes from
1603 its notion of a word. To permit word completion to work in this
1604 situation, you may enclose words in @code{'} (single quote marks) in
1605 @value{GDBN} commands.
1607 The most likely situation where you might need this is in typing the
1608 name of a C@t{++} function. This is because C@t{++} allows function
1609 overloading (multiple definitions of the same function, distinguished
1610 by argument type). For example, when you want to set a breakpoint you
1611 may need to distinguish whether you mean the version of @code{name}
1612 that takes an @code{int} parameter, @code{name(int)}, or the version
1613 that takes a @code{float} parameter, @code{name(float)}. To use the
1614 word-completion facilities in this situation, type a single quote
1615 @code{'} at the beginning of the function name. This alerts
1616 @value{GDBN} that it may need to consider more information than usual
1617 when you press @key{TAB} or @kbd{M-?} to request word completion:
1620 (@value{GDBP}) b 'bubble( @kbd{M-?}
1621 bubble(double,double) bubble(int,int)
1622 (@value{GDBP}) b 'bubble(
1625 In some cases, @value{GDBN} can tell that completing a name requires using
1626 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1627 completing as much as it can) if you do not type the quote in the first
1631 (@value{GDBP}) b bub @key{TAB}
1632 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1633 (@value{GDBP}) b 'bubble(
1637 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1638 you have not yet started typing the argument list when you ask for
1639 completion on an overloaded symbol.
1641 For more information about overloaded functions, see @ref{C Plus Plus
1642 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1643 overload-resolution off} to disable overload resolution;
1644 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1646 @cindex completion of structure field names
1647 @cindex structure field name completion
1648 @cindex completion of union field names
1649 @cindex union field name completion
1650 When completing in an expression which looks up a field in a
1651 structure, @value{GDBN} also tries@footnote{The completer can be
1652 confused by certain kinds of invalid expressions. Also, it only
1653 examines the static type of the expression, not the dynamic type.} to
1654 limit completions to the field names available in the type of the
1658 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1659 magic to_fputs to_rewind
1660 to_data to_isatty to_write
1661 to_delete to_put to_write_async_safe
1666 This is because the @code{gdb_stdout} is a variable of the type
1667 @code{struct ui_file} that is defined in @value{GDBN} sources as
1674 ui_file_flush_ftype *to_flush;
1675 ui_file_write_ftype *to_write;
1676 ui_file_write_async_safe_ftype *to_write_async_safe;
1677 ui_file_fputs_ftype *to_fputs;
1678 ui_file_read_ftype *to_read;
1679 ui_file_delete_ftype *to_delete;
1680 ui_file_isatty_ftype *to_isatty;
1681 ui_file_rewind_ftype *to_rewind;
1682 ui_file_put_ftype *to_put;
1689 @section Getting Help
1690 @cindex online documentation
1693 You can always ask @value{GDBN} itself for information on its commands,
1694 using the command @code{help}.
1697 @kindex h @r{(@code{help})}
1700 You can use @code{help} (abbreviated @code{h}) with no arguments to
1701 display a short list of named classes of commands:
1705 List of classes of commands:
1707 aliases -- Aliases of other commands
1708 breakpoints -- Making program stop at certain points
1709 data -- Examining data
1710 files -- Specifying and examining files
1711 internals -- Maintenance commands
1712 obscure -- Obscure features
1713 running -- Running the program
1714 stack -- Examining the stack
1715 status -- Status inquiries
1716 support -- Support facilities
1717 tracepoints -- Tracing of program execution without
1718 stopping the program
1719 user-defined -- User-defined commands
1721 Type "help" followed by a class name for a list of
1722 commands in that class.
1723 Type "help" followed by command name for full
1725 Command name abbreviations are allowed if unambiguous.
1728 @c the above line break eliminates huge line overfull...
1730 @item help @var{class}
1731 Using one of the general help classes as an argument, you can get a
1732 list of the individual commands in that class. For example, here is the
1733 help display for the class @code{status}:
1736 (@value{GDBP}) help status
1741 @c Line break in "show" line falsifies real output, but needed
1742 @c to fit in smallbook page size.
1743 info -- Generic command for showing things
1744 about the program being debugged
1745 show -- Generic command for showing things
1748 Type "help" followed by command name for full
1750 Command name abbreviations are allowed if unambiguous.
1754 @item help @var{command}
1755 With a command name as @code{help} argument, @value{GDBN} displays a
1756 short paragraph on how to use that command.
1759 @item apropos @var{args}
1760 The @code{apropos} command searches through all of the @value{GDBN}
1761 commands, and their documentation, for the regular expression specified in
1762 @var{args}. It prints out all matches found. For example:
1773 alias -- Define a new command that is an alias of an existing command
1774 aliases -- Aliases of other commands
1775 d -- Delete some breakpoints or auto-display expressions
1776 del -- Delete some breakpoints or auto-display expressions
1777 delete -- Delete some breakpoints or auto-display expressions
1782 @item complete @var{args}
1783 The @code{complete @var{args}} command lists all the possible completions
1784 for the beginning of a command. Use @var{args} to specify the beginning of the
1785 command you want completed. For example:
1791 @noindent results in:
1802 @noindent This is intended for use by @sc{gnu} Emacs.
1805 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1806 and @code{show} to inquire about the state of your program, or the state
1807 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1808 manual introduces each of them in the appropriate context. The listings
1809 under @code{info} and under @code{show} in the Command, Variable, and
1810 Function Index point to all the sub-commands. @xref{Command and Variable
1816 @kindex i @r{(@code{info})}
1818 This command (abbreviated @code{i}) is for describing the state of your
1819 program. For example, you can show the arguments passed to a function
1820 with @code{info args}, list the registers currently in use with @code{info
1821 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1822 You can get a complete list of the @code{info} sub-commands with
1823 @w{@code{help info}}.
1827 You can assign the result of an expression to an environment variable with
1828 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1829 @code{set prompt $}.
1833 In contrast to @code{info}, @code{show} is for describing the state of
1834 @value{GDBN} itself.
1835 You can change most of the things you can @code{show}, by using the
1836 related command @code{set}; for example, you can control what number
1837 system is used for displays with @code{set radix}, or simply inquire
1838 which is currently in use with @code{show radix}.
1841 To display all the settable parameters and their current
1842 values, you can use @code{show} with no arguments; you may also use
1843 @code{info set}. Both commands produce the same display.
1844 @c FIXME: "info set" violates the rule that "info" is for state of
1845 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1846 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1850 Here are several miscellaneous @code{show} subcommands, all of which are
1851 exceptional in lacking corresponding @code{set} commands:
1854 @kindex show version
1855 @cindex @value{GDBN} version number
1857 Show what version of @value{GDBN} is running. You should include this
1858 information in @value{GDBN} bug-reports. If multiple versions of
1859 @value{GDBN} are in use at your site, you may need to determine which
1860 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1861 commands are introduced, and old ones may wither away. Also, many
1862 system vendors ship variant versions of @value{GDBN}, and there are
1863 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1864 The version number is the same as the one announced when you start
1867 @kindex show copying
1868 @kindex info copying
1869 @cindex display @value{GDBN} copyright
1872 Display information about permission for copying @value{GDBN}.
1874 @kindex show warranty
1875 @kindex info warranty
1877 @itemx info warranty
1878 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1879 if your version of @value{GDBN} comes with one.
1881 @kindex show configuration
1882 @item show configuration
1883 Display detailed information about the way @value{GDBN} was configured
1884 when it was built. This displays the optional arguments passed to the
1885 @file{configure} script and also configuration parameters detected
1886 automatically by @command{configure}. When reporting a @value{GDBN}
1887 bug (@pxref{GDB Bugs}), it is important to include this information in
1893 @chapter Running Programs Under @value{GDBN}
1895 When you run a program under @value{GDBN}, you must first generate
1896 debugging information when you compile it.
1898 You may start @value{GDBN} with its arguments, if any, in an environment
1899 of your choice. If you are doing native debugging, you may redirect
1900 your program's input and output, debug an already running process, or
1901 kill a child process.
1904 * Compilation:: Compiling for debugging
1905 * Starting:: Starting your program
1906 * Arguments:: Your program's arguments
1907 * Environment:: Your program's environment
1909 * Working Directory:: Your program's working directory
1910 * Input/Output:: Your program's input and output
1911 * Attach:: Debugging an already-running process
1912 * Kill Process:: Killing the child process
1914 * Inferiors and Programs:: Debugging multiple inferiors and programs
1915 * Threads:: Debugging programs with multiple threads
1916 * Forks:: Debugging forks
1917 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1921 @section Compiling for Debugging
1923 In order to debug a program effectively, you need to generate
1924 debugging information when you compile it. This debugging information
1925 is stored in the object file; it describes the data type of each
1926 variable or function and the correspondence between source line numbers
1927 and addresses in the executable code.
1929 To request debugging information, specify the @samp{-g} option when you run
1932 Programs that are to be shipped to your customers are compiled with
1933 optimizations, using the @samp{-O} compiler option. However, some
1934 compilers are unable to handle the @samp{-g} and @samp{-O} options
1935 together. Using those compilers, you cannot generate optimized
1936 executables containing debugging information.
1938 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1939 without @samp{-O}, making it possible to debug optimized code. We
1940 recommend that you @emph{always} use @samp{-g} whenever you compile a
1941 program. You may think your program is correct, but there is no sense
1942 in pushing your luck. For more information, see @ref{Optimized Code}.
1944 Older versions of the @sc{gnu} C compiler permitted a variant option
1945 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1946 format; if your @sc{gnu} C compiler has this option, do not use it.
1948 @value{GDBN} knows about preprocessor macros and can show you their
1949 expansion (@pxref{Macros}). Most compilers do not include information
1950 about preprocessor macros in the debugging information if you specify
1951 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1952 the @sc{gnu} C compiler, provides macro information if you are using
1953 the DWARF debugging format, and specify the option @option{-g3}.
1955 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1956 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1957 information on @value{NGCC} options affecting debug information.
1959 You will have the best debugging experience if you use the latest
1960 version of the DWARF debugging format that your compiler supports.
1961 DWARF is currently the most expressive and best supported debugging
1962 format in @value{GDBN}.
1966 @section Starting your Program
1972 @kindex r @r{(@code{run})}
1975 Use the @code{run} command to start your program under @value{GDBN}.
1976 You must first specify the program name (except on VxWorks) with an
1977 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1978 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1979 (@pxref{Files, ,Commands to Specify Files}).
1983 If you are running your program in an execution environment that
1984 supports processes, @code{run} creates an inferior process and makes
1985 that process run your program. In some environments without processes,
1986 @code{run} jumps to the start of your program. Other targets,
1987 like @samp{remote}, are always running. If you get an error
1988 message like this one:
1991 The "remote" target does not support "run".
1992 Try "help target" or "continue".
1996 then use @code{continue} to run your program. You may need @code{load}
1997 first (@pxref{load}).
1999 The execution of a program is affected by certain information it
2000 receives from its superior. @value{GDBN} provides ways to specify this
2001 information, which you must do @emph{before} starting your program. (You
2002 can change it after starting your program, but such changes only affect
2003 your program the next time you start it.) This information may be
2004 divided into four categories:
2007 @item The @emph{arguments.}
2008 Specify the arguments to give your program as the arguments of the
2009 @code{run} command. If a shell is available on your target, the shell
2010 is used to pass the arguments, so that you may use normal conventions
2011 (such as wildcard expansion or variable substitution) in describing
2013 In Unix systems, you can control which shell is used with the
2014 @code{SHELL} environment variable.
2015 @xref{Arguments, ,Your Program's Arguments}.
2017 @item The @emph{environment.}
2018 Your program normally inherits its environment from @value{GDBN}, but you can
2019 use the @value{GDBN} commands @code{set environment} and @code{unset
2020 environment} to change parts of the environment that affect
2021 your program. @xref{Environment, ,Your Program's Environment}.
2023 @item The @emph{working directory.}
2024 Your program inherits its working directory from @value{GDBN}. You can set
2025 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2026 @xref{Working Directory, ,Your Program's Working Directory}.
2028 @item The @emph{standard input and output.}
2029 Your program normally uses the same device for standard input and
2030 standard output as @value{GDBN} is using. You can redirect input and output
2031 in the @code{run} command line, or you can use the @code{tty} command to
2032 set a different device for your program.
2033 @xref{Input/Output, ,Your Program's Input and Output}.
2036 @emph{Warning:} While input and output redirection work, you cannot use
2037 pipes to pass the output of the program you are debugging to another
2038 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2042 When you issue the @code{run} command, your program begins to execute
2043 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2044 of how to arrange for your program to stop. Once your program has
2045 stopped, you may call functions in your program, using the @code{print}
2046 or @code{call} commands. @xref{Data, ,Examining Data}.
2048 If the modification time of your symbol file has changed since the last
2049 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2050 table, and reads it again. When it does this, @value{GDBN} tries to retain
2051 your current breakpoints.
2056 @cindex run to main procedure
2057 The name of the main procedure can vary from language to language.
2058 With C or C@t{++}, the main procedure name is always @code{main}, but
2059 other languages such as Ada do not require a specific name for their
2060 main procedure. The debugger provides a convenient way to start the
2061 execution of the program and to stop at the beginning of the main
2062 procedure, depending on the language used.
2064 The @samp{start} command does the equivalent of setting a temporary
2065 breakpoint at the beginning of the main procedure and then invoking
2066 the @samp{run} command.
2068 @cindex elaboration phase
2069 Some programs contain an @dfn{elaboration} phase where some startup code is
2070 executed before the main procedure is called. This depends on the
2071 languages used to write your program. In C@t{++}, for instance,
2072 constructors for static and global objects are executed before
2073 @code{main} is called. It is therefore possible that the debugger stops
2074 before reaching the main procedure. However, the temporary breakpoint
2075 will remain to halt execution.
2077 Specify the arguments to give to your program as arguments to the
2078 @samp{start} command. These arguments will be given verbatim to the
2079 underlying @samp{run} command. Note that the same arguments will be
2080 reused if no argument is provided during subsequent calls to
2081 @samp{start} or @samp{run}.
2083 It is sometimes necessary to debug the program during elaboration. In
2084 these cases, using the @code{start} command would stop the execution of
2085 your program too late, as the program would have already completed the
2086 elaboration phase. Under these circumstances, insert breakpoints in your
2087 elaboration code before running your program.
2089 @kindex set exec-wrapper
2090 @item set exec-wrapper @var{wrapper}
2091 @itemx show exec-wrapper
2092 @itemx unset exec-wrapper
2093 When @samp{exec-wrapper} is set, the specified wrapper is used to
2094 launch programs for debugging. @value{GDBN} starts your program
2095 with a shell command of the form @kbd{exec @var{wrapper}
2096 @var{program}}. Quoting is added to @var{program} and its
2097 arguments, but not to @var{wrapper}, so you should add quotes if
2098 appropriate for your shell. The wrapper runs until it executes
2099 your program, and then @value{GDBN} takes control.
2101 You can use any program that eventually calls @code{execve} with
2102 its arguments as a wrapper. Several standard Unix utilities do
2103 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2104 with @code{exec "$@@"} will also work.
2106 For example, you can use @code{env} to pass an environment variable to
2107 the debugged program, without setting the variable in your shell's
2111 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2115 This command is available when debugging locally on most targets, excluding
2116 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2118 @kindex set disable-randomization
2119 @item set disable-randomization
2120 @itemx set disable-randomization on
2121 This option (enabled by default in @value{GDBN}) will turn off the native
2122 randomization of the virtual address space of the started program. This option
2123 is useful for multiple debugging sessions to make the execution better
2124 reproducible and memory addresses reusable across debugging sessions.
2126 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2127 On @sc{gnu}/Linux you can get the same behavior using
2130 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2133 @item set disable-randomization off
2134 Leave the behavior of the started executable unchanged. Some bugs rear their
2135 ugly heads only when the program is loaded at certain addresses. If your bug
2136 disappears when you run the program under @value{GDBN}, that might be because
2137 @value{GDBN} by default disables the address randomization on platforms, such
2138 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2139 disable-randomization off} to try to reproduce such elusive bugs.
2141 On targets where it is available, virtual address space randomization
2142 protects the programs against certain kinds of security attacks. In these
2143 cases the attacker needs to know the exact location of a concrete executable
2144 code. Randomizing its location makes it impossible to inject jumps misusing
2145 a code at its expected addresses.
2147 Prelinking shared libraries provides a startup performance advantage but it
2148 makes addresses in these libraries predictable for privileged processes by
2149 having just unprivileged access at the target system. Reading the shared
2150 library binary gives enough information for assembling the malicious code
2151 misusing it. Still even a prelinked shared library can get loaded at a new
2152 random address just requiring the regular relocation process during the
2153 startup. Shared libraries not already prelinked are always loaded at
2154 a randomly chosen address.
2156 Position independent executables (PIE) contain position independent code
2157 similar to the shared libraries and therefore such executables get loaded at
2158 a randomly chosen address upon startup. PIE executables always load even
2159 already prelinked shared libraries at a random address. You can build such
2160 executable using @command{gcc -fPIE -pie}.
2162 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2163 (as long as the randomization is enabled).
2165 @item show disable-randomization
2166 Show the current setting of the explicit disable of the native randomization of
2167 the virtual address space of the started program.
2172 @section Your Program's Arguments
2174 @cindex arguments (to your program)
2175 The arguments to your program can be specified by the arguments of the
2177 They are passed to a shell, which expands wildcard characters and
2178 performs redirection of I/O, and thence to your program. Your
2179 @code{SHELL} environment variable (if it exists) specifies what shell
2180 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2181 the default shell (@file{/bin/sh} on Unix).
2183 On non-Unix systems, the program is usually invoked directly by
2184 @value{GDBN}, which emulates I/O redirection via the appropriate system
2185 calls, and the wildcard characters are expanded by the startup code of
2186 the program, not by the shell.
2188 @code{run} with no arguments uses the same arguments used by the previous
2189 @code{run}, or those set by the @code{set args} command.
2194 Specify the arguments to be used the next time your program is run. If
2195 @code{set args} has no arguments, @code{run} executes your program
2196 with no arguments. Once you have run your program with arguments,
2197 using @code{set args} before the next @code{run} is the only way to run
2198 it again without arguments.
2202 Show the arguments to give your program when it is started.
2206 @section Your Program's Environment
2208 @cindex environment (of your program)
2209 The @dfn{environment} consists of a set of environment variables and
2210 their values. Environment variables conventionally record such things as
2211 your user name, your home directory, your terminal type, and your search
2212 path for programs to run. Usually you set up environment variables with
2213 the shell and they are inherited by all the other programs you run. When
2214 debugging, it can be useful to try running your program with a modified
2215 environment without having to start @value{GDBN} over again.
2219 @item path @var{directory}
2220 Add @var{directory} to the front of the @code{PATH} environment variable
2221 (the search path for executables) that will be passed to your program.
2222 The value of @code{PATH} used by @value{GDBN} does not change.
2223 You may specify several directory names, separated by whitespace or by a
2224 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2225 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2226 is moved to the front, so it is searched sooner.
2228 You can use the string @samp{$cwd} to refer to whatever is the current
2229 working directory at the time @value{GDBN} searches the path. If you
2230 use @samp{.} instead, it refers to the directory where you executed the
2231 @code{path} command. @value{GDBN} replaces @samp{.} in the
2232 @var{directory} argument (with the current path) before adding
2233 @var{directory} to the search path.
2234 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2235 @c document that, since repeating it would be a no-op.
2239 Display the list of search paths for executables (the @code{PATH}
2240 environment variable).
2242 @kindex show environment
2243 @item show environment @r{[}@var{varname}@r{]}
2244 Print the value of environment variable @var{varname} to be given to
2245 your program when it starts. If you do not supply @var{varname},
2246 print the names and values of all environment variables to be given to
2247 your program. You can abbreviate @code{environment} as @code{env}.
2249 @kindex set environment
2250 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2251 Set environment variable @var{varname} to @var{value}. The value
2252 changes for your program only, not for @value{GDBN} itself. @var{value} may
2253 be any string; the values of environment variables are just strings, and
2254 any interpretation is supplied by your program itself. The @var{value}
2255 parameter is optional; if it is eliminated, the variable is set to a
2257 @c "any string" here does not include leading, trailing
2258 @c blanks. Gnu asks: does anyone care?
2260 For example, this command:
2267 tells the debugged program, when subsequently run, that its user is named
2268 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2269 are not actually required.)
2271 @kindex unset environment
2272 @item unset environment @var{varname}
2273 Remove variable @var{varname} from the environment to be passed to your
2274 program. This is different from @samp{set env @var{varname} =};
2275 @code{unset environment} removes the variable from the environment,
2276 rather than assigning it an empty value.
2279 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2281 by your @code{SHELL} environment variable if it exists (or
2282 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2283 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2284 @file{.bashrc} for BASH---any variables you set in that file affect
2285 your program. You may wish to move setting of environment variables to
2286 files that are only run when you sign on, such as @file{.login} or
2289 @node Working Directory
2290 @section Your Program's Working Directory
2292 @cindex working directory (of your program)
2293 Each time you start your program with @code{run}, it inherits its
2294 working directory from the current working directory of @value{GDBN}.
2295 The @value{GDBN} working directory is initially whatever it inherited
2296 from its parent process (typically the shell), but you can specify a new
2297 working directory in @value{GDBN} with the @code{cd} command.
2299 The @value{GDBN} working directory also serves as a default for the commands
2300 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2305 @cindex change working directory
2306 @item cd @r{[}@var{directory}@r{]}
2307 Set the @value{GDBN} working directory to @var{directory}. If not
2308 given, @var{directory} uses @file{'~'}.
2312 Print the @value{GDBN} working directory.
2315 It is generally impossible to find the current working directory of
2316 the process being debugged (since a program can change its directory
2317 during its run). If you work on a system where @value{GDBN} is
2318 configured with the @file{/proc} support, you can use the @code{info
2319 proc} command (@pxref{SVR4 Process Information}) to find out the
2320 current working directory of the debuggee.
2323 @section Your Program's Input and Output
2328 By default, the program you run under @value{GDBN} does input and output to
2329 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2330 to its own terminal modes to interact with you, but it records the terminal
2331 modes your program was using and switches back to them when you continue
2332 running your program.
2335 @kindex info terminal
2337 Displays information recorded by @value{GDBN} about the terminal modes your
2341 You can redirect your program's input and/or output using shell
2342 redirection with the @code{run} command. For example,
2349 starts your program, diverting its output to the file @file{outfile}.
2352 @cindex controlling terminal
2353 Another way to specify where your program should do input and output is
2354 with the @code{tty} command. This command accepts a file name as
2355 argument, and causes this file to be the default for future @code{run}
2356 commands. It also resets the controlling terminal for the child
2357 process, for future @code{run} commands. For example,
2364 directs that processes started with subsequent @code{run} commands
2365 default to do input and output on the terminal @file{/dev/ttyb} and have
2366 that as their controlling terminal.
2368 An explicit redirection in @code{run} overrides the @code{tty} command's
2369 effect on the input/output device, but not its effect on the controlling
2372 When you use the @code{tty} command or redirect input in the @code{run}
2373 command, only the input @emph{for your program} is affected. The input
2374 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2375 for @code{set inferior-tty}.
2377 @cindex inferior tty
2378 @cindex set inferior controlling terminal
2379 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2380 display the name of the terminal that will be used for future runs of your
2384 @item set inferior-tty /dev/ttyb
2385 @kindex set inferior-tty
2386 Set the tty for the program being debugged to /dev/ttyb.
2388 @item show inferior-tty
2389 @kindex show inferior-tty
2390 Show the current tty for the program being debugged.
2394 @section Debugging an Already-running Process
2399 @item attach @var{process-id}
2400 This command attaches to a running process---one that was started
2401 outside @value{GDBN}. (@code{info files} shows your active
2402 targets.) The command takes as argument a process ID. The usual way to
2403 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2404 or with the @samp{jobs -l} shell command.
2406 @code{attach} does not repeat if you press @key{RET} a second time after
2407 executing the command.
2410 To use @code{attach}, your program must be running in an environment
2411 which supports processes; for example, @code{attach} does not work for
2412 programs on bare-board targets that lack an operating system. You must
2413 also have permission to send the process a signal.
2415 When you use @code{attach}, the debugger finds the program running in
2416 the process first by looking in the current working directory, then (if
2417 the program is not found) by using the source file search path
2418 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2419 the @code{file} command to load the program. @xref{Files, ,Commands to
2422 The first thing @value{GDBN} does after arranging to debug the specified
2423 process is to stop it. You can examine and modify an attached process
2424 with all the @value{GDBN} commands that are ordinarily available when
2425 you start processes with @code{run}. You can insert breakpoints; you
2426 can step and continue; you can modify storage. If you would rather the
2427 process continue running, you may use the @code{continue} command after
2428 attaching @value{GDBN} to the process.
2433 When you have finished debugging the attached process, you can use the
2434 @code{detach} command to release it from @value{GDBN} control. Detaching
2435 the process continues its execution. After the @code{detach} command,
2436 that process and @value{GDBN} become completely independent once more, and you
2437 are ready to @code{attach} another process or start one with @code{run}.
2438 @code{detach} does not repeat if you press @key{RET} again after
2439 executing the command.
2442 If you exit @value{GDBN} while you have an attached process, you detach
2443 that process. If you use the @code{run} command, you kill that process.
2444 By default, @value{GDBN} asks for confirmation if you try to do either of these
2445 things; you can control whether or not you need to confirm by using the
2446 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2450 @section Killing the Child Process
2455 Kill the child process in which your program is running under @value{GDBN}.
2458 This command is useful if you wish to debug a core dump instead of a
2459 running process. @value{GDBN} ignores any core dump file while your program
2462 On some operating systems, a program cannot be executed outside @value{GDBN}
2463 while you have breakpoints set on it inside @value{GDBN}. You can use the
2464 @code{kill} command in this situation to permit running your program
2465 outside the debugger.
2467 The @code{kill} command is also useful if you wish to recompile and
2468 relink your program, since on many systems it is impossible to modify an
2469 executable file while it is running in a process. In this case, when you
2470 next type @code{run}, @value{GDBN} notices that the file has changed, and
2471 reads the symbol table again (while trying to preserve your current
2472 breakpoint settings).
2474 @node Inferiors and Programs
2475 @section Debugging Multiple Inferiors and Programs
2477 @value{GDBN} lets you run and debug multiple programs in a single
2478 session. In addition, @value{GDBN} on some systems may let you run
2479 several programs simultaneously (otherwise you have to exit from one
2480 before starting another). In the most general case, you can have
2481 multiple threads of execution in each of multiple processes, launched
2482 from multiple executables.
2485 @value{GDBN} represents the state of each program execution with an
2486 object called an @dfn{inferior}. An inferior typically corresponds to
2487 a process, but is more general and applies also to targets that do not
2488 have processes. Inferiors may be created before a process runs, and
2489 may be retained after a process exits. Inferiors have unique
2490 identifiers that are different from process ids. Usually each
2491 inferior will also have its own distinct address space, although some
2492 embedded targets may have several inferiors running in different parts
2493 of a single address space. Each inferior may in turn have multiple
2494 threads running in it.
2496 To find out what inferiors exist at any moment, use @w{@code{info
2500 @kindex info inferiors
2501 @item info inferiors
2502 Print a list of all inferiors currently being managed by @value{GDBN}.
2504 @value{GDBN} displays for each inferior (in this order):
2508 the inferior number assigned by @value{GDBN}
2511 the target system's inferior identifier
2514 the name of the executable the inferior is running.
2519 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2520 indicates the current inferior.
2524 @c end table here to get a little more width for example
2527 (@value{GDBP}) info inferiors
2528 Num Description Executable
2529 2 process 2307 hello
2530 * 1 process 3401 goodbye
2533 To switch focus between inferiors, use the @code{inferior} command:
2536 @kindex inferior @var{infno}
2537 @item inferior @var{infno}
2538 Make inferior number @var{infno} the current inferior. The argument
2539 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2540 in the first field of the @samp{info inferiors} display.
2544 You can get multiple executables into a debugging session via the
2545 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2546 systems @value{GDBN} can add inferiors to the debug session
2547 automatically by following calls to @code{fork} and @code{exec}. To
2548 remove inferiors from the debugging session use the
2549 @w{@code{remove-inferiors}} command.
2552 @kindex add-inferior
2553 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2554 Adds @var{n} inferiors to be run using @var{executable} as the
2555 executable. @var{n} defaults to 1. If no executable is specified,
2556 the inferiors begins empty, with no program. You can still assign or
2557 change the program assigned to the inferior at any time by using the
2558 @code{file} command with the executable name as its argument.
2560 @kindex clone-inferior
2561 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2562 Adds @var{n} inferiors ready to execute the same program as inferior
2563 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2564 number of the current inferior. This is a convenient command when you
2565 want to run another instance of the inferior you are debugging.
2568 (@value{GDBP}) info inferiors
2569 Num Description Executable
2570 * 1 process 29964 helloworld
2571 (@value{GDBP}) clone-inferior
2574 (@value{GDBP}) info inferiors
2575 Num Description Executable
2577 * 1 process 29964 helloworld
2580 You can now simply switch focus to inferior 2 and run it.
2582 @kindex remove-inferiors
2583 @item remove-inferiors @var{infno}@dots{}
2584 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2585 possible to remove an inferior that is running with this command. For
2586 those, use the @code{kill} or @code{detach} command first.
2590 To quit debugging one of the running inferiors that is not the current
2591 inferior, you can either detach from it by using the @w{@code{detach
2592 inferior}} command (allowing it to run independently), or kill it
2593 using the @w{@code{kill inferiors}} command:
2596 @kindex detach inferiors @var{infno}@dots{}
2597 @item detach inferior @var{infno}@dots{}
2598 Detach from the inferior or inferiors identified by @value{GDBN}
2599 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2600 still stays on the list of inferiors shown by @code{info inferiors},
2601 but its Description will show @samp{<null>}.
2603 @kindex kill inferiors @var{infno}@dots{}
2604 @item kill inferiors @var{infno}@dots{}
2605 Kill the inferior or inferiors identified by @value{GDBN} inferior
2606 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2607 stays on the list of inferiors shown by @code{info inferiors}, but its
2608 Description will show @samp{<null>}.
2611 After the successful completion of a command such as @code{detach},
2612 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2613 a normal process exit, the inferior is still valid and listed with
2614 @code{info inferiors}, ready to be restarted.
2617 To be notified when inferiors are started or exit under @value{GDBN}'s
2618 control use @w{@code{set print inferior-events}}:
2621 @kindex set print inferior-events
2622 @cindex print messages on inferior start and exit
2623 @item set print inferior-events
2624 @itemx set print inferior-events on
2625 @itemx set print inferior-events off
2626 The @code{set print inferior-events} command allows you to enable or
2627 disable printing of messages when @value{GDBN} notices that new
2628 inferiors have started or that inferiors have exited or have been
2629 detached. By default, these messages will not be printed.
2631 @kindex show print inferior-events
2632 @item show print inferior-events
2633 Show whether messages will be printed when @value{GDBN} detects that
2634 inferiors have started, exited or have been detached.
2637 Many commands will work the same with multiple programs as with a
2638 single program: e.g., @code{print myglobal} will simply display the
2639 value of @code{myglobal} in the current inferior.
2642 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2643 get more info about the relationship of inferiors, programs, address
2644 spaces in a debug session. You can do that with the @w{@code{maint
2645 info program-spaces}} command.
2648 @kindex maint info program-spaces
2649 @item maint info program-spaces
2650 Print a list of all program spaces currently being managed by
2653 @value{GDBN} displays for each program space (in this order):
2657 the program space number assigned by @value{GDBN}
2660 the name of the executable loaded into the program space, with e.g.,
2661 the @code{file} command.
2666 An asterisk @samp{*} preceding the @value{GDBN} program space number
2667 indicates the current program space.
2669 In addition, below each program space line, @value{GDBN} prints extra
2670 information that isn't suitable to display in tabular form. For
2671 example, the list of inferiors bound to the program space.
2674 (@value{GDBP}) maint info program-spaces
2677 Bound inferiors: ID 1 (process 21561)
2681 Here we can see that no inferior is running the program @code{hello},
2682 while @code{process 21561} is running the program @code{goodbye}. On
2683 some targets, it is possible that multiple inferiors are bound to the
2684 same program space. The most common example is that of debugging both
2685 the parent and child processes of a @code{vfork} call. For example,
2688 (@value{GDBP}) maint info program-spaces
2691 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2694 Here, both inferior 2 and inferior 1 are running in the same program
2695 space as a result of inferior 1 having executed a @code{vfork} call.
2699 @section Debugging Programs with Multiple Threads
2701 @cindex threads of execution
2702 @cindex multiple threads
2703 @cindex switching threads
2704 In some operating systems, such as HP-UX and Solaris, a single program
2705 may have more than one @dfn{thread} of execution. The precise semantics
2706 of threads differ from one operating system to another, but in general
2707 the threads of a single program are akin to multiple processes---except
2708 that they share one address space (that is, they can all examine and
2709 modify the same variables). On the other hand, each thread has its own
2710 registers and execution stack, and perhaps private memory.
2712 @value{GDBN} provides these facilities for debugging multi-thread
2716 @item automatic notification of new threads
2717 @item @samp{thread @var{threadno}}, a command to switch among threads
2718 @item @samp{info threads}, a command to inquire about existing threads
2719 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2720 a command to apply a command to a list of threads
2721 @item thread-specific breakpoints
2722 @item @samp{set print thread-events}, which controls printing of
2723 messages on thread start and exit.
2724 @item @samp{set libthread-db-search-path @var{path}}, which lets
2725 the user specify which @code{libthread_db} to use if the default choice
2726 isn't compatible with the program.
2730 @emph{Warning:} These facilities are not yet available on every
2731 @value{GDBN} configuration where the operating system supports threads.
2732 If your @value{GDBN} does not support threads, these commands have no
2733 effect. For example, a system without thread support shows no output
2734 from @samp{info threads}, and always rejects the @code{thread} command,
2738 (@value{GDBP}) info threads
2739 (@value{GDBP}) thread 1
2740 Thread ID 1 not known. Use the "info threads" command to
2741 see the IDs of currently known threads.
2743 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2744 @c doesn't support threads"?
2747 @cindex focus of debugging
2748 @cindex current thread
2749 The @value{GDBN} thread debugging facility allows you to observe all
2750 threads while your program runs---but whenever @value{GDBN} takes
2751 control, one thread in particular is always the focus of debugging.
2752 This thread is called the @dfn{current thread}. Debugging commands show
2753 program information from the perspective of the current thread.
2755 @cindex @code{New} @var{systag} message
2756 @cindex thread identifier (system)
2757 @c FIXME-implementors!! It would be more helpful if the [New...] message
2758 @c included GDB's numeric thread handle, so you could just go to that
2759 @c thread without first checking `info threads'.
2760 Whenever @value{GDBN} detects a new thread in your program, it displays
2761 the target system's identification for the thread with a message in the
2762 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2763 whose form varies depending on the particular system. For example, on
2764 @sc{gnu}/Linux, you might see
2767 [New Thread 0x41e02940 (LWP 25582)]
2771 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2772 the @var{systag} is simply something like @samp{process 368}, with no
2775 @c FIXME!! (1) Does the [New...] message appear even for the very first
2776 @c thread of a program, or does it only appear for the
2777 @c second---i.e.@: when it becomes obvious we have a multithread
2779 @c (2) *Is* there necessarily a first thread always? Or do some
2780 @c multithread systems permit starting a program with multiple
2781 @c threads ab initio?
2783 @cindex thread number
2784 @cindex thread identifier (GDB)
2785 For debugging purposes, @value{GDBN} associates its own thread
2786 number---always a single integer---with each thread in your program.
2789 @kindex info threads
2790 @item info threads @r{[}@var{id}@dots{}@r{]}
2791 Display a summary of all threads currently in your program. Optional
2792 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2793 means to print information only about the specified thread or threads.
2794 @value{GDBN} displays for each thread (in this order):
2798 the thread number assigned by @value{GDBN}
2801 the target system's thread identifier (@var{systag})
2804 the thread's name, if one is known. A thread can either be named by
2805 the user (see @code{thread name}, below), or, in some cases, by the
2809 the current stack frame summary for that thread
2813 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2814 indicates the current thread.
2818 @c end table here to get a little more width for example
2821 (@value{GDBP}) info threads
2823 3 process 35 thread 27 0x34e5 in sigpause ()
2824 2 process 35 thread 23 0x34e5 in sigpause ()
2825 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2829 On Solaris, you can display more information about user threads with a
2830 Solaris-specific command:
2833 @item maint info sol-threads
2834 @kindex maint info sol-threads
2835 @cindex thread info (Solaris)
2836 Display info on Solaris user threads.
2840 @kindex thread @var{threadno}
2841 @item thread @var{threadno}
2842 Make thread number @var{threadno} the current thread. The command
2843 argument @var{threadno} is the internal @value{GDBN} thread number, as
2844 shown in the first field of the @samp{info threads} display.
2845 @value{GDBN} responds by displaying the system identifier of the thread
2846 you selected, and its current stack frame summary:
2849 (@value{GDBP}) thread 2
2850 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2851 #0 some_function (ignore=0x0) at example.c:8
2852 8 printf ("hello\n");
2856 As with the @samp{[New @dots{}]} message, the form of the text after
2857 @samp{Switching to} depends on your system's conventions for identifying
2860 @vindex $_thread@r{, convenience variable}
2861 The debugger convenience variable @samp{$_thread} contains the number
2862 of the current thread. You may find this useful in writing breakpoint
2863 conditional expressions, command scripts, and so forth. See
2864 @xref{Convenience Vars,, Convenience Variables}, for general
2865 information on convenience variables.
2867 @kindex thread apply
2868 @cindex apply command to several threads
2869 @item thread apply [@var{threadno} | all] @var{command}
2870 The @code{thread apply} command allows you to apply the named
2871 @var{command} to one or more threads. Specify the numbers of the
2872 threads that you want affected with the command argument
2873 @var{threadno}. It can be a single thread number, one of the numbers
2874 shown in the first field of the @samp{info threads} display; or it
2875 could be a range of thread numbers, as in @code{2-4}. To apply a
2876 command to all threads, type @kbd{thread apply all @var{command}}.
2879 @cindex name a thread
2880 @item thread name [@var{name}]
2881 This command assigns a name to the current thread. If no argument is
2882 given, any existing user-specified name is removed. The thread name
2883 appears in the @samp{info threads} display.
2885 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2886 determine the name of the thread as given by the OS. On these
2887 systems, a name specified with @samp{thread name} will override the
2888 system-give name, and removing the user-specified name will cause
2889 @value{GDBN} to once again display the system-specified name.
2892 @cindex search for a thread
2893 @item thread find [@var{regexp}]
2894 Search for and display thread ids whose name or @var{systag}
2895 matches the supplied regular expression.
2897 As well as being the complement to the @samp{thread name} command,
2898 this command also allows you to identify a thread by its target
2899 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2903 (@value{GDBN}) thread find 26688
2904 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2905 (@value{GDBN}) info thread 4
2907 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2910 @kindex set print thread-events
2911 @cindex print messages on thread start and exit
2912 @item set print thread-events
2913 @itemx set print thread-events on
2914 @itemx set print thread-events off
2915 The @code{set print thread-events} command allows you to enable or
2916 disable printing of messages when @value{GDBN} notices that new threads have
2917 started or that threads have exited. By default, these messages will
2918 be printed if detection of these events is supported by the target.
2919 Note that these messages cannot be disabled on all targets.
2921 @kindex show print thread-events
2922 @item show print thread-events
2923 Show whether messages will be printed when @value{GDBN} detects that threads
2924 have started and exited.
2927 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2928 more information about how @value{GDBN} behaves when you stop and start
2929 programs with multiple threads.
2931 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2932 watchpoints in programs with multiple threads.
2934 @anchor{set libthread-db-search-path}
2936 @kindex set libthread-db-search-path
2937 @cindex search path for @code{libthread_db}
2938 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2939 If this variable is set, @var{path} is a colon-separated list of
2940 directories @value{GDBN} will use to search for @code{libthread_db}.
2941 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2942 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2943 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2946 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2947 @code{libthread_db} library to obtain information about threads in the
2948 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2949 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2950 specific thread debugging library loading is enabled
2951 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2953 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2954 refers to the default system directories that are
2955 normally searched for loading shared libraries. The @samp{$sdir} entry
2956 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2957 (@pxref{libthread_db.so.1 file}).
2959 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2960 refers to the directory from which @code{libpthread}
2961 was loaded in the inferior process.
2963 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2964 @value{GDBN} attempts to initialize it with the current inferior process.
2965 If this initialization fails (which could happen because of a version
2966 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2967 will unload @code{libthread_db}, and continue with the next directory.
2968 If none of @code{libthread_db} libraries initialize successfully,
2969 @value{GDBN} will issue a warning and thread debugging will be disabled.
2971 Setting @code{libthread-db-search-path} is currently implemented
2972 only on some platforms.
2974 @kindex show libthread-db-search-path
2975 @item show libthread-db-search-path
2976 Display current libthread_db search path.
2978 @kindex set debug libthread-db
2979 @kindex show debug libthread-db
2980 @cindex debugging @code{libthread_db}
2981 @item set debug libthread-db
2982 @itemx show debug libthread-db
2983 Turns on or off display of @code{libthread_db}-related events.
2984 Use @code{1} to enable, @code{0} to disable.
2988 @section Debugging Forks
2990 @cindex fork, debugging programs which call
2991 @cindex multiple processes
2992 @cindex processes, multiple
2993 On most systems, @value{GDBN} has no special support for debugging
2994 programs which create additional processes using the @code{fork}
2995 function. When a program forks, @value{GDBN} will continue to debug the
2996 parent process and the child process will run unimpeded. If you have
2997 set a breakpoint in any code which the child then executes, the child
2998 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2999 will cause it to terminate.
3001 However, if you want to debug the child process there is a workaround
3002 which isn't too painful. Put a call to @code{sleep} in the code which
3003 the child process executes after the fork. It may be useful to sleep
3004 only if a certain environment variable is set, or a certain file exists,
3005 so that the delay need not occur when you don't want to run @value{GDBN}
3006 on the child. While the child is sleeping, use the @code{ps} program to
3007 get its process ID. Then tell @value{GDBN} (a new invocation of
3008 @value{GDBN} if you are also debugging the parent process) to attach to
3009 the child process (@pxref{Attach}). From that point on you can debug
3010 the child process just like any other process which you attached to.
3012 On some systems, @value{GDBN} provides support for debugging programs that
3013 create additional processes using the @code{fork} or @code{vfork} functions.
3014 Currently, the only platforms with this feature are HP-UX (11.x and later
3015 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3017 By default, when a program forks, @value{GDBN} will continue to debug
3018 the parent process and the child process will run unimpeded.
3020 If you want to follow the child process instead of the parent process,
3021 use the command @w{@code{set follow-fork-mode}}.
3024 @kindex set follow-fork-mode
3025 @item set follow-fork-mode @var{mode}
3026 Set the debugger response to a program call of @code{fork} or
3027 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3028 process. The @var{mode} argument can be:
3032 The original process is debugged after a fork. The child process runs
3033 unimpeded. This is the default.
3036 The new process is debugged after a fork. The parent process runs
3041 @kindex show follow-fork-mode
3042 @item show follow-fork-mode
3043 Display the current debugger response to a @code{fork} or @code{vfork} call.
3046 @cindex debugging multiple processes
3047 On Linux, if you want to debug both the parent and child processes, use the
3048 command @w{@code{set detach-on-fork}}.
3051 @kindex set detach-on-fork
3052 @item set detach-on-fork @var{mode}
3053 Tells gdb whether to detach one of the processes after a fork, or
3054 retain debugger control over them both.
3058 The child process (or parent process, depending on the value of
3059 @code{follow-fork-mode}) will be detached and allowed to run
3060 independently. This is the default.
3063 Both processes will be held under the control of @value{GDBN}.
3064 One process (child or parent, depending on the value of
3065 @code{follow-fork-mode}) is debugged as usual, while the other
3070 @kindex show detach-on-fork
3071 @item show detach-on-fork
3072 Show whether detach-on-fork mode is on/off.
3075 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3076 will retain control of all forked processes (including nested forks).
3077 You can list the forked processes under the control of @value{GDBN} by
3078 using the @w{@code{info inferiors}} command, and switch from one fork
3079 to another by using the @code{inferior} command (@pxref{Inferiors and
3080 Programs, ,Debugging Multiple Inferiors and Programs}).
3082 To quit debugging one of the forked processes, you can either detach
3083 from it by using the @w{@code{detach inferiors}} command (allowing it
3084 to run independently), or kill it using the @w{@code{kill inferiors}}
3085 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3088 If you ask to debug a child process and a @code{vfork} is followed by an
3089 @code{exec}, @value{GDBN} executes the new target up to the first
3090 breakpoint in the new target. If you have a breakpoint set on
3091 @code{main} in your original program, the breakpoint will also be set on
3092 the child process's @code{main}.
3094 On some systems, when a child process is spawned by @code{vfork}, you
3095 cannot debug the child or parent until an @code{exec} call completes.
3097 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3098 call executes, the new target restarts. To restart the parent
3099 process, use the @code{file} command with the parent executable name
3100 as its argument. By default, after an @code{exec} call executes,
3101 @value{GDBN} discards the symbols of the previous executable image.
3102 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3106 @kindex set follow-exec-mode
3107 @item set follow-exec-mode @var{mode}
3109 Set debugger response to a program call of @code{exec}. An
3110 @code{exec} call replaces the program image of a process.
3112 @code{follow-exec-mode} can be:
3116 @value{GDBN} creates a new inferior and rebinds the process to this
3117 new inferior. The program the process was running before the
3118 @code{exec} call can be restarted afterwards by restarting the
3124 (@value{GDBP}) info inferiors
3126 Id Description Executable
3129 process 12020 is executing new program: prog2
3130 Program exited normally.
3131 (@value{GDBP}) info inferiors
3132 Id Description Executable
3138 @value{GDBN} keeps the process bound to the same inferior. The new
3139 executable image replaces the previous executable loaded in the
3140 inferior. Restarting the inferior after the @code{exec} call, with
3141 e.g., the @code{run} command, restarts the executable the process was
3142 running after the @code{exec} call. This is the default mode.
3147 (@value{GDBP}) info inferiors
3148 Id Description Executable
3151 process 12020 is executing new program: prog2
3152 Program exited normally.
3153 (@value{GDBP}) info inferiors
3154 Id Description Executable
3161 You can use the @code{catch} command to make @value{GDBN} stop whenever
3162 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3163 Catchpoints, ,Setting Catchpoints}.
3165 @node Checkpoint/Restart
3166 @section Setting a @emph{Bookmark} to Return to Later
3171 @cindex snapshot of a process
3172 @cindex rewind program state
3174 On certain operating systems@footnote{Currently, only
3175 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3176 program's state, called a @dfn{checkpoint}, and come back to it
3179 Returning to a checkpoint effectively undoes everything that has
3180 happened in the program since the @code{checkpoint} was saved. This
3181 includes changes in memory, registers, and even (within some limits)
3182 system state. Effectively, it is like going back in time to the
3183 moment when the checkpoint was saved.
3185 Thus, if you're stepping thru a program and you think you're
3186 getting close to the point where things go wrong, you can save
3187 a checkpoint. Then, if you accidentally go too far and miss
3188 the critical statement, instead of having to restart your program
3189 from the beginning, you can just go back to the checkpoint and
3190 start again from there.
3192 This can be especially useful if it takes a lot of time or
3193 steps to reach the point where you think the bug occurs.
3195 To use the @code{checkpoint}/@code{restart} method of debugging:
3200 Save a snapshot of the debugged program's current execution state.
3201 The @code{checkpoint} command takes no arguments, but each checkpoint
3202 is assigned a small integer id, similar to a breakpoint id.
3204 @kindex info checkpoints
3205 @item info checkpoints
3206 List the checkpoints that have been saved in the current debugging
3207 session. For each checkpoint, the following information will be
3214 @item Source line, or label
3217 @kindex restart @var{checkpoint-id}
3218 @item restart @var{checkpoint-id}
3219 Restore the program state that was saved as checkpoint number
3220 @var{checkpoint-id}. All program variables, registers, stack frames
3221 etc.@: will be returned to the values that they had when the checkpoint
3222 was saved. In essence, gdb will ``wind back the clock'' to the point
3223 in time when the checkpoint was saved.
3225 Note that breakpoints, @value{GDBN} variables, command history etc.
3226 are not affected by restoring a checkpoint. In general, a checkpoint
3227 only restores things that reside in the program being debugged, not in
3230 @kindex delete checkpoint @var{checkpoint-id}
3231 @item delete checkpoint @var{checkpoint-id}
3232 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3236 Returning to a previously saved checkpoint will restore the user state
3237 of the program being debugged, plus a significant subset of the system
3238 (OS) state, including file pointers. It won't ``un-write'' data from
3239 a file, but it will rewind the file pointer to the previous location,
3240 so that the previously written data can be overwritten. For files
3241 opened in read mode, the pointer will also be restored so that the
3242 previously read data can be read again.
3244 Of course, characters that have been sent to a printer (or other
3245 external device) cannot be ``snatched back'', and characters received
3246 from eg.@: a serial device can be removed from internal program buffers,
3247 but they cannot be ``pushed back'' into the serial pipeline, ready to
3248 be received again. Similarly, the actual contents of files that have
3249 been changed cannot be restored (at this time).
3251 However, within those constraints, you actually can ``rewind'' your
3252 program to a previously saved point in time, and begin debugging it
3253 again --- and you can change the course of events so as to debug a
3254 different execution path this time.
3256 @cindex checkpoints and process id
3257 Finally, there is one bit of internal program state that will be
3258 different when you return to a checkpoint --- the program's process
3259 id. Each checkpoint will have a unique process id (or @var{pid}),
3260 and each will be different from the program's original @var{pid}.
3261 If your program has saved a local copy of its process id, this could
3262 potentially pose a problem.
3264 @subsection A Non-obvious Benefit of Using Checkpoints
3266 On some systems such as @sc{gnu}/Linux, address space randomization
3267 is performed on new processes for security reasons. This makes it
3268 difficult or impossible to set a breakpoint, or watchpoint, on an
3269 absolute address if you have to restart the program, since the
3270 absolute location of a symbol will change from one execution to the
3273 A checkpoint, however, is an @emph{identical} copy of a process.
3274 Therefore if you create a checkpoint at (eg.@:) the start of main,
3275 and simply return to that checkpoint instead of restarting the
3276 process, you can avoid the effects of address randomization and
3277 your symbols will all stay in the same place.
3280 @chapter Stopping and Continuing
3282 The principal purposes of using a debugger are so that you can stop your
3283 program before it terminates; or so that, if your program runs into
3284 trouble, you can investigate and find out why.
3286 Inside @value{GDBN}, your program may stop for any of several reasons,
3287 such as a signal, a breakpoint, or reaching a new line after a
3288 @value{GDBN} command such as @code{step}. You may then examine and
3289 change variables, set new breakpoints or remove old ones, and then
3290 continue execution. Usually, the messages shown by @value{GDBN} provide
3291 ample explanation of the status of your program---but you can also
3292 explicitly request this information at any time.
3295 @kindex info program
3297 Display information about the status of your program: whether it is
3298 running or not, what process it is, and why it stopped.
3302 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3303 * Continuing and Stepping:: Resuming execution
3304 * Skipping Over Functions and Files::
3305 Skipping over functions and files
3307 * Thread Stops:: Stopping and starting multi-thread programs
3311 @section Breakpoints, Watchpoints, and Catchpoints
3314 A @dfn{breakpoint} makes your program stop whenever a certain point in
3315 the program is reached. For each breakpoint, you can add conditions to
3316 control in finer detail whether your program stops. You can set
3317 breakpoints with the @code{break} command and its variants (@pxref{Set
3318 Breaks, ,Setting Breakpoints}), to specify the place where your program
3319 should stop by line number, function name or exact address in the
3322 On some systems, you can set breakpoints in shared libraries before
3323 the executable is run. There is a minor limitation on HP-UX systems:
3324 you must wait until the executable is run in order to set breakpoints
3325 in shared library routines that are not called directly by the program
3326 (for example, routines that are arguments in a @code{pthread_create}
3330 @cindex data breakpoints
3331 @cindex memory tracing
3332 @cindex breakpoint on memory address
3333 @cindex breakpoint on variable modification
3334 A @dfn{watchpoint} is a special breakpoint that stops your program
3335 when the value of an expression changes. The expression may be a value
3336 of a variable, or it could involve values of one or more variables
3337 combined by operators, such as @samp{a + b}. This is sometimes called
3338 @dfn{data breakpoints}. You must use a different command to set
3339 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3340 from that, you can manage a watchpoint like any other breakpoint: you
3341 enable, disable, and delete both breakpoints and watchpoints using the
3344 You can arrange to have values from your program displayed automatically
3345 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3349 @cindex breakpoint on events
3350 A @dfn{catchpoint} is another special breakpoint that stops your program
3351 when a certain kind of event occurs, such as the throwing of a C@t{++}
3352 exception or the loading of a library. As with watchpoints, you use a
3353 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3354 Catchpoints}), but aside from that, you can manage a catchpoint like any
3355 other breakpoint. (To stop when your program receives a signal, use the
3356 @code{handle} command; see @ref{Signals, ,Signals}.)
3358 @cindex breakpoint numbers
3359 @cindex numbers for breakpoints
3360 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3361 catchpoint when you create it; these numbers are successive integers
3362 starting with one. In many of the commands for controlling various
3363 features of breakpoints you use the breakpoint number to say which
3364 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3365 @dfn{disabled}; if disabled, it has no effect on your program until you
3368 @cindex breakpoint ranges
3369 @cindex ranges of breakpoints
3370 Some @value{GDBN} commands accept a range of breakpoints on which to
3371 operate. A breakpoint range is either a single breakpoint number, like
3372 @samp{5}, or two such numbers, in increasing order, separated by a
3373 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3374 all breakpoints in that range are operated on.
3377 * Set Breaks:: Setting breakpoints
3378 * Set Watchpoints:: Setting watchpoints
3379 * Set Catchpoints:: Setting catchpoints
3380 * Delete Breaks:: Deleting breakpoints
3381 * Disabling:: Disabling breakpoints
3382 * Conditions:: Break conditions
3383 * Break Commands:: Breakpoint command lists
3384 * Dynamic Printf:: Dynamic printf
3385 * Save Breakpoints:: How to save breakpoints in a file
3386 * Static Probe Points:: Listing static probe points
3387 * Error in Breakpoints:: ``Cannot insert breakpoints''
3388 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3392 @subsection Setting Breakpoints
3394 @c FIXME LMB what does GDB do if no code on line of breakpt?
3395 @c consider in particular declaration with/without initialization.
3397 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3400 @kindex b @r{(@code{break})}
3401 @vindex $bpnum@r{, convenience variable}
3402 @cindex latest breakpoint
3403 Breakpoints are set with the @code{break} command (abbreviated
3404 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3405 number of the breakpoint you've set most recently; see @ref{Convenience
3406 Vars,, Convenience Variables}, for a discussion of what you can do with
3407 convenience variables.
3410 @item break @var{location}
3411 Set a breakpoint at the given @var{location}, which can specify a
3412 function name, a line number, or an address of an instruction.
3413 (@xref{Specify Location}, for a list of all the possible ways to
3414 specify a @var{location}.) The breakpoint will stop your program just
3415 before it executes any of the code in the specified @var{location}.
3417 When using source languages that permit overloading of symbols, such as
3418 C@t{++}, a function name may refer to more than one possible place to break.
3419 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3422 It is also possible to insert a breakpoint that will stop the program
3423 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3424 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3427 When called without any arguments, @code{break} sets a breakpoint at
3428 the next instruction to be executed in the selected stack frame
3429 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3430 innermost, this makes your program stop as soon as control
3431 returns to that frame. This is similar to the effect of a
3432 @code{finish} command in the frame inside the selected frame---except
3433 that @code{finish} does not leave an active breakpoint. If you use
3434 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3435 the next time it reaches the current location; this may be useful
3438 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3439 least one instruction has been executed. If it did not do this, you
3440 would be unable to proceed past a breakpoint without first disabling the
3441 breakpoint. This rule applies whether or not the breakpoint already
3442 existed when your program stopped.
3444 @item break @dots{} if @var{cond}
3445 Set a breakpoint with condition @var{cond}; evaluate the expression
3446 @var{cond} each time the breakpoint is reached, and stop only if the
3447 value is nonzero---that is, if @var{cond} evaluates as true.
3448 @samp{@dots{}} stands for one of the possible arguments described
3449 above (or no argument) specifying where to break. @xref{Conditions,
3450 ,Break Conditions}, for more information on breakpoint conditions.
3453 @item tbreak @var{args}
3454 Set a breakpoint enabled only for one stop. @var{args} are the
3455 same as for the @code{break} command, and the breakpoint is set in the same
3456 way, but the breakpoint is automatically deleted after the first time your
3457 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3460 @cindex hardware breakpoints
3461 @item hbreak @var{args}
3462 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3463 @code{break} command and the breakpoint is set in the same way, but the
3464 breakpoint requires hardware support and some target hardware may not
3465 have this support. The main purpose of this is EPROM/ROM code
3466 debugging, so you can set a breakpoint at an instruction without
3467 changing the instruction. This can be used with the new trap-generation
3468 provided by SPARClite DSU and most x86-based targets. These targets
3469 will generate traps when a program accesses some data or instruction
3470 address that is assigned to the debug registers. However the hardware
3471 breakpoint registers can take a limited number of breakpoints. For
3472 example, on the DSU, only two data breakpoints can be set at a time, and
3473 @value{GDBN} will reject this command if more than two are used. Delete
3474 or disable unused hardware breakpoints before setting new ones
3475 (@pxref{Disabling, ,Disabling Breakpoints}).
3476 @xref{Conditions, ,Break Conditions}.
3477 For remote targets, you can restrict the number of hardware
3478 breakpoints @value{GDBN} will use, see @ref{set remote
3479 hardware-breakpoint-limit}.
3482 @item thbreak @var{args}
3483 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3484 are the same as for the @code{hbreak} command and the breakpoint is set in
3485 the same way. However, like the @code{tbreak} command,
3486 the breakpoint is automatically deleted after the
3487 first time your program stops there. Also, like the @code{hbreak}
3488 command, the breakpoint requires hardware support and some target hardware
3489 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3490 See also @ref{Conditions, ,Break Conditions}.
3493 @cindex regular expression
3494 @cindex breakpoints at functions matching a regexp
3495 @cindex set breakpoints in many functions
3496 @item rbreak @var{regex}
3497 Set breakpoints on all functions matching the regular expression
3498 @var{regex}. This command sets an unconditional breakpoint on all
3499 matches, printing a list of all breakpoints it set. Once these
3500 breakpoints are set, they are treated just like the breakpoints set with
3501 the @code{break} command. You can delete them, disable them, or make
3502 them conditional the same way as any other breakpoint.
3504 The syntax of the regular expression is the standard one used with tools
3505 like @file{grep}. Note that this is different from the syntax used by
3506 shells, so for instance @code{foo*} matches all functions that include
3507 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3508 @code{.*} leading and trailing the regular expression you supply, so to
3509 match only functions that begin with @code{foo}, use @code{^foo}.
3511 @cindex non-member C@t{++} functions, set breakpoint in
3512 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3513 breakpoints on overloaded functions that are not members of any special
3516 @cindex set breakpoints on all functions
3517 The @code{rbreak} command can be used to set breakpoints in
3518 @strong{all} the functions in a program, like this:
3521 (@value{GDBP}) rbreak .
3524 @item rbreak @var{file}:@var{regex}
3525 If @code{rbreak} is called with a filename qualification, it limits
3526 the search for functions matching the given regular expression to the
3527 specified @var{file}. This can be used, for example, to set breakpoints on
3528 every function in a given file:
3531 (@value{GDBP}) rbreak file.c:.
3534 The colon separating the filename qualifier from the regex may
3535 optionally be surrounded by spaces.
3537 @kindex info breakpoints
3538 @cindex @code{$_} and @code{info breakpoints}
3539 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3540 @itemx info break @r{[}@var{n}@dots{}@r{]}
3541 Print a table of all breakpoints, watchpoints, and catchpoints set and
3542 not deleted. Optional argument @var{n} means print information only
3543 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3544 For each breakpoint, following columns are printed:
3547 @item Breakpoint Numbers
3549 Breakpoint, watchpoint, or catchpoint.
3551 Whether the breakpoint is marked to be disabled or deleted when hit.
3552 @item Enabled or Disabled
3553 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3554 that are not enabled.
3556 Where the breakpoint is in your program, as a memory address. For a
3557 pending breakpoint whose address is not yet known, this field will
3558 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3559 library that has the symbol or line referred by breakpoint is loaded.
3560 See below for details. A breakpoint with several locations will
3561 have @samp{<MULTIPLE>} in this field---see below for details.
3563 Where the breakpoint is in the source for your program, as a file and
3564 line number. For a pending breakpoint, the original string passed to
3565 the breakpoint command will be listed as it cannot be resolved until
3566 the appropriate shared library is loaded in the future.
3570 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3571 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3572 @value{GDBN} on the host's side. If it is ``target'', then the condition
3573 is evaluated by the target. The @code{info break} command shows
3574 the condition on the line following the affected breakpoint, together with
3575 its condition evaluation mode in between parentheses.
3577 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3578 allowed to have a condition specified for it. The condition is not parsed for
3579 validity until a shared library is loaded that allows the pending
3580 breakpoint to resolve to a valid location.
3583 @code{info break} with a breakpoint
3584 number @var{n} as argument lists only that breakpoint. The
3585 convenience variable @code{$_} and the default examining-address for
3586 the @code{x} command are set to the address of the last breakpoint
3587 listed (@pxref{Memory, ,Examining Memory}).
3590 @code{info break} displays a count of the number of times the breakpoint
3591 has been hit. This is especially useful in conjunction with the
3592 @code{ignore} command. You can ignore a large number of breakpoint
3593 hits, look at the breakpoint info to see how many times the breakpoint
3594 was hit, and then run again, ignoring one less than that number. This
3595 will get you quickly to the last hit of that breakpoint.
3598 For a breakpoints with an enable count (xref) greater than 1,
3599 @code{info break} also displays that count.
3603 @value{GDBN} allows you to set any number of breakpoints at the same place in
3604 your program. There is nothing silly or meaningless about this. When
3605 the breakpoints are conditional, this is even useful
3606 (@pxref{Conditions, ,Break Conditions}).
3608 @cindex multiple locations, breakpoints
3609 @cindex breakpoints, multiple locations
3610 It is possible that a breakpoint corresponds to several locations
3611 in your program. Examples of this situation are:
3615 Multiple functions in the program may have the same name.
3618 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3619 instances of the function body, used in different cases.
3622 For a C@t{++} template function, a given line in the function can
3623 correspond to any number of instantiations.
3626 For an inlined function, a given source line can correspond to
3627 several places where that function is inlined.
3630 In all those cases, @value{GDBN} will insert a breakpoint at all
3631 the relevant locations.
3633 A breakpoint with multiple locations is displayed in the breakpoint
3634 table using several rows---one header row, followed by one row for
3635 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3636 address column. The rows for individual locations contain the actual
3637 addresses for locations, and show the functions to which those
3638 locations belong. The number column for a location is of the form
3639 @var{breakpoint-number}.@var{location-number}.
3644 Num Type Disp Enb Address What
3645 1 breakpoint keep y <MULTIPLE>
3647 breakpoint already hit 1 time
3648 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3649 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3652 Each location can be individually enabled or disabled by passing
3653 @var{breakpoint-number}.@var{location-number} as argument to the
3654 @code{enable} and @code{disable} commands. Note that you cannot
3655 delete the individual locations from the list, you can only delete the
3656 entire list of locations that belong to their parent breakpoint (with
3657 the @kbd{delete @var{num}} command, where @var{num} is the number of
3658 the parent breakpoint, 1 in the above example). Disabling or enabling
3659 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3660 that belong to that breakpoint.
3662 @cindex pending breakpoints
3663 It's quite common to have a breakpoint inside a shared library.
3664 Shared libraries can be loaded and unloaded explicitly,
3665 and possibly repeatedly, as the program is executed. To support
3666 this use case, @value{GDBN} updates breakpoint locations whenever
3667 any shared library is loaded or unloaded. Typically, you would
3668 set a breakpoint in a shared library at the beginning of your
3669 debugging session, when the library is not loaded, and when the
3670 symbols from the library are not available. When you try to set
3671 breakpoint, @value{GDBN} will ask you if you want to set
3672 a so called @dfn{pending breakpoint}---breakpoint whose address
3673 is not yet resolved.
3675 After the program is run, whenever a new shared library is loaded,
3676 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3677 shared library contains the symbol or line referred to by some
3678 pending breakpoint, that breakpoint is resolved and becomes an
3679 ordinary breakpoint. When a library is unloaded, all breakpoints
3680 that refer to its symbols or source lines become pending again.
3682 This logic works for breakpoints with multiple locations, too. For
3683 example, if you have a breakpoint in a C@t{++} template function, and
3684 a newly loaded shared library has an instantiation of that template,
3685 a new location is added to the list of locations for the breakpoint.
3687 Except for having unresolved address, pending breakpoints do not
3688 differ from regular breakpoints. You can set conditions or commands,
3689 enable and disable them and perform other breakpoint operations.
3691 @value{GDBN} provides some additional commands for controlling what
3692 happens when the @samp{break} command cannot resolve breakpoint
3693 address specification to an address:
3695 @kindex set breakpoint pending
3696 @kindex show breakpoint pending
3698 @item set breakpoint pending auto
3699 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3700 location, it queries you whether a pending breakpoint should be created.
3702 @item set breakpoint pending on
3703 This indicates that an unrecognized breakpoint location should automatically
3704 result in a pending breakpoint being created.
3706 @item set breakpoint pending off
3707 This indicates that pending breakpoints are not to be created. Any
3708 unrecognized breakpoint location results in an error. This setting does
3709 not affect any pending breakpoints previously created.
3711 @item show breakpoint pending
3712 Show the current behavior setting for creating pending breakpoints.
3715 The settings above only affect the @code{break} command and its
3716 variants. Once breakpoint is set, it will be automatically updated
3717 as shared libraries are loaded and unloaded.
3719 @cindex automatic hardware breakpoints
3720 For some targets, @value{GDBN} can automatically decide if hardware or
3721 software breakpoints should be used, depending on whether the
3722 breakpoint address is read-only or read-write. This applies to
3723 breakpoints set with the @code{break} command as well as to internal
3724 breakpoints set by commands like @code{next} and @code{finish}. For
3725 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3728 You can control this automatic behaviour with the following commands::
3730 @kindex set breakpoint auto-hw
3731 @kindex show breakpoint auto-hw
3733 @item set breakpoint auto-hw on
3734 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3735 will try to use the target memory map to decide if software or hardware
3736 breakpoint must be used.
3738 @item set breakpoint auto-hw off
3739 This indicates @value{GDBN} should not automatically select breakpoint
3740 type. If the target provides a memory map, @value{GDBN} will warn when
3741 trying to set software breakpoint at a read-only address.
3744 @value{GDBN} normally implements breakpoints by replacing the program code
3745 at the breakpoint address with a special instruction, which, when
3746 executed, given control to the debugger. By default, the program
3747 code is so modified only when the program is resumed. As soon as
3748 the program stops, @value{GDBN} restores the original instructions. This
3749 behaviour guards against leaving breakpoints inserted in the
3750 target should gdb abrubptly disconnect. However, with slow remote
3751 targets, inserting and removing breakpoint can reduce the performance.
3752 This behavior can be controlled with the following commands::
3754 @kindex set breakpoint always-inserted
3755 @kindex show breakpoint always-inserted
3757 @item set breakpoint always-inserted off
3758 All breakpoints, including newly added by the user, are inserted in
3759 the target only when the target is resumed. All breakpoints are
3760 removed from the target when it stops.
3762 @item set breakpoint always-inserted on
3763 Causes all breakpoints to be inserted in the target at all times. If
3764 the user adds a new breakpoint, or changes an existing breakpoint, the
3765 breakpoints in the target are updated immediately. A breakpoint is
3766 removed from the target only when breakpoint itself is removed.
3768 @cindex non-stop mode, and @code{breakpoint always-inserted}
3769 @item set breakpoint always-inserted auto
3770 This is the default mode. If @value{GDBN} is controlling the inferior
3771 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3772 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3773 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3774 @code{breakpoint always-inserted} mode is off.
3777 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3778 when a breakpoint breaks. If the condition is true, then the process being
3779 debugged stops, otherwise the process is resumed.
3781 If the target supports evaluating conditions on its end, @value{GDBN} may
3782 download the breakpoint, together with its conditions, to it.
3784 This feature can be controlled via the following commands:
3786 @kindex set breakpoint condition-evaluation
3787 @kindex show breakpoint condition-evaluation
3789 @item set breakpoint condition-evaluation host
3790 This option commands @value{GDBN} to evaluate the breakpoint
3791 conditions on the host's side. Unconditional breakpoints are sent to
3792 the target which in turn receives the triggers and reports them back to GDB
3793 for condition evaluation. This is the standard evaluation mode.
3795 @item set breakpoint condition-evaluation target
3796 This option commands @value{GDBN} to download breakpoint conditions
3797 to the target at the moment of their insertion. The target
3798 is responsible for evaluating the conditional expression and reporting
3799 breakpoint stop events back to @value{GDBN} whenever the condition
3800 is true. Due to limitations of target-side evaluation, some conditions
3801 cannot be evaluated there, e.g., conditions that depend on local data
3802 that is only known to the host. Examples include
3803 conditional expressions involving convenience variables, complex types
3804 that cannot be handled by the agent expression parser and expressions
3805 that are too long to be sent over to the target, specially when the
3806 target is a remote system. In these cases, the conditions will be
3807 evaluated by @value{GDBN}.
3809 @item set breakpoint condition-evaluation auto
3810 This is the default mode. If the target supports evaluating breakpoint
3811 conditions on its end, @value{GDBN} will download breakpoint conditions to
3812 the target (limitations mentioned previously apply). If the target does
3813 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3814 to evaluating all these conditions on the host's side.
3818 @cindex negative breakpoint numbers
3819 @cindex internal @value{GDBN} breakpoints
3820 @value{GDBN} itself sometimes sets breakpoints in your program for
3821 special purposes, such as proper handling of @code{longjmp} (in C
3822 programs). These internal breakpoints are assigned negative numbers,
3823 starting with @code{-1}; @samp{info breakpoints} does not display them.
3824 You can see these breakpoints with the @value{GDBN} maintenance command
3825 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3828 @node Set Watchpoints
3829 @subsection Setting Watchpoints
3831 @cindex setting watchpoints
3832 You can use a watchpoint to stop execution whenever the value of an
3833 expression changes, without having to predict a particular place where
3834 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3835 The expression may be as simple as the value of a single variable, or
3836 as complex as many variables combined by operators. Examples include:
3840 A reference to the value of a single variable.
3843 An address cast to an appropriate data type. For example,
3844 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3845 address (assuming an @code{int} occupies 4 bytes).
3848 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3849 expression can use any operators valid in the program's native
3850 language (@pxref{Languages}).
3853 You can set a watchpoint on an expression even if the expression can
3854 not be evaluated yet. For instance, you can set a watchpoint on
3855 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3856 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3857 the expression produces a valid value. If the expression becomes
3858 valid in some other way than changing a variable (e.g.@: if the memory
3859 pointed to by @samp{*global_ptr} becomes readable as the result of a
3860 @code{malloc} call), @value{GDBN} may not stop until the next time
3861 the expression changes.
3863 @cindex software watchpoints
3864 @cindex hardware watchpoints
3865 Depending on your system, watchpoints may be implemented in software or
3866 hardware. @value{GDBN} does software watchpointing by single-stepping your
3867 program and testing the variable's value each time, which is hundreds of
3868 times slower than normal execution. (But this may still be worth it, to
3869 catch errors where you have no clue what part of your program is the
3872 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3873 x86-based targets, @value{GDBN} includes support for hardware
3874 watchpoints, which do not slow down the running of your program.
3878 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3879 Set a watchpoint for an expression. @value{GDBN} will break when the
3880 expression @var{expr} is written into by the program and its value
3881 changes. The simplest (and the most popular) use of this command is
3882 to watch the value of a single variable:
3885 (@value{GDBP}) watch foo
3888 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3889 argument, @value{GDBN} breaks only when the thread identified by
3890 @var{threadnum} changes the value of @var{expr}. If any other threads
3891 change the value of @var{expr}, @value{GDBN} will not break. Note
3892 that watchpoints restricted to a single thread in this way only work
3893 with Hardware Watchpoints.
3895 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3896 (see below). The @code{-location} argument tells @value{GDBN} to
3897 instead watch the memory referred to by @var{expr}. In this case,
3898 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3899 and watch the memory at that address. The type of the result is used
3900 to determine the size of the watched memory. If the expression's
3901 result does not have an address, then @value{GDBN} will print an
3904 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3905 of masked watchpoints, if the current architecture supports this
3906 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3907 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3908 to an address to watch. The mask specifies that some bits of an address
3909 (the bits which are reset in the mask) should be ignored when matching
3910 the address accessed by the inferior against the watchpoint address.
3911 Thus, a masked watchpoint watches many addresses simultaneously---those
3912 addresses whose unmasked bits are identical to the unmasked bits in the
3913 watchpoint address. The @code{mask} argument implies @code{-location}.
3917 (@value{GDBP}) watch foo mask 0xffff00ff
3918 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3922 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3923 Set a watchpoint that will break when the value of @var{expr} is read
3927 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3928 Set a watchpoint that will break when @var{expr} is either read from
3929 or written into by the program.
3931 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3932 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3933 This command prints a list of watchpoints, using the same format as
3934 @code{info break} (@pxref{Set Breaks}).
3937 If you watch for a change in a numerically entered address you need to
3938 dereference it, as the address itself is just a constant number which will
3939 never change. @value{GDBN} refuses to create a watchpoint that watches
3940 a never-changing value:
3943 (@value{GDBP}) watch 0x600850
3944 Cannot watch constant value 0x600850.
3945 (@value{GDBP}) watch *(int *) 0x600850
3946 Watchpoint 1: *(int *) 6293584
3949 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3950 watchpoints execute very quickly, and the debugger reports a change in
3951 value at the exact instruction where the change occurs. If @value{GDBN}
3952 cannot set a hardware watchpoint, it sets a software watchpoint, which
3953 executes more slowly and reports the change in value at the next
3954 @emph{statement}, not the instruction, after the change occurs.
3956 @cindex use only software watchpoints
3957 You can force @value{GDBN} to use only software watchpoints with the
3958 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3959 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3960 the underlying system supports them. (Note that hardware-assisted
3961 watchpoints that were set @emph{before} setting
3962 @code{can-use-hw-watchpoints} to zero will still use the hardware
3963 mechanism of watching expression values.)
3966 @item set can-use-hw-watchpoints
3967 @kindex set can-use-hw-watchpoints
3968 Set whether or not to use hardware watchpoints.
3970 @item show can-use-hw-watchpoints
3971 @kindex show can-use-hw-watchpoints
3972 Show the current mode of using hardware watchpoints.
3975 For remote targets, you can restrict the number of hardware
3976 watchpoints @value{GDBN} will use, see @ref{set remote
3977 hardware-breakpoint-limit}.
3979 When you issue the @code{watch} command, @value{GDBN} reports
3982 Hardware watchpoint @var{num}: @var{expr}
3986 if it was able to set a hardware watchpoint.
3988 Currently, the @code{awatch} and @code{rwatch} commands can only set
3989 hardware watchpoints, because accesses to data that don't change the
3990 value of the watched expression cannot be detected without examining
3991 every instruction as it is being executed, and @value{GDBN} does not do
3992 that currently. If @value{GDBN} finds that it is unable to set a
3993 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3994 will print a message like this:
3997 Expression cannot be implemented with read/access watchpoint.
4000 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4001 data type of the watched expression is wider than what a hardware
4002 watchpoint on the target machine can handle. For example, some systems
4003 can only watch regions that are up to 4 bytes wide; on such systems you
4004 cannot set hardware watchpoints for an expression that yields a
4005 double-precision floating-point number (which is typically 8 bytes
4006 wide). As a work-around, it might be possible to break the large region
4007 into a series of smaller ones and watch them with separate watchpoints.
4009 If you set too many hardware watchpoints, @value{GDBN} might be unable
4010 to insert all of them when you resume the execution of your program.
4011 Since the precise number of active watchpoints is unknown until such
4012 time as the program is about to be resumed, @value{GDBN} might not be
4013 able to warn you about this when you set the watchpoints, and the
4014 warning will be printed only when the program is resumed:
4017 Hardware watchpoint @var{num}: Could not insert watchpoint
4021 If this happens, delete or disable some of the watchpoints.
4023 Watching complex expressions that reference many variables can also
4024 exhaust the resources available for hardware-assisted watchpoints.
4025 That's because @value{GDBN} needs to watch every variable in the
4026 expression with separately allocated resources.
4028 If you call a function interactively using @code{print} or @code{call},
4029 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4030 kind of breakpoint or the call completes.
4032 @value{GDBN} automatically deletes watchpoints that watch local
4033 (automatic) variables, or expressions that involve such variables, when
4034 they go out of scope, that is, when the execution leaves the block in
4035 which these variables were defined. In particular, when the program
4036 being debugged terminates, @emph{all} local variables go out of scope,
4037 and so only watchpoints that watch global variables remain set. If you
4038 rerun the program, you will need to set all such watchpoints again. One
4039 way of doing that would be to set a code breakpoint at the entry to the
4040 @code{main} function and when it breaks, set all the watchpoints.
4042 @cindex watchpoints and threads
4043 @cindex threads and watchpoints
4044 In multi-threaded programs, watchpoints will detect changes to the
4045 watched expression from every thread.
4048 @emph{Warning:} In multi-threaded programs, software watchpoints
4049 have only limited usefulness. If @value{GDBN} creates a software
4050 watchpoint, it can only watch the value of an expression @emph{in a
4051 single thread}. If you are confident that the expression can only
4052 change due to the current thread's activity (and if you are also
4053 confident that no other thread can become current), then you can use
4054 software watchpoints as usual. However, @value{GDBN} may not notice
4055 when a non-current thread's activity changes the expression. (Hardware
4056 watchpoints, in contrast, watch an expression in all threads.)
4059 @xref{set remote hardware-watchpoint-limit}.
4061 @node Set Catchpoints
4062 @subsection Setting Catchpoints
4063 @cindex catchpoints, setting
4064 @cindex exception handlers
4065 @cindex event handling
4067 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4068 kinds of program events, such as C@t{++} exceptions or the loading of a
4069 shared library. Use the @code{catch} command to set a catchpoint.
4073 @item catch @var{event}
4074 Stop when @var{event} occurs. @var{event} can be any of the following:
4077 @item throw @r{[}@var{regexp}@r{]}
4078 @itemx rethrow @r{[}@var{regexp}@r{]}
4079 @itemx catch @r{[}@var{regexp}@r{]}
4080 @cindex stop on C@t{++} exceptions
4081 The throwing, re-throwing, or catching of a C@t{++} exception.
4083 If @var{regexp} is given, then only exceptions whose type matches the
4084 regular expression will be caught.
4086 @vindex $_exception@r{, convenience variable}
4087 The convenience variable @code{$_exception} is available at an
4088 exception-related catchpoint, on some systems. This holds the
4089 exception being thrown.
4091 There are currently some limitations to C@t{++} exception handling in
4096 The support for these commands is system-dependent. Currently, only
4097 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4101 The regular expression feature and the @code{$_exception} convenience
4102 variable rely on the presence of some SDT probes in @code{libstdc++}.
4103 If these probes are not present, then these features cannot be used.
4106 The @code{$_exception} convenience variable is only valid at the
4107 instruction at which an exception-related catchpoint is set.
4110 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4111 location in the system library which implements runtime exception
4112 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4113 (@pxref{Selection}) to get to your code.
4116 If you call a function interactively, @value{GDBN} normally returns
4117 control to you when the function has finished executing. If the call
4118 raises an exception, however, the call may bypass the mechanism that
4119 returns control to you and cause your program either to abort or to
4120 simply continue running until it hits a breakpoint, catches a signal
4121 that @value{GDBN} is listening for, or exits. This is the case even if
4122 you set a catchpoint for the exception; catchpoints on exceptions are
4123 disabled within interactive calls. @xref{Calling}, for information on
4124 controlling this with @code{set unwind-on-terminating-exception}.
4127 You cannot raise an exception interactively.
4130 You cannot install an exception handler interactively.
4134 @cindex Ada exception catching
4135 @cindex catch Ada exceptions
4136 An Ada exception being raised. If an exception name is specified
4137 at the end of the command (eg @code{catch exception Program_Error}),
4138 the debugger will stop only when this specific exception is raised.
4139 Otherwise, the debugger stops execution when any Ada exception is raised.
4141 When inserting an exception catchpoint on a user-defined exception whose
4142 name is identical to one of the exceptions defined by the language, the
4143 fully qualified name must be used as the exception name. Otherwise,
4144 @value{GDBN} will assume that it should stop on the pre-defined exception
4145 rather than the user-defined one. For instance, assuming an exception
4146 called @code{Constraint_Error} is defined in package @code{Pck}, then
4147 the command to use to catch such exceptions is @kbd{catch exception
4148 Pck.Constraint_Error}.
4150 @item exception unhandled
4151 An exception that was raised but is not handled by the program.
4154 A failed Ada assertion.
4157 @cindex break on fork/exec
4158 A call to @code{exec}. This is currently only available for HP-UX
4162 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4163 @cindex break on a system call.
4164 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4165 syscall is a mechanism for application programs to request a service
4166 from the operating system (OS) or one of the OS system services.
4167 @value{GDBN} can catch some or all of the syscalls issued by the
4168 debuggee, and show the related information for each syscall. If no
4169 argument is specified, calls to and returns from all system calls
4172 @var{name} can be any system call name that is valid for the
4173 underlying OS. Just what syscalls are valid depends on the OS. On
4174 GNU and Unix systems, you can find the full list of valid syscall
4175 names on @file{/usr/include/asm/unistd.h}.
4177 @c For MS-Windows, the syscall names and the corresponding numbers
4178 @c can be found, e.g., on this URL:
4179 @c http://www.metasploit.com/users/opcode/syscalls.html
4180 @c but we don't support Windows syscalls yet.
4182 Normally, @value{GDBN} knows in advance which syscalls are valid for
4183 each OS, so you can use the @value{GDBN} command-line completion
4184 facilities (@pxref{Completion,, command completion}) to list the
4187 You may also specify the system call numerically. A syscall's
4188 number is the value passed to the OS's syscall dispatcher to
4189 identify the requested service. When you specify the syscall by its
4190 name, @value{GDBN} uses its database of syscalls to convert the name
4191 into the corresponding numeric code, but using the number directly
4192 may be useful if @value{GDBN}'s database does not have the complete
4193 list of syscalls on your system (e.g., because @value{GDBN} lags
4194 behind the OS upgrades).
4196 The example below illustrates how this command works if you don't provide
4200 (@value{GDBP}) catch syscall
4201 Catchpoint 1 (syscall)
4203 Starting program: /tmp/catch-syscall
4205 Catchpoint 1 (call to syscall 'close'), \
4206 0xffffe424 in __kernel_vsyscall ()
4210 Catchpoint 1 (returned from syscall 'close'), \
4211 0xffffe424 in __kernel_vsyscall ()
4215 Here is an example of catching a system call by name:
4218 (@value{GDBP}) catch syscall chroot
4219 Catchpoint 1 (syscall 'chroot' [61])
4221 Starting program: /tmp/catch-syscall
4223 Catchpoint 1 (call to syscall 'chroot'), \
4224 0xffffe424 in __kernel_vsyscall ()
4228 Catchpoint 1 (returned from syscall 'chroot'), \
4229 0xffffe424 in __kernel_vsyscall ()
4233 An example of specifying a system call numerically. In the case
4234 below, the syscall number has a corresponding entry in the XML
4235 file, so @value{GDBN} finds its name and prints it:
4238 (@value{GDBP}) catch syscall 252
4239 Catchpoint 1 (syscall(s) 'exit_group')
4241 Starting program: /tmp/catch-syscall
4243 Catchpoint 1 (call to syscall 'exit_group'), \
4244 0xffffe424 in __kernel_vsyscall ()
4248 Program exited normally.
4252 However, there can be situations when there is no corresponding name
4253 in XML file for that syscall number. In this case, @value{GDBN} prints
4254 a warning message saying that it was not able to find the syscall name,
4255 but the catchpoint will be set anyway. See the example below:
4258 (@value{GDBP}) catch syscall 764
4259 warning: The number '764' does not represent a known syscall.
4260 Catchpoint 2 (syscall 764)
4264 If you configure @value{GDBN} using the @samp{--without-expat} option,
4265 it will not be able to display syscall names. Also, if your
4266 architecture does not have an XML file describing its system calls,
4267 you will not be able to see the syscall names. It is important to
4268 notice that these two features are used for accessing the syscall
4269 name database. In either case, you will see a warning like this:
4272 (@value{GDBP}) catch syscall
4273 warning: Could not open "syscalls/i386-linux.xml"
4274 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4275 GDB will not be able to display syscall names.
4276 Catchpoint 1 (syscall)
4280 Of course, the file name will change depending on your architecture and system.
4282 Still using the example above, you can also try to catch a syscall by its
4283 number. In this case, you would see something like:
4286 (@value{GDBP}) catch syscall 252
4287 Catchpoint 1 (syscall(s) 252)
4290 Again, in this case @value{GDBN} would not be able to display syscall's names.
4293 A call to @code{fork}. This is currently only available for HP-UX
4297 A call to @code{vfork}. This is currently only available for HP-UX
4300 @item load @r{[}regexp@r{]}
4301 @itemx unload @r{[}regexp@r{]}
4302 The loading or unloading of a shared library. If @var{regexp} is
4303 given, then the catchpoint will stop only if the regular expression
4304 matches one of the affected libraries.
4306 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4307 The delivery of a signal.
4309 With no arguments, this catchpoint will catch any signal that is not
4310 used internally by @value{GDBN}, specifically, all signals except
4311 @samp{SIGTRAP} and @samp{SIGINT}.
4313 With the argument @samp{all}, all signals, including those used by
4314 @value{GDBN}, will be caught. This argument cannot be used with other
4317 Otherwise, the arguments are a list of signal names as given to
4318 @code{handle} (@pxref{Signals}). Only signals specified in this list
4321 One reason that @code{catch signal} can be more useful than
4322 @code{handle} is that you can attach commands and conditions to the
4325 When a signal is caught by a catchpoint, the signal's @code{stop} and
4326 @code{print} settings, as specified by @code{handle}, are ignored.
4327 However, whether the signal is still delivered to the inferior depends
4328 on the @code{pass} setting; this can be changed in the catchpoint's
4333 @item tcatch @var{event}
4334 Set a catchpoint that is enabled only for one stop. The catchpoint is
4335 automatically deleted after the first time the event is caught.
4339 Use the @code{info break} command to list the current catchpoints.
4343 @subsection Deleting Breakpoints
4345 @cindex clearing breakpoints, watchpoints, catchpoints
4346 @cindex deleting breakpoints, watchpoints, catchpoints
4347 It is often necessary to eliminate a breakpoint, watchpoint, or
4348 catchpoint once it has done its job and you no longer want your program
4349 to stop there. This is called @dfn{deleting} the breakpoint. A
4350 breakpoint that has been deleted no longer exists; it is forgotten.
4352 With the @code{clear} command you can delete breakpoints according to
4353 where they are in your program. With the @code{delete} command you can
4354 delete individual breakpoints, watchpoints, or catchpoints by specifying
4355 their breakpoint numbers.
4357 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4358 automatically ignores breakpoints on the first instruction to be executed
4359 when you continue execution without changing the execution address.
4364 Delete any breakpoints at the next instruction to be executed in the
4365 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4366 the innermost frame is selected, this is a good way to delete a
4367 breakpoint where your program just stopped.
4369 @item clear @var{location}
4370 Delete any breakpoints set at the specified @var{location}.
4371 @xref{Specify Location}, for the various forms of @var{location}; the
4372 most useful ones are listed below:
4375 @item clear @var{function}
4376 @itemx clear @var{filename}:@var{function}
4377 Delete any breakpoints set at entry to the named @var{function}.
4379 @item clear @var{linenum}
4380 @itemx clear @var{filename}:@var{linenum}
4381 Delete any breakpoints set at or within the code of the specified
4382 @var{linenum} of the specified @var{filename}.
4385 @cindex delete breakpoints
4387 @kindex d @r{(@code{delete})}
4388 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4389 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4390 ranges specified as arguments. If no argument is specified, delete all
4391 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4392 confirm off}). You can abbreviate this command as @code{d}.
4396 @subsection Disabling Breakpoints
4398 @cindex enable/disable a breakpoint
4399 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4400 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4401 it had been deleted, but remembers the information on the breakpoint so
4402 that you can @dfn{enable} it again later.
4404 You disable and enable breakpoints, watchpoints, and catchpoints with
4405 the @code{enable} and @code{disable} commands, optionally specifying
4406 one or more breakpoint numbers as arguments. Use @code{info break} to
4407 print a list of all breakpoints, watchpoints, and catchpoints if you
4408 do not know which numbers to use.
4410 Disabling and enabling a breakpoint that has multiple locations
4411 affects all of its locations.
4413 A breakpoint, watchpoint, or catchpoint can have any of several
4414 different states of enablement:
4418 Enabled. The breakpoint stops your program. A breakpoint set
4419 with the @code{break} command starts out in this state.
4421 Disabled. The breakpoint has no effect on your program.
4423 Enabled once. The breakpoint stops your program, but then becomes
4426 Enabled for a count. The breakpoint stops your program for the next
4427 N times, then becomes disabled.
4429 Enabled for deletion. The breakpoint stops your program, but
4430 immediately after it does so it is deleted permanently. A breakpoint
4431 set with the @code{tbreak} command starts out in this state.
4434 You can use the following commands to enable or disable breakpoints,
4435 watchpoints, and catchpoints:
4439 @kindex dis @r{(@code{disable})}
4440 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4441 Disable the specified breakpoints---or all breakpoints, if none are
4442 listed. A disabled breakpoint has no effect but is not forgotten. All
4443 options such as ignore-counts, conditions and commands are remembered in
4444 case the breakpoint is enabled again later. You may abbreviate
4445 @code{disable} as @code{dis}.
4448 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4449 Enable the specified breakpoints (or all defined breakpoints). They
4450 become effective once again in stopping your program.
4452 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4453 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4454 of these breakpoints immediately after stopping your program.
4456 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4457 Enable the specified breakpoints temporarily. @value{GDBN} records
4458 @var{count} with each of the specified breakpoints, and decrements a
4459 breakpoint's count when it is hit. When any count reaches 0,
4460 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4461 count (@pxref{Conditions, ,Break Conditions}), that will be
4462 decremented to 0 before @var{count} is affected.
4464 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4465 Enable the specified breakpoints to work once, then die. @value{GDBN}
4466 deletes any of these breakpoints as soon as your program stops there.
4467 Breakpoints set by the @code{tbreak} command start out in this state.
4470 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4471 @c confusing: tbreak is also initially enabled.
4472 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4473 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4474 subsequently, they become disabled or enabled only when you use one of
4475 the commands above. (The command @code{until} can set and delete a
4476 breakpoint of its own, but it does not change the state of your other
4477 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4481 @subsection Break Conditions
4482 @cindex conditional breakpoints
4483 @cindex breakpoint conditions
4485 @c FIXME what is scope of break condition expr? Context where wanted?
4486 @c in particular for a watchpoint?
4487 The simplest sort of breakpoint breaks every time your program reaches a
4488 specified place. You can also specify a @dfn{condition} for a
4489 breakpoint. A condition is just a Boolean expression in your
4490 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4491 a condition evaluates the expression each time your program reaches it,
4492 and your program stops only if the condition is @emph{true}.
4494 This is the converse of using assertions for program validation; in that
4495 situation, you want to stop when the assertion is violated---that is,
4496 when the condition is false. In C, if you want to test an assertion expressed
4497 by the condition @var{assert}, you should set the condition
4498 @samp{! @var{assert}} on the appropriate breakpoint.
4500 Conditions are also accepted for watchpoints; you may not need them,
4501 since a watchpoint is inspecting the value of an expression anyhow---but
4502 it might be simpler, say, to just set a watchpoint on a variable name,
4503 and specify a condition that tests whether the new value is an interesting
4506 Break conditions can have side effects, and may even call functions in
4507 your program. This can be useful, for example, to activate functions
4508 that log program progress, or to use your own print functions to
4509 format special data structures. The effects are completely predictable
4510 unless there is another enabled breakpoint at the same address. (In
4511 that case, @value{GDBN} might see the other breakpoint first and stop your
4512 program without checking the condition of this one.) Note that
4513 breakpoint commands are usually more convenient and flexible than break
4515 purpose of performing side effects when a breakpoint is reached
4516 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4518 Breakpoint conditions can also be evaluated on the target's side if
4519 the target supports it. Instead of evaluating the conditions locally,
4520 @value{GDBN} encodes the expression into an agent expression
4521 (@pxref{Agent Expressions}) suitable for execution on the target,
4522 independently of @value{GDBN}. Global variables become raw memory
4523 locations, locals become stack accesses, and so forth.
4525 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4526 when its condition evaluates to true. This mechanism may provide faster
4527 response times depending on the performance characteristics of the target
4528 since it does not need to keep @value{GDBN} informed about
4529 every breakpoint trigger, even those with false conditions.
4531 Break conditions can be specified when a breakpoint is set, by using
4532 @samp{if} in the arguments to the @code{break} command. @xref{Set
4533 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4534 with the @code{condition} command.
4536 You can also use the @code{if} keyword with the @code{watch} command.
4537 The @code{catch} command does not recognize the @code{if} keyword;
4538 @code{condition} is the only way to impose a further condition on a
4543 @item condition @var{bnum} @var{expression}
4544 Specify @var{expression} as the break condition for breakpoint,
4545 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4546 breakpoint @var{bnum} stops your program only if the value of
4547 @var{expression} is true (nonzero, in C). When you use
4548 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4549 syntactic correctness, and to determine whether symbols in it have
4550 referents in the context of your breakpoint. If @var{expression} uses
4551 symbols not referenced in the context of the breakpoint, @value{GDBN}
4552 prints an error message:
4555 No symbol "foo" in current context.
4560 not actually evaluate @var{expression} at the time the @code{condition}
4561 command (or a command that sets a breakpoint with a condition, like
4562 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4564 @item condition @var{bnum}
4565 Remove the condition from breakpoint number @var{bnum}. It becomes
4566 an ordinary unconditional breakpoint.
4569 @cindex ignore count (of breakpoint)
4570 A special case of a breakpoint condition is to stop only when the
4571 breakpoint has been reached a certain number of times. This is so
4572 useful that there is a special way to do it, using the @dfn{ignore
4573 count} of the breakpoint. Every breakpoint has an ignore count, which
4574 is an integer. Most of the time, the ignore count is zero, and
4575 therefore has no effect. But if your program reaches a breakpoint whose
4576 ignore count is positive, then instead of stopping, it just decrements
4577 the ignore count by one and continues. As a result, if the ignore count
4578 value is @var{n}, the breakpoint does not stop the next @var{n} times
4579 your program reaches it.
4583 @item ignore @var{bnum} @var{count}
4584 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4585 The next @var{count} times the breakpoint is reached, your program's
4586 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4589 To make the breakpoint stop the next time it is reached, specify
4592 When you use @code{continue} to resume execution of your program from a
4593 breakpoint, you can specify an ignore count directly as an argument to
4594 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4595 Stepping,,Continuing and Stepping}.
4597 If a breakpoint has a positive ignore count and a condition, the
4598 condition is not checked. Once the ignore count reaches zero,
4599 @value{GDBN} resumes checking the condition.
4601 You could achieve the effect of the ignore count with a condition such
4602 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4603 is decremented each time. @xref{Convenience Vars, ,Convenience
4607 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4610 @node Break Commands
4611 @subsection Breakpoint Command Lists
4613 @cindex breakpoint commands
4614 You can give any breakpoint (or watchpoint or catchpoint) a series of
4615 commands to execute when your program stops due to that breakpoint. For
4616 example, you might want to print the values of certain expressions, or
4617 enable other breakpoints.
4621 @kindex end@r{ (breakpoint commands)}
4622 @item commands @r{[}@var{range}@dots{}@r{]}
4623 @itemx @dots{} @var{command-list} @dots{}
4625 Specify a list of commands for the given breakpoints. The commands
4626 themselves appear on the following lines. Type a line containing just
4627 @code{end} to terminate the commands.
4629 To remove all commands from a breakpoint, type @code{commands} and
4630 follow it immediately with @code{end}; that is, give no commands.
4632 With no argument, @code{commands} refers to the last breakpoint,
4633 watchpoint, or catchpoint set (not to the breakpoint most recently
4634 encountered). If the most recent breakpoints were set with a single
4635 command, then the @code{commands} will apply to all the breakpoints
4636 set by that command. This applies to breakpoints set by
4637 @code{rbreak}, and also applies when a single @code{break} command
4638 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4642 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4643 disabled within a @var{command-list}.
4645 You can use breakpoint commands to start your program up again. Simply
4646 use the @code{continue} command, or @code{step}, or any other command
4647 that resumes execution.
4649 Any other commands in the command list, after a command that resumes
4650 execution, are ignored. This is because any time you resume execution
4651 (even with a simple @code{next} or @code{step}), you may encounter
4652 another breakpoint---which could have its own command list, leading to
4653 ambiguities about which list to execute.
4656 If the first command you specify in a command list is @code{silent}, the
4657 usual message about stopping at a breakpoint is not printed. This may
4658 be desirable for breakpoints that are to print a specific message and
4659 then continue. If none of the remaining commands print anything, you
4660 see no sign that the breakpoint was reached. @code{silent} is
4661 meaningful only at the beginning of a breakpoint command list.
4663 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4664 print precisely controlled output, and are often useful in silent
4665 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4667 For example, here is how you could use breakpoint commands to print the
4668 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4674 printf "x is %d\n",x
4679 One application for breakpoint commands is to compensate for one bug so
4680 you can test for another. Put a breakpoint just after the erroneous line
4681 of code, give it a condition to detect the case in which something
4682 erroneous has been done, and give it commands to assign correct values
4683 to any variables that need them. End with the @code{continue} command
4684 so that your program does not stop, and start with the @code{silent}
4685 command so that no output is produced. Here is an example:
4696 @node Dynamic Printf
4697 @subsection Dynamic Printf
4699 @cindex dynamic printf
4701 The dynamic printf command @code{dprintf} combines a breakpoint with
4702 formatted printing of your program's data to give you the effect of
4703 inserting @code{printf} calls into your program on-the-fly, without
4704 having to recompile it.
4706 In its most basic form, the output goes to the GDB console. However,
4707 you can set the variable @code{dprintf-style} for alternate handling.
4708 For instance, you can ask to format the output by calling your
4709 program's @code{printf} function. This has the advantage that the
4710 characters go to the program's output device, so they can recorded in
4711 redirects to files and so forth.
4713 If you are doing remote debugging with a stub or agent, you can also
4714 ask to have the printf handled by the remote agent. In addition to
4715 ensuring that the output goes to the remote program's device along
4716 with any other output the program might produce, you can also ask that
4717 the dprintf remain active even after disconnecting from the remote
4718 target. Using the stub/agent is also more efficient, as it can do
4719 everything without needing to communicate with @value{GDBN}.
4723 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4724 Whenever execution reaches @var{location}, print the values of one or
4725 more @var{expressions} under the control of the string @var{template}.
4726 To print several values, separate them with commas.
4728 @item set dprintf-style @var{style}
4729 Set the dprintf output to be handled in one of several different
4730 styles enumerated below. A change of style affects all existing
4731 dynamic printfs immediately. (If you need individual control over the
4732 print commands, simply define normal breakpoints with
4733 explicitly-supplied command lists.)
4736 @kindex dprintf-style gdb
4737 Handle the output using the @value{GDBN} @code{printf} command.
4740 @kindex dprintf-style call
4741 Handle the output by calling a function in your program (normally
4745 @kindex dprintf-style agent
4746 Have the remote debugging agent (such as @code{gdbserver}) handle
4747 the output itself. This style is only available for agents that
4748 support running commands on the target.
4750 @item set dprintf-function @var{function}
4751 Set the function to call if the dprintf style is @code{call}. By
4752 default its value is @code{printf}. You may set it to any expression.
4753 that @value{GDBN} can evaluate to a function, as per the @code{call}
4756 @item set dprintf-channel @var{channel}
4757 Set a ``channel'' for dprintf. If set to a non-empty value,
4758 @value{GDBN} will evaluate it as an expression and pass the result as
4759 a first argument to the @code{dprintf-function}, in the manner of
4760 @code{fprintf} and similar functions. Otherwise, the dprintf format
4761 string will be the first argument, in the manner of @code{printf}.
4763 As an example, if you wanted @code{dprintf} output to go to a logfile
4764 that is a standard I/O stream assigned to the variable @code{mylog},
4765 you could do the following:
4768 (gdb) set dprintf-style call
4769 (gdb) set dprintf-function fprintf
4770 (gdb) set dprintf-channel mylog
4771 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4772 Dprintf 1 at 0x123456: file main.c, line 25.
4774 1 dprintf keep y 0x00123456 in main at main.c:25
4775 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4780 Note that the @code{info break} displays the dynamic printf commands
4781 as normal breakpoint commands; you can thus easily see the effect of
4782 the variable settings.
4784 @item set disconnected-dprintf on
4785 @itemx set disconnected-dprintf off
4786 @kindex set disconnected-dprintf
4787 Choose whether @code{dprintf} commands should continue to run if
4788 @value{GDBN} has disconnected from the target. This only applies
4789 if the @code{dprintf-style} is @code{agent}.
4791 @item show disconnected-dprintf off
4792 @kindex show disconnected-dprintf
4793 Show the current choice for disconnected @code{dprintf}.
4797 @value{GDBN} does not check the validity of function and channel,
4798 relying on you to supply values that are meaningful for the contexts
4799 in which they are being used. For instance, the function and channel
4800 may be the values of local variables, but if that is the case, then
4801 all enabled dynamic prints must be at locations within the scope of
4802 those locals. If evaluation fails, @value{GDBN} will report an error.
4804 @node Save Breakpoints
4805 @subsection How to save breakpoints to a file
4807 To save breakpoint definitions to a file use the @w{@code{save
4808 breakpoints}} command.
4811 @kindex save breakpoints
4812 @cindex save breakpoints to a file for future sessions
4813 @item save breakpoints [@var{filename}]
4814 This command saves all current breakpoint definitions together with
4815 their commands and ignore counts, into a file @file{@var{filename}}
4816 suitable for use in a later debugging session. This includes all
4817 types of breakpoints (breakpoints, watchpoints, catchpoints,
4818 tracepoints). To read the saved breakpoint definitions, use the
4819 @code{source} command (@pxref{Command Files}). Note that watchpoints
4820 with expressions involving local variables may fail to be recreated
4821 because it may not be possible to access the context where the
4822 watchpoint is valid anymore. Because the saved breakpoint definitions
4823 are simply a sequence of @value{GDBN} commands that recreate the
4824 breakpoints, you can edit the file in your favorite editing program,
4825 and remove the breakpoint definitions you're not interested in, or
4826 that can no longer be recreated.
4829 @node Static Probe Points
4830 @subsection Static Probe Points
4832 @cindex static probe point, SystemTap
4833 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4834 for Statically Defined Tracing, and the probes are designed to have a tiny
4835 runtime code and data footprint, and no dynamic relocations. They are
4836 usable from assembly, C and C@t{++} languages. See
4837 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4838 for a good reference on how the @acronym{SDT} probes are implemented.
4840 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4841 @acronym{SDT} probes are supported on ELF-compatible systems. See
4842 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4843 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4844 in your applications.
4846 @cindex semaphores on static probe points
4847 Some probes have an associated semaphore variable; for instance, this
4848 happens automatically if you defined your probe using a DTrace-style
4849 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4850 automatically enable it when you specify a breakpoint using the
4851 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4852 location by some other method (e.g., @code{break file:line}), then
4853 @value{GDBN} will not automatically set the semaphore.
4855 You can examine the available static static probes using @code{info
4856 probes}, with optional arguments:
4860 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4861 If given, @var{provider} is a regular expression used to match against provider
4862 names when selecting which probes to list. If omitted, probes by all
4863 probes from all providers are listed.
4865 If given, @var{name} is a regular expression to match against probe names
4866 when selecting which probes to list. If omitted, probe names are not
4867 considered when deciding whether to display them.
4869 If given, @var{objfile} is a regular expression used to select which
4870 object files (executable or shared libraries) to examine. If not
4871 given, all object files are considered.
4873 @item info probes all
4874 List the available static probes, from all types.
4877 @vindex $_probe_arg@r{, convenience variable}
4878 A probe may specify up to twelve arguments. These are available at the
4879 point at which the probe is defined---that is, when the current PC is
4880 at the probe's location. The arguments are available using the
4881 convenience variables (@pxref{Convenience Vars})
4882 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4883 an integer of the appropriate size; types are not preserved. The
4884 convenience variable @code{$_probe_argc} holds the number of arguments
4885 at the current probe point.
4887 These variables are always available, but attempts to access them at
4888 any location other than a probe point will cause @value{GDBN} to give
4892 @c @ifclear BARETARGET
4893 @node Error in Breakpoints
4894 @subsection ``Cannot insert breakpoints''
4896 If you request too many active hardware-assisted breakpoints and
4897 watchpoints, you will see this error message:
4899 @c FIXME: the precise wording of this message may change; the relevant
4900 @c source change is not committed yet (Sep 3, 1999).
4902 Stopped; cannot insert breakpoints.
4903 You may have requested too many hardware breakpoints and watchpoints.
4907 This message is printed when you attempt to resume the program, since
4908 only then @value{GDBN} knows exactly how many hardware breakpoints and
4909 watchpoints it needs to insert.
4911 When this message is printed, you need to disable or remove some of the
4912 hardware-assisted breakpoints and watchpoints, and then continue.
4914 @node Breakpoint-related Warnings
4915 @subsection ``Breakpoint address adjusted...''
4916 @cindex breakpoint address adjusted
4918 Some processor architectures place constraints on the addresses at
4919 which breakpoints may be placed. For architectures thus constrained,
4920 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4921 with the constraints dictated by the architecture.
4923 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4924 a VLIW architecture in which a number of RISC-like instructions may be
4925 bundled together for parallel execution. The FR-V architecture
4926 constrains the location of a breakpoint instruction within such a
4927 bundle to the instruction with the lowest address. @value{GDBN}
4928 honors this constraint by adjusting a breakpoint's address to the
4929 first in the bundle.
4931 It is not uncommon for optimized code to have bundles which contain
4932 instructions from different source statements, thus it may happen that
4933 a breakpoint's address will be adjusted from one source statement to
4934 another. Since this adjustment may significantly alter @value{GDBN}'s
4935 breakpoint related behavior from what the user expects, a warning is
4936 printed when the breakpoint is first set and also when the breakpoint
4939 A warning like the one below is printed when setting a breakpoint
4940 that's been subject to address adjustment:
4943 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4946 Such warnings are printed both for user settable and @value{GDBN}'s
4947 internal breakpoints. If you see one of these warnings, you should
4948 verify that a breakpoint set at the adjusted address will have the
4949 desired affect. If not, the breakpoint in question may be removed and
4950 other breakpoints may be set which will have the desired behavior.
4951 E.g., it may be sufficient to place the breakpoint at a later
4952 instruction. A conditional breakpoint may also be useful in some
4953 cases to prevent the breakpoint from triggering too often.
4955 @value{GDBN} will also issue a warning when stopping at one of these
4956 adjusted breakpoints:
4959 warning: Breakpoint 1 address previously adjusted from 0x00010414
4963 When this warning is encountered, it may be too late to take remedial
4964 action except in cases where the breakpoint is hit earlier or more
4965 frequently than expected.
4967 @node Continuing and Stepping
4968 @section Continuing and Stepping
4972 @cindex resuming execution
4973 @dfn{Continuing} means resuming program execution until your program
4974 completes normally. In contrast, @dfn{stepping} means executing just
4975 one more ``step'' of your program, where ``step'' may mean either one
4976 line of source code, or one machine instruction (depending on what
4977 particular command you use). Either when continuing or when stepping,
4978 your program may stop even sooner, due to a breakpoint or a signal. (If
4979 it stops due to a signal, you may want to use @code{handle}, or use
4980 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4984 @kindex c @r{(@code{continue})}
4985 @kindex fg @r{(resume foreground execution)}
4986 @item continue @r{[}@var{ignore-count}@r{]}
4987 @itemx c @r{[}@var{ignore-count}@r{]}
4988 @itemx fg @r{[}@var{ignore-count}@r{]}
4989 Resume program execution, at the address where your program last stopped;
4990 any breakpoints set at that address are bypassed. The optional argument
4991 @var{ignore-count} allows you to specify a further number of times to
4992 ignore a breakpoint at this location; its effect is like that of
4993 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4995 The argument @var{ignore-count} is meaningful only when your program
4996 stopped due to a breakpoint. At other times, the argument to
4997 @code{continue} is ignored.
4999 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5000 debugged program is deemed to be the foreground program) are provided
5001 purely for convenience, and have exactly the same behavior as
5005 To resume execution at a different place, you can use @code{return}
5006 (@pxref{Returning, ,Returning from a Function}) to go back to the
5007 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5008 Different Address}) to go to an arbitrary location in your program.
5010 A typical technique for using stepping is to set a breakpoint
5011 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5012 beginning of the function or the section of your program where a problem
5013 is believed to lie, run your program until it stops at that breakpoint,
5014 and then step through the suspect area, examining the variables that are
5015 interesting, until you see the problem happen.
5019 @kindex s @r{(@code{step})}
5021 Continue running your program until control reaches a different source
5022 line, then stop it and return control to @value{GDBN}. This command is
5023 abbreviated @code{s}.
5026 @c "without debugging information" is imprecise; actually "without line
5027 @c numbers in the debugging information". (gcc -g1 has debugging info but
5028 @c not line numbers). But it seems complex to try to make that
5029 @c distinction here.
5030 @emph{Warning:} If you use the @code{step} command while control is
5031 within a function that was compiled without debugging information,
5032 execution proceeds until control reaches a function that does have
5033 debugging information. Likewise, it will not step into a function which
5034 is compiled without debugging information. To step through functions
5035 without debugging information, use the @code{stepi} command, described
5039 The @code{step} command only stops at the first instruction of a source
5040 line. This prevents the multiple stops that could otherwise occur in
5041 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5042 to stop if a function that has debugging information is called within
5043 the line. In other words, @code{step} @emph{steps inside} any functions
5044 called within the line.
5046 Also, the @code{step} command only enters a function if there is line
5047 number information for the function. Otherwise it acts like the
5048 @code{next} command. This avoids problems when using @code{cc -gl}
5049 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5050 was any debugging information about the routine.
5052 @item step @var{count}
5053 Continue running as in @code{step}, but do so @var{count} times. If a
5054 breakpoint is reached, or a signal not related to stepping occurs before
5055 @var{count} steps, stepping stops right away.
5058 @kindex n @r{(@code{next})}
5059 @item next @r{[}@var{count}@r{]}
5060 Continue to the next source line in the current (innermost) stack frame.
5061 This is similar to @code{step}, but function calls that appear within
5062 the line of code are executed without stopping. Execution stops when
5063 control reaches a different line of code at the original stack level
5064 that was executing when you gave the @code{next} command. This command
5065 is abbreviated @code{n}.
5067 An argument @var{count} is a repeat count, as for @code{step}.
5070 @c FIX ME!! Do we delete this, or is there a way it fits in with
5071 @c the following paragraph? --- Vctoria
5073 @c @code{next} within a function that lacks debugging information acts like
5074 @c @code{step}, but any function calls appearing within the code of the
5075 @c function are executed without stopping.
5077 The @code{next} command only stops at the first instruction of a
5078 source line. This prevents multiple stops that could otherwise occur in
5079 @code{switch} statements, @code{for} loops, etc.
5081 @kindex set step-mode
5083 @cindex functions without line info, and stepping
5084 @cindex stepping into functions with no line info
5085 @itemx set step-mode on
5086 The @code{set step-mode on} command causes the @code{step} command to
5087 stop at the first instruction of a function which contains no debug line
5088 information rather than stepping over it.
5090 This is useful in cases where you may be interested in inspecting the
5091 machine instructions of a function which has no symbolic info and do not
5092 want @value{GDBN} to automatically skip over this function.
5094 @item set step-mode off
5095 Causes the @code{step} command to step over any functions which contains no
5096 debug information. This is the default.
5098 @item show step-mode
5099 Show whether @value{GDBN} will stop in or step over functions without
5100 source line debug information.
5103 @kindex fin @r{(@code{finish})}
5105 Continue running until just after function in the selected stack frame
5106 returns. Print the returned value (if any). This command can be
5107 abbreviated as @code{fin}.
5109 Contrast this with the @code{return} command (@pxref{Returning,
5110 ,Returning from a Function}).
5113 @kindex u @r{(@code{until})}
5114 @cindex run until specified location
5117 Continue running until a source line past the current line, in the
5118 current stack frame, is reached. This command is used to avoid single
5119 stepping through a loop more than once. It is like the @code{next}
5120 command, except that when @code{until} encounters a jump, it
5121 automatically continues execution until the program counter is greater
5122 than the address of the jump.
5124 This means that when you reach the end of a loop after single stepping
5125 though it, @code{until} makes your program continue execution until it
5126 exits the loop. In contrast, a @code{next} command at the end of a loop
5127 simply steps back to the beginning of the loop, which forces you to step
5128 through the next iteration.
5130 @code{until} always stops your program if it attempts to exit the current
5133 @code{until} may produce somewhat counterintuitive results if the order
5134 of machine code does not match the order of the source lines. For
5135 example, in the following excerpt from a debugging session, the @code{f}
5136 (@code{frame}) command shows that execution is stopped at line
5137 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5141 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5143 (@value{GDBP}) until
5144 195 for ( ; argc > 0; NEXTARG) @{
5147 This happened because, for execution efficiency, the compiler had
5148 generated code for the loop closure test at the end, rather than the
5149 start, of the loop---even though the test in a C @code{for}-loop is
5150 written before the body of the loop. The @code{until} command appeared
5151 to step back to the beginning of the loop when it advanced to this
5152 expression; however, it has not really gone to an earlier
5153 statement---not in terms of the actual machine code.
5155 @code{until} with no argument works by means of single
5156 instruction stepping, and hence is slower than @code{until} with an
5159 @item until @var{location}
5160 @itemx u @var{location}
5161 Continue running your program until either the specified location is
5162 reached, or the current stack frame returns. @var{location} is any of
5163 the forms described in @ref{Specify Location}.
5164 This form of the command uses temporary breakpoints, and
5165 hence is quicker than @code{until} without an argument. The specified
5166 location is actually reached only if it is in the current frame. This
5167 implies that @code{until} can be used to skip over recursive function
5168 invocations. For instance in the code below, if the current location is
5169 line @code{96}, issuing @code{until 99} will execute the program up to
5170 line @code{99} in the same invocation of factorial, i.e., after the inner
5171 invocations have returned.
5174 94 int factorial (int value)
5176 96 if (value > 1) @{
5177 97 value *= factorial (value - 1);
5184 @kindex advance @var{location}
5185 @item advance @var{location}
5186 Continue running the program up to the given @var{location}. An argument is
5187 required, which should be of one of the forms described in
5188 @ref{Specify Location}.
5189 Execution will also stop upon exit from the current stack
5190 frame. This command is similar to @code{until}, but @code{advance} will
5191 not skip over recursive function calls, and the target location doesn't
5192 have to be in the same frame as the current one.
5196 @kindex si @r{(@code{stepi})}
5198 @itemx stepi @var{arg}
5200 Execute one machine instruction, then stop and return to the debugger.
5202 It is often useful to do @samp{display/i $pc} when stepping by machine
5203 instructions. This makes @value{GDBN} automatically display the next
5204 instruction to be executed, each time your program stops. @xref{Auto
5205 Display,, Automatic Display}.
5207 An argument is a repeat count, as in @code{step}.
5211 @kindex ni @r{(@code{nexti})}
5213 @itemx nexti @var{arg}
5215 Execute one machine instruction, but if it is a function call,
5216 proceed until the function returns.
5218 An argument is a repeat count, as in @code{next}.
5221 @node Skipping Over Functions and Files
5222 @section Skipping Over Functions and Files
5223 @cindex skipping over functions and files
5225 The program you are debugging may contain some functions which are
5226 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5227 skip a function or all functions in a file when stepping.
5229 For example, consider the following C function:
5240 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5241 are not interested in stepping through @code{boring}. If you run @code{step}
5242 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5243 step over both @code{foo} and @code{boring}!
5245 One solution is to @code{step} into @code{boring} and use the @code{finish}
5246 command to immediately exit it. But this can become tedious if @code{boring}
5247 is called from many places.
5249 A more flexible solution is to execute @kbd{skip boring}. This instructs
5250 @value{GDBN} never to step into @code{boring}. Now when you execute
5251 @code{step} at line 103, you'll step over @code{boring} and directly into
5254 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5255 example, @code{skip file boring.c}.
5258 @kindex skip function
5259 @item skip @r{[}@var{linespec}@r{]}
5260 @itemx skip function @r{[}@var{linespec}@r{]}
5261 After running this command, the function named by @var{linespec} or the
5262 function containing the line named by @var{linespec} will be skipped over when
5263 stepping. @xref{Specify Location}.
5265 If you do not specify @var{linespec}, the function you're currently debugging
5268 (If you have a function called @code{file} that you want to skip, use
5269 @kbd{skip function file}.)
5272 @item skip file @r{[}@var{filename}@r{]}
5273 After running this command, any function whose source lives in @var{filename}
5274 will be skipped over when stepping.
5276 If you do not specify @var{filename}, functions whose source lives in the file
5277 you're currently debugging will be skipped.
5280 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5281 These are the commands for managing your list of skips:
5285 @item info skip @r{[}@var{range}@r{]}
5286 Print details about the specified skip(s). If @var{range} is not specified,
5287 print a table with details about all functions and files marked for skipping.
5288 @code{info skip} prints the following information about each skip:
5292 A number identifying this skip.
5294 The type of this skip, either @samp{function} or @samp{file}.
5295 @item Enabled or Disabled
5296 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5298 For function skips, this column indicates the address in memory of the function
5299 being skipped. If you've set a function skip on a function which has not yet
5300 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5301 which has the function is loaded, @code{info skip} will show the function's
5304 For file skips, this field contains the filename being skipped. For functions
5305 skips, this field contains the function name and its line number in the file
5306 where it is defined.
5310 @item skip delete @r{[}@var{range}@r{]}
5311 Delete the specified skip(s). If @var{range} is not specified, delete all
5315 @item skip enable @r{[}@var{range}@r{]}
5316 Enable the specified skip(s). If @var{range} is not specified, enable all
5319 @kindex skip disable
5320 @item skip disable @r{[}@var{range}@r{]}
5321 Disable the specified skip(s). If @var{range} is not specified, disable all
5330 A signal is an asynchronous event that can happen in a program. The
5331 operating system defines the possible kinds of signals, and gives each
5332 kind a name and a number. For example, in Unix @code{SIGINT} is the
5333 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5334 @code{SIGSEGV} is the signal a program gets from referencing a place in
5335 memory far away from all the areas in use; @code{SIGALRM} occurs when
5336 the alarm clock timer goes off (which happens only if your program has
5337 requested an alarm).
5339 @cindex fatal signals
5340 Some signals, including @code{SIGALRM}, are a normal part of the
5341 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5342 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5343 program has not specified in advance some other way to handle the signal.
5344 @code{SIGINT} does not indicate an error in your program, but it is normally
5345 fatal so it can carry out the purpose of the interrupt: to kill the program.
5347 @value{GDBN} has the ability to detect any occurrence of a signal in your
5348 program. You can tell @value{GDBN} in advance what to do for each kind of
5351 @cindex handling signals
5352 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5353 @code{SIGALRM} be silently passed to your program
5354 (so as not to interfere with their role in the program's functioning)
5355 but to stop your program immediately whenever an error signal happens.
5356 You can change these settings with the @code{handle} command.
5359 @kindex info signals
5363 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5364 handle each one. You can use this to see the signal numbers of all
5365 the defined types of signals.
5367 @item info signals @var{sig}
5368 Similar, but print information only about the specified signal number.
5370 @code{info handle} is an alias for @code{info signals}.
5372 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5373 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5374 for details about this command.
5377 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5378 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5379 can be the number of a signal or its name (with or without the
5380 @samp{SIG} at the beginning); a list of signal numbers of the form
5381 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5382 known signals. Optional arguments @var{keywords}, described below,
5383 say what change to make.
5387 The keywords allowed by the @code{handle} command can be abbreviated.
5388 Their full names are:
5392 @value{GDBN} should not stop your program when this signal happens. It may
5393 still print a message telling you that the signal has come in.
5396 @value{GDBN} should stop your program when this signal happens. This implies
5397 the @code{print} keyword as well.
5400 @value{GDBN} should print a message when this signal happens.
5403 @value{GDBN} should not mention the occurrence of the signal at all. This
5404 implies the @code{nostop} keyword as well.
5408 @value{GDBN} should allow your program to see this signal; your program
5409 can handle the signal, or else it may terminate if the signal is fatal
5410 and not handled. @code{pass} and @code{noignore} are synonyms.
5414 @value{GDBN} should not allow your program to see this signal.
5415 @code{nopass} and @code{ignore} are synonyms.
5419 When a signal stops your program, the signal is not visible to the
5421 continue. Your program sees the signal then, if @code{pass} is in
5422 effect for the signal in question @emph{at that time}. In other words,
5423 after @value{GDBN} reports a signal, you can use the @code{handle}
5424 command with @code{pass} or @code{nopass} to control whether your
5425 program sees that signal when you continue.
5427 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5428 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5429 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5432 You can also use the @code{signal} command to prevent your program from
5433 seeing a signal, or cause it to see a signal it normally would not see,
5434 or to give it any signal at any time. For example, if your program stopped
5435 due to some sort of memory reference error, you might store correct
5436 values into the erroneous variables and continue, hoping to see more
5437 execution; but your program would probably terminate immediately as
5438 a result of the fatal signal once it saw the signal. To prevent this,
5439 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5442 @cindex extra signal information
5443 @anchor{extra signal information}
5445 On some targets, @value{GDBN} can inspect extra signal information
5446 associated with the intercepted signal, before it is actually
5447 delivered to the program being debugged. This information is exported
5448 by the convenience variable @code{$_siginfo}, and consists of data
5449 that is passed by the kernel to the signal handler at the time of the
5450 receipt of a signal. The data type of the information itself is
5451 target dependent. You can see the data type using the @code{ptype
5452 $_siginfo} command. On Unix systems, it typically corresponds to the
5453 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5456 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5457 referenced address that raised a segmentation fault.
5461 (@value{GDBP}) continue
5462 Program received signal SIGSEGV, Segmentation fault.
5463 0x0000000000400766 in main ()
5465 (@value{GDBP}) ptype $_siginfo
5472 struct @{...@} _kill;
5473 struct @{...@} _timer;
5475 struct @{...@} _sigchld;
5476 struct @{...@} _sigfault;
5477 struct @{...@} _sigpoll;
5480 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5484 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5485 $1 = (void *) 0x7ffff7ff7000
5489 Depending on target support, @code{$_siginfo} may also be writable.
5492 @section Stopping and Starting Multi-thread Programs
5494 @cindex stopped threads
5495 @cindex threads, stopped
5497 @cindex continuing threads
5498 @cindex threads, continuing
5500 @value{GDBN} supports debugging programs with multiple threads
5501 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5502 are two modes of controlling execution of your program within the
5503 debugger. In the default mode, referred to as @dfn{all-stop mode},
5504 when any thread in your program stops (for example, at a breakpoint
5505 or while being stepped), all other threads in the program are also stopped by
5506 @value{GDBN}. On some targets, @value{GDBN} also supports
5507 @dfn{non-stop mode}, in which other threads can continue to run freely while
5508 you examine the stopped thread in the debugger.
5511 * All-Stop Mode:: All threads stop when GDB takes control
5512 * Non-Stop Mode:: Other threads continue to execute
5513 * Background Execution:: Running your program asynchronously
5514 * Thread-Specific Breakpoints:: Controlling breakpoints
5515 * Interrupted System Calls:: GDB may interfere with system calls
5516 * Observer Mode:: GDB does not alter program behavior
5520 @subsection All-Stop Mode
5522 @cindex all-stop mode
5524 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5525 @emph{all} threads of execution stop, not just the current thread. This
5526 allows you to examine the overall state of the program, including
5527 switching between threads, without worrying that things may change
5530 Conversely, whenever you restart the program, @emph{all} threads start
5531 executing. @emph{This is true even when single-stepping} with commands
5532 like @code{step} or @code{next}.
5534 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5535 Since thread scheduling is up to your debugging target's operating
5536 system (not controlled by @value{GDBN}), other threads may
5537 execute more than one statement while the current thread completes a
5538 single step. Moreover, in general other threads stop in the middle of a
5539 statement, rather than at a clean statement boundary, when the program
5542 You might even find your program stopped in another thread after
5543 continuing or even single-stepping. This happens whenever some other
5544 thread runs into a breakpoint, a signal, or an exception before the
5545 first thread completes whatever you requested.
5547 @cindex automatic thread selection
5548 @cindex switching threads automatically
5549 @cindex threads, automatic switching
5550 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5551 signal, it automatically selects the thread where that breakpoint or
5552 signal happened. @value{GDBN} alerts you to the context switch with a
5553 message such as @samp{[Switching to Thread @var{n}]} to identify the
5556 On some OSes, you can modify @value{GDBN}'s default behavior by
5557 locking the OS scheduler to allow only a single thread to run.
5560 @item set scheduler-locking @var{mode}
5561 @cindex scheduler locking mode
5562 @cindex lock scheduler
5563 Set the scheduler locking mode. If it is @code{off}, then there is no
5564 locking and any thread may run at any time. If @code{on}, then only the
5565 current thread may run when the inferior is resumed. The @code{step}
5566 mode optimizes for single-stepping; it prevents other threads
5567 from preempting the current thread while you are stepping, so that
5568 the focus of debugging does not change unexpectedly.
5569 Other threads only rarely (or never) get a chance to run
5570 when you step. They are more likely to run when you @samp{next} over a
5571 function call, and they are completely free to run when you use commands
5572 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5573 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5574 the current thread away from the thread that you are debugging.
5576 @item show scheduler-locking
5577 Display the current scheduler locking mode.
5580 @cindex resume threads of multiple processes simultaneously
5581 By default, when you issue one of the execution commands such as
5582 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5583 threads of the current inferior to run. For example, if @value{GDBN}
5584 is attached to two inferiors, each with two threads, the
5585 @code{continue} command resumes only the two threads of the current
5586 inferior. This is useful, for example, when you debug a program that
5587 forks and you want to hold the parent stopped (so that, for instance,
5588 it doesn't run to exit), while you debug the child. In other
5589 situations, you may not be interested in inspecting the current state
5590 of any of the processes @value{GDBN} is attached to, and you may want
5591 to resume them all until some breakpoint is hit. In the latter case,
5592 you can instruct @value{GDBN} to allow all threads of all the
5593 inferiors to run with the @w{@code{set schedule-multiple}} command.
5596 @kindex set schedule-multiple
5597 @item set schedule-multiple
5598 Set the mode for allowing threads of multiple processes to be resumed
5599 when an execution command is issued. When @code{on}, all threads of
5600 all processes are allowed to run. When @code{off}, only the threads
5601 of the current process are resumed. The default is @code{off}. The
5602 @code{scheduler-locking} mode takes precedence when set to @code{on},
5603 or while you are stepping and set to @code{step}.
5605 @item show schedule-multiple
5606 Display the current mode for resuming the execution of threads of
5611 @subsection Non-Stop Mode
5613 @cindex non-stop mode
5615 @c This section is really only a place-holder, and needs to be expanded
5616 @c with more details.
5618 For some multi-threaded targets, @value{GDBN} supports an optional
5619 mode of operation in which you can examine stopped program threads in
5620 the debugger while other threads continue to execute freely. This
5621 minimizes intrusion when debugging live systems, such as programs
5622 where some threads have real-time constraints or must continue to
5623 respond to external events. This is referred to as @dfn{non-stop} mode.
5625 In non-stop mode, when a thread stops to report a debugging event,
5626 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5627 threads as well, in contrast to the all-stop mode behavior. Additionally,
5628 execution commands such as @code{continue} and @code{step} apply by default
5629 only to the current thread in non-stop mode, rather than all threads as
5630 in all-stop mode. This allows you to control threads explicitly in
5631 ways that are not possible in all-stop mode --- for example, stepping
5632 one thread while allowing others to run freely, stepping
5633 one thread while holding all others stopped, or stepping several threads
5634 independently and simultaneously.
5636 To enter non-stop mode, use this sequence of commands before you run
5637 or attach to your program:
5640 # Enable the async interface.
5643 # If using the CLI, pagination breaks non-stop.
5646 # Finally, turn it on!
5650 You can use these commands to manipulate the non-stop mode setting:
5653 @kindex set non-stop
5654 @item set non-stop on
5655 Enable selection of non-stop mode.
5656 @item set non-stop off
5657 Disable selection of non-stop mode.
5658 @kindex show non-stop
5660 Show the current non-stop enablement setting.
5663 Note these commands only reflect whether non-stop mode is enabled,
5664 not whether the currently-executing program is being run in non-stop mode.
5665 In particular, the @code{set non-stop} preference is only consulted when
5666 @value{GDBN} starts or connects to the target program, and it is generally
5667 not possible to switch modes once debugging has started. Furthermore,
5668 since not all targets support non-stop mode, even when you have enabled
5669 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5672 In non-stop mode, all execution commands apply only to the current thread
5673 by default. That is, @code{continue} only continues one thread.
5674 To continue all threads, issue @code{continue -a} or @code{c -a}.
5676 You can use @value{GDBN}'s background execution commands
5677 (@pxref{Background Execution}) to run some threads in the background
5678 while you continue to examine or step others from @value{GDBN}.
5679 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5680 always executed asynchronously in non-stop mode.
5682 Suspending execution is done with the @code{interrupt} command when
5683 running in the background, or @kbd{Ctrl-c} during foreground execution.
5684 In all-stop mode, this stops the whole process;
5685 but in non-stop mode the interrupt applies only to the current thread.
5686 To stop the whole program, use @code{interrupt -a}.
5688 Other execution commands do not currently support the @code{-a} option.
5690 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5691 that thread current, as it does in all-stop mode. This is because the
5692 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5693 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5694 changed to a different thread just as you entered a command to operate on the
5695 previously current thread.
5697 @node Background Execution
5698 @subsection Background Execution
5700 @cindex foreground execution
5701 @cindex background execution
5702 @cindex asynchronous execution
5703 @cindex execution, foreground, background and asynchronous
5705 @value{GDBN}'s execution commands have two variants: the normal
5706 foreground (synchronous) behavior, and a background
5707 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5708 the program to report that some thread has stopped before prompting for
5709 another command. In background execution, @value{GDBN} immediately gives
5710 a command prompt so that you can issue other commands while your program runs.
5712 You need to explicitly enable asynchronous mode before you can use
5713 background execution commands. You can use these commands to
5714 manipulate the asynchronous mode setting:
5717 @kindex set target-async
5718 @item set target-async on
5719 Enable asynchronous mode.
5720 @item set target-async off
5721 Disable asynchronous mode.
5722 @kindex show target-async
5723 @item show target-async
5724 Show the current target-async setting.
5727 If the target doesn't support async mode, @value{GDBN} issues an error
5728 message if you attempt to use the background execution commands.
5730 To specify background execution, add a @code{&} to the command. For example,
5731 the background form of the @code{continue} command is @code{continue&}, or
5732 just @code{c&}. The execution commands that accept background execution
5738 @xref{Starting, , Starting your Program}.
5742 @xref{Attach, , Debugging an Already-running Process}.
5746 @xref{Continuing and Stepping, step}.
5750 @xref{Continuing and Stepping, stepi}.
5754 @xref{Continuing and Stepping, next}.
5758 @xref{Continuing and Stepping, nexti}.
5762 @xref{Continuing and Stepping, continue}.
5766 @xref{Continuing and Stepping, finish}.
5770 @xref{Continuing and Stepping, until}.
5774 Background execution is especially useful in conjunction with non-stop
5775 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5776 However, you can also use these commands in the normal all-stop mode with
5777 the restriction that you cannot issue another execution command until the
5778 previous one finishes. Examples of commands that are valid in all-stop
5779 mode while the program is running include @code{help} and @code{info break}.
5781 You can interrupt your program while it is running in the background by
5782 using the @code{interrupt} command.
5789 Suspend execution of the running program. In all-stop mode,
5790 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5791 only the current thread. To stop the whole program in non-stop mode,
5792 use @code{interrupt -a}.
5795 @node Thread-Specific Breakpoints
5796 @subsection Thread-Specific Breakpoints
5798 When your program has multiple threads (@pxref{Threads,, Debugging
5799 Programs with Multiple Threads}), you can choose whether to set
5800 breakpoints on all threads, or on a particular thread.
5803 @cindex breakpoints and threads
5804 @cindex thread breakpoints
5805 @kindex break @dots{} thread @var{threadno}
5806 @item break @var{linespec} thread @var{threadno}
5807 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5808 @var{linespec} specifies source lines; there are several ways of
5809 writing them (@pxref{Specify Location}), but the effect is always to
5810 specify some source line.
5812 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5813 to specify that you only want @value{GDBN} to stop the program when a
5814 particular thread reaches this breakpoint. @var{threadno} is one of the
5815 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5816 column of the @samp{info threads} display.
5818 If you do not specify @samp{thread @var{threadno}} when you set a
5819 breakpoint, the breakpoint applies to @emph{all} threads of your
5822 You can use the @code{thread} qualifier on conditional breakpoints as
5823 well; in this case, place @samp{thread @var{threadno}} before or
5824 after the breakpoint condition, like this:
5827 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5832 @node Interrupted System Calls
5833 @subsection Interrupted System Calls
5835 @cindex thread breakpoints and system calls
5836 @cindex system calls and thread breakpoints
5837 @cindex premature return from system calls
5838 There is an unfortunate side effect when using @value{GDBN} to debug
5839 multi-threaded programs. If one thread stops for a
5840 breakpoint, or for some other reason, and another thread is blocked in a
5841 system call, then the system call may return prematurely. This is a
5842 consequence of the interaction between multiple threads and the signals
5843 that @value{GDBN} uses to implement breakpoints and other events that
5846 To handle this problem, your program should check the return value of
5847 each system call and react appropriately. This is good programming
5850 For example, do not write code like this:
5856 The call to @code{sleep} will return early if a different thread stops
5857 at a breakpoint or for some other reason.
5859 Instead, write this:
5864 unslept = sleep (unslept);
5867 A system call is allowed to return early, so the system is still
5868 conforming to its specification. But @value{GDBN} does cause your
5869 multi-threaded program to behave differently than it would without
5872 Also, @value{GDBN} uses internal breakpoints in the thread library to
5873 monitor certain events such as thread creation and thread destruction.
5874 When such an event happens, a system call in another thread may return
5875 prematurely, even though your program does not appear to stop.
5878 @subsection Observer Mode
5880 If you want to build on non-stop mode and observe program behavior
5881 without any chance of disruption by @value{GDBN}, you can set
5882 variables to disable all of the debugger's attempts to modify state,
5883 whether by writing memory, inserting breakpoints, etc. These operate
5884 at a low level, intercepting operations from all commands.
5886 When all of these are set to @code{off}, then @value{GDBN} is said to
5887 be @dfn{observer mode}. As a convenience, the variable
5888 @code{observer} can be set to disable these, plus enable non-stop
5891 Note that @value{GDBN} will not prevent you from making nonsensical
5892 combinations of these settings. For instance, if you have enabled
5893 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5894 then breakpoints that work by writing trap instructions into the code
5895 stream will still not be able to be placed.
5900 @item set observer on
5901 @itemx set observer off
5902 When set to @code{on}, this disables all the permission variables
5903 below (except for @code{insert-fast-tracepoints}), plus enables
5904 non-stop debugging. Setting this to @code{off} switches back to
5905 normal debugging, though remaining in non-stop mode.
5908 Show whether observer mode is on or off.
5910 @kindex may-write-registers
5911 @item set may-write-registers on
5912 @itemx set may-write-registers off
5913 This controls whether @value{GDBN} will attempt to alter the values of
5914 registers, such as with assignment expressions in @code{print}, or the
5915 @code{jump} command. It defaults to @code{on}.
5917 @item show may-write-registers
5918 Show the current permission to write registers.
5920 @kindex may-write-memory
5921 @item set may-write-memory on
5922 @itemx set may-write-memory off
5923 This controls whether @value{GDBN} will attempt to alter the contents
5924 of memory, such as with assignment expressions in @code{print}. It
5925 defaults to @code{on}.
5927 @item show may-write-memory
5928 Show the current permission to write memory.
5930 @kindex may-insert-breakpoints
5931 @item set may-insert-breakpoints on
5932 @itemx set may-insert-breakpoints off
5933 This controls whether @value{GDBN} will attempt to insert breakpoints.
5934 This affects all breakpoints, including internal breakpoints defined
5935 by @value{GDBN}. It defaults to @code{on}.
5937 @item show may-insert-breakpoints
5938 Show the current permission to insert breakpoints.
5940 @kindex may-insert-tracepoints
5941 @item set may-insert-tracepoints on
5942 @itemx set may-insert-tracepoints off
5943 This controls whether @value{GDBN} will attempt to insert (regular)
5944 tracepoints at the beginning of a tracing experiment. It affects only
5945 non-fast tracepoints, fast tracepoints being under the control of
5946 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5948 @item show may-insert-tracepoints
5949 Show the current permission to insert tracepoints.
5951 @kindex may-insert-fast-tracepoints
5952 @item set may-insert-fast-tracepoints on
5953 @itemx set may-insert-fast-tracepoints off
5954 This controls whether @value{GDBN} will attempt to insert fast
5955 tracepoints at the beginning of a tracing experiment. It affects only
5956 fast tracepoints, regular (non-fast) tracepoints being under the
5957 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5959 @item show may-insert-fast-tracepoints
5960 Show the current permission to insert fast tracepoints.
5962 @kindex may-interrupt
5963 @item set may-interrupt on
5964 @itemx set may-interrupt off
5965 This controls whether @value{GDBN} will attempt to interrupt or stop
5966 program execution. When this variable is @code{off}, the
5967 @code{interrupt} command will have no effect, nor will
5968 @kbd{Ctrl-c}. It defaults to @code{on}.
5970 @item show may-interrupt
5971 Show the current permission to interrupt or stop the program.
5975 @node Reverse Execution
5976 @chapter Running programs backward
5977 @cindex reverse execution
5978 @cindex running programs backward
5980 When you are debugging a program, it is not unusual to realize that
5981 you have gone too far, and some event of interest has already happened.
5982 If the target environment supports it, @value{GDBN} can allow you to
5983 ``rewind'' the program by running it backward.
5985 A target environment that supports reverse execution should be able
5986 to ``undo'' the changes in machine state that have taken place as the
5987 program was executing normally. Variables, registers etc.@: should
5988 revert to their previous values. Obviously this requires a great
5989 deal of sophistication on the part of the target environment; not
5990 all target environments can support reverse execution.
5992 When a program is executed in reverse, the instructions that
5993 have most recently been executed are ``un-executed'', in reverse
5994 order. The program counter runs backward, following the previous
5995 thread of execution in reverse. As each instruction is ``un-executed'',
5996 the values of memory and/or registers that were changed by that
5997 instruction are reverted to their previous states. After executing
5998 a piece of source code in reverse, all side effects of that code
5999 should be ``undone'', and all variables should be returned to their
6000 prior values@footnote{
6001 Note that some side effects are easier to undo than others. For instance,
6002 memory and registers are relatively easy, but device I/O is hard. Some
6003 targets may be able undo things like device I/O, and some may not.
6005 The contract between @value{GDBN} and the reverse executing target
6006 requires only that the target do something reasonable when
6007 @value{GDBN} tells it to execute backwards, and then report the
6008 results back to @value{GDBN}. Whatever the target reports back to
6009 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6010 assumes that the memory and registers that the target reports are in a
6011 consistant state, but @value{GDBN} accepts whatever it is given.
6014 If you are debugging in a target environment that supports
6015 reverse execution, @value{GDBN} provides the following commands.
6018 @kindex reverse-continue
6019 @kindex rc @r{(@code{reverse-continue})}
6020 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6021 @itemx rc @r{[}@var{ignore-count}@r{]}
6022 Beginning at the point where your program last stopped, start executing
6023 in reverse. Reverse execution will stop for breakpoints and synchronous
6024 exceptions (signals), just like normal execution. Behavior of
6025 asynchronous signals depends on the target environment.
6027 @kindex reverse-step
6028 @kindex rs @r{(@code{step})}
6029 @item reverse-step @r{[}@var{count}@r{]}
6030 Run the program backward until control reaches the start of a
6031 different source line; then stop it, and return control to @value{GDBN}.
6033 Like the @code{step} command, @code{reverse-step} will only stop
6034 at the beginning of a source line. It ``un-executes'' the previously
6035 executed source line. If the previous source line included calls to
6036 debuggable functions, @code{reverse-step} will step (backward) into
6037 the called function, stopping at the beginning of the @emph{last}
6038 statement in the called function (typically a return statement).
6040 Also, as with the @code{step} command, if non-debuggable functions are
6041 called, @code{reverse-step} will run thru them backward without stopping.
6043 @kindex reverse-stepi
6044 @kindex rsi @r{(@code{reverse-stepi})}
6045 @item reverse-stepi @r{[}@var{count}@r{]}
6046 Reverse-execute one machine instruction. Note that the instruction
6047 to be reverse-executed is @emph{not} the one pointed to by the program
6048 counter, but the instruction executed prior to that one. For instance,
6049 if the last instruction was a jump, @code{reverse-stepi} will take you
6050 back from the destination of the jump to the jump instruction itself.
6052 @kindex reverse-next
6053 @kindex rn @r{(@code{reverse-next})}
6054 @item reverse-next @r{[}@var{count}@r{]}
6055 Run backward to the beginning of the previous line executed in
6056 the current (innermost) stack frame. If the line contains function
6057 calls, they will be ``un-executed'' without stopping. Starting from
6058 the first line of a function, @code{reverse-next} will take you back
6059 to the caller of that function, @emph{before} the function was called,
6060 just as the normal @code{next} command would take you from the last
6061 line of a function back to its return to its caller
6062 @footnote{Unless the code is too heavily optimized.}.
6064 @kindex reverse-nexti
6065 @kindex rni @r{(@code{reverse-nexti})}
6066 @item reverse-nexti @r{[}@var{count}@r{]}
6067 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6068 in reverse, except that called functions are ``un-executed'' atomically.
6069 That is, if the previously executed instruction was a return from
6070 another function, @code{reverse-nexti} will continue to execute
6071 in reverse until the call to that function (from the current stack
6074 @kindex reverse-finish
6075 @item reverse-finish
6076 Just as the @code{finish} command takes you to the point where the
6077 current function returns, @code{reverse-finish} takes you to the point
6078 where it was called. Instead of ending up at the end of the current
6079 function invocation, you end up at the beginning.
6081 @kindex set exec-direction
6082 @item set exec-direction
6083 Set the direction of target execution.
6084 @item set exec-direction reverse
6085 @cindex execute forward or backward in time
6086 @value{GDBN} will perform all execution commands in reverse, until the
6087 exec-direction mode is changed to ``forward''. Affected commands include
6088 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6089 command cannot be used in reverse mode.
6090 @item set exec-direction forward
6091 @value{GDBN} will perform all execution commands in the normal fashion.
6092 This is the default.
6096 @node Process Record and Replay
6097 @chapter Recording Inferior's Execution and Replaying It
6098 @cindex process record and replay
6099 @cindex recording inferior's execution and replaying it
6101 On some platforms, @value{GDBN} provides a special @dfn{process record
6102 and replay} target that can record a log of the process execution, and
6103 replay it later with both forward and reverse execution commands.
6106 When this target is in use, if the execution log includes the record
6107 for the next instruction, @value{GDBN} will debug in @dfn{replay
6108 mode}. In the replay mode, the inferior does not really execute code
6109 instructions. Instead, all the events that normally happen during
6110 code execution are taken from the execution log. While code is not
6111 really executed in replay mode, the values of registers (including the
6112 program counter register) and the memory of the inferior are still
6113 changed as they normally would. Their contents are taken from the
6117 If the record for the next instruction is not in the execution log,
6118 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6119 inferior executes normally, and @value{GDBN} records the execution log
6122 The process record and replay target supports reverse execution
6123 (@pxref{Reverse Execution}), even if the platform on which the
6124 inferior runs does not. However, the reverse execution is limited in
6125 this case by the range of the instructions recorded in the execution
6126 log. In other words, reverse execution on platforms that don't
6127 support it directly can only be done in the replay mode.
6129 When debugging in the reverse direction, @value{GDBN} will work in
6130 replay mode as long as the execution log includes the record for the
6131 previous instruction; otherwise, it will work in record mode, if the
6132 platform supports reverse execution, or stop if not.
6134 For architecture environments that support process record and replay,
6135 @value{GDBN} provides the following commands:
6138 @kindex target record
6139 @kindex target record-full
6140 @kindex target record-btrace
6143 @kindex record btrace
6147 @item record @var{method}
6148 This command starts the process record and replay target. The
6149 recording method can be specified as parameter. Without a parameter
6150 the command uses the @code{full} recording method. The following
6151 recording methods are available:
6155 Full record/replay recording using @value{GDBN}'s software record and
6156 replay implementation. This method allows replaying and reverse
6160 Hardware-supported instruction recording. This method does not allow
6161 replaying and reverse execution.
6163 This recording method may not be available on all processors.
6166 The process record and replay target can only debug a process that is
6167 already running. Therefore, you need first to start the process with
6168 the @kbd{run} or @kbd{start} commands, and then start the recording
6169 with the @kbd{record @var{method}} command.
6171 Both @code{record @var{method}} and @code{rec @var{method}} are
6172 aliases of @code{target record-@var{method}}.
6174 @cindex displaced stepping, and process record and replay
6175 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6176 will be automatically disabled when process record and replay target
6177 is started. That's because the process record and replay target
6178 doesn't support displaced stepping.
6180 @cindex non-stop mode, and process record and replay
6181 @cindex asynchronous execution, and process record and replay
6182 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6183 the asynchronous execution mode (@pxref{Background Execution}), not
6184 all recording methods are available. The @code{full} recording method
6185 does not support these two modes.
6190 Stop the process record and replay target. When process record and
6191 replay target stops, the entire execution log will be deleted and the
6192 inferior will either be terminated, or will remain in its final state.
6194 When you stop the process record and replay target in record mode (at
6195 the end of the execution log), the inferior will be stopped at the
6196 next instruction that would have been recorded. In other words, if
6197 you record for a while and then stop recording, the inferior process
6198 will be left in the same state as if the recording never happened.
6200 On the other hand, if the process record and replay target is stopped
6201 while in replay mode (that is, not at the end of the execution log,
6202 but at some earlier point), the inferior process will become ``live''
6203 at that earlier state, and it will then be possible to continue the
6204 usual ``live'' debugging of the process from that state.
6206 When the inferior process exits, or @value{GDBN} detaches from it,
6207 process record and replay target will automatically stop itself.
6210 @item record save @var{filename}
6211 Save the execution log to a file @file{@var{filename}}.
6212 Default filename is @file{gdb_record.@var{process_id}}, where
6213 @var{process_id} is the process ID of the inferior.
6215 This command may not be available for all recording methods.
6217 @kindex record restore
6218 @item record restore @var{filename}
6219 Restore the execution log from a file @file{@var{filename}}.
6220 File must have been created with @code{record save}.
6222 @kindex set record full
6223 @item set record full insn-number-max @var{limit}
6224 @itemx set record full insn-number-max unlimited
6225 Set the limit of instructions to be recorded for the @code{full}
6226 recording method. Default value is 200000.
6228 If @var{limit} is a positive number, then @value{GDBN} will start
6229 deleting instructions from the log once the number of the record
6230 instructions becomes greater than @var{limit}. For every new recorded
6231 instruction, @value{GDBN} will delete the earliest recorded
6232 instruction to keep the number of recorded instructions at the limit.
6233 (Since deleting recorded instructions loses information, @value{GDBN}
6234 lets you control what happens when the limit is reached, by means of
6235 the @code{stop-at-limit} option, described below.)
6237 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6238 delete recorded instructions from the execution log. The number of
6239 recorded instructions is limited only by the available memory.
6241 @kindex show record full
6242 @item show record full insn-number-max
6243 Show the limit of instructions to be recorded with the @code{full}
6246 @item set record full stop-at-limit
6247 Control the behavior of the @code{full} recording method when the
6248 number of recorded instructions reaches the limit. If ON (the
6249 default), @value{GDBN} will stop when the limit is reached for the
6250 first time and ask you whether you want to stop the inferior or
6251 continue running it and recording the execution log. If you decide
6252 to continue recording, each new recorded instruction will cause the
6253 oldest one to be deleted.
6255 If this option is OFF, @value{GDBN} will automatically delete the
6256 oldest record to make room for each new one, without asking.
6258 @item show record full stop-at-limit
6259 Show the current setting of @code{stop-at-limit}.
6261 @item set record full memory-query
6262 Control the behavior when @value{GDBN} is unable to record memory
6263 changes caused by an instruction for the @code{full} recording method.
6264 If ON, @value{GDBN} will query whether to stop the inferior in that
6267 If this option is OFF (the default), @value{GDBN} will automatically
6268 ignore the effect of such instructions on memory. Later, when
6269 @value{GDBN} replays this execution log, it will mark the log of this
6270 instruction as not accessible, and it will not affect the replay
6273 @item show record full memory-query
6274 Show the current setting of @code{memory-query}.
6278 Show various statistics about the recording depending on the recording
6283 For the @code{full} recording method, it shows the state of process
6284 record and its in-memory execution log buffer, including:
6288 Whether in record mode or replay mode.
6290 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6292 Highest recorded instruction number.
6294 Current instruction about to be replayed (if in replay mode).
6296 Number of instructions contained in the execution log.
6298 Maximum number of instructions that may be contained in the execution log.
6302 For the @code{btrace} recording method, it shows the number of
6303 instructions that have been recorded and the number of blocks of
6304 sequential control-flow that is formed by the recorded instructions.
6307 @kindex record delete
6310 When record target runs in replay mode (``in the past''), delete the
6311 subsequent execution log and begin to record a new execution log starting
6312 from the current address. This means you will abandon the previously
6313 recorded ``future'' and begin recording a new ``future''.
6315 @kindex record instruction-history
6316 @kindex rec instruction-history
6317 @item record instruction-history
6318 Disassembles instructions from the recorded execution log. By
6319 default, ten instructions are disassembled. This can be changed using
6320 the @code{set record instruction-history-size} command. Instructions
6321 are printed in execution order. There are several ways to specify
6322 what part of the execution log to disassemble:
6325 @item record instruction-history @var{insn}
6326 Disassembles ten instructions starting from instruction number
6329 @item record instruction-history @var{insn}, +/-@var{n}
6330 Disassembles @var{n} instructions around instruction number
6331 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6332 @var{n} instructions after instruction number @var{insn}. If
6333 @var{n} is preceded with @code{-}, disassembles @var{n}
6334 instructions before instruction number @var{insn}.
6336 @item record instruction-history
6337 Disassembles ten more instructions after the last disassembly.
6339 @item record instruction-history -
6340 Disassembles ten more instructions before the last disassembly.
6342 @item record instruction-history @var{begin} @var{end}
6343 Disassembles instructions beginning with instruction number
6344 @var{begin} until instruction number @var{end}. The instruction
6345 number @var{end} is not included.
6348 This command may not be available for all recording methods.
6351 @item set record instruction-history-size @var{size}
6352 @itemx set record instruction-history-size unlimited
6353 Define how many instructions to disassemble in the @code{record
6354 instruction-history} command. The default value is 10.
6355 A @var{size} of @code{unlimited} means unlimited instructions.
6358 @item show record instruction-history-size
6359 Show how many instructions to disassemble in the @code{record
6360 instruction-history} command.
6362 @kindex record function-call-history
6363 @kindex rec function-call-history
6364 @item record function-call-history
6365 Prints the execution history at function granularity. It prints one
6366 line for each sequence of instructions that belong to the same
6367 function giving the name of that function, the source lines
6368 for this instruction sequence (if the @code{/l} modifier is
6369 specified), and the instructions numbers that form the sequence (if
6370 the @code{/i} modifier is specified).
6373 (@value{GDBP}) @b{list 1, 10}
6384 (@value{GDBP}) @b{record function-call-history /l}
6390 By default, ten lines are printed. This can be changed using the
6391 @code{set record function-call-history-size} command. Functions are
6392 printed in execution order. There are several ways to specify what
6396 @item record function-call-history @var{func}
6397 Prints ten functions starting from function number @var{func}.
6399 @item record function-call-history @var{func}, +/-@var{n}
6400 Prints @var{n} functions around function number @var{func}. If
6401 @var{n} is preceded with @code{+}, prints @var{n} functions after
6402 function number @var{func}. If @var{n} is preceded with @code{-},
6403 prints @var{n} functions before function number @var{func}.
6405 @item record function-call-history
6406 Prints ten more functions after the last ten-line print.
6408 @item record function-call-history -
6409 Prints ten more functions before the last ten-line print.
6411 @item record function-call-history @var{begin} @var{end}
6412 Prints functions beginning with function number @var{begin} until
6413 function number @var{end}. The function number @var{end} is not
6417 This command may not be available for all recording methods.
6419 @item set record function-call-history-size @var{size}
6420 @itemx set record function-call-history-size unlimited
6421 Define how many lines to print in the
6422 @code{record function-call-history} command. The default value is 10.
6423 A size of @code{unlimited} means unlimited lines.
6425 @item show record function-call-history-size
6426 Show how many lines to print in the
6427 @code{record function-call-history} command.
6432 @chapter Examining the Stack
6434 When your program has stopped, the first thing you need to know is where it
6435 stopped and how it got there.
6438 Each time your program performs a function call, information about the call
6440 That information includes the location of the call in your program,
6441 the arguments of the call,
6442 and the local variables of the function being called.
6443 The information is saved in a block of data called a @dfn{stack frame}.
6444 The stack frames are allocated in a region of memory called the @dfn{call
6447 When your program stops, the @value{GDBN} commands for examining the
6448 stack allow you to see all of this information.
6450 @cindex selected frame
6451 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6452 @value{GDBN} commands refer implicitly to the selected frame. In
6453 particular, whenever you ask @value{GDBN} for the value of a variable in
6454 your program, the value is found in the selected frame. There are
6455 special @value{GDBN} commands to select whichever frame you are
6456 interested in. @xref{Selection, ,Selecting a Frame}.
6458 When your program stops, @value{GDBN} automatically selects the
6459 currently executing frame and describes it briefly, similar to the
6460 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6463 * Frames:: Stack frames
6464 * Backtrace:: Backtraces
6465 * Selection:: Selecting a frame
6466 * Frame Info:: Information on a frame
6471 @section Stack Frames
6473 @cindex frame, definition
6475 The call stack is divided up into contiguous pieces called @dfn{stack
6476 frames}, or @dfn{frames} for short; each frame is the data associated
6477 with one call to one function. The frame contains the arguments given
6478 to the function, the function's local variables, and the address at
6479 which the function is executing.
6481 @cindex initial frame
6482 @cindex outermost frame
6483 @cindex innermost frame
6484 When your program is started, the stack has only one frame, that of the
6485 function @code{main}. This is called the @dfn{initial} frame or the
6486 @dfn{outermost} frame. Each time a function is called, a new frame is
6487 made. Each time a function returns, the frame for that function invocation
6488 is eliminated. If a function is recursive, there can be many frames for
6489 the same function. The frame for the function in which execution is
6490 actually occurring is called the @dfn{innermost} frame. This is the most
6491 recently created of all the stack frames that still exist.
6493 @cindex frame pointer
6494 Inside your program, stack frames are identified by their addresses. A
6495 stack frame consists of many bytes, each of which has its own address; each
6496 kind of computer has a convention for choosing one byte whose
6497 address serves as the address of the frame. Usually this address is kept
6498 in a register called the @dfn{frame pointer register}
6499 (@pxref{Registers, $fp}) while execution is going on in that frame.
6501 @cindex frame number
6502 @value{GDBN} assigns numbers to all existing stack frames, starting with
6503 zero for the innermost frame, one for the frame that called it,
6504 and so on upward. These numbers do not really exist in your program;
6505 they are assigned by @value{GDBN} to give you a way of designating stack
6506 frames in @value{GDBN} commands.
6508 @c The -fomit-frame-pointer below perennially causes hbox overflow
6509 @c underflow problems.
6510 @cindex frameless execution
6511 Some compilers provide a way to compile functions so that they operate
6512 without stack frames. (For example, the @value{NGCC} option
6514 @samp{-fomit-frame-pointer}
6516 generates functions without a frame.)
6517 This is occasionally done with heavily used library functions to save
6518 the frame setup time. @value{GDBN} has limited facilities for dealing
6519 with these function invocations. If the innermost function invocation
6520 has no stack frame, @value{GDBN} nevertheless regards it as though
6521 it had a separate frame, which is numbered zero as usual, allowing
6522 correct tracing of the function call chain. However, @value{GDBN} has
6523 no provision for frameless functions elsewhere in the stack.
6526 @kindex frame@r{, command}
6527 @cindex current stack frame
6528 @item frame @var{args}
6529 The @code{frame} command allows you to move from one stack frame to another,
6530 and to print the stack frame you select. @var{args} may be either the
6531 address of the frame or the stack frame number. Without an argument,
6532 @code{frame} prints the current stack frame.
6534 @kindex select-frame
6535 @cindex selecting frame silently
6537 The @code{select-frame} command allows you to move from one stack frame
6538 to another without printing the frame. This is the silent version of
6546 @cindex call stack traces
6547 A backtrace is a summary of how your program got where it is. It shows one
6548 line per frame, for many frames, starting with the currently executing
6549 frame (frame zero), followed by its caller (frame one), and on up the
6554 @kindex bt @r{(@code{backtrace})}
6557 Print a backtrace of the entire stack: one line per frame for all
6558 frames in the stack.
6560 You can stop the backtrace at any time by typing the system interrupt
6561 character, normally @kbd{Ctrl-c}.
6563 @item backtrace @var{n}
6565 Similar, but print only the innermost @var{n} frames.
6567 @item backtrace -@var{n}
6569 Similar, but print only the outermost @var{n} frames.
6571 @item backtrace full
6573 @itemx bt full @var{n}
6574 @itemx bt full -@var{n}
6575 Print the values of the local variables also. @var{n} specifies the
6576 number of frames to print, as described above.
6581 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6582 are additional aliases for @code{backtrace}.
6584 @cindex multiple threads, backtrace
6585 In a multi-threaded program, @value{GDBN} by default shows the
6586 backtrace only for the current thread. To display the backtrace for
6587 several or all of the threads, use the command @code{thread apply}
6588 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6589 apply all backtrace}, @value{GDBN} will display the backtrace for all
6590 the threads; this is handy when you debug a core dump of a
6591 multi-threaded program.
6593 Each line in the backtrace shows the frame number and the function name.
6594 The program counter value is also shown---unless you use @code{set
6595 print address off}. The backtrace also shows the source file name and
6596 line number, as well as the arguments to the function. The program
6597 counter value is omitted if it is at the beginning of the code for that
6600 Here is an example of a backtrace. It was made with the command
6601 @samp{bt 3}, so it shows the innermost three frames.
6605 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6607 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6608 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6610 (More stack frames follow...)
6615 The display for frame zero does not begin with a program counter
6616 value, indicating that your program has stopped at the beginning of the
6617 code for line @code{993} of @code{builtin.c}.
6620 The value of parameter @code{data} in frame 1 has been replaced by
6621 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6622 only if it is a scalar (integer, pointer, enumeration, etc). See command
6623 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6624 on how to configure the way function parameter values are printed.
6626 @cindex optimized out, in backtrace
6627 @cindex function call arguments, optimized out
6628 If your program was compiled with optimizations, some compilers will
6629 optimize away arguments passed to functions if those arguments are
6630 never used after the call. Such optimizations generate code that
6631 passes arguments through registers, but doesn't store those arguments
6632 in the stack frame. @value{GDBN} has no way of displaying such
6633 arguments in stack frames other than the innermost one. Here's what
6634 such a backtrace might look like:
6638 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6640 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6641 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6643 (More stack frames follow...)
6648 The values of arguments that were not saved in their stack frames are
6649 shown as @samp{<optimized out>}.
6651 If you need to display the values of such optimized-out arguments,
6652 either deduce that from other variables whose values depend on the one
6653 you are interested in, or recompile without optimizations.
6655 @cindex backtrace beyond @code{main} function
6656 @cindex program entry point
6657 @cindex startup code, and backtrace
6658 Most programs have a standard user entry point---a place where system
6659 libraries and startup code transition into user code. For C this is
6660 @code{main}@footnote{
6661 Note that embedded programs (the so-called ``free-standing''
6662 environment) are not required to have a @code{main} function as the
6663 entry point. They could even have multiple entry points.}.
6664 When @value{GDBN} finds the entry function in a backtrace
6665 it will terminate the backtrace, to avoid tracing into highly
6666 system-specific (and generally uninteresting) code.
6668 If you need to examine the startup code, or limit the number of levels
6669 in a backtrace, you can change this behavior:
6672 @item set backtrace past-main
6673 @itemx set backtrace past-main on
6674 @kindex set backtrace
6675 Backtraces will continue past the user entry point.
6677 @item set backtrace past-main off
6678 Backtraces will stop when they encounter the user entry point. This is the
6681 @item show backtrace past-main
6682 @kindex show backtrace
6683 Display the current user entry point backtrace policy.
6685 @item set backtrace past-entry
6686 @itemx set backtrace past-entry on
6687 Backtraces will continue past the internal entry point of an application.
6688 This entry point is encoded by the linker when the application is built,
6689 and is likely before the user entry point @code{main} (or equivalent) is called.
6691 @item set backtrace past-entry off
6692 Backtraces will stop when they encounter the internal entry point of an
6693 application. This is the default.
6695 @item show backtrace past-entry
6696 Display the current internal entry point backtrace policy.
6698 @item set backtrace limit @var{n}
6699 @itemx set backtrace limit 0
6700 @itemx set backtrace limit unlimited
6701 @cindex backtrace limit
6702 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6703 or zero means unlimited levels.
6705 @item show backtrace limit
6706 Display the current limit on backtrace levels.
6709 You can control how file names are displayed.
6712 @item set filename-display
6713 @itemx set filename-display relative
6714 @cindex filename-display
6715 Display file names relative to the compilation directory. This is the default.
6717 @item set filename-display basename
6718 Display only basename of a filename.
6720 @item set filename-display absolute
6721 Display an absolute filename.
6723 @item show filename-display
6724 Show the current way to display filenames.
6728 @section Selecting a Frame
6730 Most commands for examining the stack and other data in your program work on
6731 whichever stack frame is selected at the moment. Here are the commands for
6732 selecting a stack frame; all of them finish by printing a brief description
6733 of the stack frame just selected.
6736 @kindex frame@r{, selecting}
6737 @kindex f @r{(@code{frame})}
6740 Select frame number @var{n}. Recall that frame zero is the innermost
6741 (currently executing) frame, frame one is the frame that called the
6742 innermost one, and so on. The highest-numbered frame is the one for
6745 @item frame @var{addr}
6747 Select the frame at address @var{addr}. This is useful mainly if the
6748 chaining of stack frames has been damaged by a bug, making it
6749 impossible for @value{GDBN} to assign numbers properly to all frames. In
6750 addition, this can be useful when your program has multiple stacks and
6751 switches between them.
6753 On the SPARC architecture, @code{frame} needs two addresses to
6754 select an arbitrary frame: a frame pointer and a stack pointer.
6756 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6757 pointer and a program counter.
6759 On the 29k architecture, it needs three addresses: a register stack
6760 pointer, a program counter, and a memory stack pointer.
6764 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6765 advances toward the outermost frame, to higher frame numbers, to frames
6766 that have existed longer. @var{n} defaults to one.
6769 @kindex do @r{(@code{down})}
6771 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6772 advances toward the innermost frame, to lower frame numbers, to frames
6773 that were created more recently. @var{n} defaults to one. You may
6774 abbreviate @code{down} as @code{do}.
6777 All of these commands end by printing two lines of output describing the
6778 frame. The first line shows the frame number, the function name, the
6779 arguments, and the source file and line number of execution in that
6780 frame. The second line shows the text of that source line.
6788 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6790 10 read_input_file (argv[i]);
6794 After such a printout, the @code{list} command with no arguments
6795 prints ten lines centered on the point of execution in the frame.
6796 You can also edit the program at the point of execution with your favorite
6797 editing program by typing @code{edit}.
6798 @xref{List, ,Printing Source Lines},
6802 @kindex down-silently
6804 @item up-silently @var{n}
6805 @itemx down-silently @var{n}
6806 These two commands are variants of @code{up} and @code{down},
6807 respectively; they differ in that they do their work silently, without
6808 causing display of the new frame. They are intended primarily for use
6809 in @value{GDBN} command scripts, where the output might be unnecessary and
6814 @section Information About a Frame
6816 There are several other commands to print information about the selected
6822 When used without any argument, this command does not change which
6823 frame is selected, but prints a brief description of the currently
6824 selected stack frame. It can be abbreviated @code{f}. With an
6825 argument, this command is used to select a stack frame.
6826 @xref{Selection, ,Selecting a Frame}.
6829 @kindex info f @r{(@code{info frame})}
6832 This command prints a verbose description of the selected stack frame,
6837 the address of the frame
6839 the address of the next frame down (called by this frame)
6841 the address of the next frame up (caller of this frame)
6843 the language in which the source code corresponding to this frame is written
6845 the address of the frame's arguments
6847 the address of the frame's local variables
6849 the program counter saved in it (the address of execution in the caller frame)
6851 which registers were saved in the frame
6854 @noindent The verbose description is useful when
6855 something has gone wrong that has made the stack format fail to fit
6856 the usual conventions.
6858 @item info frame @var{addr}
6859 @itemx info f @var{addr}
6860 Print a verbose description of the frame at address @var{addr}, without
6861 selecting that frame. The selected frame remains unchanged by this
6862 command. This requires the same kind of address (more than one for some
6863 architectures) that you specify in the @code{frame} command.
6864 @xref{Selection, ,Selecting a Frame}.
6868 Print the arguments of the selected frame, each on a separate line.
6872 Print the local variables of the selected frame, each on a separate
6873 line. These are all variables (declared either static or automatic)
6874 accessible at the point of execution of the selected frame.
6880 @chapter Examining Source Files
6882 @value{GDBN} can print parts of your program's source, since the debugging
6883 information recorded in the program tells @value{GDBN} what source files were
6884 used to build it. When your program stops, @value{GDBN} spontaneously prints
6885 the line where it stopped. Likewise, when you select a stack frame
6886 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6887 execution in that frame has stopped. You can print other portions of
6888 source files by explicit command.
6890 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6891 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6892 @value{GDBN} under @sc{gnu} Emacs}.
6895 * List:: Printing source lines
6896 * Specify Location:: How to specify code locations
6897 * Edit:: Editing source files
6898 * Search:: Searching source files
6899 * Source Path:: Specifying source directories
6900 * Machine Code:: Source and machine code
6904 @section Printing Source Lines
6907 @kindex l @r{(@code{list})}
6908 To print lines from a source file, use the @code{list} command
6909 (abbreviated @code{l}). By default, ten lines are printed.
6910 There are several ways to specify what part of the file you want to
6911 print; see @ref{Specify Location}, for the full list.
6913 Here are the forms of the @code{list} command most commonly used:
6916 @item list @var{linenum}
6917 Print lines centered around line number @var{linenum} in the
6918 current source file.
6920 @item list @var{function}
6921 Print lines centered around the beginning of function
6925 Print more lines. If the last lines printed were printed with a
6926 @code{list} command, this prints lines following the last lines
6927 printed; however, if the last line printed was a solitary line printed
6928 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6929 Stack}), this prints lines centered around that line.
6932 Print lines just before the lines last printed.
6935 @cindex @code{list}, how many lines to display
6936 By default, @value{GDBN} prints ten source lines with any of these forms of
6937 the @code{list} command. You can change this using @code{set listsize}:
6940 @kindex set listsize
6941 @item set listsize @var{count}
6942 @itemx set listsize unlimited
6943 Make the @code{list} command display @var{count} source lines (unless
6944 the @code{list} argument explicitly specifies some other number).
6945 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
6947 @kindex show listsize
6949 Display the number of lines that @code{list} prints.
6952 Repeating a @code{list} command with @key{RET} discards the argument,
6953 so it is equivalent to typing just @code{list}. This is more useful
6954 than listing the same lines again. An exception is made for an
6955 argument of @samp{-}; that argument is preserved in repetition so that
6956 each repetition moves up in the source file.
6958 In general, the @code{list} command expects you to supply zero, one or two
6959 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6960 of writing them (@pxref{Specify Location}), but the effect is always
6961 to specify some source line.
6963 Here is a complete description of the possible arguments for @code{list}:
6966 @item list @var{linespec}
6967 Print lines centered around the line specified by @var{linespec}.
6969 @item list @var{first},@var{last}
6970 Print lines from @var{first} to @var{last}. Both arguments are
6971 linespecs. When a @code{list} command has two linespecs, and the
6972 source file of the second linespec is omitted, this refers to
6973 the same source file as the first linespec.
6975 @item list ,@var{last}
6976 Print lines ending with @var{last}.
6978 @item list @var{first},
6979 Print lines starting with @var{first}.
6982 Print lines just after the lines last printed.
6985 Print lines just before the lines last printed.
6988 As described in the preceding table.
6991 @node Specify Location
6992 @section Specifying a Location
6993 @cindex specifying location
6996 Several @value{GDBN} commands accept arguments that specify a location
6997 of your program's code. Since @value{GDBN} is a source-level
6998 debugger, a location usually specifies some line in the source code;
6999 for that reason, locations are also known as @dfn{linespecs}.
7001 Here are all the different ways of specifying a code location that
7002 @value{GDBN} understands:
7006 Specifies the line number @var{linenum} of the current source file.
7009 @itemx +@var{offset}
7010 Specifies the line @var{offset} lines before or after the @dfn{current
7011 line}. For the @code{list} command, the current line is the last one
7012 printed; for the breakpoint commands, this is the line at which
7013 execution stopped in the currently selected @dfn{stack frame}
7014 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7015 used as the second of the two linespecs in a @code{list} command,
7016 this specifies the line @var{offset} lines up or down from the first
7019 @item @var{filename}:@var{linenum}
7020 Specifies the line @var{linenum} in the source file @var{filename}.
7021 If @var{filename} is a relative file name, then it will match any
7022 source file name with the same trailing components. For example, if
7023 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7024 name of @file{/build/trunk/gcc/expr.c}, but not
7025 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7027 @item @var{function}
7028 Specifies the line that begins the body of the function @var{function}.
7029 For example, in C, this is the line with the open brace.
7031 @item @var{function}:@var{label}
7032 Specifies the line where @var{label} appears in @var{function}.
7034 @item @var{filename}:@var{function}
7035 Specifies the line that begins the body of the function @var{function}
7036 in the file @var{filename}. You only need the file name with a
7037 function name to avoid ambiguity when there are identically named
7038 functions in different source files.
7041 Specifies the line at which the label named @var{label} appears.
7042 @value{GDBN} searches for the label in the function corresponding to
7043 the currently selected stack frame. If there is no current selected
7044 stack frame (for instance, if the inferior is not running), then
7045 @value{GDBN} will not search for a label.
7047 @item *@var{address}
7048 Specifies the program address @var{address}. For line-oriented
7049 commands, such as @code{list} and @code{edit}, this specifies a source
7050 line that contains @var{address}. For @code{break} and other
7051 breakpoint oriented commands, this can be used to set breakpoints in
7052 parts of your program which do not have debugging information or
7055 Here @var{address} may be any expression valid in the current working
7056 language (@pxref{Languages, working language}) that specifies a code
7057 address. In addition, as a convenience, @value{GDBN} extends the
7058 semantics of expressions used in locations to cover the situations
7059 that frequently happen during debugging. Here are the various forms
7063 @item @var{expression}
7064 Any expression valid in the current working language.
7066 @item @var{funcaddr}
7067 An address of a function or procedure derived from its name. In C,
7068 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7069 simply the function's name @var{function} (and actually a special case
7070 of a valid expression). In Pascal and Modula-2, this is
7071 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7072 (although the Pascal form also works).
7074 This form specifies the address of the function's first instruction,
7075 before the stack frame and arguments have been set up.
7077 @item '@var{filename}'::@var{funcaddr}
7078 Like @var{funcaddr} above, but also specifies the name of the source
7079 file explicitly. This is useful if the name of the function does not
7080 specify the function unambiguously, e.g., if there are several
7081 functions with identical names in different source files.
7084 @cindex breakpoint at static probe point
7085 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7086 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7087 applications to embed static probes. @xref{Static Probe Points}, for more
7088 information on finding and using static probes. This form of linespec
7089 specifies the location of such a static probe.
7091 If @var{objfile} is given, only probes coming from that shared library
7092 or executable matching @var{objfile} as a regular expression are considered.
7093 If @var{provider} is given, then only probes from that provider are considered.
7094 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7095 each one of those probes.
7101 @section Editing Source Files
7102 @cindex editing source files
7105 @kindex e @r{(@code{edit})}
7106 To edit the lines in a source file, use the @code{edit} command.
7107 The editing program of your choice
7108 is invoked with the current line set to
7109 the active line in the program.
7110 Alternatively, there are several ways to specify what part of the file you
7111 want to print if you want to see other parts of the program:
7114 @item edit @var{location}
7115 Edit the source file specified by @code{location}. Editing starts at
7116 that @var{location}, e.g., at the specified source line of the
7117 specified file. @xref{Specify Location}, for all the possible forms
7118 of the @var{location} argument; here are the forms of the @code{edit}
7119 command most commonly used:
7122 @item edit @var{number}
7123 Edit the current source file with @var{number} as the active line number.
7125 @item edit @var{function}
7126 Edit the file containing @var{function} at the beginning of its definition.
7131 @subsection Choosing your Editor
7132 You can customize @value{GDBN} to use any editor you want
7134 The only restriction is that your editor (say @code{ex}), recognizes the
7135 following command-line syntax:
7137 ex +@var{number} file
7139 The optional numeric value +@var{number} specifies the number of the line in
7140 the file where to start editing.}.
7141 By default, it is @file{@value{EDITOR}}, but you can change this
7142 by setting the environment variable @code{EDITOR} before using
7143 @value{GDBN}. For example, to configure @value{GDBN} to use the
7144 @code{vi} editor, you could use these commands with the @code{sh} shell:
7150 or in the @code{csh} shell,
7152 setenv EDITOR /usr/bin/vi
7157 @section Searching Source Files
7158 @cindex searching source files
7160 There are two commands for searching through the current source file for a
7165 @kindex forward-search
7166 @kindex fo @r{(@code{forward-search})}
7167 @item forward-search @var{regexp}
7168 @itemx search @var{regexp}
7169 The command @samp{forward-search @var{regexp}} checks each line,
7170 starting with the one following the last line listed, for a match for
7171 @var{regexp}. It lists the line that is found. You can use the
7172 synonym @samp{search @var{regexp}} or abbreviate the command name as
7175 @kindex reverse-search
7176 @item reverse-search @var{regexp}
7177 The command @samp{reverse-search @var{regexp}} checks each line, starting
7178 with the one before the last line listed and going backward, for a match
7179 for @var{regexp}. It lists the line that is found. You can abbreviate
7180 this command as @code{rev}.
7184 @section Specifying Source Directories
7187 @cindex directories for source files
7188 Executable programs sometimes do not record the directories of the source
7189 files from which they were compiled, just the names. Even when they do,
7190 the directories could be moved between the compilation and your debugging
7191 session. @value{GDBN} has a list of directories to search for source files;
7192 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7193 it tries all the directories in the list, in the order they are present
7194 in the list, until it finds a file with the desired name.
7196 For example, suppose an executable references the file
7197 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7198 @file{/mnt/cross}. The file is first looked up literally; if this
7199 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7200 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7201 message is printed. @value{GDBN} does not look up the parts of the
7202 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7203 Likewise, the subdirectories of the source path are not searched: if
7204 the source path is @file{/mnt/cross}, and the binary refers to
7205 @file{foo.c}, @value{GDBN} would not find it under
7206 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7208 Plain file names, relative file names with leading directories, file
7209 names containing dots, etc.@: are all treated as described above; for
7210 instance, if the source path is @file{/mnt/cross}, and the source file
7211 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7212 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7213 that---@file{/mnt/cross/foo.c}.
7215 Note that the executable search path is @emph{not} used to locate the
7218 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7219 any information it has cached about where source files are found and where
7220 each line is in the file.
7224 When you start @value{GDBN}, its source path includes only @samp{cdir}
7225 and @samp{cwd}, in that order.
7226 To add other directories, use the @code{directory} command.
7228 The search path is used to find both program source files and @value{GDBN}
7229 script files (read using the @samp{-command} option and @samp{source} command).
7231 In addition to the source path, @value{GDBN} provides a set of commands
7232 that manage a list of source path substitution rules. A @dfn{substitution
7233 rule} specifies how to rewrite source directories stored in the program's
7234 debug information in case the sources were moved to a different
7235 directory between compilation and debugging. A rule is made of
7236 two strings, the first specifying what needs to be rewritten in
7237 the path, and the second specifying how it should be rewritten.
7238 In @ref{set substitute-path}, we name these two parts @var{from} and
7239 @var{to} respectively. @value{GDBN} does a simple string replacement
7240 of @var{from} with @var{to} at the start of the directory part of the
7241 source file name, and uses that result instead of the original file
7242 name to look up the sources.
7244 Using the previous example, suppose the @file{foo-1.0} tree has been
7245 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7246 @value{GDBN} to replace @file{/usr/src} in all source path names with
7247 @file{/mnt/cross}. The first lookup will then be
7248 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7249 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7250 substitution rule, use the @code{set substitute-path} command
7251 (@pxref{set substitute-path}).
7253 To avoid unexpected substitution results, a rule is applied only if the
7254 @var{from} part of the directory name ends at a directory separator.
7255 For instance, a rule substituting @file{/usr/source} into
7256 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7257 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7258 is applied only at the beginning of the directory name, this rule will
7259 not be applied to @file{/root/usr/source/baz.c} either.
7261 In many cases, you can achieve the same result using the @code{directory}
7262 command. However, @code{set substitute-path} can be more efficient in
7263 the case where the sources are organized in a complex tree with multiple
7264 subdirectories. With the @code{directory} command, you need to add each
7265 subdirectory of your project. If you moved the entire tree while
7266 preserving its internal organization, then @code{set substitute-path}
7267 allows you to direct the debugger to all the sources with one single
7270 @code{set substitute-path} is also more than just a shortcut command.
7271 The source path is only used if the file at the original location no
7272 longer exists. On the other hand, @code{set substitute-path} modifies
7273 the debugger behavior to look at the rewritten location instead. So, if
7274 for any reason a source file that is not relevant to your executable is
7275 located at the original location, a substitution rule is the only
7276 method available to point @value{GDBN} at the new location.
7278 @cindex @samp{--with-relocated-sources}
7279 @cindex default source path substitution
7280 You can configure a default source path substitution rule by
7281 configuring @value{GDBN} with the
7282 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7283 should be the name of a directory under @value{GDBN}'s configured
7284 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7285 directory names in debug information under @var{dir} will be adjusted
7286 automatically if the installed @value{GDBN} is moved to a new
7287 location. This is useful if @value{GDBN}, libraries or executables
7288 with debug information and corresponding source code are being moved
7292 @item directory @var{dirname} @dots{}
7293 @item dir @var{dirname} @dots{}
7294 Add directory @var{dirname} to the front of the source path. Several
7295 directory names may be given to this command, separated by @samp{:}
7296 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7297 part of absolute file names) or
7298 whitespace. You may specify a directory that is already in the source
7299 path; this moves it forward, so @value{GDBN} searches it sooner.
7303 @vindex $cdir@r{, convenience variable}
7304 @vindex $cwd@r{, convenience variable}
7305 @cindex compilation directory
7306 @cindex current directory
7307 @cindex working directory
7308 @cindex directory, current
7309 @cindex directory, compilation
7310 You can use the string @samp{$cdir} to refer to the compilation
7311 directory (if one is recorded), and @samp{$cwd} to refer to the current
7312 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7313 tracks the current working directory as it changes during your @value{GDBN}
7314 session, while the latter is immediately expanded to the current
7315 directory at the time you add an entry to the source path.
7318 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7320 @c RET-repeat for @code{directory} is explicitly disabled, but since
7321 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7323 @item set directories @var{path-list}
7324 @kindex set directories
7325 Set the source path to @var{path-list}.
7326 @samp{$cdir:$cwd} are added if missing.
7328 @item show directories
7329 @kindex show directories
7330 Print the source path: show which directories it contains.
7332 @anchor{set substitute-path}
7333 @item set substitute-path @var{from} @var{to}
7334 @kindex set substitute-path
7335 Define a source path substitution rule, and add it at the end of the
7336 current list of existing substitution rules. If a rule with the same
7337 @var{from} was already defined, then the old rule is also deleted.
7339 For example, if the file @file{/foo/bar/baz.c} was moved to
7340 @file{/mnt/cross/baz.c}, then the command
7343 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7347 will tell @value{GDBN} to replace @samp{/usr/src} with
7348 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7349 @file{baz.c} even though it was moved.
7351 In the case when more than one substitution rule have been defined,
7352 the rules are evaluated one by one in the order where they have been
7353 defined. The first one matching, if any, is selected to perform
7356 For instance, if we had entered the following commands:
7359 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7360 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7364 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7365 @file{/mnt/include/defs.h} by using the first rule. However, it would
7366 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7367 @file{/mnt/src/lib/foo.c}.
7370 @item unset substitute-path [path]
7371 @kindex unset substitute-path
7372 If a path is specified, search the current list of substitution rules
7373 for a rule that would rewrite that path. Delete that rule if found.
7374 A warning is emitted by the debugger if no rule could be found.
7376 If no path is specified, then all substitution rules are deleted.
7378 @item show substitute-path [path]
7379 @kindex show substitute-path
7380 If a path is specified, then print the source path substitution rule
7381 which would rewrite that path, if any.
7383 If no path is specified, then print all existing source path substitution
7388 If your source path is cluttered with directories that are no longer of
7389 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7390 versions of source. You can correct the situation as follows:
7394 Use @code{directory} with no argument to reset the source path to its default value.
7397 Use @code{directory} with suitable arguments to reinstall the
7398 directories you want in the source path. You can add all the
7399 directories in one command.
7403 @section Source and Machine Code
7404 @cindex source line and its code address
7406 You can use the command @code{info line} to map source lines to program
7407 addresses (and vice versa), and the command @code{disassemble} to display
7408 a range of addresses as machine instructions. You can use the command
7409 @code{set disassemble-next-line} to set whether to disassemble next
7410 source line when execution stops. When run under @sc{gnu} Emacs
7411 mode, the @code{info line} command causes the arrow to point to the
7412 line specified. Also, @code{info line} prints addresses in symbolic form as
7417 @item info line @var{linespec}
7418 Print the starting and ending addresses of the compiled code for
7419 source line @var{linespec}. You can specify source lines in any of
7420 the ways documented in @ref{Specify Location}.
7423 For example, we can use @code{info line} to discover the location of
7424 the object code for the first line of function
7425 @code{m4_changequote}:
7427 @c FIXME: I think this example should also show the addresses in
7428 @c symbolic form, as they usually would be displayed.
7430 (@value{GDBP}) info line m4_changequote
7431 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7435 @cindex code address and its source line
7436 We can also inquire (using @code{*@var{addr}} as the form for
7437 @var{linespec}) what source line covers a particular address:
7439 (@value{GDBP}) info line *0x63ff
7440 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7443 @cindex @code{$_} and @code{info line}
7444 @cindex @code{x} command, default address
7445 @kindex x@r{(examine), and} info line
7446 After @code{info line}, the default address for the @code{x} command
7447 is changed to the starting address of the line, so that @samp{x/i} is
7448 sufficient to begin examining the machine code (@pxref{Memory,
7449 ,Examining Memory}). Also, this address is saved as the value of the
7450 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7455 @cindex assembly instructions
7456 @cindex instructions, assembly
7457 @cindex machine instructions
7458 @cindex listing machine instructions
7460 @itemx disassemble /m
7461 @itemx disassemble /r
7462 This specialized command dumps a range of memory as machine
7463 instructions. It can also print mixed source+disassembly by specifying
7464 the @code{/m} modifier and print the raw instructions in hex as well as
7465 in symbolic form by specifying the @code{/r}.
7466 The default memory range is the function surrounding the
7467 program counter of the selected frame. A single argument to this
7468 command is a program counter value; @value{GDBN} dumps the function
7469 surrounding this value. When two arguments are given, they should
7470 be separated by a comma, possibly surrounded by whitespace. The
7471 arguments specify a range of addresses to dump, in one of two forms:
7474 @item @var{start},@var{end}
7475 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7476 @item @var{start},+@var{length}
7477 the addresses from @var{start} (inclusive) to
7478 @code{@var{start}+@var{length}} (exclusive).
7482 When 2 arguments are specified, the name of the function is also
7483 printed (since there could be several functions in the given range).
7485 The argument(s) can be any expression yielding a numeric value, such as
7486 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7488 If the range of memory being disassembled contains current program counter,
7489 the instruction at that location is shown with a @code{=>} marker.
7492 The following example shows the disassembly of a range of addresses of
7493 HP PA-RISC 2.0 code:
7496 (@value{GDBP}) disas 0x32c4, 0x32e4
7497 Dump of assembler code from 0x32c4 to 0x32e4:
7498 0x32c4 <main+204>: addil 0,dp
7499 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7500 0x32cc <main+212>: ldil 0x3000,r31
7501 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7502 0x32d4 <main+220>: ldo 0(r31),rp
7503 0x32d8 <main+224>: addil -0x800,dp
7504 0x32dc <main+228>: ldo 0x588(r1),r26
7505 0x32e0 <main+232>: ldil 0x3000,r31
7506 End of assembler dump.
7509 Here is an example showing mixed source+assembly for Intel x86, when the
7510 program is stopped just after function prologue:
7513 (@value{GDBP}) disas /m main
7514 Dump of assembler code for function main:
7516 0x08048330 <+0>: push %ebp
7517 0x08048331 <+1>: mov %esp,%ebp
7518 0x08048333 <+3>: sub $0x8,%esp
7519 0x08048336 <+6>: and $0xfffffff0,%esp
7520 0x08048339 <+9>: sub $0x10,%esp
7522 6 printf ("Hello.\n");
7523 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7524 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7528 0x08048348 <+24>: mov $0x0,%eax
7529 0x0804834d <+29>: leave
7530 0x0804834e <+30>: ret
7532 End of assembler dump.
7535 Here is another example showing raw instructions in hex for AMD x86-64,
7538 (gdb) disas /r 0x400281,+10
7539 Dump of assembler code from 0x400281 to 0x40028b:
7540 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7541 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7542 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7543 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7544 End of assembler dump.
7547 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7548 So, for example, if you want to disassemble function @code{bar}
7549 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7550 and not @samp{disassemble foo.c:bar}.
7552 Some architectures have more than one commonly-used set of instruction
7553 mnemonics or other syntax.
7555 For programs that were dynamically linked and use shared libraries,
7556 instructions that call functions or branch to locations in the shared
7557 libraries might show a seemingly bogus location---it's actually a
7558 location of the relocation table. On some architectures, @value{GDBN}
7559 might be able to resolve these to actual function names.
7562 @kindex set disassembly-flavor
7563 @cindex Intel disassembly flavor
7564 @cindex AT&T disassembly flavor
7565 @item set disassembly-flavor @var{instruction-set}
7566 Select the instruction set to use when disassembling the
7567 program via the @code{disassemble} or @code{x/i} commands.
7569 Currently this command is only defined for the Intel x86 family. You
7570 can set @var{instruction-set} to either @code{intel} or @code{att}.
7571 The default is @code{att}, the AT&T flavor used by default by Unix
7572 assemblers for x86-based targets.
7574 @kindex show disassembly-flavor
7575 @item show disassembly-flavor
7576 Show the current setting of the disassembly flavor.
7580 @kindex set disassemble-next-line
7581 @kindex show disassemble-next-line
7582 @item set disassemble-next-line
7583 @itemx show disassemble-next-line
7584 Control whether or not @value{GDBN} will disassemble the next source
7585 line or instruction when execution stops. If ON, @value{GDBN} will
7586 display disassembly of the next source line when execution of the
7587 program being debugged stops. This is @emph{in addition} to
7588 displaying the source line itself, which @value{GDBN} always does if
7589 possible. If the next source line cannot be displayed for some reason
7590 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7591 info in the debug info), @value{GDBN} will display disassembly of the
7592 next @emph{instruction} instead of showing the next source line. If
7593 AUTO, @value{GDBN} will display disassembly of next instruction only
7594 if the source line cannot be displayed. This setting causes
7595 @value{GDBN} to display some feedback when you step through a function
7596 with no line info or whose source file is unavailable. The default is
7597 OFF, which means never display the disassembly of the next line or
7603 @chapter Examining Data
7605 @cindex printing data
7606 @cindex examining data
7609 The usual way to examine data in your program is with the @code{print}
7610 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7611 evaluates and prints the value of an expression of the language your
7612 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7613 Different Languages}). It may also print the expression using a
7614 Python-based pretty-printer (@pxref{Pretty Printing}).
7617 @item print @var{expr}
7618 @itemx print /@var{f} @var{expr}
7619 @var{expr} is an expression (in the source language). By default the
7620 value of @var{expr} is printed in a format appropriate to its data type;
7621 you can choose a different format by specifying @samp{/@var{f}}, where
7622 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7626 @itemx print /@var{f}
7627 @cindex reprint the last value
7628 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7629 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7630 conveniently inspect the same value in an alternative format.
7633 A more low-level way of examining data is with the @code{x} command.
7634 It examines data in memory at a specified address and prints it in a
7635 specified format. @xref{Memory, ,Examining Memory}.
7637 If you are interested in information about types, or about how the
7638 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7639 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7642 @cindex exploring hierarchical data structures
7644 Another way of examining values of expressions and type information is
7645 through the Python extension command @code{explore} (available only if
7646 the @value{GDBN} build is configured with @code{--with-python}). It
7647 offers an interactive way to start at the highest level (or, the most
7648 abstract level) of the data type of an expression (or, the data type
7649 itself) and explore all the way down to leaf scalar values/fields
7650 embedded in the higher level data types.
7653 @item explore @var{arg}
7654 @var{arg} is either an expression (in the source language), or a type
7655 visible in the current context of the program being debugged.
7658 The working of the @code{explore} command can be illustrated with an
7659 example. If a data type @code{struct ComplexStruct} is defined in your
7669 struct ComplexStruct
7671 struct SimpleStruct *ss_p;
7677 followed by variable declarations as
7680 struct SimpleStruct ss = @{ 10, 1.11 @};
7681 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7685 then, the value of the variable @code{cs} can be explored using the
7686 @code{explore} command as follows.
7690 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7691 the following fields:
7693 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7694 arr = <Enter 1 to explore this field of type `int [10]'>
7696 Enter the field number of choice:
7700 Since the fields of @code{cs} are not scalar values, you are being
7701 prompted to chose the field you want to explore. Let's say you choose
7702 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7703 pointer, you will be asked if it is pointing to a single value. From
7704 the declaration of @code{cs} above, it is indeed pointing to a single
7705 value, hence you enter @code{y}. If you enter @code{n}, then you will
7706 be asked if it were pointing to an array of values, in which case this
7707 field will be explored as if it were an array.
7710 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7711 Continue exploring it as a pointer to a single value [y/n]: y
7712 The value of `*(cs.ss_p)' is a struct/class of type `struct
7713 SimpleStruct' with the following fields:
7715 i = 10 .. (Value of type `int')
7716 d = 1.1100000000000001 .. (Value of type `double')
7718 Press enter to return to parent value:
7722 If the field @code{arr} of @code{cs} was chosen for exploration by
7723 entering @code{1} earlier, then since it is as array, you will be
7724 prompted to enter the index of the element in the array that you want
7728 `cs.arr' is an array of `int'.
7729 Enter the index of the element you want to explore in `cs.arr': 5
7731 `(cs.arr)[5]' is a scalar value of type `int'.
7735 Press enter to return to parent value:
7738 In general, at any stage of exploration, you can go deeper towards the
7739 leaf values by responding to the prompts appropriately, or hit the
7740 return key to return to the enclosing data structure (the @i{higher}
7741 level data structure).
7743 Similar to exploring values, you can use the @code{explore} command to
7744 explore types. Instead of specifying a value (which is typically a
7745 variable name or an expression valid in the current context of the
7746 program being debugged), you specify a type name. If you consider the
7747 same example as above, your can explore the type
7748 @code{struct ComplexStruct} by passing the argument
7749 @code{struct ComplexStruct} to the @code{explore} command.
7752 (gdb) explore struct ComplexStruct
7756 By responding to the prompts appropriately in the subsequent interactive
7757 session, you can explore the type @code{struct ComplexStruct} in a
7758 manner similar to how the value @code{cs} was explored in the above
7761 The @code{explore} command also has two sub-commands,
7762 @code{explore value} and @code{explore type}. The former sub-command is
7763 a way to explicitly specify that value exploration of the argument is
7764 being invoked, while the latter is a way to explicitly specify that type
7765 exploration of the argument is being invoked.
7768 @item explore value @var{expr}
7769 @cindex explore value
7770 This sub-command of @code{explore} explores the value of the
7771 expression @var{expr} (if @var{expr} is an expression valid in the
7772 current context of the program being debugged). The behavior of this
7773 command is identical to that of the behavior of the @code{explore}
7774 command being passed the argument @var{expr}.
7776 @item explore type @var{arg}
7777 @cindex explore type
7778 This sub-command of @code{explore} explores the type of @var{arg} (if
7779 @var{arg} is a type visible in the current context of program being
7780 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7781 is an expression valid in the current context of the program being
7782 debugged). If @var{arg} is a type, then the behavior of this command is
7783 identical to that of the @code{explore} command being passed the
7784 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7785 this command will be identical to that of the @code{explore} command
7786 being passed the type of @var{arg} as the argument.
7790 * Expressions:: Expressions
7791 * Ambiguous Expressions:: Ambiguous Expressions
7792 * Variables:: Program variables
7793 * Arrays:: Artificial arrays
7794 * Output Formats:: Output formats
7795 * Memory:: Examining memory
7796 * Auto Display:: Automatic display
7797 * Print Settings:: Print settings
7798 * Pretty Printing:: Python pretty printing
7799 * Value History:: Value history
7800 * Convenience Vars:: Convenience variables
7801 * Convenience Funs:: Convenience functions
7802 * Registers:: Registers
7803 * Floating Point Hardware:: Floating point hardware
7804 * Vector Unit:: Vector Unit
7805 * OS Information:: Auxiliary data provided by operating system
7806 * Memory Region Attributes:: Memory region attributes
7807 * Dump/Restore Files:: Copy between memory and a file
7808 * Core File Generation:: Cause a program dump its core
7809 * Character Sets:: Debugging programs that use a different
7810 character set than GDB does
7811 * Caching Remote Data:: Data caching for remote targets
7812 * Searching Memory:: Searching memory for a sequence of bytes
7816 @section Expressions
7819 @code{print} and many other @value{GDBN} commands accept an expression and
7820 compute its value. Any kind of constant, variable or operator defined
7821 by the programming language you are using is valid in an expression in
7822 @value{GDBN}. This includes conditional expressions, function calls,
7823 casts, and string constants. It also includes preprocessor macros, if
7824 you compiled your program to include this information; see
7827 @cindex arrays in expressions
7828 @value{GDBN} supports array constants in expressions input by
7829 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7830 you can use the command @code{print @{1, 2, 3@}} to create an array
7831 of three integers. If you pass an array to a function or assign it
7832 to a program variable, @value{GDBN} copies the array to memory that
7833 is @code{malloc}ed in the target program.
7835 Because C is so widespread, most of the expressions shown in examples in
7836 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7837 Languages}, for information on how to use expressions in other
7840 In this section, we discuss operators that you can use in @value{GDBN}
7841 expressions regardless of your programming language.
7843 @cindex casts, in expressions
7844 Casts are supported in all languages, not just in C, because it is so
7845 useful to cast a number into a pointer in order to examine a structure
7846 at that address in memory.
7847 @c FIXME: casts supported---Mod2 true?
7849 @value{GDBN} supports these operators, in addition to those common
7850 to programming languages:
7854 @samp{@@} is a binary operator for treating parts of memory as arrays.
7855 @xref{Arrays, ,Artificial Arrays}, for more information.
7858 @samp{::} allows you to specify a variable in terms of the file or
7859 function where it is defined. @xref{Variables, ,Program Variables}.
7861 @cindex @{@var{type}@}
7862 @cindex type casting memory
7863 @cindex memory, viewing as typed object
7864 @cindex casts, to view memory
7865 @item @{@var{type}@} @var{addr}
7866 Refers to an object of type @var{type} stored at address @var{addr} in
7867 memory. @var{addr} may be any expression whose value is an integer or
7868 pointer (but parentheses are required around binary operators, just as in
7869 a cast). This construct is allowed regardless of what kind of data is
7870 normally supposed to reside at @var{addr}.
7873 @node Ambiguous Expressions
7874 @section Ambiguous Expressions
7875 @cindex ambiguous expressions
7877 Expressions can sometimes contain some ambiguous elements. For instance,
7878 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7879 a single function name to be defined several times, for application in
7880 different contexts. This is called @dfn{overloading}. Another example
7881 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7882 templates and is typically instantiated several times, resulting in
7883 the same function name being defined in different contexts.
7885 In some cases and depending on the language, it is possible to adjust
7886 the expression to remove the ambiguity. For instance in C@t{++}, you
7887 can specify the signature of the function you want to break on, as in
7888 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7889 qualified name of your function often makes the expression unambiguous
7892 When an ambiguity that needs to be resolved is detected, the debugger
7893 has the capability to display a menu of numbered choices for each
7894 possibility, and then waits for the selection with the prompt @samp{>}.
7895 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7896 aborts the current command. If the command in which the expression was
7897 used allows more than one choice to be selected, the next option in the
7898 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7901 For example, the following session excerpt shows an attempt to set a
7902 breakpoint at the overloaded symbol @code{String::after}.
7903 We choose three particular definitions of that function name:
7905 @c FIXME! This is likely to change to show arg type lists, at least
7908 (@value{GDBP}) b String::after
7911 [2] file:String.cc; line number:867
7912 [3] file:String.cc; line number:860
7913 [4] file:String.cc; line number:875
7914 [5] file:String.cc; line number:853
7915 [6] file:String.cc; line number:846
7916 [7] file:String.cc; line number:735
7918 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7919 Breakpoint 2 at 0xb344: file String.cc, line 875.
7920 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7921 Multiple breakpoints were set.
7922 Use the "delete" command to delete unwanted
7929 @kindex set multiple-symbols
7930 @item set multiple-symbols @var{mode}
7931 @cindex multiple-symbols menu
7933 This option allows you to adjust the debugger behavior when an expression
7936 By default, @var{mode} is set to @code{all}. If the command with which
7937 the expression is used allows more than one choice, then @value{GDBN}
7938 automatically selects all possible choices. For instance, inserting
7939 a breakpoint on a function using an ambiguous name results in a breakpoint
7940 inserted on each possible match. However, if a unique choice must be made,
7941 then @value{GDBN} uses the menu to help you disambiguate the expression.
7942 For instance, printing the address of an overloaded function will result
7943 in the use of the menu.
7945 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7946 when an ambiguity is detected.
7948 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7949 an error due to the ambiguity and the command is aborted.
7951 @kindex show multiple-symbols
7952 @item show multiple-symbols
7953 Show the current value of the @code{multiple-symbols} setting.
7957 @section Program Variables
7959 The most common kind of expression to use is the name of a variable
7962 Variables in expressions are understood in the selected stack frame
7963 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7967 global (or file-static)
7974 visible according to the scope rules of the
7975 programming language from the point of execution in that frame
7978 @noindent This means that in the function
7993 you can examine and use the variable @code{a} whenever your program is
7994 executing within the function @code{foo}, but you can only use or
7995 examine the variable @code{b} while your program is executing inside
7996 the block where @code{b} is declared.
7998 @cindex variable name conflict
7999 There is an exception: you can refer to a variable or function whose
8000 scope is a single source file even if the current execution point is not
8001 in this file. But it is possible to have more than one such variable or
8002 function with the same name (in different source files). If that
8003 happens, referring to that name has unpredictable effects. If you wish,
8004 you can specify a static variable in a particular function or file by
8005 using the colon-colon (@code{::}) notation:
8007 @cindex colon-colon, context for variables/functions
8009 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8010 @cindex @code{::}, context for variables/functions
8013 @var{file}::@var{variable}
8014 @var{function}::@var{variable}
8018 Here @var{file} or @var{function} is the name of the context for the
8019 static @var{variable}. In the case of file names, you can use quotes to
8020 make sure @value{GDBN} parses the file name as a single word---for example,
8021 to print a global value of @code{x} defined in @file{f2.c}:
8024 (@value{GDBP}) p 'f2.c'::x
8027 The @code{::} notation is normally used for referring to
8028 static variables, since you typically disambiguate uses of local variables
8029 in functions by selecting the appropriate frame and using the
8030 simple name of the variable. However, you may also use this notation
8031 to refer to local variables in frames enclosing the selected frame:
8040 process (a); /* Stop here */
8051 For example, if there is a breakpoint at the commented line,
8052 here is what you might see
8053 when the program stops after executing the call @code{bar(0)}:
8058 (@value{GDBP}) p bar::a
8061 #2 0x080483d0 in foo (a=5) at foobar.c:12
8064 (@value{GDBP}) p bar::a
8068 @cindex C@t{++} scope resolution
8069 These uses of @samp{::} are very rarely in conflict with the very similar
8070 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8071 scope resolution operator in @value{GDBN} expressions.
8072 @c FIXME: Um, so what happens in one of those rare cases where it's in
8075 @cindex wrong values
8076 @cindex variable values, wrong
8077 @cindex function entry/exit, wrong values of variables
8078 @cindex optimized code, wrong values of variables
8080 @emph{Warning:} Occasionally, a local variable may appear to have the
8081 wrong value at certain points in a function---just after entry to a new
8082 scope, and just before exit.
8084 You may see this problem when you are stepping by machine instructions.
8085 This is because, on most machines, it takes more than one instruction to
8086 set up a stack frame (including local variable definitions); if you are
8087 stepping by machine instructions, variables may appear to have the wrong
8088 values until the stack frame is completely built. On exit, it usually
8089 also takes more than one machine instruction to destroy a stack frame;
8090 after you begin stepping through that group of instructions, local
8091 variable definitions may be gone.
8093 This may also happen when the compiler does significant optimizations.
8094 To be sure of always seeing accurate values, turn off all optimization
8097 @cindex ``No symbol "foo" in current context''
8098 Another possible effect of compiler optimizations is to optimize
8099 unused variables out of existence, or assign variables to registers (as
8100 opposed to memory addresses). Depending on the support for such cases
8101 offered by the debug info format used by the compiler, @value{GDBN}
8102 might not be able to display values for such local variables. If that
8103 happens, @value{GDBN} will print a message like this:
8106 No symbol "foo" in current context.
8109 To solve such problems, either recompile without optimizations, or use a
8110 different debug info format, if the compiler supports several such
8111 formats. @xref{Compilation}, for more information on choosing compiler
8112 options. @xref{C, ,C and C@t{++}}, for more information about debug
8113 info formats that are best suited to C@t{++} programs.
8115 If you ask to print an object whose contents are unknown to
8116 @value{GDBN}, e.g., because its data type is not completely specified
8117 by the debug information, @value{GDBN} will say @samp{<incomplete
8118 type>}. @xref{Symbols, incomplete type}, for more about this.
8120 If you append @kbd{@@entry} string to a function parameter name you get its
8121 value at the time the function got called. If the value is not available an
8122 error message is printed. Entry values are available only with some compilers.
8123 Entry values are normally also printed at the function parameter list according
8124 to @ref{set print entry-values}.
8127 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8133 (gdb) print i@@entry
8137 Strings are identified as arrays of @code{char} values without specified
8138 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8139 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8140 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8141 defines literal string type @code{"char"} as @code{char} without a sign.
8146 signed char var1[] = "A";
8149 You get during debugging
8154 $2 = @{65 'A', 0 '\0'@}
8158 @section Artificial Arrays
8160 @cindex artificial array
8162 @kindex @@@r{, referencing memory as an array}
8163 It is often useful to print out several successive objects of the
8164 same type in memory; a section of an array, or an array of
8165 dynamically determined size for which only a pointer exists in the
8168 You can do this by referring to a contiguous span of memory as an
8169 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8170 operand of @samp{@@} should be the first element of the desired array
8171 and be an individual object. The right operand should be the desired length
8172 of the array. The result is an array value whose elements are all of
8173 the type of the left argument. The first element is actually the left
8174 argument; the second element comes from bytes of memory immediately
8175 following those that hold the first element, and so on. Here is an
8176 example. If a program says
8179 int *array = (int *) malloc (len * sizeof (int));
8183 you can print the contents of @code{array} with
8189 The left operand of @samp{@@} must reside in memory. Array values made
8190 with @samp{@@} in this way behave just like other arrays in terms of
8191 subscripting, and are coerced to pointers when used in expressions.
8192 Artificial arrays most often appear in expressions via the value history
8193 (@pxref{Value History, ,Value History}), after printing one out.
8195 Another way to create an artificial array is to use a cast.
8196 This re-interprets a value as if it were an array.
8197 The value need not be in memory:
8199 (@value{GDBP}) p/x (short[2])0x12345678
8200 $1 = @{0x1234, 0x5678@}
8203 As a convenience, if you leave the array length out (as in
8204 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8205 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8207 (@value{GDBP}) p/x (short[])0x12345678
8208 $2 = @{0x1234, 0x5678@}
8211 Sometimes the artificial array mechanism is not quite enough; in
8212 moderately complex data structures, the elements of interest may not
8213 actually be adjacent---for example, if you are interested in the values
8214 of pointers in an array. One useful work-around in this situation is
8215 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8216 Variables}) as a counter in an expression that prints the first
8217 interesting value, and then repeat that expression via @key{RET}. For
8218 instance, suppose you have an array @code{dtab} of pointers to
8219 structures, and you are interested in the values of a field @code{fv}
8220 in each structure. Here is an example of what you might type:
8230 @node Output Formats
8231 @section Output Formats
8233 @cindex formatted output
8234 @cindex output formats
8235 By default, @value{GDBN} prints a value according to its data type. Sometimes
8236 this is not what you want. For example, you might want to print a number
8237 in hex, or a pointer in decimal. Or you might want to view data in memory
8238 at a certain address as a character string or as an instruction. To do
8239 these things, specify an @dfn{output format} when you print a value.
8241 The simplest use of output formats is to say how to print a value
8242 already computed. This is done by starting the arguments of the
8243 @code{print} command with a slash and a format letter. The format
8244 letters supported are:
8248 Regard the bits of the value as an integer, and print the integer in
8252 Print as integer in signed decimal.
8255 Print as integer in unsigned decimal.
8258 Print as integer in octal.
8261 Print as integer in binary. The letter @samp{t} stands for ``two''.
8262 @footnote{@samp{b} cannot be used because these format letters are also
8263 used with the @code{x} command, where @samp{b} stands for ``byte'';
8264 see @ref{Memory,,Examining Memory}.}
8267 @cindex unknown address, locating
8268 @cindex locate address
8269 Print as an address, both absolute in hexadecimal and as an offset from
8270 the nearest preceding symbol. You can use this format used to discover
8271 where (in what function) an unknown address is located:
8274 (@value{GDBP}) p/a 0x54320
8275 $3 = 0x54320 <_initialize_vx+396>
8279 The command @code{info symbol 0x54320} yields similar results.
8280 @xref{Symbols, info symbol}.
8283 Regard as an integer and print it as a character constant. This
8284 prints both the numerical value and its character representation. The
8285 character representation is replaced with the octal escape @samp{\nnn}
8286 for characters outside the 7-bit @sc{ascii} range.
8288 Without this format, @value{GDBN} displays @code{char},
8289 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8290 constants. Single-byte members of vectors are displayed as integer
8294 Regard the bits of the value as a floating point number and print
8295 using typical floating point syntax.
8298 @cindex printing strings
8299 @cindex printing byte arrays
8300 Regard as a string, if possible. With this format, pointers to single-byte
8301 data are displayed as null-terminated strings and arrays of single-byte data
8302 are displayed as fixed-length strings. Other values are displayed in their
8305 Without this format, @value{GDBN} displays pointers to and arrays of
8306 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8307 strings. Single-byte members of a vector are displayed as an integer
8311 @cindex raw printing
8312 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8313 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8314 Printing}). This typically results in a higher-level display of the
8315 value's contents. The @samp{r} format bypasses any Python
8316 pretty-printer which might exist.
8319 For example, to print the program counter in hex (@pxref{Registers}), type
8326 Note that no space is required before the slash; this is because command
8327 names in @value{GDBN} cannot contain a slash.
8329 To reprint the last value in the value history with a different format,
8330 you can use the @code{print} command with just a format and no
8331 expression. For example, @samp{p/x} reprints the last value in hex.
8334 @section Examining Memory
8336 You can use the command @code{x} (for ``examine'') to examine memory in
8337 any of several formats, independently of your program's data types.
8339 @cindex examining memory
8341 @kindex x @r{(examine memory)}
8342 @item x/@var{nfu} @var{addr}
8345 Use the @code{x} command to examine memory.
8348 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8349 much memory to display and how to format it; @var{addr} is an
8350 expression giving the address where you want to start displaying memory.
8351 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8352 Several commands set convenient defaults for @var{addr}.
8355 @item @var{n}, the repeat count
8356 The repeat count is a decimal integer; the default is 1. It specifies
8357 how much memory (counting by units @var{u}) to display.
8358 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8361 @item @var{f}, the display format
8362 The display format is one of the formats used by @code{print}
8363 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8364 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8365 The default is @samp{x} (hexadecimal) initially. The default changes
8366 each time you use either @code{x} or @code{print}.
8368 @item @var{u}, the unit size
8369 The unit size is any of
8375 Halfwords (two bytes).
8377 Words (four bytes). This is the initial default.
8379 Giant words (eight bytes).
8382 Each time you specify a unit size with @code{x}, that size becomes the
8383 default unit the next time you use @code{x}. For the @samp{i} format,
8384 the unit size is ignored and is normally not written. For the @samp{s} format,
8385 the unit size defaults to @samp{b}, unless it is explicitly given.
8386 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8387 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8388 Note that the results depend on the programming language of the
8389 current compilation unit. If the language is C, the @samp{s}
8390 modifier will use the UTF-16 encoding while @samp{w} will use
8391 UTF-32. The encoding is set by the programming language and cannot
8394 @item @var{addr}, starting display address
8395 @var{addr} is the address where you want @value{GDBN} to begin displaying
8396 memory. The expression need not have a pointer value (though it may);
8397 it is always interpreted as an integer address of a byte of memory.
8398 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8399 @var{addr} is usually just after the last address examined---but several
8400 other commands also set the default address: @code{info breakpoints} (to
8401 the address of the last breakpoint listed), @code{info line} (to the
8402 starting address of a line), and @code{print} (if you use it to display
8403 a value from memory).
8406 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8407 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8408 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8409 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8410 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8412 Since the letters indicating unit sizes are all distinct from the
8413 letters specifying output formats, you do not have to remember whether
8414 unit size or format comes first; either order works. The output
8415 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8416 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8418 Even though the unit size @var{u} is ignored for the formats @samp{s}
8419 and @samp{i}, you might still want to use a count @var{n}; for example,
8420 @samp{3i} specifies that you want to see three machine instructions,
8421 including any operands. For convenience, especially when used with
8422 the @code{display} command, the @samp{i} format also prints branch delay
8423 slot instructions, if any, beyond the count specified, which immediately
8424 follow the last instruction that is within the count. The command
8425 @code{disassemble} gives an alternative way of inspecting machine
8426 instructions; see @ref{Machine Code,,Source and Machine Code}.
8428 All the defaults for the arguments to @code{x} are designed to make it
8429 easy to continue scanning memory with minimal specifications each time
8430 you use @code{x}. For example, after you have inspected three machine
8431 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8432 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8433 the repeat count @var{n} is used again; the other arguments default as
8434 for successive uses of @code{x}.
8436 When examining machine instructions, the instruction at current program
8437 counter is shown with a @code{=>} marker. For example:
8440 (@value{GDBP}) x/5i $pc-6
8441 0x804837f <main+11>: mov %esp,%ebp
8442 0x8048381 <main+13>: push %ecx
8443 0x8048382 <main+14>: sub $0x4,%esp
8444 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8445 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8448 @cindex @code{$_}, @code{$__}, and value history
8449 The addresses and contents printed by the @code{x} command are not saved
8450 in the value history because there is often too much of them and they
8451 would get in the way. Instead, @value{GDBN} makes these values available for
8452 subsequent use in expressions as values of the convenience variables
8453 @code{$_} and @code{$__}. After an @code{x} command, the last address
8454 examined is available for use in expressions in the convenience variable
8455 @code{$_}. The contents of that address, as examined, are available in
8456 the convenience variable @code{$__}.
8458 If the @code{x} command has a repeat count, the address and contents saved
8459 are from the last memory unit printed; this is not the same as the last
8460 address printed if several units were printed on the last line of output.
8462 @cindex remote memory comparison
8463 @cindex verify remote memory image
8464 When you are debugging a program running on a remote target machine
8465 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8466 remote machine's memory against the executable file you downloaded to
8467 the target. The @code{compare-sections} command is provided for such
8471 @kindex compare-sections
8472 @item compare-sections @r{[}@var{section-name}@r{]}
8473 Compare the data of a loadable section @var{section-name} in the
8474 executable file of the program being debugged with the same section in
8475 the remote machine's memory, and report any mismatches. With no
8476 arguments, compares all loadable sections. This command's
8477 availability depends on the target's support for the @code{"qCRC"}
8482 @section Automatic Display
8483 @cindex automatic display
8484 @cindex display of expressions
8486 If you find that you want to print the value of an expression frequently
8487 (to see how it changes), you might want to add it to the @dfn{automatic
8488 display list} so that @value{GDBN} prints its value each time your program stops.
8489 Each expression added to the list is given a number to identify it;
8490 to remove an expression from the list, you specify that number.
8491 The automatic display looks like this:
8495 3: bar[5] = (struct hack *) 0x3804
8499 This display shows item numbers, expressions and their current values. As with
8500 displays you request manually using @code{x} or @code{print}, you can
8501 specify the output format you prefer; in fact, @code{display} decides
8502 whether to use @code{print} or @code{x} depending your format
8503 specification---it uses @code{x} if you specify either the @samp{i}
8504 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8508 @item display @var{expr}
8509 Add the expression @var{expr} to the list of expressions to display
8510 each time your program stops. @xref{Expressions, ,Expressions}.
8512 @code{display} does not repeat if you press @key{RET} again after using it.
8514 @item display/@var{fmt} @var{expr}
8515 For @var{fmt} specifying only a display format and not a size or
8516 count, add the expression @var{expr} to the auto-display list but
8517 arrange to display it each time in the specified format @var{fmt}.
8518 @xref{Output Formats,,Output Formats}.
8520 @item display/@var{fmt} @var{addr}
8521 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8522 number of units, add the expression @var{addr} as a memory address to
8523 be examined each time your program stops. Examining means in effect
8524 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8527 For example, @samp{display/i $pc} can be helpful, to see the machine
8528 instruction about to be executed each time execution stops (@samp{$pc}
8529 is a common name for the program counter; @pxref{Registers, ,Registers}).
8532 @kindex delete display
8534 @item undisplay @var{dnums}@dots{}
8535 @itemx delete display @var{dnums}@dots{}
8536 Remove items from the list of expressions to display. Specify the
8537 numbers of the displays that you want affected with the command
8538 argument @var{dnums}. It can be a single display number, one of the
8539 numbers shown in the first field of the @samp{info display} display;
8540 or it could be a range of display numbers, as in @code{2-4}.
8542 @code{undisplay} does not repeat if you press @key{RET} after using it.
8543 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8545 @kindex disable display
8546 @item disable display @var{dnums}@dots{}
8547 Disable the display of item numbers @var{dnums}. A disabled display
8548 item is not printed automatically, but is not forgotten. It may be
8549 enabled again later. Specify the numbers of the displays that you
8550 want affected with the command argument @var{dnums}. It can be a
8551 single display number, one of the numbers shown in the first field of
8552 the @samp{info display} display; or it could be a range of display
8553 numbers, as in @code{2-4}.
8555 @kindex enable display
8556 @item enable display @var{dnums}@dots{}
8557 Enable display of item numbers @var{dnums}. It becomes effective once
8558 again in auto display of its expression, until you specify otherwise.
8559 Specify the numbers of the displays that you want affected with the
8560 command argument @var{dnums}. It can be a single display number, one
8561 of the numbers shown in the first field of the @samp{info display}
8562 display; or it could be a range of display numbers, as in @code{2-4}.
8565 Display the current values of the expressions on the list, just as is
8566 done when your program stops.
8568 @kindex info display
8570 Print the list of expressions previously set up to display
8571 automatically, each one with its item number, but without showing the
8572 values. This includes disabled expressions, which are marked as such.
8573 It also includes expressions which would not be displayed right now
8574 because they refer to automatic variables not currently available.
8577 @cindex display disabled out of scope
8578 If a display expression refers to local variables, then it does not make
8579 sense outside the lexical context for which it was set up. Such an
8580 expression is disabled when execution enters a context where one of its
8581 variables is not defined. For example, if you give the command
8582 @code{display last_char} while inside a function with an argument
8583 @code{last_char}, @value{GDBN} displays this argument while your program
8584 continues to stop inside that function. When it stops elsewhere---where
8585 there is no variable @code{last_char}---the display is disabled
8586 automatically. The next time your program stops where @code{last_char}
8587 is meaningful, you can enable the display expression once again.
8589 @node Print Settings
8590 @section Print Settings
8592 @cindex format options
8593 @cindex print settings
8594 @value{GDBN} provides the following ways to control how arrays, structures,
8595 and symbols are printed.
8598 These settings are useful for debugging programs in any language:
8602 @item set print address
8603 @itemx set print address on
8604 @cindex print/don't print memory addresses
8605 @value{GDBN} prints memory addresses showing the location of stack
8606 traces, structure values, pointer values, breakpoints, and so forth,
8607 even when it also displays the contents of those addresses. The default
8608 is @code{on}. For example, this is what a stack frame display looks like with
8609 @code{set print address on}:
8614 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8616 530 if (lquote != def_lquote)
8620 @item set print address off
8621 Do not print addresses when displaying their contents. For example,
8622 this is the same stack frame displayed with @code{set print address off}:
8626 (@value{GDBP}) set print addr off
8628 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8629 530 if (lquote != def_lquote)
8633 You can use @samp{set print address off} to eliminate all machine
8634 dependent displays from the @value{GDBN} interface. For example, with
8635 @code{print address off}, you should get the same text for backtraces on
8636 all machines---whether or not they involve pointer arguments.
8639 @item show print address
8640 Show whether or not addresses are to be printed.
8643 When @value{GDBN} prints a symbolic address, it normally prints the
8644 closest earlier symbol plus an offset. If that symbol does not uniquely
8645 identify the address (for example, it is a name whose scope is a single
8646 source file), you may need to clarify. One way to do this is with
8647 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8648 you can set @value{GDBN} to print the source file and line number when
8649 it prints a symbolic address:
8652 @item set print symbol-filename on
8653 @cindex source file and line of a symbol
8654 @cindex symbol, source file and line
8655 Tell @value{GDBN} to print the source file name and line number of a
8656 symbol in the symbolic form of an address.
8658 @item set print symbol-filename off
8659 Do not print source file name and line number of a symbol. This is the
8662 @item show print symbol-filename
8663 Show whether or not @value{GDBN} will print the source file name and
8664 line number of a symbol in the symbolic form of an address.
8667 Another situation where it is helpful to show symbol filenames and line
8668 numbers is when disassembling code; @value{GDBN} shows you the line
8669 number and source file that corresponds to each instruction.
8671 Also, you may wish to see the symbolic form only if the address being
8672 printed is reasonably close to the closest earlier symbol:
8675 @item set print max-symbolic-offset @var{max-offset}
8676 @itemx set print max-symbolic-offset unlimited
8677 @cindex maximum value for offset of closest symbol
8678 Tell @value{GDBN} to only display the symbolic form of an address if the
8679 offset between the closest earlier symbol and the address is less than
8680 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8681 to always print the symbolic form of an address if any symbol precedes
8682 it. Zero is equivalent to @code{unlimited}.
8684 @item show print max-symbolic-offset
8685 Ask how large the maximum offset is that @value{GDBN} prints in a
8689 @cindex wild pointer, interpreting
8690 @cindex pointer, finding referent
8691 If you have a pointer and you are not sure where it points, try
8692 @samp{set print symbol-filename on}. Then you can determine the name
8693 and source file location of the variable where it points, using
8694 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8695 For example, here @value{GDBN} shows that a variable @code{ptt} points
8696 at another variable @code{t}, defined in @file{hi2.c}:
8699 (@value{GDBP}) set print symbol-filename on
8700 (@value{GDBP}) p/a ptt
8701 $4 = 0xe008 <t in hi2.c>
8705 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8706 does not show the symbol name and filename of the referent, even with
8707 the appropriate @code{set print} options turned on.
8710 You can also enable @samp{/a}-like formatting all the time using
8711 @samp{set print symbol on}:
8714 @item set print symbol on
8715 Tell @value{GDBN} to print the symbol corresponding to an address, if
8718 @item set print symbol off
8719 Tell @value{GDBN} not to print the symbol corresponding to an
8720 address. In this mode, @value{GDBN} will still print the symbol
8721 corresponding to pointers to functions. This is the default.
8723 @item show print symbol
8724 Show whether @value{GDBN} will display the symbol corresponding to an
8728 Other settings control how different kinds of objects are printed:
8731 @item set print array
8732 @itemx set print array on
8733 @cindex pretty print arrays
8734 Pretty print arrays. This format is more convenient to read,
8735 but uses more space. The default is off.
8737 @item set print array off
8738 Return to compressed format for arrays.
8740 @item show print array
8741 Show whether compressed or pretty format is selected for displaying
8744 @cindex print array indexes
8745 @item set print array-indexes
8746 @itemx set print array-indexes on
8747 Print the index of each element when displaying arrays. May be more
8748 convenient to locate a given element in the array or quickly find the
8749 index of a given element in that printed array. The default is off.
8751 @item set print array-indexes off
8752 Stop printing element indexes when displaying arrays.
8754 @item show print array-indexes
8755 Show whether the index of each element is printed when displaying
8758 @item set print elements @var{number-of-elements}
8759 @itemx set print elements unlimited
8760 @cindex number of array elements to print
8761 @cindex limit on number of printed array elements
8762 Set a limit on how many elements of an array @value{GDBN} will print.
8763 If @value{GDBN} is printing a large array, it stops printing after it has
8764 printed the number of elements set by the @code{set print elements} command.
8765 This limit also applies to the display of strings.
8766 When @value{GDBN} starts, this limit is set to 200.
8767 Setting @var{number-of-elements} to @code{unlimited} or zero means
8768 that the number of elements to print is unlimited.
8770 @item show print elements
8771 Display the number of elements of a large array that @value{GDBN} will print.
8772 If the number is 0, then the printing is unlimited.
8774 @item set print frame-arguments @var{value}
8775 @kindex set print frame-arguments
8776 @cindex printing frame argument values
8777 @cindex print all frame argument values
8778 @cindex print frame argument values for scalars only
8779 @cindex do not print frame argument values
8780 This command allows to control how the values of arguments are printed
8781 when the debugger prints a frame (@pxref{Frames}). The possible
8786 The values of all arguments are printed.
8789 Print the value of an argument only if it is a scalar. The value of more
8790 complex arguments such as arrays, structures, unions, etc, is replaced
8791 by @code{@dots{}}. This is the default. Here is an example where
8792 only scalar arguments are shown:
8795 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8800 None of the argument values are printed. Instead, the value of each argument
8801 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8804 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8809 By default, only scalar arguments are printed. This command can be used
8810 to configure the debugger to print the value of all arguments, regardless
8811 of their type. However, it is often advantageous to not print the value
8812 of more complex parameters. For instance, it reduces the amount of
8813 information printed in each frame, making the backtrace more readable.
8814 Also, it improves performance when displaying Ada frames, because
8815 the computation of large arguments can sometimes be CPU-intensive,
8816 especially in large applications. Setting @code{print frame-arguments}
8817 to @code{scalars} (the default) or @code{none} avoids this computation,
8818 thus speeding up the display of each Ada frame.
8820 @item show print frame-arguments
8821 Show how the value of arguments should be displayed when printing a frame.
8823 @anchor{set print entry-values}
8824 @item set print entry-values @var{value}
8825 @kindex set print entry-values
8826 Set printing of frame argument values at function entry. In some cases
8827 @value{GDBN} can determine the value of function argument which was passed by
8828 the function caller, even if the value was modified inside the called function
8829 and therefore is different. With optimized code, the current value could be
8830 unavailable, but the entry value may still be known.
8832 The default value is @code{default} (see below for its description). Older
8833 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8834 this feature will behave in the @code{default} setting the same way as with the
8837 This functionality is currently supported only by DWARF 2 debugging format and
8838 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8839 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8842 The @var{value} parameter can be one of the following:
8846 Print only actual parameter values, never print values from function entry
8850 #0 different (val=6)
8851 #0 lost (val=<optimized out>)
8853 #0 invalid (val=<optimized out>)
8857 Print only parameter values from function entry point. The actual parameter
8858 values are never printed.
8860 #0 equal (val@@entry=5)
8861 #0 different (val@@entry=5)
8862 #0 lost (val@@entry=5)
8863 #0 born (val@@entry=<optimized out>)
8864 #0 invalid (val@@entry=<optimized out>)
8868 Print only parameter values from function entry point. If value from function
8869 entry point is not known while the actual value is known, print the actual
8870 value for such parameter.
8872 #0 equal (val@@entry=5)
8873 #0 different (val@@entry=5)
8874 #0 lost (val@@entry=5)
8876 #0 invalid (val@@entry=<optimized out>)
8880 Print actual parameter values. If actual parameter value is not known while
8881 value from function entry point is known, print the entry point value for such
8885 #0 different (val=6)
8886 #0 lost (val@@entry=5)
8888 #0 invalid (val=<optimized out>)
8892 Always print both the actual parameter value and its value from function entry
8893 point, even if values of one or both are not available due to compiler
8896 #0 equal (val=5, val@@entry=5)
8897 #0 different (val=6, val@@entry=5)
8898 #0 lost (val=<optimized out>, val@@entry=5)
8899 #0 born (val=10, val@@entry=<optimized out>)
8900 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8904 Print the actual parameter value if it is known and also its value from
8905 function entry point if it is known. If neither is known, print for the actual
8906 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8907 values are known and identical, print the shortened
8908 @code{param=param@@entry=VALUE} notation.
8910 #0 equal (val=val@@entry=5)
8911 #0 different (val=6, val@@entry=5)
8912 #0 lost (val@@entry=5)
8914 #0 invalid (val=<optimized out>)
8918 Always print the actual parameter value. Print also its value from function
8919 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8920 if both values are known and identical, print the shortened
8921 @code{param=param@@entry=VALUE} notation.
8923 #0 equal (val=val@@entry=5)
8924 #0 different (val=6, val@@entry=5)
8925 #0 lost (val=<optimized out>, val@@entry=5)
8927 #0 invalid (val=<optimized out>)
8931 For analysis messages on possible failures of frame argument values at function
8932 entry resolution see @ref{set debug entry-values}.
8934 @item show print entry-values
8935 Show the method being used for printing of frame argument values at function
8938 @item set print repeats @var{number-of-repeats}
8939 @itemx set print repeats unlimited
8940 @cindex repeated array elements
8941 Set the threshold for suppressing display of repeated array
8942 elements. When the number of consecutive identical elements of an
8943 array exceeds the threshold, @value{GDBN} prints the string
8944 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8945 identical repetitions, instead of displaying the identical elements
8946 themselves. Setting the threshold to @code{unlimited} or zero will
8947 cause all elements to be individually printed. The default threshold
8950 @item show print repeats
8951 Display the current threshold for printing repeated identical
8954 @item set print null-stop
8955 @cindex @sc{null} elements in arrays
8956 Cause @value{GDBN} to stop printing the characters of an array when the first
8957 @sc{null} is encountered. This is useful when large arrays actually
8958 contain only short strings.
8961 @item show print null-stop
8962 Show whether @value{GDBN} stops printing an array on the first
8963 @sc{null} character.
8965 @item set print pretty on
8966 @cindex print structures in indented form
8967 @cindex indentation in structure display
8968 Cause @value{GDBN} to print structures in an indented format with one member
8969 per line, like this:
8984 @item set print pretty off
8985 Cause @value{GDBN} to print structures in a compact format, like this:
8989 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8990 meat = 0x54 "Pork"@}
8995 This is the default format.
8997 @item show print pretty
8998 Show which format @value{GDBN} is using to print structures.
9000 @item set print sevenbit-strings on
9001 @cindex eight-bit characters in strings
9002 @cindex octal escapes in strings
9003 Print using only seven-bit characters; if this option is set,
9004 @value{GDBN} displays any eight-bit characters (in strings or
9005 character values) using the notation @code{\}@var{nnn}. This setting is
9006 best if you are working in English (@sc{ascii}) and you use the
9007 high-order bit of characters as a marker or ``meta'' bit.
9009 @item set print sevenbit-strings off
9010 Print full eight-bit characters. This allows the use of more
9011 international character sets, and is the default.
9013 @item show print sevenbit-strings
9014 Show whether or not @value{GDBN} is printing only seven-bit characters.
9016 @item set print union on
9017 @cindex unions in structures, printing
9018 Tell @value{GDBN} to print unions which are contained in structures
9019 and other unions. This is the default setting.
9021 @item set print union off
9022 Tell @value{GDBN} not to print unions which are contained in
9023 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9026 @item show print union
9027 Ask @value{GDBN} whether or not it will print unions which are contained in
9028 structures and other unions.
9030 For example, given the declarations
9033 typedef enum @{Tree, Bug@} Species;
9034 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9035 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9046 struct thing foo = @{Tree, @{Acorn@}@};
9050 with @code{set print union on} in effect @samp{p foo} would print
9053 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9057 and with @code{set print union off} in effect it would print
9060 $1 = @{it = Tree, form = @{...@}@}
9064 @code{set print union} affects programs written in C-like languages
9070 These settings are of interest when debugging C@t{++} programs:
9073 @cindex demangling C@t{++} names
9074 @item set print demangle
9075 @itemx set print demangle on
9076 Print C@t{++} names in their source form rather than in the encoded
9077 (``mangled'') form passed to the assembler and linker for type-safe
9078 linkage. The default is on.
9080 @item show print demangle
9081 Show whether C@t{++} names are printed in mangled or demangled form.
9083 @item set print asm-demangle
9084 @itemx set print asm-demangle on
9085 Print C@t{++} names in their source form rather than their mangled form, even
9086 in assembler code printouts such as instruction disassemblies.
9089 @item show print asm-demangle
9090 Show whether C@t{++} names in assembly listings are printed in mangled
9093 @cindex C@t{++} symbol decoding style
9094 @cindex symbol decoding style, C@t{++}
9095 @kindex set demangle-style
9096 @item set demangle-style @var{style}
9097 Choose among several encoding schemes used by different compilers to
9098 represent C@t{++} names. The choices for @var{style} are currently:
9102 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9103 This is the default.
9106 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9109 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9112 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9115 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9116 @strong{Warning:} this setting alone is not sufficient to allow
9117 debugging @code{cfront}-generated executables. @value{GDBN} would
9118 require further enhancement to permit that.
9121 If you omit @var{style}, you will see a list of possible formats.
9123 @item show demangle-style
9124 Display the encoding style currently in use for decoding C@t{++} symbols.
9126 @item set print object
9127 @itemx set print object on
9128 @cindex derived type of an object, printing
9129 @cindex display derived types
9130 When displaying a pointer to an object, identify the @emph{actual}
9131 (derived) type of the object rather than the @emph{declared} type, using
9132 the virtual function table. Note that the virtual function table is
9133 required---this feature can only work for objects that have run-time
9134 type identification; a single virtual method in the object's declared
9135 type is sufficient. Note that this setting is also taken into account when
9136 working with variable objects via MI (@pxref{GDB/MI}).
9138 @item set print object off
9139 Display only the declared type of objects, without reference to the
9140 virtual function table. This is the default setting.
9142 @item show print object
9143 Show whether actual, or declared, object types are displayed.
9145 @item set print static-members
9146 @itemx set print static-members on
9147 @cindex static members of C@t{++} objects
9148 Print static members when displaying a C@t{++} object. The default is on.
9150 @item set print static-members off
9151 Do not print static members when displaying a C@t{++} object.
9153 @item show print static-members
9154 Show whether C@t{++} static members are printed or not.
9156 @item set print pascal_static-members
9157 @itemx set print pascal_static-members on
9158 @cindex static members of Pascal objects
9159 @cindex Pascal objects, static members display
9160 Print static members when displaying a Pascal object. The default is on.
9162 @item set print pascal_static-members off
9163 Do not print static members when displaying a Pascal object.
9165 @item show print pascal_static-members
9166 Show whether Pascal static members are printed or not.
9168 @c These don't work with HP ANSI C++ yet.
9169 @item set print vtbl
9170 @itemx set print vtbl on
9171 @cindex pretty print C@t{++} virtual function tables
9172 @cindex virtual functions (C@t{++}) display
9173 @cindex VTBL display
9174 Pretty print C@t{++} virtual function tables. The default is off.
9175 (The @code{vtbl} commands do not work on programs compiled with the HP
9176 ANSI C@t{++} compiler (@code{aCC}).)
9178 @item set print vtbl off
9179 Do not pretty print C@t{++} virtual function tables.
9181 @item show print vtbl
9182 Show whether C@t{++} virtual function tables are pretty printed, or not.
9185 @node Pretty Printing
9186 @section Pretty Printing
9188 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9189 Python code. It greatly simplifies the display of complex objects. This
9190 mechanism works for both MI and the CLI.
9193 * Pretty-Printer Introduction:: Introduction to pretty-printers
9194 * Pretty-Printer Example:: An example pretty-printer
9195 * Pretty-Printer Commands:: Pretty-printer commands
9198 @node Pretty-Printer Introduction
9199 @subsection Pretty-Printer Introduction
9201 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9202 registered for the value. If there is then @value{GDBN} invokes the
9203 pretty-printer to print the value. Otherwise the value is printed normally.
9205 Pretty-printers are normally named. This makes them easy to manage.
9206 The @samp{info pretty-printer} command will list all the installed
9207 pretty-printers with their names.
9208 If a pretty-printer can handle multiple data types, then its
9209 @dfn{subprinters} are the printers for the individual data types.
9210 Each such subprinter has its own name.
9211 The format of the name is @var{printer-name};@var{subprinter-name}.
9213 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9214 Typically they are automatically loaded and registered when the corresponding
9215 debug information is loaded, thus making them available without having to
9216 do anything special.
9218 There are three places where a pretty-printer can be registered.
9222 Pretty-printers registered globally are available when debugging
9226 Pretty-printers registered with a program space are available only
9227 when debugging that program.
9228 @xref{Progspaces In Python}, for more details on program spaces in Python.
9231 Pretty-printers registered with an objfile are loaded and unloaded
9232 with the corresponding objfile (e.g., shared library).
9233 @xref{Objfiles In Python}, for more details on objfiles in Python.
9236 @xref{Selecting Pretty-Printers}, for further information on how
9237 pretty-printers are selected,
9239 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9242 @node Pretty-Printer Example
9243 @subsection Pretty-Printer Example
9245 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9248 (@value{GDBP}) print s
9250 static npos = 4294967295,
9252 <std::allocator<char>> = @{
9253 <__gnu_cxx::new_allocator<char>> = @{
9254 <No data fields>@}, <No data fields>
9256 members of std::basic_string<char, std::char_traits<char>,
9257 std::allocator<char> >::_Alloc_hider:
9258 _M_p = 0x804a014 "abcd"
9263 With a pretty-printer for @code{std::string} only the contents are printed:
9266 (@value{GDBP}) print s
9270 @node Pretty-Printer Commands
9271 @subsection Pretty-Printer Commands
9272 @cindex pretty-printer commands
9275 @kindex info pretty-printer
9276 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9277 Print the list of installed pretty-printers.
9278 This includes disabled pretty-printers, which are marked as such.
9280 @var{object-regexp} is a regular expression matching the objects
9281 whose pretty-printers to list.
9282 Objects can be @code{global}, the program space's file
9283 (@pxref{Progspaces In Python}),
9284 and the object files within that program space (@pxref{Objfiles In Python}).
9285 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9286 looks up a printer from these three objects.
9288 @var{name-regexp} is a regular expression matching the name of the printers
9291 @kindex disable pretty-printer
9292 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9293 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9294 A disabled pretty-printer is not forgotten, it may be enabled again later.
9296 @kindex enable pretty-printer
9297 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9298 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9303 Suppose we have three pretty-printers installed: one from library1.so
9304 named @code{foo} that prints objects of type @code{foo}, and
9305 another from library2.so named @code{bar} that prints two types of objects,
9306 @code{bar1} and @code{bar2}.
9309 (gdb) info pretty-printer
9316 (gdb) info pretty-printer library2
9321 (gdb) disable pretty-printer library1
9323 2 of 3 printers enabled
9324 (gdb) info pretty-printer
9331 (gdb) disable pretty-printer library2 bar:bar1
9333 1 of 3 printers enabled
9334 (gdb) info pretty-printer library2
9341 (gdb) disable pretty-printer library2 bar
9343 0 of 3 printers enabled
9344 (gdb) info pretty-printer library2
9353 Note that for @code{bar} the entire printer can be disabled,
9354 as can each individual subprinter.
9357 @section Value History
9359 @cindex value history
9360 @cindex history of values printed by @value{GDBN}
9361 Values printed by the @code{print} command are saved in the @value{GDBN}
9362 @dfn{value history}. This allows you to refer to them in other expressions.
9363 Values are kept until the symbol table is re-read or discarded
9364 (for example with the @code{file} or @code{symbol-file} commands).
9365 When the symbol table changes, the value history is discarded,
9366 since the values may contain pointers back to the types defined in the
9371 @cindex history number
9372 The values printed are given @dfn{history numbers} by which you can
9373 refer to them. These are successive integers starting with one.
9374 @code{print} shows you the history number assigned to a value by
9375 printing @samp{$@var{num} = } before the value; here @var{num} is the
9378 To refer to any previous value, use @samp{$} followed by the value's
9379 history number. The way @code{print} labels its output is designed to
9380 remind you of this. Just @code{$} refers to the most recent value in
9381 the history, and @code{$$} refers to the value before that.
9382 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9383 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9384 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9386 For example, suppose you have just printed a pointer to a structure and
9387 want to see the contents of the structure. It suffices to type
9393 If you have a chain of structures where the component @code{next} points
9394 to the next one, you can print the contents of the next one with this:
9401 You can print successive links in the chain by repeating this
9402 command---which you can do by just typing @key{RET}.
9404 Note that the history records values, not expressions. If the value of
9405 @code{x} is 4 and you type these commands:
9413 then the value recorded in the value history by the @code{print} command
9414 remains 4 even though the value of @code{x} has changed.
9419 Print the last ten values in the value history, with their item numbers.
9420 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9421 values} does not change the history.
9423 @item show values @var{n}
9424 Print ten history values centered on history item number @var{n}.
9427 Print ten history values just after the values last printed. If no more
9428 values are available, @code{show values +} produces no display.
9431 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9432 same effect as @samp{show values +}.
9434 @node Convenience Vars
9435 @section Convenience Variables
9437 @cindex convenience variables
9438 @cindex user-defined variables
9439 @value{GDBN} provides @dfn{convenience variables} that you can use within
9440 @value{GDBN} to hold on to a value and refer to it later. These variables
9441 exist entirely within @value{GDBN}; they are not part of your program, and
9442 setting a convenience variable has no direct effect on further execution
9443 of your program. That is why you can use them freely.
9445 Convenience variables are prefixed with @samp{$}. Any name preceded by
9446 @samp{$} can be used for a convenience variable, unless it is one of
9447 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9448 (Value history references, in contrast, are @emph{numbers} preceded
9449 by @samp{$}. @xref{Value History, ,Value History}.)
9451 You can save a value in a convenience variable with an assignment
9452 expression, just as you would set a variable in your program.
9456 set $foo = *object_ptr
9460 would save in @code{$foo} the value contained in the object pointed to by
9463 Using a convenience variable for the first time creates it, but its
9464 value is @code{void} until you assign a new value. You can alter the
9465 value with another assignment at any time.
9467 Convenience variables have no fixed types. You can assign a convenience
9468 variable any type of value, including structures and arrays, even if
9469 that variable already has a value of a different type. The convenience
9470 variable, when used as an expression, has the type of its current value.
9473 @kindex show convenience
9474 @cindex show all user variables and functions
9475 @item show convenience
9476 Print a list of convenience variables used so far, and their values,
9477 as well as a list of the convenience functions.
9478 Abbreviated @code{show conv}.
9480 @kindex init-if-undefined
9481 @cindex convenience variables, initializing
9482 @item init-if-undefined $@var{variable} = @var{expression}
9483 Set a convenience variable if it has not already been set. This is useful
9484 for user-defined commands that keep some state. It is similar, in concept,
9485 to using local static variables with initializers in C (except that
9486 convenience variables are global). It can also be used to allow users to
9487 override default values used in a command script.
9489 If the variable is already defined then the expression is not evaluated so
9490 any side-effects do not occur.
9493 One of the ways to use a convenience variable is as a counter to be
9494 incremented or a pointer to be advanced. For example, to print
9495 a field from successive elements of an array of structures:
9499 print bar[$i++]->contents
9503 Repeat that command by typing @key{RET}.
9505 Some convenience variables are created automatically by @value{GDBN} and given
9506 values likely to be useful.
9509 @vindex $_@r{, convenience variable}
9511 The variable @code{$_} is automatically set by the @code{x} command to
9512 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9513 commands which provide a default address for @code{x} to examine also
9514 set @code{$_} to that address; these commands include @code{info line}
9515 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9516 except when set by the @code{x} command, in which case it is a pointer
9517 to the type of @code{$__}.
9519 @vindex $__@r{, convenience variable}
9521 The variable @code{$__} is automatically set by the @code{x} command
9522 to the value found in the last address examined. Its type is chosen
9523 to match the format in which the data was printed.
9526 @vindex $_exitcode@r{, convenience variable}
9527 The variable @code{$_exitcode} is automatically set to the exit code when
9528 the program being debugged terminates.
9531 The variable @code{$_exception} is set to the exception object being
9532 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9535 @itemx $_probe_arg0@dots{}$_probe_arg11
9536 Arguments to a static probe. @xref{Static Probe Points}.
9539 @vindex $_sdata@r{, inspect, convenience variable}
9540 The variable @code{$_sdata} contains extra collected static tracepoint
9541 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9542 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9543 if extra static tracepoint data has not been collected.
9546 @vindex $_siginfo@r{, convenience variable}
9547 The variable @code{$_siginfo} contains extra signal information
9548 (@pxref{extra signal information}). Note that @code{$_siginfo}
9549 could be empty, if the application has not yet received any signals.
9550 For example, it will be empty before you execute the @code{run} command.
9553 @vindex $_tlb@r{, convenience variable}
9554 The variable @code{$_tlb} is automatically set when debugging
9555 applications running on MS-Windows in native mode or connected to
9556 gdbserver that supports the @code{qGetTIBAddr} request.
9557 @xref{General Query Packets}.
9558 This variable contains the address of the thread information block.
9562 On HP-UX systems, if you refer to a function or variable name that
9563 begins with a dollar sign, @value{GDBN} searches for a user or system
9564 name first, before it searches for a convenience variable.
9566 @node Convenience Funs
9567 @section Convenience Functions
9569 @cindex convenience functions
9570 @value{GDBN} also supplies some @dfn{convenience functions}. These
9571 have a syntax similar to convenience variables. A convenience
9572 function can be used in an expression just like an ordinary function;
9573 however, a convenience function is implemented internally to
9576 These functions require @value{GDBN} to be configured with
9577 @code{Python} support.
9581 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9582 @findex $_memeq@r{, convenience function}
9583 Returns one if the @var{length} bytes at the addresses given by
9584 @var{buf1} and @var{buf2} are equal.
9585 Otherwise it returns zero.
9587 @item $_regex(@var{str}, @var{regex})
9588 @findex $_regex@r{, convenience function}
9589 Returns one if the string @var{str} matches the regular expression
9590 @var{regex}. Otherwise it returns zero.
9591 The syntax of the regular expression is that specified by @code{Python}'s
9592 regular expression support.
9594 @item $_streq(@var{str1}, @var{str2})
9595 @findex $_streq@r{, convenience function}
9596 Returns one if the strings @var{str1} and @var{str2} are equal.
9597 Otherwise it returns zero.
9599 @item $_strlen(@var{str})
9600 @findex $_strlen@r{, convenience function}
9601 Returns the length of string @var{str}.
9605 @value{GDBN} provides the ability to list and get help on
9606 convenience functions.
9610 @kindex help function
9611 @cindex show all convenience functions
9612 Print a list of all convenience functions.
9619 You can refer to machine register contents, in expressions, as variables
9620 with names starting with @samp{$}. The names of registers are different
9621 for each machine; use @code{info registers} to see the names used on
9625 @kindex info registers
9626 @item info registers
9627 Print the names and values of all registers except floating-point
9628 and vector registers (in the selected stack frame).
9630 @kindex info all-registers
9631 @cindex floating point registers
9632 @item info all-registers
9633 Print the names and values of all registers, including floating-point
9634 and vector registers (in the selected stack frame).
9636 @item info registers @var{regname} @dots{}
9637 Print the @dfn{relativized} value of each specified register @var{regname}.
9638 As discussed in detail below, register values are normally relative to
9639 the selected stack frame. @var{regname} may be any register name valid on
9640 the machine you are using, with or without the initial @samp{$}.
9643 @cindex stack pointer register
9644 @cindex program counter register
9645 @cindex process status register
9646 @cindex frame pointer register
9647 @cindex standard registers
9648 @value{GDBN} has four ``standard'' register names that are available (in
9649 expressions) on most machines---whenever they do not conflict with an
9650 architecture's canonical mnemonics for registers. The register names
9651 @code{$pc} and @code{$sp} are used for the program counter register and
9652 the stack pointer. @code{$fp} is used for a register that contains a
9653 pointer to the current stack frame, and @code{$ps} is used for a
9654 register that contains the processor status. For example,
9655 you could print the program counter in hex with
9662 or print the instruction to be executed next with
9669 or add four to the stack pointer@footnote{This is a way of removing
9670 one word from the stack, on machines where stacks grow downward in
9671 memory (most machines, nowadays). This assumes that the innermost
9672 stack frame is selected; setting @code{$sp} is not allowed when other
9673 stack frames are selected. To pop entire frames off the stack,
9674 regardless of machine architecture, use @code{return};
9675 see @ref{Returning, ,Returning from a Function}.} with
9681 Whenever possible, these four standard register names are available on
9682 your machine even though the machine has different canonical mnemonics,
9683 so long as there is no conflict. The @code{info registers} command
9684 shows the canonical names. For example, on the SPARC, @code{info
9685 registers} displays the processor status register as @code{$psr} but you
9686 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9687 is an alias for the @sc{eflags} register.
9689 @value{GDBN} always considers the contents of an ordinary register as an
9690 integer when the register is examined in this way. Some machines have
9691 special registers which can hold nothing but floating point; these
9692 registers are considered to have floating point values. There is no way
9693 to refer to the contents of an ordinary register as floating point value
9694 (although you can @emph{print} it as a floating point value with
9695 @samp{print/f $@var{regname}}).
9697 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9698 means that the data format in which the register contents are saved by
9699 the operating system is not the same one that your program normally
9700 sees. For example, the registers of the 68881 floating point
9701 coprocessor are always saved in ``extended'' (raw) format, but all C
9702 programs expect to work with ``double'' (virtual) format. In such
9703 cases, @value{GDBN} normally works with the virtual format only (the format
9704 that makes sense for your program), but the @code{info registers} command
9705 prints the data in both formats.
9707 @cindex SSE registers (x86)
9708 @cindex MMX registers (x86)
9709 Some machines have special registers whose contents can be interpreted
9710 in several different ways. For example, modern x86-based machines
9711 have SSE and MMX registers that can hold several values packed
9712 together in several different formats. @value{GDBN} refers to such
9713 registers in @code{struct} notation:
9716 (@value{GDBP}) print $xmm1
9718 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9719 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9720 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9721 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9722 v4_int32 = @{0, 20657912, 11, 13@},
9723 v2_int64 = @{88725056443645952, 55834574859@},
9724 uint128 = 0x0000000d0000000b013b36f800000000
9729 To set values of such registers, you need to tell @value{GDBN} which
9730 view of the register you wish to change, as if you were assigning
9731 value to a @code{struct} member:
9734 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9737 Normally, register values are relative to the selected stack frame
9738 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9739 value that the register would contain if all stack frames farther in
9740 were exited and their saved registers restored. In order to see the
9741 true contents of hardware registers, you must select the innermost
9742 frame (with @samp{frame 0}).
9744 However, @value{GDBN} must deduce where registers are saved, from the machine
9745 code generated by your compiler. If some registers are not saved, or if
9746 @value{GDBN} is unable to locate the saved registers, the selected stack
9747 frame makes no difference.
9749 @node Floating Point Hardware
9750 @section Floating Point Hardware
9751 @cindex floating point
9753 Depending on the configuration, @value{GDBN} may be able to give
9754 you more information about the status of the floating point hardware.
9759 Display hardware-dependent information about the floating
9760 point unit. The exact contents and layout vary depending on the
9761 floating point chip. Currently, @samp{info float} is supported on
9762 the ARM and x86 machines.
9766 @section Vector Unit
9769 Depending on the configuration, @value{GDBN} may be able to give you
9770 more information about the status of the vector unit.
9775 Display information about the vector unit. The exact contents and
9776 layout vary depending on the hardware.
9779 @node OS Information
9780 @section Operating System Auxiliary Information
9781 @cindex OS information
9783 @value{GDBN} provides interfaces to useful OS facilities that can help
9784 you debug your program.
9786 @cindex auxiliary vector
9787 @cindex vector, auxiliary
9788 Some operating systems supply an @dfn{auxiliary vector} to programs at
9789 startup. This is akin to the arguments and environment that you
9790 specify for a program, but contains a system-dependent variety of
9791 binary values that tell system libraries important details about the
9792 hardware, operating system, and process. Each value's purpose is
9793 identified by an integer tag; the meanings are well-known but system-specific.
9794 Depending on the configuration and operating system facilities,
9795 @value{GDBN} may be able to show you this information. For remote
9796 targets, this functionality may further depend on the remote stub's
9797 support of the @samp{qXfer:auxv:read} packet, see
9798 @ref{qXfer auxiliary vector read}.
9803 Display the auxiliary vector of the inferior, which can be either a
9804 live process or a core dump file. @value{GDBN} prints each tag value
9805 numerically, and also shows names and text descriptions for recognized
9806 tags. Some values in the vector are numbers, some bit masks, and some
9807 pointers to strings or other data. @value{GDBN} displays each value in the
9808 most appropriate form for a recognized tag, and in hexadecimal for
9809 an unrecognized tag.
9812 On some targets, @value{GDBN} can access operating system-specific
9813 information and show it to you. The types of information available
9814 will differ depending on the type of operating system running on the
9815 target. The mechanism used to fetch the data is described in
9816 @ref{Operating System Information}. For remote targets, this
9817 functionality depends on the remote stub's support of the
9818 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9822 @item info os @var{infotype}
9824 Display OS information of the requested type.
9826 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9828 @anchor{linux info os infotypes}
9830 @kindex info os processes
9832 Display the list of processes on the target. For each process,
9833 @value{GDBN} prints the process identifier, the name of the user, the
9834 command corresponding to the process, and the list of processor cores
9835 that the process is currently running on. (To understand what these
9836 properties mean, for this and the following info types, please consult
9837 the general @sc{gnu}/Linux documentation.)
9839 @kindex info os procgroups
9841 Display the list of process groups on the target. For each process,
9842 @value{GDBN} prints the identifier of the process group that it belongs
9843 to, the command corresponding to the process group leader, the process
9844 identifier, and the command line of the process. The list is sorted
9845 first by the process group identifier, then by the process identifier,
9846 so that processes belonging to the same process group are grouped together
9847 and the process group leader is listed first.
9849 @kindex info os threads
9851 Display the list of threads running on the target. For each thread,
9852 @value{GDBN} prints the identifier of the process that the thread
9853 belongs to, the command of the process, the thread identifier, and the
9854 processor core that it is currently running on. The main thread of a
9855 process is not listed.
9857 @kindex info os files
9859 Display the list of open file descriptors on the target. For each
9860 file descriptor, @value{GDBN} prints the identifier of the process
9861 owning the descriptor, the command of the owning process, the value
9862 of the descriptor, and the target of the descriptor.
9864 @kindex info os sockets
9866 Display the list of Internet-domain sockets on the target. For each
9867 socket, @value{GDBN} prints the address and port of the local and
9868 remote endpoints, the current state of the connection, the creator of
9869 the socket, the IP address family of the socket, and the type of the
9874 Display the list of all System V shared-memory regions on the target.
9875 For each shared-memory region, @value{GDBN} prints the region key,
9876 the shared-memory identifier, the access permissions, the size of the
9877 region, the process that created the region, the process that last
9878 attached to or detached from the region, the current number of live
9879 attaches to the region, and the times at which the region was last
9880 attached to, detach from, and changed.
9882 @kindex info os semaphores
9884 Display the list of all System V semaphore sets on the target. For each
9885 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9886 set identifier, the access permissions, the number of semaphores in the
9887 set, the user and group of the owner and creator of the semaphore set,
9888 and the times at which the semaphore set was operated upon and changed.
9892 Display the list of all System V message queues on the target. For each
9893 message queue, @value{GDBN} prints the message queue key, the message
9894 queue identifier, the access permissions, the current number of bytes
9895 on the queue, the current number of messages on the queue, the processes
9896 that last sent and received a message on the queue, the user and group
9897 of the owner and creator of the message queue, the times at which a
9898 message was last sent and received on the queue, and the time at which
9899 the message queue was last changed.
9901 @kindex info os modules
9903 Display the list of all loaded kernel modules on the target. For each
9904 module, @value{GDBN} prints the module name, the size of the module in
9905 bytes, the number of times the module is used, the dependencies of the
9906 module, the status of the module, and the address of the loaded module
9911 If @var{infotype} is omitted, then list the possible values for
9912 @var{infotype} and the kind of OS information available for each
9913 @var{infotype}. If the target does not return a list of possible
9914 types, this command will report an error.
9917 @node Memory Region Attributes
9918 @section Memory Region Attributes
9919 @cindex memory region attributes
9921 @dfn{Memory region attributes} allow you to describe special handling
9922 required by regions of your target's memory. @value{GDBN} uses
9923 attributes to determine whether to allow certain types of memory
9924 accesses; whether to use specific width accesses; and whether to cache
9925 target memory. By default the description of memory regions is
9926 fetched from the target (if the current target supports this), but the
9927 user can override the fetched regions.
9929 Defined memory regions can be individually enabled and disabled. When a
9930 memory region is disabled, @value{GDBN} uses the default attributes when
9931 accessing memory in that region. Similarly, if no memory regions have
9932 been defined, @value{GDBN} uses the default attributes when accessing
9935 When a memory region is defined, it is given a number to identify it;
9936 to enable, disable, or remove a memory region, you specify that number.
9940 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9941 Define a memory region bounded by @var{lower} and @var{upper} with
9942 attributes @var{attributes}@dots{}, and add it to the list of regions
9943 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9944 case: it is treated as the target's maximum memory address.
9945 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9948 Discard any user changes to the memory regions and use target-supplied
9949 regions, if available, or no regions if the target does not support.
9952 @item delete mem @var{nums}@dots{}
9953 Remove memory regions @var{nums}@dots{} from the list of regions
9954 monitored by @value{GDBN}.
9957 @item disable mem @var{nums}@dots{}
9958 Disable monitoring of memory regions @var{nums}@dots{}.
9959 A disabled memory region is not forgotten.
9960 It may be enabled again later.
9963 @item enable mem @var{nums}@dots{}
9964 Enable monitoring of memory regions @var{nums}@dots{}.
9968 Print a table of all defined memory regions, with the following columns
9972 @item Memory Region Number
9973 @item Enabled or Disabled.
9974 Enabled memory regions are marked with @samp{y}.
9975 Disabled memory regions are marked with @samp{n}.
9978 The address defining the inclusive lower bound of the memory region.
9981 The address defining the exclusive upper bound of the memory region.
9984 The list of attributes set for this memory region.
9989 @subsection Attributes
9991 @subsubsection Memory Access Mode
9992 The access mode attributes set whether @value{GDBN} may make read or
9993 write accesses to a memory region.
9995 While these attributes prevent @value{GDBN} from performing invalid
9996 memory accesses, they do nothing to prevent the target system, I/O DMA,
9997 etc.@: from accessing memory.
10001 Memory is read only.
10003 Memory is write only.
10005 Memory is read/write. This is the default.
10008 @subsubsection Memory Access Size
10009 The access size attribute tells @value{GDBN} to use specific sized
10010 accesses in the memory region. Often memory mapped device registers
10011 require specific sized accesses. If no access size attribute is
10012 specified, @value{GDBN} may use accesses of any size.
10016 Use 8 bit memory accesses.
10018 Use 16 bit memory accesses.
10020 Use 32 bit memory accesses.
10022 Use 64 bit memory accesses.
10025 @c @subsubsection Hardware/Software Breakpoints
10026 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10027 @c will use hardware or software breakpoints for the internal breakpoints
10028 @c used by the step, next, finish, until, etc. commands.
10032 @c Always use hardware breakpoints
10033 @c @item swbreak (default)
10036 @subsubsection Data Cache
10037 The data cache attributes set whether @value{GDBN} will cache target
10038 memory. While this generally improves performance by reducing debug
10039 protocol overhead, it can lead to incorrect results because @value{GDBN}
10040 does not know about volatile variables or memory mapped device
10045 Enable @value{GDBN} to cache target memory.
10047 Disable @value{GDBN} from caching target memory. This is the default.
10050 @subsection Memory Access Checking
10051 @value{GDBN} can be instructed to refuse accesses to memory that is
10052 not explicitly described. This can be useful if accessing such
10053 regions has undesired effects for a specific target, or to provide
10054 better error checking. The following commands control this behaviour.
10057 @kindex set mem inaccessible-by-default
10058 @item set mem inaccessible-by-default [on|off]
10059 If @code{on} is specified, make @value{GDBN} treat memory not
10060 explicitly described by the memory ranges as non-existent and refuse accesses
10061 to such memory. The checks are only performed if there's at least one
10062 memory range defined. If @code{off} is specified, make @value{GDBN}
10063 treat the memory not explicitly described by the memory ranges as RAM.
10064 The default value is @code{on}.
10065 @kindex show mem inaccessible-by-default
10066 @item show mem inaccessible-by-default
10067 Show the current handling of accesses to unknown memory.
10071 @c @subsubsection Memory Write Verification
10072 @c The memory write verification attributes set whether @value{GDBN}
10073 @c will re-reads data after each write to verify the write was successful.
10077 @c @item noverify (default)
10080 @node Dump/Restore Files
10081 @section Copy Between Memory and a File
10082 @cindex dump/restore files
10083 @cindex append data to a file
10084 @cindex dump data to a file
10085 @cindex restore data from a file
10087 You can use the commands @code{dump}, @code{append}, and
10088 @code{restore} to copy data between target memory and a file. The
10089 @code{dump} and @code{append} commands write data to a file, and the
10090 @code{restore} command reads data from a file back into the inferior's
10091 memory. Files may be in binary, Motorola S-record, Intel hex, or
10092 Tektronix Hex format; however, @value{GDBN} can only append to binary
10098 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10099 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10100 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10101 or the value of @var{expr}, to @var{filename} in the given format.
10103 The @var{format} parameter may be any one of:
10110 Motorola S-record format.
10112 Tektronix Hex format.
10115 @value{GDBN} uses the same definitions of these formats as the
10116 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10117 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10121 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10122 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10123 Append the contents of memory from @var{start_addr} to @var{end_addr},
10124 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10125 (@value{GDBN} can only append data to files in raw binary form.)
10128 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10129 Restore the contents of file @var{filename} into memory. The
10130 @code{restore} command can automatically recognize any known @sc{bfd}
10131 file format, except for raw binary. To restore a raw binary file you
10132 must specify the optional keyword @code{binary} after the filename.
10134 If @var{bias} is non-zero, its value will be added to the addresses
10135 contained in the file. Binary files always start at address zero, so
10136 they will be restored at address @var{bias}. Other bfd files have
10137 a built-in location; they will be restored at offset @var{bias}
10138 from that location.
10140 If @var{start} and/or @var{end} are non-zero, then only data between
10141 file offset @var{start} and file offset @var{end} will be restored.
10142 These offsets are relative to the addresses in the file, before
10143 the @var{bias} argument is applied.
10147 @node Core File Generation
10148 @section How to Produce a Core File from Your Program
10149 @cindex dump core from inferior
10151 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10152 image of a running process and its process status (register values
10153 etc.). Its primary use is post-mortem debugging of a program that
10154 crashed while it ran outside a debugger. A program that crashes
10155 automatically produces a core file, unless this feature is disabled by
10156 the user. @xref{Files}, for information on invoking @value{GDBN} in
10157 the post-mortem debugging mode.
10159 Occasionally, you may wish to produce a core file of the program you
10160 are debugging in order to preserve a snapshot of its state.
10161 @value{GDBN} has a special command for that.
10165 @kindex generate-core-file
10166 @item generate-core-file [@var{file}]
10167 @itemx gcore [@var{file}]
10168 Produce a core dump of the inferior process. The optional argument
10169 @var{file} specifies the file name where to put the core dump. If not
10170 specified, the file name defaults to @file{core.@var{pid}}, where
10171 @var{pid} is the inferior process ID.
10173 Note that this command is implemented only for some systems (as of
10174 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10177 @node Character Sets
10178 @section Character Sets
10179 @cindex character sets
10181 @cindex translating between character sets
10182 @cindex host character set
10183 @cindex target character set
10185 If the program you are debugging uses a different character set to
10186 represent characters and strings than the one @value{GDBN} uses itself,
10187 @value{GDBN} can automatically translate between the character sets for
10188 you. The character set @value{GDBN} uses we call the @dfn{host
10189 character set}; the one the inferior program uses we call the
10190 @dfn{target character set}.
10192 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10193 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10194 remote protocol (@pxref{Remote Debugging}) to debug a program
10195 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10196 then the host character set is Latin-1, and the target character set is
10197 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10198 target-charset EBCDIC-US}, then @value{GDBN} translates between
10199 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10200 character and string literals in expressions.
10202 @value{GDBN} has no way to automatically recognize which character set
10203 the inferior program uses; you must tell it, using the @code{set
10204 target-charset} command, described below.
10206 Here are the commands for controlling @value{GDBN}'s character set
10210 @item set target-charset @var{charset}
10211 @kindex set target-charset
10212 Set the current target character set to @var{charset}. To display the
10213 list of supported target character sets, type
10214 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10216 @item set host-charset @var{charset}
10217 @kindex set host-charset
10218 Set the current host character set to @var{charset}.
10220 By default, @value{GDBN} uses a host character set appropriate to the
10221 system it is running on; you can override that default using the
10222 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10223 automatically determine the appropriate host character set. In this
10224 case, @value{GDBN} uses @samp{UTF-8}.
10226 @value{GDBN} can only use certain character sets as its host character
10227 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10228 @value{GDBN} will list the host character sets it supports.
10230 @item set charset @var{charset}
10231 @kindex set charset
10232 Set the current host and target character sets to @var{charset}. As
10233 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10234 @value{GDBN} will list the names of the character sets that can be used
10235 for both host and target.
10238 @kindex show charset
10239 Show the names of the current host and target character sets.
10241 @item show host-charset
10242 @kindex show host-charset
10243 Show the name of the current host character set.
10245 @item show target-charset
10246 @kindex show target-charset
10247 Show the name of the current target character set.
10249 @item set target-wide-charset @var{charset}
10250 @kindex set target-wide-charset
10251 Set the current target's wide character set to @var{charset}. This is
10252 the character set used by the target's @code{wchar_t} type. To
10253 display the list of supported wide character sets, type
10254 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10256 @item show target-wide-charset
10257 @kindex show target-wide-charset
10258 Show the name of the current target's wide character set.
10261 Here is an example of @value{GDBN}'s character set support in action.
10262 Assume that the following source code has been placed in the file
10263 @file{charset-test.c}:
10269 = @{72, 101, 108, 108, 111, 44, 32, 119,
10270 111, 114, 108, 100, 33, 10, 0@};
10271 char ibm1047_hello[]
10272 = @{200, 133, 147, 147, 150, 107, 64, 166,
10273 150, 153, 147, 132, 90, 37, 0@};
10277 printf ("Hello, world!\n");
10281 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10282 containing the string @samp{Hello, world!} followed by a newline,
10283 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10285 We compile the program, and invoke the debugger on it:
10288 $ gcc -g charset-test.c -o charset-test
10289 $ gdb -nw charset-test
10290 GNU gdb 2001-12-19-cvs
10291 Copyright 2001 Free Software Foundation, Inc.
10296 We can use the @code{show charset} command to see what character sets
10297 @value{GDBN} is currently using to interpret and display characters and
10301 (@value{GDBP}) show charset
10302 The current host and target character set is `ISO-8859-1'.
10306 For the sake of printing this manual, let's use @sc{ascii} as our
10307 initial character set:
10309 (@value{GDBP}) set charset ASCII
10310 (@value{GDBP}) show charset
10311 The current host and target character set is `ASCII'.
10315 Let's assume that @sc{ascii} is indeed the correct character set for our
10316 host system --- in other words, let's assume that if @value{GDBN} prints
10317 characters using the @sc{ascii} character set, our terminal will display
10318 them properly. Since our current target character set is also
10319 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10322 (@value{GDBP}) print ascii_hello
10323 $1 = 0x401698 "Hello, world!\n"
10324 (@value{GDBP}) print ascii_hello[0]
10329 @value{GDBN} uses the target character set for character and string
10330 literals you use in expressions:
10333 (@value{GDBP}) print '+'
10338 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10341 @value{GDBN} relies on the user to tell it which character set the
10342 target program uses. If we print @code{ibm1047_hello} while our target
10343 character set is still @sc{ascii}, we get jibberish:
10346 (@value{GDBP}) print ibm1047_hello
10347 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10348 (@value{GDBP}) print ibm1047_hello[0]
10353 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10354 @value{GDBN} tells us the character sets it supports:
10357 (@value{GDBP}) set target-charset
10358 ASCII EBCDIC-US IBM1047 ISO-8859-1
10359 (@value{GDBP}) set target-charset
10362 We can select @sc{ibm1047} as our target character set, and examine the
10363 program's strings again. Now the @sc{ascii} string is wrong, but
10364 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10365 target character set, @sc{ibm1047}, to the host character set,
10366 @sc{ascii}, and they display correctly:
10369 (@value{GDBP}) set target-charset IBM1047
10370 (@value{GDBP}) show charset
10371 The current host character set is `ASCII'.
10372 The current target character set is `IBM1047'.
10373 (@value{GDBP}) print ascii_hello
10374 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10375 (@value{GDBP}) print ascii_hello[0]
10377 (@value{GDBP}) print ibm1047_hello
10378 $8 = 0x4016a8 "Hello, world!\n"
10379 (@value{GDBP}) print ibm1047_hello[0]
10384 As above, @value{GDBN} uses the target character set for character and
10385 string literals you use in expressions:
10388 (@value{GDBP}) print '+'
10393 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10396 @node Caching Remote Data
10397 @section Caching Data of Remote Targets
10398 @cindex caching data of remote targets
10400 @value{GDBN} caches data exchanged between the debugger and a
10401 remote target (@pxref{Remote Debugging}). Such caching generally improves
10402 performance, because it reduces the overhead of the remote protocol by
10403 bundling memory reads and writes into large chunks. Unfortunately, simply
10404 caching everything would lead to incorrect results, since @value{GDBN}
10405 does not necessarily know anything about volatile values, memory-mapped I/O
10406 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10407 memory can be changed @emph{while} a gdb command is executing.
10408 Therefore, by default, @value{GDBN} only caches data
10409 known to be on the stack@footnote{In non-stop mode, it is moderately
10410 rare for a running thread to modify the stack of a stopped thread
10411 in a way that would interfere with a backtrace, and caching of
10412 stack reads provides a significant speed up of remote backtraces.}.
10413 Other regions of memory can be explicitly marked as
10414 cacheable; see @pxref{Memory Region Attributes}.
10417 @kindex set remotecache
10418 @item set remotecache on
10419 @itemx set remotecache off
10420 This option no longer does anything; it exists for compatibility
10423 @kindex show remotecache
10424 @item show remotecache
10425 Show the current state of the obsolete remotecache flag.
10427 @kindex set stack-cache
10428 @item set stack-cache on
10429 @itemx set stack-cache off
10430 Enable or disable caching of stack accesses. When @code{ON}, use
10431 caching. By default, this option is @code{ON}.
10433 @kindex show stack-cache
10434 @item show stack-cache
10435 Show the current state of data caching for memory accesses.
10437 @kindex info dcache
10438 @item info dcache @r{[}line@r{]}
10439 Print the information about the data cache performance. The
10440 information displayed includes the dcache width and depth, and for
10441 each cache line, its number, address, and how many times it was
10442 referenced. This command is useful for debugging the data cache
10445 If a line number is specified, the contents of that line will be
10448 @item set dcache size @var{size}
10449 @cindex dcache size
10450 @kindex set dcache size
10451 Set maximum number of entries in dcache (dcache depth above).
10453 @item set dcache line-size @var{line-size}
10454 @cindex dcache line-size
10455 @kindex set dcache line-size
10456 Set number of bytes each dcache entry caches (dcache width above).
10457 Must be a power of 2.
10459 @item show dcache size
10460 @kindex show dcache size
10461 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10463 @item show dcache line-size
10464 @kindex show dcache line-size
10465 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10469 @node Searching Memory
10470 @section Search Memory
10471 @cindex searching memory
10473 Memory can be searched for a particular sequence of bytes with the
10474 @code{find} command.
10478 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10479 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10480 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10481 etc. The search begins at address @var{start_addr} and continues for either
10482 @var{len} bytes or through to @var{end_addr} inclusive.
10485 @var{s} and @var{n} are optional parameters.
10486 They may be specified in either order, apart or together.
10489 @item @var{s}, search query size
10490 The size of each search query value.
10496 halfwords (two bytes)
10500 giant words (eight bytes)
10503 All values are interpreted in the current language.
10504 This means, for example, that if the current source language is C/C@t{++}
10505 then searching for the string ``hello'' includes the trailing '\0'.
10507 If the value size is not specified, it is taken from the
10508 value's type in the current language.
10509 This is useful when one wants to specify the search
10510 pattern as a mixture of types.
10511 Note that this means, for example, that in the case of C-like languages
10512 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10513 which is typically four bytes.
10515 @item @var{n}, maximum number of finds
10516 The maximum number of matches to print. The default is to print all finds.
10519 You can use strings as search values. Quote them with double-quotes
10521 The string value is copied into the search pattern byte by byte,
10522 regardless of the endianness of the target and the size specification.
10524 The address of each match found is printed as well as a count of the
10525 number of matches found.
10527 The address of the last value found is stored in convenience variable
10529 A count of the number of matches is stored in @samp{$numfound}.
10531 For example, if stopped at the @code{printf} in this function:
10537 static char hello[] = "hello-hello";
10538 static struct @{ char c; short s; int i; @}
10539 __attribute__ ((packed)) mixed
10540 = @{ 'c', 0x1234, 0x87654321 @};
10541 printf ("%s\n", hello);
10546 you get during debugging:
10549 (gdb) find &hello[0], +sizeof(hello), "hello"
10550 0x804956d <hello.1620+6>
10552 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10553 0x8049567 <hello.1620>
10554 0x804956d <hello.1620+6>
10556 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10557 0x8049567 <hello.1620>
10559 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10560 0x8049560 <mixed.1625>
10562 (gdb) print $numfound
10565 $2 = (void *) 0x8049560
10568 @node Optimized Code
10569 @chapter Debugging Optimized Code
10570 @cindex optimized code, debugging
10571 @cindex debugging optimized code
10573 Almost all compilers support optimization. With optimization
10574 disabled, the compiler generates assembly code that corresponds
10575 directly to your source code, in a simplistic way. As the compiler
10576 applies more powerful optimizations, the generated assembly code
10577 diverges from your original source code. With help from debugging
10578 information generated by the compiler, @value{GDBN} can map from
10579 the running program back to constructs from your original source.
10581 @value{GDBN} is more accurate with optimization disabled. If you
10582 can recompile without optimization, it is easier to follow the
10583 progress of your program during debugging. But, there are many cases
10584 where you may need to debug an optimized version.
10586 When you debug a program compiled with @samp{-g -O}, remember that the
10587 optimizer has rearranged your code; the debugger shows you what is
10588 really there. Do not be too surprised when the execution path does not
10589 exactly match your source file! An extreme example: if you define a
10590 variable, but never use it, @value{GDBN} never sees that
10591 variable---because the compiler optimizes it out of existence.
10593 Some things do not work as well with @samp{-g -O} as with just
10594 @samp{-g}, particularly on machines with instruction scheduling. If in
10595 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10596 please report it to us as a bug (including a test case!).
10597 @xref{Variables}, for more information about debugging optimized code.
10600 * Inline Functions:: How @value{GDBN} presents inlining
10601 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10604 @node Inline Functions
10605 @section Inline Functions
10606 @cindex inline functions, debugging
10608 @dfn{Inlining} is an optimization that inserts a copy of the function
10609 body directly at each call site, instead of jumping to a shared
10610 routine. @value{GDBN} displays inlined functions just like
10611 non-inlined functions. They appear in backtraces. You can view their
10612 arguments and local variables, step into them with @code{step}, skip
10613 them with @code{next}, and escape from them with @code{finish}.
10614 You can check whether a function was inlined by using the
10615 @code{info frame} command.
10617 For @value{GDBN} to support inlined functions, the compiler must
10618 record information about inlining in the debug information ---
10619 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10620 other compilers do also. @value{GDBN} only supports inlined functions
10621 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10622 do not emit two required attributes (@samp{DW_AT_call_file} and
10623 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10624 function calls with earlier versions of @value{NGCC}. It instead
10625 displays the arguments and local variables of inlined functions as
10626 local variables in the caller.
10628 The body of an inlined function is directly included at its call site;
10629 unlike a non-inlined function, there are no instructions devoted to
10630 the call. @value{GDBN} still pretends that the call site and the
10631 start of the inlined function are different instructions. Stepping to
10632 the call site shows the call site, and then stepping again shows
10633 the first line of the inlined function, even though no additional
10634 instructions are executed.
10636 This makes source-level debugging much clearer; you can see both the
10637 context of the call and then the effect of the call. Only stepping by
10638 a single instruction using @code{stepi} or @code{nexti} does not do
10639 this; single instruction steps always show the inlined body.
10641 There are some ways that @value{GDBN} does not pretend that inlined
10642 function calls are the same as normal calls:
10646 Setting breakpoints at the call site of an inlined function may not
10647 work, because the call site does not contain any code. @value{GDBN}
10648 may incorrectly move the breakpoint to the next line of the enclosing
10649 function, after the call. This limitation will be removed in a future
10650 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10651 or inside the inlined function instead.
10654 @value{GDBN} cannot locate the return value of inlined calls after
10655 using the @code{finish} command. This is a limitation of compiler-generated
10656 debugging information; after @code{finish}, you can step to the next line
10657 and print a variable where your program stored the return value.
10661 @node Tail Call Frames
10662 @section Tail Call Frames
10663 @cindex tail call frames, debugging
10665 Function @code{B} can call function @code{C} in its very last statement. In
10666 unoptimized compilation the call of @code{C} is immediately followed by return
10667 instruction at the end of @code{B} code. Optimizing compiler may replace the
10668 call and return in function @code{B} into one jump to function @code{C}
10669 instead. Such use of a jump instruction is called @dfn{tail call}.
10671 During execution of function @code{C}, there will be no indication in the
10672 function call stack frames that it was tail-called from @code{B}. If function
10673 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10674 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10675 some cases @value{GDBN} can determine that @code{C} was tail-called from
10676 @code{B}, and it will then create fictitious call frame for that, with the
10677 return address set up as if @code{B} called @code{C} normally.
10679 This functionality is currently supported only by DWARF 2 debugging format and
10680 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10681 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10684 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10685 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10689 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10691 Stack level 1, frame at 0x7fffffffda30:
10692 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10693 tail call frame, caller of frame at 0x7fffffffda30
10694 source language c++.
10695 Arglist at unknown address.
10696 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10699 The detection of all the possible code path executions can find them ambiguous.
10700 There is no execution history stored (possible @ref{Reverse Execution} is never
10701 used for this purpose) and the last known caller could have reached the known
10702 callee by multiple different jump sequences. In such case @value{GDBN} still
10703 tries to show at least all the unambiguous top tail callers and all the
10704 unambiguous bottom tail calees, if any.
10707 @anchor{set debug entry-values}
10708 @item set debug entry-values
10709 @kindex set debug entry-values
10710 When set to on, enables printing of analysis messages for both frame argument
10711 values at function entry and tail calls. It will show all the possible valid
10712 tail calls code paths it has considered. It will also print the intersection
10713 of them with the final unambiguous (possibly partial or even empty) code path
10716 @item show debug entry-values
10717 @kindex show debug entry-values
10718 Show the current state of analysis messages printing for both frame argument
10719 values at function entry and tail calls.
10722 The analysis messages for tail calls can for example show why the virtual tail
10723 call frame for function @code{c} has not been recognized (due to the indirect
10724 reference by variable @code{x}):
10727 static void __attribute__((noinline, noclone)) c (void);
10728 void (*x) (void) = c;
10729 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10730 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10731 int main (void) @{ x (); return 0; @}
10733 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10734 DW_TAG_GNU_call_site 0x40039a in main
10736 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10739 #1 0x000000000040039a in main () at t.c:5
10742 Another possibility is an ambiguous virtual tail call frames resolution:
10746 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10747 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10748 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10749 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10750 static void __attribute__((noinline, noclone)) b (void)
10751 @{ if (i) c (); else e (); @}
10752 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10753 int main (void) @{ a (); return 0; @}
10755 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10756 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10757 tailcall: reduced: 0x4004d2(a) |
10760 #1 0x00000000004004d2 in a () at t.c:8
10761 #2 0x0000000000400395 in main () at t.c:9
10764 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10765 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10767 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10768 @ifset HAVE_MAKEINFO_CLICK
10769 @set ARROW @click{}
10770 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10771 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10773 @ifclear HAVE_MAKEINFO_CLICK
10775 @set CALLSEQ1B @value{CALLSEQ1A}
10776 @set CALLSEQ2B @value{CALLSEQ2A}
10779 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10780 The code can have possible execution paths @value{CALLSEQ1B} or
10781 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10783 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10784 has found. It then finds another possible calling sequcen - that one is
10785 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10786 printed as the @code{reduced:} calling sequence. That one could have many
10787 futher @code{compare:} and @code{reduced:} statements as long as there remain
10788 any non-ambiguous sequence entries.
10790 For the frame of function @code{b} in both cases there are different possible
10791 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10792 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10793 therefore this one is displayed to the user while the ambiguous frames are
10796 There can be also reasons why printing of frame argument values at function
10801 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10802 static void __attribute__((noinline, noclone)) a (int i);
10803 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10804 static void __attribute__((noinline, noclone)) a (int i)
10805 @{ if (i) b (i - 1); else c (0); @}
10806 int main (void) @{ a (5); return 0; @}
10809 #0 c (i=i@@entry=0) at t.c:2
10810 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10811 function "a" at 0x400420 can call itself via tail calls
10812 i=<optimized out>) at t.c:6
10813 #2 0x000000000040036e in main () at t.c:7
10816 @value{GDBN} cannot find out from the inferior state if and how many times did
10817 function @code{a} call itself (via function @code{b}) as these calls would be
10818 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10819 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10820 prints @code{<optimized out>} instead.
10823 @chapter C Preprocessor Macros
10825 Some languages, such as C and C@t{++}, provide a way to define and invoke
10826 ``preprocessor macros'' which expand into strings of tokens.
10827 @value{GDBN} can evaluate expressions containing macro invocations, show
10828 the result of macro expansion, and show a macro's definition, including
10829 where it was defined.
10831 You may need to compile your program specially to provide @value{GDBN}
10832 with information about preprocessor macros. Most compilers do not
10833 include macros in their debugging information, even when you compile
10834 with the @option{-g} flag. @xref{Compilation}.
10836 A program may define a macro at one point, remove that definition later,
10837 and then provide a different definition after that. Thus, at different
10838 points in the program, a macro may have different definitions, or have
10839 no definition at all. If there is a current stack frame, @value{GDBN}
10840 uses the macros in scope at that frame's source code line. Otherwise,
10841 @value{GDBN} uses the macros in scope at the current listing location;
10844 Whenever @value{GDBN} evaluates an expression, it always expands any
10845 macro invocations present in the expression. @value{GDBN} also provides
10846 the following commands for working with macros explicitly.
10850 @kindex macro expand
10851 @cindex macro expansion, showing the results of preprocessor
10852 @cindex preprocessor macro expansion, showing the results of
10853 @cindex expanding preprocessor macros
10854 @item macro expand @var{expression}
10855 @itemx macro exp @var{expression}
10856 Show the results of expanding all preprocessor macro invocations in
10857 @var{expression}. Since @value{GDBN} simply expands macros, but does
10858 not parse the result, @var{expression} need not be a valid expression;
10859 it can be any string of tokens.
10862 @item macro expand-once @var{expression}
10863 @itemx macro exp1 @var{expression}
10864 @cindex expand macro once
10865 @i{(This command is not yet implemented.)} Show the results of
10866 expanding those preprocessor macro invocations that appear explicitly in
10867 @var{expression}. Macro invocations appearing in that expansion are
10868 left unchanged. This command allows you to see the effect of a
10869 particular macro more clearly, without being confused by further
10870 expansions. Since @value{GDBN} simply expands macros, but does not
10871 parse the result, @var{expression} need not be a valid expression; it
10872 can be any string of tokens.
10875 @cindex macro definition, showing
10876 @cindex definition of a macro, showing
10877 @cindex macros, from debug info
10878 @item info macro [-a|-all] [--] @var{macro}
10879 Show the current definition or all definitions of the named @var{macro},
10880 and describe the source location or compiler command-line where that
10881 definition was established. The optional double dash is to signify the end of
10882 argument processing and the beginning of @var{macro} for non C-like macros where
10883 the macro may begin with a hyphen.
10885 @kindex info macros
10886 @item info macros @var{linespec}
10887 Show all macro definitions that are in effect at the location specified
10888 by @var{linespec}, and describe the source location or compiler
10889 command-line where those definitions were established.
10891 @kindex macro define
10892 @cindex user-defined macros
10893 @cindex defining macros interactively
10894 @cindex macros, user-defined
10895 @item macro define @var{macro} @var{replacement-list}
10896 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10897 Introduce a definition for a preprocessor macro named @var{macro},
10898 invocations of which are replaced by the tokens given in
10899 @var{replacement-list}. The first form of this command defines an
10900 ``object-like'' macro, which takes no arguments; the second form
10901 defines a ``function-like'' macro, which takes the arguments given in
10904 A definition introduced by this command is in scope in every
10905 expression evaluated in @value{GDBN}, until it is removed with the
10906 @code{macro undef} command, described below. The definition overrides
10907 all definitions for @var{macro} present in the program being debugged,
10908 as well as any previous user-supplied definition.
10910 @kindex macro undef
10911 @item macro undef @var{macro}
10912 Remove any user-supplied definition for the macro named @var{macro}.
10913 This command only affects definitions provided with the @code{macro
10914 define} command, described above; it cannot remove definitions present
10915 in the program being debugged.
10919 List all the macros defined using the @code{macro define} command.
10922 @cindex macros, example of debugging with
10923 Here is a transcript showing the above commands in action. First, we
10924 show our source files:
10929 #include "sample.h"
10932 #define ADD(x) (M + x)
10937 printf ("Hello, world!\n");
10939 printf ("We're so creative.\n");
10941 printf ("Goodbye, world!\n");
10948 Now, we compile the program using the @sc{gnu} C compiler,
10949 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10950 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10951 and @option{-gdwarf-4}; we recommend always choosing the most recent
10952 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10953 includes information about preprocessor macros in the debugging
10957 $ gcc -gdwarf-2 -g3 sample.c -o sample
10961 Now, we start @value{GDBN} on our sample program:
10965 GNU gdb 2002-05-06-cvs
10966 Copyright 2002 Free Software Foundation, Inc.
10967 GDB is free software, @dots{}
10971 We can expand macros and examine their definitions, even when the
10972 program is not running. @value{GDBN} uses the current listing position
10973 to decide which macro definitions are in scope:
10976 (@value{GDBP}) list main
10979 5 #define ADD(x) (M + x)
10984 10 printf ("Hello, world!\n");
10986 12 printf ("We're so creative.\n");
10987 (@value{GDBP}) info macro ADD
10988 Defined at /home/jimb/gdb/macros/play/sample.c:5
10989 #define ADD(x) (M + x)
10990 (@value{GDBP}) info macro Q
10991 Defined at /home/jimb/gdb/macros/play/sample.h:1
10992 included at /home/jimb/gdb/macros/play/sample.c:2
10994 (@value{GDBP}) macro expand ADD(1)
10995 expands to: (42 + 1)
10996 (@value{GDBP}) macro expand-once ADD(1)
10997 expands to: once (M + 1)
11001 In the example above, note that @code{macro expand-once} expands only
11002 the macro invocation explicit in the original text --- the invocation of
11003 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11004 which was introduced by @code{ADD}.
11006 Once the program is running, @value{GDBN} uses the macro definitions in
11007 force at the source line of the current stack frame:
11010 (@value{GDBP}) break main
11011 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11013 Starting program: /home/jimb/gdb/macros/play/sample
11015 Breakpoint 1, main () at sample.c:10
11016 10 printf ("Hello, world!\n");
11020 At line 10, the definition of the macro @code{N} at line 9 is in force:
11023 (@value{GDBP}) info macro N
11024 Defined at /home/jimb/gdb/macros/play/sample.c:9
11026 (@value{GDBP}) macro expand N Q M
11027 expands to: 28 < 42
11028 (@value{GDBP}) print N Q M
11033 As we step over directives that remove @code{N}'s definition, and then
11034 give it a new definition, @value{GDBN} finds the definition (or lack
11035 thereof) in force at each point:
11038 (@value{GDBP}) next
11040 12 printf ("We're so creative.\n");
11041 (@value{GDBP}) info macro N
11042 The symbol `N' has no definition as a C/C++ preprocessor macro
11043 at /home/jimb/gdb/macros/play/sample.c:12
11044 (@value{GDBP}) next
11046 14 printf ("Goodbye, world!\n");
11047 (@value{GDBP}) info macro N
11048 Defined at /home/jimb/gdb/macros/play/sample.c:13
11050 (@value{GDBP}) macro expand N Q M
11051 expands to: 1729 < 42
11052 (@value{GDBP}) print N Q M
11057 In addition to source files, macros can be defined on the compilation command
11058 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11059 such a way, @value{GDBN} displays the location of their definition as line zero
11060 of the source file submitted to the compiler.
11063 (@value{GDBP}) info macro __STDC__
11064 Defined at /home/jimb/gdb/macros/play/sample.c:0
11071 @chapter Tracepoints
11072 @c This chapter is based on the documentation written by Michael
11073 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11075 @cindex tracepoints
11076 In some applications, it is not feasible for the debugger to interrupt
11077 the program's execution long enough for the developer to learn
11078 anything helpful about its behavior. If the program's correctness
11079 depends on its real-time behavior, delays introduced by a debugger
11080 might cause the program to change its behavior drastically, or perhaps
11081 fail, even when the code itself is correct. It is useful to be able
11082 to observe the program's behavior without interrupting it.
11084 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11085 specify locations in the program, called @dfn{tracepoints}, and
11086 arbitrary expressions to evaluate when those tracepoints are reached.
11087 Later, using the @code{tfind} command, you can examine the values
11088 those expressions had when the program hit the tracepoints. The
11089 expressions may also denote objects in memory---structures or arrays,
11090 for example---whose values @value{GDBN} should record; while visiting
11091 a particular tracepoint, you may inspect those objects as if they were
11092 in memory at that moment. However, because @value{GDBN} records these
11093 values without interacting with you, it can do so quickly and
11094 unobtrusively, hopefully not disturbing the program's behavior.
11096 The tracepoint facility is currently available only for remote
11097 targets. @xref{Targets}. In addition, your remote target must know
11098 how to collect trace data. This functionality is implemented in the
11099 remote stub; however, none of the stubs distributed with @value{GDBN}
11100 support tracepoints as of this writing. The format of the remote
11101 packets used to implement tracepoints are described in @ref{Tracepoint
11104 It is also possible to get trace data from a file, in a manner reminiscent
11105 of corefiles; you specify the filename, and use @code{tfind} to search
11106 through the file. @xref{Trace Files}, for more details.
11108 This chapter describes the tracepoint commands and features.
11111 * Set Tracepoints::
11112 * Analyze Collected Data::
11113 * Tracepoint Variables::
11117 @node Set Tracepoints
11118 @section Commands to Set Tracepoints
11120 Before running such a @dfn{trace experiment}, an arbitrary number of
11121 tracepoints can be set. A tracepoint is actually a special type of
11122 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11123 standard breakpoint commands. For instance, as with breakpoints,
11124 tracepoint numbers are successive integers starting from one, and many
11125 of the commands associated with tracepoints take the tracepoint number
11126 as their argument, to identify which tracepoint to work on.
11128 For each tracepoint, you can specify, in advance, some arbitrary set
11129 of data that you want the target to collect in the trace buffer when
11130 it hits that tracepoint. The collected data can include registers,
11131 local variables, or global data. Later, you can use @value{GDBN}
11132 commands to examine the values these data had at the time the
11133 tracepoint was hit.
11135 Tracepoints do not support every breakpoint feature. Ignore counts on
11136 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11137 commands when they are hit. Tracepoints may not be thread-specific
11140 @cindex fast tracepoints
11141 Some targets may support @dfn{fast tracepoints}, which are inserted in
11142 a different way (such as with a jump instead of a trap), that is
11143 faster but possibly restricted in where they may be installed.
11145 @cindex static tracepoints
11146 @cindex markers, static tracepoints
11147 @cindex probing markers, static tracepoints
11148 Regular and fast tracepoints are dynamic tracing facilities, meaning
11149 that they can be used to insert tracepoints at (almost) any location
11150 in the target. Some targets may also support controlling @dfn{static
11151 tracepoints} from @value{GDBN}. With static tracing, a set of
11152 instrumentation points, also known as @dfn{markers}, are embedded in
11153 the target program, and can be activated or deactivated by name or
11154 address. These are usually placed at locations which facilitate
11155 investigating what the target is actually doing. @value{GDBN}'s
11156 support for static tracing includes being able to list instrumentation
11157 points, and attach them with @value{GDBN} defined high level
11158 tracepoints that expose the whole range of convenience of
11159 @value{GDBN}'s tracepoints support. Namely, support for collecting
11160 registers values and values of global or local (to the instrumentation
11161 point) variables; tracepoint conditions and trace state variables.
11162 The act of installing a @value{GDBN} static tracepoint on an
11163 instrumentation point, or marker, is referred to as @dfn{probing} a
11164 static tracepoint marker.
11166 @code{gdbserver} supports tracepoints on some target systems.
11167 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11169 This section describes commands to set tracepoints and associated
11170 conditions and actions.
11173 * Create and Delete Tracepoints::
11174 * Enable and Disable Tracepoints::
11175 * Tracepoint Passcounts::
11176 * Tracepoint Conditions::
11177 * Trace State Variables::
11178 * Tracepoint Actions::
11179 * Listing Tracepoints::
11180 * Listing Static Tracepoint Markers::
11181 * Starting and Stopping Trace Experiments::
11182 * Tracepoint Restrictions::
11185 @node Create and Delete Tracepoints
11186 @subsection Create and Delete Tracepoints
11189 @cindex set tracepoint
11191 @item trace @var{location}
11192 The @code{trace} command is very similar to the @code{break} command.
11193 Its argument @var{location} can be a source line, a function name, or
11194 an address in the target program. @xref{Specify Location}. The
11195 @code{trace} command defines a tracepoint, which is a point in the
11196 target program where the debugger will briefly stop, collect some
11197 data, and then allow the program to continue. Setting a tracepoint or
11198 changing its actions takes effect immediately if the remote stub
11199 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11201 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11202 these changes don't take effect until the next @code{tstart}
11203 command, and once a trace experiment is running, further changes will
11204 not have any effect until the next trace experiment starts. In addition,
11205 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11206 address is not yet resolved. (This is similar to pending breakpoints.)
11207 Pending tracepoints are not downloaded to the target and not installed
11208 until they are resolved. The resolution of pending tracepoints requires
11209 @value{GDBN} support---when debugging with the remote target, and
11210 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11211 tracing}), pending tracepoints can not be resolved (and downloaded to
11212 the remote stub) while @value{GDBN} is disconnected.
11214 Here are some examples of using the @code{trace} command:
11217 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11219 (@value{GDBP}) @b{trace +2} // 2 lines forward
11221 (@value{GDBP}) @b{trace my_function} // first source line of function
11223 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11225 (@value{GDBP}) @b{trace *0x2117c4} // an address
11229 You can abbreviate @code{trace} as @code{tr}.
11231 @item trace @var{location} if @var{cond}
11232 Set a tracepoint with condition @var{cond}; evaluate the expression
11233 @var{cond} each time the tracepoint is reached, and collect data only
11234 if the value is nonzero---that is, if @var{cond} evaluates as true.
11235 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11236 information on tracepoint conditions.
11238 @item ftrace @var{location} [ if @var{cond} ]
11239 @cindex set fast tracepoint
11240 @cindex fast tracepoints, setting
11242 The @code{ftrace} command sets a fast tracepoint. For targets that
11243 support them, fast tracepoints will use a more efficient but possibly
11244 less general technique to trigger data collection, such as a jump
11245 instruction instead of a trap, or some sort of hardware support. It
11246 may not be possible to create a fast tracepoint at the desired
11247 location, in which case the command will exit with an explanatory
11250 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11253 On 32-bit x86-architecture systems, fast tracepoints normally need to
11254 be placed at an instruction that is 5 bytes or longer, but can be
11255 placed at 4-byte instructions if the low 64K of memory of the target
11256 program is available to install trampolines. Some Unix-type systems,
11257 such as @sc{gnu}/Linux, exclude low addresses from the program's
11258 address space; but for instance with the Linux kernel it is possible
11259 to let @value{GDBN} use this area by doing a @command{sysctl} command
11260 to set the @code{mmap_min_addr} kernel parameter, as in
11263 sudo sysctl -w vm.mmap_min_addr=32768
11267 which sets the low address to 32K, which leaves plenty of room for
11268 trampolines. The minimum address should be set to a page boundary.
11270 @item strace @var{location} [ if @var{cond} ]
11271 @cindex set static tracepoint
11272 @cindex static tracepoints, setting
11273 @cindex probe static tracepoint marker
11275 The @code{strace} command sets a static tracepoint. For targets that
11276 support it, setting a static tracepoint probes a static
11277 instrumentation point, or marker, found at @var{location}. It may not
11278 be possible to set a static tracepoint at the desired location, in
11279 which case the command will exit with an explanatory message.
11281 @value{GDBN} handles arguments to @code{strace} exactly as for
11282 @code{trace}, with the addition that the user can also specify
11283 @code{-m @var{marker}} as @var{location}. This probes the marker
11284 identified by the @var{marker} string identifier. This identifier
11285 depends on the static tracepoint backend library your program is
11286 using. You can find all the marker identifiers in the @samp{ID} field
11287 of the @code{info static-tracepoint-markers} command output.
11288 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11289 Markers}. For example, in the following small program using the UST
11295 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11300 the marker id is composed of joining the first two arguments to the
11301 @code{trace_mark} call with a slash, which translates to:
11304 (@value{GDBP}) info static-tracepoint-markers
11305 Cnt Enb ID Address What
11306 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11312 so you may probe the marker above with:
11315 (@value{GDBP}) strace -m ust/bar33
11318 Static tracepoints accept an extra collect action --- @code{collect
11319 $_sdata}. This collects arbitrary user data passed in the probe point
11320 call to the tracing library. In the UST example above, you'll see
11321 that the third argument to @code{trace_mark} is a printf-like format
11322 string. The user data is then the result of running that formating
11323 string against the following arguments. Note that @code{info
11324 static-tracepoint-markers} command output lists that format string in
11325 the @samp{Data:} field.
11327 You can inspect this data when analyzing the trace buffer, by printing
11328 the $_sdata variable like any other variable available to
11329 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11332 @cindex last tracepoint number
11333 @cindex recent tracepoint number
11334 @cindex tracepoint number
11335 The convenience variable @code{$tpnum} records the tracepoint number
11336 of the most recently set tracepoint.
11338 @kindex delete tracepoint
11339 @cindex tracepoint deletion
11340 @item delete tracepoint @r{[}@var{num}@r{]}
11341 Permanently delete one or more tracepoints. With no argument, the
11342 default is to delete all tracepoints. Note that the regular
11343 @code{delete} command can remove tracepoints also.
11348 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11350 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11354 You can abbreviate this command as @code{del tr}.
11357 @node Enable and Disable Tracepoints
11358 @subsection Enable and Disable Tracepoints
11360 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11363 @kindex disable tracepoint
11364 @item disable tracepoint @r{[}@var{num}@r{]}
11365 Disable tracepoint @var{num}, or all tracepoints if no argument
11366 @var{num} is given. A disabled tracepoint will have no effect during
11367 a trace experiment, but it is not forgotten. You can re-enable
11368 a disabled tracepoint using the @code{enable tracepoint} command.
11369 If the command is issued during a trace experiment and the debug target
11370 has support for disabling tracepoints during a trace experiment, then the
11371 change will be effective immediately. Otherwise, it will be applied to the
11372 next trace experiment.
11374 @kindex enable tracepoint
11375 @item enable tracepoint @r{[}@var{num}@r{]}
11376 Enable tracepoint @var{num}, or all tracepoints. If this command is
11377 issued during a trace experiment and the debug target supports enabling
11378 tracepoints during a trace experiment, then the enabled tracepoints will
11379 become effective immediately. Otherwise, they will become effective the
11380 next time a trace experiment is run.
11383 @node Tracepoint Passcounts
11384 @subsection Tracepoint Passcounts
11388 @cindex tracepoint pass count
11389 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11390 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11391 automatically stop a trace experiment. If a tracepoint's passcount is
11392 @var{n}, then the trace experiment will be automatically stopped on
11393 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11394 @var{num} is not specified, the @code{passcount} command sets the
11395 passcount of the most recently defined tracepoint. If no passcount is
11396 given, the trace experiment will run until stopped explicitly by the
11402 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11403 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11405 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11406 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11407 (@value{GDBP}) @b{trace foo}
11408 (@value{GDBP}) @b{pass 3}
11409 (@value{GDBP}) @b{trace bar}
11410 (@value{GDBP}) @b{pass 2}
11411 (@value{GDBP}) @b{trace baz}
11412 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11413 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11414 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11415 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11419 @node Tracepoint Conditions
11420 @subsection Tracepoint Conditions
11421 @cindex conditional tracepoints
11422 @cindex tracepoint conditions
11424 The simplest sort of tracepoint collects data every time your program
11425 reaches a specified place. You can also specify a @dfn{condition} for
11426 a tracepoint. A condition is just a Boolean expression in your
11427 programming language (@pxref{Expressions, ,Expressions}). A
11428 tracepoint with a condition evaluates the expression each time your
11429 program reaches it, and data collection happens only if the condition
11432 Tracepoint conditions can be specified when a tracepoint is set, by
11433 using @samp{if} in the arguments to the @code{trace} command.
11434 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11435 also be set or changed at any time with the @code{condition} command,
11436 just as with breakpoints.
11438 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11439 the conditional expression itself. Instead, @value{GDBN} encodes the
11440 expression into an agent expression (@pxref{Agent Expressions})
11441 suitable for execution on the target, independently of @value{GDBN}.
11442 Global variables become raw memory locations, locals become stack
11443 accesses, and so forth.
11445 For instance, suppose you have a function that is usually called
11446 frequently, but should not be called after an error has occurred. You
11447 could use the following tracepoint command to collect data about calls
11448 of that function that happen while the error code is propagating
11449 through the program; an unconditional tracepoint could end up
11450 collecting thousands of useless trace frames that you would have to
11454 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11457 @node Trace State Variables
11458 @subsection Trace State Variables
11459 @cindex trace state variables
11461 A @dfn{trace state variable} is a special type of variable that is
11462 created and managed by target-side code. The syntax is the same as
11463 that for GDB's convenience variables (a string prefixed with ``$''),
11464 but they are stored on the target. They must be created explicitly,
11465 using a @code{tvariable} command. They are always 64-bit signed
11468 Trace state variables are remembered by @value{GDBN}, and downloaded
11469 to the target along with tracepoint information when the trace
11470 experiment starts. There are no intrinsic limits on the number of
11471 trace state variables, beyond memory limitations of the target.
11473 @cindex convenience variables, and trace state variables
11474 Although trace state variables are managed by the target, you can use
11475 them in print commands and expressions as if they were convenience
11476 variables; @value{GDBN} will get the current value from the target
11477 while the trace experiment is running. Trace state variables share
11478 the same namespace as other ``$'' variables, which means that you
11479 cannot have trace state variables with names like @code{$23} or
11480 @code{$pc}, nor can you have a trace state variable and a convenience
11481 variable with the same name.
11485 @item tvariable $@var{name} [ = @var{expression} ]
11487 The @code{tvariable} command creates a new trace state variable named
11488 @code{$@var{name}}, and optionally gives it an initial value of
11489 @var{expression}. @var{expression} is evaluated when this command is
11490 entered; the result will be converted to an integer if possible,
11491 otherwise @value{GDBN} will report an error. A subsequent
11492 @code{tvariable} command specifying the same name does not create a
11493 variable, but instead assigns the supplied initial value to the
11494 existing variable of that name, overwriting any previous initial
11495 value. The default initial value is 0.
11497 @item info tvariables
11498 @kindex info tvariables
11499 List all the trace state variables along with their initial values.
11500 Their current values may also be displayed, if the trace experiment is
11503 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11504 @kindex delete tvariable
11505 Delete the given trace state variables, or all of them if no arguments
11510 @node Tracepoint Actions
11511 @subsection Tracepoint Action Lists
11515 @cindex tracepoint actions
11516 @item actions @r{[}@var{num}@r{]}
11517 This command will prompt for a list of actions to be taken when the
11518 tracepoint is hit. If the tracepoint number @var{num} is not
11519 specified, this command sets the actions for the one that was most
11520 recently defined (so that you can define a tracepoint and then say
11521 @code{actions} without bothering about its number). You specify the
11522 actions themselves on the following lines, one action at a time, and
11523 terminate the actions list with a line containing just @code{end}. So
11524 far, the only defined actions are @code{collect}, @code{teval}, and
11525 @code{while-stepping}.
11527 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11528 Commands, ,Breakpoint Command Lists}), except that only the defined
11529 actions are allowed; any other @value{GDBN} command is rejected.
11531 @cindex remove actions from a tracepoint
11532 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11533 and follow it immediately with @samp{end}.
11536 (@value{GDBP}) @b{collect @var{data}} // collect some data
11538 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11540 (@value{GDBP}) @b{end} // signals the end of actions.
11543 In the following example, the action list begins with @code{collect}
11544 commands indicating the things to be collected when the tracepoint is
11545 hit. Then, in order to single-step and collect additional data
11546 following the tracepoint, a @code{while-stepping} command is used,
11547 followed by the list of things to be collected after each step in a
11548 sequence of single steps. The @code{while-stepping} command is
11549 terminated by its own separate @code{end} command. Lastly, the action
11550 list is terminated by an @code{end} command.
11553 (@value{GDBP}) @b{trace foo}
11554 (@value{GDBP}) @b{actions}
11555 Enter actions for tracepoint 1, one per line:
11558 > while-stepping 12
11559 > collect $pc, arr[i]
11564 @kindex collect @r{(tracepoints)}
11565 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11566 Collect values of the given expressions when the tracepoint is hit.
11567 This command accepts a comma-separated list of any valid expressions.
11568 In addition to global, static, or local variables, the following
11569 special arguments are supported:
11573 Collect all registers.
11576 Collect all function arguments.
11579 Collect all local variables.
11582 Collect the return address. This is helpful if you want to see more
11586 Collects the number of arguments from the static probe at which the
11587 tracepoint is located.
11588 @xref{Static Probe Points}.
11590 @item $_probe_arg@var{n}
11591 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11592 from the static probe at which the tracepoint is located.
11593 @xref{Static Probe Points}.
11596 @vindex $_sdata@r{, collect}
11597 Collect static tracepoint marker specific data. Only available for
11598 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11599 Lists}. On the UST static tracepoints library backend, an
11600 instrumentation point resembles a @code{printf} function call. The
11601 tracing library is able to collect user specified data formatted to a
11602 character string using the format provided by the programmer that
11603 instrumented the program. Other backends have similar mechanisms.
11604 Here's an example of a UST marker call:
11607 const char master_name[] = "$your_name";
11608 trace_mark(channel1, marker1, "hello %s", master_name)
11611 In this case, collecting @code{$_sdata} collects the string
11612 @samp{hello $yourname}. When analyzing the trace buffer, you can
11613 inspect @samp{$_sdata} like any other variable available to
11617 You can give several consecutive @code{collect} commands, each one
11618 with a single argument, or one @code{collect} command with several
11619 arguments separated by commas; the effect is the same.
11621 The optional @var{mods} changes the usual handling of the arguments.
11622 @code{s} requests that pointers to chars be handled as strings, in
11623 particular collecting the contents of the memory being pointed at, up
11624 to the first zero. The upper bound is by default the value of the
11625 @code{print elements} variable; if @code{s} is followed by a decimal
11626 number, that is the upper bound instead. So for instance
11627 @samp{collect/s25 mystr} collects as many as 25 characters at
11630 The command @code{info scope} (@pxref{Symbols, info scope}) is
11631 particularly useful for figuring out what data to collect.
11633 @kindex teval @r{(tracepoints)}
11634 @item teval @var{expr1}, @var{expr2}, @dots{}
11635 Evaluate the given expressions when the tracepoint is hit. This
11636 command accepts a comma-separated list of expressions. The results
11637 are discarded, so this is mainly useful for assigning values to trace
11638 state variables (@pxref{Trace State Variables}) without adding those
11639 values to the trace buffer, as would be the case if the @code{collect}
11642 @kindex while-stepping @r{(tracepoints)}
11643 @item while-stepping @var{n}
11644 Perform @var{n} single-step instruction traces after the tracepoint,
11645 collecting new data after each step. The @code{while-stepping}
11646 command is followed by the list of what to collect while stepping
11647 (followed by its own @code{end} command):
11650 > while-stepping 12
11651 > collect $regs, myglobal
11657 Note that @code{$pc} is not automatically collected by
11658 @code{while-stepping}; you need to explicitly collect that register if
11659 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11662 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11663 @kindex set default-collect
11664 @cindex default collection action
11665 This variable is a list of expressions to collect at each tracepoint
11666 hit. It is effectively an additional @code{collect} action prepended
11667 to every tracepoint action list. The expressions are parsed
11668 individually for each tracepoint, so for instance a variable named
11669 @code{xyz} may be interpreted as a global for one tracepoint, and a
11670 local for another, as appropriate to the tracepoint's location.
11672 @item show default-collect
11673 @kindex show default-collect
11674 Show the list of expressions that are collected by default at each
11679 @node Listing Tracepoints
11680 @subsection Listing Tracepoints
11683 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11684 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11685 @cindex information about tracepoints
11686 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11687 Display information about the tracepoint @var{num}. If you don't
11688 specify a tracepoint number, displays information about all the
11689 tracepoints defined so far. The format is similar to that used for
11690 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11691 command, simply restricting itself to tracepoints.
11693 A tracepoint's listing may include additional information specific to
11698 its passcount as given by the @code{passcount @var{n}} command
11701 the state about installed on target of each location
11705 (@value{GDBP}) @b{info trace}
11706 Num Type Disp Enb Address What
11707 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11709 collect globfoo, $regs
11714 2 tracepoint keep y <MULTIPLE>
11716 2.1 y 0x0804859c in func4 at change-loc.h:35
11717 installed on target
11718 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11719 installed on target
11720 2.3 y <PENDING> set_tracepoint
11721 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11722 not installed on target
11727 This command can be abbreviated @code{info tp}.
11730 @node Listing Static Tracepoint Markers
11731 @subsection Listing Static Tracepoint Markers
11734 @kindex info static-tracepoint-markers
11735 @cindex information about static tracepoint markers
11736 @item info static-tracepoint-markers
11737 Display information about all static tracepoint markers defined in the
11740 For each marker, the following columns are printed:
11744 An incrementing counter, output to help readability. This is not a
11747 The marker ID, as reported by the target.
11748 @item Enabled or Disabled
11749 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11750 that are not enabled.
11752 Where the marker is in your program, as a memory address.
11754 Where the marker is in the source for your program, as a file and line
11755 number. If the debug information included in the program does not
11756 allow @value{GDBN} to locate the source of the marker, this column
11757 will be left blank.
11761 In addition, the following information may be printed for each marker:
11765 User data passed to the tracing library by the marker call. In the
11766 UST backend, this is the format string passed as argument to the
11768 @item Static tracepoints probing the marker
11769 The list of static tracepoints attached to the marker.
11773 (@value{GDBP}) info static-tracepoint-markers
11774 Cnt ID Enb Address What
11775 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11776 Data: number1 %d number2 %d
11777 Probed by static tracepoints: #2
11778 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11784 @node Starting and Stopping Trace Experiments
11785 @subsection Starting and Stopping Trace Experiments
11788 @kindex tstart [ @var{notes} ]
11789 @cindex start a new trace experiment
11790 @cindex collected data discarded
11792 This command starts the trace experiment, and begins collecting data.
11793 It has the side effect of discarding all the data collected in the
11794 trace buffer during the previous trace experiment. If any arguments
11795 are supplied, they are taken as a note and stored with the trace
11796 experiment's state. The notes may be arbitrary text, and are
11797 especially useful with disconnected tracing in a multi-user context;
11798 the notes can explain what the trace is doing, supply user contact
11799 information, and so forth.
11801 @kindex tstop [ @var{notes} ]
11802 @cindex stop a running trace experiment
11804 This command stops the trace experiment. If any arguments are
11805 supplied, they are recorded with the experiment as a note. This is
11806 useful if you are stopping a trace started by someone else, for
11807 instance if the trace is interfering with the system's behavior and
11808 needs to be stopped quickly.
11810 @strong{Note}: a trace experiment and data collection may stop
11811 automatically if any tracepoint's passcount is reached
11812 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11815 @cindex status of trace data collection
11816 @cindex trace experiment, status of
11818 This command displays the status of the current trace data
11822 Here is an example of the commands we described so far:
11825 (@value{GDBP}) @b{trace gdb_c_test}
11826 (@value{GDBP}) @b{actions}
11827 Enter actions for tracepoint #1, one per line.
11828 > collect $regs,$locals,$args
11829 > while-stepping 11
11833 (@value{GDBP}) @b{tstart}
11834 [time passes @dots{}]
11835 (@value{GDBP}) @b{tstop}
11838 @anchor{disconnected tracing}
11839 @cindex disconnected tracing
11840 You can choose to continue running the trace experiment even if
11841 @value{GDBN} disconnects from the target, voluntarily or
11842 involuntarily. For commands such as @code{detach}, the debugger will
11843 ask what you want to do with the trace. But for unexpected
11844 terminations (@value{GDBN} crash, network outage), it would be
11845 unfortunate to lose hard-won trace data, so the variable
11846 @code{disconnected-tracing} lets you decide whether the trace should
11847 continue running without @value{GDBN}.
11850 @item set disconnected-tracing on
11851 @itemx set disconnected-tracing off
11852 @kindex set disconnected-tracing
11853 Choose whether a tracing run should continue to run if @value{GDBN}
11854 has disconnected from the target. Note that @code{detach} or
11855 @code{quit} will ask you directly what to do about a running trace no
11856 matter what this variable's setting, so the variable is mainly useful
11857 for handling unexpected situations, such as loss of the network.
11859 @item show disconnected-tracing
11860 @kindex show disconnected-tracing
11861 Show the current choice for disconnected tracing.
11865 When you reconnect to the target, the trace experiment may or may not
11866 still be running; it might have filled the trace buffer in the
11867 meantime, or stopped for one of the other reasons. If it is running,
11868 it will continue after reconnection.
11870 Upon reconnection, the target will upload information about the
11871 tracepoints in effect. @value{GDBN} will then compare that
11872 information to the set of tracepoints currently defined, and attempt
11873 to match them up, allowing for the possibility that the numbers may
11874 have changed due to creation and deletion in the meantime. If one of
11875 the target's tracepoints does not match any in @value{GDBN}, the
11876 debugger will create a new tracepoint, so that you have a number with
11877 which to specify that tracepoint. This matching-up process is
11878 necessarily heuristic, and it may result in useless tracepoints being
11879 created; you may simply delete them if they are of no use.
11881 @cindex circular trace buffer
11882 If your target agent supports a @dfn{circular trace buffer}, then you
11883 can run a trace experiment indefinitely without filling the trace
11884 buffer; when space runs out, the agent deletes already-collected trace
11885 frames, oldest first, until there is enough room to continue
11886 collecting. This is especially useful if your tracepoints are being
11887 hit too often, and your trace gets terminated prematurely because the
11888 buffer is full. To ask for a circular trace buffer, simply set
11889 @samp{circular-trace-buffer} to on. You can set this at any time,
11890 including during tracing; if the agent can do it, it will change
11891 buffer handling on the fly, otherwise it will not take effect until
11895 @item set circular-trace-buffer on
11896 @itemx set circular-trace-buffer off
11897 @kindex set circular-trace-buffer
11898 Choose whether a tracing run should use a linear or circular buffer
11899 for trace data. A linear buffer will not lose any trace data, but may
11900 fill up prematurely, while a circular buffer will discard old trace
11901 data, but it will have always room for the latest tracepoint hits.
11903 @item show circular-trace-buffer
11904 @kindex show circular-trace-buffer
11905 Show the current choice for the trace buffer. Note that this may not
11906 match the agent's current buffer handling, nor is it guaranteed to
11907 match the setting that might have been in effect during a past run,
11908 for instance if you are looking at frames from a trace file.
11913 @item set trace-buffer-size @var{n}
11914 @itemx set trace-buffer-size unlimited
11915 @kindex set trace-buffer-size
11916 Request that the target use a trace buffer of @var{n} bytes. Not all
11917 targets will honor the request; they may have a compiled-in size for
11918 the trace buffer, or some other limitation. Set to a value of
11919 @code{unlimited} or @code{-1} to let the target use whatever size it
11920 likes. This is also the default.
11922 @item show trace-buffer-size
11923 @kindex show trace-buffer-size
11924 Show the current requested size for the trace buffer. Note that this
11925 will only match the actual size if the target supports size-setting,
11926 and was able to handle the requested size. For instance, if the
11927 target can only change buffer size between runs, this variable will
11928 not reflect the change until the next run starts. Use @code{tstatus}
11929 to get a report of the actual buffer size.
11933 @item set trace-user @var{text}
11934 @kindex set trace-user
11936 @item show trace-user
11937 @kindex show trace-user
11939 @item set trace-notes @var{text}
11940 @kindex set trace-notes
11941 Set the trace run's notes.
11943 @item show trace-notes
11944 @kindex show trace-notes
11945 Show the trace run's notes.
11947 @item set trace-stop-notes @var{text}
11948 @kindex set trace-stop-notes
11949 Set the trace run's stop notes. The handling of the note is as for
11950 @code{tstop} arguments; the set command is convenient way to fix a
11951 stop note that is mistaken or incomplete.
11953 @item show trace-stop-notes
11954 @kindex show trace-stop-notes
11955 Show the trace run's stop notes.
11959 @node Tracepoint Restrictions
11960 @subsection Tracepoint Restrictions
11962 @cindex tracepoint restrictions
11963 There are a number of restrictions on the use of tracepoints. As
11964 described above, tracepoint data gathering occurs on the target
11965 without interaction from @value{GDBN}. Thus the full capabilities of
11966 the debugger are not available during data gathering, and then at data
11967 examination time, you will be limited by only having what was
11968 collected. The following items describe some common problems, but it
11969 is not exhaustive, and you may run into additional difficulties not
11975 Tracepoint expressions are intended to gather objects (lvalues). Thus
11976 the full flexibility of GDB's expression evaluator is not available.
11977 You cannot call functions, cast objects to aggregate types, access
11978 convenience variables or modify values (except by assignment to trace
11979 state variables). Some language features may implicitly call
11980 functions (for instance Objective-C fields with accessors), and therefore
11981 cannot be collected either.
11984 Collection of local variables, either individually or in bulk with
11985 @code{$locals} or @code{$args}, during @code{while-stepping} may
11986 behave erratically. The stepping action may enter a new scope (for
11987 instance by stepping into a function), or the location of the variable
11988 may change (for instance it is loaded into a register). The
11989 tracepoint data recorded uses the location information for the
11990 variables that is correct for the tracepoint location. When the
11991 tracepoint is created, it is not possible, in general, to determine
11992 where the steps of a @code{while-stepping} sequence will advance the
11993 program---particularly if a conditional branch is stepped.
11996 Collection of an incompletely-initialized or partially-destroyed object
11997 may result in something that @value{GDBN} cannot display, or displays
11998 in a misleading way.
12001 When @value{GDBN} displays a pointer to character it automatically
12002 dereferences the pointer to also display characters of the string
12003 being pointed to. However, collecting the pointer during tracing does
12004 not automatically collect the string. You need to explicitly
12005 dereference the pointer and provide size information if you want to
12006 collect not only the pointer, but the memory pointed to. For example,
12007 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12011 It is not possible to collect a complete stack backtrace at a
12012 tracepoint. Instead, you may collect the registers and a few hundred
12013 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12014 (adjust to use the name of the actual stack pointer register on your
12015 target architecture, and the amount of stack you wish to capture).
12016 Then the @code{backtrace} command will show a partial backtrace when
12017 using a trace frame. The number of stack frames that can be examined
12018 depends on the sizes of the frames in the collected stack. Note that
12019 if you ask for a block so large that it goes past the bottom of the
12020 stack, the target agent may report an error trying to read from an
12024 If you do not collect registers at a tracepoint, @value{GDBN} can
12025 infer that the value of @code{$pc} must be the same as the address of
12026 the tracepoint and use that when you are looking at a trace frame
12027 for that tracepoint. However, this cannot work if the tracepoint has
12028 multiple locations (for instance if it was set in a function that was
12029 inlined), or if it has a @code{while-stepping} loop. In those cases
12030 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12035 @node Analyze Collected Data
12036 @section Using the Collected Data
12038 After the tracepoint experiment ends, you use @value{GDBN} commands
12039 for examining the trace data. The basic idea is that each tracepoint
12040 collects a trace @dfn{snapshot} every time it is hit and another
12041 snapshot every time it single-steps. All these snapshots are
12042 consecutively numbered from zero and go into a buffer, and you can
12043 examine them later. The way you examine them is to @dfn{focus} on a
12044 specific trace snapshot. When the remote stub is focused on a trace
12045 snapshot, it will respond to all @value{GDBN} requests for memory and
12046 registers by reading from the buffer which belongs to that snapshot,
12047 rather than from @emph{real} memory or registers of the program being
12048 debugged. This means that @strong{all} @value{GDBN} commands
12049 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12050 behave as if we were currently debugging the program state as it was
12051 when the tracepoint occurred. Any requests for data that are not in
12052 the buffer will fail.
12055 * tfind:: How to select a trace snapshot
12056 * tdump:: How to display all data for a snapshot
12057 * save tracepoints:: How to save tracepoints for a future run
12061 @subsection @code{tfind @var{n}}
12064 @cindex select trace snapshot
12065 @cindex find trace snapshot
12066 The basic command for selecting a trace snapshot from the buffer is
12067 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12068 counting from zero. If no argument @var{n} is given, the next
12069 snapshot is selected.
12071 Here are the various forms of using the @code{tfind} command.
12075 Find the first snapshot in the buffer. This is a synonym for
12076 @code{tfind 0} (since 0 is the number of the first snapshot).
12079 Stop debugging trace snapshots, resume @emph{live} debugging.
12082 Same as @samp{tfind none}.
12085 No argument means find the next trace snapshot.
12088 Find the previous trace snapshot before the current one. This permits
12089 retracing earlier steps.
12091 @item tfind tracepoint @var{num}
12092 Find the next snapshot associated with tracepoint @var{num}. Search
12093 proceeds forward from the last examined trace snapshot. If no
12094 argument @var{num} is given, it means find the next snapshot collected
12095 for the same tracepoint as the current snapshot.
12097 @item tfind pc @var{addr}
12098 Find the next snapshot associated with the value @var{addr} of the
12099 program counter. Search proceeds forward from the last examined trace
12100 snapshot. If no argument @var{addr} is given, it means find the next
12101 snapshot with the same value of PC as the current snapshot.
12103 @item tfind outside @var{addr1}, @var{addr2}
12104 Find the next snapshot whose PC is outside the given range of
12105 addresses (exclusive).
12107 @item tfind range @var{addr1}, @var{addr2}
12108 Find the next snapshot whose PC is between @var{addr1} and
12109 @var{addr2} (inclusive).
12111 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12112 Find the next snapshot associated with the source line @var{n}. If
12113 the optional argument @var{file} is given, refer to line @var{n} in
12114 that source file. Search proceeds forward from the last examined
12115 trace snapshot. If no argument @var{n} is given, it means find the
12116 next line other than the one currently being examined; thus saying
12117 @code{tfind line} repeatedly can appear to have the same effect as
12118 stepping from line to line in a @emph{live} debugging session.
12121 The default arguments for the @code{tfind} commands are specifically
12122 designed to make it easy to scan through the trace buffer. For
12123 instance, @code{tfind} with no argument selects the next trace
12124 snapshot, and @code{tfind -} with no argument selects the previous
12125 trace snapshot. So, by giving one @code{tfind} command, and then
12126 simply hitting @key{RET} repeatedly you can examine all the trace
12127 snapshots in order. Or, by saying @code{tfind -} and then hitting
12128 @key{RET} repeatedly you can examine the snapshots in reverse order.
12129 The @code{tfind line} command with no argument selects the snapshot
12130 for the next source line executed. The @code{tfind pc} command with
12131 no argument selects the next snapshot with the same program counter
12132 (PC) as the current frame. The @code{tfind tracepoint} command with
12133 no argument selects the next trace snapshot collected by the same
12134 tracepoint as the current one.
12136 In addition to letting you scan through the trace buffer manually,
12137 these commands make it easy to construct @value{GDBN} scripts that
12138 scan through the trace buffer and print out whatever collected data
12139 you are interested in. Thus, if we want to examine the PC, FP, and SP
12140 registers from each trace frame in the buffer, we can say this:
12143 (@value{GDBP}) @b{tfind start}
12144 (@value{GDBP}) @b{while ($trace_frame != -1)}
12145 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12146 $trace_frame, $pc, $sp, $fp
12150 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12151 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12152 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12153 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12154 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12155 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12156 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12157 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12158 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12159 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12160 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12163 Or, if we want to examine the variable @code{X} at each source line in
12167 (@value{GDBP}) @b{tfind start}
12168 (@value{GDBP}) @b{while ($trace_frame != -1)}
12169 > printf "Frame %d, X == %d\n", $trace_frame, X
12179 @subsection @code{tdump}
12181 @cindex dump all data collected at tracepoint
12182 @cindex tracepoint data, display
12184 This command takes no arguments. It prints all the data collected at
12185 the current trace snapshot.
12188 (@value{GDBP}) @b{trace 444}
12189 (@value{GDBP}) @b{actions}
12190 Enter actions for tracepoint #2, one per line:
12191 > collect $regs, $locals, $args, gdb_long_test
12194 (@value{GDBP}) @b{tstart}
12196 (@value{GDBP}) @b{tfind line 444}
12197 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12199 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12201 (@value{GDBP}) @b{tdump}
12202 Data collected at tracepoint 2, trace frame 1:
12203 d0 0xc4aa0085 -995491707
12207 d4 0x71aea3d 119204413
12210 d7 0x380035 3670069
12211 a0 0x19e24a 1696330
12212 a1 0x3000668 50333288
12214 a3 0x322000 3284992
12215 a4 0x3000698 50333336
12216 a5 0x1ad3cc 1758156
12217 fp 0x30bf3c 0x30bf3c
12218 sp 0x30bf34 0x30bf34
12220 pc 0x20b2c8 0x20b2c8
12224 p = 0x20e5b4 "gdb-test"
12231 gdb_long_test = 17 '\021'
12236 @code{tdump} works by scanning the tracepoint's current collection
12237 actions and printing the value of each expression listed. So
12238 @code{tdump} can fail, if after a run, you change the tracepoint's
12239 actions to mention variables that were not collected during the run.
12241 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12242 uses the collected value of @code{$pc} to distinguish between trace
12243 frames that were collected at the tracepoint hit, and frames that were
12244 collected while stepping. This allows it to correctly choose whether
12245 to display the basic list of collections, or the collections from the
12246 body of the while-stepping loop. However, if @code{$pc} was not collected,
12247 then @code{tdump} will always attempt to dump using the basic collection
12248 list, and may fail if a while-stepping frame does not include all the
12249 same data that is collected at the tracepoint hit.
12250 @c This is getting pretty arcane, example would be good.
12252 @node save tracepoints
12253 @subsection @code{save tracepoints @var{filename}}
12254 @kindex save tracepoints
12255 @kindex save-tracepoints
12256 @cindex save tracepoints for future sessions
12258 This command saves all current tracepoint definitions together with
12259 their actions and passcounts, into a file @file{@var{filename}}
12260 suitable for use in a later debugging session. To read the saved
12261 tracepoint definitions, use the @code{source} command (@pxref{Command
12262 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12263 alias for @w{@code{save tracepoints}}
12265 @node Tracepoint Variables
12266 @section Convenience Variables for Tracepoints
12267 @cindex tracepoint variables
12268 @cindex convenience variables for tracepoints
12271 @vindex $trace_frame
12272 @item (int) $trace_frame
12273 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12274 snapshot is selected.
12276 @vindex $tracepoint
12277 @item (int) $tracepoint
12278 The tracepoint for the current trace snapshot.
12280 @vindex $trace_line
12281 @item (int) $trace_line
12282 The line number for the current trace snapshot.
12284 @vindex $trace_file
12285 @item (char []) $trace_file
12286 The source file for the current trace snapshot.
12288 @vindex $trace_func
12289 @item (char []) $trace_func
12290 The name of the function containing @code{$tracepoint}.
12293 Note: @code{$trace_file} is not suitable for use in @code{printf},
12294 use @code{output} instead.
12296 Here's a simple example of using these convenience variables for
12297 stepping through all the trace snapshots and printing some of their
12298 data. Note that these are not the same as trace state variables,
12299 which are managed by the target.
12302 (@value{GDBP}) @b{tfind start}
12304 (@value{GDBP}) @b{while $trace_frame != -1}
12305 > output $trace_file
12306 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12312 @section Using Trace Files
12313 @cindex trace files
12315 In some situations, the target running a trace experiment may no
12316 longer be available; perhaps it crashed, or the hardware was needed
12317 for a different activity. To handle these cases, you can arrange to
12318 dump the trace data into a file, and later use that file as a source
12319 of trace data, via the @code{target tfile} command.
12324 @item tsave [ -r ] @var{filename}
12325 @itemx tsave [-ctf] @var{dirname}
12326 Save the trace data to @var{filename}. By default, this command
12327 assumes that @var{filename} refers to the host filesystem, so if
12328 necessary @value{GDBN} will copy raw trace data up from the target and
12329 then save it. If the target supports it, you can also supply the
12330 optional argument @code{-r} (``remote'') to direct the target to save
12331 the data directly into @var{filename} in its own filesystem, which may be
12332 more efficient if the trace buffer is very large. (Note, however, that
12333 @code{target tfile} can only read from files accessible to the host.)
12334 By default, this command will save trace frame in tfile format.
12335 You can supply the optional argument @code{-ctf} to save date in CTF
12336 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12337 that can be shared by multiple debugging and tracing tools. Please go to
12338 @indicateurl{http://www.efficios.com/ctf} to get more information.
12340 @kindex target tfile
12344 @item target tfile @var{filename}
12345 @itemx target ctf @var{dirname}
12346 Use the file named @var{filename} or directory named @var{dirname} as
12347 a source of trace data. Commands that examine data work as they do with
12348 a live target, but it is not possible to run any new trace experiments.
12349 @code{tstatus} will report the state of the trace run at the moment
12350 the data was saved, as well as the current trace frame you are examining.
12351 @var{filename} or @var{dirname} must be on a filesystem accessible to
12355 (@value{GDBP}) target ctf ctf.ctf
12356 (@value{GDBP}) tfind
12357 Found trace frame 0, tracepoint 2
12358 39 ++a; /* set tracepoint 1 here */
12359 (@value{GDBP}) tdump
12360 Data collected at tracepoint 2, trace frame 0:
12364 c = @{"123", "456", "789", "123", "456", "789"@}
12365 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12373 @chapter Debugging Programs That Use Overlays
12376 If your program is too large to fit completely in your target system's
12377 memory, you can sometimes use @dfn{overlays} to work around this
12378 problem. @value{GDBN} provides some support for debugging programs that
12382 * How Overlays Work:: A general explanation of overlays.
12383 * Overlay Commands:: Managing overlays in @value{GDBN}.
12384 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12385 mapped by asking the inferior.
12386 * Overlay Sample Program:: A sample program using overlays.
12389 @node How Overlays Work
12390 @section How Overlays Work
12391 @cindex mapped overlays
12392 @cindex unmapped overlays
12393 @cindex load address, overlay's
12394 @cindex mapped address
12395 @cindex overlay area
12397 Suppose you have a computer whose instruction address space is only 64
12398 kilobytes long, but which has much more memory which can be accessed by
12399 other means: special instructions, segment registers, or memory
12400 management hardware, for example. Suppose further that you want to
12401 adapt a program which is larger than 64 kilobytes to run on this system.
12403 One solution is to identify modules of your program which are relatively
12404 independent, and need not call each other directly; call these modules
12405 @dfn{overlays}. Separate the overlays from the main program, and place
12406 their machine code in the larger memory. Place your main program in
12407 instruction memory, but leave at least enough space there to hold the
12408 largest overlay as well.
12410 Now, to call a function located in an overlay, you must first copy that
12411 overlay's machine code from the large memory into the space set aside
12412 for it in the instruction memory, and then jump to its entry point
12415 @c NB: In the below the mapped area's size is greater or equal to the
12416 @c size of all overlays. This is intentional to remind the developer
12417 @c that overlays don't necessarily need to be the same size.
12421 Data Instruction Larger
12422 Address Space Address Space Address Space
12423 +-----------+ +-----------+ +-----------+
12425 +-----------+ +-----------+ +-----------+<-- overlay 1
12426 | program | | main | .----| overlay 1 | load address
12427 | variables | | program | | +-----------+
12428 | and heap | | | | | |
12429 +-----------+ | | | +-----------+<-- overlay 2
12430 | | +-----------+ | | | load address
12431 +-----------+ | | | .-| overlay 2 |
12433 mapped --->+-----------+ | | +-----------+
12434 address | | | | | |
12435 | overlay | <-' | | |
12436 | area | <---' +-----------+<-- overlay 3
12437 | | <---. | | load address
12438 +-----------+ `--| overlay 3 |
12445 @anchor{A code overlay}A code overlay
12449 The diagram (@pxref{A code overlay}) shows a system with separate data
12450 and instruction address spaces. To map an overlay, the program copies
12451 its code from the larger address space to the instruction address space.
12452 Since the overlays shown here all use the same mapped address, only one
12453 may be mapped at a time. For a system with a single address space for
12454 data and instructions, the diagram would be similar, except that the
12455 program variables and heap would share an address space with the main
12456 program and the overlay area.
12458 An overlay loaded into instruction memory and ready for use is called a
12459 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12460 instruction memory. An overlay not present (or only partially present)
12461 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12462 is its address in the larger memory. The mapped address is also called
12463 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12464 called the @dfn{load memory address}, or @dfn{LMA}.
12466 Unfortunately, overlays are not a completely transparent way to adapt a
12467 program to limited instruction memory. They introduce a new set of
12468 global constraints you must keep in mind as you design your program:
12473 Before calling or returning to a function in an overlay, your program
12474 must make sure that overlay is actually mapped. Otherwise, the call or
12475 return will transfer control to the right address, but in the wrong
12476 overlay, and your program will probably crash.
12479 If the process of mapping an overlay is expensive on your system, you
12480 will need to choose your overlays carefully to minimize their effect on
12481 your program's performance.
12484 The executable file you load onto your system must contain each
12485 overlay's instructions, appearing at the overlay's load address, not its
12486 mapped address. However, each overlay's instructions must be relocated
12487 and its symbols defined as if the overlay were at its mapped address.
12488 You can use GNU linker scripts to specify different load and relocation
12489 addresses for pieces of your program; see @ref{Overlay Description,,,
12490 ld.info, Using ld: the GNU linker}.
12493 The procedure for loading executable files onto your system must be able
12494 to load their contents into the larger address space as well as the
12495 instruction and data spaces.
12499 The overlay system described above is rather simple, and could be
12500 improved in many ways:
12505 If your system has suitable bank switch registers or memory management
12506 hardware, you could use those facilities to make an overlay's load area
12507 contents simply appear at their mapped address in instruction space.
12508 This would probably be faster than copying the overlay to its mapped
12509 area in the usual way.
12512 If your overlays are small enough, you could set aside more than one
12513 overlay area, and have more than one overlay mapped at a time.
12516 You can use overlays to manage data, as well as instructions. In
12517 general, data overlays are even less transparent to your design than
12518 code overlays: whereas code overlays only require care when you call or
12519 return to functions, data overlays require care every time you access
12520 the data. Also, if you change the contents of a data overlay, you
12521 must copy its contents back out to its load address before you can copy a
12522 different data overlay into the same mapped area.
12527 @node Overlay Commands
12528 @section Overlay Commands
12530 To use @value{GDBN}'s overlay support, each overlay in your program must
12531 correspond to a separate section of the executable file. The section's
12532 virtual memory address and load memory address must be the overlay's
12533 mapped and load addresses. Identifying overlays with sections allows
12534 @value{GDBN} to determine the appropriate address of a function or
12535 variable, depending on whether the overlay is mapped or not.
12537 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12538 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12543 Disable @value{GDBN}'s overlay support. When overlay support is
12544 disabled, @value{GDBN} assumes that all functions and variables are
12545 always present at their mapped addresses. By default, @value{GDBN}'s
12546 overlay support is disabled.
12548 @item overlay manual
12549 @cindex manual overlay debugging
12550 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12551 relies on you to tell it which overlays are mapped, and which are not,
12552 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12553 commands described below.
12555 @item overlay map-overlay @var{overlay}
12556 @itemx overlay map @var{overlay}
12557 @cindex map an overlay
12558 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12559 be the name of the object file section containing the overlay. When an
12560 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12561 functions and variables at their mapped addresses. @value{GDBN} assumes
12562 that any other overlays whose mapped ranges overlap that of
12563 @var{overlay} are now unmapped.
12565 @item overlay unmap-overlay @var{overlay}
12566 @itemx overlay unmap @var{overlay}
12567 @cindex unmap an overlay
12568 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12569 must be the name of the object file section containing the overlay.
12570 When an overlay is unmapped, @value{GDBN} assumes it can find the
12571 overlay's functions and variables at their load addresses.
12574 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12575 consults a data structure the overlay manager maintains in the inferior
12576 to see which overlays are mapped. For details, see @ref{Automatic
12577 Overlay Debugging}.
12579 @item overlay load-target
12580 @itemx overlay load
12581 @cindex reloading the overlay table
12582 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12583 re-reads the table @value{GDBN} automatically each time the inferior
12584 stops, so this command should only be necessary if you have changed the
12585 overlay mapping yourself using @value{GDBN}. This command is only
12586 useful when using automatic overlay debugging.
12588 @item overlay list-overlays
12589 @itemx overlay list
12590 @cindex listing mapped overlays
12591 Display a list of the overlays currently mapped, along with their mapped
12592 addresses, load addresses, and sizes.
12596 Normally, when @value{GDBN} prints a code address, it includes the name
12597 of the function the address falls in:
12600 (@value{GDBP}) print main
12601 $3 = @{int ()@} 0x11a0 <main>
12604 When overlay debugging is enabled, @value{GDBN} recognizes code in
12605 unmapped overlays, and prints the names of unmapped functions with
12606 asterisks around them. For example, if @code{foo} is a function in an
12607 unmapped overlay, @value{GDBN} prints it this way:
12610 (@value{GDBP}) overlay list
12611 No sections are mapped.
12612 (@value{GDBP}) print foo
12613 $5 = @{int (int)@} 0x100000 <*foo*>
12616 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12620 (@value{GDBP}) overlay list
12621 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12622 mapped at 0x1016 - 0x104a
12623 (@value{GDBP}) print foo
12624 $6 = @{int (int)@} 0x1016 <foo>
12627 When overlay debugging is enabled, @value{GDBN} can find the correct
12628 address for functions and variables in an overlay, whether or not the
12629 overlay is mapped. This allows most @value{GDBN} commands, like
12630 @code{break} and @code{disassemble}, to work normally, even on unmapped
12631 code. However, @value{GDBN}'s breakpoint support has some limitations:
12635 @cindex breakpoints in overlays
12636 @cindex overlays, setting breakpoints in
12637 You can set breakpoints in functions in unmapped overlays, as long as
12638 @value{GDBN} can write to the overlay at its load address.
12640 @value{GDBN} can not set hardware or simulator-based breakpoints in
12641 unmapped overlays. However, if you set a breakpoint at the end of your
12642 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12643 you are using manual overlay management), @value{GDBN} will re-set its
12644 breakpoints properly.
12648 @node Automatic Overlay Debugging
12649 @section Automatic Overlay Debugging
12650 @cindex automatic overlay debugging
12652 @value{GDBN} can automatically track which overlays are mapped and which
12653 are not, given some simple co-operation from the overlay manager in the
12654 inferior. If you enable automatic overlay debugging with the
12655 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12656 looks in the inferior's memory for certain variables describing the
12657 current state of the overlays.
12659 Here are the variables your overlay manager must define to support
12660 @value{GDBN}'s automatic overlay debugging:
12664 @item @code{_ovly_table}:
12665 This variable must be an array of the following structures:
12670 /* The overlay's mapped address. */
12673 /* The size of the overlay, in bytes. */
12674 unsigned long size;
12676 /* The overlay's load address. */
12679 /* Non-zero if the overlay is currently mapped;
12681 unsigned long mapped;
12685 @item @code{_novlys}:
12686 This variable must be a four-byte signed integer, holding the total
12687 number of elements in @code{_ovly_table}.
12691 To decide whether a particular overlay is mapped or not, @value{GDBN}
12692 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12693 @code{lma} members equal the VMA and LMA of the overlay's section in the
12694 executable file. When @value{GDBN} finds a matching entry, it consults
12695 the entry's @code{mapped} member to determine whether the overlay is
12698 In addition, your overlay manager may define a function called
12699 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12700 will silently set a breakpoint there. If the overlay manager then
12701 calls this function whenever it has changed the overlay table, this
12702 will enable @value{GDBN} to accurately keep track of which overlays
12703 are in program memory, and update any breakpoints that may be set
12704 in overlays. This will allow breakpoints to work even if the
12705 overlays are kept in ROM or other non-writable memory while they
12706 are not being executed.
12708 @node Overlay Sample Program
12709 @section Overlay Sample Program
12710 @cindex overlay example program
12712 When linking a program which uses overlays, you must place the overlays
12713 at their load addresses, while relocating them to run at their mapped
12714 addresses. To do this, you must write a linker script (@pxref{Overlay
12715 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12716 since linker scripts are specific to a particular host system, target
12717 architecture, and target memory layout, this manual cannot provide
12718 portable sample code demonstrating @value{GDBN}'s overlay support.
12720 However, the @value{GDBN} source distribution does contain an overlaid
12721 program, with linker scripts for a few systems, as part of its test
12722 suite. The program consists of the following files from
12723 @file{gdb/testsuite/gdb.base}:
12727 The main program file.
12729 A simple overlay manager, used by @file{overlays.c}.
12734 Overlay modules, loaded and used by @file{overlays.c}.
12737 Linker scripts for linking the test program on the @code{d10v-elf}
12738 and @code{m32r-elf} targets.
12741 You can build the test program using the @code{d10v-elf} GCC
12742 cross-compiler like this:
12745 $ d10v-elf-gcc -g -c overlays.c
12746 $ d10v-elf-gcc -g -c ovlymgr.c
12747 $ d10v-elf-gcc -g -c foo.c
12748 $ d10v-elf-gcc -g -c bar.c
12749 $ d10v-elf-gcc -g -c baz.c
12750 $ d10v-elf-gcc -g -c grbx.c
12751 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12752 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12755 The build process is identical for any other architecture, except that
12756 you must substitute the appropriate compiler and linker script for the
12757 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12761 @chapter Using @value{GDBN} with Different Languages
12764 Although programming languages generally have common aspects, they are
12765 rarely expressed in the same manner. For instance, in ANSI C,
12766 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12767 Modula-2, it is accomplished by @code{p^}. Values can also be
12768 represented (and displayed) differently. Hex numbers in C appear as
12769 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12771 @cindex working language
12772 Language-specific information is built into @value{GDBN} for some languages,
12773 allowing you to express operations like the above in your program's
12774 native language, and allowing @value{GDBN} to output values in a manner
12775 consistent with the syntax of your program's native language. The
12776 language you use to build expressions is called the @dfn{working
12780 * Setting:: Switching between source languages
12781 * Show:: Displaying the language
12782 * Checks:: Type and range checks
12783 * Supported Languages:: Supported languages
12784 * Unsupported Languages:: Unsupported languages
12788 @section Switching Between Source Languages
12790 There are two ways to control the working language---either have @value{GDBN}
12791 set it automatically, or select it manually yourself. You can use the
12792 @code{set language} command for either purpose. On startup, @value{GDBN}
12793 defaults to setting the language automatically. The working language is
12794 used to determine how expressions you type are interpreted, how values
12797 In addition to the working language, every source file that
12798 @value{GDBN} knows about has its own working language. For some object
12799 file formats, the compiler might indicate which language a particular
12800 source file is in. However, most of the time @value{GDBN} infers the
12801 language from the name of the file. The language of a source file
12802 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12803 show each frame appropriately for its own language. There is no way to
12804 set the language of a source file from within @value{GDBN}, but you can
12805 set the language associated with a filename extension. @xref{Show, ,
12806 Displaying the Language}.
12808 This is most commonly a problem when you use a program, such
12809 as @code{cfront} or @code{f2c}, that generates C but is written in
12810 another language. In that case, make the
12811 program use @code{#line} directives in its C output; that way
12812 @value{GDBN} will know the correct language of the source code of the original
12813 program, and will display that source code, not the generated C code.
12816 * Filenames:: Filename extensions and languages.
12817 * Manually:: Setting the working language manually
12818 * Automatically:: Having @value{GDBN} infer the source language
12822 @subsection List of Filename Extensions and Languages
12824 If a source file name ends in one of the following extensions, then
12825 @value{GDBN} infers that its language is the one indicated.
12843 C@t{++} source file
12849 Objective-C source file
12853 Fortran source file
12856 Modula-2 source file
12860 Assembler source file. This actually behaves almost like C, but
12861 @value{GDBN} does not skip over function prologues when stepping.
12864 In addition, you may set the language associated with a filename
12865 extension. @xref{Show, , Displaying the Language}.
12868 @subsection Setting the Working Language
12870 If you allow @value{GDBN} to set the language automatically,
12871 expressions are interpreted the same way in your debugging session and
12874 @kindex set language
12875 If you wish, you may set the language manually. To do this, issue the
12876 command @samp{set language @var{lang}}, where @var{lang} is the name of
12877 a language, such as
12878 @code{c} or @code{modula-2}.
12879 For a list of the supported languages, type @samp{set language}.
12881 Setting the language manually prevents @value{GDBN} from updating the working
12882 language automatically. This can lead to confusion if you try
12883 to debug a program when the working language is not the same as the
12884 source language, when an expression is acceptable to both
12885 languages---but means different things. For instance, if the current
12886 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12894 might not have the effect you intended. In C, this means to add
12895 @code{b} and @code{c} and place the result in @code{a}. The result
12896 printed would be the value of @code{a}. In Modula-2, this means to compare
12897 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12899 @node Automatically
12900 @subsection Having @value{GDBN} Infer the Source Language
12902 To have @value{GDBN} set the working language automatically, use
12903 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12904 then infers the working language. That is, when your program stops in a
12905 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12906 working language to the language recorded for the function in that
12907 frame. If the language for a frame is unknown (that is, if the function
12908 or block corresponding to the frame was defined in a source file that
12909 does not have a recognized extension), the current working language is
12910 not changed, and @value{GDBN} issues a warning.
12912 This may not seem necessary for most programs, which are written
12913 entirely in one source language. However, program modules and libraries
12914 written in one source language can be used by a main program written in
12915 a different source language. Using @samp{set language auto} in this
12916 case frees you from having to set the working language manually.
12919 @section Displaying the Language
12921 The following commands help you find out which language is the
12922 working language, and also what language source files were written in.
12925 @item show language
12926 @kindex show language
12927 Display the current working language. This is the
12928 language you can use with commands such as @code{print} to
12929 build and compute expressions that may involve variables in your program.
12932 @kindex info frame@r{, show the source language}
12933 Display the source language for this frame. This language becomes the
12934 working language if you use an identifier from this frame.
12935 @xref{Frame Info, ,Information about a Frame}, to identify the other
12936 information listed here.
12939 @kindex info source@r{, show the source language}
12940 Display the source language of this source file.
12941 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12942 information listed here.
12945 In unusual circumstances, you may have source files with extensions
12946 not in the standard list. You can then set the extension associated
12947 with a language explicitly:
12950 @item set extension-language @var{ext} @var{language}
12951 @kindex set extension-language
12952 Tell @value{GDBN} that source files with extension @var{ext} are to be
12953 assumed as written in the source language @var{language}.
12955 @item info extensions
12956 @kindex info extensions
12957 List all the filename extensions and the associated languages.
12961 @section Type and Range Checking
12963 Some languages are designed to guard you against making seemingly common
12964 errors through a series of compile- and run-time checks. These include
12965 checking the type of arguments to functions and operators and making
12966 sure mathematical overflows are caught at run time. Checks such as
12967 these help to ensure a program's correctness once it has been compiled
12968 by eliminating type mismatches and providing active checks for range
12969 errors when your program is running.
12971 By default @value{GDBN} checks for these errors according to the
12972 rules of the current source language. Although @value{GDBN} does not check
12973 the statements in your program, it can check expressions entered directly
12974 into @value{GDBN} for evaluation via the @code{print} command, for example.
12977 * Type Checking:: An overview of type checking
12978 * Range Checking:: An overview of range checking
12981 @cindex type checking
12982 @cindex checks, type
12983 @node Type Checking
12984 @subsection An Overview of Type Checking
12986 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12987 arguments to operators and functions have to be of the correct type,
12988 otherwise an error occurs. These checks prevent type mismatch
12989 errors from ever causing any run-time problems. For example,
12992 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12994 (@value{GDBP}) print obj.my_method (0)
12997 (@value{GDBP}) print obj.my_method (0x1234)
12998 Cannot resolve method klass::my_method to any overloaded instance
13001 The second example fails because in C@t{++} the integer constant
13002 @samp{0x1234} is not type-compatible with the pointer parameter type.
13004 For the expressions you use in @value{GDBN} commands, you can tell
13005 @value{GDBN} to not enforce strict type checking or
13006 to treat any mismatches as errors and abandon the expression;
13007 When type checking is disabled, @value{GDBN} successfully evaluates
13008 expressions like the second example above.
13010 Even if type checking is off, there may be other reasons
13011 related to type that prevent @value{GDBN} from evaluating an expression.
13012 For instance, @value{GDBN} does not know how to add an @code{int} and
13013 a @code{struct foo}. These particular type errors have nothing to do
13014 with the language in use and usually arise from expressions which make
13015 little sense to evaluate anyway.
13017 @value{GDBN} provides some additional commands for controlling type checking:
13019 @kindex set check type
13020 @kindex show check type
13022 @item set check type on
13023 @itemx set check type off
13024 Set strict type checking on or off. If any type mismatches occur in
13025 evaluating an expression while type checking is on, @value{GDBN} prints a
13026 message and aborts evaluation of the expression.
13028 @item show check type
13029 Show the current setting of type checking and whether @value{GDBN}
13030 is enforcing strict type checking rules.
13033 @cindex range checking
13034 @cindex checks, range
13035 @node Range Checking
13036 @subsection An Overview of Range Checking
13038 In some languages (such as Modula-2), it is an error to exceed the
13039 bounds of a type; this is enforced with run-time checks. Such range
13040 checking is meant to ensure program correctness by making sure
13041 computations do not overflow, or indices on an array element access do
13042 not exceed the bounds of the array.
13044 For expressions you use in @value{GDBN} commands, you can tell
13045 @value{GDBN} to treat range errors in one of three ways: ignore them,
13046 always treat them as errors and abandon the expression, or issue
13047 warnings but evaluate the expression anyway.
13049 A range error can result from numerical overflow, from exceeding an
13050 array index bound, or when you type a constant that is not a member
13051 of any type. Some languages, however, do not treat overflows as an
13052 error. In many implementations of C, mathematical overflow causes the
13053 result to ``wrap around'' to lower values---for example, if @var{m} is
13054 the largest integer value, and @var{s} is the smallest, then
13057 @var{m} + 1 @result{} @var{s}
13060 This, too, is specific to individual languages, and in some cases
13061 specific to individual compilers or machines. @xref{Supported Languages, ,
13062 Supported Languages}, for further details on specific languages.
13064 @value{GDBN} provides some additional commands for controlling the range checker:
13066 @kindex set check range
13067 @kindex show check range
13069 @item set check range auto
13070 Set range checking on or off based on the current working language.
13071 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13074 @item set check range on
13075 @itemx set check range off
13076 Set range checking on or off, overriding the default setting for the
13077 current working language. A warning is issued if the setting does not
13078 match the language default. If a range error occurs and range checking is on,
13079 then a message is printed and evaluation of the expression is aborted.
13081 @item set check range warn
13082 Output messages when the @value{GDBN} range checker detects a range error,
13083 but attempt to evaluate the expression anyway. Evaluating the
13084 expression may still be impossible for other reasons, such as accessing
13085 memory that the process does not own (a typical example from many Unix
13089 Show the current setting of the range checker, and whether or not it is
13090 being set automatically by @value{GDBN}.
13093 @node Supported Languages
13094 @section Supported Languages
13096 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13097 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13098 @c This is false ...
13099 Some @value{GDBN} features may be used in expressions regardless of the
13100 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13101 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13102 ,Expressions}) can be used with the constructs of any supported
13105 The following sections detail to what degree each source language is
13106 supported by @value{GDBN}. These sections are not meant to be language
13107 tutorials or references, but serve only as a reference guide to what the
13108 @value{GDBN} expression parser accepts, and what input and output
13109 formats should look like for different languages. There are many good
13110 books written on each of these languages; please look to these for a
13111 language reference or tutorial.
13114 * C:: C and C@t{++}
13117 * Objective-C:: Objective-C
13118 * OpenCL C:: OpenCL C
13119 * Fortran:: Fortran
13121 * Modula-2:: Modula-2
13126 @subsection C and C@t{++}
13128 @cindex C and C@t{++}
13129 @cindex expressions in C or C@t{++}
13131 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13132 to both languages. Whenever this is the case, we discuss those languages
13136 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13137 @cindex @sc{gnu} C@t{++}
13138 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13139 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13140 effectively, you must compile your C@t{++} programs with a supported
13141 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13142 compiler (@code{aCC}).
13145 * C Operators:: C and C@t{++} operators
13146 * C Constants:: C and C@t{++} constants
13147 * C Plus Plus Expressions:: C@t{++} expressions
13148 * C Defaults:: Default settings for C and C@t{++}
13149 * C Checks:: C and C@t{++} type and range checks
13150 * Debugging C:: @value{GDBN} and C
13151 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13152 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13156 @subsubsection C and C@t{++} Operators
13158 @cindex C and C@t{++} operators
13160 Operators must be defined on values of specific types. For instance,
13161 @code{+} is defined on numbers, but not on structures. Operators are
13162 often defined on groups of types.
13164 For the purposes of C and C@t{++}, the following definitions hold:
13169 @emph{Integral types} include @code{int} with any of its storage-class
13170 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13173 @emph{Floating-point types} include @code{float}, @code{double}, and
13174 @code{long double} (if supported by the target platform).
13177 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13180 @emph{Scalar types} include all of the above.
13185 The following operators are supported. They are listed here
13186 in order of increasing precedence:
13190 The comma or sequencing operator. Expressions in a comma-separated list
13191 are evaluated from left to right, with the result of the entire
13192 expression being the last expression evaluated.
13195 Assignment. The value of an assignment expression is the value
13196 assigned. Defined on scalar types.
13199 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13200 and translated to @w{@code{@var{a} = @var{a op b}}}.
13201 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13202 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13203 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13206 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13207 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13211 Logical @sc{or}. Defined on integral types.
13214 Logical @sc{and}. Defined on integral types.
13217 Bitwise @sc{or}. Defined on integral types.
13220 Bitwise exclusive-@sc{or}. Defined on integral types.
13223 Bitwise @sc{and}. Defined on integral types.
13226 Equality and inequality. Defined on scalar types. The value of these
13227 expressions is 0 for false and non-zero for true.
13229 @item <@r{, }>@r{, }<=@r{, }>=
13230 Less than, greater than, less than or equal, greater than or equal.
13231 Defined on scalar types. The value of these expressions is 0 for false
13232 and non-zero for true.
13235 left shift, and right shift. Defined on integral types.
13238 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13241 Addition and subtraction. Defined on integral types, floating-point types and
13244 @item *@r{, }/@r{, }%
13245 Multiplication, division, and modulus. Multiplication and division are
13246 defined on integral and floating-point types. Modulus is defined on
13250 Increment and decrement. When appearing before a variable, the
13251 operation is performed before the variable is used in an expression;
13252 when appearing after it, the variable's value is used before the
13253 operation takes place.
13256 Pointer dereferencing. Defined on pointer types. Same precedence as
13260 Address operator. Defined on variables. Same precedence as @code{++}.
13262 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13263 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13264 to examine the address
13265 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13269 Negative. Defined on integral and floating-point types. Same
13270 precedence as @code{++}.
13273 Logical negation. Defined on integral types. Same precedence as
13277 Bitwise complement operator. Defined on integral types. Same precedence as
13282 Structure member, and pointer-to-structure member. For convenience,
13283 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13284 pointer based on the stored type information.
13285 Defined on @code{struct} and @code{union} data.
13288 Dereferences of pointers to members.
13291 Array indexing. @code{@var{a}[@var{i}]} is defined as
13292 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13295 Function parameter list. Same precedence as @code{->}.
13298 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13299 and @code{class} types.
13302 Doubled colons also represent the @value{GDBN} scope operator
13303 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13307 If an operator is redefined in the user code, @value{GDBN} usually
13308 attempts to invoke the redefined version instead of using the operator's
13309 predefined meaning.
13312 @subsubsection C and C@t{++} Constants
13314 @cindex C and C@t{++} constants
13316 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13321 Integer constants are a sequence of digits. Octal constants are
13322 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13323 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13324 @samp{l}, specifying that the constant should be treated as a
13328 Floating point constants are a sequence of digits, followed by a decimal
13329 point, followed by a sequence of digits, and optionally followed by an
13330 exponent. An exponent is of the form:
13331 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13332 sequence of digits. The @samp{+} is optional for positive exponents.
13333 A floating-point constant may also end with a letter @samp{f} or
13334 @samp{F}, specifying that the constant should be treated as being of
13335 the @code{float} (as opposed to the default @code{double}) type; or with
13336 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13340 Enumerated constants consist of enumerated identifiers, or their
13341 integral equivalents.
13344 Character constants are a single character surrounded by single quotes
13345 (@code{'}), or a number---the ordinal value of the corresponding character
13346 (usually its @sc{ascii} value). Within quotes, the single character may
13347 be represented by a letter or by @dfn{escape sequences}, which are of
13348 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13349 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13350 @samp{@var{x}} is a predefined special character---for example,
13351 @samp{\n} for newline.
13353 Wide character constants can be written by prefixing a character
13354 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13355 form of @samp{x}. The target wide character set is used when
13356 computing the value of this constant (@pxref{Character Sets}).
13359 String constants are a sequence of character constants surrounded by
13360 double quotes (@code{"}). Any valid character constant (as described
13361 above) may appear. Double quotes within the string must be preceded by
13362 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13365 Wide string constants can be written by prefixing a string constant
13366 with @samp{L}, as in C. The target wide character set is used when
13367 computing the value of this constant (@pxref{Character Sets}).
13370 Pointer constants are an integral value. You can also write pointers
13371 to constants using the C operator @samp{&}.
13374 Array constants are comma-separated lists surrounded by braces @samp{@{}
13375 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13376 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13377 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13380 @node C Plus Plus Expressions
13381 @subsubsection C@t{++} Expressions
13383 @cindex expressions in C@t{++}
13384 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13386 @cindex debugging C@t{++} programs
13387 @cindex C@t{++} compilers
13388 @cindex debug formats and C@t{++}
13389 @cindex @value{NGCC} and C@t{++}
13391 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13392 the proper compiler and the proper debug format. Currently,
13393 @value{GDBN} works best when debugging C@t{++} code that is compiled
13394 with the most recent version of @value{NGCC} possible. The DWARF
13395 debugging format is preferred; @value{NGCC} defaults to this on most
13396 popular platforms. Other compilers and/or debug formats are likely to
13397 work badly or not at all when using @value{GDBN} to debug C@t{++}
13398 code. @xref{Compilation}.
13403 @cindex member functions
13405 Member function calls are allowed; you can use expressions like
13408 count = aml->GetOriginal(x, y)
13411 @vindex this@r{, inside C@t{++} member functions}
13412 @cindex namespace in C@t{++}
13414 While a member function is active (in the selected stack frame), your
13415 expressions have the same namespace available as the member function;
13416 that is, @value{GDBN} allows implicit references to the class instance
13417 pointer @code{this} following the same rules as C@t{++}. @code{using}
13418 declarations in the current scope are also respected by @value{GDBN}.
13420 @cindex call overloaded functions
13421 @cindex overloaded functions, calling
13422 @cindex type conversions in C@t{++}
13424 You can call overloaded functions; @value{GDBN} resolves the function
13425 call to the right definition, with some restrictions. @value{GDBN} does not
13426 perform overload resolution involving user-defined type conversions,
13427 calls to constructors, or instantiations of templates that do not exist
13428 in the program. It also cannot handle ellipsis argument lists or
13431 It does perform integral conversions and promotions, floating-point
13432 promotions, arithmetic conversions, pointer conversions, conversions of
13433 class objects to base classes, and standard conversions such as those of
13434 functions or arrays to pointers; it requires an exact match on the
13435 number of function arguments.
13437 Overload resolution is always performed, unless you have specified
13438 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13439 ,@value{GDBN} Features for C@t{++}}.
13441 You must specify @code{set overload-resolution off} in order to use an
13442 explicit function signature to call an overloaded function, as in
13444 p 'foo(char,int)'('x', 13)
13447 The @value{GDBN} command-completion facility can simplify this;
13448 see @ref{Completion, ,Command Completion}.
13450 @cindex reference declarations
13452 @value{GDBN} understands variables declared as C@t{++} references; you can use
13453 them in expressions just as you do in C@t{++} source---they are automatically
13456 In the parameter list shown when @value{GDBN} displays a frame, the values of
13457 reference variables are not displayed (unlike other variables); this
13458 avoids clutter, since references are often used for large structures.
13459 The @emph{address} of a reference variable is always shown, unless
13460 you have specified @samp{set print address off}.
13463 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13464 expressions can use it just as expressions in your program do. Since
13465 one scope may be defined in another, you can use @code{::} repeatedly if
13466 necessary, for example in an expression like
13467 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13468 resolving name scope by reference to source files, in both C and C@t{++}
13469 debugging (@pxref{Variables, ,Program Variables}).
13472 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13477 @subsubsection C and C@t{++} Defaults
13479 @cindex C and C@t{++} defaults
13481 If you allow @value{GDBN} to set range checking automatically, it
13482 defaults to @code{off} whenever the working language changes to
13483 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13484 selects the working language.
13486 If you allow @value{GDBN} to set the language automatically, it
13487 recognizes source files whose names end with @file{.c}, @file{.C}, or
13488 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13489 these files, it sets the working language to C or C@t{++}.
13490 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13491 for further details.
13494 @subsubsection C and C@t{++} Type and Range Checks
13496 @cindex C and C@t{++} checks
13498 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13499 checking is used. However, if you turn type checking off, @value{GDBN}
13500 will allow certain non-standard conversions, such as promoting integer
13501 constants to pointers.
13503 Range checking, if turned on, is done on mathematical operations. Array
13504 indices are not checked, since they are often used to index a pointer
13505 that is not itself an array.
13508 @subsubsection @value{GDBN} and C
13510 The @code{set print union} and @code{show print union} commands apply to
13511 the @code{union} type. When set to @samp{on}, any @code{union} that is
13512 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13513 appears as @samp{@{...@}}.
13515 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13516 with pointers and a memory allocation function. @xref{Expressions,
13519 @node Debugging C Plus Plus
13520 @subsubsection @value{GDBN} Features for C@t{++}
13522 @cindex commands for C@t{++}
13524 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13525 designed specifically for use with C@t{++}. Here is a summary:
13528 @cindex break in overloaded functions
13529 @item @r{breakpoint menus}
13530 When you want a breakpoint in a function whose name is overloaded,
13531 @value{GDBN} has the capability to display a menu of possible breakpoint
13532 locations to help you specify which function definition you want.
13533 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13535 @cindex overloading in C@t{++}
13536 @item rbreak @var{regex}
13537 Setting breakpoints using regular expressions is helpful for setting
13538 breakpoints on overloaded functions that are not members of any special
13540 @xref{Set Breaks, ,Setting Breakpoints}.
13542 @cindex C@t{++} exception handling
13544 @itemx catch rethrow
13546 Debug C@t{++} exception handling using these commands. @xref{Set
13547 Catchpoints, , Setting Catchpoints}.
13549 @cindex inheritance
13550 @item ptype @var{typename}
13551 Print inheritance relationships as well as other information for type
13553 @xref{Symbols, ,Examining the Symbol Table}.
13555 @item info vtbl @var{expression}.
13556 The @code{info vtbl} command can be used to display the virtual
13557 method tables of the object computed by @var{expression}. This shows
13558 one entry per virtual table; there may be multiple virtual tables when
13559 multiple inheritance is in use.
13561 @cindex C@t{++} symbol display
13562 @item set print demangle
13563 @itemx show print demangle
13564 @itemx set print asm-demangle
13565 @itemx show print asm-demangle
13566 Control whether C@t{++} symbols display in their source form, both when
13567 displaying code as C@t{++} source and when displaying disassemblies.
13568 @xref{Print Settings, ,Print Settings}.
13570 @item set print object
13571 @itemx show print object
13572 Choose whether to print derived (actual) or declared types of objects.
13573 @xref{Print Settings, ,Print Settings}.
13575 @item set print vtbl
13576 @itemx show print vtbl
13577 Control the format for printing virtual function tables.
13578 @xref{Print Settings, ,Print Settings}.
13579 (The @code{vtbl} commands do not work on programs compiled with the HP
13580 ANSI C@t{++} compiler (@code{aCC}).)
13582 @kindex set overload-resolution
13583 @cindex overloaded functions, overload resolution
13584 @item set overload-resolution on
13585 Enable overload resolution for C@t{++} expression evaluation. The default
13586 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13587 and searches for a function whose signature matches the argument types,
13588 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13589 Expressions, ,C@t{++} Expressions}, for details).
13590 If it cannot find a match, it emits a message.
13592 @item set overload-resolution off
13593 Disable overload resolution for C@t{++} expression evaluation. For
13594 overloaded functions that are not class member functions, @value{GDBN}
13595 chooses the first function of the specified name that it finds in the
13596 symbol table, whether or not its arguments are of the correct type. For
13597 overloaded functions that are class member functions, @value{GDBN}
13598 searches for a function whose signature @emph{exactly} matches the
13601 @kindex show overload-resolution
13602 @item show overload-resolution
13603 Show the current setting of overload resolution.
13605 @item @r{Overloaded symbol names}
13606 You can specify a particular definition of an overloaded symbol, using
13607 the same notation that is used to declare such symbols in C@t{++}: type
13608 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13609 also use the @value{GDBN} command-line word completion facilities to list the
13610 available choices, or to finish the type list for you.
13611 @xref{Completion,, Command Completion}, for details on how to do this.
13614 @node Decimal Floating Point
13615 @subsubsection Decimal Floating Point format
13616 @cindex decimal floating point format
13618 @value{GDBN} can examine, set and perform computations with numbers in
13619 decimal floating point format, which in the C language correspond to the
13620 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13621 specified by the extension to support decimal floating-point arithmetic.
13623 There are two encodings in use, depending on the architecture: BID (Binary
13624 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13625 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13628 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13629 to manipulate decimal floating point numbers, it is not possible to convert
13630 (using a cast, for example) integers wider than 32-bit to decimal float.
13632 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13633 point computations, error checking in decimal float operations ignores
13634 underflow, overflow and divide by zero exceptions.
13636 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13637 to inspect @code{_Decimal128} values stored in floating point registers.
13638 See @ref{PowerPC,,PowerPC} for more details.
13644 @value{GDBN} can be used to debug programs written in D and compiled with
13645 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13646 specific feature --- dynamic arrays.
13651 @cindex Go (programming language)
13652 @value{GDBN} can be used to debug programs written in Go and compiled with
13653 @file{gccgo} or @file{6g} compilers.
13655 Here is a summary of the Go-specific features and restrictions:
13658 @cindex current Go package
13659 @item The current Go package
13660 The name of the current package does not need to be specified when
13661 specifying global variables and functions.
13663 For example, given the program:
13667 var myglob = "Shall we?"
13673 When stopped inside @code{main} either of these work:
13677 (gdb) p main.myglob
13680 @cindex builtin Go types
13681 @item Builtin Go types
13682 The @code{string} type is recognized by @value{GDBN} and is printed
13685 @cindex builtin Go functions
13686 @item Builtin Go functions
13687 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13688 function and handles it internally.
13690 @cindex restrictions on Go expressions
13691 @item Restrictions on Go expressions
13692 All Go operators are supported except @code{&^}.
13693 The Go @code{_} ``blank identifier'' is not supported.
13694 Automatic dereferencing of pointers is not supported.
13698 @subsection Objective-C
13700 @cindex Objective-C
13701 This section provides information about some commands and command
13702 options that are useful for debugging Objective-C code. See also
13703 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13704 few more commands specific to Objective-C support.
13707 * Method Names in Commands::
13708 * The Print Command with Objective-C::
13711 @node Method Names in Commands
13712 @subsubsection Method Names in Commands
13714 The following commands have been extended to accept Objective-C method
13715 names as line specifications:
13717 @kindex clear@r{, and Objective-C}
13718 @kindex break@r{, and Objective-C}
13719 @kindex info line@r{, and Objective-C}
13720 @kindex jump@r{, and Objective-C}
13721 @kindex list@r{, and Objective-C}
13725 @item @code{info line}
13730 A fully qualified Objective-C method name is specified as
13733 -[@var{Class} @var{methodName}]
13736 where the minus sign is used to indicate an instance method and a
13737 plus sign (not shown) is used to indicate a class method. The class
13738 name @var{Class} and method name @var{methodName} are enclosed in
13739 brackets, similar to the way messages are specified in Objective-C
13740 source code. For example, to set a breakpoint at the @code{create}
13741 instance method of class @code{Fruit} in the program currently being
13745 break -[Fruit create]
13748 To list ten program lines around the @code{initialize} class method,
13752 list +[NSText initialize]
13755 In the current version of @value{GDBN}, the plus or minus sign is
13756 required. In future versions of @value{GDBN}, the plus or minus
13757 sign will be optional, but you can use it to narrow the search. It
13758 is also possible to specify just a method name:
13764 You must specify the complete method name, including any colons. If
13765 your program's source files contain more than one @code{create} method,
13766 you'll be presented with a numbered list of classes that implement that
13767 method. Indicate your choice by number, or type @samp{0} to exit if
13770 As another example, to clear a breakpoint established at the
13771 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13774 clear -[NSWindow makeKeyAndOrderFront:]
13777 @node The Print Command with Objective-C
13778 @subsubsection The Print Command With Objective-C
13779 @cindex Objective-C, print objects
13780 @kindex print-object
13781 @kindex po @r{(@code{print-object})}
13783 The print command has also been extended to accept methods. For example:
13786 print -[@var{object} hash]
13789 @cindex print an Objective-C object description
13790 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13792 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13793 and print the result. Also, an additional command has been added,
13794 @code{print-object} or @code{po} for short, which is meant to print
13795 the description of an object. However, this command may only work
13796 with certain Objective-C libraries that have a particular hook
13797 function, @code{_NSPrintForDebugger}, defined.
13800 @subsection OpenCL C
13803 This section provides information about @value{GDBN}s OpenCL C support.
13806 * OpenCL C Datatypes::
13807 * OpenCL C Expressions::
13808 * OpenCL C Operators::
13811 @node OpenCL C Datatypes
13812 @subsubsection OpenCL C Datatypes
13814 @cindex OpenCL C Datatypes
13815 @value{GDBN} supports the builtin scalar and vector datatypes specified
13816 by OpenCL 1.1. In addition the half- and double-precision floating point
13817 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13818 extensions are also known to @value{GDBN}.
13820 @node OpenCL C Expressions
13821 @subsubsection OpenCL C Expressions
13823 @cindex OpenCL C Expressions
13824 @value{GDBN} supports accesses to vector components including the access as
13825 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13826 supported by @value{GDBN} can be used as well.
13828 @node OpenCL C Operators
13829 @subsubsection OpenCL C Operators
13831 @cindex OpenCL C Operators
13832 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13836 @subsection Fortran
13837 @cindex Fortran-specific support in @value{GDBN}
13839 @value{GDBN} can be used to debug programs written in Fortran, but it
13840 currently supports only the features of Fortran 77 language.
13842 @cindex trailing underscore, in Fortran symbols
13843 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13844 among them) append an underscore to the names of variables and
13845 functions. When you debug programs compiled by those compilers, you
13846 will need to refer to variables and functions with a trailing
13850 * Fortran Operators:: Fortran operators and expressions
13851 * Fortran Defaults:: Default settings for Fortran
13852 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13855 @node Fortran Operators
13856 @subsubsection Fortran Operators and Expressions
13858 @cindex Fortran operators and expressions
13860 Operators must be defined on values of specific types. For instance,
13861 @code{+} is defined on numbers, but not on characters or other non-
13862 arithmetic types. Operators are often defined on groups of types.
13866 The exponentiation operator. It raises the first operand to the power
13870 The range operator. Normally used in the form of array(low:high) to
13871 represent a section of array.
13874 The access component operator. Normally used to access elements in derived
13875 types. Also suitable for unions. As unions aren't part of regular Fortran,
13876 this can only happen when accessing a register that uses a gdbarch-defined
13880 @node Fortran Defaults
13881 @subsubsection Fortran Defaults
13883 @cindex Fortran Defaults
13885 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13886 default uses case-insensitive matches for Fortran symbols. You can
13887 change that with the @samp{set case-insensitive} command, see
13888 @ref{Symbols}, for the details.
13890 @node Special Fortran Commands
13891 @subsubsection Special Fortran Commands
13893 @cindex Special Fortran commands
13895 @value{GDBN} has some commands to support Fortran-specific features,
13896 such as displaying common blocks.
13899 @cindex @code{COMMON} blocks, Fortran
13900 @kindex info common
13901 @item info common @r{[}@var{common-name}@r{]}
13902 This command prints the values contained in the Fortran @code{COMMON}
13903 block whose name is @var{common-name}. With no argument, the names of
13904 all @code{COMMON} blocks visible at the current program location are
13911 @cindex Pascal support in @value{GDBN}, limitations
13912 Debugging Pascal programs which use sets, subranges, file variables, or
13913 nested functions does not currently work. @value{GDBN} does not support
13914 entering expressions, printing values, or similar features using Pascal
13917 The Pascal-specific command @code{set print pascal_static-members}
13918 controls whether static members of Pascal objects are displayed.
13919 @xref{Print Settings, pascal_static-members}.
13922 @subsection Modula-2
13924 @cindex Modula-2, @value{GDBN} support
13926 The extensions made to @value{GDBN} to support Modula-2 only support
13927 output from the @sc{gnu} Modula-2 compiler (which is currently being
13928 developed). Other Modula-2 compilers are not currently supported, and
13929 attempting to debug executables produced by them is most likely
13930 to give an error as @value{GDBN} reads in the executable's symbol
13933 @cindex expressions in Modula-2
13935 * M2 Operators:: Built-in operators
13936 * Built-In Func/Proc:: Built-in functions and procedures
13937 * M2 Constants:: Modula-2 constants
13938 * M2 Types:: Modula-2 types
13939 * M2 Defaults:: Default settings for Modula-2
13940 * Deviations:: Deviations from standard Modula-2
13941 * M2 Checks:: Modula-2 type and range checks
13942 * M2 Scope:: The scope operators @code{::} and @code{.}
13943 * GDB/M2:: @value{GDBN} and Modula-2
13947 @subsubsection Operators
13948 @cindex Modula-2 operators
13950 Operators must be defined on values of specific types. For instance,
13951 @code{+} is defined on numbers, but not on structures. Operators are
13952 often defined on groups of types. For the purposes of Modula-2, the
13953 following definitions hold:
13958 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13962 @emph{Character types} consist of @code{CHAR} and its subranges.
13965 @emph{Floating-point types} consist of @code{REAL}.
13968 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13972 @emph{Scalar types} consist of all of the above.
13975 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13978 @emph{Boolean types} consist of @code{BOOLEAN}.
13982 The following operators are supported, and appear in order of
13983 increasing precedence:
13987 Function argument or array index separator.
13990 Assignment. The value of @var{var} @code{:=} @var{value} is
13994 Less than, greater than on integral, floating-point, or enumerated
13998 Less than or equal to, greater than or equal to
13999 on integral, floating-point and enumerated types, or set inclusion on
14000 set types. Same precedence as @code{<}.
14002 @item =@r{, }<>@r{, }#
14003 Equality and two ways of expressing inequality, valid on scalar types.
14004 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14005 available for inequality, since @code{#} conflicts with the script
14009 Set membership. Defined on set types and the types of their members.
14010 Same precedence as @code{<}.
14013 Boolean disjunction. Defined on boolean types.
14016 Boolean conjunction. Defined on boolean types.
14019 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14022 Addition and subtraction on integral and floating-point types, or union
14023 and difference on set types.
14026 Multiplication on integral and floating-point types, or set intersection
14030 Division on floating-point types, or symmetric set difference on set
14031 types. Same precedence as @code{*}.
14034 Integer division and remainder. Defined on integral types. Same
14035 precedence as @code{*}.
14038 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14041 Pointer dereferencing. Defined on pointer types.
14044 Boolean negation. Defined on boolean types. Same precedence as
14048 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14049 precedence as @code{^}.
14052 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14055 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14059 @value{GDBN} and Modula-2 scope operators.
14063 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14064 treats the use of the operator @code{IN}, or the use of operators
14065 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14066 @code{<=}, and @code{>=} on sets as an error.
14070 @node Built-In Func/Proc
14071 @subsubsection Built-in Functions and Procedures
14072 @cindex Modula-2 built-ins
14074 Modula-2 also makes available several built-in procedures and functions.
14075 In describing these, the following metavariables are used:
14080 represents an @code{ARRAY} variable.
14083 represents a @code{CHAR} constant or variable.
14086 represents a variable or constant of integral type.
14089 represents an identifier that belongs to a set. Generally used in the
14090 same function with the metavariable @var{s}. The type of @var{s} should
14091 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14094 represents a variable or constant of integral or floating-point type.
14097 represents a variable or constant of floating-point type.
14103 represents a variable.
14106 represents a variable or constant of one of many types. See the
14107 explanation of the function for details.
14110 All Modula-2 built-in procedures also return a result, described below.
14114 Returns the absolute value of @var{n}.
14117 If @var{c} is a lower case letter, it returns its upper case
14118 equivalent, otherwise it returns its argument.
14121 Returns the character whose ordinal value is @var{i}.
14124 Decrements the value in the variable @var{v} by one. Returns the new value.
14126 @item DEC(@var{v},@var{i})
14127 Decrements the value in the variable @var{v} by @var{i}. Returns the
14130 @item EXCL(@var{m},@var{s})
14131 Removes the element @var{m} from the set @var{s}. Returns the new
14134 @item FLOAT(@var{i})
14135 Returns the floating point equivalent of the integer @var{i}.
14137 @item HIGH(@var{a})
14138 Returns the index of the last member of @var{a}.
14141 Increments the value in the variable @var{v} by one. Returns the new value.
14143 @item INC(@var{v},@var{i})
14144 Increments the value in the variable @var{v} by @var{i}. Returns the
14147 @item INCL(@var{m},@var{s})
14148 Adds the element @var{m} to the set @var{s} if it is not already
14149 there. Returns the new set.
14152 Returns the maximum value of the type @var{t}.
14155 Returns the minimum value of the type @var{t}.
14158 Returns boolean TRUE if @var{i} is an odd number.
14161 Returns the ordinal value of its argument. For example, the ordinal
14162 value of a character is its @sc{ascii} value (on machines supporting the
14163 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14164 integral, character and enumerated types.
14166 @item SIZE(@var{x})
14167 Returns the size of its argument. @var{x} can be a variable or a type.
14169 @item TRUNC(@var{r})
14170 Returns the integral part of @var{r}.
14172 @item TSIZE(@var{x})
14173 Returns the size of its argument. @var{x} can be a variable or a type.
14175 @item VAL(@var{t},@var{i})
14176 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14180 @emph{Warning:} Sets and their operations are not yet supported, so
14181 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14185 @cindex Modula-2 constants
14187 @subsubsection Constants
14189 @value{GDBN} allows you to express the constants of Modula-2 in the following
14195 Integer constants are simply a sequence of digits. When used in an
14196 expression, a constant is interpreted to be type-compatible with the
14197 rest of the expression. Hexadecimal integers are specified by a
14198 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14201 Floating point constants appear as a sequence of digits, followed by a
14202 decimal point and another sequence of digits. An optional exponent can
14203 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14204 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14205 digits of the floating point constant must be valid decimal (base 10)
14209 Character constants consist of a single character enclosed by a pair of
14210 like quotes, either single (@code{'}) or double (@code{"}). They may
14211 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14212 followed by a @samp{C}.
14215 String constants consist of a sequence of characters enclosed by a
14216 pair of like quotes, either single (@code{'}) or double (@code{"}).
14217 Escape sequences in the style of C are also allowed. @xref{C
14218 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14222 Enumerated constants consist of an enumerated identifier.
14225 Boolean constants consist of the identifiers @code{TRUE} and
14229 Pointer constants consist of integral values only.
14232 Set constants are not yet supported.
14236 @subsubsection Modula-2 Types
14237 @cindex Modula-2 types
14239 Currently @value{GDBN} can print the following data types in Modula-2
14240 syntax: array types, record types, set types, pointer types, procedure
14241 types, enumerated types, subrange types and base types. You can also
14242 print the contents of variables declared using these type.
14243 This section gives a number of simple source code examples together with
14244 sample @value{GDBN} sessions.
14246 The first example contains the following section of code:
14255 and you can request @value{GDBN} to interrogate the type and value of
14256 @code{r} and @code{s}.
14259 (@value{GDBP}) print s
14261 (@value{GDBP}) ptype s
14263 (@value{GDBP}) print r
14265 (@value{GDBP}) ptype r
14270 Likewise if your source code declares @code{s} as:
14274 s: SET ['A'..'Z'] ;
14278 then you may query the type of @code{s} by:
14281 (@value{GDBP}) ptype s
14282 type = SET ['A'..'Z']
14286 Note that at present you cannot interactively manipulate set
14287 expressions using the debugger.
14289 The following example shows how you might declare an array in Modula-2
14290 and how you can interact with @value{GDBN} to print its type and contents:
14294 s: ARRAY [-10..10] OF CHAR ;
14298 (@value{GDBP}) ptype s
14299 ARRAY [-10..10] OF CHAR
14302 Note that the array handling is not yet complete and although the type
14303 is printed correctly, expression handling still assumes that all
14304 arrays have a lower bound of zero and not @code{-10} as in the example
14307 Here are some more type related Modula-2 examples:
14311 colour = (blue, red, yellow, green) ;
14312 t = [blue..yellow] ;
14320 The @value{GDBN} interaction shows how you can query the data type
14321 and value of a variable.
14324 (@value{GDBP}) print s
14326 (@value{GDBP}) ptype t
14327 type = [blue..yellow]
14331 In this example a Modula-2 array is declared and its contents
14332 displayed. Observe that the contents are written in the same way as
14333 their @code{C} counterparts.
14337 s: ARRAY [1..5] OF CARDINAL ;
14343 (@value{GDBP}) print s
14344 $1 = @{1, 0, 0, 0, 0@}
14345 (@value{GDBP}) ptype s
14346 type = ARRAY [1..5] OF CARDINAL
14349 The Modula-2 language interface to @value{GDBN} also understands
14350 pointer types as shown in this example:
14354 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14361 and you can request that @value{GDBN} describes the type of @code{s}.
14364 (@value{GDBP}) ptype s
14365 type = POINTER TO ARRAY [1..5] OF CARDINAL
14368 @value{GDBN} handles compound types as we can see in this example.
14369 Here we combine array types, record types, pointer types and subrange
14380 myarray = ARRAY myrange OF CARDINAL ;
14381 myrange = [-2..2] ;
14383 s: POINTER TO ARRAY myrange OF foo ;
14387 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14391 (@value{GDBP}) ptype s
14392 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14395 f3 : ARRAY [-2..2] OF CARDINAL;
14400 @subsubsection Modula-2 Defaults
14401 @cindex Modula-2 defaults
14403 If type and range checking are set automatically by @value{GDBN}, they
14404 both default to @code{on} whenever the working language changes to
14405 Modula-2. This happens regardless of whether you or @value{GDBN}
14406 selected the working language.
14408 If you allow @value{GDBN} to set the language automatically, then entering
14409 code compiled from a file whose name ends with @file{.mod} sets the
14410 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14411 Infer the Source Language}, for further details.
14414 @subsubsection Deviations from Standard Modula-2
14415 @cindex Modula-2, deviations from
14417 A few changes have been made to make Modula-2 programs easier to debug.
14418 This is done primarily via loosening its type strictness:
14422 Unlike in standard Modula-2, pointer constants can be formed by
14423 integers. This allows you to modify pointer variables during
14424 debugging. (In standard Modula-2, the actual address contained in a
14425 pointer variable is hidden from you; it can only be modified
14426 through direct assignment to another pointer variable or expression that
14427 returned a pointer.)
14430 C escape sequences can be used in strings and characters to represent
14431 non-printable characters. @value{GDBN} prints out strings with these
14432 escape sequences embedded. Single non-printable characters are
14433 printed using the @samp{CHR(@var{nnn})} format.
14436 The assignment operator (@code{:=}) returns the value of its right-hand
14440 All built-in procedures both modify @emph{and} return their argument.
14444 @subsubsection Modula-2 Type and Range Checks
14445 @cindex Modula-2 checks
14448 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14451 @c FIXME remove warning when type/range checks added
14453 @value{GDBN} considers two Modula-2 variables type equivalent if:
14457 They are of types that have been declared equivalent via a @code{TYPE
14458 @var{t1} = @var{t2}} statement
14461 They have been declared on the same line. (Note: This is true of the
14462 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14465 As long as type checking is enabled, any attempt to combine variables
14466 whose types are not equivalent is an error.
14468 Range checking is done on all mathematical operations, assignment, array
14469 index bounds, and all built-in functions and procedures.
14472 @subsubsection The Scope Operators @code{::} and @code{.}
14474 @cindex @code{.}, Modula-2 scope operator
14475 @cindex colon, doubled as scope operator
14477 @vindex colon-colon@r{, in Modula-2}
14478 @c Info cannot handle :: but TeX can.
14481 @vindex ::@r{, in Modula-2}
14484 There are a few subtle differences between the Modula-2 scope operator
14485 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14490 @var{module} . @var{id}
14491 @var{scope} :: @var{id}
14495 where @var{scope} is the name of a module or a procedure,
14496 @var{module} the name of a module, and @var{id} is any declared
14497 identifier within your program, except another module.
14499 Using the @code{::} operator makes @value{GDBN} search the scope
14500 specified by @var{scope} for the identifier @var{id}. If it is not
14501 found in the specified scope, then @value{GDBN} searches all scopes
14502 enclosing the one specified by @var{scope}.
14504 Using the @code{.} operator makes @value{GDBN} search the current scope for
14505 the identifier specified by @var{id} that was imported from the
14506 definition module specified by @var{module}. With this operator, it is
14507 an error if the identifier @var{id} was not imported from definition
14508 module @var{module}, or if @var{id} is not an identifier in
14512 @subsubsection @value{GDBN} and Modula-2
14514 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14515 Five subcommands of @code{set print} and @code{show print} apply
14516 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14517 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14518 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14519 analogue in Modula-2.
14521 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14522 with any language, is not useful with Modula-2. Its
14523 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14524 created in Modula-2 as they can in C or C@t{++}. However, because an
14525 address can be specified by an integral constant, the construct
14526 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14528 @cindex @code{#} in Modula-2
14529 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14530 interpreted as the beginning of a comment. Use @code{<>} instead.
14536 The extensions made to @value{GDBN} for Ada only support
14537 output from the @sc{gnu} Ada (GNAT) compiler.
14538 Other Ada compilers are not currently supported, and
14539 attempting to debug executables produced by them is most likely
14543 @cindex expressions in Ada
14545 * Ada Mode Intro:: General remarks on the Ada syntax
14546 and semantics supported by Ada mode
14548 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14549 * Additions to Ada:: Extensions of the Ada expression syntax.
14550 * Stopping Before Main Program:: Debugging the program during elaboration.
14551 * Ada Tasks:: Listing and setting breakpoints in tasks.
14552 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14553 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14555 * Ada Glitches:: Known peculiarities of Ada mode.
14558 @node Ada Mode Intro
14559 @subsubsection Introduction
14560 @cindex Ada mode, general
14562 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14563 syntax, with some extensions.
14564 The philosophy behind the design of this subset is
14568 That @value{GDBN} should provide basic literals and access to operations for
14569 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14570 leaving more sophisticated computations to subprograms written into the
14571 program (which therefore may be called from @value{GDBN}).
14574 That type safety and strict adherence to Ada language restrictions
14575 are not particularly important to the @value{GDBN} user.
14578 That brevity is important to the @value{GDBN} user.
14581 Thus, for brevity, the debugger acts as if all names declared in
14582 user-written packages are directly visible, even if they are not visible
14583 according to Ada rules, thus making it unnecessary to fully qualify most
14584 names with their packages, regardless of context. Where this causes
14585 ambiguity, @value{GDBN} asks the user's intent.
14587 The debugger will start in Ada mode if it detects an Ada main program.
14588 As for other languages, it will enter Ada mode when stopped in a program that
14589 was translated from an Ada source file.
14591 While in Ada mode, you may use `@t{--}' for comments. This is useful
14592 mostly for documenting command files. The standard @value{GDBN} comment
14593 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14594 middle (to allow based literals).
14596 The debugger supports limited overloading. Given a subprogram call in which
14597 the function symbol has multiple definitions, it will use the number of
14598 actual parameters and some information about their types to attempt to narrow
14599 the set of definitions. It also makes very limited use of context, preferring
14600 procedures to functions in the context of the @code{call} command, and
14601 functions to procedures elsewhere.
14603 @node Omissions from Ada
14604 @subsubsection Omissions from Ada
14605 @cindex Ada, omissions from
14607 Here are the notable omissions from the subset:
14611 Only a subset of the attributes are supported:
14615 @t{'First}, @t{'Last}, and @t{'Length}
14616 on array objects (not on types and subtypes).
14619 @t{'Min} and @t{'Max}.
14622 @t{'Pos} and @t{'Val}.
14628 @t{'Range} on array objects (not subtypes), but only as the right
14629 operand of the membership (@code{in}) operator.
14632 @t{'Access}, @t{'Unchecked_Access}, and
14633 @t{'Unrestricted_Access} (a GNAT extension).
14641 @code{Characters.Latin_1} are not available and
14642 concatenation is not implemented. Thus, escape characters in strings are
14643 not currently available.
14646 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14647 equality of representations. They will generally work correctly
14648 for strings and arrays whose elements have integer or enumeration types.
14649 They may not work correctly for arrays whose element
14650 types have user-defined equality, for arrays of real values
14651 (in particular, IEEE-conformant floating point, because of negative
14652 zeroes and NaNs), and for arrays whose elements contain unused bits with
14653 indeterminate values.
14656 The other component-by-component array operations (@code{and}, @code{or},
14657 @code{xor}, @code{not}, and relational tests other than equality)
14658 are not implemented.
14661 @cindex array aggregates (Ada)
14662 @cindex record aggregates (Ada)
14663 @cindex aggregates (Ada)
14664 There is limited support for array and record aggregates. They are
14665 permitted only on the right sides of assignments, as in these examples:
14668 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14669 (@value{GDBP}) set An_Array := (1, others => 0)
14670 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14671 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14672 (@value{GDBP}) set A_Record := (1, "Peter", True);
14673 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14677 discriminant's value by assigning an aggregate has an
14678 undefined effect if that discriminant is used within the record.
14679 However, you can first modify discriminants by directly assigning to
14680 them (which normally would not be allowed in Ada), and then performing an
14681 aggregate assignment. For example, given a variable @code{A_Rec}
14682 declared to have a type such as:
14685 type Rec (Len : Small_Integer := 0) is record
14687 Vals : IntArray (1 .. Len);
14691 you can assign a value with a different size of @code{Vals} with two
14695 (@value{GDBP}) set A_Rec.Len := 4
14696 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14699 As this example also illustrates, @value{GDBN} is very loose about the usual
14700 rules concerning aggregates. You may leave out some of the
14701 components of an array or record aggregate (such as the @code{Len}
14702 component in the assignment to @code{A_Rec} above); they will retain their
14703 original values upon assignment. You may freely use dynamic values as
14704 indices in component associations. You may even use overlapping or
14705 redundant component associations, although which component values are
14706 assigned in such cases is not defined.
14709 Calls to dispatching subprograms are not implemented.
14712 The overloading algorithm is much more limited (i.e., less selective)
14713 than that of real Ada. It makes only limited use of the context in
14714 which a subexpression appears to resolve its meaning, and it is much
14715 looser in its rules for allowing type matches. As a result, some
14716 function calls will be ambiguous, and the user will be asked to choose
14717 the proper resolution.
14720 The @code{new} operator is not implemented.
14723 Entry calls are not implemented.
14726 Aside from printing, arithmetic operations on the native VAX floating-point
14727 formats are not supported.
14730 It is not possible to slice a packed array.
14733 The names @code{True} and @code{False}, when not part of a qualified name,
14734 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14736 Should your program
14737 redefine these names in a package or procedure (at best a dubious practice),
14738 you will have to use fully qualified names to access their new definitions.
14741 @node Additions to Ada
14742 @subsubsection Additions to Ada
14743 @cindex Ada, deviations from
14745 As it does for other languages, @value{GDBN} makes certain generic
14746 extensions to Ada (@pxref{Expressions}):
14750 If the expression @var{E} is a variable residing in memory (typically
14751 a local variable or array element) and @var{N} is a positive integer,
14752 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14753 @var{N}-1 adjacent variables following it in memory as an array. In
14754 Ada, this operator is generally not necessary, since its prime use is
14755 in displaying parts of an array, and slicing will usually do this in
14756 Ada. However, there are occasional uses when debugging programs in
14757 which certain debugging information has been optimized away.
14760 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14761 appears in function or file @var{B}.'' When @var{B} is a file name,
14762 you must typically surround it in single quotes.
14765 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14766 @var{type} that appears at address @var{addr}.''
14769 A name starting with @samp{$} is a convenience variable
14770 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14773 In addition, @value{GDBN} provides a few other shortcuts and outright
14774 additions specific to Ada:
14778 The assignment statement is allowed as an expression, returning
14779 its right-hand operand as its value. Thus, you may enter
14782 (@value{GDBP}) set x := y + 3
14783 (@value{GDBP}) print A(tmp := y + 1)
14787 The semicolon is allowed as an ``operator,'' returning as its value
14788 the value of its right-hand operand.
14789 This allows, for example,
14790 complex conditional breaks:
14793 (@value{GDBP}) break f
14794 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14798 Rather than use catenation and symbolic character names to introduce special
14799 characters into strings, one may instead use a special bracket notation,
14800 which is also used to print strings. A sequence of characters of the form
14801 @samp{["@var{XX}"]} within a string or character literal denotes the
14802 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14803 sequence of characters @samp{["""]} also denotes a single quotation mark
14804 in strings. For example,
14806 "One line.["0a"]Next line.["0a"]"
14809 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14813 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14814 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14818 (@value{GDBP}) print 'max(x, y)
14822 When printing arrays, @value{GDBN} uses positional notation when the
14823 array has a lower bound of 1, and uses a modified named notation otherwise.
14824 For example, a one-dimensional array of three integers with a lower bound
14825 of 3 might print as
14832 That is, in contrast to valid Ada, only the first component has a @code{=>}
14836 You may abbreviate attributes in expressions with any unique,
14837 multi-character subsequence of
14838 their names (an exact match gets preference).
14839 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14840 in place of @t{a'length}.
14843 @cindex quoting Ada internal identifiers
14844 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14845 to lower case. The GNAT compiler uses upper-case characters for
14846 some of its internal identifiers, which are normally of no interest to users.
14847 For the rare occasions when you actually have to look at them,
14848 enclose them in angle brackets to avoid the lower-case mapping.
14851 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14855 Printing an object of class-wide type or dereferencing an
14856 access-to-class-wide value will display all the components of the object's
14857 specific type (as indicated by its run-time tag). Likewise, component
14858 selection on such a value will operate on the specific type of the
14863 @node Stopping Before Main Program
14864 @subsubsection Stopping at the Very Beginning
14866 @cindex breakpointing Ada elaboration code
14867 It is sometimes necessary to debug the program during elaboration, and
14868 before reaching the main procedure.
14869 As defined in the Ada Reference
14870 Manual, the elaboration code is invoked from a procedure called
14871 @code{adainit}. To run your program up to the beginning of
14872 elaboration, simply use the following two commands:
14873 @code{tbreak adainit} and @code{run}.
14876 @subsubsection Extensions for Ada Tasks
14877 @cindex Ada, tasking
14879 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14880 @value{GDBN} provides the following task-related commands:
14885 This command shows a list of current Ada tasks, as in the following example:
14892 (@value{GDBP}) info tasks
14893 ID TID P-ID Pri State Name
14894 1 8088000 0 15 Child Activation Wait main_task
14895 2 80a4000 1 15 Accept Statement b
14896 3 809a800 1 15 Child Activation Wait a
14897 * 4 80ae800 3 15 Runnable c
14902 In this listing, the asterisk before the last task indicates it to be the
14903 task currently being inspected.
14907 Represents @value{GDBN}'s internal task number.
14913 The parent's task ID (@value{GDBN}'s internal task number).
14916 The base priority of the task.
14919 Current state of the task.
14923 The task has been created but has not been activated. It cannot be
14927 The task is not blocked for any reason known to Ada. (It may be waiting
14928 for a mutex, though.) It is conceptually "executing" in normal mode.
14931 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14932 that were waiting on terminate alternatives have been awakened and have
14933 terminated themselves.
14935 @item Child Activation Wait
14936 The task is waiting for created tasks to complete activation.
14938 @item Accept Statement
14939 The task is waiting on an accept or selective wait statement.
14941 @item Waiting on entry call
14942 The task is waiting on an entry call.
14944 @item Async Select Wait
14945 The task is waiting to start the abortable part of an asynchronous
14949 The task is waiting on a select statement with only a delay
14952 @item Child Termination Wait
14953 The task is sleeping having completed a master within itself, and is
14954 waiting for the tasks dependent on that master to become terminated or
14955 waiting on a terminate Phase.
14957 @item Wait Child in Term Alt
14958 The task is sleeping waiting for tasks on terminate alternatives to
14959 finish terminating.
14961 @item Accepting RV with @var{taskno}
14962 The task is accepting a rendez-vous with the task @var{taskno}.
14966 Name of the task in the program.
14970 @kindex info task @var{taskno}
14971 @item info task @var{taskno}
14972 This command shows detailled informations on the specified task, as in
14973 the following example:
14978 (@value{GDBP}) info tasks
14979 ID TID P-ID Pri State Name
14980 1 8077880 0 15 Child Activation Wait main_task
14981 * 2 807c468 1 15 Runnable task_1
14982 (@value{GDBP}) info task 2
14983 Ada Task: 0x807c468
14986 Parent: 1 (main_task)
14992 @kindex task@r{ (Ada)}
14993 @cindex current Ada task ID
14994 This command prints the ID of the current task.
15000 (@value{GDBP}) info tasks
15001 ID TID P-ID Pri State Name
15002 1 8077870 0 15 Child Activation Wait main_task
15003 * 2 807c458 1 15 Runnable t
15004 (@value{GDBP}) task
15005 [Current task is 2]
15008 @item task @var{taskno}
15009 @cindex Ada task switching
15010 This command is like the @code{thread @var{threadno}}
15011 command (@pxref{Threads}). It switches the context of debugging
15012 from the current task to the given task.
15018 (@value{GDBP}) info tasks
15019 ID TID P-ID Pri State Name
15020 1 8077870 0 15 Child Activation Wait main_task
15021 * 2 807c458 1 15 Runnable t
15022 (@value{GDBP}) task 1
15023 [Switching to task 1]
15024 #0 0x8067726 in pthread_cond_wait ()
15026 #0 0x8067726 in pthread_cond_wait ()
15027 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15028 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15029 #3 0x806153e in system.tasking.stages.activate_tasks ()
15030 #4 0x804aacc in un () at un.adb:5
15033 @item break @var{linespec} task @var{taskno}
15034 @itemx break @var{linespec} task @var{taskno} if @dots{}
15035 @cindex breakpoints and tasks, in Ada
15036 @cindex task breakpoints, in Ada
15037 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15038 These commands are like the @code{break @dots{} thread @dots{}}
15039 command (@pxref{Thread Stops}).
15040 @var{linespec} specifies source lines, as described
15041 in @ref{Specify Location}.
15043 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15044 to specify that you only want @value{GDBN} to stop the program when a
15045 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15046 numeric task identifiers assigned by @value{GDBN}, shown in the first
15047 column of the @samp{info tasks} display.
15049 If you do not specify @samp{task @var{taskno}} when you set a
15050 breakpoint, the breakpoint applies to @emph{all} tasks of your
15053 You can use the @code{task} qualifier on conditional breakpoints as
15054 well; in this case, place @samp{task @var{taskno}} before the
15055 breakpoint condition (before the @code{if}).
15063 (@value{GDBP}) info tasks
15064 ID TID P-ID Pri State Name
15065 1 140022020 0 15 Child Activation Wait main_task
15066 2 140045060 1 15 Accept/Select Wait t2
15067 3 140044840 1 15 Runnable t1
15068 * 4 140056040 1 15 Runnable t3
15069 (@value{GDBP}) b 15 task 2
15070 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15071 (@value{GDBP}) cont
15076 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15078 (@value{GDBP}) info tasks
15079 ID TID P-ID Pri State Name
15080 1 140022020 0 15 Child Activation Wait main_task
15081 * 2 140045060 1 15 Runnable t2
15082 3 140044840 1 15 Runnable t1
15083 4 140056040 1 15 Delay Sleep t3
15087 @node Ada Tasks and Core Files
15088 @subsubsection Tasking Support when Debugging Core Files
15089 @cindex Ada tasking and core file debugging
15091 When inspecting a core file, as opposed to debugging a live program,
15092 tasking support may be limited or even unavailable, depending on
15093 the platform being used.
15094 For instance, on x86-linux, the list of tasks is available, but task
15095 switching is not supported. On Tru64, however, task switching will work
15098 On certain platforms, including Tru64, the debugger needs to perform some
15099 memory writes in order to provide Ada tasking support. When inspecting
15100 a core file, this means that the core file must be opened with read-write
15101 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15102 Under these circumstances, you should make a backup copy of the core
15103 file before inspecting it with @value{GDBN}.
15105 @node Ravenscar Profile
15106 @subsubsection Tasking Support when using the Ravenscar Profile
15107 @cindex Ravenscar Profile
15109 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15110 specifically designed for systems with safety-critical real-time
15114 @kindex set ravenscar task-switching on
15115 @cindex task switching with program using Ravenscar Profile
15116 @item set ravenscar task-switching on
15117 Allows task switching when debugging a program that uses the Ravenscar
15118 Profile. This is the default.
15120 @kindex set ravenscar task-switching off
15121 @item set ravenscar task-switching off
15122 Turn off task switching when debugging a program that uses the Ravenscar
15123 Profile. This is mostly intended to disable the code that adds support
15124 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15125 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15126 To be effective, this command should be run before the program is started.
15128 @kindex show ravenscar task-switching
15129 @item show ravenscar task-switching
15130 Show whether it is possible to switch from task to task in a program
15131 using the Ravenscar Profile.
15136 @subsubsection Known Peculiarities of Ada Mode
15137 @cindex Ada, problems
15139 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15140 we know of several problems with and limitations of Ada mode in
15142 some of which will be fixed with planned future releases of the debugger
15143 and the GNU Ada compiler.
15147 Static constants that the compiler chooses not to materialize as objects in
15148 storage are invisible to the debugger.
15151 Named parameter associations in function argument lists are ignored (the
15152 argument lists are treated as positional).
15155 Many useful library packages are currently invisible to the debugger.
15158 Fixed-point arithmetic, conversions, input, and output is carried out using
15159 floating-point arithmetic, and may give results that only approximate those on
15163 The GNAT compiler never generates the prefix @code{Standard} for any of
15164 the standard symbols defined by the Ada language. @value{GDBN} knows about
15165 this: it will strip the prefix from names when you use it, and will never
15166 look for a name you have so qualified among local symbols, nor match against
15167 symbols in other packages or subprograms. If you have
15168 defined entities anywhere in your program other than parameters and
15169 local variables whose simple names match names in @code{Standard},
15170 GNAT's lack of qualification here can cause confusion. When this happens,
15171 you can usually resolve the confusion
15172 by qualifying the problematic names with package
15173 @code{Standard} explicitly.
15176 Older versions of the compiler sometimes generate erroneous debugging
15177 information, resulting in the debugger incorrectly printing the value
15178 of affected entities. In some cases, the debugger is able to work
15179 around an issue automatically. In other cases, the debugger is able
15180 to work around the issue, but the work-around has to be specifically
15183 @kindex set ada trust-PAD-over-XVS
15184 @kindex show ada trust-PAD-over-XVS
15187 @item set ada trust-PAD-over-XVS on
15188 Configure GDB to strictly follow the GNAT encoding when computing the
15189 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15190 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15191 a complete description of the encoding used by the GNAT compiler).
15192 This is the default.
15194 @item set ada trust-PAD-over-XVS off
15195 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15196 sometimes prints the wrong value for certain entities, changing @code{ada
15197 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15198 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15199 @code{off}, but this incurs a slight performance penalty, so it is
15200 recommended to leave this setting to @code{on} unless necessary.
15204 @node Unsupported Languages
15205 @section Unsupported Languages
15207 @cindex unsupported languages
15208 @cindex minimal language
15209 In addition to the other fully-supported programming languages,
15210 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15211 It does not represent a real programming language, but provides a set
15212 of capabilities close to what the C or assembly languages provide.
15213 This should allow most simple operations to be performed while debugging
15214 an application that uses a language currently not supported by @value{GDBN}.
15216 If the language is set to @code{auto}, @value{GDBN} will automatically
15217 select this language if the current frame corresponds to an unsupported
15221 @chapter Examining the Symbol Table
15223 The commands described in this chapter allow you to inquire about the
15224 symbols (names of variables, functions and types) defined in your
15225 program. This information is inherent in the text of your program and
15226 does not change as your program executes. @value{GDBN} finds it in your
15227 program's symbol table, in the file indicated when you started @value{GDBN}
15228 (@pxref{File Options, ,Choosing Files}), or by one of the
15229 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15231 @cindex symbol names
15232 @cindex names of symbols
15233 @cindex quoting names
15234 Occasionally, you may need to refer to symbols that contain unusual
15235 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15236 most frequent case is in referring to static variables in other
15237 source files (@pxref{Variables,,Program Variables}). File names
15238 are recorded in object files as debugging symbols, but @value{GDBN} would
15239 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15240 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15241 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15248 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15251 @cindex case-insensitive symbol names
15252 @cindex case sensitivity in symbol names
15253 @kindex set case-sensitive
15254 @item set case-sensitive on
15255 @itemx set case-sensitive off
15256 @itemx set case-sensitive auto
15257 Normally, when @value{GDBN} looks up symbols, it matches their names
15258 with case sensitivity determined by the current source language.
15259 Occasionally, you may wish to control that. The command @code{set
15260 case-sensitive} lets you do that by specifying @code{on} for
15261 case-sensitive matches or @code{off} for case-insensitive ones. If
15262 you specify @code{auto}, case sensitivity is reset to the default
15263 suitable for the source language. The default is case-sensitive
15264 matches for all languages except for Fortran, for which the default is
15265 case-insensitive matches.
15267 @kindex show case-sensitive
15268 @item show case-sensitive
15269 This command shows the current setting of case sensitivity for symbols
15272 @kindex set print type methods
15273 @item set print type methods
15274 @itemx set print type methods on
15275 @itemx set print type methods off
15276 Normally, when @value{GDBN} prints a class, it displays any methods
15277 declared in that class. You can control this behavior either by
15278 passing the appropriate flag to @code{ptype}, or using @command{set
15279 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15280 display the methods; this is the default. Specifying @code{off} will
15281 cause @value{GDBN} to omit the methods.
15283 @kindex show print type methods
15284 @item show print type methods
15285 This command shows the current setting of method display when printing
15288 @kindex set print type typedefs
15289 @item set print type typedefs
15290 @itemx set print type typedefs on
15291 @itemx set print type typedefs off
15293 Normally, when @value{GDBN} prints a class, it displays any typedefs
15294 defined in that class. You can control this behavior either by
15295 passing the appropriate flag to @code{ptype}, or using @command{set
15296 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15297 display the typedef definitions; this is the default. Specifying
15298 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15299 Note that this controls whether the typedef definition itself is
15300 printed, not whether typedef names are substituted when printing other
15303 @kindex show print type typedefs
15304 @item show print type typedefs
15305 This command shows the current setting of typedef display when
15308 @kindex info address
15309 @cindex address of a symbol
15310 @item info address @var{symbol}
15311 Describe where the data for @var{symbol} is stored. For a register
15312 variable, this says which register it is kept in. For a non-register
15313 local variable, this prints the stack-frame offset at which the variable
15316 Note the contrast with @samp{print &@var{symbol}}, which does not work
15317 at all for a register variable, and for a stack local variable prints
15318 the exact address of the current instantiation of the variable.
15320 @kindex info symbol
15321 @cindex symbol from address
15322 @cindex closest symbol and offset for an address
15323 @item info symbol @var{addr}
15324 Print the name of a symbol which is stored at the address @var{addr}.
15325 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15326 nearest symbol and an offset from it:
15329 (@value{GDBP}) info symbol 0x54320
15330 _initialize_vx + 396 in section .text
15334 This is the opposite of the @code{info address} command. You can use
15335 it to find out the name of a variable or a function given its address.
15337 For dynamically linked executables, the name of executable or shared
15338 library containing the symbol is also printed:
15341 (@value{GDBP}) info symbol 0x400225
15342 _start + 5 in section .text of /tmp/a.out
15343 (@value{GDBP}) info symbol 0x2aaaac2811cf
15344 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15348 @item whatis[/@var{flags}] [@var{arg}]
15349 Print the data type of @var{arg}, which can be either an expression
15350 or a name of a data type. With no argument, print the data type of
15351 @code{$}, the last value in the value history.
15353 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15354 is not actually evaluated, and any side-effecting operations (such as
15355 assignments or function calls) inside it do not take place.
15357 If @var{arg} is a variable or an expression, @code{whatis} prints its
15358 literal type as it is used in the source code. If the type was
15359 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15360 the data type underlying the @code{typedef}. If the type of the
15361 variable or the expression is a compound data type, such as
15362 @code{struct} or @code{class}, @code{whatis} never prints their
15363 fields or methods. It just prints the @code{struct}/@code{class}
15364 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15365 such a compound data type, use @code{ptype}.
15367 If @var{arg} is a type name that was defined using @code{typedef},
15368 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15369 Unrolling means that @code{whatis} will show the underlying type used
15370 in the @code{typedef} declaration of @var{arg}. However, if that
15371 underlying type is also a @code{typedef}, @code{whatis} will not
15374 For C code, the type names may also have the form @samp{class
15375 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15376 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15378 @var{flags} can be used to modify how the type is displayed.
15379 Available flags are:
15383 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15384 parameters and typedefs defined in a class when printing the class'
15385 members. The @code{/r} flag disables this.
15388 Do not print methods defined in the class.
15391 Print methods defined in the class. This is the default, but the flag
15392 exists in case you change the default with @command{set print type methods}.
15395 Do not print typedefs defined in the class. Note that this controls
15396 whether the typedef definition itself is printed, not whether typedef
15397 names are substituted when printing other types.
15400 Print typedefs defined in the class. This is the default, but the flag
15401 exists in case you change the default with @command{set print type typedefs}.
15405 @item ptype[/@var{flags}] [@var{arg}]
15406 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15407 detailed description of the type, instead of just the name of the type.
15408 @xref{Expressions, ,Expressions}.
15410 Contrary to @code{whatis}, @code{ptype} always unrolls any
15411 @code{typedef}s in its argument declaration, whether the argument is
15412 a variable, expression, or a data type. This means that @code{ptype}
15413 of a variable or an expression will not print literally its type as
15414 present in the source code---use @code{whatis} for that. @code{typedef}s at
15415 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15416 fields, methods and inner @code{class typedef}s of @code{struct}s,
15417 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15419 For example, for this variable declaration:
15422 typedef double real_t;
15423 struct complex @{ real_t real; double imag; @};
15424 typedef struct complex complex_t;
15426 real_t *real_pointer_var;
15430 the two commands give this output:
15434 (@value{GDBP}) whatis var
15436 (@value{GDBP}) ptype var
15437 type = struct complex @{
15441 (@value{GDBP}) whatis complex_t
15442 type = struct complex
15443 (@value{GDBP}) whatis struct complex
15444 type = struct complex
15445 (@value{GDBP}) ptype struct complex
15446 type = struct complex @{
15450 (@value{GDBP}) whatis real_pointer_var
15452 (@value{GDBP}) ptype real_pointer_var
15458 As with @code{whatis}, using @code{ptype} without an argument refers to
15459 the type of @code{$}, the last value in the value history.
15461 @cindex incomplete type
15462 Sometimes, programs use opaque data types or incomplete specifications
15463 of complex data structure. If the debug information included in the
15464 program does not allow @value{GDBN} to display a full declaration of
15465 the data type, it will say @samp{<incomplete type>}. For example,
15466 given these declarations:
15470 struct foo *fooptr;
15474 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15477 (@value{GDBP}) ptype foo
15478 $1 = <incomplete type>
15482 ``Incomplete type'' is C terminology for data types that are not
15483 completely specified.
15486 @item info types @var{regexp}
15488 Print a brief description of all types whose names match the regular
15489 expression @var{regexp} (or all types in your program, if you supply
15490 no argument). Each complete typename is matched as though it were a
15491 complete line; thus, @samp{i type value} gives information on all
15492 types in your program whose names include the string @code{value}, but
15493 @samp{i type ^value$} gives information only on types whose complete
15494 name is @code{value}.
15496 This command differs from @code{ptype} in two ways: first, like
15497 @code{whatis}, it does not print a detailed description; second, it
15498 lists all source files where a type is defined.
15500 @kindex info type-printers
15501 @item info type-printers
15502 Versions of @value{GDBN} that ship with Python scripting enabled may
15503 have ``type printers'' available. When using @command{ptype} or
15504 @command{whatis}, these printers are consulted when the name of a type
15505 is needed. @xref{Type Printing API}, for more information on writing
15508 @code{info type-printers} displays all the available type printers.
15510 @kindex enable type-printer
15511 @kindex disable type-printer
15512 @item enable type-printer @var{name}@dots{}
15513 @item disable type-printer @var{name}@dots{}
15514 These commands can be used to enable or disable type printers.
15517 @cindex local variables
15518 @item info scope @var{location}
15519 List all the variables local to a particular scope. This command
15520 accepts a @var{location} argument---a function name, a source line, or
15521 an address preceded by a @samp{*}, and prints all the variables local
15522 to the scope defined by that location. (@xref{Specify Location}, for
15523 details about supported forms of @var{location}.) For example:
15526 (@value{GDBP}) @b{info scope command_line_handler}
15527 Scope for command_line_handler:
15528 Symbol rl is an argument at stack/frame offset 8, length 4.
15529 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15530 Symbol linelength is in static storage at address 0x150a1c, length 4.
15531 Symbol p is a local variable in register $esi, length 4.
15532 Symbol p1 is a local variable in register $ebx, length 4.
15533 Symbol nline is a local variable in register $edx, length 4.
15534 Symbol repeat is a local variable at frame offset -8, length 4.
15538 This command is especially useful for determining what data to collect
15539 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15542 @kindex info source
15544 Show information about the current source file---that is, the source file for
15545 the function containing the current point of execution:
15548 the name of the source file, and the directory containing it,
15550 the directory it was compiled in,
15552 its length, in lines,
15554 which programming language it is written in,
15556 whether the executable includes debugging information for that file, and
15557 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15559 whether the debugging information includes information about
15560 preprocessor macros.
15564 @kindex info sources
15566 Print the names of all source files in your program for which there is
15567 debugging information, organized into two lists: files whose symbols
15568 have already been read, and files whose symbols will be read when needed.
15570 @kindex info functions
15571 @item info functions
15572 Print the names and data types of all defined functions.
15574 @item info functions @var{regexp}
15575 Print the names and data types of all defined functions
15576 whose names contain a match for regular expression @var{regexp}.
15577 Thus, @samp{info fun step} finds all functions whose names
15578 include @code{step}; @samp{info fun ^step} finds those whose names
15579 start with @code{step}. If a function name contains characters
15580 that conflict with the regular expression language (e.g.@:
15581 @samp{operator*()}), they may be quoted with a backslash.
15583 @kindex info variables
15584 @item info variables
15585 Print the names and data types of all variables that are defined
15586 outside of functions (i.e.@: excluding local variables).
15588 @item info variables @var{regexp}
15589 Print the names and data types of all variables (except for local
15590 variables) whose names contain a match for regular expression
15593 @kindex info classes
15594 @cindex Objective-C, classes and selectors
15596 @itemx info classes @var{regexp}
15597 Display all Objective-C classes in your program, or
15598 (with the @var{regexp} argument) all those matching a particular regular
15601 @kindex info selectors
15602 @item info selectors
15603 @itemx info selectors @var{regexp}
15604 Display all Objective-C selectors in your program, or
15605 (with the @var{regexp} argument) all those matching a particular regular
15609 This was never implemented.
15610 @kindex info methods
15612 @itemx info methods @var{regexp}
15613 The @code{info methods} command permits the user to examine all defined
15614 methods within C@t{++} program, or (with the @var{regexp} argument) a
15615 specific set of methods found in the various C@t{++} classes. Many
15616 C@t{++} classes provide a large number of methods. Thus, the output
15617 from the @code{ptype} command can be overwhelming and hard to use. The
15618 @code{info-methods} command filters the methods, printing only those
15619 which match the regular-expression @var{regexp}.
15622 @cindex opaque data types
15623 @kindex set opaque-type-resolution
15624 @item set opaque-type-resolution on
15625 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15626 declared as a pointer to a @code{struct}, @code{class}, or
15627 @code{union}---for example, @code{struct MyType *}---that is used in one
15628 source file although the full declaration of @code{struct MyType} is in
15629 another source file. The default is on.
15631 A change in the setting of this subcommand will not take effect until
15632 the next time symbols for a file are loaded.
15634 @item set opaque-type-resolution off
15635 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15636 is printed as follows:
15638 @{<no data fields>@}
15641 @kindex show opaque-type-resolution
15642 @item show opaque-type-resolution
15643 Show whether opaque types are resolved or not.
15645 @kindex maint print symbols
15646 @cindex symbol dump
15647 @kindex maint print psymbols
15648 @cindex partial symbol dump
15649 @item maint print symbols @var{filename}
15650 @itemx maint print psymbols @var{filename}
15651 @itemx maint print msymbols @var{filename}
15652 Write a dump of debugging symbol data into the file @var{filename}.
15653 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15654 symbols with debugging data are included. If you use @samp{maint print
15655 symbols}, @value{GDBN} includes all the symbols for which it has already
15656 collected full details: that is, @var{filename} reflects symbols for
15657 only those files whose symbols @value{GDBN} has read. You can use the
15658 command @code{info sources} to find out which files these are. If you
15659 use @samp{maint print psymbols} instead, the dump shows information about
15660 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15661 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15662 @samp{maint print msymbols} dumps just the minimal symbol information
15663 required for each object file from which @value{GDBN} has read some symbols.
15664 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15665 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15667 @kindex maint info symtabs
15668 @kindex maint info psymtabs
15669 @cindex listing @value{GDBN}'s internal symbol tables
15670 @cindex symbol tables, listing @value{GDBN}'s internal
15671 @cindex full symbol tables, listing @value{GDBN}'s internal
15672 @cindex partial symbol tables, listing @value{GDBN}'s internal
15673 @item maint info symtabs @r{[} @var{regexp} @r{]}
15674 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15676 List the @code{struct symtab} or @code{struct partial_symtab}
15677 structures whose names match @var{regexp}. If @var{regexp} is not
15678 given, list them all. The output includes expressions which you can
15679 copy into a @value{GDBN} debugging this one to examine a particular
15680 structure in more detail. For example:
15683 (@value{GDBP}) maint info psymtabs dwarf2read
15684 @{ objfile /home/gnu/build/gdb/gdb
15685 ((struct objfile *) 0x82e69d0)
15686 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15687 ((struct partial_symtab *) 0x8474b10)
15690 text addresses 0x814d3c8 -- 0x8158074
15691 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15692 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15693 dependencies (none)
15696 (@value{GDBP}) maint info symtabs
15700 We see that there is one partial symbol table whose filename contains
15701 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15702 and we see that @value{GDBN} has not read in any symtabs yet at all.
15703 If we set a breakpoint on a function, that will cause @value{GDBN} to
15704 read the symtab for the compilation unit containing that function:
15707 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15708 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15710 (@value{GDBP}) maint info symtabs
15711 @{ objfile /home/gnu/build/gdb/gdb
15712 ((struct objfile *) 0x82e69d0)
15713 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15714 ((struct symtab *) 0x86c1f38)
15717 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15718 linetable ((struct linetable *) 0x8370fa0)
15719 debugformat DWARF 2
15728 @chapter Altering Execution
15730 Once you think you have found an error in your program, you might want to
15731 find out for certain whether correcting the apparent error would lead to
15732 correct results in the rest of the run. You can find the answer by
15733 experiment, using the @value{GDBN} features for altering execution of the
15736 For example, you can store new values into variables or memory
15737 locations, give your program a signal, restart it at a different
15738 address, or even return prematurely from a function.
15741 * Assignment:: Assignment to variables
15742 * Jumping:: Continuing at a different address
15743 * Signaling:: Giving your program a signal
15744 * Returning:: Returning from a function
15745 * Calling:: Calling your program's functions
15746 * Patching:: Patching your program
15750 @section Assignment to Variables
15753 @cindex setting variables
15754 To alter the value of a variable, evaluate an assignment expression.
15755 @xref{Expressions, ,Expressions}. For example,
15762 stores the value 4 into the variable @code{x}, and then prints the
15763 value of the assignment expression (which is 4).
15764 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15765 information on operators in supported languages.
15767 @kindex set variable
15768 @cindex variables, setting
15769 If you are not interested in seeing the value of the assignment, use the
15770 @code{set} command instead of the @code{print} command. @code{set} is
15771 really the same as @code{print} except that the expression's value is
15772 not printed and is not put in the value history (@pxref{Value History,
15773 ,Value History}). The expression is evaluated only for its effects.
15775 If the beginning of the argument string of the @code{set} command
15776 appears identical to a @code{set} subcommand, use the @code{set
15777 variable} command instead of just @code{set}. This command is identical
15778 to @code{set} except for its lack of subcommands. For example, if your
15779 program has a variable @code{width}, you get an error if you try to set
15780 a new value with just @samp{set width=13}, because @value{GDBN} has the
15781 command @code{set width}:
15784 (@value{GDBP}) whatis width
15786 (@value{GDBP}) p width
15788 (@value{GDBP}) set width=47
15789 Invalid syntax in expression.
15793 The invalid expression, of course, is @samp{=47}. In
15794 order to actually set the program's variable @code{width}, use
15797 (@value{GDBP}) set var width=47
15800 Because the @code{set} command has many subcommands that can conflict
15801 with the names of program variables, it is a good idea to use the
15802 @code{set variable} command instead of just @code{set}. For example, if
15803 your program has a variable @code{g}, you run into problems if you try
15804 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15805 the command @code{set gnutarget}, abbreviated @code{set g}:
15809 (@value{GDBP}) whatis g
15813 (@value{GDBP}) set g=4
15817 The program being debugged has been started already.
15818 Start it from the beginning? (y or n) y
15819 Starting program: /home/smith/cc_progs/a.out
15820 "/home/smith/cc_progs/a.out": can't open to read symbols:
15821 Invalid bfd target.
15822 (@value{GDBP}) show g
15823 The current BFD target is "=4".
15828 The program variable @code{g} did not change, and you silently set the
15829 @code{gnutarget} to an invalid value. In order to set the variable
15833 (@value{GDBP}) set var g=4
15836 @value{GDBN} allows more implicit conversions in assignments than C; you can
15837 freely store an integer value into a pointer variable or vice versa,
15838 and you can convert any structure to any other structure that is the
15839 same length or shorter.
15840 @comment FIXME: how do structs align/pad in these conversions?
15841 @comment /doc@cygnus.com 18dec1990
15843 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15844 construct to generate a value of specified type at a specified address
15845 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15846 to memory location @code{0x83040} as an integer (which implies a certain size
15847 and representation in memory), and
15850 set @{int@}0x83040 = 4
15854 stores the value 4 into that memory location.
15857 @section Continuing at a Different Address
15859 Ordinarily, when you continue your program, you do so at the place where
15860 it stopped, with the @code{continue} command. You can instead continue at
15861 an address of your own choosing, with the following commands:
15865 @kindex j @r{(@code{jump})}
15866 @item jump @var{linespec}
15867 @itemx j @var{linespec}
15868 @itemx jump @var{location}
15869 @itemx j @var{location}
15870 Resume execution at line @var{linespec} or at address given by
15871 @var{location}. Execution stops again immediately if there is a
15872 breakpoint there. @xref{Specify Location}, for a description of the
15873 different forms of @var{linespec} and @var{location}. It is common
15874 practice to use the @code{tbreak} command in conjunction with
15875 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15877 The @code{jump} command does not change the current stack frame, or
15878 the stack pointer, or the contents of any memory location or any
15879 register other than the program counter. If line @var{linespec} is in
15880 a different function from the one currently executing, the results may
15881 be bizarre if the two functions expect different patterns of arguments or
15882 of local variables. For this reason, the @code{jump} command requests
15883 confirmation if the specified line is not in the function currently
15884 executing. However, even bizarre results are predictable if you are
15885 well acquainted with the machine-language code of your program.
15888 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15889 On many systems, you can get much the same effect as the @code{jump}
15890 command by storing a new value into the register @code{$pc}. The
15891 difference is that this does not start your program running; it only
15892 changes the address of where it @emph{will} run when you continue. For
15900 makes the next @code{continue} command or stepping command execute at
15901 address @code{0x485}, rather than at the address where your program stopped.
15902 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15904 The most common occasion to use the @code{jump} command is to back
15905 up---perhaps with more breakpoints set---over a portion of a program
15906 that has already executed, in order to examine its execution in more
15911 @section Giving your Program a Signal
15912 @cindex deliver a signal to a program
15916 @item signal @var{signal}
15917 Resume execution where your program stopped, but immediately give it the
15918 signal @var{signal}. @var{signal} can be the name or the number of a
15919 signal. For example, on many systems @code{signal 2} and @code{signal
15920 SIGINT} are both ways of sending an interrupt signal.
15922 Alternatively, if @var{signal} is zero, continue execution without
15923 giving a signal. This is useful when your program stopped on account of
15924 a signal and would ordinarily see the signal when resumed with the
15925 @code{continue} command; @samp{signal 0} causes it to resume without a
15928 @code{signal} does not repeat when you press @key{RET} a second time
15929 after executing the command.
15933 Invoking the @code{signal} command is not the same as invoking the
15934 @code{kill} utility from the shell. Sending a signal with @code{kill}
15935 causes @value{GDBN} to decide what to do with the signal depending on
15936 the signal handling tables (@pxref{Signals}). The @code{signal} command
15937 passes the signal directly to your program.
15941 @section Returning from a Function
15944 @cindex returning from a function
15947 @itemx return @var{expression}
15948 You can cancel execution of a function call with the @code{return}
15949 command. If you give an
15950 @var{expression} argument, its value is used as the function's return
15954 When you use @code{return}, @value{GDBN} discards the selected stack frame
15955 (and all frames within it). You can think of this as making the
15956 discarded frame return prematurely. If you wish to specify a value to
15957 be returned, give that value as the argument to @code{return}.
15959 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15960 Frame}), and any other frames inside of it, leaving its caller as the
15961 innermost remaining frame. That frame becomes selected. The
15962 specified value is stored in the registers used for returning values
15965 The @code{return} command does not resume execution; it leaves the
15966 program stopped in the state that would exist if the function had just
15967 returned. In contrast, the @code{finish} command (@pxref{Continuing
15968 and Stepping, ,Continuing and Stepping}) resumes execution until the
15969 selected stack frame returns naturally.
15971 @value{GDBN} needs to know how the @var{expression} argument should be set for
15972 the inferior. The concrete registers assignment depends on the OS ABI and the
15973 type being returned by the selected stack frame. For example it is common for
15974 OS ABI to return floating point values in FPU registers while integer values in
15975 CPU registers. Still some ABIs return even floating point values in CPU
15976 registers. Larger integer widths (such as @code{long long int}) also have
15977 specific placement rules. @value{GDBN} already knows the OS ABI from its
15978 current target so it needs to find out also the type being returned to make the
15979 assignment into the right register(s).
15981 Normally, the selected stack frame has debug info. @value{GDBN} will always
15982 use the debug info instead of the implicit type of @var{expression} when the
15983 debug info is available. For example, if you type @kbd{return -1}, and the
15984 function in the current stack frame is declared to return a @code{long long
15985 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15986 into a @code{long long int}:
15989 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15991 (@value{GDBP}) return -1
15992 Make func return now? (y or n) y
15993 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15994 43 printf ("result=%lld\n", func ());
15998 However, if the selected stack frame does not have a debug info, e.g., if the
15999 function was compiled without debug info, @value{GDBN} has to find out the type
16000 to return from user. Specifying a different type by mistake may set the value
16001 in different inferior registers than the caller code expects. For example,
16002 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16003 of a @code{long long int} result for a debug info less function (on 32-bit
16004 architectures). Therefore the user is required to specify the return type by
16005 an appropriate cast explicitly:
16008 Breakpoint 2, 0x0040050b in func ()
16009 (@value{GDBP}) return -1
16010 Return value type not available for selected stack frame.
16011 Please use an explicit cast of the value to return.
16012 (@value{GDBP}) return (long long int) -1
16013 Make selected stack frame return now? (y or n) y
16014 #0 0x00400526 in main ()
16019 @section Calling Program Functions
16022 @cindex calling functions
16023 @cindex inferior functions, calling
16024 @item print @var{expr}
16025 Evaluate the expression @var{expr} and display the resulting value.
16026 @var{expr} may include calls to functions in the program being
16030 @item call @var{expr}
16031 Evaluate the expression @var{expr} without displaying @code{void}
16034 You can use this variant of the @code{print} command if you want to
16035 execute a function from your program that does not return anything
16036 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16037 with @code{void} returned values that @value{GDBN} will otherwise
16038 print. If the result is not void, it is printed and saved in the
16042 It is possible for the function you call via the @code{print} or
16043 @code{call} command to generate a signal (e.g., if there's a bug in
16044 the function, or if you passed it incorrect arguments). What happens
16045 in that case is controlled by the @code{set unwindonsignal} command.
16047 Similarly, with a C@t{++} program it is possible for the function you
16048 call via the @code{print} or @code{call} command to generate an
16049 exception that is not handled due to the constraints of the dummy
16050 frame. In this case, any exception that is raised in the frame, but has
16051 an out-of-frame exception handler will not be found. GDB builds a
16052 dummy-frame for the inferior function call, and the unwinder cannot
16053 seek for exception handlers outside of this dummy-frame. What happens
16054 in that case is controlled by the
16055 @code{set unwind-on-terminating-exception} command.
16058 @item set unwindonsignal
16059 @kindex set unwindonsignal
16060 @cindex unwind stack in called functions
16061 @cindex call dummy stack unwinding
16062 Set unwinding of the stack if a signal is received while in a function
16063 that @value{GDBN} called in the program being debugged. If set to on,
16064 @value{GDBN} unwinds the stack it created for the call and restores
16065 the context to what it was before the call. If set to off (the
16066 default), @value{GDBN} stops in the frame where the signal was
16069 @item show unwindonsignal
16070 @kindex show unwindonsignal
16071 Show the current setting of stack unwinding in the functions called by
16074 @item set unwind-on-terminating-exception
16075 @kindex set unwind-on-terminating-exception
16076 @cindex unwind stack in called functions with unhandled exceptions
16077 @cindex call dummy stack unwinding on unhandled exception.
16078 Set unwinding of the stack if a C@t{++} exception is raised, but left
16079 unhandled while in a function that @value{GDBN} called in the program being
16080 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16081 it created for the call and restores the context to what it was before
16082 the call. If set to off, @value{GDBN} the exception is delivered to
16083 the default C@t{++} exception handler and the inferior terminated.
16085 @item show unwind-on-terminating-exception
16086 @kindex show unwind-on-terminating-exception
16087 Show the current setting of stack unwinding in the functions called by
16092 @cindex weak alias functions
16093 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16094 for another function. In such case, @value{GDBN} might not pick up
16095 the type information, including the types of the function arguments,
16096 which causes @value{GDBN} to call the inferior function incorrectly.
16097 As a result, the called function will function erroneously and may
16098 even crash. A solution to that is to use the name of the aliased
16102 @section Patching Programs
16104 @cindex patching binaries
16105 @cindex writing into executables
16106 @cindex writing into corefiles
16108 By default, @value{GDBN} opens the file containing your program's
16109 executable code (or the corefile) read-only. This prevents accidental
16110 alterations to machine code; but it also prevents you from intentionally
16111 patching your program's binary.
16113 If you'd like to be able to patch the binary, you can specify that
16114 explicitly with the @code{set write} command. For example, you might
16115 want to turn on internal debugging flags, or even to make emergency
16121 @itemx set write off
16122 If you specify @samp{set write on}, @value{GDBN} opens executable and
16123 core files for both reading and writing; if you specify @kbd{set write
16124 off} (the default), @value{GDBN} opens them read-only.
16126 If you have already loaded a file, you must load it again (using the
16127 @code{exec-file} or @code{core-file} command) after changing @code{set
16128 write}, for your new setting to take effect.
16132 Display whether executable files and core files are opened for writing
16133 as well as reading.
16137 @chapter @value{GDBN} Files
16139 @value{GDBN} needs to know the file name of the program to be debugged,
16140 both in order to read its symbol table and in order to start your
16141 program. To debug a core dump of a previous run, you must also tell
16142 @value{GDBN} the name of the core dump file.
16145 * Files:: Commands to specify files
16146 * Separate Debug Files:: Debugging information in separate files
16147 * MiniDebugInfo:: Debugging information in a special section
16148 * Index Files:: Index files speed up GDB
16149 * Symbol Errors:: Errors reading symbol files
16150 * Data Files:: GDB data files
16154 @section Commands to Specify Files
16156 @cindex symbol table
16157 @cindex core dump file
16159 You may want to specify executable and core dump file names. The usual
16160 way to do this is at start-up time, using the arguments to
16161 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16162 Out of @value{GDBN}}).
16164 Occasionally it is necessary to change to a different file during a
16165 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16166 specify a file you want to use. Or you are debugging a remote target
16167 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16168 Program}). In these situations the @value{GDBN} commands to specify
16169 new files are useful.
16172 @cindex executable file
16174 @item file @var{filename}
16175 Use @var{filename} as the program to be debugged. It is read for its
16176 symbols and for the contents of pure memory. It is also the program
16177 executed when you use the @code{run} command. If you do not specify a
16178 directory and the file is not found in the @value{GDBN} working directory,
16179 @value{GDBN} uses the environment variable @code{PATH} as a list of
16180 directories to search, just as the shell does when looking for a program
16181 to run. You can change the value of this variable, for both @value{GDBN}
16182 and your program, using the @code{path} command.
16184 @cindex unlinked object files
16185 @cindex patching object files
16186 You can load unlinked object @file{.o} files into @value{GDBN} using
16187 the @code{file} command. You will not be able to ``run'' an object
16188 file, but you can disassemble functions and inspect variables. Also,
16189 if the underlying BFD functionality supports it, you could use
16190 @kbd{gdb -write} to patch object files using this technique. Note
16191 that @value{GDBN} can neither interpret nor modify relocations in this
16192 case, so branches and some initialized variables will appear to go to
16193 the wrong place. But this feature is still handy from time to time.
16196 @code{file} with no argument makes @value{GDBN} discard any information it
16197 has on both executable file and the symbol table.
16200 @item exec-file @r{[} @var{filename} @r{]}
16201 Specify that the program to be run (but not the symbol table) is found
16202 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16203 if necessary to locate your program. Omitting @var{filename} means to
16204 discard information on the executable file.
16206 @kindex symbol-file
16207 @item symbol-file @r{[} @var{filename} @r{]}
16208 Read symbol table information from file @var{filename}. @code{PATH} is
16209 searched when necessary. Use the @code{file} command to get both symbol
16210 table and program to run from the same file.
16212 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16213 program's symbol table.
16215 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16216 some breakpoints and auto-display expressions. This is because they may
16217 contain pointers to the internal data recording symbols and data types,
16218 which are part of the old symbol table data being discarded inside
16221 @code{symbol-file} does not repeat if you press @key{RET} again after
16224 When @value{GDBN} is configured for a particular environment, it
16225 understands debugging information in whatever format is the standard
16226 generated for that environment; you may use either a @sc{gnu} compiler, or
16227 other compilers that adhere to the local conventions.
16228 Best results are usually obtained from @sc{gnu} compilers; for example,
16229 using @code{@value{NGCC}} you can generate debugging information for
16232 For most kinds of object files, with the exception of old SVR3 systems
16233 using COFF, the @code{symbol-file} command does not normally read the
16234 symbol table in full right away. Instead, it scans the symbol table
16235 quickly to find which source files and which symbols are present. The
16236 details are read later, one source file at a time, as they are needed.
16238 The purpose of this two-stage reading strategy is to make @value{GDBN}
16239 start up faster. For the most part, it is invisible except for
16240 occasional pauses while the symbol table details for a particular source
16241 file are being read. (The @code{set verbose} command can turn these
16242 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16243 Warnings and Messages}.)
16245 We have not implemented the two-stage strategy for COFF yet. When the
16246 symbol table is stored in COFF format, @code{symbol-file} reads the
16247 symbol table data in full right away. Note that ``stabs-in-COFF''
16248 still does the two-stage strategy, since the debug info is actually
16252 @cindex reading symbols immediately
16253 @cindex symbols, reading immediately
16254 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16255 @itemx file @r{[} -readnow @r{]} @var{filename}
16256 You can override the @value{GDBN} two-stage strategy for reading symbol
16257 tables by using the @samp{-readnow} option with any of the commands that
16258 load symbol table information, if you want to be sure @value{GDBN} has the
16259 entire symbol table available.
16261 @c FIXME: for now no mention of directories, since this seems to be in
16262 @c flux. 13mar1992 status is that in theory GDB would look either in
16263 @c current dir or in same dir as myprog; but issues like competing
16264 @c GDB's, or clutter in system dirs, mean that in practice right now
16265 @c only current dir is used. FFish says maybe a special GDB hierarchy
16266 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16270 @item core-file @r{[}@var{filename}@r{]}
16272 Specify the whereabouts of a core dump file to be used as the ``contents
16273 of memory''. Traditionally, core files contain only some parts of the
16274 address space of the process that generated them; @value{GDBN} can access the
16275 executable file itself for other parts.
16277 @code{core-file} with no argument specifies that no core file is
16280 Note that the core file is ignored when your program is actually running
16281 under @value{GDBN}. So, if you have been running your program and you
16282 wish to debug a core file instead, you must kill the subprocess in which
16283 the program is running. To do this, use the @code{kill} command
16284 (@pxref{Kill Process, ,Killing the Child Process}).
16286 @kindex add-symbol-file
16287 @cindex dynamic linking
16288 @item add-symbol-file @var{filename} @var{address}
16289 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16290 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16291 The @code{add-symbol-file} command reads additional symbol table
16292 information from the file @var{filename}. You would use this command
16293 when @var{filename} has been dynamically loaded (by some other means)
16294 into the program that is running. @var{address} should be the memory
16295 address at which the file has been loaded; @value{GDBN} cannot figure
16296 this out for itself. You can additionally specify an arbitrary number
16297 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16298 section name and base address for that section. You can specify any
16299 @var{address} as an expression.
16301 The symbol table of the file @var{filename} is added to the symbol table
16302 originally read with the @code{symbol-file} command. You can use the
16303 @code{add-symbol-file} command any number of times; the new symbol data
16304 thus read keeps adding to the old. To discard all old symbol data
16305 instead, use the @code{symbol-file} command without any arguments.
16307 @cindex relocatable object files, reading symbols from
16308 @cindex object files, relocatable, reading symbols from
16309 @cindex reading symbols from relocatable object files
16310 @cindex symbols, reading from relocatable object files
16311 @cindex @file{.o} files, reading symbols from
16312 Although @var{filename} is typically a shared library file, an
16313 executable file, or some other object file which has been fully
16314 relocated for loading into a process, you can also load symbolic
16315 information from relocatable @file{.o} files, as long as:
16319 the file's symbolic information refers only to linker symbols defined in
16320 that file, not to symbols defined by other object files,
16322 every section the file's symbolic information refers to has actually
16323 been loaded into the inferior, as it appears in the file, and
16325 you can determine the address at which every section was loaded, and
16326 provide these to the @code{add-symbol-file} command.
16330 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16331 relocatable files into an already running program; such systems
16332 typically make the requirements above easy to meet. However, it's
16333 important to recognize that many native systems use complex link
16334 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16335 assembly, for example) that make the requirements difficult to meet. In
16336 general, one cannot assume that using @code{add-symbol-file} to read a
16337 relocatable object file's symbolic information will have the same effect
16338 as linking the relocatable object file into the program in the normal
16341 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16343 @kindex add-symbol-file-from-memory
16344 @cindex @code{syscall DSO}
16345 @cindex load symbols from memory
16346 @item add-symbol-file-from-memory @var{address}
16347 Load symbols from the given @var{address} in a dynamically loaded
16348 object file whose image is mapped directly into the inferior's memory.
16349 For example, the Linux kernel maps a @code{syscall DSO} into each
16350 process's address space; this DSO provides kernel-specific code for
16351 some system calls. The argument can be any expression whose
16352 evaluation yields the address of the file's shared object file header.
16353 For this command to work, you must have used @code{symbol-file} or
16354 @code{exec-file} commands in advance.
16356 @kindex add-shared-symbol-files
16358 @item add-shared-symbol-files @var{library-file}
16359 @itemx assf @var{library-file}
16360 The @code{add-shared-symbol-files} command can currently be used only
16361 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16362 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16363 @value{GDBN} automatically looks for shared libraries, however if
16364 @value{GDBN} does not find yours, you can invoke
16365 @code{add-shared-symbol-files}. It takes one argument: the shared
16366 library's file name. @code{assf} is a shorthand alias for
16367 @code{add-shared-symbol-files}.
16370 @item section @var{section} @var{addr}
16371 The @code{section} command changes the base address of the named
16372 @var{section} of the exec file to @var{addr}. This can be used if the
16373 exec file does not contain section addresses, (such as in the
16374 @code{a.out} format), or when the addresses specified in the file
16375 itself are wrong. Each section must be changed separately. The
16376 @code{info files} command, described below, lists all the sections and
16380 @kindex info target
16383 @code{info files} and @code{info target} are synonymous; both print the
16384 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16385 including the names of the executable and core dump files currently in
16386 use by @value{GDBN}, and the files from which symbols were loaded. The
16387 command @code{help target} lists all possible targets rather than
16390 @kindex maint info sections
16391 @item maint info sections
16392 Another command that can give you extra information about program sections
16393 is @code{maint info sections}. In addition to the section information
16394 displayed by @code{info files}, this command displays the flags and file
16395 offset of each section in the executable and core dump files. In addition,
16396 @code{maint info sections} provides the following command options (which
16397 may be arbitrarily combined):
16401 Display sections for all loaded object files, including shared libraries.
16402 @item @var{sections}
16403 Display info only for named @var{sections}.
16404 @item @var{section-flags}
16405 Display info only for sections for which @var{section-flags} are true.
16406 The section flags that @value{GDBN} currently knows about are:
16409 Section will have space allocated in the process when loaded.
16410 Set for all sections except those containing debug information.
16412 Section will be loaded from the file into the child process memory.
16413 Set for pre-initialized code and data, clear for @code{.bss} sections.
16415 Section needs to be relocated before loading.
16417 Section cannot be modified by the child process.
16419 Section contains executable code only.
16421 Section contains data only (no executable code).
16423 Section will reside in ROM.
16425 Section contains data for constructor/destructor lists.
16427 Section is not empty.
16429 An instruction to the linker to not output the section.
16430 @item COFF_SHARED_LIBRARY
16431 A notification to the linker that the section contains
16432 COFF shared library information.
16434 Section contains common symbols.
16437 @kindex set trust-readonly-sections
16438 @cindex read-only sections
16439 @item set trust-readonly-sections on
16440 Tell @value{GDBN} that readonly sections in your object file
16441 really are read-only (i.e.@: that their contents will not change).
16442 In that case, @value{GDBN} can fetch values from these sections
16443 out of the object file, rather than from the target program.
16444 For some targets (notably embedded ones), this can be a significant
16445 enhancement to debugging performance.
16447 The default is off.
16449 @item set trust-readonly-sections off
16450 Tell @value{GDBN} not to trust readonly sections. This means that
16451 the contents of the section might change while the program is running,
16452 and must therefore be fetched from the target when needed.
16454 @item show trust-readonly-sections
16455 Show the current setting of trusting readonly sections.
16458 All file-specifying commands allow both absolute and relative file names
16459 as arguments. @value{GDBN} always converts the file name to an absolute file
16460 name and remembers it that way.
16462 @cindex shared libraries
16463 @anchor{Shared Libraries}
16464 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16465 and IBM RS/6000 AIX shared libraries.
16467 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16468 shared libraries. @xref{Expat}.
16470 @value{GDBN} automatically loads symbol definitions from shared libraries
16471 when you use the @code{run} command, or when you examine a core file.
16472 (Before you issue the @code{run} command, @value{GDBN} does not understand
16473 references to a function in a shared library, however---unless you are
16474 debugging a core file).
16476 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16477 automatically loads the symbols at the time of the @code{shl_load} call.
16479 @c FIXME: some @value{GDBN} release may permit some refs to undef
16480 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16481 @c FIXME...lib; check this from time to time when updating manual
16483 There are times, however, when you may wish to not automatically load
16484 symbol definitions from shared libraries, such as when they are
16485 particularly large or there are many of them.
16487 To control the automatic loading of shared library symbols, use the
16491 @kindex set auto-solib-add
16492 @item set auto-solib-add @var{mode}
16493 If @var{mode} is @code{on}, symbols from all shared object libraries
16494 will be loaded automatically when the inferior begins execution, you
16495 attach to an independently started inferior, or when the dynamic linker
16496 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16497 is @code{off}, symbols must be loaded manually, using the
16498 @code{sharedlibrary} command. The default value is @code{on}.
16500 @cindex memory used for symbol tables
16501 If your program uses lots of shared libraries with debug info that
16502 takes large amounts of memory, you can decrease the @value{GDBN}
16503 memory footprint by preventing it from automatically loading the
16504 symbols from shared libraries. To that end, type @kbd{set
16505 auto-solib-add off} before running the inferior, then load each
16506 library whose debug symbols you do need with @kbd{sharedlibrary
16507 @var{regexp}}, where @var{regexp} is a regular expression that matches
16508 the libraries whose symbols you want to be loaded.
16510 @kindex show auto-solib-add
16511 @item show auto-solib-add
16512 Display the current autoloading mode.
16515 @cindex load shared library
16516 To explicitly load shared library symbols, use the @code{sharedlibrary}
16520 @kindex info sharedlibrary
16522 @item info share @var{regex}
16523 @itemx info sharedlibrary @var{regex}
16524 Print the names of the shared libraries which are currently loaded
16525 that match @var{regex}. If @var{regex} is omitted then print
16526 all shared libraries that are loaded.
16528 @kindex sharedlibrary
16530 @item sharedlibrary @var{regex}
16531 @itemx share @var{regex}
16532 Load shared object library symbols for files matching a
16533 Unix regular expression.
16534 As with files loaded automatically, it only loads shared libraries
16535 required by your program for a core file or after typing @code{run}. If
16536 @var{regex} is omitted all shared libraries required by your program are
16539 @item nosharedlibrary
16540 @kindex nosharedlibrary
16541 @cindex unload symbols from shared libraries
16542 Unload all shared object library symbols. This discards all symbols
16543 that have been loaded from all shared libraries. Symbols from shared
16544 libraries that were loaded by explicit user requests are not
16548 Sometimes you may wish that @value{GDBN} stops and gives you control
16549 when any of shared library events happen. The best way to do this is
16550 to use @code{catch load} and @code{catch unload} (@pxref{Set
16553 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16554 command for this. This command exists for historical reasons. It is
16555 less useful than setting a catchpoint, because it does not allow for
16556 conditions or commands as a catchpoint does.
16559 @item set stop-on-solib-events
16560 @kindex set stop-on-solib-events
16561 This command controls whether @value{GDBN} should give you control
16562 when the dynamic linker notifies it about some shared library event.
16563 The most common event of interest is loading or unloading of a new
16566 @item show stop-on-solib-events
16567 @kindex show stop-on-solib-events
16568 Show whether @value{GDBN} stops and gives you control when shared
16569 library events happen.
16572 Shared libraries are also supported in many cross or remote debugging
16573 configurations. @value{GDBN} needs to have access to the target's libraries;
16574 this can be accomplished either by providing copies of the libraries
16575 on the host system, or by asking @value{GDBN} to automatically retrieve the
16576 libraries from the target. If copies of the target libraries are
16577 provided, they need to be the same as the target libraries, although the
16578 copies on the target can be stripped as long as the copies on the host are
16581 @cindex where to look for shared libraries
16582 For remote debugging, you need to tell @value{GDBN} where the target
16583 libraries are, so that it can load the correct copies---otherwise, it
16584 may try to load the host's libraries. @value{GDBN} has two variables
16585 to specify the search directories for target libraries.
16588 @cindex prefix for shared library file names
16589 @cindex system root, alternate
16590 @kindex set solib-absolute-prefix
16591 @kindex set sysroot
16592 @item set sysroot @var{path}
16593 Use @var{path} as the system root for the program being debugged. Any
16594 absolute shared library paths will be prefixed with @var{path}; many
16595 runtime loaders store the absolute paths to the shared library in the
16596 target program's memory. If you use @code{set sysroot} to find shared
16597 libraries, they need to be laid out in the same way that they are on
16598 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16601 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16602 retrieve the target libraries from the remote system. This is only
16603 supported when using a remote target that supports the @code{remote get}
16604 command (@pxref{File Transfer,,Sending files to a remote system}).
16605 The part of @var{path} following the initial @file{remote:}
16606 (if present) is used as system root prefix on the remote file system.
16607 @footnote{If you want to specify a local system root using a directory
16608 that happens to be named @file{remote:}, you need to use some equivalent
16609 variant of the name like @file{./remote:}.}
16611 For targets with an MS-DOS based filesystem, such as MS-Windows and
16612 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16613 absolute file name with @var{path}. But first, on Unix hosts,
16614 @value{GDBN} converts all backslash directory separators into forward
16615 slashes, because the backslash is not a directory separator on Unix:
16618 c:\foo\bar.dll @result{} c:/foo/bar.dll
16621 Then, @value{GDBN} attempts prefixing the target file name with
16622 @var{path}, and looks for the resulting file name in the host file
16626 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16629 If that does not find the shared library, @value{GDBN} tries removing
16630 the @samp{:} character from the drive spec, both for convenience, and,
16631 for the case of the host file system not supporting file names with
16635 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16638 This makes it possible to have a system root that mirrors a target
16639 with more than one drive. E.g., you may want to setup your local
16640 copies of the target system shared libraries like so (note @samp{c} vs
16644 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16645 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16646 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16650 and point the system root at @file{/path/to/sysroot}, so that
16651 @value{GDBN} can find the correct copies of both
16652 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16654 If that still does not find the shared library, @value{GDBN} tries
16655 removing the whole drive spec from the target file name:
16658 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16661 This last lookup makes it possible to not care about the drive name,
16662 if you don't want or need to.
16664 The @code{set solib-absolute-prefix} command is an alias for @code{set
16667 @cindex default system root
16668 @cindex @samp{--with-sysroot}
16669 You can set the default system root by using the configure-time
16670 @samp{--with-sysroot} option. If the system root is inside
16671 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16672 @samp{--exec-prefix}), then the default system root will be updated
16673 automatically if the installed @value{GDBN} is moved to a new
16676 @kindex show sysroot
16678 Display the current shared library prefix.
16680 @kindex set solib-search-path
16681 @item set solib-search-path @var{path}
16682 If this variable is set, @var{path} is a colon-separated list of
16683 directories to search for shared libraries. @samp{solib-search-path}
16684 is used after @samp{sysroot} fails to locate the library, or if the
16685 path to the library is relative instead of absolute. If you want to
16686 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16687 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16688 finding your host's libraries. @samp{sysroot} is preferred; setting
16689 it to a nonexistent directory may interfere with automatic loading
16690 of shared library symbols.
16692 @kindex show solib-search-path
16693 @item show solib-search-path
16694 Display the current shared library search path.
16696 @cindex DOS file-name semantics of file names.
16697 @kindex set target-file-system-kind (unix|dos-based|auto)
16698 @kindex show target-file-system-kind
16699 @item set target-file-system-kind @var{kind}
16700 Set assumed file system kind for target reported file names.
16702 Shared library file names as reported by the target system may not
16703 make sense as is on the system @value{GDBN} is running on. For
16704 example, when remote debugging a target that has MS-DOS based file
16705 system semantics, from a Unix host, the target may be reporting to
16706 @value{GDBN} a list of loaded shared libraries with file names such as
16707 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16708 drive letters, so the @samp{c:\} prefix is not normally understood as
16709 indicating an absolute file name, and neither is the backslash
16710 normally considered a directory separator character. In that case,
16711 the native file system would interpret this whole absolute file name
16712 as a relative file name with no directory components. This would make
16713 it impossible to point @value{GDBN} at a copy of the remote target's
16714 shared libraries on the host using @code{set sysroot}, and impractical
16715 with @code{set solib-search-path}. Setting
16716 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16717 to interpret such file names similarly to how the target would, and to
16718 map them to file names valid on @value{GDBN}'s native file system
16719 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16720 to one of the supported file system kinds. In that case, @value{GDBN}
16721 tries to determine the appropriate file system variant based on the
16722 current target's operating system (@pxref{ABI, ,Configuring the
16723 Current ABI}). The supported file system settings are:
16727 Instruct @value{GDBN} to assume the target file system is of Unix
16728 kind. Only file names starting the forward slash (@samp{/}) character
16729 are considered absolute, and the directory separator character is also
16733 Instruct @value{GDBN} to assume the target file system is DOS based.
16734 File names starting with either a forward slash, or a drive letter
16735 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16736 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16737 considered directory separators.
16740 Instruct @value{GDBN} to use the file system kind associated with the
16741 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16742 This is the default.
16746 @cindex file name canonicalization
16747 @cindex base name differences
16748 When processing file names provided by the user, @value{GDBN}
16749 frequently needs to compare them to the file names recorded in the
16750 program's debug info. Normally, @value{GDBN} compares just the
16751 @dfn{base names} of the files as strings, which is reasonably fast
16752 even for very large programs. (The base name of a file is the last
16753 portion of its name, after stripping all the leading directories.)
16754 This shortcut in comparison is based upon the assumption that files
16755 cannot have more than one base name. This is usually true, but
16756 references to files that use symlinks or similar filesystem
16757 facilities violate that assumption. If your program records files
16758 using such facilities, or if you provide file names to @value{GDBN}
16759 using symlinks etc., you can set @code{basenames-may-differ} to
16760 @code{true} to instruct @value{GDBN} to completely canonicalize each
16761 pair of file names it needs to compare. This will make file-name
16762 comparisons accurate, but at a price of a significant slowdown.
16765 @item set basenames-may-differ
16766 @kindex set basenames-may-differ
16767 Set whether a source file may have multiple base names.
16769 @item show basenames-may-differ
16770 @kindex show basenames-may-differ
16771 Show whether a source file may have multiple base names.
16774 @node Separate Debug Files
16775 @section Debugging Information in Separate Files
16776 @cindex separate debugging information files
16777 @cindex debugging information in separate files
16778 @cindex @file{.debug} subdirectories
16779 @cindex debugging information directory, global
16780 @cindex global debugging information directories
16781 @cindex build ID, and separate debugging files
16782 @cindex @file{.build-id} directory
16784 @value{GDBN} allows you to put a program's debugging information in a
16785 file separate from the executable itself, in a way that allows
16786 @value{GDBN} to find and load the debugging information automatically.
16787 Since debugging information can be very large---sometimes larger
16788 than the executable code itself---some systems distribute debugging
16789 information for their executables in separate files, which users can
16790 install only when they need to debug a problem.
16792 @value{GDBN} supports two ways of specifying the separate debug info
16797 The executable contains a @dfn{debug link} that specifies the name of
16798 the separate debug info file. The separate debug file's name is
16799 usually @file{@var{executable}.debug}, where @var{executable} is the
16800 name of the corresponding executable file without leading directories
16801 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16802 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16803 checksum for the debug file, which @value{GDBN} uses to validate that
16804 the executable and the debug file came from the same build.
16807 The executable contains a @dfn{build ID}, a unique bit string that is
16808 also present in the corresponding debug info file. (This is supported
16809 only on some operating systems, notably those which use the ELF format
16810 for binary files and the @sc{gnu} Binutils.) For more details about
16811 this feature, see the description of the @option{--build-id}
16812 command-line option in @ref{Options, , Command Line Options, ld.info,
16813 The GNU Linker}. The debug info file's name is not specified
16814 explicitly by the build ID, but can be computed from the build ID, see
16818 Depending on the way the debug info file is specified, @value{GDBN}
16819 uses two different methods of looking for the debug file:
16823 For the ``debug link'' method, @value{GDBN} looks up the named file in
16824 the directory of the executable file, then in a subdirectory of that
16825 directory named @file{.debug}, and finally under each one of the global debug
16826 directories, in a subdirectory whose name is identical to the leading
16827 directories of the executable's absolute file name.
16830 For the ``build ID'' method, @value{GDBN} looks in the
16831 @file{.build-id} subdirectory of each one of the global debug directories for
16832 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16833 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16834 are the rest of the bit string. (Real build ID strings are 32 or more
16835 hex characters, not 10.)
16838 So, for example, suppose you ask @value{GDBN} to debug
16839 @file{/usr/bin/ls}, which has a debug link that specifies the
16840 file @file{ls.debug}, and a build ID whose value in hex is
16841 @code{abcdef1234}. If the list of the global debug directories includes
16842 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16843 debug information files, in the indicated order:
16847 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16849 @file{/usr/bin/ls.debug}
16851 @file{/usr/bin/.debug/ls.debug}
16853 @file{/usr/lib/debug/usr/bin/ls.debug}.
16856 @anchor{debug-file-directory}
16857 Global debugging info directories default to what is set by @value{GDBN}
16858 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16859 you can also set the global debugging info directories, and view the list
16860 @value{GDBN} is currently using.
16864 @kindex set debug-file-directory
16865 @item set debug-file-directory @var{directories}
16866 Set the directories which @value{GDBN} searches for separate debugging
16867 information files to @var{directory}. Multiple path components can be set
16868 concatenating them by a path separator.
16870 @kindex show debug-file-directory
16871 @item show debug-file-directory
16872 Show the directories @value{GDBN} searches for separate debugging
16877 @cindex @code{.gnu_debuglink} sections
16878 @cindex debug link sections
16879 A debug link is a special section of the executable file named
16880 @code{.gnu_debuglink}. The section must contain:
16884 A filename, with any leading directory components removed, followed by
16887 zero to three bytes of padding, as needed to reach the next four-byte
16888 boundary within the section, and
16890 a four-byte CRC checksum, stored in the same endianness used for the
16891 executable file itself. The checksum is computed on the debugging
16892 information file's full contents by the function given below, passing
16893 zero as the @var{crc} argument.
16896 Any executable file format can carry a debug link, as long as it can
16897 contain a section named @code{.gnu_debuglink} with the contents
16900 @cindex @code{.note.gnu.build-id} sections
16901 @cindex build ID sections
16902 The build ID is a special section in the executable file (and in other
16903 ELF binary files that @value{GDBN} may consider). This section is
16904 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16905 It contains unique identification for the built files---the ID remains
16906 the same across multiple builds of the same build tree. The default
16907 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16908 content for the build ID string. The same section with an identical
16909 value is present in the original built binary with symbols, in its
16910 stripped variant, and in the separate debugging information file.
16912 The debugging information file itself should be an ordinary
16913 executable, containing a full set of linker symbols, sections, and
16914 debugging information. The sections of the debugging information file
16915 should have the same names, addresses, and sizes as the original file,
16916 but they need not contain any data---much like a @code{.bss} section
16917 in an ordinary executable.
16919 The @sc{gnu} binary utilities (Binutils) package includes the
16920 @samp{objcopy} utility that can produce
16921 the separated executable / debugging information file pairs using the
16922 following commands:
16925 @kbd{objcopy --only-keep-debug foo foo.debug}
16930 These commands remove the debugging
16931 information from the executable file @file{foo} and place it in the file
16932 @file{foo.debug}. You can use the first, second or both methods to link the
16937 The debug link method needs the following additional command to also leave
16938 behind a debug link in @file{foo}:
16941 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16944 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16945 a version of the @code{strip} command such that the command @kbd{strip foo -f
16946 foo.debug} has the same functionality as the two @code{objcopy} commands and
16947 the @code{ln -s} command above, together.
16950 Build ID gets embedded into the main executable using @code{ld --build-id} or
16951 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16952 compatibility fixes for debug files separation are present in @sc{gnu} binary
16953 utilities (Binutils) package since version 2.18.
16958 @cindex CRC algorithm definition
16959 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16960 IEEE 802.3 using the polynomial:
16962 @c TexInfo requires naked braces for multi-digit exponents for Tex
16963 @c output, but this causes HTML output to barf. HTML has to be set using
16964 @c raw commands. So we end up having to specify this equation in 2
16969 <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>
16970 + <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
16976 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16977 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16981 The function is computed byte at a time, taking the least
16982 significant bit of each byte first. The initial pattern
16983 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16984 the final result is inverted to ensure trailing zeros also affect the
16987 @emph{Note:} This is the same CRC polynomial as used in handling the
16988 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16989 , @value{GDBN} Remote Serial Protocol}). However in the
16990 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16991 significant bit first, and the result is not inverted, so trailing
16992 zeros have no effect on the CRC value.
16994 To complete the description, we show below the code of the function
16995 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16996 initially supplied @code{crc} argument means that an initial call to
16997 this function passing in zero will start computing the CRC using
17000 @kindex gnu_debuglink_crc32
17003 gnu_debuglink_crc32 (unsigned long crc,
17004 unsigned char *buf, size_t len)
17006 static const unsigned long crc32_table[256] =
17008 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17009 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17010 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17011 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17012 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17013 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17014 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17015 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17016 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17017 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17018 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17019 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17020 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17021 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17022 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17023 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17024 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17025 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17026 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17027 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17028 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17029 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17030 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17031 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17032 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17033 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17034 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17035 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17036 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17037 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17038 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17039 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17040 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17041 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17042 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17043 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17044 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17045 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17046 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17047 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17048 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17049 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17050 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17051 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17052 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17053 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17054 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17055 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17056 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17057 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17058 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17061 unsigned char *end;
17063 crc = ~crc & 0xffffffff;
17064 for (end = buf + len; buf < end; ++buf)
17065 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17066 return ~crc & 0xffffffff;
17071 This computation does not apply to the ``build ID'' method.
17073 @node MiniDebugInfo
17074 @section Debugging information in a special section
17075 @cindex separate debug sections
17076 @cindex @samp{.gnu_debugdata} section
17078 Some systems ship pre-built executables and libraries that have a
17079 special @samp{.gnu_debugdata} section. This feature is called
17080 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17081 is used to supply extra symbols for backtraces.
17083 The intent of this section is to provide extra minimal debugging
17084 information for use in simple backtraces. It is not intended to be a
17085 replacement for full separate debugging information (@pxref{Separate
17086 Debug Files}). The example below shows the intended use; however,
17087 @value{GDBN} does not currently put restrictions on what sort of
17088 debugging information might be included in the section.
17090 @value{GDBN} has support for this extension. If the section exists,
17091 then it is used provided that no other source of debugging information
17092 can be found, and that @value{GDBN} was configured with LZMA support.
17094 This section can be easily created using @command{objcopy} and other
17095 standard utilities:
17098 # Extract the dynamic symbols from the main binary, there is no need
17099 # to also have these in the normal symbol table
17100 nm -D @var{binary} --format=posix --defined-only \
17101 | awk '@{ print $1 @}' | sort > dynsyms
17103 # Extract all the text (i.e. function) symbols from the debuginfo .
17104 nm @var{binary} --format=posix --defined-only \
17105 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
17108 # Keep all the function symbols not already in the dynamic symbol
17110 comm -13 dynsyms funcsyms > keep_symbols
17112 # Copy the full debuginfo, keeping only a minimal set of symbols and
17113 # removing some unnecessary sections.
17114 objcopy -S --remove-section .gdb_index --remove-section .comment \
17115 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
17117 # Inject the compressed data into the .gnu_debugdata section of the
17120 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17124 @section Index Files Speed Up @value{GDBN}
17125 @cindex index files
17126 @cindex @samp{.gdb_index} section
17128 When @value{GDBN} finds a symbol file, it scans the symbols in the
17129 file in order to construct an internal symbol table. This lets most
17130 @value{GDBN} operations work quickly---at the cost of a delay early
17131 on. For large programs, this delay can be quite lengthy, so
17132 @value{GDBN} provides a way to build an index, which speeds up
17135 The index is stored as a section in the symbol file. @value{GDBN} can
17136 write the index to a file, then you can put it into the symbol file
17137 using @command{objcopy}.
17139 To create an index file, use the @code{save gdb-index} command:
17142 @item save gdb-index @var{directory}
17143 @kindex save gdb-index
17144 Create an index file for each symbol file currently known by
17145 @value{GDBN}. Each file is named after its corresponding symbol file,
17146 with @samp{.gdb-index} appended, and is written into the given
17150 Once you have created an index file you can merge it into your symbol
17151 file, here named @file{symfile}, using @command{objcopy}:
17154 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17155 --set-section-flags .gdb_index=readonly symfile symfile
17158 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17159 sections that have been deprecated. Usually they are deprecated because
17160 they are missing a new feature or have performance issues.
17161 To tell @value{GDBN} to use a deprecated index section anyway
17162 specify @code{set use-deprecated-index-sections on}.
17163 The default is @code{off}.
17164 This can speed up startup, but may result in some functionality being lost.
17165 @xref{Index Section Format}.
17167 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17168 must be done before gdb reads the file. The following will not work:
17171 $ gdb -ex "set use-deprecated-index-sections on" <program>
17174 Instead you must do, for example,
17177 $ gdb -iex "set use-deprecated-index-sections on" <program>
17180 There are currently some limitation on indices. They only work when
17181 for DWARF debugging information, not stabs. And, they do not
17182 currently work for programs using Ada.
17184 @node Symbol Errors
17185 @section Errors Reading Symbol Files
17187 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17188 such as symbol types it does not recognize, or known bugs in compiler
17189 output. By default, @value{GDBN} does not notify you of such problems, since
17190 they are relatively common and primarily of interest to people
17191 debugging compilers. If you are interested in seeing information
17192 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17193 only one message about each such type of problem, no matter how many
17194 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17195 to see how many times the problems occur, with the @code{set
17196 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17199 The messages currently printed, and their meanings, include:
17202 @item inner block not inside outer block in @var{symbol}
17204 The symbol information shows where symbol scopes begin and end
17205 (such as at the start of a function or a block of statements). This
17206 error indicates that an inner scope block is not fully contained
17207 in its outer scope blocks.
17209 @value{GDBN} circumvents the problem by treating the inner block as if it had
17210 the same scope as the outer block. In the error message, @var{symbol}
17211 may be shown as ``@code{(don't know)}'' if the outer block is not a
17214 @item block at @var{address} out of order
17216 The symbol information for symbol scope blocks should occur in
17217 order of increasing addresses. This error indicates that it does not
17220 @value{GDBN} does not circumvent this problem, and has trouble
17221 locating symbols in the source file whose symbols it is reading. (You
17222 can often determine what source file is affected by specifying
17223 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17226 @item bad block start address patched
17228 The symbol information for a symbol scope block has a start address
17229 smaller than the address of the preceding source line. This is known
17230 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17232 @value{GDBN} circumvents the problem by treating the symbol scope block as
17233 starting on the previous source line.
17235 @item bad string table offset in symbol @var{n}
17238 Symbol number @var{n} contains a pointer into the string table which is
17239 larger than the size of the string table.
17241 @value{GDBN} circumvents the problem by considering the symbol to have the
17242 name @code{foo}, which may cause other problems if many symbols end up
17245 @item unknown symbol type @code{0x@var{nn}}
17247 The symbol information contains new data types that @value{GDBN} does
17248 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17249 uncomprehended information, in hexadecimal.
17251 @value{GDBN} circumvents the error by ignoring this symbol information.
17252 This usually allows you to debug your program, though certain symbols
17253 are not accessible. If you encounter such a problem and feel like
17254 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17255 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17256 and examine @code{*bufp} to see the symbol.
17258 @item stub type has NULL name
17260 @value{GDBN} could not find the full definition for a struct or class.
17262 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17263 The symbol information for a C@t{++} member function is missing some
17264 information that recent versions of the compiler should have output for
17267 @item info mismatch between compiler and debugger
17269 @value{GDBN} could not parse a type specification output by the compiler.
17274 @section GDB Data Files
17276 @cindex prefix for data files
17277 @value{GDBN} will sometimes read an auxiliary data file. These files
17278 are kept in a directory known as the @dfn{data directory}.
17280 You can set the data directory's name, and view the name @value{GDBN}
17281 is currently using.
17284 @kindex set data-directory
17285 @item set data-directory @var{directory}
17286 Set the directory which @value{GDBN} searches for auxiliary data files
17287 to @var{directory}.
17289 @kindex show data-directory
17290 @item show data-directory
17291 Show the directory @value{GDBN} searches for auxiliary data files.
17294 @cindex default data directory
17295 @cindex @samp{--with-gdb-datadir}
17296 You can set the default data directory by using the configure-time
17297 @samp{--with-gdb-datadir} option. If the data directory is inside
17298 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17299 @samp{--exec-prefix}), then the default data directory will be updated
17300 automatically if the installed @value{GDBN} is moved to a new
17303 The data directory may also be specified with the
17304 @code{--data-directory} command line option.
17305 @xref{Mode Options}.
17308 @chapter Specifying a Debugging Target
17310 @cindex debugging target
17311 A @dfn{target} is the execution environment occupied by your program.
17313 Often, @value{GDBN} runs in the same host environment as your program;
17314 in that case, the debugging target is specified as a side effect when
17315 you use the @code{file} or @code{core} commands. When you need more
17316 flexibility---for example, running @value{GDBN} on a physically separate
17317 host, or controlling a standalone system over a serial port or a
17318 realtime system over a TCP/IP connection---you can use the @code{target}
17319 command to specify one of the target types configured for @value{GDBN}
17320 (@pxref{Target Commands, ,Commands for Managing Targets}).
17322 @cindex target architecture
17323 It is possible to build @value{GDBN} for several different @dfn{target
17324 architectures}. When @value{GDBN} is built like that, you can choose
17325 one of the available architectures with the @kbd{set architecture}
17329 @kindex set architecture
17330 @kindex show architecture
17331 @item set architecture @var{arch}
17332 This command sets the current target architecture to @var{arch}. The
17333 value of @var{arch} can be @code{"auto"}, in addition to one of the
17334 supported architectures.
17336 @item show architecture
17337 Show the current target architecture.
17339 @item set processor
17341 @kindex set processor
17342 @kindex show processor
17343 These are alias commands for, respectively, @code{set architecture}
17344 and @code{show architecture}.
17348 * Active Targets:: Active targets
17349 * Target Commands:: Commands for managing targets
17350 * Byte Order:: Choosing target byte order
17353 @node Active Targets
17354 @section Active Targets
17356 @cindex stacking targets
17357 @cindex active targets
17358 @cindex multiple targets
17360 There are multiple classes of targets such as: processes, executable files or
17361 recording sessions. Core files belong to the process class, making core file
17362 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17363 on multiple active targets, one in each class. This allows you to (for
17364 example) start a process and inspect its activity, while still having access to
17365 the executable file after the process finishes. Or if you start process
17366 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17367 presented a virtual layer of the recording target, while the process target
17368 remains stopped at the chronologically last point of the process execution.
17370 Use the @code{core-file} and @code{exec-file} commands to select a new core
17371 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17372 specify as a target a process that is already running, use the @code{attach}
17373 command (@pxref{Attach, ,Debugging an Already-running Process}).
17375 @node Target Commands
17376 @section Commands for Managing Targets
17379 @item target @var{type} @var{parameters}
17380 Connects the @value{GDBN} host environment to a target machine or
17381 process. A target is typically a protocol for talking to debugging
17382 facilities. You use the argument @var{type} to specify the type or
17383 protocol of the target machine.
17385 Further @var{parameters} are interpreted by the target protocol, but
17386 typically include things like device names or host names to connect
17387 with, process numbers, and baud rates.
17389 The @code{target} command does not repeat if you press @key{RET} again
17390 after executing the command.
17392 @kindex help target
17394 Displays the names of all targets available. To display targets
17395 currently selected, use either @code{info target} or @code{info files}
17396 (@pxref{Files, ,Commands to Specify Files}).
17398 @item help target @var{name}
17399 Describe a particular target, including any parameters necessary to
17402 @kindex set gnutarget
17403 @item set gnutarget @var{args}
17404 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17405 knows whether it is reading an @dfn{executable},
17406 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17407 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17408 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17411 @emph{Warning:} To specify a file format with @code{set gnutarget},
17412 you must know the actual BFD name.
17416 @xref{Files, , Commands to Specify Files}.
17418 @kindex show gnutarget
17419 @item show gnutarget
17420 Use the @code{show gnutarget} command to display what file format
17421 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17422 @value{GDBN} will determine the file format for each file automatically,
17423 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17426 @cindex common targets
17427 Here are some common targets (available, or not, depending on the GDB
17432 @item target exec @var{program}
17433 @cindex executable file target
17434 An executable file. @samp{target exec @var{program}} is the same as
17435 @samp{exec-file @var{program}}.
17437 @item target core @var{filename}
17438 @cindex core dump file target
17439 A core dump file. @samp{target core @var{filename}} is the same as
17440 @samp{core-file @var{filename}}.
17442 @item target remote @var{medium}
17443 @cindex remote target
17444 A remote system connected to @value{GDBN} via a serial line or network
17445 connection. This command tells @value{GDBN} to use its own remote
17446 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17448 For example, if you have a board connected to @file{/dev/ttya} on the
17449 machine running @value{GDBN}, you could say:
17452 target remote /dev/ttya
17455 @code{target remote} supports the @code{load} command. This is only
17456 useful if you have some other way of getting the stub to the target
17457 system, and you can put it somewhere in memory where it won't get
17458 clobbered by the download.
17460 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17461 @cindex built-in simulator target
17462 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17470 works; however, you cannot assume that a specific memory map, device
17471 drivers, or even basic I/O is available, although some simulators do
17472 provide these. For info about any processor-specific simulator details,
17473 see the appropriate section in @ref{Embedded Processors, ,Embedded
17478 Some configurations may include these targets as well:
17482 @item target nrom @var{dev}
17483 @cindex NetROM ROM emulator target
17484 NetROM ROM emulator. This target only supports downloading.
17488 Different targets are available on different configurations of @value{GDBN};
17489 your configuration may have more or fewer targets.
17491 Many remote targets require you to download the executable's code once
17492 you've successfully established a connection. You may wish to control
17493 various aspects of this process.
17498 @kindex set hash@r{, for remote monitors}
17499 @cindex hash mark while downloading
17500 This command controls whether a hash mark @samp{#} is displayed while
17501 downloading a file to the remote monitor. If on, a hash mark is
17502 displayed after each S-record is successfully downloaded to the
17506 @kindex show hash@r{, for remote monitors}
17507 Show the current status of displaying the hash mark.
17509 @item set debug monitor
17510 @kindex set debug monitor
17511 @cindex display remote monitor communications
17512 Enable or disable display of communications messages between
17513 @value{GDBN} and the remote monitor.
17515 @item show debug monitor
17516 @kindex show debug monitor
17517 Show the current status of displaying communications between
17518 @value{GDBN} and the remote monitor.
17523 @kindex load @var{filename}
17524 @item load @var{filename}
17526 Depending on what remote debugging facilities are configured into
17527 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17528 is meant to make @var{filename} (an executable) available for debugging
17529 on the remote system---by downloading, or dynamic linking, for example.
17530 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17531 the @code{add-symbol-file} command.
17533 If your @value{GDBN} does not have a @code{load} command, attempting to
17534 execute it gets the error message ``@code{You can't do that when your
17535 target is @dots{}}''
17537 The file is loaded at whatever address is specified in the executable.
17538 For some object file formats, you can specify the load address when you
17539 link the program; for other formats, like a.out, the object file format
17540 specifies a fixed address.
17541 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17543 Depending on the remote side capabilities, @value{GDBN} may be able to
17544 load programs into flash memory.
17546 @code{load} does not repeat if you press @key{RET} again after using it.
17550 @section Choosing Target Byte Order
17552 @cindex choosing target byte order
17553 @cindex target byte order
17555 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17556 offer the ability to run either big-endian or little-endian byte
17557 orders. Usually the executable or symbol will include a bit to
17558 designate the endian-ness, and you will not need to worry about
17559 which to use. However, you may still find it useful to adjust
17560 @value{GDBN}'s idea of processor endian-ness manually.
17564 @item set endian big
17565 Instruct @value{GDBN} to assume the target is big-endian.
17567 @item set endian little
17568 Instruct @value{GDBN} to assume the target is little-endian.
17570 @item set endian auto
17571 Instruct @value{GDBN} to use the byte order associated with the
17575 Display @value{GDBN}'s current idea of the target byte order.
17579 Note that these commands merely adjust interpretation of symbolic
17580 data on the host, and that they have absolutely no effect on the
17584 @node Remote Debugging
17585 @chapter Debugging Remote Programs
17586 @cindex remote debugging
17588 If you are trying to debug a program running on a machine that cannot run
17589 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17590 For example, you might use remote debugging on an operating system kernel,
17591 or on a small system which does not have a general purpose operating system
17592 powerful enough to run a full-featured debugger.
17594 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17595 to make this work with particular debugging targets. In addition,
17596 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17597 but not specific to any particular target system) which you can use if you
17598 write the remote stubs---the code that runs on the remote system to
17599 communicate with @value{GDBN}.
17601 Other remote targets may be available in your
17602 configuration of @value{GDBN}; use @code{help target} to list them.
17605 * Connecting:: Connecting to a remote target
17606 * File Transfer:: Sending files to a remote system
17607 * Server:: Using the gdbserver program
17608 * Remote Configuration:: Remote configuration
17609 * Remote Stub:: Implementing a remote stub
17613 @section Connecting to a Remote Target
17615 On the @value{GDBN} host machine, you will need an unstripped copy of
17616 your program, since @value{GDBN} needs symbol and debugging information.
17617 Start up @value{GDBN} as usual, using the name of the local copy of your
17618 program as the first argument.
17620 @cindex @code{target remote}
17621 @value{GDBN} can communicate with the target over a serial line, or
17622 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17623 each case, @value{GDBN} uses the same protocol for debugging your
17624 program; only the medium carrying the debugging packets varies. The
17625 @code{target remote} command establishes a connection to the target.
17626 Its arguments indicate which medium to use:
17630 @item target remote @var{serial-device}
17631 @cindex serial line, @code{target remote}
17632 Use @var{serial-device} to communicate with the target. For example,
17633 to use a serial line connected to the device named @file{/dev/ttyb}:
17636 target remote /dev/ttyb
17639 If you're using a serial line, you may want to give @value{GDBN} the
17640 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17641 (@pxref{Remote Configuration, set remotebaud}) before the
17642 @code{target} command.
17644 @item target remote @code{@var{host}:@var{port}}
17645 @itemx target remote @code{tcp:@var{host}:@var{port}}
17646 @cindex @acronym{TCP} port, @code{target remote}
17647 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17648 The @var{host} may be either a host name or a numeric @acronym{IP}
17649 address; @var{port} must be a decimal number. The @var{host} could be
17650 the target machine itself, if it is directly connected to the net, or
17651 it might be a terminal server which in turn has a serial line to the
17654 For example, to connect to port 2828 on a terminal server named
17658 target remote manyfarms:2828
17661 If your remote target is actually running on the same machine as your
17662 debugger session (e.g.@: a simulator for your target running on the
17663 same host), you can omit the hostname. For example, to connect to
17664 port 1234 on your local machine:
17667 target remote :1234
17671 Note that the colon is still required here.
17673 @item target remote @code{udp:@var{host}:@var{port}}
17674 @cindex @acronym{UDP} port, @code{target remote}
17675 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17676 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17679 target remote udp:manyfarms:2828
17682 When using a @acronym{UDP} connection for remote debugging, you should
17683 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17684 can silently drop packets on busy or unreliable networks, which will
17685 cause havoc with your debugging session.
17687 @item target remote | @var{command}
17688 @cindex pipe, @code{target remote} to
17689 Run @var{command} in the background and communicate with it using a
17690 pipe. The @var{command} is a shell command, to be parsed and expanded
17691 by the system's command shell, @code{/bin/sh}; it should expect remote
17692 protocol packets on its standard input, and send replies on its
17693 standard output. You could use this to run a stand-alone simulator
17694 that speaks the remote debugging protocol, to make net connections
17695 using programs like @code{ssh}, or for other similar tricks.
17697 If @var{command} closes its standard output (perhaps by exiting),
17698 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17699 program has already exited, this will have no effect.)
17703 Once the connection has been established, you can use all the usual
17704 commands to examine and change data. The remote program is already
17705 running; you can use @kbd{step} and @kbd{continue}, and you do not
17706 need to use @kbd{run}.
17708 @cindex interrupting remote programs
17709 @cindex remote programs, interrupting
17710 Whenever @value{GDBN} is waiting for the remote program, if you type the
17711 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17712 program. This may or may not succeed, depending in part on the hardware
17713 and the serial drivers the remote system uses. If you type the
17714 interrupt character once again, @value{GDBN} displays this prompt:
17717 Interrupted while waiting for the program.
17718 Give up (and stop debugging it)? (y or n)
17721 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17722 (If you decide you want to try again later, you can use @samp{target
17723 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17724 goes back to waiting.
17727 @kindex detach (remote)
17729 When you have finished debugging the remote program, you can use the
17730 @code{detach} command to release it from @value{GDBN} control.
17731 Detaching from the target normally resumes its execution, but the results
17732 will depend on your particular remote stub. After the @code{detach}
17733 command, @value{GDBN} is free to connect to another target.
17737 The @code{disconnect} command behaves like @code{detach}, except that
17738 the target is generally not resumed. It will wait for @value{GDBN}
17739 (this instance or another one) to connect and continue debugging. After
17740 the @code{disconnect} command, @value{GDBN} is again free to connect to
17743 @cindex send command to remote monitor
17744 @cindex extend @value{GDBN} for remote targets
17745 @cindex add new commands for external monitor
17747 @item monitor @var{cmd}
17748 This command allows you to send arbitrary commands directly to the
17749 remote monitor. Since @value{GDBN} doesn't care about the commands it
17750 sends like this, this command is the way to extend @value{GDBN}---you
17751 can add new commands that only the external monitor will understand
17755 @node File Transfer
17756 @section Sending files to a remote system
17757 @cindex remote target, file transfer
17758 @cindex file transfer
17759 @cindex sending files to remote systems
17761 Some remote targets offer the ability to transfer files over the same
17762 connection used to communicate with @value{GDBN}. This is convenient
17763 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17764 running @code{gdbserver} over a network interface. For other targets,
17765 e.g.@: embedded devices with only a single serial port, this may be
17766 the only way to upload or download files.
17768 Not all remote targets support these commands.
17772 @item remote put @var{hostfile} @var{targetfile}
17773 Copy file @var{hostfile} from the host system (the machine running
17774 @value{GDBN}) to @var{targetfile} on the target system.
17777 @item remote get @var{targetfile} @var{hostfile}
17778 Copy file @var{targetfile} from the target system to @var{hostfile}
17779 on the host system.
17781 @kindex remote delete
17782 @item remote delete @var{targetfile}
17783 Delete @var{targetfile} from the target system.
17788 @section Using the @code{gdbserver} Program
17791 @cindex remote connection without stubs
17792 @code{gdbserver} is a control program for Unix-like systems, which
17793 allows you to connect your program with a remote @value{GDBN} via
17794 @code{target remote}---but without linking in the usual debugging stub.
17796 @code{gdbserver} is not a complete replacement for the debugging stubs,
17797 because it requires essentially the same operating-system facilities
17798 that @value{GDBN} itself does. In fact, a system that can run
17799 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17800 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17801 because it is a much smaller program than @value{GDBN} itself. It is
17802 also easier to port than all of @value{GDBN}, so you may be able to get
17803 started more quickly on a new system by using @code{gdbserver}.
17804 Finally, if you develop code for real-time systems, you may find that
17805 the tradeoffs involved in real-time operation make it more convenient to
17806 do as much development work as possible on another system, for example
17807 by cross-compiling. You can use @code{gdbserver} to make a similar
17808 choice for debugging.
17810 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17811 or a TCP connection, using the standard @value{GDBN} remote serial
17815 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17816 Do not run @code{gdbserver} connected to any public network; a
17817 @value{GDBN} connection to @code{gdbserver} provides access to the
17818 target system with the same privileges as the user running
17822 @subsection Running @code{gdbserver}
17823 @cindex arguments, to @code{gdbserver}
17824 @cindex @code{gdbserver}, command-line arguments
17826 Run @code{gdbserver} on the target system. You need a copy of the
17827 program you want to debug, including any libraries it requires.
17828 @code{gdbserver} does not need your program's symbol table, so you can
17829 strip the program if necessary to save space. @value{GDBN} on the host
17830 system does all the symbol handling.
17832 To use the server, you must tell it how to communicate with @value{GDBN};
17833 the name of your program; and the arguments for your program. The usual
17837 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17840 @var{comm} is either a device name (to use a serial line), or a TCP
17841 hostname and portnumber, or @code{-} or @code{stdio} to use
17842 stdin/stdout of @code{gdbserver}.
17843 For example, to debug Emacs with the argument
17844 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17848 target> gdbserver /dev/com1 emacs foo.txt
17851 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17854 To use a TCP connection instead of a serial line:
17857 target> gdbserver host:2345 emacs foo.txt
17860 The only difference from the previous example is the first argument,
17861 specifying that you are communicating with the host @value{GDBN} via
17862 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17863 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17864 (Currently, the @samp{host} part is ignored.) You can choose any number
17865 you want for the port number as long as it does not conflict with any
17866 TCP ports already in use on the target system (for example, @code{23} is
17867 reserved for @code{telnet}).@footnote{If you choose a port number that
17868 conflicts with another service, @code{gdbserver} prints an error message
17869 and exits.} You must use the same port number with the host @value{GDBN}
17870 @code{target remote} command.
17872 The @code{stdio} connection is useful when starting @code{gdbserver}
17876 (gdb) target remote | ssh -T hostname gdbserver - hello
17879 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17880 and we don't want escape-character handling. Ssh does this by default when
17881 a command is provided, the flag is provided to make it explicit.
17882 You could elide it if you want to.
17884 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17885 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17886 display through a pipe connected to gdbserver.
17887 Both @code{stdout} and @code{stderr} use the same pipe.
17889 @subsubsection Attaching to a Running Program
17890 @cindex attach to a program, @code{gdbserver}
17891 @cindex @option{--attach}, @code{gdbserver} option
17893 On some targets, @code{gdbserver} can also attach to running programs.
17894 This is accomplished via the @code{--attach} argument. The syntax is:
17897 target> gdbserver --attach @var{comm} @var{pid}
17900 @var{pid} is the process ID of a currently running process. It isn't necessary
17901 to point @code{gdbserver} at a binary for the running process.
17904 You can debug processes by name instead of process ID if your target has the
17905 @code{pidof} utility:
17908 target> gdbserver --attach @var{comm} `pidof @var{program}`
17911 In case more than one copy of @var{program} is running, or @var{program}
17912 has multiple threads, most versions of @code{pidof} support the
17913 @code{-s} option to only return the first process ID.
17915 @subsubsection Multi-Process Mode for @code{gdbserver}
17916 @cindex @code{gdbserver}, multiple processes
17917 @cindex multiple processes with @code{gdbserver}
17919 When you connect to @code{gdbserver} using @code{target remote},
17920 @code{gdbserver} debugs the specified program only once. When the
17921 program exits, or you detach from it, @value{GDBN} closes the connection
17922 and @code{gdbserver} exits.
17924 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17925 enters multi-process mode. When the debugged program exits, or you
17926 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17927 though no program is running. The @code{run} and @code{attach}
17928 commands instruct @code{gdbserver} to run or attach to a new program.
17929 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17930 remote exec-file}) to select the program to run. Command line
17931 arguments are supported, except for wildcard expansion and I/O
17932 redirection (@pxref{Arguments}).
17934 @cindex @option{--multi}, @code{gdbserver} option
17935 To start @code{gdbserver} without supplying an initial command to run
17936 or process ID to attach, use the @option{--multi} command line option.
17937 Then you can connect using @kbd{target extended-remote} and start
17938 the program you want to debug.
17940 In multi-process mode @code{gdbserver} does not automatically exit unless you
17941 use the option @option{--once}. You can terminate it by using
17942 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17943 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17944 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17945 @option{--multi} option to @code{gdbserver} has no influence on that.
17947 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17949 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17951 @code{gdbserver} normally terminates after all of its debugged processes have
17952 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17953 extended-remote}, @code{gdbserver} stays running even with no processes left.
17954 @value{GDBN} normally terminates the spawned debugged process on its exit,
17955 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17956 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17957 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17958 stays running even in the @kbd{target remote} mode.
17960 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17961 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17962 completeness, at most one @value{GDBN} can be connected at a time.
17964 @cindex @option{--once}, @code{gdbserver} option
17965 By default, @code{gdbserver} keeps the listening TCP port open, so that
17966 additional connections are possible. However, if you start @code{gdbserver}
17967 with the @option{--once} option, it will stop listening for any further
17968 connection attempts after connecting to the first @value{GDBN} session. This
17969 means no further connections to @code{gdbserver} will be possible after the
17970 first one. It also means @code{gdbserver} will terminate after the first
17971 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17972 connections and even in the @kbd{target extended-remote} mode. The
17973 @option{--once} option allows reusing the same port number for connecting to
17974 multiple instances of @code{gdbserver} running on the same host, since each
17975 instance closes its port after the first connection.
17977 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17979 @cindex @option{--debug}, @code{gdbserver} option
17980 The @option{--debug} option tells @code{gdbserver} to display extra
17981 status information about the debugging process.
17982 @cindex @option{--remote-debug}, @code{gdbserver} option
17983 The @option{--remote-debug} option tells @code{gdbserver} to display
17984 remote protocol debug output. These options are intended for
17985 @code{gdbserver} development and for bug reports to the developers.
17987 @cindex @option{--wrapper}, @code{gdbserver} option
17988 The @option{--wrapper} option specifies a wrapper to launch programs
17989 for debugging. The option should be followed by the name of the
17990 wrapper, then any command-line arguments to pass to the wrapper, then
17991 @kbd{--} indicating the end of the wrapper arguments.
17993 @code{gdbserver} runs the specified wrapper program with a combined
17994 command line including the wrapper arguments, then the name of the
17995 program to debug, then any arguments to the program. The wrapper
17996 runs until it executes your program, and then @value{GDBN} gains control.
17998 You can use any program that eventually calls @code{execve} with
17999 its arguments as a wrapper. Several standard Unix utilities do
18000 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18001 with @code{exec "$@@"} will also work.
18003 For example, you can use @code{env} to pass an environment variable to
18004 the debugged program, without setting the variable in @code{gdbserver}'s
18008 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18011 @subsection Connecting to @code{gdbserver}
18013 Run @value{GDBN} on the host system.
18015 First make sure you have the necessary symbol files. Load symbols for
18016 your application using the @code{file} command before you connect. Use
18017 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18018 was compiled with the correct sysroot using @code{--with-sysroot}).
18020 The symbol file and target libraries must exactly match the executable
18021 and libraries on the target, with one exception: the files on the host
18022 system should not be stripped, even if the files on the target system
18023 are. Mismatched or missing files will lead to confusing results
18024 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18025 files may also prevent @code{gdbserver} from debugging multi-threaded
18028 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18029 For TCP connections, you must start up @code{gdbserver} prior to using
18030 the @code{target remote} command. Otherwise you may get an error whose
18031 text depends on the host system, but which usually looks something like
18032 @samp{Connection refused}. Don't use the @code{load}
18033 command in @value{GDBN} when using @code{gdbserver}, since the program is
18034 already on the target.
18036 @subsection Monitor Commands for @code{gdbserver}
18037 @cindex monitor commands, for @code{gdbserver}
18038 @anchor{Monitor Commands for gdbserver}
18040 During a @value{GDBN} session using @code{gdbserver}, you can use the
18041 @code{monitor} command to send special requests to @code{gdbserver}.
18042 Here are the available commands.
18046 List the available monitor commands.
18048 @item monitor set debug 0
18049 @itemx monitor set debug 1
18050 Disable or enable general debugging messages.
18052 @item monitor set remote-debug 0
18053 @itemx monitor set remote-debug 1
18054 Disable or enable specific debugging messages associated with the remote
18055 protocol (@pxref{Remote Protocol}).
18057 @item monitor set libthread-db-search-path [PATH]
18058 @cindex gdbserver, search path for @code{libthread_db}
18059 When this command is issued, @var{path} is a colon-separated list of
18060 directories to search for @code{libthread_db} (@pxref{Threads,,set
18061 libthread-db-search-path}). If you omit @var{path},
18062 @samp{libthread-db-search-path} will be reset to its default value.
18064 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18065 not supported in @code{gdbserver}.
18068 Tell gdbserver to exit immediately. This command should be followed by
18069 @code{disconnect} to close the debugging session. @code{gdbserver} will
18070 detach from any attached processes and kill any processes it created.
18071 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18072 of a multi-process mode debug session.
18076 @subsection Tracepoints support in @code{gdbserver}
18077 @cindex tracepoints support in @code{gdbserver}
18079 On some targets, @code{gdbserver} supports tracepoints, fast
18080 tracepoints and static tracepoints.
18082 For fast or static tracepoints to work, a special library called the
18083 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18084 This library is built and distributed as an integral part of
18085 @code{gdbserver}. In addition, support for static tracepoints
18086 requires building the in-process agent library with static tracepoints
18087 support. At present, the UST (LTTng Userspace Tracer,
18088 @url{http://lttng.org/ust}) tracing engine is supported. This support
18089 is automatically available if UST development headers are found in the
18090 standard include path when @code{gdbserver} is built, or if
18091 @code{gdbserver} was explicitly configured using @option{--with-ust}
18092 to point at such headers. You can explicitly disable the support
18093 using @option{--with-ust=no}.
18095 There are several ways to load the in-process agent in your program:
18098 @item Specifying it as dependency at link time
18100 You can link your program dynamically with the in-process agent
18101 library. On most systems, this is accomplished by adding
18102 @code{-linproctrace} to the link command.
18104 @item Using the system's preloading mechanisms
18106 You can force loading the in-process agent at startup time by using
18107 your system's support for preloading shared libraries. Many Unixes
18108 support the concept of preloading user defined libraries. In most
18109 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18110 in the environment. See also the description of @code{gdbserver}'s
18111 @option{--wrapper} command line option.
18113 @item Using @value{GDBN} to force loading the agent at run time
18115 On some systems, you can force the inferior to load a shared library,
18116 by calling a dynamic loader function in the inferior that takes care
18117 of dynamically looking up and loading a shared library. On most Unix
18118 systems, the function is @code{dlopen}. You'll use the @code{call}
18119 command for that. For example:
18122 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18125 Note that on most Unix systems, for the @code{dlopen} function to be
18126 available, the program needs to be linked with @code{-ldl}.
18129 On systems that have a userspace dynamic loader, like most Unix
18130 systems, when you connect to @code{gdbserver} using @code{target
18131 remote}, you'll find that the program is stopped at the dynamic
18132 loader's entry point, and no shared library has been loaded in the
18133 program's address space yet, including the in-process agent. In that
18134 case, before being able to use any of the fast or static tracepoints
18135 features, you need to let the loader run and load the shared
18136 libraries. The simplest way to do that is to run the program to the
18137 main procedure. E.g., if debugging a C or C@t{++} program, start
18138 @code{gdbserver} like so:
18141 $ gdbserver :9999 myprogram
18144 Start GDB and connect to @code{gdbserver} like so, and run to main:
18148 (@value{GDBP}) target remote myhost:9999
18149 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18150 (@value{GDBP}) b main
18151 (@value{GDBP}) continue
18154 The in-process tracing agent library should now be loaded into the
18155 process; you can confirm it with the @code{info sharedlibrary}
18156 command, which will list @file{libinproctrace.so} as loaded in the
18157 process. You are now ready to install fast tracepoints, list static
18158 tracepoint markers, probe static tracepoints markers, and start
18161 @node Remote Configuration
18162 @section Remote Configuration
18165 @kindex show remote
18166 This section documents the configuration options available when
18167 debugging remote programs. For the options related to the File I/O
18168 extensions of the remote protocol, see @ref{system,
18169 system-call-allowed}.
18172 @item set remoteaddresssize @var{bits}
18173 @cindex address size for remote targets
18174 @cindex bits in remote address
18175 Set the maximum size of address in a memory packet to the specified
18176 number of bits. @value{GDBN} will mask off the address bits above
18177 that number, when it passes addresses to the remote target. The
18178 default value is the number of bits in the target's address.
18180 @item show remoteaddresssize
18181 Show the current value of remote address size in bits.
18183 @item set remotebaud @var{n}
18184 @cindex baud rate for remote targets
18185 Set the baud rate for the remote serial I/O to @var{n} baud. The
18186 value is used to set the speed of the serial port used for debugging
18189 @item show remotebaud
18190 Show the current speed of the remote connection.
18192 @item set remotebreak
18193 @cindex interrupt remote programs
18194 @cindex BREAK signal instead of Ctrl-C
18195 @anchor{set remotebreak}
18196 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18197 when you type @kbd{Ctrl-c} to interrupt the program running
18198 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18199 character instead. The default is off, since most remote systems
18200 expect to see @samp{Ctrl-C} as the interrupt signal.
18202 @item show remotebreak
18203 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18204 interrupt the remote program.
18206 @item set remoteflow on
18207 @itemx set remoteflow off
18208 @kindex set remoteflow
18209 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18210 on the serial port used to communicate to the remote target.
18212 @item show remoteflow
18213 @kindex show remoteflow
18214 Show the current setting of hardware flow control.
18216 @item set remotelogbase @var{base}
18217 Set the base (a.k.a.@: radix) of logging serial protocol
18218 communications to @var{base}. Supported values of @var{base} are:
18219 @code{ascii}, @code{octal}, and @code{hex}. The default is
18222 @item show remotelogbase
18223 Show the current setting of the radix for logging remote serial
18226 @item set remotelogfile @var{file}
18227 @cindex record serial communications on file
18228 Record remote serial communications on the named @var{file}. The
18229 default is not to record at all.
18231 @item show remotelogfile.
18232 Show the current setting of the file name on which to record the
18233 serial communications.
18235 @item set remotetimeout @var{num}
18236 @cindex timeout for serial communications
18237 @cindex remote timeout
18238 Set the timeout limit to wait for the remote target to respond to
18239 @var{num} seconds. The default is 2 seconds.
18241 @item show remotetimeout
18242 Show the current number of seconds to wait for the remote target
18245 @cindex limit hardware breakpoints and watchpoints
18246 @cindex remote target, limit break- and watchpoints
18247 @anchor{set remote hardware-watchpoint-limit}
18248 @anchor{set remote hardware-breakpoint-limit}
18249 @item set remote hardware-watchpoint-limit @var{limit}
18250 @itemx set remote hardware-breakpoint-limit @var{limit}
18251 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18252 watchpoints. A limit of -1, the default, is treated as unlimited.
18254 @cindex limit hardware watchpoints length
18255 @cindex remote target, limit watchpoints length
18256 @anchor{set remote hardware-watchpoint-length-limit}
18257 @item set remote hardware-watchpoint-length-limit @var{limit}
18258 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18259 a remote hardware watchpoint. A limit of -1, the default, is treated
18262 @item show remote hardware-watchpoint-length-limit
18263 Show the current limit (in bytes) of the maximum length of
18264 a remote hardware watchpoint.
18266 @item set remote exec-file @var{filename}
18267 @itemx show remote exec-file
18268 @anchor{set remote exec-file}
18269 @cindex executable file, for remote target
18270 Select the file used for @code{run} with @code{target
18271 extended-remote}. This should be set to a filename valid on the
18272 target system. If it is not set, the target will use a default
18273 filename (e.g.@: the last program run).
18275 @item set remote interrupt-sequence
18276 @cindex interrupt remote programs
18277 @cindex select Ctrl-C, BREAK or BREAK-g
18278 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18279 @samp{BREAK-g} as the
18280 sequence to the remote target in order to interrupt the execution.
18281 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18282 is high level of serial line for some certain time.
18283 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18284 It is @code{BREAK} signal followed by character @code{g}.
18286 @item show interrupt-sequence
18287 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18288 is sent by @value{GDBN} to interrupt the remote program.
18289 @code{BREAK-g} is BREAK signal followed by @code{g} and
18290 also known as Magic SysRq g.
18292 @item set remote interrupt-on-connect
18293 @cindex send interrupt-sequence on start
18294 Specify whether interrupt-sequence is sent to remote target when
18295 @value{GDBN} connects to it. This is mostly needed when you debug
18296 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18297 which is known as Magic SysRq g in order to connect @value{GDBN}.
18299 @item show interrupt-on-connect
18300 Show whether interrupt-sequence is sent
18301 to remote target when @value{GDBN} connects to it.
18305 @item set tcp auto-retry on
18306 @cindex auto-retry, for remote TCP target
18307 Enable auto-retry for remote TCP connections. This is useful if the remote
18308 debugging agent is launched in parallel with @value{GDBN}; there is a race
18309 condition because the agent may not become ready to accept the connection
18310 before @value{GDBN} attempts to connect. When auto-retry is
18311 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18312 to establish the connection using the timeout specified by
18313 @code{set tcp connect-timeout}.
18315 @item set tcp auto-retry off
18316 Do not auto-retry failed TCP connections.
18318 @item show tcp auto-retry
18319 Show the current auto-retry setting.
18321 @item set tcp connect-timeout @var{seconds}
18322 @itemx set tcp connect-timeout unlimited
18323 @cindex connection timeout, for remote TCP target
18324 @cindex timeout, for remote target connection
18325 Set the timeout for establishing a TCP connection to the remote target to
18326 @var{seconds}. The timeout affects both polling to retry failed connections
18327 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18328 that are merely slow to complete, and represents an approximate cumulative
18329 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18330 @value{GDBN} will keep attempting to establish a connection forever,
18331 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18333 @item show tcp connect-timeout
18334 Show the current connection timeout setting.
18337 @cindex remote packets, enabling and disabling
18338 The @value{GDBN} remote protocol autodetects the packets supported by
18339 your debugging stub. If you need to override the autodetection, you
18340 can use these commands to enable or disable individual packets. Each
18341 packet can be set to @samp{on} (the remote target supports this
18342 packet), @samp{off} (the remote target does not support this packet),
18343 or @samp{auto} (detect remote target support for this packet). They
18344 all default to @samp{auto}. For more information about each packet,
18345 see @ref{Remote Protocol}.
18347 During normal use, you should not have to use any of these commands.
18348 If you do, that may be a bug in your remote debugging stub, or a bug
18349 in @value{GDBN}. You may want to report the problem to the
18350 @value{GDBN} developers.
18352 For each packet @var{name}, the command to enable or disable the
18353 packet is @code{set remote @var{name}-packet}. The available settings
18356 @multitable @columnfractions 0.28 0.32 0.25
18359 @tab Related Features
18361 @item @code{fetch-register}
18363 @tab @code{info registers}
18365 @item @code{set-register}
18369 @item @code{binary-download}
18371 @tab @code{load}, @code{set}
18373 @item @code{read-aux-vector}
18374 @tab @code{qXfer:auxv:read}
18375 @tab @code{info auxv}
18377 @item @code{symbol-lookup}
18378 @tab @code{qSymbol}
18379 @tab Detecting multiple threads
18381 @item @code{attach}
18382 @tab @code{vAttach}
18385 @item @code{verbose-resume}
18387 @tab Stepping or resuming multiple threads
18393 @item @code{software-breakpoint}
18397 @item @code{hardware-breakpoint}
18401 @item @code{write-watchpoint}
18405 @item @code{read-watchpoint}
18409 @item @code{access-watchpoint}
18413 @item @code{target-features}
18414 @tab @code{qXfer:features:read}
18415 @tab @code{set architecture}
18417 @item @code{library-info}
18418 @tab @code{qXfer:libraries:read}
18419 @tab @code{info sharedlibrary}
18421 @item @code{memory-map}
18422 @tab @code{qXfer:memory-map:read}
18423 @tab @code{info mem}
18425 @item @code{read-sdata-object}
18426 @tab @code{qXfer:sdata:read}
18427 @tab @code{print $_sdata}
18429 @item @code{read-spu-object}
18430 @tab @code{qXfer:spu:read}
18431 @tab @code{info spu}
18433 @item @code{write-spu-object}
18434 @tab @code{qXfer:spu:write}
18435 @tab @code{info spu}
18437 @item @code{read-siginfo-object}
18438 @tab @code{qXfer:siginfo:read}
18439 @tab @code{print $_siginfo}
18441 @item @code{write-siginfo-object}
18442 @tab @code{qXfer:siginfo:write}
18443 @tab @code{set $_siginfo}
18445 @item @code{threads}
18446 @tab @code{qXfer:threads:read}
18447 @tab @code{info threads}
18449 @item @code{get-thread-local-@*storage-address}
18450 @tab @code{qGetTLSAddr}
18451 @tab Displaying @code{__thread} variables
18453 @item @code{get-thread-information-block-address}
18454 @tab @code{qGetTIBAddr}
18455 @tab Display MS-Windows Thread Information Block.
18457 @item @code{search-memory}
18458 @tab @code{qSearch:memory}
18461 @item @code{supported-packets}
18462 @tab @code{qSupported}
18463 @tab Remote communications parameters
18465 @item @code{pass-signals}
18466 @tab @code{QPassSignals}
18467 @tab @code{handle @var{signal}}
18469 @item @code{program-signals}
18470 @tab @code{QProgramSignals}
18471 @tab @code{handle @var{signal}}
18473 @item @code{hostio-close-packet}
18474 @tab @code{vFile:close}
18475 @tab @code{remote get}, @code{remote put}
18477 @item @code{hostio-open-packet}
18478 @tab @code{vFile:open}
18479 @tab @code{remote get}, @code{remote put}
18481 @item @code{hostio-pread-packet}
18482 @tab @code{vFile:pread}
18483 @tab @code{remote get}, @code{remote put}
18485 @item @code{hostio-pwrite-packet}
18486 @tab @code{vFile:pwrite}
18487 @tab @code{remote get}, @code{remote put}
18489 @item @code{hostio-unlink-packet}
18490 @tab @code{vFile:unlink}
18491 @tab @code{remote delete}
18493 @item @code{hostio-readlink-packet}
18494 @tab @code{vFile:readlink}
18497 @item @code{noack-packet}
18498 @tab @code{QStartNoAckMode}
18499 @tab Packet acknowledgment
18501 @item @code{osdata}
18502 @tab @code{qXfer:osdata:read}
18503 @tab @code{info os}
18505 @item @code{query-attached}
18506 @tab @code{qAttached}
18507 @tab Querying remote process attach state.
18509 @item @code{trace-buffer-size}
18510 @tab @code{QTBuffer:size}
18511 @tab @code{set trace-buffer-size}
18513 @item @code{trace-status}
18514 @tab @code{qTStatus}
18515 @tab @code{tstatus}
18517 @item @code{traceframe-info}
18518 @tab @code{qXfer:traceframe-info:read}
18519 @tab Traceframe info
18521 @item @code{install-in-trace}
18522 @tab @code{InstallInTrace}
18523 @tab Install tracepoint in tracing
18525 @item @code{disable-randomization}
18526 @tab @code{QDisableRandomization}
18527 @tab @code{set disable-randomization}
18529 @item @code{conditional-breakpoints-packet}
18530 @tab @code{Z0 and Z1}
18531 @tab @code{Support for target-side breakpoint condition evaluation}
18535 @section Implementing a Remote Stub
18537 @cindex debugging stub, example
18538 @cindex remote stub, example
18539 @cindex stub example, remote debugging
18540 The stub files provided with @value{GDBN} implement the target side of the
18541 communication protocol, and the @value{GDBN} side is implemented in the
18542 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18543 these subroutines to communicate, and ignore the details. (If you're
18544 implementing your own stub file, you can still ignore the details: start
18545 with one of the existing stub files. @file{sparc-stub.c} is the best
18546 organized, and therefore the easiest to read.)
18548 @cindex remote serial debugging, overview
18549 To debug a program running on another machine (the debugging
18550 @dfn{target} machine), you must first arrange for all the usual
18551 prerequisites for the program to run by itself. For example, for a C
18556 A startup routine to set up the C runtime environment; these usually
18557 have a name like @file{crt0}. The startup routine may be supplied by
18558 your hardware supplier, or you may have to write your own.
18561 A C subroutine library to support your program's
18562 subroutine calls, notably managing input and output.
18565 A way of getting your program to the other machine---for example, a
18566 download program. These are often supplied by the hardware
18567 manufacturer, but you may have to write your own from hardware
18571 The next step is to arrange for your program to use a serial port to
18572 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18573 machine). In general terms, the scheme looks like this:
18577 @value{GDBN} already understands how to use this protocol; when everything
18578 else is set up, you can simply use the @samp{target remote} command
18579 (@pxref{Targets,,Specifying a Debugging Target}).
18581 @item On the target,
18582 you must link with your program a few special-purpose subroutines that
18583 implement the @value{GDBN} remote serial protocol. The file containing these
18584 subroutines is called a @dfn{debugging stub}.
18586 On certain remote targets, you can use an auxiliary program
18587 @code{gdbserver} instead of linking a stub into your program.
18588 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18591 The debugging stub is specific to the architecture of the remote
18592 machine; for example, use @file{sparc-stub.c} to debug programs on
18595 @cindex remote serial stub list
18596 These working remote stubs are distributed with @value{GDBN}:
18601 @cindex @file{i386-stub.c}
18604 For Intel 386 and compatible architectures.
18607 @cindex @file{m68k-stub.c}
18608 @cindex Motorola 680x0
18610 For Motorola 680x0 architectures.
18613 @cindex @file{sh-stub.c}
18616 For Renesas SH architectures.
18619 @cindex @file{sparc-stub.c}
18621 For @sc{sparc} architectures.
18623 @item sparcl-stub.c
18624 @cindex @file{sparcl-stub.c}
18627 For Fujitsu @sc{sparclite} architectures.
18631 The @file{README} file in the @value{GDBN} distribution may list other
18632 recently added stubs.
18635 * Stub Contents:: What the stub can do for you
18636 * Bootstrapping:: What you must do for the stub
18637 * Debug Session:: Putting it all together
18640 @node Stub Contents
18641 @subsection What the Stub Can Do for You
18643 @cindex remote serial stub
18644 The debugging stub for your architecture supplies these three
18648 @item set_debug_traps
18649 @findex set_debug_traps
18650 @cindex remote serial stub, initialization
18651 This routine arranges for @code{handle_exception} to run when your
18652 program stops. You must call this subroutine explicitly in your
18653 program's startup code.
18655 @item handle_exception
18656 @findex handle_exception
18657 @cindex remote serial stub, main routine
18658 This is the central workhorse, but your program never calls it
18659 explicitly---the setup code arranges for @code{handle_exception} to
18660 run when a trap is triggered.
18662 @code{handle_exception} takes control when your program stops during
18663 execution (for example, on a breakpoint), and mediates communications
18664 with @value{GDBN} on the host machine. This is where the communications
18665 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18666 representative on the target machine. It begins by sending summary
18667 information on the state of your program, then continues to execute,
18668 retrieving and transmitting any information @value{GDBN} needs, until you
18669 execute a @value{GDBN} command that makes your program resume; at that point,
18670 @code{handle_exception} returns control to your own code on the target
18674 @cindex @code{breakpoint} subroutine, remote
18675 Use this auxiliary subroutine to make your program contain a
18676 breakpoint. Depending on the particular situation, this may be the only
18677 way for @value{GDBN} to get control. For instance, if your target
18678 machine has some sort of interrupt button, you won't need to call this;
18679 pressing the interrupt button transfers control to
18680 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18681 simply receiving characters on the serial port may also trigger a trap;
18682 again, in that situation, you don't need to call @code{breakpoint} from
18683 your own program---simply running @samp{target remote} from the host
18684 @value{GDBN} session gets control.
18686 Call @code{breakpoint} if none of these is true, or if you simply want
18687 to make certain your program stops at a predetermined point for the
18688 start of your debugging session.
18691 @node Bootstrapping
18692 @subsection What You Must Do for the Stub
18694 @cindex remote stub, support routines
18695 The debugging stubs that come with @value{GDBN} are set up for a particular
18696 chip architecture, but they have no information about the rest of your
18697 debugging target machine.
18699 First of all you need to tell the stub how to communicate with the
18703 @item int getDebugChar()
18704 @findex getDebugChar
18705 Write this subroutine to read a single character from the serial port.
18706 It may be identical to @code{getchar} for your target system; a
18707 different name is used to allow you to distinguish the two if you wish.
18709 @item void putDebugChar(int)
18710 @findex putDebugChar
18711 Write this subroutine to write a single character to the serial port.
18712 It may be identical to @code{putchar} for your target system; a
18713 different name is used to allow you to distinguish the two if you wish.
18716 @cindex control C, and remote debugging
18717 @cindex interrupting remote targets
18718 If you want @value{GDBN} to be able to stop your program while it is
18719 running, you need to use an interrupt-driven serial driver, and arrange
18720 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18721 character). That is the character which @value{GDBN} uses to tell the
18722 remote system to stop.
18724 Getting the debugging target to return the proper status to @value{GDBN}
18725 probably requires changes to the standard stub; one quick and dirty way
18726 is to just execute a breakpoint instruction (the ``dirty'' part is that
18727 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18729 Other routines you need to supply are:
18732 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18733 @findex exceptionHandler
18734 Write this function to install @var{exception_address} in the exception
18735 handling tables. You need to do this because the stub does not have any
18736 way of knowing what the exception handling tables on your target system
18737 are like (for example, the processor's table might be in @sc{rom},
18738 containing entries which point to a table in @sc{ram}).
18739 @var{exception_number} is the exception number which should be changed;
18740 its meaning is architecture-dependent (for example, different numbers
18741 might represent divide by zero, misaligned access, etc). When this
18742 exception occurs, control should be transferred directly to
18743 @var{exception_address}, and the processor state (stack, registers,
18744 and so on) should be just as it is when a processor exception occurs. So if
18745 you want to use a jump instruction to reach @var{exception_address}, it
18746 should be a simple jump, not a jump to subroutine.
18748 For the 386, @var{exception_address} should be installed as an interrupt
18749 gate so that interrupts are masked while the handler runs. The gate
18750 should be at privilege level 0 (the most privileged level). The
18751 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18752 help from @code{exceptionHandler}.
18754 @item void flush_i_cache()
18755 @findex flush_i_cache
18756 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18757 instruction cache, if any, on your target machine. If there is no
18758 instruction cache, this subroutine may be a no-op.
18760 On target machines that have instruction caches, @value{GDBN} requires this
18761 function to make certain that the state of your program is stable.
18765 You must also make sure this library routine is available:
18768 @item void *memset(void *, int, int)
18770 This is the standard library function @code{memset} that sets an area of
18771 memory to a known value. If you have one of the free versions of
18772 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18773 either obtain it from your hardware manufacturer, or write your own.
18776 If you do not use the GNU C compiler, you may need other standard
18777 library subroutines as well; this varies from one stub to another,
18778 but in general the stubs are likely to use any of the common library
18779 subroutines which @code{@value{NGCC}} generates as inline code.
18782 @node Debug Session
18783 @subsection Putting it All Together
18785 @cindex remote serial debugging summary
18786 In summary, when your program is ready to debug, you must follow these
18791 Make sure you have defined the supporting low-level routines
18792 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18794 @code{getDebugChar}, @code{putDebugChar},
18795 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18799 Insert these lines in your program's startup code, before the main
18800 procedure is called:
18807 On some machines, when a breakpoint trap is raised, the hardware
18808 automatically makes the PC point to the instruction after the
18809 breakpoint. If your machine doesn't do that, you may need to adjust
18810 @code{handle_exception} to arrange for it to return to the instruction
18811 after the breakpoint on this first invocation, so that your program
18812 doesn't keep hitting the initial breakpoint instead of making
18816 For the 680x0 stub only, you need to provide a variable called
18817 @code{exceptionHook}. Normally you just use:
18820 void (*exceptionHook)() = 0;
18824 but if before calling @code{set_debug_traps}, you set it to point to a
18825 function in your program, that function is called when
18826 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18827 error). The function indicated by @code{exceptionHook} is called with
18828 one parameter: an @code{int} which is the exception number.
18831 Compile and link together: your program, the @value{GDBN} debugging stub for
18832 your target architecture, and the supporting subroutines.
18835 Make sure you have a serial connection between your target machine and
18836 the @value{GDBN} host, and identify the serial port on the host.
18839 @c The "remote" target now provides a `load' command, so we should
18840 @c document that. FIXME.
18841 Download your program to your target machine (or get it there by
18842 whatever means the manufacturer provides), and start it.
18845 Start @value{GDBN} on the host, and connect to the target
18846 (@pxref{Connecting,,Connecting to a Remote Target}).
18850 @node Configurations
18851 @chapter Configuration-Specific Information
18853 While nearly all @value{GDBN} commands are available for all native and
18854 cross versions of the debugger, there are some exceptions. This chapter
18855 describes things that are only available in certain configurations.
18857 There are three major categories of configurations: native
18858 configurations, where the host and target are the same, embedded
18859 operating system configurations, which are usually the same for several
18860 different processor architectures, and bare embedded processors, which
18861 are quite different from each other.
18866 * Embedded Processors::
18873 This section describes details specific to particular native
18878 * BSD libkvm Interface:: Debugging BSD kernel memory images
18879 * SVR4 Process Information:: SVR4 process information
18880 * DJGPP Native:: Features specific to the DJGPP port
18881 * Cygwin Native:: Features specific to the Cygwin port
18882 * Hurd Native:: Features specific to @sc{gnu} Hurd
18883 * Darwin:: Features specific to Darwin
18889 On HP-UX systems, if you refer to a function or variable name that
18890 begins with a dollar sign, @value{GDBN} searches for a user or system
18891 name first, before it searches for a convenience variable.
18894 @node BSD libkvm Interface
18895 @subsection BSD libkvm Interface
18898 @cindex kernel memory image
18899 @cindex kernel crash dump
18901 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18902 interface that provides a uniform interface for accessing kernel virtual
18903 memory images, including live systems and crash dumps. @value{GDBN}
18904 uses this interface to allow you to debug live kernels and kernel crash
18905 dumps on many native BSD configurations. This is implemented as a
18906 special @code{kvm} debugging target. For debugging a live system, load
18907 the currently running kernel into @value{GDBN} and connect to the
18911 (@value{GDBP}) @b{target kvm}
18914 For debugging crash dumps, provide the file name of the crash dump as an
18918 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18921 Once connected to the @code{kvm} target, the following commands are
18927 Set current context from the @dfn{Process Control Block} (PCB) address.
18930 Set current context from proc address. This command isn't available on
18931 modern FreeBSD systems.
18934 @node SVR4 Process Information
18935 @subsection SVR4 Process Information
18937 @cindex examine process image
18938 @cindex process info via @file{/proc}
18940 Many versions of SVR4 and compatible systems provide a facility called
18941 @samp{/proc} that can be used to examine the image of a running
18942 process using file-system subroutines.
18944 If @value{GDBN} is configured for an operating system with this
18945 facility, the command @code{info proc} is available to report
18946 information about the process running your program, or about any
18947 process running on your system. This includes, as of this writing,
18948 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18949 not HP-UX, for example.
18951 This command may also work on core files that were created on a system
18952 that has the @samp{/proc} facility.
18958 @itemx info proc @var{process-id}
18959 Summarize available information about any running process. If a
18960 process ID is specified by @var{process-id}, display information about
18961 that process; otherwise display information about the program being
18962 debugged. The summary includes the debugged process ID, the command
18963 line used to invoke it, its current working directory, and its
18964 executable file's absolute file name.
18966 On some systems, @var{process-id} can be of the form
18967 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18968 within a process. If the optional @var{pid} part is missing, it means
18969 a thread from the process being debugged (the leading @samp{/} still
18970 needs to be present, or else @value{GDBN} will interpret the number as
18971 a process ID rather than a thread ID).
18973 @item info proc cmdline
18974 @cindex info proc cmdline
18975 Show the original command line of the process. This command is
18976 specific to @sc{gnu}/Linux.
18978 @item info proc cwd
18979 @cindex info proc cwd
18980 Show the current working directory of the process. This command is
18981 specific to @sc{gnu}/Linux.
18983 @item info proc exe
18984 @cindex info proc exe
18985 Show the name of executable of the process. This command is specific
18988 @item info proc mappings
18989 @cindex memory address space mappings
18990 Report the memory address space ranges accessible in the program, with
18991 information on whether the process has read, write, or execute access
18992 rights to each range. On @sc{gnu}/Linux systems, each memory range
18993 includes the object file which is mapped to that range, instead of the
18994 memory access rights to that range.
18996 @item info proc stat
18997 @itemx info proc status
18998 @cindex process detailed status information
18999 These subcommands are specific to @sc{gnu}/Linux systems. They show
19000 the process-related information, including the user ID and group ID;
19001 how many threads are there in the process; its virtual memory usage;
19002 the signals that are pending, blocked, and ignored; its TTY; its
19003 consumption of system and user time; its stack size; its @samp{nice}
19004 value; etc. For more information, see the @samp{proc} man page
19005 (type @kbd{man 5 proc} from your shell prompt).
19007 @item info proc all
19008 Show all the information about the process described under all of the
19009 above @code{info proc} subcommands.
19012 @comment These sub-options of 'info proc' were not included when
19013 @comment procfs.c was re-written. Keep their descriptions around
19014 @comment against the day when someone finds the time to put them back in.
19015 @kindex info proc times
19016 @item info proc times
19017 Starting time, user CPU time, and system CPU time for your program and
19020 @kindex info proc id
19022 Report on the process IDs related to your program: its own process ID,
19023 the ID of its parent, the process group ID, and the session ID.
19026 @item set procfs-trace
19027 @kindex set procfs-trace
19028 @cindex @code{procfs} API calls
19029 This command enables and disables tracing of @code{procfs} API calls.
19031 @item show procfs-trace
19032 @kindex show procfs-trace
19033 Show the current state of @code{procfs} API call tracing.
19035 @item set procfs-file @var{file}
19036 @kindex set procfs-file
19037 Tell @value{GDBN} to write @code{procfs} API trace to the named
19038 @var{file}. @value{GDBN} appends the trace info to the previous
19039 contents of the file. The default is to display the trace on the
19042 @item show procfs-file
19043 @kindex show procfs-file
19044 Show the file to which @code{procfs} API trace is written.
19046 @item proc-trace-entry
19047 @itemx proc-trace-exit
19048 @itemx proc-untrace-entry
19049 @itemx proc-untrace-exit
19050 @kindex proc-trace-entry
19051 @kindex proc-trace-exit
19052 @kindex proc-untrace-entry
19053 @kindex proc-untrace-exit
19054 These commands enable and disable tracing of entries into and exits
19055 from the @code{syscall} interface.
19058 @kindex info pidlist
19059 @cindex process list, QNX Neutrino
19060 For QNX Neutrino only, this command displays the list of all the
19061 processes and all the threads within each process.
19064 @kindex info meminfo
19065 @cindex mapinfo list, QNX Neutrino
19066 For QNX Neutrino only, this command displays the list of all mapinfos.
19070 @subsection Features for Debugging @sc{djgpp} Programs
19071 @cindex @sc{djgpp} debugging
19072 @cindex native @sc{djgpp} debugging
19073 @cindex MS-DOS-specific commands
19076 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19077 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19078 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19079 top of real-mode DOS systems and their emulations.
19081 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19082 defines a few commands specific to the @sc{djgpp} port. This
19083 subsection describes those commands.
19088 This is a prefix of @sc{djgpp}-specific commands which print
19089 information about the target system and important OS structures.
19092 @cindex MS-DOS system info
19093 @cindex free memory information (MS-DOS)
19094 @item info dos sysinfo
19095 This command displays assorted information about the underlying
19096 platform: the CPU type and features, the OS version and flavor, the
19097 DPMI version, and the available conventional and DPMI memory.
19102 @cindex segment descriptor tables
19103 @cindex descriptor tables display
19105 @itemx info dos ldt
19106 @itemx info dos idt
19107 These 3 commands display entries from, respectively, Global, Local,
19108 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19109 tables are data structures which store a descriptor for each segment
19110 that is currently in use. The segment's selector is an index into a
19111 descriptor table; the table entry for that index holds the
19112 descriptor's base address and limit, and its attributes and access
19115 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19116 segment (used for both data and the stack), and a DOS segment (which
19117 allows access to DOS/BIOS data structures and absolute addresses in
19118 conventional memory). However, the DPMI host will usually define
19119 additional segments in order to support the DPMI environment.
19121 @cindex garbled pointers
19122 These commands allow to display entries from the descriptor tables.
19123 Without an argument, all entries from the specified table are
19124 displayed. An argument, which should be an integer expression, means
19125 display a single entry whose index is given by the argument. For
19126 example, here's a convenient way to display information about the
19127 debugged program's data segment:
19130 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19131 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19135 This comes in handy when you want to see whether a pointer is outside
19136 the data segment's limit (i.e.@: @dfn{garbled}).
19138 @cindex page tables display (MS-DOS)
19140 @itemx info dos pte
19141 These two commands display entries from, respectively, the Page
19142 Directory and the Page Tables. Page Directories and Page Tables are
19143 data structures which control how virtual memory addresses are mapped
19144 into physical addresses. A Page Table includes an entry for every
19145 page of memory that is mapped into the program's address space; there
19146 may be several Page Tables, each one holding up to 4096 entries. A
19147 Page Directory has up to 4096 entries, one each for every Page Table
19148 that is currently in use.
19150 Without an argument, @kbd{info dos pde} displays the entire Page
19151 Directory, and @kbd{info dos pte} displays all the entries in all of
19152 the Page Tables. An argument, an integer expression, given to the
19153 @kbd{info dos pde} command means display only that entry from the Page
19154 Directory table. An argument given to the @kbd{info dos pte} command
19155 means display entries from a single Page Table, the one pointed to by
19156 the specified entry in the Page Directory.
19158 @cindex direct memory access (DMA) on MS-DOS
19159 These commands are useful when your program uses @dfn{DMA} (Direct
19160 Memory Access), which needs physical addresses to program the DMA
19163 These commands are supported only with some DPMI servers.
19165 @cindex physical address from linear address
19166 @item info dos address-pte @var{addr}
19167 This command displays the Page Table entry for a specified linear
19168 address. The argument @var{addr} is a linear address which should
19169 already have the appropriate segment's base address added to it,
19170 because this command accepts addresses which may belong to @emph{any}
19171 segment. For example, here's how to display the Page Table entry for
19172 the page where a variable @code{i} is stored:
19175 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19176 @exdent @code{Page Table entry for address 0x11a00d30:}
19177 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19181 This says that @code{i} is stored at offset @code{0xd30} from the page
19182 whose physical base address is @code{0x02698000}, and shows all the
19183 attributes of that page.
19185 Note that you must cast the addresses of variables to a @code{char *},
19186 since otherwise the value of @code{__djgpp_base_address}, the base
19187 address of all variables and functions in a @sc{djgpp} program, will
19188 be added using the rules of C pointer arithmetics: if @code{i} is
19189 declared an @code{int}, @value{GDBN} will add 4 times the value of
19190 @code{__djgpp_base_address} to the address of @code{i}.
19192 Here's another example, it displays the Page Table entry for the
19196 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19197 @exdent @code{Page Table entry for address 0x29110:}
19198 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19202 (The @code{+ 3} offset is because the transfer buffer's address is the
19203 3rd member of the @code{_go32_info_block} structure.) The output
19204 clearly shows that this DPMI server maps the addresses in conventional
19205 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19206 linear (@code{0x29110}) addresses are identical.
19208 This command is supported only with some DPMI servers.
19211 @cindex DOS serial data link, remote debugging
19212 In addition to native debugging, the DJGPP port supports remote
19213 debugging via a serial data link. The following commands are specific
19214 to remote serial debugging in the DJGPP port of @value{GDBN}.
19217 @kindex set com1base
19218 @kindex set com1irq
19219 @kindex set com2base
19220 @kindex set com2irq
19221 @kindex set com3base
19222 @kindex set com3irq
19223 @kindex set com4base
19224 @kindex set com4irq
19225 @item set com1base @var{addr}
19226 This command sets the base I/O port address of the @file{COM1} serial
19229 @item set com1irq @var{irq}
19230 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19231 for the @file{COM1} serial port.
19233 There are similar commands @samp{set com2base}, @samp{set com3irq},
19234 etc.@: for setting the port address and the @code{IRQ} lines for the
19237 @kindex show com1base
19238 @kindex show com1irq
19239 @kindex show com2base
19240 @kindex show com2irq
19241 @kindex show com3base
19242 @kindex show com3irq
19243 @kindex show com4base
19244 @kindex show com4irq
19245 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19246 display the current settings of the base address and the @code{IRQ}
19247 lines used by the COM ports.
19250 @kindex info serial
19251 @cindex DOS serial port status
19252 This command prints the status of the 4 DOS serial ports. For each
19253 port, it prints whether it's active or not, its I/O base address and
19254 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19255 counts of various errors encountered so far.
19259 @node Cygwin Native
19260 @subsection Features for Debugging MS Windows PE Executables
19261 @cindex MS Windows debugging
19262 @cindex native Cygwin debugging
19263 @cindex Cygwin-specific commands
19265 @value{GDBN} supports native debugging of MS Windows programs, including
19266 DLLs with and without symbolic debugging information.
19268 @cindex Ctrl-BREAK, MS-Windows
19269 @cindex interrupt debuggee on MS-Windows
19270 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19271 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19272 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19273 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19274 sequence, which can be used to interrupt the debuggee even if it
19277 There are various additional Cygwin-specific commands, described in
19278 this section. Working with DLLs that have no debugging symbols is
19279 described in @ref{Non-debug DLL Symbols}.
19284 This is a prefix of MS Windows-specific commands which print
19285 information about the target system and important OS structures.
19287 @item info w32 selector
19288 This command displays information returned by
19289 the Win32 API @code{GetThreadSelectorEntry} function.
19290 It takes an optional argument that is evaluated to
19291 a long value to give the information about this given selector.
19292 Without argument, this command displays information
19293 about the six segment registers.
19295 @item info w32 thread-information-block
19296 This command displays thread specific information stored in the
19297 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19298 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19302 This is a Cygwin-specific alias of @code{info shared}.
19304 @kindex dll-symbols
19306 This command loads symbols from a dll similarly to
19307 add-sym command but without the need to specify a base address.
19309 @kindex set cygwin-exceptions
19310 @cindex debugging the Cygwin DLL
19311 @cindex Cygwin DLL, debugging
19312 @item set cygwin-exceptions @var{mode}
19313 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19314 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19315 @value{GDBN} will delay recognition of exceptions, and may ignore some
19316 exceptions which seem to be caused by internal Cygwin DLL
19317 ``bookkeeping''. This option is meant primarily for debugging the
19318 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19319 @value{GDBN} users with false @code{SIGSEGV} signals.
19321 @kindex show cygwin-exceptions
19322 @item show cygwin-exceptions
19323 Displays whether @value{GDBN} will break on exceptions that happen
19324 inside the Cygwin DLL itself.
19326 @kindex set new-console
19327 @item set new-console @var{mode}
19328 If @var{mode} is @code{on} the debuggee will
19329 be started in a new console on next start.
19330 If @var{mode} is @code{off}, the debuggee will
19331 be started in the same console as the debugger.
19333 @kindex show new-console
19334 @item show new-console
19335 Displays whether a new console is used
19336 when the debuggee is started.
19338 @kindex set new-group
19339 @item set new-group @var{mode}
19340 This boolean value controls whether the debuggee should
19341 start a new group or stay in the same group as the debugger.
19342 This affects the way the Windows OS handles
19345 @kindex show new-group
19346 @item show new-group
19347 Displays current value of new-group boolean.
19349 @kindex set debugevents
19350 @item set debugevents
19351 This boolean value adds debug output concerning kernel events related
19352 to the debuggee seen by the debugger. This includes events that
19353 signal thread and process creation and exit, DLL loading and
19354 unloading, console interrupts, and debugging messages produced by the
19355 Windows @code{OutputDebugString} API call.
19357 @kindex set debugexec
19358 @item set debugexec
19359 This boolean value adds debug output concerning execute events
19360 (such as resume thread) seen by the debugger.
19362 @kindex set debugexceptions
19363 @item set debugexceptions
19364 This boolean value adds debug output concerning exceptions in the
19365 debuggee seen by the debugger.
19367 @kindex set debugmemory
19368 @item set debugmemory
19369 This boolean value adds debug output concerning debuggee memory reads
19370 and writes by the debugger.
19374 This boolean values specifies whether the debuggee is called
19375 via a shell or directly (default value is on).
19379 Displays if the debuggee will be started with a shell.
19384 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19387 @node Non-debug DLL Symbols
19388 @subsubsection Support for DLLs without Debugging Symbols
19389 @cindex DLLs with no debugging symbols
19390 @cindex Minimal symbols and DLLs
19392 Very often on windows, some of the DLLs that your program relies on do
19393 not include symbolic debugging information (for example,
19394 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19395 symbols in a DLL, it relies on the minimal amount of symbolic
19396 information contained in the DLL's export table. This section
19397 describes working with such symbols, known internally to @value{GDBN} as
19398 ``minimal symbols''.
19400 Note that before the debugged program has started execution, no DLLs
19401 will have been loaded. The easiest way around this problem is simply to
19402 start the program --- either by setting a breakpoint or letting the
19403 program run once to completion. It is also possible to force
19404 @value{GDBN} to load a particular DLL before starting the executable ---
19405 see the shared library information in @ref{Files}, or the
19406 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19407 explicitly loading symbols from a DLL with no debugging information will
19408 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19409 which may adversely affect symbol lookup performance.
19411 @subsubsection DLL Name Prefixes
19413 In keeping with the naming conventions used by the Microsoft debugging
19414 tools, DLL export symbols are made available with a prefix based on the
19415 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19416 also entered into the symbol table, so @code{CreateFileA} is often
19417 sufficient. In some cases there will be name clashes within a program
19418 (particularly if the executable itself includes full debugging symbols)
19419 necessitating the use of the fully qualified name when referring to the
19420 contents of the DLL. Use single-quotes around the name to avoid the
19421 exclamation mark (``!'') being interpreted as a language operator.
19423 Note that the internal name of the DLL may be all upper-case, even
19424 though the file name of the DLL is lower-case, or vice-versa. Since
19425 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19426 some confusion. If in doubt, try the @code{info functions} and
19427 @code{info variables} commands or even @code{maint print msymbols}
19428 (@pxref{Symbols}). Here's an example:
19431 (@value{GDBP}) info function CreateFileA
19432 All functions matching regular expression "CreateFileA":
19434 Non-debugging symbols:
19435 0x77e885f4 CreateFileA
19436 0x77e885f4 KERNEL32!CreateFileA
19440 (@value{GDBP}) info function !
19441 All functions matching regular expression "!":
19443 Non-debugging symbols:
19444 0x6100114c cygwin1!__assert
19445 0x61004034 cygwin1!_dll_crt0@@0
19446 0x61004240 cygwin1!dll_crt0(per_process *)
19450 @subsubsection Working with Minimal Symbols
19452 Symbols extracted from a DLL's export table do not contain very much
19453 type information. All that @value{GDBN} can do is guess whether a symbol
19454 refers to a function or variable depending on the linker section that
19455 contains the symbol. Also note that the actual contents of the memory
19456 contained in a DLL are not available unless the program is running. This
19457 means that you cannot examine the contents of a variable or disassemble
19458 a function within a DLL without a running program.
19460 Variables are generally treated as pointers and dereferenced
19461 automatically. For this reason, it is often necessary to prefix a
19462 variable name with the address-of operator (``&'') and provide explicit
19463 type information in the command. Here's an example of the type of
19467 (@value{GDBP}) print 'cygwin1!__argv'
19472 (@value{GDBP}) x 'cygwin1!__argv'
19473 0x10021610: "\230y\""
19476 And two possible solutions:
19479 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19480 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19484 (@value{GDBP}) x/2x &'cygwin1!__argv'
19485 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19486 (@value{GDBP}) x/x 0x10021608
19487 0x10021608: 0x0022fd98
19488 (@value{GDBP}) x/s 0x0022fd98
19489 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19492 Setting a break point within a DLL is possible even before the program
19493 starts execution. However, under these circumstances, @value{GDBN} can't
19494 examine the initial instructions of the function in order to skip the
19495 function's frame set-up code. You can work around this by using ``*&''
19496 to set the breakpoint at a raw memory address:
19499 (@value{GDBP}) break *&'python22!PyOS_Readline'
19500 Breakpoint 1 at 0x1e04eff0
19503 The author of these extensions is not entirely convinced that setting a
19504 break point within a shared DLL like @file{kernel32.dll} is completely
19508 @subsection Commands Specific to @sc{gnu} Hurd Systems
19509 @cindex @sc{gnu} Hurd debugging
19511 This subsection describes @value{GDBN} commands specific to the
19512 @sc{gnu} Hurd native debugging.
19517 @kindex set signals@r{, Hurd command}
19518 @kindex set sigs@r{, Hurd command}
19519 This command toggles the state of inferior signal interception by
19520 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19521 affected by this command. @code{sigs} is a shorthand alias for
19526 @kindex show signals@r{, Hurd command}
19527 @kindex show sigs@r{, Hurd command}
19528 Show the current state of intercepting inferior's signals.
19530 @item set signal-thread
19531 @itemx set sigthread
19532 @kindex set signal-thread
19533 @kindex set sigthread
19534 This command tells @value{GDBN} which thread is the @code{libc} signal
19535 thread. That thread is run when a signal is delivered to a running
19536 process. @code{set sigthread} is the shorthand alias of @code{set
19539 @item show signal-thread
19540 @itemx show sigthread
19541 @kindex show signal-thread
19542 @kindex show sigthread
19543 These two commands show which thread will run when the inferior is
19544 delivered a signal.
19547 @kindex set stopped@r{, Hurd command}
19548 This commands tells @value{GDBN} that the inferior process is stopped,
19549 as with the @code{SIGSTOP} signal. The stopped process can be
19550 continued by delivering a signal to it.
19553 @kindex show stopped@r{, Hurd command}
19554 This command shows whether @value{GDBN} thinks the debuggee is
19557 @item set exceptions
19558 @kindex set exceptions@r{, Hurd command}
19559 Use this command to turn off trapping of exceptions in the inferior.
19560 When exception trapping is off, neither breakpoints nor
19561 single-stepping will work. To restore the default, set exception
19564 @item show exceptions
19565 @kindex show exceptions@r{, Hurd command}
19566 Show the current state of trapping exceptions in the inferior.
19568 @item set task pause
19569 @kindex set task@r{, Hurd commands}
19570 @cindex task attributes (@sc{gnu} Hurd)
19571 @cindex pause current task (@sc{gnu} Hurd)
19572 This command toggles task suspension when @value{GDBN} has control.
19573 Setting it to on takes effect immediately, and the task is suspended
19574 whenever @value{GDBN} gets control. Setting it to off will take
19575 effect the next time the inferior is continued. If this option is set
19576 to off, you can use @code{set thread default pause on} or @code{set
19577 thread pause on} (see below) to pause individual threads.
19579 @item show task pause
19580 @kindex show task@r{, Hurd commands}
19581 Show the current state of task suspension.
19583 @item set task detach-suspend-count
19584 @cindex task suspend count
19585 @cindex detach from task, @sc{gnu} Hurd
19586 This command sets the suspend count the task will be left with when
19587 @value{GDBN} detaches from it.
19589 @item show task detach-suspend-count
19590 Show the suspend count the task will be left with when detaching.
19592 @item set task exception-port
19593 @itemx set task excp
19594 @cindex task exception port, @sc{gnu} Hurd
19595 This command sets the task exception port to which @value{GDBN} will
19596 forward exceptions. The argument should be the value of the @dfn{send
19597 rights} of the task. @code{set task excp} is a shorthand alias.
19599 @item set noninvasive
19600 @cindex noninvasive task options
19601 This command switches @value{GDBN} to a mode that is the least
19602 invasive as far as interfering with the inferior is concerned. This
19603 is the same as using @code{set task pause}, @code{set exceptions}, and
19604 @code{set signals} to values opposite to the defaults.
19606 @item info send-rights
19607 @itemx info receive-rights
19608 @itemx info port-rights
19609 @itemx info port-sets
19610 @itemx info dead-names
19613 @cindex send rights, @sc{gnu} Hurd
19614 @cindex receive rights, @sc{gnu} Hurd
19615 @cindex port rights, @sc{gnu} Hurd
19616 @cindex port sets, @sc{gnu} Hurd
19617 @cindex dead names, @sc{gnu} Hurd
19618 These commands display information about, respectively, send rights,
19619 receive rights, port rights, port sets, and dead names of a task.
19620 There are also shorthand aliases: @code{info ports} for @code{info
19621 port-rights} and @code{info psets} for @code{info port-sets}.
19623 @item set thread pause
19624 @kindex set thread@r{, Hurd command}
19625 @cindex thread properties, @sc{gnu} Hurd
19626 @cindex pause current thread (@sc{gnu} Hurd)
19627 This command toggles current thread suspension when @value{GDBN} has
19628 control. Setting it to on takes effect immediately, and the current
19629 thread is suspended whenever @value{GDBN} gets control. Setting it to
19630 off will take effect the next time the inferior is continued.
19631 Normally, this command has no effect, since when @value{GDBN} has
19632 control, the whole task is suspended. However, if you used @code{set
19633 task pause off} (see above), this command comes in handy to suspend
19634 only the current thread.
19636 @item show thread pause
19637 @kindex show thread@r{, Hurd command}
19638 This command shows the state of current thread suspension.
19640 @item set thread run
19641 This command sets whether the current thread is allowed to run.
19643 @item show thread run
19644 Show whether the current thread is allowed to run.
19646 @item set thread detach-suspend-count
19647 @cindex thread suspend count, @sc{gnu} Hurd
19648 @cindex detach from thread, @sc{gnu} Hurd
19649 This command sets the suspend count @value{GDBN} will leave on a
19650 thread when detaching. This number is relative to the suspend count
19651 found by @value{GDBN} when it notices the thread; use @code{set thread
19652 takeover-suspend-count} to force it to an absolute value.
19654 @item show thread detach-suspend-count
19655 Show the suspend count @value{GDBN} will leave on the thread when
19658 @item set thread exception-port
19659 @itemx set thread excp
19660 Set the thread exception port to which to forward exceptions. This
19661 overrides the port set by @code{set task exception-port} (see above).
19662 @code{set thread excp} is the shorthand alias.
19664 @item set thread takeover-suspend-count
19665 Normally, @value{GDBN}'s thread suspend counts are relative to the
19666 value @value{GDBN} finds when it notices each thread. This command
19667 changes the suspend counts to be absolute instead.
19669 @item set thread default
19670 @itemx show thread default
19671 @cindex thread default settings, @sc{gnu} Hurd
19672 Each of the above @code{set thread} commands has a @code{set thread
19673 default} counterpart (e.g., @code{set thread default pause}, @code{set
19674 thread default exception-port}, etc.). The @code{thread default}
19675 variety of commands sets the default thread properties for all
19676 threads; you can then change the properties of individual threads with
19677 the non-default commands.
19684 @value{GDBN} provides the following commands specific to the Darwin target:
19687 @item set debug darwin @var{num}
19688 @kindex set debug darwin
19689 When set to a non zero value, enables debugging messages specific to
19690 the Darwin support. Higher values produce more verbose output.
19692 @item show debug darwin
19693 @kindex show debug darwin
19694 Show the current state of Darwin messages.
19696 @item set debug mach-o @var{num}
19697 @kindex set debug mach-o
19698 When set to a non zero value, enables debugging messages while
19699 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19700 file format used on Darwin for object and executable files.) Higher
19701 values produce more verbose output. This is a command to diagnose
19702 problems internal to @value{GDBN} and should not be needed in normal
19705 @item show debug mach-o
19706 @kindex show debug mach-o
19707 Show the current state of Mach-O file messages.
19709 @item set mach-exceptions on
19710 @itemx set mach-exceptions off
19711 @kindex set mach-exceptions
19712 On Darwin, faults are first reported as a Mach exception and are then
19713 mapped to a Posix signal. Use this command to turn on trapping of
19714 Mach exceptions in the inferior. This might be sometimes useful to
19715 better understand the cause of a fault. The default is off.
19717 @item show mach-exceptions
19718 @kindex show mach-exceptions
19719 Show the current state of exceptions trapping.
19724 @section Embedded Operating Systems
19726 This section describes configurations involving the debugging of
19727 embedded operating systems that are available for several different
19731 * VxWorks:: Using @value{GDBN} with VxWorks
19734 @value{GDBN} includes the ability to debug programs running on
19735 various real-time operating systems.
19738 @subsection Using @value{GDBN} with VxWorks
19744 @kindex target vxworks
19745 @item target vxworks @var{machinename}
19746 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19747 is the target system's machine name or IP address.
19751 On VxWorks, @code{load} links @var{filename} dynamically on the
19752 current target system as well as adding its symbols in @value{GDBN}.
19754 @value{GDBN} enables developers to spawn and debug tasks running on networked
19755 VxWorks targets from a Unix host. Already-running tasks spawned from
19756 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19757 both the Unix host and on the VxWorks target. The program
19758 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19759 installed with the name @code{vxgdb}, to distinguish it from a
19760 @value{GDBN} for debugging programs on the host itself.)
19763 @item VxWorks-timeout @var{args}
19764 @kindex vxworks-timeout
19765 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19766 This option is set by the user, and @var{args} represents the number of
19767 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19768 your VxWorks target is a slow software simulator or is on the far side
19769 of a thin network line.
19772 The following information on connecting to VxWorks was current when
19773 this manual was produced; newer releases of VxWorks may use revised
19776 @findex INCLUDE_RDB
19777 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19778 to include the remote debugging interface routines in the VxWorks
19779 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19780 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19781 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19782 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19783 information on configuring and remaking VxWorks, see the manufacturer's
19785 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19787 Once you have included @file{rdb.a} in your VxWorks system image and set
19788 your Unix execution search path to find @value{GDBN}, you are ready to
19789 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19790 @code{vxgdb}, depending on your installation).
19792 @value{GDBN} comes up showing the prompt:
19799 * VxWorks Connection:: Connecting to VxWorks
19800 * VxWorks Download:: VxWorks download
19801 * VxWorks Attach:: Running tasks
19804 @node VxWorks Connection
19805 @subsubsection Connecting to VxWorks
19807 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19808 network. To connect to a target whose host name is ``@code{tt}'', type:
19811 (vxgdb) target vxworks tt
19815 @value{GDBN} displays messages like these:
19818 Attaching remote machine across net...
19823 @value{GDBN} then attempts to read the symbol tables of any object modules
19824 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19825 these files by searching the directories listed in the command search
19826 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19827 to find an object file, it displays a message such as:
19830 prog.o: No such file or directory.
19833 When this happens, add the appropriate directory to the search path with
19834 the @value{GDBN} command @code{path}, and execute the @code{target}
19837 @node VxWorks Download
19838 @subsubsection VxWorks Download
19840 @cindex download to VxWorks
19841 If you have connected to the VxWorks target and you want to debug an
19842 object that has not yet been loaded, you can use the @value{GDBN}
19843 @code{load} command to download a file from Unix to VxWorks
19844 incrementally. The object file given as an argument to the @code{load}
19845 command is actually opened twice: first by the VxWorks target in order
19846 to download the code, then by @value{GDBN} in order to read the symbol
19847 table. This can lead to problems if the current working directories on
19848 the two systems differ. If both systems have NFS mounted the same
19849 filesystems, you can avoid these problems by using absolute paths.
19850 Otherwise, it is simplest to set the working directory on both systems
19851 to the directory in which the object file resides, and then to reference
19852 the file by its name, without any path. For instance, a program
19853 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19854 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19855 program, type this on VxWorks:
19858 -> cd "@var{vxpath}/vw/demo/rdb"
19862 Then, in @value{GDBN}, type:
19865 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19866 (vxgdb) load prog.o
19869 @value{GDBN} displays a response similar to this:
19872 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19875 You can also use the @code{load} command to reload an object module
19876 after editing and recompiling the corresponding source file. Note that
19877 this makes @value{GDBN} delete all currently-defined breakpoints,
19878 auto-displays, and convenience variables, and to clear the value
19879 history. (This is necessary in order to preserve the integrity of
19880 debugger's data structures that reference the target system's symbol
19883 @node VxWorks Attach
19884 @subsubsection Running Tasks
19886 @cindex running VxWorks tasks
19887 You can also attach to an existing task using the @code{attach} command as
19891 (vxgdb) attach @var{task}
19895 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19896 or suspended when you attach to it. Running tasks are suspended at
19897 the time of attachment.
19899 @node Embedded Processors
19900 @section Embedded Processors
19902 This section goes into details specific to particular embedded
19905 @cindex send command to simulator
19906 Whenever a specific embedded processor has a simulator, @value{GDBN}
19907 allows to send an arbitrary command to the simulator.
19910 @item sim @var{command}
19911 @kindex sim@r{, a command}
19912 Send an arbitrary @var{command} string to the simulator. Consult the
19913 documentation for the specific simulator in use for information about
19914 acceptable commands.
19920 * M32R/D:: Renesas M32R/D
19921 * M68K:: Motorola M68K
19922 * MicroBlaze:: Xilinx MicroBlaze
19923 * MIPS Embedded:: MIPS Embedded
19924 * PowerPC Embedded:: PowerPC Embedded
19925 * PA:: HP PA Embedded
19926 * Sparclet:: Tsqware Sparclet
19927 * Sparclite:: Fujitsu Sparclite
19928 * Z8000:: Zilog Z8000
19931 * Super-H:: Renesas Super-H
19940 @item target rdi @var{dev}
19941 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19942 use this target to communicate with both boards running the Angel
19943 monitor, or with the EmbeddedICE JTAG debug device.
19946 @item target rdp @var{dev}
19951 @value{GDBN} provides the following ARM-specific commands:
19954 @item set arm disassembler
19956 This commands selects from a list of disassembly styles. The
19957 @code{"std"} style is the standard style.
19959 @item show arm disassembler
19961 Show the current disassembly style.
19963 @item set arm apcs32
19964 @cindex ARM 32-bit mode
19965 This command toggles ARM operation mode between 32-bit and 26-bit.
19967 @item show arm apcs32
19968 Display the current usage of the ARM 32-bit mode.
19970 @item set arm fpu @var{fputype}
19971 This command sets the ARM floating-point unit (FPU) type. The
19972 argument @var{fputype} can be one of these:
19976 Determine the FPU type by querying the OS ABI.
19978 Software FPU, with mixed-endian doubles on little-endian ARM
19981 GCC-compiled FPA co-processor.
19983 Software FPU with pure-endian doubles.
19989 Show the current type of the FPU.
19992 This command forces @value{GDBN} to use the specified ABI.
19995 Show the currently used ABI.
19997 @item set arm fallback-mode (arm|thumb|auto)
19998 @value{GDBN} uses the symbol table, when available, to determine
19999 whether instructions are ARM or Thumb. This command controls
20000 @value{GDBN}'s default behavior when the symbol table is not
20001 available. The default is @samp{auto}, which causes @value{GDBN} to
20002 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20005 @item show arm fallback-mode
20006 Show the current fallback instruction mode.
20008 @item set arm force-mode (arm|thumb|auto)
20009 This command overrides use of the symbol table to determine whether
20010 instructions are ARM or Thumb. The default is @samp{auto}, which
20011 causes @value{GDBN} to use the symbol table and then the setting
20012 of @samp{set arm fallback-mode}.
20014 @item show arm force-mode
20015 Show the current forced instruction mode.
20017 @item set debug arm
20018 Toggle whether to display ARM-specific debugging messages from the ARM
20019 target support subsystem.
20021 @item show debug arm
20022 Show whether ARM-specific debugging messages are enabled.
20025 The following commands are available when an ARM target is debugged
20026 using the RDI interface:
20029 @item rdilogfile @r{[}@var{file}@r{]}
20031 @cindex ADP (Angel Debugger Protocol) logging
20032 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20033 With an argument, sets the log file to the specified @var{file}. With
20034 no argument, show the current log file name. The default log file is
20037 @item rdilogenable @r{[}@var{arg}@r{]}
20038 @kindex rdilogenable
20039 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20040 enables logging, with an argument 0 or @code{"no"} disables it. With
20041 no arguments displays the current setting. When logging is enabled,
20042 ADP packets exchanged between @value{GDBN} and the RDI target device
20043 are logged to a file.
20045 @item set rdiromatzero
20046 @kindex set rdiromatzero
20047 @cindex ROM at zero address, RDI
20048 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20049 vector catching is disabled, so that zero address can be used. If off
20050 (the default), vector catching is enabled. For this command to take
20051 effect, it needs to be invoked prior to the @code{target rdi} command.
20053 @item show rdiromatzero
20054 @kindex show rdiromatzero
20055 Show the current setting of ROM at zero address.
20057 @item set rdiheartbeat
20058 @kindex set rdiheartbeat
20059 @cindex RDI heartbeat
20060 Enable or disable RDI heartbeat packets. It is not recommended to
20061 turn on this option, since it confuses ARM and EPI JTAG interface, as
20062 well as the Angel monitor.
20064 @item show rdiheartbeat
20065 @kindex show rdiheartbeat
20066 Show the setting of RDI heartbeat packets.
20070 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20071 The @value{GDBN} ARM simulator accepts the following optional arguments.
20074 @item --swi-support=@var{type}
20075 Tell the simulator which SWI interfaces to support.
20076 @var{type} may be a comma separated list of the following values.
20077 The default value is @code{all}.
20090 @subsection Renesas M32R/D and M32R/SDI
20093 @kindex target m32r
20094 @item target m32r @var{dev}
20095 Renesas M32R/D ROM monitor.
20097 @kindex target m32rsdi
20098 @item target m32rsdi @var{dev}
20099 Renesas M32R SDI server, connected via parallel port to the board.
20102 The following @value{GDBN} commands are specific to the M32R monitor:
20105 @item set download-path @var{path}
20106 @kindex set download-path
20107 @cindex find downloadable @sc{srec} files (M32R)
20108 Set the default path for finding downloadable @sc{srec} files.
20110 @item show download-path
20111 @kindex show download-path
20112 Show the default path for downloadable @sc{srec} files.
20114 @item set board-address @var{addr}
20115 @kindex set board-address
20116 @cindex M32-EVA target board address
20117 Set the IP address for the M32R-EVA target board.
20119 @item show board-address
20120 @kindex show board-address
20121 Show the current IP address of the target board.
20123 @item set server-address @var{addr}
20124 @kindex set server-address
20125 @cindex download server address (M32R)
20126 Set the IP address for the download server, which is the @value{GDBN}'s
20129 @item show server-address
20130 @kindex show server-address
20131 Display the IP address of the download server.
20133 @item upload @r{[}@var{file}@r{]}
20134 @kindex upload@r{, M32R}
20135 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20136 upload capability. If no @var{file} argument is given, the current
20137 executable file is uploaded.
20139 @item tload @r{[}@var{file}@r{]}
20140 @kindex tload@r{, M32R}
20141 Test the @code{upload} command.
20144 The following commands are available for M32R/SDI:
20149 @cindex reset SDI connection, M32R
20150 This command resets the SDI connection.
20154 This command shows the SDI connection status.
20157 @kindex debug_chaos
20158 @cindex M32R/Chaos debugging
20159 Instructs the remote that M32R/Chaos debugging is to be used.
20161 @item use_debug_dma
20162 @kindex use_debug_dma
20163 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20166 @kindex use_mon_code
20167 Instructs the remote to use the MON_CODE method of accessing memory.
20170 @kindex use_ib_break
20171 Instructs the remote to set breakpoints by IB break.
20173 @item use_dbt_break
20174 @kindex use_dbt_break
20175 Instructs the remote to set breakpoints by DBT.
20181 The Motorola m68k configuration includes ColdFire support, and a
20182 target command for the following ROM monitor.
20186 @kindex target dbug
20187 @item target dbug @var{dev}
20188 dBUG ROM monitor for Motorola ColdFire.
20193 @subsection MicroBlaze
20194 @cindex Xilinx MicroBlaze
20195 @cindex XMD, Xilinx Microprocessor Debugger
20197 The MicroBlaze is a soft-core processor supported on various Xilinx
20198 FPGAs, such as Spartan or Virtex series. Boards with these processors
20199 usually have JTAG ports which connect to a host system running the Xilinx
20200 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20201 This host system is used to download the configuration bitstream to
20202 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20203 communicates with the target board using the JTAG interface and
20204 presents a @code{gdbserver} interface to the board. By default
20205 @code{xmd} uses port @code{1234}. (While it is possible to change
20206 this default port, it requires the use of undocumented @code{xmd}
20207 commands. Contact Xilinx support if you need to do this.)
20209 Use these GDB commands to connect to the MicroBlaze target processor.
20212 @item target remote :1234
20213 Use this command to connect to the target if you are running @value{GDBN}
20214 on the same system as @code{xmd}.
20216 @item target remote @var{xmd-host}:1234
20217 Use this command to connect to the target if it is connected to @code{xmd}
20218 running on a different system named @var{xmd-host}.
20221 Use this command to download a program to the MicroBlaze target.
20223 @item set debug microblaze @var{n}
20224 Enable MicroBlaze-specific debugging messages if non-zero.
20226 @item show debug microblaze @var{n}
20227 Show MicroBlaze-specific debugging level.
20230 @node MIPS Embedded
20231 @subsection @acronym{MIPS} Embedded
20233 @cindex @acronym{MIPS} boards
20234 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20235 @acronym{MIPS} board attached to a serial line. This is available when
20236 you configure @value{GDBN} with @samp{--target=mips-elf}.
20239 Use these @value{GDBN} commands to specify the connection to your target board:
20242 @item target mips @var{port}
20243 @kindex target mips @var{port}
20244 To run a program on the board, start up @code{@value{GDBP}} with the
20245 name of your program as the argument. To connect to the board, use the
20246 command @samp{target mips @var{port}}, where @var{port} is the name of
20247 the serial port connected to the board. If the program has not already
20248 been downloaded to the board, you may use the @code{load} command to
20249 download it. You can then use all the usual @value{GDBN} commands.
20251 For example, this sequence connects to the target board through a serial
20252 port, and loads and runs a program called @var{prog} through the
20256 host$ @value{GDBP} @var{prog}
20257 @value{GDBN} is free software and @dots{}
20258 (@value{GDBP}) target mips /dev/ttyb
20259 (@value{GDBP}) load @var{prog}
20263 @item target mips @var{hostname}:@var{portnumber}
20264 On some @value{GDBN} host configurations, you can specify a TCP
20265 connection (for instance, to a serial line managed by a terminal
20266 concentrator) instead of a serial port, using the syntax
20267 @samp{@var{hostname}:@var{portnumber}}.
20269 @item target pmon @var{port}
20270 @kindex target pmon @var{port}
20273 @item target ddb @var{port}
20274 @kindex target ddb @var{port}
20275 NEC's DDB variant of PMON for Vr4300.
20277 @item target lsi @var{port}
20278 @kindex target lsi @var{port}
20279 LSI variant of PMON.
20281 @kindex target r3900
20282 @item target r3900 @var{dev}
20283 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20285 @kindex target array
20286 @item target array @var{dev}
20287 Array Tech LSI33K RAID controller board.
20293 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20296 @item set mipsfpu double
20297 @itemx set mipsfpu single
20298 @itemx set mipsfpu none
20299 @itemx set mipsfpu auto
20300 @itemx show mipsfpu
20301 @kindex set mipsfpu
20302 @kindex show mipsfpu
20303 @cindex @acronym{MIPS} remote floating point
20304 @cindex floating point, @acronym{MIPS} remote
20305 If your target board does not support the @acronym{MIPS} floating point
20306 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20307 need this, you may wish to put the command in your @value{GDBN} init
20308 file). This tells @value{GDBN} how to find the return value of
20309 functions which return floating point values. It also allows
20310 @value{GDBN} to avoid saving the floating point registers when calling
20311 functions on the board. If you are using a floating point coprocessor
20312 with only single precision floating point support, as on the @sc{r4650}
20313 processor, use the command @samp{set mipsfpu single}. The default
20314 double precision floating point coprocessor may be selected using
20315 @samp{set mipsfpu double}.
20317 In previous versions the only choices were double precision or no
20318 floating point, so @samp{set mipsfpu on} will select double precision
20319 and @samp{set mipsfpu off} will select no floating point.
20321 As usual, you can inquire about the @code{mipsfpu} variable with
20322 @samp{show mipsfpu}.
20324 @item set timeout @var{seconds}
20325 @itemx set retransmit-timeout @var{seconds}
20326 @itemx show timeout
20327 @itemx show retransmit-timeout
20328 @cindex @code{timeout}, @acronym{MIPS} protocol
20329 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20330 @kindex set timeout
20331 @kindex show timeout
20332 @kindex set retransmit-timeout
20333 @kindex show retransmit-timeout
20334 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20335 remote protocol, with the @code{set timeout @var{seconds}} command. The
20336 default is 5 seconds. Similarly, you can control the timeout used while
20337 waiting for an acknowledgment of a packet with the @code{set
20338 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20339 You can inspect both values with @code{show timeout} and @code{show
20340 retransmit-timeout}. (These commands are @emph{only} available when
20341 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20343 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20344 is waiting for your program to stop. In that case, @value{GDBN} waits
20345 forever because it has no way of knowing how long the program is going
20346 to run before stopping.
20348 @item set syn-garbage-limit @var{num}
20349 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20350 @cindex synchronize with remote @acronym{MIPS} target
20351 Limit the maximum number of characters @value{GDBN} should ignore when
20352 it tries to synchronize with the remote target. The default is 10
20353 characters. Setting the limit to -1 means there's no limit.
20355 @item show syn-garbage-limit
20356 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20357 Show the current limit on the number of characters to ignore when
20358 trying to synchronize with the remote system.
20360 @item set monitor-prompt @var{prompt}
20361 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20362 @cindex remote monitor prompt
20363 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20364 remote monitor. The default depends on the target:
20374 @item show monitor-prompt
20375 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20376 Show the current strings @value{GDBN} expects as the prompt from the
20379 @item set monitor-warnings
20380 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20381 Enable or disable monitor warnings about hardware breakpoints. This
20382 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20383 display warning messages whose codes are returned by the @code{lsi}
20384 PMON monitor for breakpoint commands.
20386 @item show monitor-warnings
20387 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20388 Show the current setting of printing monitor warnings.
20390 @item pmon @var{command}
20391 @kindex pmon@r{, @acronym{MIPS} remote}
20392 @cindex send PMON command
20393 This command allows sending an arbitrary @var{command} string to the
20394 monitor. The monitor must be in debug mode for this to work.
20397 @node PowerPC Embedded
20398 @subsection PowerPC Embedded
20400 @cindex DVC register
20401 @value{GDBN} supports using the DVC (Data Value Compare) register to
20402 implement in hardware simple hardware watchpoint conditions of the form:
20405 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20406 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20409 The DVC register will be automatically used when @value{GDBN} detects
20410 such pattern in a condition expression, and the created watchpoint uses one
20411 debug register (either the @code{exact-watchpoints} option is on and the
20412 variable is scalar, or the variable has a length of one byte). This feature
20413 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20416 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20417 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20418 in which case watchpoints using only one debug register are created when
20419 watching variables of scalar types.
20421 You can create an artificial array to watch an arbitrary memory
20422 region using one of the following commands (@pxref{Expressions}):
20425 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20426 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20429 PowerPC embedded processors support masked watchpoints. See the discussion
20430 about the @code{mask} argument in @ref{Set Watchpoints}.
20432 @cindex ranged breakpoint
20433 PowerPC embedded processors support hardware accelerated
20434 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20435 the inferior whenever it executes an instruction at any address within
20436 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20437 use the @code{break-range} command.
20439 @value{GDBN} provides the following PowerPC-specific commands:
20442 @kindex break-range
20443 @item break-range @var{start-location}, @var{end-location}
20444 Set a breakpoint for an address range.
20445 @var{start-location} and @var{end-location} can specify a function name,
20446 a line number, an offset of lines from the current line or from the start
20447 location, or an address of an instruction (see @ref{Specify Location},
20448 for a list of all the possible ways to specify a @var{location}.)
20449 The breakpoint will stop execution of the inferior whenever it
20450 executes an instruction at any address within the specified range,
20451 (including @var{start-location} and @var{end-location}.)
20453 @kindex set powerpc
20454 @item set powerpc soft-float
20455 @itemx show powerpc soft-float
20456 Force @value{GDBN} to use (or not use) a software floating point calling
20457 convention. By default, @value{GDBN} selects the calling convention based
20458 on the selected architecture and the provided executable file.
20460 @item set powerpc vector-abi
20461 @itemx show powerpc vector-abi
20462 Force @value{GDBN} to use the specified calling convention for vector
20463 arguments and return values. The valid options are @samp{auto};
20464 @samp{generic}, to avoid vector registers even if they are present;
20465 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20466 registers. By default, @value{GDBN} selects the calling convention
20467 based on the selected architecture and the provided executable file.
20469 @item set powerpc exact-watchpoints
20470 @itemx show powerpc exact-watchpoints
20471 Allow @value{GDBN} to use only one debug register when watching a variable
20472 of scalar type, thus assuming that the variable is accessed through the
20473 address of its first byte.
20475 @kindex target dink32
20476 @item target dink32 @var{dev}
20477 DINK32 ROM monitor.
20479 @kindex target ppcbug
20480 @item target ppcbug @var{dev}
20481 @kindex target ppcbug1
20482 @item target ppcbug1 @var{dev}
20483 PPCBUG ROM monitor for PowerPC.
20486 @item target sds @var{dev}
20487 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20490 @cindex SDS protocol
20491 The following commands specific to the SDS protocol are supported
20495 @item set sdstimeout @var{nsec}
20496 @kindex set sdstimeout
20497 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20498 default is 2 seconds.
20500 @item show sdstimeout
20501 @kindex show sdstimeout
20502 Show the current value of the SDS timeout.
20504 @item sds @var{command}
20505 @kindex sds@r{, a command}
20506 Send the specified @var{command} string to the SDS monitor.
20511 @subsection HP PA Embedded
20515 @kindex target op50n
20516 @item target op50n @var{dev}
20517 OP50N monitor, running on an OKI HPPA board.
20519 @kindex target w89k
20520 @item target w89k @var{dev}
20521 W89K monitor, running on a Winbond HPPA board.
20526 @subsection Tsqware Sparclet
20530 @value{GDBN} enables developers to debug tasks running on
20531 Sparclet targets from a Unix host.
20532 @value{GDBN} uses code that runs on
20533 both the Unix host and on the Sparclet target. The program
20534 @code{@value{GDBP}} is installed and executed on the Unix host.
20537 @item remotetimeout @var{args}
20538 @kindex remotetimeout
20539 @value{GDBN} supports the option @code{remotetimeout}.
20540 This option is set by the user, and @var{args} represents the number of
20541 seconds @value{GDBN} waits for responses.
20544 @cindex compiling, on Sparclet
20545 When compiling for debugging, include the options @samp{-g} to get debug
20546 information and @samp{-Ttext} to relocate the program to where you wish to
20547 load it on the target. You may also want to add the options @samp{-n} or
20548 @samp{-N} in order to reduce the size of the sections. Example:
20551 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20554 You can use @code{objdump} to verify that the addresses are what you intended:
20557 sparclet-aout-objdump --headers --syms prog
20560 @cindex running, on Sparclet
20562 your Unix execution search path to find @value{GDBN}, you are ready to
20563 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20564 (or @code{sparclet-aout-gdb}, depending on your installation).
20566 @value{GDBN} comes up showing the prompt:
20573 * Sparclet File:: Setting the file to debug
20574 * Sparclet Connection:: Connecting to Sparclet
20575 * Sparclet Download:: Sparclet download
20576 * Sparclet Execution:: Running and debugging
20579 @node Sparclet File
20580 @subsubsection Setting File to Debug
20582 The @value{GDBN} command @code{file} lets you choose with program to debug.
20585 (gdbslet) file prog
20589 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20590 @value{GDBN} locates
20591 the file by searching the directories listed in the command search
20593 If the file was compiled with debug information (option @samp{-g}), source
20594 files will be searched as well.
20595 @value{GDBN} locates
20596 the source files by searching the directories listed in the directory search
20597 path (@pxref{Environment, ,Your Program's Environment}).
20599 to find a file, it displays a message such as:
20602 prog: No such file or directory.
20605 When this happens, add the appropriate directories to the search paths with
20606 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20607 @code{target} command again.
20609 @node Sparclet Connection
20610 @subsubsection Connecting to Sparclet
20612 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20613 To connect to a target on serial port ``@code{ttya}'', type:
20616 (gdbslet) target sparclet /dev/ttya
20617 Remote target sparclet connected to /dev/ttya
20618 main () at ../prog.c:3
20622 @value{GDBN} displays messages like these:
20628 @node Sparclet Download
20629 @subsubsection Sparclet Download
20631 @cindex download to Sparclet
20632 Once connected to the Sparclet target,
20633 you can use the @value{GDBN}
20634 @code{load} command to download the file from the host to the target.
20635 The file name and load offset should be given as arguments to the @code{load}
20637 Since the file format is aout, the program must be loaded to the starting
20638 address. You can use @code{objdump} to find out what this value is. The load
20639 offset is an offset which is added to the VMA (virtual memory address)
20640 of each of the file's sections.
20641 For instance, if the program
20642 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20643 and bss at 0x12010170, in @value{GDBN}, type:
20646 (gdbslet) load prog 0x12010000
20647 Loading section .text, size 0xdb0 vma 0x12010000
20650 If the code is loaded at a different address then what the program was linked
20651 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20652 to tell @value{GDBN} where to map the symbol table.
20654 @node Sparclet Execution
20655 @subsubsection Running and Debugging
20657 @cindex running and debugging Sparclet programs
20658 You can now begin debugging the task using @value{GDBN}'s execution control
20659 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20660 manual for the list of commands.
20664 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20666 Starting program: prog
20667 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20668 3 char *symarg = 0;
20670 4 char *execarg = "hello!";
20675 @subsection Fujitsu Sparclite
20679 @kindex target sparclite
20680 @item target sparclite @var{dev}
20681 Fujitsu sparclite boards, used only for the purpose of loading.
20682 You must use an additional command to debug the program.
20683 For example: target remote @var{dev} using @value{GDBN} standard
20689 @subsection Zilog Z8000
20692 @cindex simulator, Z8000
20693 @cindex Zilog Z8000 simulator
20695 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20698 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20699 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20700 segmented variant). The simulator recognizes which architecture is
20701 appropriate by inspecting the object code.
20704 @item target sim @var{args}
20706 @kindex target sim@r{, with Z8000}
20707 Debug programs on a simulated CPU. If the simulator supports setup
20708 options, specify them via @var{args}.
20712 After specifying this target, you can debug programs for the simulated
20713 CPU in the same style as programs for your host computer; use the
20714 @code{file} command to load a new program image, the @code{run} command
20715 to run your program, and so on.
20717 As well as making available all the usual machine registers
20718 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20719 additional items of information as specially named registers:
20724 Counts clock-ticks in the simulator.
20727 Counts instructions run in the simulator.
20730 Execution time in 60ths of a second.
20734 You can refer to these values in @value{GDBN} expressions with the usual
20735 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20736 conditional breakpoint that suspends only after at least 5000
20737 simulated clock ticks.
20740 @subsection Atmel AVR
20743 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20744 following AVR-specific commands:
20747 @item info io_registers
20748 @kindex info io_registers@r{, AVR}
20749 @cindex I/O registers (Atmel AVR)
20750 This command displays information about the AVR I/O registers. For
20751 each register, @value{GDBN} prints its number and value.
20758 When configured for debugging CRIS, @value{GDBN} provides the
20759 following CRIS-specific commands:
20762 @item set cris-version @var{ver}
20763 @cindex CRIS version
20764 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20765 The CRIS version affects register names and sizes. This command is useful in
20766 case autodetection of the CRIS version fails.
20768 @item show cris-version
20769 Show the current CRIS version.
20771 @item set cris-dwarf2-cfi
20772 @cindex DWARF-2 CFI and CRIS
20773 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20774 Change to @samp{off} when using @code{gcc-cris} whose version is below
20777 @item show cris-dwarf2-cfi
20778 Show the current state of using DWARF-2 CFI.
20780 @item set cris-mode @var{mode}
20782 Set the current CRIS mode to @var{mode}. It should only be changed when
20783 debugging in guru mode, in which case it should be set to
20784 @samp{guru} (the default is @samp{normal}).
20786 @item show cris-mode
20787 Show the current CRIS mode.
20791 @subsection Renesas Super-H
20794 For the Renesas Super-H processor, @value{GDBN} provides these
20798 @item set sh calling-convention @var{convention}
20799 @kindex set sh calling-convention
20800 Set the calling-convention used when calling functions from @value{GDBN}.
20801 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20802 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20803 convention. If the DWARF-2 information of the called function specifies
20804 that the function follows the Renesas calling convention, the function
20805 is called using the Renesas calling convention. If the calling convention
20806 is set to @samp{renesas}, the Renesas calling convention is always used,
20807 regardless of the DWARF-2 information. This can be used to override the
20808 default of @samp{gcc} if debug information is missing, or the compiler
20809 does not emit the DWARF-2 calling convention entry for a function.
20811 @item show sh calling-convention
20812 @kindex show sh calling-convention
20813 Show the current calling convention setting.
20818 @node Architectures
20819 @section Architectures
20821 This section describes characteristics of architectures that affect
20822 all uses of @value{GDBN} with the architecture, both native and cross.
20829 * HPPA:: HP PA architecture
20830 * SPU:: Cell Broadband Engine SPU architecture
20835 @subsection AArch64
20836 @cindex AArch64 support
20838 When @value{GDBN} is debugging the AArch64 architecture, it provides the
20839 following special commands:
20842 @item set debug aarch64
20843 @kindex set debug aarch64
20844 This command determines whether AArch64 architecture-specific debugging
20845 messages are to be displayed.
20847 @item show debug aarch64
20848 Show whether AArch64 debugging messages are displayed.
20853 @subsection x86 Architecture-specific Issues
20856 @item set struct-convention @var{mode}
20857 @kindex set struct-convention
20858 @cindex struct return convention
20859 @cindex struct/union returned in registers
20860 Set the convention used by the inferior to return @code{struct}s and
20861 @code{union}s from functions to @var{mode}. Possible values of
20862 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20863 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20864 are returned on the stack, while @code{"reg"} means that a
20865 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20866 be returned in a register.
20868 @item show struct-convention
20869 @kindex show struct-convention
20870 Show the current setting of the convention to return @code{struct}s
20877 See the following section.
20880 @subsection @acronym{MIPS}
20882 @cindex stack on Alpha
20883 @cindex stack on @acronym{MIPS}
20884 @cindex Alpha stack
20885 @cindex @acronym{MIPS} stack
20886 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20887 sometimes requires @value{GDBN} to search backward in the object code to
20888 find the beginning of a function.
20890 @cindex response time, @acronym{MIPS} debugging
20891 To improve response time (especially for embedded applications, where
20892 @value{GDBN} may be restricted to a slow serial line for this search)
20893 you may want to limit the size of this search, using one of these
20897 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20898 @item set heuristic-fence-post @var{limit}
20899 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20900 search for the beginning of a function. A value of @var{0} (the
20901 default) means there is no limit. However, except for @var{0}, the
20902 larger the limit the more bytes @code{heuristic-fence-post} must search
20903 and therefore the longer it takes to run. You should only need to use
20904 this command when debugging a stripped executable.
20906 @item show heuristic-fence-post
20907 Display the current limit.
20911 These commands are available @emph{only} when @value{GDBN} is configured
20912 for debugging programs on Alpha or @acronym{MIPS} processors.
20914 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20918 @item set mips abi @var{arg}
20919 @kindex set mips abi
20920 @cindex set ABI for @acronym{MIPS}
20921 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20922 values of @var{arg} are:
20926 The default ABI associated with the current binary (this is the
20936 @item show mips abi
20937 @kindex show mips abi
20938 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20940 @item set mips compression @var{arg}
20941 @kindex set mips compression
20942 @cindex code compression, @acronym{MIPS}
20943 Tell @value{GDBN} which @acronym{MIPS} compressed
20944 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20945 inferior. @value{GDBN} uses this for code disassembly and other
20946 internal interpretation purposes. This setting is only referred to
20947 when no executable has been associated with the debugging session or
20948 the executable does not provide information about the encoding it uses.
20949 Otherwise this setting is automatically updated from information
20950 provided by the executable.
20952 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20953 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20954 executables containing @acronym{MIPS16} code frequently are not
20955 identified as such.
20957 This setting is ``sticky''; that is, it retains its value across
20958 debugging sessions until reset either explicitly with this command or
20959 implicitly from an executable.
20961 The compiler and/or assembler typically add symbol table annotations to
20962 identify functions compiled for the @acronym{MIPS16} or
20963 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20964 are present, @value{GDBN} uses them in preference to the global
20965 compressed @acronym{ISA} encoding setting.
20967 @item show mips compression
20968 @kindex show mips compression
20969 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20970 @value{GDBN} to debug the inferior.
20973 @itemx show mipsfpu
20974 @xref{MIPS Embedded, set mipsfpu}.
20976 @item set mips mask-address @var{arg}
20977 @kindex set mips mask-address
20978 @cindex @acronym{MIPS} addresses, masking
20979 This command determines whether the most-significant 32 bits of 64-bit
20980 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20981 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20982 setting, which lets @value{GDBN} determine the correct value.
20984 @item show mips mask-address
20985 @kindex show mips mask-address
20986 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20989 @item set remote-mips64-transfers-32bit-regs
20990 @kindex set remote-mips64-transfers-32bit-regs
20991 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20992 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20993 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20994 and 64 bits for other registers, set this option to @samp{on}.
20996 @item show remote-mips64-transfers-32bit-regs
20997 @kindex show remote-mips64-transfers-32bit-regs
20998 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21000 @item set debug mips
21001 @kindex set debug mips
21002 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21003 target code in @value{GDBN}.
21005 @item show debug mips
21006 @kindex show debug mips
21007 Show the current setting of @acronym{MIPS} debugging messages.
21013 @cindex HPPA support
21015 When @value{GDBN} is debugging the HP PA architecture, it provides the
21016 following special commands:
21019 @item set debug hppa
21020 @kindex set debug hppa
21021 This command determines whether HPPA architecture-specific debugging
21022 messages are to be displayed.
21024 @item show debug hppa
21025 Show whether HPPA debugging messages are displayed.
21027 @item maint print unwind @var{address}
21028 @kindex maint print unwind@r{, HPPA}
21029 This command displays the contents of the unwind table entry at the
21030 given @var{address}.
21036 @subsection Cell Broadband Engine SPU architecture
21037 @cindex Cell Broadband Engine
21040 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21041 it provides the following special commands:
21044 @item info spu event
21046 Display SPU event facility status. Shows current event mask
21047 and pending event status.
21049 @item info spu signal
21050 Display SPU signal notification facility status. Shows pending
21051 signal-control word and signal notification mode of both signal
21052 notification channels.
21054 @item info spu mailbox
21055 Display SPU mailbox facility status. Shows all pending entries,
21056 in order of processing, in each of the SPU Write Outbound,
21057 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21060 Display MFC DMA status. Shows all pending commands in the MFC
21061 DMA queue. For each entry, opcode, tag, class IDs, effective
21062 and local store addresses and transfer size are shown.
21064 @item info spu proxydma
21065 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21066 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21067 and local store addresses and transfer size are shown.
21071 When @value{GDBN} is debugging a combined PowerPC/SPU application
21072 on the Cell Broadband Engine, it provides in addition the following
21076 @item set spu stop-on-load @var{arg}
21078 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21079 will give control to the user when a new SPE thread enters its @code{main}
21080 function. The default is @code{off}.
21082 @item show spu stop-on-load
21084 Show whether to stop for new SPE threads.
21086 @item set spu auto-flush-cache @var{arg}
21087 Set whether to automatically flush the software-managed cache. When set to
21088 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21089 cache to be flushed whenever SPE execution stops. This provides a consistent
21090 view of PowerPC memory that is accessed via the cache. If an application
21091 does not use the software-managed cache, this option has no effect.
21093 @item show spu auto-flush-cache
21094 Show whether to automatically flush the software-managed cache.
21099 @subsection PowerPC
21100 @cindex PowerPC architecture
21102 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21103 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21104 numbers stored in the floating point registers. These values must be stored
21105 in two consecutive registers, always starting at an even register like
21106 @code{f0} or @code{f2}.
21108 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21109 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21110 @code{f2} and @code{f3} for @code{$dl1} and so on.
21112 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21113 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21116 @node Controlling GDB
21117 @chapter Controlling @value{GDBN}
21119 You can alter the way @value{GDBN} interacts with you by using the
21120 @code{set} command. For commands controlling how @value{GDBN} displays
21121 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21126 * Editing:: Command editing
21127 * Command History:: Command history
21128 * Screen Size:: Screen size
21129 * Numbers:: Numbers
21130 * ABI:: Configuring the current ABI
21131 * Auto-loading:: Automatically loading associated files
21132 * Messages/Warnings:: Optional warnings and messages
21133 * Debugging Output:: Optional messages about internal happenings
21134 * Other Misc Settings:: Other Miscellaneous Settings
21142 @value{GDBN} indicates its readiness to read a command by printing a string
21143 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21144 can change the prompt string with the @code{set prompt} command. For
21145 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21146 the prompt in one of the @value{GDBN} sessions so that you can always tell
21147 which one you are talking to.
21149 @emph{Note:} @code{set prompt} does not add a space for you after the
21150 prompt you set. This allows you to set a prompt which ends in a space
21151 or a prompt that does not.
21155 @item set prompt @var{newprompt}
21156 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21158 @kindex show prompt
21160 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21163 Versions of @value{GDBN} that ship with Python scripting enabled have
21164 prompt extensions. The commands for interacting with these extensions
21168 @kindex set extended-prompt
21169 @item set extended-prompt @var{prompt}
21170 Set an extended prompt that allows for substitutions.
21171 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21172 substitution. Any escape sequences specified as part of the prompt
21173 string are replaced with the corresponding strings each time the prompt
21179 set extended-prompt Current working directory: \w (gdb)
21182 Note that when an extended-prompt is set, it takes control of the
21183 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21185 @kindex show extended-prompt
21186 @item show extended-prompt
21187 Prints the extended prompt. Any escape sequences specified as part of
21188 the prompt string with @code{set extended-prompt}, are replaced with the
21189 corresponding strings each time the prompt is displayed.
21193 @section Command Editing
21195 @cindex command line editing
21197 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21198 @sc{gnu} library provides consistent behavior for programs which provide a
21199 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21200 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21201 substitution, and a storage and recall of command history across
21202 debugging sessions.
21204 You may control the behavior of command line editing in @value{GDBN} with the
21205 command @code{set}.
21208 @kindex set editing
21211 @itemx set editing on
21212 Enable command line editing (enabled by default).
21214 @item set editing off
21215 Disable command line editing.
21217 @kindex show editing
21219 Show whether command line editing is enabled.
21222 @ifset SYSTEM_READLINE
21223 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21225 @ifclear SYSTEM_READLINE
21226 @xref{Command Line Editing},
21228 for more details about the Readline
21229 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21230 encouraged to read that chapter.
21232 @node Command History
21233 @section Command History
21234 @cindex command history
21236 @value{GDBN} can keep track of the commands you type during your
21237 debugging sessions, so that you can be certain of precisely what
21238 happened. Use these commands to manage the @value{GDBN} command
21241 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21242 package, to provide the history facility.
21243 @ifset SYSTEM_READLINE
21244 @xref{Using History Interactively, , , history, GNU History Library},
21246 @ifclear SYSTEM_READLINE
21247 @xref{Using History Interactively},
21249 for the detailed description of the History library.
21251 To issue a command to @value{GDBN} without affecting certain aspects of
21252 the state which is seen by users, prefix it with @samp{server }
21253 (@pxref{Server Prefix}). This
21254 means that this command will not affect the command history, nor will it
21255 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21256 pressed on a line by itself.
21258 @cindex @code{server}, command prefix
21259 The server prefix does not affect the recording of values into the value
21260 history; to print a value without recording it into the value history,
21261 use the @code{output} command instead of the @code{print} command.
21263 Here is the description of @value{GDBN} commands related to command
21267 @cindex history substitution
21268 @cindex history file
21269 @kindex set history filename
21270 @cindex @env{GDBHISTFILE}, environment variable
21271 @item set history filename @var{fname}
21272 Set the name of the @value{GDBN} command history file to @var{fname}.
21273 This is the file where @value{GDBN} reads an initial command history
21274 list, and where it writes the command history from this session when it
21275 exits. You can access this list through history expansion or through
21276 the history command editing characters listed below. This file defaults
21277 to the value of the environment variable @code{GDBHISTFILE}, or to
21278 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21281 @cindex save command history
21282 @kindex set history save
21283 @item set history save
21284 @itemx set history save on
21285 Record command history in a file, whose name may be specified with the
21286 @code{set history filename} command. By default, this option is disabled.
21288 @item set history save off
21289 Stop recording command history in a file.
21291 @cindex history size
21292 @kindex set history size
21293 @cindex @env{HISTSIZE}, environment variable
21294 @item set history size @var{size}
21295 @itemx set history size unlimited
21296 Set the number of commands which @value{GDBN} keeps in its history list.
21297 This defaults to the value of the environment variable
21298 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21299 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21300 history list is unlimited.
21303 History expansion assigns special meaning to the character @kbd{!}.
21304 @ifset SYSTEM_READLINE
21305 @xref{Event Designators, , , history, GNU History Library},
21307 @ifclear SYSTEM_READLINE
21308 @xref{Event Designators},
21312 @cindex history expansion, turn on/off
21313 Since @kbd{!} is also the logical not operator in C, history expansion
21314 is off by default. If you decide to enable history expansion with the
21315 @code{set history expansion on} command, you may sometimes need to
21316 follow @kbd{!} (when it is used as logical not, in an expression) with
21317 a space or a tab to prevent it from being expanded. The readline
21318 history facilities do not attempt substitution on the strings
21319 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21321 The commands to control history expansion are:
21324 @item set history expansion on
21325 @itemx set history expansion
21326 @kindex set history expansion
21327 Enable history expansion. History expansion is off by default.
21329 @item set history expansion off
21330 Disable history expansion.
21333 @kindex show history
21335 @itemx show history filename
21336 @itemx show history save
21337 @itemx show history size
21338 @itemx show history expansion
21339 These commands display the state of the @value{GDBN} history parameters.
21340 @code{show history} by itself displays all four states.
21345 @kindex show commands
21346 @cindex show last commands
21347 @cindex display command history
21348 @item show commands
21349 Display the last ten commands in the command history.
21351 @item show commands @var{n}
21352 Print ten commands centered on command number @var{n}.
21354 @item show commands +
21355 Print ten commands just after the commands last printed.
21359 @section Screen Size
21360 @cindex size of screen
21361 @cindex pauses in output
21363 Certain commands to @value{GDBN} may produce large amounts of
21364 information output to the screen. To help you read all of it,
21365 @value{GDBN} pauses and asks you for input at the end of each page of
21366 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21367 to discard the remaining output. Also, the screen width setting
21368 determines when to wrap lines of output. Depending on what is being
21369 printed, @value{GDBN} tries to break the line at a readable place,
21370 rather than simply letting it overflow onto the following line.
21372 Normally @value{GDBN} knows the size of the screen from the terminal
21373 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21374 together with the value of the @code{TERM} environment variable and the
21375 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21376 you can override it with the @code{set height} and @code{set
21383 @kindex show height
21384 @item set height @var{lpp}
21385 @itemx set height unlimited
21387 @itemx set width @var{cpl}
21388 @itemx set width unlimited
21390 These @code{set} commands specify a screen height of @var{lpp} lines and
21391 a screen width of @var{cpl} characters. The associated @code{show}
21392 commands display the current settings.
21394 If you specify a height of either @code{unlimited} or zero lines,
21395 @value{GDBN} does not pause during output no matter how long the
21396 output is. This is useful if output is to a file or to an editor
21399 Likewise, you can specify @samp{set width unlimited} or @samp{set
21400 width 0} to prevent @value{GDBN} from wrapping its output.
21402 @item set pagination on
21403 @itemx set pagination off
21404 @kindex set pagination
21405 Turn the output pagination on or off; the default is on. Turning
21406 pagination off is the alternative to @code{set height unlimited}. Note that
21407 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21408 Options, -batch}) also automatically disables pagination.
21410 @item show pagination
21411 @kindex show pagination
21412 Show the current pagination mode.
21417 @cindex number representation
21418 @cindex entering numbers
21420 You can always enter numbers in octal, decimal, or hexadecimal in
21421 @value{GDBN} by the usual conventions: octal numbers begin with
21422 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21423 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21424 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21425 10; likewise, the default display for numbers---when no particular
21426 format is specified---is base 10. You can change the default base for
21427 both input and output with the commands described below.
21430 @kindex set input-radix
21431 @item set input-radix @var{base}
21432 Set the default base for numeric input. Supported choices
21433 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21434 specified either unambiguously or using the current input radix; for
21438 set input-radix 012
21439 set input-radix 10.
21440 set input-radix 0xa
21444 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21445 leaves the input radix unchanged, no matter what it was, since
21446 @samp{10}, being without any leading or trailing signs of its base, is
21447 interpreted in the current radix. Thus, if the current radix is 16,
21448 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21451 @kindex set output-radix
21452 @item set output-radix @var{base}
21453 Set the default base for numeric display. Supported choices
21454 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21455 specified either unambiguously or using the current input radix.
21457 @kindex show input-radix
21458 @item show input-radix
21459 Display the current default base for numeric input.
21461 @kindex show output-radix
21462 @item show output-radix
21463 Display the current default base for numeric display.
21465 @item set radix @r{[}@var{base}@r{]}
21469 These commands set and show the default base for both input and output
21470 of numbers. @code{set radix} sets the radix of input and output to
21471 the same base; without an argument, it resets the radix back to its
21472 default value of 10.
21477 @section Configuring the Current ABI
21479 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21480 application automatically. However, sometimes you need to override its
21481 conclusions. Use these commands to manage @value{GDBN}'s view of the
21487 @cindex Newlib OS ABI and its influence on the longjmp handling
21489 One @value{GDBN} configuration can debug binaries for multiple operating
21490 system targets, either via remote debugging or native emulation.
21491 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21492 but you can override its conclusion using the @code{set osabi} command.
21493 One example where this is useful is in debugging of binaries which use
21494 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21495 not have the same identifying marks that the standard C library for your
21498 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21499 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21500 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21501 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21505 Show the OS ABI currently in use.
21508 With no argument, show the list of registered available OS ABI's.
21510 @item set osabi @var{abi}
21511 Set the current OS ABI to @var{abi}.
21514 @cindex float promotion
21516 Generally, the way that an argument of type @code{float} is passed to a
21517 function depends on whether the function is prototyped. For a prototyped
21518 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21519 according to the architecture's convention for @code{float}. For unprototyped
21520 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21521 @code{double} and then passed.
21523 Unfortunately, some forms of debug information do not reliably indicate whether
21524 a function is prototyped. If @value{GDBN} calls a function that is not marked
21525 as prototyped, it consults @kbd{set coerce-float-to-double}.
21528 @kindex set coerce-float-to-double
21529 @item set coerce-float-to-double
21530 @itemx set coerce-float-to-double on
21531 Arguments of type @code{float} will be promoted to @code{double} when passed
21532 to an unprototyped function. This is the default setting.
21534 @item set coerce-float-to-double off
21535 Arguments of type @code{float} will be passed directly to unprototyped
21538 @kindex show coerce-float-to-double
21539 @item show coerce-float-to-double
21540 Show the current setting of promoting @code{float} to @code{double}.
21544 @kindex show cp-abi
21545 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21546 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21547 used to build your application. @value{GDBN} only fully supports
21548 programs with a single C@t{++} ABI; if your program contains code using
21549 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21550 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21551 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21552 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21553 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21554 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21559 Show the C@t{++} ABI currently in use.
21562 With no argument, show the list of supported C@t{++} ABI's.
21564 @item set cp-abi @var{abi}
21565 @itemx set cp-abi auto
21566 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21570 @section Automatically loading associated files
21571 @cindex auto-loading
21573 @value{GDBN} sometimes reads files with commands and settings automatically,
21574 without being explicitly told so by the user. We call this feature
21575 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21576 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21577 results or introduce security risks (e.g., if the file comes from untrusted
21580 Note that loading of these associated files (including the local @file{.gdbinit}
21581 file) requires accordingly configured @code{auto-load safe-path}
21582 (@pxref{Auto-loading safe path}).
21584 For these reasons, @value{GDBN} includes commands and options to let you
21585 control when to auto-load files and which files should be auto-loaded.
21588 @anchor{set auto-load off}
21589 @kindex set auto-load off
21590 @item set auto-load off
21591 Globally disable loading of all auto-loaded files.
21592 You may want to use this command with the @samp{-iex} option
21593 (@pxref{Option -init-eval-command}) such as:
21595 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21598 Be aware that system init file (@pxref{System-wide configuration})
21599 and init files from your home directory (@pxref{Home Directory Init File})
21600 still get read (as they come from generally trusted directories).
21601 To prevent @value{GDBN} from auto-loading even those init files, use the
21602 @option{-nx} option (@pxref{Mode Options}), in addition to
21603 @code{set auto-load no}.
21605 @anchor{show auto-load}
21606 @kindex show auto-load
21607 @item show auto-load
21608 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21612 (gdb) show auto-load
21613 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21614 libthread-db: Auto-loading of inferior specific libthread_db is on.
21615 local-gdbinit: Auto-loading of .gdbinit script from current directory
21617 python-scripts: Auto-loading of Python scripts is on.
21618 safe-path: List of directories from which it is safe to auto-load files
21619 is $debugdir:$datadir/auto-load.
21620 scripts-directory: List of directories from which to load auto-loaded scripts
21621 is $debugdir:$datadir/auto-load.
21624 @anchor{info auto-load}
21625 @kindex info auto-load
21626 @item info auto-load
21627 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21631 (gdb) info auto-load
21634 Yes /home/user/gdb/gdb-gdb.gdb
21635 libthread-db: No auto-loaded libthread-db.
21636 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21640 Yes /home/user/gdb/gdb-gdb.py
21644 These are various kinds of files @value{GDBN} can automatically load:
21648 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21650 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21652 @xref{dotdebug_gdb_scripts section},
21653 controlled by @ref{set auto-load python-scripts}.
21655 @xref{Init File in the Current Directory},
21656 controlled by @ref{set auto-load local-gdbinit}.
21658 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21661 These are @value{GDBN} control commands for the auto-loading:
21663 @multitable @columnfractions .5 .5
21664 @item @xref{set auto-load off}.
21665 @tab Disable auto-loading globally.
21666 @item @xref{show auto-load}.
21667 @tab Show setting of all kinds of files.
21668 @item @xref{info auto-load}.
21669 @tab Show state of all kinds of files.
21670 @item @xref{set auto-load gdb-scripts}.
21671 @tab Control for @value{GDBN} command scripts.
21672 @item @xref{show auto-load gdb-scripts}.
21673 @tab Show setting of @value{GDBN} command scripts.
21674 @item @xref{info auto-load gdb-scripts}.
21675 @tab Show state of @value{GDBN} command scripts.
21676 @item @xref{set auto-load python-scripts}.
21677 @tab Control for @value{GDBN} Python scripts.
21678 @item @xref{show auto-load python-scripts}.
21679 @tab Show setting of @value{GDBN} Python scripts.
21680 @item @xref{info auto-load python-scripts}.
21681 @tab Show state of @value{GDBN} Python scripts.
21682 @item @xref{set auto-load scripts-directory}.
21683 @tab Control for @value{GDBN} auto-loaded scripts location.
21684 @item @xref{show auto-load scripts-directory}.
21685 @tab Show @value{GDBN} auto-loaded scripts location.
21686 @item @xref{set auto-load local-gdbinit}.
21687 @tab Control for init file in the current directory.
21688 @item @xref{show auto-load local-gdbinit}.
21689 @tab Show setting of init file in the current directory.
21690 @item @xref{info auto-load local-gdbinit}.
21691 @tab Show state of init file in the current directory.
21692 @item @xref{set auto-load libthread-db}.
21693 @tab Control for thread debugging library.
21694 @item @xref{show auto-load libthread-db}.
21695 @tab Show setting of thread debugging library.
21696 @item @xref{info auto-load libthread-db}.
21697 @tab Show state of thread debugging library.
21698 @item @xref{set auto-load safe-path}.
21699 @tab Control directories trusted for automatic loading.
21700 @item @xref{show auto-load safe-path}.
21701 @tab Show directories trusted for automatic loading.
21702 @item @xref{add-auto-load-safe-path}.
21703 @tab Add directory trusted for automatic loading.
21707 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21708 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21709 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21710 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21711 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21712 @xref{Python Auto-loading}.
21715 @node Init File in the Current Directory
21716 @subsection Automatically loading init file in the current directory
21717 @cindex auto-loading init file in the current directory
21719 By default, @value{GDBN} reads and executes the canned sequences of commands
21720 from init file (if any) in the current working directory,
21721 see @ref{Init File in the Current Directory during Startup}.
21723 Note that loading of this local @file{.gdbinit} file also requires accordingly
21724 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21727 @anchor{set auto-load local-gdbinit}
21728 @kindex set auto-load local-gdbinit
21729 @item set auto-load local-gdbinit [on|off]
21730 Enable or disable the auto-loading of canned sequences of commands
21731 (@pxref{Sequences}) found in init file in the current directory.
21733 @anchor{show auto-load local-gdbinit}
21734 @kindex show auto-load local-gdbinit
21735 @item show auto-load local-gdbinit
21736 Show whether auto-loading of canned sequences of commands from init file in the
21737 current directory is enabled or disabled.
21739 @anchor{info auto-load local-gdbinit}
21740 @kindex info auto-load local-gdbinit
21741 @item info auto-load local-gdbinit
21742 Print whether canned sequences of commands from init file in the
21743 current directory have been auto-loaded.
21746 @node libthread_db.so.1 file
21747 @subsection Automatically loading thread debugging library
21748 @cindex auto-loading libthread_db.so.1
21750 This feature is currently present only on @sc{gnu}/Linux native hosts.
21752 @value{GDBN} reads in some cases thread debugging library from places specific
21753 to the inferior (@pxref{set libthread-db-search-path}).
21755 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21756 without checking this @samp{set auto-load libthread-db} switch as system
21757 libraries have to be trusted in general. In all other cases of
21758 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21759 auto-load libthread-db} is enabled before trying to open such thread debugging
21762 Note that loading of this debugging library also requires accordingly configured
21763 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21766 @anchor{set auto-load libthread-db}
21767 @kindex set auto-load libthread-db
21768 @item set auto-load libthread-db [on|off]
21769 Enable or disable the auto-loading of inferior specific thread debugging library.
21771 @anchor{show auto-load libthread-db}
21772 @kindex show auto-load libthread-db
21773 @item show auto-load libthread-db
21774 Show whether auto-loading of inferior specific thread debugging library is
21775 enabled or disabled.
21777 @anchor{info auto-load libthread-db}
21778 @kindex info auto-load libthread-db
21779 @item info auto-load libthread-db
21780 Print the list of all loaded inferior specific thread debugging libraries and
21781 for each such library print list of inferior @var{pid}s using it.
21784 @node objfile-gdb.gdb file
21785 @subsection The @file{@var{objfile}-gdb.gdb} file
21786 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21788 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21789 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21790 auto-load gdb-scripts} is set to @samp{on}.
21792 Note that loading of this script file also requires accordingly configured
21793 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21795 For more background refer to the similar Python scripts auto-loading
21796 description (@pxref{objfile-gdb.py file}).
21799 @anchor{set auto-load gdb-scripts}
21800 @kindex set auto-load gdb-scripts
21801 @item set auto-load gdb-scripts [on|off]
21802 Enable or disable the auto-loading of canned sequences of commands scripts.
21804 @anchor{show auto-load gdb-scripts}
21805 @kindex show auto-load gdb-scripts
21806 @item show auto-load gdb-scripts
21807 Show whether auto-loading of canned sequences of commands scripts is enabled or
21810 @anchor{info auto-load gdb-scripts}
21811 @kindex info auto-load gdb-scripts
21812 @cindex print list of auto-loaded canned sequences of commands scripts
21813 @item info auto-load gdb-scripts [@var{regexp}]
21814 Print the list of all canned sequences of commands scripts that @value{GDBN}
21818 If @var{regexp} is supplied only canned sequences of commands scripts with
21819 matching names are printed.
21821 @node Auto-loading safe path
21822 @subsection Security restriction for auto-loading
21823 @cindex auto-loading safe-path
21825 As the files of inferior can come from untrusted source (such as submitted by
21826 an application user) @value{GDBN} does not always load any files automatically.
21827 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21828 directories trusted for loading files not explicitly requested by user.
21829 Each directory can also be a shell wildcard pattern.
21831 If the path is not set properly you will see a warning and the file will not
21836 Reading symbols from /home/user/gdb/gdb...done.
21837 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21838 declined by your `auto-load safe-path' set
21839 to "$debugdir:$datadir/auto-load".
21840 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21841 declined by your `auto-load safe-path' set
21842 to "$debugdir:$datadir/auto-load".
21846 To instruct @value{GDBN} to go ahead and use the init files anyway,
21847 invoke @value{GDBN} like this:
21850 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
21853 The list of trusted directories is controlled by the following commands:
21856 @anchor{set auto-load safe-path}
21857 @kindex set auto-load safe-path
21858 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21859 Set the list of directories (and their subdirectories) trusted for automatic
21860 loading and execution of scripts. You can also enter a specific trusted file.
21861 Each directory can also be a shell wildcard pattern; wildcards do not match
21862 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21863 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21864 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21865 its default value as specified during @value{GDBN} compilation.
21867 The list of directories uses path separator (@samp{:} on GNU and Unix
21868 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21869 to the @env{PATH} environment variable.
21871 @anchor{show auto-load safe-path}
21872 @kindex show auto-load safe-path
21873 @item show auto-load safe-path
21874 Show the list of directories trusted for automatic loading and execution of
21877 @anchor{add-auto-load-safe-path}
21878 @kindex add-auto-load-safe-path
21879 @item add-auto-load-safe-path
21880 Add an entry (or list of entries) the list of directories trusted for automatic
21881 loading and execution of scripts. Multiple entries may be delimited by the
21882 host platform path separator in use.
21885 This variable defaults to what @code{--with-auto-load-dir} has been configured
21886 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21887 substitution applies the same as for @ref{set auto-load scripts-directory}.
21888 The default @code{set auto-load safe-path} value can be also overriden by
21889 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21891 Setting this variable to @file{/} disables this security protection,
21892 corresponding @value{GDBN} configuration option is
21893 @option{--without-auto-load-safe-path}.
21894 This variable is supposed to be set to the system directories writable by the
21895 system superuser only. Users can add their source directories in init files in
21896 their home directories (@pxref{Home Directory Init File}). See also deprecated
21897 init file in the current directory
21898 (@pxref{Init File in the Current Directory during Startup}).
21900 To force @value{GDBN} to load the files it declined to load in the previous
21901 example, you could use one of the following ways:
21904 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21905 Specify this trusted directory (or a file) as additional component of the list.
21906 You have to specify also any existing directories displayed by
21907 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21909 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21910 Specify this directory as in the previous case but just for a single
21911 @value{GDBN} session.
21913 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21914 Disable auto-loading safety for a single @value{GDBN} session.
21915 This assumes all the files you debug during this @value{GDBN} session will come
21916 from trusted sources.
21918 @item @kbd{./configure --without-auto-load-safe-path}
21919 During compilation of @value{GDBN} you may disable any auto-loading safety.
21920 This assumes all the files you will ever debug with this @value{GDBN} come from
21924 On the other hand you can also explicitly forbid automatic files loading which
21925 also suppresses any such warning messages:
21928 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21929 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21931 @item @file{~/.gdbinit}: @samp{set auto-load no}
21932 Disable auto-loading globally for the user
21933 (@pxref{Home Directory Init File}). While it is improbable, you could also
21934 use system init file instead (@pxref{System-wide configuration}).
21937 This setting applies to the file names as entered by user. If no entry matches
21938 @value{GDBN} tries as a last resort to also resolve all the file names into
21939 their canonical form (typically resolving symbolic links) and compare the
21940 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21941 own before starting the comparison so a canonical form of directories is
21942 recommended to be entered.
21944 @node Auto-loading verbose mode
21945 @subsection Displaying files tried for auto-load
21946 @cindex auto-loading verbose mode
21948 For better visibility of all the file locations where you can place scripts to
21949 be auto-loaded with inferior --- or to protect yourself against accidental
21950 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21951 all the files attempted to be loaded. Both existing and non-existing files may
21954 For example the list of directories from which it is safe to auto-load files
21955 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21956 may not be too obvious while setting it up.
21959 (gdb) set debug auto-load on
21960 (gdb) file ~/src/t/true
21961 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21962 for objfile "/tmp/true".
21963 auto-load: Updating directories of "/usr:/opt".
21964 auto-load: Using directory "/usr".
21965 auto-load: Using directory "/opt".
21966 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21967 by your `auto-load safe-path' set to "/usr:/opt".
21971 @anchor{set debug auto-load}
21972 @kindex set debug auto-load
21973 @item set debug auto-load [on|off]
21974 Set whether to print the filenames attempted to be auto-loaded.
21976 @anchor{show debug auto-load}
21977 @kindex show debug auto-load
21978 @item show debug auto-load
21979 Show whether printing of the filenames attempted to be auto-loaded is turned
21983 @node Messages/Warnings
21984 @section Optional Warnings and Messages
21986 @cindex verbose operation
21987 @cindex optional warnings
21988 By default, @value{GDBN} is silent about its inner workings. If you are
21989 running on a slow machine, you may want to use the @code{set verbose}
21990 command. This makes @value{GDBN} tell you when it does a lengthy
21991 internal operation, so you will not think it has crashed.
21993 Currently, the messages controlled by @code{set verbose} are those
21994 which announce that the symbol table for a source file is being read;
21995 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21998 @kindex set verbose
21999 @item set verbose on
22000 Enables @value{GDBN} output of certain informational messages.
22002 @item set verbose off
22003 Disables @value{GDBN} output of certain informational messages.
22005 @kindex show verbose
22007 Displays whether @code{set verbose} is on or off.
22010 By default, if @value{GDBN} encounters bugs in the symbol table of an
22011 object file, it is silent; but if you are debugging a compiler, you may
22012 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22017 @kindex set complaints
22018 @item set complaints @var{limit}
22019 Permits @value{GDBN} to output @var{limit} complaints about each type of
22020 unusual symbols before becoming silent about the problem. Set
22021 @var{limit} to zero to suppress all complaints; set it to a large number
22022 to prevent complaints from being suppressed.
22024 @kindex show complaints
22025 @item show complaints
22026 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22030 @anchor{confirmation requests}
22031 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22032 lot of stupid questions to confirm certain commands. For example, if
22033 you try to run a program which is already running:
22037 The program being debugged has been started already.
22038 Start it from the beginning? (y or n)
22041 If you are willing to unflinchingly face the consequences of your own
22042 commands, you can disable this ``feature'':
22046 @kindex set confirm
22048 @cindex confirmation
22049 @cindex stupid questions
22050 @item set confirm off
22051 Disables confirmation requests. Note that running @value{GDBN} with
22052 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22053 automatically disables confirmation requests.
22055 @item set confirm on
22056 Enables confirmation requests (the default).
22058 @kindex show confirm
22060 Displays state of confirmation requests.
22064 @cindex command tracing
22065 If you need to debug user-defined commands or sourced files you may find it
22066 useful to enable @dfn{command tracing}. In this mode each command will be
22067 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22068 quantity denoting the call depth of each command.
22071 @kindex set trace-commands
22072 @cindex command scripts, debugging
22073 @item set trace-commands on
22074 Enable command tracing.
22075 @item set trace-commands off
22076 Disable command tracing.
22077 @item show trace-commands
22078 Display the current state of command tracing.
22081 @node Debugging Output
22082 @section Optional Messages about Internal Happenings
22083 @cindex optional debugging messages
22085 @value{GDBN} has commands that enable optional debugging messages from
22086 various @value{GDBN} subsystems; normally these commands are of
22087 interest to @value{GDBN} maintainers, or when reporting a bug. This
22088 section documents those commands.
22091 @kindex set exec-done-display
22092 @item set exec-done-display
22093 Turns on or off the notification of asynchronous commands'
22094 completion. When on, @value{GDBN} will print a message when an
22095 asynchronous command finishes its execution. The default is off.
22096 @kindex show exec-done-display
22097 @item show exec-done-display
22098 Displays the current setting of asynchronous command completion
22101 @cindex ARM AArch64
22102 @item set debug aarch64
22103 Turns on or off display of debugging messages related to ARM AArch64.
22104 The default is off.
22106 @item show debug aarch64
22107 Displays the current state of displaying debugging messages related to
22109 @cindex gdbarch debugging info
22110 @cindex architecture debugging info
22111 @item set debug arch
22112 Turns on or off display of gdbarch debugging info. The default is off
22113 @item show debug arch
22114 Displays the current state of displaying gdbarch debugging info.
22115 @item set debug aix-thread
22116 @cindex AIX threads
22117 Display debugging messages about inner workings of the AIX thread
22119 @item show debug aix-thread
22120 Show the current state of AIX thread debugging info display.
22121 @item set debug check-physname
22123 Check the results of the ``physname'' computation. When reading DWARF
22124 debugging information for C@t{++}, @value{GDBN} attempts to compute
22125 each entity's name. @value{GDBN} can do this computation in two
22126 different ways, depending on exactly what information is present.
22127 When enabled, this setting causes @value{GDBN} to compute the names
22128 both ways and display any discrepancies.
22129 @item show debug check-physname
22130 Show the current state of ``physname'' checking.
22131 @item set debug coff-pe-read
22132 @cindex COFF/PE exported symbols
22133 Control display of debugging messages related to reading of COFF/PE
22134 exported symbols. The default is off.
22135 @item show debug coff-pe-read
22136 Displays the current state of displaying debugging messages related to
22137 reading of COFF/PE exported symbols.
22138 @item set debug dwarf2-die
22139 @cindex DWARF2 DIEs
22140 Dump DWARF2 DIEs after they are read in.
22141 The value is the number of nesting levels to print.
22142 A value of zero turns off the display.
22143 @item show debug dwarf2-die
22144 Show the current state of DWARF2 DIE debugging.
22145 @item set debug dwarf2-read
22146 @cindex DWARF2 Reading
22147 Turns on or off display of debugging messages related to reading
22148 DWARF debug info. The default is off.
22149 @item show debug dwarf2-read
22150 Show the current state of DWARF2 reader debugging.
22151 @item set debug displaced
22152 @cindex displaced stepping debugging info
22153 Turns on or off display of @value{GDBN} debugging info for the
22154 displaced stepping support. The default is off.
22155 @item show debug displaced
22156 Displays the current state of displaying @value{GDBN} debugging info
22157 related to displaced stepping.
22158 @item set debug event
22159 @cindex event debugging info
22160 Turns on or off display of @value{GDBN} event debugging info. The
22162 @item show debug event
22163 Displays the current state of displaying @value{GDBN} event debugging
22165 @item set debug expression
22166 @cindex expression debugging info
22167 Turns on or off display of debugging info about @value{GDBN}
22168 expression parsing. The default is off.
22169 @item show debug expression
22170 Displays the current state of displaying debugging info about
22171 @value{GDBN} expression parsing.
22172 @item set debug frame
22173 @cindex frame debugging info
22174 Turns on or off display of @value{GDBN} frame debugging info. The
22176 @item show debug frame
22177 Displays the current state of displaying @value{GDBN} frame debugging
22179 @item set debug gnu-nat
22180 @cindex @sc{gnu}/Hurd debug messages
22181 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22182 @item show debug gnu-nat
22183 Show the current state of @sc{gnu}/Hurd debugging messages.
22184 @item set debug infrun
22185 @cindex inferior debugging info
22186 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22187 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22188 for implementing operations such as single-stepping the inferior.
22189 @item show debug infrun
22190 Displays the current state of @value{GDBN} inferior debugging.
22191 @item set debug jit
22192 @cindex just-in-time compilation, debugging messages
22193 Turns on or off debugging messages from JIT debug support.
22194 @item show debug jit
22195 Displays the current state of @value{GDBN} JIT debugging.
22196 @item set debug lin-lwp
22197 @cindex @sc{gnu}/Linux LWP debug messages
22198 @cindex Linux lightweight processes
22199 Turns on or off debugging messages from the Linux LWP debug support.
22200 @item show debug lin-lwp
22201 Show the current state of Linux LWP debugging messages.
22202 @item set debug mach-o
22203 @cindex Mach-O symbols processing
22204 Control display of debugging messages related to Mach-O symbols
22205 processing. The default is off.
22206 @item show debug mach-o
22207 Displays the current state of displaying debugging messages related to
22208 reading of COFF/PE exported symbols.
22209 @item set debug notification
22210 @cindex remote async notification debugging info
22211 Turns on or off debugging messages about remote async notification.
22212 The default is off.
22213 @item show debug notification
22214 Displays the current state of remote async notification debugging messages.
22215 @item set debug observer
22216 @cindex observer debugging info
22217 Turns on or off display of @value{GDBN} observer debugging. This
22218 includes info such as the notification of observable events.
22219 @item show debug observer
22220 Displays the current state of observer debugging.
22221 @item set debug overload
22222 @cindex C@t{++} overload debugging info
22223 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22224 info. This includes info such as ranking of functions, etc. The default
22226 @item show debug overload
22227 Displays the current state of displaying @value{GDBN} C@t{++} overload
22229 @cindex expression parser, debugging info
22230 @cindex debug expression parser
22231 @item set debug parser
22232 Turns on or off the display of expression parser debugging output.
22233 Internally, this sets the @code{yydebug} variable in the expression
22234 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22235 details. The default is off.
22236 @item show debug parser
22237 Show the current state of expression parser debugging.
22238 @cindex packets, reporting on stdout
22239 @cindex serial connections, debugging
22240 @cindex debug remote protocol
22241 @cindex remote protocol debugging
22242 @cindex display remote packets
22243 @item set debug remote
22244 Turns on or off display of reports on all packets sent back and forth across
22245 the serial line to the remote machine. The info is printed on the
22246 @value{GDBN} standard output stream. The default is off.
22247 @item show debug remote
22248 Displays the state of display of remote packets.
22249 @item set debug serial
22250 Turns on or off display of @value{GDBN} serial debugging info. The
22252 @item show debug serial
22253 Displays the current state of displaying @value{GDBN} serial debugging
22255 @item set debug solib-frv
22256 @cindex FR-V shared-library debugging
22257 Turns on or off debugging messages for FR-V shared-library code.
22258 @item show debug solib-frv
22259 Display the current state of FR-V shared-library code debugging
22261 @item set debug symtab-create
22262 @cindex symbol table creation
22263 Turns on or off display of debugging messages related to symbol table creation.
22264 The default is off.
22265 @item show debug symtab-create
22266 Show the current state of symbol table creation debugging.
22267 @item set debug target
22268 @cindex target debugging info
22269 Turns on or off display of @value{GDBN} target debugging info. This info
22270 includes what is going on at the target level of GDB, as it happens. The
22271 default is 0. Set it to 1 to track events, and to 2 to also track the
22272 value of large memory transfers. Changes to this flag do not take effect
22273 until the next time you connect to a target or use the @code{run} command.
22274 @item show debug target
22275 Displays the current state of displaying @value{GDBN} target debugging
22277 @item set debug timestamp
22278 @cindex timestampping debugging info
22279 Turns on or off display of timestamps with @value{GDBN} debugging info.
22280 When enabled, seconds and microseconds are displayed before each debugging
22282 @item show debug timestamp
22283 Displays the current state of displaying timestamps with @value{GDBN}
22285 @item set debugvarobj
22286 @cindex variable object debugging info
22287 Turns on or off display of @value{GDBN} variable object debugging
22288 info. The default is off.
22289 @item show debugvarobj
22290 Displays the current state of displaying @value{GDBN} variable object
22292 @item set debug xml
22293 @cindex XML parser debugging
22294 Turns on or off debugging messages for built-in XML parsers.
22295 @item show debug xml
22296 Displays the current state of XML debugging messages.
22299 @node Other Misc Settings
22300 @section Other Miscellaneous Settings
22301 @cindex miscellaneous settings
22304 @kindex set interactive-mode
22305 @item set interactive-mode
22306 If @code{on}, forces @value{GDBN} to assume that GDB was started
22307 in a terminal. In practice, this means that @value{GDBN} should wait
22308 for the user to answer queries generated by commands entered at
22309 the command prompt. If @code{off}, forces @value{GDBN} to operate
22310 in the opposite mode, and it uses the default answers to all queries.
22311 If @code{auto} (the default), @value{GDBN} tries to determine whether
22312 its standard input is a terminal, and works in interactive-mode if it
22313 is, non-interactively otherwise.
22315 In the vast majority of cases, the debugger should be able to guess
22316 correctly which mode should be used. But this setting can be useful
22317 in certain specific cases, such as running a MinGW @value{GDBN}
22318 inside a cygwin window.
22320 @kindex show interactive-mode
22321 @item show interactive-mode
22322 Displays whether the debugger is operating in interactive mode or not.
22325 @node Extending GDB
22326 @chapter Extending @value{GDBN}
22327 @cindex extending GDB
22329 @value{GDBN} provides three mechanisms for extension. The first is based
22330 on composition of @value{GDBN} commands, the second is based on the
22331 Python scripting language, and the third is for defining new aliases of
22334 To facilitate the use of the first two extensions, @value{GDBN} is capable
22335 of evaluating the contents of a file. When doing so, @value{GDBN}
22336 can recognize which scripting language is being used by looking at
22337 the filename extension. Files with an unrecognized filename extension
22338 are always treated as a @value{GDBN} Command Files.
22339 @xref{Command Files,, Command files}.
22341 You can control how @value{GDBN} evaluates these files with the following
22345 @kindex set script-extension
22346 @kindex show script-extension
22347 @item set script-extension off
22348 All scripts are always evaluated as @value{GDBN} Command Files.
22350 @item set script-extension soft
22351 The debugger determines the scripting language based on filename
22352 extension. If this scripting language is supported, @value{GDBN}
22353 evaluates the script using that language. Otherwise, it evaluates
22354 the file as a @value{GDBN} Command File.
22356 @item set script-extension strict
22357 The debugger determines the scripting language based on filename
22358 extension, and evaluates the script using that language. If the
22359 language is not supported, then the evaluation fails.
22361 @item show script-extension
22362 Display the current value of the @code{script-extension} option.
22367 * Sequences:: Canned Sequences of Commands
22368 * Python:: Scripting @value{GDBN} using Python
22369 * Aliases:: Creating new spellings of existing commands
22373 @section Canned Sequences of Commands
22375 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22376 Command Lists}), @value{GDBN} provides two ways to store sequences of
22377 commands for execution as a unit: user-defined commands and command
22381 * Define:: How to define your own commands
22382 * Hooks:: Hooks for user-defined commands
22383 * Command Files:: How to write scripts of commands to be stored in a file
22384 * Output:: Commands for controlled output
22388 @subsection User-defined Commands
22390 @cindex user-defined command
22391 @cindex arguments, to user-defined commands
22392 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22393 which you assign a new name as a command. This is done with the
22394 @code{define} command. User commands may accept up to 10 arguments
22395 separated by whitespace. Arguments are accessed within the user command
22396 via @code{$arg0@dots{}$arg9}. A trivial example:
22400 print $arg0 + $arg1 + $arg2
22405 To execute the command use:
22412 This defines the command @code{adder}, which prints the sum of
22413 its three arguments. Note the arguments are text substitutions, so they may
22414 reference variables, use complex expressions, or even perform inferior
22417 @cindex argument count in user-defined commands
22418 @cindex how many arguments (user-defined commands)
22419 In addition, @code{$argc} may be used to find out how many arguments have
22420 been passed. This expands to a number in the range 0@dots{}10.
22425 print $arg0 + $arg1
22428 print $arg0 + $arg1 + $arg2
22436 @item define @var{commandname}
22437 Define a command named @var{commandname}. If there is already a command
22438 by that name, you are asked to confirm that you want to redefine it.
22439 @var{commandname} may be a bare command name consisting of letters,
22440 numbers, dashes, and underscores. It may also start with any predefined
22441 prefix command. For example, @samp{define target my-target} creates
22442 a user-defined @samp{target my-target} command.
22444 The definition of the command is made up of other @value{GDBN} command lines,
22445 which are given following the @code{define} command. The end of these
22446 commands is marked by a line containing @code{end}.
22449 @kindex end@r{ (user-defined commands)}
22450 @item document @var{commandname}
22451 Document the user-defined command @var{commandname}, so that it can be
22452 accessed by @code{help}. The command @var{commandname} must already be
22453 defined. This command reads lines of documentation just as @code{define}
22454 reads the lines of the command definition, ending with @code{end}.
22455 After the @code{document} command is finished, @code{help} on command
22456 @var{commandname} displays the documentation you have written.
22458 You may use the @code{document} command again to change the
22459 documentation of a command. Redefining the command with @code{define}
22460 does not change the documentation.
22462 @kindex dont-repeat
22463 @cindex don't repeat command
22465 Used inside a user-defined command, this tells @value{GDBN} that this
22466 command should not be repeated when the user hits @key{RET}
22467 (@pxref{Command Syntax, repeat last command}).
22469 @kindex help user-defined
22470 @item help user-defined
22471 List all user-defined commands and all python commands defined in class
22472 COMAND_USER. The first line of the documentation or docstring is
22477 @itemx show user @var{commandname}
22478 Display the @value{GDBN} commands used to define @var{commandname} (but
22479 not its documentation). If no @var{commandname} is given, display the
22480 definitions for all user-defined commands.
22481 This does not work for user-defined python commands.
22483 @cindex infinite recursion in user-defined commands
22484 @kindex show max-user-call-depth
22485 @kindex set max-user-call-depth
22486 @item show max-user-call-depth
22487 @itemx set max-user-call-depth
22488 The value of @code{max-user-call-depth} controls how many recursion
22489 levels are allowed in user-defined commands before @value{GDBN} suspects an
22490 infinite recursion and aborts the command.
22491 This does not apply to user-defined python commands.
22494 In addition to the above commands, user-defined commands frequently
22495 use control flow commands, described in @ref{Command Files}.
22497 When user-defined commands are executed, the
22498 commands of the definition are not printed. An error in any command
22499 stops execution of the user-defined command.
22501 If used interactively, commands that would ask for confirmation proceed
22502 without asking when used inside a user-defined command. Many @value{GDBN}
22503 commands that normally print messages to say what they are doing omit the
22504 messages when used in a user-defined command.
22507 @subsection User-defined Command Hooks
22508 @cindex command hooks
22509 @cindex hooks, for commands
22510 @cindex hooks, pre-command
22513 You may define @dfn{hooks}, which are a special kind of user-defined
22514 command. Whenever you run the command @samp{foo}, if the user-defined
22515 command @samp{hook-foo} exists, it is executed (with no arguments)
22516 before that command.
22518 @cindex hooks, post-command
22520 A hook may also be defined which is run after the command you executed.
22521 Whenever you run the command @samp{foo}, if the user-defined command
22522 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22523 that command. Post-execution hooks may exist simultaneously with
22524 pre-execution hooks, for the same command.
22526 It is valid for a hook to call the command which it hooks. If this
22527 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22529 @c It would be nice if hookpost could be passed a parameter indicating
22530 @c if the command it hooks executed properly or not. FIXME!
22532 @kindex stop@r{, a pseudo-command}
22533 In addition, a pseudo-command, @samp{stop} exists. Defining
22534 (@samp{hook-stop}) makes the associated commands execute every time
22535 execution stops in your program: before breakpoint commands are run,
22536 displays are printed, or the stack frame is printed.
22538 For example, to ignore @code{SIGALRM} signals while
22539 single-stepping, but treat them normally during normal execution,
22544 handle SIGALRM nopass
22548 handle SIGALRM pass
22551 define hook-continue
22552 handle SIGALRM pass
22556 As a further example, to hook at the beginning and end of the @code{echo}
22557 command, and to add extra text to the beginning and end of the message,
22565 define hookpost-echo
22569 (@value{GDBP}) echo Hello World
22570 <<<---Hello World--->>>
22575 You can define a hook for any single-word command in @value{GDBN}, but
22576 not for command aliases; you should define a hook for the basic command
22577 name, e.g.@: @code{backtrace} rather than @code{bt}.
22578 @c FIXME! So how does Joe User discover whether a command is an alias
22580 You can hook a multi-word command by adding @code{hook-} or
22581 @code{hookpost-} to the last word of the command, e.g.@:
22582 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22584 If an error occurs during the execution of your hook, execution of
22585 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22586 (before the command that you actually typed had a chance to run).
22588 If you try to define a hook which does not match any known command, you
22589 get a warning from the @code{define} command.
22591 @node Command Files
22592 @subsection Command Files
22594 @cindex command files
22595 @cindex scripting commands
22596 A command file for @value{GDBN} is a text file made of lines that are
22597 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22598 also be included. An empty line in a command file does nothing; it
22599 does not mean to repeat the last command, as it would from the
22602 You can request the execution of a command file with the @code{source}
22603 command. Note that the @code{source} command is also used to evaluate
22604 scripts that are not Command Files. The exact behavior can be configured
22605 using the @code{script-extension} setting.
22606 @xref{Extending GDB,, Extending GDB}.
22610 @cindex execute commands from a file
22611 @item source [-s] [-v] @var{filename}
22612 Execute the command file @var{filename}.
22615 The lines in a command file are generally executed sequentially,
22616 unless the order of execution is changed by one of the
22617 @emph{flow-control commands} described below. The commands are not
22618 printed as they are executed. An error in any command terminates
22619 execution of the command file and control is returned to the console.
22621 @value{GDBN} first searches for @var{filename} in the current directory.
22622 If the file is not found there, and @var{filename} does not specify a
22623 directory, then @value{GDBN} also looks for the file on the source search path
22624 (specified with the @samp{directory} command);
22625 except that @file{$cdir} is not searched because the compilation directory
22626 is not relevant to scripts.
22628 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22629 on the search path even if @var{filename} specifies a directory.
22630 The search is done by appending @var{filename} to each element of the
22631 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22632 and the search path contains @file{/home/user} then @value{GDBN} will
22633 look for the script @file{/home/user/mylib/myscript}.
22634 The search is also done if @var{filename} is an absolute path.
22635 For example, if @var{filename} is @file{/tmp/myscript} and
22636 the search path contains @file{/home/user} then @value{GDBN} will
22637 look for the script @file{/home/user/tmp/myscript}.
22638 For DOS-like systems, if @var{filename} contains a drive specification,
22639 it is stripped before concatenation. For example, if @var{filename} is
22640 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22641 will look for the script @file{c:/tmp/myscript}.
22643 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22644 each command as it is executed. The option must be given before
22645 @var{filename}, and is interpreted as part of the filename anywhere else.
22647 Commands that would ask for confirmation if used interactively proceed
22648 without asking when used in a command file. Many @value{GDBN} commands that
22649 normally print messages to say what they are doing omit the messages
22650 when called from command files.
22652 @value{GDBN} also accepts command input from standard input. In this
22653 mode, normal output goes to standard output and error output goes to
22654 standard error. Errors in a command file supplied on standard input do
22655 not terminate execution of the command file---execution continues with
22659 gdb < cmds > log 2>&1
22662 (The syntax above will vary depending on the shell used.) This example
22663 will execute commands from the file @file{cmds}. All output and errors
22664 would be directed to @file{log}.
22666 Since commands stored on command files tend to be more general than
22667 commands typed interactively, they frequently need to deal with
22668 complicated situations, such as different or unexpected values of
22669 variables and symbols, changes in how the program being debugged is
22670 built, etc. @value{GDBN} provides a set of flow-control commands to
22671 deal with these complexities. Using these commands, you can write
22672 complex scripts that loop over data structures, execute commands
22673 conditionally, etc.
22680 This command allows to include in your script conditionally executed
22681 commands. The @code{if} command takes a single argument, which is an
22682 expression to evaluate. It is followed by a series of commands that
22683 are executed only if the expression is true (its value is nonzero).
22684 There can then optionally be an @code{else} line, followed by a series
22685 of commands that are only executed if the expression was false. The
22686 end of the list is marked by a line containing @code{end}.
22690 This command allows to write loops. Its syntax is similar to
22691 @code{if}: the command takes a single argument, which is an expression
22692 to evaluate, and must be followed by the commands to execute, one per
22693 line, terminated by an @code{end}. These commands are called the
22694 @dfn{body} of the loop. The commands in the body of @code{while} are
22695 executed repeatedly as long as the expression evaluates to true.
22699 This command exits the @code{while} loop in whose body it is included.
22700 Execution of the script continues after that @code{while}s @code{end}
22703 @kindex loop_continue
22704 @item loop_continue
22705 This command skips the execution of the rest of the body of commands
22706 in the @code{while} loop in whose body it is included. Execution
22707 branches to the beginning of the @code{while} loop, where it evaluates
22708 the controlling expression.
22710 @kindex end@r{ (if/else/while commands)}
22712 Terminate the block of commands that are the body of @code{if},
22713 @code{else}, or @code{while} flow-control commands.
22718 @subsection Commands for Controlled Output
22720 During the execution of a command file or a user-defined command, normal
22721 @value{GDBN} output is suppressed; the only output that appears is what is
22722 explicitly printed by the commands in the definition. This section
22723 describes three commands useful for generating exactly the output you
22728 @item echo @var{text}
22729 @c I do not consider backslash-space a standard C escape sequence
22730 @c because it is not in ANSI.
22731 Print @var{text}. Nonprinting characters can be included in
22732 @var{text} using C escape sequences, such as @samp{\n} to print a
22733 newline. @strong{No newline is printed unless you specify one.}
22734 In addition to the standard C escape sequences, a backslash followed
22735 by a space stands for a space. This is useful for displaying a
22736 string with spaces at the beginning or the end, since leading and
22737 trailing spaces are otherwise trimmed from all arguments.
22738 To print @samp{@w{ }and foo =@w{ }}, use the command
22739 @samp{echo \@w{ }and foo = \@w{ }}.
22741 A backslash at the end of @var{text} can be used, as in C, to continue
22742 the command onto subsequent lines. For example,
22745 echo This is some text\n\
22746 which is continued\n\
22747 onto several lines.\n
22750 produces the same output as
22753 echo This is some text\n
22754 echo which is continued\n
22755 echo onto several lines.\n
22759 @item output @var{expression}
22760 Print the value of @var{expression} and nothing but that value: no
22761 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22762 value history either. @xref{Expressions, ,Expressions}, for more information
22765 @item output/@var{fmt} @var{expression}
22766 Print the value of @var{expression} in format @var{fmt}. You can use
22767 the same formats as for @code{print}. @xref{Output Formats,,Output
22768 Formats}, for more information.
22771 @item printf @var{template}, @var{expressions}@dots{}
22772 Print the values of one or more @var{expressions} under the control of
22773 the string @var{template}. To print several values, make
22774 @var{expressions} be a comma-separated list of individual expressions,
22775 which may be either numbers or pointers. Their values are printed as
22776 specified by @var{template}, exactly as a C program would do by
22777 executing the code below:
22780 printf (@var{template}, @var{expressions}@dots{});
22783 As in @code{C} @code{printf}, ordinary characters in @var{template}
22784 are printed verbatim, while @dfn{conversion specification} introduced
22785 by the @samp{%} character cause subsequent @var{expressions} to be
22786 evaluated, their values converted and formatted according to type and
22787 style information encoded in the conversion specifications, and then
22790 For example, you can print two values in hex like this:
22793 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22796 @code{printf} supports all the standard @code{C} conversion
22797 specifications, including the flags and modifiers between the @samp{%}
22798 character and the conversion letter, with the following exceptions:
22802 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22805 The modifier @samp{*} is not supported for specifying precision or
22809 The @samp{'} flag (for separation of digits into groups according to
22810 @code{LC_NUMERIC'}) is not supported.
22813 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22817 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22820 The conversion letters @samp{a} and @samp{A} are not supported.
22824 Note that the @samp{ll} type modifier is supported only if the
22825 underlying @code{C} implementation used to build @value{GDBN} supports
22826 the @code{long long int} type, and the @samp{L} type modifier is
22827 supported only if @code{long double} type is available.
22829 As in @code{C}, @code{printf} supports simple backslash-escape
22830 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22831 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22832 single character. Octal and hexadecimal escape sequences are not
22835 Additionally, @code{printf} supports conversion specifications for DFP
22836 (@dfn{Decimal Floating Point}) types using the following length modifiers
22837 together with a floating point specifier.
22842 @samp{H} for printing @code{Decimal32} types.
22845 @samp{D} for printing @code{Decimal64} types.
22848 @samp{DD} for printing @code{Decimal128} types.
22851 If the underlying @code{C} implementation used to build @value{GDBN} has
22852 support for the three length modifiers for DFP types, other modifiers
22853 such as width and precision will also be available for @value{GDBN} to use.
22855 In case there is no such @code{C} support, no additional modifiers will be
22856 available and the value will be printed in the standard way.
22858 Here's an example of printing DFP types using the above conversion letters:
22860 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22864 @item eval @var{template}, @var{expressions}@dots{}
22865 Convert the values of one or more @var{expressions} under the control of
22866 the string @var{template} to a command line, and call it.
22871 @section Scripting @value{GDBN} using Python
22872 @cindex python scripting
22873 @cindex scripting with python
22875 You can script @value{GDBN} using the @uref{http://www.python.org/,
22876 Python programming language}. This feature is available only if
22877 @value{GDBN} was configured using @option{--with-python}.
22879 @cindex python directory
22880 Python scripts used by @value{GDBN} should be installed in
22881 @file{@var{data-directory}/python}, where @var{data-directory} is
22882 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22883 This directory, known as the @dfn{python directory},
22884 is automatically added to the Python Search Path in order to allow
22885 the Python interpreter to locate all scripts installed at this location.
22887 Additionally, @value{GDBN} commands and convenience functions which
22888 are written in Python and are located in the
22889 @file{@var{data-directory}/python/gdb/command} or
22890 @file{@var{data-directory}/python/gdb/function} directories are
22891 automatically imported when @value{GDBN} starts.
22894 * Python Commands:: Accessing Python from @value{GDBN}.
22895 * Python API:: Accessing @value{GDBN} from Python.
22896 * Python Auto-loading:: Automatically loading Python code.
22897 * Python modules:: Python modules provided by @value{GDBN}.
22900 @node Python Commands
22901 @subsection Python Commands
22902 @cindex python commands
22903 @cindex commands to access python
22905 @value{GDBN} provides two commands for accessing the Python interpreter,
22906 and one related setting:
22909 @kindex python-interactive
22911 @item python-interactive @r{[}@var{command}@r{]}
22912 @itemx pi @r{[}@var{command}@r{]}
22913 Without an argument, the @code{python-interactive} command can be used
22914 to start an interactive Python prompt. To return to @value{GDBN},
22915 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22917 Alternatively, a single-line Python command can be given as an
22918 argument and evaluated. If the command is an expression, the result
22919 will be printed; otherwise, nothing will be printed. For example:
22922 (@value{GDBP}) python-interactive 2 + 3
22928 @item python @r{[}@var{command}@r{]}
22929 @itemx py @r{[}@var{command}@r{]}
22930 The @code{python} command can be used to evaluate Python code.
22932 If given an argument, the @code{python} command will evaluate the
22933 argument as a Python command. For example:
22936 (@value{GDBP}) python print 23
22940 If you do not provide an argument to @code{python}, it will act as a
22941 multi-line command, like @code{define}. In this case, the Python
22942 script is made up of subsequent command lines, given after the
22943 @code{python} command. This command list is terminated using a line
22944 containing @code{end}. For example:
22947 (@value{GDBP}) python
22949 End with a line saying just "end".
22955 @kindex set python print-stack
22956 @item set python print-stack
22957 By default, @value{GDBN} will print only the message component of a
22958 Python exception when an error occurs in a Python script. This can be
22959 controlled using @code{set python print-stack}: if @code{full}, then
22960 full Python stack printing is enabled; if @code{none}, then Python stack
22961 and message printing is disabled; if @code{message}, the default, only
22962 the message component of the error is printed.
22965 It is also possible to execute a Python script from the @value{GDBN}
22969 @item source @file{script-name}
22970 The script name must end with @samp{.py} and @value{GDBN} must be configured
22971 to recognize the script language based on filename extension using
22972 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22974 @item python execfile ("script-name")
22975 This method is based on the @code{execfile} Python built-in function,
22976 and thus is always available.
22980 @subsection Python API
22982 @cindex programming in python
22984 @cindex python stdout
22985 @cindex python pagination
22986 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22987 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22988 A Python program which outputs to one of these streams may have its
22989 output interrupted by the user (@pxref{Screen Size}). In this
22990 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22993 * Basic Python:: Basic Python Functions.
22994 * Exception Handling:: How Python exceptions are translated.
22995 * Values From Inferior:: Python representation of values.
22996 * Types In Python:: Python representation of types.
22997 * Pretty Printing API:: Pretty-printing values.
22998 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22999 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23000 * Type Printing API:: Pretty-printing types.
23001 * Inferiors In Python:: Python representation of inferiors (processes)
23002 * Events In Python:: Listening for events from @value{GDBN}.
23003 * Threads In Python:: Accessing inferior threads from Python.
23004 * Commands In Python:: Implementing new commands in Python.
23005 * Parameters In Python:: Adding new @value{GDBN} parameters.
23006 * Functions In Python:: Writing new convenience functions.
23007 * Progspaces In Python:: Program spaces.
23008 * Objfiles In Python:: Object files.
23009 * Frames In Python:: Accessing inferior stack frames from Python.
23010 * Blocks In Python:: Accessing frame blocks from Python.
23011 * Symbols In Python:: Python representation of symbols.
23012 * Symbol Tables In Python:: Python representation of symbol tables.
23013 * Breakpoints In Python:: Manipulating breakpoints using Python.
23014 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23016 * Lazy Strings In Python:: Python representation of lazy strings.
23017 * Architectures In Python:: Python representation of architectures.
23021 @subsubsection Basic Python
23023 @cindex python functions
23024 @cindex python module
23026 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23027 methods and classes added by @value{GDBN} are placed in this module.
23028 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23029 use in all scripts evaluated by the @code{python} command.
23031 @findex gdb.PYTHONDIR
23032 @defvar gdb.PYTHONDIR
23033 A string containing the python directory (@pxref{Python}).
23036 @findex gdb.execute
23037 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23038 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23039 If a GDB exception happens while @var{command} runs, it is
23040 translated as described in @ref{Exception Handling,,Exception Handling}.
23042 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23043 command as having originated from the user invoking it interactively.
23044 It must be a boolean value. If omitted, it defaults to @code{False}.
23046 By default, any output produced by @var{command} is sent to
23047 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23048 @code{True}, then output will be collected by @code{gdb.execute} and
23049 returned as a string. The default is @code{False}, in which case the
23050 return value is @code{None}. If @var{to_string} is @code{True}, the
23051 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23052 and height, and its pagination will be disabled; @pxref{Screen Size}.
23055 @findex gdb.breakpoints
23056 @defun gdb.breakpoints ()
23057 Return a sequence holding all of @value{GDBN}'s breakpoints.
23058 @xref{Breakpoints In Python}, for more information.
23061 @findex gdb.parameter
23062 @defun gdb.parameter (parameter)
23063 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23064 string naming the parameter to look up; @var{parameter} may contain
23065 spaces if the parameter has a multi-part name. For example,
23066 @samp{print object} is a valid parameter name.
23068 If the named parameter does not exist, this function throws a
23069 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23070 parameter's value is converted to a Python value of the appropriate
23071 type, and returned.
23074 @findex gdb.history
23075 @defun gdb.history (number)
23076 Return a value from @value{GDBN}'s value history (@pxref{Value
23077 History}). @var{number} indicates which history element to return.
23078 If @var{number} is negative, then @value{GDBN} will take its absolute value
23079 and count backward from the last element (i.e., the most recent element) to
23080 find the value to return. If @var{number} is zero, then @value{GDBN} will
23081 return the most recent element. If the element specified by @var{number}
23082 doesn't exist in the value history, a @code{gdb.error} exception will be
23085 If no exception is raised, the return value is always an instance of
23086 @code{gdb.Value} (@pxref{Values From Inferior}).
23089 @findex gdb.parse_and_eval
23090 @defun gdb.parse_and_eval (expression)
23091 Parse @var{expression} as an expression in the current language,
23092 evaluate it, and return the result as a @code{gdb.Value}.
23093 @var{expression} must be a string.
23095 This function can be useful when implementing a new command
23096 (@pxref{Commands In Python}), as it provides a way to parse the
23097 command's argument as an expression. It is also useful simply to
23098 compute values, for example, it is the only way to get the value of a
23099 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23102 @findex gdb.find_pc_line
23103 @defun gdb.find_pc_line (pc)
23104 Return the @code{gdb.Symtab_and_line} object corresponding to the
23105 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23106 value of @var{pc} is passed as an argument, then the @code{symtab} and
23107 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23108 will be @code{None} and 0 respectively.
23111 @findex gdb.post_event
23112 @defun gdb.post_event (event)
23113 Put @var{event}, a callable object taking no arguments, into
23114 @value{GDBN}'s internal event queue. This callable will be invoked at
23115 some later point, during @value{GDBN}'s event processing. Events
23116 posted using @code{post_event} will be run in the order in which they
23117 were posted; however, there is no way to know when they will be
23118 processed relative to other events inside @value{GDBN}.
23120 @value{GDBN} is not thread-safe. If your Python program uses multiple
23121 threads, you must be careful to only call @value{GDBN}-specific
23122 functions in the main @value{GDBN} thread. @code{post_event} ensures
23126 (@value{GDBP}) python
23130 > def __init__(self, message):
23131 > self.message = message;
23132 > def __call__(self):
23133 > gdb.write(self.message)
23135 >class MyThread1 (threading.Thread):
23137 > gdb.post_event(Writer("Hello "))
23139 >class MyThread2 (threading.Thread):
23141 > gdb.post_event(Writer("World\n"))
23143 >MyThread1().start()
23144 >MyThread2().start()
23146 (@value{GDBP}) Hello World
23151 @defun gdb.write (string @r{[}, stream{]})
23152 Print a string to @value{GDBN}'s paginated output stream. The
23153 optional @var{stream} determines the stream to print to. The default
23154 stream is @value{GDBN}'s standard output stream. Possible stream
23161 @value{GDBN}'s standard output stream.
23166 @value{GDBN}'s standard error stream.
23171 @value{GDBN}'s log stream (@pxref{Logging Output}).
23174 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23175 call this function and will automatically direct the output to the
23180 @defun gdb.flush ()
23181 Flush the buffer of a @value{GDBN} paginated stream so that the
23182 contents are displayed immediately. @value{GDBN} will flush the
23183 contents of a stream automatically when it encounters a newline in the
23184 buffer. The optional @var{stream} determines the stream to flush. The
23185 default stream is @value{GDBN}'s standard output stream. Possible
23192 @value{GDBN}'s standard output stream.
23197 @value{GDBN}'s standard error stream.
23202 @value{GDBN}'s log stream (@pxref{Logging Output}).
23206 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23207 call this function for the relevant stream.
23210 @findex gdb.target_charset
23211 @defun gdb.target_charset ()
23212 Return the name of the current target character set (@pxref{Character
23213 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23214 that @samp{auto} is never returned.
23217 @findex gdb.target_wide_charset
23218 @defun gdb.target_wide_charset ()
23219 Return the name of the current target wide character set
23220 (@pxref{Character Sets}). This differs from
23221 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23225 @findex gdb.solib_name
23226 @defun gdb.solib_name (address)
23227 Return the name of the shared library holding the given @var{address}
23228 as a string, or @code{None}.
23231 @findex gdb.decode_line
23232 @defun gdb.decode_line @r{[}expression@r{]}
23233 Return locations of the line specified by @var{expression}, or of the
23234 current line if no argument was given. This function returns a Python
23235 tuple containing two elements. The first element contains a string
23236 holding any unparsed section of @var{expression} (or @code{None} if
23237 the expression has been fully parsed). The second element contains
23238 either @code{None} or another tuple that contains all the locations
23239 that match the expression represented as @code{gdb.Symtab_and_line}
23240 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23241 provided, it is decoded the way that @value{GDBN}'s inbuilt
23242 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23245 @defun gdb.prompt_hook (current_prompt)
23246 @anchor{prompt_hook}
23248 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23249 assigned to this operation before a prompt is displayed by
23252 The parameter @code{current_prompt} contains the current @value{GDBN}
23253 prompt. This method must return a Python string, or @code{None}. If
23254 a string is returned, the @value{GDBN} prompt will be set to that
23255 string. If @code{None} is returned, @value{GDBN} will continue to use
23256 the current prompt.
23258 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23259 such as those used by readline for command input, and annotation
23260 related prompts are prohibited from being changed.
23263 @node Exception Handling
23264 @subsubsection Exception Handling
23265 @cindex python exceptions
23266 @cindex exceptions, python
23268 When executing the @code{python} command, Python exceptions
23269 uncaught within the Python code are translated to calls to
23270 @value{GDBN} error-reporting mechanism. If the command that called
23271 @code{python} does not handle the error, @value{GDBN} will
23272 terminate it and print an error message containing the Python
23273 exception name, the associated value, and the Python call stack
23274 backtrace at the point where the exception was raised. Example:
23277 (@value{GDBP}) python print foo
23278 Traceback (most recent call last):
23279 File "<string>", line 1, in <module>
23280 NameError: name 'foo' is not defined
23283 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23284 Python code are converted to Python exceptions. The type of the
23285 Python exception depends on the error.
23289 This is the base class for most exceptions generated by @value{GDBN}.
23290 It is derived from @code{RuntimeError}, for compatibility with earlier
23291 versions of @value{GDBN}.
23293 If an error occurring in @value{GDBN} does not fit into some more
23294 specific category, then the generated exception will have this type.
23296 @item gdb.MemoryError
23297 This is a subclass of @code{gdb.error} which is thrown when an
23298 operation tried to access invalid memory in the inferior.
23300 @item KeyboardInterrupt
23301 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23302 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23305 In all cases, your exception handler will see the @value{GDBN} error
23306 message as its value and the Python call stack backtrace at the Python
23307 statement closest to where the @value{GDBN} error occured as the
23310 @findex gdb.GdbError
23311 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23312 it is useful to be able to throw an exception that doesn't cause a
23313 traceback to be printed. For example, the user may have invoked the
23314 command incorrectly. Use the @code{gdb.GdbError} exception
23315 to handle this case. Example:
23319 >class HelloWorld (gdb.Command):
23320 > """Greet the whole world."""
23321 > def __init__ (self):
23322 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23323 > def invoke (self, args, from_tty):
23324 > argv = gdb.string_to_argv (args)
23325 > if len (argv) != 0:
23326 > raise gdb.GdbError ("hello-world takes no arguments")
23327 > print "Hello, World!"
23330 (gdb) hello-world 42
23331 hello-world takes no arguments
23334 @node Values From Inferior
23335 @subsubsection Values From Inferior
23336 @cindex values from inferior, with Python
23337 @cindex python, working with values from inferior
23339 @cindex @code{gdb.Value}
23340 @value{GDBN} provides values it obtains from the inferior program in
23341 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23342 for its internal bookkeeping of the inferior's values, and for
23343 fetching values when necessary.
23345 Inferior values that are simple scalars can be used directly in
23346 Python expressions that are valid for the value's data type. Here's
23347 an example for an integer or floating-point value @code{some_val}:
23354 As result of this, @code{bar} will also be a @code{gdb.Value} object
23355 whose values are of the same type as those of @code{some_val}.
23357 Inferior values that are structures or instances of some class can
23358 be accessed using the Python @dfn{dictionary syntax}. For example, if
23359 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23360 can access its @code{foo} element with:
23363 bar = some_val['foo']
23366 Again, @code{bar} will also be a @code{gdb.Value} object.
23368 A @code{gdb.Value} that represents a function can be executed via
23369 inferior function call. Any arguments provided to the call must match
23370 the function's prototype, and must be provided in the order specified
23373 For example, @code{some_val} is a @code{gdb.Value} instance
23374 representing a function that takes two integers as arguments. To
23375 execute this function, call it like so:
23378 result = some_val (10,20)
23381 Any values returned from a function call will be stored as a
23384 The following attributes are provided:
23386 @defvar Value.address
23387 If this object is addressable, this read-only attribute holds a
23388 @code{gdb.Value} object representing the address. Otherwise,
23389 this attribute holds @code{None}.
23392 @cindex optimized out value in Python
23393 @defvar Value.is_optimized_out
23394 This read-only boolean attribute is true if the compiler optimized out
23395 this value, thus it is not available for fetching from the inferior.
23399 The type of this @code{gdb.Value}. The value of this attribute is a
23400 @code{gdb.Type} object (@pxref{Types In Python}).
23403 @defvar Value.dynamic_type
23404 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23405 type information (@acronym{RTTI}) to determine the dynamic type of the
23406 value. If this value is of class type, it will return the class in
23407 which the value is embedded, if any. If this value is of pointer or
23408 reference to a class type, it will compute the dynamic type of the
23409 referenced object, and return a pointer or reference to that type,
23410 respectively. In all other cases, it will return the value's static
23413 Note that this feature will only work when debugging a C@t{++} program
23414 that includes @acronym{RTTI} for the object in question. Otherwise,
23415 it will just return the static type of the value as in @kbd{ptype foo}
23416 (@pxref{Symbols, ptype}).
23419 @defvar Value.is_lazy
23420 The value of this read-only boolean attribute is @code{True} if this
23421 @code{gdb.Value} has not yet been fetched from the inferior.
23422 @value{GDBN} does not fetch values until necessary, for efficiency.
23426 myval = gdb.parse_and_eval ('somevar')
23429 The value of @code{somevar} is not fetched at this time. It will be
23430 fetched when the value is needed, or when the @code{fetch_lazy}
23434 The following methods are provided:
23436 @defun Value.__init__ (@var{val})
23437 Many Python values can be converted directly to a @code{gdb.Value} via
23438 this object initializer. Specifically:
23441 @item Python boolean
23442 A Python boolean is converted to the boolean type from the current
23445 @item Python integer
23446 A Python integer is converted to the C @code{long} type for the
23447 current architecture.
23450 A Python long is converted to the C @code{long long} type for the
23451 current architecture.
23454 A Python float is converted to the C @code{double} type for the
23455 current architecture.
23457 @item Python string
23458 A Python string is converted to a target string, using the current
23461 @item @code{gdb.Value}
23462 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23464 @item @code{gdb.LazyString}
23465 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23466 Python}), then the lazy string's @code{value} method is called, and
23467 its result is used.
23471 @defun Value.cast (type)
23472 Return a new instance of @code{gdb.Value} that is the result of
23473 casting this instance to the type described by @var{type}, which must
23474 be a @code{gdb.Type} object. If the cast cannot be performed for some
23475 reason, this method throws an exception.
23478 @defun Value.dereference ()
23479 For pointer data types, this method returns a new @code{gdb.Value} object
23480 whose contents is the object pointed to by the pointer. For example, if
23481 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23488 then you can use the corresponding @code{gdb.Value} to access what
23489 @code{foo} points to like this:
23492 bar = foo.dereference ()
23495 The result @code{bar} will be a @code{gdb.Value} object holding the
23496 value pointed to by @code{foo}.
23498 A similar function @code{Value.referenced_value} exists which also
23499 returns @code{gdb.Value} objects corresonding to the values pointed to
23500 by pointer values (and additionally, values referenced by reference
23501 values). However, the behavior of @code{Value.dereference}
23502 differs from @code{Value.referenced_value} by the fact that the
23503 behavior of @code{Value.dereference} is identical to applying the C
23504 unary operator @code{*} on a given value. For example, consider a
23505 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23509 typedef int *intptr;
23513 intptr &ptrref = ptr;
23516 Though @code{ptrref} is a reference value, one can apply the method
23517 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23518 to it and obtain a @code{gdb.Value} which is identical to that
23519 corresponding to @code{val}. However, if you apply the method
23520 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23521 object identical to that corresponding to @code{ptr}.
23524 py_ptrref = gdb.parse_and_eval ("ptrref")
23525 py_val = py_ptrref.dereference ()
23526 py_ptr = py_ptrref.referenced_value ()
23529 The @code{gdb.Value} object @code{py_val} is identical to that
23530 corresponding to @code{val}, and @code{py_ptr} is identical to that
23531 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23532 be applied whenever the C unary operator @code{*} can be applied
23533 to the corresponding C value. For those cases where applying both
23534 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23535 the results obtained need not be identical (as we have seen in the above
23536 example). The results are however identical when applied on
23537 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23538 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23541 @defun Value.referenced_value ()
23542 For pointer or reference data types, this method returns a new
23543 @code{gdb.Value} object corresponding to the value referenced by the
23544 pointer/reference value. For pointer data types,
23545 @code{Value.dereference} and @code{Value.referenced_value} produce
23546 identical results. The difference between these methods is that
23547 @code{Value.dereference} cannot get the values referenced by reference
23548 values. For example, consider a reference to an @code{int}, declared
23549 in your C@t{++} program as
23557 then applying @code{Value.dereference} to the @code{gdb.Value} object
23558 corresponding to @code{ref} will result in an error, while applying
23559 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23560 identical to that corresponding to @code{val}.
23563 py_ref = gdb.parse_and_eval ("ref")
23564 er_ref = py_ref.dereference () # Results in error
23565 py_val = py_ref.referenced_value () # Returns the referenced value
23568 The @code{gdb.Value} object @code{py_val} is identical to that
23569 corresponding to @code{val}.
23572 @defun Value.dynamic_cast (type)
23573 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23574 operator were used. Consult a C@t{++} reference for details.
23577 @defun Value.reinterpret_cast (type)
23578 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23579 operator were used. Consult a C@t{++} reference for details.
23582 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23583 If this @code{gdb.Value} represents a string, then this method
23584 converts the contents to a Python string. Otherwise, this method will
23585 throw an exception.
23587 Strings are recognized in a language-specific way; whether a given
23588 @code{gdb.Value} represents a string is determined by the current
23591 For C-like languages, a value is a string if it is a pointer to or an
23592 array of characters or ints. The string is assumed to be terminated
23593 by a zero of the appropriate width. However if the optional length
23594 argument is given, the string will be converted to that given length,
23595 ignoring any embedded zeros that the string may contain.
23597 If the optional @var{encoding} argument is given, it must be a string
23598 naming the encoding of the string in the @code{gdb.Value}, such as
23599 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23600 the same encodings as the corresponding argument to Python's
23601 @code{string.decode} method, and the Python codec machinery will be used
23602 to convert the string. If @var{encoding} is not given, or if
23603 @var{encoding} is the empty string, then either the @code{target-charset}
23604 (@pxref{Character Sets}) will be used, or a language-specific encoding
23605 will be used, if the current language is able to supply one.
23607 The optional @var{errors} argument is the same as the corresponding
23608 argument to Python's @code{string.decode} method.
23610 If the optional @var{length} argument is given, the string will be
23611 fetched and converted to the given length.
23614 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23615 If this @code{gdb.Value} represents a string, then this method
23616 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23617 In Python}). Otherwise, this method will throw an exception.
23619 If the optional @var{encoding} argument is given, it must be a string
23620 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23621 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23622 @var{encoding} argument is an encoding that @value{GDBN} does
23623 recognize, @value{GDBN} will raise an error.
23625 When a lazy string is printed, the @value{GDBN} encoding machinery is
23626 used to convert the string during printing. If the optional
23627 @var{encoding} argument is not provided, or is an empty string,
23628 @value{GDBN} will automatically select the encoding most suitable for
23629 the string type. For further information on encoding in @value{GDBN}
23630 please see @ref{Character Sets}.
23632 If the optional @var{length} argument is given, the string will be
23633 fetched and encoded to the length of characters specified. If
23634 the @var{length} argument is not provided, the string will be fetched
23635 and encoded until a null of appropriate width is found.
23638 @defun Value.fetch_lazy ()
23639 If the @code{gdb.Value} object is currently a lazy value
23640 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23641 fetched from the inferior. Any errors that occur in the process
23642 will produce a Python exception.
23644 If the @code{gdb.Value} object is not a lazy value, this method
23647 This method does not return a value.
23651 @node Types In Python
23652 @subsubsection Types In Python
23653 @cindex types in Python
23654 @cindex Python, working with types
23657 @value{GDBN} represents types from the inferior using the class
23660 The following type-related functions are available in the @code{gdb}
23663 @findex gdb.lookup_type
23664 @defun gdb.lookup_type (name @r{[}, block@r{]})
23665 This function looks up a type by name. @var{name} is the name of the
23666 type to look up. It must be a string.
23668 If @var{block} is given, then @var{name} is looked up in that scope.
23669 Otherwise, it is searched for globally.
23671 Ordinarily, this function will return an instance of @code{gdb.Type}.
23672 If the named type cannot be found, it will throw an exception.
23675 If the type is a structure or class type, or an enum type, the fields
23676 of that type can be accessed using the Python @dfn{dictionary syntax}.
23677 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23678 a structure type, you can access its @code{foo} field with:
23681 bar = some_type['foo']
23684 @code{bar} will be a @code{gdb.Field} object; see below under the
23685 description of the @code{Type.fields} method for a description of the
23686 @code{gdb.Field} class.
23688 An instance of @code{Type} has the following attributes:
23691 The type code for this type. The type code will be one of the
23692 @code{TYPE_CODE_} constants defined below.
23695 @defvar Type.sizeof
23696 The size of this type, in target @code{char} units. Usually, a
23697 target's @code{char} type will be an 8-bit byte. However, on some
23698 unusual platforms, this type may have a different size.
23702 The tag name for this type. The tag name is the name after
23703 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23704 languages have this concept. If this type has no tag name, then
23705 @code{None} is returned.
23708 The following methods are provided:
23710 @defun Type.fields ()
23711 For structure and union types, this method returns the fields. Range
23712 types have two fields, the minimum and maximum values. Enum types
23713 have one field per enum constant. Function and method types have one
23714 field per parameter. The base types of C@t{++} classes are also
23715 represented as fields. If the type has no fields, or does not fit
23716 into one of these categories, an empty sequence will be returned.
23718 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23721 This attribute is not available for @code{static} fields (as in
23722 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23723 position of the field. For @code{enum} fields, the value is the
23724 enumeration member's integer representation.
23727 The name of the field, or @code{None} for anonymous fields.
23730 This is @code{True} if the field is artificial, usually meaning that
23731 it was provided by the compiler and not the user. This attribute is
23732 always provided, and is @code{False} if the field is not artificial.
23734 @item is_base_class
23735 This is @code{True} if the field represents a base class of a C@t{++}
23736 structure. This attribute is always provided, and is @code{False}
23737 if the field is not a base class of the type that is the argument of
23738 @code{fields}, or if that type was not a C@t{++} class.
23741 If the field is packed, or is a bitfield, then this will have a
23742 non-zero value, which is the size of the field in bits. Otherwise,
23743 this will be zero; in this case the field's size is given by its type.
23746 The type of the field. This is usually an instance of @code{Type},
23747 but it can be @code{None} in some situations.
23751 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23752 Return a new @code{gdb.Type} object which represents an array of this
23753 type. If one argument is given, it is the inclusive upper bound of
23754 the array; in this case the lower bound is zero. If two arguments are
23755 given, the first argument is the lower bound of the array, and the
23756 second argument is the upper bound of the array. An array's length
23757 must not be negative, but the bounds can be.
23760 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23761 Return a new @code{gdb.Type} object which represents a vector of this
23762 type. If one argument is given, it is the inclusive upper bound of
23763 the vector; in this case the lower bound is zero. If two arguments are
23764 given, the first argument is the lower bound of the vector, and the
23765 second argument is the upper bound of the vector. A vector's length
23766 must not be negative, but the bounds can be.
23768 The difference between an @code{array} and a @code{vector} is that
23769 arrays behave like in C: when used in expressions they decay to a pointer
23770 to the first element whereas vectors are treated as first class values.
23773 @defun Type.const ()
23774 Return a new @code{gdb.Type} object which represents a
23775 @code{const}-qualified variant of this type.
23778 @defun Type.volatile ()
23779 Return a new @code{gdb.Type} object which represents a
23780 @code{volatile}-qualified variant of this type.
23783 @defun Type.unqualified ()
23784 Return a new @code{gdb.Type} object which represents an unqualified
23785 variant of this type. That is, the result is neither @code{const} nor
23789 @defun Type.range ()
23790 Return a Python @code{Tuple} object that contains two elements: the
23791 low bound of the argument type and the high bound of that type. If
23792 the type does not have a range, @value{GDBN} will raise a
23793 @code{gdb.error} exception (@pxref{Exception Handling}).
23796 @defun Type.reference ()
23797 Return a new @code{gdb.Type} object which represents a reference to this
23801 @defun Type.pointer ()
23802 Return a new @code{gdb.Type} object which represents a pointer to this
23806 @defun Type.strip_typedefs ()
23807 Return a new @code{gdb.Type} that represents the real type,
23808 after removing all layers of typedefs.
23811 @defun Type.target ()
23812 Return a new @code{gdb.Type} object which represents the target type
23815 For a pointer type, the target type is the type of the pointed-to
23816 object. For an array type (meaning C-like arrays), the target type is
23817 the type of the elements of the array. For a function or method type,
23818 the target type is the type of the return value. For a complex type,
23819 the target type is the type of the elements. For a typedef, the
23820 target type is the aliased type.
23822 If the type does not have a target, this method will throw an
23826 @defun Type.template_argument (n @r{[}, block@r{]})
23827 If this @code{gdb.Type} is an instantiation of a template, this will
23828 return a new @code{gdb.Type} which represents the type of the
23829 @var{n}th template argument.
23831 If this @code{gdb.Type} is not a template type, this will throw an
23832 exception. Ordinarily, only C@t{++} code will have template types.
23834 If @var{block} is given, then @var{name} is looked up in that scope.
23835 Otherwise, it is searched for globally.
23839 Each type has a code, which indicates what category this type falls
23840 into. The available type categories are represented by constants
23841 defined in the @code{gdb} module:
23844 @findex TYPE_CODE_PTR
23845 @findex gdb.TYPE_CODE_PTR
23846 @item gdb.TYPE_CODE_PTR
23847 The type is a pointer.
23849 @findex TYPE_CODE_ARRAY
23850 @findex gdb.TYPE_CODE_ARRAY
23851 @item gdb.TYPE_CODE_ARRAY
23852 The type is an array.
23854 @findex TYPE_CODE_STRUCT
23855 @findex gdb.TYPE_CODE_STRUCT
23856 @item gdb.TYPE_CODE_STRUCT
23857 The type is a structure.
23859 @findex TYPE_CODE_UNION
23860 @findex gdb.TYPE_CODE_UNION
23861 @item gdb.TYPE_CODE_UNION
23862 The type is a union.
23864 @findex TYPE_CODE_ENUM
23865 @findex gdb.TYPE_CODE_ENUM
23866 @item gdb.TYPE_CODE_ENUM
23867 The type is an enum.
23869 @findex TYPE_CODE_FLAGS
23870 @findex gdb.TYPE_CODE_FLAGS
23871 @item gdb.TYPE_CODE_FLAGS
23872 A bit flags type, used for things such as status registers.
23874 @findex TYPE_CODE_FUNC
23875 @findex gdb.TYPE_CODE_FUNC
23876 @item gdb.TYPE_CODE_FUNC
23877 The type is a function.
23879 @findex TYPE_CODE_INT
23880 @findex gdb.TYPE_CODE_INT
23881 @item gdb.TYPE_CODE_INT
23882 The type is an integer type.
23884 @findex TYPE_CODE_FLT
23885 @findex gdb.TYPE_CODE_FLT
23886 @item gdb.TYPE_CODE_FLT
23887 A floating point type.
23889 @findex TYPE_CODE_VOID
23890 @findex gdb.TYPE_CODE_VOID
23891 @item gdb.TYPE_CODE_VOID
23892 The special type @code{void}.
23894 @findex TYPE_CODE_SET
23895 @findex gdb.TYPE_CODE_SET
23896 @item gdb.TYPE_CODE_SET
23899 @findex TYPE_CODE_RANGE
23900 @findex gdb.TYPE_CODE_RANGE
23901 @item gdb.TYPE_CODE_RANGE
23902 A range type, that is, an integer type with bounds.
23904 @findex TYPE_CODE_STRING
23905 @findex gdb.TYPE_CODE_STRING
23906 @item gdb.TYPE_CODE_STRING
23907 A string type. Note that this is only used for certain languages with
23908 language-defined string types; C strings are not represented this way.
23910 @findex TYPE_CODE_BITSTRING
23911 @findex gdb.TYPE_CODE_BITSTRING
23912 @item gdb.TYPE_CODE_BITSTRING
23913 A string of bits. It is deprecated.
23915 @findex TYPE_CODE_ERROR
23916 @findex gdb.TYPE_CODE_ERROR
23917 @item gdb.TYPE_CODE_ERROR
23918 An unknown or erroneous type.
23920 @findex TYPE_CODE_METHOD
23921 @findex gdb.TYPE_CODE_METHOD
23922 @item gdb.TYPE_CODE_METHOD
23923 A method type, as found in C@t{++} or Java.
23925 @findex TYPE_CODE_METHODPTR
23926 @findex gdb.TYPE_CODE_METHODPTR
23927 @item gdb.TYPE_CODE_METHODPTR
23928 A pointer-to-member-function.
23930 @findex TYPE_CODE_MEMBERPTR
23931 @findex gdb.TYPE_CODE_MEMBERPTR
23932 @item gdb.TYPE_CODE_MEMBERPTR
23933 A pointer-to-member.
23935 @findex TYPE_CODE_REF
23936 @findex gdb.TYPE_CODE_REF
23937 @item gdb.TYPE_CODE_REF
23940 @findex TYPE_CODE_CHAR
23941 @findex gdb.TYPE_CODE_CHAR
23942 @item gdb.TYPE_CODE_CHAR
23945 @findex TYPE_CODE_BOOL
23946 @findex gdb.TYPE_CODE_BOOL
23947 @item gdb.TYPE_CODE_BOOL
23950 @findex TYPE_CODE_COMPLEX
23951 @findex gdb.TYPE_CODE_COMPLEX
23952 @item gdb.TYPE_CODE_COMPLEX
23953 A complex float type.
23955 @findex TYPE_CODE_TYPEDEF
23956 @findex gdb.TYPE_CODE_TYPEDEF
23957 @item gdb.TYPE_CODE_TYPEDEF
23958 A typedef to some other type.
23960 @findex TYPE_CODE_NAMESPACE
23961 @findex gdb.TYPE_CODE_NAMESPACE
23962 @item gdb.TYPE_CODE_NAMESPACE
23963 A C@t{++} namespace.
23965 @findex TYPE_CODE_DECFLOAT
23966 @findex gdb.TYPE_CODE_DECFLOAT
23967 @item gdb.TYPE_CODE_DECFLOAT
23968 A decimal floating point type.
23970 @findex TYPE_CODE_INTERNAL_FUNCTION
23971 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23972 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23973 A function internal to @value{GDBN}. This is the type used to represent
23974 convenience functions.
23977 Further support for types is provided in the @code{gdb.types}
23978 Python module (@pxref{gdb.types}).
23980 @node Pretty Printing API
23981 @subsubsection Pretty Printing API
23983 An example output is provided (@pxref{Pretty Printing}).
23985 A pretty-printer is just an object that holds a value and implements a
23986 specific interface, defined here.
23988 @defun pretty_printer.children (self)
23989 @value{GDBN} will call this method on a pretty-printer to compute the
23990 children of the pretty-printer's value.
23992 This method must return an object conforming to the Python iterator
23993 protocol. Each item returned by the iterator must be a tuple holding
23994 two elements. The first element is the ``name'' of the child; the
23995 second element is the child's value. The value can be any Python
23996 object which is convertible to a @value{GDBN} value.
23998 This method is optional. If it does not exist, @value{GDBN} will act
23999 as though the value has no children.
24002 @defun pretty_printer.display_hint (self)
24003 The CLI may call this method and use its result to change the
24004 formatting of a value. The result will also be supplied to an MI
24005 consumer as a @samp{displayhint} attribute of the variable being
24008 This method is optional. If it does exist, this method must return a
24011 Some display hints are predefined by @value{GDBN}:
24015 Indicate that the object being printed is ``array-like''. The CLI
24016 uses this to respect parameters such as @code{set print elements} and
24017 @code{set print array}.
24020 Indicate that the object being printed is ``map-like'', and that the
24021 children of this value can be assumed to alternate between keys and
24025 Indicate that the object being printed is ``string-like''. If the
24026 printer's @code{to_string} method returns a Python string of some
24027 kind, then @value{GDBN} will call its internal language-specific
24028 string-printing function to format the string. For the CLI this means
24029 adding quotation marks, possibly escaping some characters, respecting
24030 @code{set print elements}, and the like.
24034 @defun pretty_printer.to_string (self)
24035 @value{GDBN} will call this method to display the string
24036 representation of the value passed to the object's constructor.
24038 When printing from the CLI, if the @code{to_string} method exists,
24039 then @value{GDBN} will prepend its result to the values returned by
24040 @code{children}. Exactly how this formatting is done is dependent on
24041 the display hint, and may change as more hints are added. Also,
24042 depending on the print settings (@pxref{Print Settings}), the CLI may
24043 print just the result of @code{to_string} in a stack trace, omitting
24044 the result of @code{children}.
24046 If this method returns a string, it is printed verbatim.
24048 Otherwise, if this method returns an instance of @code{gdb.Value},
24049 then @value{GDBN} prints this value. This may result in a call to
24050 another pretty-printer.
24052 If instead the method returns a Python value which is convertible to a
24053 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24054 the resulting value. Again, this may result in a call to another
24055 pretty-printer. Python scalars (integers, floats, and booleans) and
24056 strings are convertible to @code{gdb.Value}; other types are not.
24058 Finally, if this method returns @code{None} then no further operations
24059 are peformed in this method and nothing is printed.
24061 If the result is not one of these types, an exception is raised.
24064 @value{GDBN} provides a function which can be used to look up the
24065 default pretty-printer for a @code{gdb.Value}:
24067 @findex gdb.default_visualizer
24068 @defun gdb.default_visualizer (value)
24069 This function takes a @code{gdb.Value} object as an argument. If a
24070 pretty-printer for this value exists, then it is returned. If no such
24071 printer exists, then this returns @code{None}.
24074 @node Selecting Pretty-Printers
24075 @subsubsection Selecting Pretty-Printers
24077 The Python list @code{gdb.pretty_printers} contains an array of
24078 functions or callable objects that have been registered via addition
24079 as a pretty-printer. Printers in this list are called @code{global}
24080 printers, they're available when debugging all inferiors.
24081 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24082 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24085 Each function on these lists is passed a single @code{gdb.Value}
24086 argument and should return a pretty-printer object conforming to the
24087 interface definition above (@pxref{Pretty Printing API}). If a function
24088 cannot create a pretty-printer for the value, it should return
24091 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24092 @code{gdb.Objfile} in the current program space and iteratively calls
24093 each enabled lookup routine in the list for that @code{gdb.Objfile}
24094 until it receives a pretty-printer object.
24095 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24096 searches the pretty-printer list of the current program space,
24097 calling each enabled function until an object is returned.
24098 After these lists have been exhausted, it tries the global
24099 @code{gdb.pretty_printers} list, again calling each enabled function until an
24100 object is returned.
24102 The order in which the objfiles are searched is not specified. For a
24103 given list, functions are always invoked from the head of the list,
24104 and iterated over sequentially until the end of the list, or a printer
24105 object is returned.
24107 For various reasons a pretty-printer may not work.
24108 For example, the underlying data structure may have changed and
24109 the pretty-printer is out of date.
24111 The consequences of a broken pretty-printer are severe enough that
24112 @value{GDBN} provides support for enabling and disabling individual
24113 printers. For example, if @code{print frame-arguments} is on,
24114 a backtrace can become highly illegible if any argument is printed
24115 with a broken printer.
24117 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24118 attribute to the registered function or callable object. If this attribute
24119 is present and its value is @code{False}, the printer is disabled, otherwise
24120 the printer is enabled.
24122 @node Writing a Pretty-Printer
24123 @subsubsection Writing a Pretty-Printer
24124 @cindex writing a pretty-printer
24126 A pretty-printer consists of two parts: a lookup function to detect
24127 if the type is supported, and the printer itself.
24129 Here is an example showing how a @code{std::string} printer might be
24130 written. @xref{Pretty Printing API}, for details on the API this class
24134 class StdStringPrinter(object):
24135 "Print a std::string"
24137 def __init__(self, val):
24140 def to_string(self):
24141 return self.val['_M_dataplus']['_M_p']
24143 def display_hint(self):
24147 And here is an example showing how a lookup function for the printer
24148 example above might be written.
24151 def str_lookup_function(val):
24152 lookup_tag = val.type.tag
24153 if lookup_tag == None:
24155 regex = re.compile("^std::basic_string<char,.*>$")
24156 if regex.match(lookup_tag):
24157 return StdStringPrinter(val)
24161 The example lookup function extracts the value's type, and attempts to
24162 match it to a type that it can pretty-print. If it is a type the
24163 printer can pretty-print, it will return a printer object. If not, it
24164 returns @code{None}.
24166 We recommend that you put your core pretty-printers into a Python
24167 package. If your pretty-printers are for use with a library, we
24168 further recommend embedding a version number into the package name.
24169 This practice will enable @value{GDBN} to load multiple versions of
24170 your pretty-printers at the same time, because they will have
24173 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24174 can be evaluated multiple times without changing its meaning. An
24175 ideal auto-load file will consist solely of @code{import}s of your
24176 printer modules, followed by a call to a register pretty-printers with
24177 the current objfile.
24179 Taken as a whole, this approach will scale nicely to multiple
24180 inferiors, each potentially using a different library version.
24181 Embedding a version number in the Python package name will ensure that
24182 @value{GDBN} is able to load both sets of printers simultaneously.
24183 Then, because the search for pretty-printers is done by objfile, and
24184 because your auto-loaded code took care to register your library's
24185 printers with a specific objfile, @value{GDBN} will find the correct
24186 printers for the specific version of the library used by each
24189 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24190 this code might appear in @code{gdb.libstdcxx.v6}:
24193 def register_printers(objfile):
24194 objfile.pretty_printers.append(str_lookup_function)
24198 And then the corresponding contents of the auto-load file would be:
24201 import gdb.libstdcxx.v6
24202 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24205 The previous example illustrates a basic pretty-printer.
24206 There are a few things that can be improved on.
24207 The printer doesn't have a name, making it hard to identify in a
24208 list of installed printers. The lookup function has a name, but
24209 lookup functions can have arbitrary, even identical, names.
24211 Second, the printer only handles one type, whereas a library typically has
24212 several types. One could install a lookup function for each desired type
24213 in the library, but one could also have a single lookup function recognize
24214 several types. The latter is the conventional way this is handled.
24215 If a pretty-printer can handle multiple data types, then its
24216 @dfn{subprinters} are the printers for the individual data types.
24218 The @code{gdb.printing} module provides a formal way of solving these
24219 problems (@pxref{gdb.printing}).
24220 Here is another example that handles multiple types.
24222 These are the types we are going to pretty-print:
24225 struct foo @{ int a, b; @};
24226 struct bar @{ struct foo x, y; @};
24229 Here are the printers:
24233 """Print a foo object."""
24235 def __init__(self, val):
24238 def to_string(self):
24239 return ("a=<" + str(self.val["a"]) +
24240 "> b=<" + str(self.val["b"]) + ">")
24243 """Print a bar object."""
24245 def __init__(self, val):
24248 def to_string(self):
24249 return ("x=<" + str(self.val["x"]) +
24250 "> y=<" + str(self.val["y"]) + ">")
24253 This example doesn't need a lookup function, that is handled by the
24254 @code{gdb.printing} module. Instead a function is provided to build up
24255 the object that handles the lookup.
24258 import gdb.printing
24260 def build_pretty_printer():
24261 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24263 pp.add_printer('foo', '^foo$', fooPrinter)
24264 pp.add_printer('bar', '^bar$', barPrinter)
24268 And here is the autoload support:
24271 import gdb.printing
24273 gdb.printing.register_pretty_printer(
24274 gdb.current_objfile(),
24275 my_library.build_pretty_printer())
24278 Finally, when this printer is loaded into @value{GDBN}, here is the
24279 corresponding output of @samp{info pretty-printer}:
24282 (gdb) info pretty-printer
24289 @node Type Printing API
24290 @subsubsection Type Printing API
24291 @cindex type printing API for Python
24293 @value{GDBN} provides a way for Python code to customize type display.
24294 This is mainly useful for substituting canonical typedef names for
24297 @cindex type printer
24298 A @dfn{type printer} is just a Python object conforming to a certain
24299 protocol. A simple base class implementing the protocol is provided;
24300 see @ref{gdb.types}. A type printer must supply at least:
24302 @defivar type_printer enabled
24303 A boolean which is True if the printer is enabled, and False
24304 otherwise. This is manipulated by the @code{enable type-printer}
24305 and @code{disable type-printer} commands.
24308 @defivar type_printer name
24309 The name of the type printer. This must be a string. This is used by
24310 the @code{enable type-printer} and @code{disable type-printer}
24314 @defmethod type_printer instantiate (self)
24315 This is called by @value{GDBN} at the start of type-printing. It is
24316 only called if the type printer is enabled. This method must return a
24317 new object that supplies a @code{recognize} method, as described below.
24321 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24322 will compute a list of type recognizers. This is done by iterating
24323 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24324 followed by the per-progspace type printers (@pxref{Progspaces In
24325 Python}), and finally the global type printers.
24327 @value{GDBN} will call the @code{instantiate} method of each enabled
24328 type printer. If this method returns @code{None}, then the result is
24329 ignored; otherwise, it is appended to the list of recognizers.
24331 Then, when @value{GDBN} is going to display a type name, it iterates
24332 over the list of recognizers. For each one, it calls the recognition
24333 function, stopping if the function returns a non-@code{None} value.
24334 The recognition function is defined as:
24336 @defmethod type_recognizer recognize (self, type)
24337 If @var{type} is not recognized, return @code{None}. Otherwise,
24338 return a string which is to be printed as the name of @var{type}.
24339 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24343 @value{GDBN} uses this two-pass approach so that type printers can
24344 efficiently cache information without holding on to it too long. For
24345 example, it can be convenient to look up type information in a type
24346 printer and hold it for a recognizer's lifetime; if a single pass were
24347 done then type printers would have to make use of the event system in
24348 order to avoid holding information that could become stale as the
24351 @node Inferiors In Python
24352 @subsubsection Inferiors In Python
24353 @cindex inferiors in Python
24355 @findex gdb.Inferior
24356 Programs which are being run under @value{GDBN} are called inferiors
24357 (@pxref{Inferiors and Programs}). Python scripts can access
24358 information about and manipulate inferiors controlled by @value{GDBN}
24359 via objects of the @code{gdb.Inferior} class.
24361 The following inferior-related functions are available in the @code{gdb}
24364 @defun gdb.inferiors ()
24365 Return a tuple containing all inferior objects.
24368 @defun gdb.selected_inferior ()
24369 Return an object representing the current inferior.
24372 A @code{gdb.Inferior} object has the following attributes:
24374 @defvar Inferior.num
24375 ID of inferior, as assigned by GDB.
24378 @defvar Inferior.pid
24379 Process ID of the inferior, as assigned by the underlying operating
24383 @defvar Inferior.was_attached
24384 Boolean signaling whether the inferior was created using `attach', or
24385 started by @value{GDBN} itself.
24388 A @code{gdb.Inferior} object has the following methods:
24390 @defun Inferior.is_valid ()
24391 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24392 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24393 if the inferior no longer exists within @value{GDBN}. All other
24394 @code{gdb.Inferior} methods will throw an exception if it is invalid
24395 at the time the method is called.
24398 @defun Inferior.threads ()
24399 This method returns a tuple holding all the threads which are valid
24400 when it is called. If there are no valid threads, the method will
24401 return an empty tuple.
24404 @findex Inferior.read_memory
24405 @defun Inferior.read_memory (address, length)
24406 Read @var{length} bytes of memory from the inferior, starting at
24407 @var{address}. Returns a buffer object, which behaves much like an array
24408 or a string. It can be modified and given to the
24409 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24410 value is a @code{memoryview} object.
24413 @findex Inferior.write_memory
24414 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24415 Write the contents of @var{buffer} to the inferior, starting at
24416 @var{address}. The @var{buffer} parameter must be a Python object
24417 which supports the buffer protocol, i.e., a string, an array or the
24418 object returned from @code{Inferior.read_memory}. If given, @var{length}
24419 determines the number of bytes from @var{buffer} to be written.
24422 @findex gdb.search_memory
24423 @defun Inferior.search_memory (address, length, pattern)
24424 Search a region of the inferior memory starting at @var{address} with
24425 the given @var{length} using the search pattern supplied in
24426 @var{pattern}. The @var{pattern} parameter must be a Python object
24427 which supports the buffer protocol, i.e., a string, an array or the
24428 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24429 containing the address where the pattern was found, or @code{None} if
24430 the pattern could not be found.
24433 @node Events In Python
24434 @subsubsection Events In Python
24435 @cindex inferior events in Python
24437 @value{GDBN} provides a general event facility so that Python code can be
24438 notified of various state changes, particularly changes that occur in
24441 An @dfn{event} is just an object that describes some state change. The
24442 type of the object and its attributes will vary depending on the details
24443 of the change. All the existing events are described below.
24445 In order to be notified of an event, you must register an event handler
24446 with an @dfn{event registry}. An event registry is an object in the
24447 @code{gdb.events} module which dispatches particular events. A registry
24448 provides methods to register and unregister event handlers:
24450 @defun EventRegistry.connect (object)
24451 Add the given callable @var{object} to the registry. This object will be
24452 called when an event corresponding to this registry occurs.
24455 @defun EventRegistry.disconnect (object)
24456 Remove the given @var{object} from the registry. Once removed, the object
24457 will no longer receive notifications of events.
24460 Here is an example:
24463 def exit_handler (event):
24464 print "event type: exit"
24465 print "exit code: %d" % (event.exit_code)
24467 gdb.events.exited.connect (exit_handler)
24470 In the above example we connect our handler @code{exit_handler} to the
24471 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24472 called when the inferior exits. The argument @dfn{event} in this example is
24473 of type @code{gdb.ExitedEvent}. As you can see in the example the
24474 @code{ExitedEvent} object has an attribute which indicates the exit code of
24477 The following is a listing of the event registries that are available and
24478 details of the events they emit:
24483 Emits @code{gdb.ThreadEvent}.
24485 Some events can be thread specific when @value{GDBN} is running in non-stop
24486 mode. When represented in Python, these events all extend
24487 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24488 events which are emitted by this or other modules might extend this event.
24489 Examples of these events are @code{gdb.BreakpointEvent} and
24490 @code{gdb.ContinueEvent}.
24492 @defvar ThreadEvent.inferior_thread
24493 In non-stop mode this attribute will be set to the specific thread which was
24494 involved in the emitted event. Otherwise, it will be set to @code{None}.
24497 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24499 This event indicates that the inferior has been continued after a stop. For
24500 inherited attribute refer to @code{gdb.ThreadEvent} above.
24502 @item events.exited
24503 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24504 @code{events.ExitedEvent} has two attributes:
24505 @defvar ExitedEvent.exit_code
24506 An integer representing the exit code, if available, which the inferior
24507 has returned. (The exit code could be unavailable if, for example,
24508 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24509 the attribute does not exist.
24511 @defvar ExitedEvent inferior
24512 A reference to the inferior which triggered the @code{exited} event.
24516 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24518 Indicates that the inferior has stopped. All events emitted by this registry
24519 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24520 will indicate the stopped thread when @value{GDBN} is running in non-stop
24521 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24523 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24525 This event indicates that the inferior or one of its threads has received as
24526 signal. @code{gdb.SignalEvent} has the following attributes:
24528 @defvar SignalEvent.stop_signal
24529 A string representing the signal received by the inferior. A list of possible
24530 signal values can be obtained by running the command @code{info signals} in
24531 the @value{GDBN} command prompt.
24534 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24536 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24537 been hit, and has the following attributes:
24539 @defvar BreakpointEvent.breakpoints
24540 A sequence containing references to all the breakpoints (type
24541 @code{gdb.Breakpoint}) that were hit.
24542 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24544 @defvar BreakpointEvent.breakpoint
24545 A reference to the first breakpoint that was hit.
24546 This function is maintained for backward compatibility and is now deprecated
24547 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24550 @item events.new_objfile
24551 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24552 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24554 @defvar NewObjFileEvent.new_objfile
24555 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24556 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24561 @node Threads In Python
24562 @subsubsection Threads In Python
24563 @cindex threads in python
24565 @findex gdb.InferiorThread
24566 Python scripts can access information about, and manipulate inferior threads
24567 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24569 The following thread-related functions are available in the @code{gdb}
24572 @findex gdb.selected_thread
24573 @defun gdb.selected_thread ()
24574 This function returns the thread object for the selected thread. If there
24575 is no selected thread, this will return @code{None}.
24578 A @code{gdb.InferiorThread} object has the following attributes:
24580 @defvar InferiorThread.name
24581 The name of the thread. If the user specified a name using
24582 @code{thread name}, then this returns that name. Otherwise, if an
24583 OS-supplied name is available, then it is returned. Otherwise, this
24584 returns @code{None}.
24586 This attribute can be assigned to. The new value must be a string
24587 object, which sets the new name, or @code{None}, which removes any
24588 user-specified thread name.
24591 @defvar InferiorThread.num
24592 ID of the thread, as assigned by GDB.
24595 @defvar InferiorThread.ptid
24596 ID of the thread, as assigned by the operating system. This attribute is a
24597 tuple containing three integers. The first is the Process ID (PID); the second
24598 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24599 Either the LWPID or TID may be 0, which indicates that the operating system
24600 does not use that identifier.
24603 A @code{gdb.InferiorThread} object has the following methods:
24605 @defun InferiorThread.is_valid ()
24606 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24607 @code{False} if not. A @code{gdb.InferiorThread} object will become
24608 invalid if the thread exits, or the inferior that the thread belongs
24609 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24610 exception if it is invalid at the time the method is called.
24613 @defun InferiorThread.switch ()
24614 This changes @value{GDBN}'s currently selected thread to the one represented
24618 @defun InferiorThread.is_stopped ()
24619 Return a Boolean indicating whether the thread is stopped.
24622 @defun InferiorThread.is_running ()
24623 Return a Boolean indicating whether the thread is running.
24626 @defun InferiorThread.is_exited ()
24627 Return a Boolean indicating whether the thread is exited.
24630 @node Commands In Python
24631 @subsubsection Commands In Python
24633 @cindex commands in python
24634 @cindex python commands
24635 You can implement new @value{GDBN} CLI commands in Python. A CLI
24636 command is implemented using an instance of the @code{gdb.Command}
24637 class, most commonly using a subclass.
24639 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24640 The object initializer for @code{Command} registers the new command
24641 with @value{GDBN}. This initializer is normally invoked from the
24642 subclass' own @code{__init__} method.
24644 @var{name} is the name of the command. If @var{name} consists of
24645 multiple words, then the initial words are looked for as prefix
24646 commands. In this case, if one of the prefix commands does not exist,
24647 an exception is raised.
24649 There is no support for multi-line commands.
24651 @var{command_class} should be one of the @samp{COMMAND_} constants
24652 defined below. This argument tells @value{GDBN} how to categorize the
24653 new command in the help system.
24655 @var{completer_class} is an optional argument. If given, it should be
24656 one of the @samp{COMPLETE_} constants defined below. This argument
24657 tells @value{GDBN} how to perform completion for this command. If not
24658 given, @value{GDBN} will attempt to complete using the object's
24659 @code{complete} method (see below); if no such method is found, an
24660 error will occur when completion is attempted.
24662 @var{prefix} is an optional argument. If @code{True}, then the new
24663 command is a prefix command; sub-commands of this command may be
24666 The help text for the new command is taken from the Python
24667 documentation string for the command's class, if there is one. If no
24668 documentation string is provided, the default value ``This command is
24669 not documented.'' is used.
24672 @cindex don't repeat Python command
24673 @defun Command.dont_repeat ()
24674 By default, a @value{GDBN} command is repeated when the user enters a
24675 blank line at the command prompt. A command can suppress this
24676 behavior by invoking the @code{dont_repeat} method. This is similar
24677 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24680 @defun Command.invoke (argument, from_tty)
24681 This method is called by @value{GDBN} when this command is invoked.
24683 @var{argument} is a string. It is the argument to the command, after
24684 leading and trailing whitespace has been stripped.
24686 @var{from_tty} is a boolean argument. When true, this means that the
24687 command was entered by the user at the terminal; when false it means
24688 that the command came from elsewhere.
24690 If this method throws an exception, it is turned into a @value{GDBN}
24691 @code{error} call. Otherwise, the return value is ignored.
24693 @findex gdb.string_to_argv
24694 To break @var{argument} up into an argv-like string use
24695 @code{gdb.string_to_argv}. This function behaves identically to
24696 @value{GDBN}'s internal argument lexer @code{buildargv}.
24697 It is recommended to use this for consistency.
24698 Arguments are separated by spaces and may be quoted.
24702 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24703 ['1', '2 "3', '4 "5', "6 '7"]
24708 @cindex completion of Python commands
24709 @defun Command.complete (text, word)
24710 This method is called by @value{GDBN} when the user attempts
24711 completion on this command. All forms of completion are handled by
24712 this method, that is, the @key{TAB} and @key{M-?} key bindings
24713 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24716 The arguments @var{text} and @var{word} are both strings. @var{text}
24717 holds the complete command line up to the cursor's location.
24718 @var{word} holds the last word of the command line; this is computed
24719 using a word-breaking heuristic.
24721 The @code{complete} method can return several values:
24724 If the return value is a sequence, the contents of the sequence are
24725 used as the completions. It is up to @code{complete} to ensure that the
24726 contents actually do complete the word. A zero-length sequence is
24727 allowed, it means that there were no completions available. Only
24728 string elements of the sequence are used; other elements in the
24729 sequence are ignored.
24732 If the return value is one of the @samp{COMPLETE_} constants defined
24733 below, then the corresponding @value{GDBN}-internal completion
24734 function is invoked, and its result is used.
24737 All other results are treated as though there were no available
24742 When a new command is registered, it must be declared as a member of
24743 some general class of commands. This is used to classify top-level
24744 commands in the on-line help system; note that prefix commands are not
24745 listed under their own category but rather that of their top-level
24746 command. The available classifications are represented by constants
24747 defined in the @code{gdb} module:
24750 @findex COMMAND_NONE
24751 @findex gdb.COMMAND_NONE
24752 @item gdb.COMMAND_NONE
24753 The command does not belong to any particular class. A command in
24754 this category will not be displayed in any of the help categories.
24756 @findex COMMAND_RUNNING
24757 @findex gdb.COMMAND_RUNNING
24758 @item gdb.COMMAND_RUNNING
24759 The command is related to running the inferior. For example,
24760 @code{start}, @code{step}, and @code{continue} are in this category.
24761 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24762 commands in this category.
24764 @findex COMMAND_DATA
24765 @findex gdb.COMMAND_DATA
24766 @item gdb.COMMAND_DATA
24767 The command is related to data or variables. For example,
24768 @code{call}, @code{find}, and @code{print} are in this category. Type
24769 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24772 @findex COMMAND_STACK
24773 @findex gdb.COMMAND_STACK
24774 @item gdb.COMMAND_STACK
24775 The command has to do with manipulation of the stack. For example,
24776 @code{backtrace}, @code{frame}, and @code{return} are in this
24777 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24778 list of commands in this category.
24780 @findex COMMAND_FILES
24781 @findex gdb.COMMAND_FILES
24782 @item gdb.COMMAND_FILES
24783 This class is used for file-related commands. For example,
24784 @code{file}, @code{list} and @code{section} are in this category.
24785 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24786 commands in this category.
24788 @findex COMMAND_SUPPORT
24789 @findex gdb.COMMAND_SUPPORT
24790 @item gdb.COMMAND_SUPPORT
24791 This should be used for ``support facilities'', generally meaning
24792 things that are useful to the user when interacting with @value{GDBN},
24793 but not related to the state of the inferior. For example,
24794 @code{help}, @code{make}, and @code{shell} are in this category. Type
24795 @kbd{help support} at the @value{GDBN} prompt to see a list of
24796 commands in this category.
24798 @findex COMMAND_STATUS
24799 @findex gdb.COMMAND_STATUS
24800 @item gdb.COMMAND_STATUS
24801 The command is an @samp{info}-related command, that is, related to the
24802 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24803 and @code{show} are in this category. Type @kbd{help status} at the
24804 @value{GDBN} prompt to see a list of commands in this category.
24806 @findex COMMAND_BREAKPOINTS
24807 @findex gdb.COMMAND_BREAKPOINTS
24808 @item gdb.COMMAND_BREAKPOINTS
24809 The command has to do with breakpoints. For example, @code{break},
24810 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24811 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24814 @findex COMMAND_TRACEPOINTS
24815 @findex gdb.COMMAND_TRACEPOINTS
24816 @item gdb.COMMAND_TRACEPOINTS
24817 The command has to do with tracepoints. For example, @code{trace},
24818 @code{actions}, and @code{tfind} are in this category. Type
24819 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24820 commands in this category.
24822 @findex COMMAND_USER
24823 @findex gdb.COMMAND_USER
24824 @item gdb.COMMAND_USER
24825 The command is a general purpose command for the user, and typically
24826 does not fit in one of the other categories.
24827 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24828 a list of commands in this category, as well as the list of gdb macros
24829 (@pxref{Sequences}).
24831 @findex COMMAND_OBSCURE
24832 @findex gdb.COMMAND_OBSCURE
24833 @item gdb.COMMAND_OBSCURE
24834 The command is only used in unusual circumstances, or is not of
24835 general interest to users. For example, @code{checkpoint},
24836 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24837 obscure} at the @value{GDBN} prompt to see a list of commands in this
24840 @findex COMMAND_MAINTENANCE
24841 @findex gdb.COMMAND_MAINTENANCE
24842 @item gdb.COMMAND_MAINTENANCE
24843 The command is only useful to @value{GDBN} maintainers. The
24844 @code{maintenance} and @code{flushregs} commands are in this category.
24845 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24846 commands in this category.
24849 A new command can use a predefined completion function, either by
24850 specifying it via an argument at initialization, or by returning it
24851 from the @code{complete} method. These predefined completion
24852 constants are all defined in the @code{gdb} module:
24855 @findex COMPLETE_NONE
24856 @findex gdb.COMPLETE_NONE
24857 @item gdb.COMPLETE_NONE
24858 This constant means that no completion should be done.
24860 @findex COMPLETE_FILENAME
24861 @findex gdb.COMPLETE_FILENAME
24862 @item gdb.COMPLETE_FILENAME
24863 This constant means that filename completion should be performed.
24865 @findex COMPLETE_LOCATION
24866 @findex gdb.COMPLETE_LOCATION
24867 @item gdb.COMPLETE_LOCATION
24868 This constant means that location completion should be done.
24869 @xref{Specify Location}.
24871 @findex COMPLETE_COMMAND
24872 @findex gdb.COMPLETE_COMMAND
24873 @item gdb.COMPLETE_COMMAND
24874 This constant means that completion should examine @value{GDBN}
24877 @findex COMPLETE_SYMBOL
24878 @findex gdb.COMPLETE_SYMBOL
24879 @item gdb.COMPLETE_SYMBOL
24880 This constant means that completion should be done using symbol names
24884 The following code snippet shows how a trivial CLI command can be
24885 implemented in Python:
24888 class HelloWorld (gdb.Command):
24889 """Greet the whole world."""
24891 def __init__ (self):
24892 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24894 def invoke (self, arg, from_tty):
24895 print "Hello, World!"
24900 The last line instantiates the class, and is necessary to trigger the
24901 registration of the command with @value{GDBN}. Depending on how the
24902 Python code is read into @value{GDBN}, you may need to import the
24903 @code{gdb} module explicitly.
24905 @node Parameters In Python
24906 @subsubsection Parameters In Python
24908 @cindex parameters in python
24909 @cindex python parameters
24910 @tindex gdb.Parameter
24912 You can implement new @value{GDBN} parameters using Python. A new
24913 parameter is implemented as an instance of the @code{gdb.Parameter}
24916 Parameters are exposed to the user via the @code{set} and
24917 @code{show} commands. @xref{Help}.
24919 There are many parameters that already exist and can be set in
24920 @value{GDBN}. Two examples are: @code{set follow fork} and
24921 @code{set charset}. Setting these parameters influences certain
24922 behavior in @value{GDBN}. Similarly, you can define parameters that
24923 can be used to influence behavior in custom Python scripts and commands.
24925 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24926 The object initializer for @code{Parameter} registers the new
24927 parameter with @value{GDBN}. This initializer is normally invoked
24928 from the subclass' own @code{__init__} method.
24930 @var{name} is the name of the new parameter. If @var{name} consists
24931 of multiple words, then the initial words are looked for as prefix
24932 parameters. An example of this can be illustrated with the
24933 @code{set print} set of parameters. If @var{name} is
24934 @code{print foo}, then @code{print} will be searched as the prefix
24935 parameter. In this case the parameter can subsequently be accessed in
24936 @value{GDBN} as @code{set print foo}.
24938 If @var{name} consists of multiple words, and no prefix parameter group
24939 can be found, an exception is raised.
24941 @var{command-class} should be one of the @samp{COMMAND_} constants
24942 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24943 categorize the new parameter in the help system.
24945 @var{parameter-class} should be one of the @samp{PARAM_} constants
24946 defined below. This argument tells @value{GDBN} the type of the new
24947 parameter; this information is used for input validation and
24950 If @var{parameter-class} is @code{PARAM_ENUM}, then
24951 @var{enum-sequence} must be a sequence of strings. These strings
24952 represent the possible values for the parameter.
24954 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24955 of a fourth argument will cause an exception to be thrown.
24957 The help text for the new parameter is taken from the Python
24958 documentation string for the parameter's class, if there is one. If
24959 there is no documentation string, a default value is used.
24962 @defvar Parameter.set_doc
24963 If this attribute exists, and is a string, then its value is used as
24964 the help text for this parameter's @code{set} command. The value is
24965 examined when @code{Parameter.__init__} is invoked; subsequent changes
24969 @defvar Parameter.show_doc
24970 If this attribute exists, and is a string, then its value is used as
24971 the help text for this parameter's @code{show} command. The value is
24972 examined when @code{Parameter.__init__} is invoked; subsequent changes
24976 @defvar Parameter.value
24977 The @code{value} attribute holds the underlying value of the
24978 parameter. It can be read and assigned to just as any other
24979 attribute. @value{GDBN} does validation when assignments are made.
24982 There are two methods that should be implemented in any
24983 @code{Parameter} class. These are:
24985 @defun Parameter.get_set_string (self)
24986 @value{GDBN} will call this method when a @var{parameter}'s value has
24987 been changed via the @code{set} API (for example, @kbd{set foo off}).
24988 The @code{value} attribute has already been populated with the new
24989 value and may be used in output. This method must return a string.
24992 @defun Parameter.get_show_string (self, svalue)
24993 @value{GDBN} will call this method when a @var{parameter}'s
24994 @code{show} API has been invoked (for example, @kbd{show foo}). The
24995 argument @code{svalue} receives the string representation of the
24996 current value. This method must return a string.
24999 When a new parameter is defined, its type must be specified. The
25000 available types are represented by constants defined in the @code{gdb}
25004 @findex PARAM_BOOLEAN
25005 @findex gdb.PARAM_BOOLEAN
25006 @item gdb.PARAM_BOOLEAN
25007 The value is a plain boolean. The Python boolean values, @code{True}
25008 and @code{False} are the only valid values.
25010 @findex PARAM_AUTO_BOOLEAN
25011 @findex gdb.PARAM_AUTO_BOOLEAN
25012 @item gdb.PARAM_AUTO_BOOLEAN
25013 The value has three possible states: true, false, and @samp{auto}. In
25014 Python, true and false are represented using boolean constants, and
25015 @samp{auto} is represented using @code{None}.
25017 @findex PARAM_UINTEGER
25018 @findex gdb.PARAM_UINTEGER
25019 @item gdb.PARAM_UINTEGER
25020 The value is an unsigned integer. The value of 0 should be
25021 interpreted to mean ``unlimited''.
25023 @findex PARAM_INTEGER
25024 @findex gdb.PARAM_INTEGER
25025 @item gdb.PARAM_INTEGER
25026 The value is a signed integer. The value of 0 should be interpreted
25027 to mean ``unlimited''.
25029 @findex PARAM_STRING
25030 @findex gdb.PARAM_STRING
25031 @item gdb.PARAM_STRING
25032 The value is a string. When the user modifies the string, any escape
25033 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
25034 translated into corresponding characters and encoded into the current
25037 @findex PARAM_STRING_NOESCAPE
25038 @findex gdb.PARAM_STRING_NOESCAPE
25039 @item gdb.PARAM_STRING_NOESCAPE
25040 The value is a string. When the user modifies the string, escapes are
25041 passed through untranslated.
25043 @findex PARAM_OPTIONAL_FILENAME
25044 @findex gdb.PARAM_OPTIONAL_FILENAME
25045 @item gdb.PARAM_OPTIONAL_FILENAME
25046 The value is a either a filename (a string), or @code{None}.
25048 @findex PARAM_FILENAME
25049 @findex gdb.PARAM_FILENAME
25050 @item gdb.PARAM_FILENAME
25051 The value is a filename. This is just like
25052 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
25054 @findex PARAM_ZINTEGER
25055 @findex gdb.PARAM_ZINTEGER
25056 @item gdb.PARAM_ZINTEGER
25057 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
25058 is interpreted as itself.
25061 @findex gdb.PARAM_ENUM
25062 @item gdb.PARAM_ENUM
25063 The value is a string, which must be one of a collection string
25064 constants provided when the parameter is created.
25067 @node Functions In Python
25068 @subsubsection Writing new convenience functions
25070 @cindex writing convenience functions
25071 @cindex convenience functions in python
25072 @cindex python convenience functions
25073 @tindex gdb.Function
25075 You can implement new convenience functions (@pxref{Convenience Vars})
25076 in Python. A convenience function is an instance of a subclass of the
25077 class @code{gdb.Function}.
25079 @defun Function.__init__ (name)
25080 The initializer for @code{Function} registers the new function with
25081 @value{GDBN}. The argument @var{name} is the name of the function,
25082 a string. The function will be visible to the user as a convenience
25083 variable of type @code{internal function}, whose name is the same as
25084 the given @var{name}.
25086 The documentation for the new function is taken from the documentation
25087 string for the new class.
25090 @defun Function.invoke (@var{*args})
25091 When a convenience function is evaluated, its arguments are converted
25092 to instances of @code{gdb.Value}, and then the function's
25093 @code{invoke} method is called. Note that @value{GDBN} does not
25094 predetermine the arity of convenience functions. Instead, all
25095 available arguments are passed to @code{invoke}, following the
25096 standard Python calling convention. In particular, a convenience
25097 function can have default values for parameters without ill effect.
25099 The return value of this method is used as its value in the enclosing
25100 expression. If an ordinary Python value is returned, it is converted
25101 to a @code{gdb.Value} following the usual rules.
25104 The following code snippet shows how a trivial convenience function can
25105 be implemented in Python:
25108 class Greet (gdb.Function):
25109 """Return string to greet someone.
25110 Takes a name as argument."""
25112 def __init__ (self):
25113 super (Greet, self).__init__ ("greet")
25115 def invoke (self, name):
25116 return "Hello, %s!" % name.string ()
25121 The last line instantiates the class, and is necessary to trigger the
25122 registration of the function with @value{GDBN}. Depending on how the
25123 Python code is read into @value{GDBN}, you may need to import the
25124 @code{gdb} module explicitly.
25126 Now you can use the function in an expression:
25129 (gdb) print $greet("Bob")
25133 @node Progspaces In Python
25134 @subsubsection Program Spaces In Python
25136 @cindex progspaces in python
25137 @tindex gdb.Progspace
25139 A program space, or @dfn{progspace}, represents a symbolic view
25140 of an address space.
25141 It consists of all of the objfiles of the program.
25142 @xref{Objfiles In Python}.
25143 @xref{Inferiors and Programs, program spaces}, for more details
25144 about program spaces.
25146 The following progspace-related functions are available in the
25149 @findex gdb.current_progspace
25150 @defun gdb.current_progspace ()
25151 This function returns the program space of the currently selected inferior.
25152 @xref{Inferiors and Programs}.
25155 @findex gdb.progspaces
25156 @defun gdb.progspaces ()
25157 Return a sequence of all the progspaces currently known to @value{GDBN}.
25160 Each progspace is represented by an instance of the @code{gdb.Progspace}
25163 @defvar Progspace.filename
25164 The file name of the progspace as a string.
25167 @defvar Progspace.pretty_printers
25168 The @code{pretty_printers} attribute is a list of functions. It is
25169 used to look up pretty-printers. A @code{Value} is passed to each
25170 function in order; if the function returns @code{None}, then the
25171 search continues. Otherwise, the return value should be an object
25172 which is used to format the value. @xref{Pretty Printing API}, for more
25176 @defvar Progspace.type_printers
25177 The @code{type_printers} attribute is a list of type printer objects.
25178 @xref{Type Printing API}, for more information.
25181 @node Objfiles In Python
25182 @subsubsection Objfiles In Python
25184 @cindex objfiles in python
25185 @tindex gdb.Objfile
25187 @value{GDBN} loads symbols for an inferior from various
25188 symbol-containing files (@pxref{Files}). These include the primary
25189 executable file, any shared libraries used by the inferior, and any
25190 separate debug info files (@pxref{Separate Debug Files}).
25191 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
25193 The following objfile-related functions are available in the
25196 @findex gdb.current_objfile
25197 @defun gdb.current_objfile ()
25198 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
25199 sets the ``current objfile'' to the corresponding objfile. This
25200 function returns the current objfile. If there is no current objfile,
25201 this function returns @code{None}.
25204 @findex gdb.objfiles
25205 @defun gdb.objfiles ()
25206 Return a sequence of all the objfiles current known to @value{GDBN}.
25207 @xref{Objfiles In Python}.
25210 Each objfile is represented by an instance of the @code{gdb.Objfile}
25213 @defvar Objfile.filename
25214 The file name of the objfile as a string.
25217 @defvar Objfile.pretty_printers
25218 The @code{pretty_printers} attribute is a list of functions. It is
25219 used to look up pretty-printers. A @code{Value} is passed to each
25220 function in order; if the function returns @code{None}, then the
25221 search continues. Otherwise, the return value should be an object
25222 which is used to format the value. @xref{Pretty Printing API}, for more
25226 @defvar Objfile.type_printers
25227 The @code{type_printers} attribute is a list of type printer objects.
25228 @xref{Type Printing API}, for more information.
25231 A @code{gdb.Objfile} object has the following methods:
25233 @defun Objfile.is_valid ()
25234 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25235 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25236 if the object file it refers to is not loaded in @value{GDBN} any
25237 longer. All other @code{gdb.Objfile} methods will throw an exception
25238 if it is invalid at the time the method is called.
25241 @node Frames In Python
25242 @subsubsection Accessing inferior stack frames from Python.
25244 @cindex frames in python
25245 When the debugged program stops, @value{GDBN} is able to analyze its call
25246 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25247 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25248 while its corresponding frame exists in the inferior's stack. If you try
25249 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25250 exception (@pxref{Exception Handling}).
25252 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25256 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25260 The following frame-related functions are available in the @code{gdb} module:
25262 @findex gdb.selected_frame
25263 @defun gdb.selected_frame ()
25264 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25267 @findex gdb.newest_frame
25268 @defun gdb.newest_frame ()
25269 Return the newest frame object for the selected thread.
25272 @defun gdb.frame_stop_reason_string (reason)
25273 Return a string explaining the reason why @value{GDBN} stopped unwinding
25274 frames, as expressed by the given @var{reason} code (an integer, see the
25275 @code{unwind_stop_reason} method further down in this section).
25278 A @code{gdb.Frame} object has the following methods:
25280 @defun Frame.is_valid ()
25281 Returns true if the @code{gdb.Frame} object is valid, false if not.
25282 A frame object can become invalid if the frame it refers to doesn't
25283 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25284 an exception if it is invalid at the time the method is called.
25287 @defun Frame.name ()
25288 Returns the function name of the frame, or @code{None} if it can't be
25292 @defun Frame.architecture ()
25293 Returns the @code{gdb.Architecture} object corresponding to the frame's
25294 architecture. @xref{Architectures In Python}.
25297 @defun Frame.type ()
25298 Returns the type of the frame. The value can be one of:
25300 @item gdb.NORMAL_FRAME
25301 An ordinary stack frame.
25303 @item gdb.DUMMY_FRAME
25304 A fake stack frame that was created by @value{GDBN} when performing an
25305 inferior function call.
25307 @item gdb.INLINE_FRAME
25308 A frame representing an inlined function. The function was inlined
25309 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25311 @item gdb.TAILCALL_FRAME
25312 A frame representing a tail call. @xref{Tail Call Frames}.
25314 @item gdb.SIGTRAMP_FRAME
25315 A signal trampoline frame. This is the frame created by the OS when
25316 it calls into a signal handler.
25318 @item gdb.ARCH_FRAME
25319 A fake stack frame representing a cross-architecture call.
25321 @item gdb.SENTINEL_FRAME
25322 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25327 @defun Frame.unwind_stop_reason ()
25328 Return an integer representing the reason why it's not possible to find
25329 more frames toward the outermost frame. Use
25330 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25331 function to a string. The value can be one of:
25334 @item gdb.FRAME_UNWIND_NO_REASON
25335 No particular reason (older frames should be available).
25337 @item gdb.FRAME_UNWIND_NULL_ID
25338 The previous frame's analyzer returns an invalid result.
25340 @item gdb.FRAME_UNWIND_OUTERMOST
25341 This frame is the outermost.
25343 @item gdb.FRAME_UNWIND_UNAVAILABLE
25344 Cannot unwind further, because that would require knowing the
25345 values of registers or memory that have not been collected.
25347 @item gdb.FRAME_UNWIND_INNER_ID
25348 This frame ID looks like it ought to belong to a NEXT frame,
25349 but we got it for a PREV frame. Normally, this is a sign of
25350 unwinder failure. It could also indicate stack corruption.
25352 @item gdb.FRAME_UNWIND_SAME_ID
25353 This frame has the same ID as the previous one. That means
25354 that unwinding further would almost certainly give us another
25355 frame with exactly the same ID, so break the chain. Normally,
25356 this is a sign of unwinder failure. It could also indicate
25359 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25360 The frame unwinder did not find any saved PC, but we needed
25361 one to unwind further.
25363 @item gdb.FRAME_UNWIND_FIRST_ERROR
25364 Any stop reason greater or equal to this value indicates some kind
25365 of error. This special value facilitates writing code that tests
25366 for errors in unwinding in a way that will work correctly even if
25367 the list of the other values is modified in future @value{GDBN}
25368 versions. Using it, you could write:
25370 reason = gdb.selected_frame().unwind_stop_reason ()
25371 reason_str = gdb.frame_stop_reason_string (reason)
25372 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25373 print "An error occured: %s" % reason_str
25380 Returns the frame's resume address.
25383 @defun Frame.block ()
25384 Return the frame's code block. @xref{Blocks In Python}.
25387 @defun Frame.function ()
25388 Return the symbol for the function corresponding to this frame.
25389 @xref{Symbols In Python}.
25392 @defun Frame.older ()
25393 Return the frame that called this frame.
25396 @defun Frame.newer ()
25397 Return the frame called by this frame.
25400 @defun Frame.find_sal ()
25401 Return the frame's symtab and line object.
25402 @xref{Symbol Tables In Python}.
25405 @defun Frame.read_var (variable @r{[}, block@r{]})
25406 Return the value of @var{variable} in this frame. If the optional
25407 argument @var{block} is provided, search for the variable from that
25408 block; otherwise start at the frame's current block (which is
25409 determined by the frame's current program counter). @var{variable}
25410 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25411 @code{gdb.Block} object.
25414 @defun Frame.select ()
25415 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25419 @node Blocks In Python
25420 @subsubsection Accessing frame blocks from Python.
25422 @cindex blocks in python
25425 Within each frame, @value{GDBN} maintains information on each block
25426 stored in that frame. These blocks are organized hierarchically, and
25427 are represented individually in Python as a @code{gdb.Block}.
25428 Please see @ref{Frames In Python}, for a more in-depth discussion on
25429 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25430 detailed technical information on @value{GDBN}'s book-keeping of the
25433 A @code{gdb.Block} is iterable. The iterator returns the symbols
25434 (@pxref{Symbols In Python}) local to the block. Python programs
25435 should not assume that a specific block object will always contain a
25436 given symbol, since changes in @value{GDBN} features and
25437 infrastructure may cause symbols move across blocks in a symbol
25440 The following block-related functions are available in the @code{gdb}
25443 @findex gdb.block_for_pc
25444 @defun gdb.block_for_pc (pc)
25445 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25446 block cannot be found for the @var{pc} value specified, the function
25447 will return @code{None}.
25450 A @code{gdb.Block} object has the following methods:
25452 @defun Block.is_valid ()
25453 Returns @code{True} if the @code{gdb.Block} object is valid,
25454 @code{False} if not. A block object can become invalid if the block it
25455 refers to doesn't exist anymore in the inferior. All other
25456 @code{gdb.Block} methods will throw an exception if it is invalid at
25457 the time the method is called. The block's validity is also checked
25458 during iteration over symbols of the block.
25461 A @code{gdb.Block} object has the following attributes:
25463 @defvar Block.start
25464 The start address of the block. This attribute is not writable.
25468 The end address of the block. This attribute is not writable.
25471 @defvar Block.function
25472 The name of the block represented as a @code{gdb.Symbol}. If the
25473 block is not named, then this attribute holds @code{None}. This
25474 attribute is not writable.
25477 @defvar Block.superblock
25478 The block containing this block. If this parent block does not exist,
25479 this attribute holds @code{None}. This attribute is not writable.
25482 @defvar Block.global_block
25483 The global block associated with this block. This attribute is not
25487 @defvar Block.static_block
25488 The static block associated with this block. This attribute is not
25492 @defvar Block.is_global
25493 @code{True} if the @code{gdb.Block} object is a global block,
25494 @code{False} if not. This attribute is not
25498 @defvar Block.is_static
25499 @code{True} if the @code{gdb.Block} object is a static block,
25500 @code{False} if not. This attribute is not writable.
25503 @node Symbols In Python
25504 @subsubsection Python representation of Symbols.
25506 @cindex symbols in python
25509 @value{GDBN} represents every variable, function and type as an
25510 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25511 Similarly, Python represents these symbols in @value{GDBN} with the
25512 @code{gdb.Symbol} object.
25514 The following symbol-related functions are available in the @code{gdb}
25517 @findex gdb.lookup_symbol
25518 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25519 This function searches for a symbol by name. The search scope can be
25520 restricted to the parameters defined in the optional domain and block
25523 @var{name} is the name of the symbol. It must be a string. The
25524 optional @var{block} argument restricts the search to symbols visible
25525 in that @var{block}. The @var{block} argument must be a
25526 @code{gdb.Block} object. If omitted, the block for the current frame
25527 is used. The optional @var{domain} argument restricts
25528 the search to the domain type. The @var{domain} argument must be a
25529 domain constant defined in the @code{gdb} module and described later
25532 The result is a tuple of two elements.
25533 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25535 If the symbol is found, the second element is @code{True} if the symbol
25536 is a field of a method's object (e.g., @code{this} in C@t{++}),
25537 otherwise it is @code{False}.
25538 If the symbol is not found, the second element is @code{False}.
25541 @findex gdb.lookup_global_symbol
25542 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25543 This function searches for a global symbol by name.
25544 The search scope can be restricted to by the domain argument.
25546 @var{name} is the name of the symbol. It must be a string.
25547 The optional @var{domain} argument restricts the search to the domain type.
25548 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25549 module and described later in this chapter.
25551 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25555 A @code{gdb.Symbol} object has the following attributes:
25557 @defvar Symbol.type
25558 The type of the symbol or @code{None} if no type is recorded.
25559 This attribute is represented as a @code{gdb.Type} object.
25560 @xref{Types In Python}. This attribute is not writable.
25563 @defvar Symbol.symtab
25564 The symbol table in which the symbol appears. This attribute is
25565 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25566 Python}. This attribute is not writable.
25569 @defvar Symbol.line
25570 The line number in the source code at which the symbol was defined.
25571 This is an integer.
25574 @defvar Symbol.name
25575 The name of the symbol as a string. This attribute is not writable.
25578 @defvar Symbol.linkage_name
25579 The name of the symbol, as used by the linker (i.e., may be mangled).
25580 This attribute is not writable.
25583 @defvar Symbol.print_name
25584 The name of the symbol in a form suitable for output. This is either
25585 @code{name} or @code{linkage_name}, depending on whether the user
25586 asked @value{GDBN} to display demangled or mangled names.
25589 @defvar Symbol.addr_class
25590 The address class of the symbol. This classifies how to find the value
25591 of a symbol. Each address class is a constant defined in the
25592 @code{gdb} module and described later in this chapter.
25595 @defvar Symbol.needs_frame
25596 This is @code{True} if evaluating this symbol's value requires a frame
25597 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25598 local variables will require a frame, but other symbols will not.
25601 @defvar Symbol.is_argument
25602 @code{True} if the symbol is an argument of a function.
25605 @defvar Symbol.is_constant
25606 @code{True} if the symbol is a constant.
25609 @defvar Symbol.is_function
25610 @code{True} if the symbol is a function or a method.
25613 @defvar Symbol.is_variable
25614 @code{True} if the symbol is a variable.
25617 A @code{gdb.Symbol} object has the following methods:
25619 @defun Symbol.is_valid ()
25620 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25621 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25622 the symbol it refers to does not exist in @value{GDBN} any longer.
25623 All other @code{gdb.Symbol} methods will throw an exception if it is
25624 invalid at the time the method is called.
25627 @defun Symbol.value (@r{[}frame@r{]})
25628 Compute the value of the symbol, as a @code{gdb.Value}. For
25629 functions, this computes the address of the function, cast to the
25630 appropriate type. If the symbol requires a frame in order to compute
25631 its value, then @var{frame} must be given. If @var{frame} is not
25632 given, or if @var{frame} is invalid, then this method will throw an
25636 The available domain categories in @code{gdb.Symbol} are represented
25637 as constants in the @code{gdb} module:
25640 @findex SYMBOL_UNDEF_DOMAIN
25641 @findex gdb.SYMBOL_UNDEF_DOMAIN
25642 @item gdb.SYMBOL_UNDEF_DOMAIN
25643 This is used when a domain has not been discovered or none of the
25644 following domains apply. This usually indicates an error either
25645 in the symbol information or in @value{GDBN}'s handling of symbols.
25646 @findex SYMBOL_VAR_DOMAIN
25647 @findex gdb.SYMBOL_VAR_DOMAIN
25648 @item gdb.SYMBOL_VAR_DOMAIN
25649 This domain contains variables, function names, typedef names and enum
25651 @findex SYMBOL_STRUCT_DOMAIN
25652 @findex gdb.SYMBOL_STRUCT_DOMAIN
25653 @item gdb.SYMBOL_STRUCT_DOMAIN
25654 This domain holds struct, union and enum type names.
25655 @findex SYMBOL_LABEL_DOMAIN
25656 @findex gdb.SYMBOL_LABEL_DOMAIN
25657 @item gdb.SYMBOL_LABEL_DOMAIN
25658 This domain contains names of labels (for gotos).
25659 @findex SYMBOL_VARIABLES_DOMAIN
25660 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25661 @item gdb.SYMBOL_VARIABLES_DOMAIN
25662 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25663 contains everything minus functions and types.
25664 @findex SYMBOL_FUNCTIONS_DOMAIN
25665 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25666 @item gdb.SYMBOL_FUNCTION_DOMAIN
25667 This domain contains all functions.
25668 @findex SYMBOL_TYPES_DOMAIN
25669 @findex gdb.SYMBOL_TYPES_DOMAIN
25670 @item gdb.SYMBOL_TYPES_DOMAIN
25671 This domain contains all types.
25674 The available address class categories in @code{gdb.Symbol} are represented
25675 as constants in the @code{gdb} module:
25678 @findex SYMBOL_LOC_UNDEF
25679 @findex gdb.SYMBOL_LOC_UNDEF
25680 @item gdb.SYMBOL_LOC_UNDEF
25681 If this is returned by address class, it indicates an error either in
25682 the symbol information or in @value{GDBN}'s handling of symbols.
25683 @findex SYMBOL_LOC_CONST
25684 @findex gdb.SYMBOL_LOC_CONST
25685 @item gdb.SYMBOL_LOC_CONST
25686 Value is constant int.
25687 @findex SYMBOL_LOC_STATIC
25688 @findex gdb.SYMBOL_LOC_STATIC
25689 @item gdb.SYMBOL_LOC_STATIC
25690 Value is at a fixed address.
25691 @findex SYMBOL_LOC_REGISTER
25692 @findex gdb.SYMBOL_LOC_REGISTER
25693 @item gdb.SYMBOL_LOC_REGISTER
25694 Value is in a register.
25695 @findex SYMBOL_LOC_ARG
25696 @findex gdb.SYMBOL_LOC_ARG
25697 @item gdb.SYMBOL_LOC_ARG
25698 Value is an argument. This value is at the offset stored within the
25699 symbol inside the frame's argument list.
25700 @findex SYMBOL_LOC_REF_ARG
25701 @findex gdb.SYMBOL_LOC_REF_ARG
25702 @item gdb.SYMBOL_LOC_REF_ARG
25703 Value address is stored in the frame's argument list. Just like
25704 @code{LOC_ARG} except that the value's address is stored at the
25705 offset, not the value itself.
25706 @findex SYMBOL_LOC_REGPARM_ADDR
25707 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25708 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25709 Value is a specified register. Just like @code{LOC_REGISTER} except
25710 the register holds the address of the argument instead of the argument
25712 @findex SYMBOL_LOC_LOCAL
25713 @findex gdb.SYMBOL_LOC_LOCAL
25714 @item gdb.SYMBOL_LOC_LOCAL
25715 Value is a local variable.
25716 @findex SYMBOL_LOC_TYPEDEF
25717 @findex gdb.SYMBOL_LOC_TYPEDEF
25718 @item gdb.SYMBOL_LOC_TYPEDEF
25719 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25721 @findex SYMBOL_LOC_BLOCK
25722 @findex gdb.SYMBOL_LOC_BLOCK
25723 @item gdb.SYMBOL_LOC_BLOCK
25725 @findex SYMBOL_LOC_CONST_BYTES
25726 @findex gdb.SYMBOL_LOC_CONST_BYTES
25727 @item gdb.SYMBOL_LOC_CONST_BYTES
25728 Value is a byte-sequence.
25729 @findex SYMBOL_LOC_UNRESOLVED
25730 @findex gdb.SYMBOL_LOC_UNRESOLVED
25731 @item gdb.SYMBOL_LOC_UNRESOLVED
25732 Value is at a fixed address, but the address of the variable has to be
25733 determined from the minimal symbol table whenever the variable is
25735 @findex SYMBOL_LOC_OPTIMIZED_OUT
25736 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25737 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25738 The value does not actually exist in the program.
25739 @findex SYMBOL_LOC_COMPUTED
25740 @findex gdb.SYMBOL_LOC_COMPUTED
25741 @item gdb.SYMBOL_LOC_COMPUTED
25742 The value's address is a computed location.
25745 @node Symbol Tables In Python
25746 @subsubsection Symbol table representation in Python.
25748 @cindex symbol tables in python
25750 @tindex gdb.Symtab_and_line
25752 Access to symbol table data maintained by @value{GDBN} on the inferior
25753 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25754 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25755 from the @code{find_sal} method in @code{gdb.Frame} object.
25756 @xref{Frames In Python}.
25758 For more information on @value{GDBN}'s symbol table management, see
25759 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25761 A @code{gdb.Symtab_and_line} object has the following attributes:
25763 @defvar Symtab_and_line.symtab
25764 The symbol table object (@code{gdb.Symtab}) for this frame.
25765 This attribute is not writable.
25768 @defvar Symtab_and_line.pc
25769 Indicates the start of the address range occupied by code for the
25770 current source line. This attribute is not writable.
25773 @defvar Symtab_and_line.last
25774 Indicates the end of the address range occupied by code for the current
25775 source line. This attribute is not writable.
25778 @defvar Symtab_and_line.line
25779 Indicates the current line number for this object. This
25780 attribute is not writable.
25783 A @code{gdb.Symtab_and_line} object has the following methods:
25785 @defun Symtab_and_line.is_valid ()
25786 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25787 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25788 invalid if the Symbol table and line object it refers to does not
25789 exist in @value{GDBN} any longer. All other
25790 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25791 invalid at the time the method is called.
25794 A @code{gdb.Symtab} object has the following attributes:
25796 @defvar Symtab.filename
25797 The symbol table's source filename. This attribute is not writable.
25800 @defvar Symtab.objfile
25801 The symbol table's backing object file. @xref{Objfiles In Python}.
25802 This attribute is not writable.
25805 A @code{gdb.Symtab} object has the following methods:
25807 @defun Symtab.is_valid ()
25808 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25809 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25810 the symbol table it refers to does not exist in @value{GDBN} any
25811 longer. All other @code{gdb.Symtab} methods will throw an exception
25812 if it is invalid at the time the method is called.
25815 @defun Symtab.fullname ()
25816 Return the symbol table's source absolute file name.
25819 @defun Symtab.global_block ()
25820 Return the global block of the underlying symbol table.
25821 @xref{Blocks In Python}.
25824 @defun Symtab.static_block ()
25825 Return the static block of the underlying symbol table.
25826 @xref{Blocks In Python}.
25829 @node Breakpoints In Python
25830 @subsubsection Manipulating breakpoints using Python
25832 @cindex breakpoints in python
25833 @tindex gdb.Breakpoint
25835 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25838 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25839 Create a new breakpoint. @var{spec} is a string naming the
25840 location of the breakpoint, or an expression that defines a
25841 watchpoint. The contents can be any location recognized by the
25842 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25843 command. The optional @var{type} denotes the breakpoint to create
25844 from the types defined later in this chapter. This argument can be
25845 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25846 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25847 allows the breakpoint to become invisible to the user. The breakpoint
25848 will neither be reported when created, nor will it be listed in the
25849 output from @code{info breakpoints} (but will be listed with the
25850 @code{maint info breakpoints} command). The optional @var{wp_class}
25851 argument defines the class of watchpoint to create, if @var{type} is
25852 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25853 assumed to be a @code{gdb.WP_WRITE} class.
25856 @defun Breakpoint.stop (self)
25857 The @code{gdb.Breakpoint} class can be sub-classed and, in
25858 particular, you may choose to implement the @code{stop} method.
25859 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25860 it will be called when the inferior reaches any location of a
25861 breakpoint which instantiates that sub-class. If the method returns
25862 @code{True}, the inferior will be stopped at the location of the
25863 breakpoint, otherwise the inferior will continue.
25865 If there are multiple breakpoints at the same location with a
25866 @code{stop} method, each one will be called regardless of the
25867 return status of the previous. This ensures that all @code{stop}
25868 methods have a chance to execute at that location. In this scenario
25869 if one of the methods returns @code{True} but the others return
25870 @code{False}, the inferior will still be stopped.
25872 You should not alter the execution state of the inferior (i.e.@:, step,
25873 next, etc.), alter the current frame context (i.e.@:, change the current
25874 active frame), or alter, add or delete any breakpoint. As a general
25875 rule, you should not alter any data within @value{GDBN} or the inferior
25878 Example @code{stop} implementation:
25881 class MyBreakpoint (gdb.Breakpoint):
25883 inf_val = gdb.parse_and_eval("foo")
25890 The available watchpoint types represented by constants are defined in the
25895 @findex gdb.WP_READ
25897 Read only watchpoint.
25900 @findex gdb.WP_WRITE
25902 Write only watchpoint.
25905 @findex gdb.WP_ACCESS
25906 @item gdb.WP_ACCESS
25907 Read/Write watchpoint.
25910 @defun Breakpoint.is_valid ()
25911 Return @code{True} if this @code{Breakpoint} object is valid,
25912 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25913 if the user deletes the breakpoint. In this case, the object still
25914 exists, but the underlying breakpoint does not. In the cases of
25915 watchpoint scope, the watchpoint remains valid even if execution of the
25916 inferior leaves the scope of that watchpoint.
25919 @defun Breakpoint.delete
25920 Permanently deletes the @value{GDBN} breakpoint. This also
25921 invalidates the Python @code{Breakpoint} object. Any further access
25922 to this object's attributes or methods will raise an error.
25925 @defvar Breakpoint.enabled
25926 This attribute is @code{True} if the breakpoint is enabled, and
25927 @code{False} otherwise. This attribute is writable.
25930 @defvar Breakpoint.silent
25931 This attribute is @code{True} if the breakpoint is silent, and
25932 @code{False} otherwise. This attribute is writable.
25934 Note that a breakpoint can also be silent if it has commands and the
25935 first command is @code{silent}. This is not reported by the
25936 @code{silent} attribute.
25939 @defvar Breakpoint.thread
25940 If the breakpoint is thread-specific, this attribute holds the thread
25941 id. If the breakpoint is not thread-specific, this attribute is
25942 @code{None}. This attribute is writable.
25945 @defvar Breakpoint.task
25946 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25947 id. If the breakpoint is not task-specific (or the underlying
25948 language is not Ada), this attribute is @code{None}. This attribute
25952 @defvar Breakpoint.ignore_count
25953 This attribute holds the ignore count for the breakpoint, an integer.
25954 This attribute is writable.
25957 @defvar Breakpoint.number
25958 This attribute holds the breakpoint's number --- the identifier used by
25959 the user to manipulate the breakpoint. This attribute is not writable.
25962 @defvar Breakpoint.type
25963 This attribute holds the breakpoint's type --- the identifier used to
25964 determine the actual breakpoint type or use-case. This attribute is not
25968 @defvar Breakpoint.visible
25969 This attribute tells whether the breakpoint is visible to the user
25970 when set, or when the @samp{info breakpoints} command is run. This
25971 attribute is not writable.
25974 The available types are represented by constants defined in the @code{gdb}
25978 @findex BP_BREAKPOINT
25979 @findex gdb.BP_BREAKPOINT
25980 @item gdb.BP_BREAKPOINT
25981 Normal code breakpoint.
25983 @findex BP_WATCHPOINT
25984 @findex gdb.BP_WATCHPOINT
25985 @item gdb.BP_WATCHPOINT
25986 Watchpoint breakpoint.
25988 @findex BP_HARDWARE_WATCHPOINT
25989 @findex gdb.BP_HARDWARE_WATCHPOINT
25990 @item gdb.BP_HARDWARE_WATCHPOINT
25991 Hardware assisted watchpoint.
25993 @findex BP_READ_WATCHPOINT
25994 @findex gdb.BP_READ_WATCHPOINT
25995 @item gdb.BP_READ_WATCHPOINT
25996 Hardware assisted read watchpoint.
25998 @findex BP_ACCESS_WATCHPOINT
25999 @findex gdb.BP_ACCESS_WATCHPOINT
26000 @item gdb.BP_ACCESS_WATCHPOINT
26001 Hardware assisted access watchpoint.
26004 @defvar Breakpoint.hit_count
26005 This attribute holds the hit count for the breakpoint, an integer.
26006 This attribute is writable, but currently it can only be set to zero.
26009 @defvar Breakpoint.location
26010 This attribute holds the location of the breakpoint, as specified by
26011 the user. It is a string. If the breakpoint does not have a location
26012 (that is, it is a watchpoint) the attribute's value is @code{None}. This
26013 attribute is not writable.
26016 @defvar Breakpoint.expression
26017 This attribute holds a breakpoint expression, as specified by
26018 the user. It is a string. If the breakpoint does not have an
26019 expression (the breakpoint is not a watchpoint) the attribute's value
26020 is @code{None}. This attribute is not writable.
26023 @defvar Breakpoint.condition
26024 This attribute holds the condition of the breakpoint, as specified by
26025 the user. It is a string. If there is no condition, this attribute's
26026 value is @code{None}. This attribute is writable.
26029 @defvar Breakpoint.commands
26030 This attribute holds the commands attached to the breakpoint. If
26031 there are commands, this attribute's value is a string holding all the
26032 commands, separated by newlines. If there are no commands, this
26033 attribute is @code{None}. This attribute is not writable.
26036 @node Finish Breakpoints in Python
26037 @subsubsection Finish Breakpoints
26039 @cindex python finish breakpoints
26040 @tindex gdb.FinishBreakpoint
26042 A finish breakpoint is a temporary breakpoint set at the return address of
26043 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
26044 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
26045 and deleted when the execution will run out of the breakpoint scope (i.e.@:
26046 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
26047 Finish breakpoints are thread specific and must be create with the right
26050 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
26051 Create a finish breakpoint at the return address of the @code{gdb.Frame}
26052 object @var{frame}. If @var{frame} is not provided, this defaults to the
26053 newest frame. The optional @var{internal} argument allows the breakpoint to
26054 become invisible to the user. @xref{Breakpoints In Python}, for further
26055 details about this argument.
26058 @defun FinishBreakpoint.out_of_scope (self)
26059 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
26060 @code{return} command, @dots{}), a function may not properly terminate, and
26061 thus never hit the finish breakpoint. When @value{GDBN} notices such a
26062 situation, the @code{out_of_scope} callback will be triggered.
26064 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
26068 class MyFinishBreakpoint (gdb.FinishBreakpoint)
26070 print "normal finish"
26073 def out_of_scope ():
26074 print "abnormal finish"
26078 @defvar FinishBreakpoint.return_value
26079 When @value{GDBN} is stopped at a finish breakpoint and the frame
26080 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
26081 attribute will contain a @code{gdb.Value} object corresponding to the return
26082 value of the function. The value will be @code{None} if the function return
26083 type is @code{void} or if the return value was not computable. This attribute
26087 @node Lazy Strings In Python
26088 @subsubsection Python representation of lazy strings.
26090 @cindex lazy strings in python
26091 @tindex gdb.LazyString
26093 A @dfn{lazy string} is a string whose contents is not retrieved or
26094 encoded until it is needed.
26096 A @code{gdb.LazyString} is represented in @value{GDBN} as an
26097 @code{address} that points to a region of memory, an @code{encoding}
26098 that will be used to encode that region of memory, and a @code{length}
26099 to delimit the region of memory that represents the string. The
26100 difference between a @code{gdb.LazyString} and a string wrapped within
26101 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
26102 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
26103 retrieved and encoded during printing, while a @code{gdb.Value}
26104 wrapping a string is immediately retrieved and encoded on creation.
26106 A @code{gdb.LazyString} object has the following functions:
26108 @defun LazyString.value ()
26109 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
26110 will point to the string in memory, but will lose all the delayed
26111 retrieval, encoding and handling that @value{GDBN} applies to a
26112 @code{gdb.LazyString}.
26115 @defvar LazyString.address
26116 This attribute holds the address of the string. This attribute is not
26120 @defvar LazyString.length
26121 This attribute holds the length of the string in characters. If the
26122 length is -1, then the string will be fetched and encoded up to the
26123 first null of appropriate width. This attribute is not writable.
26126 @defvar LazyString.encoding
26127 This attribute holds the encoding that will be applied to the string
26128 when the string is printed by @value{GDBN}. If the encoding is not
26129 set, or contains an empty string, then @value{GDBN} will select the
26130 most appropriate encoding when the string is printed. This attribute
26134 @defvar LazyString.type
26135 This attribute holds the type that is represented by the lazy string's
26136 type. For a lazy string this will always be a pointer type. To
26137 resolve this to the lazy string's character type, use the type's
26138 @code{target} method. @xref{Types In Python}. This attribute is not
26142 @node Architectures In Python
26143 @subsubsection Python representation of architectures
26144 @cindex Python architectures
26146 @value{GDBN} uses architecture specific parameters and artifacts in a
26147 number of its various computations. An architecture is represented
26148 by an instance of the @code{gdb.Architecture} class.
26150 A @code{gdb.Architecture} class has the following methods:
26152 @defun Architecture.name ()
26153 Return the name (string value) of the architecture.
26156 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
26157 Return a list of disassembled instructions starting from the memory
26158 address @var{start_pc}. The optional arguments @var{end_pc} and
26159 @var{count} determine the number of instructions in the returned list.
26160 If both the optional arguments @var{end_pc} and @var{count} are
26161 specified, then a list of at most @var{count} disassembled instructions
26162 whose start address falls in the closed memory address interval from
26163 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
26164 specified, but @var{count} is specified, then @var{count} number of
26165 instructions starting from the address @var{start_pc} are returned. If
26166 @var{count} is not specified but @var{end_pc} is specified, then all
26167 instructions whose start address falls in the closed memory address
26168 interval from @var{start_pc} to @var{end_pc} are returned. If neither
26169 @var{end_pc} nor @var{count} are specified, then a single instruction at
26170 @var{start_pc} is returned. For all of these cases, each element of the
26171 returned list is a Python @code{dict} with the following string keys:
26176 The value corresponding to this key is a Python long integer capturing
26177 the memory address of the instruction.
26180 The value corresponding to this key is a string value which represents
26181 the instruction with assembly language mnemonics. The assembly
26182 language flavor used is the same as that specified by the current CLI
26183 variable @code{disassembly-flavor}. @xref{Machine Code}.
26186 The value corresponding to this key is the length (integer value) of the
26187 instruction in bytes.
26192 @node Python Auto-loading
26193 @subsection Python Auto-loading
26194 @cindex Python auto-loading
26196 When a new object file is read (for example, due to the @code{file}
26197 command, or because the inferior has loaded a shared library),
26198 @value{GDBN} will look for Python support scripts in several ways:
26199 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
26200 and @code{.debug_gdb_scripts} section
26201 (@pxref{dotdebug_gdb_scripts section}).
26203 The auto-loading feature is useful for supplying application-specific
26204 debugging commands and scripts.
26206 Auto-loading can be enabled or disabled,
26207 and the list of auto-loaded scripts can be printed.
26210 @anchor{set auto-load python-scripts}
26211 @kindex set auto-load python-scripts
26212 @item set auto-load python-scripts [on|off]
26213 Enable or disable the auto-loading of Python scripts.
26215 @anchor{show auto-load python-scripts}
26216 @kindex show auto-load python-scripts
26217 @item show auto-load python-scripts
26218 Show whether auto-loading of Python scripts is enabled or disabled.
26220 @anchor{info auto-load python-scripts}
26221 @kindex info auto-load python-scripts
26222 @cindex print list of auto-loaded Python scripts
26223 @item info auto-load python-scripts [@var{regexp}]
26224 Print the list of all Python scripts that @value{GDBN} auto-loaded.
26226 Also printed is the list of Python scripts that were mentioned in
26227 the @code{.debug_gdb_scripts} section and were not found
26228 (@pxref{dotdebug_gdb_scripts section}).
26229 This is useful because their names are not printed when @value{GDBN}
26230 tries to load them and fails. There may be many of them, and printing
26231 an error message for each one is problematic.
26233 If @var{regexp} is supplied only Python scripts with matching names are printed.
26238 (gdb) info auto-load python-scripts
26240 Yes py-section-script.py
26241 full name: /tmp/py-section-script.py
26242 No my-foo-pretty-printers.py
26246 When reading an auto-loaded file, @value{GDBN} sets the
26247 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
26248 function (@pxref{Objfiles In Python}). This can be useful for
26249 registering objfile-specific pretty-printers.
26252 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26253 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26254 * Which flavor to choose?::
26257 @node objfile-gdb.py file
26258 @subsubsection The @file{@var{objfile}-gdb.py} file
26259 @cindex @file{@var{objfile}-gdb.py}
26261 When a new object file is read, @value{GDBN} looks for
26262 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26263 where @var{objfile} is the object file's real name, formed by ensuring
26264 that the file name is absolute, following all symlinks, and resolving
26265 @code{.} and @code{..} components. If this file exists and is
26266 readable, @value{GDBN} will evaluate it as a Python script.
26268 If this file does not exist, then @value{GDBN} will look for
26269 @var{script-name} file in all of the directories as specified below.
26271 Note that loading of this script file also requires accordingly configured
26272 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26274 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26275 scripts normally according to its @file{.exe} filename. But if no scripts are
26276 found @value{GDBN} also tries script filenames matching the object file without
26277 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26278 is attempted on any platform. This makes the script filenames compatible
26279 between Unix and MS-Windows hosts.
26282 @anchor{set auto-load scripts-directory}
26283 @kindex set auto-load scripts-directory
26284 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26285 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26286 may be delimited by the host platform path separator in use
26287 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26289 Each entry here needs to be covered also by the security setting
26290 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26292 @anchor{with-auto-load-dir}
26293 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26294 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26295 configuration option @option{--with-auto-load-dir}.
26297 Any reference to @file{$debugdir} will get replaced by
26298 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26299 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26300 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26301 @file{$datadir} must be placed as a directory component --- either alone or
26302 delimited by @file{/} or @file{\} directory separators, depending on the host
26305 The list of directories uses path separator (@samp{:} on GNU and Unix
26306 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26307 to the @env{PATH} environment variable.
26309 @anchor{show auto-load scripts-directory}
26310 @kindex show auto-load scripts-directory
26311 @item show auto-load scripts-directory
26312 Show @value{GDBN} auto-loaded scripts location.
26315 @value{GDBN} does not track which files it has already auto-loaded this way.
26316 @value{GDBN} will load the associated script every time the corresponding
26317 @var{objfile} is opened.
26318 So your @file{-gdb.py} file should be careful to avoid errors if it
26319 is evaluated more than once.
26321 @node dotdebug_gdb_scripts section
26322 @subsubsection The @code{.debug_gdb_scripts} section
26323 @cindex @code{.debug_gdb_scripts} section
26325 For systems using file formats like ELF and COFF,
26326 when @value{GDBN} loads a new object file
26327 it will look for a special section named @samp{.debug_gdb_scripts}.
26328 If this section exists, its contents is a list of names of scripts to load.
26330 @value{GDBN} will look for each specified script file first in the
26331 current directory and then along the source search path
26332 (@pxref{Source Path, ,Specifying Source Directories}),
26333 except that @file{$cdir} is not searched, since the compilation
26334 directory is not relevant to scripts.
26336 Entries can be placed in section @code{.debug_gdb_scripts} with,
26337 for example, this GCC macro:
26340 /* Note: The "MS" section flags are to remove duplicates. */
26341 #define DEFINE_GDB_SCRIPT(script_name) \
26343 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26345 .asciz \"" script_name "\"\n\
26351 Then one can reference the macro in a header or source file like this:
26354 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26357 The script name may include directories if desired.
26359 Note that loading of this script file also requires accordingly configured
26360 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26362 If the macro is put in a header, any application or library
26363 using this header will get a reference to the specified script.
26365 @node Which flavor to choose?
26366 @subsubsection Which flavor to choose?
26368 Given the multiple ways of auto-loading Python scripts, it might not always
26369 be clear which one to choose. This section provides some guidance.
26371 Benefits of the @file{-gdb.py} way:
26375 Can be used with file formats that don't support multiple sections.
26378 Ease of finding scripts for public libraries.
26380 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26381 in the source search path.
26382 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26383 isn't a source directory in which to find the script.
26386 Doesn't require source code additions.
26389 Benefits of the @code{.debug_gdb_scripts} way:
26393 Works with static linking.
26395 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26396 trigger their loading. When an application is statically linked the only
26397 objfile available is the executable, and it is cumbersome to attach all the
26398 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26401 Works with classes that are entirely inlined.
26403 Some classes can be entirely inlined, and thus there may not be an associated
26404 shared library to attach a @file{-gdb.py} script to.
26407 Scripts needn't be copied out of the source tree.
26409 In some circumstances, apps can be built out of large collections of internal
26410 libraries, and the build infrastructure necessary to install the
26411 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26412 cumbersome. It may be easier to specify the scripts in the
26413 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26414 top of the source tree to the source search path.
26417 @node Python modules
26418 @subsection Python modules
26419 @cindex python modules
26421 @value{GDBN} comes with several modules to assist writing Python code.
26424 * gdb.printing:: Building and registering pretty-printers.
26425 * gdb.types:: Utilities for working with types.
26426 * gdb.prompt:: Utilities for prompt value substitution.
26430 @subsubsection gdb.printing
26431 @cindex gdb.printing
26433 This module provides a collection of utilities for working with
26437 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26438 This class specifies the API that makes @samp{info pretty-printer},
26439 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26440 Pretty-printers should generally inherit from this class.
26442 @item SubPrettyPrinter (@var{name})
26443 For printers that handle multiple types, this class specifies the
26444 corresponding API for the subprinters.
26446 @item RegexpCollectionPrettyPrinter (@var{name})
26447 Utility class for handling multiple printers, all recognized via
26448 regular expressions.
26449 @xref{Writing a Pretty-Printer}, for an example.
26451 @item FlagEnumerationPrinter (@var{name})
26452 A pretty-printer which handles printing of @code{enum} values. Unlike
26453 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26454 work properly when there is some overlap between the enumeration
26455 constants. @var{name} is the name of the printer and also the name of
26456 the @code{enum} type to look up.
26458 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26459 Register @var{printer} with the pretty-printer list of @var{obj}.
26460 If @var{replace} is @code{True} then any existing copy of the printer
26461 is replaced. Otherwise a @code{RuntimeError} exception is raised
26462 if a printer with the same name already exists.
26466 @subsubsection gdb.types
26469 This module provides a collection of utilities for working with
26470 @code{gdb.Type} objects.
26473 @item get_basic_type (@var{type})
26474 Return @var{type} with const and volatile qualifiers stripped,
26475 and with typedefs and C@t{++} references converted to the underlying type.
26480 typedef const int const_int;
26482 const_int& foo_ref (foo);
26483 int main () @{ return 0; @}
26490 (gdb) python import gdb.types
26491 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26492 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26496 @item has_field (@var{type}, @var{field})
26497 Return @code{True} if @var{type}, assumed to be a type with fields
26498 (e.g., a structure or union), has field @var{field}.
26500 @item make_enum_dict (@var{enum_type})
26501 Return a Python @code{dictionary} type produced from @var{enum_type}.
26503 @item deep_items (@var{type})
26504 Returns a Python iterator similar to the standard
26505 @code{gdb.Type.iteritems} method, except that the iterator returned
26506 by @code{deep_items} will recursively traverse anonymous struct or
26507 union fields. For example:
26521 Then in @value{GDBN}:
26523 (@value{GDBP}) python import gdb.types
26524 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26525 (@value{GDBP}) python print struct_a.keys ()
26527 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26528 @{['a', 'b0', 'b1']@}
26531 @item get_type_recognizers ()
26532 Return a list of the enabled type recognizers for the current context.
26533 This is called by @value{GDBN} during the type-printing process
26534 (@pxref{Type Printing API}).
26536 @item apply_type_recognizers (recognizers, type_obj)
26537 Apply the type recognizers, @var{recognizers}, to the type object
26538 @var{type_obj}. If any recognizer returns a string, return that
26539 string. Otherwise, return @code{None}. This is called by
26540 @value{GDBN} during the type-printing process (@pxref{Type Printing
26543 @item register_type_printer (locus, printer)
26544 This is a convenience function to register a type printer.
26545 @var{printer} is the type printer to register. It must implement the
26546 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26547 which case the printer is registered with that objfile; a
26548 @code{gdb.Progspace}, in which case the printer is registered with
26549 that progspace; or @code{None}, in which case the printer is
26550 registered globally.
26553 This is a base class that implements the type printer protocol. Type
26554 printers are encouraged, but not required, to derive from this class.
26555 It defines a constructor:
26557 @defmethod TypePrinter __init__ (self, name)
26558 Initialize the type printer with the given name. The new printer
26559 starts in the enabled state.
26565 @subsubsection gdb.prompt
26568 This module provides a method for prompt value-substitution.
26571 @item substitute_prompt (@var{string})
26572 Return @var{string} with escape sequences substituted by values. Some
26573 escape sequences take arguments. You can specify arguments inside
26574 ``@{@}'' immediately following the escape sequence.
26576 The escape sequences you can pass to this function are:
26580 Substitute a backslash.
26582 Substitute an ESC character.
26584 Substitute the selected frame; an argument names a frame parameter.
26586 Substitute a newline.
26588 Substitute a parameter's value; the argument names the parameter.
26590 Substitute a carriage return.
26592 Substitute the selected thread; an argument names a thread parameter.
26594 Substitute the version of GDB.
26596 Substitute the current working directory.
26598 Begin a sequence of non-printing characters. These sequences are
26599 typically used with the ESC character, and are not counted in the string
26600 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26601 blue-colored ``(gdb)'' prompt where the length is five.
26603 End a sequence of non-printing characters.
26609 substitute_prompt (``frame: \f,
26610 print arguments: \p@{print frame-arguments@}'')
26613 @exdent will return the string:
26616 "frame: main, print arguments: scalars"
26621 @section Creating new spellings of existing commands
26622 @cindex aliases for commands
26624 It is often useful to define alternate spellings of existing commands.
26625 For example, if a new @value{GDBN} command defined in Python has
26626 a long name to type, it is handy to have an abbreviated version of it
26627 that involves less typing.
26629 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26630 of the @samp{step} command even though it is otherwise an ambiguous
26631 abbreviation of other commands like @samp{set} and @samp{show}.
26633 Aliases are also used to provide shortened or more common versions
26634 of multi-word commands. For example, @value{GDBN} provides the
26635 @samp{tty} alias of the @samp{set inferior-tty} command.
26637 You can define a new alias with the @samp{alias} command.
26642 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26646 @var{ALIAS} specifies the name of the new alias.
26647 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26650 @var{COMMAND} specifies the name of an existing command
26651 that is being aliased.
26653 The @samp{-a} option specifies that the new alias is an abbreviation
26654 of the command. Abbreviations are not shown in command
26655 lists displayed by the @samp{help} command.
26657 The @samp{--} option specifies the end of options,
26658 and is useful when @var{ALIAS} begins with a dash.
26660 Here is a simple example showing how to make an abbreviation
26661 of a command so that there is less to type.
26662 Suppose you were tired of typing @samp{disas}, the current
26663 shortest unambiguous abbreviation of the @samp{disassemble} command
26664 and you wanted an even shorter version named @samp{di}.
26665 The following will accomplish this.
26668 (gdb) alias -a di = disas
26671 Note that aliases are different from user-defined commands.
26672 With a user-defined command, you also need to write documentation
26673 for it with the @samp{document} command.
26674 An alias automatically picks up the documentation of the existing command.
26676 Here is an example where we make @samp{elms} an abbreviation of
26677 @samp{elements} in the @samp{set print elements} command.
26678 This is to show that you can make an abbreviation of any part
26682 (gdb) alias -a set print elms = set print elements
26683 (gdb) alias -a show print elms = show print elements
26684 (gdb) set p elms 20
26686 Limit on string chars or array elements to print is 200.
26689 Note that if you are defining an alias of a @samp{set} command,
26690 and you want to have an alias for the corresponding @samp{show}
26691 command, then you need to define the latter separately.
26693 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26694 @var{ALIAS}, just as they are normally.
26697 (gdb) alias -a set pr elms = set p ele
26700 Finally, here is an example showing the creation of a one word
26701 alias for a more complex command.
26702 This creates alias @samp{spe} of the command @samp{set print elements}.
26705 (gdb) alias spe = set print elements
26710 @chapter Command Interpreters
26711 @cindex command interpreters
26713 @value{GDBN} supports multiple command interpreters, and some command
26714 infrastructure to allow users or user interface writers to switch
26715 between interpreters or run commands in other interpreters.
26717 @value{GDBN} currently supports two command interpreters, the console
26718 interpreter (sometimes called the command-line interpreter or @sc{cli})
26719 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26720 describes both of these interfaces in great detail.
26722 By default, @value{GDBN} will start with the console interpreter.
26723 However, the user may choose to start @value{GDBN} with another
26724 interpreter by specifying the @option{-i} or @option{--interpreter}
26725 startup options. Defined interpreters include:
26729 @cindex console interpreter
26730 The traditional console or command-line interpreter. This is the most often
26731 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26732 @value{GDBN} will use this interpreter.
26735 @cindex mi interpreter
26736 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26737 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26738 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26742 @cindex mi2 interpreter
26743 The current @sc{gdb/mi} interface.
26746 @cindex mi1 interpreter
26747 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26751 @cindex invoke another interpreter
26752 The interpreter being used by @value{GDBN} may not be dynamically
26753 switched at runtime. Although possible, this could lead to a very
26754 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26755 enters the command "interpreter-set console" in a console view,
26756 @value{GDBN} would switch to using the console interpreter, rendering
26757 the IDE inoperable!
26759 @kindex interpreter-exec
26760 Although you may only choose a single interpreter at startup, you may execute
26761 commands in any interpreter from the current interpreter using the appropriate
26762 command. If you are running the console interpreter, simply use the
26763 @code{interpreter-exec} command:
26766 interpreter-exec mi "-data-list-register-names"
26769 @sc{gdb/mi} has a similar command, although it is only available in versions of
26770 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26773 @chapter @value{GDBN} Text User Interface
26775 @cindex Text User Interface
26778 * TUI Overview:: TUI overview
26779 * TUI Keys:: TUI key bindings
26780 * TUI Single Key Mode:: TUI single key mode
26781 * TUI Commands:: TUI-specific commands
26782 * TUI Configuration:: TUI configuration variables
26785 The @value{GDBN} Text User Interface (TUI) is a terminal
26786 interface which uses the @code{curses} library to show the source
26787 file, the assembly output, the program registers and @value{GDBN}
26788 commands in separate text windows. The TUI mode is supported only
26789 on platforms where a suitable version of the @code{curses} library
26792 The TUI mode is enabled by default when you invoke @value{GDBN} as
26793 @samp{@value{GDBP} -tui}.
26794 You can also switch in and out of TUI mode while @value{GDBN} runs by
26795 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26796 @xref{TUI Keys, ,TUI Key Bindings}.
26799 @section TUI Overview
26801 In TUI mode, @value{GDBN} can display several text windows:
26805 This window is the @value{GDBN} command window with the @value{GDBN}
26806 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26807 managed using readline.
26810 The source window shows the source file of the program. The current
26811 line and active breakpoints are displayed in this window.
26814 The assembly window shows the disassembly output of the program.
26817 This window shows the processor registers. Registers are highlighted
26818 when their values change.
26821 The source and assembly windows show the current program position
26822 by highlighting the current line and marking it with a @samp{>} marker.
26823 Breakpoints are indicated with two markers. The first marker
26824 indicates the breakpoint type:
26828 Breakpoint which was hit at least once.
26831 Breakpoint which was never hit.
26834 Hardware breakpoint which was hit at least once.
26837 Hardware breakpoint which was never hit.
26840 The second marker indicates whether the breakpoint is enabled or not:
26844 Breakpoint is enabled.
26847 Breakpoint is disabled.
26850 The source, assembly and register windows are updated when the current
26851 thread changes, when the frame changes, or when the program counter
26854 These windows are not all visible at the same time. The command
26855 window is always visible. The others can be arranged in several
26866 source and assembly,
26869 source and registers, or
26872 assembly and registers.
26875 A status line above the command window shows the following information:
26879 Indicates the current @value{GDBN} target.
26880 (@pxref{Targets, ,Specifying a Debugging Target}).
26883 Gives the current process or thread number.
26884 When no process is being debugged, this field is set to @code{No process}.
26887 Gives the current function name for the selected frame.
26888 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26889 When there is no symbol corresponding to the current program counter,
26890 the string @code{??} is displayed.
26893 Indicates the current line number for the selected frame.
26894 When the current line number is not known, the string @code{??} is displayed.
26897 Indicates the current program counter address.
26901 @section TUI Key Bindings
26902 @cindex TUI key bindings
26904 The TUI installs several key bindings in the readline keymaps
26905 @ifset SYSTEM_READLINE
26906 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26908 @ifclear SYSTEM_READLINE
26909 (@pxref{Command Line Editing}).
26911 The following key bindings are installed for both TUI mode and the
26912 @value{GDBN} standard mode.
26921 Enter or leave the TUI mode. When leaving the TUI mode,
26922 the curses window management stops and @value{GDBN} operates using
26923 its standard mode, writing on the terminal directly. When reentering
26924 the TUI mode, control is given back to the curses windows.
26925 The screen is then refreshed.
26929 Use a TUI layout with only one window. The layout will
26930 either be @samp{source} or @samp{assembly}. When the TUI mode
26931 is not active, it will switch to the TUI mode.
26933 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26937 Use a TUI layout with at least two windows. When the current
26938 layout already has two windows, the next layout with two windows is used.
26939 When a new layout is chosen, one window will always be common to the
26940 previous layout and the new one.
26942 Think of it as the Emacs @kbd{C-x 2} binding.
26946 Change the active window. The TUI associates several key bindings
26947 (like scrolling and arrow keys) with the active window. This command
26948 gives the focus to the next TUI window.
26950 Think of it as the Emacs @kbd{C-x o} binding.
26954 Switch in and out of the TUI SingleKey mode that binds single
26955 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26958 The following key bindings only work in the TUI mode:
26963 Scroll the active window one page up.
26967 Scroll the active window one page down.
26971 Scroll the active window one line up.
26975 Scroll the active window one line down.
26979 Scroll the active window one column left.
26983 Scroll the active window one column right.
26987 Refresh the screen.
26990 Because the arrow keys scroll the active window in the TUI mode, they
26991 are not available for their normal use by readline unless the command
26992 window has the focus. When another window is active, you must use
26993 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26994 and @kbd{C-f} to control the command window.
26996 @node TUI Single Key Mode
26997 @section TUI Single Key Mode
26998 @cindex TUI single key mode
27000 The TUI also provides a @dfn{SingleKey} mode, which binds several
27001 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
27002 switch into this mode, where the following key bindings are used:
27005 @kindex c @r{(SingleKey TUI key)}
27009 @kindex d @r{(SingleKey TUI key)}
27013 @kindex f @r{(SingleKey TUI key)}
27017 @kindex n @r{(SingleKey TUI key)}
27021 @kindex q @r{(SingleKey TUI key)}
27023 exit the SingleKey mode.
27025 @kindex r @r{(SingleKey TUI key)}
27029 @kindex s @r{(SingleKey TUI key)}
27033 @kindex u @r{(SingleKey TUI key)}
27037 @kindex v @r{(SingleKey TUI key)}
27041 @kindex w @r{(SingleKey TUI key)}
27046 Other keys temporarily switch to the @value{GDBN} command prompt.
27047 The key that was pressed is inserted in the editing buffer so that
27048 it is possible to type most @value{GDBN} commands without interaction
27049 with the TUI SingleKey mode. Once the command is entered the TUI
27050 SingleKey mode is restored. The only way to permanently leave
27051 this mode is by typing @kbd{q} or @kbd{C-x s}.
27055 @section TUI-specific Commands
27056 @cindex TUI commands
27058 The TUI has specific commands to control the text windows.
27059 These commands are always available, even when @value{GDBN} is not in
27060 the TUI mode. When @value{GDBN} is in the standard mode, most
27061 of these commands will automatically switch to the TUI mode.
27063 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27064 terminal, or @value{GDBN} has been started with the machine interface
27065 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27066 these commands will fail with an error, because it would not be
27067 possible or desirable to enable curses window management.
27072 List and give the size of all displayed windows.
27076 Display the next layout.
27079 Display the previous layout.
27082 Display the source window only.
27085 Display the assembly window only.
27088 Display the source and assembly window.
27091 Display the register window together with the source or assembly window.
27095 Make the next window active for scrolling.
27098 Make the previous window active for scrolling.
27101 Make the source window active for scrolling.
27104 Make the assembly window active for scrolling.
27107 Make the register window active for scrolling.
27110 Make the command window active for scrolling.
27114 Refresh the screen. This is similar to typing @kbd{C-L}.
27116 @item tui reg float
27118 Show the floating point registers in the register window.
27120 @item tui reg general
27121 Show the general registers in the register window.
27124 Show the next register group. The list of register groups as well as
27125 their order is target specific. The predefined register groups are the
27126 following: @code{general}, @code{float}, @code{system}, @code{vector},
27127 @code{all}, @code{save}, @code{restore}.
27129 @item tui reg system
27130 Show the system registers in the register window.
27134 Update the source window and the current execution point.
27136 @item winheight @var{name} +@var{count}
27137 @itemx winheight @var{name} -@var{count}
27139 Change the height of the window @var{name} by @var{count}
27140 lines. Positive counts increase the height, while negative counts
27143 @item tabset @var{nchars}
27145 Set the width of tab stops to be @var{nchars} characters.
27148 @node TUI Configuration
27149 @section TUI Configuration Variables
27150 @cindex TUI configuration variables
27152 Several configuration variables control the appearance of TUI windows.
27155 @item set tui border-kind @var{kind}
27156 @kindex set tui border-kind
27157 Select the border appearance for the source, assembly and register windows.
27158 The possible values are the following:
27161 Use a space character to draw the border.
27164 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27167 Use the Alternate Character Set to draw the border. The border is
27168 drawn using character line graphics if the terminal supports them.
27171 @item set tui border-mode @var{mode}
27172 @kindex set tui border-mode
27173 @itemx set tui active-border-mode @var{mode}
27174 @kindex set tui active-border-mode
27175 Select the display attributes for the borders of the inactive windows
27176 or the active window. The @var{mode} can be one of the following:
27179 Use normal attributes to display the border.
27185 Use reverse video mode.
27188 Use half bright mode.
27190 @item half-standout
27191 Use half bright and standout mode.
27194 Use extra bright or bold mode.
27196 @item bold-standout
27197 Use extra bright or bold and standout mode.
27202 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27205 @cindex @sc{gnu} Emacs
27206 A special interface allows you to use @sc{gnu} Emacs to view (and
27207 edit) the source files for the program you are debugging with
27210 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27211 executable file you want to debug as an argument. This command starts
27212 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27213 created Emacs buffer.
27214 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27216 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27221 All ``terminal'' input and output goes through an Emacs buffer, called
27224 This applies both to @value{GDBN} commands and their output, and to the input
27225 and output done by the program you are debugging.
27227 This is useful because it means that you can copy the text of previous
27228 commands and input them again; you can even use parts of the output
27231 All the facilities of Emacs' Shell mode are available for interacting
27232 with your program. In particular, you can send signals the usual
27233 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27237 @value{GDBN} displays source code through Emacs.
27239 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27240 source file for that frame and puts an arrow (@samp{=>}) at the
27241 left margin of the current line. Emacs uses a separate buffer for
27242 source display, and splits the screen to show both your @value{GDBN} session
27245 Explicit @value{GDBN} @code{list} or search commands still produce output as
27246 usual, but you probably have no reason to use them from Emacs.
27249 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27250 a graphical mode, enabled by default, which provides further buffers
27251 that can control the execution and describe the state of your program.
27252 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27254 If you specify an absolute file name when prompted for the @kbd{M-x
27255 gdb} argument, then Emacs sets your current working directory to where
27256 your program resides. If you only specify the file name, then Emacs
27257 sets your current working directory to the directory associated
27258 with the previous buffer. In this case, @value{GDBN} may find your
27259 program by searching your environment's @code{PATH} variable, but on
27260 some operating systems it might not find the source. So, although the
27261 @value{GDBN} input and output session proceeds normally, the auxiliary
27262 buffer does not display the current source and line of execution.
27264 The initial working directory of @value{GDBN} is printed on the top
27265 line of the GUD buffer and this serves as a default for the commands
27266 that specify files for @value{GDBN} to operate on. @xref{Files,
27267 ,Commands to Specify Files}.
27269 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27270 need to call @value{GDBN} by a different name (for example, if you
27271 keep several configurations around, with different names) you can
27272 customize the Emacs variable @code{gud-gdb-command-name} to run the
27275 In the GUD buffer, you can use these special Emacs commands in
27276 addition to the standard Shell mode commands:
27280 Describe the features of Emacs' GUD Mode.
27283 Execute to another source line, like the @value{GDBN} @code{step} command; also
27284 update the display window to show the current file and location.
27287 Execute to next source line in this function, skipping all function
27288 calls, like the @value{GDBN} @code{next} command. Then update the display window
27289 to show the current file and location.
27292 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27293 display window accordingly.
27296 Execute until exit from the selected stack frame, like the @value{GDBN}
27297 @code{finish} command.
27300 Continue execution of your program, like the @value{GDBN} @code{continue}
27304 Go up the number of frames indicated by the numeric argument
27305 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27306 like the @value{GDBN} @code{up} command.
27309 Go down the number of frames indicated by the numeric argument, like the
27310 @value{GDBN} @code{down} command.
27313 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27314 tells @value{GDBN} to set a breakpoint on the source line point is on.
27316 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27317 separate frame which shows a backtrace when the GUD buffer is current.
27318 Move point to any frame in the stack and type @key{RET} to make it
27319 become the current frame and display the associated source in the
27320 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27321 selected frame become the current one. In graphical mode, the
27322 speedbar displays watch expressions.
27324 If you accidentally delete the source-display buffer, an easy way to get
27325 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27326 request a frame display; when you run under Emacs, this recreates
27327 the source buffer if necessary to show you the context of the current
27330 The source files displayed in Emacs are in ordinary Emacs buffers
27331 which are visiting the source files in the usual way. You can edit
27332 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27333 communicates with Emacs in terms of line numbers. If you add or
27334 delete lines from the text, the line numbers that @value{GDBN} knows cease
27335 to correspond properly with the code.
27337 A more detailed description of Emacs' interaction with @value{GDBN} is
27338 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27342 @chapter The @sc{gdb/mi} Interface
27344 @unnumberedsec Function and Purpose
27346 @cindex @sc{gdb/mi}, its purpose
27347 @sc{gdb/mi} is a line based machine oriented text interface to
27348 @value{GDBN} and is activated by specifying using the
27349 @option{--interpreter} command line option (@pxref{Mode Options}). It
27350 is specifically intended to support the development of systems which
27351 use the debugger as just one small component of a larger system.
27353 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27354 in the form of a reference manual.
27356 Note that @sc{gdb/mi} is still under construction, so some of the
27357 features described below are incomplete and subject to change
27358 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27360 @unnumberedsec Notation and Terminology
27362 @cindex notational conventions, for @sc{gdb/mi}
27363 This chapter uses the following notation:
27367 @code{|} separates two alternatives.
27370 @code{[ @var{something} ]} indicates that @var{something} is optional:
27371 it may or may not be given.
27374 @code{( @var{group} )*} means that @var{group} inside the parentheses
27375 may repeat zero or more times.
27378 @code{( @var{group} )+} means that @var{group} inside the parentheses
27379 may repeat one or more times.
27382 @code{"@var{string}"} means a literal @var{string}.
27386 @heading Dependencies
27390 * GDB/MI General Design::
27391 * GDB/MI Command Syntax::
27392 * GDB/MI Compatibility with CLI::
27393 * GDB/MI Development and Front Ends::
27394 * GDB/MI Output Records::
27395 * GDB/MI Simple Examples::
27396 * GDB/MI Command Description Format::
27397 * GDB/MI Breakpoint Commands::
27398 * GDB/MI Catchpoint Commands::
27399 * GDB/MI Program Context::
27400 * GDB/MI Thread Commands::
27401 * GDB/MI Ada Tasking Commands::
27402 * GDB/MI Program Execution::
27403 * GDB/MI Stack Manipulation::
27404 * GDB/MI Variable Objects::
27405 * GDB/MI Data Manipulation::
27406 * GDB/MI Tracepoint Commands::
27407 * GDB/MI Symbol Query::
27408 * GDB/MI File Commands::
27410 * GDB/MI Kod Commands::
27411 * GDB/MI Memory Overlay Commands::
27412 * GDB/MI Signal Handling Commands::
27414 * GDB/MI Target Manipulation::
27415 * GDB/MI File Transfer Commands::
27416 * GDB/MI Miscellaneous Commands::
27419 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27420 @node GDB/MI General Design
27421 @section @sc{gdb/mi} General Design
27422 @cindex GDB/MI General Design
27424 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27425 parts---commands sent to @value{GDBN}, responses to those commands
27426 and notifications. Each command results in exactly one response,
27427 indicating either successful completion of the command, or an error.
27428 For the commands that do not resume the target, the response contains the
27429 requested information. For the commands that resume the target, the
27430 response only indicates whether the target was successfully resumed.
27431 Notifications is the mechanism for reporting changes in the state of the
27432 target, or in @value{GDBN} state, that cannot conveniently be associated with
27433 a command and reported as part of that command response.
27435 The important examples of notifications are:
27439 Exec notifications. These are used to report changes in
27440 target state---when a target is resumed, or stopped. It would not
27441 be feasible to include this information in response of resuming
27442 commands, because one resume commands can result in multiple events in
27443 different threads. Also, quite some time may pass before any event
27444 happens in the target, while a frontend needs to know whether the resuming
27445 command itself was successfully executed.
27448 Console output, and status notifications. Console output
27449 notifications are used to report output of CLI commands, as well as
27450 diagnostics for other commands. Status notifications are used to
27451 report the progress of a long-running operation. Naturally, including
27452 this information in command response would mean no output is produced
27453 until the command is finished, which is undesirable.
27456 General notifications. Commands may have various side effects on
27457 the @value{GDBN} or target state beyond their official purpose. For example,
27458 a command may change the selected thread. Although such changes can
27459 be included in command response, using notification allows for more
27460 orthogonal frontend design.
27464 There's no guarantee that whenever an MI command reports an error,
27465 @value{GDBN} or the target are in any specific state, and especially,
27466 the state is not reverted to the state before the MI command was
27467 processed. Therefore, whenever an MI command results in an error,
27468 we recommend that the frontend refreshes all the information shown in
27469 the user interface.
27473 * Context management::
27474 * Asynchronous and non-stop modes::
27478 @node Context management
27479 @subsection Context management
27481 In most cases when @value{GDBN} accesses the target, this access is
27482 done in context of a specific thread and frame (@pxref{Frames}).
27483 Often, even when accessing global data, the target requires that a thread
27484 be specified. The CLI interface maintains the selected thread and frame,
27485 and supplies them to target on each command. This is convenient,
27486 because a command line user would not want to specify that information
27487 explicitly on each command, and because user interacts with
27488 @value{GDBN} via a single terminal, so no confusion is possible as
27489 to what thread and frame are the current ones.
27491 In the case of MI, the concept of selected thread and frame is less
27492 useful. First, a frontend can easily remember this information
27493 itself. Second, a graphical frontend can have more than one window,
27494 each one used for debugging a different thread, and the frontend might
27495 want to access additional threads for internal purposes. This
27496 increases the risk that by relying on implicitly selected thread, the
27497 frontend may be operating on a wrong one. Therefore, each MI command
27498 should explicitly specify which thread and frame to operate on. To
27499 make it possible, each MI command accepts the @samp{--thread} and
27500 @samp{--frame} options, the value to each is @value{GDBN} identifier
27501 for thread and frame to operate on.
27503 Usually, each top-level window in a frontend allows the user to select
27504 a thread and a frame, and remembers the user selection for further
27505 operations. However, in some cases @value{GDBN} may suggest that the
27506 current thread be changed. For example, when stopping on a breakpoint
27507 it is reasonable to switch to the thread where breakpoint is hit. For
27508 another example, if the user issues the CLI @samp{thread} command via
27509 the frontend, it is desirable to change the frontend's selected thread to the
27510 one specified by user. @value{GDBN} communicates the suggestion to
27511 change current thread using the @samp{=thread-selected} notification.
27512 No such notification is available for the selected frame at the moment.
27514 Note that historically, MI shares the selected thread with CLI, so
27515 frontends used the @code{-thread-select} to execute commands in the
27516 right context. However, getting this to work right is cumbersome. The
27517 simplest way is for frontend to emit @code{-thread-select} command
27518 before every command. This doubles the number of commands that need
27519 to be sent. The alternative approach is to suppress @code{-thread-select}
27520 if the selected thread in @value{GDBN} is supposed to be identical to the
27521 thread the frontend wants to operate on. However, getting this
27522 optimization right can be tricky. In particular, if the frontend
27523 sends several commands to @value{GDBN}, and one of the commands changes the
27524 selected thread, then the behaviour of subsequent commands will
27525 change. So, a frontend should either wait for response from such
27526 problematic commands, or explicitly add @code{-thread-select} for
27527 all subsequent commands. No frontend is known to do this exactly
27528 right, so it is suggested to just always pass the @samp{--thread} and
27529 @samp{--frame} options.
27531 @node Asynchronous and non-stop modes
27532 @subsection Asynchronous command execution and non-stop mode
27534 On some targets, @value{GDBN} is capable of processing MI commands
27535 even while the target is running. This is called @dfn{asynchronous
27536 command execution} (@pxref{Background Execution}). The frontend may
27537 specify a preferrence for asynchronous execution using the
27538 @code{-gdb-set target-async 1} command, which should be emitted before
27539 either running the executable or attaching to the target. After the
27540 frontend has started the executable or attached to the target, it can
27541 find if asynchronous execution is enabled using the
27542 @code{-list-target-features} command.
27544 Even if @value{GDBN} can accept a command while target is running,
27545 many commands that access the target do not work when the target is
27546 running. Therefore, asynchronous command execution is most useful
27547 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27548 it is possible to examine the state of one thread, while other threads
27551 When a given thread is running, MI commands that try to access the
27552 target in the context of that thread may not work, or may work only on
27553 some targets. In particular, commands that try to operate on thread's
27554 stack will not work, on any target. Commands that read memory, or
27555 modify breakpoints, may work or not work, depending on the target. Note
27556 that even commands that operate on global state, such as @code{print},
27557 @code{set}, and breakpoint commands, still access the target in the
27558 context of a specific thread, so frontend should try to find a
27559 stopped thread and perform the operation on that thread (using the
27560 @samp{--thread} option).
27562 Which commands will work in the context of a running thread is
27563 highly target dependent. However, the two commands
27564 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27565 to find the state of a thread, will always work.
27567 @node Thread groups
27568 @subsection Thread groups
27569 @value{GDBN} may be used to debug several processes at the same time.
27570 On some platfroms, @value{GDBN} may support debugging of several
27571 hardware systems, each one having several cores with several different
27572 processes running on each core. This section describes the MI
27573 mechanism to support such debugging scenarios.
27575 The key observation is that regardless of the structure of the
27576 target, MI can have a global list of threads, because most commands that
27577 accept the @samp{--thread} option do not need to know what process that
27578 thread belongs to. Therefore, it is not necessary to introduce
27579 neither additional @samp{--process} option, nor an notion of the
27580 current process in the MI interface. The only strictly new feature
27581 that is required is the ability to find how the threads are grouped
27584 To allow the user to discover such grouping, and to support arbitrary
27585 hierarchy of machines/cores/processes, MI introduces the concept of a
27586 @dfn{thread group}. Thread group is a collection of threads and other
27587 thread groups. A thread group always has a string identifier, a type,
27588 and may have additional attributes specific to the type. A new
27589 command, @code{-list-thread-groups}, returns the list of top-level
27590 thread groups, which correspond to processes that @value{GDBN} is
27591 debugging at the moment. By passing an identifier of a thread group
27592 to the @code{-list-thread-groups} command, it is possible to obtain
27593 the members of specific thread group.
27595 To allow the user to easily discover processes, and other objects, he
27596 wishes to debug, a concept of @dfn{available thread group} is
27597 introduced. Available thread group is an thread group that
27598 @value{GDBN} is not debugging, but that can be attached to, using the
27599 @code{-target-attach} command. The list of available top-level thread
27600 groups can be obtained using @samp{-list-thread-groups --available}.
27601 In general, the content of a thread group may be only retrieved only
27602 after attaching to that thread group.
27604 Thread groups are related to inferiors (@pxref{Inferiors and
27605 Programs}). Each inferior corresponds to a thread group of a special
27606 type @samp{process}, and some additional operations are permitted on
27607 such thread groups.
27609 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27610 @node GDB/MI Command Syntax
27611 @section @sc{gdb/mi} Command Syntax
27614 * GDB/MI Input Syntax::
27615 * GDB/MI Output Syntax::
27618 @node GDB/MI Input Syntax
27619 @subsection @sc{gdb/mi} Input Syntax
27621 @cindex input syntax for @sc{gdb/mi}
27622 @cindex @sc{gdb/mi}, input syntax
27624 @item @var{command} @expansion{}
27625 @code{@var{cli-command} | @var{mi-command}}
27627 @item @var{cli-command} @expansion{}
27628 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27629 @var{cli-command} is any existing @value{GDBN} CLI command.
27631 @item @var{mi-command} @expansion{}
27632 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27633 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27635 @item @var{token} @expansion{}
27636 "any sequence of digits"
27638 @item @var{option} @expansion{}
27639 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27641 @item @var{parameter} @expansion{}
27642 @code{@var{non-blank-sequence} | @var{c-string}}
27644 @item @var{operation} @expansion{}
27645 @emph{any of the operations described in this chapter}
27647 @item @var{non-blank-sequence} @expansion{}
27648 @emph{anything, provided it doesn't contain special characters such as
27649 "-", @var{nl}, """ and of course " "}
27651 @item @var{c-string} @expansion{}
27652 @code{""" @var{seven-bit-iso-c-string-content} """}
27654 @item @var{nl} @expansion{}
27663 The CLI commands are still handled by the @sc{mi} interpreter; their
27664 output is described below.
27667 The @code{@var{token}}, when present, is passed back when the command
27671 Some @sc{mi} commands accept optional arguments as part of the parameter
27672 list. Each option is identified by a leading @samp{-} (dash) and may be
27673 followed by an optional argument parameter. Options occur first in the
27674 parameter list and can be delimited from normal parameters using
27675 @samp{--} (this is useful when some parameters begin with a dash).
27682 We want easy access to the existing CLI syntax (for debugging).
27685 We want it to be easy to spot a @sc{mi} operation.
27688 @node GDB/MI Output Syntax
27689 @subsection @sc{gdb/mi} Output Syntax
27691 @cindex output syntax of @sc{gdb/mi}
27692 @cindex @sc{gdb/mi}, output syntax
27693 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27694 followed, optionally, by a single result record. This result record
27695 is for the most recent command. The sequence of output records is
27696 terminated by @samp{(gdb)}.
27698 If an input command was prefixed with a @code{@var{token}} then the
27699 corresponding output for that command will also be prefixed by that same
27703 @item @var{output} @expansion{}
27704 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27706 @item @var{result-record} @expansion{}
27707 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27709 @item @var{out-of-band-record} @expansion{}
27710 @code{@var{async-record} | @var{stream-record}}
27712 @item @var{async-record} @expansion{}
27713 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27715 @item @var{exec-async-output} @expansion{}
27716 @code{[ @var{token} ] "*" @var{async-output}}
27718 @item @var{status-async-output} @expansion{}
27719 @code{[ @var{token} ] "+" @var{async-output}}
27721 @item @var{notify-async-output} @expansion{}
27722 @code{[ @var{token} ] "=" @var{async-output}}
27724 @item @var{async-output} @expansion{}
27725 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27727 @item @var{result-class} @expansion{}
27728 @code{"done" | "running" | "connected" | "error" | "exit"}
27730 @item @var{async-class} @expansion{}
27731 @code{"stopped" | @var{others}} (where @var{others} will be added
27732 depending on the needs---this is still in development).
27734 @item @var{result} @expansion{}
27735 @code{ @var{variable} "=" @var{value}}
27737 @item @var{variable} @expansion{}
27738 @code{ @var{string} }
27740 @item @var{value} @expansion{}
27741 @code{ @var{const} | @var{tuple} | @var{list} }
27743 @item @var{const} @expansion{}
27744 @code{@var{c-string}}
27746 @item @var{tuple} @expansion{}
27747 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27749 @item @var{list} @expansion{}
27750 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27751 @var{result} ( "," @var{result} )* "]" }
27753 @item @var{stream-record} @expansion{}
27754 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27756 @item @var{console-stream-output} @expansion{}
27757 @code{"~" @var{c-string}}
27759 @item @var{target-stream-output} @expansion{}
27760 @code{"@@" @var{c-string}}
27762 @item @var{log-stream-output} @expansion{}
27763 @code{"&" @var{c-string}}
27765 @item @var{nl} @expansion{}
27768 @item @var{token} @expansion{}
27769 @emph{any sequence of digits}.
27777 All output sequences end in a single line containing a period.
27780 The @code{@var{token}} is from the corresponding request. Note that
27781 for all async output, while the token is allowed by the grammar and
27782 may be output by future versions of @value{GDBN} for select async
27783 output messages, it is generally omitted. Frontends should treat
27784 all async output as reporting general changes in the state of the
27785 target and there should be no need to associate async output to any
27789 @cindex status output in @sc{gdb/mi}
27790 @var{status-async-output} contains on-going status information about the
27791 progress of a slow operation. It can be discarded. All status output is
27792 prefixed by @samp{+}.
27795 @cindex async output in @sc{gdb/mi}
27796 @var{exec-async-output} contains asynchronous state change on the target
27797 (stopped, started, disappeared). All async output is prefixed by
27801 @cindex notify output in @sc{gdb/mi}
27802 @var{notify-async-output} contains supplementary information that the
27803 client should handle (e.g., a new breakpoint information). All notify
27804 output is prefixed by @samp{=}.
27807 @cindex console output in @sc{gdb/mi}
27808 @var{console-stream-output} is output that should be displayed as is in the
27809 console. It is the textual response to a CLI command. All the console
27810 output is prefixed by @samp{~}.
27813 @cindex target output in @sc{gdb/mi}
27814 @var{target-stream-output} is the output produced by the target program.
27815 All the target output is prefixed by @samp{@@}.
27818 @cindex log output in @sc{gdb/mi}
27819 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27820 instance messages that should be displayed as part of an error log. All
27821 the log output is prefixed by @samp{&}.
27824 @cindex list output in @sc{gdb/mi}
27825 New @sc{gdb/mi} commands should only output @var{lists} containing
27831 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27832 details about the various output records.
27834 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27835 @node GDB/MI Compatibility with CLI
27836 @section @sc{gdb/mi} Compatibility with CLI
27838 @cindex compatibility, @sc{gdb/mi} and CLI
27839 @cindex @sc{gdb/mi}, compatibility with CLI
27841 For the developers convenience CLI commands can be entered directly,
27842 but there may be some unexpected behaviour. For example, commands
27843 that query the user will behave as if the user replied yes, breakpoint
27844 command lists are not executed and some CLI commands, such as
27845 @code{if}, @code{when} and @code{define}, prompt for further input with
27846 @samp{>}, which is not valid MI output.
27848 This feature may be removed at some stage in the future and it is
27849 recommended that front ends use the @code{-interpreter-exec} command
27850 (@pxref{-interpreter-exec}).
27852 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27853 @node GDB/MI Development and Front Ends
27854 @section @sc{gdb/mi} Development and Front Ends
27855 @cindex @sc{gdb/mi} development
27857 The application which takes the MI output and presents the state of the
27858 program being debugged to the user is called a @dfn{front end}.
27860 Although @sc{gdb/mi} is still incomplete, it is currently being used
27861 by a variety of front ends to @value{GDBN}. This makes it difficult
27862 to introduce new functionality without breaking existing usage. This
27863 section tries to minimize the problems by describing how the protocol
27866 Some changes in MI need not break a carefully designed front end, and
27867 for these the MI version will remain unchanged. The following is a
27868 list of changes that may occur within one level, so front ends should
27869 parse MI output in a way that can handle them:
27873 New MI commands may be added.
27876 New fields may be added to the output of any MI command.
27879 The range of values for fields with specified values, e.g.,
27880 @code{in_scope} (@pxref{-var-update}) may be extended.
27882 @c The format of field's content e.g type prefix, may change so parse it
27883 @c at your own risk. Yes, in general?
27885 @c The order of fields may change? Shouldn't really matter but it might
27886 @c resolve inconsistencies.
27889 If the changes are likely to break front ends, the MI version level
27890 will be increased by one. This will allow the front end to parse the
27891 output according to the MI version. Apart from mi0, new versions of
27892 @value{GDBN} will not support old versions of MI and it will be the
27893 responsibility of the front end to work with the new one.
27895 @c Starting with mi3, add a new command -mi-version that prints the MI
27898 The best way to avoid unexpected changes in MI that might break your front
27899 end is to make your project known to @value{GDBN} developers and
27900 follow development on @email{gdb@@sourceware.org} and
27901 @email{gdb-patches@@sourceware.org}.
27902 @cindex mailing lists
27904 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27905 @node GDB/MI Output Records
27906 @section @sc{gdb/mi} Output Records
27909 * GDB/MI Result Records::
27910 * GDB/MI Stream Records::
27911 * GDB/MI Async Records::
27912 * GDB/MI Breakpoint Information::
27913 * GDB/MI Frame Information::
27914 * GDB/MI Thread Information::
27915 * GDB/MI Ada Exception Information::
27918 @node GDB/MI Result Records
27919 @subsection @sc{gdb/mi} Result Records
27921 @cindex result records in @sc{gdb/mi}
27922 @cindex @sc{gdb/mi}, result records
27923 In addition to a number of out-of-band notifications, the response to a
27924 @sc{gdb/mi} command includes one of the following result indications:
27928 @item "^done" [ "," @var{results} ]
27929 The synchronous operation was successful, @code{@var{results}} are the return
27934 This result record is equivalent to @samp{^done}. Historically, it
27935 was output instead of @samp{^done} if the command has resumed the
27936 target. This behaviour is maintained for backward compatibility, but
27937 all frontends should treat @samp{^done} and @samp{^running}
27938 identically and rely on the @samp{*running} output record to determine
27939 which threads are resumed.
27943 @value{GDBN} has connected to a remote target.
27945 @item "^error" "," @var{c-string}
27947 The operation failed. The @code{@var{c-string}} contains the corresponding
27952 @value{GDBN} has terminated.
27956 @node GDB/MI Stream Records
27957 @subsection @sc{gdb/mi} Stream Records
27959 @cindex @sc{gdb/mi}, stream records
27960 @cindex stream records in @sc{gdb/mi}
27961 @value{GDBN} internally maintains a number of output streams: the console, the
27962 target, and the log. The output intended for each of these streams is
27963 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27965 Each stream record begins with a unique @dfn{prefix character} which
27966 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27967 Syntax}). In addition to the prefix, each stream record contains a
27968 @code{@var{string-output}}. This is either raw text (with an implicit new
27969 line) or a quoted C string (which does not contain an implicit newline).
27972 @item "~" @var{string-output}
27973 The console output stream contains text that should be displayed in the
27974 CLI console window. It contains the textual responses to CLI commands.
27976 @item "@@" @var{string-output}
27977 The target output stream contains any textual output from the running
27978 target. This is only present when GDB's event loop is truly
27979 asynchronous, which is currently only the case for remote targets.
27981 @item "&" @var{string-output}
27982 The log stream contains debugging messages being produced by @value{GDBN}'s
27986 @node GDB/MI Async Records
27987 @subsection @sc{gdb/mi} Async Records
27989 @cindex async records in @sc{gdb/mi}
27990 @cindex @sc{gdb/mi}, async records
27991 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27992 additional changes that have occurred. Those changes can either be a
27993 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27994 target activity (e.g., target stopped).
27996 The following is the list of possible async records:
28000 @item *running,thread-id="@var{thread}"
28001 The target is now running. The @var{thread} field tells which
28002 specific thread is now running, and can be @samp{all} if all threads
28003 are running. The frontend should assume that no interaction with a
28004 running thread is possible after this notification is produced.
28005 The frontend should not assume that this notification is output
28006 only once for any command. @value{GDBN} may emit this notification
28007 several times, either for different threads, because it cannot resume
28008 all threads together, or even for a single thread, if the thread must
28009 be stepped though some code before letting it run freely.
28011 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28012 The target has stopped. The @var{reason} field can have one of the
28016 @item breakpoint-hit
28017 A breakpoint was reached.
28018 @item watchpoint-trigger
28019 A watchpoint was triggered.
28020 @item read-watchpoint-trigger
28021 A read watchpoint was triggered.
28022 @item access-watchpoint-trigger
28023 An access watchpoint was triggered.
28024 @item function-finished
28025 An -exec-finish or similar CLI command was accomplished.
28026 @item location-reached
28027 An -exec-until or similar CLI command was accomplished.
28028 @item watchpoint-scope
28029 A watchpoint has gone out of scope.
28030 @item end-stepping-range
28031 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28032 similar CLI command was accomplished.
28033 @item exited-signalled
28034 The inferior exited because of a signal.
28036 The inferior exited.
28037 @item exited-normally
28038 The inferior exited normally.
28039 @item signal-received
28040 A signal was received by the inferior.
28042 The inferior has stopped due to a library being loaded or unloaded.
28043 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28044 set or when a @code{catch load} or @code{catch unload} catchpoint is
28045 in use (@pxref{Set Catchpoints}).
28047 The inferior has forked. This is reported when @code{catch fork}
28048 (@pxref{Set Catchpoints}) has been used.
28050 The inferior has vforked. This is reported in when @code{catch vfork}
28051 (@pxref{Set Catchpoints}) has been used.
28052 @item syscall-entry
28053 The inferior entered a system call. This is reported when @code{catch
28054 syscall} (@pxref{Set Catchpoints}) has been used.
28055 @item syscall-entry
28056 The inferior returned from a system call. This is reported when
28057 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28059 The inferior called @code{exec}. This is reported when @code{catch exec}
28060 (@pxref{Set Catchpoints}) has been used.
28063 The @var{id} field identifies the thread that directly caused the stop
28064 -- for example by hitting a breakpoint. Depending on whether all-stop
28065 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28066 stop all threads, or only the thread that directly triggered the stop.
28067 If all threads are stopped, the @var{stopped} field will have the
28068 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28069 field will be a list of thread identifiers. Presently, this list will
28070 always include a single thread, but frontend should be prepared to see
28071 several threads in the list. The @var{core} field reports the
28072 processor core on which the stop event has happened. This field may be absent
28073 if such information is not available.
28075 @item =thread-group-added,id="@var{id}"
28076 @itemx =thread-group-removed,id="@var{id}"
28077 A thread group was either added or removed. The @var{id} field
28078 contains the @value{GDBN} identifier of the thread group. When a thread
28079 group is added, it generally might not be associated with a running
28080 process. When a thread group is removed, its id becomes invalid and
28081 cannot be used in any way.
28083 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28084 A thread group became associated with a running program,
28085 either because the program was just started or the thread group
28086 was attached to a program. The @var{id} field contains the
28087 @value{GDBN} identifier of the thread group. The @var{pid} field
28088 contains process identifier, specific to the operating system.
28090 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28091 A thread group is no longer associated with a running program,
28092 either because the program has exited, or because it was detached
28093 from. The @var{id} field contains the @value{GDBN} identifier of the
28094 thread group. @var{code} is the exit code of the inferior; it exists
28095 only when the inferior exited with some code.
28097 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28098 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28099 A thread either was created, or has exited. The @var{id} field
28100 contains the @value{GDBN} identifier of the thread. The @var{gid}
28101 field identifies the thread group this thread belongs to.
28103 @item =thread-selected,id="@var{id}"
28104 Informs that the selected thread was changed as result of the last
28105 command. This notification is not emitted as result of @code{-thread-select}
28106 command but is emitted whenever an MI command that is not documented
28107 to change the selected thread actually changes it. In particular,
28108 invoking, directly or indirectly (via user-defined command), the CLI
28109 @code{thread} command, will generate this notification.
28111 We suggest that in response to this notification, front ends
28112 highlight the selected thread and cause subsequent commands to apply to
28115 @item =library-loaded,...
28116 Reports that a new library file was loaded by the program. This
28117 notification has 4 fields---@var{id}, @var{target-name},
28118 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
28119 opaque identifier of the library. For remote debugging case,
28120 @var{target-name} and @var{host-name} fields give the name of the
28121 library file on the target, and on the host respectively. For native
28122 debugging, both those fields have the same value. The
28123 @var{symbols-loaded} field is emitted only for backward compatibility
28124 and should not be relied on to convey any useful information. The
28125 @var{thread-group} field, if present, specifies the id of the thread
28126 group in whose context the library was loaded. If the field is
28127 absent, it means the library was loaded in the context of all present
28130 @item =library-unloaded,...
28131 Reports that a library was unloaded by the program. This notification
28132 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28133 the same meaning as for the @code{=library-loaded} notification.
28134 The @var{thread-group} field, if present, specifies the id of the
28135 thread group in whose context the library was unloaded. If the field is
28136 absent, it means the library was unloaded in the context of all present
28139 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28140 @itemx =traceframe-changed,end
28141 Reports that the trace frame was changed and its new number is
28142 @var{tfnum}. The number of the tracepoint associated with this trace
28143 frame is @var{tpnum}.
28145 @item =tsv-created,name=@var{name},initial=@var{initial}
28146 Reports that the new trace state variable @var{name} is created with
28147 initial value @var{initial}.
28149 @item =tsv-deleted,name=@var{name}
28150 @itemx =tsv-deleted
28151 Reports that the trace state variable @var{name} is deleted or all
28152 trace state variables are deleted.
28154 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28155 Reports that the trace state variable @var{name} is modified with
28156 the initial value @var{initial}. The current value @var{current} of
28157 trace state variable is optional and is reported if the current
28158 value of trace state variable is known.
28160 @item =breakpoint-created,bkpt=@{...@}
28161 @itemx =breakpoint-modified,bkpt=@{...@}
28162 @itemx =breakpoint-deleted,id=@var{number}
28163 Reports that a breakpoint was created, modified, or deleted,
28164 respectively. Only user-visible breakpoints are reported to the MI
28167 The @var{bkpt} argument is of the same form as returned by the various
28168 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28169 @var{number} is the ordinal number of the breakpoint.
28171 Note that if a breakpoint is emitted in the result record of a
28172 command, then it will not also be emitted in an async record.
28174 @item =record-started,thread-group="@var{id}"
28175 @itemx =record-stopped,thread-group="@var{id}"
28176 Execution log recording was either started or stopped on an
28177 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28178 group corresponding to the affected inferior.
28180 @item =cmd-param-changed,param=@var{param},value=@var{value}
28181 Reports that a parameter of the command @code{set @var{param}} is
28182 changed to @var{value}. In the multi-word @code{set} command,
28183 the @var{param} is the whole parameter list to @code{set} command.
28184 For example, In command @code{set check type on}, @var{param}
28185 is @code{check type} and @var{value} is @code{on}.
28187 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28188 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28189 written in an inferior. The @var{id} is the identifier of the
28190 thread group corresponding to the affected inferior. The optional
28191 @code{type="code"} part is reported if the memory written to holds
28195 @node GDB/MI Breakpoint Information
28196 @subsection @sc{gdb/mi} Breakpoint Information
28198 When @value{GDBN} reports information about a breakpoint, a
28199 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28204 The breakpoint number. For a breakpoint that represents one location
28205 of a multi-location breakpoint, this will be a dotted pair, like
28209 The type of the breakpoint. For ordinary breakpoints this will be
28210 @samp{breakpoint}, but many values are possible.
28213 If the type of the breakpoint is @samp{catchpoint}, then this
28214 indicates the exact type of catchpoint.
28217 This is the breakpoint disposition---either @samp{del}, meaning that
28218 the breakpoint will be deleted at the next stop, or @samp{keep},
28219 meaning that the breakpoint will not be deleted.
28222 This indicates whether the breakpoint is enabled, in which case the
28223 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28224 Note that this is not the same as the field @code{enable}.
28227 The address of the breakpoint. This may be a hexidecimal number,
28228 giving the address; or the string @samp{<PENDING>}, for a pending
28229 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28230 multiple locations. This field will not be present if no address can
28231 be determined. For example, a watchpoint does not have an address.
28234 If known, the function in which the breakpoint appears.
28235 If not known, this field is not present.
28238 The name of the source file which contains this function, if known.
28239 If not known, this field is not present.
28242 The full file name of the source file which contains this function, if
28243 known. If not known, this field is not present.
28246 The line number at which this breakpoint appears, if known.
28247 If not known, this field is not present.
28250 If the source file is not known, this field may be provided. If
28251 provided, this holds the address of the breakpoint, possibly followed
28255 If this breakpoint is pending, this field is present and holds the
28256 text used to set the breakpoint, as entered by the user.
28259 Where this breakpoint's condition is evaluated, either @samp{host} or
28263 If this is a thread-specific breakpoint, then this identifies the
28264 thread in which the breakpoint can trigger.
28267 If this breakpoint is restricted to a particular Ada task, then this
28268 field will hold the task identifier.
28271 If the breakpoint is conditional, this is the condition expression.
28274 The ignore count of the breakpoint.
28277 The enable count of the breakpoint.
28279 @item traceframe-usage
28282 @item static-tracepoint-marker-string-id
28283 For a static tracepoint, the name of the static tracepoint marker.
28286 For a masked watchpoint, this is the mask.
28289 A tracepoint's pass count.
28291 @item original-location
28292 The location of the breakpoint as originally specified by the user.
28293 This field is optional.
28296 The number of times the breakpoint has been hit.
28299 This field is only given for tracepoints. This is either @samp{y},
28300 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28304 Some extra data, the exact contents of which are type-dependent.
28308 For example, here is what the output of @code{-break-insert}
28309 (@pxref{GDB/MI Breakpoint Commands}) might be:
28312 -> -break-insert main
28313 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28314 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28315 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28320 @node GDB/MI Frame Information
28321 @subsection @sc{gdb/mi} Frame Information
28323 Response from many MI commands includes an information about stack
28324 frame. This information is a tuple that may have the following
28329 The level of the stack frame. The innermost frame has the level of
28330 zero. This field is always present.
28333 The name of the function corresponding to the frame. This field may
28334 be absent if @value{GDBN} is unable to determine the function name.
28337 The code address for the frame. This field is always present.
28340 The name of the source files that correspond to the frame's code
28341 address. This field may be absent.
28344 The source line corresponding to the frames' code address. This field
28348 The name of the binary file (either executable or shared library) the
28349 corresponds to the frame's code address. This field may be absent.
28353 @node GDB/MI Thread Information
28354 @subsection @sc{gdb/mi} Thread Information
28356 Whenever @value{GDBN} has to report an information about a thread, it
28357 uses a tuple with the following fields:
28361 The numeric id assigned to the thread by @value{GDBN}. This field is
28365 Target-specific string identifying the thread. This field is always present.
28368 Additional information about the thread provided by the target.
28369 It is supposed to be human-readable and not interpreted by the
28370 frontend. This field is optional.
28373 Either @samp{stopped} or @samp{running}, depending on whether the
28374 thread is presently running. This field is always present.
28377 The value of this field is an integer number of the processor core the
28378 thread was last seen on. This field is optional.
28381 @node GDB/MI Ada Exception Information
28382 @subsection @sc{gdb/mi} Ada Exception Information
28384 Whenever a @code{*stopped} record is emitted because the program
28385 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28386 @value{GDBN} provides the name of the exception that was raised via
28387 the @code{exception-name} field.
28389 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28390 @node GDB/MI Simple Examples
28391 @section Simple Examples of @sc{gdb/mi} Interaction
28392 @cindex @sc{gdb/mi}, simple examples
28394 This subsection presents several simple examples of interaction using
28395 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28396 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28397 the output received from @sc{gdb/mi}.
28399 Note the line breaks shown in the examples are here only for
28400 readability, they don't appear in the real output.
28402 @subheading Setting a Breakpoint
28404 Setting a breakpoint generates synchronous output which contains detailed
28405 information of the breakpoint.
28408 -> -break-insert main
28409 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28410 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28411 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28416 @subheading Program Execution
28418 Program execution generates asynchronous records and MI gives the
28419 reason that execution stopped.
28425 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28426 frame=@{addr="0x08048564",func="main",
28427 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28428 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28433 <- *stopped,reason="exited-normally"
28437 @subheading Quitting @value{GDBN}
28439 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28447 Please note that @samp{^exit} is printed immediately, but it might
28448 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28449 performs necessary cleanups, including killing programs being debugged
28450 or disconnecting from debug hardware, so the frontend should wait till
28451 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28452 fails to exit in reasonable time.
28454 @subheading A Bad Command
28456 Here's what happens if you pass a non-existent command:
28460 <- ^error,msg="Undefined MI command: rubbish"
28465 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28466 @node GDB/MI Command Description Format
28467 @section @sc{gdb/mi} Command Description Format
28469 The remaining sections describe blocks of commands. Each block of
28470 commands is laid out in a fashion similar to this section.
28472 @subheading Motivation
28474 The motivation for this collection of commands.
28476 @subheading Introduction
28478 A brief introduction to this collection of commands as a whole.
28480 @subheading Commands
28482 For each command in the block, the following is described:
28484 @subsubheading Synopsis
28487 -command @var{args}@dots{}
28490 @subsubheading Result
28492 @subsubheading @value{GDBN} Command
28494 The corresponding @value{GDBN} CLI command(s), if any.
28496 @subsubheading Example
28498 Example(s) formatted for readability. Some of the described commands have
28499 not been implemented yet and these are labeled N.A.@: (not available).
28502 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28503 @node GDB/MI Breakpoint Commands
28504 @section @sc{gdb/mi} Breakpoint Commands
28506 @cindex breakpoint commands for @sc{gdb/mi}
28507 @cindex @sc{gdb/mi}, breakpoint commands
28508 This section documents @sc{gdb/mi} commands for manipulating
28511 @subheading The @code{-break-after} Command
28512 @findex -break-after
28514 @subsubheading Synopsis
28517 -break-after @var{number} @var{count}
28520 The breakpoint number @var{number} is not in effect until it has been
28521 hit @var{count} times. To see how this is reflected in the output of
28522 the @samp{-break-list} command, see the description of the
28523 @samp{-break-list} command below.
28525 @subsubheading @value{GDBN} Command
28527 The corresponding @value{GDBN} command is @samp{ignore}.
28529 @subsubheading Example
28534 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28535 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28536 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28544 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28545 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28546 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28547 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28548 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28549 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28550 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28551 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28552 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28553 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28558 @subheading The @code{-break-catch} Command
28559 @findex -break-catch
28562 @subheading The @code{-break-commands} Command
28563 @findex -break-commands
28565 @subsubheading Synopsis
28568 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28571 Specifies the CLI commands that should be executed when breakpoint
28572 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28573 are the commands. If no command is specified, any previously-set
28574 commands are cleared. @xref{Break Commands}. Typical use of this
28575 functionality is tracing a program, that is, printing of values of
28576 some variables whenever breakpoint is hit and then continuing.
28578 @subsubheading @value{GDBN} Command
28580 The corresponding @value{GDBN} command is @samp{commands}.
28582 @subsubheading Example
28587 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28588 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28589 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28592 -break-commands 1 "print v" "continue"
28597 @subheading The @code{-break-condition} Command
28598 @findex -break-condition
28600 @subsubheading Synopsis
28603 -break-condition @var{number} @var{expr}
28606 Breakpoint @var{number} will stop the program only if the condition in
28607 @var{expr} is true. The condition becomes part of the
28608 @samp{-break-list} output (see the description of the @samp{-break-list}
28611 @subsubheading @value{GDBN} Command
28613 The corresponding @value{GDBN} command is @samp{condition}.
28615 @subsubheading Example
28619 -break-condition 1 1
28623 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28624 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28625 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28626 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28627 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28628 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28629 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28630 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28631 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28632 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28636 @subheading The @code{-break-delete} Command
28637 @findex -break-delete
28639 @subsubheading Synopsis
28642 -break-delete ( @var{breakpoint} )+
28645 Delete the breakpoint(s) whose number(s) are specified in the argument
28646 list. This is obviously reflected in the breakpoint list.
28648 @subsubheading @value{GDBN} Command
28650 The corresponding @value{GDBN} command is @samp{delete}.
28652 @subsubheading Example
28660 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28661 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28662 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28663 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28664 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28665 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28666 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28671 @subheading The @code{-break-disable} Command
28672 @findex -break-disable
28674 @subsubheading Synopsis
28677 -break-disable ( @var{breakpoint} )+
28680 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28681 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28683 @subsubheading @value{GDBN} Command
28685 The corresponding @value{GDBN} command is @samp{disable}.
28687 @subsubheading Example
28695 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28696 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28697 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28698 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28699 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28700 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28701 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28702 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28703 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28704 line="5",thread-groups=["i1"],times="0"@}]@}
28708 @subheading The @code{-break-enable} Command
28709 @findex -break-enable
28711 @subsubheading Synopsis
28714 -break-enable ( @var{breakpoint} )+
28717 Enable (previously disabled) @var{breakpoint}(s).
28719 @subsubheading @value{GDBN} Command
28721 The corresponding @value{GDBN} command is @samp{enable}.
28723 @subsubheading Example
28731 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28732 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28733 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28734 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28735 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28736 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28737 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28738 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28739 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28740 line="5",thread-groups=["i1"],times="0"@}]@}
28744 @subheading The @code{-break-info} Command
28745 @findex -break-info
28747 @subsubheading Synopsis
28750 -break-info @var{breakpoint}
28754 Get information about a single breakpoint.
28756 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28757 Information}, for details on the format of each breakpoint in the
28760 @subsubheading @value{GDBN} Command
28762 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28764 @subsubheading Example
28767 @subheading The @code{-break-insert} Command
28768 @findex -break-insert
28770 @subsubheading Synopsis
28773 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28774 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28775 [ -p @var{thread-id} ] [ @var{location} ]
28779 If specified, @var{location}, can be one of:
28786 @item filename:linenum
28787 @item filename:function
28791 The possible optional parameters of this command are:
28795 Insert a temporary breakpoint.
28797 Insert a hardware breakpoint.
28799 If @var{location} cannot be parsed (for example if it
28800 refers to unknown files or functions), create a pending
28801 breakpoint. Without this flag, @value{GDBN} will report
28802 an error, and won't create a breakpoint, if @var{location}
28805 Create a disabled breakpoint.
28807 Create a tracepoint. @xref{Tracepoints}. When this parameter
28808 is used together with @samp{-h}, a fast tracepoint is created.
28809 @item -c @var{condition}
28810 Make the breakpoint conditional on @var{condition}.
28811 @item -i @var{ignore-count}
28812 Initialize the @var{ignore-count}.
28813 @item -p @var{thread-id}
28814 Restrict the breakpoint to the specified @var{thread-id}.
28817 @subsubheading Result
28819 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28820 resulting breakpoint.
28822 Note: this format is open to change.
28823 @c An out-of-band breakpoint instead of part of the result?
28825 @subsubheading @value{GDBN} Command
28827 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28828 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28830 @subsubheading Example
28835 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28836 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28839 -break-insert -t foo
28840 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28841 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28845 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28846 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28847 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28848 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28849 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28850 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28851 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28852 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28853 addr="0x0001072c", func="main",file="recursive2.c",
28854 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28856 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28857 addr="0x00010774",func="foo",file="recursive2.c",
28858 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28861 @c -break-insert -r foo.*
28862 @c ~int foo(int, int);
28863 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28864 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28869 @subheading The @code{-break-list} Command
28870 @findex -break-list
28872 @subsubheading Synopsis
28878 Displays the list of inserted breakpoints, showing the following fields:
28882 number of the breakpoint
28884 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28886 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28889 is the breakpoint enabled or no: @samp{y} or @samp{n}
28891 memory location at which the breakpoint is set
28893 logical location of the breakpoint, expressed by function name, file
28895 @item Thread-groups
28896 list of thread groups to which this breakpoint applies
28898 number of times the breakpoint has been hit
28901 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28902 @code{body} field is an empty list.
28904 @subsubheading @value{GDBN} Command
28906 The corresponding @value{GDBN} command is @samp{info break}.
28908 @subsubheading Example
28913 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28914 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28915 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28916 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28917 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28918 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28919 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28920 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28921 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28923 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28924 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28925 line="13",thread-groups=["i1"],times="0"@}]@}
28929 Here's an example of the result when there are no breakpoints:
28934 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28935 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28936 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28937 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28938 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28939 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28940 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28945 @subheading The @code{-break-passcount} Command
28946 @findex -break-passcount
28948 @subsubheading Synopsis
28951 -break-passcount @var{tracepoint-number} @var{passcount}
28954 Set the passcount for tracepoint @var{tracepoint-number} to
28955 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28956 is not a tracepoint, error is emitted. This corresponds to CLI
28957 command @samp{passcount}.
28959 @subheading The @code{-break-watch} Command
28960 @findex -break-watch
28962 @subsubheading Synopsis
28965 -break-watch [ -a | -r ]
28968 Create a watchpoint. With the @samp{-a} option it will create an
28969 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28970 read from or on a write to the memory location. With the @samp{-r}
28971 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28972 trigger only when the memory location is accessed for reading. Without
28973 either of the options, the watchpoint created is a regular watchpoint,
28974 i.e., it will trigger when the memory location is accessed for writing.
28975 @xref{Set Watchpoints, , Setting Watchpoints}.
28977 Note that @samp{-break-list} will report a single list of watchpoints and
28978 breakpoints inserted.
28980 @subsubheading @value{GDBN} Command
28982 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28985 @subsubheading Example
28987 Setting a watchpoint on a variable in the @code{main} function:
28992 ^done,wpt=@{number="2",exp="x"@}
28997 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28998 value=@{old="-268439212",new="55"@},
28999 frame=@{func="main",args=[],file="recursive2.c",
29000 fullname="/home/foo/bar/recursive2.c",line="5"@}
29004 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29005 the program execution twice: first for the variable changing value, then
29006 for the watchpoint going out of scope.
29011 ^done,wpt=@{number="5",exp="C"@}
29016 *stopped,reason="watchpoint-trigger",
29017 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29018 frame=@{func="callee4",args=[],
29019 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29020 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29025 *stopped,reason="watchpoint-scope",wpnum="5",
29026 frame=@{func="callee3",args=[@{name="strarg",
29027 value="0x11940 \"A string argument.\""@}],
29028 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29029 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29033 Listing breakpoints and watchpoints, at different points in the program
29034 execution. Note that once the watchpoint goes out of scope, it is
29040 ^done,wpt=@{number="2",exp="C"@}
29043 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29044 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29045 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29046 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29047 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29048 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29049 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29050 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29051 addr="0x00010734",func="callee4",
29052 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29053 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29055 bkpt=@{number="2",type="watchpoint",disp="keep",
29056 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29061 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29062 value=@{old="-276895068",new="3"@},
29063 frame=@{func="callee4",args=[],
29064 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29065 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29068 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29069 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29070 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29071 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29072 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29073 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29074 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29075 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29076 addr="0x00010734",func="callee4",
29077 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29078 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29080 bkpt=@{number="2",type="watchpoint",disp="keep",
29081 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29085 ^done,reason="watchpoint-scope",wpnum="2",
29086 frame=@{func="callee3",args=[@{name="strarg",
29087 value="0x11940 \"A string argument.\""@}],
29088 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29089 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29092 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29093 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29094 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29095 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29096 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29097 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29098 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29099 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29100 addr="0x00010734",func="callee4",
29101 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29102 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29103 thread-groups=["i1"],times="1"@}]@}
29108 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29109 @node GDB/MI Catchpoint Commands
29110 @section @sc{gdb/mi} Catchpoint Commands
29112 This section documents @sc{gdb/mi} commands for manipulating
29115 @subheading The @code{-catch-load} Command
29116 @findex -catch-load
29118 @subsubheading Synopsis
29121 -catch-load [ -t ] [ -d ] @var{regexp}
29124 Add a catchpoint for library load events. If the @samp{-t} option is used,
29125 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29126 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29127 in a disabled state. The @samp{regexp} argument is a regular
29128 expression used to match the name of the loaded library.
29131 @subsubheading @value{GDBN} Command
29133 The corresponding @value{GDBN} command is @samp{catch load}.
29135 @subsubheading Example
29138 -catch-load -t foo.so
29139 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29140 what="load of library matching foo.so",catch-type="load",times="0"@}
29145 @subheading The @code{-catch-unload} Command
29146 @findex -catch-unload
29148 @subsubheading Synopsis
29151 -catch-unload [ -t ] [ -d ] @var{regexp}
29154 Add a catchpoint for library unload events. If the @samp{-t} option is
29155 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29156 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29157 created in a disabled state. The @samp{regexp} argument is a regular
29158 expression used to match the name of the unloaded library.
29160 @subsubheading @value{GDBN} Command
29162 The corresponding @value{GDBN} command is @samp{catch unload}.
29164 @subsubheading Example
29167 -catch-unload -d bar.so
29168 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29169 what="load of library matching bar.so",catch-type="unload",times="0"@}
29174 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29175 @node GDB/MI Program Context
29176 @section @sc{gdb/mi} Program Context
29178 @subheading The @code{-exec-arguments} Command
29179 @findex -exec-arguments
29182 @subsubheading Synopsis
29185 -exec-arguments @var{args}
29188 Set the inferior program arguments, to be used in the next
29191 @subsubheading @value{GDBN} Command
29193 The corresponding @value{GDBN} command is @samp{set args}.
29195 @subsubheading Example
29199 -exec-arguments -v word
29206 @subheading The @code{-exec-show-arguments} Command
29207 @findex -exec-show-arguments
29209 @subsubheading Synopsis
29212 -exec-show-arguments
29215 Print the arguments of the program.
29217 @subsubheading @value{GDBN} Command
29219 The corresponding @value{GDBN} command is @samp{show args}.
29221 @subsubheading Example
29226 @subheading The @code{-environment-cd} Command
29227 @findex -environment-cd
29229 @subsubheading Synopsis
29232 -environment-cd @var{pathdir}
29235 Set @value{GDBN}'s working directory.
29237 @subsubheading @value{GDBN} Command
29239 The corresponding @value{GDBN} command is @samp{cd}.
29241 @subsubheading Example
29245 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29251 @subheading The @code{-environment-directory} Command
29252 @findex -environment-directory
29254 @subsubheading Synopsis
29257 -environment-directory [ -r ] [ @var{pathdir} ]+
29260 Add directories @var{pathdir} to beginning of search path for source files.
29261 If the @samp{-r} option is used, the search path is reset to the default
29262 search path. If directories @var{pathdir} are supplied in addition to the
29263 @samp{-r} option, the search path is first reset and then addition
29265 Multiple directories may be specified, separated by blanks. Specifying
29266 multiple directories in a single command
29267 results in the directories added to the beginning of the
29268 search path in the same order they were presented in the command.
29269 If blanks are needed as
29270 part of a directory name, double-quotes should be used around
29271 the name. In the command output, the path will show up separated
29272 by the system directory-separator character. The directory-separator
29273 character must not be used
29274 in any directory name.
29275 If no directories are specified, the current search path is displayed.
29277 @subsubheading @value{GDBN} Command
29279 The corresponding @value{GDBN} command is @samp{dir}.
29281 @subsubheading Example
29285 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29286 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29288 -environment-directory ""
29289 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29291 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29292 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29294 -environment-directory -r
29295 ^done,source-path="$cdir:$cwd"
29300 @subheading The @code{-environment-path} Command
29301 @findex -environment-path
29303 @subsubheading Synopsis
29306 -environment-path [ -r ] [ @var{pathdir} ]+
29309 Add directories @var{pathdir} to beginning of search path for object files.
29310 If the @samp{-r} option is used, the search path is reset to the original
29311 search path that existed at gdb start-up. If directories @var{pathdir} are
29312 supplied in addition to the
29313 @samp{-r} option, the search path is first reset and then addition
29315 Multiple directories may be specified, separated by blanks. Specifying
29316 multiple directories in a single command
29317 results in the directories added to the beginning of the
29318 search path in the same order they were presented in the command.
29319 If blanks are needed as
29320 part of a directory name, double-quotes should be used around
29321 the name. In the command output, the path will show up separated
29322 by the system directory-separator character. The directory-separator
29323 character must not be used
29324 in any directory name.
29325 If no directories are specified, the current path is displayed.
29328 @subsubheading @value{GDBN} Command
29330 The corresponding @value{GDBN} command is @samp{path}.
29332 @subsubheading Example
29337 ^done,path="/usr/bin"
29339 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29340 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29342 -environment-path -r /usr/local/bin
29343 ^done,path="/usr/local/bin:/usr/bin"
29348 @subheading The @code{-environment-pwd} Command
29349 @findex -environment-pwd
29351 @subsubheading Synopsis
29357 Show the current working directory.
29359 @subsubheading @value{GDBN} Command
29361 The corresponding @value{GDBN} command is @samp{pwd}.
29363 @subsubheading Example
29368 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29372 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29373 @node GDB/MI Thread Commands
29374 @section @sc{gdb/mi} Thread Commands
29377 @subheading The @code{-thread-info} Command
29378 @findex -thread-info
29380 @subsubheading Synopsis
29383 -thread-info [ @var{thread-id} ]
29386 Reports information about either a specific thread, if
29387 the @var{thread-id} parameter is present, or about all
29388 threads. When printing information about all threads,
29389 also reports the current thread.
29391 @subsubheading @value{GDBN} Command
29393 The @samp{info thread} command prints the same information
29396 @subsubheading Result
29398 The result is a list of threads. The following attributes are
29399 defined for a given thread:
29403 This field exists only for the current thread. It has the value @samp{*}.
29406 The identifier that @value{GDBN} uses to refer to the thread.
29409 The identifier that the target uses to refer to the thread.
29412 Extra information about the thread, in a target-specific format. This
29416 The name of the thread. If the user specified a name using the
29417 @code{thread name} command, then this name is given. Otherwise, if
29418 @value{GDBN} can extract the thread name from the target, then that
29419 name is given. If @value{GDBN} cannot find the thread name, then this
29423 The stack frame currently executing in the thread.
29426 The thread's state. The @samp{state} field may have the following
29431 The thread is stopped. Frame information is available for stopped
29435 The thread is running. There's no frame information for running
29441 If @value{GDBN} can find the CPU core on which this thread is running,
29442 then this field is the core identifier. This field is optional.
29446 @subsubheading Example
29451 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29452 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29453 args=[]@},state="running"@},
29454 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29455 frame=@{level="0",addr="0x0804891f",func="foo",
29456 args=[@{name="i",value="10"@}],
29457 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29458 state="running"@}],
29459 current-thread-id="1"
29463 @subheading The @code{-thread-list-ids} Command
29464 @findex -thread-list-ids
29466 @subsubheading Synopsis
29472 Produces a list of the currently known @value{GDBN} thread ids. At the
29473 end of the list it also prints the total number of such threads.
29475 This command is retained for historical reasons, the
29476 @code{-thread-info} command should be used instead.
29478 @subsubheading @value{GDBN} Command
29480 Part of @samp{info threads} supplies the same information.
29482 @subsubheading Example
29487 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29488 current-thread-id="1",number-of-threads="3"
29493 @subheading The @code{-thread-select} Command
29494 @findex -thread-select
29496 @subsubheading Synopsis
29499 -thread-select @var{threadnum}
29502 Make @var{threadnum} the current thread. It prints the number of the new
29503 current thread, and the topmost frame for that thread.
29505 This command is deprecated in favor of explicitly using the
29506 @samp{--thread} option to each command.
29508 @subsubheading @value{GDBN} Command
29510 The corresponding @value{GDBN} command is @samp{thread}.
29512 @subsubheading Example
29519 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29520 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29524 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29525 number-of-threads="3"
29528 ^done,new-thread-id="3",
29529 frame=@{level="0",func="vprintf",
29530 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29531 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29535 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29536 @node GDB/MI Ada Tasking Commands
29537 @section @sc{gdb/mi} Ada Tasking Commands
29539 @subheading The @code{-ada-task-info} Command
29540 @findex -ada-task-info
29542 @subsubheading Synopsis
29545 -ada-task-info [ @var{task-id} ]
29548 Reports information about either a specific Ada task, if the
29549 @var{task-id} parameter is present, or about all Ada tasks.
29551 @subsubheading @value{GDBN} Command
29553 The @samp{info tasks} command prints the same information
29554 about all Ada tasks (@pxref{Ada Tasks}).
29556 @subsubheading Result
29558 The result is a table of Ada tasks. The following columns are
29559 defined for each Ada task:
29563 This field exists only for the current thread. It has the value @samp{*}.
29566 The identifier that @value{GDBN} uses to refer to the Ada task.
29569 The identifier that the target uses to refer to the Ada task.
29572 The identifier of the thread corresponding to the Ada task.
29574 This field should always exist, as Ada tasks are always implemented
29575 on top of a thread. But if @value{GDBN} cannot find this corresponding
29576 thread for any reason, the field is omitted.
29579 This field exists only when the task was created by another task.
29580 In this case, it provides the ID of the parent task.
29583 The base priority of the task.
29586 The current state of the task. For a detailed description of the
29587 possible states, see @ref{Ada Tasks}.
29590 The name of the task.
29594 @subsubheading Example
29598 ^done,tasks=@{nr_rows="3",nr_cols="8",
29599 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29600 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29601 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29602 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29603 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29604 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29605 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29606 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29607 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29608 state="Child Termination Wait",name="main_task"@}]@}
29612 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29613 @node GDB/MI Program Execution
29614 @section @sc{gdb/mi} Program Execution
29616 These are the asynchronous commands which generate the out-of-band
29617 record @samp{*stopped}. Currently @value{GDBN} only really executes
29618 asynchronously with remote targets and this interaction is mimicked in
29621 @subheading The @code{-exec-continue} Command
29622 @findex -exec-continue
29624 @subsubheading Synopsis
29627 -exec-continue [--reverse] [--all|--thread-group N]
29630 Resumes the execution of the inferior program, which will continue
29631 to execute until it reaches a debugger stop event. If the
29632 @samp{--reverse} option is specified, execution resumes in reverse until
29633 it reaches a stop event. Stop events may include
29636 breakpoints or watchpoints
29638 signals or exceptions
29640 the end of the process (or its beginning under @samp{--reverse})
29642 the end or beginning of a replay log if one is being used.
29644 In all-stop mode (@pxref{All-Stop
29645 Mode}), may resume only one thread, or all threads, depending on the
29646 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29647 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29648 ignored in all-stop mode. If the @samp{--thread-group} options is
29649 specified, then all threads in that thread group are resumed.
29651 @subsubheading @value{GDBN} Command
29653 The corresponding @value{GDBN} corresponding is @samp{continue}.
29655 @subsubheading Example
29662 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29663 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29669 @subheading The @code{-exec-finish} Command
29670 @findex -exec-finish
29672 @subsubheading Synopsis
29675 -exec-finish [--reverse]
29678 Resumes the execution of the inferior program until the current
29679 function is exited. Displays the results returned by the function.
29680 If the @samp{--reverse} option is specified, resumes the reverse
29681 execution of the inferior program until the point where current
29682 function was called.
29684 @subsubheading @value{GDBN} Command
29686 The corresponding @value{GDBN} command is @samp{finish}.
29688 @subsubheading Example
29690 Function returning @code{void}.
29697 *stopped,reason="function-finished",frame=@{func="main",args=[],
29698 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29702 Function returning other than @code{void}. The name of the internal
29703 @value{GDBN} variable storing the result is printed, together with the
29710 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29711 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29712 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29713 gdb-result-var="$1",return-value="0"
29718 @subheading The @code{-exec-interrupt} Command
29719 @findex -exec-interrupt
29721 @subsubheading Synopsis
29724 -exec-interrupt [--all|--thread-group N]
29727 Interrupts the background execution of the target. Note how the token
29728 associated with the stop message is the one for the execution command
29729 that has been interrupted. The token for the interrupt itself only
29730 appears in the @samp{^done} output. If the user is trying to
29731 interrupt a non-running program, an error message will be printed.
29733 Note that when asynchronous execution is enabled, this command is
29734 asynchronous just like other execution commands. That is, first the
29735 @samp{^done} response will be printed, and the target stop will be
29736 reported after that using the @samp{*stopped} notification.
29738 In non-stop mode, only the context thread is interrupted by default.
29739 All threads (in all inferiors) will be interrupted if the
29740 @samp{--all} option is specified. If the @samp{--thread-group}
29741 option is specified, all threads in that group will be interrupted.
29743 @subsubheading @value{GDBN} Command
29745 The corresponding @value{GDBN} command is @samp{interrupt}.
29747 @subsubheading Example
29758 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29759 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29760 fullname="/home/foo/bar/try.c",line="13"@}
29765 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29769 @subheading The @code{-exec-jump} Command
29772 @subsubheading Synopsis
29775 -exec-jump @var{location}
29778 Resumes execution of the inferior program at the location specified by
29779 parameter. @xref{Specify Location}, for a description of the
29780 different forms of @var{location}.
29782 @subsubheading @value{GDBN} Command
29784 The corresponding @value{GDBN} command is @samp{jump}.
29786 @subsubheading Example
29789 -exec-jump foo.c:10
29790 *running,thread-id="all"
29795 @subheading The @code{-exec-next} Command
29798 @subsubheading Synopsis
29801 -exec-next [--reverse]
29804 Resumes execution of the inferior program, stopping when the beginning
29805 of the next source line is reached.
29807 If the @samp{--reverse} option is specified, resumes reverse execution
29808 of the inferior program, stopping at the beginning of the previous
29809 source line. If you issue this command on the first line of a
29810 function, it will take you back to the caller of that function, to the
29811 source line where the function was called.
29814 @subsubheading @value{GDBN} Command
29816 The corresponding @value{GDBN} command is @samp{next}.
29818 @subsubheading Example
29824 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29829 @subheading The @code{-exec-next-instruction} Command
29830 @findex -exec-next-instruction
29832 @subsubheading Synopsis
29835 -exec-next-instruction [--reverse]
29838 Executes one machine instruction. If the instruction is a function
29839 call, continues until the function returns. If the program stops at an
29840 instruction in the middle of a source line, the address will be
29843 If the @samp{--reverse} option is specified, resumes reverse execution
29844 of the inferior program, stopping at the previous instruction. If the
29845 previously executed instruction was a return from another function,
29846 it will continue to execute in reverse until the call to that function
29847 (from the current stack frame) is reached.
29849 @subsubheading @value{GDBN} Command
29851 The corresponding @value{GDBN} command is @samp{nexti}.
29853 @subsubheading Example
29857 -exec-next-instruction
29861 *stopped,reason="end-stepping-range",
29862 addr="0x000100d4",line="5",file="hello.c"
29867 @subheading The @code{-exec-return} Command
29868 @findex -exec-return
29870 @subsubheading Synopsis
29876 Makes current function return immediately. Doesn't execute the inferior.
29877 Displays the new current frame.
29879 @subsubheading @value{GDBN} Command
29881 The corresponding @value{GDBN} command is @samp{return}.
29883 @subsubheading Example
29887 200-break-insert callee4
29888 200^done,bkpt=@{number="1",addr="0x00010734",
29889 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29894 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29895 frame=@{func="callee4",args=[],
29896 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29897 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29903 111^done,frame=@{level="0",func="callee3",
29904 args=[@{name="strarg",
29905 value="0x11940 \"A string argument.\""@}],
29906 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29907 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29912 @subheading The @code{-exec-run} Command
29915 @subsubheading Synopsis
29918 -exec-run [--all | --thread-group N]
29921 Starts execution of the inferior from the beginning. The inferior
29922 executes until either a breakpoint is encountered or the program
29923 exits. In the latter case the output will include an exit code, if
29924 the program has exited exceptionally.
29926 When no option is specified, the current inferior is started. If the
29927 @samp{--thread-group} option is specified, it should refer to a thread
29928 group of type @samp{process}, and that thread group will be started.
29929 If the @samp{--all} option is specified, then all inferiors will be started.
29931 @subsubheading @value{GDBN} Command
29933 The corresponding @value{GDBN} command is @samp{run}.
29935 @subsubheading Examples
29940 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29945 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29946 frame=@{func="main",args=[],file="recursive2.c",
29947 fullname="/home/foo/bar/recursive2.c",line="4"@}
29952 Program exited normally:
29960 *stopped,reason="exited-normally"
29965 Program exited exceptionally:
29973 *stopped,reason="exited",exit-code="01"
29977 Another way the program can terminate is if it receives a signal such as
29978 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29982 *stopped,reason="exited-signalled",signal-name="SIGINT",
29983 signal-meaning="Interrupt"
29987 @c @subheading -exec-signal
29990 @subheading The @code{-exec-step} Command
29993 @subsubheading Synopsis
29996 -exec-step [--reverse]
29999 Resumes execution of the inferior program, stopping when the beginning
30000 of the next source line is reached, if the next source line is not a
30001 function call. If it is, stop at the first instruction of the called
30002 function. If the @samp{--reverse} option is specified, resumes reverse
30003 execution of the inferior program, stopping at the beginning of the
30004 previously executed source line.
30006 @subsubheading @value{GDBN} Command
30008 The corresponding @value{GDBN} command is @samp{step}.
30010 @subsubheading Example
30012 Stepping into a function:
30018 *stopped,reason="end-stepping-range",
30019 frame=@{func="foo",args=[@{name="a",value="10"@},
30020 @{name="b",value="0"@}],file="recursive2.c",
30021 fullname="/home/foo/bar/recursive2.c",line="11"@}
30031 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30036 @subheading The @code{-exec-step-instruction} Command
30037 @findex -exec-step-instruction
30039 @subsubheading Synopsis
30042 -exec-step-instruction [--reverse]
30045 Resumes the inferior which executes one machine instruction. If the
30046 @samp{--reverse} option is specified, resumes reverse execution of the
30047 inferior program, stopping at the previously executed instruction.
30048 The output, once @value{GDBN} has stopped, will vary depending on
30049 whether we have stopped in the middle of a source line or not. In the
30050 former case, the address at which the program stopped will be printed
30053 @subsubheading @value{GDBN} Command
30055 The corresponding @value{GDBN} command is @samp{stepi}.
30057 @subsubheading Example
30061 -exec-step-instruction
30065 *stopped,reason="end-stepping-range",
30066 frame=@{func="foo",args=[],file="try.c",
30067 fullname="/home/foo/bar/try.c",line="10"@}
30069 -exec-step-instruction
30073 *stopped,reason="end-stepping-range",
30074 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30075 fullname="/home/foo/bar/try.c",line="10"@}
30080 @subheading The @code{-exec-until} Command
30081 @findex -exec-until
30083 @subsubheading Synopsis
30086 -exec-until [ @var{location} ]
30089 Executes the inferior until the @var{location} specified in the
30090 argument is reached. If there is no argument, the inferior executes
30091 until a source line greater than the current one is reached. The
30092 reason for stopping in this case will be @samp{location-reached}.
30094 @subsubheading @value{GDBN} Command
30096 The corresponding @value{GDBN} command is @samp{until}.
30098 @subsubheading Example
30102 -exec-until recursive2.c:6
30106 *stopped,reason="location-reached",frame=@{func="main",args=[],
30107 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
30112 @subheading -file-clear
30113 Is this going away????
30116 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30117 @node GDB/MI Stack Manipulation
30118 @section @sc{gdb/mi} Stack Manipulation Commands
30121 @subheading The @code{-stack-info-frame} Command
30122 @findex -stack-info-frame
30124 @subsubheading Synopsis
30130 Get info on the selected frame.
30132 @subsubheading @value{GDBN} Command
30134 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30135 (without arguments).
30137 @subsubheading Example
30142 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30143 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30144 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
30148 @subheading The @code{-stack-info-depth} Command
30149 @findex -stack-info-depth
30151 @subsubheading Synopsis
30154 -stack-info-depth [ @var{max-depth} ]
30157 Return the depth of the stack. If the integer argument @var{max-depth}
30158 is specified, do not count beyond @var{max-depth} frames.
30160 @subsubheading @value{GDBN} Command
30162 There's no equivalent @value{GDBN} command.
30164 @subsubheading Example
30166 For a stack with frame levels 0 through 11:
30173 -stack-info-depth 4
30176 -stack-info-depth 12
30179 -stack-info-depth 11
30182 -stack-info-depth 13
30187 @subheading The @code{-stack-list-arguments} Command
30188 @findex -stack-list-arguments
30190 @subsubheading Synopsis
30193 -stack-list-arguments @var{print-values}
30194 [ @var{low-frame} @var{high-frame} ]
30197 Display a list of the arguments for the frames between @var{low-frame}
30198 and @var{high-frame} (inclusive). If @var{low-frame} and
30199 @var{high-frame} are not provided, list the arguments for the whole
30200 call stack. If the two arguments are equal, show the single frame
30201 at the corresponding level. It is an error if @var{low-frame} is
30202 larger than the actual number of frames. On the other hand,
30203 @var{high-frame} may be larger than the actual number of frames, in
30204 which case only existing frames will be returned.
30206 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30207 the variables; if it is 1 or @code{--all-values}, print also their
30208 values; and if it is 2 or @code{--simple-values}, print the name,
30209 type and value for simple data types, and the name and type for arrays,
30210 structures and unions.
30212 Use of this command to obtain arguments in a single frame is
30213 deprecated in favor of the @samp{-stack-list-variables} command.
30215 @subsubheading @value{GDBN} Command
30217 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30218 @samp{gdb_get_args} command which partially overlaps with the
30219 functionality of @samp{-stack-list-arguments}.
30221 @subsubheading Example
30228 frame=@{level="0",addr="0x00010734",func="callee4",
30229 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30230 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
30231 frame=@{level="1",addr="0x0001076c",func="callee3",
30232 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30233 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
30234 frame=@{level="2",addr="0x0001078c",func="callee2",
30235 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30236 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30237 frame=@{level="3",addr="0x000107b4",func="callee1",
30238 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30239 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30240 frame=@{level="4",addr="0x000107e0",func="main",
30241 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30242 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30244 -stack-list-arguments 0
30247 frame=@{level="0",args=[]@},
30248 frame=@{level="1",args=[name="strarg"]@},
30249 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30250 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30251 frame=@{level="4",args=[]@}]
30253 -stack-list-arguments 1
30256 frame=@{level="0",args=[]@},
30258 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30259 frame=@{level="2",args=[
30260 @{name="intarg",value="2"@},
30261 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30262 @{frame=@{level="3",args=[
30263 @{name="intarg",value="2"@},
30264 @{name="strarg",value="0x11940 \"A string argument.\""@},
30265 @{name="fltarg",value="3.5"@}]@},
30266 frame=@{level="4",args=[]@}]
30268 -stack-list-arguments 0 2 2
30269 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30271 -stack-list-arguments 1 2 2
30272 ^done,stack-args=[frame=@{level="2",
30273 args=[@{name="intarg",value="2"@},
30274 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30278 @c @subheading -stack-list-exception-handlers
30281 @subheading The @code{-stack-list-frames} Command
30282 @findex -stack-list-frames
30284 @subsubheading Synopsis
30287 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
30290 List the frames currently on the stack. For each frame it displays the
30295 The frame number, 0 being the topmost frame, i.e., the innermost function.
30297 The @code{$pc} value for that frame.
30301 File name of the source file where the function lives.
30302 @item @var{fullname}
30303 The full file name of the source file where the function lives.
30305 Line number corresponding to the @code{$pc}.
30307 The shared library where this function is defined. This is only given
30308 if the frame's function is not known.
30311 If invoked without arguments, this command prints a backtrace for the
30312 whole stack. If given two integer arguments, it shows the frames whose
30313 levels are between the two arguments (inclusive). If the two arguments
30314 are equal, it shows the single frame at the corresponding level. It is
30315 an error if @var{low-frame} is larger than the actual number of
30316 frames. On the other hand, @var{high-frame} may be larger than the
30317 actual number of frames, in which case only existing frames will be returned.
30319 @subsubheading @value{GDBN} Command
30321 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30323 @subsubheading Example
30325 Full stack backtrace:
30331 [frame=@{level="0",addr="0x0001076c",func="foo",
30332 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30333 frame=@{level="1",addr="0x000107a4",func="foo",
30334 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30335 frame=@{level="2",addr="0x000107a4",func="foo",
30336 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30337 frame=@{level="3",addr="0x000107a4",func="foo",
30338 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30339 frame=@{level="4",addr="0x000107a4",func="foo",
30340 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30341 frame=@{level="5",addr="0x000107a4",func="foo",
30342 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30343 frame=@{level="6",addr="0x000107a4",func="foo",
30344 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30345 frame=@{level="7",addr="0x000107a4",func="foo",
30346 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30347 frame=@{level="8",addr="0x000107a4",func="foo",
30348 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30349 frame=@{level="9",addr="0x000107a4",func="foo",
30350 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30351 frame=@{level="10",addr="0x000107a4",func="foo",
30352 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30353 frame=@{level="11",addr="0x00010738",func="main",
30354 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30358 Show frames between @var{low_frame} and @var{high_frame}:
30362 -stack-list-frames 3 5
30364 [frame=@{level="3",addr="0x000107a4",func="foo",
30365 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30366 frame=@{level="4",addr="0x000107a4",func="foo",
30367 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30368 frame=@{level="5",addr="0x000107a4",func="foo",
30369 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30373 Show a single frame:
30377 -stack-list-frames 3 3
30379 [frame=@{level="3",addr="0x000107a4",func="foo",
30380 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30385 @subheading The @code{-stack-list-locals} Command
30386 @findex -stack-list-locals
30388 @subsubheading Synopsis
30391 -stack-list-locals @var{print-values}
30394 Display the local variable names for the selected frame. If
30395 @var{print-values} is 0 or @code{--no-values}, print only the names of
30396 the variables; if it is 1 or @code{--all-values}, print also their
30397 values; and if it is 2 or @code{--simple-values}, print the name,
30398 type and value for simple data types, and the name and type for arrays,
30399 structures and unions. In this last case, a frontend can immediately
30400 display the value of simple data types and create variable objects for
30401 other data types when the user wishes to explore their values in
30404 This command is deprecated in favor of the
30405 @samp{-stack-list-variables} command.
30407 @subsubheading @value{GDBN} Command
30409 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30411 @subsubheading Example
30415 -stack-list-locals 0
30416 ^done,locals=[name="A",name="B",name="C"]
30418 -stack-list-locals --all-values
30419 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30420 @{name="C",value="@{1, 2, 3@}"@}]
30421 -stack-list-locals --simple-values
30422 ^done,locals=[@{name="A",type="int",value="1"@},
30423 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30427 @subheading The @code{-stack-list-variables} Command
30428 @findex -stack-list-variables
30430 @subsubheading Synopsis
30433 -stack-list-variables @var{print-values}
30436 Display the names of local variables and function arguments for the selected frame. If
30437 @var{print-values} is 0 or @code{--no-values}, print only the names of
30438 the variables; if it is 1 or @code{--all-values}, print also their
30439 values; and if it is 2 or @code{--simple-values}, print the name,
30440 type and value for simple data types, and the name and type for arrays,
30441 structures and unions.
30443 @subsubheading Example
30447 -stack-list-variables --thread 1 --frame 0 --all-values
30448 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30453 @subheading The @code{-stack-select-frame} Command
30454 @findex -stack-select-frame
30456 @subsubheading Synopsis
30459 -stack-select-frame @var{framenum}
30462 Change the selected frame. Select a different frame @var{framenum} on
30465 This command in deprecated in favor of passing the @samp{--frame}
30466 option to every command.
30468 @subsubheading @value{GDBN} Command
30470 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30471 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30473 @subsubheading Example
30477 -stack-select-frame 2
30482 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30483 @node GDB/MI Variable Objects
30484 @section @sc{gdb/mi} Variable Objects
30488 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30490 For the implementation of a variable debugger window (locals, watched
30491 expressions, etc.), we are proposing the adaptation of the existing code
30492 used by @code{Insight}.
30494 The two main reasons for that are:
30498 It has been proven in practice (it is already on its second generation).
30501 It will shorten development time (needless to say how important it is
30505 The original interface was designed to be used by Tcl code, so it was
30506 slightly changed so it could be used through @sc{gdb/mi}. This section
30507 describes the @sc{gdb/mi} operations that will be available and gives some
30508 hints about their use.
30510 @emph{Note}: In addition to the set of operations described here, we
30511 expect the @sc{gui} implementation of a variable window to require, at
30512 least, the following operations:
30515 @item @code{-gdb-show} @code{output-radix}
30516 @item @code{-stack-list-arguments}
30517 @item @code{-stack-list-locals}
30518 @item @code{-stack-select-frame}
30523 @subheading Introduction to Variable Objects
30525 @cindex variable objects in @sc{gdb/mi}
30527 Variable objects are "object-oriented" MI interface for examining and
30528 changing values of expressions. Unlike some other MI interfaces that
30529 work with expressions, variable objects are specifically designed for
30530 simple and efficient presentation in the frontend. A variable object
30531 is identified by string name. When a variable object is created, the
30532 frontend specifies the expression for that variable object. The
30533 expression can be a simple variable, or it can be an arbitrary complex
30534 expression, and can even involve CPU registers. After creating a
30535 variable object, the frontend can invoke other variable object
30536 operations---for example to obtain or change the value of a variable
30537 object, or to change display format.
30539 Variable objects have hierarchical tree structure. Any variable object
30540 that corresponds to a composite type, such as structure in C, has
30541 a number of child variable objects, for example corresponding to each
30542 element of a structure. A child variable object can itself have
30543 children, recursively. Recursion ends when we reach
30544 leaf variable objects, which always have built-in types. Child variable
30545 objects are created only by explicit request, so if a frontend
30546 is not interested in the children of a particular variable object, no
30547 child will be created.
30549 For a leaf variable object it is possible to obtain its value as a
30550 string, or set the value from a string. String value can be also
30551 obtained for a non-leaf variable object, but it's generally a string
30552 that only indicates the type of the object, and does not list its
30553 contents. Assignment to a non-leaf variable object is not allowed.
30555 A frontend does not need to read the values of all variable objects each time
30556 the program stops. Instead, MI provides an update command that lists all
30557 variable objects whose values has changed since the last update
30558 operation. This considerably reduces the amount of data that must
30559 be transferred to the frontend. As noted above, children variable
30560 objects are created on demand, and only leaf variable objects have a
30561 real value. As result, gdb will read target memory only for leaf
30562 variables that frontend has created.
30564 The automatic update is not always desirable. For example, a frontend
30565 might want to keep a value of some expression for future reference,
30566 and never update it. For another example, fetching memory is
30567 relatively slow for embedded targets, so a frontend might want
30568 to disable automatic update for the variables that are either not
30569 visible on the screen, or ``closed''. This is possible using so
30570 called ``frozen variable objects''. Such variable objects are never
30571 implicitly updated.
30573 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30574 fixed variable object, the expression is parsed when the variable
30575 object is created, including associating identifiers to specific
30576 variables. The meaning of expression never changes. For a floating
30577 variable object the values of variables whose names appear in the
30578 expressions are re-evaluated every time in the context of the current
30579 frame. Consider this example:
30584 struct work_state state;
30591 If a fixed variable object for the @code{state} variable is created in
30592 this function, and we enter the recursive call, the variable
30593 object will report the value of @code{state} in the top-level
30594 @code{do_work} invocation. On the other hand, a floating variable
30595 object will report the value of @code{state} in the current frame.
30597 If an expression specified when creating a fixed variable object
30598 refers to a local variable, the variable object becomes bound to the
30599 thread and frame in which the variable object is created. When such
30600 variable object is updated, @value{GDBN} makes sure that the
30601 thread/frame combination the variable object is bound to still exists,
30602 and re-evaluates the variable object in context of that thread/frame.
30604 The following is the complete set of @sc{gdb/mi} operations defined to
30605 access this functionality:
30607 @multitable @columnfractions .4 .6
30608 @item @strong{Operation}
30609 @tab @strong{Description}
30611 @item @code{-enable-pretty-printing}
30612 @tab enable Python-based pretty-printing
30613 @item @code{-var-create}
30614 @tab create a variable object
30615 @item @code{-var-delete}
30616 @tab delete the variable object and/or its children
30617 @item @code{-var-set-format}
30618 @tab set the display format of this variable
30619 @item @code{-var-show-format}
30620 @tab show the display format of this variable
30621 @item @code{-var-info-num-children}
30622 @tab tells how many children this object has
30623 @item @code{-var-list-children}
30624 @tab return a list of the object's children
30625 @item @code{-var-info-type}
30626 @tab show the type of this variable object
30627 @item @code{-var-info-expression}
30628 @tab print parent-relative expression that this variable object represents
30629 @item @code{-var-info-path-expression}
30630 @tab print full expression that this variable object represents
30631 @item @code{-var-show-attributes}
30632 @tab is this variable editable? does it exist here?
30633 @item @code{-var-evaluate-expression}
30634 @tab get the value of this variable
30635 @item @code{-var-assign}
30636 @tab set the value of this variable
30637 @item @code{-var-update}
30638 @tab update the variable and its children
30639 @item @code{-var-set-frozen}
30640 @tab set frozeness attribute
30641 @item @code{-var-set-update-range}
30642 @tab set range of children to display on update
30645 In the next subsection we describe each operation in detail and suggest
30646 how it can be used.
30648 @subheading Description And Use of Operations on Variable Objects
30650 @subheading The @code{-enable-pretty-printing} Command
30651 @findex -enable-pretty-printing
30654 -enable-pretty-printing
30657 @value{GDBN} allows Python-based visualizers to affect the output of the
30658 MI variable object commands. However, because there was no way to
30659 implement this in a fully backward-compatible way, a front end must
30660 request that this functionality be enabled.
30662 Once enabled, this feature cannot be disabled.
30664 Note that if Python support has not been compiled into @value{GDBN},
30665 this command will still succeed (and do nothing).
30667 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30668 may work differently in future versions of @value{GDBN}.
30670 @subheading The @code{-var-create} Command
30671 @findex -var-create
30673 @subsubheading Synopsis
30676 -var-create @{@var{name} | "-"@}
30677 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30680 This operation creates a variable object, which allows the monitoring of
30681 a variable, the result of an expression, a memory cell or a CPU
30684 The @var{name} parameter is the string by which the object can be
30685 referenced. It must be unique. If @samp{-} is specified, the varobj
30686 system will generate a string ``varNNNNNN'' automatically. It will be
30687 unique provided that one does not specify @var{name} of that format.
30688 The command fails if a duplicate name is found.
30690 The frame under which the expression should be evaluated can be
30691 specified by @var{frame-addr}. A @samp{*} indicates that the current
30692 frame should be used. A @samp{@@} indicates that a floating variable
30693 object must be created.
30695 @var{expression} is any expression valid on the current language set (must not
30696 begin with a @samp{*}), or one of the following:
30700 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30703 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30706 @samp{$@var{regname}} --- a CPU register name
30709 @cindex dynamic varobj
30710 A varobj's contents may be provided by a Python-based pretty-printer. In this
30711 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30712 have slightly different semantics in some cases. If the
30713 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30714 will never create a dynamic varobj. This ensures backward
30715 compatibility for existing clients.
30717 @subsubheading Result
30719 This operation returns attributes of the newly-created varobj. These
30724 The name of the varobj.
30727 The number of children of the varobj. This number is not necessarily
30728 reliable for a dynamic varobj. Instead, you must examine the
30729 @samp{has_more} attribute.
30732 The varobj's scalar value. For a varobj whose type is some sort of
30733 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30734 will not be interesting.
30737 The varobj's type. This is a string representation of the type, as
30738 would be printed by the @value{GDBN} CLI. If @samp{print object}
30739 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30740 @emph{actual} (derived) type of the object is shown rather than the
30741 @emph{declared} one.
30744 If a variable object is bound to a specific thread, then this is the
30745 thread's identifier.
30748 For a dynamic varobj, this indicates whether there appear to be any
30749 children available. For a non-dynamic varobj, this will be 0.
30752 This attribute will be present and have the value @samp{1} if the
30753 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30754 then this attribute will not be present.
30757 A dynamic varobj can supply a display hint to the front end. The
30758 value comes directly from the Python pretty-printer object's
30759 @code{display_hint} method. @xref{Pretty Printing API}.
30762 Typical output will look like this:
30765 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30766 has_more="@var{has_more}"
30770 @subheading The @code{-var-delete} Command
30771 @findex -var-delete
30773 @subsubheading Synopsis
30776 -var-delete [ -c ] @var{name}
30779 Deletes a previously created variable object and all of its children.
30780 With the @samp{-c} option, just deletes the children.
30782 Returns an error if the object @var{name} is not found.
30785 @subheading The @code{-var-set-format} Command
30786 @findex -var-set-format
30788 @subsubheading Synopsis
30791 -var-set-format @var{name} @var{format-spec}
30794 Sets the output format for the value of the object @var{name} to be
30797 @anchor{-var-set-format}
30798 The syntax for the @var{format-spec} is as follows:
30801 @var{format-spec} @expansion{}
30802 @{binary | decimal | hexadecimal | octal | natural@}
30805 The natural format is the default format choosen automatically
30806 based on the variable type (like decimal for an @code{int}, hex
30807 for pointers, etc.).
30809 For a variable with children, the format is set only on the
30810 variable itself, and the children are not affected.
30812 @subheading The @code{-var-show-format} Command
30813 @findex -var-show-format
30815 @subsubheading Synopsis
30818 -var-show-format @var{name}
30821 Returns the format used to display the value of the object @var{name}.
30824 @var{format} @expansion{}
30829 @subheading The @code{-var-info-num-children} Command
30830 @findex -var-info-num-children
30832 @subsubheading Synopsis
30835 -var-info-num-children @var{name}
30838 Returns the number of children of a variable object @var{name}:
30844 Note that this number is not completely reliable for a dynamic varobj.
30845 It will return the current number of children, but more children may
30849 @subheading The @code{-var-list-children} Command
30850 @findex -var-list-children
30852 @subsubheading Synopsis
30855 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30857 @anchor{-var-list-children}
30859 Return a list of the children of the specified variable object and
30860 create variable objects for them, if they do not already exist. With
30861 a single argument or if @var{print-values} has a value of 0 or
30862 @code{--no-values}, print only the names of the variables; if
30863 @var{print-values} is 1 or @code{--all-values}, also print their
30864 values; and if it is 2 or @code{--simple-values} print the name and
30865 value for simple data types and just the name for arrays, structures
30868 @var{from} and @var{to}, if specified, indicate the range of children
30869 to report. If @var{from} or @var{to} is less than zero, the range is
30870 reset and all children will be reported. Otherwise, children starting
30871 at @var{from} (zero-based) and up to and excluding @var{to} will be
30874 If a child range is requested, it will only affect the current call to
30875 @code{-var-list-children}, but not future calls to @code{-var-update}.
30876 For this, you must instead use @code{-var-set-update-range}. The
30877 intent of this approach is to enable a front end to implement any
30878 update approach it likes; for example, scrolling a view may cause the
30879 front end to request more children with @code{-var-list-children}, and
30880 then the front end could call @code{-var-set-update-range} with a
30881 different range to ensure that future updates are restricted to just
30884 For each child the following results are returned:
30889 Name of the variable object created for this child.
30892 The expression to be shown to the user by the front end to designate this child.
30893 For example this may be the name of a structure member.
30895 For a dynamic varobj, this value cannot be used to form an
30896 expression. There is no way to do this at all with a dynamic varobj.
30898 For C/C@t{++} structures there are several pseudo children returned to
30899 designate access qualifiers. For these pseudo children @var{exp} is
30900 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30901 type and value are not present.
30903 A dynamic varobj will not report the access qualifying
30904 pseudo-children, regardless of the language. This information is not
30905 available at all with a dynamic varobj.
30908 Number of children this child has. For a dynamic varobj, this will be
30912 The type of the child. If @samp{print object}
30913 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30914 @emph{actual} (derived) type of the object is shown rather than the
30915 @emph{declared} one.
30918 If values were requested, this is the value.
30921 If this variable object is associated with a thread, this is the thread id.
30922 Otherwise this result is not present.
30925 If the variable object is frozen, this variable will be present with a value of 1.
30928 The result may have its own attributes:
30932 A dynamic varobj can supply a display hint to the front end. The
30933 value comes directly from the Python pretty-printer object's
30934 @code{display_hint} method. @xref{Pretty Printing API}.
30937 This is an integer attribute which is nonzero if there are children
30938 remaining after the end of the selected range.
30941 @subsubheading Example
30945 -var-list-children n
30946 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30947 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30949 -var-list-children --all-values n
30950 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30951 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30955 @subheading The @code{-var-info-type} Command
30956 @findex -var-info-type
30958 @subsubheading Synopsis
30961 -var-info-type @var{name}
30964 Returns the type of the specified variable @var{name}. The type is
30965 returned as a string in the same format as it is output by the
30969 type=@var{typename}
30973 @subheading The @code{-var-info-expression} Command
30974 @findex -var-info-expression
30976 @subsubheading Synopsis
30979 -var-info-expression @var{name}
30982 Returns a string that is suitable for presenting this
30983 variable object in user interface. The string is generally
30984 not valid expression in the current language, and cannot be evaluated.
30986 For example, if @code{a} is an array, and variable object
30987 @code{A} was created for @code{a}, then we'll get this output:
30990 (gdb) -var-info-expression A.1
30991 ^done,lang="C",exp="1"
30995 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30997 Note that the output of the @code{-var-list-children} command also
30998 includes those expressions, so the @code{-var-info-expression} command
31001 @subheading The @code{-var-info-path-expression} Command
31002 @findex -var-info-path-expression
31004 @subsubheading Synopsis
31007 -var-info-path-expression @var{name}
31010 Returns an expression that can be evaluated in the current
31011 context and will yield the same value that a variable object has.
31012 Compare this with the @code{-var-info-expression} command, which
31013 result can be used only for UI presentation. Typical use of
31014 the @code{-var-info-path-expression} command is creating a
31015 watchpoint from a variable object.
31017 This command is currently not valid for children of a dynamic varobj,
31018 and will give an error when invoked on one.
31020 For example, suppose @code{C} is a C@t{++} class, derived from class
31021 @code{Base}, and that the @code{Base} class has a member called
31022 @code{m_size}. Assume a variable @code{c} is has the type of
31023 @code{C} and a variable object @code{C} was created for variable
31024 @code{c}. Then, we'll get this output:
31026 (gdb) -var-info-path-expression C.Base.public.m_size
31027 ^done,path_expr=((Base)c).m_size)
31030 @subheading The @code{-var-show-attributes} Command
31031 @findex -var-show-attributes
31033 @subsubheading Synopsis
31036 -var-show-attributes @var{name}
31039 List attributes of the specified variable object @var{name}:
31042 status=@var{attr} [ ( ,@var{attr} )* ]
31046 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31048 @subheading The @code{-var-evaluate-expression} Command
31049 @findex -var-evaluate-expression
31051 @subsubheading Synopsis
31054 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31057 Evaluates the expression that is represented by the specified variable
31058 object and returns its value as a string. The format of the string
31059 can be specified with the @samp{-f} option. The possible values of
31060 this option are the same as for @code{-var-set-format}
31061 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31062 the current display format will be used. The current display format
31063 can be changed using the @code{-var-set-format} command.
31069 Note that one must invoke @code{-var-list-children} for a variable
31070 before the value of a child variable can be evaluated.
31072 @subheading The @code{-var-assign} Command
31073 @findex -var-assign
31075 @subsubheading Synopsis
31078 -var-assign @var{name} @var{expression}
31081 Assigns the value of @var{expression} to the variable object specified
31082 by @var{name}. The object must be @samp{editable}. If the variable's
31083 value is altered by the assign, the variable will show up in any
31084 subsequent @code{-var-update} list.
31086 @subsubheading Example
31094 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31098 @subheading The @code{-var-update} Command
31099 @findex -var-update
31101 @subsubheading Synopsis
31104 -var-update [@var{print-values}] @{@var{name} | "*"@}
31107 Reevaluate the expressions corresponding to the variable object
31108 @var{name} and all its direct and indirect children, and return the
31109 list of variable objects whose values have changed; @var{name} must
31110 be a root variable object. Here, ``changed'' means that the result of
31111 @code{-var-evaluate-expression} before and after the
31112 @code{-var-update} is different. If @samp{*} is used as the variable
31113 object names, all existing variable objects are updated, except
31114 for frozen ones (@pxref{-var-set-frozen}). The option
31115 @var{print-values} determines whether both names and values, or just
31116 names are printed. The possible values of this option are the same
31117 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31118 recommended to use the @samp{--all-values} option, to reduce the
31119 number of MI commands needed on each program stop.
31121 With the @samp{*} parameter, if a variable object is bound to a
31122 currently running thread, it will not be updated, without any
31125 If @code{-var-set-update-range} was previously used on a varobj, then
31126 only the selected range of children will be reported.
31128 @code{-var-update} reports all the changed varobjs in a tuple named
31131 Each item in the change list is itself a tuple holding:
31135 The name of the varobj.
31138 If values were requested for this update, then this field will be
31139 present and will hold the value of the varobj.
31142 @anchor{-var-update}
31143 This field is a string which may take one of three values:
31147 The variable object's current value is valid.
31150 The variable object does not currently hold a valid value but it may
31151 hold one in the future if its associated expression comes back into
31155 The variable object no longer holds a valid value.
31156 This can occur when the executable file being debugged has changed,
31157 either through recompilation or by using the @value{GDBN} @code{file}
31158 command. The front end should normally choose to delete these variable
31162 In the future new values may be added to this list so the front should
31163 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31166 This is only present if the varobj is still valid. If the type
31167 changed, then this will be the string @samp{true}; otherwise it will
31170 When a varobj's type changes, its children are also likely to have
31171 become incorrect. Therefore, the varobj's children are automatically
31172 deleted when this attribute is @samp{true}. Also, the varobj's update
31173 range, when set using the @code{-var-set-update-range} command, is
31177 If the varobj's type changed, then this field will be present and will
31180 @item new_num_children
31181 For a dynamic varobj, if the number of children changed, or if the
31182 type changed, this will be the new number of children.
31184 The @samp{numchild} field in other varobj responses is generally not
31185 valid for a dynamic varobj -- it will show the number of children that
31186 @value{GDBN} knows about, but because dynamic varobjs lazily
31187 instantiate their children, this will not reflect the number of
31188 children which may be available.
31190 The @samp{new_num_children} attribute only reports changes to the
31191 number of children known by @value{GDBN}. This is the only way to
31192 detect whether an update has removed children (which necessarily can
31193 only happen at the end of the update range).
31196 The display hint, if any.
31199 This is an integer value, which will be 1 if there are more children
31200 available outside the varobj's update range.
31203 This attribute will be present and have the value @samp{1} if the
31204 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31205 then this attribute will not be present.
31208 If new children were added to a dynamic varobj within the selected
31209 update range (as set by @code{-var-set-update-range}), then they will
31210 be listed in this attribute.
31213 @subsubheading Example
31220 -var-update --all-values var1
31221 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31222 type_changed="false"@}]
31226 @subheading The @code{-var-set-frozen} Command
31227 @findex -var-set-frozen
31228 @anchor{-var-set-frozen}
31230 @subsubheading Synopsis
31233 -var-set-frozen @var{name} @var{flag}
31236 Set the frozenness flag on the variable object @var{name}. The
31237 @var{flag} parameter should be either @samp{1} to make the variable
31238 frozen or @samp{0} to make it unfrozen. If a variable object is
31239 frozen, then neither itself, nor any of its children, are
31240 implicitly updated by @code{-var-update} of
31241 a parent variable or by @code{-var-update *}. Only
31242 @code{-var-update} of the variable itself will update its value and
31243 values of its children. After a variable object is unfrozen, it is
31244 implicitly updated by all subsequent @code{-var-update} operations.
31245 Unfreezing a variable does not update it, only subsequent
31246 @code{-var-update} does.
31248 @subsubheading Example
31252 -var-set-frozen V 1
31257 @subheading The @code{-var-set-update-range} command
31258 @findex -var-set-update-range
31259 @anchor{-var-set-update-range}
31261 @subsubheading Synopsis
31264 -var-set-update-range @var{name} @var{from} @var{to}
31267 Set the range of children to be returned by future invocations of
31268 @code{-var-update}.
31270 @var{from} and @var{to} indicate the range of children to report. If
31271 @var{from} or @var{to} is less than zero, the range is reset and all
31272 children will be reported. Otherwise, children starting at @var{from}
31273 (zero-based) and up to and excluding @var{to} will be reported.
31275 @subsubheading Example
31279 -var-set-update-range V 1 2
31283 @subheading The @code{-var-set-visualizer} command
31284 @findex -var-set-visualizer
31285 @anchor{-var-set-visualizer}
31287 @subsubheading Synopsis
31290 -var-set-visualizer @var{name} @var{visualizer}
31293 Set a visualizer for the variable object @var{name}.
31295 @var{visualizer} is the visualizer to use. The special value
31296 @samp{None} means to disable any visualizer in use.
31298 If not @samp{None}, @var{visualizer} must be a Python expression.
31299 This expression must evaluate to a callable object which accepts a
31300 single argument. @value{GDBN} will call this object with the value of
31301 the varobj @var{name} as an argument (this is done so that the same
31302 Python pretty-printing code can be used for both the CLI and MI).
31303 When called, this object must return an object which conforms to the
31304 pretty-printing interface (@pxref{Pretty Printing API}).
31306 The pre-defined function @code{gdb.default_visualizer} may be used to
31307 select a visualizer by following the built-in process
31308 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31309 a varobj is created, and so ordinarily is not needed.
31311 This feature is only available if Python support is enabled. The MI
31312 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
31313 can be used to check this.
31315 @subsubheading Example
31317 Resetting the visualizer:
31321 -var-set-visualizer V None
31325 Reselecting the default (type-based) visualizer:
31329 -var-set-visualizer V gdb.default_visualizer
31333 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31334 can be used to instantiate this class for a varobj:
31338 -var-set-visualizer V "lambda val: SomeClass()"
31342 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31343 @node GDB/MI Data Manipulation
31344 @section @sc{gdb/mi} Data Manipulation
31346 @cindex data manipulation, in @sc{gdb/mi}
31347 @cindex @sc{gdb/mi}, data manipulation
31348 This section describes the @sc{gdb/mi} commands that manipulate data:
31349 examine memory and registers, evaluate expressions, etc.
31351 @c REMOVED FROM THE INTERFACE.
31352 @c @subheading -data-assign
31353 @c Change the value of a program variable. Plenty of side effects.
31354 @c @subsubheading GDB Command
31356 @c @subsubheading Example
31359 @subheading The @code{-data-disassemble} Command
31360 @findex -data-disassemble
31362 @subsubheading Synopsis
31366 [ -s @var{start-addr} -e @var{end-addr} ]
31367 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31375 @item @var{start-addr}
31376 is the beginning address (or @code{$pc})
31377 @item @var{end-addr}
31379 @item @var{filename}
31380 is the name of the file to disassemble
31381 @item @var{linenum}
31382 is the line number to disassemble around
31384 is the number of disassembly lines to be produced. If it is -1,
31385 the whole function will be disassembled, in case no @var{end-addr} is
31386 specified. If @var{end-addr} is specified as a non-zero value, and
31387 @var{lines} is lower than the number of disassembly lines between
31388 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31389 displayed; if @var{lines} is higher than the number of lines between
31390 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31393 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31394 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31395 mixed source and disassembly with raw opcodes).
31398 @subsubheading Result
31400 The result of the @code{-data-disassemble} command will be a list named
31401 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31402 used with the @code{-data-disassemble} command.
31404 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31409 The address at which this instruction was disassembled.
31412 The name of the function this instruction is within.
31415 The decimal offset in bytes from the start of @samp{func-name}.
31418 The text disassembly for this @samp{address}.
31421 This field is only present for mode 2. This contains the raw opcode
31422 bytes for the @samp{inst} field.
31426 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31427 @samp{src_and_asm_line}, each of which has the following fields:
31431 The line number within @samp{file}.
31434 The file name from the compilation unit. This might be an absolute
31435 file name or a relative file name depending on the compile command
31439 Absolute file name of @samp{file}. It is converted to a canonical form
31440 using the source file search path
31441 (@pxref{Source Path, ,Specifying Source Directories})
31442 and after resolving all the symbolic links.
31444 If the source file is not found this field will contain the path as
31445 present in the debug information.
31447 @item line_asm_insn
31448 This is a list of tuples containing the disassembly for @samp{line} in
31449 @samp{file}. The fields of each tuple are the same as for
31450 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31451 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31456 Note that whatever included in the @samp{inst} field, is not
31457 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31460 @subsubheading @value{GDBN} Command
31462 The corresponding @value{GDBN} command is @samp{disassemble}.
31464 @subsubheading Example
31466 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31470 -data-disassemble -s $pc -e "$pc + 20" -- 0
31473 @{address="0x000107c0",func-name="main",offset="4",
31474 inst="mov 2, %o0"@},
31475 @{address="0x000107c4",func-name="main",offset="8",
31476 inst="sethi %hi(0x11800), %o2"@},
31477 @{address="0x000107c8",func-name="main",offset="12",
31478 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31479 @{address="0x000107cc",func-name="main",offset="16",
31480 inst="sethi %hi(0x11800), %o2"@},
31481 @{address="0x000107d0",func-name="main",offset="20",
31482 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31486 Disassemble the whole @code{main} function. Line 32 is part of
31490 -data-disassemble -f basics.c -l 32 -- 0
31492 @{address="0x000107bc",func-name="main",offset="0",
31493 inst="save %sp, -112, %sp"@},
31494 @{address="0x000107c0",func-name="main",offset="4",
31495 inst="mov 2, %o0"@},
31496 @{address="0x000107c4",func-name="main",offset="8",
31497 inst="sethi %hi(0x11800), %o2"@},
31499 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31500 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31504 Disassemble 3 instructions from the start of @code{main}:
31508 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31510 @{address="0x000107bc",func-name="main",offset="0",
31511 inst="save %sp, -112, %sp"@},
31512 @{address="0x000107c0",func-name="main",offset="4",
31513 inst="mov 2, %o0"@},
31514 @{address="0x000107c4",func-name="main",offset="8",
31515 inst="sethi %hi(0x11800), %o2"@}]
31519 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31523 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31525 src_and_asm_line=@{line="31",
31526 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31527 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31528 line_asm_insn=[@{address="0x000107bc",
31529 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31530 src_and_asm_line=@{line="32",
31531 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31532 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31533 line_asm_insn=[@{address="0x000107c0",
31534 func-name="main",offset="4",inst="mov 2, %o0"@},
31535 @{address="0x000107c4",func-name="main",offset="8",
31536 inst="sethi %hi(0x11800), %o2"@}]@}]
31541 @subheading The @code{-data-evaluate-expression} Command
31542 @findex -data-evaluate-expression
31544 @subsubheading Synopsis
31547 -data-evaluate-expression @var{expr}
31550 Evaluate @var{expr} as an expression. The expression could contain an
31551 inferior function call. The function call will execute synchronously.
31552 If the expression contains spaces, it must be enclosed in double quotes.
31554 @subsubheading @value{GDBN} Command
31556 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31557 @samp{call}. In @code{gdbtk} only, there's a corresponding
31558 @samp{gdb_eval} command.
31560 @subsubheading Example
31562 In the following example, the numbers that precede the commands are the
31563 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31564 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31568 211-data-evaluate-expression A
31571 311-data-evaluate-expression &A
31572 311^done,value="0xefffeb7c"
31574 411-data-evaluate-expression A+3
31577 511-data-evaluate-expression "A + 3"
31583 @subheading The @code{-data-list-changed-registers} Command
31584 @findex -data-list-changed-registers
31586 @subsubheading Synopsis
31589 -data-list-changed-registers
31592 Display a list of the registers that have changed.
31594 @subsubheading @value{GDBN} Command
31596 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31597 has the corresponding command @samp{gdb_changed_register_list}.
31599 @subsubheading Example
31601 On a PPC MBX board:
31609 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31610 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31613 -data-list-changed-registers
31614 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31615 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31616 "24","25","26","27","28","30","31","64","65","66","67","69"]
31621 @subheading The @code{-data-list-register-names} Command
31622 @findex -data-list-register-names
31624 @subsubheading Synopsis
31627 -data-list-register-names [ ( @var{regno} )+ ]
31630 Show a list of register names for the current target. If no arguments
31631 are given, it shows a list of the names of all the registers. If
31632 integer numbers are given as arguments, it will print a list of the
31633 names of the registers corresponding to the arguments. To ensure
31634 consistency between a register name and its number, the output list may
31635 include empty register names.
31637 @subsubheading @value{GDBN} Command
31639 @value{GDBN} does not have a command which corresponds to
31640 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31641 corresponding command @samp{gdb_regnames}.
31643 @subsubheading Example
31645 For the PPC MBX board:
31648 -data-list-register-names
31649 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31650 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31651 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31652 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31653 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31654 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31655 "", "pc","ps","cr","lr","ctr","xer"]
31657 -data-list-register-names 1 2 3
31658 ^done,register-names=["r1","r2","r3"]
31662 @subheading The @code{-data-list-register-values} Command
31663 @findex -data-list-register-values
31665 @subsubheading Synopsis
31668 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31671 Display the registers' contents. @var{fmt} is the format according to
31672 which the registers' contents are to be returned, followed by an optional
31673 list of numbers specifying the registers to display. A missing list of
31674 numbers indicates that the contents of all the registers must be returned.
31676 Allowed formats for @var{fmt} are:
31693 @subsubheading @value{GDBN} Command
31695 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31696 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31698 @subsubheading Example
31700 For a PPC MBX board (note: line breaks are for readability only, they
31701 don't appear in the actual output):
31705 -data-list-register-values r 64 65
31706 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31707 @{number="65",value="0x00029002"@}]
31709 -data-list-register-values x
31710 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31711 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31712 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31713 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31714 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31715 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31716 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31717 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31718 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31719 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31720 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31721 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31722 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31723 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31724 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31725 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31726 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31727 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31728 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31729 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31730 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31731 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31732 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31733 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31734 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31735 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31736 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31737 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31738 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31739 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31740 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31741 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31742 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31743 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31744 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31745 @{number="69",value="0x20002b03"@}]
31750 @subheading The @code{-data-read-memory} Command
31751 @findex -data-read-memory
31753 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31755 @subsubheading Synopsis
31758 -data-read-memory [ -o @var{byte-offset} ]
31759 @var{address} @var{word-format} @var{word-size}
31760 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31767 @item @var{address}
31768 An expression specifying the address of the first memory word to be
31769 read. Complex expressions containing embedded white space should be
31770 quoted using the C convention.
31772 @item @var{word-format}
31773 The format to be used to print the memory words. The notation is the
31774 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31777 @item @var{word-size}
31778 The size of each memory word in bytes.
31780 @item @var{nr-rows}
31781 The number of rows in the output table.
31783 @item @var{nr-cols}
31784 The number of columns in the output table.
31787 If present, indicates that each row should include an @sc{ascii} dump. The
31788 value of @var{aschar} is used as a padding character when a byte is not a
31789 member of the printable @sc{ascii} character set (printable @sc{ascii}
31790 characters are those whose code is between 32 and 126, inclusively).
31792 @item @var{byte-offset}
31793 An offset to add to the @var{address} before fetching memory.
31796 This command displays memory contents as a table of @var{nr-rows} by
31797 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31798 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31799 (returned as @samp{total-bytes}). Should less than the requested number
31800 of bytes be returned by the target, the missing words are identified
31801 using @samp{N/A}. The number of bytes read from the target is returned
31802 in @samp{nr-bytes} and the starting address used to read memory in
31805 The address of the next/previous row or page is available in
31806 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31809 @subsubheading @value{GDBN} Command
31811 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31812 @samp{gdb_get_mem} memory read command.
31814 @subsubheading Example
31816 Read six bytes of memory starting at @code{bytes+6} but then offset by
31817 @code{-6} bytes. Format as three rows of two columns. One byte per
31818 word. Display each word in hex.
31822 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31823 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31824 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31825 prev-page="0x0000138a",memory=[
31826 @{addr="0x00001390",data=["0x00","0x01"]@},
31827 @{addr="0x00001392",data=["0x02","0x03"]@},
31828 @{addr="0x00001394",data=["0x04","0x05"]@}]
31832 Read two bytes of memory starting at address @code{shorts + 64} and
31833 display as a single word formatted in decimal.
31837 5-data-read-memory shorts+64 d 2 1 1
31838 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31839 next-row="0x00001512",prev-row="0x0000150e",
31840 next-page="0x00001512",prev-page="0x0000150e",memory=[
31841 @{addr="0x00001510",data=["128"]@}]
31845 Read thirty two bytes of memory starting at @code{bytes+16} and format
31846 as eight rows of four columns. Include a string encoding with @samp{x}
31847 used as the non-printable character.
31851 4-data-read-memory bytes+16 x 1 8 4 x
31852 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31853 next-row="0x000013c0",prev-row="0x0000139c",
31854 next-page="0x000013c0",prev-page="0x00001380",memory=[
31855 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31856 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31857 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31858 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31859 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31860 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31861 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31862 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31866 @subheading The @code{-data-read-memory-bytes} Command
31867 @findex -data-read-memory-bytes
31869 @subsubheading Synopsis
31872 -data-read-memory-bytes [ -o @var{byte-offset} ]
31873 @var{address} @var{count}
31880 @item @var{address}
31881 An expression specifying the address of the first memory word to be
31882 read. Complex expressions containing embedded white space should be
31883 quoted using the C convention.
31886 The number of bytes to read. This should be an integer literal.
31888 @item @var{byte-offset}
31889 The offsets in bytes relative to @var{address} at which to start
31890 reading. This should be an integer literal. This option is provided
31891 so that a frontend is not required to first evaluate address and then
31892 perform address arithmetics itself.
31896 This command attempts to read all accessible memory regions in the
31897 specified range. First, all regions marked as unreadable in the memory
31898 map (if one is defined) will be skipped. @xref{Memory Region
31899 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31900 regions. For each one, if reading full region results in an errors,
31901 @value{GDBN} will try to read a subset of the region.
31903 In general, every single byte in the region may be readable or not,
31904 and the only way to read every readable byte is to try a read at
31905 every address, which is not practical. Therefore, @value{GDBN} will
31906 attempt to read all accessible bytes at either beginning or the end
31907 of the region, using a binary division scheme. This heuristic works
31908 well for reading accross a memory map boundary. Note that if a region
31909 has a readable range that is neither at the beginning or the end,
31910 @value{GDBN} will not read it.
31912 The result record (@pxref{GDB/MI Result Records}) that is output of
31913 the command includes a field named @samp{memory} whose content is a
31914 list of tuples. Each tuple represent a successfully read memory block
31915 and has the following fields:
31919 The start address of the memory block, as hexadecimal literal.
31922 The end address of the memory block, as hexadecimal literal.
31925 The offset of the memory block, as hexadecimal literal, relative to
31926 the start address passed to @code{-data-read-memory-bytes}.
31929 The contents of the memory block, in hex.
31935 @subsubheading @value{GDBN} Command
31937 The corresponding @value{GDBN} command is @samp{x}.
31939 @subsubheading Example
31943 -data-read-memory-bytes &a 10
31944 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31946 contents="01000000020000000300"@}]
31951 @subheading The @code{-data-write-memory-bytes} Command
31952 @findex -data-write-memory-bytes
31954 @subsubheading Synopsis
31957 -data-write-memory-bytes @var{address} @var{contents}
31958 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31965 @item @var{address}
31966 An expression specifying the address of the first memory word to be
31967 read. Complex expressions containing embedded white space should be
31968 quoted using the C convention.
31970 @item @var{contents}
31971 The hex-encoded bytes to write.
31974 Optional argument indicating the number of bytes to be written. If @var{count}
31975 is greater than @var{contents}' length, @value{GDBN} will repeatedly
31976 write @var{contents} until it fills @var{count} bytes.
31980 @subsubheading @value{GDBN} Command
31982 There's no corresponding @value{GDBN} command.
31984 @subsubheading Example
31988 -data-write-memory-bytes &a "aabbccdd"
31995 -data-write-memory-bytes &a "aabbccdd" 16e
32000 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32001 @node GDB/MI Tracepoint Commands
32002 @section @sc{gdb/mi} Tracepoint Commands
32004 The commands defined in this section implement MI support for
32005 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32007 @subheading The @code{-trace-find} Command
32008 @findex -trace-find
32010 @subsubheading Synopsis
32013 -trace-find @var{mode} [@var{parameters}@dots{}]
32016 Find a trace frame using criteria defined by @var{mode} and
32017 @var{parameters}. The following table lists permissible
32018 modes and their parameters. For details of operation, see @ref{tfind}.
32023 No parameters are required. Stops examining trace frames.
32026 An integer is required as parameter. Selects tracepoint frame with
32029 @item tracepoint-number
32030 An integer is required as parameter. Finds next
32031 trace frame that corresponds to tracepoint with the specified number.
32034 An address is required as parameter. Finds
32035 next trace frame that corresponds to any tracepoint at the specified
32038 @item pc-inside-range
32039 Two addresses are required as parameters. Finds next trace
32040 frame that corresponds to a tracepoint at an address inside the
32041 specified range. Both bounds are considered to be inside the range.
32043 @item pc-outside-range
32044 Two addresses are required as parameters. Finds
32045 next trace frame that corresponds to a tracepoint at an address outside
32046 the specified range. Both bounds are considered to be inside the range.
32049 Line specification is required as parameter. @xref{Specify Location}.
32050 Finds next trace frame that corresponds to a tracepoint at
32051 the specified location.
32055 If @samp{none} was passed as @var{mode}, the response does not
32056 have fields. Otherwise, the response may have the following fields:
32060 This field has either @samp{0} or @samp{1} as the value, depending
32061 on whether a matching tracepoint was found.
32064 The index of the found traceframe. This field is present iff
32065 the @samp{found} field has value of @samp{1}.
32068 The index of the found tracepoint. This field is present iff
32069 the @samp{found} field has value of @samp{1}.
32072 The information about the frame corresponding to the found trace
32073 frame. This field is present only if a trace frame was found.
32074 @xref{GDB/MI Frame Information}, for description of this field.
32078 @subsubheading @value{GDBN} Command
32080 The corresponding @value{GDBN} command is @samp{tfind}.
32082 @subheading -trace-define-variable
32083 @findex -trace-define-variable
32085 @subsubheading Synopsis
32088 -trace-define-variable @var{name} [ @var{value} ]
32091 Create trace variable @var{name} if it does not exist. If
32092 @var{value} is specified, sets the initial value of the specified
32093 trace variable to that value. Note that the @var{name} should start
32094 with the @samp{$} character.
32096 @subsubheading @value{GDBN} Command
32098 The corresponding @value{GDBN} command is @samp{tvariable}.
32100 @subheading -trace-list-variables
32101 @findex -trace-list-variables
32103 @subsubheading Synopsis
32106 -trace-list-variables
32109 Return a table of all defined trace variables. Each element of the
32110 table has the following fields:
32114 The name of the trace variable. This field is always present.
32117 The initial value. This is a 64-bit signed integer. This
32118 field is always present.
32121 The value the trace variable has at the moment. This is a 64-bit
32122 signed integer. This field is absent iff current value is
32123 not defined, for example if the trace was never run, or is
32128 @subsubheading @value{GDBN} Command
32130 The corresponding @value{GDBN} command is @samp{tvariables}.
32132 @subsubheading Example
32136 -trace-list-variables
32137 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32138 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32139 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32140 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32141 body=[variable=@{name="$trace_timestamp",initial="0"@}
32142 variable=@{name="$foo",initial="10",current="15"@}]@}
32146 @subheading -trace-save
32147 @findex -trace-save
32149 @subsubheading Synopsis
32152 -trace-save [-r ] @var{filename}
32155 Saves the collected trace data to @var{filename}. Without the
32156 @samp{-r} option, the data is downloaded from the target and saved
32157 in a local file. With the @samp{-r} option the target is asked
32158 to perform the save.
32160 @subsubheading @value{GDBN} Command
32162 The corresponding @value{GDBN} command is @samp{tsave}.
32165 @subheading -trace-start
32166 @findex -trace-start
32168 @subsubheading Synopsis
32174 Starts a tracing experiments. The result of this command does not
32177 @subsubheading @value{GDBN} Command
32179 The corresponding @value{GDBN} command is @samp{tstart}.
32181 @subheading -trace-status
32182 @findex -trace-status
32184 @subsubheading Synopsis
32190 Obtains the status of a tracing experiment. The result may include
32191 the following fields:
32196 May have a value of either @samp{0}, when no tracing operations are
32197 supported, @samp{1}, when all tracing operations are supported, or
32198 @samp{file} when examining trace file. In the latter case, examining
32199 of trace frame is possible but new tracing experiement cannot be
32200 started. This field is always present.
32203 May have a value of either @samp{0} or @samp{1} depending on whether
32204 tracing experiement is in progress on target. This field is present
32205 if @samp{supported} field is not @samp{0}.
32208 Report the reason why the tracing was stopped last time. This field
32209 may be absent iff tracing was never stopped on target yet. The
32210 value of @samp{request} means the tracing was stopped as result of
32211 the @code{-trace-stop} command. The value of @samp{overflow} means
32212 the tracing buffer is full. The value of @samp{disconnection} means
32213 tracing was automatically stopped when @value{GDBN} has disconnected.
32214 The value of @samp{passcount} means tracing was stopped when a
32215 tracepoint was passed a maximal number of times for that tracepoint.
32216 This field is present if @samp{supported} field is not @samp{0}.
32218 @item stopping-tracepoint
32219 The number of tracepoint whose passcount as exceeded. This field is
32220 present iff the @samp{stop-reason} field has the value of
32224 @itemx frames-created
32225 The @samp{frames} field is a count of the total number of trace frames
32226 in the trace buffer, while @samp{frames-created} is the total created
32227 during the run, including ones that were discarded, such as when a
32228 circular trace buffer filled up. Both fields are optional.
32232 These fields tell the current size of the tracing buffer and the
32233 remaining space. These fields are optional.
32236 The value of the circular trace buffer flag. @code{1} means that the
32237 trace buffer is circular and old trace frames will be discarded if
32238 necessary to make room, @code{0} means that the trace buffer is linear
32242 The value of the disconnected tracing flag. @code{1} means that
32243 tracing will continue after @value{GDBN} disconnects, @code{0} means
32244 that the trace run will stop.
32247 The filename of the trace file being examined. This field is
32248 optional, and only present when examining a trace file.
32252 @subsubheading @value{GDBN} Command
32254 The corresponding @value{GDBN} command is @samp{tstatus}.
32256 @subheading -trace-stop
32257 @findex -trace-stop
32259 @subsubheading Synopsis
32265 Stops a tracing experiment. The result of this command has the same
32266 fields as @code{-trace-status}, except that the @samp{supported} and
32267 @samp{running} fields are not output.
32269 @subsubheading @value{GDBN} Command
32271 The corresponding @value{GDBN} command is @samp{tstop}.
32274 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32275 @node GDB/MI Symbol Query
32276 @section @sc{gdb/mi} Symbol Query Commands
32280 @subheading The @code{-symbol-info-address} Command
32281 @findex -symbol-info-address
32283 @subsubheading Synopsis
32286 -symbol-info-address @var{symbol}
32289 Describe where @var{symbol} is stored.
32291 @subsubheading @value{GDBN} Command
32293 The corresponding @value{GDBN} command is @samp{info address}.
32295 @subsubheading Example
32299 @subheading The @code{-symbol-info-file} Command
32300 @findex -symbol-info-file
32302 @subsubheading Synopsis
32308 Show the file for the symbol.
32310 @subsubheading @value{GDBN} Command
32312 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32313 @samp{gdb_find_file}.
32315 @subsubheading Example
32319 @subheading The @code{-symbol-info-function} Command
32320 @findex -symbol-info-function
32322 @subsubheading Synopsis
32325 -symbol-info-function
32328 Show which function the symbol lives in.
32330 @subsubheading @value{GDBN} Command
32332 @samp{gdb_get_function} in @code{gdbtk}.
32334 @subsubheading Example
32338 @subheading The @code{-symbol-info-line} Command
32339 @findex -symbol-info-line
32341 @subsubheading Synopsis
32347 Show the core addresses of the code for a source line.
32349 @subsubheading @value{GDBN} Command
32351 The corresponding @value{GDBN} command is @samp{info line}.
32352 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32354 @subsubheading Example
32358 @subheading The @code{-symbol-info-symbol} Command
32359 @findex -symbol-info-symbol
32361 @subsubheading Synopsis
32364 -symbol-info-symbol @var{addr}
32367 Describe what symbol is at location @var{addr}.
32369 @subsubheading @value{GDBN} Command
32371 The corresponding @value{GDBN} command is @samp{info symbol}.
32373 @subsubheading Example
32377 @subheading The @code{-symbol-list-functions} Command
32378 @findex -symbol-list-functions
32380 @subsubheading Synopsis
32383 -symbol-list-functions
32386 List the functions in the executable.
32388 @subsubheading @value{GDBN} Command
32390 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32391 @samp{gdb_search} in @code{gdbtk}.
32393 @subsubheading Example
32398 @subheading The @code{-symbol-list-lines} Command
32399 @findex -symbol-list-lines
32401 @subsubheading Synopsis
32404 -symbol-list-lines @var{filename}
32407 Print the list of lines that contain code and their associated program
32408 addresses for the given source filename. The entries are sorted in
32409 ascending PC order.
32411 @subsubheading @value{GDBN} Command
32413 There is no corresponding @value{GDBN} command.
32415 @subsubheading Example
32418 -symbol-list-lines basics.c
32419 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32425 @subheading The @code{-symbol-list-types} Command
32426 @findex -symbol-list-types
32428 @subsubheading Synopsis
32434 List all the type names.
32436 @subsubheading @value{GDBN} Command
32438 The corresponding commands are @samp{info types} in @value{GDBN},
32439 @samp{gdb_search} in @code{gdbtk}.
32441 @subsubheading Example
32445 @subheading The @code{-symbol-list-variables} Command
32446 @findex -symbol-list-variables
32448 @subsubheading Synopsis
32451 -symbol-list-variables
32454 List all the global and static variable names.
32456 @subsubheading @value{GDBN} Command
32458 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32460 @subsubheading Example
32464 @subheading The @code{-symbol-locate} Command
32465 @findex -symbol-locate
32467 @subsubheading Synopsis
32473 @subsubheading @value{GDBN} Command
32475 @samp{gdb_loc} in @code{gdbtk}.
32477 @subsubheading Example
32481 @subheading The @code{-symbol-type} Command
32482 @findex -symbol-type
32484 @subsubheading Synopsis
32487 -symbol-type @var{variable}
32490 Show type of @var{variable}.
32492 @subsubheading @value{GDBN} Command
32494 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32495 @samp{gdb_obj_variable}.
32497 @subsubheading Example
32502 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32503 @node GDB/MI File Commands
32504 @section @sc{gdb/mi} File Commands
32506 This section describes the GDB/MI commands to specify executable file names
32507 and to read in and obtain symbol table information.
32509 @subheading The @code{-file-exec-and-symbols} Command
32510 @findex -file-exec-and-symbols
32512 @subsubheading Synopsis
32515 -file-exec-and-symbols @var{file}
32518 Specify the executable file to be debugged. This file is the one from
32519 which the symbol table is also read. If no file is specified, the
32520 command clears the executable and symbol information. If breakpoints
32521 are set when using this command with no arguments, @value{GDBN} will produce
32522 error messages. Otherwise, no output is produced, except a completion
32525 @subsubheading @value{GDBN} Command
32527 The corresponding @value{GDBN} command is @samp{file}.
32529 @subsubheading Example
32533 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32539 @subheading The @code{-file-exec-file} Command
32540 @findex -file-exec-file
32542 @subsubheading Synopsis
32545 -file-exec-file @var{file}
32548 Specify the executable file to be debugged. Unlike
32549 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32550 from this file. If used without argument, @value{GDBN} clears the information
32551 about the executable file. No output is produced, except a completion
32554 @subsubheading @value{GDBN} Command
32556 The corresponding @value{GDBN} command is @samp{exec-file}.
32558 @subsubheading Example
32562 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32569 @subheading The @code{-file-list-exec-sections} Command
32570 @findex -file-list-exec-sections
32572 @subsubheading Synopsis
32575 -file-list-exec-sections
32578 List the sections of the current executable file.
32580 @subsubheading @value{GDBN} Command
32582 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32583 information as this command. @code{gdbtk} has a corresponding command
32584 @samp{gdb_load_info}.
32586 @subsubheading Example
32591 @subheading The @code{-file-list-exec-source-file} Command
32592 @findex -file-list-exec-source-file
32594 @subsubheading Synopsis
32597 -file-list-exec-source-file
32600 List the line number, the current source file, and the absolute path
32601 to the current source file for the current executable. The macro
32602 information field has a value of @samp{1} or @samp{0} depending on
32603 whether or not the file includes preprocessor macro information.
32605 @subsubheading @value{GDBN} Command
32607 The @value{GDBN} equivalent is @samp{info source}
32609 @subsubheading Example
32613 123-file-list-exec-source-file
32614 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32619 @subheading The @code{-file-list-exec-source-files} Command
32620 @findex -file-list-exec-source-files
32622 @subsubheading Synopsis
32625 -file-list-exec-source-files
32628 List the source files for the current executable.
32630 It will always output both the filename and fullname (absolute file
32631 name) of a source file.
32633 @subsubheading @value{GDBN} Command
32635 The @value{GDBN} equivalent is @samp{info sources}.
32636 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32638 @subsubheading Example
32641 -file-list-exec-source-files
32643 @{file=foo.c,fullname=/home/foo.c@},
32644 @{file=/home/bar.c,fullname=/home/bar.c@},
32645 @{file=gdb_could_not_find_fullpath.c@}]
32650 @subheading The @code{-file-list-shared-libraries} Command
32651 @findex -file-list-shared-libraries
32653 @subsubheading Synopsis
32656 -file-list-shared-libraries
32659 List the shared libraries in the program.
32661 @subsubheading @value{GDBN} Command
32663 The corresponding @value{GDBN} command is @samp{info shared}.
32665 @subsubheading Example
32669 @subheading The @code{-file-list-symbol-files} Command
32670 @findex -file-list-symbol-files
32672 @subsubheading Synopsis
32675 -file-list-symbol-files
32680 @subsubheading @value{GDBN} Command
32682 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32684 @subsubheading Example
32689 @subheading The @code{-file-symbol-file} Command
32690 @findex -file-symbol-file
32692 @subsubheading Synopsis
32695 -file-symbol-file @var{file}
32698 Read symbol table info from the specified @var{file} argument. When
32699 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32700 produced, except for a completion notification.
32702 @subsubheading @value{GDBN} Command
32704 The corresponding @value{GDBN} command is @samp{symbol-file}.
32706 @subsubheading Example
32710 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32716 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32717 @node GDB/MI Memory Overlay Commands
32718 @section @sc{gdb/mi} Memory Overlay Commands
32720 The memory overlay commands are not implemented.
32722 @c @subheading -overlay-auto
32724 @c @subheading -overlay-list-mapping-state
32726 @c @subheading -overlay-list-overlays
32728 @c @subheading -overlay-map
32730 @c @subheading -overlay-off
32732 @c @subheading -overlay-on
32734 @c @subheading -overlay-unmap
32736 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32737 @node GDB/MI Signal Handling Commands
32738 @section @sc{gdb/mi} Signal Handling Commands
32740 Signal handling commands are not implemented.
32742 @c @subheading -signal-handle
32744 @c @subheading -signal-list-handle-actions
32746 @c @subheading -signal-list-signal-types
32750 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32751 @node GDB/MI Target Manipulation
32752 @section @sc{gdb/mi} Target Manipulation Commands
32755 @subheading The @code{-target-attach} Command
32756 @findex -target-attach
32758 @subsubheading Synopsis
32761 -target-attach @var{pid} | @var{gid} | @var{file}
32764 Attach to a process @var{pid} or a file @var{file} outside of
32765 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32766 group, the id previously returned by
32767 @samp{-list-thread-groups --available} must be used.
32769 @subsubheading @value{GDBN} Command
32771 The corresponding @value{GDBN} command is @samp{attach}.
32773 @subsubheading Example
32777 =thread-created,id="1"
32778 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32784 @subheading The @code{-target-compare-sections} Command
32785 @findex -target-compare-sections
32787 @subsubheading Synopsis
32790 -target-compare-sections [ @var{section} ]
32793 Compare data of section @var{section} on target to the exec file.
32794 Without the argument, all sections are compared.
32796 @subsubheading @value{GDBN} Command
32798 The @value{GDBN} equivalent is @samp{compare-sections}.
32800 @subsubheading Example
32805 @subheading The @code{-target-detach} Command
32806 @findex -target-detach
32808 @subsubheading Synopsis
32811 -target-detach [ @var{pid} | @var{gid} ]
32814 Detach from the remote target which normally resumes its execution.
32815 If either @var{pid} or @var{gid} is specified, detaches from either
32816 the specified process, or specified thread group. There's no output.
32818 @subsubheading @value{GDBN} Command
32820 The corresponding @value{GDBN} command is @samp{detach}.
32822 @subsubheading Example
32832 @subheading The @code{-target-disconnect} Command
32833 @findex -target-disconnect
32835 @subsubheading Synopsis
32841 Disconnect from the remote target. There's no output and the target is
32842 generally not resumed.
32844 @subsubheading @value{GDBN} Command
32846 The corresponding @value{GDBN} command is @samp{disconnect}.
32848 @subsubheading Example
32858 @subheading The @code{-target-download} Command
32859 @findex -target-download
32861 @subsubheading Synopsis
32867 Loads the executable onto the remote target.
32868 It prints out an update message every half second, which includes the fields:
32872 The name of the section.
32874 The size of what has been sent so far for that section.
32876 The size of the section.
32878 The total size of what was sent so far (the current and the previous sections).
32880 The size of the overall executable to download.
32884 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32885 @sc{gdb/mi} Output Syntax}).
32887 In addition, it prints the name and size of the sections, as they are
32888 downloaded. These messages include the following fields:
32892 The name of the section.
32894 The size of the section.
32896 The size of the overall executable to download.
32900 At the end, a summary is printed.
32902 @subsubheading @value{GDBN} Command
32904 The corresponding @value{GDBN} command is @samp{load}.
32906 @subsubheading Example
32908 Note: each status message appears on a single line. Here the messages
32909 have been broken down so that they can fit onto a page.
32914 +download,@{section=".text",section-size="6668",total-size="9880"@}
32915 +download,@{section=".text",section-sent="512",section-size="6668",
32916 total-sent="512",total-size="9880"@}
32917 +download,@{section=".text",section-sent="1024",section-size="6668",
32918 total-sent="1024",total-size="9880"@}
32919 +download,@{section=".text",section-sent="1536",section-size="6668",
32920 total-sent="1536",total-size="9880"@}
32921 +download,@{section=".text",section-sent="2048",section-size="6668",
32922 total-sent="2048",total-size="9880"@}
32923 +download,@{section=".text",section-sent="2560",section-size="6668",
32924 total-sent="2560",total-size="9880"@}
32925 +download,@{section=".text",section-sent="3072",section-size="6668",
32926 total-sent="3072",total-size="9880"@}
32927 +download,@{section=".text",section-sent="3584",section-size="6668",
32928 total-sent="3584",total-size="9880"@}
32929 +download,@{section=".text",section-sent="4096",section-size="6668",
32930 total-sent="4096",total-size="9880"@}
32931 +download,@{section=".text",section-sent="4608",section-size="6668",
32932 total-sent="4608",total-size="9880"@}
32933 +download,@{section=".text",section-sent="5120",section-size="6668",
32934 total-sent="5120",total-size="9880"@}
32935 +download,@{section=".text",section-sent="5632",section-size="6668",
32936 total-sent="5632",total-size="9880"@}
32937 +download,@{section=".text",section-sent="6144",section-size="6668",
32938 total-sent="6144",total-size="9880"@}
32939 +download,@{section=".text",section-sent="6656",section-size="6668",
32940 total-sent="6656",total-size="9880"@}
32941 +download,@{section=".init",section-size="28",total-size="9880"@}
32942 +download,@{section=".fini",section-size="28",total-size="9880"@}
32943 +download,@{section=".data",section-size="3156",total-size="9880"@}
32944 +download,@{section=".data",section-sent="512",section-size="3156",
32945 total-sent="7236",total-size="9880"@}
32946 +download,@{section=".data",section-sent="1024",section-size="3156",
32947 total-sent="7748",total-size="9880"@}
32948 +download,@{section=".data",section-sent="1536",section-size="3156",
32949 total-sent="8260",total-size="9880"@}
32950 +download,@{section=".data",section-sent="2048",section-size="3156",
32951 total-sent="8772",total-size="9880"@}
32952 +download,@{section=".data",section-sent="2560",section-size="3156",
32953 total-sent="9284",total-size="9880"@}
32954 +download,@{section=".data",section-sent="3072",section-size="3156",
32955 total-sent="9796",total-size="9880"@}
32956 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32963 @subheading The @code{-target-exec-status} Command
32964 @findex -target-exec-status
32966 @subsubheading Synopsis
32969 -target-exec-status
32972 Provide information on the state of the target (whether it is running or
32973 not, for instance).
32975 @subsubheading @value{GDBN} Command
32977 There's no equivalent @value{GDBN} command.
32979 @subsubheading Example
32983 @subheading The @code{-target-list-available-targets} Command
32984 @findex -target-list-available-targets
32986 @subsubheading Synopsis
32989 -target-list-available-targets
32992 List the possible targets to connect to.
32994 @subsubheading @value{GDBN} Command
32996 The corresponding @value{GDBN} command is @samp{help target}.
32998 @subsubheading Example
33002 @subheading The @code{-target-list-current-targets} Command
33003 @findex -target-list-current-targets
33005 @subsubheading Synopsis
33008 -target-list-current-targets
33011 Describe the current target.
33013 @subsubheading @value{GDBN} Command
33015 The corresponding information is printed by @samp{info file} (among
33018 @subsubheading Example
33022 @subheading The @code{-target-list-parameters} Command
33023 @findex -target-list-parameters
33025 @subsubheading Synopsis
33028 -target-list-parameters
33034 @subsubheading @value{GDBN} Command
33038 @subsubheading Example
33042 @subheading The @code{-target-select} Command
33043 @findex -target-select
33045 @subsubheading Synopsis
33048 -target-select @var{type} @var{parameters @dots{}}
33051 Connect @value{GDBN} to the remote target. This command takes two args:
33055 The type of target, for instance @samp{remote}, etc.
33056 @item @var{parameters}
33057 Device names, host names and the like. @xref{Target Commands, ,
33058 Commands for Managing Targets}, for more details.
33061 The output is a connection notification, followed by the address at
33062 which the target program is, in the following form:
33065 ^connected,addr="@var{address}",func="@var{function name}",
33066 args=[@var{arg list}]
33069 @subsubheading @value{GDBN} Command
33071 The corresponding @value{GDBN} command is @samp{target}.
33073 @subsubheading Example
33077 -target-select remote /dev/ttya
33078 ^connected,addr="0xfe00a300",func="??",args=[]
33082 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33083 @node GDB/MI File Transfer Commands
33084 @section @sc{gdb/mi} File Transfer Commands
33087 @subheading The @code{-target-file-put} Command
33088 @findex -target-file-put
33090 @subsubheading Synopsis
33093 -target-file-put @var{hostfile} @var{targetfile}
33096 Copy file @var{hostfile} from the host system (the machine running
33097 @value{GDBN}) to @var{targetfile} on the target system.
33099 @subsubheading @value{GDBN} Command
33101 The corresponding @value{GDBN} command is @samp{remote put}.
33103 @subsubheading Example
33107 -target-file-put localfile remotefile
33113 @subheading The @code{-target-file-get} Command
33114 @findex -target-file-get
33116 @subsubheading Synopsis
33119 -target-file-get @var{targetfile} @var{hostfile}
33122 Copy file @var{targetfile} from the target system to @var{hostfile}
33123 on the host system.
33125 @subsubheading @value{GDBN} Command
33127 The corresponding @value{GDBN} command is @samp{remote get}.
33129 @subsubheading Example
33133 -target-file-get remotefile localfile
33139 @subheading The @code{-target-file-delete} Command
33140 @findex -target-file-delete
33142 @subsubheading Synopsis
33145 -target-file-delete @var{targetfile}
33148 Delete @var{targetfile} from the target system.
33150 @subsubheading @value{GDBN} Command
33152 The corresponding @value{GDBN} command is @samp{remote delete}.
33154 @subsubheading Example
33158 -target-file-delete remotefile
33164 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33165 @node GDB/MI Miscellaneous Commands
33166 @section Miscellaneous @sc{gdb/mi} Commands
33168 @c @subheading -gdb-complete
33170 @subheading The @code{-gdb-exit} Command
33173 @subsubheading Synopsis
33179 Exit @value{GDBN} immediately.
33181 @subsubheading @value{GDBN} Command
33183 Approximately corresponds to @samp{quit}.
33185 @subsubheading Example
33195 @subheading The @code{-exec-abort} Command
33196 @findex -exec-abort
33198 @subsubheading Synopsis
33204 Kill the inferior running program.
33206 @subsubheading @value{GDBN} Command
33208 The corresponding @value{GDBN} command is @samp{kill}.
33210 @subsubheading Example
33215 @subheading The @code{-gdb-set} Command
33218 @subsubheading Synopsis
33224 Set an internal @value{GDBN} variable.
33225 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33227 @subsubheading @value{GDBN} Command
33229 The corresponding @value{GDBN} command is @samp{set}.
33231 @subsubheading Example
33241 @subheading The @code{-gdb-show} Command
33244 @subsubheading Synopsis
33250 Show the current value of a @value{GDBN} variable.
33252 @subsubheading @value{GDBN} Command
33254 The corresponding @value{GDBN} command is @samp{show}.
33256 @subsubheading Example
33265 @c @subheading -gdb-source
33268 @subheading The @code{-gdb-version} Command
33269 @findex -gdb-version
33271 @subsubheading Synopsis
33277 Show version information for @value{GDBN}. Used mostly in testing.
33279 @subsubheading @value{GDBN} Command
33281 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33282 default shows this information when you start an interactive session.
33284 @subsubheading Example
33286 @c This example modifies the actual output from GDB to avoid overfull
33292 ~Copyright 2000 Free Software Foundation, Inc.
33293 ~GDB is free software, covered by the GNU General Public License, and
33294 ~you are welcome to change it and/or distribute copies of it under
33295 ~ certain conditions.
33296 ~Type "show copying" to see the conditions.
33297 ~There is absolutely no warranty for GDB. Type "show warranty" for
33299 ~This GDB was configured as
33300 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33305 @subheading The @code{-list-features} Command
33306 @findex -list-features
33308 Returns a list of particular features of the MI protocol that
33309 this version of gdb implements. A feature can be a command,
33310 or a new field in an output of some command, or even an
33311 important bugfix. While a frontend can sometimes detect presence
33312 of a feature at runtime, it is easier to perform detection at debugger
33315 The command returns a list of strings, with each string naming an
33316 available feature. Each returned string is just a name, it does not
33317 have any internal structure. The list of possible feature names
33323 (gdb) -list-features
33324 ^done,result=["feature1","feature2"]
33327 The current list of features is:
33330 @item frozen-varobjs
33331 Indicates support for the @code{-var-set-frozen} command, as well
33332 as possible presense of the @code{frozen} field in the output
33333 of @code{-varobj-create}.
33334 @item pending-breakpoints
33335 Indicates support for the @option{-f} option to the @code{-break-insert}
33338 Indicates Python scripting support, Python-based
33339 pretty-printing commands, and possible presence of the
33340 @samp{display_hint} field in the output of @code{-var-list-children}
33342 Indicates support for the @code{-thread-info} command.
33343 @item data-read-memory-bytes
33344 Indicates support for the @code{-data-read-memory-bytes} and the
33345 @code{-data-write-memory-bytes} commands.
33346 @item breakpoint-notifications
33347 Indicates that changes to breakpoints and breakpoints created via the
33348 CLI will be announced via async records.
33349 @item ada-task-info
33350 Indicates support for the @code{-ada-task-info} command.
33353 @subheading The @code{-list-target-features} Command
33354 @findex -list-target-features
33356 Returns a list of particular features that are supported by the
33357 target. Those features affect the permitted MI commands, but
33358 unlike the features reported by the @code{-list-features} command, the
33359 features depend on which target GDB is using at the moment. Whenever
33360 a target can change, due to commands such as @code{-target-select},
33361 @code{-target-attach} or @code{-exec-run}, the list of target features
33362 may change, and the frontend should obtain it again.
33366 (gdb) -list-features
33367 ^done,result=["async"]
33370 The current list of features is:
33374 Indicates that the target is capable of asynchronous command
33375 execution, which means that @value{GDBN} will accept further commands
33376 while the target is running.
33379 Indicates that the target is capable of reverse execution.
33380 @xref{Reverse Execution}, for more information.
33384 @subheading The @code{-list-thread-groups} Command
33385 @findex -list-thread-groups
33387 @subheading Synopsis
33390 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33393 Lists thread groups (@pxref{Thread groups}). When a single thread
33394 group is passed as the argument, lists the children of that group.
33395 When several thread group are passed, lists information about those
33396 thread groups. Without any parameters, lists information about all
33397 top-level thread groups.
33399 Normally, thread groups that are being debugged are reported.
33400 With the @samp{--available} option, @value{GDBN} reports thread groups
33401 available on the target.
33403 The output of this command may have either a @samp{threads} result or
33404 a @samp{groups} result. The @samp{thread} result has a list of tuples
33405 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33406 Information}). The @samp{groups} result has a list of tuples as value,
33407 each tuple describing a thread group. If top-level groups are
33408 requested (that is, no parameter is passed), or when several groups
33409 are passed, the output always has a @samp{groups} result. The format
33410 of the @samp{group} result is described below.
33412 To reduce the number of roundtrips it's possible to list thread groups
33413 together with their children, by passing the @samp{--recurse} option
33414 and the recursion depth. Presently, only recursion depth of 1 is
33415 permitted. If this option is present, then every reported thread group
33416 will also include its children, either as @samp{group} or
33417 @samp{threads} field.
33419 In general, any combination of option and parameters is permitted, with
33420 the following caveats:
33424 When a single thread group is passed, the output will typically
33425 be the @samp{threads} result. Because threads may not contain
33426 anything, the @samp{recurse} option will be ignored.
33429 When the @samp{--available} option is passed, limited information may
33430 be available. In particular, the list of threads of a process might
33431 be inaccessible. Further, specifying specific thread groups might
33432 not give any performance advantage over listing all thread groups.
33433 The frontend should assume that @samp{-list-thread-groups --available}
33434 is always an expensive operation and cache the results.
33438 The @samp{groups} result is a list of tuples, where each tuple may
33439 have the following fields:
33443 Identifier of the thread group. This field is always present.
33444 The identifier is an opaque string; frontends should not try to
33445 convert it to an integer, even though it might look like one.
33448 The type of the thread group. At present, only @samp{process} is a
33452 The target-specific process identifier. This field is only present
33453 for thread groups of type @samp{process} and only if the process exists.
33456 The number of children this thread group has. This field may be
33457 absent for an available thread group.
33460 This field has a list of tuples as value, each tuple describing a
33461 thread. It may be present if the @samp{--recurse} option is
33462 specified, and it's actually possible to obtain the threads.
33465 This field is a list of integers, each identifying a core that one
33466 thread of the group is running on. This field may be absent if
33467 such information is not available.
33470 The name of the executable file that corresponds to this thread group.
33471 The field is only present for thread groups of type @samp{process},
33472 and only if there is a corresponding executable file.
33476 @subheading Example
33480 -list-thread-groups
33481 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33482 -list-thread-groups 17
33483 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33484 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33485 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33486 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33487 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33488 -list-thread-groups --available
33489 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33490 -list-thread-groups --available --recurse 1
33491 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33492 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33493 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33494 -list-thread-groups --available --recurse 1 17 18
33495 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33496 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33497 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33500 @subheading The @code{-info-os} Command
33503 @subsubheading Synopsis
33506 -info-os [ @var{type} ]
33509 If no argument is supplied, the command returns a table of available
33510 operating-system-specific information types. If one of these types is
33511 supplied as an argument @var{type}, then the command returns a table
33512 of data of that type.
33514 The types of information available depend on the target operating
33517 @subsubheading @value{GDBN} Command
33519 The corresponding @value{GDBN} command is @samp{info os}.
33521 @subsubheading Example
33523 When run on a @sc{gnu}/Linux system, the output will look something
33529 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33530 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33531 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33532 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33533 body=[item=@{col0="processes",col1="Listing of all processes",
33534 col2="Processes"@},
33535 item=@{col0="procgroups",col1="Listing of all process groups",
33536 col2="Process groups"@},
33537 item=@{col0="threads",col1="Listing of all threads",
33539 item=@{col0="files",col1="Listing of all file descriptors",
33540 col2="File descriptors"@},
33541 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33543 item=@{col0="shm",col1="Listing of all shared-memory regions",
33544 col2="Shared-memory regions"@},
33545 item=@{col0="semaphores",col1="Listing of all semaphores",
33546 col2="Semaphores"@},
33547 item=@{col0="msg",col1="Listing of all message queues",
33548 col2="Message queues"@},
33549 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33550 col2="Kernel modules"@}]@}
33553 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33554 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33555 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33556 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33557 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33558 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33559 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33560 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33562 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33563 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33567 (Note that the MI output here includes a @code{"Title"} column that
33568 does not appear in command-line @code{info os}; this column is useful
33569 for MI clients that want to enumerate the types of data, such as in a
33570 popup menu, but is needless clutter on the command line, and
33571 @code{info os} omits it.)
33573 @subheading The @code{-add-inferior} Command
33574 @findex -add-inferior
33576 @subheading Synopsis
33582 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33583 inferior is not associated with any executable. Such association may
33584 be established with the @samp{-file-exec-and-symbols} command
33585 (@pxref{GDB/MI File Commands}). The command response has a single
33586 field, @samp{thread-group}, whose value is the identifier of the
33587 thread group corresponding to the new inferior.
33589 @subheading Example
33594 ^done,thread-group="i3"
33597 @subheading The @code{-interpreter-exec} Command
33598 @findex -interpreter-exec
33600 @subheading Synopsis
33603 -interpreter-exec @var{interpreter} @var{command}
33605 @anchor{-interpreter-exec}
33607 Execute the specified @var{command} in the given @var{interpreter}.
33609 @subheading @value{GDBN} Command
33611 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33613 @subheading Example
33617 -interpreter-exec console "break main"
33618 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33619 &"During symbol reading, bad structure-type format.\n"
33620 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33625 @subheading The @code{-inferior-tty-set} Command
33626 @findex -inferior-tty-set
33628 @subheading Synopsis
33631 -inferior-tty-set /dev/pts/1
33634 Set terminal for future runs of the program being debugged.
33636 @subheading @value{GDBN} Command
33638 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33640 @subheading Example
33644 -inferior-tty-set /dev/pts/1
33649 @subheading The @code{-inferior-tty-show} Command
33650 @findex -inferior-tty-show
33652 @subheading Synopsis
33658 Show terminal for future runs of program being debugged.
33660 @subheading @value{GDBN} Command
33662 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33664 @subheading Example
33668 -inferior-tty-set /dev/pts/1
33672 ^done,inferior_tty_terminal="/dev/pts/1"
33676 @subheading The @code{-enable-timings} Command
33677 @findex -enable-timings
33679 @subheading Synopsis
33682 -enable-timings [yes | no]
33685 Toggle the printing of the wallclock, user and system times for an MI
33686 command as a field in its output. This command is to help frontend
33687 developers optimize the performance of their code. No argument is
33688 equivalent to @samp{yes}.
33690 @subheading @value{GDBN} Command
33694 @subheading Example
33702 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33703 addr="0x080484ed",func="main",file="myprog.c",
33704 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33706 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33714 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33715 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33716 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33717 fullname="/home/nickrob/myprog.c",line="73"@}
33722 @chapter @value{GDBN} Annotations
33724 This chapter describes annotations in @value{GDBN}. Annotations were
33725 designed to interface @value{GDBN} to graphical user interfaces or other
33726 similar programs which want to interact with @value{GDBN} at a
33727 relatively high level.
33729 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33733 This is Edition @value{EDITION}, @value{DATE}.
33737 * Annotations Overview:: What annotations are; the general syntax.
33738 * Server Prefix:: Issuing a command without affecting user state.
33739 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33740 * Errors:: Annotations for error messages.
33741 * Invalidation:: Some annotations describe things now invalid.
33742 * Annotations for Running::
33743 Whether the program is running, how it stopped, etc.
33744 * Source Annotations:: Annotations describing source code.
33747 @node Annotations Overview
33748 @section What is an Annotation?
33749 @cindex annotations
33751 Annotations start with a newline character, two @samp{control-z}
33752 characters, and the name of the annotation. If there is no additional
33753 information associated with this annotation, the name of the annotation
33754 is followed immediately by a newline. If there is additional
33755 information, the name of the annotation is followed by a space, the
33756 additional information, and a newline. The additional information
33757 cannot contain newline characters.
33759 Any output not beginning with a newline and two @samp{control-z}
33760 characters denotes literal output from @value{GDBN}. Currently there is
33761 no need for @value{GDBN} to output a newline followed by two
33762 @samp{control-z} characters, but if there was such a need, the
33763 annotations could be extended with an @samp{escape} annotation which
33764 means those three characters as output.
33766 The annotation @var{level}, which is specified using the
33767 @option{--annotate} command line option (@pxref{Mode Options}), controls
33768 how much information @value{GDBN} prints together with its prompt,
33769 values of expressions, source lines, and other types of output. Level 0
33770 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33771 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33772 for programs that control @value{GDBN}, and level 2 annotations have
33773 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33774 Interface, annotate, GDB's Obsolete Annotations}).
33777 @kindex set annotate
33778 @item set annotate @var{level}
33779 The @value{GDBN} command @code{set annotate} sets the level of
33780 annotations to the specified @var{level}.
33782 @item show annotate
33783 @kindex show annotate
33784 Show the current annotation level.
33787 This chapter describes level 3 annotations.
33789 A simple example of starting up @value{GDBN} with annotations is:
33792 $ @kbd{gdb --annotate=3}
33794 Copyright 2003 Free Software Foundation, Inc.
33795 GDB is free software, covered by the GNU General Public License,
33796 and you are welcome to change it and/or distribute copies of it
33797 under certain conditions.
33798 Type "show copying" to see the conditions.
33799 There is absolutely no warranty for GDB. Type "show warranty"
33801 This GDB was configured as "i386-pc-linux-gnu"
33812 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33813 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33814 denotes a @samp{control-z} character) are annotations; the rest is
33815 output from @value{GDBN}.
33817 @node Server Prefix
33818 @section The Server Prefix
33819 @cindex server prefix
33821 If you prefix a command with @samp{server } then it will not affect
33822 the command history, nor will it affect @value{GDBN}'s notion of which
33823 command to repeat if @key{RET} is pressed on a line by itself. This
33824 means that commands can be run behind a user's back by a front-end in
33825 a transparent manner.
33827 The @code{server } prefix does not affect the recording of values into
33828 the value history; to print a value without recording it into the
33829 value history, use the @code{output} command instead of the
33830 @code{print} command.
33832 Using this prefix also disables confirmation requests
33833 (@pxref{confirmation requests}).
33836 @section Annotation for @value{GDBN} Input
33838 @cindex annotations for prompts
33839 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33840 to know when to send output, when the output from a given command is
33843 Different kinds of input each have a different @dfn{input type}. Each
33844 input type has three annotations: a @code{pre-} annotation, which
33845 denotes the beginning of any prompt which is being output, a plain
33846 annotation, which denotes the end of the prompt, and then a @code{post-}
33847 annotation which denotes the end of any echo which may (or may not) be
33848 associated with the input. For example, the @code{prompt} input type
33849 features the following annotations:
33857 The input types are
33860 @findex pre-prompt annotation
33861 @findex prompt annotation
33862 @findex post-prompt annotation
33864 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33866 @findex pre-commands annotation
33867 @findex commands annotation
33868 @findex post-commands annotation
33870 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33871 command. The annotations are repeated for each command which is input.
33873 @findex pre-overload-choice annotation
33874 @findex overload-choice annotation
33875 @findex post-overload-choice annotation
33876 @item overload-choice
33877 When @value{GDBN} wants the user to select between various overloaded functions.
33879 @findex pre-query annotation
33880 @findex query annotation
33881 @findex post-query annotation
33883 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33885 @findex pre-prompt-for-continue annotation
33886 @findex prompt-for-continue annotation
33887 @findex post-prompt-for-continue annotation
33888 @item prompt-for-continue
33889 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33890 expect this to work well; instead use @code{set height 0} to disable
33891 prompting. This is because the counting of lines is buggy in the
33892 presence of annotations.
33897 @cindex annotations for errors, warnings and interrupts
33899 @findex quit annotation
33904 This annotation occurs right before @value{GDBN} responds to an interrupt.
33906 @findex error annotation
33911 This annotation occurs right before @value{GDBN} responds to an error.
33913 Quit and error annotations indicate that any annotations which @value{GDBN} was
33914 in the middle of may end abruptly. For example, if a
33915 @code{value-history-begin} annotation is followed by a @code{error}, one
33916 cannot expect to receive the matching @code{value-history-end}. One
33917 cannot expect not to receive it either, however; an error annotation
33918 does not necessarily mean that @value{GDBN} is immediately returning all the way
33921 @findex error-begin annotation
33922 A quit or error annotation may be preceded by
33928 Any output between that and the quit or error annotation is the error
33931 Warning messages are not yet annotated.
33932 @c If we want to change that, need to fix warning(), type_error(),
33933 @c range_error(), and possibly other places.
33936 @section Invalidation Notices
33938 @cindex annotations for invalidation messages
33939 The following annotations say that certain pieces of state may have
33943 @findex frames-invalid annotation
33944 @item ^Z^Zframes-invalid
33946 The frames (for example, output from the @code{backtrace} command) may
33949 @findex breakpoints-invalid annotation
33950 @item ^Z^Zbreakpoints-invalid
33952 The breakpoints may have changed. For example, the user just added or
33953 deleted a breakpoint.
33956 @node Annotations for Running
33957 @section Running the Program
33958 @cindex annotations for running programs
33960 @findex starting annotation
33961 @findex stopping annotation
33962 When the program starts executing due to a @value{GDBN} command such as
33963 @code{step} or @code{continue},
33969 is output. When the program stops,
33975 is output. Before the @code{stopped} annotation, a variety of
33976 annotations describe how the program stopped.
33979 @findex exited annotation
33980 @item ^Z^Zexited @var{exit-status}
33981 The program exited, and @var{exit-status} is the exit status (zero for
33982 successful exit, otherwise nonzero).
33984 @findex signalled annotation
33985 @findex signal-name annotation
33986 @findex signal-name-end annotation
33987 @findex signal-string annotation
33988 @findex signal-string-end annotation
33989 @item ^Z^Zsignalled
33990 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33991 annotation continues:
33997 ^Z^Zsignal-name-end
34001 ^Z^Zsignal-string-end
34006 where @var{name} is the name of the signal, such as @code{SIGILL} or
34007 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34008 as @code{Illegal Instruction} or @code{Segmentation fault}.
34009 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34010 user's benefit and have no particular format.
34012 @findex signal annotation
34014 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34015 just saying that the program received the signal, not that it was
34016 terminated with it.
34018 @findex breakpoint annotation
34019 @item ^Z^Zbreakpoint @var{number}
34020 The program hit breakpoint number @var{number}.
34022 @findex watchpoint annotation
34023 @item ^Z^Zwatchpoint @var{number}
34024 The program hit watchpoint number @var{number}.
34027 @node Source Annotations
34028 @section Displaying Source
34029 @cindex annotations for source display
34031 @findex source annotation
34032 The following annotation is used instead of displaying source code:
34035 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34038 where @var{filename} is an absolute file name indicating which source
34039 file, @var{line} is the line number within that file (where 1 is the
34040 first line in the file), @var{character} is the character position
34041 within the file (where 0 is the first character in the file) (for most
34042 debug formats this will necessarily point to the beginning of a line),
34043 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34044 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34045 @var{addr} is the address in the target program associated with the
34046 source which is being displayed. @var{addr} is in the form @samp{0x}
34047 followed by one or more lowercase hex digits (note that this does not
34048 depend on the language).
34050 @node JIT Interface
34051 @chapter JIT Compilation Interface
34052 @cindex just-in-time compilation
34053 @cindex JIT compilation interface
34055 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34056 interface. A JIT compiler is a program or library that generates native
34057 executable code at runtime and executes it, usually in order to achieve good
34058 performance while maintaining platform independence.
34060 Programs that use JIT compilation are normally difficult to debug because
34061 portions of their code are generated at runtime, instead of being loaded from
34062 object files, which is where @value{GDBN} normally finds the program's symbols
34063 and debug information. In order to debug programs that use JIT compilation,
34064 @value{GDBN} has an interface that allows the program to register in-memory
34065 symbol files with @value{GDBN} at runtime.
34067 If you are using @value{GDBN} to debug a program that uses this interface, then
34068 it should work transparently so long as you have not stripped the binary. If
34069 you are developing a JIT compiler, then the interface is documented in the rest
34070 of this chapter. At this time, the only known client of this interface is the
34073 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34074 JIT compiler communicates with @value{GDBN} by writing data into a global
34075 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34076 attaches, it reads a linked list of symbol files from the global variable to
34077 find existing code, and puts a breakpoint in the function so that it can find
34078 out about additional code.
34081 * Declarations:: Relevant C struct declarations
34082 * Registering Code:: Steps to register code
34083 * Unregistering Code:: Steps to unregister code
34084 * Custom Debug Info:: Emit debug information in a custom format
34088 @section JIT Declarations
34090 These are the relevant struct declarations that a C program should include to
34091 implement the interface:
34101 struct jit_code_entry
34103 struct jit_code_entry *next_entry;
34104 struct jit_code_entry *prev_entry;
34105 const char *symfile_addr;
34106 uint64_t symfile_size;
34109 struct jit_descriptor
34112 /* This type should be jit_actions_t, but we use uint32_t
34113 to be explicit about the bitwidth. */
34114 uint32_t action_flag;
34115 struct jit_code_entry *relevant_entry;
34116 struct jit_code_entry *first_entry;
34119 /* GDB puts a breakpoint in this function. */
34120 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34122 /* Make sure to specify the version statically, because the
34123 debugger may check the version before we can set it. */
34124 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34127 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34128 modifications to this global data properly, which can easily be done by putting
34129 a global mutex around modifications to these structures.
34131 @node Registering Code
34132 @section Registering Code
34134 To register code with @value{GDBN}, the JIT should follow this protocol:
34138 Generate an object file in memory with symbols and other desired debug
34139 information. The file must include the virtual addresses of the sections.
34142 Create a code entry for the file, which gives the start and size of the symbol
34146 Add it to the linked list in the JIT descriptor.
34149 Point the relevant_entry field of the descriptor at the entry.
34152 Set @code{action_flag} to @code{JIT_REGISTER} and call
34153 @code{__jit_debug_register_code}.
34156 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34157 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34158 new code. However, the linked list must still be maintained in order to allow
34159 @value{GDBN} to attach to a running process and still find the symbol files.
34161 @node Unregistering Code
34162 @section Unregistering Code
34164 If code is freed, then the JIT should use the following protocol:
34168 Remove the code entry corresponding to the code from the linked list.
34171 Point the @code{relevant_entry} field of the descriptor at the code entry.
34174 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34175 @code{__jit_debug_register_code}.
34178 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34179 and the JIT will leak the memory used for the associated symbol files.
34181 @node Custom Debug Info
34182 @section Custom Debug Info
34183 @cindex custom JIT debug info
34184 @cindex JIT debug info reader
34186 Generating debug information in platform-native file formats (like ELF
34187 or COFF) may be an overkill for JIT compilers; especially if all the
34188 debug info is used for is displaying a meaningful backtrace. The
34189 issue can be resolved by having the JIT writers decide on a debug info
34190 format and also provide a reader that parses the debug info generated
34191 by the JIT compiler. This section gives a brief overview on writing
34192 such a parser. More specific details can be found in the source file
34193 @file{gdb/jit-reader.in}, which is also installed as a header at
34194 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34196 The reader is implemented as a shared object (so this functionality is
34197 not available on platforms which don't allow loading shared objects at
34198 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34199 @code{jit-reader-unload} are provided, to be used to load and unload
34200 the readers from a preconfigured directory. Once loaded, the shared
34201 object is used the parse the debug information emitted by the JIT
34205 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34206 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34209 @node Using JIT Debug Info Readers
34210 @subsection Using JIT Debug Info Readers
34211 @kindex jit-reader-load
34212 @kindex jit-reader-unload
34214 Readers can be loaded and unloaded using the @code{jit-reader-load}
34215 and @code{jit-reader-unload} commands.
34218 @item jit-reader-load @var{reader}
34219 Load the JIT reader named @var{reader}. @var{reader} is a shared
34220 object specified as either an absolute or a relative file name. In
34221 the latter case, @value{GDBN} will try to load the reader from a
34222 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34223 system (here @var{libdir} is the system library directory, often
34224 @file{/usr/local/lib}).
34226 Only one reader can be active at a time; trying to load a second
34227 reader when one is already loaded will result in @value{GDBN}
34228 reporting an error. A new JIT reader can be loaded by first unloading
34229 the current one using @code{jit-reader-unload} and then invoking
34230 @code{jit-reader-load}.
34232 @item jit-reader-unload
34233 Unload the currently loaded JIT reader.
34237 @node Writing JIT Debug Info Readers
34238 @subsection Writing JIT Debug Info Readers
34239 @cindex writing JIT debug info readers
34241 As mentioned, a reader is essentially a shared object conforming to a
34242 certain ABI. This ABI is described in @file{jit-reader.h}.
34244 @file{jit-reader.h} defines the structures, macros and functions
34245 required to write a reader. It is installed (along with
34246 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34247 the system include directory.
34249 Readers need to be released under a GPL compatible license. A reader
34250 can be declared as released under such a license by placing the macro
34251 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34253 The entry point for readers is the symbol @code{gdb_init_reader},
34254 which is expected to be a function with the prototype
34256 @findex gdb_init_reader
34258 extern struct gdb_reader_funcs *gdb_init_reader (void);
34261 @cindex @code{struct gdb_reader_funcs}
34263 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34264 functions. These functions are executed to read the debug info
34265 generated by the JIT compiler (@code{read}), to unwind stack frames
34266 (@code{unwind}) and to create canonical frame IDs
34267 (@code{get_Frame_id}). It also has a callback that is called when the
34268 reader is being unloaded (@code{destroy}). The struct looks like this
34271 struct gdb_reader_funcs
34273 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34274 int reader_version;
34276 /* For use by the reader. */
34279 gdb_read_debug_info *read;
34280 gdb_unwind_frame *unwind;
34281 gdb_get_frame_id *get_frame_id;
34282 gdb_destroy_reader *destroy;
34286 @cindex @code{struct gdb_symbol_callbacks}
34287 @cindex @code{struct gdb_unwind_callbacks}
34289 The callbacks are provided with another set of callbacks by
34290 @value{GDBN} to do their job. For @code{read}, these callbacks are
34291 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34292 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34293 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34294 files and new symbol tables inside those object files. @code{struct
34295 gdb_unwind_callbacks} has callbacks to read registers off the current
34296 frame and to write out the values of the registers in the previous
34297 frame. Both have a callback (@code{target_read}) to read bytes off the
34298 target's address space.
34300 @node In-Process Agent
34301 @chapter In-Process Agent
34302 @cindex debugging agent
34303 The traditional debugging model is conceptually low-speed, but works fine,
34304 because most bugs can be reproduced in debugging-mode execution. However,
34305 as multi-core or many-core processors are becoming mainstream, and
34306 multi-threaded programs become more and more popular, there should be more
34307 and more bugs that only manifest themselves at normal-mode execution, for
34308 example, thread races, because debugger's interference with the program's
34309 timing may conceal the bugs. On the other hand, in some applications,
34310 it is not feasible for the debugger to interrupt the program's execution
34311 long enough for the developer to learn anything helpful about its behavior.
34312 If the program's correctness depends on its real-time behavior, delays
34313 introduced by a debugger might cause the program to fail, even when the
34314 code itself is correct. It is useful to be able to observe the program's
34315 behavior without interrupting it.
34317 Therefore, traditional debugging model is too intrusive to reproduce
34318 some bugs. In order to reduce the interference with the program, we can
34319 reduce the number of operations performed by debugger. The
34320 @dfn{In-Process Agent}, a shared library, is running within the same
34321 process with inferior, and is able to perform some debugging operations
34322 itself. As a result, debugger is only involved when necessary, and
34323 performance of debugging can be improved accordingly. Note that
34324 interference with program can be reduced but can't be removed completely,
34325 because the in-process agent will still stop or slow down the program.
34327 The in-process agent can interpret and execute Agent Expressions
34328 (@pxref{Agent Expressions}) during performing debugging operations. The
34329 agent expressions can be used for different purposes, such as collecting
34330 data in tracepoints, and condition evaluation in breakpoints.
34332 @anchor{Control Agent}
34333 You can control whether the in-process agent is used as an aid for
34334 debugging with the following commands:
34337 @kindex set agent on
34339 Causes the in-process agent to perform some operations on behalf of the
34340 debugger. Just which operations requested by the user will be done
34341 by the in-process agent depends on the its capabilities. For example,
34342 if you request to evaluate breakpoint conditions in the in-process agent,
34343 and the in-process agent has such capability as well, then breakpoint
34344 conditions will be evaluated in the in-process agent.
34346 @kindex set agent off
34347 @item set agent off
34348 Disables execution of debugging operations by the in-process agent. All
34349 of the operations will be performed by @value{GDBN}.
34353 Display the current setting of execution of debugging operations by
34354 the in-process agent.
34358 * In-Process Agent Protocol::
34361 @node In-Process Agent Protocol
34362 @section In-Process Agent Protocol
34363 @cindex in-process agent protocol
34365 The in-process agent is able to communicate with both @value{GDBN} and
34366 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34367 used for communications between @value{GDBN} or GDBserver and the IPA.
34368 In general, @value{GDBN} or GDBserver sends commands
34369 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34370 in-process agent replies back with the return result of the command, or
34371 some other information. The data sent to in-process agent is composed
34372 of primitive data types, such as 4-byte or 8-byte type, and composite
34373 types, which are called objects (@pxref{IPA Protocol Objects}).
34376 * IPA Protocol Objects::
34377 * IPA Protocol Commands::
34380 @node IPA Protocol Objects
34381 @subsection IPA Protocol Objects
34382 @cindex ipa protocol objects
34384 The commands sent to and results received from agent may contain some
34385 complex data types called @dfn{objects}.
34387 The in-process agent is running on the same machine with @value{GDBN}
34388 or GDBserver, so it doesn't have to handle as much differences between
34389 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34390 However, there are still some differences of two ends in two processes:
34394 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34395 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34397 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34398 GDBserver is compiled with one, and in-process agent is compiled with
34402 Here are the IPA Protocol Objects:
34406 agent expression object. It represents an agent expression
34407 (@pxref{Agent Expressions}).
34408 @anchor{agent expression object}
34410 tracepoint action object. It represents a tracepoint action
34411 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34412 memory, static trace data and to evaluate expression.
34413 @anchor{tracepoint action object}
34415 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34416 @anchor{tracepoint object}
34420 The following table describes important attributes of each IPA protocol
34423 @multitable @columnfractions .30 .20 .50
34424 @headitem Name @tab Size @tab Description
34425 @item @emph{agent expression object} @tab @tab
34426 @item length @tab 4 @tab length of bytes code
34427 @item byte code @tab @var{length} @tab contents of byte code
34428 @item @emph{tracepoint action for collecting memory} @tab @tab
34429 @item 'M' @tab 1 @tab type of tracepoint action
34430 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34431 address of the lowest byte to collect, otherwise @var{addr} is the offset
34432 of @var{basereg} for memory collecting.
34433 @item len @tab 8 @tab length of memory for collecting
34434 @item basereg @tab 4 @tab the register number containing the starting
34435 memory address for collecting.
34436 @item @emph{tracepoint action for collecting registers} @tab @tab
34437 @item 'R' @tab 1 @tab type of tracepoint action
34438 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34439 @item 'L' @tab 1 @tab type of tracepoint action
34440 @item @emph{tracepoint action for expression evaluation} @tab @tab
34441 @item 'X' @tab 1 @tab type of tracepoint action
34442 @item agent expression @tab length of @tab @ref{agent expression object}
34443 @item @emph{tracepoint object} @tab @tab
34444 @item number @tab 4 @tab number of tracepoint
34445 @item address @tab 8 @tab address of tracepoint inserted on
34446 @item type @tab 4 @tab type of tracepoint
34447 @item enabled @tab 1 @tab enable or disable of tracepoint
34448 @item step_count @tab 8 @tab step
34449 @item pass_count @tab 8 @tab pass
34450 @item numactions @tab 4 @tab number of tracepoint actions
34451 @item hit count @tab 8 @tab hit count
34452 @item trace frame usage @tab 8 @tab trace frame usage
34453 @item compiled_cond @tab 8 @tab compiled condition
34454 @item orig_size @tab 8 @tab orig size
34455 @item condition @tab 4 if condition is NULL otherwise length of
34456 @ref{agent expression object}
34457 @tab zero if condition is NULL, otherwise is
34458 @ref{agent expression object}
34459 @item actions @tab variable
34460 @tab numactions number of @ref{tracepoint action object}
34463 @node IPA Protocol Commands
34464 @subsection IPA Protocol Commands
34465 @cindex ipa protocol commands
34467 The spaces in each command are delimiters to ease reading this commands
34468 specification. They don't exist in real commands.
34472 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34473 Installs a new fast tracepoint described by @var{tracepoint_object}
34474 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34475 head of @dfn{jumppad}, which is used to jump to data collection routine
34480 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34481 @var{target_address} is address of tracepoint in the inferior.
34482 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34483 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34484 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34485 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34492 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34493 is about to kill inferiors.
34501 @item probe_marker_at:@var{address}
34502 Asks in-process agent to probe the marker at @var{address}.
34509 @item unprobe_marker_at:@var{address}
34510 Asks in-process agent to unprobe the marker at @var{address}.
34514 @chapter Reporting Bugs in @value{GDBN}
34515 @cindex bugs in @value{GDBN}
34516 @cindex reporting bugs in @value{GDBN}
34518 Your bug reports play an essential role in making @value{GDBN} reliable.
34520 Reporting a bug may help you by bringing a solution to your problem, or it
34521 may not. But in any case the principal function of a bug report is to help
34522 the entire community by making the next version of @value{GDBN} work better. Bug
34523 reports are your contribution to the maintenance of @value{GDBN}.
34525 In order for a bug report to serve its purpose, you must include the
34526 information that enables us to fix the bug.
34529 * Bug Criteria:: Have you found a bug?
34530 * Bug Reporting:: How to report bugs
34534 @section Have You Found a Bug?
34535 @cindex bug criteria
34537 If you are not sure whether you have found a bug, here are some guidelines:
34540 @cindex fatal signal
34541 @cindex debugger crash
34542 @cindex crash of debugger
34544 If the debugger gets a fatal signal, for any input whatever, that is a
34545 @value{GDBN} bug. Reliable debuggers never crash.
34547 @cindex error on valid input
34549 If @value{GDBN} produces an error message for valid input, that is a
34550 bug. (Note that if you're cross debugging, the problem may also be
34551 somewhere in the connection to the target.)
34553 @cindex invalid input
34555 If @value{GDBN} does not produce an error message for invalid input,
34556 that is a bug. However, you should note that your idea of
34557 ``invalid input'' might be our idea of ``an extension'' or ``support
34558 for traditional practice''.
34561 If you are an experienced user of debugging tools, your suggestions
34562 for improvement of @value{GDBN} are welcome in any case.
34565 @node Bug Reporting
34566 @section How to Report Bugs
34567 @cindex bug reports
34568 @cindex @value{GDBN} bugs, reporting
34570 A number of companies and individuals offer support for @sc{gnu} products.
34571 If you obtained @value{GDBN} from a support organization, we recommend you
34572 contact that organization first.
34574 You can find contact information for many support companies and
34575 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34577 @c should add a web page ref...
34580 @ifset BUGURL_DEFAULT
34581 In any event, we also recommend that you submit bug reports for
34582 @value{GDBN}. The preferred method is to submit them directly using
34583 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34584 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34587 @strong{Do not send bug reports to @samp{info-gdb}, or to
34588 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34589 not want to receive bug reports. Those that do have arranged to receive
34592 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34593 serves as a repeater. The mailing list and the newsgroup carry exactly
34594 the same messages. Often people think of posting bug reports to the
34595 newsgroup instead of mailing them. This appears to work, but it has one
34596 problem which can be crucial: a newsgroup posting often lacks a mail
34597 path back to the sender. Thus, if we need to ask for more information,
34598 we may be unable to reach you. For this reason, it is better to send
34599 bug reports to the mailing list.
34601 @ifclear BUGURL_DEFAULT
34602 In any event, we also recommend that you submit bug reports for
34603 @value{GDBN} to @value{BUGURL}.
34607 The fundamental principle of reporting bugs usefully is this:
34608 @strong{report all the facts}. If you are not sure whether to state a
34609 fact or leave it out, state it!
34611 Often people omit facts because they think they know what causes the
34612 problem and assume that some details do not matter. Thus, you might
34613 assume that the name of the variable you use in an example does not matter.
34614 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34615 stray memory reference which happens to fetch from the location where that
34616 name is stored in memory; perhaps, if the name were different, the contents
34617 of that location would fool the debugger into doing the right thing despite
34618 the bug. Play it safe and give a specific, complete example. That is the
34619 easiest thing for you to do, and the most helpful.
34621 Keep in mind that the purpose of a bug report is to enable us to fix the
34622 bug. It may be that the bug has been reported previously, but neither
34623 you nor we can know that unless your bug report is complete and
34626 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34627 bell?'' Those bug reports are useless, and we urge everyone to
34628 @emph{refuse to respond to them} except to chide the sender to report
34631 To enable us to fix the bug, you should include all these things:
34635 The version of @value{GDBN}. @value{GDBN} announces it if you start
34636 with no arguments; you can also print it at any time using @code{show
34639 Without this, we will not know whether there is any point in looking for
34640 the bug in the current version of @value{GDBN}.
34643 The type of machine you are using, and the operating system name and
34647 The details of the @value{GDBN} build-time configuration.
34648 @value{GDBN} shows these details if you invoke it with the
34649 @option{--configuration} command-line option, or if you type
34650 @code{show configuration} at @value{GDBN}'s prompt.
34653 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34654 ``@value{GCC}--2.8.1''.
34657 What compiler (and its version) was used to compile the program you are
34658 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34659 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34660 to get this information; for other compilers, see the documentation for
34664 The command arguments you gave the compiler to compile your example and
34665 observe the bug. For example, did you use @samp{-O}? To guarantee
34666 you will not omit something important, list them all. A copy of the
34667 Makefile (or the output from make) is sufficient.
34669 If we were to try to guess the arguments, we would probably guess wrong
34670 and then we might not encounter the bug.
34673 A complete input script, and all necessary source files, that will
34677 A description of what behavior you observe that you believe is
34678 incorrect. For example, ``It gets a fatal signal.''
34680 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34681 will certainly notice it. But if the bug is incorrect output, we might
34682 not notice unless it is glaringly wrong. You might as well not give us
34683 a chance to make a mistake.
34685 Even if the problem you experience is a fatal signal, you should still
34686 say so explicitly. Suppose something strange is going on, such as, your
34687 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34688 the C library on your system. (This has happened!) Your copy might
34689 crash and ours would not. If you told us to expect a crash, then when
34690 ours fails to crash, we would know that the bug was not happening for
34691 us. If you had not told us to expect a crash, then we would not be able
34692 to draw any conclusion from our observations.
34695 @cindex recording a session script
34696 To collect all this information, you can use a session recording program
34697 such as @command{script}, which is available on many Unix systems.
34698 Just run your @value{GDBN} session inside @command{script} and then
34699 include the @file{typescript} file with your bug report.
34701 Another way to record a @value{GDBN} session is to run @value{GDBN}
34702 inside Emacs and then save the entire buffer to a file.
34705 If you wish to suggest changes to the @value{GDBN} source, send us context
34706 diffs. If you even discuss something in the @value{GDBN} source, refer to
34707 it by context, not by line number.
34709 The line numbers in our development sources will not match those in your
34710 sources. Your line numbers would convey no useful information to us.
34714 Here are some things that are not necessary:
34718 A description of the envelope of the bug.
34720 Often people who encounter a bug spend a lot of time investigating
34721 which changes to the input file will make the bug go away and which
34722 changes will not affect it.
34724 This is often time consuming and not very useful, because the way we
34725 will find the bug is by running a single example under the debugger
34726 with breakpoints, not by pure deduction from a series of examples.
34727 We recommend that you save your time for something else.
34729 Of course, if you can find a simpler example to report @emph{instead}
34730 of the original one, that is a convenience for us. Errors in the
34731 output will be easier to spot, running under the debugger will take
34732 less time, and so on.
34734 However, simplification is not vital; if you do not want to do this,
34735 report the bug anyway and send us the entire test case you used.
34738 A patch for the bug.
34740 A patch for the bug does help us if it is a good one. But do not omit
34741 the necessary information, such as the test case, on the assumption that
34742 a patch is all we need. We might see problems with your patch and decide
34743 to fix the problem another way, or we might not understand it at all.
34745 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34746 construct an example that will make the program follow a certain path
34747 through the code. If you do not send us the example, we will not be able
34748 to construct one, so we will not be able to verify that the bug is fixed.
34750 And if we cannot understand what bug you are trying to fix, or why your
34751 patch should be an improvement, we will not install it. A test case will
34752 help us to understand.
34755 A guess about what the bug is or what it depends on.
34757 Such guesses are usually wrong. Even we cannot guess right about such
34758 things without first using the debugger to find the facts.
34761 @c The readline documentation is distributed with the readline code
34762 @c and consists of the two following files:
34765 @c Use -I with makeinfo to point to the appropriate directory,
34766 @c environment var TEXINPUTS with TeX.
34767 @ifclear SYSTEM_READLINE
34768 @include rluser.texi
34769 @include hsuser.texi
34773 @appendix In Memoriam
34775 The @value{GDBN} project mourns the loss of the following long-time
34780 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34781 to Free Software in general. Outside of @value{GDBN}, he was known in
34782 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34784 @item Michael Snyder
34785 Michael was one of the Global Maintainers of the @value{GDBN} project,
34786 with contributions recorded as early as 1996, until 2011. In addition
34787 to his day to day participation, he was a large driving force behind
34788 adding Reverse Debugging to @value{GDBN}.
34791 Beyond their technical contributions to the project, they were also
34792 enjoyable members of the Free Software Community. We will miss them.
34794 @node Formatting Documentation
34795 @appendix Formatting Documentation
34797 @cindex @value{GDBN} reference card
34798 @cindex reference card
34799 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34800 for printing with PostScript or Ghostscript, in the @file{gdb}
34801 subdirectory of the main source directory@footnote{In
34802 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34803 release.}. If you can use PostScript or Ghostscript with your printer,
34804 you can print the reference card immediately with @file{refcard.ps}.
34806 The release also includes the source for the reference card. You
34807 can format it, using @TeX{}, by typing:
34813 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34814 mode on US ``letter'' size paper;
34815 that is, on a sheet 11 inches wide by 8.5 inches
34816 high. You will need to specify this form of printing as an option to
34817 your @sc{dvi} output program.
34819 @cindex documentation
34821 All the documentation for @value{GDBN} comes as part of the machine-readable
34822 distribution. The documentation is written in Texinfo format, which is
34823 a documentation system that uses a single source file to produce both
34824 on-line information and a printed manual. You can use one of the Info
34825 formatting commands to create the on-line version of the documentation
34826 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34828 @value{GDBN} includes an already formatted copy of the on-line Info
34829 version of this manual in the @file{gdb} subdirectory. The main Info
34830 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34831 subordinate files matching @samp{gdb.info*} in the same directory. If
34832 necessary, you can print out these files, or read them with any editor;
34833 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34834 Emacs or the standalone @code{info} program, available as part of the
34835 @sc{gnu} Texinfo distribution.
34837 If you want to format these Info files yourself, you need one of the
34838 Info formatting programs, such as @code{texinfo-format-buffer} or
34841 If you have @code{makeinfo} installed, and are in the top level
34842 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34843 version @value{GDBVN}), you can make the Info file by typing:
34850 If you want to typeset and print copies of this manual, you need @TeX{},
34851 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34852 Texinfo definitions file.
34854 @TeX{} is a typesetting program; it does not print files directly, but
34855 produces output files called @sc{dvi} files. To print a typeset
34856 document, you need a program to print @sc{dvi} files. If your system
34857 has @TeX{} installed, chances are it has such a program. The precise
34858 command to use depends on your system; @kbd{lpr -d} is common; another
34859 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34860 require a file name without any extension or a @samp{.dvi} extension.
34862 @TeX{} also requires a macro definitions file called
34863 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34864 written in Texinfo format. On its own, @TeX{} cannot either read or
34865 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34866 and is located in the @file{gdb-@var{version-number}/texinfo}
34869 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34870 typeset and print this manual. First switch to the @file{gdb}
34871 subdirectory of the main source directory (for example, to
34872 @file{gdb-@value{GDBVN}/gdb}) and type:
34878 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34880 @node Installing GDB
34881 @appendix Installing @value{GDBN}
34882 @cindex installation
34885 * Requirements:: Requirements for building @value{GDBN}
34886 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34887 * Separate Objdir:: Compiling @value{GDBN} in another directory
34888 * Config Names:: Specifying names for hosts and targets
34889 * Configure Options:: Summary of options for configure
34890 * System-wide configuration:: Having a system-wide init file
34894 @section Requirements for Building @value{GDBN}
34895 @cindex building @value{GDBN}, requirements for
34897 Building @value{GDBN} requires various tools and packages to be available.
34898 Other packages will be used only if they are found.
34900 @heading Tools/Packages Necessary for Building @value{GDBN}
34902 @item ISO C90 compiler
34903 @value{GDBN} is written in ISO C90. It should be buildable with any
34904 working C90 compiler, e.g.@: GCC.
34908 @heading Tools/Packages Optional for Building @value{GDBN}
34912 @value{GDBN} can use the Expat XML parsing library. This library may be
34913 included with your operating system distribution; if it is not, you
34914 can get the latest version from @url{http://expat.sourceforge.net}.
34915 The @file{configure} script will search for this library in several
34916 standard locations; if it is installed in an unusual path, you can
34917 use the @option{--with-libexpat-prefix} option to specify its location.
34923 Remote protocol memory maps (@pxref{Memory Map Format})
34925 Target descriptions (@pxref{Target Descriptions})
34927 Remote shared library lists (@xref{Library List Format},
34928 or alternatively @pxref{Library List Format for SVR4 Targets})
34930 MS-Windows shared libraries (@pxref{Shared Libraries})
34932 Traceframe info (@pxref{Traceframe Info Format})
34934 Branch trace (@pxref{Branch Trace Format})
34938 @cindex compressed debug sections
34939 @value{GDBN} will use the @samp{zlib} library, if available, to read
34940 compressed debug sections. Some linkers, such as GNU gold, are capable
34941 of producing binaries with compressed debug sections. If @value{GDBN}
34942 is compiled with @samp{zlib}, it will be able to read the debug
34943 information in such binaries.
34945 The @samp{zlib} library is likely included with your operating system
34946 distribution; if it is not, you can get the latest version from
34947 @url{http://zlib.net}.
34950 @value{GDBN}'s features related to character sets (@pxref{Character
34951 Sets}) require a functioning @code{iconv} implementation. If you are
34952 on a GNU system, then this is provided by the GNU C Library. Some
34953 other systems also provide a working @code{iconv}.
34955 If @value{GDBN} is using the @code{iconv} program which is installed
34956 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34957 This is done with @option{--with-iconv-bin} which specifies the
34958 directory that contains the @code{iconv} program.
34960 On systems without @code{iconv}, you can install GNU Libiconv. If you
34961 have previously installed Libiconv, you can use the
34962 @option{--with-libiconv-prefix} option to configure.
34964 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34965 arrange to build Libiconv if a directory named @file{libiconv} appears
34966 in the top-most source directory. If Libiconv is built this way, and
34967 if the operating system does not provide a suitable @code{iconv}
34968 implementation, then the just-built library will automatically be used
34969 by @value{GDBN}. One easy way to set this up is to download GNU
34970 Libiconv, unpack it, and then rename the directory holding the
34971 Libiconv source code to @samp{libiconv}.
34974 @node Running Configure
34975 @section Invoking the @value{GDBN} @file{configure} Script
34976 @cindex configuring @value{GDBN}
34977 @value{GDBN} comes with a @file{configure} script that automates the process
34978 of preparing @value{GDBN} for installation; you can then use @code{make} to
34979 build the @code{gdb} program.
34981 @c irrelevant in info file; it's as current as the code it lives with.
34982 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34983 look at the @file{README} file in the sources; we may have improved the
34984 installation procedures since publishing this manual.}
34987 The @value{GDBN} distribution includes all the source code you need for
34988 @value{GDBN} in a single directory, whose name is usually composed by
34989 appending the version number to @samp{gdb}.
34991 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34992 @file{gdb-@value{GDBVN}} directory. That directory contains:
34995 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34996 script for configuring @value{GDBN} and all its supporting libraries
34998 @item gdb-@value{GDBVN}/gdb
34999 the source specific to @value{GDBN} itself
35001 @item gdb-@value{GDBVN}/bfd
35002 source for the Binary File Descriptor library
35004 @item gdb-@value{GDBVN}/include
35005 @sc{gnu} include files
35007 @item gdb-@value{GDBVN}/libiberty
35008 source for the @samp{-liberty} free software library
35010 @item gdb-@value{GDBVN}/opcodes
35011 source for the library of opcode tables and disassemblers
35013 @item gdb-@value{GDBVN}/readline
35014 source for the @sc{gnu} command-line interface
35016 @item gdb-@value{GDBVN}/glob
35017 source for the @sc{gnu} filename pattern-matching subroutine
35019 @item gdb-@value{GDBVN}/mmalloc
35020 source for the @sc{gnu} memory-mapped malloc package
35023 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35024 from the @file{gdb-@var{version-number}} source directory, which in
35025 this example is the @file{gdb-@value{GDBVN}} directory.
35027 First switch to the @file{gdb-@var{version-number}} source directory
35028 if you are not already in it; then run @file{configure}. Pass the
35029 identifier for the platform on which @value{GDBN} will run as an
35035 cd gdb-@value{GDBVN}
35036 ./configure @var{host}
35041 where @var{host} is an identifier such as @samp{sun4} or
35042 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
35043 (You can often leave off @var{host}; @file{configure} tries to guess the
35044 correct value by examining your system.)
35046 Running @samp{configure @var{host}} and then running @code{make} builds the
35047 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
35048 libraries, then @code{gdb} itself. The configured source files, and the
35049 binaries, are left in the corresponding source directories.
35052 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35053 system does not recognize this automatically when you run a different
35054 shell, you may need to run @code{sh} on it explicitly:
35057 sh configure @var{host}
35060 If you run @file{configure} from a directory that contains source
35061 directories for multiple libraries or programs, such as the
35062 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
35064 creates configuration files for every directory level underneath (unless
35065 you tell it not to, with the @samp{--norecursion} option).
35067 You should run the @file{configure} script from the top directory in the
35068 source tree, the @file{gdb-@var{version-number}} directory. If you run
35069 @file{configure} from one of the subdirectories, you will configure only
35070 that subdirectory. That is usually not what you want. In particular,
35071 if you run the first @file{configure} from the @file{gdb} subdirectory
35072 of the @file{gdb-@var{version-number}} directory, you will omit the
35073 configuration of @file{bfd}, @file{readline}, and other sibling
35074 directories of the @file{gdb} subdirectory. This leads to build errors
35075 about missing include files such as @file{bfd/bfd.h}.
35077 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
35078 However, you should make sure that the shell on your path (named by
35079 the @samp{SHELL} environment variable) is publicly readable. Remember
35080 that @value{GDBN} uses the shell to start your program---some systems refuse to
35081 let @value{GDBN} debug child processes whose programs are not readable.
35083 @node Separate Objdir
35084 @section Compiling @value{GDBN} in Another Directory
35086 If you want to run @value{GDBN} versions for several host or target machines,
35087 you need a different @code{gdb} compiled for each combination of
35088 host and target. @file{configure} is designed to make this easy by
35089 allowing you to generate each configuration in a separate subdirectory,
35090 rather than in the source directory. If your @code{make} program
35091 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35092 @code{make} in each of these directories builds the @code{gdb}
35093 program specified there.
35095 To build @code{gdb} in a separate directory, run @file{configure}
35096 with the @samp{--srcdir} option to specify where to find the source.
35097 (You also need to specify a path to find @file{configure}
35098 itself from your working directory. If the path to @file{configure}
35099 would be the same as the argument to @samp{--srcdir}, you can leave out
35100 the @samp{--srcdir} option; it is assumed.)
35102 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35103 separate directory for a Sun 4 like this:
35107 cd gdb-@value{GDBVN}
35110 ../gdb-@value{GDBVN}/configure sun4
35115 When @file{configure} builds a configuration using a remote source
35116 directory, it creates a tree for the binaries with the same structure
35117 (and using the same names) as the tree under the source directory. In
35118 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35119 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35120 @file{gdb-sun4/gdb}.
35122 Make sure that your path to the @file{configure} script has just one
35123 instance of @file{gdb} in it. If your path to @file{configure} looks
35124 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35125 one subdirectory of @value{GDBN}, not the whole package. This leads to
35126 build errors about missing include files such as @file{bfd/bfd.h}.
35128 One popular reason to build several @value{GDBN} configurations in separate
35129 directories is to configure @value{GDBN} for cross-compiling (where
35130 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35131 programs that run on another machine---the @dfn{target}).
35132 You specify a cross-debugging target by
35133 giving the @samp{--target=@var{target}} option to @file{configure}.
35135 When you run @code{make} to build a program or library, you must run
35136 it in a configured directory---whatever directory you were in when you
35137 called @file{configure} (or one of its subdirectories).
35139 The @code{Makefile} that @file{configure} generates in each source
35140 directory also runs recursively. If you type @code{make} in a source
35141 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35142 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35143 will build all the required libraries, and then build GDB.
35145 When you have multiple hosts or targets configured in separate
35146 directories, you can run @code{make} on them in parallel (for example,
35147 if they are NFS-mounted on each of the hosts); they will not interfere
35151 @section Specifying Names for Hosts and Targets
35153 The specifications used for hosts and targets in the @file{configure}
35154 script are based on a three-part naming scheme, but some short predefined
35155 aliases are also supported. The full naming scheme encodes three pieces
35156 of information in the following pattern:
35159 @var{architecture}-@var{vendor}-@var{os}
35162 For example, you can use the alias @code{sun4} as a @var{host} argument,
35163 or as the value for @var{target} in a @code{--target=@var{target}}
35164 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35166 The @file{configure} script accompanying @value{GDBN} does not provide
35167 any query facility to list all supported host and target names or
35168 aliases. @file{configure} calls the Bourne shell script
35169 @code{config.sub} to map abbreviations to full names; you can read the
35170 script, if you wish, or you can use it to test your guesses on
35171 abbreviations---for example:
35174 % sh config.sub i386-linux
35176 % sh config.sub alpha-linux
35177 alpha-unknown-linux-gnu
35178 % sh config.sub hp9k700
35180 % sh config.sub sun4
35181 sparc-sun-sunos4.1.1
35182 % sh config.sub sun3
35183 m68k-sun-sunos4.1.1
35184 % sh config.sub i986v
35185 Invalid configuration `i986v': machine `i986v' not recognized
35189 @code{config.sub} is also distributed in the @value{GDBN} source
35190 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35192 @node Configure Options
35193 @section @file{configure} Options
35195 Here is a summary of the @file{configure} options and arguments that
35196 are most often useful for building @value{GDBN}. @file{configure} also has
35197 several other options not listed here. @inforef{What Configure
35198 Does,,configure.info}, for a full explanation of @file{configure}.
35201 configure @r{[}--help@r{]}
35202 @r{[}--prefix=@var{dir}@r{]}
35203 @r{[}--exec-prefix=@var{dir}@r{]}
35204 @r{[}--srcdir=@var{dirname}@r{]}
35205 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35206 @r{[}--target=@var{target}@r{]}
35211 You may introduce options with a single @samp{-} rather than
35212 @samp{--} if you prefer; but you may abbreviate option names if you use
35217 Display a quick summary of how to invoke @file{configure}.
35219 @item --prefix=@var{dir}
35220 Configure the source to install programs and files under directory
35223 @item --exec-prefix=@var{dir}
35224 Configure the source to install programs under directory
35227 @c avoid splitting the warning from the explanation:
35229 @item --srcdir=@var{dirname}
35230 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35231 @code{make} that implements the @code{VPATH} feature.}@*
35232 Use this option to make configurations in directories separate from the
35233 @value{GDBN} source directories. Among other things, you can use this to
35234 build (or maintain) several configurations simultaneously, in separate
35235 directories. @file{configure} writes configuration-specific files in
35236 the current directory, but arranges for them to use the source in the
35237 directory @var{dirname}. @file{configure} creates directories under
35238 the working directory in parallel to the source directories below
35241 @item --norecursion
35242 Configure only the directory level where @file{configure} is executed; do not
35243 propagate configuration to subdirectories.
35245 @item --target=@var{target}
35246 Configure @value{GDBN} for cross-debugging programs running on the specified
35247 @var{target}. Without this option, @value{GDBN} is configured to debug
35248 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35250 There is no convenient way to generate a list of all available targets.
35252 @item @var{host} @dots{}
35253 Configure @value{GDBN} to run on the specified @var{host}.
35255 There is no convenient way to generate a list of all available hosts.
35258 There are many other options available as well, but they are generally
35259 needed for special purposes only.
35261 @node System-wide configuration
35262 @section System-wide configuration and settings
35263 @cindex system-wide init file
35265 @value{GDBN} can be configured to have a system-wide init file;
35266 this file will be read and executed at startup (@pxref{Startup, , What
35267 @value{GDBN} does during startup}).
35269 Here is the corresponding configure option:
35272 @item --with-system-gdbinit=@var{file}
35273 Specify that the default location of the system-wide init file is
35277 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35278 it may be subject to relocation. Two possible cases:
35282 If the default location of this init file contains @file{$prefix},
35283 it will be subject to relocation. Suppose that the configure options
35284 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35285 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35286 init file is looked for as @file{$install/etc/gdbinit} instead of
35287 @file{$prefix/etc/gdbinit}.
35290 By contrast, if the default location does not contain the prefix,
35291 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35292 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35293 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35294 wherever @value{GDBN} is installed.
35297 If the configured location of the system-wide init file (as given by the
35298 @option{--with-system-gdbinit} option at configure time) is in the
35299 data-directory (as specified by @option{--with-gdb-datadir} at configure
35300 time) or in one of its subdirectories, then @value{GDBN} will look for the
35301 system-wide init file in the directory specified by the
35302 @option{--data-directory} command-line option.
35303 Note that the system-wide init file is only read once, during @value{GDBN}
35304 initialization. If the data-directory is changed after @value{GDBN} has
35305 started with the @code{set data-directory} command, the file will not be
35308 @node Maintenance Commands
35309 @appendix Maintenance Commands
35310 @cindex maintenance commands
35311 @cindex internal commands
35313 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35314 includes a number of commands intended for @value{GDBN} developers,
35315 that are not documented elsewhere in this manual. These commands are
35316 provided here for reference. (For commands that turn on debugging
35317 messages, see @ref{Debugging Output}.)
35320 @kindex maint agent
35321 @kindex maint agent-eval
35322 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35323 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35324 Translate the given @var{expression} into remote agent bytecodes.
35325 This command is useful for debugging the Agent Expression mechanism
35326 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35327 expression useful for data collection, such as by tracepoints, while
35328 @samp{maint agent-eval} produces an expression that evaluates directly
35329 to a result. For instance, a collection expression for @code{globa +
35330 globb} will include bytecodes to record four bytes of memory at each
35331 of the addresses of @code{globa} and @code{globb}, while discarding
35332 the result of the addition, while an evaluation expression will do the
35333 addition and return the sum.
35334 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35335 If not, generate remote agent bytecode for current frame PC address.
35337 @kindex maint agent-printf
35338 @item maint agent-printf @var{format},@var{expr},...
35339 Translate the given format string and list of argument expressions
35340 into remote agent bytecodes and display them as a disassembled list.
35341 This command is useful for debugging the agent version of dynamic
35342 printf (@pxref{Dynamic Printf}).
35344 @kindex maint info breakpoints
35345 @item @anchor{maint info breakpoints}maint info breakpoints
35346 Using the same format as @samp{info breakpoints}, display both the
35347 breakpoints you've set explicitly, and those @value{GDBN} is using for
35348 internal purposes. Internal breakpoints are shown with negative
35349 breakpoint numbers. The type column identifies what kind of breakpoint
35354 Normal, explicitly set breakpoint.
35357 Normal, explicitly set watchpoint.
35360 Internal breakpoint, used to handle correctly stepping through
35361 @code{longjmp} calls.
35363 @item longjmp resume
35364 Internal breakpoint at the target of a @code{longjmp}.
35367 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35370 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35373 Shared library events.
35377 @kindex maint info bfds
35378 @item maint info bfds
35379 This prints information about each @code{bfd} object that is known to
35380 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
35382 @kindex set displaced-stepping
35383 @kindex show displaced-stepping
35384 @cindex displaced stepping support
35385 @cindex out-of-line single-stepping
35386 @item set displaced-stepping
35387 @itemx show displaced-stepping
35388 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35389 if the target supports it. Displaced stepping is a way to single-step
35390 over breakpoints without removing them from the inferior, by executing
35391 an out-of-line copy of the instruction that was originally at the
35392 breakpoint location. It is also known as out-of-line single-stepping.
35395 @item set displaced-stepping on
35396 If the target architecture supports it, @value{GDBN} will use
35397 displaced stepping to step over breakpoints.
35399 @item set displaced-stepping off
35400 @value{GDBN} will not use displaced stepping to step over breakpoints,
35401 even if such is supported by the target architecture.
35403 @cindex non-stop mode, and @samp{set displaced-stepping}
35404 @item set displaced-stepping auto
35405 This is the default mode. @value{GDBN} will use displaced stepping
35406 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35407 architecture supports displaced stepping.
35410 @kindex maint check-symtabs
35411 @item maint check-symtabs
35412 Check the consistency of psymtabs and symtabs.
35414 @kindex maint cplus first_component
35415 @item maint cplus first_component @var{name}
35416 Print the first C@t{++} class/namespace component of @var{name}.
35418 @kindex maint cplus namespace
35419 @item maint cplus namespace
35420 Print the list of possible C@t{++} namespaces.
35422 @kindex maint demangle
35423 @item maint demangle @var{name}
35424 Demangle a C@t{++} or Objective-C mangled @var{name}.
35426 @kindex maint deprecate
35427 @kindex maint undeprecate
35428 @cindex deprecated commands
35429 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35430 @itemx maint undeprecate @var{command}
35431 Deprecate or undeprecate the named @var{command}. Deprecated commands
35432 cause @value{GDBN} to issue a warning when you use them. The optional
35433 argument @var{replacement} says which newer command should be used in
35434 favor of the deprecated one; if it is given, @value{GDBN} will mention
35435 the replacement as part of the warning.
35437 @kindex maint dump-me
35438 @item maint dump-me
35439 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35440 Cause a fatal signal in the debugger and force it to dump its core.
35441 This is supported only on systems which support aborting a program
35442 with the @code{SIGQUIT} signal.
35444 @kindex maint internal-error
35445 @kindex maint internal-warning
35446 @item maint internal-error @r{[}@var{message-text}@r{]}
35447 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35448 Cause @value{GDBN} to call the internal function @code{internal_error}
35449 or @code{internal_warning} and hence behave as though an internal error
35450 or internal warning has been detected. In addition to reporting the
35451 internal problem, these functions give the user the opportunity to
35452 either quit @value{GDBN} or create a core file of the current
35453 @value{GDBN} session.
35455 These commands take an optional parameter @var{message-text} that is
35456 used as the text of the error or warning message.
35458 Here's an example of using @code{internal-error}:
35461 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35462 @dots{}/maint.c:121: internal-error: testing, 1, 2
35463 A problem internal to GDB has been detected. Further
35464 debugging may prove unreliable.
35465 Quit this debugging session? (y or n) @kbd{n}
35466 Create a core file? (y or n) @kbd{n}
35470 @cindex @value{GDBN} internal error
35471 @cindex internal errors, control of @value{GDBN} behavior
35473 @kindex maint set internal-error
35474 @kindex maint show internal-error
35475 @kindex maint set internal-warning
35476 @kindex maint show internal-warning
35477 @item maint set internal-error @var{action} [ask|yes|no]
35478 @itemx maint show internal-error @var{action}
35479 @itemx maint set internal-warning @var{action} [ask|yes|no]
35480 @itemx maint show internal-warning @var{action}
35481 When @value{GDBN} reports an internal problem (error or warning) it
35482 gives the user the opportunity to both quit @value{GDBN} and create a
35483 core file of the current @value{GDBN} session. These commands let you
35484 override the default behaviour for each particular @var{action},
35485 described in the table below.
35489 You can specify that @value{GDBN} should always (yes) or never (no)
35490 quit. The default is to ask the user what to do.
35493 You can specify that @value{GDBN} should always (yes) or never (no)
35494 create a core file. The default is to ask the user what to do.
35497 @kindex maint packet
35498 @item maint packet @var{text}
35499 If @value{GDBN} is talking to an inferior via the serial protocol,
35500 then this command sends the string @var{text} to the inferior, and
35501 displays the response packet. @value{GDBN} supplies the initial
35502 @samp{$} character, the terminating @samp{#} character, and the
35505 @kindex maint print architecture
35506 @item maint print architecture @r{[}@var{file}@r{]}
35507 Print the entire architecture configuration. The optional argument
35508 @var{file} names the file where the output goes.
35510 @kindex maint print c-tdesc
35511 @item maint print c-tdesc
35512 Print the current target description (@pxref{Target Descriptions}) as
35513 a C source file. The created source file can be used in @value{GDBN}
35514 when an XML parser is not available to parse the description.
35516 @kindex maint print dummy-frames
35517 @item maint print dummy-frames
35518 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35521 (@value{GDBP}) @kbd{b add}
35523 (@value{GDBP}) @kbd{print add(2,3)}
35524 Breakpoint 2, add (a=2, b=3) at @dots{}
35526 The program being debugged stopped while in a function called from GDB.
35528 (@value{GDBP}) @kbd{maint print dummy-frames}
35529 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35530 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35531 call_lo=0x01014000 call_hi=0x01014001
35535 Takes an optional file parameter.
35537 @kindex maint print registers
35538 @kindex maint print raw-registers
35539 @kindex maint print cooked-registers
35540 @kindex maint print register-groups
35541 @kindex maint print remote-registers
35542 @item maint print registers @r{[}@var{file}@r{]}
35543 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35544 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35545 @itemx maint print register-groups @r{[}@var{file}@r{]}
35546 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35547 Print @value{GDBN}'s internal register data structures.
35549 The command @code{maint print raw-registers} includes the contents of
35550 the raw register cache; the command @code{maint print
35551 cooked-registers} includes the (cooked) value of all registers,
35552 including registers which aren't available on the target nor visible
35553 to user; the command @code{maint print register-groups} includes the
35554 groups that each register is a member of; and the command @code{maint
35555 print remote-registers} includes the remote target's register numbers
35556 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35557 @value{GDBN} Internals}.
35559 These commands take an optional parameter, a file name to which to
35560 write the information.
35562 @kindex maint print reggroups
35563 @item maint print reggroups @r{[}@var{file}@r{]}
35564 Print @value{GDBN}'s internal register group data structures. The
35565 optional argument @var{file} tells to what file to write the
35568 The register groups info looks like this:
35571 (@value{GDBP}) @kbd{maint print reggroups}
35584 This command forces @value{GDBN} to flush its internal register cache.
35586 @kindex maint print objfiles
35587 @cindex info for known object files
35588 @item maint print objfiles
35589 Print a dump of all known object files. For each object file, this
35590 command prints its name, address in memory, and all of its psymtabs
35593 @kindex maint print section-scripts
35594 @cindex info for known .debug_gdb_scripts-loaded scripts
35595 @item maint print section-scripts [@var{regexp}]
35596 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35597 If @var{regexp} is specified, only print scripts loaded by object files
35598 matching @var{regexp}.
35599 For each script, this command prints its name as specified in the objfile,
35600 and the full path if known.
35601 @xref{dotdebug_gdb_scripts section}.
35603 @kindex maint print statistics
35604 @cindex bcache statistics
35605 @item maint print statistics
35606 This command prints, for each object file in the program, various data
35607 about that object file followed by the byte cache (@dfn{bcache})
35608 statistics for the object file. The objfile data includes the number
35609 of minimal, partial, full, and stabs symbols, the number of types
35610 defined by the objfile, the number of as yet unexpanded psym tables,
35611 the number of line tables and string tables, and the amount of memory
35612 used by the various tables. The bcache statistics include the counts,
35613 sizes, and counts of duplicates of all and unique objects, max,
35614 average, and median entry size, total memory used and its overhead and
35615 savings, and various measures of the hash table size and chain
35618 @kindex maint print target-stack
35619 @cindex target stack description
35620 @item maint print target-stack
35621 A @dfn{target} is an interface between the debugger and a particular
35622 kind of file or process. Targets can be stacked in @dfn{strata},
35623 so that more than one target can potentially respond to a request.
35624 In particular, memory accesses will walk down the stack of targets
35625 until they find a target that is interested in handling that particular
35628 This command prints a short description of each layer that was pushed on
35629 the @dfn{target stack}, starting from the top layer down to the bottom one.
35631 @kindex maint print type
35632 @cindex type chain of a data type
35633 @item maint print type @var{expr}
35634 Print the type chain for a type specified by @var{expr}. The argument
35635 can be either a type name or a symbol. If it is a symbol, the type of
35636 that symbol is described. The type chain produced by this command is
35637 a recursive definition of the data type as stored in @value{GDBN}'s
35638 data structures, including its flags and contained types.
35640 @kindex maint set dwarf2 always-disassemble
35641 @kindex maint show dwarf2 always-disassemble
35642 @item maint set dwarf2 always-disassemble
35643 @item maint show dwarf2 always-disassemble
35644 Control the behavior of @code{info address} when using DWARF debugging
35647 The default is @code{off}, which means that @value{GDBN} should try to
35648 describe a variable's location in an easily readable format. When
35649 @code{on}, @value{GDBN} will instead display the DWARF location
35650 expression in an assembly-like format. Note that some locations are
35651 too complex for @value{GDBN} to describe simply; in this case you will
35652 always see the disassembly form.
35654 Here is an example of the resulting disassembly:
35657 (gdb) info addr argc
35658 Symbol "argc" is a complex DWARF expression:
35662 For more information on these expressions, see
35663 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35665 @kindex maint set dwarf2 max-cache-age
35666 @kindex maint show dwarf2 max-cache-age
35667 @item maint set dwarf2 max-cache-age
35668 @itemx maint show dwarf2 max-cache-age
35669 Control the DWARF 2 compilation unit cache.
35671 @cindex DWARF 2 compilation units cache
35672 In object files with inter-compilation-unit references, such as those
35673 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35674 reader needs to frequently refer to previously read compilation units.
35675 This setting controls how long a compilation unit will remain in the
35676 cache if it is not referenced. A higher limit means that cached
35677 compilation units will be stored in memory longer, and more total
35678 memory will be used. Setting it to zero disables caching, which will
35679 slow down @value{GDBN} startup, but reduce memory consumption.
35681 @kindex maint set profile
35682 @kindex maint show profile
35683 @cindex profiling GDB
35684 @item maint set profile
35685 @itemx maint show profile
35686 Control profiling of @value{GDBN}.
35688 Profiling will be disabled until you use the @samp{maint set profile}
35689 command to enable it. When you enable profiling, the system will begin
35690 collecting timing and execution count data; when you disable profiling or
35691 exit @value{GDBN}, the results will be written to a log file. Remember that
35692 if you use profiling, @value{GDBN} will overwrite the profiling log file
35693 (often called @file{gmon.out}). If you have a record of important profiling
35694 data in a @file{gmon.out} file, be sure to move it to a safe location.
35696 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35697 compiled with the @samp{-pg} compiler option.
35699 @kindex maint set show-debug-regs
35700 @kindex maint show show-debug-regs
35701 @cindex hardware debug registers
35702 @item maint set show-debug-regs
35703 @itemx maint show show-debug-regs
35704 Control whether to show variables that mirror the hardware debug
35705 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35706 enabled, the debug registers values are shown when @value{GDBN} inserts or
35707 removes a hardware breakpoint or watchpoint, and when the inferior
35708 triggers a hardware-assisted breakpoint or watchpoint.
35710 @kindex maint set show-all-tib
35711 @kindex maint show show-all-tib
35712 @item maint set show-all-tib
35713 @itemx maint show show-all-tib
35714 Control whether to show all non zero areas within a 1k block starting
35715 at thread local base, when using the @samp{info w32 thread-information-block}
35718 @kindex maint set per-command
35719 @kindex maint show per-command
35720 @item maint set per-command
35721 @itemx maint show per-command
35722 @cindex resources used by commands
35724 @value{GDBN} can display the resources used by each command.
35725 This is useful in debugging performance problems.
35728 @item maint set per-command space [on|off]
35729 @itemx maint show per-command space
35730 Enable or disable the printing of the memory used by GDB for each command.
35731 If enabled, @value{GDBN} will display how much memory each command
35732 took, following the command's own output.
35733 This can also be requested by invoking @value{GDBN} with the
35734 @option{--statistics} command-line switch (@pxref{Mode Options}).
35736 @item maint set per-command time [on|off]
35737 @itemx maint show per-command time
35738 Enable or disable the printing of the execution time of @value{GDBN}
35740 If enabled, @value{GDBN} will display how much time it
35741 took to execute each command, following the command's own output.
35742 Both CPU time and wallclock time are printed.
35743 Printing both is useful when trying to determine whether the cost is
35744 CPU or, e.g., disk/network latency.
35745 Note that the CPU time printed is for @value{GDBN} only, it does not include
35746 the execution time of the inferior because there's no mechanism currently
35747 to compute how much time was spent by @value{GDBN} and how much time was
35748 spent by the program been debugged.
35749 This can also be requested by invoking @value{GDBN} with the
35750 @option{--statistics} command-line switch (@pxref{Mode Options}).
35752 @item maint set per-command symtab [on|off]
35753 @itemx maint show per-command symtab
35754 Enable or disable the printing of basic symbol table statistics
35756 If enabled, @value{GDBN} will display the following information:
35760 number of symbol tables
35762 number of primary symbol tables
35764 number of blocks in the blockvector
35768 @kindex maint space
35769 @cindex memory used by commands
35770 @item maint space @var{value}
35771 An alias for @code{maint set per-command space}.
35772 A non-zero value enables it, zero disables it.
35775 @cindex time of command execution
35776 @item maint time @var{value}
35777 An alias for @code{maint set per-command time}.
35778 A non-zero value enables it, zero disables it.
35780 @kindex maint translate-address
35781 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35782 Find the symbol stored at the location specified by the address
35783 @var{addr} and an optional section name @var{section}. If found,
35784 @value{GDBN} prints the name of the closest symbol and an offset from
35785 the symbol's location to the specified address. This is similar to
35786 the @code{info address} command (@pxref{Symbols}), except that this
35787 command also allows to find symbols in other sections.
35789 If section was not specified, the section in which the symbol was found
35790 is also printed. For dynamically linked executables, the name of
35791 executable or shared library containing the symbol is printed as well.
35795 The following command is useful for non-interactive invocations of
35796 @value{GDBN}, such as in the test suite.
35799 @item set watchdog @var{nsec}
35800 @kindex set watchdog
35801 @cindex watchdog timer
35802 @cindex timeout for commands
35803 Set the maximum number of seconds @value{GDBN} will wait for the
35804 target operation to finish. If this time expires, @value{GDBN}
35805 reports and error and the command is aborted.
35807 @item show watchdog
35808 Show the current setting of the target wait timeout.
35811 @node Remote Protocol
35812 @appendix @value{GDBN} Remote Serial Protocol
35817 * Stop Reply Packets::
35818 * General Query Packets::
35819 * Architecture-Specific Protocol Details::
35820 * Tracepoint Packets::
35821 * Host I/O Packets::
35823 * Notification Packets::
35824 * Remote Non-Stop::
35825 * Packet Acknowledgment::
35827 * File-I/O Remote Protocol Extension::
35828 * Library List Format::
35829 * Library List Format for SVR4 Targets::
35830 * Memory Map Format::
35831 * Thread List Format::
35832 * Traceframe Info Format::
35833 * Branch Trace Format::
35839 There may be occasions when you need to know something about the
35840 protocol---for example, if there is only one serial port to your target
35841 machine, you might want your program to do something special if it
35842 recognizes a packet meant for @value{GDBN}.
35844 In the examples below, @samp{->} and @samp{<-} are used to indicate
35845 transmitted and received data, respectively.
35847 @cindex protocol, @value{GDBN} remote serial
35848 @cindex serial protocol, @value{GDBN} remote
35849 @cindex remote serial protocol
35850 All @value{GDBN} commands and responses (other than acknowledgments
35851 and notifications, see @ref{Notification Packets}) are sent as a
35852 @var{packet}. A @var{packet} is introduced with the character
35853 @samp{$}, the actual @var{packet-data}, and the terminating character
35854 @samp{#} followed by a two-digit @var{checksum}:
35857 @code{$}@var{packet-data}@code{#}@var{checksum}
35861 @cindex checksum, for @value{GDBN} remote
35863 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35864 characters between the leading @samp{$} and the trailing @samp{#} (an
35865 eight bit unsigned checksum).
35867 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35868 specification also included an optional two-digit @var{sequence-id}:
35871 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35874 @cindex sequence-id, for @value{GDBN} remote
35876 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35877 has never output @var{sequence-id}s. Stubs that handle packets added
35878 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35880 When either the host or the target machine receives a packet, the first
35881 response expected is an acknowledgment: either @samp{+} (to indicate
35882 the package was received correctly) or @samp{-} (to request
35886 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35891 The @samp{+}/@samp{-} acknowledgments can be disabled
35892 once a connection is established.
35893 @xref{Packet Acknowledgment}, for details.
35895 The host (@value{GDBN}) sends @var{command}s, and the target (the
35896 debugging stub incorporated in your program) sends a @var{response}. In
35897 the case of step and continue @var{command}s, the response is only sent
35898 when the operation has completed, and the target has again stopped all
35899 threads in all attached processes. This is the default all-stop mode
35900 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35901 execution mode; see @ref{Remote Non-Stop}, for details.
35903 @var{packet-data} consists of a sequence of characters with the
35904 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35907 @cindex remote protocol, field separator
35908 Fields within the packet should be separated using @samp{,} @samp{;} or
35909 @samp{:}. Except where otherwise noted all numbers are represented in
35910 @sc{hex} with leading zeros suppressed.
35912 Implementors should note that prior to @value{GDBN} 5.0, the character
35913 @samp{:} could not appear as the third character in a packet (as it
35914 would potentially conflict with the @var{sequence-id}).
35916 @cindex remote protocol, binary data
35917 @anchor{Binary Data}
35918 Binary data in most packets is encoded either as two hexadecimal
35919 digits per byte of binary data. This allowed the traditional remote
35920 protocol to work over connections which were only seven-bit clean.
35921 Some packets designed more recently assume an eight-bit clean
35922 connection, and use a more efficient encoding to send and receive
35925 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35926 as an escape character. Any escaped byte is transmitted as the escape
35927 character followed by the original character XORed with @code{0x20}.
35928 For example, the byte @code{0x7d} would be transmitted as the two
35929 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35930 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35931 @samp{@}}) must always be escaped. Responses sent by the stub
35932 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35933 is not interpreted as the start of a run-length encoded sequence
35936 Response @var{data} can be run-length encoded to save space.
35937 Run-length encoding replaces runs of identical characters with one
35938 instance of the repeated character, followed by a @samp{*} and a
35939 repeat count. The repeat count is itself sent encoded, to avoid
35940 binary characters in @var{data}: a value of @var{n} is sent as
35941 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35942 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35943 code 32) for a repeat count of 3. (This is because run-length
35944 encoding starts to win for counts 3 or more.) Thus, for example,
35945 @samp{0* } is a run-length encoding of ``0000'': the space character
35946 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35949 The printable characters @samp{#} and @samp{$} or with a numeric value
35950 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35951 seven repeats (@samp{$}) can be expanded using a repeat count of only
35952 five (@samp{"}). For example, @samp{00000000} can be encoded as
35955 The error response returned for some packets includes a two character
35956 error number. That number is not well defined.
35958 @cindex empty response, for unsupported packets
35959 For any @var{command} not supported by the stub, an empty response
35960 (@samp{$#00}) should be returned. That way it is possible to extend the
35961 protocol. A newer @value{GDBN} can tell if a packet is supported based
35964 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35965 commands for register access, and the @samp{m} and @samp{M} commands
35966 for memory access. Stubs that only control single-threaded targets
35967 can implement run control with the @samp{c} (continue), and @samp{s}
35968 (step) commands. Stubs that support multi-threading targets should
35969 support the @samp{vCont} command. All other commands are optional.
35974 The following table provides a complete list of all currently defined
35975 @var{command}s and their corresponding response @var{data}.
35976 @xref{File-I/O Remote Protocol Extension}, for details about the File
35977 I/O extension of the remote protocol.
35979 Each packet's description has a template showing the packet's overall
35980 syntax, followed by an explanation of the packet's meaning. We
35981 include spaces in some of the templates for clarity; these are not
35982 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35983 separate its components. For example, a template like @samp{foo
35984 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35985 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35986 @var{baz}. @value{GDBN} does not transmit a space character between the
35987 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35990 @cindex @var{thread-id}, in remote protocol
35991 @anchor{thread-id syntax}
35992 Several packets and replies include a @var{thread-id} field to identify
35993 a thread. Normally these are positive numbers with a target-specific
35994 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35995 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35998 In addition, the remote protocol supports a multiprocess feature in
35999 which the @var{thread-id} syntax is extended to optionally include both
36000 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
36001 The @var{pid} (process) and @var{tid} (thread) components each have the
36002 format described above: a positive number with target-specific
36003 interpretation formatted as a big-endian hex string, literal @samp{-1}
36004 to indicate all processes or threads (respectively), or @samp{0} to
36005 indicate an arbitrary process or thread. Specifying just a process, as
36006 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
36007 error to specify all processes but a specific thread, such as
36008 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
36009 for those packets and replies explicitly documented to include a process
36010 ID, rather than a @var{thread-id}.
36012 The multiprocess @var{thread-id} syntax extensions are only used if both
36013 @value{GDBN} and the stub report support for the @samp{multiprocess}
36014 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
36017 Note that all packet forms beginning with an upper- or lower-case
36018 letter, other than those described here, are reserved for future use.
36020 Here are the packet descriptions.
36025 @cindex @samp{!} packet
36026 @anchor{extended mode}
36027 Enable extended mode. In extended mode, the remote server is made
36028 persistent. The @samp{R} packet is used to restart the program being
36034 The remote target both supports and has enabled extended mode.
36038 @cindex @samp{?} packet
36039 Indicate the reason the target halted. The reply is the same as for
36040 step and continue. This packet has a special interpretation when the
36041 target is in non-stop mode; see @ref{Remote Non-Stop}.
36044 @xref{Stop Reply Packets}, for the reply specifications.
36046 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36047 @cindex @samp{A} packet
36048 Initialized @code{argv[]} array passed into program. @var{arglen}
36049 specifies the number of bytes in the hex encoded byte stream
36050 @var{arg}. See @code{gdbserver} for more details.
36055 The arguments were set.
36061 @cindex @samp{b} packet
36062 (Don't use this packet; its behavior is not well-defined.)
36063 Change the serial line speed to @var{baud}.
36065 JTC: @emph{When does the transport layer state change? When it's
36066 received, or after the ACK is transmitted. In either case, there are
36067 problems if the command or the acknowledgment packet is dropped.}
36069 Stan: @emph{If people really wanted to add something like this, and get
36070 it working for the first time, they ought to modify ser-unix.c to send
36071 some kind of out-of-band message to a specially-setup stub and have the
36072 switch happen "in between" packets, so that from remote protocol's point
36073 of view, nothing actually happened.}
36075 @item B @var{addr},@var{mode}
36076 @cindex @samp{B} packet
36077 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36078 breakpoint at @var{addr}.
36080 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36081 (@pxref{insert breakpoint or watchpoint packet}).
36083 @cindex @samp{bc} packet
36086 Backward continue. Execute the target system in reverse. No parameter.
36087 @xref{Reverse Execution}, for more information.
36090 @xref{Stop Reply Packets}, for the reply specifications.
36092 @cindex @samp{bs} packet
36095 Backward single step. Execute one instruction in reverse. No parameter.
36096 @xref{Reverse Execution}, for more information.
36099 @xref{Stop Reply Packets}, for the reply specifications.
36101 @item c @r{[}@var{addr}@r{]}
36102 @cindex @samp{c} packet
36103 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
36104 resume at current address.
36106 This packet is deprecated for multi-threading support. @xref{vCont
36110 @xref{Stop Reply Packets}, for the reply specifications.
36112 @item C @var{sig}@r{[};@var{addr}@r{]}
36113 @cindex @samp{C} packet
36114 Continue with signal @var{sig} (hex signal number). If
36115 @samp{;@var{addr}} is omitted, resume at same address.
36117 This packet is deprecated for multi-threading support. @xref{vCont
36121 @xref{Stop Reply Packets}, for the reply specifications.
36124 @cindex @samp{d} packet
36127 Don't use this packet; instead, define a general set packet
36128 (@pxref{General Query Packets}).
36132 @cindex @samp{D} packet
36133 The first form of the packet is used to detach @value{GDBN} from the
36134 remote system. It is sent to the remote target
36135 before @value{GDBN} disconnects via the @code{detach} command.
36137 The second form, including a process ID, is used when multiprocess
36138 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36139 detach only a specific process. The @var{pid} is specified as a
36140 big-endian hex string.
36150 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36151 @cindex @samp{F} packet
36152 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36153 This is part of the File-I/O protocol extension. @xref{File-I/O
36154 Remote Protocol Extension}, for the specification.
36157 @anchor{read registers packet}
36158 @cindex @samp{g} packet
36159 Read general registers.
36163 @item @var{XX@dots{}}
36164 Each byte of register data is described by two hex digits. The bytes
36165 with the register are transmitted in target byte order. The size of
36166 each register and their position within the @samp{g} packet are
36167 determined by the @value{GDBN} internal gdbarch functions
36168 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
36169 specification of several standard @samp{g} packets is specified below.
36171 When reading registers from a trace frame (@pxref{Analyze Collected
36172 Data,,Using the Collected Data}), the stub may also return a string of
36173 literal @samp{x}'s in place of the register data digits, to indicate
36174 that the corresponding register has not been collected, thus its value
36175 is unavailable. For example, for an architecture with 4 registers of
36176 4 bytes each, the following reply indicates to @value{GDBN} that
36177 registers 0 and 2 have not been collected, while registers 1 and 3
36178 have been collected, and both have zero value:
36182 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36189 @item G @var{XX@dots{}}
36190 @cindex @samp{G} packet
36191 Write general registers. @xref{read registers packet}, for a
36192 description of the @var{XX@dots{}} data.
36202 @item H @var{op} @var{thread-id}
36203 @cindex @samp{H} packet
36204 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36205 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
36206 it should be @samp{c} for step and continue operations (note that this
36207 is deprecated, supporting the @samp{vCont} command is a better
36208 option), @samp{g} for other operations. The thread designator
36209 @var{thread-id} has the format and interpretation described in
36210 @ref{thread-id syntax}.
36221 @c 'H': How restrictive (or permissive) is the thread model. If a
36222 @c thread is selected and stopped, are other threads allowed
36223 @c to continue to execute? As I mentioned above, I think the
36224 @c semantics of each command when a thread is selected must be
36225 @c described. For example:
36227 @c 'g': If the stub supports threads and a specific thread is
36228 @c selected, returns the register block from that thread;
36229 @c otherwise returns current registers.
36231 @c 'G' If the stub supports threads and a specific thread is
36232 @c selected, sets the registers of the register block of
36233 @c that thread; otherwise sets current registers.
36235 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36236 @anchor{cycle step packet}
36237 @cindex @samp{i} packet
36238 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36239 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36240 step starting at that address.
36243 @cindex @samp{I} packet
36244 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36248 @cindex @samp{k} packet
36251 FIXME: @emph{There is no description of how to operate when a specific
36252 thread context has been selected (i.e.@: does 'k' kill only that
36255 @item m @var{addr},@var{length}
36256 @cindex @samp{m} packet
36257 Read @var{length} bytes of memory starting at address @var{addr}.
36258 Note that @var{addr} may not be aligned to any particular boundary.
36260 The stub need not use any particular size or alignment when gathering
36261 data from memory for the response; even if @var{addr} is word-aligned
36262 and @var{length} is a multiple of the word size, the stub is free to
36263 use byte accesses, or not. For this reason, this packet may not be
36264 suitable for accessing memory-mapped I/O devices.
36265 @cindex alignment of remote memory accesses
36266 @cindex size of remote memory accesses
36267 @cindex memory, alignment and size of remote accesses
36271 @item @var{XX@dots{}}
36272 Memory contents; each byte is transmitted as a two-digit hexadecimal
36273 number. The reply may contain fewer bytes than requested if the
36274 server was able to read only part of the region of memory.
36279 @item M @var{addr},@var{length}:@var{XX@dots{}}
36280 @cindex @samp{M} packet
36281 Write @var{length} bytes of memory starting at address @var{addr}.
36282 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
36283 hexadecimal number.
36290 for an error (this includes the case where only part of the data was
36295 @cindex @samp{p} packet
36296 Read the value of register @var{n}; @var{n} is in hex.
36297 @xref{read registers packet}, for a description of how the returned
36298 register value is encoded.
36302 @item @var{XX@dots{}}
36303 the register's value
36307 Indicating an unrecognized @var{query}.
36310 @item P @var{n@dots{}}=@var{r@dots{}}
36311 @anchor{write register packet}
36312 @cindex @samp{P} packet
36313 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36314 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36315 digits for each byte in the register (target byte order).
36325 @item q @var{name} @var{params}@dots{}
36326 @itemx Q @var{name} @var{params}@dots{}
36327 @cindex @samp{q} packet
36328 @cindex @samp{Q} packet
36329 General query (@samp{q}) and set (@samp{Q}). These packets are
36330 described fully in @ref{General Query Packets}.
36333 @cindex @samp{r} packet
36334 Reset the entire system.
36336 Don't use this packet; use the @samp{R} packet instead.
36339 @cindex @samp{R} packet
36340 Restart the program being debugged. @var{XX}, while needed, is ignored.
36341 This packet is only available in extended mode (@pxref{extended mode}).
36343 The @samp{R} packet has no reply.
36345 @item s @r{[}@var{addr}@r{]}
36346 @cindex @samp{s} packet
36347 Single step. @var{addr} is the address at which to resume. If
36348 @var{addr} is omitted, resume at same address.
36350 This packet is deprecated for multi-threading support. @xref{vCont
36354 @xref{Stop Reply Packets}, for the reply specifications.
36356 @item S @var{sig}@r{[};@var{addr}@r{]}
36357 @anchor{step with signal packet}
36358 @cindex @samp{S} packet
36359 Step with signal. This is analogous to the @samp{C} packet, but
36360 requests a single-step, rather than a normal resumption of execution.
36362 This packet is deprecated for multi-threading support. @xref{vCont
36366 @xref{Stop Reply Packets}, for the reply specifications.
36368 @item t @var{addr}:@var{PP},@var{MM}
36369 @cindex @samp{t} packet
36370 Search backwards starting at address @var{addr} for a match with pattern
36371 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
36372 @var{addr} must be at least 3 digits.
36374 @item T @var{thread-id}
36375 @cindex @samp{T} packet
36376 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36381 thread is still alive
36387 Packets starting with @samp{v} are identified by a multi-letter name,
36388 up to the first @samp{;} or @samp{?} (or the end of the packet).
36390 @item vAttach;@var{pid}
36391 @cindex @samp{vAttach} packet
36392 Attach to a new process with the specified process ID @var{pid}.
36393 The process ID is a
36394 hexadecimal integer identifying the process. In all-stop mode, all
36395 threads in the attached process are stopped; in non-stop mode, it may be
36396 attached without being stopped if that is supported by the target.
36398 @c In non-stop mode, on a successful vAttach, the stub should set the
36399 @c current thread to a thread of the newly-attached process. After
36400 @c attaching, GDB queries for the attached process's thread ID with qC.
36401 @c Also note that, from a user perspective, whether or not the
36402 @c target is stopped on attach in non-stop mode depends on whether you
36403 @c use the foreground or background version of the attach command, not
36404 @c on what vAttach does; GDB does the right thing with respect to either
36405 @c stopping or restarting threads.
36407 This packet is only available in extended mode (@pxref{extended mode}).
36413 @item @r{Any stop packet}
36414 for success in all-stop mode (@pxref{Stop Reply Packets})
36416 for success in non-stop mode (@pxref{Remote Non-Stop})
36419 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36420 @cindex @samp{vCont} packet
36421 @anchor{vCont packet}
36422 Resume the inferior, specifying different actions for each thread.
36423 If an action is specified with no @var{thread-id}, then it is applied to any
36424 threads that don't have a specific action specified; if no default action is
36425 specified then other threads should remain stopped in all-stop mode and
36426 in their current state in non-stop mode.
36427 Specifying multiple
36428 default actions is an error; specifying no actions is also an error.
36429 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36431 Currently supported actions are:
36437 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36441 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36446 The optional argument @var{addr} normally associated with the
36447 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36448 not supported in @samp{vCont}.
36450 The @samp{t} action is only relevant in non-stop mode
36451 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36452 A stop reply should be generated for any affected thread not already stopped.
36453 When a thread is stopped by means of a @samp{t} action,
36454 the corresponding stop reply should indicate that the thread has stopped with
36455 signal @samp{0}, regardless of whether the target uses some other signal
36456 as an implementation detail.
36458 The stub must support @samp{vCont} if it reports support for
36459 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36460 this case @samp{vCont} actions can be specified to apply to all threads
36461 in a process by using the @samp{p@var{pid}.-1} form of the
36465 @xref{Stop Reply Packets}, for the reply specifications.
36468 @cindex @samp{vCont?} packet
36469 Request a list of actions supported by the @samp{vCont} packet.
36473 @item vCont@r{[};@var{action}@dots{}@r{]}
36474 The @samp{vCont} packet is supported. Each @var{action} is a supported
36475 command in the @samp{vCont} packet.
36477 The @samp{vCont} packet is not supported.
36480 @item vFile:@var{operation}:@var{parameter}@dots{}
36481 @cindex @samp{vFile} packet
36482 Perform a file operation on the target system. For details,
36483 see @ref{Host I/O Packets}.
36485 @item vFlashErase:@var{addr},@var{length}
36486 @cindex @samp{vFlashErase} packet
36487 Direct the stub to erase @var{length} bytes of flash starting at
36488 @var{addr}. The region may enclose any number of flash blocks, but
36489 its start and end must fall on block boundaries, as indicated by the
36490 flash block size appearing in the memory map (@pxref{Memory Map
36491 Format}). @value{GDBN} groups flash memory programming operations
36492 together, and sends a @samp{vFlashDone} request after each group; the
36493 stub is allowed to delay erase operation until the @samp{vFlashDone}
36494 packet is received.
36504 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36505 @cindex @samp{vFlashWrite} packet
36506 Direct the stub to write data to flash address @var{addr}. The data
36507 is passed in binary form using the same encoding as for the @samp{X}
36508 packet (@pxref{Binary Data}). The memory ranges specified by
36509 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36510 not overlap, and must appear in order of increasing addresses
36511 (although @samp{vFlashErase} packets for higher addresses may already
36512 have been received; the ordering is guaranteed only between
36513 @samp{vFlashWrite} packets). If a packet writes to an address that was
36514 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36515 target-specific method, the results are unpredictable.
36523 for vFlashWrite addressing non-flash memory
36529 @cindex @samp{vFlashDone} packet
36530 Indicate to the stub that flash programming operation is finished.
36531 The stub is permitted to delay or batch the effects of a group of
36532 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36533 @samp{vFlashDone} packet is received. The contents of the affected
36534 regions of flash memory are unpredictable until the @samp{vFlashDone}
36535 request is completed.
36537 @item vKill;@var{pid}
36538 @cindex @samp{vKill} packet
36539 Kill the process with the specified process ID. @var{pid} is a
36540 hexadecimal integer identifying the process. This packet is used in
36541 preference to @samp{k} when multiprocess protocol extensions are
36542 supported; see @ref{multiprocess extensions}.
36552 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36553 @cindex @samp{vRun} packet
36554 Run the program @var{filename}, passing it each @var{argument} on its
36555 command line. The file and arguments are hex-encoded strings. If
36556 @var{filename} is an empty string, the stub may use a default program
36557 (e.g.@: the last program run). The program is created in the stopped
36560 @c FIXME: What about non-stop mode?
36562 This packet is only available in extended mode (@pxref{extended mode}).
36568 @item @r{Any stop packet}
36569 for success (@pxref{Stop Reply Packets})
36573 @cindex @samp{vStopped} packet
36574 @xref{Notification Packets}.
36576 @item X @var{addr},@var{length}:@var{XX@dots{}}
36578 @cindex @samp{X} packet
36579 Write data to memory, where the data is transmitted in binary.
36580 @var{addr} is address, @var{length} is number of bytes,
36581 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36591 @item z @var{type},@var{addr},@var{kind}
36592 @itemx Z @var{type},@var{addr},@var{kind}
36593 @anchor{insert breakpoint or watchpoint packet}
36594 @cindex @samp{z} packet
36595 @cindex @samp{Z} packets
36596 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36597 watchpoint starting at address @var{address} of kind @var{kind}.
36599 Each breakpoint and watchpoint packet @var{type} is documented
36602 @emph{Implementation notes: A remote target shall return an empty string
36603 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36604 remote target shall support either both or neither of a given
36605 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36606 avoid potential problems with duplicate packets, the operations should
36607 be implemented in an idempotent way.}
36609 @item z0,@var{addr},@var{kind}
36610 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36611 @cindex @samp{z0} packet
36612 @cindex @samp{Z0} packet
36613 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36614 @var{addr} of type @var{kind}.
36616 A memory breakpoint is implemented by replacing the instruction at
36617 @var{addr} with a software breakpoint or trap instruction. The
36618 @var{kind} is target-specific and typically indicates the size of
36619 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36620 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36621 architectures have additional meanings for @var{kind};
36622 @var{cond_list} is an optional list of conditional expressions in bytecode
36623 form that should be evaluated on the target's side. These are the
36624 conditions that should be taken into consideration when deciding if
36625 the breakpoint trigger should be reported back to @var{GDBN}.
36627 The @var{cond_list} parameter is comprised of a series of expressions,
36628 concatenated without separators. Each expression has the following form:
36632 @item X @var{len},@var{expr}
36633 @var{len} is the length of the bytecode expression and @var{expr} is the
36634 actual conditional expression in bytecode form.
36638 The optional @var{cmd_list} parameter introduces commands that may be
36639 run on the target, rather than being reported back to @value{GDBN}.
36640 The parameter starts with a numeric flag @var{persist}; if the flag is
36641 nonzero, then the breakpoint may remain active and the commands
36642 continue to be run even when @value{GDBN} disconnects from the target.
36643 Following this flag is a series of expressions concatenated with no
36644 separators. Each expression has the following form:
36648 @item X @var{len},@var{expr}
36649 @var{len} is the length of the bytecode expression and @var{expr} is the
36650 actual conditional expression in bytecode form.
36654 see @ref{Architecture-Specific Protocol Details}.
36656 @emph{Implementation note: It is possible for a target to copy or move
36657 code that contains memory breakpoints (e.g., when implementing
36658 overlays). The behavior of this packet, in the presence of such a
36659 target, is not defined.}
36671 @item z1,@var{addr},@var{kind}
36672 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36673 @cindex @samp{z1} packet
36674 @cindex @samp{Z1} packet
36675 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36676 address @var{addr}.
36678 A hardware breakpoint is implemented using a mechanism that is not
36679 dependant on being able to modify the target's memory. @var{kind}
36680 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36682 @emph{Implementation note: A hardware breakpoint is not affected by code
36695 @item z2,@var{addr},@var{kind}
36696 @itemx Z2,@var{addr},@var{kind}
36697 @cindex @samp{z2} packet
36698 @cindex @samp{Z2} packet
36699 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36700 @var{kind} is interpreted as the number of bytes to watch.
36712 @item z3,@var{addr},@var{kind}
36713 @itemx Z3,@var{addr},@var{kind}
36714 @cindex @samp{z3} packet
36715 @cindex @samp{Z3} packet
36716 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36717 @var{kind} is interpreted as the number of bytes to watch.
36729 @item z4,@var{addr},@var{kind}
36730 @itemx Z4,@var{addr},@var{kind}
36731 @cindex @samp{z4} packet
36732 @cindex @samp{Z4} packet
36733 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36734 @var{kind} is interpreted as the number of bytes to watch.
36748 @node Stop Reply Packets
36749 @section Stop Reply Packets
36750 @cindex stop reply packets
36752 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36753 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36754 receive any of the below as a reply. Except for @samp{?}
36755 and @samp{vStopped}, that reply is only returned
36756 when the target halts. In the below the exact meaning of @dfn{signal
36757 number} is defined by the header @file{include/gdb/signals.h} in the
36758 @value{GDBN} source code.
36760 As in the description of request packets, we include spaces in the
36761 reply templates for clarity; these are not part of the reply packet's
36762 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36768 The program received signal number @var{AA} (a two-digit hexadecimal
36769 number). This is equivalent to a @samp{T} response with no
36770 @var{n}:@var{r} pairs.
36772 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36773 @cindex @samp{T} packet reply
36774 The program received signal number @var{AA} (a two-digit hexadecimal
36775 number). This is equivalent to an @samp{S} response, except that the
36776 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36777 and other information directly in the stop reply packet, reducing
36778 round-trip latency. Single-step and breakpoint traps are reported
36779 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36783 If @var{n} is a hexadecimal number, it is a register number, and the
36784 corresponding @var{r} gives that register's value. @var{r} is a
36785 series of bytes in target byte order, with each byte given by a
36786 two-digit hex number.
36789 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36790 the stopped thread, as specified in @ref{thread-id syntax}.
36793 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36794 the core on which the stop event was detected.
36797 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36798 specific event that stopped the target. The currently defined stop
36799 reasons are listed below. @var{aa} should be @samp{05}, the trap
36800 signal. At most one stop reason should be present.
36803 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36804 and go on to the next; this allows us to extend the protocol in the
36808 The currently defined stop reasons are:
36814 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36817 @cindex shared library events, remote reply
36819 The packet indicates that the loaded libraries have changed.
36820 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36821 list of loaded libraries. @var{r} is ignored.
36823 @cindex replay log events, remote reply
36825 The packet indicates that the target cannot continue replaying
36826 logged execution events, because it has reached the end (or the
36827 beginning when executing backward) of the log. The value of @var{r}
36828 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36829 for more information.
36833 @itemx W @var{AA} ; process:@var{pid}
36834 The process exited, and @var{AA} is the exit status. This is only
36835 applicable to certain targets.
36837 The second form of the response, including the process ID of the exited
36838 process, can be used only when @value{GDBN} has reported support for
36839 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36840 The @var{pid} is formatted as a big-endian hex string.
36843 @itemx X @var{AA} ; process:@var{pid}
36844 The process terminated with signal @var{AA}.
36846 The second form of the response, including the process ID of the
36847 terminated process, can be used only when @value{GDBN} has reported
36848 support for multiprocess protocol extensions; see @ref{multiprocess
36849 extensions}. The @var{pid} is formatted as a big-endian hex string.
36851 @item O @var{XX}@dots{}
36852 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36853 written as the program's console output. This can happen at any time
36854 while the program is running and the debugger should continue to wait
36855 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36857 @item F @var{call-id},@var{parameter}@dots{}
36858 @var{call-id} is the identifier which says which host system call should
36859 be called. This is just the name of the function. Translation into the
36860 correct system call is only applicable as it's defined in @value{GDBN}.
36861 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36864 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36865 this very system call.
36867 The target replies with this packet when it expects @value{GDBN} to
36868 call a host system call on behalf of the target. @value{GDBN} replies
36869 with an appropriate @samp{F} packet and keeps up waiting for the next
36870 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36871 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36872 Protocol Extension}, for more details.
36876 @node General Query Packets
36877 @section General Query Packets
36878 @cindex remote query requests
36880 Packets starting with @samp{q} are @dfn{general query packets};
36881 packets starting with @samp{Q} are @dfn{general set packets}. General
36882 query and set packets are a semi-unified form for retrieving and
36883 sending information to and from the stub.
36885 The initial letter of a query or set packet is followed by a name
36886 indicating what sort of thing the packet applies to. For example,
36887 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36888 definitions with the stub. These packet names follow some
36893 The name must not contain commas, colons or semicolons.
36895 Most @value{GDBN} query and set packets have a leading upper case
36898 The names of custom vendor packets should use a company prefix, in
36899 lower case, followed by a period. For example, packets designed at
36900 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36901 foos) or @samp{Qacme.bar} (for setting bars).
36904 The name of a query or set packet should be separated from any
36905 parameters by a @samp{:}; the parameters themselves should be
36906 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36907 full packet name, and check for a separator or the end of the packet,
36908 in case two packet names share a common prefix. New packets should not begin
36909 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36910 packets predate these conventions, and have arguments without any terminator
36911 for the packet name; we suspect they are in widespread use in places that
36912 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36913 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36916 Like the descriptions of the other packets, each description here
36917 has a template showing the packet's overall syntax, followed by an
36918 explanation of the packet's meaning. We include spaces in some of the
36919 templates for clarity; these are not part of the packet's syntax. No
36920 @value{GDBN} packet uses spaces to separate its components.
36922 Here are the currently defined query and set packets:
36928 Turn on or off the agent as a helper to perform some debugging operations
36929 delegated from @value{GDBN} (@pxref{Control Agent}).
36931 @item QAllow:@var{op}:@var{val}@dots{}
36932 @cindex @samp{QAllow} packet
36933 Specify which operations @value{GDBN} expects to request of the
36934 target, as a semicolon-separated list of operation name and value
36935 pairs. Possible values for @var{op} include @samp{WriteReg},
36936 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36937 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36938 indicating that @value{GDBN} will not request the operation, or 1,
36939 indicating that it may. (The target can then use this to set up its
36940 own internals optimally, for instance if the debugger never expects to
36941 insert breakpoints, it may not need to install its own trap handler.)
36944 @cindex current thread, remote request
36945 @cindex @samp{qC} packet
36946 Return the current thread ID.
36950 @item QC @var{thread-id}
36951 Where @var{thread-id} is a thread ID as documented in
36952 @ref{thread-id syntax}.
36953 @item @r{(anything else)}
36954 Any other reply implies the old thread ID.
36957 @item qCRC:@var{addr},@var{length}
36958 @cindex CRC of memory block, remote request
36959 @cindex @samp{qCRC} packet
36960 Compute the CRC checksum of a block of memory using CRC-32 defined in
36961 IEEE 802.3. The CRC is computed byte at a time, taking the most
36962 significant bit of each byte first. The initial pattern code
36963 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36965 @emph{Note:} This is the same CRC used in validating separate debug
36966 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36967 Files}). However the algorithm is slightly different. When validating
36968 separate debug files, the CRC is computed taking the @emph{least}
36969 significant bit of each byte first, and the final result is inverted to
36970 detect trailing zeros.
36975 An error (such as memory fault)
36976 @item C @var{crc32}
36977 The specified memory region's checksum is @var{crc32}.
36980 @item QDisableRandomization:@var{value}
36981 @cindex disable address space randomization, remote request
36982 @cindex @samp{QDisableRandomization} packet
36983 Some target operating systems will randomize the virtual address space
36984 of the inferior process as a security feature, but provide a feature
36985 to disable such randomization, e.g.@: to allow for a more deterministic
36986 debugging experience. On such systems, this packet with a @var{value}
36987 of 1 directs the target to disable address space randomization for
36988 processes subsequently started via @samp{vRun} packets, while a packet
36989 with a @var{value} of 0 tells the target to enable address space
36992 This packet is only available in extended mode (@pxref{extended mode}).
36997 The request succeeded.
37000 An error occurred. @var{nn} are hex digits.
37003 An empty reply indicates that @samp{QDisableRandomization} is not supported
37007 This packet is not probed by default; the remote stub must request it,
37008 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37009 This should only be done on targets that actually support disabling
37010 address space randomization.
37013 @itemx qsThreadInfo
37014 @cindex list active threads, remote request
37015 @cindex @samp{qfThreadInfo} packet
37016 @cindex @samp{qsThreadInfo} packet
37017 Obtain a list of all active thread IDs from the target (OS). Since there
37018 may be too many active threads to fit into one reply packet, this query
37019 works iteratively: it may require more than one query/reply sequence to
37020 obtain the entire list of threads. The first query of the sequence will
37021 be the @samp{qfThreadInfo} query; subsequent queries in the
37022 sequence will be the @samp{qsThreadInfo} query.
37024 NOTE: This packet replaces the @samp{qL} query (see below).
37028 @item m @var{thread-id}
37030 @item m @var{thread-id},@var{thread-id}@dots{}
37031 a comma-separated list of thread IDs
37033 (lower case letter @samp{L}) denotes end of list.
37036 In response to each query, the target will reply with a list of one or
37037 more thread IDs, separated by commas.
37038 @value{GDBN} will respond to each reply with a request for more thread
37039 ids (using the @samp{qs} form of the query), until the target responds
37040 with @samp{l} (lower-case ell, for @dfn{last}).
37041 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37044 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37045 @cindex get thread-local storage address, remote request
37046 @cindex @samp{qGetTLSAddr} packet
37047 Fetch the address associated with thread local storage specified
37048 by @var{thread-id}, @var{offset}, and @var{lm}.
37050 @var{thread-id} is the thread ID associated with the
37051 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37053 @var{offset} is the (big endian, hex encoded) offset associated with the
37054 thread local variable. (This offset is obtained from the debug
37055 information associated with the variable.)
37057 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37058 load module associated with the thread local storage. For example,
37059 a @sc{gnu}/Linux system will pass the link map address of the shared
37060 object associated with the thread local storage under consideration.
37061 Other operating environments may choose to represent the load module
37062 differently, so the precise meaning of this parameter will vary.
37066 @item @var{XX}@dots{}
37067 Hex encoded (big endian) bytes representing the address of the thread
37068 local storage requested.
37071 An error occurred. @var{nn} are hex digits.
37074 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37077 @item qGetTIBAddr:@var{thread-id}
37078 @cindex get thread information block address
37079 @cindex @samp{qGetTIBAddr} packet
37080 Fetch address of the Windows OS specific Thread Information Block.
37082 @var{thread-id} is the thread ID associated with the thread.
37086 @item @var{XX}@dots{}
37087 Hex encoded (big endian) bytes representing the linear address of the
37088 thread information block.
37091 An error occured. This means that either the thread was not found, or the
37092 address could not be retrieved.
37095 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37098 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37099 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37100 digit) is one to indicate the first query and zero to indicate a
37101 subsequent query; @var{threadcount} (two hex digits) is the maximum
37102 number of threads the response packet can contain; and @var{nextthread}
37103 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37104 returned in the response as @var{argthread}.
37106 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37110 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37111 Where: @var{count} (two hex digits) is the number of threads being
37112 returned; @var{done} (one hex digit) is zero to indicate more threads
37113 and one indicates no further threads; @var{argthreadid} (eight hex
37114 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37115 is a sequence of thread IDs from the target. @var{threadid} (eight hex
37116 digits). See @code{remote.c:parse_threadlist_response()}.
37120 @cindex section offsets, remote request
37121 @cindex @samp{qOffsets} packet
37122 Get section offsets that the target used when relocating the downloaded
37127 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37128 Relocate the @code{Text} section by @var{xxx} from its original address.
37129 Relocate the @code{Data} section by @var{yyy} from its original address.
37130 If the object file format provides segment information (e.g.@: @sc{elf}
37131 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37132 segments by the supplied offsets.
37134 @emph{Note: while a @code{Bss} offset may be included in the response,
37135 @value{GDBN} ignores this and instead applies the @code{Data} offset
37136 to the @code{Bss} section.}
37138 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37139 Relocate the first segment of the object file, which conventionally
37140 contains program code, to a starting address of @var{xxx}. If
37141 @samp{DataSeg} is specified, relocate the second segment, which
37142 conventionally contains modifiable data, to a starting address of
37143 @var{yyy}. @value{GDBN} will report an error if the object file
37144 does not contain segment information, or does not contain at least
37145 as many segments as mentioned in the reply. Extra segments are
37146 kept at fixed offsets relative to the last relocated segment.
37149 @item qP @var{mode} @var{thread-id}
37150 @cindex thread information, remote request
37151 @cindex @samp{qP} packet
37152 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37153 encoded 32 bit mode; @var{thread-id} is a thread ID
37154 (@pxref{thread-id syntax}).
37156 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37159 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37163 @cindex non-stop mode, remote request
37164 @cindex @samp{QNonStop} packet
37166 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37167 @xref{Remote Non-Stop}, for more information.
37172 The request succeeded.
37175 An error occurred. @var{nn} are hex digits.
37178 An empty reply indicates that @samp{QNonStop} is not supported by
37182 This packet is not probed by default; the remote stub must request it,
37183 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37184 Use of this packet is controlled by the @code{set non-stop} command;
37185 @pxref{Non-Stop Mode}.
37187 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37188 @cindex pass signals to inferior, remote request
37189 @cindex @samp{QPassSignals} packet
37190 @anchor{QPassSignals}
37191 Each listed @var{signal} should be passed directly to the inferior process.
37192 Signals are numbered identically to continue packets and stop replies
37193 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37194 strictly greater than the previous item. These signals do not need to stop
37195 the inferior, or be reported to @value{GDBN}. All other signals should be
37196 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37197 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37198 new list. This packet improves performance when using @samp{handle
37199 @var{signal} nostop noprint pass}.
37204 The request succeeded.
37207 An error occurred. @var{nn} are hex digits.
37210 An empty reply indicates that @samp{QPassSignals} is not supported by
37214 Use of this packet is controlled by the @code{set remote pass-signals}
37215 command (@pxref{Remote Configuration, set remote pass-signals}).
37216 This packet is not probed by default; the remote stub must request it,
37217 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37219 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37220 @cindex signals the inferior may see, remote request
37221 @cindex @samp{QProgramSignals} packet
37222 @anchor{QProgramSignals}
37223 Each listed @var{signal} may be delivered to the inferior process.
37224 Others should be silently discarded.
37226 In some cases, the remote stub may need to decide whether to deliver a
37227 signal to the program or not without @value{GDBN} involvement. One
37228 example of that is while detaching --- the program's threads may have
37229 stopped for signals that haven't yet had a chance of being reported to
37230 @value{GDBN}, and so the remote stub can use the signal list specified
37231 by this packet to know whether to deliver or ignore those pending
37234 This does not influence whether to deliver a signal as requested by a
37235 resumption packet (@pxref{vCont packet}).
37237 Signals are numbered identically to continue packets and stop replies
37238 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37239 strictly greater than the previous item. Multiple
37240 @samp{QProgramSignals} packets do not combine; any earlier
37241 @samp{QProgramSignals} list is completely replaced by the new list.
37246 The request succeeded.
37249 An error occurred. @var{nn} are hex digits.
37252 An empty reply indicates that @samp{QProgramSignals} is not supported
37256 Use of this packet is controlled by the @code{set remote program-signals}
37257 command (@pxref{Remote Configuration, set remote program-signals}).
37258 This packet is not probed by default; the remote stub must request it,
37259 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37261 @item qRcmd,@var{command}
37262 @cindex execute remote command, remote request
37263 @cindex @samp{qRcmd} packet
37264 @var{command} (hex encoded) is passed to the local interpreter for
37265 execution. Invalid commands should be reported using the output
37266 string. Before the final result packet, the target may also respond
37267 with a number of intermediate @samp{O@var{output}} console output
37268 packets. @emph{Implementors should note that providing access to a
37269 stubs's interpreter may have security implications}.
37274 A command response with no output.
37276 A command response with the hex encoded output string @var{OUTPUT}.
37278 Indicate a badly formed request.
37280 An empty reply indicates that @samp{qRcmd} is not recognized.
37283 (Note that the @code{qRcmd} packet's name is separated from the
37284 command by a @samp{,}, not a @samp{:}, contrary to the naming
37285 conventions above. Please don't use this packet as a model for new
37288 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37289 @cindex searching memory, in remote debugging
37291 @cindex @samp{qSearch:memory} packet
37293 @cindex @samp{qSearch memory} packet
37294 @anchor{qSearch memory}
37295 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37296 @var{address} and @var{length} are encoded in hex.
37297 @var{search-pattern} is a sequence of bytes, hex encoded.
37302 The pattern was not found.
37304 The pattern was found at @var{address}.
37306 A badly formed request or an error was encountered while searching memory.
37308 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37311 @item QStartNoAckMode
37312 @cindex @samp{QStartNoAckMode} packet
37313 @anchor{QStartNoAckMode}
37314 Request that the remote stub disable the normal @samp{+}/@samp{-}
37315 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37320 The stub has switched to no-acknowledgment mode.
37321 @value{GDBN} acknowledges this reponse,
37322 but neither the stub nor @value{GDBN} shall send or expect further
37323 @samp{+}/@samp{-} acknowledgments in the current connection.
37325 An empty reply indicates that the stub does not support no-acknowledgment mode.
37328 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37329 @cindex supported packets, remote query
37330 @cindex features of the remote protocol
37331 @cindex @samp{qSupported} packet
37332 @anchor{qSupported}
37333 Tell the remote stub about features supported by @value{GDBN}, and
37334 query the stub for features it supports. This packet allows
37335 @value{GDBN} and the remote stub to take advantage of each others'
37336 features. @samp{qSupported} also consolidates multiple feature probes
37337 at startup, to improve @value{GDBN} performance---a single larger
37338 packet performs better than multiple smaller probe packets on
37339 high-latency links. Some features may enable behavior which must not
37340 be on by default, e.g.@: because it would confuse older clients or
37341 stubs. Other features may describe packets which could be
37342 automatically probed for, but are not. These features must be
37343 reported before @value{GDBN} will use them. This ``default
37344 unsupported'' behavior is not appropriate for all packets, but it
37345 helps to keep the initial connection time under control with new
37346 versions of @value{GDBN} which support increasing numbers of packets.
37350 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37351 The stub supports or does not support each returned @var{stubfeature},
37352 depending on the form of each @var{stubfeature} (see below for the
37355 An empty reply indicates that @samp{qSupported} is not recognized,
37356 or that no features needed to be reported to @value{GDBN}.
37359 The allowed forms for each feature (either a @var{gdbfeature} in the
37360 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37364 @item @var{name}=@var{value}
37365 The remote protocol feature @var{name} is supported, and associated
37366 with the specified @var{value}. The format of @var{value} depends
37367 on the feature, but it must not include a semicolon.
37369 The remote protocol feature @var{name} is supported, and does not
37370 need an associated value.
37372 The remote protocol feature @var{name} is not supported.
37374 The remote protocol feature @var{name} may be supported, and
37375 @value{GDBN} should auto-detect support in some other way when it is
37376 needed. This form will not be used for @var{gdbfeature} notifications,
37377 but may be used for @var{stubfeature} responses.
37380 Whenever the stub receives a @samp{qSupported} request, the
37381 supplied set of @value{GDBN} features should override any previous
37382 request. This allows @value{GDBN} to put the stub in a known
37383 state, even if the stub had previously been communicating with
37384 a different version of @value{GDBN}.
37386 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37391 This feature indicates whether @value{GDBN} supports multiprocess
37392 extensions to the remote protocol. @value{GDBN} does not use such
37393 extensions unless the stub also reports that it supports them by
37394 including @samp{multiprocess+} in its @samp{qSupported} reply.
37395 @xref{multiprocess extensions}, for details.
37398 This feature indicates that @value{GDBN} supports the XML target
37399 description. If the stub sees @samp{xmlRegisters=} with target
37400 specific strings separated by a comma, it will report register
37404 This feature indicates whether @value{GDBN} supports the
37405 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37406 instruction reply packet}).
37409 Stubs should ignore any unknown values for
37410 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37411 packet supports receiving packets of unlimited length (earlier
37412 versions of @value{GDBN} may reject overly long responses). Additional values
37413 for @var{gdbfeature} may be defined in the future to let the stub take
37414 advantage of new features in @value{GDBN}, e.g.@: incompatible
37415 improvements in the remote protocol---the @samp{multiprocess} feature is
37416 an example of such a feature. The stub's reply should be independent
37417 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37418 describes all the features it supports, and then the stub replies with
37419 all the features it supports.
37421 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37422 responses, as long as each response uses one of the standard forms.
37424 Some features are flags. A stub which supports a flag feature
37425 should respond with a @samp{+} form response. Other features
37426 require values, and the stub should respond with an @samp{=}
37429 Each feature has a default value, which @value{GDBN} will use if
37430 @samp{qSupported} is not available or if the feature is not mentioned
37431 in the @samp{qSupported} response. The default values are fixed; a
37432 stub is free to omit any feature responses that match the defaults.
37434 Not all features can be probed, but for those which can, the probing
37435 mechanism is useful: in some cases, a stub's internal
37436 architecture may not allow the protocol layer to know some information
37437 about the underlying target in advance. This is especially common in
37438 stubs which may be configured for multiple targets.
37440 These are the currently defined stub features and their properties:
37442 @multitable @columnfractions 0.35 0.2 0.12 0.2
37443 @c NOTE: The first row should be @headitem, but we do not yet require
37444 @c a new enough version of Texinfo (4.7) to use @headitem.
37446 @tab Value Required
37450 @item @samp{PacketSize}
37455 @item @samp{qXfer:auxv:read}
37460 @item @samp{qXfer:btrace:read}
37465 @item @samp{qXfer:features:read}
37470 @item @samp{qXfer:libraries:read}
37475 @item @samp{qXfer:memory-map:read}
37480 @item @samp{qXfer:sdata:read}
37485 @item @samp{qXfer:spu:read}
37490 @item @samp{qXfer:spu:write}
37495 @item @samp{qXfer:siginfo:read}
37500 @item @samp{qXfer:siginfo:write}
37505 @item @samp{qXfer:threads:read}
37510 @item @samp{qXfer:traceframe-info:read}
37515 @item @samp{qXfer:uib:read}
37520 @item @samp{qXfer:fdpic:read}
37525 @item @samp{Qbtrace:off}
37530 @item @samp{Qbtrace:bts}
37535 @item @samp{QNonStop}
37540 @item @samp{QPassSignals}
37545 @item @samp{QStartNoAckMode}
37550 @item @samp{multiprocess}
37555 @item @samp{ConditionalBreakpoints}
37560 @item @samp{ConditionalTracepoints}
37565 @item @samp{ReverseContinue}
37570 @item @samp{ReverseStep}
37575 @item @samp{TracepointSource}
37580 @item @samp{QAgent}
37585 @item @samp{QAllow}
37590 @item @samp{QDisableRandomization}
37595 @item @samp{EnableDisableTracepoints}
37600 @item @samp{QTBuffer:size}
37605 @item @samp{tracenz}
37610 @item @samp{BreakpointCommands}
37617 These are the currently defined stub features, in more detail:
37620 @cindex packet size, remote protocol
37621 @item PacketSize=@var{bytes}
37622 The remote stub can accept packets up to at least @var{bytes} in
37623 length. @value{GDBN} will send packets up to this size for bulk
37624 transfers, and will never send larger packets. This is a limit on the
37625 data characters in the packet, including the frame and checksum.
37626 There is no trailing NUL byte in a remote protocol packet; if the stub
37627 stores packets in a NUL-terminated format, it should allow an extra
37628 byte in its buffer for the NUL. If this stub feature is not supported,
37629 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37631 @item qXfer:auxv:read
37632 The remote stub understands the @samp{qXfer:auxv:read} packet
37633 (@pxref{qXfer auxiliary vector read}).
37635 @item qXfer:btrace:read
37636 The remote stub understands the @samp{qXfer:btrace:read}
37637 packet (@pxref{qXfer btrace read}).
37639 @item qXfer:features:read
37640 The remote stub understands the @samp{qXfer:features:read} packet
37641 (@pxref{qXfer target description read}).
37643 @item qXfer:libraries:read
37644 The remote stub understands the @samp{qXfer:libraries:read} packet
37645 (@pxref{qXfer library list read}).
37647 @item qXfer:libraries-svr4:read
37648 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37649 (@pxref{qXfer svr4 library list read}).
37651 @item qXfer:memory-map:read
37652 The remote stub understands the @samp{qXfer:memory-map:read} packet
37653 (@pxref{qXfer memory map read}).
37655 @item qXfer:sdata:read
37656 The remote stub understands the @samp{qXfer:sdata:read} packet
37657 (@pxref{qXfer sdata read}).
37659 @item qXfer:spu:read
37660 The remote stub understands the @samp{qXfer:spu:read} packet
37661 (@pxref{qXfer spu read}).
37663 @item qXfer:spu:write
37664 The remote stub understands the @samp{qXfer:spu:write} packet
37665 (@pxref{qXfer spu write}).
37667 @item qXfer:siginfo:read
37668 The remote stub understands the @samp{qXfer:siginfo:read} packet
37669 (@pxref{qXfer siginfo read}).
37671 @item qXfer:siginfo:write
37672 The remote stub understands the @samp{qXfer:siginfo:write} packet
37673 (@pxref{qXfer siginfo write}).
37675 @item qXfer:threads:read
37676 The remote stub understands the @samp{qXfer:threads:read} packet
37677 (@pxref{qXfer threads read}).
37679 @item qXfer:traceframe-info:read
37680 The remote stub understands the @samp{qXfer:traceframe-info:read}
37681 packet (@pxref{qXfer traceframe info read}).
37683 @item qXfer:uib:read
37684 The remote stub understands the @samp{qXfer:uib:read}
37685 packet (@pxref{qXfer unwind info block}).
37687 @item qXfer:fdpic:read
37688 The remote stub understands the @samp{qXfer:fdpic:read}
37689 packet (@pxref{qXfer fdpic loadmap read}).
37692 The remote stub understands the @samp{QNonStop} packet
37693 (@pxref{QNonStop}).
37696 The remote stub understands the @samp{QPassSignals} packet
37697 (@pxref{QPassSignals}).
37699 @item QStartNoAckMode
37700 The remote stub understands the @samp{QStartNoAckMode} packet and
37701 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37704 @anchor{multiprocess extensions}
37705 @cindex multiprocess extensions, in remote protocol
37706 The remote stub understands the multiprocess extensions to the remote
37707 protocol syntax. The multiprocess extensions affect the syntax of
37708 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37709 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37710 replies. Note that reporting this feature indicates support for the
37711 syntactic extensions only, not that the stub necessarily supports
37712 debugging of more than one process at a time. The stub must not use
37713 multiprocess extensions in packet replies unless @value{GDBN} has also
37714 indicated it supports them in its @samp{qSupported} request.
37716 @item qXfer:osdata:read
37717 The remote stub understands the @samp{qXfer:osdata:read} packet
37718 ((@pxref{qXfer osdata read}).
37720 @item ConditionalBreakpoints
37721 The target accepts and implements evaluation of conditional expressions
37722 defined for breakpoints. The target will only report breakpoint triggers
37723 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37725 @item ConditionalTracepoints
37726 The remote stub accepts and implements conditional expressions defined
37727 for tracepoints (@pxref{Tracepoint Conditions}).
37729 @item ReverseContinue
37730 The remote stub accepts and implements the reverse continue packet
37734 The remote stub accepts and implements the reverse step packet
37737 @item TracepointSource
37738 The remote stub understands the @samp{QTDPsrc} packet that supplies
37739 the source form of tracepoint definitions.
37742 The remote stub understands the @samp{QAgent} packet.
37745 The remote stub understands the @samp{QAllow} packet.
37747 @item QDisableRandomization
37748 The remote stub understands the @samp{QDisableRandomization} packet.
37750 @item StaticTracepoint
37751 @cindex static tracepoints, in remote protocol
37752 The remote stub supports static tracepoints.
37754 @item InstallInTrace
37755 @anchor{install tracepoint in tracing}
37756 The remote stub supports installing tracepoint in tracing.
37758 @item EnableDisableTracepoints
37759 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37760 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37761 to be enabled and disabled while a trace experiment is running.
37763 @item QTBuffer:size
37764 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37765 packet that allows to change the size of the trace buffer.
37768 @cindex string tracing, in remote protocol
37769 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37770 See @ref{Bytecode Descriptions} for details about the bytecode.
37772 @item BreakpointCommands
37773 @cindex breakpoint commands, in remote protocol
37774 The remote stub supports running a breakpoint's command list itself,
37775 rather than reporting the hit to @value{GDBN}.
37778 The remote stub understands the @samp{Qbtrace:off} packet.
37781 The remote stub understands the @samp{Qbtrace:bts} packet.
37786 @cindex symbol lookup, remote request
37787 @cindex @samp{qSymbol} packet
37788 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37789 requests. Accept requests from the target for the values of symbols.
37794 The target does not need to look up any (more) symbols.
37795 @item qSymbol:@var{sym_name}
37796 The target requests the value of symbol @var{sym_name} (hex encoded).
37797 @value{GDBN} may provide the value by using the
37798 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37802 @item qSymbol:@var{sym_value}:@var{sym_name}
37803 Set the value of @var{sym_name} to @var{sym_value}.
37805 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37806 target has previously requested.
37808 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37809 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37815 The target does not need to look up any (more) symbols.
37816 @item qSymbol:@var{sym_name}
37817 The target requests the value of a new symbol @var{sym_name} (hex
37818 encoded). @value{GDBN} will continue to supply the values of symbols
37819 (if available), until the target ceases to request them.
37824 @itemx QTDisconnected
37831 @itemx qTMinFTPILen
37833 @xref{Tracepoint Packets}.
37835 @item qThreadExtraInfo,@var{thread-id}
37836 @cindex thread attributes info, remote request
37837 @cindex @samp{qThreadExtraInfo} packet
37838 Obtain a printable string description of a thread's attributes from
37839 the target OS. @var{thread-id} is a thread ID;
37840 see @ref{thread-id syntax}. This
37841 string may contain anything that the target OS thinks is interesting
37842 for @value{GDBN} to tell the user about the thread. The string is
37843 displayed in @value{GDBN}'s @code{info threads} display. Some
37844 examples of possible thread extra info strings are @samp{Runnable}, or
37845 @samp{Blocked on Mutex}.
37849 @item @var{XX}@dots{}
37850 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37851 comprising the printable string containing the extra information about
37852 the thread's attributes.
37855 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37856 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37857 conventions above. Please don't use this packet as a model for new
37876 @xref{Tracepoint Packets}.
37878 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37879 @cindex read special object, remote request
37880 @cindex @samp{qXfer} packet
37881 @anchor{qXfer read}
37882 Read uninterpreted bytes from the target's special data area
37883 identified by the keyword @var{object}. Request @var{length} bytes
37884 starting at @var{offset} bytes into the data. The content and
37885 encoding of @var{annex} is specific to @var{object}; it can supply
37886 additional details about what data to access.
37888 Here are the specific requests of this form defined so far. All
37889 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37890 formats, listed below.
37893 @item qXfer:auxv:read::@var{offset},@var{length}
37894 @anchor{qXfer auxiliary vector read}
37895 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37896 auxiliary vector}. Note @var{annex} must be empty.
37898 This packet is not probed by default; the remote stub must request it,
37899 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37901 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37902 @anchor{qXfer btrace read}
37904 Return a description of the current branch trace.
37905 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37906 packet may have one of the following values:
37910 Returns all available branch trace.
37913 Returns all available branch trace if the branch trace changed since
37914 the last read request.
37917 This packet is not probed by default; the remote stub must request it
37918 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37920 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37921 @anchor{qXfer target description read}
37922 Access the @dfn{target description}. @xref{Target Descriptions}. The
37923 annex specifies which XML document to access. The main description is
37924 always loaded from the @samp{target.xml} annex.
37926 This packet is not probed by default; the remote stub must request it,
37927 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37929 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37930 @anchor{qXfer library list read}
37931 Access the target's list of loaded libraries. @xref{Library List Format}.
37932 The annex part of the generic @samp{qXfer} packet must be empty
37933 (@pxref{qXfer read}).
37935 Targets which maintain a list of libraries in the program's memory do
37936 not need to implement this packet; it is designed for platforms where
37937 the operating system manages the list of loaded libraries.
37939 This packet is not probed by default; the remote stub must request it,
37940 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37942 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37943 @anchor{qXfer svr4 library list read}
37944 Access the target's list of loaded libraries when the target is an SVR4
37945 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37946 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37948 This packet is optional for better performance on SVR4 targets.
37949 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37951 This packet is not probed by default; the remote stub must request it,
37952 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37954 @item qXfer:memory-map:read::@var{offset},@var{length}
37955 @anchor{qXfer memory map read}
37956 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37957 annex part of the generic @samp{qXfer} packet must be empty
37958 (@pxref{qXfer read}).
37960 This packet is not probed by default; the remote stub must request it,
37961 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37963 @item qXfer:sdata:read::@var{offset},@var{length}
37964 @anchor{qXfer sdata read}
37966 Read contents of the extra collected static tracepoint marker
37967 information. The annex part of the generic @samp{qXfer} packet must
37968 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37971 This packet is not probed by default; the remote stub must request it,
37972 by supplying an appropriate @samp{qSupported} response
37973 (@pxref{qSupported}).
37975 @item qXfer:siginfo:read::@var{offset},@var{length}
37976 @anchor{qXfer siginfo read}
37977 Read contents of the extra signal information on the target
37978 system. The annex part of the generic @samp{qXfer} packet must be
37979 empty (@pxref{qXfer read}).
37981 This packet is not probed by default; the remote stub must request it,
37982 by supplying an appropriate @samp{qSupported} response
37983 (@pxref{qSupported}).
37985 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37986 @anchor{qXfer spu read}
37987 Read contents of an @code{spufs} file on the target system. The
37988 annex specifies which file to read; it must be of the form
37989 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37990 in the target process, and @var{name} identifes the @code{spufs} file
37991 in that context to be accessed.
37993 This packet is not probed by default; the remote stub must request it,
37994 by supplying an appropriate @samp{qSupported} response
37995 (@pxref{qSupported}).
37997 @item qXfer:threads:read::@var{offset},@var{length}
37998 @anchor{qXfer threads read}
37999 Access the list of threads on target. @xref{Thread List Format}. The
38000 annex part of the generic @samp{qXfer} packet must be empty
38001 (@pxref{qXfer read}).
38003 This packet is not probed by default; the remote stub must request it,
38004 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38006 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38007 @anchor{qXfer traceframe info read}
38009 Return a description of the current traceframe's contents.
38010 @xref{Traceframe Info Format}. The annex part of the generic
38011 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38013 This packet is not probed by default; the remote stub must request it,
38014 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38016 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38017 @anchor{qXfer unwind info block}
38019 Return the unwind information block for @var{pc}. This packet is used
38020 on OpenVMS/ia64 to ask the kernel unwind information.
38022 This packet is not probed by default.
38024 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38025 @anchor{qXfer fdpic loadmap read}
38026 Read contents of @code{loadmap}s on the target system. The
38027 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38028 executable @code{loadmap} or interpreter @code{loadmap} to read.
38030 This packet is not probed by default; the remote stub must request it,
38031 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38033 @item qXfer:osdata:read::@var{offset},@var{length}
38034 @anchor{qXfer osdata read}
38035 Access the target's @dfn{operating system information}.
38036 @xref{Operating System Information}.
38043 Data @var{data} (@pxref{Binary Data}) has been read from the
38044 target. There may be more data at a higher address (although
38045 it is permitted to return @samp{m} even for the last valid
38046 block of data, as long as at least one byte of data was read).
38047 @var{data} may have fewer bytes than the @var{length} in the
38051 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38052 There is no more data to be read. @var{data} may have fewer bytes
38053 than the @var{length} in the request.
38056 The @var{offset} in the request is at the end of the data.
38057 There is no more data to be read.
38060 The request was malformed, or @var{annex} was invalid.
38063 The offset was invalid, or there was an error encountered reading the data.
38064 @var{nn} is a hex-encoded @code{errno} value.
38067 An empty reply indicates the @var{object} string was not recognized by
38068 the stub, or that the object does not support reading.
38071 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38072 @cindex write data into object, remote request
38073 @anchor{qXfer write}
38074 Write uninterpreted bytes into the target's special data area
38075 identified by the keyword @var{object}, starting at @var{offset} bytes
38076 into the data. @var{data}@dots{} is the binary-encoded data
38077 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
38078 is specific to @var{object}; it can supply additional details about what data
38081 Here are the specific requests of this form defined so far. All
38082 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38083 formats, listed below.
38086 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38087 @anchor{qXfer siginfo write}
38088 Write @var{data} to the extra signal information on the target system.
38089 The annex part of the generic @samp{qXfer} packet must be
38090 empty (@pxref{qXfer write}).
38092 This packet is not probed by default; the remote stub must request it,
38093 by supplying an appropriate @samp{qSupported} response
38094 (@pxref{qSupported}).
38096 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38097 @anchor{qXfer spu write}
38098 Write @var{data} to an @code{spufs} file on the target system. The
38099 annex specifies which file to write; it must be of the form
38100 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38101 in the target process, and @var{name} identifes the @code{spufs} file
38102 in that context to be accessed.
38104 This packet is not probed by default; the remote stub must request it,
38105 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38111 @var{nn} (hex encoded) is the number of bytes written.
38112 This may be fewer bytes than supplied in the request.
38115 The request was malformed, or @var{annex} was invalid.
38118 The offset was invalid, or there was an error encountered writing the data.
38119 @var{nn} is a hex-encoded @code{errno} value.
38122 An empty reply indicates the @var{object} string was not
38123 recognized by the stub, or that the object does not support writing.
38126 @item qXfer:@var{object}:@var{operation}:@dots{}
38127 Requests of this form may be added in the future. When a stub does
38128 not recognize the @var{object} keyword, or its support for
38129 @var{object} does not recognize the @var{operation} keyword, the stub
38130 must respond with an empty packet.
38132 @item qAttached:@var{pid}
38133 @cindex query attached, remote request
38134 @cindex @samp{qAttached} packet
38135 Return an indication of whether the remote server attached to an
38136 existing process or created a new process. When the multiprocess
38137 protocol extensions are supported (@pxref{multiprocess extensions}),
38138 @var{pid} is an integer in hexadecimal format identifying the target
38139 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38140 the query packet will be simplified as @samp{qAttached}.
38142 This query is used, for example, to know whether the remote process
38143 should be detached or killed when a @value{GDBN} session is ended with
38144 the @code{quit} command.
38149 The remote server attached to an existing process.
38151 The remote server created a new process.
38153 A badly formed request or an error was encountered.
38157 Enable branch tracing for the current thread using bts tracing.
38162 Branch tracing has been enabled.
38164 A badly formed request or an error was encountered.
38168 Disable branch tracing for the current thread.
38173 Branch tracing has been disabled.
38175 A badly formed request or an error was encountered.
38180 @node Architecture-Specific Protocol Details
38181 @section Architecture-Specific Protocol Details
38183 This section describes how the remote protocol is applied to specific
38184 target architectures. Also see @ref{Standard Target Features}, for
38185 details of XML target descriptions for each architecture.
38188 * ARM-Specific Protocol Details::
38189 * MIPS-Specific Protocol Details::
38192 @node ARM-Specific Protocol Details
38193 @subsection @acronym{ARM}-specific Protocol Details
38196 * ARM Breakpoint Kinds::
38199 @node ARM Breakpoint Kinds
38200 @subsubsection @acronym{ARM} Breakpoint Kinds
38201 @cindex breakpoint kinds, @acronym{ARM}
38203 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38208 16-bit Thumb mode breakpoint.
38211 32-bit Thumb mode (Thumb-2) breakpoint.
38214 32-bit @acronym{ARM} mode breakpoint.
38218 @node MIPS-Specific Protocol Details
38219 @subsection @acronym{MIPS}-specific Protocol Details
38222 * MIPS Register packet Format::
38223 * MIPS Breakpoint Kinds::
38226 @node MIPS Register packet Format
38227 @subsubsection @acronym{MIPS} Register Packet Format
38228 @cindex register packet format, @acronym{MIPS}
38230 The following @code{g}/@code{G} packets have previously been defined.
38231 In the below, some thirty-two bit registers are transferred as
38232 sixty-four bits. Those registers should be zero/sign extended (which?)
38233 to fill the space allocated. Register bytes are transferred in target
38234 byte order. The two nibbles within a register byte are transferred
38235 most-significant -- least-significant.
38240 All registers are transferred as thirty-two bit quantities in the order:
38241 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38242 registers; fsr; fir; fp.
38245 All registers are transferred as sixty-four bit quantities (including
38246 thirty-two bit registers such as @code{sr}). The ordering is the same
38251 @node MIPS Breakpoint Kinds
38252 @subsubsection @acronym{MIPS} Breakpoint Kinds
38253 @cindex breakpoint kinds, @acronym{MIPS}
38255 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38260 16-bit @acronym{MIPS16} mode breakpoint.
38263 16-bit @acronym{microMIPS} mode breakpoint.
38266 32-bit standard @acronym{MIPS} mode breakpoint.
38269 32-bit @acronym{microMIPS} mode breakpoint.
38273 @node Tracepoint Packets
38274 @section Tracepoint Packets
38275 @cindex tracepoint packets
38276 @cindex packets, tracepoint
38278 Here we describe the packets @value{GDBN} uses to implement
38279 tracepoints (@pxref{Tracepoints}).
38283 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38284 @cindex @samp{QTDP} packet
38285 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38286 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38287 the tracepoint is disabled. @var{step} is the tracepoint's step
38288 count, and @var{pass} is its pass count. If an @samp{F} is present,
38289 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38290 the number of bytes that the target should copy elsewhere to make room
38291 for the tracepoint. If an @samp{X} is present, it introduces a
38292 tracepoint condition, which consists of a hexadecimal length, followed
38293 by a comma and hex-encoded bytes, in a manner similar to action
38294 encodings as described below. If the trailing @samp{-} is present,
38295 further @samp{QTDP} packets will follow to specify this tracepoint's
38301 The packet was understood and carried out.
38303 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38305 The packet was not recognized.
38308 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38309 Define actions to be taken when a tracepoint is hit. @var{n} and
38310 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38311 this tracepoint. This packet may only be sent immediately after
38312 another @samp{QTDP} packet that ended with a @samp{-}. If the
38313 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38314 specifying more actions for this tracepoint.
38316 In the series of action packets for a given tracepoint, at most one
38317 can have an @samp{S} before its first @var{action}. If such a packet
38318 is sent, it and the following packets define ``while-stepping''
38319 actions. Any prior packets define ordinary actions --- that is, those
38320 taken when the tracepoint is first hit. If no action packet has an
38321 @samp{S}, then all the packets in the series specify ordinary
38322 tracepoint actions.
38324 The @samp{@var{action}@dots{}} portion of the packet is a series of
38325 actions, concatenated without separators. Each action has one of the
38331 Collect the registers whose bits are set in @var{mask}. @var{mask} is
38332 a hexadecimal number whose @var{i}'th bit is set if register number
38333 @var{i} should be collected. (The least significant bit is numbered
38334 zero.) Note that @var{mask} may be any number of digits long; it may
38335 not fit in a 32-bit word.
38337 @item M @var{basereg},@var{offset},@var{len}
38338 Collect @var{len} bytes of memory starting at the address in register
38339 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38340 @samp{-1}, then the range has a fixed address: @var{offset} is the
38341 address of the lowest byte to collect. The @var{basereg},
38342 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38343 values (the @samp{-1} value for @var{basereg} is a special case).
38345 @item X @var{len},@var{expr}
38346 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38347 it directs. @var{expr} is an agent expression, as described in
38348 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38349 two-digit hex number in the packet; @var{len} is the number of bytes
38350 in the expression (and thus one-half the number of hex digits in the
38355 Any number of actions may be packed together in a single @samp{QTDP}
38356 packet, as long as the packet does not exceed the maximum packet
38357 length (400 bytes, for many stubs). There may be only one @samp{R}
38358 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38359 actions. Any registers referred to by @samp{M} and @samp{X} actions
38360 must be collected by a preceding @samp{R} action. (The
38361 ``while-stepping'' actions are treated as if they were attached to a
38362 separate tracepoint, as far as these restrictions are concerned.)
38367 The packet was understood and carried out.
38369 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38371 The packet was not recognized.
38374 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38375 @cindex @samp{QTDPsrc} packet
38376 Specify a source string of tracepoint @var{n} at address @var{addr}.
38377 This is useful to get accurate reproduction of the tracepoints
38378 originally downloaded at the beginning of the trace run. @var{type}
38379 is the name of the tracepoint part, such as @samp{cond} for the
38380 tracepoint's conditional expression (see below for a list of types), while
38381 @var{bytes} is the string, encoded in hexadecimal.
38383 @var{start} is the offset of the @var{bytes} within the overall source
38384 string, while @var{slen} is the total length of the source string.
38385 This is intended for handling source strings that are longer than will
38386 fit in a single packet.
38387 @c Add detailed example when this info is moved into a dedicated
38388 @c tracepoint descriptions section.
38390 The available string types are @samp{at} for the location,
38391 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38392 @value{GDBN} sends a separate packet for each command in the action
38393 list, in the same order in which the commands are stored in the list.
38395 The target does not need to do anything with source strings except
38396 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38399 Although this packet is optional, and @value{GDBN} will only send it
38400 if the target replies with @samp{TracepointSource} @xref{General
38401 Query Packets}, it makes both disconnected tracing and trace files
38402 much easier to use. Otherwise the user must be careful that the
38403 tracepoints in effect while looking at trace frames are identical to
38404 the ones in effect during the trace run; even a small discrepancy
38405 could cause @samp{tdump} not to work, or a particular trace frame not
38408 @item QTDV:@var{n}:@var{value}
38409 @cindex define trace state variable, remote request
38410 @cindex @samp{QTDV} packet
38411 Create a new trace state variable, number @var{n}, with an initial
38412 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38413 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38414 the option of not using this packet for initial values of zero; the
38415 target should simply create the trace state variables as they are
38416 mentioned in expressions.
38418 @item QTFrame:@var{n}
38419 @cindex @samp{QTFrame} packet
38420 Select the @var{n}'th tracepoint frame from the buffer, and use the
38421 register and memory contents recorded there to answer subsequent
38422 request packets from @value{GDBN}.
38424 A successful reply from the stub indicates that the stub has found the
38425 requested frame. The response is a series of parts, concatenated
38426 without separators, describing the frame we selected. Each part has
38427 one of the following forms:
38431 The selected frame is number @var{n} in the trace frame buffer;
38432 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38433 was no frame matching the criteria in the request packet.
38436 The selected trace frame records a hit of tracepoint number @var{t};
38437 @var{t} is a hexadecimal number.
38441 @item QTFrame:pc:@var{addr}
38442 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38443 currently selected frame whose PC is @var{addr};
38444 @var{addr} is a hexadecimal number.
38446 @item QTFrame:tdp:@var{t}
38447 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38448 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38449 is a hexadecimal number.
38451 @item QTFrame:range:@var{start}:@var{end}
38452 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38453 currently selected frame whose PC is between @var{start} (inclusive)
38454 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38457 @item QTFrame:outside:@var{start}:@var{end}
38458 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38459 frame @emph{outside} the given range of addresses (exclusive).
38462 @cindex @samp{qTMinFTPILen} packet
38463 This packet requests the minimum length of instruction at which a fast
38464 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38465 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38466 it depends on the target system being able to create trampolines in
38467 the first 64K of memory, which might or might not be possible for that
38468 system. So the reply to this packet will be 4 if it is able to
38475 The minimum instruction length is currently unknown.
38477 The minimum instruction length is @var{length}, where @var{length} is greater
38478 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
38479 that a fast tracepoint may be placed on any instruction regardless of size.
38481 An error has occurred.
38483 An empty reply indicates that the request is not supported by the stub.
38487 @cindex @samp{QTStart} packet
38488 Begin the tracepoint experiment. Begin collecting data from
38489 tracepoint hits in the trace frame buffer. This packet supports the
38490 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38491 instruction reply packet}).
38494 @cindex @samp{QTStop} packet
38495 End the tracepoint experiment. Stop collecting trace frames.
38497 @item QTEnable:@var{n}:@var{addr}
38499 @cindex @samp{QTEnable} packet
38500 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38501 experiment. If the tracepoint was previously disabled, then collection
38502 of data from it will resume.
38504 @item QTDisable:@var{n}:@var{addr}
38506 @cindex @samp{QTDisable} packet
38507 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38508 experiment. No more data will be collected from the tracepoint unless
38509 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38512 @cindex @samp{QTinit} packet
38513 Clear the table of tracepoints, and empty the trace frame buffer.
38515 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38516 @cindex @samp{QTro} packet
38517 Establish the given ranges of memory as ``transparent''. The stub
38518 will answer requests for these ranges from memory's current contents,
38519 if they were not collected as part of the tracepoint hit.
38521 @value{GDBN} uses this to mark read-only regions of memory, like those
38522 containing program code. Since these areas never change, they should
38523 still have the same contents they did when the tracepoint was hit, so
38524 there's no reason for the stub to refuse to provide their contents.
38526 @item QTDisconnected:@var{value}
38527 @cindex @samp{QTDisconnected} packet
38528 Set the choice to what to do with the tracing run when @value{GDBN}
38529 disconnects from the target. A @var{value} of 1 directs the target to
38530 continue the tracing run, while 0 tells the target to stop tracing if
38531 @value{GDBN} is no longer in the picture.
38534 @cindex @samp{qTStatus} packet
38535 Ask the stub if there is a trace experiment running right now.
38537 The reply has the form:
38541 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38542 @var{running} is a single digit @code{1} if the trace is presently
38543 running, or @code{0} if not. It is followed by semicolon-separated
38544 optional fields that an agent may use to report additional status.
38548 If the trace is not running, the agent may report any of several
38549 explanations as one of the optional fields:
38554 No trace has been run yet.
38556 @item tstop[:@var{text}]:0
38557 The trace was stopped by a user-originated stop command. The optional
38558 @var{text} field is a user-supplied string supplied as part of the
38559 stop command (for instance, an explanation of why the trace was
38560 stopped manually). It is hex-encoded.
38563 The trace stopped because the trace buffer filled up.
38565 @item tdisconnected:0
38566 The trace stopped because @value{GDBN} disconnected from the target.
38568 @item tpasscount:@var{tpnum}
38569 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38571 @item terror:@var{text}:@var{tpnum}
38572 The trace stopped because tracepoint @var{tpnum} had an error. The
38573 string @var{text} is available to describe the nature of the error
38574 (for instance, a divide by zero in the condition expression).
38575 @var{text} is hex encoded.
38578 The trace stopped for some other reason.
38582 Additional optional fields supply statistical and other information.
38583 Although not required, they are extremely useful for users monitoring
38584 the progress of a trace run. If a trace has stopped, and these
38585 numbers are reported, they must reflect the state of the just-stopped
38590 @item tframes:@var{n}
38591 The number of trace frames in the buffer.
38593 @item tcreated:@var{n}
38594 The total number of trace frames created during the run. This may
38595 be larger than the trace frame count, if the buffer is circular.
38597 @item tsize:@var{n}
38598 The total size of the trace buffer, in bytes.
38600 @item tfree:@var{n}
38601 The number of bytes still unused in the buffer.
38603 @item circular:@var{n}
38604 The value of the circular trace buffer flag. @code{1} means that the
38605 trace buffer is circular and old trace frames will be discarded if
38606 necessary to make room, @code{0} means that the trace buffer is linear
38609 @item disconn:@var{n}
38610 The value of the disconnected tracing flag. @code{1} means that
38611 tracing will continue after @value{GDBN} disconnects, @code{0} means
38612 that the trace run will stop.
38616 @item qTP:@var{tp}:@var{addr}
38617 @cindex tracepoint status, remote request
38618 @cindex @samp{qTP} packet
38619 Ask the stub for the current state of tracepoint number @var{tp} at
38620 address @var{addr}.
38624 @item V@var{hits}:@var{usage}
38625 The tracepoint has been hit @var{hits} times so far during the trace
38626 run, and accounts for @var{usage} in the trace buffer. Note that
38627 @code{while-stepping} steps are not counted as separate hits, but the
38628 steps' space consumption is added into the usage number.
38632 @item qTV:@var{var}
38633 @cindex trace state variable value, remote request
38634 @cindex @samp{qTV} packet
38635 Ask the stub for the value of the trace state variable number @var{var}.
38640 The value of the variable is @var{value}. This will be the current
38641 value of the variable if the user is examining a running target, or a
38642 saved value if the variable was collected in the trace frame that the
38643 user is looking at. Note that multiple requests may result in
38644 different reply values, such as when requesting values while the
38645 program is running.
38648 The value of the variable is unknown. This would occur, for example,
38649 if the user is examining a trace frame in which the requested variable
38654 @cindex @samp{qTfP} packet
38656 @cindex @samp{qTsP} packet
38657 These packets request data about tracepoints that are being used by
38658 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38659 of data, and multiple @code{qTsP} to get additional pieces. Replies
38660 to these packets generally take the form of the @code{QTDP} packets
38661 that define tracepoints. (FIXME add detailed syntax)
38664 @cindex @samp{qTfV} packet
38666 @cindex @samp{qTsV} packet
38667 These packets request data about trace state variables that are on the
38668 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38669 and multiple @code{qTsV} to get additional variables. Replies to
38670 these packets follow the syntax of the @code{QTDV} packets that define
38671 trace state variables.
38677 @cindex @samp{qTfSTM} packet
38678 @cindex @samp{qTsSTM} packet
38679 These packets request data about static tracepoint markers that exist
38680 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38681 first piece of data, and multiple @code{qTsSTM} to get additional
38682 pieces. Replies to these packets take the following form:
38686 @item m @var{address}:@var{id}:@var{extra}
38688 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38689 a comma-separated list of markers
38691 (lower case letter @samp{L}) denotes end of list.
38693 An error occurred. @var{nn} are hex digits.
38695 An empty reply indicates that the request is not supported by the
38699 @var{address} is encoded in hex.
38700 @var{id} and @var{extra} are strings encoded in hex.
38702 In response to each query, the target will reply with a list of one or
38703 more markers, separated by commas. @value{GDBN} will respond to each
38704 reply with a request for more markers (using the @samp{qs} form of the
38705 query), until the target responds with @samp{l} (lower-case ell, for
38708 @item qTSTMat:@var{address}
38710 @cindex @samp{qTSTMat} packet
38711 This packets requests data about static tracepoint markers in the
38712 target program at @var{address}. Replies to this packet follow the
38713 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38714 tracepoint markers.
38716 @item QTSave:@var{filename}
38717 @cindex @samp{QTSave} packet
38718 This packet directs the target to save trace data to the file name
38719 @var{filename} in the target's filesystem. @var{filename} is encoded
38720 as a hex string; the interpretation of the file name (relative vs
38721 absolute, wild cards, etc) is up to the target.
38723 @item qTBuffer:@var{offset},@var{len}
38724 @cindex @samp{qTBuffer} packet
38725 Return up to @var{len} bytes of the current contents of trace buffer,
38726 starting at @var{offset}. The trace buffer is treated as if it were
38727 a contiguous collection of traceframes, as per the trace file format.
38728 The reply consists as many hex-encoded bytes as the target can deliver
38729 in a packet; it is not an error to return fewer than were asked for.
38730 A reply consisting of just @code{l} indicates that no bytes are
38733 @item QTBuffer:circular:@var{value}
38734 This packet directs the target to use a circular trace buffer if
38735 @var{value} is 1, or a linear buffer if the value is 0.
38737 @item QTBuffer:size:@var{size}
38738 @anchor{QTBuffer-size}
38739 @cindex @samp{QTBuffer size} packet
38740 This packet directs the target to make the trace buffer be of size
38741 @var{size} if possible. A value of @code{-1} tells the target to
38742 use whatever size it prefers.
38744 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38745 @cindex @samp{QTNotes} packet
38746 This packet adds optional textual notes to the trace run. Allowable
38747 types include @code{user}, @code{notes}, and @code{tstop}, the
38748 @var{text} fields are arbitrary strings, hex-encoded.
38752 @subsection Relocate instruction reply packet
38753 When installing fast tracepoints in memory, the target may need to
38754 relocate the instruction currently at the tracepoint address to a
38755 different address in memory. For most instructions, a simple copy is
38756 enough, but, for example, call instructions that implicitly push the
38757 return address on the stack, and relative branches or other
38758 PC-relative instructions require offset adjustment, so that the effect
38759 of executing the instruction at a different address is the same as if
38760 it had executed in the original location.
38762 In response to several of the tracepoint packets, the target may also
38763 respond with a number of intermediate @samp{qRelocInsn} request
38764 packets before the final result packet, to have @value{GDBN} handle
38765 this relocation operation. If a packet supports this mechanism, its
38766 documentation will explicitly say so. See for example the above
38767 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38768 format of the request is:
38771 @item qRelocInsn:@var{from};@var{to}
38773 This requests @value{GDBN} to copy instruction at address @var{from}
38774 to address @var{to}, possibly adjusted so that executing the
38775 instruction at @var{to} has the same effect as executing it at
38776 @var{from}. @value{GDBN} writes the adjusted instruction to target
38777 memory starting at @var{to}.
38782 @item qRelocInsn:@var{adjusted_size}
38783 Informs the stub the relocation is complete. @var{adjusted_size} is
38784 the length in bytes of resulting relocated instruction sequence.
38786 A badly formed request was detected, or an error was encountered while
38787 relocating the instruction.
38790 @node Host I/O Packets
38791 @section Host I/O Packets
38792 @cindex Host I/O, remote protocol
38793 @cindex file transfer, remote protocol
38795 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38796 operations on the far side of a remote link. For example, Host I/O is
38797 used to upload and download files to a remote target with its own
38798 filesystem. Host I/O uses the same constant values and data structure
38799 layout as the target-initiated File-I/O protocol. However, the
38800 Host I/O packets are structured differently. The target-initiated
38801 protocol relies on target memory to store parameters and buffers.
38802 Host I/O requests are initiated by @value{GDBN}, and the
38803 target's memory is not involved. @xref{File-I/O Remote Protocol
38804 Extension}, for more details on the target-initiated protocol.
38806 The Host I/O request packets all encode a single operation along with
38807 its arguments. They have this format:
38811 @item vFile:@var{operation}: @var{parameter}@dots{}
38812 @var{operation} is the name of the particular request; the target
38813 should compare the entire packet name up to the second colon when checking
38814 for a supported operation. The format of @var{parameter} depends on
38815 the operation. Numbers are always passed in hexadecimal. Negative
38816 numbers have an explicit minus sign (i.e.@: two's complement is not
38817 used). Strings (e.g.@: filenames) are encoded as a series of
38818 hexadecimal bytes. The last argument to a system call may be a
38819 buffer of escaped binary data (@pxref{Binary Data}).
38823 The valid responses to Host I/O packets are:
38827 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38828 @var{result} is the integer value returned by this operation, usually
38829 non-negative for success and -1 for errors. If an error has occured,
38830 @var{errno} will be included in the result. @var{errno} will have a
38831 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38832 operations which return data, @var{attachment} supplies the data as a
38833 binary buffer. Binary buffers in response packets are escaped in the
38834 normal way (@pxref{Binary Data}). See the individual packet
38835 documentation for the interpretation of @var{result} and
38839 An empty response indicates that this operation is not recognized.
38843 These are the supported Host I/O operations:
38846 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38847 Open a file at @var{pathname} and return a file descriptor for it, or
38848 return -1 if an error occurs. @var{pathname} is a string,
38849 @var{flags} is an integer indicating a mask of open flags
38850 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38851 of mode bits to use if the file is created (@pxref{mode_t Values}).
38852 @xref{open}, for details of the open flags and mode values.
38854 @item vFile:close: @var{fd}
38855 Close the open file corresponding to @var{fd} and return 0, or
38856 -1 if an error occurs.
38858 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38859 Read data from the open file corresponding to @var{fd}. Up to
38860 @var{count} bytes will be read from the file, starting at @var{offset}
38861 relative to the start of the file. The target may read fewer bytes;
38862 common reasons include packet size limits and an end-of-file
38863 condition. The number of bytes read is returned. Zero should only be
38864 returned for a successful read at the end of the file, or if
38865 @var{count} was zero.
38867 The data read should be returned as a binary attachment on success.
38868 If zero bytes were read, the response should include an empty binary
38869 attachment (i.e.@: a trailing semicolon). The return value is the
38870 number of target bytes read; the binary attachment may be longer if
38871 some characters were escaped.
38873 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38874 Write @var{data} (a binary buffer) to the open file corresponding
38875 to @var{fd}. Start the write at @var{offset} from the start of the
38876 file. Unlike many @code{write} system calls, there is no
38877 separate @var{count} argument; the length of @var{data} in the
38878 packet is used. @samp{vFile:write} returns the number of bytes written,
38879 which may be shorter than the length of @var{data}, or -1 if an
38882 @item vFile:unlink: @var{pathname}
38883 Delete the file at @var{pathname} on the target. Return 0,
38884 or -1 if an error occurs. @var{pathname} is a string.
38886 @item vFile:readlink: @var{filename}
38887 Read value of symbolic link @var{filename} on the target. Return
38888 the number of bytes read, or -1 if an error occurs.
38890 The data read should be returned as a binary attachment on success.
38891 If zero bytes were read, the response should include an empty binary
38892 attachment (i.e.@: a trailing semicolon). The return value is the
38893 number of target bytes read; the binary attachment may be longer if
38894 some characters were escaped.
38899 @section Interrupts
38900 @cindex interrupts (remote protocol)
38902 When a program on the remote target is running, @value{GDBN} may
38903 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38904 a @code{BREAK} followed by @code{g},
38905 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38907 The precise meaning of @code{BREAK} is defined by the transport
38908 mechanism and may, in fact, be undefined. @value{GDBN} does not
38909 currently define a @code{BREAK} mechanism for any of the network
38910 interfaces except for TCP, in which case @value{GDBN} sends the
38911 @code{telnet} BREAK sequence.
38913 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38914 transport mechanisms. It is represented by sending the single byte
38915 @code{0x03} without any of the usual packet overhead described in
38916 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38917 transmitted as part of a packet, it is considered to be packet data
38918 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38919 (@pxref{X packet}), used for binary downloads, may include an unescaped
38920 @code{0x03} as part of its packet.
38922 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38923 When Linux kernel receives this sequence from serial port,
38924 it stops execution and connects to gdb.
38926 Stubs are not required to recognize these interrupt mechanisms and the
38927 precise meaning associated with receipt of the interrupt is
38928 implementation defined. If the target supports debugging of multiple
38929 threads and/or processes, it should attempt to interrupt all
38930 currently-executing threads and processes.
38931 If the stub is successful at interrupting the
38932 running program, it should send one of the stop
38933 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38934 of successfully stopping the program in all-stop mode, and a stop reply
38935 for each stopped thread in non-stop mode.
38936 Interrupts received while the
38937 program is stopped are discarded.
38939 @node Notification Packets
38940 @section Notification Packets
38941 @cindex notification packets
38942 @cindex packets, notification
38944 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38945 packets that require no acknowledgment. Both the GDB and the stub
38946 may send notifications (although the only notifications defined at
38947 present are sent by the stub). Notifications carry information
38948 without incurring the round-trip latency of an acknowledgment, and so
38949 are useful for low-impact communications where occasional packet loss
38952 A notification packet has the form @samp{% @var{data} #
38953 @var{checksum}}, where @var{data} is the content of the notification,
38954 and @var{checksum} is a checksum of @var{data}, computed and formatted
38955 as for ordinary @value{GDBN} packets. A notification's @var{data}
38956 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38957 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38958 to acknowledge the notification's receipt or to report its corruption.
38960 Every notification's @var{data} begins with a name, which contains no
38961 colon characters, followed by a colon character.
38963 Recipients should silently ignore corrupted notifications and
38964 notifications they do not understand. Recipients should restart
38965 timeout periods on receipt of a well-formed notification, whether or
38966 not they understand it.
38968 Senders should only send the notifications described here when this
38969 protocol description specifies that they are permitted. In the
38970 future, we may extend the protocol to permit existing notifications in
38971 new contexts; this rule helps older senders avoid confusing newer
38974 (Older versions of @value{GDBN} ignore bytes received until they see
38975 the @samp{$} byte that begins an ordinary packet, so new stubs may
38976 transmit notifications without fear of confusing older clients. There
38977 are no notifications defined for @value{GDBN} to send at the moment, but we
38978 assume that most older stubs would ignore them, as well.)
38980 Each notification is comprised of three parts:
38982 @item @var{name}:@var{event}
38983 The notification packet is sent by the side that initiates the
38984 exchange (currently, only the stub does that), with @var{event}
38985 carrying the specific information about the notification.
38986 @var{name} is the name of the notification.
38988 The acknowledge sent by the other side, usually @value{GDBN}, to
38989 acknowledge the exchange and request the event.
38992 The purpose of an asynchronous notification mechanism is to report to
38993 @value{GDBN} that something interesting happened in the remote stub.
38995 The remote stub may send notification @var{name}:@var{event}
38996 at any time, but @value{GDBN} acknowledges the notification when
38997 appropriate. The notification event is pending before @value{GDBN}
38998 acknowledges. Only one notification at a time may be pending; if
38999 additional events occur before @value{GDBN} has acknowledged the
39000 previous notification, they must be queued by the stub for later
39001 synchronous transmission in response to @var{ack} packets from
39002 @value{GDBN}. Because the notification mechanism is unreliable,
39003 the stub is permitted to resend a notification if it believes
39004 @value{GDBN} may not have received it.
39006 Specifically, notifications may appear when @value{GDBN} is not
39007 otherwise reading input from the stub, or when @value{GDBN} is
39008 expecting to read a normal synchronous response or a
39009 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39010 Notification packets are distinct from any other communication from
39011 the stub so there is no ambiguity.
39013 After receiving a notification, @value{GDBN} shall acknowledge it by
39014 sending a @var{ack} packet as a regular, synchronous request to the
39015 stub. Such acknowledgment is not required to happen immediately, as
39016 @value{GDBN} is permitted to send other, unrelated packets to the
39017 stub first, which the stub should process normally.
39019 Upon receiving a @var{ack} packet, if the stub has other queued
39020 events to report to @value{GDBN}, it shall respond by sending a
39021 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39022 packet to solicit further responses; again, it is permitted to send
39023 other, unrelated packets as well which the stub should process
39026 If the stub receives a @var{ack} packet and there are no additional
39027 @var{event} to report, the stub shall return an @samp{OK} response.
39028 At this point, @value{GDBN} has finished processing a notification
39029 and the stub has completed sending any queued events. @value{GDBN}
39030 won't accept any new notifications until the final @samp{OK} is
39031 received . If further notification events occur, the stub shall send
39032 a new notification, @value{GDBN} shall accept the notification, and
39033 the process shall be repeated.
39035 The process of asynchronous notification can be illustrated by the
39038 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39041 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39043 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39048 The following notifications are defined:
39049 @multitable @columnfractions 0.12 0.12 0.38 0.38
39058 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39059 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39060 for information on how these notifications are acknowledged by
39062 @tab Report an asynchronous stop event in non-stop mode.
39066 @node Remote Non-Stop
39067 @section Remote Protocol Support for Non-Stop Mode
39069 @value{GDBN}'s remote protocol supports non-stop debugging of
39070 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39071 supports non-stop mode, it should report that to @value{GDBN} by including
39072 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39074 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39075 establishing a new connection with the stub. Entering non-stop mode
39076 does not alter the state of any currently-running threads, but targets
39077 must stop all threads in any already-attached processes when entering
39078 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39079 probe the target state after a mode change.
39081 In non-stop mode, when an attached process encounters an event that
39082 would otherwise be reported with a stop reply, it uses the
39083 asynchronous notification mechanism (@pxref{Notification Packets}) to
39084 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39085 in all processes are stopped when a stop reply is sent, in non-stop
39086 mode only the thread reporting the stop event is stopped. That is,
39087 when reporting a @samp{S} or @samp{T} response to indicate completion
39088 of a step operation, hitting a breakpoint, or a fault, only the
39089 affected thread is stopped; any other still-running threads continue
39090 to run. When reporting a @samp{W} or @samp{X} response, all running
39091 threads belonging to other attached processes continue to run.
39093 In non-stop mode, the target shall respond to the @samp{?} packet as
39094 follows. First, any incomplete stop reply notification/@samp{vStopped}
39095 sequence in progress is abandoned. The target must begin a new
39096 sequence reporting stop events for all stopped threads, whether or not
39097 it has previously reported those events to @value{GDBN}. The first
39098 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39099 subsequent stop replies are sent as responses to @samp{vStopped} packets
39100 using the mechanism described above. The target must not send
39101 asynchronous stop reply notifications until the sequence is complete.
39102 If all threads are running when the target receives the @samp{?} packet,
39103 or if the target is not attached to any process, it shall respond
39106 @node Packet Acknowledgment
39107 @section Packet Acknowledgment
39109 @cindex acknowledgment, for @value{GDBN} remote
39110 @cindex packet acknowledgment, for @value{GDBN} remote
39111 By default, when either the host or the target machine receives a packet,
39112 the first response expected is an acknowledgment: either @samp{+} (to indicate
39113 the package was received correctly) or @samp{-} (to request retransmission).
39114 This mechanism allows the @value{GDBN} remote protocol to operate over
39115 unreliable transport mechanisms, such as a serial line.
39117 In cases where the transport mechanism is itself reliable (such as a pipe or
39118 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39119 It may be desirable to disable them in that case to reduce communication
39120 overhead, or for other reasons. This can be accomplished by means of the
39121 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39123 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39124 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39125 and response format still includes the normal checksum, as described in
39126 @ref{Overview}, but the checksum may be ignored by the receiver.
39128 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39129 no-acknowledgment mode, it should report that to @value{GDBN}
39130 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39131 @pxref{qSupported}.
39132 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39133 disabled via the @code{set remote noack-packet off} command
39134 (@pxref{Remote Configuration}),
39135 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39136 Only then may the stub actually turn off packet acknowledgments.
39137 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39138 response, which can be safely ignored by the stub.
39140 Note that @code{set remote noack-packet} command only affects negotiation
39141 between @value{GDBN} and the stub when subsequent connections are made;
39142 it does not affect the protocol acknowledgment state for any current
39144 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39145 new connection is established,
39146 there is also no protocol request to re-enable the acknowledgments
39147 for the current connection, once disabled.
39152 Example sequence of a target being re-started. Notice how the restart
39153 does not get any direct output:
39158 @emph{target restarts}
39161 <- @code{T001:1234123412341234}
39165 Example sequence of a target being stepped by a single instruction:
39168 -> @code{G1445@dots{}}
39173 <- @code{T001:1234123412341234}
39177 <- @code{1455@dots{}}
39181 @node File-I/O Remote Protocol Extension
39182 @section File-I/O Remote Protocol Extension
39183 @cindex File-I/O remote protocol extension
39186 * File-I/O Overview::
39187 * Protocol Basics::
39188 * The F Request Packet::
39189 * The F Reply Packet::
39190 * The Ctrl-C Message::
39192 * List of Supported Calls::
39193 * Protocol-specific Representation of Datatypes::
39195 * File-I/O Examples::
39198 @node File-I/O Overview
39199 @subsection File-I/O Overview
39200 @cindex file-i/o overview
39202 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39203 target to use the host's file system and console I/O to perform various
39204 system calls. System calls on the target system are translated into a
39205 remote protocol packet to the host system, which then performs the needed
39206 actions and returns a response packet to the target system.
39207 This simulates file system operations even on targets that lack file systems.
39209 The protocol is defined to be independent of both the host and target systems.
39210 It uses its own internal representation of datatypes and values. Both
39211 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39212 translating the system-dependent value representations into the internal
39213 protocol representations when data is transmitted.
39215 The communication is synchronous. A system call is possible only when
39216 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39217 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39218 the target is stopped to allow deterministic access to the target's
39219 memory. Therefore File-I/O is not interruptible by target signals. On
39220 the other hand, it is possible to interrupt File-I/O by a user interrupt
39221 (@samp{Ctrl-C}) within @value{GDBN}.
39223 The target's request to perform a host system call does not finish
39224 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39225 after finishing the system call, the target returns to continuing the
39226 previous activity (continue, step). No additional continue or step
39227 request from @value{GDBN} is required.
39230 (@value{GDBP}) continue
39231 <- target requests 'system call X'
39232 target is stopped, @value{GDBN} executes system call
39233 -> @value{GDBN} returns result
39234 ... target continues, @value{GDBN} returns to wait for the target
39235 <- target hits breakpoint and sends a Txx packet
39238 The protocol only supports I/O on the console and to regular files on
39239 the host file system. Character or block special devices, pipes,
39240 named pipes, sockets or any other communication method on the host
39241 system are not supported by this protocol.
39243 File I/O is not supported in non-stop mode.
39245 @node Protocol Basics
39246 @subsection Protocol Basics
39247 @cindex protocol basics, file-i/o
39249 The File-I/O protocol uses the @code{F} packet as the request as well
39250 as reply packet. Since a File-I/O system call can only occur when
39251 @value{GDBN} is waiting for a response from the continuing or stepping target,
39252 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39253 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39254 This @code{F} packet contains all information needed to allow @value{GDBN}
39255 to call the appropriate host system call:
39259 A unique identifier for the requested system call.
39262 All parameters to the system call. Pointers are given as addresses
39263 in the target memory address space. Pointers to strings are given as
39264 pointer/length pair. Numerical values are given as they are.
39265 Numerical control flags are given in a protocol-specific representation.
39269 At this point, @value{GDBN} has to perform the following actions.
39273 If the parameters include pointer values to data needed as input to a
39274 system call, @value{GDBN} requests this data from the target with a
39275 standard @code{m} packet request. This additional communication has to be
39276 expected by the target implementation and is handled as any other @code{m}
39280 @value{GDBN} translates all value from protocol representation to host
39281 representation as needed. Datatypes are coerced into the host types.
39284 @value{GDBN} calls the system call.
39287 It then coerces datatypes back to protocol representation.
39290 If the system call is expected to return data in buffer space specified
39291 by pointer parameters to the call, the data is transmitted to the
39292 target using a @code{M} or @code{X} packet. This packet has to be expected
39293 by the target implementation and is handled as any other @code{M} or @code{X}
39298 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39299 necessary information for the target to continue. This at least contains
39306 @code{errno}, if has been changed by the system call.
39313 After having done the needed type and value coercion, the target continues
39314 the latest continue or step action.
39316 @node The F Request Packet
39317 @subsection The @code{F} Request Packet
39318 @cindex file-i/o request packet
39319 @cindex @code{F} request packet
39321 The @code{F} request packet has the following format:
39324 @item F@var{call-id},@var{parameter@dots{}}
39326 @var{call-id} is the identifier to indicate the host system call to be called.
39327 This is just the name of the function.
39329 @var{parameter@dots{}} are the parameters to the system call.
39330 Parameters are hexadecimal integer values, either the actual values in case
39331 of scalar datatypes, pointers to target buffer space in case of compound
39332 datatypes and unspecified memory areas, or pointer/length pairs in case
39333 of string parameters. These are appended to the @var{call-id} as a
39334 comma-delimited list. All values are transmitted in ASCII
39335 string representation, pointer/length pairs separated by a slash.
39341 @node The F Reply Packet
39342 @subsection The @code{F} Reply Packet
39343 @cindex file-i/o reply packet
39344 @cindex @code{F} reply packet
39346 The @code{F} reply packet has the following format:
39350 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39352 @var{retcode} is the return code of the system call as hexadecimal value.
39354 @var{errno} is the @code{errno} set by the call, in protocol-specific
39356 This parameter can be omitted if the call was successful.
39358 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39359 case, @var{errno} must be sent as well, even if the call was successful.
39360 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39367 or, if the call was interrupted before the host call has been performed:
39374 assuming 4 is the protocol-specific representation of @code{EINTR}.
39379 @node The Ctrl-C Message
39380 @subsection The @samp{Ctrl-C} Message
39381 @cindex ctrl-c message, in file-i/o protocol
39383 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39384 reply packet (@pxref{The F Reply Packet}),
39385 the target should behave as if it had
39386 gotten a break message. The meaning for the target is ``system call
39387 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39388 (as with a break message) and return to @value{GDBN} with a @code{T02}
39391 It's important for the target to know in which
39392 state the system call was interrupted. There are two possible cases:
39396 The system call hasn't been performed on the host yet.
39399 The system call on the host has been finished.
39403 These two states can be distinguished by the target by the value of the
39404 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39405 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39406 on POSIX systems. In any other case, the target may presume that the
39407 system call has been finished --- successfully or not --- and should behave
39408 as if the break message arrived right after the system call.
39410 @value{GDBN} must behave reliably. If the system call has not been called
39411 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39412 @code{errno} in the packet. If the system call on the host has been finished
39413 before the user requests a break, the full action must be finished by
39414 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39415 The @code{F} packet may only be sent when either nothing has happened
39416 or the full action has been completed.
39419 @subsection Console I/O
39420 @cindex console i/o as part of file-i/o
39422 By default and if not explicitly closed by the target system, the file
39423 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39424 on the @value{GDBN} console is handled as any other file output operation
39425 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39426 by @value{GDBN} so that after the target read request from file descriptor
39427 0 all following typing is buffered until either one of the following
39432 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39434 system call is treated as finished.
39437 The user presses @key{RET}. This is treated as end of input with a trailing
39441 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39442 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39446 If the user has typed more characters than fit in the buffer given to
39447 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39448 either another @code{read(0, @dots{})} is requested by the target, or debugging
39449 is stopped at the user's request.
39452 @node List of Supported Calls
39453 @subsection List of Supported Calls
39454 @cindex list of supported file-i/o calls
39471 @unnumberedsubsubsec open
39472 @cindex open, file-i/o system call
39477 int open(const char *pathname, int flags);
39478 int open(const char *pathname, int flags, mode_t mode);
39482 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39485 @var{flags} is the bitwise @code{OR} of the following values:
39489 If the file does not exist it will be created. The host
39490 rules apply as far as file ownership and time stamps
39494 When used with @code{O_CREAT}, if the file already exists it is
39495 an error and open() fails.
39498 If the file already exists and the open mode allows
39499 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39500 truncated to zero length.
39503 The file is opened in append mode.
39506 The file is opened for reading only.
39509 The file is opened for writing only.
39512 The file is opened for reading and writing.
39516 Other bits are silently ignored.
39520 @var{mode} is the bitwise @code{OR} of the following values:
39524 User has read permission.
39527 User has write permission.
39530 Group has read permission.
39533 Group has write permission.
39536 Others have read permission.
39539 Others have write permission.
39543 Other bits are silently ignored.
39546 @item Return value:
39547 @code{open} returns the new file descriptor or -1 if an error
39554 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39557 @var{pathname} refers to a directory.
39560 The requested access is not allowed.
39563 @var{pathname} was too long.
39566 A directory component in @var{pathname} does not exist.
39569 @var{pathname} refers to a device, pipe, named pipe or socket.
39572 @var{pathname} refers to a file on a read-only filesystem and
39573 write access was requested.
39576 @var{pathname} is an invalid pointer value.
39579 No space on device to create the file.
39582 The process already has the maximum number of files open.
39585 The limit on the total number of files open on the system
39589 The call was interrupted by the user.
39595 @unnumberedsubsubsec close
39596 @cindex close, file-i/o system call
39605 @samp{Fclose,@var{fd}}
39607 @item Return value:
39608 @code{close} returns zero on success, or -1 if an error occurred.
39614 @var{fd} isn't a valid open file descriptor.
39617 The call was interrupted by the user.
39623 @unnumberedsubsubsec read
39624 @cindex read, file-i/o system call
39629 int read(int fd, void *buf, unsigned int count);
39633 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39635 @item Return value:
39636 On success, the number of bytes read is returned.
39637 Zero indicates end of file. If count is zero, read
39638 returns zero as well. On error, -1 is returned.
39644 @var{fd} is not a valid file descriptor or is not open for
39648 @var{bufptr} is an invalid pointer value.
39651 The call was interrupted by the user.
39657 @unnumberedsubsubsec write
39658 @cindex write, file-i/o system call
39663 int write(int fd, const void *buf, unsigned int count);
39667 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39669 @item Return value:
39670 On success, the number of bytes written are returned.
39671 Zero indicates nothing was written. On error, -1
39678 @var{fd} is not a valid file descriptor or is not open for
39682 @var{bufptr} is an invalid pointer value.
39685 An attempt was made to write a file that exceeds the
39686 host-specific maximum file size allowed.
39689 No space on device to write the data.
39692 The call was interrupted by the user.
39698 @unnumberedsubsubsec lseek
39699 @cindex lseek, file-i/o system call
39704 long lseek (int fd, long offset, int flag);
39708 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39710 @var{flag} is one of:
39714 The offset is set to @var{offset} bytes.
39717 The offset is set to its current location plus @var{offset}
39721 The offset is set to the size of the file plus @var{offset}
39725 @item Return value:
39726 On success, the resulting unsigned offset in bytes from
39727 the beginning of the file is returned. Otherwise, a
39728 value of -1 is returned.
39734 @var{fd} is not a valid open file descriptor.
39737 @var{fd} is associated with the @value{GDBN} console.
39740 @var{flag} is not a proper value.
39743 The call was interrupted by the user.
39749 @unnumberedsubsubsec rename
39750 @cindex rename, file-i/o system call
39755 int rename(const char *oldpath, const char *newpath);
39759 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39761 @item Return value:
39762 On success, zero is returned. On error, -1 is returned.
39768 @var{newpath} is an existing directory, but @var{oldpath} is not a
39772 @var{newpath} is a non-empty directory.
39775 @var{oldpath} or @var{newpath} is a directory that is in use by some
39779 An attempt was made to make a directory a subdirectory
39783 A component used as a directory in @var{oldpath} or new
39784 path is not a directory. Or @var{oldpath} is a directory
39785 and @var{newpath} exists but is not a directory.
39788 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39791 No access to the file or the path of the file.
39795 @var{oldpath} or @var{newpath} was too long.
39798 A directory component in @var{oldpath} or @var{newpath} does not exist.
39801 The file is on a read-only filesystem.
39804 The device containing the file has no room for the new
39808 The call was interrupted by the user.
39814 @unnumberedsubsubsec unlink
39815 @cindex unlink, file-i/o system call
39820 int unlink(const char *pathname);
39824 @samp{Funlink,@var{pathnameptr}/@var{len}}
39826 @item Return value:
39827 On success, zero is returned. On error, -1 is returned.
39833 No access to the file or the path of the file.
39836 The system does not allow unlinking of directories.
39839 The file @var{pathname} cannot be unlinked because it's
39840 being used by another process.
39843 @var{pathnameptr} is an invalid pointer value.
39846 @var{pathname} was too long.
39849 A directory component in @var{pathname} does not exist.
39852 A component of the path is not a directory.
39855 The file is on a read-only filesystem.
39858 The call was interrupted by the user.
39864 @unnumberedsubsubsec stat/fstat
39865 @cindex fstat, file-i/o system call
39866 @cindex stat, file-i/o system call
39871 int stat(const char *pathname, struct stat *buf);
39872 int fstat(int fd, struct stat *buf);
39876 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39877 @samp{Ffstat,@var{fd},@var{bufptr}}
39879 @item Return value:
39880 On success, zero is returned. On error, -1 is returned.
39886 @var{fd} is not a valid open file.
39889 A directory component in @var{pathname} does not exist or the
39890 path is an empty string.
39893 A component of the path is not a directory.
39896 @var{pathnameptr} is an invalid pointer value.
39899 No access to the file or the path of the file.
39902 @var{pathname} was too long.
39905 The call was interrupted by the user.
39911 @unnumberedsubsubsec gettimeofday
39912 @cindex gettimeofday, file-i/o system call
39917 int gettimeofday(struct timeval *tv, void *tz);
39921 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39923 @item Return value:
39924 On success, 0 is returned, -1 otherwise.
39930 @var{tz} is a non-NULL pointer.
39933 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39939 @unnumberedsubsubsec isatty
39940 @cindex isatty, file-i/o system call
39945 int isatty(int fd);
39949 @samp{Fisatty,@var{fd}}
39951 @item Return value:
39952 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39958 The call was interrupted by the user.
39963 Note that the @code{isatty} call is treated as a special case: it returns
39964 1 to the target if the file descriptor is attached
39965 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39966 would require implementing @code{ioctl} and would be more complex than
39971 @unnumberedsubsubsec system
39972 @cindex system, file-i/o system call
39977 int system(const char *command);
39981 @samp{Fsystem,@var{commandptr}/@var{len}}
39983 @item Return value:
39984 If @var{len} is zero, the return value indicates whether a shell is
39985 available. A zero return value indicates a shell is not available.
39986 For non-zero @var{len}, the value returned is -1 on error and the
39987 return status of the command otherwise. Only the exit status of the
39988 command is returned, which is extracted from the host's @code{system}
39989 return value by calling @code{WEXITSTATUS(retval)}. In case
39990 @file{/bin/sh} could not be executed, 127 is returned.
39996 The call was interrupted by the user.
40001 @value{GDBN} takes over the full task of calling the necessary host calls
40002 to perform the @code{system} call. The return value of @code{system} on
40003 the host is simplified before it's returned
40004 to the target. Any termination signal information from the child process
40005 is discarded, and the return value consists
40006 entirely of the exit status of the called command.
40008 Due to security concerns, the @code{system} call is by default refused
40009 by @value{GDBN}. The user has to allow this call explicitly with the
40010 @code{set remote system-call-allowed 1} command.
40013 @item set remote system-call-allowed
40014 @kindex set remote system-call-allowed
40015 Control whether to allow the @code{system} calls in the File I/O
40016 protocol for the remote target. The default is zero (disabled).
40018 @item show remote system-call-allowed
40019 @kindex show remote system-call-allowed
40020 Show whether the @code{system} calls are allowed in the File I/O
40024 @node Protocol-specific Representation of Datatypes
40025 @subsection Protocol-specific Representation of Datatypes
40026 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40029 * Integral Datatypes::
40031 * Memory Transfer::
40036 @node Integral Datatypes
40037 @unnumberedsubsubsec Integral Datatypes
40038 @cindex integral datatypes, in file-i/o protocol
40040 The integral datatypes used in the system calls are @code{int},
40041 @code{unsigned int}, @code{long}, @code{unsigned long},
40042 @code{mode_t}, and @code{time_t}.
40044 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40045 implemented as 32 bit values in this protocol.
40047 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40049 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40050 in @file{limits.h}) to allow range checking on host and target.
40052 @code{time_t} datatypes are defined as seconds since the Epoch.
40054 All integral datatypes transferred as part of a memory read or write of a
40055 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40058 @node Pointer Values
40059 @unnumberedsubsubsec Pointer Values
40060 @cindex pointer values, in file-i/o protocol
40062 Pointers to target data are transmitted as they are. An exception
40063 is made for pointers to buffers for which the length isn't
40064 transmitted as part of the function call, namely strings. Strings
40065 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40072 which is a pointer to data of length 18 bytes at position 0x1aaf.
40073 The length is defined as the full string length in bytes, including
40074 the trailing null byte. For example, the string @code{"hello world"}
40075 at address 0x123456 is transmitted as
40081 @node Memory Transfer
40082 @unnumberedsubsubsec Memory Transfer
40083 @cindex memory transfer, in file-i/o protocol
40085 Structured data which is transferred using a memory read or write (for
40086 example, a @code{struct stat}) is expected to be in a protocol-specific format
40087 with all scalar multibyte datatypes being big endian. Translation to
40088 this representation needs to be done both by the target before the @code{F}
40089 packet is sent, and by @value{GDBN} before
40090 it transfers memory to the target. Transferred pointers to structured
40091 data should point to the already-coerced data at any time.
40095 @unnumberedsubsubsec struct stat
40096 @cindex struct stat, in file-i/o protocol
40098 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40099 is defined as follows:
40103 unsigned int st_dev; /* device */
40104 unsigned int st_ino; /* inode */
40105 mode_t st_mode; /* protection */
40106 unsigned int st_nlink; /* number of hard links */
40107 unsigned int st_uid; /* user ID of owner */
40108 unsigned int st_gid; /* group ID of owner */
40109 unsigned int st_rdev; /* device type (if inode device) */
40110 unsigned long st_size; /* total size, in bytes */
40111 unsigned long st_blksize; /* blocksize for filesystem I/O */
40112 unsigned long st_blocks; /* number of blocks allocated */
40113 time_t st_atime; /* time of last access */
40114 time_t st_mtime; /* time of last modification */
40115 time_t st_ctime; /* time of last change */
40119 The integral datatypes conform to the definitions given in the
40120 appropriate section (see @ref{Integral Datatypes}, for details) so this
40121 structure is of size 64 bytes.
40123 The values of several fields have a restricted meaning and/or
40129 A value of 0 represents a file, 1 the console.
40132 No valid meaning for the target. Transmitted unchanged.
40135 Valid mode bits are described in @ref{Constants}. Any other
40136 bits have currently no meaning for the target.
40141 No valid meaning for the target. Transmitted unchanged.
40146 These values have a host and file system dependent
40147 accuracy. Especially on Windows hosts, the file system may not
40148 support exact timing values.
40151 The target gets a @code{struct stat} of the above representation and is
40152 responsible for coercing it to the target representation before
40155 Note that due to size differences between the host, target, and protocol
40156 representations of @code{struct stat} members, these members could eventually
40157 get truncated on the target.
40159 @node struct timeval
40160 @unnumberedsubsubsec struct timeval
40161 @cindex struct timeval, in file-i/o protocol
40163 The buffer of type @code{struct timeval} used by the File-I/O protocol
40164 is defined as follows:
40168 time_t tv_sec; /* second */
40169 long tv_usec; /* microsecond */
40173 The integral datatypes conform to the definitions given in the
40174 appropriate section (see @ref{Integral Datatypes}, for details) so this
40175 structure is of size 8 bytes.
40178 @subsection Constants
40179 @cindex constants, in file-i/o protocol
40181 The following values are used for the constants inside of the
40182 protocol. @value{GDBN} and target are responsible for translating these
40183 values before and after the call as needed.
40194 @unnumberedsubsubsec Open Flags
40195 @cindex open flags, in file-i/o protocol
40197 All values are given in hexadecimal representation.
40209 @node mode_t Values
40210 @unnumberedsubsubsec mode_t Values
40211 @cindex mode_t values, in file-i/o protocol
40213 All values are given in octal representation.
40230 @unnumberedsubsubsec Errno Values
40231 @cindex errno values, in file-i/o protocol
40233 All values are given in decimal representation.
40258 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40259 any error value not in the list of supported error numbers.
40262 @unnumberedsubsubsec Lseek Flags
40263 @cindex lseek flags, in file-i/o protocol
40272 @unnumberedsubsubsec Limits
40273 @cindex limits, in file-i/o protocol
40275 All values are given in decimal representation.
40278 INT_MIN -2147483648
40280 UINT_MAX 4294967295
40281 LONG_MIN -9223372036854775808
40282 LONG_MAX 9223372036854775807
40283 ULONG_MAX 18446744073709551615
40286 @node File-I/O Examples
40287 @subsection File-I/O Examples
40288 @cindex file-i/o examples
40290 Example sequence of a write call, file descriptor 3, buffer is at target
40291 address 0x1234, 6 bytes should be written:
40294 <- @code{Fwrite,3,1234,6}
40295 @emph{request memory read from target}
40298 @emph{return "6 bytes written"}
40302 Example sequence of a read call, file descriptor 3, buffer is at target
40303 address 0x1234, 6 bytes should be read:
40306 <- @code{Fread,3,1234,6}
40307 @emph{request memory write to target}
40308 -> @code{X1234,6:XXXXXX}
40309 @emph{return "6 bytes read"}
40313 Example sequence of a read call, call fails on the host due to invalid
40314 file descriptor (@code{EBADF}):
40317 <- @code{Fread,3,1234,6}
40321 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40325 <- @code{Fread,3,1234,6}
40330 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40334 <- @code{Fread,3,1234,6}
40335 -> @code{X1234,6:XXXXXX}
40339 @node Library List Format
40340 @section Library List Format
40341 @cindex library list format, remote protocol
40343 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40344 same process as your application to manage libraries. In this case,
40345 @value{GDBN} can use the loader's symbol table and normal memory
40346 operations to maintain a list of shared libraries. On other
40347 platforms, the operating system manages loaded libraries.
40348 @value{GDBN} can not retrieve the list of currently loaded libraries
40349 through memory operations, so it uses the @samp{qXfer:libraries:read}
40350 packet (@pxref{qXfer library list read}) instead. The remote stub
40351 queries the target's operating system and reports which libraries
40354 The @samp{qXfer:libraries:read} packet returns an XML document which
40355 lists loaded libraries and their offsets. Each library has an
40356 associated name and one or more segment or section base addresses,
40357 which report where the library was loaded in memory.
40359 For the common case of libraries that are fully linked binaries, the
40360 library should have a list of segments. If the target supports
40361 dynamic linking of a relocatable object file, its library XML element
40362 should instead include a list of allocated sections. The segment or
40363 section bases are start addresses, not relocation offsets; they do not
40364 depend on the library's link-time base addresses.
40366 @value{GDBN} must be linked with the Expat library to support XML
40367 library lists. @xref{Expat}.
40369 A simple memory map, with one loaded library relocated by a single
40370 offset, looks like this:
40374 <library name="/lib/libc.so.6">
40375 <segment address="0x10000000"/>
40380 Another simple memory map, with one loaded library with three
40381 allocated sections (.text, .data, .bss), looks like this:
40385 <library name="sharedlib.o">
40386 <section address="0x10000000"/>
40387 <section address="0x20000000"/>
40388 <section address="0x30000000"/>
40393 The format of a library list is described by this DTD:
40396 <!-- library-list: Root element with versioning -->
40397 <!ELEMENT library-list (library)*>
40398 <!ATTLIST library-list version CDATA #FIXED "1.0">
40399 <!ELEMENT library (segment*, section*)>
40400 <!ATTLIST library name CDATA #REQUIRED>
40401 <!ELEMENT segment EMPTY>
40402 <!ATTLIST segment address CDATA #REQUIRED>
40403 <!ELEMENT section EMPTY>
40404 <!ATTLIST section address CDATA #REQUIRED>
40407 In addition, segments and section descriptors cannot be mixed within a
40408 single library element, and you must supply at least one segment or
40409 section for each library.
40411 @node Library List Format for SVR4 Targets
40412 @section Library List Format for SVR4 Targets
40413 @cindex library list format, remote protocol
40415 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40416 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40417 shared libraries. Still a special library list provided by this packet is
40418 more efficient for the @value{GDBN} remote protocol.
40420 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40421 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40422 target, the following parameters are reported:
40426 @code{name}, the absolute file name from the @code{l_name} field of
40427 @code{struct link_map}.
40429 @code{lm} with address of @code{struct link_map} used for TLS
40430 (Thread Local Storage) access.
40432 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40433 @code{struct link_map}. For prelinked libraries this is not an absolute
40434 memory address. It is a displacement of absolute memory address against
40435 address the file was prelinked to during the library load.
40437 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40440 Additionally the single @code{main-lm} attribute specifies address of
40441 @code{struct link_map} used for the main executable. This parameter is used
40442 for TLS access and its presence is optional.
40444 @value{GDBN} must be linked with the Expat library to support XML
40445 SVR4 library lists. @xref{Expat}.
40447 A simple memory map, with two loaded libraries (which do not use prelink),
40451 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40452 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40454 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40456 </library-list-svr>
40459 The format of an SVR4 library list is described by this DTD:
40462 <!-- library-list-svr4: Root element with versioning -->
40463 <!ELEMENT library-list-svr4 (library)*>
40464 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40465 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40466 <!ELEMENT library EMPTY>
40467 <!ATTLIST library name CDATA #REQUIRED>
40468 <!ATTLIST library lm CDATA #REQUIRED>
40469 <!ATTLIST library l_addr CDATA #REQUIRED>
40470 <!ATTLIST library l_ld CDATA #REQUIRED>
40473 @node Memory Map Format
40474 @section Memory Map Format
40475 @cindex memory map format
40477 To be able to write into flash memory, @value{GDBN} needs to obtain a
40478 memory map from the target. This section describes the format of the
40481 The memory map is obtained using the @samp{qXfer:memory-map:read}
40482 (@pxref{qXfer memory map read}) packet and is an XML document that
40483 lists memory regions.
40485 @value{GDBN} must be linked with the Expat library to support XML
40486 memory maps. @xref{Expat}.
40488 The top-level structure of the document is shown below:
40491 <?xml version="1.0"?>
40492 <!DOCTYPE memory-map
40493 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40494 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40500 Each region can be either:
40505 A region of RAM starting at @var{addr} and extending for @var{length}
40509 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40514 A region of read-only memory:
40517 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40522 A region of flash memory, with erasure blocks @var{blocksize}
40526 <memory type="flash" start="@var{addr}" length="@var{length}">
40527 <property name="blocksize">@var{blocksize}</property>
40533 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40534 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40535 packets to write to addresses in such ranges.
40537 The formal DTD for memory map format is given below:
40540 <!-- ................................................... -->
40541 <!-- Memory Map XML DTD ................................ -->
40542 <!-- File: memory-map.dtd .............................. -->
40543 <!-- .................................... .............. -->
40544 <!-- memory-map.dtd -->
40545 <!-- memory-map: Root element with versioning -->
40546 <!ELEMENT memory-map (memory | property)>
40547 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40548 <!ELEMENT memory (property)>
40549 <!-- memory: Specifies a memory region,
40550 and its type, or device. -->
40551 <!ATTLIST memory type CDATA #REQUIRED
40552 start CDATA #REQUIRED
40553 length CDATA #REQUIRED
40554 device CDATA #IMPLIED>
40555 <!-- property: Generic attribute tag -->
40556 <!ELEMENT property (#PCDATA | property)*>
40557 <!ATTLIST property name CDATA #REQUIRED>
40560 @node Thread List Format
40561 @section Thread List Format
40562 @cindex thread list format
40564 To efficiently update the list of threads and their attributes,
40565 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40566 (@pxref{qXfer threads read}) and obtains the XML document with
40567 the following structure:
40570 <?xml version="1.0"?>
40572 <thread id="id" core="0">
40573 ... description ...
40578 Each @samp{thread} element must have the @samp{id} attribute that
40579 identifies the thread (@pxref{thread-id syntax}). The
40580 @samp{core} attribute, if present, specifies which processor core
40581 the thread was last executing on. The content of the of @samp{thread}
40582 element is interpreted as human-readable auxilliary information.
40584 @node Traceframe Info Format
40585 @section Traceframe Info Format
40586 @cindex traceframe info format
40588 To be able to know which objects in the inferior can be examined when
40589 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40590 memory ranges, registers and trace state variables that have been
40591 collected in a traceframe.
40593 This list is obtained using the @samp{qXfer:traceframe-info:read}
40594 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40596 @value{GDBN} must be linked with the Expat library to support XML
40597 traceframe info discovery. @xref{Expat}.
40599 The top-level structure of the document is shown below:
40602 <?xml version="1.0"?>
40603 <!DOCTYPE traceframe-info
40604 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40605 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40611 Each traceframe block can be either:
40616 A region of collected memory starting at @var{addr} and extending for
40617 @var{length} bytes from there:
40620 <memory start="@var{addr}" length="@var{length}"/>
40625 The formal DTD for the traceframe info format is given below:
40628 <!ELEMENT traceframe-info (memory)* >
40629 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40631 <!ELEMENT memory EMPTY>
40632 <!ATTLIST memory start CDATA #REQUIRED
40633 length CDATA #REQUIRED>
40636 @node Branch Trace Format
40637 @section Branch Trace Format
40638 @cindex branch trace format
40640 In order to display the branch trace of an inferior thread,
40641 @value{GDBN} needs to obtain the list of branches. This list is
40642 represented as list of sequential code blocks that are connected via
40643 branches. The code in each block has been executed sequentially.
40645 This list is obtained using the @samp{qXfer:btrace:read}
40646 (@pxref{qXfer btrace read}) packet and is an XML document.
40648 @value{GDBN} must be linked with the Expat library to support XML
40649 traceframe info discovery. @xref{Expat}.
40651 The top-level structure of the document is shown below:
40654 <?xml version="1.0"?>
40656 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40657 "http://sourceware.org/gdb/gdb-btrace.dtd">
40666 A block of sequentially executed instructions starting at @var{begin}
40667 and ending at @var{end}:
40670 <block begin="@var{begin}" end="@var{end}"/>
40675 The formal DTD for the branch trace format is given below:
40678 <!ELEMENT btrace (block)* >
40679 <!ATTLIST btrace version CDATA #FIXED "1.0">
40681 <!ELEMENT block EMPTY>
40682 <!ATTLIST block begin CDATA #REQUIRED
40683 end CDATA #REQUIRED>
40686 @include agentexpr.texi
40688 @node Target Descriptions
40689 @appendix Target Descriptions
40690 @cindex target descriptions
40692 One of the challenges of using @value{GDBN} to debug embedded systems
40693 is that there are so many minor variants of each processor
40694 architecture in use. It is common practice for vendors to start with
40695 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40696 and then make changes to adapt it to a particular market niche. Some
40697 architectures have hundreds of variants, available from dozens of
40698 vendors. This leads to a number of problems:
40702 With so many different customized processors, it is difficult for
40703 the @value{GDBN} maintainers to keep up with the changes.
40705 Since individual variants may have short lifetimes or limited
40706 audiences, it may not be worthwhile to carry information about every
40707 variant in the @value{GDBN} source tree.
40709 When @value{GDBN} does support the architecture of the embedded system
40710 at hand, the task of finding the correct architecture name to give the
40711 @command{set architecture} command can be error-prone.
40714 To address these problems, the @value{GDBN} remote protocol allows a
40715 target system to not only identify itself to @value{GDBN}, but to
40716 actually describe its own features. This lets @value{GDBN} support
40717 processor variants it has never seen before --- to the extent that the
40718 descriptions are accurate, and that @value{GDBN} understands them.
40720 @value{GDBN} must be linked with the Expat library to support XML
40721 target descriptions. @xref{Expat}.
40724 * Retrieving Descriptions:: How descriptions are fetched from a target.
40725 * Target Description Format:: The contents of a target description.
40726 * Predefined Target Types:: Standard types available for target
40728 * Standard Target Features:: Features @value{GDBN} knows about.
40731 @node Retrieving Descriptions
40732 @section Retrieving Descriptions
40734 Target descriptions can be read from the target automatically, or
40735 specified by the user manually. The default behavior is to read the
40736 description from the target. @value{GDBN} retrieves it via the remote
40737 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40738 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40739 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40740 XML document, of the form described in @ref{Target Description
40743 Alternatively, you can specify a file to read for the target description.
40744 If a file is set, the target will not be queried. The commands to
40745 specify a file are:
40748 @cindex set tdesc filename
40749 @item set tdesc filename @var{path}
40750 Read the target description from @var{path}.
40752 @cindex unset tdesc filename
40753 @item unset tdesc filename
40754 Do not read the XML target description from a file. @value{GDBN}
40755 will use the description supplied by the current target.
40757 @cindex show tdesc filename
40758 @item show tdesc filename
40759 Show the filename to read for a target description, if any.
40763 @node Target Description Format
40764 @section Target Description Format
40765 @cindex target descriptions, XML format
40767 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40768 document which complies with the Document Type Definition provided in
40769 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40770 means you can use generally available tools like @command{xmllint} to
40771 check that your feature descriptions are well-formed and valid.
40772 However, to help people unfamiliar with XML write descriptions for
40773 their targets, we also describe the grammar here.
40775 Target descriptions can identify the architecture of the remote target
40776 and (for some architectures) provide information about custom register
40777 sets. They can also identify the OS ABI of the remote target.
40778 @value{GDBN} can use this information to autoconfigure for your
40779 target, or to warn you if you connect to an unsupported target.
40781 Here is a simple target description:
40784 <target version="1.0">
40785 <architecture>i386:x86-64</architecture>
40790 This minimal description only says that the target uses
40791 the x86-64 architecture.
40793 A target description has the following overall form, with [ ] marking
40794 optional elements and @dots{} marking repeatable elements. The elements
40795 are explained further below.
40798 <?xml version="1.0"?>
40799 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40800 <target version="1.0">
40801 @r{[}@var{architecture}@r{]}
40802 @r{[}@var{osabi}@r{]}
40803 @r{[}@var{compatible}@r{]}
40804 @r{[}@var{feature}@dots{}@r{]}
40809 The description is generally insensitive to whitespace and line
40810 breaks, under the usual common-sense rules. The XML version
40811 declaration and document type declaration can generally be omitted
40812 (@value{GDBN} does not require them), but specifying them may be
40813 useful for XML validation tools. The @samp{version} attribute for
40814 @samp{<target>} may also be omitted, but we recommend
40815 including it; if future versions of @value{GDBN} use an incompatible
40816 revision of @file{gdb-target.dtd}, they will detect and report
40817 the version mismatch.
40819 @subsection Inclusion
40820 @cindex target descriptions, inclusion
40823 @cindex <xi:include>
40826 It can sometimes be valuable to split a target description up into
40827 several different annexes, either for organizational purposes, or to
40828 share files between different possible target descriptions. You can
40829 divide a description into multiple files by replacing any element of
40830 the target description with an inclusion directive of the form:
40833 <xi:include href="@var{document}"/>
40837 When @value{GDBN} encounters an element of this form, it will retrieve
40838 the named XML @var{document}, and replace the inclusion directive with
40839 the contents of that document. If the current description was read
40840 using @samp{qXfer}, then so will be the included document;
40841 @var{document} will be interpreted as the name of an annex. If the
40842 current description was read from a file, @value{GDBN} will look for
40843 @var{document} as a file in the same directory where it found the
40844 original description.
40846 @subsection Architecture
40847 @cindex <architecture>
40849 An @samp{<architecture>} element has this form:
40852 <architecture>@var{arch}</architecture>
40855 @var{arch} is one of the architectures from the set accepted by
40856 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40859 @cindex @code{<osabi>}
40861 This optional field was introduced in @value{GDBN} version 7.0.
40862 Previous versions of @value{GDBN} ignore it.
40864 An @samp{<osabi>} element has this form:
40867 <osabi>@var{abi-name}</osabi>
40870 @var{abi-name} is an OS ABI name from the same selection accepted by
40871 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40873 @subsection Compatible Architecture
40874 @cindex @code{<compatible>}
40876 This optional field was introduced in @value{GDBN} version 7.0.
40877 Previous versions of @value{GDBN} ignore it.
40879 A @samp{<compatible>} element has this form:
40882 <compatible>@var{arch}</compatible>
40885 @var{arch} is one of the architectures from the set accepted by
40886 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40888 A @samp{<compatible>} element is used to specify that the target
40889 is able to run binaries in some other than the main target architecture
40890 given by the @samp{<architecture>} element. For example, on the
40891 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40892 or @code{powerpc:common64}, but the system is able to run binaries
40893 in the @code{spu} architecture as well. The way to describe this
40894 capability with @samp{<compatible>} is as follows:
40897 <architecture>powerpc:common</architecture>
40898 <compatible>spu</compatible>
40901 @subsection Features
40904 Each @samp{<feature>} describes some logical portion of the target
40905 system. Features are currently used to describe available CPU
40906 registers and the types of their contents. A @samp{<feature>} element
40910 <feature name="@var{name}">
40911 @r{[}@var{type}@dots{}@r{]}
40917 Each feature's name should be unique within the description. The name
40918 of a feature does not matter unless @value{GDBN} has some special
40919 knowledge of the contents of that feature; if it does, the feature
40920 should have its standard name. @xref{Standard Target Features}.
40924 Any register's value is a collection of bits which @value{GDBN} must
40925 interpret. The default interpretation is a two's complement integer,
40926 but other types can be requested by name in the register description.
40927 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40928 Target Types}), and the description can define additional composite types.
40930 Each type element must have an @samp{id} attribute, which gives
40931 a unique (within the containing @samp{<feature>}) name to the type.
40932 Types must be defined before they are used.
40935 Some targets offer vector registers, which can be treated as arrays
40936 of scalar elements. These types are written as @samp{<vector>} elements,
40937 specifying the array element type, @var{type}, and the number of elements,
40941 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40945 If a register's value is usefully viewed in multiple ways, define it
40946 with a union type containing the useful representations. The
40947 @samp{<union>} element contains one or more @samp{<field>} elements,
40948 each of which has a @var{name} and a @var{type}:
40951 <union id="@var{id}">
40952 <field name="@var{name}" type="@var{type}"/>
40958 If a register's value is composed from several separate values, define
40959 it with a structure type. There are two forms of the @samp{<struct>}
40960 element; a @samp{<struct>} element must either contain only bitfields
40961 or contain no bitfields. If the structure contains only bitfields,
40962 its total size in bytes must be specified, each bitfield must have an
40963 explicit start and end, and bitfields are automatically assigned an
40964 integer type. The field's @var{start} should be less than or
40965 equal to its @var{end}, and zero represents the least significant bit.
40968 <struct id="@var{id}" size="@var{size}">
40969 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40974 If the structure contains no bitfields, then each field has an
40975 explicit type, and no implicit padding is added.
40978 <struct id="@var{id}">
40979 <field name="@var{name}" type="@var{type}"/>
40985 If a register's value is a series of single-bit flags, define it with
40986 a flags type. The @samp{<flags>} element has an explicit @var{size}
40987 and contains one or more @samp{<field>} elements. Each field has a
40988 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40992 <flags id="@var{id}" size="@var{size}">
40993 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40998 @subsection Registers
41001 Each register is represented as an element with this form:
41004 <reg name="@var{name}"
41005 bitsize="@var{size}"
41006 @r{[}regnum="@var{num}"@r{]}
41007 @r{[}save-restore="@var{save-restore}"@r{]}
41008 @r{[}type="@var{type}"@r{]}
41009 @r{[}group="@var{group}"@r{]}/>
41013 The components are as follows:
41018 The register's name; it must be unique within the target description.
41021 The register's size, in bits.
41024 The register's number. If omitted, a register's number is one greater
41025 than that of the previous register (either in the current feature or in
41026 a preceding feature); the first register in the target description
41027 defaults to zero. This register number is used to read or write
41028 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41029 packets, and registers appear in the @code{g} and @code{G} packets
41030 in order of increasing register number.
41033 Whether the register should be preserved across inferior function
41034 calls; this must be either @code{yes} or @code{no}. The default is
41035 @code{yes}, which is appropriate for most registers except for
41036 some system control registers; this is not related to the target's
41040 The type of the register. @var{type} may be a predefined type, a type
41041 defined in the current feature, or one of the special types @code{int}
41042 and @code{float}. @code{int} is an integer type of the correct size
41043 for @var{bitsize}, and @code{float} is a floating point type (in the
41044 architecture's normal floating point format) of the correct size for
41045 @var{bitsize}. The default is @code{int}.
41048 The register group to which this register belongs. @var{group} must
41049 be either @code{general}, @code{float}, or @code{vector}. If no
41050 @var{group} is specified, @value{GDBN} will not display the register
41051 in @code{info registers}.
41055 @node Predefined Target Types
41056 @section Predefined Target Types
41057 @cindex target descriptions, predefined types
41059 Type definitions in the self-description can build up composite types
41060 from basic building blocks, but can not define fundamental types. Instead,
41061 standard identifiers are provided by @value{GDBN} for the fundamental
41062 types. The currently supported types are:
41071 Signed integer types holding the specified number of bits.
41078 Unsigned integer types holding the specified number of bits.
41082 Pointers to unspecified code and data. The program counter and
41083 any dedicated return address register may be marked as code
41084 pointers; printing a code pointer converts it into a symbolic
41085 address. The stack pointer and any dedicated address registers
41086 may be marked as data pointers.
41089 Single precision IEEE floating point.
41092 Double precision IEEE floating point.
41095 The 12-byte extended precision format used by ARM FPA registers.
41098 The 10-byte extended precision format used by x87 registers.
41101 32bit @sc{eflags} register used by x86.
41104 32bit @sc{mxcsr} register used by x86.
41108 @node Standard Target Features
41109 @section Standard Target Features
41110 @cindex target descriptions, standard features
41112 A target description must contain either no registers or all the
41113 target's registers. If the description contains no registers, then
41114 @value{GDBN} will assume a default register layout, selected based on
41115 the architecture. If the description contains any registers, the
41116 default layout will not be used; the standard registers must be
41117 described in the target description, in such a way that @value{GDBN}
41118 can recognize them.
41120 This is accomplished by giving specific names to feature elements
41121 which contain standard registers. @value{GDBN} will look for features
41122 with those names and verify that they contain the expected registers;
41123 if any known feature is missing required registers, or if any required
41124 feature is missing, @value{GDBN} will reject the target
41125 description. You can add additional registers to any of the
41126 standard features --- @value{GDBN} will display them just as if
41127 they were added to an unrecognized feature.
41129 This section lists the known features and their expected contents.
41130 Sample XML documents for these features are included in the
41131 @value{GDBN} source tree, in the directory @file{gdb/features}.
41133 Names recognized by @value{GDBN} should include the name of the
41134 company or organization which selected the name, and the overall
41135 architecture to which the feature applies; so e.g.@: the feature
41136 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41138 The names of registers are not case sensitive for the purpose
41139 of recognizing standard features, but @value{GDBN} will only display
41140 registers using the capitalization used in the description.
41143 * AArch64 Features::
41148 * PowerPC Features::
41153 @node AArch64 Features
41154 @subsection AArch64 Features
41155 @cindex target descriptions, AArch64 features
41157 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41158 targets. It should contain registers @samp{x0} through @samp{x30},
41159 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41161 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41162 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41166 @subsection ARM Features
41167 @cindex target descriptions, ARM features
41169 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41171 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41172 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41174 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41175 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41176 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41179 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41180 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41182 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41183 it should contain at least registers @samp{wR0} through @samp{wR15} and
41184 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41185 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41187 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41188 should contain at least registers @samp{d0} through @samp{d15}. If
41189 they are present, @samp{d16} through @samp{d31} should also be included.
41190 @value{GDBN} will synthesize the single-precision registers from
41191 halves of the double-precision registers.
41193 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41194 need to contain registers; it instructs @value{GDBN} to display the
41195 VFP double-precision registers as vectors and to synthesize the
41196 quad-precision registers from pairs of double-precision registers.
41197 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41198 be present and include 32 double-precision registers.
41200 @node i386 Features
41201 @subsection i386 Features
41202 @cindex target descriptions, i386 features
41204 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41205 targets. It should describe the following registers:
41209 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41211 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41213 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41214 @samp{fs}, @samp{gs}
41216 @samp{st0} through @samp{st7}
41218 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41219 @samp{foseg}, @samp{fooff} and @samp{fop}
41222 The register sets may be different, depending on the target.
41224 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41225 describe registers:
41229 @samp{xmm0} through @samp{xmm7} for i386
41231 @samp{xmm0} through @samp{xmm15} for amd64
41236 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41237 @samp{org.gnu.gdb.i386.sse} feature. It should
41238 describe the upper 128 bits of @sc{ymm} registers:
41242 @samp{ymm0h} through @samp{ymm7h} for i386
41244 @samp{ymm0h} through @samp{ymm15h} for amd64
41247 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41248 describe a single register, @samp{orig_eax}.
41250 @node MIPS Features
41251 @subsection @acronym{MIPS} Features
41252 @cindex target descriptions, @acronym{MIPS} features
41254 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41255 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41256 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41259 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41260 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41261 registers. They may be 32-bit or 64-bit depending on the target.
41263 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41264 it may be optional in a future version of @value{GDBN}. It should
41265 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41266 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41268 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41269 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41270 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41271 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41273 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41274 contain a single register, @samp{restart}, which is used by the
41275 Linux kernel to control restartable syscalls.
41277 @node M68K Features
41278 @subsection M68K Features
41279 @cindex target descriptions, M68K features
41282 @item @samp{org.gnu.gdb.m68k.core}
41283 @itemx @samp{org.gnu.gdb.coldfire.core}
41284 @itemx @samp{org.gnu.gdb.fido.core}
41285 One of those features must be always present.
41286 The feature that is present determines which flavor of m68k is
41287 used. The feature that is present should contain registers
41288 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41289 @samp{sp}, @samp{ps} and @samp{pc}.
41291 @item @samp{org.gnu.gdb.coldfire.fp}
41292 This feature is optional. If present, it should contain registers
41293 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41297 @node PowerPC Features
41298 @subsection PowerPC Features
41299 @cindex target descriptions, PowerPC features
41301 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41302 targets. It should contain registers @samp{r0} through @samp{r31},
41303 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41304 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41306 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41307 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41309 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41310 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41313 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41314 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41315 will combine these registers with the floating point registers
41316 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41317 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41318 through @samp{vs63}, the set of vector registers for POWER7.
41320 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41321 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41322 @samp{spefscr}. SPE targets should provide 32-bit registers in
41323 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41324 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41325 these to present registers @samp{ev0} through @samp{ev31} to the
41328 @node TIC6x Features
41329 @subsection TMS320C6x Features
41330 @cindex target descriptions, TIC6x features
41331 @cindex target descriptions, TMS320C6x features
41332 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41333 targets. It should contain registers @samp{A0} through @samp{A15},
41334 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41336 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41337 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41338 through @samp{B31}.
41340 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41341 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41343 @node Operating System Information
41344 @appendix Operating System Information
41345 @cindex operating system information
41351 Users of @value{GDBN} often wish to obtain information about the state of
41352 the operating system running on the target---for example the list of
41353 processes, or the list of open files. This section describes the
41354 mechanism that makes it possible. This mechanism is similar to the
41355 target features mechanism (@pxref{Target Descriptions}), but focuses
41356 on a different aspect of target.
41358 Operating system information is retrived from the target via the
41359 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41360 read}). The object name in the request should be @samp{osdata}, and
41361 the @var{annex} identifies the data to be fetched.
41364 @appendixsection Process list
41365 @cindex operating system information, process list
41367 When requesting the process list, the @var{annex} field in the
41368 @samp{qXfer} request should be @samp{processes}. The returned data is
41369 an XML document. The formal syntax of this document is defined in
41370 @file{gdb/features/osdata.dtd}.
41372 An example document is:
41375 <?xml version="1.0"?>
41376 <!DOCTYPE target SYSTEM "osdata.dtd">
41377 <osdata type="processes">
41379 <column name="pid">1</column>
41380 <column name="user">root</column>
41381 <column name="command">/sbin/init</column>
41382 <column name="cores">1,2,3</column>
41387 Each item should include a column whose name is @samp{pid}. The value
41388 of that column should identify the process on the target. The
41389 @samp{user} and @samp{command} columns are optional, and will be
41390 displayed by @value{GDBN}. The @samp{cores} column, if present,
41391 should contain a comma-separated list of cores that this process
41392 is running on. Target may provide additional columns,
41393 which @value{GDBN} currently ignores.
41395 @node Trace File Format
41396 @appendix Trace File Format
41397 @cindex trace file format
41399 The trace file comes in three parts: a header, a textual description
41400 section, and a trace frame section with binary data.
41402 The header has the form @code{\x7fTRACE0\n}. The first byte is
41403 @code{0x7f} so as to indicate that the file contains binary data,
41404 while the @code{0} is a version number that may have different values
41407 The description section consists of multiple lines of @sc{ascii} text
41408 separated by newline characters (@code{0xa}). The lines may include a
41409 variety of optional descriptive or context-setting information, such
41410 as tracepoint definitions or register set size. @value{GDBN} will
41411 ignore any line that it does not recognize. An empty line marks the end
41414 @c FIXME add some specific types of data
41416 The trace frame section consists of a number of consecutive frames.
41417 Each frame begins with a two-byte tracepoint number, followed by a
41418 four-byte size giving the amount of data in the frame. The data in
41419 the frame consists of a number of blocks, each introduced by a
41420 character indicating its type (at least register, memory, and trace
41421 state variable). The data in this section is raw binary, not a
41422 hexadecimal or other encoding; its endianness matches the target's
41425 @c FIXME bi-arch may require endianness/arch info in description section
41428 @item R @var{bytes}
41429 Register block. The number and ordering of bytes matches that of a
41430 @code{g} packet in the remote protocol. Note that these are the
41431 actual bytes, in target order and @value{GDBN} register order, not a
41432 hexadecimal encoding.
41434 @item M @var{address} @var{length} @var{bytes}...
41435 Memory block. This is a contiguous block of memory, at the 8-byte
41436 address @var{address}, with a 2-byte length @var{length}, followed by
41437 @var{length} bytes.
41439 @item V @var{number} @var{value}
41440 Trace state variable block. This records the 8-byte signed value
41441 @var{value} of trace state variable numbered @var{number}.
41445 Future enhancements of the trace file format may include additional types
41448 @node Index Section Format
41449 @appendix @code{.gdb_index} section format
41450 @cindex .gdb_index section format
41451 @cindex index section format
41453 This section documents the index section that is created by @code{save
41454 gdb-index} (@pxref{Index Files}). The index section is
41455 DWARF-specific; some knowledge of DWARF is assumed in this
41458 The mapped index file format is designed to be directly
41459 @code{mmap}able on any architecture. In most cases, a datum is
41460 represented using a little-endian 32-bit integer value, called an
41461 @code{offset_type}. Big endian machines must byte-swap the values
41462 before using them. Exceptions to this rule are noted. The data is
41463 laid out such that alignment is always respected.
41465 A mapped index consists of several areas, laid out in order.
41469 The file header. This is a sequence of values, of @code{offset_type}
41470 unless otherwise noted:
41474 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41475 Version 4 uses a different hashing function from versions 5 and 6.
41476 Version 6 includes symbols for inlined functions, whereas versions 4
41477 and 5 do not. Version 7 adds attributes to the CU indices in the
41478 symbol table. Version 8 specifies that symbols from DWARF type units
41479 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41480 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41482 @value{GDBN} will only read version 4, 5, or 6 indices
41483 by specifying @code{set use-deprecated-index-sections on}.
41484 GDB has a workaround for potentially broken version 7 indices so it is
41485 currently not flagged as deprecated.
41488 The offset, from the start of the file, of the CU list.
41491 The offset, from the start of the file, of the types CU list. Note
41492 that this area can be empty, in which case this offset will be equal
41493 to the next offset.
41496 The offset, from the start of the file, of the address area.
41499 The offset, from the start of the file, of the symbol table.
41502 The offset, from the start of the file, of the constant pool.
41506 The CU list. This is a sequence of pairs of 64-bit little-endian
41507 values, sorted by the CU offset. The first element in each pair is
41508 the offset of a CU in the @code{.debug_info} section. The second
41509 element in each pair is the length of that CU. References to a CU
41510 elsewhere in the map are done using a CU index, which is just the
41511 0-based index into this table. Note that if there are type CUs, then
41512 conceptually CUs and type CUs form a single list for the purposes of
41516 The types CU list. This is a sequence of triplets of 64-bit
41517 little-endian values. In a triplet, the first value is the CU offset,
41518 the second value is the type offset in the CU, and the third value is
41519 the type signature. The types CU list is not sorted.
41522 The address area. The address area consists of a sequence of address
41523 entries. Each address entry has three elements:
41527 The low address. This is a 64-bit little-endian value.
41530 The high address. This is a 64-bit little-endian value. Like
41531 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41534 The CU index. This is an @code{offset_type} value.
41538 The symbol table. This is an open-addressed hash table. The size of
41539 the hash table is always a power of 2.
41541 Each slot in the hash table consists of a pair of @code{offset_type}
41542 values. The first value is the offset of the symbol's name in the
41543 constant pool. The second value is the offset of the CU vector in the
41546 If both values are 0, then this slot in the hash table is empty. This
41547 is ok because while 0 is a valid constant pool index, it cannot be a
41548 valid index for both a string and a CU vector.
41550 The hash value for a table entry is computed by applying an
41551 iterative hash function to the symbol's name. Starting with an
41552 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41553 the string is incorporated into the hash using the formula depending on the
41558 The formula is @code{r = r * 67 + c - 113}.
41560 @item Versions 5 to 7
41561 The formula is @code{r = r * 67 + tolower (c) - 113}.
41564 The terminating @samp{\0} is not incorporated into the hash.
41566 The step size used in the hash table is computed via
41567 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41568 value, and @samp{size} is the size of the hash table. The step size
41569 is used to find the next candidate slot when handling a hash
41572 The names of C@t{++} symbols in the hash table are canonicalized. We
41573 don't currently have a simple description of the canonicalization
41574 algorithm; if you intend to create new index sections, you must read
41578 The constant pool. This is simply a bunch of bytes. It is organized
41579 so that alignment is correct: CU vectors are stored first, followed by
41582 A CU vector in the constant pool is a sequence of @code{offset_type}
41583 values. The first value is the number of CU indices in the vector.
41584 Each subsequent value is the index and symbol attributes of a CU in
41585 the CU list. This element in the hash table is used to indicate which
41586 CUs define the symbol and how the symbol is used.
41587 See below for the format of each CU index+attributes entry.
41589 A string in the constant pool is zero-terminated.
41592 Attributes were added to CU index values in @code{.gdb_index} version 7.
41593 If a symbol has multiple uses within a CU then there is one
41594 CU index+attributes value for each use.
41596 The format of each CU index+attributes entry is as follows
41602 This is the index of the CU in the CU list.
41604 These bits are reserved for future purposes and must be zero.
41606 The kind of the symbol in the CU.
41610 This value is reserved and should not be used.
41611 By reserving zero the full @code{offset_type} value is backwards compatible
41612 with previous versions of the index.
41614 The symbol is a type.
41616 The symbol is a variable or an enum value.
41618 The symbol is a function.
41620 Any other kind of symbol.
41622 These values are reserved.
41626 This bit is zero if the value is global and one if it is static.
41628 The determination of whether a symbol is global or static is complicated.
41629 The authorative reference is the file @file{dwarf2read.c} in
41630 @value{GDBN} sources.
41634 This pseudo-code describes the computation of a symbol's kind and
41635 global/static attributes in the index.
41638 is_external = get_attribute (die, DW_AT_external);
41639 language = get_attribute (cu_die, DW_AT_language);
41642 case DW_TAG_typedef:
41643 case DW_TAG_base_type:
41644 case DW_TAG_subrange_type:
41648 case DW_TAG_enumerator:
41650 is_static = (language != CPLUS && language != JAVA);
41652 case DW_TAG_subprogram:
41654 is_static = ! (is_external || language == ADA);
41656 case DW_TAG_constant:
41658 is_static = ! is_external;
41660 case DW_TAG_variable:
41662 is_static = ! is_external;
41664 case DW_TAG_namespace:
41668 case DW_TAG_class_type:
41669 case DW_TAG_interface_type:
41670 case DW_TAG_structure_type:
41671 case DW_TAG_union_type:
41672 case DW_TAG_enumeration_type:
41674 is_static = (language != CPLUS && language != JAVA);
41682 @appendix Manual pages
41686 * gdb man:: The GNU Debugger man page
41687 * gdbserver man:: Remote Server for the GNU Debugger man page
41688 * gcore man:: Generate a core file of a running program
41689 * gdbinit man:: gdbinit scripts
41695 @c man title gdb The GNU Debugger
41697 @c man begin SYNOPSIS gdb
41698 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41699 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41700 [@option{-b}@w{ }@var{bps}]
41701 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41702 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41703 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41704 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41705 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41708 @c man begin DESCRIPTION gdb
41709 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41710 going on ``inside'' another program while it executes -- or what another
41711 program was doing at the moment it crashed.
41713 @value{GDBN} can do four main kinds of things (plus other things in support of
41714 these) to help you catch bugs in the act:
41718 Start your program, specifying anything that might affect its behavior.
41721 Make your program stop on specified conditions.
41724 Examine what has happened, when your program has stopped.
41727 Change things in your program, so you can experiment with correcting the
41728 effects of one bug and go on to learn about another.
41731 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41734 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41735 commands from the terminal until you tell it to exit with the @value{GDBN}
41736 command @code{quit}. You can get online help from @value{GDBN} itself
41737 by using the command @code{help}.
41739 You can run @code{gdb} with no arguments or options; but the most
41740 usual way to start @value{GDBN} is with one argument or two, specifying an
41741 executable program as the argument:
41747 You can also start with both an executable program and a core file specified:
41753 You can, instead, specify a process ID as a second argument, if you want
41754 to debug a running process:
41762 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41763 named @file{1234}; @value{GDBN} does check for a core file first).
41764 With option @option{-p} you can omit the @var{program} filename.
41766 Here are some of the most frequently needed @value{GDBN} commands:
41768 @c pod2man highlights the right hand side of the @item lines.
41770 @item break [@var{file}:]@var{functiop}
41771 Set a breakpoint at @var{function} (in @var{file}).
41773 @item run [@var{arglist}]
41774 Start your program (with @var{arglist}, if specified).
41777 Backtrace: display the program stack.
41779 @item print @var{expr}
41780 Display the value of an expression.
41783 Continue running your program (after stopping, e.g. at a breakpoint).
41786 Execute next program line (after stopping); step @emph{over} any
41787 function calls in the line.
41789 @item edit [@var{file}:]@var{function}
41790 look at the program line where it is presently stopped.
41792 @item list [@var{file}:]@var{function}
41793 type the text of the program in the vicinity of where it is presently stopped.
41796 Execute next program line (after stopping); step @emph{into} any
41797 function calls in the line.
41799 @item help [@var{name}]
41800 Show information about @value{GDBN} command @var{name}, or general information
41801 about using @value{GDBN}.
41804 Exit from @value{GDBN}.
41808 For full details on @value{GDBN},
41809 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41810 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41811 as the @code{gdb} entry in the @code{info} program.
41815 @c man begin OPTIONS gdb
41816 Any arguments other than options specify an executable
41817 file and core file (or process ID); that is, the first argument
41818 encountered with no
41819 associated option flag is equivalent to a @option{-se} option, and the second,
41820 if any, is equivalent to a @option{-c} option if it's the name of a file.
41822 both long and short forms; both are shown here. The long forms are also
41823 recognized if you truncate them, so long as enough of the option is
41824 present to be unambiguous. (If you prefer, you can flag option
41825 arguments with @option{+} rather than @option{-}, though we illustrate the
41826 more usual convention.)
41828 All the options and command line arguments you give are processed
41829 in sequential order. The order makes a difference when the @option{-x}
41835 List all options, with brief explanations.
41837 @item -symbols=@var{file}
41838 @itemx -s @var{file}
41839 Read symbol table from file @var{file}.
41842 Enable writing into executable and core files.
41844 @item -exec=@var{file}
41845 @itemx -e @var{file}
41846 Use file @var{file} as the executable file to execute when
41847 appropriate, and for examining pure data in conjunction with a core
41850 @item -se=@var{file}
41851 Read symbol table from file @var{file} and use it as the executable
41854 @item -core=@var{file}
41855 @itemx -c @var{file}
41856 Use file @var{file} as a core dump to examine.
41858 @item -command=@var{file}
41859 @itemx -x @var{file}
41860 Execute @value{GDBN} commands from file @var{file}.
41862 @item -ex @var{command}
41863 Execute given @value{GDBN} @var{command}.
41865 @item -directory=@var{directory}
41866 @itemx -d @var{directory}
41867 Add @var{directory} to the path to search for source files.
41870 Do not execute commands from @file{~/.gdbinit}.
41874 Do not execute commands from any @file{.gdbinit} initialization files.
41878 ``Quiet''. Do not print the introductory and copyright messages. These
41879 messages are also suppressed in batch mode.
41882 Run in batch mode. Exit with status @code{0} after processing all the command
41883 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41884 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41885 commands in the command files.
41887 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41888 download and run a program on another computer; in order to make this
41889 more useful, the message
41892 Program exited normally.
41896 (which is ordinarily issued whenever a program running under @value{GDBN} control
41897 terminates) is not issued when running in batch mode.
41899 @item -cd=@var{directory}
41900 Run @value{GDBN} using @var{directory} as its working directory,
41901 instead of the current directory.
41905 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41906 @value{GDBN} to output the full file name and line number in a standard,
41907 recognizable fashion each time a stack frame is displayed (which
41908 includes each time the program stops). This recognizable format looks
41909 like two @samp{\032} characters, followed by the file name, line number
41910 and character position separated by colons, and a newline. The
41911 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41912 characters as a signal to display the source code for the frame.
41915 Set the line speed (baud rate or bits per second) of any serial
41916 interface used by @value{GDBN} for remote debugging.
41918 @item -tty=@var{device}
41919 Run using @var{device} for your program's standard input and output.
41923 @c man begin SEEALSO gdb
41925 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41926 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41927 documentation are properly installed at your site, the command
41934 should give you access to the complete manual.
41936 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41937 Richard M. Stallman and Roland H. Pesch, July 1991.
41941 @node gdbserver man
41942 @heading gdbserver man
41944 @c man title gdbserver Remote Server for the GNU Debugger
41946 @c man begin SYNOPSIS gdbserver
41947 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41949 gdbserver --attach @var{comm} @var{pid}
41951 gdbserver --multi @var{comm}
41955 @c man begin DESCRIPTION gdbserver
41956 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41957 than the one which is running the program being debugged.
41960 @subheading Usage (server (target) side)
41963 Usage (server (target) side):
41966 First, you need to have a copy of the program you want to debug put onto
41967 the target system. The program can be stripped to save space if needed, as
41968 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41969 the @value{GDBN} running on the host system.
41971 To use the server, you log on to the target system, and run the @command{gdbserver}
41972 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41973 your program, and (c) its arguments. The general syntax is:
41976 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41979 For example, using a serial port, you might say:
41983 @c @file would wrap it as F</dev/com1>.
41984 target> gdbserver /dev/com1 emacs foo.txt
41987 target> gdbserver @file{/dev/com1} emacs foo.txt
41991 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41992 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41993 waits patiently for the host @value{GDBN} to communicate with it.
41995 To use a TCP connection, you could say:
41998 target> gdbserver host:2345 emacs foo.txt
42001 This says pretty much the same thing as the last example, except that we are
42002 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42003 that we are expecting to see a TCP connection from @code{host} to local TCP port
42004 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42005 want for the port number as long as it does not conflict with any existing TCP
42006 ports on the target system. This same port number must be used in the host
42007 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42008 you chose a port number that conflicts with another service, @command{gdbserver} will
42009 print an error message and exit.
42011 @command{gdbserver} can also attach to running programs.
42012 This is accomplished via the @option{--attach} argument. The syntax is:
42015 target> gdbserver --attach @var{comm} @var{pid}
42018 @var{pid} is the process ID of a currently running process. It isn't
42019 necessary to point @command{gdbserver} at a binary for the running process.
42021 To start @code{gdbserver} without supplying an initial command to run
42022 or process ID to attach, use the @option{--multi} command line option.
42023 In such case you should connect using @kbd{target extended-remote} to start
42024 the program you want to debug.
42027 target> gdbserver --multi @var{comm}
42031 @subheading Usage (host side)
42037 You need an unstripped copy of the target program on your host system, since
42038 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42039 would, with the target program as the first argument. (You may need to use the
42040 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42041 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42042 new command you need to know about is @code{target remote}
42043 (or @code{target extended-remote}). Its argument is either
42044 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42045 descriptor. For example:
42049 @c @file would wrap it as F</dev/ttyb>.
42050 (gdb) target remote /dev/ttyb
42053 (gdb) target remote @file{/dev/ttyb}
42058 communicates with the server via serial line @file{/dev/ttyb}, and:
42061 (gdb) target remote the-target:2345
42065 communicates via a TCP connection to port 2345 on host `the-target', where
42066 you previously started up @command{gdbserver} with the same port number. Note that for
42067 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42068 command, otherwise you may get an error that looks something like
42069 `Connection refused'.
42071 @command{gdbserver} can also debug multiple inferiors at once,
42074 the @value{GDBN} manual in node @code{Inferiors and Programs}
42075 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42078 @ref{Inferiors and Programs}.
42080 In such case use the @code{extended-remote} @value{GDBN} command variant:
42083 (gdb) target extended-remote the-target:2345
42086 The @command{gdbserver} option @option{--multi} may or may not be used in such
42090 @c man begin OPTIONS gdbserver
42091 There are three different modes for invoking @command{gdbserver}:
42096 Debug a specific program specified by its program name:
42099 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42102 The @var{comm} parameter specifies how should the server communicate
42103 with @value{GDBN}; it is either a device name (to use a serial line),
42104 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42105 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42106 debug in @var{prog}. Any remaining arguments will be passed to the
42107 program verbatim. When the program exits, @value{GDBN} will close the
42108 connection, and @code{gdbserver} will exit.
42111 Debug a specific program by specifying the process ID of a running
42115 gdbserver --attach @var{comm} @var{pid}
42118 The @var{comm} parameter is as described above. Supply the process ID
42119 of a running program in @var{pid}; @value{GDBN} will do everything
42120 else. Like with the previous mode, when the process @var{pid} exits,
42121 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42124 Multi-process mode -- debug more than one program/process:
42127 gdbserver --multi @var{comm}
42130 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42131 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42132 close the connection when a process being debugged exits, so you can
42133 debug several processes in the same session.
42136 In each of the modes you may specify these options:
42141 List all options, with brief explanations.
42144 This option causes @command{gdbserver} to print its version number and exit.
42147 @command{gdbserver} will attach to a running program. The syntax is:
42150 target> gdbserver --attach @var{comm} @var{pid}
42153 @var{pid} is the process ID of a currently running process. It isn't
42154 necessary to point @command{gdbserver} at a binary for the running process.
42157 To start @code{gdbserver} without supplying an initial command to run
42158 or process ID to attach, use this command line option.
42159 Then you can connect using @kbd{target extended-remote} and start
42160 the program you want to debug. The syntax is:
42163 target> gdbserver --multi @var{comm}
42167 Instruct @code{gdbserver} to display extra status information about the debugging
42169 This option is intended for @code{gdbserver} development and for bug reports to
42172 @item --remote-debug
42173 Instruct @code{gdbserver} to display remote protocol debug output.
42174 This option is intended for @code{gdbserver} development and for bug reports to
42178 Specify a wrapper to launch programs
42179 for debugging. The option should be followed by the name of the
42180 wrapper, then any command-line arguments to pass to the wrapper, then
42181 @kbd{--} indicating the end of the wrapper arguments.
42184 By default, @command{gdbserver} keeps the listening TCP port open, so that
42185 additional connections are possible. However, if you start @code{gdbserver}
42186 with the @option{--once} option, it will stop listening for any further
42187 connection attempts after connecting to the first @value{GDBN} session.
42189 @c --disable-packet is not documented for users.
42191 @c --disable-randomization and --no-disable-randomization are superseded by
42192 @c QDisableRandomization.
42197 @c man begin SEEALSO gdbserver
42199 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42200 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42201 documentation are properly installed at your site, the command
42207 should give you access to the complete manual.
42209 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42210 Richard M. Stallman and Roland H. Pesch, July 1991.
42217 @c man title gcore Generate a core file of a running program
42220 @c man begin SYNOPSIS gcore
42221 gcore [-o @var{filename}] @var{pid}
42225 @c man begin DESCRIPTION gcore
42226 Generate a core dump of a running program with process ID @var{pid}.
42227 Produced file is equivalent to a kernel produced core file as if the process
42228 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42229 limit). Unlike after a crash, after @command{gcore} the program remains
42230 running without any change.
42233 @c man begin OPTIONS gcore
42235 @item -o @var{filename}
42236 The optional argument
42237 @var{filename} specifies the file name where to put the core dump.
42238 If not specified, the file name defaults to @file{core.@var{pid}},
42239 where @var{pid} is the running program process ID.
42243 @c man begin SEEALSO gcore
42245 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42246 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42247 documentation are properly installed at your site, the command
42254 should give you access to the complete manual.
42256 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42257 Richard M. Stallman and Roland H. Pesch, July 1991.
42264 @c man title gdbinit GDB initialization scripts
42267 @c man begin SYNOPSIS gdbinit
42268 @ifset SYSTEM_GDBINIT
42269 @value{SYSTEM_GDBINIT}
42278 @c man begin DESCRIPTION gdbinit
42279 These files contain @value{GDBN} commands to automatically execute during
42280 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42283 the @value{GDBN} manual in node @code{Sequences}
42284 -- shell command @code{info -f gdb -n Sequences}.
42290 Please read more in
42292 the @value{GDBN} manual in node @code{Startup}
42293 -- shell command @code{info -f gdb -n Startup}.
42300 @ifset SYSTEM_GDBINIT
42301 @item @value{SYSTEM_GDBINIT}
42303 @ifclear SYSTEM_GDBINIT
42304 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42306 System-wide initialization file. It is executed unless user specified
42307 @value{GDBN} option @code{-nx} or @code{-n}.
42310 the @value{GDBN} manual in node @code{System-wide configuration}
42311 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42314 @ref{System-wide configuration}.
42318 User initialization file. It is executed unless user specified
42319 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42322 Initialization file for current directory. It may need to be enabled with
42323 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42326 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42327 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42330 @ref{Init File in the Current Directory}.
42335 @c man begin SEEALSO gdbinit
42337 gdb(1), @code{info -f gdb -n Startup}
42339 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42340 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42341 documentation are properly installed at your site, the command
42347 should give you access to the complete manual.
42349 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42350 Richard M. Stallman and Roland H. Pesch, July 1991.
42356 @node GNU Free Documentation License
42357 @appendix GNU Free Documentation License
42360 @node Concept Index
42361 @unnumbered Concept Index
42365 @node Command and Variable Index
42366 @unnumbered Command, Variable, and Function Index
42371 % I think something like @@colophon should be in texinfo. In the
42373 \long\def\colophon{\hbox to0pt{}\vfill
42374 \centerline{The body of this manual is set in}
42375 \centerline{\fontname\tenrm,}
42376 \centerline{with headings in {\bf\fontname\tenbf}}
42377 \centerline{and examples in {\tt\fontname\tentt}.}
42378 \centerline{{\it\fontname\tenit\/},}
42379 \centerline{{\bf\fontname\tenbf}, and}
42380 \centerline{{\sl\fontname\tensl\/}}
42381 \centerline{are used for emphasis.}\vfill}
42383 % Blame: doc@@cygnus.com, 1991.