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{$_exception} convenience
4102 variable rely on the presence of some SDT probes in @code{libstdc++}.
4103 If these probes are not present, then these features cannot be used.
4104 These probes were first available in the GCC 4.8 release, but whether
4105 or not they are available in your GCC also depends on how it was
4109 The @code{$_exception} convenience variable is only valid at the
4110 instruction at which an exception-related catchpoint is set.
4113 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4114 location in the system library which implements runtime exception
4115 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4116 (@pxref{Selection}) to get to your code.
4119 If you call a function interactively, @value{GDBN} normally returns
4120 control to you when the function has finished executing. If the call
4121 raises an exception, however, the call may bypass the mechanism that
4122 returns control to you and cause your program either to abort or to
4123 simply continue running until it hits a breakpoint, catches a signal
4124 that @value{GDBN} is listening for, or exits. This is the case even if
4125 you set a catchpoint for the exception; catchpoints on exceptions are
4126 disabled within interactive calls. @xref{Calling}, for information on
4127 controlling this with @code{set unwind-on-terminating-exception}.
4130 You cannot raise an exception interactively.
4133 You cannot install an exception handler interactively.
4137 @cindex Ada exception catching
4138 @cindex catch Ada exceptions
4139 An Ada exception being raised. If an exception name is specified
4140 at the end of the command (eg @code{catch exception Program_Error}),
4141 the debugger will stop only when this specific exception is raised.
4142 Otherwise, the debugger stops execution when any Ada exception is raised.
4144 When inserting an exception catchpoint on a user-defined exception whose
4145 name is identical to one of the exceptions defined by the language, the
4146 fully qualified name must be used as the exception name. Otherwise,
4147 @value{GDBN} will assume that it should stop on the pre-defined exception
4148 rather than the user-defined one. For instance, assuming an exception
4149 called @code{Constraint_Error} is defined in package @code{Pck}, then
4150 the command to use to catch such exceptions is @kbd{catch exception
4151 Pck.Constraint_Error}.
4153 @item exception unhandled
4154 An exception that was raised but is not handled by the program.
4157 A failed Ada assertion.
4160 @cindex break on fork/exec
4161 A call to @code{exec}. This is currently only available for HP-UX
4165 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4166 @cindex break on a system call.
4167 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4168 syscall is a mechanism for application programs to request a service
4169 from the operating system (OS) or one of the OS system services.
4170 @value{GDBN} can catch some or all of the syscalls issued by the
4171 debuggee, and show the related information for each syscall. If no
4172 argument is specified, calls to and returns from all system calls
4175 @var{name} can be any system call name that is valid for the
4176 underlying OS. Just what syscalls are valid depends on the OS. On
4177 GNU and Unix systems, you can find the full list of valid syscall
4178 names on @file{/usr/include/asm/unistd.h}.
4180 @c For MS-Windows, the syscall names and the corresponding numbers
4181 @c can be found, e.g., on this URL:
4182 @c http://www.metasploit.com/users/opcode/syscalls.html
4183 @c but we don't support Windows syscalls yet.
4185 Normally, @value{GDBN} knows in advance which syscalls are valid for
4186 each OS, so you can use the @value{GDBN} command-line completion
4187 facilities (@pxref{Completion,, command completion}) to list the
4190 You may also specify the system call numerically. A syscall's
4191 number is the value passed to the OS's syscall dispatcher to
4192 identify the requested service. When you specify the syscall by its
4193 name, @value{GDBN} uses its database of syscalls to convert the name
4194 into the corresponding numeric code, but using the number directly
4195 may be useful if @value{GDBN}'s database does not have the complete
4196 list of syscalls on your system (e.g., because @value{GDBN} lags
4197 behind the OS upgrades).
4199 The example below illustrates how this command works if you don't provide
4203 (@value{GDBP}) catch syscall
4204 Catchpoint 1 (syscall)
4206 Starting program: /tmp/catch-syscall
4208 Catchpoint 1 (call to syscall 'close'), \
4209 0xffffe424 in __kernel_vsyscall ()
4213 Catchpoint 1 (returned from syscall 'close'), \
4214 0xffffe424 in __kernel_vsyscall ()
4218 Here is an example of catching a system call by name:
4221 (@value{GDBP}) catch syscall chroot
4222 Catchpoint 1 (syscall 'chroot' [61])
4224 Starting program: /tmp/catch-syscall
4226 Catchpoint 1 (call to syscall 'chroot'), \
4227 0xffffe424 in __kernel_vsyscall ()
4231 Catchpoint 1 (returned from syscall 'chroot'), \
4232 0xffffe424 in __kernel_vsyscall ()
4236 An example of specifying a system call numerically. In the case
4237 below, the syscall number has a corresponding entry in the XML
4238 file, so @value{GDBN} finds its name and prints it:
4241 (@value{GDBP}) catch syscall 252
4242 Catchpoint 1 (syscall(s) 'exit_group')
4244 Starting program: /tmp/catch-syscall
4246 Catchpoint 1 (call to syscall 'exit_group'), \
4247 0xffffe424 in __kernel_vsyscall ()
4251 Program exited normally.
4255 However, there can be situations when there is no corresponding name
4256 in XML file for that syscall number. In this case, @value{GDBN} prints
4257 a warning message saying that it was not able to find the syscall name,
4258 but the catchpoint will be set anyway. See the example below:
4261 (@value{GDBP}) catch syscall 764
4262 warning: The number '764' does not represent a known syscall.
4263 Catchpoint 2 (syscall 764)
4267 If you configure @value{GDBN} using the @samp{--without-expat} option,
4268 it will not be able to display syscall names. Also, if your
4269 architecture does not have an XML file describing its system calls,
4270 you will not be able to see the syscall names. It is important to
4271 notice that these two features are used for accessing the syscall
4272 name database. In either case, you will see a warning like this:
4275 (@value{GDBP}) catch syscall
4276 warning: Could not open "syscalls/i386-linux.xml"
4277 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4278 GDB will not be able to display syscall names.
4279 Catchpoint 1 (syscall)
4283 Of course, the file name will change depending on your architecture and system.
4285 Still using the example above, you can also try to catch a syscall by its
4286 number. In this case, you would see something like:
4289 (@value{GDBP}) catch syscall 252
4290 Catchpoint 1 (syscall(s) 252)
4293 Again, in this case @value{GDBN} would not be able to display syscall's names.
4296 A call to @code{fork}. This is currently only available for HP-UX
4300 A call to @code{vfork}. This is currently only available for HP-UX
4303 @item load @r{[}regexp@r{]}
4304 @itemx unload @r{[}regexp@r{]}
4305 The loading or unloading of a shared library. If @var{regexp} is
4306 given, then the catchpoint will stop only if the regular expression
4307 matches one of the affected libraries.
4309 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4310 The delivery of a signal.
4312 With no arguments, this catchpoint will catch any signal that is not
4313 used internally by @value{GDBN}, specifically, all signals except
4314 @samp{SIGTRAP} and @samp{SIGINT}.
4316 With the argument @samp{all}, all signals, including those used by
4317 @value{GDBN}, will be caught. This argument cannot be used with other
4320 Otherwise, the arguments are a list of signal names as given to
4321 @code{handle} (@pxref{Signals}). Only signals specified in this list
4324 One reason that @code{catch signal} can be more useful than
4325 @code{handle} is that you can attach commands and conditions to the
4328 When a signal is caught by a catchpoint, the signal's @code{stop} and
4329 @code{print} settings, as specified by @code{handle}, are ignored.
4330 However, whether the signal is still delivered to the inferior depends
4331 on the @code{pass} setting; this can be changed in the catchpoint's
4336 @item tcatch @var{event}
4337 Set a catchpoint that is enabled only for one stop. The catchpoint is
4338 automatically deleted after the first time the event is caught.
4342 Use the @code{info break} command to list the current catchpoints.
4346 @subsection Deleting Breakpoints
4348 @cindex clearing breakpoints, watchpoints, catchpoints
4349 @cindex deleting breakpoints, watchpoints, catchpoints
4350 It is often necessary to eliminate a breakpoint, watchpoint, or
4351 catchpoint once it has done its job and you no longer want your program
4352 to stop there. This is called @dfn{deleting} the breakpoint. A
4353 breakpoint that has been deleted no longer exists; it is forgotten.
4355 With the @code{clear} command you can delete breakpoints according to
4356 where they are in your program. With the @code{delete} command you can
4357 delete individual breakpoints, watchpoints, or catchpoints by specifying
4358 their breakpoint numbers.
4360 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4361 automatically ignores breakpoints on the first instruction to be executed
4362 when you continue execution without changing the execution address.
4367 Delete any breakpoints at the next instruction to be executed in the
4368 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4369 the innermost frame is selected, this is a good way to delete a
4370 breakpoint where your program just stopped.
4372 @item clear @var{location}
4373 Delete any breakpoints set at the specified @var{location}.
4374 @xref{Specify Location}, for the various forms of @var{location}; the
4375 most useful ones are listed below:
4378 @item clear @var{function}
4379 @itemx clear @var{filename}:@var{function}
4380 Delete any breakpoints set at entry to the named @var{function}.
4382 @item clear @var{linenum}
4383 @itemx clear @var{filename}:@var{linenum}
4384 Delete any breakpoints set at or within the code of the specified
4385 @var{linenum} of the specified @var{filename}.
4388 @cindex delete breakpoints
4390 @kindex d @r{(@code{delete})}
4391 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4392 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4393 ranges specified as arguments. If no argument is specified, delete all
4394 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4395 confirm off}). You can abbreviate this command as @code{d}.
4399 @subsection Disabling Breakpoints
4401 @cindex enable/disable a breakpoint
4402 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4403 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4404 it had been deleted, but remembers the information on the breakpoint so
4405 that you can @dfn{enable} it again later.
4407 You disable and enable breakpoints, watchpoints, and catchpoints with
4408 the @code{enable} and @code{disable} commands, optionally specifying
4409 one or more breakpoint numbers as arguments. Use @code{info break} to
4410 print a list of all breakpoints, watchpoints, and catchpoints if you
4411 do not know which numbers to use.
4413 Disabling and enabling a breakpoint that has multiple locations
4414 affects all of its locations.
4416 A breakpoint, watchpoint, or catchpoint can have any of several
4417 different states of enablement:
4421 Enabled. The breakpoint stops your program. A breakpoint set
4422 with the @code{break} command starts out in this state.
4424 Disabled. The breakpoint has no effect on your program.
4426 Enabled once. The breakpoint stops your program, but then becomes
4429 Enabled for a count. The breakpoint stops your program for the next
4430 N times, then becomes disabled.
4432 Enabled for deletion. The breakpoint stops your program, but
4433 immediately after it does so it is deleted permanently. A breakpoint
4434 set with the @code{tbreak} command starts out in this state.
4437 You can use the following commands to enable or disable breakpoints,
4438 watchpoints, and catchpoints:
4442 @kindex dis @r{(@code{disable})}
4443 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4444 Disable the specified breakpoints---or all breakpoints, if none are
4445 listed. A disabled breakpoint has no effect but is not forgotten. All
4446 options such as ignore-counts, conditions and commands are remembered in
4447 case the breakpoint is enabled again later. You may abbreviate
4448 @code{disable} as @code{dis}.
4451 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4452 Enable the specified breakpoints (or all defined breakpoints). They
4453 become effective once again in stopping your program.
4455 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4456 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4457 of these breakpoints immediately after stopping your program.
4459 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4460 Enable the specified breakpoints temporarily. @value{GDBN} records
4461 @var{count} with each of the specified breakpoints, and decrements a
4462 breakpoint's count when it is hit. When any count reaches 0,
4463 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4464 count (@pxref{Conditions, ,Break Conditions}), that will be
4465 decremented to 0 before @var{count} is affected.
4467 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4468 Enable the specified breakpoints to work once, then die. @value{GDBN}
4469 deletes any of these breakpoints as soon as your program stops there.
4470 Breakpoints set by the @code{tbreak} command start out in this state.
4473 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4474 @c confusing: tbreak is also initially enabled.
4475 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4476 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4477 subsequently, they become disabled or enabled only when you use one of
4478 the commands above. (The command @code{until} can set and delete a
4479 breakpoint of its own, but it does not change the state of your other
4480 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4484 @subsection Break Conditions
4485 @cindex conditional breakpoints
4486 @cindex breakpoint conditions
4488 @c FIXME what is scope of break condition expr? Context where wanted?
4489 @c in particular for a watchpoint?
4490 The simplest sort of breakpoint breaks every time your program reaches a
4491 specified place. You can also specify a @dfn{condition} for a
4492 breakpoint. A condition is just a Boolean expression in your
4493 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4494 a condition evaluates the expression each time your program reaches it,
4495 and your program stops only if the condition is @emph{true}.
4497 This is the converse of using assertions for program validation; in that
4498 situation, you want to stop when the assertion is violated---that is,
4499 when the condition is false. In C, if you want to test an assertion expressed
4500 by the condition @var{assert}, you should set the condition
4501 @samp{! @var{assert}} on the appropriate breakpoint.
4503 Conditions are also accepted for watchpoints; you may not need them,
4504 since a watchpoint is inspecting the value of an expression anyhow---but
4505 it might be simpler, say, to just set a watchpoint on a variable name,
4506 and specify a condition that tests whether the new value is an interesting
4509 Break conditions can have side effects, and may even call functions in
4510 your program. This can be useful, for example, to activate functions
4511 that log program progress, or to use your own print functions to
4512 format special data structures. The effects are completely predictable
4513 unless there is another enabled breakpoint at the same address. (In
4514 that case, @value{GDBN} might see the other breakpoint first and stop your
4515 program without checking the condition of this one.) Note that
4516 breakpoint commands are usually more convenient and flexible than break
4518 purpose of performing side effects when a breakpoint is reached
4519 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4521 Breakpoint conditions can also be evaluated on the target's side if
4522 the target supports it. Instead of evaluating the conditions locally,
4523 @value{GDBN} encodes the expression into an agent expression
4524 (@pxref{Agent Expressions}) suitable for execution on the target,
4525 independently of @value{GDBN}. Global variables become raw memory
4526 locations, locals become stack accesses, and so forth.
4528 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4529 when its condition evaluates to true. This mechanism may provide faster
4530 response times depending on the performance characteristics of the target
4531 since it does not need to keep @value{GDBN} informed about
4532 every breakpoint trigger, even those with false conditions.
4534 Break conditions can be specified when a breakpoint is set, by using
4535 @samp{if} in the arguments to the @code{break} command. @xref{Set
4536 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4537 with the @code{condition} command.
4539 You can also use the @code{if} keyword with the @code{watch} command.
4540 The @code{catch} command does not recognize the @code{if} keyword;
4541 @code{condition} is the only way to impose a further condition on a
4546 @item condition @var{bnum} @var{expression}
4547 Specify @var{expression} as the break condition for breakpoint,
4548 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4549 breakpoint @var{bnum} stops your program only if the value of
4550 @var{expression} is true (nonzero, in C). When you use
4551 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4552 syntactic correctness, and to determine whether symbols in it have
4553 referents in the context of your breakpoint. If @var{expression} uses
4554 symbols not referenced in the context of the breakpoint, @value{GDBN}
4555 prints an error message:
4558 No symbol "foo" in current context.
4563 not actually evaluate @var{expression} at the time the @code{condition}
4564 command (or a command that sets a breakpoint with a condition, like
4565 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4567 @item condition @var{bnum}
4568 Remove the condition from breakpoint number @var{bnum}. It becomes
4569 an ordinary unconditional breakpoint.
4572 @cindex ignore count (of breakpoint)
4573 A special case of a breakpoint condition is to stop only when the
4574 breakpoint has been reached a certain number of times. This is so
4575 useful that there is a special way to do it, using the @dfn{ignore
4576 count} of the breakpoint. Every breakpoint has an ignore count, which
4577 is an integer. Most of the time, the ignore count is zero, and
4578 therefore has no effect. But if your program reaches a breakpoint whose
4579 ignore count is positive, then instead of stopping, it just decrements
4580 the ignore count by one and continues. As a result, if the ignore count
4581 value is @var{n}, the breakpoint does not stop the next @var{n} times
4582 your program reaches it.
4586 @item ignore @var{bnum} @var{count}
4587 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4588 The next @var{count} times the breakpoint is reached, your program's
4589 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4592 To make the breakpoint stop the next time it is reached, specify
4595 When you use @code{continue} to resume execution of your program from a
4596 breakpoint, you can specify an ignore count directly as an argument to
4597 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4598 Stepping,,Continuing and Stepping}.
4600 If a breakpoint has a positive ignore count and a condition, the
4601 condition is not checked. Once the ignore count reaches zero,
4602 @value{GDBN} resumes checking the condition.
4604 You could achieve the effect of the ignore count with a condition such
4605 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4606 is decremented each time. @xref{Convenience Vars, ,Convenience
4610 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4613 @node Break Commands
4614 @subsection Breakpoint Command Lists
4616 @cindex breakpoint commands
4617 You can give any breakpoint (or watchpoint or catchpoint) a series of
4618 commands to execute when your program stops due to that breakpoint. For
4619 example, you might want to print the values of certain expressions, or
4620 enable other breakpoints.
4624 @kindex end@r{ (breakpoint commands)}
4625 @item commands @r{[}@var{range}@dots{}@r{]}
4626 @itemx @dots{} @var{command-list} @dots{}
4628 Specify a list of commands for the given breakpoints. The commands
4629 themselves appear on the following lines. Type a line containing just
4630 @code{end} to terminate the commands.
4632 To remove all commands from a breakpoint, type @code{commands} and
4633 follow it immediately with @code{end}; that is, give no commands.
4635 With no argument, @code{commands} refers to the last breakpoint,
4636 watchpoint, or catchpoint set (not to the breakpoint most recently
4637 encountered). If the most recent breakpoints were set with a single
4638 command, then the @code{commands} will apply to all the breakpoints
4639 set by that command. This applies to breakpoints set by
4640 @code{rbreak}, and also applies when a single @code{break} command
4641 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4645 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4646 disabled within a @var{command-list}.
4648 You can use breakpoint commands to start your program up again. Simply
4649 use the @code{continue} command, or @code{step}, or any other command
4650 that resumes execution.
4652 Any other commands in the command list, after a command that resumes
4653 execution, are ignored. This is because any time you resume execution
4654 (even with a simple @code{next} or @code{step}), you may encounter
4655 another breakpoint---which could have its own command list, leading to
4656 ambiguities about which list to execute.
4659 If the first command you specify in a command list is @code{silent}, the
4660 usual message about stopping at a breakpoint is not printed. This may
4661 be desirable for breakpoints that are to print a specific message and
4662 then continue. If none of the remaining commands print anything, you
4663 see no sign that the breakpoint was reached. @code{silent} is
4664 meaningful only at the beginning of a breakpoint command list.
4666 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4667 print precisely controlled output, and are often useful in silent
4668 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4670 For example, here is how you could use breakpoint commands to print the
4671 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4677 printf "x is %d\n",x
4682 One application for breakpoint commands is to compensate for one bug so
4683 you can test for another. Put a breakpoint just after the erroneous line
4684 of code, give it a condition to detect the case in which something
4685 erroneous has been done, and give it commands to assign correct values
4686 to any variables that need them. End with the @code{continue} command
4687 so that your program does not stop, and start with the @code{silent}
4688 command so that no output is produced. Here is an example:
4699 @node Dynamic Printf
4700 @subsection Dynamic Printf
4702 @cindex dynamic printf
4704 The dynamic printf command @code{dprintf} combines a breakpoint with
4705 formatted printing of your program's data to give you the effect of
4706 inserting @code{printf} calls into your program on-the-fly, without
4707 having to recompile it.
4709 In its most basic form, the output goes to the GDB console. However,
4710 you can set the variable @code{dprintf-style} for alternate handling.
4711 For instance, you can ask to format the output by calling your
4712 program's @code{printf} function. This has the advantage that the
4713 characters go to the program's output device, so they can recorded in
4714 redirects to files and so forth.
4716 If you are doing remote debugging with a stub or agent, you can also
4717 ask to have the printf handled by the remote agent. In addition to
4718 ensuring that the output goes to the remote program's device along
4719 with any other output the program might produce, you can also ask that
4720 the dprintf remain active even after disconnecting from the remote
4721 target. Using the stub/agent is also more efficient, as it can do
4722 everything without needing to communicate with @value{GDBN}.
4726 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4727 Whenever execution reaches @var{location}, print the values of one or
4728 more @var{expressions} under the control of the string @var{template}.
4729 To print several values, separate them with commas.
4731 @item set dprintf-style @var{style}
4732 Set the dprintf output to be handled in one of several different
4733 styles enumerated below. A change of style affects all existing
4734 dynamic printfs immediately. (If you need individual control over the
4735 print commands, simply define normal breakpoints with
4736 explicitly-supplied command lists.)
4739 @kindex dprintf-style gdb
4740 Handle the output using the @value{GDBN} @code{printf} command.
4743 @kindex dprintf-style call
4744 Handle the output by calling a function in your program (normally
4748 @kindex dprintf-style agent
4749 Have the remote debugging agent (such as @code{gdbserver}) handle
4750 the output itself. This style is only available for agents that
4751 support running commands on the target.
4753 @item set dprintf-function @var{function}
4754 Set the function to call if the dprintf style is @code{call}. By
4755 default its value is @code{printf}. You may set it to any expression.
4756 that @value{GDBN} can evaluate to a function, as per the @code{call}
4759 @item set dprintf-channel @var{channel}
4760 Set a ``channel'' for dprintf. If set to a non-empty value,
4761 @value{GDBN} will evaluate it as an expression and pass the result as
4762 a first argument to the @code{dprintf-function}, in the manner of
4763 @code{fprintf} and similar functions. Otherwise, the dprintf format
4764 string will be the first argument, in the manner of @code{printf}.
4766 As an example, if you wanted @code{dprintf} output to go to a logfile
4767 that is a standard I/O stream assigned to the variable @code{mylog},
4768 you could do the following:
4771 (gdb) set dprintf-style call
4772 (gdb) set dprintf-function fprintf
4773 (gdb) set dprintf-channel mylog
4774 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4775 Dprintf 1 at 0x123456: file main.c, line 25.
4777 1 dprintf keep y 0x00123456 in main at main.c:25
4778 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4783 Note that the @code{info break} displays the dynamic printf commands
4784 as normal breakpoint commands; you can thus easily see the effect of
4785 the variable settings.
4787 @item set disconnected-dprintf on
4788 @itemx set disconnected-dprintf off
4789 @kindex set disconnected-dprintf
4790 Choose whether @code{dprintf} commands should continue to run if
4791 @value{GDBN} has disconnected from the target. This only applies
4792 if the @code{dprintf-style} is @code{agent}.
4794 @item show disconnected-dprintf off
4795 @kindex show disconnected-dprintf
4796 Show the current choice for disconnected @code{dprintf}.
4800 @value{GDBN} does not check the validity of function and channel,
4801 relying on you to supply values that are meaningful for the contexts
4802 in which they are being used. For instance, the function and channel
4803 may be the values of local variables, but if that is the case, then
4804 all enabled dynamic prints must be at locations within the scope of
4805 those locals. If evaluation fails, @value{GDBN} will report an error.
4807 @node Save Breakpoints
4808 @subsection How to save breakpoints to a file
4810 To save breakpoint definitions to a file use the @w{@code{save
4811 breakpoints}} command.
4814 @kindex save breakpoints
4815 @cindex save breakpoints to a file for future sessions
4816 @item save breakpoints [@var{filename}]
4817 This command saves all current breakpoint definitions together with
4818 their commands and ignore counts, into a file @file{@var{filename}}
4819 suitable for use in a later debugging session. This includes all
4820 types of breakpoints (breakpoints, watchpoints, catchpoints,
4821 tracepoints). To read the saved breakpoint definitions, use the
4822 @code{source} command (@pxref{Command Files}). Note that watchpoints
4823 with expressions involving local variables may fail to be recreated
4824 because it may not be possible to access the context where the
4825 watchpoint is valid anymore. Because the saved breakpoint definitions
4826 are simply a sequence of @value{GDBN} commands that recreate the
4827 breakpoints, you can edit the file in your favorite editing program,
4828 and remove the breakpoint definitions you're not interested in, or
4829 that can no longer be recreated.
4832 @node Static Probe Points
4833 @subsection Static Probe Points
4835 @cindex static probe point, SystemTap
4836 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4837 for Statically Defined Tracing, and the probes are designed to have a tiny
4838 runtime code and data footprint, and no dynamic relocations. They are
4839 usable from assembly, C and C@t{++} languages. See
4840 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4841 for a good reference on how the @acronym{SDT} probes are implemented.
4843 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4844 @acronym{SDT} probes are supported on ELF-compatible systems. See
4845 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4846 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4847 in your applications.
4849 @cindex semaphores on static probe points
4850 Some probes have an associated semaphore variable; for instance, this
4851 happens automatically if you defined your probe using a DTrace-style
4852 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4853 automatically enable it when you specify a breakpoint using the
4854 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4855 location by some other method (e.g., @code{break file:line}), then
4856 @value{GDBN} will not automatically set the semaphore.
4858 You can examine the available static static probes using @code{info
4859 probes}, with optional arguments:
4863 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4864 If given, @var{provider} is a regular expression used to match against provider
4865 names when selecting which probes to list. If omitted, probes by all
4866 probes from all providers are listed.
4868 If given, @var{name} is a regular expression to match against probe names
4869 when selecting which probes to list. If omitted, probe names are not
4870 considered when deciding whether to display them.
4872 If given, @var{objfile} is a regular expression used to select which
4873 object files (executable or shared libraries) to examine. If not
4874 given, all object files are considered.
4876 @item info probes all
4877 List the available static probes, from all types.
4880 @vindex $_probe_arg@r{, convenience variable}
4881 A probe may specify up to twelve arguments. These are available at the
4882 point at which the probe is defined---that is, when the current PC is
4883 at the probe's location. The arguments are available using the
4884 convenience variables (@pxref{Convenience Vars})
4885 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4886 an integer of the appropriate size; types are not preserved. The
4887 convenience variable @code{$_probe_argc} holds the number of arguments
4888 at the current probe point.
4890 These variables are always available, but attempts to access them at
4891 any location other than a probe point will cause @value{GDBN} to give
4895 @c @ifclear BARETARGET
4896 @node Error in Breakpoints
4897 @subsection ``Cannot insert breakpoints''
4899 If you request too many active hardware-assisted breakpoints and
4900 watchpoints, you will see this error message:
4902 @c FIXME: the precise wording of this message may change; the relevant
4903 @c source change is not committed yet (Sep 3, 1999).
4905 Stopped; cannot insert breakpoints.
4906 You may have requested too many hardware breakpoints and watchpoints.
4910 This message is printed when you attempt to resume the program, since
4911 only then @value{GDBN} knows exactly how many hardware breakpoints and
4912 watchpoints it needs to insert.
4914 When this message is printed, you need to disable or remove some of the
4915 hardware-assisted breakpoints and watchpoints, and then continue.
4917 @node Breakpoint-related Warnings
4918 @subsection ``Breakpoint address adjusted...''
4919 @cindex breakpoint address adjusted
4921 Some processor architectures place constraints on the addresses at
4922 which breakpoints may be placed. For architectures thus constrained,
4923 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4924 with the constraints dictated by the architecture.
4926 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4927 a VLIW architecture in which a number of RISC-like instructions may be
4928 bundled together for parallel execution. The FR-V architecture
4929 constrains the location of a breakpoint instruction within such a
4930 bundle to the instruction with the lowest address. @value{GDBN}
4931 honors this constraint by adjusting a breakpoint's address to the
4932 first in the bundle.
4934 It is not uncommon for optimized code to have bundles which contain
4935 instructions from different source statements, thus it may happen that
4936 a breakpoint's address will be adjusted from one source statement to
4937 another. Since this adjustment may significantly alter @value{GDBN}'s
4938 breakpoint related behavior from what the user expects, a warning is
4939 printed when the breakpoint is first set and also when the breakpoint
4942 A warning like the one below is printed when setting a breakpoint
4943 that's been subject to address adjustment:
4946 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4949 Such warnings are printed both for user settable and @value{GDBN}'s
4950 internal breakpoints. If you see one of these warnings, you should
4951 verify that a breakpoint set at the adjusted address will have the
4952 desired affect. If not, the breakpoint in question may be removed and
4953 other breakpoints may be set which will have the desired behavior.
4954 E.g., it may be sufficient to place the breakpoint at a later
4955 instruction. A conditional breakpoint may also be useful in some
4956 cases to prevent the breakpoint from triggering too often.
4958 @value{GDBN} will also issue a warning when stopping at one of these
4959 adjusted breakpoints:
4962 warning: Breakpoint 1 address previously adjusted from 0x00010414
4966 When this warning is encountered, it may be too late to take remedial
4967 action except in cases where the breakpoint is hit earlier or more
4968 frequently than expected.
4970 @node Continuing and Stepping
4971 @section Continuing and Stepping
4975 @cindex resuming execution
4976 @dfn{Continuing} means resuming program execution until your program
4977 completes normally. In contrast, @dfn{stepping} means executing just
4978 one more ``step'' of your program, where ``step'' may mean either one
4979 line of source code, or one machine instruction (depending on what
4980 particular command you use). Either when continuing or when stepping,
4981 your program may stop even sooner, due to a breakpoint or a signal. (If
4982 it stops due to a signal, you may want to use @code{handle}, or use
4983 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4987 @kindex c @r{(@code{continue})}
4988 @kindex fg @r{(resume foreground execution)}
4989 @item continue @r{[}@var{ignore-count}@r{]}
4990 @itemx c @r{[}@var{ignore-count}@r{]}
4991 @itemx fg @r{[}@var{ignore-count}@r{]}
4992 Resume program execution, at the address where your program last stopped;
4993 any breakpoints set at that address are bypassed. The optional argument
4994 @var{ignore-count} allows you to specify a further number of times to
4995 ignore a breakpoint at this location; its effect is like that of
4996 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4998 The argument @var{ignore-count} is meaningful only when your program
4999 stopped due to a breakpoint. At other times, the argument to
5000 @code{continue} is ignored.
5002 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5003 debugged program is deemed to be the foreground program) are provided
5004 purely for convenience, and have exactly the same behavior as
5008 To resume execution at a different place, you can use @code{return}
5009 (@pxref{Returning, ,Returning from a Function}) to go back to the
5010 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5011 Different Address}) to go to an arbitrary location in your program.
5013 A typical technique for using stepping is to set a breakpoint
5014 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5015 beginning of the function or the section of your program where a problem
5016 is believed to lie, run your program until it stops at that breakpoint,
5017 and then step through the suspect area, examining the variables that are
5018 interesting, until you see the problem happen.
5022 @kindex s @r{(@code{step})}
5024 Continue running your program until control reaches a different source
5025 line, then stop it and return control to @value{GDBN}. This command is
5026 abbreviated @code{s}.
5029 @c "without debugging information" is imprecise; actually "without line
5030 @c numbers in the debugging information". (gcc -g1 has debugging info but
5031 @c not line numbers). But it seems complex to try to make that
5032 @c distinction here.
5033 @emph{Warning:} If you use the @code{step} command while control is
5034 within a function that was compiled without debugging information,
5035 execution proceeds until control reaches a function that does have
5036 debugging information. Likewise, it will not step into a function which
5037 is compiled without debugging information. To step through functions
5038 without debugging information, use the @code{stepi} command, described
5042 The @code{step} command only stops at the first instruction of a source
5043 line. This prevents the multiple stops that could otherwise occur in
5044 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5045 to stop if a function that has debugging information is called within
5046 the line. In other words, @code{step} @emph{steps inside} any functions
5047 called within the line.
5049 Also, the @code{step} command only enters a function if there is line
5050 number information for the function. Otherwise it acts like the
5051 @code{next} command. This avoids problems when using @code{cc -gl}
5052 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5053 was any debugging information about the routine.
5055 @item step @var{count}
5056 Continue running as in @code{step}, but do so @var{count} times. If a
5057 breakpoint is reached, or a signal not related to stepping occurs before
5058 @var{count} steps, stepping stops right away.
5061 @kindex n @r{(@code{next})}
5062 @item next @r{[}@var{count}@r{]}
5063 Continue to the next source line in the current (innermost) stack frame.
5064 This is similar to @code{step}, but function calls that appear within
5065 the line of code are executed without stopping. Execution stops when
5066 control reaches a different line of code at the original stack level
5067 that was executing when you gave the @code{next} command. This command
5068 is abbreviated @code{n}.
5070 An argument @var{count} is a repeat count, as for @code{step}.
5073 @c FIX ME!! Do we delete this, or is there a way it fits in with
5074 @c the following paragraph? --- Vctoria
5076 @c @code{next} within a function that lacks debugging information acts like
5077 @c @code{step}, but any function calls appearing within the code of the
5078 @c function are executed without stopping.
5080 The @code{next} command only stops at the first instruction of a
5081 source line. This prevents multiple stops that could otherwise occur in
5082 @code{switch} statements, @code{for} loops, etc.
5084 @kindex set step-mode
5086 @cindex functions without line info, and stepping
5087 @cindex stepping into functions with no line info
5088 @itemx set step-mode on
5089 The @code{set step-mode on} command causes the @code{step} command to
5090 stop at the first instruction of a function which contains no debug line
5091 information rather than stepping over it.
5093 This is useful in cases where you may be interested in inspecting the
5094 machine instructions of a function which has no symbolic info and do not
5095 want @value{GDBN} to automatically skip over this function.
5097 @item set step-mode off
5098 Causes the @code{step} command to step over any functions which contains no
5099 debug information. This is the default.
5101 @item show step-mode
5102 Show whether @value{GDBN} will stop in or step over functions without
5103 source line debug information.
5106 @kindex fin @r{(@code{finish})}
5108 Continue running until just after function in the selected stack frame
5109 returns. Print the returned value (if any). This command can be
5110 abbreviated as @code{fin}.
5112 Contrast this with the @code{return} command (@pxref{Returning,
5113 ,Returning from a Function}).
5116 @kindex u @r{(@code{until})}
5117 @cindex run until specified location
5120 Continue running until a source line past the current line, in the
5121 current stack frame, is reached. This command is used to avoid single
5122 stepping through a loop more than once. It is like the @code{next}
5123 command, except that when @code{until} encounters a jump, it
5124 automatically continues execution until the program counter is greater
5125 than the address of the jump.
5127 This means that when you reach the end of a loop after single stepping
5128 though it, @code{until} makes your program continue execution until it
5129 exits the loop. In contrast, a @code{next} command at the end of a loop
5130 simply steps back to the beginning of the loop, which forces you to step
5131 through the next iteration.
5133 @code{until} always stops your program if it attempts to exit the current
5136 @code{until} may produce somewhat counterintuitive results if the order
5137 of machine code does not match the order of the source lines. For
5138 example, in the following excerpt from a debugging session, the @code{f}
5139 (@code{frame}) command shows that execution is stopped at line
5140 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5144 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5146 (@value{GDBP}) until
5147 195 for ( ; argc > 0; NEXTARG) @{
5150 This happened because, for execution efficiency, the compiler had
5151 generated code for the loop closure test at the end, rather than the
5152 start, of the loop---even though the test in a C @code{for}-loop is
5153 written before the body of the loop. The @code{until} command appeared
5154 to step back to the beginning of the loop when it advanced to this
5155 expression; however, it has not really gone to an earlier
5156 statement---not in terms of the actual machine code.
5158 @code{until} with no argument works by means of single
5159 instruction stepping, and hence is slower than @code{until} with an
5162 @item until @var{location}
5163 @itemx u @var{location}
5164 Continue running your program until either the specified location is
5165 reached, or the current stack frame returns. @var{location} is any of
5166 the forms described in @ref{Specify Location}.
5167 This form of the command uses temporary breakpoints, and
5168 hence is quicker than @code{until} without an argument. The specified
5169 location is actually reached only if it is in the current frame. This
5170 implies that @code{until} can be used to skip over recursive function
5171 invocations. For instance in the code below, if the current location is
5172 line @code{96}, issuing @code{until 99} will execute the program up to
5173 line @code{99} in the same invocation of factorial, i.e., after the inner
5174 invocations have returned.
5177 94 int factorial (int value)
5179 96 if (value > 1) @{
5180 97 value *= factorial (value - 1);
5187 @kindex advance @var{location}
5188 @item advance @var{location}
5189 Continue running the program up to the given @var{location}. An argument is
5190 required, which should be of one of the forms described in
5191 @ref{Specify Location}.
5192 Execution will also stop upon exit from the current stack
5193 frame. This command is similar to @code{until}, but @code{advance} will
5194 not skip over recursive function calls, and the target location doesn't
5195 have to be in the same frame as the current one.
5199 @kindex si @r{(@code{stepi})}
5201 @itemx stepi @var{arg}
5203 Execute one machine instruction, then stop and return to the debugger.
5205 It is often useful to do @samp{display/i $pc} when stepping by machine
5206 instructions. This makes @value{GDBN} automatically display the next
5207 instruction to be executed, each time your program stops. @xref{Auto
5208 Display,, Automatic Display}.
5210 An argument is a repeat count, as in @code{step}.
5214 @kindex ni @r{(@code{nexti})}
5216 @itemx nexti @var{arg}
5218 Execute one machine instruction, but if it is a function call,
5219 proceed until the function returns.
5221 An argument is a repeat count, as in @code{next}.
5225 @anchor{range stepping}
5226 @cindex range stepping
5227 @cindex target-assisted range stepping
5228 By default, and if available, @value{GDBN} makes use of
5229 target-assisted @dfn{range stepping}. In other words, whenever you
5230 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5231 tells the target to step the corresponding range of instruction
5232 addresses instead of issuing multiple single-steps. This speeds up
5233 line stepping, particularly for remote targets. Ideally, there should
5234 be no reason you would want to turn range stepping off. However, it's
5235 possible that a bug in the debug info, a bug in the remote stub (for
5236 remote targets), or even a bug in @value{GDBN} could make line
5237 stepping behave incorrectly when target-assisted range stepping is
5238 enabled. You can use the following command to turn off range stepping
5242 @kindex set range-stepping
5243 @kindex show range-stepping
5244 @item set range-stepping
5245 @itemx show range-stepping
5246 Control whether range stepping is enabled.
5248 If @code{on}, and the target supports it, @value{GDBN} tells the
5249 target to step a range of addresses itself, instead of issuing
5250 multiple single-steps. If @code{off}, @value{GDBN} always issues
5251 single-steps, even if range stepping is supported by the target. The
5252 default is @code{on}.
5256 @node Skipping Over Functions and Files
5257 @section Skipping Over Functions and Files
5258 @cindex skipping over functions and files
5260 The program you are debugging may contain some functions which are
5261 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5262 skip a function or all functions in a file when stepping.
5264 For example, consider the following C function:
5275 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5276 are not interested in stepping through @code{boring}. If you run @code{step}
5277 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5278 step over both @code{foo} and @code{boring}!
5280 One solution is to @code{step} into @code{boring} and use the @code{finish}
5281 command to immediately exit it. But this can become tedious if @code{boring}
5282 is called from many places.
5284 A more flexible solution is to execute @kbd{skip boring}. This instructs
5285 @value{GDBN} never to step into @code{boring}. Now when you execute
5286 @code{step} at line 103, you'll step over @code{boring} and directly into
5289 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5290 example, @code{skip file boring.c}.
5293 @kindex skip function
5294 @item skip @r{[}@var{linespec}@r{]}
5295 @itemx skip function @r{[}@var{linespec}@r{]}
5296 After running this command, the function named by @var{linespec} or the
5297 function containing the line named by @var{linespec} will be skipped over when
5298 stepping. @xref{Specify Location}.
5300 If you do not specify @var{linespec}, the function you're currently debugging
5303 (If you have a function called @code{file} that you want to skip, use
5304 @kbd{skip function file}.)
5307 @item skip file @r{[}@var{filename}@r{]}
5308 After running this command, any function whose source lives in @var{filename}
5309 will be skipped over when stepping.
5311 If you do not specify @var{filename}, functions whose source lives in the file
5312 you're currently debugging will be skipped.
5315 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5316 These are the commands for managing your list of skips:
5320 @item info skip @r{[}@var{range}@r{]}
5321 Print details about the specified skip(s). If @var{range} is not specified,
5322 print a table with details about all functions and files marked for skipping.
5323 @code{info skip} prints the following information about each skip:
5327 A number identifying this skip.
5329 The type of this skip, either @samp{function} or @samp{file}.
5330 @item Enabled or Disabled
5331 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5333 For function skips, this column indicates the address in memory of the function
5334 being skipped. If you've set a function skip on a function which has not yet
5335 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5336 which has the function is loaded, @code{info skip} will show the function's
5339 For file skips, this field contains the filename being skipped. For functions
5340 skips, this field contains the function name and its line number in the file
5341 where it is defined.
5345 @item skip delete @r{[}@var{range}@r{]}
5346 Delete the specified skip(s). If @var{range} is not specified, delete all
5350 @item skip enable @r{[}@var{range}@r{]}
5351 Enable the specified skip(s). If @var{range} is not specified, enable all
5354 @kindex skip disable
5355 @item skip disable @r{[}@var{range}@r{]}
5356 Disable the specified skip(s). If @var{range} is not specified, disable all
5365 A signal is an asynchronous event that can happen in a program. The
5366 operating system defines the possible kinds of signals, and gives each
5367 kind a name and a number. For example, in Unix @code{SIGINT} is the
5368 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5369 @code{SIGSEGV} is the signal a program gets from referencing a place in
5370 memory far away from all the areas in use; @code{SIGALRM} occurs when
5371 the alarm clock timer goes off (which happens only if your program has
5372 requested an alarm).
5374 @cindex fatal signals
5375 Some signals, including @code{SIGALRM}, are a normal part of the
5376 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5377 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5378 program has not specified in advance some other way to handle the signal.
5379 @code{SIGINT} does not indicate an error in your program, but it is normally
5380 fatal so it can carry out the purpose of the interrupt: to kill the program.
5382 @value{GDBN} has the ability to detect any occurrence of a signal in your
5383 program. You can tell @value{GDBN} in advance what to do for each kind of
5386 @cindex handling signals
5387 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5388 @code{SIGALRM} be silently passed to your program
5389 (so as not to interfere with their role in the program's functioning)
5390 but to stop your program immediately whenever an error signal happens.
5391 You can change these settings with the @code{handle} command.
5394 @kindex info signals
5398 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5399 handle each one. You can use this to see the signal numbers of all
5400 the defined types of signals.
5402 @item info signals @var{sig}
5403 Similar, but print information only about the specified signal number.
5405 @code{info handle} is an alias for @code{info signals}.
5407 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5408 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5409 for details about this command.
5412 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5413 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5414 can be the number of a signal or its name (with or without the
5415 @samp{SIG} at the beginning); a list of signal numbers of the form
5416 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5417 known signals. Optional arguments @var{keywords}, described below,
5418 say what change to make.
5422 The keywords allowed by the @code{handle} command can be abbreviated.
5423 Their full names are:
5427 @value{GDBN} should not stop your program when this signal happens. It may
5428 still print a message telling you that the signal has come in.
5431 @value{GDBN} should stop your program when this signal happens. This implies
5432 the @code{print} keyword as well.
5435 @value{GDBN} should print a message when this signal happens.
5438 @value{GDBN} should not mention the occurrence of the signal at all. This
5439 implies the @code{nostop} keyword as well.
5443 @value{GDBN} should allow your program to see this signal; your program
5444 can handle the signal, or else it may terminate if the signal is fatal
5445 and not handled. @code{pass} and @code{noignore} are synonyms.
5449 @value{GDBN} should not allow your program to see this signal.
5450 @code{nopass} and @code{ignore} are synonyms.
5454 When a signal stops your program, the signal is not visible to the
5456 continue. Your program sees the signal then, if @code{pass} is in
5457 effect for the signal in question @emph{at that time}. In other words,
5458 after @value{GDBN} reports a signal, you can use the @code{handle}
5459 command with @code{pass} or @code{nopass} to control whether your
5460 program sees that signal when you continue.
5462 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5463 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5464 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5467 You can also use the @code{signal} command to prevent your program from
5468 seeing a signal, or cause it to see a signal it normally would not see,
5469 or to give it any signal at any time. For example, if your program stopped
5470 due to some sort of memory reference error, you might store correct
5471 values into the erroneous variables and continue, hoping to see more
5472 execution; but your program would probably terminate immediately as
5473 a result of the fatal signal once it saw the signal. To prevent this,
5474 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5477 @cindex extra signal information
5478 @anchor{extra signal information}
5480 On some targets, @value{GDBN} can inspect extra signal information
5481 associated with the intercepted signal, before it is actually
5482 delivered to the program being debugged. This information is exported
5483 by the convenience variable @code{$_siginfo}, and consists of data
5484 that is passed by the kernel to the signal handler at the time of the
5485 receipt of a signal. The data type of the information itself is
5486 target dependent. You can see the data type using the @code{ptype
5487 $_siginfo} command. On Unix systems, it typically corresponds to the
5488 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5491 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5492 referenced address that raised a segmentation fault.
5496 (@value{GDBP}) continue
5497 Program received signal SIGSEGV, Segmentation fault.
5498 0x0000000000400766 in main ()
5500 (@value{GDBP}) ptype $_siginfo
5507 struct @{...@} _kill;
5508 struct @{...@} _timer;
5510 struct @{...@} _sigchld;
5511 struct @{...@} _sigfault;
5512 struct @{...@} _sigpoll;
5515 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5519 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5520 $1 = (void *) 0x7ffff7ff7000
5524 Depending on target support, @code{$_siginfo} may also be writable.
5527 @section Stopping and Starting Multi-thread Programs
5529 @cindex stopped threads
5530 @cindex threads, stopped
5532 @cindex continuing threads
5533 @cindex threads, continuing
5535 @value{GDBN} supports debugging programs with multiple threads
5536 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5537 are two modes of controlling execution of your program within the
5538 debugger. In the default mode, referred to as @dfn{all-stop mode},
5539 when any thread in your program stops (for example, at a breakpoint
5540 or while being stepped), all other threads in the program are also stopped by
5541 @value{GDBN}. On some targets, @value{GDBN} also supports
5542 @dfn{non-stop mode}, in which other threads can continue to run freely while
5543 you examine the stopped thread in the debugger.
5546 * All-Stop Mode:: All threads stop when GDB takes control
5547 * Non-Stop Mode:: Other threads continue to execute
5548 * Background Execution:: Running your program asynchronously
5549 * Thread-Specific Breakpoints:: Controlling breakpoints
5550 * Interrupted System Calls:: GDB may interfere with system calls
5551 * Observer Mode:: GDB does not alter program behavior
5555 @subsection All-Stop Mode
5557 @cindex all-stop mode
5559 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5560 @emph{all} threads of execution stop, not just the current thread. This
5561 allows you to examine the overall state of the program, including
5562 switching between threads, without worrying that things may change
5565 Conversely, whenever you restart the program, @emph{all} threads start
5566 executing. @emph{This is true even when single-stepping} with commands
5567 like @code{step} or @code{next}.
5569 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5570 Since thread scheduling is up to your debugging target's operating
5571 system (not controlled by @value{GDBN}), other threads may
5572 execute more than one statement while the current thread completes a
5573 single step. Moreover, in general other threads stop in the middle of a
5574 statement, rather than at a clean statement boundary, when the program
5577 You might even find your program stopped in another thread after
5578 continuing or even single-stepping. This happens whenever some other
5579 thread runs into a breakpoint, a signal, or an exception before the
5580 first thread completes whatever you requested.
5582 @cindex automatic thread selection
5583 @cindex switching threads automatically
5584 @cindex threads, automatic switching
5585 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5586 signal, it automatically selects the thread where that breakpoint or
5587 signal happened. @value{GDBN} alerts you to the context switch with a
5588 message such as @samp{[Switching to Thread @var{n}]} to identify the
5591 On some OSes, you can modify @value{GDBN}'s default behavior by
5592 locking the OS scheduler to allow only a single thread to run.
5595 @item set scheduler-locking @var{mode}
5596 @cindex scheduler locking mode
5597 @cindex lock scheduler
5598 Set the scheduler locking mode. If it is @code{off}, then there is no
5599 locking and any thread may run at any time. If @code{on}, then only the
5600 current thread may run when the inferior is resumed. The @code{step}
5601 mode optimizes for single-stepping; it prevents other threads
5602 from preempting the current thread while you are stepping, so that
5603 the focus of debugging does not change unexpectedly.
5604 Other threads only rarely (or never) get a chance to run
5605 when you step. They are more likely to run when you @samp{next} over a
5606 function call, and they are completely free to run when you use commands
5607 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5608 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5609 the current thread away from the thread that you are debugging.
5611 @item show scheduler-locking
5612 Display the current scheduler locking mode.
5615 @cindex resume threads of multiple processes simultaneously
5616 By default, when you issue one of the execution commands such as
5617 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5618 threads of the current inferior to run. For example, if @value{GDBN}
5619 is attached to two inferiors, each with two threads, the
5620 @code{continue} command resumes only the two threads of the current
5621 inferior. This is useful, for example, when you debug a program that
5622 forks and you want to hold the parent stopped (so that, for instance,
5623 it doesn't run to exit), while you debug the child. In other
5624 situations, you may not be interested in inspecting the current state
5625 of any of the processes @value{GDBN} is attached to, and you may want
5626 to resume them all until some breakpoint is hit. In the latter case,
5627 you can instruct @value{GDBN} to allow all threads of all the
5628 inferiors to run with the @w{@code{set schedule-multiple}} command.
5631 @kindex set schedule-multiple
5632 @item set schedule-multiple
5633 Set the mode for allowing threads of multiple processes to be resumed
5634 when an execution command is issued. When @code{on}, all threads of
5635 all processes are allowed to run. When @code{off}, only the threads
5636 of the current process are resumed. The default is @code{off}. The
5637 @code{scheduler-locking} mode takes precedence when set to @code{on},
5638 or while you are stepping and set to @code{step}.
5640 @item show schedule-multiple
5641 Display the current mode for resuming the execution of threads of
5646 @subsection Non-Stop Mode
5648 @cindex non-stop mode
5650 @c This section is really only a place-holder, and needs to be expanded
5651 @c with more details.
5653 For some multi-threaded targets, @value{GDBN} supports an optional
5654 mode of operation in which you can examine stopped program threads in
5655 the debugger while other threads continue to execute freely. This
5656 minimizes intrusion when debugging live systems, such as programs
5657 where some threads have real-time constraints or must continue to
5658 respond to external events. This is referred to as @dfn{non-stop} mode.
5660 In non-stop mode, when a thread stops to report a debugging event,
5661 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5662 threads as well, in contrast to the all-stop mode behavior. Additionally,
5663 execution commands such as @code{continue} and @code{step} apply by default
5664 only to the current thread in non-stop mode, rather than all threads as
5665 in all-stop mode. This allows you to control threads explicitly in
5666 ways that are not possible in all-stop mode --- for example, stepping
5667 one thread while allowing others to run freely, stepping
5668 one thread while holding all others stopped, or stepping several threads
5669 independently and simultaneously.
5671 To enter non-stop mode, use this sequence of commands before you run
5672 or attach to your program:
5675 # Enable the async interface.
5678 # If using the CLI, pagination breaks non-stop.
5681 # Finally, turn it on!
5685 You can use these commands to manipulate the non-stop mode setting:
5688 @kindex set non-stop
5689 @item set non-stop on
5690 Enable selection of non-stop mode.
5691 @item set non-stop off
5692 Disable selection of non-stop mode.
5693 @kindex show non-stop
5695 Show the current non-stop enablement setting.
5698 Note these commands only reflect whether non-stop mode is enabled,
5699 not whether the currently-executing program is being run in non-stop mode.
5700 In particular, the @code{set non-stop} preference is only consulted when
5701 @value{GDBN} starts or connects to the target program, and it is generally
5702 not possible to switch modes once debugging has started. Furthermore,
5703 since not all targets support non-stop mode, even when you have enabled
5704 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5707 In non-stop mode, all execution commands apply only to the current thread
5708 by default. That is, @code{continue} only continues one thread.
5709 To continue all threads, issue @code{continue -a} or @code{c -a}.
5711 You can use @value{GDBN}'s background execution commands
5712 (@pxref{Background Execution}) to run some threads in the background
5713 while you continue to examine or step others from @value{GDBN}.
5714 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5715 always executed asynchronously in non-stop mode.
5717 Suspending execution is done with the @code{interrupt} command when
5718 running in the background, or @kbd{Ctrl-c} during foreground execution.
5719 In all-stop mode, this stops the whole process;
5720 but in non-stop mode the interrupt applies only to the current thread.
5721 To stop the whole program, use @code{interrupt -a}.
5723 Other execution commands do not currently support the @code{-a} option.
5725 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5726 that thread current, as it does in all-stop mode. This is because the
5727 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5728 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5729 changed to a different thread just as you entered a command to operate on the
5730 previously current thread.
5732 @node Background Execution
5733 @subsection Background Execution
5735 @cindex foreground execution
5736 @cindex background execution
5737 @cindex asynchronous execution
5738 @cindex execution, foreground, background and asynchronous
5740 @value{GDBN}'s execution commands have two variants: the normal
5741 foreground (synchronous) behavior, and a background
5742 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5743 the program to report that some thread has stopped before prompting for
5744 another command. In background execution, @value{GDBN} immediately gives
5745 a command prompt so that you can issue other commands while your program runs.
5747 You need to explicitly enable asynchronous mode before you can use
5748 background execution commands. You can use these commands to
5749 manipulate the asynchronous mode setting:
5752 @kindex set target-async
5753 @item set target-async on
5754 Enable asynchronous mode.
5755 @item set target-async off
5756 Disable asynchronous mode.
5757 @kindex show target-async
5758 @item show target-async
5759 Show the current target-async setting.
5762 If the target doesn't support async mode, @value{GDBN} issues an error
5763 message if you attempt to use the background execution commands.
5765 To specify background execution, add a @code{&} to the command. For example,
5766 the background form of the @code{continue} command is @code{continue&}, or
5767 just @code{c&}. The execution commands that accept background execution
5773 @xref{Starting, , Starting your Program}.
5777 @xref{Attach, , Debugging an Already-running Process}.
5781 @xref{Continuing and Stepping, step}.
5785 @xref{Continuing and Stepping, stepi}.
5789 @xref{Continuing and Stepping, next}.
5793 @xref{Continuing and Stepping, nexti}.
5797 @xref{Continuing and Stepping, continue}.
5801 @xref{Continuing and Stepping, finish}.
5805 @xref{Continuing and Stepping, until}.
5809 Background execution is especially useful in conjunction with non-stop
5810 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5811 However, you can also use these commands in the normal all-stop mode with
5812 the restriction that you cannot issue another execution command until the
5813 previous one finishes. Examples of commands that are valid in all-stop
5814 mode while the program is running include @code{help} and @code{info break}.
5816 You can interrupt your program while it is running in the background by
5817 using the @code{interrupt} command.
5824 Suspend execution of the running program. In all-stop mode,
5825 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5826 only the current thread. To stop the whole program in non-stop mode,
5827 use @code{interrupt -a}.
5830 @node Thread-Specific Breakpoints
5831 @subsection Thread-Specific Breakpoints
5833 When your program has multiple threads (@pxref{Threads,, Debugging
5834 Programs with Multiple Threads}), you can choose whether to set
5835 breakpoints on all threads, or on a particular thread.
5838 @cindex breakpoints and threads
5839 @cindex thread breakpoints
5840 @kindex break @dots{} thread @var{threadno}
5841 @item break @var{linespec} thread @var{threadno}
5842 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5843 @var{linespec} specifies source lines; there are several ways of
5844 writing them (@pxref{Specify Location}), but the effect is always to
5845 specify some source line.
5847 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5848 to specify that you only want @value{GDBN} to stop the program when a
5849 particular thread reaches this breakpoint. @var{threadno} is one of the
5850 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5851 column of the @samp{info threads} display.
5853 If you do not specify @samp{thread @var{threadno}} when you set a
5854 breakpoint, the breakpoint applies to @emph{all} threads of your
5857 You can use the @code{thread} qualifier on conditional breakpoints as
5858 well; in this case, place @samp{thread @var{threadno}} before or
5859 after the breakpoint condition, like this:
5862 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5867 @node Interrupted System Calls
5868 @subsection Interrupted System Calls
5870 @cindex thread breakpoints and system calls
5871 @cindex system calls and thread breakpoints
5872 @cindex premature return from system calls
5873 There is an unfortunate side effect when using @value{GDBN} to debug
5874 multi-threaded programs. If one thread stops for a
5875 breakpoint, or for some other reason, and another thread is blocked in a
5876 system call, then the system call may return prematurely. This is a
5877 consequence of the interaction between multiple threads and the signals
5878 that @value{GDBN} uses to implement breakpoints and other events that
5881 To handle this problem, your program should check the return value of
5882 each system call and react appropriately. This is good programming
5885 For example, do not write code like this:
5891 The call to @code{sleep} will return early if a different thread stops
5892 at a breakpoint or for some other reason.
5894 Instead, write this:
5899 unslept = sleep (unslept);
5902 A system call is allowed to return early, so the system is still
5903 conforming to its specification. But @value{GDBN} does cause your
5904 multi-threaded program to behave differently than it would without
5907 Also, @value{GDBN} uses internal breakpoints in the thread library to
5908 monitor certain events such as thread creation and thread destruction.
5909 When such an event happens, a system call in another thread may return
5910 prematurely, even though your program does not appear to stop.
5913 @subsection Observer Mode
5915 If you want to build on non-stop mode and observe program behavior
5916 without any chance of disruption by @value{GDBN}, you can set
5917 variables to disable all of the debugger's attempts to modify state,
5918 whether by writing memory, inserting breakpoints, etc. These operate
5919 at a low level, intercepting operations from all commands.
5921 When all of these are set to @code{off}, then @value{GDBN} is said to
5922 be @dfn{observer mode}. As a convenience, the variable
5923 @code{observer} can be set to disable these, plus enable non-stop
5926 Note that @value{GDBN} will not prevent you from making nonsensical
5927 combinations of these settings. For instance, if you have enabled
5928 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5929 then breakpoints that work by writing trap instructions into the code
5930 stream will still not be able to be placed.
5935 @item set observer on
5936 @itemx set observer off
5937 When set to @code{on}, this disables all the permission variables
5938 below (except for @code{insert-fast-tracepoints}), plus enables
5939 non-stop debugging. Setting this to @code{off} switches back to
5940 normal debugging, though remaining in non-stop mode.
5943 Show whether observer mode is on or off.
5945 @kindex may-write-registers
5946 @item set may-write-registers on
5947 @itemx set may-write-registers off
5948 This controls whether @value{GDBN} will attempt to alter the values of
5949 registers, such as with assignment expressions in @code{print}, or the
5950 @code{jump} command. It defaults to @code{on}.
5952 @item show may-write-registers
5953 Show the current permission to write registers.
5955 @kindex may-write-memory
5956 @item set may-write-memory on
5957 @itemx set may-write-memory off
5958 This controls whether @value{GDBN} will attempt to alter the contents
5959 of memory, such as with assignment expressions in @code{print}. It
5960 defaults to @code{on}.
5962 @item show may-write-memory
5963 Show the current permission to write memory.
5965 @kindex may-insert-breakpoints
5966 @item set may-insert-breakpoints on
5967 @itemx set may-insert-breakpoints off
5968 This controls whether @value{GDBN} will attempt to insert breakpoints.
5969 This affects all breakpoints, including internal breakpoints defined
5970 by @value{GDBN}. It defaults to @code{on}.
5972 @item show may-insert-breakpoints
5973 Show the current permission to insert breakpoints.
5975 @kindex may-insert-tracepoints
5976 @item set may-insert-tracepoints on
5977 @itemx set may-insert-tracepoints off
5978 This controls whether @value{GDBN} will attempt to insert (regular)
5979 tracepoints at the beginning of a tracing experiment. It affects only
5980 non-fast tracepoints, fast tracepoints being under the control of
5981 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5983 @item show may-insert-tracepoints
5984 Show the current permission to insert tracepoints.
5986 @kindex may-insert-fast-tracepoints
5987 @item set may-insert-fast-tracepoints on
5988 @itemx set may-insert-fast-tracepoints off
5989 This controls whether @value{GDBN} will attempt to insert fast
5990 tracepoints at the beginning of a tracing experiment. It affects only
5991 fast tracepoints, regular (non-fast) tracepoints being under the
5992 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5994 @item show may-insert-fast-tracepoints
5995 Show the current permission to insert fast tracepoints.
5997 @kindex may-interrupt
5998 @item set may-interrupt on
5999 @itemx set may-interrupt off
6000 This controls whether @value{GDBN} will attempt to interrupt or stop
6001 program execution. When this variable is @code{off}, the
6002 @code{interrupt} command will have no effect, nor will
6003 @kbd{Ctrl-c}. It defaults to @code{on}.
6005 @item show may-interrupt
6006 Show the current permission to interrupt or stop the program.
6010 @node Reverse Execution
6011 @chapter Running programs backward
6012 @cindex reverse execution
6013 @cindex running programs backward
6015 When you are debugging a program, it is not unusual to realize that
6016 you have gone too far, and some event of interest has already happened.
6017 If the target environment supports it, @value{GDBN} can allow you to
6018 ``rewind'' the program by running it backward.
6020 A target environment that supports reverse execution should be able
6021 to ``undo'' the changes in machine state that have taken place as the
6022 program was executing normally. Variables, registers etc.@: should
6023 revert to their previous values. Obviously this requires a great
6024 deal of sophistication on the part of the target environment; not
6025 all target environments can support reverse execution.
6027 When a program is executed in reverse, the instructions that
6028 have most recently been executed are ``un-executed'', in reverse
6029 order. The program counter runs backward, following the previous
6030 thread of execution in reverse. As each instruction is ``un-executed'',
6031 the values of memory and/or registers that were changed by that
6032 instruction are reverted to their previous states. After executing
6033 a piece of source code in reverse, all side effects of that code
6034 should be ``undone'', and all variables should be returned to their
6035 prior values@footnote{
6036 Note that some side effects are easier to undo than others. For instance,
6037 memory and registers are relatively easy, but device I/O is hard. Some
6038 targets may be able undo things like device I/O, and some may not.
6040 The contract between @value{GDBN} and the reverse executing target
6041 requires only that the target do something reasonable when
6042 @value{GDBN} tells it to execute backwards, and then report the
6043 results back to @value{GDBN}. Whatever the target reports back to
6044 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6045 assumes that the memory and registers that the target reports are in a
6046 consistant state, but @value{GDBN} accepts whatever it is given.
6049 If you are debugging in a target environment that supports
6050 reverse execution, @value{GDBN} provides the following commands.
6053 @kindex reverse-continue
6054 @kindex rc @r{(@code{reverse-continue})}
6055 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6056 @itemx rc @r{[}@var{ignore-count}@r{]}
6057 Beginning at the point where your program last stopped, start executing
6058 in reverse. Reverse execution will stop for breakpoints and synchronous
6059 exceptions (signals), just like normal execution. Behavior of
6060 asynchronous signals depends on the target environment.
6062 @kindex reverse-step
6063 @kindex rs @r{(@code{step})}
6064 @item reverse-step @r{[}@var{count}@r{]}
6065 Run the program backward until control reaches the start of a
6066 different source line; then stop it, and return control to @value{GDBN}.
6068 Like the @code{step} command, @code{reverse-step} will only stop
6069 at the beginning of a source line. It ``un-executes'' the previously
6070 executed source line. If the previous source line included calls to
6071 debuggable functions, @code{reverse-step} will step (backward) into
6072 the called function, stopping at the beginning of the @emph{last}
6073 statement in the called function (typically a return statement).
6075 Also, as with the @code{step} command, if non-debuggable functions are
6076 called, @code{reverse-step} will run thru them backward without stopping.
6078 @kindex reverse-stepi
6079 @kindex rsi @r{(@code{reverse-stepi})}
6080 @item reverse-stepi @r{[}@var{count}@r{]}
6081 Reverse-execute one machine instruction. Note that the instruction
6082 to be reverse-executed is @emph{not} the one pointed to by the program
6083 counter, but the instruction executed prior to that one. For instance,
6084 if the last instruction was a jump, @code{reverse-stepi} will take you
6085 back from the destination of the jump to the jump instruction itself.
6087 @kindex reverse-next
6088 @kindex rn @r{(@code{reverse-next})}
6089 @item reverse-next @r{[}@var{count}@r{]}
6090 Run backward to the beginning of the previous line executed in
6091 the current (innermost) stack frame. If the line contains function
6092 calls, they will be ``un-executed'' without stopping. Starting from
6093 the first line of a function, @code{reverse-next} will take you back
6094 to the caller of that function, @emph{before} the function was called,
6095 just as the normal @code{next} command would take you from the last
6096 line of a function back to its return to its caller
6097 @footnote{Unless the code is too heavily optimized.}.
6099 @kindex reverse-nexti
6100 @kindex rni @r{(@code{reverse-nexti})}
6101 @item reverse-nexti @r{[}@var{count}@r{]}
6102 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6103 in reverse, except that called functions are ``un-executed'' atomically.
6104 That is, if the previously executed instruction was a return from
6105 another function, @code{reverse-nexti} will continue to execute
6106 in reverse until the call to that function (from the current stack
6109 @kindex reverse-finish
6110 @item reverse-finish
6111 Just as the @code{finish} command takes you to the point where the
6112 current function returns, @code{reverse-finish} takes you to the point
6113 where it was called. Instead of ending up at the end of the current
6114 function invocation, you end up at the beginning.
6116 @kindex set exec-direction
6117 @item set exec-direction
6118 Set the direction of target execution.
6119 @item set exec-direction reverse
6120 @cindex execute forward or backward in time
6121 @value{GDBN} will perform all execution commands in reverse, until the
6122 exec-direction mode is changed to ``forward''. Affected commands include
6123 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6124 command cannot be used in reverse mode.
6125 @item set exec-direction forward
6126 @value{GDBN} will perform all execution commands in the normal fashion.
6127 This is the default.
6131 @node Process Record and Replay
6132 @chapter Recording Inferior's Execution and Replaying It
6133 @cindex process record and replay
6134 @cindex recording inferior's execution and replaying it
6136 On some platforms, @value{GDBN} provides a special @dfn{process record
6137 and replay} target that can record a log of the process execution, and
6138 replay it later with both forward and reverse execution commands.
6141 When this target is in use, if the execution log includes the record
6142 for the next instruction, @value{GDBN} will debug in @dfn{replay
6143 mode}. In the replay mode, the inferior does not really execute code
6144 instructions. Instead, all the events that normally happen during
6145 code execution are taken from the execution log. While code is not
6146 really executed in replay mode, the values of registers (including the
6147 program counter register) and the memory of the inferior are still
6148 changed as they normally would. Their contents are taken from the
6152 If the record for the next instruction is not in the execution log,
6153 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6154 inferior executes normally, and @value{GDBN} records the execution log
6157 The process record and replay target supports reverse execution
6158 (@pxref{Reverse Execution}), even if the platform on which the
6159 inferior runs does not. However, the reverse execution is limited in
6160 this case by the range of the instructions recorded in the execution
6161 log. In other words, reverse execution on platforms that don't
6162 support it directly can only be done in the replay mode.
6164 When debugging in the reverse direction, @value{GDBN} will work in
6165 replay mode as long as the execution log includes the record for the
6166 previous instruction; otherwise, it will work in record mode, if the
6167 platform supports reverse execution, or stop if not.
6169 For architecture environments that support process record and replay,
6170 @value{GDBN} provides the following commands:
6173 @kindex target record
6174 @kindex target record-full
6175 @kindex target record-btrace
6178 @kindex record btrace
6182 @item record @var{method}
6183 This command starts the process record and replay target. The
6184 recording method can be specified as parameter. Without a parameter
6185 the command uses the @code{full} recording method. The following
6186 recording methods are available:
6190 Full record/replay recording using @value{GDBN}'s software record and
6191 replay implementation. This method allows replaying and reverse
6195 Hardware-supported instruction recording. This method does not allow
6196 replaying and reverse execution.
6198 This recording method may not be available on all processors.
6201 The process record and replay target can only debug a process that is
6202 already running. Therefore, you need first to start the process with
6203 the @kbd{run} or @kbd{start} commands, and then start the recording
6204 with the @kbd{record @var{method}} command.
6206 Both @code{record @var{method}} and @code{rec @var{method}} are
6207 aliases of @code{target record-@var{method}}.
6209 @cindex displaced stepping, and process record and replay
6210 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6211 will be automatically disabled when process record and replay target
6212 is started. That's because the process record and replay target
6213 doesn't support displaced stepping.
6215 @cindex non-stop mode, and process record and replay
6216 @cindex asynchronous execution, and process record and replay
6217 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6218 the asynchronous execution mode (@pxref{Background Execution}), not
6219 all recording methods are available. The @code{full} recording method
6220 does not support these two modes.
6225 Stop the process record and replay target. When process record and
6226 replay target stops, the entire execution log will be deleted and the
6227 inferior will either be terminated, or will remain in its final state.
6229 When you stop the process record and replay target in record mode (at
6230 the end of the execution log), the inferior will be stopped at the
6231 next instruction that would have been recorded. In other words, if
6232 you record for a while and then stop recording, the inferior process
6233 will be left in the same state as if the recording never happened.
6235 On the other hand, if the process record and replay target is stopped
6236 while in replay mode (that is, not at the end of the execution log,
6237 but at some earlier point), the inferior process will become ``live''
6238 at that earlier state, and it will then be possible to continue the
6239 usual ``live'' debugging of the process from that state.
6241 When the inferior process exits, or @value{GDBN} detaches from it,
6242 process record and replay target will automatically stop itself.
6246 Go to a specific location in the execution log. There are several
6247 ways to specify the location to go to:
6250 @item record goto begin
6251 @itemx record goto start
6252 Go to the beginning of the execution log.
6254 @item record goto end
6255 Go to the end of the execution log.
6257 @item record goto @var{n}
6258 Go to instruction number @var{n} in the execution log.
6262 @item record save @var{filename}
6263 Save the execution log to a file @file{@var{filename}}.
6264 Default filename is @file{gdb_record.@var{process_id}}, where
6265 @var{process_id} is the process ID of the inferior.
6267 This command may not be available for all recording methods.
6269 @kindex record restore
6270 @item record restore @var{filename}
6271 Restore the execution log from a file @file{@var{filename}}.
6272 File must have been created with @code{record save}.
6274 @kindex set record full
6275 @item set record full insn-number-max @var{limit}
6276 @itemx set record full insn-number-max unlimited
6277 Set the limit of instructions to be recorded for the @code{full}
6278 recording method. Default value is 200000.
6280 If @var{limit} is a positive number, then @value{GDBN} will start
6281 deleting instructions from the log once the number of the record
6282 instructions becomes greater than @var{limit}. For every new recorded
6283 instruction, @value{GDBN} will delete the earliest recorded
6284 instruction to keep the number of recorded instructions at the limit.
6285 (Since deleting recorded instructions loses information, @value{GDBN}
6286 lets you control what happens when the limit is reached, by means of
6287 the @code{stop-at-limit} option, described below.)
6289 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6290 delete recorded instructions from the execution log. The number of
6291 recorded instructions is limited only by the available memory.
6293 @kindex show record full
6294 @item show record full insn-number-max
6295 Show the limit of instructions to be recorded with the @code{full}
6298 @item set record full stop-at-limit
6299 Control the behavior of the @code{full} recording method when the
6300 number of recorded instructions reaches the limit. If ON (the
6301 default), @value{GDBN} will stop when the limit is reached for the
6302 first time and ask you whether you want to stop the inferior or
6303 continue running it and recording the execution log. If you decide
6304 to continue recording, each new recorded instruction will cause the
6305 oldest one to be deleted.
6307 If this option is OFF, @value{GDBN} will automatically delete the
6308 oldest record to make room for each new one, without asking.
6310 @item show record full stop-at-limit
6311 Show the current setting of @code{stop-at-limit}.
6313 @item set record full memory-query
6314 Control the behavior when @value{GDBN} is unable to record memory
6315 changes caused by an instruction for the @code{full} recording method.
6316 If ON, @value{GDBN} will query whether to stop the inferior in that
6319 If this option is OFF (the default), @value{GDBN} will automatically
6320 ignore the effect of such instructions on memory. Later, when
6321 @value{GDBN} replays this execution log, it will mark the log of this
6322 instruction as not accessible, and it will not affect the replay
6325 @item show record full memory-query
6326 Show the current setting of @code{memory-query}.
6330 Show various statistics about the recording depending on the recording
6335 For the @code{full} recording method, it shows the state of process
6336 record and its in-memory execution log buffer, including:
6340 Whether in record mode or replay mode.
6342 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6344 Highest recorded instruction number.
6346 Current instruction about to be replayed (if in replay mode).
6348 Number of instructions contained in the execution log.
6350 Maximum number of instructions that may be contained in the execution log.
6354 For the @code{btrace} recording method, it shows the number of
6355 instructions that have been recorded and the number of blocks of
6356 sequential control-flow that is formed by the recorded instructions.
6359 @kindex record delete
6362 When record target runs in replay mode (``in the past''), delete the
6363 subsequent execution log and begin to record a new execution log starting
6364 from the current address. This means you will abandon the previously
6365 recorded ``future'' and begin recording a new ``future''.
6367 @kindex record instruction-history
6368 @kindex rec instruction-history
6369 @item record instruction-history
6370 Disassembles instructions from the recorded execution log. By
6371 default, ten instructions are disassembled. This can be changed using
6372 the @code{set record instruction-history-size} command. Instructions
6373 are printed in execution order. There are several ways to specify
6374 what part of the execution log to disassemble:
6377 @item record instruction-history @var{insn}
6378 Disassembles ten instructions starting from instruction number
6381 @item record instruction-history @var{insn}, +/-@var{n}
6382 Disassembles @var{n} instructions around instruction number
6383 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6384 @var{n} instructions after instruction number @var{insn}. If
6385 @var{n} is preceded with @code{-}, disassembles @var{n}
6386 instructions before instruction number @var{insn}.
6388 @item record instruction-history
6389 Disassembles ten more instructions after the last disassembly.
6391 @item record instruction-history -
6392 Disassembles ten more instructions before the last disassembly.
6394 @item record instruction-history @var{begin} @var{end}
6395 Disassembles instructions beginning with instruction number
6396 @var{begin} until instruction number @var{end}. The instruction
6397 number @var{end} is not included.
6400 This command may not be available for all recording methods.
6403 @item set record instruction-history-size @var{size}
6404 @itemx set record instruction-history-size unlimited
6405 Define how many instructions to disassemble in the @code{record
6406 instruction-history} command. The default value is 10.
6407 A @var{size} of @code{unlimited} means unlimited instructions.
6410 @item show record instruction-history-size
6411 Show how many instructions to disassemble in the @code{record
6412 instruction-history} command.
6414 @kindex record function-call-history
6415 @kindex rec function-call-history
6416 @item record function-call-history
6417 Prints the execution history at function granularity. It prints one
6418 line for each sequence of instructions that belong to the same
6419 function giving the name of that function, the source lines
6420 for this instruction sequence (if the @code{/l} modifier is
6421 specified), and the instructions numbers that form the sequence (if
6422 the @code{/i} modifier is specified).
6425 (@value{GDBP}) @b{list 1, 10}
6436 (@value{GDBP}) @b{record function-call-history /l}
6442 By default, ten lines are printed. This can be changed using the
6443 @code{set record function-call-history-size} command. Functions are
6444 printed in execution order. There are several ways to specify what
6448 @item record function-call-history @var{func}
6449 Prints ten functions starting from function number @var{func}.
6451 @item record function-call-history @var{func}, +/-@var{n}
6452 Prints @var{n} functions around function number @var{func}. If
6453 @var{n} is preceded with @code{+}, prints @var{n} functions after
6454 function number @var{func}. If @var{n} is preceded with @code{-},
6455 prints @var{n} functions before function number @var{func}.
6457 @item record function-call-history
6458 Prints ten more functions after the last ten-line print.
6460 @item record function-call-history -
6461 Prints ten more functions before the last ten-line print.
6463 @item record function-call-history @var{begin} @var{end}
6464 Prints functions beginning with function number @var{begin} until
6465 function number @var{end}. The function number @var{end} is not
6469 This command may not be available for all recording methods.
6471 @item set record function-call-history-size @var{size}
6472 @itemx set record function-call-history-size unlimited
6473 Define how many lines to print in the
6474 @code{record function-call-history} command. The default value is 10.
6475 A size of @code{unlimited} means unlimited lines.
6477 @item show record function-call-history-size
6478 Show how many lines to print in the
6479 @code{record function-call-history} command.
6484 @chapter Examining the Stack
6486 When your program has stopped, the first thing you need to know is where it
6487 stopped and how it got there.
6490 Each time your program performs a function call, information about the call
6492 That information includes the location of the call in your program,
6493 the arguments of the call,
6494 and the local variables of the function being called.
6495 The information is saved in a block of data called a @dfn{stack frame}.
6496 The stack frames are allocated in a region of memory called the @dfn{call
6499 When your program stops, the @value{GDBN} commands for examining the
6500 stack allow you to see all of this information.
6502 @cindex selected frame
6503 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6504 @value{GDBN} commands refer implicitly to the selected frame. In
6505 particular, whenever you ask @value{GDBN} for the value of a variable in
6506 your program, the value is found in the selected frame. There are
6507 special @value{GDBN} commands to select whichever frame you are
6508 interested in. @xref{Selection, ,Selecting a Frame}.
6510 When your program stops, @value{GDBN} automatically selects the
6511 currently executing frame and describes it briefly, similar to the
6512 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6515 * Frames:: Stack frames
6516 * Backtrace:: Backtraces
6517 * Frame Filter Management:: Managing frame filters
6518 * Selection:: Selecting a frame
6519 * Frame Info:: Information on a frame
6524 @section Stack Frames
6526 @cindex frame, definition
6528 The call stack is divided up into contiguous pieces called @dfn{stack
6529 frames}, or @dfn{frames} for short; each frame is the data associated
6530 with one call to one function. The frame contains the arguments given
6531 to the function, the function's local variables, and the address at
6532 which the function is executing.
6534 @cindex initial frame
6535 @cindex outermost frame
6536 @cindex innermost frame
6537 When your program is started, the stack has only one frame, that of the
6538 function @code{main}. This is called the @dfn{initial} frame or the
6539 @dfn{outermost} frame. Each time a function is called, a new frame is
6540 made. Each time a function returns, the frame for that function invocation
6541 is eliminated. If a function is recursive, there can be many frames for
6542 the same function. The frame for the function in which execution is
6543 actually occurring is called the @dfn{innermost} frame. This is the most
6544 recently created of all the stack frames that still exist.
6546 @cindex frame pointer
6547 Inside your program, stack frames are identified by their addresses. A
6548 stack frame consists of many bytes, each of which has its own address; each
6549 kind of computer has a convention for choosing one byte whose
6550 address serves as the address of the frame. Usually this address is kept
6551 in a register called the @dfn{frame pointer register}
6552 (@pxref{Registers, $fp}) while execution is going on in that frame.
6554 @cindex frame number
6555 @value{GDBN} assigns numbers to all existing stack frames, starting with
6556 zero for the innermost frame, one for the frame that called it,
6557 and so on upward. These numbers do not really exist in your program;
6558 they are assigned by @value{GDBN} to give you a way of designating stack
6559 frames in @value{GDBN} commands.
6561 @c The -fomit-frame-pointer below perennially causes hbox overflow
6562 @c underflow problems.
6563 @cindex frameless execution
6564 Some compilers provide a way to compile functions so that they operate
6565 without stack frames. (For example, the @value{NGCC} option
6567 @samp{-fomit-frame-pointer}
6569 generates functions without a frame.)
6570 This is occasionally done with heavily used library functions to save
6571 the frame setup time. @value{GDBN} has limited facilities for dealing
6572 with these function invocations. If the innermost function invocation
6573 has no stack frame, @value{GDBN} nevertheless regards it as though
6574 it had a separate frame, which is numbered zero as usual, allowing
6575 correct tracing of the function call chain. However, @value{GDBN} has
6576 no provision for frameless functions elsewhere in the stack.
6579 @kindex frame@r{, command}
6580 @cindex current stack frame
6581 @item frame @var{args}
6582 The @code{frame} command allows you to move from one stack frame to another,
6583 and to print the stack frame you select. @var{args} may be either the
6584 address of the frame or the stack frame number. Without an argument,
6585 @code{frame} prints the current stack frame.
6587 @kindex select-frame
6588 @cindex selecting frame silently
6590 The @code{select-frame} command allows you to move from one stack frame
6591 to another without printing the frame. This is the silent version of
6599 @cindex call stack traces
6600 A backtrace is a summary of how your program got where it is. It shows one
6601 line per frame, for many frames, starting with the currently executing
6602 frame (frame zero), followed by its caller (frame one), and on up the
6605 @anchor{backtrace-command}
6608 @kindex bt @r{(@code{backtrace})}
6611 Print a backtrace of the entire stack: one line per frame for all
6612 frames in the stack.
6614 You can stop the backtrace at any time by typing the system interrupt
6615 character, normally @kbd{Ctrl-c}.
6617 @item backtrace @var{n}
6619 Similar, but print only the innermost @var{n} frames.
6621 @item backtrace -@var{n}
6623 Similar, but print only the outermost @var{n} frames.
6625 @item backtrace full
6627 @itemx bt full @var{n}
6628 @itemx bt full -@var{n}
6629 Print the values of the local variables also. @var{n} specifies the
6630 number of frames to print, as described above.
6632 @item backtrace no-filters
6633 @itemx bt no-filters
6634 @itemx bt no-filters @var{n}
6635 @itemx bt no-filters -@var{n}
6636 @itemx bt no-filters full
6637 @itemx bt no-filters full @var{n}
6638 @itemx bt no-filters full -@var{n}
6639 Do not run Python frame filters on this backtrace. @xref{Frame
6640 Filter API}, for more information. Additionally use @ref{disable
6641 frame-filter all} to turn off all frame filters. This is only
6642 relevant when @value{GDBN} has been configured with @code{Python}
6648 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6649 are additional aliases for @code{backtrace}.
6651 @cindex multiple threads, backtrace
6652 In a multi-threaded program, @value{GDBN} by default shows the
6653 backtrace only for the current thread. To display the backtrace for
6654 several or all of the threads, use the command @code{thread apply}
6655 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6656 apply all backtrace}, @value{GDBN} will display the backtrace for all
6657 the threads; this is handy when you debug a core dump of a
6658 multi-threaded program.
6660 Each line in the backtrace shows the frame number and the function name.
6661 The program counter value is also shown---unless you use @code{set
6662 print address off}. The backtrace also shows the source file name and
6663 line number, as well as the arguments to the function. The program
6664 counter value is omitted if it is at the beginning of the code for that
6667 Here is an example of a backtrace. It was made with the command
6668 @samp{bt 3}, so it shows the innermost three frames.
6672 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6674 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6675 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6677 (More stack frames follow...)
6682 The display for frame zero does not begin with a program counter
6683 value, indicating that your program has stopped at the beginning of the
6684 code for line @code{993} of @code{builtin.c}.
6687 The value of parameter @code{data} in frame 1 has been replaced by
6688 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6689 only if it is a scalar (integer, pointer, enumeration, etc). See command
6690 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6691 on how to configure the way function parameter values are printed.
6693 @cindex optimized out, in backtrace
6694 @cindex function call arguments, optimized out
6695 If your program was compiled with optimizations, some compilers will
6696 optimize away arguments passed to functions if those arguments are
6697 never used after the call. Such optimizations generate code that
6698 passes arguments through registers, but doesn't store those arguments
6699 in the stack frame. @value{GDBN} has no way of displaying such
6700 arguments in stack frames other than the innermost one. Here's what
6701 such a backtrace might look like:
6705 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6707 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6708 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6710 (More stack frames follow...)
6715 The values of arguments that were not saved in their stack frames are
6716 shown as @samp{<optimized out>}.
6718 If you need to display the values of such optimized-out arguments,
6719 either deduce that from other variables whose values depend on the one
6720 you are interested in, or recompile without optimizations.
6722 @cindex backtrace beyond @code{main} function
6723 @cindex program entry point
6724 @cindex startup code, and backtrace
6725 Most programs have a standard user entry point---a place where system
6726 libraries and startup code transition into user code. For C this is
6727 @code{main}@footnote{
6728 Note that embedded programs (the so-called ``free-standing''
6729 environment) are not required to have a @code{main} function as the
6730 entry point. They could even have multiple entry points.}.
6731 When @value{GDBN} finds the entry function in a backtrace
6732 it will terminate the backtrace, to avoid tracing into highly
6733 system-specific (and generally uninteresting) code.
6735 If you need to examine the startup code, or limit the number of levels
6736 in a backtrace, you can change this behavior:
6739 @item set backtrace past-main
6740 @itemx set backtrace past-main on
6741 @kindex set backtrace
6742 Backtraces will continue past the user entry point.
6744 @item set backtrace past-main off
6745 Backtraces will stop when they encounter the user entry point. This is the
6748 @item show backtrace past-main
6749 @kindex show backtrace
6750 Display the current user entry point backtrace policy.
6752 @item set backtrace past-entry
6753 @itemx set backtrace past-entry on
6754 Backtraces will continue past the internal entry point of an application.
6755 This entry point is encoded by the linker when the application is built,
6756 and is likely before the user entry point @code{main} (or equivalent) is called.
6758 @item set backtrace past-entry off
6759 Backtraces will stop when they encounter the internal entry point of an
6760 application. This is the default.
6762 @item show backtrace past-entry
6763 Display the current internal entry point backtrace policy.
6765 @item set backtrace limit @var{n}
6766 @itemx set backtrace limit 0
6767 @itemx set backtrace limit unlimited
6768 @cindex backtrace limit
6769 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6770 or zero means unlimited levels.
6772 @item show backtrace limit
6773 Display the current limit on backtrace levels.
6776 You can control how file names are displayed.
6779 @item set filename-display
6780 @itemx set filename-display relative
6781 @cindex filename-display
6782 Display file names relative to the compilation directory. This is the default.
6784 @item set filename-display basename
6785 Display only basename of a filename.
6787 @item set filename-display absolute
6788 Display an absolute filename.
6790 @item show filename-display
6791 Show the current way to display filenames.
6794 @node Frame Filter Management
6795 @section Management of Frame Filters.
6796 @cindex managing frame filters
6798 Frame filters are Python based utilities to manage and decorate the
6799 output of frames. @xref{Frame Filter API}, for further information.
6801 Managing frame filters is performed by several commands available
6802 within @value{GDBN}, detailed here.
6805 @kindex info frame-filter
6806 @item info frame-filter
6807 Print a list of installed frame filters from all dictionaries, showing
6808 their name, priority and enabled status.
6810 @kindex disable frame-filter
6811 @anchor{disable frame-filter all}
6812 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6813 Disable a frame filter in the dictionary matching
6814 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6815 @var{filter-dictionary} may be @code{all}, @code{global},
6816 @code{progspace} or the name of the object file where the frame filter
6817 dictionary resides. When @code{all} is specified, all frame filters
6818 across all dictionaries are disabled. @var{filter-name} is the name
6819 of the frame filter and is used when @code{all} is not the option for
6820 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6821 may be enabled again later.
6823 @kindex enable frame-filter
6824 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6825 Enable a frame filter in the dictionary matching
6826 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6827 @var{filter-dictionary} may be @code{all}, @code{global},
6828 @code{progspace} or the name of the object file where the frame filter
6829 dictionary resides. When @code{all} is specified, all frame filters across
6830 all dictionaries are enabled. @var{filter-name} is the name of the frame
6831 filter and is used when @code{all} is not the option for
6832 @var{filter-dictionary}.
6837 (gdb) info frame-filter
6839 global frame-filters:
6840 Priority Enabled Name
6841 1000 No PrimaryFunctionFilter
6844 progspace /build/test frame-filters:
6845 Priority Enabled Name
6846 100 Yes ProgspaceFilter
6848 objfile /build/test frame-filters:
6849 Priority Enabled Name
6850 999 Yes BuildProgra Filter
6852 (gdb) disable frame-filter /build/test BuildProgramFilter
6853 (gdb) info frame-filter
6855 global frame-filters:
6856 Priority Enabled Name
6857 1000 No PrimaryFunctionFilter
6860 progspace /build/test frame-filters:
6861 Priority Enabled Name
6862 100 Yes ProgspaceFilter
6864 objfile /build/test frame-filters:
6865 Priority Enabled Name
6866 999 No BuildProgramFilter
6868 (gdb) enable frame-filter global PrimaryFunctionFilter
6869 (gdb) info frame-filter
6871 global frame-filters:
6872 Priority Enabled Name
6873 1000 Yes PrimaryFunctionFilter
6876 progspace /build/test frame-filters:
6877 Priority Enabled Name
6878 100 Yes ProgspaceFilter
6880 objfile /build/test frame-filters:
6881 Priority Enabled Name
6882 999 No BuildProgramFilter
6885 @kindex set frame-filter priority
6886 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
6887 Set the @var{priority} of a frame filter in the dictionary matching
6888 @var{filter-dictionary}, and the frame filter name matching
6889 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6890 @code{progspace} or the name of the object file where the frame filter
6891 dictionary resides. @var{priority} is an integer.
6893 @kindex show frame-filter priority
6894 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
6895 Show the @var{priority} of a frame filter in the dictionary matching
6896 @var{filter-dictionary}, and the frame filter name matching
6897 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6898 @code{progspace} or the name of the object file where the frame filter
6904 (gdb) info frame-filter
6906 global frame-filters:
6907 Priority Enabled Name
6908 1000 Yes PrimaryFunctionFilter
6911 progspace /build/test frame-filters:
6912 Priority Enabled Name
6913 100 Yes ProgspaceFilter
6915 objfile /build/test frame-filters:
6916 Priority Enabled Name
6917 999 No BuildProgramFilter
6919 (gdb) set frame-filter priority global Reverse 50
6920 (gdb) info frame-filter
6922 global frame-filters:
6923 Priority Enabled Name
6924 1000 Yes PrimaryFunctionFilter
6927 progspace /build/test frame-filters:
6928 Priority Enabled Name
6929 100 Yes ProgspaceFilter
6931 objfile /build/test frame-filters:
6932 Priority Enabled Name
6933 999 No BuildProgramFilter
6938 @section Selecting a Frame
6940 Most commands for examining the stack and other data in your program work on
6941 whichever stack frame is selected at the moment. Here are the commands for
6942 selecting a stack frame; all of them finish by printing a brief description
6943 of the stack frame just selected.
6946 @kindex frame@r{, selecting}
6947 @kindex f @r{(@code{frame})}
6950 Select frame number @var{n}. Recall that frame zero is the innermost
6951 (currently executing) frame, frame one is the frame that called the
6952 innermost one, and so on. The highest-numbered frame is the one for
6955 @item frame @var{addr}
6957 Select the frame at address @var{addr}. This is useful mainly if the
6958 chaining of stack frames has been damaged by a bug, making it
6959 impossible for @value{GDBN} to assign numbers properly to all frames. In
6960 addition, this can be useful when your program has multiple stacks and
6961 switches between them.
6963 On the SPARC architecture, @code{frame} needs two addresses to
6964 select an arbitrary frame: a frame pointer and a stack pointer.
6966 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6967 pointer and a program counter.
6969 On the 29k architecture, it needs three addresses: a register stack
6970 pointer, a program counter, and a memory stack pointer.
6974 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6975 advances toward the outermost frame, to higher frame numbers, to frames
6976 that have existed longer. @var{n} defaults to one.
6979 @kindex do @r{(@code{down})}
6981 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6982 advances toward the innermost frame, to lower frame numbers, to frames
6983 that were created more recently. @var{n} defaults to one. You may
6984 abbreviate @code{down} as @code{do}.
6987 All of these commands end by printing two lines of output describing the
6988 frame. The first line shows the frame number, the function name, the
6989 arguments, and the source file and line number of execution in that
6990 frame. The second line shows the text of that source line.
6998 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7000 10 read_input_file (argv[i]);
7004 After such a printout, the @code{list} command with no arguments
7005 prints ten lines centered on the point of execution in the frame.
7006 You can also edit the program at the point of execution with your favorite
7007 editing program by typing @code{edit}.
7008 @xref{List, ,Printing Source Lines},
7012 @kindex down-silently
7014 @item up-silently @var{n}
7015 @itemx down-silently @var{n}
7016 These two commands are variants of @code{up} and @code{down},
7017 respectively; they differ in that they do their work silently, without
7018 causing display of the new frame. They are intended primarily for use
7019 in @value{GDBN} command scripts, where the output might be unnecessary and
7024 @section Information About a Frame
7026 There are several other commands to print information about the selected
7032 When used without any argument, this command does not change which
7033 frame is selected, but prints a brief description of the currently
7034 selected stack frame. It can be abbreviated @code{f}. With an
7035 argument, this command is used to select a stack frame.
7036 @xref{Selection, ,Selecting a Frame}.
7039 @kindex info f @r{(@code{info frame})}
7042 This command prints a verbose description of the selected stack frame,
7047 the address of the frame
7049 the address of the next frame down (called by this frame)
7051 the address of the next frame up (caller of this frame)
7053 the language in which the source code corresponding to this frame is written
7055 the address of the frame's arguments
7057 the address of the frame's local variables
7059 the program counter saved in it (the address of execution in the caller frame)
7061 which registers were saved in the frame
7064 @noindent The verbose description is useful when
7065 something has gone wrong that has made the stack format fail to fit
7066 the usual conventions.
7068 @item info frame @var{addr}
7069 @itemx info f @var{addr}
7070 Print a verbose description of the frame at address @var{addr}, without
7071 selecting that frame. The selected frame remains unchanged by this
7072 command. This requires the same kind of address (more than one for some
7073 architectures) that you specify in the @code{frame} command.
7074 @xref{Selection, ,Selecting a Frame}.
7078 Print the arguments of the selected frame, each on a separate line.
7082 Print the local variables of the selected frame, each on a separate
7083 line. These are all variables (declared either static or automatic)
7084 accessible at the point of execution of the selected frame.
7090 @chapter Examining Source Files
7092 @value{GDBN} can print parts of your program's source, since the debugging
7093 information recorded in the program tells @value{GDBN} what source files were
7094 used to build it. When your program stops, @value{GDBN} spontaneously prints
7095 the line where it stopped. Likewise, when you select a stack frame
7096 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7097 execution in that frame has stopped. You can print other portions of
7098 source files by explicit command.
7100 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7101 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7102 @value{GDBN} under @sc{gnu} Emacs}.
7105 * List:: Printing source lines
7106 * Specify Location:: How to specify code locations
7107 * Edit:: Editing source files
7108 * Search:: Searching source files
7109 * Source Path:: Specifying source directories
7110 * Machine Code:: Source and machine code
7114 @section Printing Source Lines
7117 @kindex l @r{(@code{list})}
7118 To print lines from a source file, use the @code{list} command
7119 (abbreviated @code{l}). By default, ten lines are printed.
7120 There are several ways to specify what part of the file you want to
7121 print; see @ref{Specify Location}, for the full list.
7123 Here are the forms of the @code{list} command most commonly used:
7126 @item list @var{linenum}
7127 Print lines centered around line number @var{linenum} in the
7128 current source file.
7130 @item list @var{function}
7131 Print lines centered around the beginning of function
7135 Print more lines. If the last lines printed were printed with a
7136 @code{list} command, this prints lines following the last lines
7137 printed; however, if the last line printed was a solitary line printed
7138 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7139 Stack}), this prints lines centered around that line.
7142 Print lines just before the lines last printed.
7145 @cindex @code{list}, how many lines to display
7146 By default, @value{GDBN} prints ten source lines with any of these forms of
7147 the @code{list} command. You can change this using @code{set listsize}:
7150 @kindex set listsize
7151 @item set listsize @var{count}
7152 @itemx set listsize unlimited
7153 Make the @code{list} command display @var{count} source lines (unless
7154 the @code{list} argument explicitly specifies some other number).
7155 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7157 @kindex show listsize
7159 Display the number of lines that @code{list} prints.
7162 Repeating a @code{list} command with @key{RET} discards the argument,
7163 so it is equivalent to typing just @code{list}. This is more useful
7164 than listing the same lines again. An exception is made for an
7165 argument of @samp{-}; that argument is preserved in repetition so that
7166 each repetition moves up in the source file.
7168 In general, the @code{list} command expects you to supply zero, one or two
7169 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7170 of writing them (@pxref{Specify Location}), but the effect is always
7171 to specify some source line.
7173 Here is a complete description of the possible arguments for @code{list}:
7176 @item list @var{linespec}
7177 Print lines centered around the line specified by @var{linespec}.
7179 @item list @var{first},@var{last}
7180 Print lines from @var{first} to @var{last}. Both arguments are
7181 linespecs. When a @code{list} command has two linespecs, and the
7182 source file of the second linespec is omitted, this refers to
7183 the same source file as the first linespec.
7185 @item list ,@var{last}
7186 Print lines ending with @var{last}.
7188 @item list @var{first},
7189 Print lines starting with @var{first}.
7192 Print lines just after the lines last printed.
7195 Print lines just before the lines last printed.
7198 As described in the preceding table.
7201 @node Specify Location
7202 @section Specifying a Location
7203 @cindex specifying location
7206 Several @value{GDBN} commands accept arguments that specify a location
7207 of your program's code. Since @value{GDBN} is a source-level
7208 debugger, a location usually specifies some line in the source code;
7209 for that reason, locations are also known as @dfn{linespecs}.
7211 Here are all the different ways of specifying a code location that
7212 @value{GDBN} understands:
7216 Specifies the line number @var{linenum} of the current source file.
7219 @itemx +@var{offset}
7220 Specifies the line @var{offset} lines before or after the @dfn{current
7221 line}. For the @code{list} command, the current line is the last one
7222 printed; for the breakpoint commands, this is the line at which
7223 execution stopped in the currently selected @dfn{stack frame}
7224 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7225 used as the second of the two linespecs in a @code{list} command,
7226 this specifies the line @var{offset} lines up or down from the first
7229 @item @var{filename}:@var{linenum}
7230 Specifies the line @var{linenum} in the source file @var{filename}.
7231 If @var{filename} is a relative file name, then it will match any
7232 source file name with the same trailing components. For example, if
7233 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7234 name of @file{/build/trunk/gcc/expr.c}, but not
7235 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7237 @item @var{function}
7238 Specifies the line that begins the body of the function @var{function}.
7239 For example, in C, this is the line with the open brace.
7241 @item @var{function}:@var{label}
7242 Specifies the line where @var{label} appears in @var{function}.
7244 @item @var{filename}:@var{function}
7245 Specifies the line that begins the body of the function @var{function}
7246 in the file @var{filename}. You only need the file name with a
7247 function name to avoid ambiguity when there are identically named
7248 functions in different source files.
7251 Specifies the line at which the label named @var{label} appears.
7252 @value{GDBN} searches for the label in the function corresponding to
7253 the currently selected stack frame. If there is no current selected
7254 stack frame (for instance, if the inferior is not running), then
7255 @value{GDBN} will not search for a label.
7257 @item *@var{address}
7258 Specifies the program address @var{address}. For line-oriented
7259 commands, such as @code{list} and @code{edit}, this specifies a source
7260 line that contains @var{address}. For @code{break} and other
7261 breakpoint oriented commands, this can be used to set breakpoints in
7262 parts of your program which do not have debugging information or
7265 Here @var{address} may be any expression valid in the current working
7266 language (@pxref{Languages, working language}) that specifies a code
7267 address. In addition, as a convenience, @value{GDBN} extends the
7268 semantics of expressions used in locations to cover the situations
7269 that frequently happen during debugging. Here are the various forms
7273 @item @var{expression}
7274 Any expression valid in the current working language.
7276 @item @var{funcaddr}
7277 An address of a function or procedure derived from its name. In C,
7278 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7279 simply the function's name @var{function} (and actually a special case
7280 of a valid expression). In Pascal and Modula-2, this is
7281 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7282 (although the Pascal form also works).
7284 This form specifies the address of the function's first instruction,
7285 before the stack frame and arguments have been set up.
7287 @item '@var{filename}'::@var{funcaddr}
7288 Like @var{funcaddr} above, but also specifies the name of the source
7289 file explicitly. This is useful if the name of the function does not
7290 specify the function unambiguously, e.g., if there are several
7291 functions with identical names in different source files.
7294 @cindex breakpoint at static probe point
7295 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7296 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7297 applications to embed static probes. @xref{Static Probe Points}, for more
7298 information on finding and using static probes. This form of linespec
7299 specifies the location of such a static probe.
7301 If @var{objfile} is given, only probes coming from that shared library
7302 or executable matching @var{objfile} as a regular expression are considered.
7303 If @var{provider} is given, then only probes from that provider are considered.
7304 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7305 each one of those probes.
7311 @section Editing Source Files
7312 @cindex editing source files
7315 @kindex e @r{(@code{edit})}
7316 To edit the lines in a source file, use the @code{edit} command.
7317 The editing program of your choice
7318 is invoked with the current line set to
7319 the active line in the program.
7320 Alternatively, there are several ways to specify what part of the file you
7321 want to print if you want to see other parts of the program:
7324 @item edit @var{location}
7325 Edit the source file specified by @code{location}. Editing starts at
7326 that @var{location}, e.g., at the specified source line of the
7327 specified file. @xref{Specify Location}, for all the possible forms
7328 of the @var{location} argument; here are the forms of the @code{edit}
7329 command most commonly used:
7332 @item edit @var{number}
7333 Edit the current source file with @var{number} as the active line number.
7335 @item edit @var{function}
7336 Edit the file containing @var{function} at the beginning of its definition.
7341 @subsection Choosing your Editor
7342 You can customize @value{GDBN} to use any editor you want
7344 The only restriction is that your editor (say @code{ex}), recognizes the
7345 following command-line syntax:
7347 ex +@var{number} file
7349 The optional numeric value +@var{number} specifies the number of the line in
7350 the file where to start editing.}.
7351 By default, it is @file{@value{EDITOR}}, but you can change this
7352 by setting the environment variable @code{EDITOR} before using
7353 @value{GDBN}. For example, to configure @value{GDBN} to use the
7354 @code{vi} editor, you could use these commands with the @code{sh} shell:
7360 or in the @code{csh} shell,
7362 setenv EDITOR /usr/bin/vi
7367 @section Searching Source Files
7368 @cindex searching source files
7370 There are two commands for searching through the current source file for a
7375 @kindex forward-search
7376 @kindex fo @r{(@code{forward-search})}
7377 @item forward-search @var{regexp}
7378 @itemx search @var{regexp}
7379 The command @samp{forward-search @var{regexp}} checks each line,
7380 starting with the one following the last line listed, for a match for
7381 @var{regexp}. It lists the line that is found. You can use the
7382 synonym @samp{search @var{regexp}} or abbreviate the command name as
7385 @kindex reverse-search
7386 @item reverse-search @var{regexp}
7387 The command @samp{reverse-search @var{regexp}} checks each line, starting
7388 with the one before the last line listed and going backward, for a match
7389 for @var{regexp}. It lists the line that is found. You can abbreviate
7390 this command as @code{rev}.
7394 @section Specifying Source Directories
7397 @cindex directories for source files
7398 Executable programs sometimes do not record the directories of the source
7399 files from which they were compiled, just the names. Even when they do,
7400 the directories could be moved between the compilation and your debugging
7401 session. @value{GDBN} has a list of directories to search for source files;
7402 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7403 it tries all the directories in the list, in the order they are present
7404 in the list, until it finds a file with the desired name.
7406 For example, suppose an executable references the file
7407 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7408 @file{/mnt/cross}. The file is first looked up literally; if this
7409 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7410 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7411 message is printed. @value{GDBN} does not look up the parts of the
7412 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7413 Likewise, the subdirectories of the source path are not searched: if
7414 the source path is @file{/mnt/cross}, and the binary refers to
7415 @file{foo.c}, @value{GDBN} would not find it under
7416 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7418 Plain file names, relative file names with leading directories, file
7419 names containing dots, etc.@: are all treated as described above; for
7420 instance, if the source path is @file{/mnt/cross}, and the source file
7421 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7422 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7423 that---@file{/mnt/cross/foo.c}.
7425 Note that the executable search path is @emph{not} used to locate the
7428 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7429 any information it has cached about where source files are found and where
7430 each line is in the file.
7434 When you start @value{GDBN}, its source path includes only @samp{cdir}
7435 and @samp{cwd}, in that order.
7436 To add other directories, use the @code{directory} command.
7438 The search path is used to find both program source files and @value{GDBN}
7439 script files (read using the @samp{-command} option and @samp{source} command).
7441 In addition to the source path, @value{GDBN} provides a set of commands
7442 that manage a list of source path substitution rules. A @dfn{substitution
7443 rule} specifies how to rewrite source directories stored in the program's
7444 debug information in case the sources were moved to a different
7445 directory between compilation and debugging. A rule is made of
7446 two strings, the first specifying what needs to be rewritten in
7447 the path, and the second specifying how it should be rewritten.
7448 In @ref{set substitute-path}, we name these two parts @var{from} and
7449 @var{to} respectively. @value{GDBN} does a simple string replacement
7450 of @var{from} with @var{to} at the start of the directory part of the
7451 source file name, and uses that result instead of the original file
7452 name to look up the sources.
7454 Using the previous example, suppose the @file{foo-1.0} tree has been
7455 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7456 @value{GDBN} to replace @file{/usr/src} in all source path names with
7457 @file{/mnt/cross}. The first lookup will then be
7458 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7459 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7460 substitution rule, use the @code{set substitute-path} command
7461 (@pxref{set substitute-path}).
7463 To avoid unexpected substitution results, a rule is applied only if the
7464 @var{from} part of the directory name ends at a directory separator.
7465 For instance, a rule substituting @file{/usr/source} into
7466 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7467 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7468 is applied only at the beginning of the directory name, this rule will
7469 not be applied to @file{/root/usr/source/baz.c} either.
7471 In many cases, you can achieve the same result using the @code{directory}
7472 command. However, @code{set substitute-path} can be more efficient in
7473 the case where the sources are organized in a complex tree with multiple
7474 subdirectories. With the @code{directory} command, you need to add each
7475 subdirectory of your project. If you moved the entire tree while
7476 preserving its internal organization, then @code{set substitute-path}
7477 allows you to direct the debugger to all the sources with one single
7480 @code{set substitute-path} is also more than just a shortcut command.
7481 The source path is only used if the file at the original location no
7482 longer exists. On the other hand, @code{set substitute-path} modifies
7483 the debugger behavior to look at the rewritten location instead. So, if
7484 for any reason a source file that is not relevant to your executable is
7485 located at the original location, a substitution rule is the only
7486 method available to point @value{GDBN} at the new location.
7488 @cindex @samp{--with-relocated-sources}
7489 @cindex default source path substitution
7490 You can configure a default source path substitution rule by
7491 configuring @value{GDBN} with the
7492 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7493 should be the name of a directory under @value{GDBN}'s configured
7494 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7495 directory names in debug information under @var{dir} will be adjusted
7496 automatically if the installed @value{GDBN} is moved to a new
7497 location. This is useful if @value{GDBN}, libraries or executables
7498 with debug information and corresponding source code are being moved
7502 @item directory @var{dirname} @dots{}
7503 @item dir @var{dirname} @dots{}
7504 Add directory @var{dirname} to the front of the source path. Several
7505 directory names may be given to this command, separated by @samp{:}
7506 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7507 part of absolute file names) or
7508 whitespace. You may specify a directory that is already in the source
7509 path; this moves it forward, so @value{GDBN} searches it sooner.
7513 @vindex $cdir@r{, convenience variable}
7514 @vindex $cwd@r{, convenience variable}
7515 @cindex compilation directory
7516 @cindex current directory
7517 @cindex working directory
7518 @cindex directory, current
7519 @cindex directory, compilation
7520 You can use the string @samp{$cdir} to refer to the compilation
7521 directory (if one is recorded), and @samp{$cwd} to refer to the current
7522 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7523 tracks the current working directory as it changes during your @value{GDBN}
7524 session, while the latter is immediately expanded to the current
7525 directory at the time you add an entry to the source path.
7528 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7530 @c RET-repeat for @code{directory} is explicitly disabled, but since
7531 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7533 @item set directories @var{path-list}
7534 @kindex set directories
7535 Set the source path to @var{path-list}.
7536 @samp{$cdir:$cwd} are added if missing.
7538 @item show directories
7539 @kindex show directories
7540 Print the source path: show which directories it contains.
7542 @anchor{set substitute-path}
7543 @item set substitute-path @var{from} @var{to}
7544 @kindex set substitute-path
7545 Define a source path substitution rule, and add it at the end of the
7546 current list of existing substitution rules. If a rule with the same
7547 @var{from} was already defined, then the old rule is also deleted.
7549 For example, if the file @file{/foo/bar/baz.c} was moved to
7550 @file{/mnt/cross/baz.c}, then the command
7553 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7557 will tell @value{GDBN} to replace @samp{/usr/src} with
7558 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7559 @file{baz.c} even though it was moved.
7561 In the case when more than one substitution rule have been defined,
7562 the rules are evaluated one by one in the order where they have been
7563 defined. The first one matching, if any, is selected to perform
7566 For instance, if we had entered the following commands:
7569 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7570 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7574 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7575 @file{/mnt/include/defs.h} by using the first rule. However, it would
7576 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7577 @file{/mnt/src/lib/foo.c}.
7580 @item unset substitute-path [path]
7581 @kindex unset substitute-path
7582 If a path is specified, search the current list of substitution rules
7583 for a rule that would rewrite that path. Delete that rule if found.
7584 A warning is emitted by the debugger if no rule could be found.
7586 If no path is specified, then all substitution rules are deleted.
7588 @item show substitute-path [path]
7589 @kindex show substitute-path
7590 If a path is specified, then print the source path substitution rule
7591 which would rewrite that path, if any.
7593 If no path is specified, then print all existing source path substitution
7598 If your source path is cluttered with directories that are no longer of
7599 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7600 versions of source. You can correct the situation as follows:
7604 Use @code{directory} with no argument to reset the source path to its default value.
7607 Use @code{directory} with suitable arguments to reinstall the
7608 directories you want in the source path. You can add all the
7609 directories in one command.
7613 @section Source and Machine Code
7614 @cindex source line and its code address
7616 You can use the command @code{info line} to map source lines to program
7617 addresses (and vice versa), and the command @code{disassemble} to display
7618 a range of addresses as machine instructions. You can use the command
7619 @code{set disassemble-next-line} to set whether to disassemble next
7620 source line when execution stops. When run under @sc{gnu} Emacs
7621 mode, the @code{info line} command causes the arrow to point to the
7622 line specified. Also, @code{info line} prints addresses in symbolic form as
7627 @item info line @var{linespec}
7628 Print the starting and ending addresses of the compiled code for
7629 source line @var{linespec}. You can specify source lines in any of
7630 the ways documented in @ref{Specify Location}.
7633 For example, we can use @code{info line} to discover the location of
7634 the object code for the first line of function
7635 @code{m4_changequote}:
7637 @c FIXME: I think this example should also show the addresses in
7638 @c symbolic form, as they usually would be displayed.
7640 (@value{GDBP}) info line m4_changequote
7641 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7645 @cindex code address and its source line
7646 We can also inquire (using @code{*@var{addr}} as the form for
7647 @var{linespec}) what source line covers a particular address:
7649 (@value{GDBP}) info line *0x63ff
7650 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7653 @cindex @code{$_} and @code{info line}
7654 @cindex @code{x} command, default address
7655 @kindex x@r{(examine), and} info line
7656 After @code{info line}, the default address for the @code{x} command
7657 is changed to the starting address of the line, so that @samp{x/i} is
7658 sufficient to begin examining the machine code (@pxref{Memory,
7659 ,Examining Memory}). Also, this address is saved as the value of the
7660 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7665 @cindex assembly instructions
7666 @cindex instructions, assembly
7667 @cindex machine instructions
7668 @cindex listing machine instructions
7670 @itemx disassemble /m
7671 @itemx disassemble /r
7672 This specialized command dumps a range of memory as machine
7673 instructions. It can also print mixed source+disassembly by specifying
7674 the @code{/m} modifier and print the raw instructions in hex as well as
7675 in symbolic form by specifying the @code{/r}.
7676 The default memory range is the function surrounding the
7677 program counter of the selected frame. A single argument to this
7678 command is a program counter value; @value{GDBN} dumps the function
7679 surrounding this value. When two arguments are given, they should
7680 be separated by a comma, possibly surrounded by whitespace. The
7681 arguments specify a range of addresses to dump, in one of two forms:
7684 @item @var{start},@var{end}
7685 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7686 @item @var{start},+@var{length}
7687 the addresses from @var{start} (inclusive) to
7688 @code{@var{start}+@var{length}} (exclusive).
7692 When 2 arguments are specified, the name of the function is also
7693 printed (since there could be several functions in the given range).
7695 The argument(s) can be any expression yielding a numeric value, such as
7696 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7698 If the range of memory being disassembled contains current program counter,
7699 the instruction at that location is shown with a @code{=>} marker.
7702 The following example shows the disassembly of a range of addresses of
7703 HP PA-RISC 2.0 code:
7706 (@value{GDBP}) disas 0x32c4, 0x32e4
7707 Dump of assembler code from 0x32c4 to 0x32e4:
7708 0x32c4 <main+204>: addil 0,dp
7709 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7710 0x32cc <main+212>: ldil 0x3000,r31
7711 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7712 0x32d4 <main+220>: ldo 0(r31),rp
7713 0x32d8 <main+224>: addil -0x800,dp
7714 0x32dc <main+228>: ldo 0x588(r1),r26
7715 0x32e0 <main+232>: ldil 0x3000,r31
7716 End of assembler dump.
7719 Here is an example showing mixed source+assembly for Intel x86, when the
7720 program is stopped just after function prologue:
7723 (@value{GDBP}) disas /m main
7724 Dump of assembler code for function main:
7726 0x08048330 <+0>: push %ebp
7727 0x08048331 <+1>: mov %esp,%ebp
7728 0x08048333 <+3>: sub $0x8,%esp
7729 0x08048336 <+6>: and $0xfffffff0,%esp
7730 0x08048339 <+9>: sub $0x10,%esp
7732 6 printf ("Hello.\n");
7733 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7734 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7738 0x08048348 <+24>: mov $0x0,%eax
7739 0x0804834d <+29>: leave
7740 0x0804834e <+30>: ret
7742 End of assembler dump.
7745 Here is another example showing raw instructions in hex for AMD x86-64,
7748 (gdb) disas /r 0x400281,+10
7749 Dump of assembler code from 0x400281 to 0x40028b:
7750 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7751 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7752 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7753 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7754 End of assembler dump.
7757 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7758 So, for example, if you want to disassemble function @code{bar}
7759 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7760 and not @samp{disassemble foo.c:bar}.
7762 Some architectures have more than one commonly-used set of instruction
7763 mnemonics or other syntax.
7765 For programs that were dynamically linked and use shared libraries,
7766 instructions that call functions or branch to locations in the shared
7767 libraries might show a seemingly bogus location---it's actually a
7768 location of the relocation table. On some architectures, @value{GDBN}
7769 might be able to resolve these to actual function names.
7772 @kindex set disassembly-flavor
7773 @cindex Intel disassembly flavor
7774 @cindex AT&T disassembly flavor
7775 @item set disassembly-flavor @var{instruction-set}
7776 Select the instruction set to use when disassembling the
7777 program via the @code{disassemble} or @code{x/i} commands.
7779 Currently this command is only defined for the Intel x86 family. You
7780 can set @var{instruction-set} to either @code{intel} or @code{att}.
7781 The default is @code{att}, the AT&T flavor used by default by Unix
7782 assemblers for x86-based targets.
7784 @kindex show disassembly-flavor
7785 @item show disassembly-flavor
7786 Show the current setting of the disassembly flavor.
7790 @kindex set disassemble-next-line
7791 @kindex show disassemble-next-line
7792 @item set disassemble-next-line
7793 @itemx show disassemble-next-line
7794 Control whether or not @value{GDBN} will disassemble the next source
7795 line or instruction when execution stops. If ON, @value{GDBN} will
7796 display disassembly of the next source line when execution of the
7797 program being debugged stops. This is @emph{in addition} to
7798 displaying the source line itself, which @value{GDBN} always does if
7799 possible. If the next source line cannot be displayed for some reason
7800 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7801 info in the debug info), @value{GDBN} will display disassembly of the
7802 next @emph{instruction} instead of showing the next source line. If
7803 AUTO, @value{GDBN} will display disassembly of next instruction only
7804 if the source line cannot be displayed. This setting causes
7805 @value{GDBN} to display some feedback when you step through a function
7806 with no line info or whose source file is unavailable. The default is
7807 OFF, which means never display the disassembly of the next line or
7813 @chapter Examining Data
7815 @cindex printing data
7816 @cindex examining data
7819 The usual way to examine data in your program is with the @code{print}
7820 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7821 evaluates and prints the value of an expression of the language your
7822 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7823 Different Languages}). It may also print the expression using a
7824 Python-based pretty-printer (@pxref{Pretty Printing}).
7827 @item print @var{expr}
7828 @itemx print /@var{f} @var{expr}
7829 @var{expr} is an expression (in the source language). By default the
7830 value of @var{expr} is printed in a format appropriate to its data type;
7831 you can choose a different format by specifying @samp{/@var{f}}, where
7832 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7836 @itemx print /@var{f}
7837 @cindex reprint the last value
7838 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7839 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7840 conveniently inspect the same value in an alternative format.
7843 A more low-level way of examining data is with the @code{x} command.
7844 It examines data in memory at a specified address and prints it in a
7845 specified format. @xref{Memory, ,Examining Memory}.
7847 If you are interested in information about types, or about how the
7848 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7849 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7852 @cindex exploring hierarchical data structures
7854 Another way of examining values of expressions and type information is
7855 through the Python extension command @code{explore} (available only if
7856 the @value{GDBN} build is configured with @code{--with-python}). It
7857 offers an interactive way to start at the highest level (or, the most
7858 abstract level) of the data type of an expression (or, the data type
7859 itself) and explore all the way down to leaf scalar values/fields
7860 embedded in the higher level data types.
7863 @item explore @var{arg}
7864 @var{arg} is either an expression (in the source language), or a type
7865 visible in the current context of the program being debugged.
7868 The working of the @code{explore} command can be illustrated with an
7869 example. If a data type @code{struct ComplexStruct} is defined in your
7879 struct ComplexStruct
7881 struct SimpleStruct *ss_p;
7887 followed by variable declarations as
7890 struct SimpleStruct ss = @{ 10, 1.11 @};
7891 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7895 then, the value of the variable @code{cs} can be explored using the
7896 @code{explore} command as follows.
7900 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7901 the following fields:
7903 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7904 arr = <Enter 1 to explore this field of type `int [10]'>
7906 Enter the field number of choice:
7910 Since the fields of @code{cs} are not scalar values, you are being
7911 prompted to chose the field you want to explore. Let's say you choose
7912 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7913 pointer, you will be asked if it is pointing to a single value. From
7914 the declaration of @code{cs} above, it is indeed pointing to a single
7915 value, hence you enter @code{y}. If you enter @code{n}, then you will
7916 be asked if it were pointing to an array of values, in which case this
7917 field will be explored as if it were an array.
7920 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7921 Continue exploring it as a pointer to a single value [y/n]: y
7922 The value of `*(cs.ss_p)' is a struct/class of type `struct
7923 SimpleStruct' with the following fields:
7925 i = 10 .. (Value of type `int')
7926 d = 1.1100000000000001 .. (Value of type `double')
7928 Press enter to return to parent value:
7932 If the field @code{arr} of @code{cs} was chosen for exploration by
7933 entering @code{1} earlier, then since it is as array, you will be
7934 prompted to enter the index of the element in the array that you want
7938 `cs.arr' is an array of `int'.
7939 Enter the index of the element you want to explore in `cs.arr': 5
7941 `(cs.arr)[5]' is a scalar value of type `int'.
7945 Press enter to return to parent value:
7948 In general, at any stage of exploration, you can go deeper towards the
7949 leaf values by responding to the prompts appropriately, or hit the
7950 return key to return to the enclosing data structure (the @i{higher}
7951 level data structure).
7953 Similar to exploring values, you can use the @code{explore} command to
7954 explore types. Instead of specifying a value (which is typically a
7955 variable name or an expression valid in the current context of the
7956 program being debugged), you specify a type name. If you consider the
7957 same example as above, your can explore the type
7958 @code{struct ComplexStruct} by passing the argument
7959 @code{struct ComplexStruct} to the @code{explore} command.
7962 (gdb) explore struct ComplexStruct
7966 By responding to the prompts appropriately in the subsequent interactive
7967 session, you can explore the type @code{struct ComplexStruct} in a
7968 manner similar to how the value @code{cs} was explored in the above
7971 The @code{explore} command also has two sub-commands,
7972 @code{explore value} and @code{explore type}. The former sub-command is
7973 a way to explicitly specify that value exploration of the argument is
7974 being invoked, while the latter is a way to explicitly specify that type
7975 exploration of the argument is being invoked.
7978 @item explore value @var{expr}
7979 @cindex explore value
7980 This sub-command of @code{explore} explores the value of the
7981 expression @var{expr} (if @var{expr} is an expression valid in the
7982 current context of the program being debugged). The behavior of this
7983 command is identical to that of the behavior of the @code{explore}
7984 command being passed the argument @var{expr}.
7986 @item explore type @var{arg}
7987 @cindex explore type
7988 This sub-command of @code{explore} explores the type of @var{arg} (if
7989 @var{arg} is a type visible in the current context of program being
7990 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7991 is an expression valid in the current context of the program being
7992 debugged). If @var{arg} is a type, then the behavior of this command is
7993 identical to that of the @code{explore} command being passed the
7994 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7995 this command will be identical to that of the @code{explore} command
7996 being passed the type of @var{arg} as the argument.
8000 * Expressions:: Expressions
8001 * Ambiguous Expressions:: Ambiguous Expressions
8002 * Variables:: Program variables
8003 * Arrays:: Artificial arrays
8004 * Output Formats:: Output formats
8005 * Memory:: Examining memory
8006 * Auto Display:: Automatic display
8007 * Print Settings:: Print settings
8008 * Pretty Printing:: Python pretty printing
8009 * Value History:: Value history
8010 * Convenience Vars:: Convenience variables
8011 * Convenience Funs:: Convenience functions
8012 * Registers:: Registers
8013 * Floating Point Hardware:: Floating point hardware
8014 * Vector Unit:: Vector Unit
8015 * OS Information:: Auxiliary data provided by operating system
8016 * Memory Region Attributes:: Memory region attributes
8017 * Dump/Restore Files:: Copy between memory and a file
8018 * Core File Generation:: Cause a program dump its core
8019 * Character Sets:: Debugging programs that use a different
8020 character set than GDB does
8021 * Caching Remote Data:: Data caching for remote targets
8022 * Searching Memory:: Searching memory for a sequence of bytes
8026 @section Expressions
8029 @code{print} and many other @value{GDBN} commands accept an expression and
8030 compute its value. Any kind of constant, variable or operator defined
8031 by the programming language you are using is valid in an expression in
8032 @value{GDBN}. This includes conditional expressions, function calls,
8033 casts, and string constants. It also includes preprocessor macros, if
8034 you compiled your program to include this information; see
8037 @cindex arrays in expressions
8038 @value{GDBN} supports array constants in expressions input by
8039 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8040 you can use the command @code{print @{1, 2, 3@}} to create an array
8041 of three integers. If you pass an array to a function or assign it
8042 to a program variable, @value{GDBN} copies the array to memory that
8043 is @code{malloc}ed in the target program.
8045 Because C is so widespread, most of the expressions shown in examples in
8046 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8047 Languages}, for information on how to use expressions in other
8050 In this section, we discuss operators that you can use in @value{GDBN}
8051 expressions regardless of your programming language.
8053 @cindex casts, in expressions
8054 Casts are supported in all languages, not just in C, because it is so
8055 useful to cast a number into a pointer in order to examine a structure
8056 at that address in memory.
8057 @c FIXME: casts supported---Mod2 true?
8059 @value{GDBN} supports these operators, in addition to those common
8060 to programming languages:
8064 @samp{@@} is a binary operator for treating parts of memory as arrays.
8065 @xref{Arrays, ,Artificial Arrays}, for more information.
8068 @samp{::} allows you to specify a variable in terms of the file or
8069 function where it is defined. @xref{Variables, ,Program Variables}.
8071 @cindex @{@var{type}@}
8072 @cindex type casting memory
8073 @cindex memory, viewing as typed object
8074 @cindex casts, to view memory
8075 @item @{@var{type}@} @var{addr}
8076 Refers to an object of type @var{type} stored at address @var{addr} in
8077 memory. @var{addr} may be any expression whose value is an integer or
8078 pointer (but parentheses are required around binary operators, just as in
8079 a cast). This construct is allowed regardless of what kind of data is
8080 normally supposed to reside at @var{addr}.
8083 @node Ambiguous Expressions
8084 @section Ambiguous Expressions
8085 @cindex ambiguous expressions
8087 Expressions can sometimes contain some ambiguous elements. For instance,
8088 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8089 a single function name to be defined several times, for application in
8090 different contexts. This is called @dfn{overloading}. Another example
8091 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8092 templates and is typically instantiated several times, resulting in
8093 the same function name being defined in different contexts.
8095 In some cases and depending on the language, it is possible to adjust
8096 the expression to remove the ambiguity. For instance in C@t{++}, you
8097 can specify the signature of the function you want to break on, as in
8098 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8099 qualified name of your function often makes the expression unambiguous
8102 When an ambiguity that needs to be resolved is detected, the debugger
8103 has the capability to display a menu of numbered choices for each
8104 possibility, and then waits for the selection with the prompt @samp{>}.
8105 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8106 aborts the current command. If the command in which the expression was
8107 used allows more than one choice to be selected, the next option in the
8108 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8111 For example, the following session excerpt shows an attempt to set a
8112 breakpoint at the overloaded symbol @code{String::after}.
8113 We choose three particular definitions of that function name:
8115 @c FIXME! This is likely to change to show arg type lists, at least
8118 (@value{GDBP}) b String::after
8121 [2] file:String.cc; line number:867
8122 [3] file:String.cc; line number:860
8123 [4] file:String.cc; line number:875
8124 [5] file:String.cc; line number:853
8125 [6] file:String.cc; line number:846
8126 [7] file:String.cc; line number:735
8128 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8129 Breakpoint 2 at 0xb344: file String.cc, line 875.
8130 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8131 Multiple breakpoints were set.
8132 Use the "delete" command to delete unwanted
8139 @kindex set multiple-symbols
8140 @item set multiple-symbols @var{mode}
8141 @cindex multiple-symbols menu
8143 This option allows you to adjust the debugger behavior when an expression
8146 By default, @var{mode} is set to @code{all}. If the command with which
8147 the expression is used allows more than one choice, then @value{GDBN}
8148 automatically selects all possible choices. For instance, inserting
8149 a breakpoint on a function using an ambiguous name results in a breakpoint
8150 inserted on each possible match. However, if a unique choice must be made,
8151 then @value{GDBN} uses the menu to help you disambiguate the expression.
8152 For instance, printing the address of an overloaded function will result
8153 in the use of the menu.
8155 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8156 when an ambiguity is detected.
8158 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8159 an error due to the ambiguity and the command is aborted.
8161 @kindex show multiple-symbols
8162 @item show multiple-symbols
8163 Show the current value of the @code{multiple-symbols} setting.
8167 @section Program Variables
8169 The most common kind of expression to use is the name of a variable
8172 Variables in expressions are understood in the selected stack frame
8173 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8177 global (or file-static)
8184 visible according to the scope rules of the
8185 programming language from the point of execution in that frame
8188 @noindent This means that in the function
8203 you can examine and use the variable @code{a} whenever your program is
8204 executing within the function @code{foo}, but you can only use or
8205 examine the variable @code{b} while your program is executing inside
8206 the block where @code{b} is declared.
8208 @cindex variable name conflict
8209 There is an exception: you can refer to a variable or function whose
8210 scope is a single source file even if the current execution point is not
8211 in this file. But it is possible to have more than one such variable or
8212 function with the same name (in different source files). If that
8213 happens, referring to that name has unpredictable effects. If you wish,
8214 you can specify a static variable in a particular function or file by
8215 using the colon-colon (@code{::}) notation:
8217 @cindex colon-colon, context for variables/functions
8219 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8220 @cindex @code{::}, context for variables/functions
8223 @var{file}::@var{variable}
8224 @var{function}::@var{variable}
8228 Here @var{file} or @var{function} is the name of the context for the
8229 static @var{variable}. In the case of file names, you can use quotes to
8230 make sure @value{GDBN} parses the file name as a single word---for example,
8231 to print a global value of @code{x} defined in @file{f2.c}:
8234 (@value{GDBP}) p 'f2.c'::x
8237 The @code{::} notation is normally used for referring to
8238 static variables, since you typically disambiguate uses of local variables
8239 in functions by selecting the appropriate frame and using the
8240 simple name of the variable. However, you may also use this notation
8241 to refer to local variables in frames enclosing the selected frame:
8250 process (a); /* Stop here */
8261 For example, if there is a breakpoint at the commented line,
8262 here is what you might see
8263 when the program stops after executing the call @code{bar(0)}:
8268 (@value{GDBP}) p bar::a
8271 #2 0x080483d0 in foo (a=5) at foobar.c:12
8274 (@value{GDBP}) p bar::a
8278 @cindex C@t{++} scope resolution
8279 These uses of @samp{::} are very rarely in conflict with the very similar
8280 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8281 scope resolution operator in @value{GDBN} expressions.
8282 @c FIXME: Um, so what happens in one of those rare cases where it's in
8285 @cindex wrong values
8286 @cindex variable values, wrong
8287 @cindex function entry/exit, wrong values of variables
8288 @cindex optimized code, wrong values of variables
8290 @emph{Warning:} Occasionally, a local variable may appear to have the
8291 wrong value at certain points in a function---just after entry to a new
8292 scope, and just before exit.
8294 You may see this problem when you are stepping by machine instructions.
8295 This is because, on most machines, it takes more than one instruction to
8296 set up a stack frame (including local variable definitions); if you are
8297 stepping by machine instructions, variables may appear to have the wrong
8298 values until the stack frame is completely built. On exit, it usually
8299 also takes more than one machine instruction to destroy a stack frame;
8300 after you begin stepping through that group of instructions, local
8301 variable definitions may be gone.
8303 This may also happen when the compiler does significant optimizations.
8304 To be sure of always seeing accurate values, turn off all optimization
8307 @cindex ``No symbol "foo" in current context''
8308 Another possible effect of compiler optimizations is to optimize
8309 unused variables out of existence, or assign variables to registers (as
8310 opposed to memory addresses). Depending on the support for such cases
8311 offered by the debug info format used by the compiler, @value{GDBN}
8312 might not be able to display values for such local variables. If that
8313 happens, @value{GDBN} will print a message like this:
8316 No symbol "foo" in current context.
8319 To solve such problems, either recompile without optimizations, or use a
8320 different debug info format, if the compiler supports several such
8321 formats. @xref{Compilation}, for more information on choosing compiler
8322 options. @xref{C, ,C and C@t{++}}, for more information about debug
8323 info formats that are best suited to C@t{++} programs.
8325 If you ask to print an object whose contents are unknown to
8326 @value{GDBN}, e.g., because its data type is not completely specified
8327 by the debug information, @value{GDBN} will say @samp{<incomplete
8328 type>}. @xref{Symbols, incomplete type}, for more about this.
8330 If you append @kbd{@@entry} string to a function parameter name you get its
8331 value at the time the function got called. If the value is not available an
8332 error message is printed. Entry values are available only with some compilers.
8333 Entry values are normally also printed at the function parameter list according
8334 to @ref{set print entry-values}.
8337 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8343 (gdb) print i@@entry
8347 Strings are identified as arrays of @code{char} values without specified
8348 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8349 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8350 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8351 defines literal string type @code{"char"} as @code{char} without a sign.
8356 signed char var1[] = "A";
8359 You get during debugging
8364 $2 = @{65 'A', 0 '\0'@}
8368 @section Artificial Arrays
8370 @cindex artificial array
8372 @kindex @@@r{, referencing memory as an array}
8373 It is often useful to print out several successive objects of the
8374 same type in memory; a section of an array, or an array of
8375 dynamically determined size for which only a pointer exists in the
8378 You can do this by referring to a contiguous span of memory as an
8379 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8380 operand of @samp{@@} should be the first element of the desired array
8381 and be an individual object. The right operand should be the desired length
8382 of the array. The result is an array value whose elements are all of
8383 the type of the left argument. The first element is actually the left
8384 argument; the second element comes from bytes of memory immediately
8385 following those that hold the first element, and so on. Here is an
8386 example. If a program says
8389 int *array = (int *) malloc (len * sizeof (int));
8393 you can print the contents of @code{array} with
8399 The left operand of @samp{@@} must reside in memory. Array values made
8400 with @samp{@@} in this way behave just like other arrays in terms of
8401 subscripting, and are coerced to pointers when used in expressions.
8402 Artificial arrays most often appear in expressions via the value history
8403 (@pxref{Value History, ,Value History}), after printing one out.
8405 Another way to create an artificial array is to use a cast.
8406 This re-interprets a value as if it were an array.
8407 The value need not be in memory:
8409 (@value{GDBP}) p/x (short[2])0x12345678
8410 $1 = @{0x1234, 0x5678@}
8413 As a convenience, if you leave the array length out (as in
8414 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8415 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8417 (@value{GDBP}) p/x (short[])0x12345678
8418 $2 = @{0x1234, 0x5678@}
8421 Sometimes the artificial array mechanism is not quite enough; in
8422 moderately complex data structures, the elements of interest may not
8423 actually be adjacent---for example, if you are interested in the values
8424 of pointers in an array. One useful work-around in this situation is
8425 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8426 Variables}) as a counter in an expression that prints the first
8427 interesting value, and then repeat that expression via @key{RET}. For
8428 instance, suppose you have an array @code{dtab} of pointers to
8429 structures, and you are interested in the values of a field @code{fv}
8430 in each structure. Here is an example of what you might type:
8440 @node Output Formats
8441 @section Output Formats
8443 @cindex formatted output
8444 @cindex output formats
8445 By default, @value{GDBN} prints a value according to its data type. Sometimes
8446 this is not what you want. For example, you might want to print a number
8447 in hex, or a pointer in decimal. Or you might want to view data in memory
8448 at a certain address as a character string or as an instruction. To do
8449 these things, specify an @dfn{output format} when you print a value.
8451 The simplest use of output formats is to say how to print a value
8452 already computed. This is done by starting the arguments of the
8453 @code{print} command with a slash and a format letter. The format
8454 letters supported are:
8458 Regard the bits of the value as an integer, and print the integer in
8462 Print as integer in signed decimal.
8465 Print as integer in unsigned decimal.
8468 Print as integer in octal.
8471 Print as integer in binary. The letter @samp{t} stands for ``two''.
8472 @footnote{@samp{b} cannot be used because these format letters are also
8473 used with the @code{x} command, where @samp{b} stands for ``byte'';
8474 see @ref{Memory,,Examining Memory}.}
8477 @cindex unknown address, locating
8478 @cindex locate address
8479 Print as an address, both absolute in hexadecimal and as an offset from
8480 the nearest preceding symbol. You can use this format used to discover
8481 where (in what function) an unknown address is located:
8484 (@value{GDBP}) p/a 0x54320
8485 $3 = 0x54320 <_initialize_vx+396>
8489 The command @code{info symbol 0x54320} yields similar results.
8490 @xref{Symbols, info symbol}.
8493 Regard as an integer and print it as a character constant. This
8494 prints both the numerical value and its character representation. The
8495 character representation is replaced with the octal escape @samp{\nnn}
8496 for characters outside the 7-bit @sc{ascii} range.
8498 Without this format, @value{GDBN} displays @code{char},
8499 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8500 constants. Single-byte members of vectors are displayed as integer
8504 Regard the bits of the value as a floating point number and print
8505 using typical floating point syntax.
8508 @cindex printing strings
8509 @cindex printing byte arrays
8510 Regard as a string, if possible. With this format, pointers to single-byte
8511 data are displayed as null-terminated strings and arrays of single-byte data
8512 are displayed as fixed-length strings. Other values are displayed in their
8515 Without this format, @value{GDBN} displays pointers to and arrays of
8516 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8517 strings. Single-byte members of a vector are displayed as an integer
8521 Like @samp{x} formatting, the value is treated as an integer and
8522 printed as hexadecimal, but leading zeros are printed to pad the value
8523 to the size of the integer type.
8526 @cindex raw printing
8527 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8528 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8529 Printing}). This typically results in a higher-level display of the
8530 value's contents. The @samp{r} format bypasses any Python
8531 pretty-printer which might exist.
8534 For example, to print the program counter in hex (@pxref{Registers}), type
8541 Note that no space is required before the slash; this is because command
8542 names in @value{GDBN} cannot contain a slash.
8544 To reprint the last value in the value history with a different format,
8545 you can use the @code{print} command with just a format and no
8546 expression. For example, @samp{p/x} reprints the last value in hex.
8549 @section Examining Memory
8551 You can use the command @code{x} (for ``examine'') to examine memory in
8552 any of several formats, independently of your program's data types.
8554 @cindex examining memory
8556 @kindex x @r{(examine memory)}
8557 @item x/@var{nfu} @var{addr}
8560 Use the @code{x} command to examine memory.
8563 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8564 much memory to display and how to format it; @var{addr} is an
8565 expression giving the address where you want to start displaying memory.
8566 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8567 Several commands set convenient defaults for @var{addr}.
8570 @item @var{n}, the repeat count
8571 The repeat count is a decimal integer; the default is 1. It specifies
8572 how much memory (counting by units @var{u}) to display.
8573 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8576 @item @var{f}, the display format
8577 The display format is one of the formats used by @code{print}
8578 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8579 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8580 The default is @samp{x} (hexadecimal) initially. The default changes
8581 each time you use either @code{x} or @code{print}.
8583 @item @var{u}, the unit size
8584 The unit size is any of
8590 Halfwords (two bytes).
8592 Words (four bytes). This is the initial default.
8594 Giant words (eight bytes).
8597 Each time you specify a unit size with @code{x}, that size becomes the
8598 default unit the next time you use @code{x}. For the @samp{i} format,
8599 the unit size is ignored and is normally not written. For the @samp{s} format,
8600 the unit size defaults to @samp{b}, unless it is explicitly given.
8601 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8602 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8603 Note that the results depend on the programming language of the
8604 current compilation unit. If the language is C, the @samp{s}
8605 modifier will use the UTF-16 encoding while @samp{w} will use
8606 UTF-32. The encoding is set by the programming language and cannot
8609 @item @var{addr}, starting display address
8610 @var{addr} is the address where you want @value{GDBN} to begin displaying
8611 memory. The expression need not have a pointer value (though it may);
8612 it is always interpreted as an integer address of a byte of memory.
8613 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8614 @var{addr} is usually just after the last address examined---but several
8615 other commands also set the default address: @code{info breakpoints} (to
8616 the address of the last breakpoint listed), @code{info line} (to the
8617 starting address of a line), and @code{print} (if you use it to display
8618 a value from memory).
8621 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8622 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8623 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8624 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8625 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8627 Since the letters indicating unit sizes are all distinct from the
8628 letters specifying output formats, you do not have to remember whether
8629 unit size or format comes first; either order works. The output
8630 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8631 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8633 Even though the unit size @var{u} is ignored for the formats @samp{s}
8634 and @samp{i}, you might still want to use a count @var{n}; for example,
8635 @samp{3i} specifies that you want to see three machine instructions,
8636 including any operands. For convenience, especially when used with
8637 the @code{display} command, the @samp{i} format also prints branch delay
8638 slot instructions, if any, beyond the count specified, which immediately
8639 follow the last instruction that is within the count. The command
8640 @code{disassemble} gives an alternative way of inspecting machine
8641 instructions; see @ref{Machine Code,,Source and Machine Code}.
8643 All the defaults for the arguments to @code{x} are designed to make it
8644 easy to continue scanning memory with minimal specifications each time
8645 you use @code{x}. For example, after you have inspected three machine
8646 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8647 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8648 the repeat count @var{n} is used again; the other arguments default as
8649 for successive uses of @code{x}.
8651 When examining machine instructions, the instruction at current program
8652 counter is shown with a @code{=>} marker. For example:
8655 (@value{GDBP}) x/5i $pc-6
8656 0x804837f <main+11>: mov %esp,%ebp
8657 0x8048381 <main+13>: push %ecx
8658 0x8048382 <main+14>: sub $0x4,%esp
8659 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8660 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8663 @cindex @code{$_}, @code{$__}, and value history
8664 The addresses and contents printed by the @code{x} command are not saved
8665 in the value history because there is often too much of them and they
8666 would get in the way. Instead, @value{GDBN} makes these values available for
8667 subsequent use in expressions as values of the convenience variables
8668 @code{$_} and @code{$__}. After an @code{x} command, the last address
8669 examined is available for use in expressions in the convenience variable
8670 @code{$_}. The contents of that address, as examined, are available in
8671 the convenience variable @code{$__}.
8673 If the @code{x} command has a repeat count, the address and contents saved
8674 are from the last memory unit printed; this is not the same as the last
8675 address printed if several units were printed on the last line of output.
8677 @cindex remote memory comparison
8678 @cindex verify remote memory image
8679 When you are debugging a program running on a remote target machine
8680 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8681 remote machine's memory against the executable file you downloaded to
8682 the target. The @code{compare-sections} command is provided for such
8686 @kindex compare-sections
8687 @item compare-sections @r{[}@var{section-name}@r{]}
8688 Compare the data of a loadable section @var{section-name} in the
8689 executable file of the program being debugged with the same section in
8690 the remote machine's memory, and report any mismatches. With no
8691 arguments, compares all loadable sections. This command's
8692 availability depends on the target's support for the @code{"qCRC"}
8697 @section Automatic Display
8698 @cindex automatic display
8699 @cindex display of expressions
8701 If you find that you want to print the value of an expression frequently
8702 (to see how it changes), you might want to add it to the @dfn{automatic
8703 display list} so that @value{GDBN} prints its value each time your program stops.
8704 Each expression added to the list is given a number to identify it;
8705 to remove an expression from the list, you specify that number.
8706 The automatic display looks like this:
8710 3: bar[5] = (struct hack *) 0x3804
8714 This display shows item numbers, expressions and their current values. As with
8715 displays you request manually using @code{x} or @code{print}, you can
8716 specify the output format you prefer; in fact, @code{display} decides
8717 whether to use @code{print} or @code{x} depending your format
8718 specification---it uses @code{x} if you specify either the @samp{i}
8719 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8723 @item display @var{expr}
8724 Add the expression @var{expr} to the list of expressions to display
8725 each time your program stops. @xref{Expressions, ,Expressions}.
8727 @code{display} does not repeat if you press @key{RET} again after using it.
8729 @item display/@var{fmt} @var{expr}
8730 For @var{fmt} specifying only a display format and not a size or
8731 count, add the expression @var{expr} to the auto-display list but
8732 arrange to display it each time in the specified format @var{fmt}.
8733 @xref{Output Formats,,Output Formats}.
8735 @item display/@var{fmt} @var{addr}
8736 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8737 number of units, add the expression @var{addr} as a memory address to
8738 be examined each time your program stops. Examining means in effect
8739 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8742 For example, @samp{display/i $pc} can be helpful, to see the machine
8743 instruction about to be executed each time execution stops (@samp{$pc}
8744 is a common name for the program counter; @pxref{Registers, ,Registers}).
8747 @kindex delete display
8749 @item undisplay @var{dnums}@dots{}
8750 @itemx delete display @var{dnums}@dots{}
8751 Remove items from the list of expressions to display. Specify the
8752 numbers of the displays that you want affected with the command
8753 argument @var{dnums}. It can be a single display number, one of the
8754 numbers shown in the first field of the @samp{info display} display;
8755 or it could be a range of display numbers, as in @code{2-4}.
8757 @code{undisplay} does not repeat if you press @key{RET} after using it.
8758 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8760 @kindex disable display
8761 @item disable display @var{dnums}@dots{}
8762 Disable the display of item numbers @var{dnums}. A disabled display
8763 item is not printed automatically, but is not forgotten. It may be
8764 enabled again later. Specify the numbers of the displays that you
8765 want affected with the command argument @var{dnums}. It can be a
8766 single display number, one of the numbers shown in the first field of
8767 the @samp{info display} display; or it could be a range of display
8768 numbers, as in @code{2-4}.
8770 @kindex enable display
8771 @item enable display @var{dnums}@dots{}
8772 Enable display of item numbers @var{dnums}. It becomes effective once
8773 again in auto display of its expression, until you specify otherwise.
8774 Specify the numbers of the displays that you want affected with the
8775 command argument @var{dnums}. It can be a single display number, one
8776 of the numbers shown in the first field of the @samp{info display}
8777 display; or it could be a range of display numbers, as in @code{2-4}.
8780 Display the current values of the expressions on the list, just as is
8781 done when your program stops.
8783 @kindex info display
8785 Print the list of expressions previously set up to display
8786 automatically, each one with its item number, but without showing the
8787 values. This includes disabled expressions, which are marked as such.
8788 It also includes expressions which would not be displayed right now
8789 because they refer to automatic variables not currently available.
8792 @cindex display disabled out of scope
8793 If a display expression refers to local variables, then it does not make
8794 sense outside the lexical context for which it was set up. Such an
8795 expression is disabled when execution enters a context where one of its
8796 variables is not defined. For example, if you give the command
8797 @code{display last_char} while inside a function with an argument
8798 @code{last_char}, @value{GDBN} displays this argument while your program
8799 continues to stop inside that function. When it stops elsewhere---where
8800 there is no variable @code{last_char}---the display is disabled
8801 automatically. The next time your program stops where @code{last_char}
8802 is meaningful, you can enable the display expression once again.
8804 @node Print Settings
8805 @section Print Settings
8807 @cindex format options
8808 @cindex print settings
8809 @value{GDBN} provides the following ways to control how arrays, structures,
8810 and symbols are printed.
8813 These settings are useful for debugging programs in any language:
8817 @item set print address
8818 @itemx set print address on
8819 @cindex print/don't print memory addresses
8820 @value{GDBN} prints memory addresses showing the location of stack
8821 traces, structure values, pointer values, breakpoints, and so forth,
8822 even when it also displays the contents of those addresses. The default
8823 is @code{on}. For example, this is what a stack frame display looks like with
8824 @code{set print address on}:
8829 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8831 530 if (lquote != def_lquote)
8835 @item set print address off
8836 Do not print addresses when displaying their contents. For example,
8837 this is the same stack frame displayed with @code{set print address off}:
8841 (@value{GDBP}) set print addr off
8843 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8844 530 if (lquote != def_lquote)
8848 You can use @samp{set print address off} to eliminate all machine
8849 dependent displays from the @value{GDBN} interface. For example, with
8850 @code{print address off}, you should get the same text for backtraces on
8851 all machines---whether or not they involve pointer arguments.
8854 @item show print address
8855 Show whether or not addresses are to be printed.
8858 When @value{GDBN} prints a symbolic address, it normally prints the
8859 closest earlier symbol plus an offset. If that symbol does not uniquely
8860 identify the address (for example, it is a name whose scope is a single
8861 source file), you may need to clarify. One way to do this is with
8862 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8863 you can set @value{GDBN} to print the source file and line number when
8864 it prints a symbolic address:
8867 @item set print symbol-filename on
8868 @cindex source file and line of a symbol
8869 @cindex symbol, source file and line
8870 Tell @value{GDBN} to print the source file name and line number of a
8871 symbol in the symbolic form of an address.
8873 @item set print symbol-filename off
8874 Do not print source file name and line number of a symbol. This is the
8877 @item show print symbol-filename
8878 Show whether or not @value{GDBN} will print the source file name and
8879 line number of a symbol in the symbolic form of an address.
8882 Another situation where it is helpful to show symbol filenames and line
8883 numbers is when disassembling code; @value{GDBN} shows you the line
8884 number and source file that corresponds to each instruction.
8886 Also, you may wish to see the symbolic form only if the address being
8887 printed is reasonably close to the closest earlier symbol:
8890 @item set print max-symbolic-offset @var{max-offset}
8891 @itemx set print max-symbolic-offset unlimited
8892 @cindex maximum value for offset of closest symbol
8893 Tell @value{GDBN} to only display the symbolic form of an address if the
8894 offset between the closest earlier symbol and the address is less than
8895 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8896 to always print the symbolic form of an address if any symbol precedes
8897 it. Zero is equivalent to @code{unlimited}.
8899 @item show print max-symbolic-offset
8900 Ask how large the maximum offset is that @value{GDBN} prints in a
8904 @cindex wild pointer, interpreting
8905 @cindex pointer, finding referent
8906 If you have a pointer and you are not sure where it points, try
8907 @samp{set print symbol-filename on}. Then you can determine the name
8908 and source file location of the variable where it points, using
8909 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8910 For example, here @value{GDBN} shows that a variable @code{ptt} points
8911 at another variable @code{t}, defined in @file{hi2.c}:
8914 (@value{GDBP}) set print symbol-filename on
8915 (@value{GDBP}) p/a ptt
8916 $4 = 0xe008 <t in hi2.c>
8920 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8921 does not show the symbol name and filename of the referent, even with
8922 the appropriate @code{set print} options turned on.
8925 You can also enable @samp{/a}-like formatting all the time using
8926 @samp{set print symbol on}:
8929 @item set print symbol on
8930 Tell @value{GDBN} to print the symbol corresponding to an address, if
8933 @item set print symbol off
8934 Tell @value{GDBN} not to print the symbol corresponding to an
8935 address. In this mode, @value{GDBN} will still print the symbol
8936 corresponding to pointers to functions. This is the default.
8938 @item show print symbol
8939 Show whether @value{GDBN} will display the symbol corresponding to an
8943 Other settings control how different kinds of objects are printed:
8946 @item set print array
8947 @itemx set print array on
8948 @cindex pretty print arrays
8949 Pretty print arrays. This format is more convenient to read,
8950 but uses more space. The default is off.
8952 @item set print array off
8953 Return to compressed format for arrays.
8955 @item show print array
8956 Show whether compressed or pretty format is selected for displaying
8959 @cindex print array indexes
8960 @item set print array-indexes
8961 @itemx set print array-indexes on
8962 Print the index of each element when displaying arrays. May be more
8963 convenient to locate a given element in the array or quickly find the
8964 index of a given element in that printed array. The default is off.
8966 @item set print array-indexes off
8967 Stop printing element indexes when displaying arrays.
8969 @item show print array-indexes
8970 Show whether the index of each element is printed when displaying
8973 @item set print elements @var{number-of-elements}
8974 @itemx set print elements unlimited
8975 @cindex number of array elements to print
8976 @cindex limit on number of printed array elements
8977 Set a limit on how many elements of an array @value{GDBN} will print.
8978 If @value{GDBN} is printing a large array, it stops printing after it has
8979 printed the number of elements set by the @code{set print elements} command.
8980 This limit also applies to the display of strings.
8981 When @value{GDBN} starts, this limit is set to 200.
8982 Setting @var{number-of-elements} to @code{unlimited} or zero means
8983 that the number of elements to print is unlimited.
8985 @item show print elements
8986 Display the number of elements of a large array that @value{GDBN} will print.
8987 If the number is 0, then the printing is unlimited.
8989 @item set print frame-arguments @var{value}
8990 @kindex set print frame-arguments
8991 @cindex printing frame argument values
8992 @cindex print all frame argument values
8993 @cindex print frame argument values for scalars only
8994 @cindex do not print frame argument values
8995 This command allows to control how the values of arguments are printed
8996 when the debugger prints a frame (@pxref{Frames}). The possible
9001 The values of all arguments are printed.
9004 Print the value of an argument only if it is a scalar. The value of more
9005 complex arguments such as arrays, structures, unions, etc, is replaced
9006 by @code{@dots{}}. This is the default. Here is an example where
9007 only scalar arguments are shown:
9010 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9015 None of the argument values are printed. Instead, the value of each argument
9016 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9019 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9024 By default, only scalar arguments are printed. This command can be used
9025 to configure the debugger to print the value of all arguments, regardless
9026 of their type. However, it is often advantageous to not print the value
9027 of more complex parameters. For instance, it reduces the amount of
9028 information printed in each frame, making the backtrace more readable.
9029 Also, it improves performance when displaying Ada frames, because
9030 the computation of large arguments can sometimes be CPU-intensive,
9031 especially in large applications. Setting @code{print frame-arguments}
9032 to @code{scalars} (the default) or @code{none} avoids this computation,
9033 thus speeding up the display of each Ada frame.
9035 @item show print frame-arguments
9036 Show how the value of arguments should be displayed when printing a frame.
9038 @item set print raw frame-arguments on
9039 Print frame arguments in raw, non pretty-printed, form.
9041 @item set print raw frame-arguments off
9042 Print frame arguments in pretty-printed form, if there is a pretty-printer
9043 for the value (@pxref{Pretty Printing}),
9044 otherwise print the value in raw form.
9045 This is the default.
9047 @item show print raw frame-arguments
9048 Show whether to print frame arguments in raw form.
9050 @anchor{set print entry-values}
9051 @item set print entry-values @var{value}
9052 @kindex set print entry-values
9053 Set printing of frame argument values at function entry. In some cases
9054 @value{GDBN} can determine the value of function argument which was passed by
9055 the function caller, even if the value was modified inside the called function
9056 and therefore is different. With optimized code, the current value could be
9057 unavailable, but the entry value may still be known.
9059 The default value is @code{default} (see below for its description). Older
9060 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9061 this feature will behave in the @code{default} setting the same way as with the
9064 This functionality is currently supported only by DWARF 2 debugging format and
9065 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9066 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9069 The @var{value} parameter can be one of the following:
9073 Print only actual parameter values, never print values from function entry
9077 #0 different (val=6)
9078 #0 lost (val=<optimized out>)
9080 #0 invalid (val=<optimized out>)
9084 Print only parameter values from function entry point. The actual parameter
9085 values are never printed.
9087 #0 equal (val@@entry=5)
9088 #0 different (val@@entry=5)
9089 #0 lost (val@@entry=5)
9090 #0 born (val@@entry=<optimized out>)
9091 #0 invalid (val@@entry=<optimized out>)
9095 Print only parameter values from function entry point. If value from function
9096 entry point is not known while the actual value is known, print the actual
9097 value for such parameter.
9099 #0 equal (val@@entry=5)
9100 #0 different (val@@entry=5)
9101 #0 lost (val@@entry=5)
9103 #0 invalid (val@@entry=<optimized out>)
9107 Print actual parameter values. If actual parameter value is not known while
9108 value from function entry point is known, print the entry point value for such
9112 #0 different (val=6)
9113 #0 lost (val@@entry=5)
9115 #0 invalid (val=<optimized out>)
9119 Always print both the actual parameter value and its value from function entry
9120 point, even if values of one or both are not available due to compiler
9123 #0 equal (val=5, val@@entry=5)
9124 #0 different (val=6, val@@entry=5)
9125 #0 lost (val=<optimized out>, val@@entry=5)
9126 #0 born (val=10, val@@entry=<optimized out>)
9127 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9131 Print the actual parameter value if it is known and also its value from
9132 function entry point if it is known. If neither is known, print for the actual
9133 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9134 values are known and identical, print the shortened
9135 @code{param=param@@entry=VALUE} notation.
9137 #0 equal (val=val@@entry=5)
9138 #0 different (val=6, val@@entry=5)
9139 #0 lost (val@@entry=5)
9141 #0 invalid (val=<optimized out>)
9145 Always print the actual parameter value. Print also its value from function
9146 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9147 if both values are known and identical, print the shortened
9148 @code{param=param@@entry=VALUE} notation.
9150 #0 equal (val=val@@entry=5)
9151 #0 different (val=6, val@@entry=5)
9152 #0 lost (val=<optimized out>, val@@entry=5)
9154 #0 invalid (val=<optimized out>)
9158 For analysis messages on possible failures of frame argument values at function
9159 entry resolution see @ref{set debug entry-values}.
9161 @item show print entry-values
9162 Show the method being used for printing of frame argument values at function
9165 @item set print repeats @var{number-of-repeats}
9166 @itemx set print repeats unlimited
9167 @cindex repeated array elements
9168 Set the threshold for suppressing display of repeated array
9169 elements. When the number of consecutive identical elements of an
9170 array exceeds the threshold, @value{GDBN} prints the string
9171 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9172 identical repetitions, instead of displaying the identical elements
9173 themselves. Setting the threshold to @code{unlimited} or zero will
9174 cause all elements to be individually printed. The default threshold
9177 @item show print repeats
9178 Display the current threshold for printing repeated identical
9181 @item set print null-stop
9182 @cindex @sc{null} elements in arrays
9183 Cause @value{GDBN} to stop printing the characters of an array when the first
9184 @sc{null} is encountered. This is useful when large arrays actually
9185 contain only short strings.
9188 @item show print null-stop
9189 Show whether @value{GDBN} stops printing an array on the first
9190 @sc{null} character.
9192 @item set print pretty on
9193 @cindex print structures in indented form
9194 @cindex indentation in structure display
9195 Cause @value{GDBN} to print structures in an indented format with one member
9196 per line, like this:
9211 @item set print pretty off
9212 Cause @value{GDBN} to print structures in a compact format, like this:
9216 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9217 meat = 0x54 "Pork"@}
9222 This is the default format.
9224 @item show print pretty
9225 Show which format @value{GDBN} is using to print structures.
9227 @item set print sevenbit-strings on
9228 @cindex eight-bit characters in strings
9229 @cindex octal escapes in strings
9230 Print using only seven-bit characters; if this option is set,
9231 @value{GDBN} displays any eight-bit characters (in strings or
9232 character values) using the notation @code{\}@var{nnn}. This setting is
9233 best if you are working in English (@sc{ascii}) and you use the
9234 high-order bit of characters as a marker or ``meta'' bit.
9236 @item set print sevenbit-strings off
9237 Print full eight-bit characters. This allows the use of more
9238 international character sets, and is the default.
9240 @item show print sevenbit-strings
9241 Show whether or not @value{GDBN} is printing only seven-bit characters.
9243 @item set print union on
9244 @cindex unions in structures, printing
9245 Tell @value{GDBN} to print unions which are contained in structures
9246 and other unions. This is the default setting.
9248 @item set print union off
9249 Tell @value{GDBN} not to print unions which are contained in
9250 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9253 @item show print union
9254 Ask @value{GDBN} whether or not it will print unions which are contained in
9255 structures and other unions.
9257 For example, given the declarations
9260 typedef enum @{Tree, Bug@} Species;
9261 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9262 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9273 struct thing foo = @{Tree, @{Acorn@}@};
9277 with @code{set print union on} in effect @samp{p foo} would print
9280 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9284 and with @code{set print union off} in effect it would print
9287 $1 = @{it = Tree, form = @{...@}@}
9291 @code{set print union} affects programs written in C-like languages
9297 These settings are of interest when debugging C@t{++} programs:
9300 @cindex demangling C@t{++} names
9301 @item set print demangle
9302 @itemx set print demangle on
9303 Print C@t{++} names in their source form rather than in the encoded
9304 (``mangled'') form passed to the assembler and linker for type-safe
9305 linkage. The default is on.
9307 @item show print demangle
9308 Show whether C@t{++} names are printed in mangled or demangled form.
9310 @item set print asm-demangle
9311 @itemx set print asm-demangle on
9312 Print C@t{++} names in their source form rather than their mangled form, even
9313 in assembler code printouts such as instruction disassemblies.
9316 @item show print asm-demangle
9317 Show whether C@t{++} names in assembly listings are printed in mangled
9320 @cindex C@t{++} symbol decoding style
9321 @cindex symbol decoding style, C@t{++}
9322 @kindex set demangle-style
9323 @item set demangle-style @var{style}
9324 Choose among several encoding schemes used by different compilers to
9325 represent C@t{++} names. The choices for @var{style} are currently:
9329 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9330 This is the default.
9333 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9336 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9339 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9342 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9343 @strong{Warning:} this setting alone is not sufficient to allow
9344 debugging @code{cfront}-generated executables. @value{GDBN} would
9345 require further enhancement to permit that.
9348 If you omit @var{style}, you will see a list of possible formats.
9350 @item show demangle-style
9351 Display the encoding style currently in use for decoding C@t{++} symbols.
9353 @item set print object
9354 @itemx set print object on
9355 @cindex derived type of an object, printing
9356 @cindex display derived types
9357 When displaying a pointer to an object, identify the @emph{actual}
9358 (derived) type of the object rather than the @emph{declared} type, using
9359 the virtual function table. Note that the virtual function table is
9360 required---this feature can only work for objects that have run-time
9361 type identification; a single virtual method in the object's declared
9362 type is sufficient. Note that this setting is also taken into account when
9363 working with variable objects via MI (@pxref{GDB/MI}).
9365 @item set print object off
9366 Display only the declared type of objects, without reference to the
9367 virtual function table. This is the default setting.
9369 @item show print object
9370 Show whether actual, or declared, object types are displayed.
9372 @item set print static-members
9373 @itemx set print static-members on
9374 @cindex static members of C@t{++} objects
9375 Print static members when displaying a C@t{++} object. The default is on.
9377 @item set print static-members off
9378 Do not print static members when displaying a C@t{++} object.
9380 @item show print static-members
9381 Show whether C@t{++} static members are printed or not.
9383 @item set print pascal_static-members
9384 @itemx set print pascal_static-members on
9385 @cindex static members of Pascal objects
9386 @cindex Pascal objects, static members display
9387 Print static members when displaying a Pascal object. The default is on.
9389 @item set print pascal_static-members off
9390 Do not print static members when displaying a Pascal object.
9392 @item show print pascal_static-members
9393 Show whether Pascal static members are printed or not.
9395 @c These don't work with HP ANSI C++ yet.
9396 @item set print vtbl
9397 @itemx set print vtbl on
9398 @cindex pretty print C@t{++} virtual function tables
9399 @cindex virtual functions (C@t{++}) display
9400 @cindex VTBL display
9401 Pretty print C@t{++} virtual function tables. The default is off.
9402 (The @code{vtbl} commands do not work on programs compiled with the HP
9403 ANSI C@t{++} compiler (@code{aCC}).)
9405 @item set print vtbl off
9406 Do not pretty print C@t{++} virtual function tables.
9408 @item show print vtbl
9409 Show whether C@t{++} virtual function tables are pretty printed, or not.
9412 @node Pretty Printing
9413 @section Pretty Printing
9415 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9416 Python code. It greatly simplifies the display of complex objects. This
9417 mechanism works for both MI and the CLI.
9420 * Pretty-Printer Introduction:: Introduction to pretty-printers
9421 * Pretty-Printer Example:: An example pretty-printer
9422 * Pretty-Printer Commands:: Pretty-printer commands
9425 @node Pretty-Printer Introduction
9426 @subsection Pretty-Printer Introduction
9428 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9429 registered for the value. If there is then @value{GDBN} invokes the
9430 pretty-printer to print the value. Otherwise the value is printed normally.
9432 Pretty-printers are normally named. This makes them easy to manage.
9433 The @samp{info pretty-printer} command will list all the installed
9434 pretty-printers with their names.
9435 If a pretty-printer can handle multiple data types, then its
9436 @dfn{subprinters} are the printers for the individual data types.
9437 Each such subprinter has its own name.
9438 The format of the name is @var{printer-name};@var{subprinter-name}.
9440 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9441 Typically they are automatically loaded and registered when the corresponding
9442 debug information is loaded, thus making them available without having to
9443 do anything special.
9445 There are three places where a pretty-printer can be registered.
9449 Pretty-printers registered globally are available when debugging
9453 Pretty-printers registered with a program space are available only
9454 when debugging that program.
9455 @xref{Progspaces In Python}, for more details on program spaces in Python.
9458 Pretty-printers registered with an objfile are loaded and unloaded
9459 with the corresponding objfile (e.g., shared library).
9460 @xref{Objfiles In Python}, for more details on objfiles in Python.
9463 @xref{Selecting Pretty-Printers}, for further information on how
9464 pretty-printers are selected,
9466 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9469 @node Pretty-Printer Example
9470 @subsection Pretty-Printer Example
9472 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9475 (@value{GDBP}) print s
9477 static npos = 4294967295,
9479 <std::allocator<char>> = @{
9480 <__gnu_cxx::new_allocator<char>> = @{
9481 <No data fields>@}, <No data fields>
9483 members of std::basic_string<char, std::char_traits<char>,
9484 std::allocator<char> >::_Alloc_hider:
9485 _M_p = 0x804a014 "abcd"
9490 With a pretty-printer for @code{std::string} only the contents are printed:
9493 (@value{GDBP}) print s
9497 @node Pretty-Printer Commands
9498 @subsection Pretty-Printer Commands
9499 @cindex pretty-printer commands
9502 @kindex info pretty-printer
9503 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9504 Print the list of installed pretty-printers.
9505 This includes disabled pretty-printers, which are marked as such.
9507 @var{object-regexp} is a regular expression matching the objects
9508 whose pretty-printers to list.
9509 Objects can be @code{global}, the program space's file
9510 (@pxref{Progspaces In Python}),
9511 and the object files within that program space (@pxref{Objfiles In Python}).
9512 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9513 looks up a printer from these three objects.
9515 @var{name-regexp} is a regular expression matching the name of the printers
9518 @kindex disable pretty-printer
9519 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9520 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9521 A disabled pretty-printer is not forgotten, it may be enabled again later.
9523 @kindex enable pretty-printer
9524 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9525 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9530 Suppose we have three pretty-printers installed: one from library1.so
9531 named @code{foo} that prints objects of type @code{foo}, and
9532 another from library2.so named @code{bar} that prints two types of objects,
9533 @code{bar1} and @code{bar2}.
9536 (gdb) info pretty-printer
9543 (gdb) info pretty-printer library2
9548 (gdb) disable pretty-printer library1
9550 2 of 3 printers enabled
9551 (gdb) info pretty-printer
9558 (gdb) disable pretty-printer library2 bar:bar1
9560 1 of 3 printers enabled
9561 (gdb) info pretty-printer library2
9568 (gdb) disable pretty-printer library2 bar
9570 0 of 3 printers enabled
9571 (gdb) info pretty-printer library2
9580 Note that for @code{bar} the entire printer can be disabled,
9581 as can each individual subprinter.
9584 @section Value History
9586 @cindex value history
9587 @cindex history of values printed by @value{GDBN}
9588 Values printed by the @code{print} command are saved in the @value{GDBN}
9589 @dfn{value history}. This allows you to refer to them in other expressions.
9590 Values are kept until the symbol table is re-read or discarded
9591 (for example with the @code{file} or @code{symbol-file} commands).
9592 When the symbol table changes, the value history is discarded,
9593 since the values may contain pointers back to the types defined in the
9598 @cindex history number
9599 The values printed are given @dfn{history numbers} by which you can
9600 refer to them. These are successive integers starting with one.
9601 @code{print} shows you the history number assigned to a value by
9602 printing @samp{$@var{num} = } before the value; here @var{num} is the
9605 To refer to any previous value, use @samp{$} followed by the value's
9606 history number. The way @code{print} labels its output is designed to
9607 remind you of this. Just @code{$} refers to the most recent value in
9608 the history, and @code{$$} refers to the value before that.
9609 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9610 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9611 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9613 For example, suppose you have just printed a pointer to a structure and
9614 want to see the contents of the structure. It suffices to type
9620 If you have a chain of structures where the component @code{next} points
9621 to the next one, you can print the contents of the next one with this:
9628 You can print successive links in the chain by repeating this
9629 command---which you can do by just typing @key{RET}.
9631 Note that the history records values, not expressions. If the value of
9632 @code{x} is 4 and you type these commands:
9640 then the value recorded in the value history by the @code{print} command
9641 remains 4 even though the value of @code{x} has changed.
9646 Print the last ten values in the value history, with their item numbers.
9647 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9648 values} does not change the history.
9650 @item show values @var{n}
9651 Print ten history values centered on history item number @var{n}.
9654 Print ten history values just after the values last printed. If no more
9655 values are available, @code{show values +} produces no display.
9658 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9659 same effect as @samp{show values +}.
9661 @node Convenience Vars
9662 @section Convenience Variables
9664 @cindex convenience variables
9665 @cindex user-defined variables
9666 @value{GDBN} provides @dfn{convenience variables} that you can use within
9667 @value{GDBN} to hold on to a value and refer to it later. These variables
9668 exist entirely within @value{GDBN}; they are not part of your program, and
9669 setting a convenience variable has no direct effect on further execution
9670 of your program. That is why you can use them freely.
9672 Convenience variables are prefixed with @samp{$}. Any name preceded by
9673 @samp{$} can be used for a convenience variable, unless it is one of
9674 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9675 (Value history references, in contrast, are @emph{numbers} preceded
9676 by @samp{$}. @xref{Value History, ,Value History}.)
9678 You can save a value in a convenience variable with an assignment
9679 expression, just as you would set a variable in your program.
9683 set $foo = *object_ptr
9687 would save in @code{$foo} the value contained in the object pointed to by
9690 Using a convenience variable for the first time creates it, but its
9691 value is @code{void} until you assign a new value. You can alter the
9692 value with another assignment at any time.
9694 Convenience variables have no fixed types. You can assign a convenience
9695 variable any type of value, including structures and arrays, even if
9696 that variable already has a value of a different type. The convenience
9697 variable, when used as an expression, has the type of its current value.
9700 @kindex show convenience
9701 @cindex show all user variables and functions
9702 @item show convenience
9703 Print a list of convenience variables used so far, and their values,
9704 as well as a list of the convenience functions.
9705 Abbreviated @code{show conv}.
9707 @kindex init-if-undefined
9708 @cindex convenience variables, initializing
9709 @item init-if-undefined $@var{variable} = @var{expression}
9710 Set a convenience variable if it has not already been set. This is useful
9711 for user-defined commands that keep some state. It is similar, in concept,
9712 to using local static variables with initializers in C (except that
9713 convenience variables are global). It can also be used to allow users to
9714 override default values used in a command script.
9716 If the variable is already defined then the expression is not evaluated so
9717 any side-effects do not occur.
9720 One of the ways to use a convenience variable is as a counter to be
9721 incremented or a pointer to be advanced. For example, to print
9722 a field from successive elements of an array of structures:
9726 print bar[$i++]->contents
9730 Repeat that command by typing @key{RET}.
9732 Some convenience variables are created automatically by @value{GDBN} and given
9733 values likely to be useful.
9736 @vindex $_@r{, convenience variable}
9738 The variable @code{$_} is automatically set by the @code{x} command to
9739 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9740 commands which provide a default address for @code{x} to examine also
9741 set @code{$_} to that address; these commands include @code{info line}
9742 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9743 except when set by the @code{x} command, in which case it is a pointer
9744 to the type of @code{$__}.
9746 @vindex $__@r{, convenience variable}
9748 The variable @code{$__} is automatically set by the @code{x} command
9749 to the value found in the last address examined. Its type is chosen
9750 to match the format in which the data was printed.
9753 @vindex $_exitcode@r{, convenience variable}
9754 The variable @code{$_exitcode} is automatically set to the exit code when
9755 the program being debugged terminates.
9758 The variable @code{$_exception} is set to the exception object being
9759 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9762 @itemx $_probe_arg0@dots{}$_probe_arg11
9763 Arguments to a static probe. @xref{Static Probe Points}.
9766 @vindex $_sdata@r{, inspect, convenience variable}
9767 The variable @code{$_sdata} contains extra collected static tracepoint
9768 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9769 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9770 if extra static tracepoint data has not been collected.
9773 @vindex $_siginfo@r{, convenience variable}
9774 The variable @code{$_siginfo} contains extra signal information
9775 (@pxref{extra signal information}). Note that @code{$_siginfo}
9776 could be empty, if the application has not yet received any signals.
9777 For example, it will be empty before you execute the @code{run} command.
9780 @vindex $_tlb@r{, convenience variable}
9781 The variable @code{$_tlb} is automatically set when debugging
9782 applications running on MS-Windows in native mode or connected to
9783 gdbserver that supports the @code{qGetTIBAddr} request.
9784 @xref{General Query Packets}.
9785 This variable contains the address of the thread information block.
9789 On HP-UX systems, if you refer to a function or variable name that
9790 begins with a dollar sign, @value{GDBN} searches for a user or system
9791 name first, before it searches for a convenience variable.
9793 @node Convenience Funs
9794 @section Convenience Functions
9796 @cindex convenience functions
9797 @value{GDBN} also supplies some @dfn{convenience functions}. These
9798 have a syntax similar to convenience variables. A convenience
9799 function can be used in an expression just like an ordinary function;
9800 however, a convenience function is implemented internally to
9803 These functions require @value{GDBN} to be configured with
9804 @code{Python} support.
9808 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9809 @findex $_memeq@r{, convenience function}
9810 Returns one if the @var{length} bytes at the addresses given by
9811 @var{buf1} and @var{buf2} are equal.
9812 Otherwise it returns zero.
9814 @item $_regex(@var{str}, @var{regex})
9815 @findex $_regex@r{, convenience function}
9816 Returns one if the string @var{str} matches the regular expression
9817 @var{regex}. Otherwise it returns zero.
9818 The syntax of the regular expression is that specified by @code{Python}'s
9819 regular expression support.
9821 @item $_streq(@var{str1}, @var{str2})
9822 @findex $_streq@r{, convenience function}
9823 Returns one if the strings @var{str1} and @var{str2} are equal.
9824 Otherwise it returns zero.
9826 @item $_strlen(@var{str})
9827 @findex $_strlen@r{, convenience function}
9828 Returns the length of string @var{str}.
9832 @value{GDBN} provides the ability to list and get help on
9833 convenience functions.
9837 @kindex help function
9838 @cindex show all convenience functions
9839 Print a list of all convenience functions.
9846 You can refer to machine register contents, in expressions, as variables
9847 with names starting with @samp{$}. The names of registers are different
9848 for each machine; use @code{info registers} to see the names used on
9852 @kindex info registers
9853 @item info registers
9854 Print the names and values of all registers except floating-point
9855 and vector registers (in the selected stack frame).
9857 @kindex info all-registers
9858 @cindex floating point registers
9859 @item info all-registers
9860 Print the names and values of all registers, including floating-point
9861 and vector registers (in the selected stack frame).
9863 @item info registers @var{regname} @dots{}
9864 Print the @dfn{relativized} value of each specified register @var{regname}.
9865 As discussed in detail below, register values are normally relative to
9866 the selected stack frame. @var{regname} may be any register name valid on
9867 the machine you are using, with or without the initial @samp{$}.
9870 @cindex stack pointer register
9871 @cindex program counter register
9872 @cindex process status register
9873 @cindex frame pointer register
9874 @cindex standard registers
9875 @value{GDBN} has four ``standard'' register names that are available (in
9876 expressions) on most machines---whenever they do not conflict with an
9877 architecture's canonical mnemonics for registers. The register names
9878 @code{$pc} and @code{$sp} are used for the program counter register and
9879 the stack pointer. @code{$fp} is used for a register that contains a
9880 pointer to the current stack frame, and @code{$ps} is used for a
9881 register that contains the processor status. For example,
9882 you could print the program counter in hex with
9889 or print the instruction to be executed next with
9896 or add four to the stack pointer@footnote{This is a way of removing
9897 one word from the stack, on machines where stacks grow downward in
9898 memory (most machines, nowadays). This assumes that the innermost
9899 stack frame is selected; setting @code{$sp} is not allowed when other
9900 stack frames are selected. To pop entire frames off the stack,
9901 regardless of machine architecture, use @code{return};
9902 see @ref{Returning, ,Returning from a Function}.} with
9908 Whenever possible, these four standard register names are available on
9909 your machine even though the machine has different canonical mnemonics,
9910 so long as there is no conflict. The @code{info registers} command
9911 shows the canonical names. For example, on the SPARC, @code{info
9912 registers} displays the processor status register as @code{$psr} but you
9913 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9914 is an alias for the @sc{eflags} register.
9916 @value{GDBN} always considers the contents of an ordinary register as an
9917 integer when the register is examined in this way. Some machines have
9918 special registers which can hold nothing but floating point; these
9919 registers are considered to have floating point values. There is no way
9920 to refer to the contents of an ordinary register as floating point value
9921 (although you can @emph{print} it as a floating point value with
9922 @samp{print/f $@var{regname}}).
9924 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9925 means that the data format in which the register contents are saved by
9926 the operating system is not the same one that your program normally
9927 sees. For example, the registers of the 68881 floating point
9928 coprocessor are always saved in ``extended'' (raw) format, but all C
9929 programs expect to work with ``double'' (virtual) format. In such
9930 cases, @value{GDBN} normally works with the virtual format only (the format
9931 that makes sense for your program), but the @code{info registers} command
9932 prints the data in both formats.
9934 @cindex SSE registers (x86)
9935 @cindex MMX registers (x86)
9936 Some machines have special registers whose contents can be interpreted
9937 in several different ways. For example, modern x86-based machines
9938 have SSE and MMX registers that can hold several values packed
9939 together in several different formats. @value{GDBN} refers to such
9940 registers in @code{struct} notation:
9943 (@value{GDBP}) print $xmm1
9945 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9946 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9947 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9948 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9949 v4_int32 = @{0, 20657912, 11, 13@},
9950 v2_int64 = @{88725056443645952, 55834574859@},
9951 uint128 = 0x0000000d0000000b013b36f800000000
9956 To set values of such registers, you need to tell @value{GDBN} which
9957 view of the register you wish to change, as if you were assigning
9958 value to a @code{struct} member:
9961 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9964 Normally, register values are relative to the selected stack frame
9965 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9966 value that the register would contain if all stack frames farther in
9967 were exited and their saved registers restored. In order to see the
9968 true contents of hardware registers, you must select the innermost
9969 frame (with @samp{frame 0}).
9971 However, @value{GDBN} must deduce where registers are saved, from the machine
9972 code generated by your compiler. If some registers are not saved, or if
9973 @value{GDBN} is unable to locate the saved registers, the selected stack
9974 frame makes no difference.
9976 @node Floating Point Hardware
9977 @section Floating Point Hardware
9978 @cindex floating point
9980 Depending on the configuration, @value{GDBN} may be able to give
9981 you more information about the status of the floating point hardware.
9986 Display hardware-dependent information about the floating
9987 point unit. The exact contents and layout vary depending on the
9988 floating point chip. Currently, @samp{info float} is supported on
9989 the ARM and x86 machines.
9993 @section Vector Unit
9996 Depending on the configuration, @value{GDBN} may be able to give you
9997 more information about the status of the vector unit.
10000 @kindex info vector
10002 Display information about the vector unit. The exact contents and
10003 layout vary depending on the hardware.
10006 @node OS Information
10007 @section Operating System Auxiliary Information
10008 @cindex OS information
10010 @value{GDBN} provides interfaces to useful OS facilities that can help
10011 you debug your program.
10013 @cindex auxiliary vector
10014 @cindex vector, auxiliary
10015 Some operating systems supply an @dfn{auxiliary vector} to programs at
10016 startup. This is akin to the arguments and environment that you
10017 specify for a program, but contains a system-dependent variety of
10018 binary values that tell system libraries important details about the
10019 hardware, operating system, and process. Each value's purpose is
10020 identified by an integer tag; the meanings are well-known but system-specific.
10021 Depending on the configuration and operating system facilities,
10022 @value{GDBN} may be able to show you this information. For remote
10023 targets, this functionality may further depend on the remote stub's
10024 support of the @samp{qXfer:auxv:read} packet, see
10025 @ref{qXfer auxiliary vector read}.
10030 Display the auxiliary vector of the inferior, which can be either a
10031 live process or a core dump file. @value{GDBN} prints each tag value
10032 numerically, and also shows names and text descriptions for recognized
10033 tags. Some values in the vector are numbers, some bit masks, and some
10034 pointers to strings or other data. @value{GDBN} displays each value in the
10035 most appropriate form for a recognized tag, and in hexadecimal for
10036 an unrecognized tag.
10039 On some targets, @value{GDBN} can access operating system-specific
10040 information and show it to you. The types of information available
10041 will differ depending on the type of operating system running on the
10042 target. The mechanism used to fetch the data is described in
10043 @ref{Operating System Information}. For remote targets, this
10044 functionality depends on the remote stub's support of the
10045 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10049 @item info os @var{infotype}
10051 Display OS information of the requested type.
10053 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10055 @anchor{linux info os infotypes}
10057 @kindex info os processes
10059 Display the list of processes on the target. For each process,
10060 @value{GDBN} prints the process identifier, the name of the user, the
10061 command corresponding to the process, and the list of processor cores
10062 that the process is currently running on. (To understand what these
10063 properties mean, for this and the following info types, please consult
10064 the general @sc{gnu}/Linux documentation.)
10066 @kindex info os procgroups
10068 Display the list of process groups on the target. For each process,
10069 @value{GDBN} prints the identifier of the process group that it belongs
10070 to, the command corresponding to the process group leader, the process
10071 identifier, and the command line of the process. The list is sorted
10072 first by the process group identifier, then by the process identifier,
10073 so that processes belonging to the same process group are grouped together
10074 and the process group leader is listed first.
10076 @kindex info os threads
10078 Display the list of threads running on the target. For each thread,
10079 @value{GDBN} prints the identifier of the process that the thread
10080 belongs to, the command of the process, the thread identifier, and the
10081 processor core that it is currently running on. The main thread of a
10082 process is not listed.
10084 @kindex info os files
10086 Display the list of open file descriptors on the target. For each
10087 file descriptor, @value{GDBN} prints the identifier of the process
10088 owning the descriptor, the command of the owning process, the value
10089 of the descriptor, and the target of the descriptor.
10091 @kindex info os sockets
10093 Display the list of Internet-domain sockets on the target. For each
10094 socket, @value{GDBN} prints the address and port of the local and
10095 remote endpoints, the current state of the connection, the creator of
10096 the socket, the IP address family of the socket, and the type of the
10099 @kindex info os shm
10101 Display the list of all System V shared-memory regions on the target.
10102 For each shared-memory region, @value{GDBN} prints the region key,
10103 the shared-memory identifier, the access permissions, the size of the
10104 region, the process that created the region, the process that last
10105 attached to or detached from the region, the current number of live
10106 attaches to the region, and the times at which the region was last
10107 attached to, detach from, and changed.
10109 @kindex info os semaphores
10111 Display the list of all System V semaphore sets on the target. For each
10112 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10113 set identifier, the access permissions, the number of semaphores in the
10114 set, the user and group of the owner and creator of the semaphore set,
10115 and the times at which the semaphore set was operated upon and changed.
10117 @kindex info os msg
10119 Display the list of all System V message queues on the target. For each
10120 message queue, @value{GDBN} prints the message queue key, the message
10121 queue identifier, the access permissions, the current number of bytes
10122 on the queue, the current number of messages on the queue, the processes
10123 that last sent and received a message on the queue, the user and group
10124 of the owner and creator of the message queue, the times at which a
10125 message was last sent and received on the queue, and the time at which
10126 the message queue was last changed.
10128 @kindex info os modules
10130 Display the list of all loaded kernel modules on the target. For each
10131 module, @value{GDBN} prints the module name, the size of the module in
10132 bytes, the number of times the module is used, the dependencies of the
10133 module, the status of the module, and the address of the loaded module
10138 If @var{infotype} is omitted, then list the possible values for
10139 @var{infotype} and the kind of OS information available for each
10140 @var{infotype}. If the target does not return a list of possible
10141 types, this command will report an error.
10144 @node Memory Region Attributes
10145 @section Memory Region Attributes
10146 @cindex memory region attributes
10148 @dfn{Memory region attributes} allow you to describe special handling
10149 required by regions of your target's memory. @value{GDBN} uses
10150 attributes to determine whether to allow certain types of memory
10151 accesses; whether to use specific width accesses; and whether to cache
10152 target memory. By default the description of memory regions is
10153 fetched from the target (if the current target supports this), but the
10154 user can override the fetched regions.
10156 Defined memory regions can be individually enabled and disabled. When a
10157 memory region is disabled, @value{GDBN} uses the default attributes when
10158 accessing memory in that region. Similarly, if no memory regions have
10159 been defined, @value{GDBN} uses the default attributes when accessing
10162 When a memory region is defined, it is given a number to identify it;
10163 to enable, disable, or remove a memory region, you specify that number.
10167 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10168 Define a memory region bounded by @var{lower} and @var{upper} with
10169 attributes @var{attributes}@dots{}, and add it to the list of regions
10170 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10171 case: it is treated as the target's maximum memory address.
10172 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10175 Discard any user changes to the memory regions and use target-supplied
10176 regions, if available, or no regions if the target does not support.
10179 @item delete mem @var{nums}@dots{}
10180 Remove memory regions @var{nums}@dots{} from the list of regions
10181 monitored by @value{GDBN}.
10183 @kindex disable mem
10184 @item disable mem @var{nums}@dots{}
10185 Disable monitoring of memory regions @var{nums}@dots{}.
10186 A disabled memory region is not forgotten.
10187 It may be enabled again later.
10190 @item enable mem @var{nums}@dots{}
10191 Enable monitoring of memory regions @var{nums}@dots{}.
10195 Print a table of all defined memory regions, with the following columns
10199 @item Memory Region Number
10200 @item Enabled or Disabled.
10201 Enabled memory regions are marked with @samp{y}.
10202 Disabled memory regions are marked with @samp{n}.
10205 The address defining the inclusive lower bound of the memory region.
10208 The address defining the exclusive upper bound of the memory region.
10211 The list of attributes set for this memory region.
10216 @subsection Attributes
10218 @subsubsection Memory Access Mode
10219 The access mode attributes set whether @value{GDBN} may make read or
10220 write accesses to a memory region.
10222 While these attributes prevent @value{GDBN} from performing invalid
10223 memory accesses, they do nothing to prevent the target system, I/O DMA,
10224 etc.@: from accessing memory.
10228 Memory is read only.
10230 Memory is write only.
10232 Memory is read/write. This is the default.
10235 @subsubsection Memory Access Size
10236 The access size attribute tells @value{GDBN} to use specific sized
10237 accesses in the memory region. Often memory mapped device registers
10238 require specific sized accesses. If no access size attribute is
10239 specified, @value{GDBN} may use accesses of any size.
10243 Use 8 bit memory accesses.
10245 Use 16 bit memory accesses.
10247 Use 32 bit memory accesses.
10249 Use 64 bit memory accesses.
10252 @c @subsubsection Hardware/Software Breakpoints
10253 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10254 @c will use hardware or software breakpoints for the internal breakpoints
10255 @c used by the step, next, finish, until, etc. commands.
10259 @c Always use hardware breakpoints
10260 @c @item swbreak (default)
10263 @subsubsection Data Cache
10264 The data cache attributes set whether @value{GDBN} will cache target
10265 memory. While this generally improves performance by reducing debug
10266 protocol overhead, it can lead to incorrect results because @value{GDBN}
10267 does not know about volatile variables or memory mapped device
10272 Enable @value{GDBN} to cache target memory.
10274 Disable @value{GDBN} from caching target memory. This is the default.
10277 @subsection Memory Access Checking
10278 @value{GDBN} can be instructed to refuse accesses to memory that is
10279 not explicitly described. This can be useful if accessing such
10280 regions has undesired effects for a specific target, or to provide
10281 better error checking. The following commands control this behaviour.
10284 @kindex set mem inaccessible-by-default
10285 @item set mem inaccessible-by-default [on|off]
10286 If @code{on} is specified, make @value{GDBN} treat memory not
10287 explicitly described by the memory ranges as non-existent and refuse accesses
10288 to such memory. The checks are only performed if there's at least one
10289 memory range defined. If @code{off} is specified, make @value{GDBN}
10290 treat the memory not explicitly described by the memory ranges as RAM.
10291 The default value is @code{on}.
10292 @kindex show mem inaccessible-by-default
10293 @item show mem inaccessible-by-default
10294 Show the current handling of accesses to unknown memory.
10298 @c @subsubsection Memory Write Verification
10299 @c The memory write verification attributes set whether @value{GDBN}
10300 @c will re-reads data after each write to verify the write was successful.
10304 @c @item noverify (default)
10307 @node Dump/Restore Files
10308 @section Copy Between Memory and a File
10309 @cindex dump/restore files
10310 @cindex append data to a file
10311 @cindex dump data to a file
10312 @cindex restore data from a file
10314 You can use the commands @code{dump}, @code{append}, and
10315 @code{restore} to copy data between target memory and a file. The
10316 @code{dump} and @code{append} commands write data to a file, and the
10317 @code{restore} command reads data from a file back into the inferior's
10318 memory. Files may be in binary, Motorola S-record, Intel hex, or
10319 Tektronix Hex format; however, @value{GDBN} can only append to binary
10325 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10326 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10327 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10328 or the value of @var{expr}, to @var{filename} in the given format.
10330 The @var{format} parameter may be any one of:
10337 Motorola S-record format.
10339 Tektronix Hex format.
10342 @value{GDBN} uses the same definitions of these formats as the
10343 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10344 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10348 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10349 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10350 Append the contents of memory from @var{start_addr} to @var{end_addr},
10351 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10352 (@value{GDBN} can only append data to files in raw binary form.)
10355 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10356 Restore the contents of file @var{filename} into memory. The
10357 @code{restore} command can automatically recognize any known @sc{bfd}
10358 file format, except for raw binary. To restore a raw binary file you
10359 must specify the optional keyword @code{binary} after the filename.
10361 If @var{bias} is non-zero, its value will be added to the addresses
10362 contained in the file. Binary files always start at address zero, so
10363 they will be restored at address @var{bias}. Other bfd files have
10364 a built-in location; they will be restored at offset @var{bias}
10365 from that location.
10367 If @var{start} and/or @var{end} are non-zero, then only data between
10368 file offset @var{start} and file offset @var{end} will be restored.
10369 These offsets are relative to the addresses in the file, before
10370 the @var{bias} argument is applied.
10374 @node Core File Generation
10375 @section How to Produce a Core File from Your Program
10376 @cindex dump core from inferior
10378 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10379 image of a running process and its process status (register values
10380 etc.). Its primary use is post-mortem debugging of a program that
10381 crashed while it ran outside a debugger. A program that crashes
10382 automatically produces a core file, unless this feature is disabled by
10383 the user. @xref{Files}, for information on invoking @value{GDBN} in
10384 the post-mortem debugging mode.
10386 Occasionally, you may wish to produce a core file of the program you
10387 are debugging in order to preserve a snapshot of its state.
10388 @value{GDBN} has a special command for that.
10392 @kindex generate-core-file
10393 @item generate-core-file [@var{file}]
10394 @itemx gcore [@var{file}]
10395 Produce a core dump of the inferior process. The optional argument
10396 @var{file} specifies the file name where to put the core dump. If not
10397 specified, the file name defaults to @file{core.@var{pid}}, where
10398 @var{pid} is the inferior process ID.
10400 Note that this command is implemented only for some systems (as of
10401 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10404 @node Character Sets
10405 @section Character Sets
10406 @cindex character sets
10408 @cindex translating between character sets
10409 @cindex host character set
10410 @cindex target character set
10412 If the program you are debugging uses a different character set to
10413 represent characters and strings than the one @value{GDBN} uses itself,
10414 @value{GDBN} can automatically translate between the character sets for
10415 you. The character set @value{GDBN} uses we call the @dfn{host
10416 character set}; the one the inferior program uses we call the
10417 @dfn{target character set}.
10419 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10420 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10421 remote protocol (@pxref{Remote Debugging}) to debug a program
10422 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10423 then the host character set is Latin-1, and the target character set is
10424 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10425 target-charset EBCDIC-US}, then @value{GDBN} translates between
10426 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10427 character and string literals in expressions.
10429 @value{GDBN} has no way to automatically recognize which character set
10430 the inferior program uses; you must tell it, using the @code{set
10431 target-charset} command, described below.
10433 Here are the commands for controlling @value{GDBN}'s character set
10437 @item set target-charset @var{charset}
10438 @kindex set target-charset
10439 Set the current target character set to @var{charset}. To display the
10440 list of supported target character sets, type
10441 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10443 @item set host-charset @var{charset}
10444 @kindex set host-charset
10445 Set the current host character set to @var{charset}.
10447 By default, @value{GDBN} uses a host character set appropriate to the
10448 system it is running on; you can override that default using the
10449 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10450 automatically determine the appropriate host character set. In this
10451 case, @value{GDBN} uses @samp{UTF-8}.
10453 @value{GDBN} can only use certain character sets as its host character
10454 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10455 @value{GDBN} will list the host character sets it supports.
10457 @item set charset @var{charset}
10458 @kindex set charset
10459 Set the current host and target character sets to @var{charset}. As
10460 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10461 @value{GDBN} will list the names of the character sets that can be used
10462 for both host and target.
10465 @kindex show charset
10466 Show the names of the current host and target character sets.
10468 @item show host-charset
10469 @kindex show host-charset
10470 Show the name of the current host character set.
10472 @item show target-charset
10473 @kindex show target-charset
10474 Show the name of the current target character set.
10476 @item set target-wide-charset @var{charset}
10477 @kindex set target-wide-charset
10478 Set the current target's wide character set to @var{charset}. This is
10479 the character set used by the target's @code{wchar_t} type. To
10480 display the list of supported wide character sets, type
10481 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10483 @item show target-wide-charset
10484 @kindex show target-wide-charset
10485 Show the name of the current target's wide character set.
10488 Here is an example of @value{GDBN}'s character set support in action.
10489 Assume that the following source code has been placed in the file
10490 @file{charset-test.c}:
10496 = @{72, 101, 108, 108, 111, 44, 32, 119,
10497 111, 114, 108, 100, 33, 10, 0@};
10498 char ibm1047_hello[]
10499 = @{200, 133, 147, 147, 150, 107, 64, 166,
10500 150, 153, 147, 132, 90, 37, 0@};
10504 printf ("Hello, world!\n");
10508 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10509 containing the string @samp{Hello, world!} followed by a newline,
10510 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10512 We compile the program, and invoke the debugger on it:
10515 $ gcc -g charset-test.c -o charset-test
10516 $ gdb -nw charset-test
10517 GNU gdb 2001-12-19-cvs
10518 Copyright 2001 Free Software Foundation, Inc.
10523 We can use the @code{show charset} command to see what character sets
10524 @value{GDBN} is currently using to interpret and display characters and
10528 (@value{GDBP}) show charset
10529 The current host and target character set is `ISO-8859-1'.
10533 For the sake of printing this manual, let's use @sc{ascii} as our
10534 initial character set:
10536 (@value{GDBP}) set charset ASCII
10537 (@value{GDBP}) show charset
10538 The current host and target character set is `ASCII'.
10542 Let's assume that @sc{ascii} is indeed the correct character set for our
10543 host system --- in other words, let's assume that if @value{GDBN} prints
10544 characters using the @sc{ascii} character set, our terminal will display
10545 them properly. Since our current target character set is also
10546 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10549 (@value{GDBP}) print ascii_hello
10550 $1 = 0x401698 "Hello, world!\n"
10551 (@value{GDBP}) print ascii_hello[0]
10556 @value{GDBN} uses the target character set for character and string
10557 literals you use in expressions:
10560 (@value{GDBP}) print '+'
10565 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10568 @value{GDBN} relies on the user to tell it which character set the
10569 target program uses. If we print @code{ibm1047_hello} while our target
10570 character set is still @sc{ascii}, we get jibberish:
10573 (@value{GDBP}) print ibm1047_hello
10574 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10575 (@value{GDBP}) print ibm1047_hello[0]
10580 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10581 @value{GDBN} tells us the character sets it supports:
10584 (@value{GDBP}) set target-charset
10585 ASCII EBCDIC-US IBM1047 ISO-8859-1
10586 (@value{GDBP}) set target-charset
10589 We can select @sc{ibm1047} as our target character set, and examine the
10590 program's strings again. Now the @sc{ascii} string is wrong, but
10591 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10592 target character set, @sc{ibm1047}, to the host character set,
10593 @sc{ascii}, and they display correctly:
10596 (@value{GDBP}) set target-charset IBM1047
10597 (@value{GDBP}) show charset
10598 The current host character set is `ASCII'.
10599 The current target character set is `IBM1047'.
10600 (@value{GDBP}) print ascii_hello
10601 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10602 (@value{GDBP}) print ascii_hello[0]
10604 (@value{GDBP}) print ibm1047_hello
10605 $8 = 0x4016a8 "Hello, world!\n"
10606 (@value{GDBP}) print ibm1047_hello[0]
10611 As above, @value{GDBN} uses the target character set for character and
10612 string literals you use in expressions:
10615 (@value{GDBP}) print '+'
10620 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10623 @node Caching Remote Data
10624 @section Caching Data of Remote Targets
10625 @cindex caching data of remote targets
10627 @value{GDBN} caches data exchanged between the debugger and a
10628 remote target (@pxref{Remote Debugging}). Such caching generally improves
10629 performance, because it reduces the overhead of the remote protocol by
10630 bundling memory reads and writes into large chunks. Unfortunately, simply
10631 caching everything would lead to incorrect results, since @value{GDBN}
10632 does not necessarily know anything about volatile values, memory-mapped I/O
10633 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10634 memory can be changed @emph{while} a gdb command is executing.
10635 Therefore, by default, @value{GDBN} only caches data
10636 known to be on the stack@footnote{In non-stop mode, it is moderately
10637 rare for a running thread to modify the stack of a stopped thread
10638 in a way that would interfere with a backtrace, and caching of
10639 stack reads provides a significant speed up of remote backtraces.}.
10640 Other regions of memory can be explicitly marked as
10641 cacheable; see @pxref{Memory Region Attributes}.
10644 @kindex set remotecache
10645 @item set remotecache on
10646 @itemx set remotecache off
10647 This option no longer does anything; it exists for compatibility
10650 @kindex show remotecache
10651 @item show remotecache
10652 Show the current state of the obsolete remotecache flag.
10654 @kindex set stack-cache
10655 @item set stack-cache on
10656 @itemx set stack-cache off
10657 Enable or disable caching of stack accesses. When @code{ON}, use
10658 caching. By default, this option is @code{ON}.
10660 @kindex show stack-cache
10661 @item show stack-cache
10662 Show the current state of data caching for memory accesses.
10664 @kindex info dcache
10665 @item info dcache @r{[}line@r{]}
10666 Print the information about the data cache performance. The
10667 information displayed includes the dcache width and depth, and for
10668 each cache line, its number, address, and how many times it was
10669 referenced. This command is useful for debugging the data cache
10672 If a line number is specified, the contents of that line will be
10675 @item set dcache size @var{size}
10676 @cindex dcache size
10677 @kindex set dcache size
10678 Set maximum number of entries in dcache (dcache depth above).
10680 @item set dcache line-size @var{line-size}
10681 @cindex dcache line-size
10682 @kindex set dcache line-size
10683 Set number of bytes each dcache entry caches (dcache width above).
10684 Must be a power of 2.
10686 @item show dcache size
10687 @kindex show dcache size
10688 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10690 @item show dcache line-size
10691 @kindex show dcache line-size
10692 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10696 @node Searching Memory
10697 @section Search Memory
10698 @cindex searching memory
10700 Memory can be searched for a particular sequence of bytes with the
10701 @code{find} command.
10705 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10706 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10707 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10708 etc. The search begins at address @var{start_addr} and continues for either
10709 @var{len} bytes or through to @var{end_addr} inclusive.
10712 @var{s} and @var{n} are optional parameters.
10713 They may be specified in either order, apart or together.
10716 @item @var{s}, search query size
10717 The size of each search query value.
10723 halfwords (two bytes)
10727 giant words (eight bytes)
10730 All values are interpreted in the current language.
10731 This means, for example, that if the current source language is C/C@t{++}
10732 then searching for the string ``hello'' includes the trailing '\0'.
10734 If the value size is not specified, it is taken from the
10735 value's type in the current language.
10736 This is useful when one wants to specify the search
10737 pattern as a mixture of types.
10738 Note that this means, for example, that in the case of C-like languages
10739 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10740 which is typically four bytes.
10742 @item @var{n}, maximum number of finds
10743 The maximum number of matches to print. The default is to print all finds.
10746 You can use strings as search values. Quote them with double-quotes
10748 The string value is copied into the search pattern byte by byte,
10749 regardless of the endianness of the target and the size specification.
10751 The address of each match found is printed as well as a count of the
10752 number of matches found.
10754 The address of the last value found is stored in convenience variable
10756 A count of the number of matches is stored in @samp{$numfound}.
10758 For example, if stopped at the @code{printf} in this function:
10764 static char hello[] = "hello-hello";
10765 static struct @{ char c; short s; int i; @}
10766 __attribute__ ((packed)) mixed
10767 = @{ 'c', 0x1234, 0x87654321 @};
10768 printf ("%s\n", hello);
10773 you get during debugging:
10776 (gdb) find &hello[0], +sizeof(hello), "hello"
10777 0x804956d <hello.1620+6>
10779 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10780 0x8049567 <hello.1620>
10781 0x804956d <hello.1620+6>
10783 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10784 0x8049567 <hello.1620>
10786 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10787 0x8049560 <mixed.1625>
10789 (gdb) print $numfound
10792 $2 = (void *) 0x8049560
10795 @node Optimized Code
10796 @chapter Debugging Optimized Code
10797 @cindex optimized code, debugging
10798 @cindex debugging optimized code
10800 Almost all compilers support optimization. With optimization
10801 disabled, the compiler generates assembly code that corresponds
10802 directly to your source code, in a simplistic way. As the compiler
10803 applies more powerful optimizations, the generated assembly code
10804 diverges from your original source code. With help from debugging
10805 information generated by the compiler, @value{GDBN} can map from
10806 the running program back to constructs from your original source.
10808 @value{GDBN} is more accurate with optimization disabled. If you
10809 can recompile without optimization, it is easier to follow the
10810 progress of your program during debugging. But, there are many cases
10811 where you may need to debug an optimized version.
10813 When you debug a program compiled with @samp{-g -O}, remember that the
10814 optimizer has rearranged your code; the debugger shows you what is
10815 really there. Do not be too surprised when the execution path does not
10816 exactly match your source file! An extreme example: if you define a
10817 variable, but never use it, @value{GDBN} never sees that
10818 variable---because the compiler optimizes it out of existence.
10820 Some things do not work as well with @samp{-g -O} as with just
10821 @samp{-g}, particularly on machines with instruction scheduling. If in
10822 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10823 please report it to us as a bug (including a test case!).
10824 @xref{Variables}, for more information about debugging optimized code.
10827 * Inline Functions:: How @value{GDBN} presents inlining
10828 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10831 @node Inline Functions
10832 @section Inline Functions
10833 @cindex inline functions, debugging
10835 @dfn{Inlining} is an optimization that inserts a copy of the function
10836 body directly at each call site, instead of jumping to a shared
10837 routine. @value{GDBN} displays inlined functions just like
10838 non-inlined functions. They appear in backtraces. You can view their
10839 arguments and local variables, step into them with @code{step}, skip
10840 them with @code{next}, and escape from them with @code{finish}.
10841 You can check whether a function was inlined by using the
10842 @code{info frame} command.
10844 For @value{GDBN} to support inlined functions, the compiler must
10845 record information about inlining in the debug information ---
10846 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10847 other compilers do also. @value{GDBN} only supports inlined functions
10848 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10849 do not emit two required attributes (@samp{DW_AT_call_file} and
10850 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10851 function calls with earlier versions of @value{NGCC}. It instead
10852 displays the arguments and local variables of inlined functions as
10853 local variables in the caller.
10855 The body of an inlined function is directly included at its call site;
10856 unlike a non-inlined function, there are no instructions devoted to
10857 the call. @value{GDBN} still pretends that the call site and the
10858 start of the inlined function are different instructions. Stepping to
10859 the call site shows the call site, and then stepping again shows
10860 the first line of the inlined function, even though no additional
10861 instructions are executed.
10863 This makes source-level debugging much clearer; you can see both the
10864 context of the call and then the effect of the call. Only stepping by
10865 a single instruction using @code{stepi} or @code{nexti} does not do
10866 this; single instruction steps always show the inlined body.
10868 There are some ways that @value{GDBN} does not pretend that inlined
10869 function calls are the same as normal calls:
10873 Setting breakpoints at the call site of an inlined function may not
10874 work, because the call site does not contain any code. @value{GDBN}
10875 may incorrectly move the breakpoint to the next line of the enclosing
10876 function, after the call. This limitation will be removed in a future
10877 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10878 or inside the inlined function instead.
10881 @value{GDBN} cannot locate the return value of inlined calls after
10882 using the @code{finish} command. This is a limitation of compiler-generated
10883 debugging information; after @code{finish}, you can step to the next line
10884 and print a variable where your program stored the return value.
10888 @node Tail Call Frames
10889 @section Tail Call Frames
10890 @cindex tail call frames, debugging
10892 Function @code{B} can call function @code{C} in its very last statement. In
10893 unoptimized compilation the call of @code{C} is immediately followed by return
10894 instruction at the end of @code{B} code. Optimizing compiler may replace the
10895 call and return in function @code{B} into one jump to function @code{C}
10896 instead. Such use of a jump instruction is called @dfn{tail call}.
10898 During execution of function @code{C}, there will be no indication in the
10899 function call stack frames that it was tail-called from @code{B}. If function
10900 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10901 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10902 some cases @value{GDBN} can determine that @code{C} was tail-called from
10903 @code{B}, and it will then create fictitious call frame for that, with the
10904 return address set up as if @code{B} called @code{C} normally.
10906 This functionality is currently supported only by DWARF 2 debugging format and
10907 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10908 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10911 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10912 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10916 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10918 Stack level 1, frame at 0x7fffffffda30:
10919 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10920 tail call frame, caller of frame at 0x7fffffffda30
10921 source language c++.
10922 Arglist at unknown address.
10923 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10926 The detection of all the possible code path executions can find them ambiguous.
10927 There is no execution history stored (possible @ref{Reverse Execution} is never
10928 used for this purpose) and the last known caller could have reached the known
10929 callee by multiple different jump sequences. In such case @value{GDBN} still
10930 tries to show at least all the unambiguous top tail callers and all the
10931 unambiguous bottom tail calees, if any.
10934 @anchor{set debug entry-values}
10935 @item set debug entry-values
10936 @kindex set debug entry-values
10937 When set to on, enables printing of analysis messages for both frame argument
10938 values at function entry and tail calls. It will show all the possible valid
10939 tail calls code paths it has considered. It will also print the intersection
10940 of them with the final unambiguous (possibly partial or even empty) code path
10943 @item show debug entry-values
10944 @kindex show debug entry-values
10945 Show the current state of analysis messages printing for both frame argument
10946 values at function entry and tail calls.
10949 The analysis messages for tail calls can for example show why the virtual tail
10950 call frame for function @code{c} has not been recognized (due to the indirect
10951 reference by variable @code{x}):
10954 static void __attribute__((noinline, noclone)) c (void);
10955 void (*x) (void) = c;
10956 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10957 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10958 int main (void) @{ x (); return 0; @}
10960 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10961 DW_TAG_GNU_call_site 0x40039a in main
10963 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10966 #1 0x000000000040039a in main () at t.c:5
10969 Another possibility is an ambiguous virtual tail call frames resolution:
10973 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10974 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10975 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10976 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10977 static void __attribute__((noinline, noclone)) b (void)
10978 @{ if (i) c (); else e (); @}
10979 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10980 int main (void) @{ a (); return 0; @}
10982 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10983 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10984 tailcall: reduced: 0x4004d2(a) |
10987 #1 0x00000000004004d2 in a () at t.c:8
10988 #2 0x0000000000400395 in main () at t.c:9
10991 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10992 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10994 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10995 @ifset HAVE_MAKEINFO_CLICK
10996 @set ARROW @click{}
10997 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10998 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11000 @ifclear HAVE_MAKEINFO_CLICK
11002 @set CALLSEQ1B @value{CALLSEQ1A}
11003 @set CALLSEQ2B @value{CALLSEQ2A}
11006 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11007 The code can have possible execution paths @value{CALLSEQ1B} or
11008 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11010 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11011 has found. It then finds another possible calling sequcen - that one is
11012 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11013 printed as the @code{reduced:} calling sequence. That one could have many
11014 futher @code{compare:} and @code{reduced:} statements as long as there remain
11015 any non-ambiguous sequence entries.
11017 For the frame of function @code{b} in both cases there are different possible
11018 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11019 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11020 therefore this one is displayed to the user while the ambiguous frames are
11023 There can be also reasons why printing of frame argument values at function
11028 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11029 static void __attribute__((noinline, noclone)) a (int i);
11030 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11031 static void __attribute__((noinline, noclone)) a (int i)
11032 @{ if (i) b (i - 1); else c (0); @}
11033 int main (void) @{ a (5); return 0; @}
11036 #0 c (i=i@@entry=0) at t.c:2
11037 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11038 function "a" at 0x400420 can call itself via tail calls
11039 i=<optimized out>) at t.c:6
11040 #2 0x000000000040036e in main () at t.c:7
11043 @value{GDBN} cannot find out from the inferior state if and how many times did
11044 function @code{a} call itself (via function @code{b}) as these calls would be
11045 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11046 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11047 prints @code{<optimized out>} instead.
11050 @chapter C Preprocessor Macros
11052 Some languages, such as C and C@t{++}, provide a way to define and invoke
11053 ``preprocessor macros'' which expand into strings of tokens.
11054 @value{GDBN} can evaluate expressions containing macro invocations, show
11055 the result of macro expansion, and show a macro's definition, including
11056 where it was defined.
11058 You may need to compile your program specially to provide @value{GDBN}
11059 with information about preprocessor macros. Most compilers do not
11060 include macros in their debugging information, even when you compile
11061 with the @option{-g} flag. @xref{Compilation}.
11063 A program may define a macro at one point, remove that definition later,
11064 and then provide a different definition after that. Thus, at different
11065 points in the program, a macro may have different definitions, or have
11066 no definition at all. If there is a current stack frame, @value{GDBN}
11067 uses the macros in scope at that frame's source code line. Otherwise,
11068 @value{GDBN} uses the macros in scope at the current listing location;
11071 Whenever @value{GDBN} evaluates an expression, it always expands any
11072 macro invocations present in the expression. @value{GDBN} also provides
11073 the following commands for working with macros explicitly.
11077 @kindex macro expand
11078 @cindex macro expansion, showing the results of preprocessor
11079 @cindex preprocessor macro expansion, showing the results of
11080 @cindex expanding preprocessor macros
11081 @item macro expand @var{expression}
11082 @itemx macro exp @var{expression}
11083 Show the results of expanding all preprocessor macro invocations in
11084 @var{expression}. Since @value{GDBN} simply expands macros, but does
11085 not parse the result, @var{expression} need not be a valid expression;
11086 it can be any string of tokens.
11089 @item macro expand-once @var{expression}
11090 @itemx macro exp1 @var{expression}
11091 @cindex expand macro once
11092 @i{(This command is not yet implemented.)} Show the results of
11093 expanding those preprocessor macro invocations that appear explicitly in
11094 @var{expression}. Macro invocations appearing in that expansion are
11095 left unchanged. This command allows you to see the effect of a
11096 particular macro more clearly, without being confused by further
11097 expansions. Since @value{GDBN} simply expands macros, but does not
11098 parse the result, @var{expression} need not be a valid expression; it
11099 can be any string of tokens.
11102 @cindex macro definition, showing
11103 @cindex definition of a macro, showing
11104 @cindex macros, from debug info
11105 @item info macro [-a|-all] [--] @var{macro}
11106 Show the current definition or all definitions of the named @var{macro},
11107 and describe the source location or compiler command-line where that
11108 definition was established. The optional double dash is to signify the end of
11109 argument processing and the beginning of @var{macro} for non C-like macros where
11110 the macro may begin with a hyphen.
11112 @kindex info macros
11113 @item info macros @var{linespec}
11114 Show all macro definitions that are in effect at the location specified
11115 by @var{linespec}, and describe the source location or compiler
11116 command-line where those definitions were established.
11118 @kindex macro define
11119 @cindex user-defined macros
11120 @cindex defining macros interactively
11121 @cindex macros, user-defined
11122 @item macro define @var{macro} @var{replacement-list}
11123 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11124 Introduce a definition for a preprocessor macro named @var{macro},
11125 invocations of which are replaced by the tokens given in
11126 @var{replacement-list}. The first form of this command defines an
11127 ``object-like'' macro, which takes no arguments; the second form
11128 defines a ``function-like'' macro, which takes the arguments given in
11131 A definition introduced by this command is in scope in every
11132 expression evaluated in @value{GDBN}, until it is removed with the
11133 @code{macro undef} command, described below. The definition overrides
11134 all definitions for @var{macro} present in the program being debugged,
11135 as well as any previous user-supplied definition.
11137 @kindex macro undef
11138 @item macro undef @var{macro}
11139 Remove any user-supplied definition for the macro named @var{macro}.
11140 This command only affects definitions provided with the @code{macro
11141 define} command, described above; it cannot remove definitions present
11142 in the program being debugged.
11146 List all the macros defined using the @code{macro define} command.
11149 @cindex macros, example of debugging with
11150 Here is a transcript showing the above commands in action. First, we
11151 show our source files:
11156 #include "sample.h"
11159 #define ADD(x) (M + x)
11164 printf ("Hello, world!\n");
11166 printf ("We're so creative.\n");
11168 printf ("Goodbye, world!\n");
11175 Now, we compile the program using the @sc{gnu} C compiler,
11176 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11177 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11178 and @option{-gdwarf-4}; we recommend always choosing the most recent
11179 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11180 includes information about preprocessor macros in the debugging
11184 $ gcc -gdwarf-2 -g3 sample.c -o sample
11188 Now, we start @value{GDBN} on our sample program:
11192 GNU gdb 2002-05-06-cvs
11193 Copyright 2002 Free Software Foundation, Inc.
11194 GDB is free software, @dots{}
11198 We can expand macros and examine their definitions, even when the
11199 program is not running. @value{GDBN} uses the current listing position
11200 to decide which macro definitions are in scope:
11203 (@value{GDBP}) list main
11206 5 #define ADD(x) (M + x)
11211 10 printf ("Hello, world!\n");
11213 12 printf ("We're so creative.\n");
11214 (@value{GDBP}) info macro ADD
11215 Defined at /home/jimb/gdb/macros/play/sample.c:5
11216 #define ADD(x) (M + x)
11217 (@value{GDBP}) info macro Q
11218 Defined at /home/jimb/gdb/macros/play/sample.h:1
11219 included at /home/jimb/gdb/macros/play/sample.c:2
11221 (@value{GDBP}) macro expand ADD(1)
11222 expands to: (42 + 1)
11223 (@value{GDBP}) macro expand-once ADD(1)
11224 expands to: once (M + 1)
11228 In the example above, note that @code{macro expand-once} expands only
11229 the macro invocation explicit in the original text --- the invocation of
11230 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11231 which was introduced by @code{ADD}.
11233 Once the program is running, @value{GDBN} uses the macro definitions in
11234 force at the source line of the current stack frame:
11237 (@value{GDBP}) break main
11238 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11240 Starting program: /home/jimb/gdb/macros/play/sample
11242 Breakpoint 1, main () at sample.c:10
11243 10 printf ("Hello, world!\n");
11247 At line 10, the definition of the macro @code{N} at line 9 is in force:
11250 (@value{GDBP}) info macro N
11251 Defined at /home/jimb/gdb/macros/play/sample.c:9
11253 (@value{GDBP}) macro expand N Q M
11254 expands to: 28 < 42
11255 (@value{GDBP}) print N Q M
11260 As we step over directives that remove @code{N}'s definition, and then
11261 give it a new definition, @value{GDBN} finds the definition (or lack
11262 thereof) in force at each point:
11265 (@value{GDBP}) next
11267 12 printf ("We're so creative.\n");
11268 (@value{GDBP}) info macro N
11269 The symbol `N' has no definition as a C/C++ preprocessor macro
11270 at /home/jimb/gdb/macros/play/sample.c:12
11271 (@value{GDBP}) next
11273 14 printf ("Goodbye, world!\n");
11274 (@value{GDBP}) info macro N
11275 Defined at /home/jimb/gdb/macros/play/sample.c:13
11277 (@value{GDBP}) macro expand N Q M
11278 expands to: 1729 < 42
11279 (@value{GDBP}) print N Q M
11284 In addition to source files, macros can be defined on the compilation command
11285 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11286 such a way, @value{GDBN} displays the location of their definition as line zero
11287 of the source file submitted to the compiler.
11290 (@value{GDBP}) info macro __STDC__
11291 Defined at /home/jimb/gdb/macros/play/sample.c:0
11298 @chapter Tracepoints
11299 @c This chapter is based on the documentation written by Michael
11300 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11302 @cindex tracepoints
11303 In some applications, it is not feasible for the debugger to interrupt
11304 the program's execution long enough for the developer to learn
11305 anything helpful about its behavior. If the program's correctness
11306 depends on its real-time behavior, delays introduced by a debugger
11307 might cause the program to change its behavior drastically, or perhaps
11308 fail, even when the code itself is correct. It is useful to be able
11309 to observe the program's behavior without interrupting it.
11311 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11312 specify locations in the program, called @dfn{tracepoints}, and
11313 arbitrary expressions to evaluate when those tracepoints are reached.
11314 Later, using the @code{tfind} command, you can examine the values
11315 those expressions had when the program hit the tracepoints. The
11316 expressions may also denote objects in memory---structures or arrays,
11317 for example---whose values @value{GDBN} should record; while visiting
11318 a particular tracepoint, you may inspect those objects as if they were
11319 in memory at that moment. However, because @value{GDBN} records these
11320 values without interacting with you, it can do so quickly and
11321 unobtrusively, hopefully not disturbing the program's behavior.
11323 The tracepoint facility is currently available only for remote
11324 targets. @xref{Targets}. In addition, your remote target must know
11325 how to collect trace data. This functionality is implemented in the
11326 remote stub; however, none of the stubs distributed with @value{GDBN}
11327 support tracepoints as of this writing. The format of the remote
11328 packets used to implement tracepoints are described in @ref{Tracepoint
11331 It is also possible to get trace data from a file, in a manner reminiscent
11332 of corefiles; you specify the filename, and use @code{tfind} to search
11333 through the file. @xref{Trace Files}, for more details.
11335 This chapter describes the tracepoint commands and features.
11338 * Set Tracepoints::
11339 * Analyze Collected Data::
11340 * Tracepoint Variables::
11344 @node Set Tracepoints
11345 @section Commands to Set Tracepoints
11347 Before running such a @dfn{trace experiment}, an arbitrary number of
11348 tracepoints can be set. A tracepoint is actually a special type of
11349 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11350 standard breakpoint commands. For instance, as with breakpoints,
11351 tracepoint numbers are successive integers starting from one, and many
11352 of the commands associated with tracepoints take the tracepoint number
11353 as their argument, to identify which tracepoint to work on.
11355 For each tracepoint, you can specify, in advance, some arbitrary set
11356 of data that you want the target to collect in the trace buffer when
11357 it hits that tracepoint. The collected data can include registers,
11358 local variables, or global data. Later, you can use @value{GDBN}
11359 commands to examine the values these data had at the time the
11360 tracepoint was hit.
11362 Tracepoints do not support every breakpoint feature. Ignore counts on
11363 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11364 commands when they are hit. Tracepoints may not be thread-specific
11367 @cindex fast tracepoints
11368 Some targets may support @dfn{fast tracepoints}, which are inserted in
11369 a different way (such as with a jump instead of a trap), that is
11370 faster but possibly restricted in where they may be installed.
11372 @cindex static tracepoints
11373 @cindex markers, static tracepoints
11374 @cindex probing markers, static tracepoints
11375 Regular and fast tracepoints are dynamic tracing facilities, meaning
11376 that they can be used to insert tracepoints at (almost) any location
11377 in the target. Some targets may also support controlling @dfn{static
11378 tracepoints} from @value{GDBN}. With static tracing, a set of
11379 instrumentation points, also known as @dfn{markers}, are embedded in
11380 the target program, and can be activated or deactivated by name or
11381 address. These are usually placed at locations which facilitate
11382 investigating what the target is actually doing. @value{GDBN}'s
11383 support for static tracing includes being able to list instrumentation
11384 points, and attach them with @value{GDBN} defined high level
11385 tracepoints that expose the whole range of convenience of
11386 @value{GDBN}'s tracepoints support. Namely, support for collecting
11387 registers values and values of global or local (to the instrumentation
11388 point) variables; tracepoint conditions and trace state variables.
11389 The act of installing a @value{GDBN} static tracepoint on an
11390 instrumentation point, or marker, is referred to as @dfn{probing} a
11391 static tracepoint marker.
11393 @code{gdbserver} supports tracepoints on some target systems.
11394 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11396 This section describes commands to set tracepoints and associated
11397 conditions and actions.
11400 * Create and Delete Tracepoints::
11401 * Enable and Disable Tracepoints::
11402 * Tracepoint Passcounts::
11403 * Tracepoint Conditions::
11404 * Trace State Variables::
11405 * Tracepoint Actions::
11406 * Listing Tracepoints::
11407 * Listing Static Tracepoint Markers::
11408 * Starting and Stopping Trace Experiments::
11409 * Tracepoint Restrictions::
11412 @node Create and Delete Tracepoints
11413 @subsection Create and Delete Tracepoints
11416 @cindex set tracepoint
11418 @item trace @var{location}
11419 The @code{trace} command is very similar to the @code{break} command.
11420 Its argument @var{location} can be a source line, a function name, or
11421 an address in the target program. @xref{Specify Location}. The
11422 @code{trace} command defines a tracepoint, which is a point in the
11423 target program where the debugger will briefly stop, collect some
11424 data, and then allow the program to continue. Setting a tracepoint or
11425 changing its actions takes effect immediately if the remote stub
11426 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11428 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11429 these changes don't take effect until the next @code{tstart}
11430 command, and once a trace experiment is running, further changes will
11431 not have any effect until the next trace experiment starts. In addition,
11432 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11433 address is not yet resolved. (This is similar to pending breakpoints.)
11434 Pending tracepoints are not downloaded to the target and not installed
11435 until they are resolved. The resolution of pending tracepoints requires
11436 @value{GDBN} support---when debugging with the remote target, and
11437 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11438 tracing}), pending tracepoints can not be resolved (and downloaded to
11439 the remote stub) while @value{GDBN} is disconnected.
11441 Here are some examples of using the @code{trace} command:
11444 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11446 (@value{GDBP}) @b{trace +2} // 2 lines forward
11448 (@value{GDBP}) @b{trace my_function} // first source line of function
11450 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11452 (@value{GDBP}) @b{trace *0x2117c4} // an address
11456 You can abbreviate @code{trace} as @code{tr}.
11458 @item trace @var{location} if @var{cond}
11459 Set a tracepoint with condition @var{cond}; evaluate the expression
11460 @var{cond} each time the tracepoint is reached, and collect data only
11461 if the value is nonzero---that is, if @var{cond} evaluates as true.
11462 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11463 information on tracepoint conditions.
11465 @item ftrace @var{location} [ if @var{cond} ]
11466 @cindex set fast tracepoint
11467 @cindex fast tracepoints, setting
11469 The @code{ftrace} command sets a fast tracepoint. For targets that
11470 support them, fast tracepoints will use a more efficient but possibly
11471 less general technique to trigger data collection, such as a jump
11472 instruction instead of a trap, or some sort of hardware support. It
11473 may not be possible to create a fast tracepoint at the desired
11474 location, in which case the command will exit with an explanatory
11477 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11480 On 32-bit x86-architecture systems, fast tracepoints normally need to
11481 be placed at an instruction that is 5 bytes or longer, but can be
11482 placed at 4-byte instructions if the low 64K of memory of the target
11483 program is available to install trampolines. Some Unix-type systems,
11484 such as @sc{gnu}/Linux, exclude low addresses from the program's
11485 address space; but for instance with the Linux kernel it is possible
11486 to let @value{GDBN} use this area by doing a @command{sysctl} command
11487 to set the @code{mmap_min_addr} kernel parameter, as in
11490 sudo sysctl -w vm.mmap_min_addr=32768
11494 which sets the low address to 32K, which leaves plenty of room for
11495 trampolines. The minimum address should be set to a page boundary.
11497 @item strace @var{location} [ if @var{cond} ]
11498 @cindex set static tracepoint
11499 @cindex static tracepoints, setting
11500 @cindex probe static tracepoint marker
11502 The @code{strace} command sets a static tracepoint. For targets that
11503 support it, setting a static tracepoint probes a static
11504 instrumentation point, or marker, found at @var{location}. It may not
11505 be possible to set a static tracepoint at the desired location, in
11506 which case the command will exit with an explanatory message.
11508 @value{GDBN} handles arguments to @code{strace} exactly as for
11509 @code{trace}, with the addition that the user can also specify
11510 @code{-m @var{marker}} as @var{location}. This probes the marker
11511 identified by the @var{marker} string identifier. This identifier
11512 depends on the static tracepoint backend library your program is
11513 using. You can find all the marker identifiers in the @samp{ID} field
11514 of the @code{info static-tracepoint-markers} command output.
11515 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11516 Markers}. For example, in the following small program using the UST
11522 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11527 the marker id is composed of joining the first two arguments to the
11528 @code{trace_mark} call with a slash, which translates to:
11531 (@value{GDBP}) info static-tracepoint-markers
11532 Cnt Enb ID Address What
11533 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11539 so you may probe the marker above with:
11542 (@value{GDBP}) strace -m ust/bar33
11545 Static tracepoints accept an extra collect action --- @code{collect
11546 $_sdata}. This collects arbitrary user data passed in the probe point
11547 call to the tracing library. In the UST example above, you'll see
11548 that the third argument to @code{trace_mark} is a printf-like format
11549 string. The user data is then the result of running that formating
11550 string against the following arguments. Note that @code{info
11551 static-tracepoint-markers} command output lists that format string in
11552 the @samp{Data:} field.
11554 You can inspect this data when analyzing the trace buffer, by printing
11555 the $_sdata variable like any other variable available to
11556 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11559 @cindex last tracepoint number
11560 @cindex recent tracepoint number
11561 @cindex tracepoint number
11562 The convenience variable @code{$tpnum} records the tracepoint number
11563 of the most recently set tracepoint.
11565 @kindex delete tracepoint
11566 @cindex tracepoint deletion
11567 @item delete tracepoint @r{[}@var{num}@r{]}
11568 Permanently delete one or more tracepoints. With no argument, the
11569 default is to delete all tracepoints. Note that the regular
11570 @code{delete} command can remove tracepoints also.
11575 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11577 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11581 You can abbreviate this command as @code{del tr}.
11584 @node Enable and Disable Tracepoints
11585 @subsection Enable and Disable Tracepoints
11587 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11590 @kindex disable tracepoint
11591 @item disable tracepoint @r{[}@var{num}@r{]}
11592 Disable tracepoint @var{num}, or all tracepoints if no argument
11593 @var{num} is given. A disabled tracepoint will have no effect during
11594 a trace experiment, but it is not forgotten. You can re-enable
11595 a disabled tracepoint using the @code{enable tracepoint} command.
11596 If the command is issued during a trace experiment and the debug target
11597 has support for disabling tracepoints during a trace experiment, then the
11598 change will be effective immediately. Otherwise, it will be applied to the
11599 next trace experiment.
11601 @kindex enable tracepoint
11602 @item enable tracepoint @r{[}@var{num}@r{]}
11603 Enable tracepoint @var{num}, or all tracepoints. If this command is
11604 issued during a trace experiment and the debug target supports enabling
11605 tracepoints during a trace experiment, then the enabled tracepoints will
11606 become effective immediately. Otherwise, they will become effective the
11607 next time a trace experiment is run.
11610 @node Tracepoint Passcounts
11611 @subsection Tracepoint Passcounts
11615 @cindex tracepoint pass count
11616 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11617 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11618 automatically stop a trace experiment. If a tracepoint's passcount is
11619 @var{n}, then the trace experiment will be automatically stopped on
11620 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11621 @var{num} is not specified, the @code{passcount} command sets the
11622 passcount of the most recently defined tracepoint. If no passcount is
11623 given, the trace experiment will run until stopped explicitly by the
11629 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11630 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11632 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11633 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11634 (@value{GDBP}) @b{trace foo}
11635 (@value{GDBP}) @b{pass 3}
11636 (@value{GDBP}) @b{trace bar}
11637 (@value{GDBP}) @b{pass 2}
11638 (@value{GDBP}) @b{trace baz}
11639 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11640 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11641 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11642 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11646 @node Tracepoint Conditions
11647 @subsection Tracepoint Conditions
11648 @cindex conditional tracepoints
11649 @cindex tracepoint conditions
11651 The simplest sort of tracepoint collects data every time your program
11652 reaches a specified place. You can also specify a @dfn{condition} for
11653 a tracepoint. A condition is just a Boolean expression in your
11654 programming language (@pxref{Expressions, ,Expressions}). A
11655 tracepoint with a condition evaluates the expression each time your
11656 program reaches it, and data collection happens only if the condition
11659 Tracepoint conditions can be specified when a tracepoint is set, by
11660 using @samp{if} in the arguments to the @code{trace} command.
11661 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11662 also be set or changed at any time with the @code{condition} command,
11663 just as with breakpoints.
11665 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11666 the conditional expression itself. Instead, @value{GDBN} encodes the
11667 expression into an agent expression (@pxref{Agent Expressions})
11668 suitable for execution on the target, independently of @value{GDBN}.
11669 Global variables become raw memory locations, locals become stack
11670 accesses, and so forth.
11672 For instance, suppose you have a function that is usually called
11673 frequently, but should not be called after an error has occurred. You
11674 could use the following tracepoint command to collect data about calls
11675 of that function that happen while the error code is propagating
11676 through the program; an unconditional tracepoint could end up
11677 collecting thousands of useless trace frames that you would have to
11681 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11684 @node Trace State Variables
11685 @subsection Trace State Variables
11686 @cindex trace state variables
11688 A @dfn{trace state variable} is a special type of variable that is
11689 created and managed by target-side code. The syntax is the same as
11690 that for GDB's convenience variables (a string prefixed with ``$''),
11691 but they are stored on the target. They must be created explicitly,
11692 using a @code{tvariable} command. They are always 64-bit signed
11695 Trace state variables are remembered by @value{GDBN}, and downloaded
11696 to the target along with tracepoint information when the trace
11697 experiment starts. There are no intrinsic limits on the number of
11698 trace state variables, beyond memory limitations of the target.
11700 @cindex convenience variables, and trace state variables
11701 Although trace state variables are managed by the target, you can use
11702 them in print commands and expressions as if they were convenience
11703 variables; @value{GDBN} will get the current value from the target
11704 while the trace experiment is running. Trace state variables share
11705 the same namespace as other ``$'' variables, which means that you
11706 cannot have trace state variables with names like @code{$23} or
11707 @code{$pc}, nor can you have a trace state variable and a convenience
11708 variable with the same name.
11712 @item tvariable $@var{name} [ = @var{expression} ]
11714 The @code{tvariable} command creates a new trace state variable named
11715 @code{$@var{name}}, and optionally gives it an initial value of
11716 @var{expression}. @var{expression} is evaluated when this command is
11717 entered; the result will be converted to an integer if possible,
11718 otherwise @value{GDBN} will report an error. A subsequent
11719 @code{tvariable} command specifying the same name does not create a
11720 variable, but instead assigns the supplied initial value to the
11721 existing variable of that name, overwriting any previous initial
11722 value. The default initial value is 0.
11724 @item info tvariables
11725 @kindex info tvariables
11726 List all the trace state variables along with their initial values.
11727 Their current values may also be displayed, if the trace experiment is
11730 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11731 @kindex delete tvariable
11732 Delete the given trace state variables, or all of them if no arguments
11737 @node Tracepoint Actions
11738 @subsection Tracepoint Action Lists
11742 @cindex tracepoint actions
11743 @item actions @r{[}@var{num}@r{]}
11744 This command will prompt for a list of actions to be taken when the
11745 tracepoint is hit. If the tracepoint number @var{num} is not
11746 specified, this command sets the actions for the one that was most
11747 recently defined (so that you can define a tracepoint and then say
11748 @code{actions} without bothering about its number). You specify the
11749 actions themselves on the following lines, one action at a time, and
11750 terminate the actions list with a line containing just @code{end}. So
11751 far, the only defined actions are @code{collect}, @code{teval}, and
11752 @code{while-stepping}.
11754 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11755 Commands, ,Breakpoint Command Lists}), except that only the defined
11756 actions are allowed; any other @value{GDBN} command is rejected.
11758 @cindex remove actions from a tracepoint
11759 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11760 and follow it immediately with @samp{end}.
11763 (@value{GDBP}) @b{collect @var{data}} // collect some data
11765 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11767 (@value{GDBP}) @b{end} // signals the end of actions.
11770 In the following example, the action list begins with @code{collect}
11771 commands indicating the things to be collected when the tracepoint is
11772 hit. Then, in order to single-step and collect additional data
11773 following the tracepoint, a @code{while-stepping} command is used,
11774 followed by the list of things to be collected after each step in a
11775 sequence of single steps. The @code{while-stepping} command is
11776 terminated by its own separate @code{end} command. Lastly, the action
11777 list is terminated by an @code{end} command.
11780 (@value{GDBP}) @b{trace foo}
11781 (@value{GDBP}) @b{actions}
11782 Enter actions for tracepoint 1, one per line:
11785 > while-stepping 12
11786 > collect $pc, arr[i]
11791 @kindex collect @r{(tracepoints)}
11792 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11793 Collect values of the given expressions when the tracepoint is hit.
11794 This command accepts a comma-separated list of any valid expressions.
11795 In addition to global, static, or local variables, the following
11796 special arguments are supported:
11800 Collect all registers.
11803 Collect all function arguments.
11806 Collect all local variables.
11809 Collect the return address. This is helpful if you want to see more
11813 Collects the number of arguments from the static probe at which the
11814 tracepoint is located.
11815 @xref{Static Probe Points}.
11817 @item $_probe_arg@var{n}
11818 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11819 from the static probe at which the tracepoint is located.
11820 @xref{Static Probe Points}.
11823 @vindex $_sdata@r{, collect}
11824 Collect static tracepoint marker specific data. Only available for
11825 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11826 Lists}. On the UST static tracepoints library backend, an
11827 instrumentation point resembles a @code{printf} function call. The
11828 tracing library is able to collect user specified data formatted to a
11829 character string using the format provided by the programmer that
11830 instrumented the program. Other backends have similar mechanisms.
11831 Here's an example of a UST marker call:
11834 const char master_name[] = "$your_name";
11835 trace_mark(channel1, marker1, "hello %s", master_name)
11838 In this case, collecting @code{$_sdata} collects the string
11839 @samp{hello $yourname}. When analyzing the trace buffer, you can
11840 inspect @samp{$_sdata} like any other variable available to
11844 You can give several consecutive @code{collect} commands, each one
11845 with a single argument, or one @code{collect} command with several
11846 arguments separated by commas; the effect is the same.
11848 The optional @var{mods} changes the usual handling of the arguments.
11849 @code{s} requests that pointers to chars be handled as strings, in
11850 particular collecting the contents of the memory being pointed at, up
11851 to the first zero. The upper bound is by default the value of the
11852 @code{print elements} variable; if @code{s} is followed by a decimal
11853 number, that is the upper bound instead. So for instance
11854 @samp{collect/s25 mystr} collects as many as 25 characters at
11857 The command @code{info scope} (@pxref{Symbols, info scope}) is
11858 particularly useful for figuring out what data to collect.
11860 @kindex teval @r{(tracepoints)}
11861 @item teval @var{expr1}, @var{expr2}, @dots{}
11862 Evaluate the given expressions when the tracepoint is hit. This
11863 command accepts a comma-separated list of expressions. The results
11864 are discarded, so this is mainly useful for assigning values to trace
11865 state variables (@pxref{Trace State Variables}) without adding those
11866 values to the trace buffer, as would be the case if the @code{collect}
11869 @kindex while-stepping @r{(tracepoints)}
11870 @item while-stepping @var{n}
11871 Perform @var{n} single-step instruction traces after the tracepoint,
11872 collecting new data after each step. The @code{while-stepping}
11873 command is followed by the list of what to collect while stepping
11874 (followed by its own @code{end} command):
11877 > while-stepping 12
11878 > collect $regs, myglobal
11884 Note that @code{$pc} is not automatically collected by
11885 @code{while-stepping}; you need to explicitly collect that register if
11886 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11889 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11890 @kindex set default-collect
11891 @cindex default collection action
11892 This variable is a list of expressions to collect at each tracepoint
11893 hit. It is effectively an additional @code{collect} action prepended
11894 to every tracepoint action list. The expressions are parsed
11895 individually for each tracepoint, so for instance a variable named
11896 @code{xyz} may be interpreted as a global for one tracepoint, and a
11897 local for another, as appropriate to the tracepoint's location.
11899 @item show default-collect
11900 @kindex show default-collect
11901 Show the list of expressions that are collected by default at each
11906 @node Listing Tracepoints
11907 @subsection Listing Tracepoints
11910 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11911 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11912 @cindex information about tracepoints
11913 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11914 Display information about the tracepoint @var{num}. If you don't
11915 specify a tracepoint number, displays information about all the
11916 tracepoints defined so far. The format is similar to that used for
11917 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11918 command, simply restricting itself to tracepoints.
11920 A tracepoint's listing may include additional information specific to
11925 its passcount as given by the @code{passcount @var{n}} command
11928 the state about installed on target of each location
11932 (@value{GDBP}) @b{info trace}
11933 Num Type Disp Enb Address What
11934 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11936 collect globfoo, $regs
11941 2 tracepoint keep y <MULTIPLE>
11943 2.1 y 0x0804859c in func4 at change-loc.h:35
11944 installed on target
11945 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11946 installed on target
11947 2.3 y <PENDING> set_tracepoint
11948 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11949 not installed on target
11954 This command can be abbreviated @code{info tp}.
11957 @node Listing Static Tracepoint Markers
11958 @subsection Listing Static Tracepoint Markers
11961 @kindex info static-tracepoint-markers
11962 @cindex information about static tracepoint markers
11963 @item info static-tracepoint-markers
11964 Display information about all static tracepoint markers defined in the
11967 For each marker, the following columns are printed:
11971 An incrementing counter, output to help readability. This is not a
11974 The marker ID, as reported by the target.
11975 @item Enabled or Disabled
11976 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11977 that are not enabled.
11979 Where the marker is in your program, as a memory address.
11981 Where the marker is in the source for your program, as a file and line
11982 number. If the debug information included in the program does not
11983 allow @value{GDBN} to locate the source of the marker, this column
11984 will be left blank.
11988 In addition, the following information may be printed for each marker:
11992 User data passed to the tracing library by the marker call. In the
11993 UST backend, this is the format string passed as argument to the
11995 @item Static tracepoints probing the marker
11996 The list of static tracepoints attached to the marker.
12000 (@value{GDBP}) info static-tracepoint-markers
12001 Cnt ID Enb Address What
12002 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12003 Data: number1 %d number2 %d
12004 Probed by static tracepoints: #2
12005 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12011 @node Starting and Stopping Trace Experiments
12012 @subsection Starting and Stopping Trace Experiments
12015 @kindex tstart [ @var{notes} ]
12016 @cindex start a new trace experiment
12017 @cindex collected data discarded
12019 This command starts the trace experiment, and begins collecting data.
12020 It has the side effect of discarding all the data collected in the
12021 trace buffer during the previous trace experiment. If any arguments
12022 are supplied, they are taken as a note and stored with the trace
12023 experiment's state. The notes may be arbitrary text, and are
12024 especially useful with disconnected tracing in a multi-user context;
12025 the notes can explain what the trace is doing, supply user contact
12026 information, and so forth.
12028 @kindex tstop [ @var{notes} ]
12029 @cindex stop a running trace experiment
12031 This command stops the trace experiment. If any arguments are
12032 supplied, they are recorded with the experiment as a note. This is
12033 useful if you are stopping a trace started by someone else, for
12034 instance if the trace is interfering with the system's behavior and
12035 needs to be stopped quickly.
12037 @strong{Note}: a trace experiment and data collection may stop
12038 automatically if any tracepoint's passcount is reached
12039 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12042 @cindex status of trace data collection
12043 @cindex trace experiment, status of
12045 This command displays the status of the current trace data
12049 Here is an example of the commands we described so far:
12052 (@value{GDBP}) @b{trace gdb_c_test}
12053 (@value{GDBP}) @b{actions}
12054 Enter actions for tracepoint #1, one per line.
12055 > collect $regs,$locals,$args
12056 > while-stepping 11
12060 (@value{GDBP}) @b{tstart}
12061 [time passes @dots{}]
12062 (@value{GDBP}) @b{tstop}
12065 @anchor{disconnected tracing}
12066 @cindex disconnected tracing
12067 You can choose to continue running the trace experiment even if
12068 @value{GDBN} disconnects from the target, voluntarily or
12069 involuntarily. For commands such as @code{detach}, the debugger will
12070 ask what you want to do with the trace. But for unexpected
12071 terminations (@value{GDBN} crash, network outage), it would be
12072 unfortunate to lose hard-won trace data, so the variable
12073 @code{disconnected-tracing} lets you decide whether the trace should
12074 continue running without @value{GDBN}.
12077 @item set disconnected-tracing on
12078 @itemx set disconnected-tracing off
12079 @kindex set disconnected-tracing
12080 Choose whether a tracing run should continue to run if @value{GDBN}
12081 has disconnected from the target. Note that @code{detach} or
12082 @code{quit} will ask you directly what to do about a running trace no
12083 matter what this variable's setting, so the variable is mainly useful
12084 for handling unexpected situations, such as loss of the network.
12086 @item show disconnected-tracing
12087 @kindex show disconnected-tracing
12088 Show the current choice for disconnected tracing.
12092 When you reconnect to the target, the trace experiment may or may not
12093 still be running; it might have filled the trace buffer in the
12094 meantime, or stopped for one of the other reasons. If it is running,
12095 it will continue after reconnection.
12097 Upon reconnection, the target will upload information about the
12098 tracepoints in effect. @value{GDBN} will then compare that
12099 information to the set of tracepoints currently defined, and attempt
12100 to match them up, allowing for the possibility that the numbers may
12101 have changed due to creation and deletion in the meantime. If one of
12102 the target's tracepoints does not match any in @value{GDBN}, the
12103 debugger will create a new tracepoint, so that you have a number with
12104 which to specify that tracepoint. This matching-up process is
12105 necessarily heuristic, and it may result in useless tracepoints being
12106 created; you may simply delete them if they are of no use.
12108 @cindex circular trace buffer
12109 If your target agent supports a @dfn{circular trace buffer}, then you
12110 can run a trace experiment indefinitely without filling the trace
12111 buffer; when space runs out, the agent deletes already-collected trace
12112 frames, oldest first, until there is enough room to continue
12113 collecting. This is especially useful if your tracepoints are being
12114 hit too often, and your trace gets terminated prematurely because the
12115 buffer is full. To ask for a circular trace buffer, simply set
12116 @samp{circular-trace-buffer} to on. You can set this at any time,
12117 including during tracing; if the agent can do it, it will change
12118 buffer handling on the fly, otherwise it will not take effect until
12122 @item set circular-trace-buffer on
12123 @itemx set circular-trace-buffer off
12124 @kindex set circular-trace-buffer
12125 Choose whether a tracing run should use a linear or circular buffer
12126 for trace data. A linear buffer will not lose any trace data, but may
12127 fill up prematurely, while a circular buffer will discard old trace
12128 data, but it will have always room for the latest tracepoint hits.
12130 @item show circular-trace-buffer
12131 @kindex show circular-trace-buffer
12132 Show the current choice for the trace buffer. Note that this may not
12133 match the agent's current buffer handling, nor is it guaranteed to
12134 match the setting that might have been in effect during a past run,
12135 for instance if you are looking at frames from a trace file.
12140 @item set trace-buffer-size @var{n}
12141 @itemx set trace-buffer-size unlimited
12142 @kindex set trace-buffer-size
12143 Request that the target use a trace buffer of @var{n} bytes. Not all
12144 targets will honor the request; they may have a compiled-in size for
12145 the trace buffer, or some other limitation. Set to a value of
12146 @code{unlimited} or @code{-1} to let the target use whatever size it
12147 likes. This is also the default.
12149 @item show trace-buffer-size
12150 @kindex show trace-buffer-size
12151 Show the current requested size for the trace buffer. Note that this
12152 will only match the actual size if the target supports size-setting,
12153 and was able to handle the requested size. For instance, if the
12154 target can only change buffer size between runs, this variable will
12155 not reflect the change until the next run starts. Use @code{tstatus}
12156 to get a report of the actual buffer size.
12160 @item set trace-user @var{text}
12161 @kindex set trace-user
12163 @item show trace-user
12164 @kindex show trace-user
12166 @item set trace-notes @var{text}
12167 @kindex set trace-notes
12168 Set the trace run's notes.
12170 @item show trace-notes
12171 @kindex show trace-notes
12172 Show the trace run's notes.
12174 @item set trace-stop-notes @var{text}
12175 @kindex set trace-stop-notes
12176 Set the trace run's stop notes. The handling of the note is as for
12177 @code{tstop} arguments; the set command is convenient way to fix a
12178 stop note that is mistaken or incomplete.
12180 @item show trace-stop-notes
12181 @kindex show trace-stop-notes
12182 Show the trace run's stop notes.
12186 @node Tracepoint Restrictions
12187 @subsection Tracepoint Restrictions
12189 @cindex tracepoint restrictions
12190 There are a number of restrictions on the use of tracepoints. As
12191 described above, tracepoint data gathering occurs on the target
12192 without interaction from @value{GDBN}. Thus the full capabilities of
12193 the debugger are not available during data gathering, and then at data
12194 examination time, you will be limited by only having what was
12195 collected. The following items describe some common problems, but it
12196 is not exhaustive, and you may run into additional difficulties not
12202 Tracepoint expressions are intended to gather objects (lvalues). Thus
12203 the full flexibility of GDB's expression evaluator is not available.
12204 You cannot call functions, cast objects to aggregate types, access
12205 convenience variables or modify values (except by assignment to trace
12206 state variables). Some language features may implicitly call
12207 functions (for instance Objective-C fields with accessors), and therefore
12208 cannot be collected either.
12211 Collection of local variables, either individually or in bulk with
12212 @code{$locals} or @code{$args}, during @code{while-stepping} may
12213 behave erratically. The stepping action may enter a new scope (for
12214 instance by stepping into a function), or the location of the variable
12215 may change (for instance it is loaded into a register). The
12216 tracepoint data recorded uses the location information for the
12217 variables that is correct for the tracepoint location. When the
12218 tracepoint is created, it is not possible, in general, to determine
12219 where the steps of a @code{while-stepping} sequence will advance the
12220 program---particularly if a conditional branch is stepped.
12223 Collection of an incompletely-initialized or partially-destroyed object
12224 may result in something that @value{GDBN} cannot display, or displays
12225 in a misleading way.
12228 When @value{GDBN} displays a pointer to character it automatically
12229 dereferences the pointer to also display characters of the string
12230 being pointed to. However, collecting the pointer during tracing does
12231 not automatically collect the string. You need to explicitly
12232 dereference the pointer and provide size information if you want to
12233 collect not only the pointer, but the memory pointed to. For example,
12234 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12238 It is not possible to collect a complete stack backtrace at a
12239 tracepoint. Instead, you may collect the registers and a few hundred
12240 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12241 (adjust to use the name of the actual stack pointer register on your
12242 target architecture, and the amount of stack you wish to capture).
12243 Then the @code{backtrace} command will show a partial backtrace when
12244 using a trace frame. The number of stack frames that can be examined
12245 depends on the sizes of the frames in the collected stack. Note that
12246 if you ask for a block so large that it goes past the bottom of the
12247 stack, the target agent may report an error trying to read from an
12251 If you do not collect registers at a tracepoint, @value{GDBN} can
12252 infer that the value of @code{$pc} must be the same as the address of
12253 the tracepoint and use that when you are looking at a trace frame
12254 for that tracepoint. However, this cannot work if the tracepoint has
12255 multiple locations (for instance if it was set in a function that was
12256 inlined), or if it has a @code{while-stepping} loop. In those cases
12257 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12262 @node Analyze Collected Data
12263 @section Using the Collected Data
12265 After the tracepoint experiment ends, you use @value{GDBN} commands
12266 for examining the trace data. The basic idea is that each tracepoint
12267 collects a trace @dfn{snapshot} every time it is hit and another
12268 snapshot every time it single-steps. All these snapshots are
12269 consecutively numbered from zero and go into a buffer, and you can
12270 examine them later. The way you examine them is to @dfn{focus} on a
12271 specific trace snapshot. When the remote stub is focused on a trace
12272 snapshot, it will respond to all @value{GDBN} requests for memory and
12273 registers by reading from the buffer which belongs to that snapshot,
12274 rather than from @emph{real} memory or registers of the program being
12275 debugged. This means that @strong{all} @value{GDBN} commands
12276 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12277 behave as if we were currently debugging the program state as it was
12278 when the tracepoint occurred. Any requests for data that are not in
12279 the buffer will fail.
12282 * tfind:: How to select a trace snapshot
12283 * tdump:: How to display all data for a snapshot
12284 * save tracepoints:: How to save tracepoints for a future run
12288 @subsection @code{tfind @var{n}}
12291 @cindex select trace snapshot
12292 @cindex find trace snapshot
12293 The basic command for selecting a trace snapshot from the buffer is
12294 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12295 counting from zero. If no argument @var{n} is given, the next
12296 snapshot is selected.
12298 Here are the various forms of using the @code{tfind} command.
12302 Find the first snapshot in the buffer. This is a synonym for
12303 @code{tfind 0} (since 0 is the number of the first snapshot).
12306 Stop debugging trace snapshots, resume @emph{live} debugging.
12309 Same as @samp{tfind none}.
12312 No argument means find the next trace snapshot.
12315 Find the previous trace snapshot before the current one. This permits
12316 retracing earlier steps.
12318 @item tfind tracepoint @var{num}
12319 Find the next snapshot associated with tracepoint @var{num}. Search
12320 proceeds forward from the last examined trace snapshot. If no
12321 argument @var{num} is given, it means find the next snapshot collected
12322 for the same tracepoint as the current snapshot.
12324 @item tfind pc @var{addr}
12325 Find the next snapshot associated with the value @var{addr} of the
12326 program counter. Search proceeds forward from the last examined trace
12327 snapshot. If no argument @var{addr} is given, it means find the next
12328 snapshot with the same value of PC as the current snapshot.
12330 @item tfind outside @var{addr1}, @var{addr2}
12331 Find the next snapshot whose PC is outside the given range of
12332 addresses (exclusive).
12334 @item tfind range @var{addr1}, @var{addr2}
12335 Find the next snapshot whose PC is between @var{addr1} and
12336 @var{addr2} (inclusive).
12338 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12339 Find the next snapshot associated with the source line @var{n}. If
12340 the optional argument @var{file} is given, refer to line @var{n} in
12341 that source file. Search proceeds forward from the last examined
12342 trace snapshot. If no argument @var{n} is given, it means find the
12343 next line other than the one currently being examined; thus saying
12344 @code{tfind line} repeatedly can appear to have the same effect as
12345 stepping from line to line in a @emph{live} debugging session.
12348 The default arguments for the @code{tfind} commands are specifically
12349 designed to make it easy to scan through the trace buffer. For
12350 instance, @code{tfind} with no argument selects the next trace
12351 snapshot, and @code{tfind -} with no argument selects the previous
12352 trace snapshot. So, by giving one @code{tfind} command, and then
12353 simply hitting @key{RET} repeatedly you can examine all the trace
12354 snapshots in order. Or, by saying @code{tfind -} and then hitting
12355 @key{RET} repeatedly you can examine the snapshots in reverse order.
12356 The @code{tfind line} command with no argument selects the snapshot
12357 for the next source line executed. The @code{tfind pc} command with
12358 no argument selects the next snapshot with the same program counter
12359 (PC) as the current frame. The @code{tfind tracepoint} command with
12360 no argument selects the next trace snapshot collected by the same
12361 tracepoint as the current one.
12363 In addition to letting you scan through the trace buffer manually,
12364 these commands make it easy to construct @value{GDBN} scripts that
12365 scan through the trace buffer and print out whatever collected data
12366 you are interested in. Thus, if we want to examine the PC, FP, and SP
12367 registers from each trace frame in the buffer, we can say this:
12370 (@value{GDBP}) @b{tfind start}
12371 (@value{GDBP}) @b{while ($trace_frame != -1)}
12372 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12373 $trace_frame, $pc, $sp, $fp
12377 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12378 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12379 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12380 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12381 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12382 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12383 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12384 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12385 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12386 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12387 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12390 Or, if we want to examine the variable @code{X} at each source line in
12394 (@value{GDBP}) @b{tfind start}
12395 (@value{GDBP}) @b{while ($trace_frame != -1)}
12396 > printf "Frame %d, X == %d\n", $trace_frame, X
12406 @subsection @code{tdump}
12408 @cindex dump all data collected at tracepoint
12409 @cindex tracepoint data, display
12411 This command takes no arguments. It prints all the data collected at
12412 the current trace snapshot.
12415 (@value{GDBP}) @b{trace 444}
12416 (@value{GDBP}) @b{actions}
12417 Enter actions for tracepoint #2, one per line:
12418 > collect $regs, $locals, $args, gdb_long_test
12421 (@value{GDBP}) @b{tstart}
12423 (@value{GDBP}) @b{tfind line 444}
12424 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12426 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12428 (@value{GDBP}) @b{tdump}
12429 Data collected at tracepoint 2, trace frame 1:
12430 d0 0xc4aa0085 -995491707
12434 d4 0x71aea3d 119204413
12437 d7 0x380035 3670069
12438 a0 0x19e24a 1696330
12439 a1 0x3000668 50333288
12441 a3 0x322000 3284992
12442 a4 0x3000698 50333336
12443 a5 0x1ad3cc 1758156
12444 fp 0x30bf3c 0x30bf3c
12445 sp 0x30bf34 0x30bf34
12447 pc 0x20b2c8 0x20b2c8
12451 p = 0x20e5b4 "gdb-test"
12458 gdb_long_test = 17 '\021'
12463 @code{tdump} works by scanning the tracepoint's current collection
12464 actions and printing the value of each expression listed. So
12465 @code{tdump} can fail, if after a run, you change the tracepoint's
12466 actions to mention variables that were not collected during the run.
12468 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12469 uses the collected value of @code{$pc} to distinguish between trace
12470 frames that were collected at the tracepoint hit, and frames that were
12471 collected while stepping. This allows it to correctly choose whether
12472 to display the basic list of collections, or the collections from the
12473 body of the while-stepping loop. However, if @code{$pc} was not collected,
12474 then @code{tdump} will always attempt to dump using the basic collection
12475 list, and may fail if a while-stepping frame does not include all the
12476 same data that is collected at the tracepoint hit.
12477 @c This is getting pretty arcane, example would be good.
12479 @node save tracepoints
12480 @subsection @code{save tracepoints @var{filename}}
12481 @kindex save tracepoints
12482 @kindex save-tracepoints
12483 @cindex save tracepoints for future sessions
12485 This command saves all current tracepoint definitions together with
12486 their actions and passcounts, into a file @file{@var{filename}}
12487 suitable for use in a later debugging session. To read the saved
12488 tracepoint definitions, use the @code{source} command (@pxref{Command
12489 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12490 alias for @w{@code{save tracepoints}}
12492 @node Tracepoint Variables
12493 @section Convenience Variables for Tracepoints
12494 @cindex tracepoint variables
12495 @cindex convenience variables for tracepoints
12498 @vindex $trace_frame
12499 @item (int) $trace_frame
12500 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12501 snapshot is selected.
12503 @vindex $tracepoint
12504 @item (int) $tracepoint
12505 The tracepoint for the current trace snapshot.
12507 @vindex $trace_line
12508 @item (int) $trace_line
12509 The line number for the current trace snapshot.
12511 @vindex $trace_file
12512 @item (char []) $trace_file
12513 The source file for the current trace snapshot.
12515 @vindex $trace_func
12516 @item (char []) $trace_func
12517 The name of the function containing @code{$tracepoint}.
12520 Note: @code{$trace_file} is not suitable for use in @code{printf},
12521 use @code{output} instead.
12523 Here's a simple example of using these convenience variables for
12524 stepping through all the trace snapshots and printing some of their
12525 data. Note that these are not the same as trace state variables,
12526 which are managed by the target.
12529 (@value{GDBP}) @b{tfind start}
12531 (@value{GDBP}) @b{while $trace_frame != -1}
12532 > output $trace_file
12533 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12539 @section Using Trace Files
12540 @cindex trace files
12542 In some situations, the target running a trace experiment may no
12543 longer be available; perhaps it crashed, or the hardware was needed
12544 for a different activity. To handle these cases, you can arrange to
12545 dump the trace data into a file, and later use that file as a source
12546 of trace data, via the @code{target tfile} command.
12551 @item tsave [ -r ] @var{filename}
12552 @itemx tsave [-ctf] @var{dirname}
12553 Save the trace data to @var{filename}. By default, this command
12554 assumes that @var{filename} refers to the host filesystem, so if
12555 necessary @value{GDBN} will copy raw trace data up from the target and
12556 then save it. If the target supports it, you can also supply the
12557 optional argument @code{-r} (``remote'') to direct the target to save
12558 the data directly into @var{filename} in its own filesystem, which may be
12559 more efficient if the trace buffer is very large. (Note, however, that
12560 @code{target tfile} can only read from files accessible to the host.)
12561 By default, this command will save trace frame in tfile format.
12562 You can supply the optional argument @code{-ctf} to save date in CTF
12563 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12564 that can be shared by multiple debugging and tracing tools. Please go to
12565 @indicateurl{http://www.efficios.com/ctf} to get more information.
12567 @kindex target tfile
12571 @item target tfile @var{filename}
12572 @itemx target ctf @var{dirname}
12573 Use the file named @var{filename} or directory named @var{dirname} as
12574 a source of trace data. Commands that examine data work as they do with
12575 a live target, but it is not possible to run any new trace experiments.
12576 @code{tstatus} will report the state of the trace run at the moment
12577 the data was saved, as well as the current trace frame you are examining.
12578 @var{filename} or @var{dirname} must be on a filesystem accessible to
12582 (@value{GDBP}) target ctf ctf.ctf
12583 (@value{GDBP}) tfind
12584 Found trace frame 0, tracepoint 2
12585 39 ++a; /* set tracepoint 1 here */
12586 (@value{GDBP}) tdump
12587 Data collected at tracepoint 2, trace frame 0:
12591 c = @{"123", "456", "789", "123", "456", "789"@}
12592 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12600 @chapter Debugging Programs That Use Overlays
12603 If your program is too large to fit completely in your target system's
12604 memory, you can sometimes use @dfn{overlays} to work around this
12605 problem. @value{GDBN} provides some support for debugging programs that
12609 * How Overlays Work:: A general explanation of overlays.
12610 * Overlay Commands:: Managing overlays in @value{GDBN}.
12611 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12612 mapped by asking the inferior.
12613 * Overlay Sample Program:: A sample program using overlays.
12616 @node How Overlays Work
12617 @section How Overlays Work
12618 @cindex mapped overlays
12619 @cindex unmapped overlays
12620 @cindex load address, overlay's
12621 @cindex mapped address
12622 @cindex overlay area
12624 Suppose you have a computer whose instruction address space is only 64
12625 kilobytes long, but which has much more memory which can be accessed by
12626 other means: special instructions, segment registers, or memory
12627 management hardware, for example. Suppose further that you want to
12628 adapt a program which is larger than 64 kilobytes to run on this system.
12630 One solution is to identify modules of your program which are relatively
12631 independent, and need not call each other directly; call these modules
12632 @dfn{overlays}. Separate the overlays from the main program, and place
12633 their machine code in the larger memory. Place your main program in
12634 instruction memory, but leave at least enough space there to hold the
12635 largest overlay as well.
12637 Now, to call a function located in an overlay, you must first copy that
12638 overlay's machine code from the large memory into the space set aside
12639 for it in the instruction memory, and then jump to its entry point
12642 @c NB: In the below the mapped area's size is greater or equal to the
12643 @c size of all overlays. This is intentional to remind the developer
12644 @c that overlays don't necessarily need to be the same size.
12648 Data Instruction Larger
12649 Address Space Address Space Address Space
12650 +-----------+ +-----------+ +-----------+
12652 +-----------+ +-----------+ +-----------+<-- overlay 1
12653 | program | | main | .----| overlay 1 | load address
12654 | variables | | program | | +-----------+
12655 | and heap | | | | | |
12656 +-----------+ | | | +-----------+<-- overlay 2
12657 | | +-----------+ | | | load address
12658 +-----------+ | | | .-| overlay 2 |
12660 mapped --->+-----------+ | | +-----------+
12661 address | | | | | |
12662 | overlay | <-' | | |
12663 | area | <---' +-----------+<-- overlay 3
12664 | | <---. | | load address
12665 +-----------+ `--| overlay 3 |
12672 @anchor{A code overlay}A code overlay
12676 The diagram (@pxref{A code overlay}) shows a system with separate data
12677 and instruction address spaces. To map an overlay, the program copies
12678 its code from the larger address space to the instruction address space.
12679 Since the overlays shown here all use the same mapped address, only one
12680 may be mapped at a time. For a system with a single address space for
12681 data and instructions, the diagram would be similar, except that the
12682 program variables and heap would share an address space with the main
12683 program and the overlay area.
12685 An overlay loaded into instruction memory and ready for use is called a
12686 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12687 instruction memory. An overlay not present (or only partially present)
12688 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12689 is its address in the larger memory. The mapped address is also called
12690 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12691 called the @dfn{load memory address}, or @dfn{LMA}.
12693 Unfortunately, overlays are not a completely transparent way to adapt a
12694 program to limited instruction memory. They introduce a new set of
12695 global constraints you must keep in mind as you design your program:
12700 Before calling or returning to a function in an overlay, your program
12701 must make sure that overlay is actually mapped. Otherwise, the call or
12702 return will transfer control to the right address, but in the wrong
12703 overlay, and your program will probably crash.
12706 If the process of mapping an overlay is expensive on your system, you
12707 will need to choose your overlays carefully to minimize their effect on
12708 your program's performance.
12711 The executable file you load onto your system must contain each
12712 overlay's instructions, appearing at the overlay's load address, not its
12713 mapped address. However, each overlay's instructions must be relocated
12714 and its symbols defined as if the overlay were at its mapped address.
12715 You can use GNU linker scripts to specify different load and relocation
12716 addresses for pieces of your program; see @ref{Overlay Description,,,
12717 ld.info, Using ld: the GNU linker}.
12720 The procedure for loading executable files onto your system must be able
12721 to load their contents into the larger address space as well as the
12722 instruction and data spaces.
12726 The overlay system described above is rather simple, and could be
12727 improved in many ways:
12732 If your system has suitable bank switch registers or memory management
12733 hardware, you could use those facilities to make an overlay's load area
12734 contents simply appear at their mapped address in instruction space.
12735 This would probably be faster than copying the overlay to its mapped
12736 area in the usual way.
12739 If your overlays are small enough, you could set aside more than one
12740 overlay area, and have more than one overlay mapped at a time.
12743 You can use overlays to manage data, as well as instructions. In
12744 general, data overlays are even less transparent to your design than
12745 code overlays: whereas code overlays only require care when you call or
12746 return to functions, data overlays require care every time you access
12747 the data. Also, if you change the contents of a data overlay, you
12748 must copy its contents back out to its load address before you can copy a
12749 different data overlay into the same mapped area.
12754 @node Overlay Commands
12755 @section Overlay Commands
12757 To use @value{GDBN}'s overlay support, each overlay in your program must
12758 correspond to a separate section of the executable file. The section's
12759 virtual memory address and load memory address must be the overlay's
12760 mapped and load addresses. Identifying overlays with sections allows
12761 @value{GDBN} to determine the appropriate address of a function or
12762 variable, depending on whether the overlay is mapped or not.
12764 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12765 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12770 Disable @value{GDBN}'s overlay support. When overlay support is
12771 disabled, @value{GDBN} assumes that all functions and variables are
12772 always present at their mapped addresses. By default, @value{GDBN}'s
12773 overlay support is disabled.
12775 @item overlay manual
12776 @cindex manual overlay debugging
12777 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12778 relies on you to tell it which overlays are mapped, and which are not,
12779 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12780 commands described below.
12782 @item overlay map-overlay @var{overlay}
12783 @itemx overlay map @var{overlay}
12784 @cindex map an overlay
12785 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12786 be the name of the object file section containing the overlay. When an
12787 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12788 functions and variables at their mapped addresses. @value{GDBN} assumes
12789 that any other overlays whose mapped ranges overlap that of
12790 @var{overlay} are now unmapped.
12792 @item overlay unmap-overlay @var{overlay}
12793 @itemx overlay unmap @var{overlay}
12794 @cindex unmap an overlay
12795 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12796 must be the name of the object file section containing the overlay.
12797 When an overlay is unmapped, @value{GDBN} assumes it can find the
12798 overlay's functions and variables at their load addresses.
12801 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12802 consults a data structure the overlay manager maintains in the inferior
12803 to see which overlays are mapped. For details, see @ref{Automatic
12804 Overlay Debugging}.
12806 @item overlay load-target
12807 @itemx overlay load
12808 @cindex reloading the overlay table
12809 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12810 re-reads the table @value{GDBN} automatically each time the inferior
12811 stops, so this command should only be necessary if you have changed the
12812 overlay mapping yourself using @value{GDBN}. This command is only
12813 useful when using automatic overlay debugging.
12815 @item overlay list-overlays
12816 @itemx overlay list
12817 @cindex listing mapped overlays
12818 Display a list of the overlays currently mapped, along with their mapped
12819 addresses, load addresses, and sizes.
12823 Normally, when @value{GDBN} prints a code address, it includes the name
12824 of the function the address falls in:
12827 (@value{GDBP}) print main
12828 $3 = @{int ()@} 0x11a0 <main>
12831 When overlay debugging is enabled, @value{GDBN} recognizes code in
12832 unmapped overlays, and prints the names of unmapped functions with
12833 asterisks around them. For example, if @code{foo} is a function in an
12834 unmapped overlay, @value{GDBN} prints it this way:
12837 (@value{GDBP}) overlay list
12838 No sections are mapped.
12839 (@value{GDBP}) print foo
12840 $5 = @{int (int)@} 0x100000 <*foo*>
12843 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12847 (@value{GDBP}) overlay list
12848 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12849 mapped at 0x1016 - 0x104a
12850 (@value{GDBP}) print foo
12851 $6 = @{int (int)@} 0x1016 <foo>
12854 When overlay debugging is enabled, @value{GDBN} can find the correct
12855 address for functions and variables in an overlay, whether or not the
12856 overlay is mapped. This allows most @value{GDBN} commands, like
12857 @code{break} and @code{disassemble}, to work normally, even on unmapped
12858 code. However, @value{GDBN}'s breakpoint support has some limitations:
12862 @cindex breakpoints in overlays
12863 @cindex overlays, setting breakpoints in
12864 You can set breakpoints in functions in unmapped overlays, as long as
12865 @value{GDBN} can write to the overlay at its load address.
12867 @value{GDBN} can not set hardware or simulator-based breakpoints in
12868 unmapped overlays. However, if you set a breakpoint at the end of your
12869 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12870 you are using manual overlay management), @value{GDBN} will re-set its
12871 breakpoints properly.
12875 @node Automatic Overlay Debugging
12876 @section Automatic Overlay Debugging
12877 @cindex automatic overlay debugging
12879 @value{GDBN} can automatically track which overlays are mapped and which
12880 are not, given some simple co-operation from the overlay manager in the
12881 inferior. If you enable automatic overlay debugging with the
12882 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12883 looks in the inferior's memory for certain variables describing the
12884 current state of the overlays.
12886 Here are the variables your overlay manager must define to support
12887 @value{GDBN}'s automatic overlay debugging:
12891 @item @code{_ovly_table}:
12892 This variable must be an array of the following structures:
12897 /* The overlay's mapped address. */
12900 /* The size of the overlay, in bytes. */
12901 unsigned long size;
12903 /* The overlay's load address. */
12906 /* Non-zero if the overlay is currently mapped;
12908 unsigned long mapped;
12912 @item @code{_novlys}:
12913 This variable must be a four-byte signed integer, holding the total
12914 number of elements in @code{_ovly_table}.
12918 To decide whether a particular overlay is mapped or not, @value{GDBN}
12919 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12920 @code{lma} members equal the VMA and LMA of the overlay's section in the
12921 executable file. When @value{GDBN} finds a matching entry, it consults
12922 the entry's @code{mapped} member to determine whether the overlay is
12925 In addition, your overlay manager may define a function called
12926 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12927 will silently set a breakpoint there. If the overlay manager then
12928 calls this function whenever it has changed the overlay table, this
12929 will enable @value{GDBN} to accurately keep track of which overlays
12930 are in program memory, and update any breakpoints that may be set
12931 in overlays. This will allow breakpoints to work even if the
12932 overlays are kept in ROM or other non-writable memory while they
12933 are not being executed.
12935 @node Overlay Sample Program
12936 @section Overlay Sample Program
12937 @cindex overlay example program
12939 When linking a program which uses overlays, you must place the overlays
12940 at their load addresses, while relocating them to run at their mapped
12941 addresses. To do this, you must write a linker script (@pxref{Overlay
12942 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12943 since linker scripts are specific to a particular host system, target
12944 architecture, and target memory layout, this manual cannot provide
12945 portable sample code demonstrating @value{GDBN}'s overlay support.
12947 However, the @value{GDBN} source distribution does contain an overlaid
12948 program, with linker scripts for a few systems, as part of its test
12949 suite. The program consists of the following files from
12950 @file{gdb/testsuite/gdb.base}:
12954 The main program file.
12956 A simple overlay manager, used by @file{overlays.c}.
12961 Overlay modules, loaded and used by @file{overlays.c}.
12964 Linker scripts for linking the test program on the @code{d10v-elf}
12965 and @code{m32r-elf} targets.
12968 You can build the test program using the @code{d10v-elf} GCC
12969 cross-compiler like this:
12972 $ d10v-elf-gcc -g -c overlays.c
12973 $ d10v-elf-gcc -g -c ovlymgr.c
12974 $ d10v-elf-gcc -g -c foo.c
12975 $ d10v-elf-gcc -g -c bar.c
12976 $ d10v-elf-gcc -g -c baz.c
12977 $ d10v-elf-gcc -g -c grbx.c
12978 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12979 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12982 The build process is identical for any other architecture, except that
12983 you must substitute the appropriate compiler and linker script for the
12984 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12988 @chapter Using @value{GDBN} with Different Languages
12991 Although programming languages generally have common aspects, they are
12992 rarely expressed in the same manner. For instance, in ANSI C,
12993 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12994 Modula-2, it is accomplished by @code{p^}. Values can also be
12995 represented (and displayed) differently. Hex numbers in C appear as
12996 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12998 @cindex working language
12999 Language-specific information is built into @value{GDBN} for some languages,
13000 allowing you to express operations like the above in your program's
13001 native language, and allowing @value{GDBN} to output values in a manner
13002 consistent with the syntax of your program's native language. The
13003 language you use to build expressions is called the @dfn{working
13007 * Setting:: Switching between source languages
13008 * Show:: Displaying the language
13009 * Checks:: Type and range checks
13010 * Supported Languages:: Supported languages
13011 * Unsupported Languages:: Unsupported languages
13015 @section Switching Between Source Languages
13017 There are two ways to control the working language---either have @value{GDBN}
13018 set it automatically, or select it manually yourself. You can use the
13019 @code{set language} command for either purpose. On startup, @value{GDBN}
13020 defaults to setting the language automatically. The working language is
13021 used to determine how expressions you type are interpreted, how values
13024 In addition to the working language, every source file that
13025 @value{GDBN} knows about has its own working language. For some object
13026 file formats, the compiler might indicate which language a particular
13027 source file is in. However, most of the time @value{GDBN} infers the
13028 language from the name of the file. The language of a source file
13029 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13030 show each frame appropriately for its own language. There is no way to
13031 set the language of a source file from within @value{GDBN}, but you can
13032 set the language associated with a filename extension. @xref{Show, ,
13033 Displaying the Language}.
13035 This is most commonly a problem when you use a program, such
13036 as @code{cfront} or @code{f2c}, that generates C but is written in
13037 another language. In that case, make the
13038 program use @code{#line} directives in its C output; that way
13039 @value{GDBN} will know the correct language of the source code of the original
13040 program, and will display that source code, not the generated C code.
13043 * Filenames:: Filename extensions and languages.
13044 * Manually:: Setting the working language manually
13045 * Automatically:: Having @value{GDBN} infer the source language
13049 @subsection List of Filename Extensions and Languages
13051 If a source file name ends in one of the following extensions, then
13052 @value{GDBN} infers that its language is the one indicated.
13070 C@t{++} source file
13076 Objective-C source file
13080 Fortran source file
13083 Modula-2 source file
13087 Assembler source file. This actually behaves almost like C, but
13088 @value{GDBN} does not skip over function prologues when stepping.
13091 In addition, you may set the language associated with a filename
13092 extension. @xref{Show, , Displaying the Language}.
13095 @subsection Setting the Working Language
13097 If you allow @value{GDBN} to set the language automatically,
13098 expressions are interpreted the same way in your debugging session and
13101 @kindex set language
13102 If you wish, you may set the language manually. To do this, issue the
13103 command @samp{set language @var{lang}}, where @var{lang} is the name of
13104 a language, such as
13105 @code{c} or @code{modula-2}.
13106 For a list of the supported languages, type @samp{set language}.
13108 Setting the language manually prevents @value{GDBN} from updating the working
13109 language automatically. This can lead to confusion if you try
13110 to debug a program when the working language is not the same as the
13111 source language, when an expression is acceptable to both
13112 languages---but means different things. For instance, if the current
13113 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13121 might not have the effect you intended. In C, this means to add
13122 @code{b} and @code{c} and place the result in @code{a}. The result
13123 printed would be the value of @code{a}. In Modula-2, this means to compare
13124 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13126 @node Automatically
13127 @subsection Having @value{GDBN} Infer the Source Language
13129 To have @value{GDBN} set the working language automatically, use
13130 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13131 then infers the working language. That is, when your program stops in a
13132 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13133 working language to the language recorded for the function in that
13134 frame. If the language for a frame is unknown (that is, if the function
13135 or block corresponding to the frame was defined in a source file that
13136 does not have a recognized extension), the current working language is
13137 not changed, and @value{GDBN} issues a warning.
13139 This may not seem necessary for most programs, which are written
13140 entirely in one source language. However, program modules and libraries
13141 written in one source language can be used by a main program written in
13142 a different source language. Using @samp{set language auto} in this
13143 case frees you from having to set the working language manually.
13146 @section Displaying the Language
13148 The following commands help you find out which language is the
13149 working language, and also what language source files were written in.
13152 @item show language
13153 @kindex show language
13154 Display the current working language. This is the
13155 language you can use with commands such as @code{print} to
13156 build and compute expressions that may involve variables in your program.
13159 @kindex info frame@r{, show the source language}
13160 Display the source language for this frame. This language becomes the
13161 working language if you use an identifier from this frame.
13162 @xref{Frame Info, ,Information about a Frame}, to identify the other
13163 information listed here.
13166 @kindex info source@r{, show the source language}
13167 Display the source language of this source file.
13168 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13169 information listed here.
13172 In unusual circumstances, you may have source files with extensions
13173 not in the standard list. You can then set the extension associated
13174 with a language explicitly:
13177 @item set extension-language @var{ext} @var{language}
13178 @kindex set extension-language
13179 Tell @value{GDBN} that source files with extension @var{ext} are to be
13180 assumed as written in the source language @var{language}.
13182 @item info extensions
13183 @kindex info extensions
13184 List all the filename extensions and the associated languages.
13188 @section Type and Range Checking
13190 Some languages are designed to guard you against making seemingly common
13191 errors through a series of compile- and run-time checks. These include
13192 checking the type of arguments to functions and operators and making
13193 sure mathematical overflows are caught at run time. Checks such as
13194 these help to ensure a program's correctness once it has been compiled
13195 by eliminating type mismatches and providing active checks for range
13196 errors when your program is running.
13198 By default @value{GDBN} checks for these errors according to the
13199 rules of the current source language. Although @value{GDBN} does not check
13200 the statements in your program, it can check expressions entered directly
13201 into @value{GDBN} for evaluation via the @code{print} command, for example.
13204 * Type Checking:: An overview of type checking
13205 * Range Checking:: An overview of range checking
13208 @cindex type checking
13209 @cindex checks, type
13210 @node Type Checking
13211 @subsection An Overview of Type Checking
13213 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13214 arguments to operators and functions have to be of the correct type,
13215 otherwise an error occurs. These checks prevent type mismatch
13216 errors from ever causing any run-time problems. For example,
13219 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13221 (@value{GDBP}) print obj.my_method (0)
13224 (@value{GDBP}) print obj.my_method (0x1234)
13225 Cannot resolve method klass::my_method to any overloaded instance
13228 The second example fails because in C@t{++} the integer constant
13229 @samp{0x1234} is not type-compatible with the pointer parameter type.
13231 For the expressions you use in @value{GDBN} commands, you can tell
13232 @value{GDBN} to not enforce strict type checking or
13233 to treat any mismatches as errors and abandon the expression;
13234 When type checking is disabled, @value{GDBN} successfully evaluates
13235 expressions like the second example above.
13237 Even if type checking is off, there may be other reasons
13238 related to type that prevent @value{GDBN} from evaluating an expression.
13239 For instance, @value{GDBN} does not know how to add an @code{int} and
13240 a @code{struct foo}. These particular type errors have nothing to do
13241 with the language in use and usually arise from expressions which make
13242 little sense to evaluate anyway.
13244 @value{GDBN} provides some additional commands for controlling type checking:
13246 @kindex set check type
13247 @kindex show check type
13249 @item set check type on
13250 @itemx set check type off
13251 Set strict type checking on or off. If any type mismatches occur in
13252 evaluating an expression while type checking is on, @value{GDBN} prints a
13253 message and aborts evaluation of the expression.
13255 @item show check type
13256 Show the current setting of type checking and whether @value{GDBN}
13257 is enforcing strict type checking rules.
13260 @cindex range checking
13261 @cindex checks, range
13262 @node Range Checking
13263 @subsection An Overview of Range Checking
13265 In some languages (such as Modula-2), it is an error to exceed the
13266 bounds of a type; this is enforced with run-time checks. Such range
13267 checking is meant to ensure program correctness by making sure
13268 computations do not overflow, or indices on an array element access do
13269 not exceed the bounds of the array.
13271 For expressions you use in @value{GDBN} commands, you can tell
13272 @value{GDBN} to treat range errors in one of three ways: ignore them,
13273 always treat them as errors and abandon the expression, or issue
13274 warnings but evaluate the expression anyway.
13276 A range error can result from numerical overflow, from exceeding an
13277 array index bound, or when you type a constant that is not a member
13278 of any type. Some languages, however, do not treat overflows as an
13279 error. In many implementations of C, mathematical overflow causes the
13280 result to ``wrap around'' to lower values---for example, if @var{m} is
13281 the largest integer value, and @var{s} is the smallest, then
13284 @var{m} + 1 @result{} @var{s}
13287 This, too, is specific to individual languages, and in some cases
13288 specific to individual compilers or machines. @xref{Supported Languages, ,
13289 Supported Languages}, for further details on specific languages.
13291 @value{GDBN} provides some additional commands for controlling the range checker:
13293 @kindex set check range
13294 @kindex show check range
13296 @item set check range auto
13297 Set range checking on or off based on the current working language.
13298 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13301 @item set check range on
13302 @itemx set check range off
13303 Set range checking on or off, overriding the default setting for the
13304 current working language. A warning is issued if the setting does not
13305 match the language default. If a range error occurs and range checking is on,
13306 then a message is printed and evaluation of the expression is aborted.
13308 @item set check range warn
13309 Output messages when the @value{GDBN} range checker detects a range error,
13310 but attempt to evaluate the expression anyway. Evaluating the
13311 expression may still be impossible for other reasons, such as accessing
13312 memory that the process does not own (a typical example from many Unix
13316 Show the current setting of the range checker, and whether or not it is
13317 being set automatically by @value{GDBN}.
13320 @node Supported Languages
13321 @section Supported Languages
13323 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13324 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13325 @c This is false ...
13326 Some @value{GDBN} features may be used in expressions regardless of the
13327 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13328 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13329 ,Expressions}) can be used with the constructs of any supported
13332 The following sections detail to what degree each source language is
13333 supported by @value{GDBN}. These sections are not meant to be language
13334 tutorials or references, but serve only as a reference guide to what the
13335 @value{GDBN} expression parser accepts, and what input and output
13336 formats should look like for different languages. There are many good
13337 books written on each of these languages; please look to these for a
13338 language reference or tutorial.
13341 * C:: C and C@t{++}
13344 * Objective-C:: Objective-C
13345 * OpenCL C:: OpenCL C
13346 * Fortran:: Fortran
13348 * Modula-2:: Modula-2
13353 @subsection C and C@t{++}
13355 @cindex C and C@t{++}
13356 @cindex expressions in C or C@t{++}
13358 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13359 to both languages. Whenever this is the case, we discuss those languages
13363 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13364 @cindex @sc{gnu} C@t{++}
13365 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13366 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13367 effectively, you must compile your C@t{++} programs with a supported
13368 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13369 compiler (@code{aCC}).
13372 * C Operators:: C and C@t{++} operators
13373 * C Constants:: C and C@t{++} constants
13374 * C Plus Plus Expressions:: C@t{++} expressions
13375 * C Defaults:: Default settings for C and C@t{++}
13376 * C Checks:: C and C@t{++} type and range checks
13377 * Debugging C:: @value{GDBN} and C
13378 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13379 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13383 @subsubsection C and C@t{++} Operators
13385 @cindex C and C@t{++} operators
13387 Operators must be defined on values of specific types. For instance,
13388 @code{+} is defined on numbers, but not on structures. Operators are
13389 often defined on groups of types.
13391 For the purposes of C and C@t{++}, the following definitions hold:
13396 @emph{Integral types} include @code{int} with any of its storage-class
13397 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13400 @emph{Floating-point types} include @code{float}, @code{double}, and
13401 @code{long double} (if supported by the target platform).
13404 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13407 @emph{Scalar types} include all of the above.
13412 The following operators are supported. They are listed here
13413 in order of increasing precedence:
13417 The comma or sequencing operator. Expressions in a comma-separated list
13418 are evaluated from left to right, with the result of the entire
13419 expression being the last expression evaluated.
13422 Assignment. The value of an assignment expression is the value
13423 assigned. Defined on scalar types.
13426 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13427 and translated to @w{@code{@var{a} = @var{a op b}}}.
13428 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13429 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13430 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13433 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13434 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13438 Logical @sc{or}. Defined on integral types.
13441 Logical @sc{and}. Defined on integral types.
13444 Bitwise @sc{or}. Defined on integral types.
13447 Bitwise exclusive-@sc{or}. Defined on integral types.
13450 Bitwise @sc{and}. Defined on integral types.
13453 Equality and inequality. Defined on scalar types. The value of these
13454 expressions is 0 for false and non-zero for true.
13456 @item <@r{, }>@r{, }<=@r{, }>=
13457 Less than, greater than, less than or equal, greater than or equal.
13458 Defined on scalar types. The value of these expressions is 0 for false
13459 and non-zero for true.
13462 left shift, and right shift. Defined on integral types.
13465 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13468 Addition and subtraction. Defined on integral types, floating-point types and
13471 @item *@r{, }/@r{, }%
13472 Multiplication, division, and modulus. Multiplication and division are
13473 defined on integral and floating-point types. Modulus is defined on
13477 Increment and decrement. When appearing before a variable, the
13478 operation is performed before the variable is used in an expression;
13479 when appearing after it, the variable's value is used before the
13480 operation takes place.
13483 Pointer dereferencing. Defined on pointer types. Same precedence as
13487 Address operator. Defined on variables. Same precedence as @code{++}.
13489 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13490 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13491 to examine the address
13492 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13496 Negative. Defined on integral and floating-point types. Same
13497 precedence as @code{++}.
13500 Logical negation. Defined on integral types. Same precedence as
13504 Bitwise complement operator. Defined on integral types. Same precedence as
13509 Structure member, and pointer-to-structure member. For convenience,
13510 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13511 pointer based on the stored type information.
13512 Defined on @code{struct} and @code{union} data.
13515 Dereferences of pointers to members.
13518 Array indexing. @code{@var{a}[@var{i}]} is defined as
13519 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13522 Function parameter list. Same precedence as @code{->}.
13525 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13526 and @code{class} types.
13529 Doubled colons also represent the @value{GDBN} scope operator
13530 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13534 If an operator is redefined in the user code, @value{GDBN} usually
13535 attempts to invoke the redefined version instead of using the operator's
13536 predefined meaning.
13539 @subsubsection C and C@t{++} Constants
13541 @cindex C and C@t{++} constants
13543 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13548 Integer constants are a sequence of digits. Octal constants are
13549 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13550 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13551 @samp{l}, specifying that the constant should be treated as a
13555 Floating point constants are a sequence of digits, followed by a decimal
13556 point, followed by a sequence of digits, and optionally followed by an
13557 exponent. An exponent is of the form:
13558 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13559 sequence of digits. The @samp{+} is optional for positive exponents.
13560 A floating-point constant may also end with a letter @samp{f} or
13561 @samp{F}, specifying that the constant should be treated as being of
13562 the @code{float} (as opposed to the default @code{double}) type; or with
13563 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13567 Enumerated constants consist of enumerated identifiers, or their
13568 integral equivalents.
13571 Character constants are a single character surrounded by single quotes
13572 (@code{'}), or a number---the ordinal value of the corresponding character
13573 (usually its @sc{ascii} value). Within quotes, the single character may
13574 be represented by a letter or by @dfn{escape sequences}, which are of
13575 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13576 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13577 @samp{@var{x}} is a predefined special character---for example,
13578 @samp{\n} for newline.
13580 Wide character constants can be written by prefixing a character
13581 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13582 form of @samp{x}. The target wide character set is used when
13583 computing the value of this constant (@pxref{Character Sets}).
13586 String constants are a sequence of character constants surrounded by
13587 double quotes (@code{"}). Any valid character constant (as described
13588 above) may appear. Double quotes within the string must be preceded by
13589 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13592 Wide string constants can be written by prefixing a string constant
13593 with @samp{L}, as in C. The target wide character set is used when
13594 computing the value of this constant (@pxref{Character Sets}).
13597 Pointer constants are an integral value. You can also write pointers
13598 to constants using the C operator @samp{&}.
13601 Array constants are comma-separated lists surrounded by braces @samp{@{}
13602 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13603 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13604 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13607 @node C Plus Plus Expressions
13608 @subsubsection C@t{++} Expressions
13610 @cindex expressions in C@t{++}
13611 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13613 @cindex debugging C@t{++} programs
13614 @cindex C@t{++} compilers
13615 @cindex debug formats and C@t{++}
13616 @cindex @value{NGCC} and C@t{++}
13618 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13619 the proper compiler and the proper debug format. Currently,
13620 @value{GDBN} works best when debugging C@t{++} code that is compiled
13621 with the most recent version of @value{NGCC} possible. The DWARF
13622 debugging format is preferred; @value{NGCC} defaults to this on most
13623 popular platforms. Other compilers and/or debug formats are likely to
13624 work badly or not at all when using @value{GDBN} to debug C@t{++}
13625 code. @xref{Compilation}.
13630 @cindex member functions
13632 Member function calls are allowed; you can use expressions like
13635 count = aml->GetOriginal(x, y)
13638 @vindex this@r{, inside C@t{++} member functions}
13639 @cindex namespace in C@t{++}
13641 While a member function is active (in the selected stack frame), your
13642 expressions have the same namespace available as the member function;
13643 that is, @value{GDBN} allows implicit references to the class instance
13644 pointer @code{this} following the same rules as C@t{++}. @code{using}
13645 declarations in the current scope are also respected by @value{GDBN}.
13647 @cindex call overloaded functions
13648 @cindex overloaded functions, calling
13649 @cindex type conversions in C@t{++}
13651 You can call overloaded functions; @value{GDBN} resolves the function
13652 call to the right definition, with some restrictions. @value{GDBN} does not
13653 perform overload resolution involving user-defined type conversions,
13654 calls to constructors, or instantiations of templates that do not exist
13655 in the program. It also cannot handle ellipsis argument lists or
13658 It does perform integral conversions and promotions, floating-point
13659 promotions, arithmetic conversions, pointer conversions, conversions of
13660 class objects to base classes, and standard conversions such as those of
13661 functions or arrays to pointers; it requires an exact match on the
13662 number of function arguments.
13664 Overload resolution is always performed, unless you have specified
13665 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13666 ,@value{GDBN} Features for C@t{++}}.
13668 You must specify @code{set overload-resolution off} in order to use an
13669 explicit function signature to call an overloaded function, as in
13671 p 'foo(char,int)'('x', 13)
13674 The @value{GDBN} command-completion facility can simplify this;
13675 see @ref{Completion, ,Command Completion}.
13677 @cindex reference declarations
13679 @value{GDBN} understands variables declared as C@t{++} references; you can use
13680 them in expressions just as you do in C@t{++} source---they are automatically
13683 In the parameter list shown when @value{GDBN} displays a frame, the values of
13684 reference variables are not displayed (unlike other variables); this
13685 avoids clutter, since references are often used for large structures.
13686 The @emph{address} of a reference variable is always shown, unless
13687 you have specified @samp{set print address off}.
13690 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13691 expressions can use it just as expressions in your program do. Since
13692 one scope may be defined in another, you can use @code{::} repeatedly if
13693 necessary, for example in an expression like
13694 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13695 resolving name scope by reference to source files, in both C and C@t{++}
13696 debugging (@pxref{Variables, ,Program Variables}).
13699 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13704 @subsubsection C and C@t{++} Defaults
13706 @cindex C and C@t{++} defaults
13708 If you allow @value{GDBN} to set range checking automatically, it
13709 defaults to @code{off} whenever the working language changes to
13710 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13711 selects the working language.
13713 If you allow @value{GDBN} to set the language automatically, it
13714 recognizes source files whose names end with @file{.c}, @file{.C}, or
13715 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13716 these files, it sets the working language to C or C@t{++}.
13717 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13718 for further details.
13721 @subsubsection C and C@t{++} Type and Range Checks
13723 @cindex C and C@t{++} checks
13725 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13726 checking is used. However, if you turn type checking off, @value{GDBN}
13727 will allow certain non-standard conversions, such as promoting integer
13728 constants to pointers.
13730 Range checking, if turned on, is done on mathematical operations. Array
13731 indices are not checked, since they are often used to index a pointer
13732 that is not itself an array.
13735 @subsubsection @value{GDBN} and C
13737 The @code{set print union} and @code{show print union} commands apply to
13738 the @code{union} type. When set to @samp{on}, any @code{union} that is
13739 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13740 appears as @samp{@{...@}}.
13742 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13743 with pointers and a memory allocation function. @xref{Expressions,
13746 @node Debugging C Plus Plus
13747 @subsubsection @value{GDBN} Features for C@t{++}
13749 @cindex commands for C@t{++}
13751 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13752 designed specifically for use with C@t{++}. Here is a summary:
13755 @cindex break in overloaded functions
13756 @item @r{breakpoint menus}
13757 When you want a breakpoint in a function whose name is overloaded,
13758 @value{GDBN} has the capability to display a menu of possible breakpoint
13759 locations to help you specify which function definition you want.
13760 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13762 @cindex overloading in C@t{++}
13763 @item rbreak @var{regex}
13764 Setting breakpoints using regular expressions is helpful for setting
13765 breakpoints on overloaded functions that are not members of any special
13767 @xref{Set Breaks, ,Setting Breakpoints}.
13769 @cindex C@t{++} exception handling
13771 @itemx catch rethrow
13773 Debug C@t{++} exception handling using these commands. @xref{Set
13774 Catchpoints, , Setting Catchpoints}.
13776 @cindex inheritance
13777 @item ptype @var{typename}
13778 Print inheritance relationships as well as other information for type
13780 @xref{Symbols, ,Examining the Symbol Table}.
13782 @item info vtbl @var{expression}.
13783 The @code{info vtbl} command can be used to display the virtual
13784 method tables of the object computed by @var{expression}. This shows
13785 one entry per virtual table; there may be multiple virtual tables when
13786 multiple inheritance is in use.
13788 @cindex C@t{++} symbol display
13789 @item set print demangle
13790 @itemx show print demangle
13791 @itemx set print asm-demangle
13792 @itemx show print asm-demangle
13793 Control whether C@t{++} symbols display in their source form, both when
13794 displaying code as C@t{++} source and when displaying disassemblies.
13795 @xref{Print Settings, ,Print Settings}.
13797 @item set print object
13798 @itemx show print object
13799 Choose whether to print derived (actual) or declared types of objects.
13800 @xref{Print Settings, ,Print Settings}.
13802 @item set print vtbl
13803 @itemx show print vtbl
13804 Control the format for printing virtual function tables.
13805 @xref{Print Settings, ,Print Settings}.
13806 (The @code{vtbl} commands do not work on programs compiled with the HP
13807 ANSI C@t{++} compiler (@code{aCC}).)
13809 @kindex set overload-resolution
13810 @cindex overloaded functions, overload resolution
13811 @item set overload-resolution on
13812 Enable overload resolution for C@t{++} expression evaluation. The default
13813 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13814 and searches for a function whose signature matches the argument types,
13815 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13816 Expressions, ,C@t{++} Expressions}, for details).
13817 If it cannot find a match, it emits a message.
13819 @item set overload-resolution off
13820 Disable overload resolution for C@t{++} expression evaluation. For
13821 overloaded functions that are not class member functions, @value{GDBN}
13822 chooses the first function of the specified name that it finds in the
13823 symbol table, whether or not its arguments are of the correct type. For
13824 overloaded functions that are class member functions, @value{GDBN}
13825 searches for a function whose signature @emph{exactly} matches the
13828 @kindex show overload-resolution
13829 @item show overload-resolution
13830 Show the current setting of overload resolution.
13832 @item @r{Overloaded symbol names}
13833 You can specify a particular definition of an overloaded symbol, using
13834 the same notation that is used to declare such symbols in C@t{++}: type
13835 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13836 also use the @value{GDBN} command-line word completion facilities to list the
13837 available choices, or to finish the type list for you.
13838 @xref{Completion,, Command Completion}, for details on how to do this.
13841 @node Decimal Floating Point
13842 @subsubsection Decimal Floating Point format
13843 @cindex decimal floating point format
13845 @value{GDBN} can examine, set and perform computations with numbers in
13846 decimal floating point format, which in the C language correspond to the
13847 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13848 specified by the extension to support decimal floating-point arithmetic.
13850 There are two encodings in use, depending on the architecture: BID (Binary
13851 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13852 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13855 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13856 to manipulate decimal floating point numbers, it is not possible to convert
13857 (using a cast, for example) integers wider than 32-bit to decimal float.
13859 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13860 point computations, error checking in decimal float operations ignores
13861 underflow, overflow and divide by zero exceptions.
13863 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13864 to inspect @code{_Decimal128} values stored in floating point registers.
13865 See @ref{PowerPC,,PowerPC} for more details.
13871 @value{GDBN} can be used to debug programs written in D and compiled with
13872 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13873 specific feature --- dynamic arrays.
13878 @cindex Go (programming language)
13879 @value{GDBN} can be used to debug programs written in Go and compiled with
13880 @file{gccgo} or @file{6g} compilers.
13882 Here is a summary of the Go-specific features and restrictions:
13885 @cindex current Go package
13886 @item The current Go package
13887 The name of the current package does not need to be specified when
13888 specifying global variables and functions.
13890 For example, given the program:
13894 var myglob = "Shall we?"
13900 When stopped inside @code{main} either of these work:
13904 (gdb) p main.myglob
13907 @cindex builtin Go types
13908 @item Builtin Go types
13909 The @code{string} type is recognized by @value{GDBN} and is printed
13912 @cindex builtin Go functions
13913 @item Builtin Go functions
13914 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13915 function and handles it internally.
13917 @cindex restrictions on Go expressions
13918 @item Restrictions on Go expressions
13919 All Go operators are supported except @code{&^}.
13920 The Go @code{_} ``blank identifier'' is not supported.
13921 Automatic dereferencing of pointers is not supported.
13925 @subsection Objective-C
13927 @cindex Objective-C
13928 This section provides information about some commands and command
13929 options that are useful for debugging Objective-C code. See also
13930 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13931 few more commands specific to Objective-C support.
13934 * Method Names in Commands::
13935 * The Print Command with Objective-C::
13938 @node Method Names in Commands
13939 @subsubsection Method Names in Commands
13941 The following commands have been extended to accept Objective-C method
13942 names as line specifications:
13944 @kindex clear@r{, and Objective-C}
13945 @kindex break@r{, and Objective-C}
13946 @kindex info line@r{, and Objective-C}
13947 @kindex jump@r{, and Objective-C}
13948 @kindex list@r{, and Objective-C}
13952 @item @code{info line}
13957 A fully qualified Objective-C method name is specified as
13960 -[@var{Class} @var{methodName}]
13963 where the minus sign is used to indicate an instance method and a
13964 plus sign (not shown) is used to indicate a class method. The class
13965 name @var{Class} and method name @var{methodName} are enclosed in
13966 brackets, similar to the way messages are specified in Objective-C
13967 source code. For example, to set a breakpoint at the @code{create}
13968 instance method of class @code{Fruit} in the program currently being
13972 break -[Fruit create]
13975 To list ten program lines around the @code{initialize} class method,
13979 list +[NSText initialize]
13982 In the current version of @value{GDBN}, the plus or minus sign is
13983 required. In future versions of @value{GDBN}, the plus or minus
13984 sign will be optional, but you can use it to narrow the search. It
13985 is also possible to specify just a method name:
13991 You must specify the complete method name, including any colons. If
13992 your program's source files contain more than one @code{create} method,
13993 you'll be presented with a numbered list of classes that implement that
13994 method. Indicate your choice by number, or type @samp{0} to exit if
13997 As another example, to clear a breakpoint established at the
13998 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14001 clear -[NSWindow makeKeyAndOrderFront:]
14004 @node The Print Command with Objective-C
14005 @subsubsection The Print Command With Objective-C
14006 @cindex Objective-C, print objects
14007 @kindex print-object
14008 @kindex po @r{(@code{print-object})}
14010 The print command has also been extended to accept methods. For example:
14013 print -[@var{object} hash]
14016 @cindex print an Objective-C object description
14017 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14019 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14020 and print the result. Also, an additional command has been added,
14021 @code{print-object} or @code{po} for short, which is meant to print
14022 the description of an object. However, this command may only work
14023 with certain Objective-C libraries that have a particular hook
14024 function, @code{_NSPrintForDebugger}, defined.
14027 @subsection OpenCL C
14030 This section provides information about @value{GDBN}s OpenCL C support.
14033 * OpenCL C Datatypes::
14034 * OpenCL C Expressions::
14035 * OpenCL C Operators::
14038 @node OpenCL C Datatypes
14039 @subsubsection OpenCL C Datatypes
14041 @cindex OpenCL C Datatypes
14042 @value{GDBN} supports the builtin scalar and vector datatypes specified
14043 by OpenCL 1.1. In addition the half- and double-precision floating point
14044 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14045 extensions are also known to @value{GDBN}.
14047 @node OpenCL C Expressions
14048 @subsubsection OpenCL C Expressions
14050 @cindex OpenCL C Expressions
14051 @value{GDBN} supports accesses to vector components including the access as
14052 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14053 supported by @value{GDBN} can be used as well.
14055 @node OpenCL C Operators
14056 @subsubsection OpenCL C Operators
14058 @cindex OpenCL C Operators
14059 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14063 @subsection Fortran
14064 @cindex Fortran-specific support in @value{GDBN}
14066 @value{GDBN} can be used to debug programs written in Fortran, but it
14067 currently supports only the features of Fortran 77 language.
14069 @cindex trailing underscore, in Fortran symbols
14070 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14071 among them) append an underscore to the names of variables and
14072 functions. When you debug programs compiled by those compilers, you
14073 will need to refer to variables and functions with a trailing
14077 * Fortran Operators:: Fortran operators and expressions
14078 * Fortran Defaults:: Default settings for Fortran
14079 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14082 @node Fortran Operators
14083 @subsubsection Fortran Operators and Expressions
14085 @cindex Fortran operators and expressions
14087 Operators must be defined on values of specific types. For instance,
14088 @code{+} is defined on numbers, but not on characters or other non-
14089 arithmetic types. Operators are often defined on groups of types.
14093 The exponentiation operator. It raises the first operand to the power
14097 The range operator. Normally used in the form of array(low:high) to
14098 represent a section of array.
14101 The access component operator. Normally used to access elements in derived
14102 types. Also suitable for unions. As unions aren't part of regular Fortran,
14103 this can only happen when accessing a register that uses a gdbarch-defined
14107 @node Fortran Defaults
14108 @subsubsection Fortran Defaults
14110 @cindex Fortran Defaults
14112 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14113 default uses case-insensitive matches for Fortran symbols. You can
14114 change that with the @samp{set case-insensitive} command, see
14115 @ref{Symbols}, for the details.
14117 @node Special Fortran Commands
14118 @subsubsection Special Fortran Commands
14120 @cindex Special Fortran commands
14122 @value{GDBN} has some commands to support Fortran-specific features,
14123 such as displaying common blocks.
14126 @cindex @code{COMMON} blocks, Fortran
14127 @kindex info common
14128 @item info common @r{[}@var{common-name}@r{]}
14129 This command prints the values contained in the Fortran @code{COMMON}
14130 block whose name is @var{common-name}. With no argument, the names of
14131 all @code{COMMON} blocks visible at the current program location are
14138 @cindex Pascal support in @value{GDBN}, limitations
14139 Debugging Pascal programs which use sets, subranges, file variables, or
14140 nested functions does not currently work. @value{GDBN} does not support
14141 entering expressions, printing values, or similar features using Pascal
14144 The Pascal-specific command @code{set print pascal_static-members}
14145 controls whether static members of Pascal objects are displayed.
14146 @xref{Print Settings, pascal_static-members}.
14149 @subsection Modula-2
14151 @cindex Modula-2, @value{GDBN} support
14153 The extensions made to @value{GDBN} to support Modula-2 only support
14154 output from the @sc{gnu} Modula-2 compiler (which is currently being
14155 developed). Other Modula-2 compilers are not currently supported, and
14156 attempting to debug executables produced by them is most likely
14157 to give an error as @value{GDBN} reads in the executable's symbol
14160 @cindex expressions in Modula-2
14162 * M2 Operators:: Built-in operators
14163 * Built-In Func/Proc:: Built-in functions and procedures
14164 * M2 Constants:: Modula-2 constants
14165 * M2 Types:: Modula-2 types
14166 * M2 Defaults:: Default settings for Modula-2
14167 * Deviations:: Deviations from standard Modula-2
14168 * M2 Checks:: Modula-2 type and range checks
14169 * M2 Scope:: The scope operators @code{::} and @code{.}
14170 * GDB/M2:: @value{GDBN} and Modula-2
14174 @subsubsection Operators
14175 @cindex Modula-2 operators
14177 Operators must be defined on values of specific types. For instance,
14178 @code{+} is defined on numbers, but not on structures. Operators are
14179 often defined on groups of types. For the purposes of Modula-2, the
14180 following definitions hold:
14185 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14189 @emph{Character types} consist of @code{CHAR} and its subranges.
14192 @emph{Floating-point types} consist of @code{REAL}.
14195 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14199 @emph{Scalar types} consist of all of the above.
14202 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14205 @emph{Boolean types} consist of @code{BOOLEAN}.
14209 The following operators are supported, and appear in order of
14210 increasing precedence:
14214 Function argument or array index separator.
14217 Assignment. The value of @var{var} @code{:=} @var{value} is
14221 Less than, greater than on integral, floating-point, or enumerated
14225 Less than or equal to, greater than or equal to
14226 on integral, floating-point and enumerated types, or set inclusion on
14227 set types. Same precedence as @code{<}.
14229 @item =@r{, }<>@r{, }#
14230 Equality and two ways of expressing inequality, valid on scalar types.
14231 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14232 available for inequality, since @code{#} conflicts with the script
14236 Set membership. Defined on set types and the types of their members.
14237 Same precedence as @code{<}.
14240 Boolean disjunction. Defined on boolean types.
14243 Boolean conjunction. Defined on boolean types.
14246 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14249 Addition and subtraction on integral and floating-point types, or union
14250 and difference on set types.
14253 Multiplication on integral and floating-point types, or set intersection
14257 Division on floating-point types, or symmetric set difference on set
14258 types. Same precedence as @code{*}.
14261 Integer division and remainder. Defined on integral types. Same
14262 precedence as @code{*}.
14265 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14268 Pointer dereferencing. Defined on pointer types.
14271 Boolean negation. Defined on boolean types. Same precedence as
14275 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14276 precedence as @code{^}.
14279 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14282 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14286 @value{GDBN} and Modula-2 scope operators.
14290 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14291 treats the use of the operator @code{IN}, or the use of operators
14292 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14293 @code{<=}, and @code{>=} on sets as an error.
14297 @node Built-In Func/Proc
14298 @subsubsection Built-in Functions and Procedures
14299 @cindex Modula-2 built-ins
14301 Modula-2 also makes available several built-in procedures and functions.
14302 In describing these, the following metavariables are used:
14307 represents an @code{ARRAY} variable.
14310 represents a @code{CHAR} constant or variable.
14313 represents a variable or constant of integral type.
14316 represents an identifier that belongs to a set. Generally used in the
14317 same function with the metavariable @var{s}. The type of @var{s} should
14318 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14321 represents a variable or constant of integral or floating-point type.
14324 represents a variable or constant of floating-point type.
14330 represents a variable.
14333 represents a variable or constant of one of many types. See the
14334 explanation of the function for details.
14337 All Modula-2 built-in procedures also return a result, described below.
14341 Returns the absolute value of @var{n}.
14344 If @var{c} is a lower case letter, it returns its upper case
14345 equivalent, otherwise it returns its argument.
14348 Returns the character whose ordinal value is @var{i}.
14351 Decrements the value in the variable @var{v} by one. Returns the new value.
14353 @item DEC(@var{v},@var{i})
14354 Decrements the value in the variable @var{v} by @var{i}. Returns the
14357 @item EXCL(@var{m},@var{s})
14358 Removes the element @var{m} from the set @var{s}. Returns the new
14361 @item FLOAT(@var{i})
14362 Returns the floating point equivalent of the integer @var{i}.
14364 @item HIGH(@var{a})
14365 Returns the index of the last member of @var{a}.
14368 Increments the value in the variable @var{v} by one. Returns the new value.
14370 @item INC(@var{v},@var{i})
14371 Increments the value in the variable @var{v} by @var{i}. Returns the
14374 @item INCL(@var{m},@var{s})
14375 Adds the element @var{m} to the set @var{s} if it is not already
14376 there. Returns the new set.
14379 Returns the maximum value of the type @var{t}.
14382 Returns the minimum value of the type @var{t}.
14385 Returns boolean TRUE if @var{i} is an odd number.
14388 Returns the ordinal value of its argument. For example, the ordinal
14389 value of a character is its @sc{ascii} value (on machines supporting the
14390 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14391 integral, character and enumerated types.
14393 @item SIZE(@var{x})
14394 Returns the size of its argument. @var{x} can be a variable or a type.
14396 @item TRUNC(@var{r})
14397 Returns the integral part of @var{r}.
14399 @item TSIZE(@var{x})
14400 Returns the size of its argument. @var{x} can be a variable or a type.
14402 @item VAL(@var{t},@var{i})
14403 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14407 @emph{Warning:} Sets and their operations are not yet supported, so
14408 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14412 @cindex Modula-2 constants
14414 @subsubsection Constants
14416 @value{GDBN} allows you to express the constants of Modula-2 in the following
14422 Integer constants are simply a sequence of digits. When used in an
14423 expression, a constant is interpreted to be type-compatible with the
14424 rest of the expression. Hexadecimal integers are specified by a
14425 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14428 Floating point constants appear as a sequence of digits, followed by a
14429 decimal point and another sequence of digits. An optional exponent can
14430 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14431 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14432 digits of the floating point constant must be valid decimal (base 10)
14436 Character constants consist of a single character enclosed by a pair of
14437 like quotes, either single (@code{'}) or double (@code{"}). They may
14438 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14439 followed by a @samp{C}.
14442 String constants consist of a sequence of characters enclosed by a
14443 pair of like quotes, either single (@code{'}) or double (@code{"}).
14444 Escape sequences in the style of C are also allowed. @xref{C
14445 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14449 Enumerated constants consist of an enumerated identifier.
14452 Boolean constants consist of the identifiers @code{TRUE} and
14456 Pointer constants consist of integral values only.
14459 Set constants are not yet supported.
14463 @subsubsection Modula-2 Types
14464 @cindex Modula-2 types
14466 Currently @value{GDBN} can print the following data types in Modula-2
14467 syntax: array types, record types, set types, pointer types, procedure
14468 types, enumerated types, subrange types and base types. You can also
14469 print the contents of variables declared using these type.
14470 This section gives a number of simple source code examples together with
14471 sample @value{GDBN} sessions.
14473 The first example contains the following section of code:
14482 and you can request @value{GDBN} to interrogate the type and value of
14483 @code{r} and @code{s}.
14486 (@value{GDBP}) print s
14488 (@value{GDBP}) ptype s
14490 (@value{GDBP}) print r
14492 (@value{GDBP}) ptype r
14497 Likewise if your source code declares @code{s} as:
14501 s: SET ['A'..'Z'] ;
14505 then you may query the type of @code{s} by:
14508 (@value{GDBP}) ptype s
14509 type = SET ['A'..'Z']
14513 Note that at present you cannot interactively manipulate set
14514 expressions using the debugger.
14516 The following example shows how you might declare an array in Modula-2
14517 and how you can interact with @value{GDBN} to print its type and contents:
14521 s: ARRAY [-10..10] OF CHAR ;
14525 (@value{GDBP}) ptype s
14526 ARRAY [-10..10] OF CHAR
14529 Note that the array handling is not yet complete and although the type
14530 is printed correctly, expression handling still assumes that all
14531 arrays have a lower bound of zero and not @code{-10} as in the example
14534 Here are some more type related Modula-2 examples:
14538 colour = (blue, red, yellow, green) ;
14539 t = [blue..yellow] ;
14547 The @value{GDBN} interaction shows how you can query the data type
14548 and value of a variable.
14551 (@value{GDBP}) print s
14553 (@value{GDBP}) ptype t
14554 type = [blue..yellow]
14558 In this example a Modula-2 array is declared and its contents
14559 displayed. Observe that the contents are written in the same way as
14560 their @code{C} counterparts.
14564 s: ARRAY [1..5] OF CARDINAL ;
14570 (@value{GDBP}) print s
14571 $1 = @{1, 0, 0, 0, 0@}
14572 (@value{GDBP}) ptype s
14573 type = ARRAY [1..5] OF CARDINAL
14576 The Modula-2 language interface to @value{GDBN} also understands
14577 pointer types as shown in this example:
14581 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14588 and you can request that @value{GDBN} describes the type of @code{s}.
14591 (@value{GDBP}) ptype s
14592 type = POINTER TO ARRAY [1..5] OF CARDINAL
14595 @value{GDBN} handles compound types as we can see in this example.
14596 Here we combine array types, record types, pointer types and subrange
14607 myarray = ARRAY myrange OF CARDINAL ;
14608 myrange = [-2..2] ;
14610 s: POINTER TO ARRAY myrange OF foo ;
14614 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14618 (@value{GDBP}) ptype s
14619 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14622 f3 : ARRAY [-2..2] OF CARDINAL;
14627 @subsubsection Modula-2 Defaults
14628 @cindex Modula-2 defaults
14630 If type and range checking are set automatically by @value{GDBN}, they
14631 both default to @code{on} whenever the working language changes to
14632 Modula-2. This happens regardless of whether you or @value{GDBN}
14633 selected the working language.
14635 If you allow @value{GDBN} to set the language automatically, then entering
14636 code compiled from a file whose name ends with @file{.mod} sets the
14637 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14638 Infer the Source Language}, for further details.
14641 @subsubsection Deviations from Standard Modula-2
14642 @cindex Modula-2, deviations from
14644 A few changes have been made to make Modula-2 programs easier to debug.
14645 This is done primarily via loosening its type strictness:
14649 Unlike in standard Modula-2, pointer constants can be formed by
14650 integers. This allows you to modify pointer variables during
14651 debugging. (In standard Modula-2, the actual address contained in a
14652 pointer variable is hidden from you; it can only be modified
14653 through direct assignment to another pointer variable or expression that
14654 returned a pointer.)
14657 C escape sequences can be used in strings and characters to represent
14658 non-printable characters. @value{GDBN} prints out strings with these
14659 escape sequences embedded. Single non-printable characters are
14660 printed using the @samp{CHR(@var{nnn})} format.
14663 The assignment operator (@code{:=}) returns the value of its right-hand
14667 All built-in procedures both modify @emph{and} return their argument.
14671 @subsubsection Modula-2 Type and Range Checks
14672 @cindex Modula-2 checks
14675 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14678 @c FIXME remove warning when type/range checks added
14680 @value{GDBN} considers two Modula-2 variables type equivalent if:
14684 They are of types that have been declared equivalent via a @code{TYPE
14685 @var{t1} = @var{t2}} statement
14688 They have been declared on the same line. (Note: This is true of the
14689 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14692 As long as type checking is enabled, any attempt to combine variables
14693 whose types are not equivalent is an error.
14695 Range checking is done on all mathematical operations, assignment, array
14696 index bounds, and all built-in functions and procedures.
14699 @subsubsection The Scope Operators @code{::} and @code{.}
14701 @cindex @code{.}, Modula-2 scope operator
14702 @cindex colon, doubled as scope operator
14704 @vindex colon-colon@r{, in Modula-2}
14705 @c Info cannot handle :: but TeX can.
14708 @vindex ::@r{, in Modula-2}
14711 There are a few subtle differences between the Modula-2 scope operator
14712 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14717 @var{module} . @var{id}
14718 @var{scope} :: @var{id}
14722 where @var{scope} is the name of a module or a procedure,
14723 @var{module} the name of a module, and @var{id} is any declared
14724 identifier within your program, except another module.
14726 Using the @code{::} operator makes @value{GDBN} search the scope
14727 specified by @var{scope} for the identifier @var{id}. If it is not
14728 found in the specified scope, then @value{GDBN} searches all scopes
14729 enclosing the one specified by @var{scope}.
14731 Using the @code{.} operator makes @value{GDBN} search the current scope for
14732 the identifier specified by @var{id} that was imported from the
14733 definition module specified by @var{module}. With this operator, it is
14734 an error if the identifier @var{id} was not imported from definition
14735 module @var{module}, or if @var{id} is not an identifier in
14739 @subsubsection @value{GDBN} and Modula-2
14741 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14742 Five subcommands of @code{set print} and @code{show print} apply
14743 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14744 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14745 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14746 analogue in Modula-2.
14748 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14749 with any language, is not useful with Modula-2. Its
14750 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14751 created in Modula-2 as they can in C or C@t{++}. However, because an
14752 address can be specified by an integral constant, the construct
14753 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14755 @cindex @code{#} in Modula-2
14756 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14757 interpreted as the beginning of a comment. Use @code{<>} instead.
14763 The extensions made to @value{GDBN} for Ada only support
14764 output from the @sc{gnu} Ada (GNAT) compiler.
14765 Other Ada compilers are not currently supported, and
14766 attempting to debug executables produced by them is most likely
14770 @cindex expressions in Ada
14772 * Ada Mode Intro:: General remarks on the Ada syntax
14773 and semantics supported by Ada mode
14775 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14776 * Additions to Ada:: Extensions of the Ada expression syntax.
14777 * Stopping Before Main Program:: Debugging the program during elaboration.
14778 * Ada Tasks:: Listing and setting breakpoints in tasks.
14779 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14780 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14782 * Ada Glitches:: Known peculiarities of Ada mode.
14785 @node Ada Mode Intro
14786 @subsubsection Introduction
14787 @cindex Ada mode, general
14789 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14790 syntax, with some extensions.
14791 The philosophy behind the design of this subset is
14795 That @value{GDBN} should provide basic literals and access to operations for
14796 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14797 leaving more sophisticated computations to subprograms written into the
14798 program (which therefore may be called from @value{GDBN}).
14801 That type safety and strict adherence to Ada language restrictions
14802 are not particularly important to the @value{GDBN} user.
14805 That brevity is important to the @value{GDBN} user.
14808 Thus, for brevity, the debugger acts as if all names declared in
14809 user-written packages are directly visible, even if they are not visible
14810 according to Ada rules, thus making it unnecessary to fully qualify most
14811 names with their packages, regardless of context. Where this causes
14812 ambiguity, @value{GDBN} asks the user's intent.
14814 The debugger will start in Ada mode if it detects an Ada main program.
14815 As for other languages, it will enter Ada mode when stopped in a program that
14816 was translated from an Ada source file.
14818 While in Ada mode, you may use `@t{--}' for comments. This is useful
14819 mostly for documenting command files. The standard @value{GDBN} comment
14820 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14821 middle (to allow based literals).
14823 The debugger supports limited overloading. Given a subprogram call in which
14824 the function symbol has multiple definitions, it will use the number of
14825 actual parameters and some information about their types to attempt to narrow
14826 the set of definitions. It also makes very limited use of context, preferring
14827 procedures to functions in the context of the @code{call} command, and
14828 functions to procedures elsewhere.
14830 @node Omissions from Ada
14831 @subsubsection Omissions from Ada
14832 @cindex Ada, omissions from
14834 Here are the notable omissions from the subset:
14838 Only a subset of the attributes are supported:
14842 @t{'First}, @t{'Last}, and @t{'Length}
14843 on array objects (not on types and subtypes).
14846 @t{'Min} and @t{'Max}.
14849 @t{'Pos} and @t{'Val}.
14855 @t{'Range} on array objects (not subtypes), but only as the right
14856 operand of the membership (@code{in}) operator.
14859 @t{'Access}, @t{'Unchecked_Access}, and
14860 @t{'Unrestricted_Access} (a GNAT extension).
14868 @code{Characters.Latin_1} are not available and
14869 concatenation is not implemented. Thus, escape characters in strings are
14870 not currently available.
14873 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14874 equality of representations. They will generally work correctly
14875 for strings and arrays whose elements have integer or enumeration types.
14876 They may not work correctly for arrays whose element
14877 types have user-defined equality, for arrays of real values
14878 (in particular, IEEE-conformant floating point, because of negative
14879 zeroes and NaNs), and for arrays whose elements contain unused bits with
14880 indeterminate values.
14883 The other component-by-component array operations (@code{and}, @code{or},
14884 @code{xor}, @code{not}, and relational tests other than equality)
14885 are not implemented.
14888 @cindex array aggregates (Ada)
14889 @cindex record aggregates (Ada)
14890 @cindex aggregates (Ada)
14891 There is limited support for array and record aggregates. They are
14892 permitted only on the right sides of assignments, as in these examples:
14895 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14896 (@value{GDBP}) set An_Array := (1, others => 0)
14897 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14898 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14899 (@value{GDBP}) set A_Record := (1, "Peter", True);
14900 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14904 discriminant's value by assigning an aggregate has an
14905 undefined effect if that discriminant is used within the record.
14906 However, you can first modify discriminants by directly assigning to
14907 them (which normally would not be allowed in Ada), and then performing an
14908 aggregate assignment. For example, given a variable @code{A_Rec}
14909 declared to have a type such as:
14912 type Rec (Len : Small_Integer := 0) is record
14914 Vals : IntArray (1 .. Len);
14918 you can assign a value with a different size of @code{Vals} with two
14922 (@value{GDBP}) set A_Rec.Len := 4
14923 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14926 As this example also illustrates, @value{GDBN} is very loose about the usual
14927 rules concerning aggregates. You may leave out some of the
14928 components of an array or record aggregate (such as the @code{Len}
14929 component in the assignment to @code{A_Rec} above); they will retain their
14930 original values upon assignment. You may freely use dynamic values as
14931 indices in component associations. You may even use overlapping or
14932 redundant component associations, although which component values are
14933 assigned in such cases is not defined.
14936 Calls to dispatching subprograms are not implemented.
14939 The overloading algorithm is much more limited (i.e., less selective)
14940 than that of real Ada. It makes only limited use of the context in
14941 which a subexpression appears to resolve its meaning, and it is much
14942 looser in its rules for allowing type matches. As a result, some
14943 function calls will be ambiguous, and the user will be asked to choose
14944 the proper resolution.
14947 The @code{new} operator is not implemented.
14950 Entry calls are not implemented.
14953 Aside from printing, arithmetic operations on the native VAX floating-point
14954 formats are not supported.
14957 It is not possible to slice a packed array.
14960 The names @code{True} and @code{False}, when not part of a qualified name,
14961 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14963 Should your program
14964 redefine these names in a package or procedure (at best a dubious practice),
14965 you will have to use fully qualified names to access their new definitions.
14968 @node Additions to Ada
14969 @subsubsection Additions to Ada
14970 @cindex Ada, deviations from
14972 As it does for other languages, @value{GDBN} makes certain generic
14973 extensions to Ada (@pxref{Expressions}):
14977 If the expression @var{E} is a variable residing in memory (typically
14978 a local variable or array element) and @var{N} is a positive integer,
14979 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14980 @var{N}-1 adjacent variables following it in memory as an array. In
14981 Ada, this operator is generally not necessary, since its prime use is
14982 in displaying parts of an array, and slicing will usually do this in
14983 Ada. However, there are occasional uses when debugging programs in
14984 which certain debugging information has been optimized away.
14987 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14988 appears in function or file @var{B}.'' When @var{B} is a file name,
14989 you must typically surround it in single quotes.
14992 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14993 @var{type} that appears at address @var{addr}.''
14996 A name starting with @samp{$} is a convenience variable
14997 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15000 In addition, @value{GDBN} provides a few other shortcuts and outright
15001 additions specific to Ada:
15005 The assignment statement is allowed as an expression, returning
15006 its right-hand operand as its value. Thus, you may enter
15009 (@value{GDBP}) set x := y + 3
15010 (@value{GDBP}) print A(tmp := y + 1)
15014 The semicolon is allowed as an ``operator,'' returning as its value
15015 the value of its right-hand operand.
15016 This allows, for example,
15017 complex conditional breaks:
15020 (@value{GDBP}) break f
15021 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15025 Rather than use catenation and symbolic character names to introduce special
15026 characters into strings, one may instead use a special bracket notation,
15027 which is also used to print strings. A sequence of characters of the form
15028 @samp{["@var{XX}"]} within a string or character literal denotes the
15029 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15030 sequence of characters @samp{["""]} also denotes a single quotation mark
15031 in strings. For example,
15033 "One line.["0a"]Next line.["0a"]"
15036 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15040 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15041 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15045 (@value{GDBP}) print 'max(x, y)
15049 When printing arrays, @value{GDBN} uses positional notation when the
15050 array has a lower bound of 1, and uses a modified named notation otherwise.
15051 For example, a one-dimensional array of three integers with a lower bound
15052 of 3 might print as
15059 That is, in contrast to valid Ada, only the first component has a @code{=>}
15063 You may abbreviate attributes in expressions with any unique,
15064 multi-character subsequence of
15065 their names (an exact match gets preference).
15066 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15067 in place of @t{a'length}.
15070 @cindex quoting Ada internal identifiers
15071 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15072 to lower case. The GNAT compiler uses upper-case characters for
15073 some of its internal identifiers, which are normally of no interest to users.
15074 For the rare occasions when you actually have to look at them,
15075 enclose them in angle brackets to avoid the lower-case mapping.
15078 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15082 Printing an object of class-wide type or dereferencing an
15083 access-to-class-wide value will display all the components of the object's
15084 specific type (as indicated by its run-time tag). Likewise, component
15085 selection on such a value will operate on the specific type of the
15090 @node Stopping Before Main Program
15091 @subsubsection Stopping at the Very Beginning
15093 @cindex breakpointing Ada elaboration code
15094 It is sometimes necessary to debug the program during elaboration, and
15095 before reaching the main procedure.
15096 As defined in the Ada Reference
15097 Manual, the elaboration code is invoked from a procedure called
15098 @code{adainit}. To run your program up to the beginning of
15099 elaboration, simply use the following two commands:
15100 @code{tbreak adainit} and @code{run}.
15103 @subsubsection Extensions for Ada Tasks
15104 @cindex Ada, tasking
15106 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15107 @value{GDBN} provides the following task-related commands:
15112 This command shows a list of current Ada tasks, as in the following example:
15119 (@value{GDBP}) info tasks
15120 ID TID P-ID Pri State Name
15121 1 8088000 0 15 Child Activation Wait main_task
15122 2 80a4000 1 15 Accept Statement b
15123 3 809a800 1 15 Child Activation Wait a
15124 * 4 80ae800 3 15 Runnable c
15129 In this listing, the asterisk before the last task indicates it to be the
15130 task currently being inspected.
15134 Represents @value{GDBN}'s internal task number.
15140 The parent's task ID (@value{GDBN}'s internal task number).
15143 The base priority of the task.
15146 Current state of the task.
15150 The task has been created but has not been activated. It cannot be
15154 The task is not blocked for any reason known to Ada. (It may be waiting
15155 for a mutex, though.) It is conceptually "executing" in normal mode.
15158 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15159 that were waiting on terminate alternatives have been awakened and have
15160 terminated themselves.
15162 @item Child Activation Wait
15163 The task is waiting for created tasks to complete activation.
15165 @item Accept Statement
15166 The task is waiting on an accept or selective wait statement.
15168 @item Waiting on entry call
15169 The task is waiting on an entry call.
15171 @item Async Select Wait
15172 The task is waiting to start the abortable part of an asynchronous
15176 The task is waiting on a select statement with only a delay
15179 @item Child Termination Wait
15180 The task is sleeping having completed a master within itself, and is
15181 waiting for the tasks dependent on that master to become terminated or
15182 waiting on a terminate Phase.
15184 @item Wait Child in Term Alt
15185 The task is sleeping waiting for tasks on terminate alternatives to
15186 finish terminating.
15188 @item Accepting RV with @var{taskno}
15189 The task is accepting a rendez-vous with the task @var{taskno}.
15193 Name of the task in the program.
15197 @kindex info task @var{taskno}
15198 @item info task @var{taskno}
15199 This command shows detailled informations on the specified task, as in
15200 the following example:
15205 (@value{GDBP}) info tasks
15206 ID TID P-ID Pri State Name
15207 1 8077880 0 15 Child Activation Wait main_task
15208 * 2 807c468 1 15 Runnable task_1
15209 (@value{GDBP}) info task 2
15210 Ada Task: 0x807c468
15213 Parent: 1 (main_task)
15219 @kindex task@r{ (Ada)}
15220 @cindex current Ada task ID
15221 This command prints the ID of the current task.
15227 (@value{GDBP}) info tasks
15228 ID TID P-ID Pri State Name
15229 1 8077870 0 15 Child Activation Wait main_task
15230 * 2 807c458 1 15 Runnable t
15231 (@value{GDBP}) task
15232 [Current task is 2]
15235 @item task @var{taskno}
15236 @cindex Ada task switching
15237 This command is like the @code{thread @var{threadno}}
15238 command (@pxref{Threads}). It switches the context of debugging
15239 from the current task to the given task.
15245 (@value{GDBP}) info tasks
15246 ID TID P-ID Pri State Name
15247 1 8077870 0 15 Child Activation Wait main_task
15248 * 2 807c458 1 15 Runnable t
15249 (@value{GDBP}) task 1
15250 [Switching to task 1]
15251 #0 0x8067726 in pthread_cond_wait ()
15253 #0 0x8067726 in pthread_cond_wait ()
15254 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15255 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15256 #3 0x806153e in system.tasking.stages.activate_tasks ()
15257 #4 0x804aacc in un () at un.adb:5
15260 @item break @var{linespec} task @var{taskno}
15261 @itemx break @var{linespec} task @var{taskno} if @dots{}
15262 @cindex breakpoints and tasks, in Ada
15263 @cindex task breakpoints, in Ada
15264 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15265 These commands are like the @code{break @dots{} thread @dots{}}
15266 command (@pxref{Thread Stops}).
15267 @var{linespec} specifies source lines, as described
15268 in @ref{Specify Location}.
15270 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15271 to specify that you only want @value{GDBN} to stop the program when a
15272 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15273 numeric task identifiers assigned by @value{GDBN}, shown in the first
15274 column of the @samp{info tasks} display.
15276 If you do not specify @samp{task @var{taskno}} when you set a
15277 breakpoint, the breakpoint applies to @emph{all} tasks of your
15280 You can use the @code{task} qualifier on conditional breakpoints as
15281 well; in this case, place @samp{task @var{taskno}} before the
15282 breakpoint condition (before the @code{if}).
15290 (@value{GDBP}) info tasks
15291 ID TID P-ID Pri State Name
15292 1 140022020 0 15 Child Activation Wait main_task
15293 2 140045060 1 15 Accept/Select Wait t2
15294 3 140044840 1 15 Runnable t1
15295 * 4 140056040 1 15 Runnable t3
15296 (@value{GDBP}) b 15 task 2
15297 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15298 (@value{GDBP}) cont
15303 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15305 (@value{GDBP}) info tasks
15306 ID TID P-ID Pri State Name
15307 1 140022020 0 15 Child Activation Wait main_task
15308 * 2 140045060 1 15 Runnable t2
15309 3 140044840 1 15 Runnable t1
15310 4 140056040 1 15 Delay Sleep t3
15314 @node Ada Tasks and Core Files
15315 @subsubsection Tasking Support when Debugging Core Files
15316 @cindex Ada tasking and core file debugging
15318 When inspecting a core file, as opposed to debugging a live program,
15319 tasking support may be limited or even unavailable, depending on
15320 the platform being used.
15321 For instance, on x86-linux, the list of tasks is available, but task
15322 switching is not supported. On Tru64, however, task switching will work
15325 On certain platforms, including Tru64, the debugger needs to perform some
15326 memory writes in order to provide Ada tasking support. When inspecting
15327 a core file, this means that the core file must be opened with read-write
15328 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15329 Under these circumstances, you should make a backup copy of the core
15330 file before inspecting it with @value{GDBN}.
15332 @node Ravenscar Profile
15333 @subsubsection Tasking Support when using the Ravenscar Profile
15334 @cindex Ravenscar Profile
15336 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15337 specifically designed for systems with safety-critical real-time
15341 @kindex set ravenscar task-switching on
15342 @cindex task switching with program using Ravenscar Profile
15343 @item set ravenscar task-switching on
15344 Allows task switching when debugging a program that uses the Ravenscar
15345 Profile. This is the default.
15347 @kindex set ravenscar task-switching off
15348 @item set ravenscar task-switching off
15349 Turn off task switching when debugging a program that uses the Ravenscar
15350 Profile. This is mostly intended to disable the code that adds support
15351 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15352 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15353 To be effective, this command should be run before the program is started.
15355 @kindex show ravenscar task-switching
15356 @item show ravenscar task-switching
15357 Show whether it is possible to switch from task to task in a program
15358 using the Ravenscar Profile.
15363 @subsubsection Known Peculiarities of Ada Mode
15364 @cindex Ada, problems
15366 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15367 we know of several problems with and limitations of Ada mode in
15369 some of which will be fixed with planned future releases of the debugger
15370 and the GNU Ada compiler.
15374 Static constants that the compiler chooses not to materialize as objects in
15375 storage are invisible to the debugger.
15378 Named parameter associations in function argument lists are ignored (the
15379 argument lists are treated as positional).
15382 Many useful library packages are currently invisible to the debugger.
15385 Fixed-point arithmetic, conversions, input, and output is carried out using
15386 floating-point arithmetic, and may give results that only approximate those on
15390 The GNAT compiler never generates the prefix @code{Standard} for any of
15391 the standard symbols defined by the Ada language. @value{GDBN} knows about
15392 this: it will strip the prefix from names when you use it, and will never
15393 look for a name you have so qualified among local symbols, nor match against
15394 symbols in other packages or subprograms. If you have
15395 defined entities anywhere in your program other than parameters and
15396 local variables whose simple names match names in @code{Standard},
15397 GNAT's lack of qualification here can cause confusion. When this happens,
15398 you can usually resolve the confusion
15399 by qualifying the problematic names with package
15400 @code{Standard} explicitly.
15403 Older versions of the compiler sometimes generate erroneous debugging
15404 information, resulting in the debugger incorrectly printing the value
15405 of affected entities. In some cases, the debugger is able to work
15406 around an issue automatically. In other cases, the debugger is able
15407 to work around the issue, but the work-around has to be specifically
15410 @kindex set ada trust-PAD-over-XVS
15411 @kindex show ada trust-PAD-over-XVS
15414 @item set ada trust-PAD-over-XVS on
15415 Configure GDB to strictly follow the GNAT encoding when computing the
15416 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15417 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15418 a complete description of the encoding used by the GNAT compiler).
15419 This is the default.
15421 @item set ada trust-PAD-over-XVS off
15422 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15423 sometimes prints the wrong value for certain entities, changing @code{ada
15424 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15425 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15426 @code{off}, but this incurs a slight performance penalty, so it is
15427 recommended to leave this setting to @code{on} unless necessary.
15431 @node Unsupported Languages
15432 @section Unsupported Languages
15434 @cindex unsupported languages
15435 @cindex minimal language
15436 In addition to the other fully-supported programming languages,
15437 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15438 It does not represent a real programming language, but provides a set
15439 of capabilities close to what the C or assembly languages provide.
15440 This should allow most simple operations to be performed while debugging
15441 an application that uses a language currently not supported by @value{GDBN}.
15443 If the language is set to @code{auto}, @value{GDBN} will automatically
15444 select this language if the current frame corresponds to an unsupported
15448 @chapter Examining the Symbol Table
15450 The commands described in this chapter allow you to inquire about the
15451 symbols (names of variables, functions and types) defined in your
15452 program. This information is inherent in the text of your program and
15453 does not change as your program executes. @value{GDBN} finds it in your
15454 program's symbol table, in the file indicated when you started @value{GDBN}
15455 (@pxref{File Options, ,Choosing Files}), or by one of the
15456 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15458 @cindex symbol names
15459 @cindex names of symbols
15460 @cindex quoting names
15461 Occasionally, you may need to refer to symbols that contain unusual
15462 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15463 most frequent case is in referring to static variables in other
15464 source files (@pxref{Variables,,Program Variables}). File names
15465 are recorded in object files as debugging symbols, but @value{GDBN} would
15466 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15467 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15468 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15475 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15478 @cindex case-insensitive symbol names
15479 @cindex case sensitivity in symbol names
15480 @kindex set case-sensitive
15481 @item set case-sensitive on
15482 @itemx set case-sensitive off
15483 @itemx set case-sensitive auto
15484 Normally, when @value{GDBN} looks up symbols, it matches their names
15485 with case sensitivity determined by the current source language.
15486 Occasionally, you may wish to control that. The command @code{set
15487 case-sensitive} lets you do that by specifying @code{on} for
15488 case-sensitive matches or @code{off} for case-insensitive ones. If
15489 you specify @code{auto}, case sensitivity is reset to the default
15490 suitable for the source language. The default is case-sensitive
15491 matches for all languages except for Fortran, for which the default is
15492 case-insensitive matches.
15494 @kindex show case-sensitive
15495 @item show case-sensitive
15496 This command shows the current setting of case sensitivity for symbols
15499 @kindex set print type methods
15500 @item set print type methods
15501 @itemx set print type methods on
15502 @itemx set print type methods off
15503 Normally, when @value{GDBN} prints a class, it displays any methods
15504 declared in that class. You can control this behavior either by
15505 passing the appropriate flag to @code{ptype}, or using @command{set
15506 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15507 display the methods; this is the default. Specifying @code{off} will
15508 cause @value{GDBN} to omit the methods.
15510 @kindex show print type methods
15511 @item show print type methods
15512 This command shows the current setting of method display when printing
15515 @kindex set print type typedefs
15516 @item set print type typedefs
15517 @itemx set print type typedefs on
15518 @itemx set print type typedefs off
15520 Normally, when @value{GDBN} prints a class, it displays any typedefs
15521 defined in that class. You can control this behavior either by
15522 passing the appropriate flag to @code{ptype}, or using @command{set
15523 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15524 display the typedef definitions; this is the default. Specifying
15525 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15526 Note that this controls whether the typedef definition itself is
15527 printed, not whether typedef names are substituted when printing other
15530 @kindex show print type typedefs
15531 @item show print type typedefs
15532 This command shows the current setting of typedef display when
15535 @kindex info address
15536 @cindex address of a symbol
15537 @item info address @var{symbol}
15538 Describe where the data for @var{symbol} is stored. For a register
15539 variable, this says which register it is kept in. For a non-register
15540 local variable, this prints the stack-frame offset at which the variable
15543 Note the contrast with @samp{print &@var{symbol}}, which does not work
15544 at all for a register variable, and for a stack local variable prints
15545 the exact address of the current instantiation of the variable.
15547 @kindex info symbol
15548 @cindex symbol from address
15549 @cindex closest symbol and offset for an address
15550 @item info symbol @var{addr}
15551 Print the name of a symbol which is stored at the address @var{addr}.
15552 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15553 nearest symbol and an offset from it:
15556 (@value{GDBP}) info symbol 0x54320
15557 _initialize_vx + 396 in section .text
15561 This is the opposite of the @code{info address} command. You can use
15562 it to find out the name of a variable or a function given its address.
15564 For dynamically linked executables, the name of executable or shared
15565 library containing the symbol is also printed:
15568 (@value{GDBP}) info symbol 0x400225
15569 _start + 5 in section .text of /tmp/a.out
15570 (@value{GDBP}) info symbol 0x2aaaac2811cf
15571 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15575 @item whatis[/@var{flags}] [@var{arg}]
15576 Print the data type of @var{arg}, which can be either an expression
15577 or a name of a data type. With no argument, print the data type of
15578 @code{$}, the last value in the value history.
15580 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15581 is not actually evaluated, and any side-effecting operations (such as
15582 assignments or function calls) inside it do not take place.
15584 If @var{arg} is a variable or an expression, @code{whatis} prints its
15585 literal type as it is used in the source code. If the type was
15586 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15587 the data type underlying the @code{typedef}. If the type of the
15588 variable or the expression is a compound data type, such as
15589 @code{struct} or @code{class}, @code{whatis} never prints their
15590 fields or methods. It just prints the @code{struct}/@code{class}
15591 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15592 such a compound data type, use @code{ptype}.
15594 If @var{arg} is a type name that was defined using @code{typedef},
15595 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15596 Unrolling means that @code{whatis} will show the underlying type used
15597 in the @code{typedef} declaration of @var{arg}. However, if that
15598 underlying type is also a @code{typedef}, @code{whatis} will not
15601 For C code, the type names may also have the form @samp{class
15602 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15603 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15605 @var{flags} can be used to modify how the type is displayed.
15606 Available flags are:
15610 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15611 parameters and typedefs defined in a class when printing the class'
15612 members. The @code{/r} flag disables this.
15615 Do not print methods defined in the class.
15618 Print methods defined in the class. This is the default, but the flag
15619 exists in case you change the default with @command{set print type methods}.
15622 Do not print typedefs defined in the class. Note that this controls
15623 whether the typedef definition itself is printed, not whether typedef
15624 names are substituted when printing other types.
15627 Print typedefs defined in the class. This is the default, but the flag
15628 exists in case you change the default with @command{set print type typedefs}.
15632 @item ptype[/@var{flags}] [@var{arg}]
15633 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15634 detailed description of the type, instead of just the name of the type.
15635 @xref{Expressions, ,Expressions}.
15637 Contrary to @code{whatis}, @code{ptype} always unrolls any
15638 @code{typedef}s in its argument declaration, whether the argument is
15639 a variable, expression, or a data type. This means that @code{ptype}
15640 of a variable or an expression will not print literally its type as
15641 present in the source code---use @code{whatis} for that. @code{typedef}s at
15642 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15643 fields, methods and inner @code{class typedef}s of @code{struct}s,
15644 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15646 For example, for this variable declaration:
15649 typedef double real_t;
15650 struct complex @{ real_t real; double imag; @};
15651 typedef struct complex complex_t;
15653 real_t *real_pointer_var;
15657 the two commands give this output:
15661 (@value{GDBP}) whatis var
15663 (@value{GDBP}) ptype var
15664 type = struct complex @{
15668 (@value{GDBP}) whatis complex_t
15669 type = struct complex
15670 (@value{GDBP}) whatis struct complex
15671 type = struct complex
15672 (@value{GDBP}) ptype struct complex
15673 type = struct complex @{
15677 (@value{GDBP}) whatis real_pointer_var
15679 (@value{GDBP}) ptype real_pointer_var
15685 As with @code{whatis}, using @code{ptype} without an argument refers to
15686 the type of @code{$}, the last value in the value history.
15688 @cindex incomplete type
15689 Sometimes, programs use opaque data types or incomplete specifications
15690 of complex data structure. If the debug information included in the
15691 program does not allow @value{GDBN} to display a full declaration of
15692 the data type, it will say @samp{<incomplete type>}. For example,
15693 given these declarations:
15697 struct foo *fooptr;
15701 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15704 (@value{GDBP}) ptype foo
15705 $1 = <incomplete type>
15709 ``Incomplete type'' is C terminology for data types that are not
15710 completely specified.
15713 @item info types @var{regexp}
15715 Print a brief description of all types whose names match the regular
15716 expression @var{regexp} (or all types in your program, if you supply
15717 no argument). Each complete typename is matched as though it were a
15718 complete line; thus, @samp{i type value} gives information on all
15719 types in your program whose names include the string @code{value}, but
15720 @samp{i type ^value$} gives information only on types whose complete
15721 name is @code{value}.
15723 This command differs from @code{ptype} in two ways: first, like
15724 @code{whatis}, it does not print a detailed description; second, it
15725 lists all source files where a type is defined.
15727 @kindex info type-printers
15728 @item info type-printers
15729 Versions of @value{GDBN} that ship with Python scripting enabled may
15730 have ``type printers'' available. When using @command{ptype} or
15731 @command{whatis}, these printers are consulted when the name of a type
15732 is needed. @xref{Type Printing API}, for more information on writing
15735 @code{info type-printers} displays all the available type printers.
15737 @kindex enable type-printer
15738 @kindex disable type-printer
15739 @item enable type-printer @var{name}@dots{}
15740 @item disable type-printer @var{name}@dots{}
15741 These commands can be used to enable or disable type printers.
15744 @cindex local variables
15745 @item info scope @var{location}
15746 List all the variables local to a particular scope. This command
15747 accepts a @var{location} argument---a function name, a source line, or
15748 an address preceded by a @samp{*}, and prints all the variables local
15749 to the scope defined by that location. (@xref{Specify Location}, for
15750 details about supported forms of @var{location}.) For example:
15753 (@value{GDBP}) @b{info scope command_line_handler}
15754 Scope for command_line_handler:
15755 Symbol rl is an argument at stack/frame offset 8, length 4.
15756 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15757 Symbol linelength is in static storage at address 0x150a1c, length 4.
15758 Symbol p is a local variable in register $esi, length 4.
15759 Symbol p1 is a local variable in register $ebx, length 4.
15760 Symbol nline is a local variable in register $edx, length 4.
15761 Symbol repeat is a local variable at frame offset -8, length 4.
15765 This command is especially useful for determining what data to collect
15766 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15769 @kindex info source
15771 Show information about the current source file---that is, the source file for
15772 the function containing the current point of execution:
15775 the name of the source file, and the directory containing it,
15777 the directory it was compiled in,
15779 its length, in lines,
15781 which programming language it is written in,
15783 whether the executable includes debugging information for that file, and
15784 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15786 whether the debugging information includes information about
15787 preprocessor macros.
15791 @kindex info sources
15793 Print the names of all source files in your program for which there is
15794 debugging information, organized into two lists: files whose symbols
15795 have already been read, and files whose symbols will be read when needed.
15797 @kindex info functions
15798 @item info functions
15799 Print the names and data types of all defined functions.
15801 @item info functions @var{regexp}
15802 Print the names and data types of all defined functions
15803 whose names contain a match for regular expression @var{regexp}.
15804 Thus, @samp{info fun step} finds all functions whose names
15805 include @code{step}; @samp{info fun ^step} finds those whose names
15806 start with @code{step}. If a function name contains characters
15807 that conflict with the regular expression language (e.g.@:
15808 @samp{operator*()}), they may be quoted with a backslash.
15810 @kindex info variables
15811 @item info variables
15812 Print the names and data types of all variables that are defined
15813 outside of functions (i.e.@: excluding local variables).
15815 @item info variables @var{regexp}
15816 Print the names and data types of all variables (except for local
15817 variables) whose names contain a match for regular expression
15820 @kindex info classes
15821 @cindex Objective-C, classes and selectors
15823 @itemx info classes @var{regexp}
15824 Display all Objective-C classes in your program, or
15825 (with the @var{regexp} argument) all those matching a particular regular
15828 @kindex info selectors
15829 @item info selectors
15830 @itemx info selectors @var{regexp}
15831 Display all Objective-C selectors in your program, or
15832 (with the @var{regexp} argument) all those matching a particular regular
15836 This was never implemented.
15837 @kindex info methods
15839 @itemx info methods @var{regexp}
15840 The @code{info methods} command permits the user to examine all defined
15841 methods within C@t{++} program, or (with the @var{regexp} argument) a
15842 specific set of methods found in the various C@t{++} classes. Many
15843 C@t{++} classes provide a large number of methods. Thus, the output
15844 from the @code{ptype} command can be overwhelming and hard to use. The
15845 @code{info-methods} command filters the methods, printing only those
15846 which match the regular-expression @var{regexp}.
15849 @cindex opaque data types
15850 @kindex set opaque-type-resolution
15851 @item set opaque-type-resolution on
15852 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15853 declared as a pointer to a @code{struct}, @code{class}, or
15854 @code{union}---for example, @code{struct MyType *}---that is used in one
15855 source file although the full declaration of @code{struct MyType} is in
15856 another source file. The default is on.
15858 A change in the setting of this subcommand will not take effect until
15859 the next time symbols for a file are loaded.
15861 @item set opaque-type-resolution off
15862 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15863 is printed as follows:
15865 @{<no data fields>@}
15868 @kindex show opaque-type-resolution
15869 @item show opaque-type-resolution
15870 Show whether opaque types are resolved or not.
15872 @kindex maint print symbols
15873 @cindex symbol dump
15874 @kindex maint print psymbols
15875 @cindex partial symbol dump
15876 @kindex maint print msymbols
15877 @cindex minimal symbol dump
15878 @item maint print symbols @var{filename}
15879 @itemx maint print psymbols @var{filename}
15880 @itemx maint print msymbols @var{filename}
15881 Write a dump of debugging symbol data into the file @var{filename}.
15882 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15883 symbols with debugging data are included. If you use @samp{maint print
15884 symbols}, @value{GDBN} includes all the symbols for which it has already
15885 collected full details: that is, @var{filename} reflects symbols for
15886 only those files whose symbols @value{GDBN} has read. You can use the
15887 command @code{info sources} to find out which files these are. If you
15888 use @samp{maint print psymbols} instead, the dump shows information about
15889 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15890 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15891 @samp{maint print msymbols} dumps just the minimal symbol information
15892 required for each object file from which @value{GDBN} has read some symbols.
15893 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15894 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15896 @kindex maint info symtabs
15897 @kindex maint info psymtabs
15898 @cindex listing @value{GDBN}'s internal symbol tables
15899 @cindex symbol tables, listing @value{GDBN}'s internal
15900 @cindex full symbol tables, listing @value{GDBN}'s internal
15901 @cindex partial symbol tables, listing @value{GDBN}'s internal
15902 @item maint info symtabs @r{[} @var{regexp} @r{]}
15903 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15905 List the @code{struct symtab} or @code{struct partial_symtab}
15906 structures whose names match @var{regexp}. If @var{regexp} is not
15907 given, list them all. The output includes expressions which you can
15908 copy into a @value{GDBN} debugging this one to examine a particular
15909 structure in more detail. For example:
15912 (@value{GDBP}) maint info psymtabs dwarf2read
15913 @{ objfile /home/gnu/build/gdb/gdb
15914 ((struct objfile *) 0x82e69d0)
15915 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15916 ((struct partial_symtab *) 0x8474b10)
15919 text addresses 0x814d3c8 -- 0x8158074
15920 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15921 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15922 dependencies (none)
15925 (@value{GDBP}) maint info symtabs
15929 We see that there is one partial symbol table whose filename contains
15930 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15931 and we see that @value{GDBN} has not read in any symtabs yet at all.
15932 If we set a breakpoint on a function, that will cause @value{GDBN} to
15933 read the symtab for the compilation unit containing that function:
15936 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15937 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15939 (@value{GDBP}) maint info symtabs
15940 @{ objfile /home/gnu/build/gdb/gdb
15941 ((struct objfile *) 0x82e69d0)
15942 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15943 ((struct symtab *) 0x86c1f38)
15946 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15947 linetable ((struct linetable *) 0x8370fa0)
15948 debugformat DWARF 2
15957 @chapter Altering Execution
15959 Once you think you have found an error in your program, you might want to
15960 find out for certain whether correcting the apparent error would lead to
15961 correct results in the rest of the run. You can find the answer by
15962 experiment, using the @value{GDBN} features for altering execution of the
15965 For example, you can store new values into variables or memory
15966 locations, give your program a signal, restart it at a different
15967 address, or even return prematurely from a function.
15970 * Assignment:: Assignment to variables
15971 * Jumping:: Continuing at a different address
15972 * Signaling:: Giving your program a signal
15973 * Returning:: Returning from a function
15974 * Calling:: Calling your program's functions
15975 * Patching:: Patching your program
15979 @section Assignment to Variables
15982 @cindex setting variables
15983 To alter the value of a variable, evaluate an assignment expression.
15984 @xref{Expressions, ,Expressions}. For example,
15991 stores the value 4 into the variable @code{x}, and then prints the
15992 value of the assignment expression (which is 4).
15993 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15994 information on operators in supported languages.
15996 @kindex set variable
15997 @cindex variables, setting
15998 If you are not interested in seeing the value of the assignment, use the
15999 @code{set} command instead of the @code{print} command. @code{set} is
16000 really the same as @code{print} except that the expression's value is
16001 not printed and is not put in the value history (@pxref{Value History,
16002 ,Value History}). The expression is evaluated only for its effects.
16004 If the beginning of the argument string of the @code{set} command
16005 appears identical to a @code{set} subcommand, use the @code{set
16006 variable} command instead of just @code{set}. This command is identical
16007 to @code{set} except for its lack of subcommands. For example, if your
16008 program has a variable @code{width}, you get an error if you try to set
16009 a new value with just @samp{set width=13}, because @value{GDBN} has the
16010 command @code{set width}:
16013 (@value{GDBP}) whatis width
16015 (@value{GDBP}) p width
16017 (@value{GDBP}) set width=47
16018 Invalid syntax in expression.
16022 The invalid expression, of course, is @samp{=47}. In
16023 order to actually set the program's variable @code{width}, use
16026 (@value{GDBP}) set var width=47
16029 Because the @code{set} command has many subcommands that can conflict
16030 with the names of program variables, it is a good idea to use the
16031 @code{set variable} command instead of just @code{set}. For example, if
16032 your program has a variable @code{g}, you run into problems if you try
16033 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16034 the command @code{set gnutarget}, abbreviated @code{set g}:
16038 (@value{GDBP}) whatis g
16042 (@value{GDBP}) set g=4
16046 The program being debugged has been started already.
16047 Start it from the beginning? (y or n) y
16048 Starting program: /home/smith/cc_progs/a.out
16049 "/home/smith/cc_progs/a.out": can't open to read symbols:
16050 Invalid bfd target.
16051 (@value{GDBP}) show g
16052 The current BFD target is "=4".
16057 The program variable @code{g} did not change, and you silently set the
16058 @code{gnutarget} to an invalid value. In order to set the variable
16062 (@value{GDBP}) set var g=4
16065 @value{GDBN} allows more implicit conversions in assignments than C; you can
16066 freely store an integer value into a pointer variable or vice versa,
16067 and you can convert any structure to any other structure that is the
16068 same length or shorter.
16069 @comment FIXME: how do structs align/pad in these conversions?
16070 @comment /doc@cygnus.com 18dec1990
16072 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16073 construct to generate a value of specified type at a specified address
16074 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16075 to memory location @code{0x83040} as an integer (which implies a certain size
16076 and representation in memory), and
16079 set @{int@}0x83040 = 4
16083 stores the value 4 into that memory location.
16086 @section Continuing at a Different Address
16088 Ordinarily, when you continue your program, you do so at the place where
16089 it stopped, with the @code{continue} command. You can instead continue at
16090 an address of your own choosing, with the following commands:
16094 @kindex j @r{(@code{jump})}
16095 @item jump @var{linespec}
16096 @itemx j @var{linespec}
16097 @itemx jump @var{location}
16098 @itemx j @var{location}
16099 Resume execution at line @var{linespec} or at address given by
16100 @var{location}. Execution stops again immediately if there is a
16101 breakpoint there. @xref{Specify Location}, for a description of the
16102 different forms of @var{linespec} and @var{location}. It is common
16103 practice to use the @code{tbreak} command in conjunction with
16104 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16106 The @code{jump} command does not change the current stack frame, or
16107 the stack pointer, or the contents of any memory location or any
16108 register other than the program counter. If line @var{linespec} is in
16109 a different function from the one currently executing, the results may
16110 be bizarre if the two functions expect different patterns of arguments or
16111 of local variables. For this reason, the @code{jump} command requests
16112 confirmation if the specified line is not in the function currently
16113 executing. However, even bizarre results are predictable if you are
16114 well acquainted with the machine-language code of your program.
16117 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16118 On many systems, you can get much the same effect as the @code{jump}
16119 command by storing a new value into the register @code{$pc}. The
16120 difference is that this does not start your program running; it only
16121 changes the address of where it @emph{will} run when you continue. For
16129 makes the next @code{continue} command or stepping command execute at
16130 address @code{0x485}, rather than at the address where your program stopped.
16131 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16133 The most common occasion to use the @code{jump} command is to back
16134 up---perhaps with more breakpoints set---over a portion of a program
16135 that has already executed, in order to examine its execution in more
16140 @section Giving your Program a Signal
16141 @cindex deliver a signal to a program
16145 @item signal @var{signal}
16146 Resume execution where your program stopped, but immediately give it the
16147 signal @var{signal}. @var{signal} can be the name or the number of a
16148 signal. For example, on many systems @code{signal 2} and @code{signal
16149 SIGINT} are both ways of sending an interrupt signal.
16151 Alternatively, if @var{signal} is zero, continue execution without
16152 giving a signal. This is useful when your program stopped on account of
16153 a signal and would ordinarily see the signal when resumed with the
16154 @code{continue} command; @samp{signal 0} causes it to resume without a
16157 @code{signal} does not repeat when you press @key{RET} a second time
16158 after executing the command.
16162 Invoking the @code{signal} command is not the same as invoking the
16163 @code{kill} utility from the shell. Sending a signal with @code{kill}
16164 causes @value{GDBN} to decide what to do with the signal depending on
16165 the signal handling tables (@pxref{Signals}). The @code{signal} command
16166 passes the signal directly to your program.
16170 @section Returning from a Function
16173 @cindex returning from a function
16176 @itemx return @var{expression}
16177 You can cancel execution of a function call with the @code{return}
16178 command. If you give an
16179 @var{expression} argument, its value is used as the function's return
16183 When you use @code{return}, @value{GDBN} discards the selected stack frame
16184 (and all frames within it). You can think of this as making the
16185 discarded frame return prematurely. If you wish to specify a value to
16186 be returned, give that value as the argument to @code{return}.
16188 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16189 Frame}), and any other frames inside of it, leaving its caller as the
16190 innermost remaining frame. That frame becomes selected. The
16191 specified value is stored in the registers used for returning values
16194 The @code{return} command does not resume execution; it leaves the
16195 program stopped in the state that would exist if the function had just
16196 returned. In contrast, the @code{finish} command (@pxref{Continuing
16197 and Stepping, ,Continuing and Stepping}) resumes execution until the
16198 selected stack frame returns naturally.
16200 @value{GDBN} needs to know how the @var{expression} argument should be set for
16201 the inferior. The concrete registers assignment depends on the OS ABI and the
16202 type being returned by the selected stack frame. For example it is common for
16203 OS ABI to return floating point values in FPU registers while integer values in
16204 CPU registers. Still some ABIs return even floating point values in CPU
16205 registers. Larger integer widths (such as @code{long long int}) also have
16206 specific placement rules. @value{GDBN} already knows the OS ABI from its
16207 current target so it needs to find out also the type being returned to make the
16208 assignment into the right register(s).
16210 Normally, the selected stack frame has debug info. @value{GDBN} will always
16211 use the debug info instead of the implicit type of @var{expression} when the
16212 debug info is available. For example, if you type @kbd{return -1}, and the
16213 function in the current stack frame is declared to return a @code{long long
16214 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16215 into a @code{long long int}:
16218 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16220 (@value{GDBP}) return -1
16221 Make func return now? (y or n) y
16222 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16223 43 printf ("result=%lld\n", func ());
16227 However, if the selected stack frame does not have a debug info, e.g., if the
16228 function was compiled without debug info, @value{GDBN} has to find out the type
16229 to return from user. Specifying a different type by mistake may set the value
16230 in different inferior registers than the caller code expects. For example,
16231 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16232 of a @code{long long int} result for a debug info less function (on 32-bit
16233 architectures). Therefore the user is required to specify the return type by
16234 an appropriate cast explicitly:
16237 Breakpoint 2, 0x0040050b in func ()
16238 (@value{GDBP}) return -1
16239 Return value type not available for selected stack frame.
16240 Please use an explicit cast of the value to return.
16241 (@value{GDBP}) return (long long int) -1
16242 Make selected stack frame return now? (y or n) y
16243 #0 0x00400526 in main ()
16248 @section Calling Program Functions
16251 @cindex calling functions
16252 @cindex inferior functions, calling
16253 @item print @var{expr}
16254 Evaluate the expression @var{expr} and display the resulting value.
16255 @var{expr} may include calls to functions in the program being
16259 @item call @var{expr}
16260 Evaluate the expression @var{expr} without displaying @code{void}
16263 You can use this variant of the @code{print} command if you want to
16264 execute a function from your program that does not return anything
16265 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16266 with @code{void} returned values that @value{GDBN} will otherwise
16267 print. If the result is not void, it is printed and saved in the
16271 It is possible for the function you call via the @code{print} or
16272 @code{call} command to generate a signal (e.g., if there's a bug in
16273 the function, or if you passed it incorrect arguments). What happens
16274 in that case is controlled by the @code{set unwindonsignal} command.
16276 Similarly, with a C@t{++} program it is possible for the function you
16277 call via the @code{print} or @code{call} command to generate an
16278 exception that is not handled due to the constraints of the dummy
16279 frame. In this case, any exception that is raised in the frame, but has
16280 an out-of-frame exception handler will not be found. GDB builds a
16281 dummy-frame for the inferior function call, and the unwinder cannot
16282 seek for exception handlers outside of this dummy-frame. What happens
16283 in that case is controlled by the
16284 @code{set unwind-on-terminating-exception} command.
16287 @item set unwindonsignal
16288 @kindex set unwindonsignal
16289 @cindex unwind stack in called functions
16290 @cindex call dummy stack unwinding
16291 Set unwinding of the stack if a signal is received while in a function
16292 that @value{GDBN} called in the program being debugged. If set to on,
16293 @value{GDBN} unwinds the stack it created for the call and restores
16294 the context to what it was before the call. If set to off (the
16295 default), @value{GDBN} stops in the frame where the signal was
16298 @item show unwindonsignal
16299 @kindex show unwindonsignal
16300 Show the current setting of stack unwinding in the functions called by
16303 @item set unwind-on-terminating-exception
16304 @kindex set unwind-on-terminating-exception
16305 @cindex unwind stack in called functions with unhandled exceptions
16306 @cindex call dummy stack unwinding on unhandled exception.
16307 Set unwinding of the stack if a C@t{++} exception is raised, but left
16308 unhandled while in a function that @value{GDBN} called in the program being
16309 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16310 it created for the call and restores the context to what it was before
16311 the call. If set to off, @value{GDBN} the exception is delivered to
16312 the default C@t{++} exception handler and the inferior terminated.
16314 @item show unwind-on-terminating-exception
16315 @kindex show unwind-on-terminating-exception
16316 Show the current setting of stack unwinding in the functions called by
16321 @cindex weak alias functions
16322 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16323 for another function. In such case, @value{GDBN} might not pick up
16324 the type information, including the types of the function arguments,
16325 which causes @value{GDBN} to call the inferior function incorrectly.
16326 As a result, the called function will function erroneously and may
16327 even crash. A solution to that is to use the name of the aliased
16331 @section Patching Programs
16333 @cindex patching binaries
16334 @cindex writing into executables
16335 @cindex writing into corefiles
16337 By default, @value{GDBN} opens the file containing your program's
16338 executable code (or the corefile) read-only. This prevents accidental
16339 alterations to machine code; but it also prevents you from intentionally
16340 patching your program's binary.
16342 If you'd like to be able to patch the binary, you can specify that
16343 explicitly with the @code{set write} command. For example, you might
16344 want to turn on internal debugging flags, or even to make emergency
16350 @itemx set write off
16351 If you specify @samp{set write on}, @value{GDBN} opens executable and
16352 core files for both reading and writing; if you specify @kbd{set write
16353 off} (the default), @value{GDBN} opens them read-only.
16355 If you have already loaded a file, you must load it again (using the
16356 @code{exec-file} or @code{core-file} command) after changing @code{set
16357 write}, for your new setting to take effect.
16361 Display whether executable files and core files are opened for writing
16362 as well as reading.
16366 @chapter @value{GDBN} Files
16368 @value{GDBN} needs to know the file name of the program to be debugged,
16369 both in order to read its symbol table and in order to start your
16370 program. To debug a core dump of a previous run, you must also tell
16371 @value{GDBN} the name of the core dump file.
16374 * Files:: Commands to specify files
16375 * Separate Debug Files:: Debugging information in separate files
16376 * MiniDebugInfo:: Debugging information in a special section
16377 * Index Files:: Index files speed up GDB
16378 * Symbol Errors:: Errors reading symbol files
16379 * Data Files:: GDB data files
16383 @section Commands to Specify Files
16385 @cindex symbol table
16386 @cindex core dump file
16388 You may want to specify executable and core dump file names. The usual
16389 way to do this is at start-up time, using the arguments to
16390 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16391 Out of @value{GDBN}}).
16393 Occasionally it is necessary to change to a different file during a
16394 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16395 specify a file you want to use. Or you are debugging a remote target
16396 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16397 Program}). In these situations the @value{GDBN} commands to specify
16398 new files are useful.
16401 @cindex executable file
16403 @item file @var{filename}
16404 Use @var{filename} as the program to be debugged. It is read for its
16405 symbols and for the contents of pure memory. It is also the program
16406 executed when you use the @code{run} command. If you do not specify a
16407 directory and the file is not found in the @value{GDBN} working directory,
16408 @value{GDBN} uses the environment variable @code{PATH} as a list of
16409 directories to search, just as the shell does when looking for a program
16410 to run. You can change the value of this variable, for both @value{GDBN}
16411 and your program, using the @code{path} command.
16413 @cindex unlinked object files
16414 @cindex patching object files
16415 You can load unlinked object @file{.o} files into @value{GDBN} using
16416 the @code{file} command. You will not be able to ``run'' an object
16417 file, but you can disassemble functions and inspect variables. Also,
16418 if the underlying BFD functionality supports it, you could use
16419 @kbd{gdb -write} to patch object files using this technique. Note
16420 that @value{GDBN} can neither interpret nor modify relocations in this
16421 case, so branches and some initialized variables will appear to go to
16422 the wrong place. But this feature is still handy from time to time.
16425 @code{file} with no argument makes @value{GDBN} discard any information it
16426 has on both executable file and the symbol table.
16429 @item exec-file @r{[} @var{filename} @r{]}
16430 Specify that the program to be run (but not the symbol table) is found
16431 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16432 if necessary to locate your program. Omitting @var{filename} means to
16433 discard information on the executable file.
16435 @kindex symbol-file
16436 @item symbol-file @r{[} @var{filename} @r{]}
16437 Read symbol table information from file @var{filename}. @code{PATH} is
16438 searched when necessary. Use the @code{file} command to get both symbol
16439 table and program to run from the same file.
16441 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16442 program's symbol table.
16444 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16445 some breakpoints and auto-display expressions. This is because they may
16446 contain pointers to the internal data recording symbols and data types,
16447 which are part of the old symbol table data being discarded inside
16450 @code{symbol-file} does not repeat if you press @key{RET} again after
16453 When @value{GDBN} is configured for a particular environment, it
16454 understands debugging information in whatever format is the standard
16455 generated for that environment; you may use either a @sc{gnu} compiler, or
16456 other compilers that adhere to the local conventions.
16457 Best results are usually obtained from @sc{gnu} compilers; for example,
16458 using @code{@value{NGCC}} you can generate debugging information for
16461 For most kinds of object files, with the exception of old SVR3 systems
16462 using COFF, the @code{symbol-file} command does not normally read the
16463 symbol table in full right away. Instead, it scans the symbol table
16464 quickly to find which source files and which symbols are present. The
16465 details are read later, one source file at a time, as they are needed.
16467 The purpose of this two-stage reading strategy is to make @value{GDBN}
16468 start up faster. For the most part, it is invisible except for
16469 occasional pauses while the symbol table details for a particular source
16470 file are being read. (The @code{set verbose} command can turn these
16471 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16472 Warnings and Messages}.)
16474 We have not implemented the two-stage strategy for COFF yet. When the
16475 symbol table is stored in COFF format, @code{symbol-file} reads the
16476 symbol table data in full right away. Note that ``stabs-in-COFF''
16477 still does the two-stage strategy, since the debug info is actually
16481 @cindex reading symbols immediately
16482 @cindex symbols, reading immediately
16483 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16484 @itemx file @r{[} -readnow @r{]} @var{filename}
16485 You can override the @value{GDBN} two-stage strategy for reading symbol
16486 tables by using the @samp{-readnow} option with any of the commands that
16487 load symbol table information, if you want to be sure @value{GDBN} has the
16488 entire symbol table available.
16490 @c FIXME: for now no mention of directories, since this seems to be in
16491 @c flux. 13mar1992 status is that in theory GDB would look either in
16492 @c current dir or in same dir as myprog; but issues like competing
16493 @c GDB's, or clutter in system dirs, mean that in practice right now
16494 @c only current dir is used. FFish says maybe a special GDB hierarchy
16495 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16499 @item core-file @r{[}@var{filename}@r{]}
16501 Specify the whereabouts of a core dump file to be used as the ``contents
16502 of memory''. Traditionally, core files contain only some parts of the
16503 address space of the process that generated them; @value{GDBN} can access the
16504 executable file itself for other parts.
16506 @code{core-file} with no argument specifies that no core file is
16509 Note that the core file is ignored when your program is actually running
16510 under @value{GDBN}. So, if you have been running your program and you
16511 wish to debug a core file instead, you must kill the subprocess in which
16512 the program is running. To do this, use the @code{kill} command
16513 (@pxref{Kill Process, ,Killing the Child Process}).
16515 @kindex add-symbol-file
16516 @cindex dynamic linking
16517 @item add-symbol-file @var{filename} @var{address}
16518 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16519 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16520 The @code{add-symbol-file} command reads additional symbol table
16521 information from the file @var{filename}. You would use this command
16522 when @var{filename} has been dynamically loaded (by some other means)
16523 into the program that is running. @var{address} should be the memory
16524 address at which the file has been loaded; @value{GDBN} cannot figure
16525 this out for itself. You can additionally specify an arbitrary number
16526 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16527 section name and base address for that section. You can specify any
16528 @var{address} as an expression.
16530 The symbol table of the file @var{filename} is added to the symbol table
16531 originally read with the @code{symbol-file} command. You can use the
16532 @code{add-symbol-file} command any number of times; the new symbol data
16533 thus read keeps adding to the old. To discard all old symbol data
16534 instead, use the @code{symbol-file} command without any arguments.
16536 @cindex relocatable object files, reading symbols from
16537 @cindex object files, relocatable, reading symbols from
16538 @cindex reading symbols from relocatable object files
16539 @cindex symbols, reading from relocatable object files
16540 @cindex @file{.o} files, reading symbols from
16541 Although @var{filename} is typically a shared library file, an
16542 executable file, or some other object file which has been fully
16543 relocated for loading into a process, you can also load symbolic
16544 information from relocatable @file{.o} files, as long as:
16548 the file's symbolic information refers only to linker symbols defined in
16549 that file, not to symbols defined by other object files,
16551 every section the file's symbolic information refers to has actually
16552 been loaded into the inferior, as it appears in the file, and
16554 you can determine the address at which every section was loaded, and
16555 provide these to the @code{add-symbol-file} command.
16559 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16560 relocatable files into an already running program; such systems
16561 typically make the requirements above easy to meet. However, it's
16562 important to recognize that many native systems use complex link
16563 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16564 assembly, for example) that make the requirements difficult to meet. In
16565 general, one cannot assume that using @code{add-symbol-file} to read a
16566 relocatable object file's symbolic information will have the same effect
16567 as linking the relocatable object file into the program in the normal
16570 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16572 @kindex add-symbol-file-from-memory
16573 @cindex @code{syscall DSO}
16574 @cindex load symbols from memory
16575 @item add-symbol-file-from-memory @var{address}
16576 Load symbols from the given @var{address} in a dynamically loaded
16577 object file whose image is mapped directly into the inferior's memory.
16578 For example, the Linux kernel maps a @code{syscall DSO} into each
16579 process's address space; this DSO provides kernel-specific code for
16580 some system calls. The argument can be any expression whose
16581 evaluation yields the address of the file's shared object file header.
16582 For this command to work, you must have used @code{symbol-file} or
16583 @code{exec-file} commands in advance.
16585 @kindex add-shared-symbol-files
16587 @item add-shared-symbol-files @var{library-file}
16588 @itemx assf @var{library-file}
16589 The @code{add-shared-symbol-files} command can currently be used only
16590 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16591 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16592 @value{GDBN} automatically looks for shared libraries, however if
16593 @value{GDBN} does not find yours, you can invoke
16594 @code{add-shared-symbol-files}. It takes one argument: the shared
16595 library's file name. @code{assf} is a shorthand alias for
16596 @code{add-shared-symbol-files}.
16599 @item section @var{section} @var{addr}
16600 The @code{section} command changes the base address of the named
16601 @var{section} of the exec file to @var{addr}. This can be used if the
16602 exec file does not contain section addresses, (such as in the
16603 @code{a.out} format), or when the addresses specified in the file
16604 itself are wrong. Each section must be changed separately. The
16605 @code{info files} command, described below, lists all the sections and
16609 @kindex info target
16612 @code{info files} and @code{info target} are synonymous; both print the
16613 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16614 including the names of the executable and core dump files currently in
16615 use by @value{GDBN}, and the files from which symbols were loaded. The
16616 command @code{help target} lists all possible targets rather than
16619 @kindex maint info sections
16620 @item maint info sections
16621 Another command that can give you extra information about program sections
16622 is @code{maint info sections}. In addition to the section information
16623 displayed by @code{info files}, this command displays the flags and file
16624 offset of each section in the executable and core dump files. In addition,
16625 @code{maint info sections} provides the following command options (which
16626 may be arbitrarily combined):
16630 Display sections for all loaded object files, including shared libraries.
16631 @item @var{sections}
16632 Display info only for named @var{sections}.
16633 @item @var{section-flags}
16634 Display info only for sections for which @var{section-flags} are true.
16635 The section flags that @value{GDBN} currently knows about are:
16638 Section will have space allocated in the process when loaded.
16639 Set for all sections except those containing debug information.
16641 Section will be loaded from the file into the child process memory.
16642 Set for pre-initialized code and data, clear for @code{.bss} sections.
16644 Section needs to be relocated before loading.
16646 Section cannot be modified by the child process.
16648 Section contains executable code only.
16650 Section contains data only (no executable code).
16652 Section will reside in ROM.
16654 Section contains data for constructor/destructor lists.
16656 Section is not empty.
16658 An instruction to the linker to not output the section.
16659 @item COFF_SHARED_LIBRARY
16660 A notification to the linker that the section contains
16661 COFF shared library information.
16663 Section contains common symbols.
16666 @kindex set trust-readonly-sections
16667 @cindex read-only sections
16668 @item set trust-readonly-sections on
16669 Tell @value{GDBN} that readonly sections in your object file
16670 really are read-only (i.e.@: that their contents will not change).
16671 In that case, @value{GDBN} can fetch values from these sections
16672 out of the object file, rather than from the target program.
16673 For some targets (notably embedded ones), this can be a significant
16674 enhancement to debugging performance.
16676 The default is off.
16678 @item set trust-readonly-sections off
16679 Tell @value{GDBN} not to trust readonly sections. This means that
16680 the contents of the section might change while the program is running,
16681 and must therefore be fetched from the target when needed.
16683 @item show trust-readonly-sections
16684 Show the current setting of trusting readonly sections.
16687 All file-specifying commands allow both absolute and relative file names
16688 as arguments. @value{GDBN} always converts the file name to an absolute file
16689 name and remembers it that way.
16691 @cindex shared libraries
16692 @anchor{Shared Libraries}
16693 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16694 and IBM RS/6000 AIX shared libraries.
16696 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16697 shared libraries. @xref{Expat}.
16699 @value{GDBN} automatically loads symbol definitions from shared libraries
16700 when you use the @code{run} command, or when you examine a core file.
16701 (Before you issue the @code{run} command, @value{GDBN} does not understand
16702 references to a function in a shared library, however---unless you are
16703 debugging a core file).
16705 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16706 automatically loads the symbols at the time of the @code{shl_load} call.
16708 @c FIXME: some @value{GDBN} release may permit some refs to undef
16709 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16710 @c FIXME...lib; check this from time to time when updating manual
16712 There are times, however, when you may wish to not automatically load
16713 symbol definitions from shared libraries, such as when they are
16714 particularly large or there are many of them.
16716 To control the automatic loading of shared library symbols, use the
16720 @kindex set auto-solib-add
16721 @item set auto-solib-add @var{mode}
16722 If @var{mode} is @code{on}, symbols from all shared object libraries
16723 will be loaded automatically when the inferior begins execution, you
16724 attach to an independently started inferior, or when the dynamic linker
16725 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16726 is @code{off}, symbols must be loaded manually, using the
16727 @code{sharedlibrary} command. The default value is @code{on}.
16729 @cindex memory used for symbol tables
16730 If your program uses lots of shared libraries with debug info that
16731 takes large amounts of memory, you can decrease the @value{GDBN}
16732 memory footprint by preventing it from automatically loading the
16733 symbols from shared libraries. To that end, type @kbd{set
16734 auto-solib-add off} before running the inferior, then load each
16735 library whose debug symbols you do need with @kbd{sharedlibrary
16736 @var{regexp}}, where @var{regexp} is a regular expression that matches
16737 the libraries whose symbols you want to be loaded.
16739 @kindex show auto-solib-add
16740 @item show auto-solib-add
16741 Display the current autoloading mode.
16744 @cindex load shared library
16745 To explicitly load shared library symbols, use the @code{sharedlibrary}
16749 @kindex info sharedlibrary
16751 @item info share @var{regex}
16752 @itemx info sharedlibrary @var{regex}
16753 Print the names of the shared libraries which are currently loaded
16754 that match @var{regex}. If @var{regex} is omitted then print
16755 all shared libraries that are loaded.
16757 @kindex sharedlibrary
16759 @item sharedlibrary @var{regex}
16760 @itemx share @var{regex}
16761 Load shared object library symbols for files matching a
16762 Unix regular expression.
16763 As with files loaded automatically, it only loads shared libraries
16764 required by your program for a core file or after typing @code{run}. If
16765 @var{regex} is omitted all shared libraries required by your program are
16768 @item nosharedlibrary
16769 @kindex nosharedlibrary
16770 @cindex unload symbols from shared libraries
16771 Unload all shared object library symbols. This discards all symbols
16772 that have been loaded from all shared libraries. Symbols from shared
16773 libraries that were loaded by explicit user requests are not
16777 Sometimes you may wish that @value{GDBN} stops and gives you control
16778 when any of shared library events happen. The best way to do this is
16779 to use @code{catch load} and @code{catch unload} (@pxref{Set
16782 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16783 command for this. This command exists for historical reasons. It is
16784 less useful than setting a catchpoint, because it does not allow for
16785 conditions or commands as a catchpoint does.
16788 @item set stop-on-solib-events
16789 @kindex set stop-on-solib-events
16790 This command controls whether @value{GDBN} should give you control
16791 when the dynamic linker notifies it about some shared library event.
16792 The most common event of interest is loading or unloading of a new
16795 @item show stop-on-solib-events
16796 @kindex show stop-on-solib-events
16797 Show whether @value{GDBN} stops and gives you control when shared
16798 library events happen.
16801 Shared libraries are also supported in many cross or remote debugging
16802 configurations. @value{GDBN} needs to have access to the target's libraries;
16803 this can be accomplished either by providing copies of the libraries
16804 on the host system, or by asking @value{GDBN} to automatically retrieve the
16805 libraries from the target. If copies of the target libraries are
16806 provided, they need to be the same as the target libraries, although the
16807 copies on the target can be stripped as long as the copies on the host are
16810 @cindex where to look for shared libraries
16811 For remote debugging, you need to tell @value{GDBN} where the target
16812 libraries are, so that it can load the correct copies---otherwise, it
16813 may try to load the host's libraries. @value{GDBN} has two variables
16814 to specify the search directories for target libraries.
16817 @cindex prefix for shared library file names
16818 @cindex system root, alternate
16819 @kindex set solib-absolute-prefix
16820 @kindex set sysroot
16821 @item set sysroot @var{path}
16822 Use @var{path} as the system root for the program being debugged. Any
16823 absolute shared library paths will be prefixed with @var{path}; many
16824 runtime loaders store the absolute paths to the shared library in the
16825 target program's memory. If you use @code{set sysroot} to find shared
16826 libraries, they need to be laid out in the same way that they are on
16827 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16830 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16831 retrieve the target libraries from the remote system. This is only
16832 supported when using a remote target that supports the @code{remote get}
16833 command (@pxref{File Transfer,,Sending files to a remote system}).
16834 The part of @var{path} following the initial @file{remote:}
16835 (if present) is used as system root prefix on the remote file system.
16836 @footnote{If you want to specify a local system root using a directory
16837 that happens to be named @file{remote:}, you need to use some equivalent
16838 variant of the name like @file{./remote:}.}
16840 For targets with an MS-DOS based filesystem, such as MS-Windows and
16841 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16842 absolute file name with @var{path}. But first, on Unix hosts,
16843 @value{GDBN} converts all backslash directory separators into forward
16844 slashes, because the backslash is not a directory separator on Unix:
16847 c:\foo\bar.dll @result{} c:/foo/bar.dll
16850 Then, @value{GDBN} attempts prefixing the target file name with
16851 @var{path}, and looks for the resulting file name in the host file
16855 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16858 If that does not find the shared library, @value{GDBN} tries removing
16859 the @samp{:} character from the drive spec, both for convenience, and,
16860 for the case of the host file system not supporting file names with
16864 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16867 This makes it possible to have a system root that mirrors a target
16868 with more than one drive. E.g., you may want to setup your local
16869 copies of the target system shared libraries like so (note @samp{c} vs
16873 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16874 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16875 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16879 and point the system root at @file{/path/to/sysroot}, so that
16880 @value{GDBN} can find the correct copies of both
16881 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16883 If that still does not find the shared library, @value{GDBN} tries
16884 removing the whole drive spec from the target file name:
16887 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16890 This last lookup makes it possible to not care about the drive name,
16891 if you don't want or need to.
16893 The @code{set solib-absolute-prefix} command is an alias for @code{set
16896 @cindex default system root
16897 @cindex @samp{--with-sysroot}
16898 You can set the default system root by using the configure-time
16899 @samp{--with-sysroot} option. If the system root is inside
16900 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16901 @samp{--exec-prefix}), then the default system root will be updated
16902 automatically if the installed @value{GDBN} is moved to a new
16905 @kindex show sysroot
16907 Display the current shared library prefix.
16909 @kindex set solib-search-path
16910 @item set solib-search-path @var{path}
16911 If this variable is set, @var{path} is a colon-separated list of
16912 directories to search for shared libraries. @samp{solib-search-path}
16913 is used after @samp{sysroot} fails to locate the library, or if the
16914 path to the library is relative instead of absolute. If you want to
16915 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16916 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16917 finding your host's libraries. @samp{sysroot} is preferred; setting
16918 it to a nonexistent directory may interfere with automatic loading
16919 of shared library symbols.
16921 @kindex show solib-search-path
16922 @item show solib-search-path
16923 Display the current shared library search path.
16925 @cindex DOS file-name semantics of file names.
16926 @kindex set target-file-system-kind (unix|dos-based|auto)
16927 @kindex show target-file-system-kind
16928 @item set target-file-system-kind @var{kind}
16929 Set assumed file system kind for target reported file names.
16931 Shared library file names as reported by the target system may not
16932 make sense as is on the system @value{GDBN} is running on. For
16933 example, when remote debugging a target that has MS-DOS based file
16934 system semantics, from a Unix host, the target may be reporting to
16935 @value{GDBN} a list of loaded shared libraries with file names such as
16936 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16937 drive letters, so the @samp{c:\} prefix is not normally understood as
16938 indicating an absolute file name, and neither is the backslash
16939 normally considered a directory separator character. In that case,
16940 the native file system would interpret this whole absolute file name
16941 as a relative file name with no directory components. This would make
16942 it impossible to point @value{GDBN} at a copy of the remote target's
16943 shared libraries on the host using @code{set sysroot}, and impractical
16944 with @code{set solib-search-path}. Setting
16945 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16946 to interpret such file names similarly to how the target would, and to
16947 map them to file names valid on @value{GDBN}'s native file system
16948 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16949 to one of the supported file system kinds. In that case, @value{GDBN}
16950 tries to determine the appropriate file system variant based on the
16951 current target's operating system (@pxref{ABI, ,Configuring the
16952 Current ABI}). The supported file system settings are:
16956 Instruct @value{GDBN} to assume the target file system is of Unix
16957 kind. Only file names starting the forward slash (@samp{/}) character
16958 are considered absolute, and the directory separator character is also
16962 Instruct @value{GDBN} to assume the target file system is DOS based.
16963 File names starting with either a forward slash, or a drive letter
16964 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16965 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16966 considered directory separators.
16969 Instruct @value{GDBN} to use the file system kind associated with the
16970 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16971 This is the default.
16975 @cindex file name canonicalization
16976 @cindex base name differences
16977 When processing file names provided by the user, @value{GDBN}
16978 frequently needs to compare them to the file names recorded in the
16979 program's debug info. Normally, @value{GDBN} compares just the
16980 @dfn{base names} of the files as strings, which is reasonably fast
16981 even for very large programs. (The base name of a file is the last
16982 portion of its name, after stripping all the leading directories.)
16983 This shortcut in comparison is based upon the assumption that files
16984 cannot have more than one base name. This is usually true, but
16985 references to files that use symlinks or similar filesystem
16986 facilities violate that assumption. If your program records files
16987 using such facilities, or if you provide file names to @value{GDBN}
16988 using symlinks etc., you can set @code{basenames-may-differ} to
16989 @code{true} to instruct @value{GDBN} to completely canonicalize each
16990 pair of file names it needs to compare. This will make file-name
16991 comparisons accurate, but at a price of a significant slowdown.
16994 @item set basenames-may-differ
16995 @kindex set basenames-may-differ
16996 Set whether a source file may have multiple base names.
16998 @item show basenames-may-differ
16999 @kindex show basenames-may-differ
17000 Show whether a source file may have multiple base names.
17003 @node Separate Debug Files
17004 @section Debugging Information in Separate Files
17005 @cindex separate debugging information files
17006 @cindex debugging information in separate files
17007 @cindex @file{.debug} subdirectories
17008 @cindex debugging information directory, global
17009 @cindex global debugging information directories
17010 @cindex build ID, and separate debugging files
17011 @cindex @file{.build-id} directory
17013 @value{GDBN} allows you to put a program's debugging information in a
17014 file separate from the executable itself, in a way that allows
17015 @value{GDBN} to find and load the debugging information automatically.
17016 Since debugging information can be very large---sometimes larger
17017 than the executable code itself---some systems distribute debugging
17018 information for their executables in separate files, which users can
17019 install only when they need to debug a problem.
17021 @value{GDBN} supports two ways of specifying the separate debug info
17026 The executable contains a @dfn{debug link} that specifies the name of
17027 the separate debug info file. The separate debug file's name is
17028 usually @file{@var{executable}.debug}, where @var{executable} is the
17029 name of the corresponding executable file without leading directories
17030 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17031 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17032 checksum for the debug file, which @value{GDBN} uses to validate that
17033 the executable and the debug file came from the same build.
17036 The executable contains a @dfn{build ID}, a unique bit string that is
17037 also present in the corresponding debug info file. (This is supported
17038 only on some operating systems, notably those which use the ELF format
17039 for binary files and the @sc{gnu} Binutils.) For more details about
17040 this feature, see the description of the @option{--build-id}
17041 command-line option in @ref{Options, , Command Line Options, ld.info,
17042 The GNU Linker}. The debug info file's name is not specified
17043 explicitly by the build ID, but can be computed from the build ID, see
17047 Depending on the way the debug info file is specified, @value{GDBN}
17048 uses two different methods of looking for the debug file:
17052 For the ``debug link'' method, @value{GDBN} looks up the named file in
17053 the directory of the executable file, then in a subdirectory of that
17054 directory named @file{.debug}, and finally under each one of the global debug
17055 directories, in a subdirectory whose name is identical to the leading
17056 directories of the executable's absolute file name.
17059 For the ``build ID'' method, @value{GDBN} looks in the
17060 @file{.build-id} subdirectory of each one of the global debug directories for
17061 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17062 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17063 are the rest of the bit string. (Real build ID strings are 32 or more
17064 hex characters, not 10.)
17067 So, for example, suppose you ask @value{GDBN} to debug
17068 @file{/usr/bin/ls}, which has a debug link that specifies the
17069 file @file{ls.debug}, and a build ID whose value in hex is
17070 @code{abcdef1234}. If the list of the global debug directories includes
17071 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17072 debug information files, in the indicated order:
17076 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17078 @file{/usr/bin/ls.debug}
17080 @file{/usr/bin/.debug/ls.debug}
17082 @file{/usr/lib/debug/usr/bin/ls.debug}.
17085 @anchor{debug-file-directory}
17086 Global debugging info directories default to what is set by @value{GDBN}
17087 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17088 you can also set the global debugging info directories, and view the list
17089 @value{GDBN} is currently using.
17093 @kindex set debug-file-directory
17094 @item set debug-file-directory @var{directories}
17095 Set the directories which @value{GDBN} searches for separate debugging
17096 information files to @var{directory}. Multiple path components can be set
17097 concatenating them by a path separator.
17099 @kindex show debug-file-directory
17100 @item show debug-file-directory
17101 Show the directories @value{GDBN} searches for separate debugging
17106 @cindex @code{.gnu_debuglink} sections
17107 @cindex debug link sections
17108 A debug link is a special section of the executable file named
17109 @code{.gnu_debuglink}. The section must contain:
17113 A filename, with any leading directory components removed, followed by
17116 zero to three bytes of padding, as needed to reach the next four-byte
17117 boundary within the section, and
17119 a four-byte CRC checksum, stored in the same endianness used for the
17120 executable file itself. The checksum is computed on the debugging
17121 information file's full contents by the function given below, passing
17122 zero as the @var{crc} argument.
17125 Any executable file format can carry a debug link, as long as it can
17126 contain a section named @code{.gnu_debuglink} with the contents
17129 @cindex @code{.note.gnu.build-id} sections
17130 @cindex build ID sections
17131 The build ID is a special section in the executable file (and in other
17132 ELF binary files that @value{GDBN} may consider). This section is
17133 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17134 It contains unique identification for the built files---the ID remains
17135 the same across multiple builds of the same build tree. The default
17136 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17137 content for the build ID string. The same section with an identical
17138 value is present in the original built binary with symbols, in its
17139 stripped variant, and in the separate debugging information file.
17141 The debugging information file itself should be an ordinary
17142 executable, containing a full set of linker symbols, sections, and
17143 debugging information. The sections of the debugging information file
17144 should have the same names, addresses, and sizes as the original file,
17145 but they need not contain any data---much like a @code{.bss} section
17146 in an ordinary executable.
17148 The @sc{gnu} binary utilities (Binutils) package includes the
17149 @samp{objcopy} utility that can produce
17150 the separated executable / debugging information file pairs using the
17151 following commands:
17154 @kbd{objcopy --only-keep-debug foo foo.debug}
17159 These commands remove the debugging
17160 information from the executable file @file{foo} and place it in the file
17161 @file{foo.debug}. You can use the first, second or both methods to link the
17166 The debug link method needs the following additional command to also leave
17167 behind a debug link in @file{foo}:
17170 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17173 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17174 a version of the @code{strip} command such that the command @kbd{strip foo -f
17175 foo.debug} has the same functionality as the two @code{objcopy} commands and
17176 the @code{ln -s} command above, together.
17179 Build ID gets embedded into the main executable using @code{ld --build-id} or
17180 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17181 compatibility fixes for debug files separation are present in @sc{gnu} binary
17182 utilities (Binutils) package since version 2.18.
17187 @cindex CRC algorithm definition
17188 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17189 IEEE 802.3 using the polynomial:
17191 @c TexInfo requires naked braces for multi-digit exponents for Tex
17192 @c output, but this causes HTML output to barf. HTML has to be set using
17193 @c raw commands. So we end up having to specify this equation in 2
17198 <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>
17199 + <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
17205 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17206 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17210 The function is computed byte at a time, taking the least
17211 significant bit of each byte first. The initial pattern
17212 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17213 the final result is inverted to ensure trailing zeros also affect the
17216 @emph{Note:} This is the same CRC polynomial as used in handling the
17217 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17218 , @value{GDBN} Remote Serial Protocol}). However in the
17219 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17220 significant bit first, and the result is not inverted, so trailing
17221 zeros have no effect on the CRC value.
17223 To complete the description, we show below the code of the function
17224 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17225 initially supplied @code{crc} argument means that an initial call to
17226 this function passing in zero will start computing the CRC using
17229 @kindex gnu_debuglink_crc32
17232 gnu_debuglink_crc32 (unsigned long crc,
17233 unsigned char *buf, size_t len)
17235 static const unsigned long crc32_table[256] =
17237 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17238 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17239 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17240 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17241 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17242 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17243 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17244 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17245 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17246 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17247 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17248 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17249 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17250 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17251 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17252 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17253 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17254 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17255 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17256 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17257 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17258 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17259 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17260 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17261 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17262 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17263 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17264 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17265 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17266 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17267 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17268 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17269 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17270 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17271 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17272 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17273 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17274 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17275 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17276 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17277 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17278 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17279 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17280 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17281 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17282 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17283 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17284 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17285 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17286 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17287 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17290 unsigned char *end;
17292 crc = ~crc & 0xffffffff;
17293 for (end = buf + len; buf < end; ++buf)
17294 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17295 return ~crc & 0xffffffff;
17300 This computation does not apply to the ``build ID'' method.
17302 @node MiniDebugInfo
17303 @section Debugging information in a special section
17304 @cindex separate debug sections
17305 @cindex @samp{.gnu_debugdata} section
17307 Some systems ship pre-built executables and libraries that have a
17308 special @samp{.gnu_debugdata} section. This feature is called
17309 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17310 is used to supply extra symbols for backtraces.
17312 The intent of this section is to provide extra minimal debugging
17313 information for use in simple backtraces. It is not intended to be a
17314 replacement for full separate debugging information (@pxref{Separate
17315 Debug Files}). The example below shows the intended use; however,
17316 @value{GDBN} does not currently put restrictions on what sort of
17317 debugging information might be included in the section.
17319 @value{GDBN} has support for this extension. If the section exists,
17320 then it is used provided that no other source of debugging information
17321 can be found, and that @value{GDBN} was configured with LZMA support.
17323 This section can be easily created using @command{objcopy} and other
17324 standard utilities:
17327 # Extract the dynamic symbols from the main binary, there is no need
17328 # to also have these in the normal symbol table.
17329 nm -D @var{binary} --format=posix --defined-only \
17330 | awk '@{ print $1 @}' | sort > dynsyms
17332 # Extract all the text (i.e. function) symbols from the debuginfo.
17333 # (Note that we actually also accept "D" symbols, for the benefit
17334 # of platforms like PowerPC64 that use function descriptors.)
17335 nm @var{binary} --format=posix --defined-only \
17336 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17339 # Keep all the function symbols not already in the dynamic symbol
17341 comm -13 dynsyms funcsyms > keep_symbols
17343 # Copy the full debuginfo, keeping only a minimal set of symbols and
17344 # removing some unnecessary sections.
17345 objcopy -S --remove-section .gdb_index --remove-section .comment \
17346 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
17348 # Inject the compressed data into the .gnu_debugdata section of the
17351 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17355 @section Index Files Speed Up @value{GDBN}
17356 @cindex index files
17357 @cindex @samp{.gdb_index} section
17359 When @value{GDBN} finds a symbol file, it scans the symbols in the
17360 file in order to construct an internal symbol table. This lets most
17361 @value{GDBN} operations work quickly---at the cost of a delay early
17362 on. For large programs, this delay can be quite lengthy, so
17363 @value{GDBN} provides a way to build an index, which speeds up
17366 The index is stored as a section in the symbol file. @value{GDBN} can
17367 write the index to a file, then you can put it into the symbol file
17368 using @command{objcopy}.
17370 To create an index file, use the @code{save gdb-index} command:
17373 @item save gdb-index @var{directory}
17374 @kindex save gdb-index
17375 Create an index file for each symbol file currently known by
17376 @value{GDBN}. Each file is named after its corresponding symbol file,
17377 with @samp{.gdb-index} appended, and is written into the given
17381 Once you have created an index file you can merge it into your symbol
17382 file, here named @file{symfile}, using @command{objcopy}:
17385 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17386 --set-section-flags .gdb_index=readonly symfile symfile
17389 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17390 sections that have been deprecated. Usually they are deprecated because
17391 they are missing a new feature or have performance issues.
17392 To tell @value{GDBN} to use a deprecated index section anyway
17393 specify @code{set use-deprecated-index-sections on}.
17394 The default is @code{off}.
17395 This can speed up startup, but may result in some functionality being lost.
17396 @xref{Index Section Format}.
17398 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17399 must be done before gdb reads the file. The following will not work:
17402 $ gdb -ex "set use-deprecated-index-sections on" <program>
17405 Instead you must do, for example,
17408 $ gdb -iex "set use-deprecated-index-sections on" <program>
17411 There are currently some limitation on indices. They only work when
17412 for DWARF debugging information, not stabs. And, they do not
17413 currently work for programs using Ada.
17415 @node Symbol Errors
17416 @section Errors Reading Symbol Files
17418 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17419 such as symbol types it does not recognize, or known bugs in compiler
17420 output. By default, @value{GDBN} does not notify you of such problems, since
17421 they are relatively common and primarily of interest to people
17422 debugging compilers. If you are interested in seeing information
17423 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17424 only one message about each such type of problem, no matter how many
17425 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17426 to see how many times the problems occur, with the @code{set
17427 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17430 The messages currently printed, and their meanings, include:
17433 @item inner block not inside outer block in @var{symbol}
17435 The symbol information shows where symbol scopes begin and end
17436 (such as at the start of a function or a block of statements). This
17437 error indicates that an inner scope block is not fully contained
17438 in its outer scope blocks.
17440 @value{GDBN} circumvents the problem by treating the inner block as if it had
17441 the same scope as the outer block. In the error message, @var{symbol}
17442 may be shown as ``@code{(don't know)}'' if the outer block is not a
17445 @item block at @var{address} out of order
17447 The symbol information for symbol scope blocks should occur in
17448 order of increasing addresses. This error indicates that it does not
17451 @value{GDBN} does not circumvent this problem, and has trouble
17452 locating symbols in the source file whose symbols it is reading. (You
17453 can often determine what source file is affected by specifying
17454 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17457 @item bad block start address patched
17459 The symbol information for a symbol scope block has a start address
17460 smaller than the address of the preceding source line. This is known
17461 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17463 @value{GDBN} circumvents the problem by treating the symbol scope block as
17464 starting on the previous source line.
17466 @item bad string table offset in symbol @var{n}
17469 Symbol number @var{n} contains a pointer into the string table which is
17470 larger than the size of the string table.
17472 @value{GDBN} circumvents the problem by considering the symbol to have the
17473 name @code{foo}, which may cause other problems if many symbols end up
17476 @item unknown symbol type @code{0x@var{nn}}
17478 The symbol information contains new data types that @value{GDBN} does
17479 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17480 uncomprehended information, in hexadecimal.
17482 @value{GDBN} circumvents the error by ignoring this symbol information.
17483 This usually allows you to debug your program, though certain symbols
17484 are not accessible. If you encounter such a problem and feel like
17485 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17486 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17487 and examine @code{*bufp} to see the symbol.
17489 @item stub type has NULL name
17491 @value{GDBN} could not find the full definition for a struct or class.
17493 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17494 The symbol information for a C@t{++} member function is missing some
17495 information that recent versions of the compiler should have output for
17498 @item info mismatch between compiler and debugger
17500 @value{GDBN} could not parse a type specification output by the compiler.
17505 @section GDB Data Files
17507 @cindex prefix for data files
17508 @value{GDBN} will sometimes read an auxiliary data file. These files
17509 are kept in a directory known as the @dfn{data directory}.
17511 You can set the data directory's name, and view the name @value{GDBN}
17512 is currently using.
17515 @kindex set data-directory
17516 @item set data-directory @var{directory}
17517 Set the directory which @value{GDBN} searches for auxiliary data files
17518 to @var{directory}.
17520 @kindex show data-directory
17521 @item show data-directory
17522 Show the directory @value{GDBN} searches for auxiliary data files.
17525 @cindex default data directory
17526 @cindex @samp{--with-gdb-datadir}
17527 You can set the default data directory by using the configure-time
17528 @samp{--with-gdb-datadir} option. If the data directory is inside
17529 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17530 @samp{--exec-prefix}), then the default data directory will be updated
17531 automatically if the installed @value{GDBN} is moved to a new
17534 The data directory may also be specified with the
17535 @code{--data-directory} command line option.
17536 @xref{Mode Options}.
17539 @chapter Specifying a Debugging Target
17541 @cindex debugging target
17542 A @dfn{target} is the execution environment occupied by your program.
17544 Often, @value{GDBN} runs in the same host environment as your program;
17545 in that case, the debugging target is specified as a side effect when
17546 you use the @code{file} or @code{core} commands. When you need more
17547 flexibility---for example, running @value{GDBN} on a physically separate
17548 host, or controlling a standalone system over a serial port or a
17549 realtime system over a TCP/IP connection---you can use the @code{target}
17550 command to specify one of the target types configured for @value{GDBN}
17551 (@pxref{Target Commands, ,Commands for Managing Targets}).
17553 @cindex target architecture
17554 It is possible to build @value{GDBN} for several different @dfn{target
17555 architectures}. When @value{GDBN} is built like that, you can choose
17556 one of the available architectures with the @kbd{set architecture}
17560 @kindex set architecture
17561 @kindex show architecture
17562 @item set architecture @var{arch}
17563 This command sets the current target architecture to @var{arch}. The
17564 value of @var{arch} can be @code{"auto"}, in addition to one of the
17565 supported architectures.
17567 @item show architecture
17568 Show the current target architecture.
17570 @item set processor
17572 @kindex set processor
17573 @kindex show processor
17574 These are alias commands for, respectively, @code{set architecture}
17575 and @code{show architecture}.
17579 * Active Targets:: Active targets
17580 * Target Commands:: Commands for managing targets
17581 * Byte Order:: Choosing target byte order
17584 @node Active Targets
17585 @section Active Targets
17587 @cindex stacking targets
17588 @cindex active targets
17589 @cindex multiple targets
17591 There are multiple classes of targets such as: processes, executable files or
17592 recording sessions. Core files belong to the process class, making core file
17593 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17594 on multiple active targets, one in each class. This allows you to (for
17595 example) start a process and inspect its activity, while still having access to
17596 the executable file after the process finishes. Or if you start process
17597 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17598 presented a virtual layer of the recording target, while the process target
17599 remains stopped at the chronologically last point of the process execution.
17601 Use the @code{core-file} and @code{exec-file} commands to select a new core
17602 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17603 specify as a target a process that is already running, use the @code{attach}
17604 command (@pxref{Attach, ,Debugging an Already-running Process}).
17606 @node Target Commands
17607 @section Commands for Managing Targets
17610 @item target @var{type} @var{parameters}
17611 Connects the @value{GDBN} host environment to a target machine or
17612 process. A target is typically a protocol for talking to debugging
17613 facilities. You use the argument @var{type} to specify the type or
17614 protocol of the target machine.
17616 Further @var{parameters} are interpreted by the target protocol, but
17617 typically include things like device names or host names to connect
17618 with, process numbers, and baud rates.
17620 The @code{target} command does not repeat if you press @key{RET} again
17621 after executing the command.
17623 @kindex help target
17625 Displays the names of all targets available. To display targets
17626 currently selected, use either @code{info target} or @code{info files}
17627 (@pxref{Files, ,Commands to Specify Files}).
17629 @item help target @var{name}
17630 Describe a particular target, including any parameters necessary to
17633 @kindex set gnutarget
17634 @item set gnutarget @var{args}
17635 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17636 knows whether it is reading an @dfn{executable},
17637 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17638 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17639 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17642 @emph{Warning:} To specify a file format with @code{set gnutarget},
17643 you must know the actual BFD name.
17647 @xref{Files, , Commands to Specify Files}.
17649 @kindex show gnutarget
17650 @item show gnutarget
17651 Use the @code{show gnutarget} command to display what file format
17652 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17653 @value{GDBN} will determine the file format for each file automatically,
17654 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17657 @cindex common targets
17658 Here are some common targets (available, or not, depending on the GDB
17663 @item target exec @var{program}
17664 @cindex executable file target
17665 An executable file. @samp{target exec @var{program}} is the same as
17666 @samp{exec-file @var{program}}.
17668 @item target core @var{filename}
17669 @cindex core dump file target
17670 A core dump file. @samp{target core @var{filename}} is the same as
17671 @samp{core-file @var{filename}}.
17673 @item target remote @var{medium}
17674 @cindex remote target
17675 A remote system connected to @value{GDBN} via a serial line or network
17676 connection. This command tells @value{GDBN} to use its own remote
17677 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17679 For example, if you have a board connected to @file{/dev/ttya} on the
17680 machine running @value{GDBN}, you could say:
17683 target remote /dev/ttya
17686 @code{target remote} supports the @code{load} command. This is only
17687 useful if you have some other way of getting the stub to the target
17688 system, and you can put it somewhere in memory where it won't get
17689 clobbered by the download.
17691 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17692 @cindex built-in simulator target
17693 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17701 works; however, you cannot assume that a specific memory map, device
17702 drivers, or even basic I/O is available, although some simulators do
17703 provide these. For info about any processor-specific simulator details,
17704 see the appropriate section in @ref{Embedded Processors, ,Embedded
17709 Different targets are available on different configurations of @value{GDBN};
17710 your configuration may have more or fewer targets.
17712 Many remote targets require you to download the executable's code once
17713 you've successfully established a connection. You may wish to control
17714 various aspects of this process.
17719 @kindex set hash@r{, for remote monitors}
17720 @cindex hash mark while downloading
17721 This command controls whether a hash mark @samp{#} is displayed while
17722 downloading a file to the remote monitor. If on, a hash mark is
17723 displayed after each S-record is successfully downloaded to the
17727 @kindex show hash@r{, for remote monitors}
17728 Show the current status of displaying the hash mark.
17730 @item set debug monitor
17731 @kindex set debug monitor
17732 @cindex display remote monitor communications
17733 Enable or disable display of communications messages between
17734 @value{GDBN} and the remote monitor.
17736 @item show debug monitor
17737 @kindex show debug monitor
17738 Show the current status of displaying communications between
17739 @value{GDBN} and the remote monitor.
17744 @kindex load @var{filename}
17745 @item load @var{filename}
17747 Depending on what remote debugging facilities are configured into
17748 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17749 is meant to make @var{filename} (an executable) available for debugging
17750 on the remote system---by downloading, or dynamic linking, for example.
17751 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17752 the @code{add-symbol-file} command.
17754 If your @value{GDBN} does not have a @code{load} command, attempting to
17755 execute it gets the error message ``@code{You can't do that when your
17756 target is @dots{}}''
17758 The file is loaded at whatever address is specified in the executable.
17759 For some object file formats, you can specify the load address when you
17760 link the program; for other formats, like a.out, the object file format
17761 specifies a fixed address.
17762 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17764 Depending on the remote side capabilities, @value{GDBN} may be able to
17765 load programs into flash memory.
17767 @code{load} does not repeat if you press @key{RET} again after using it.
17771 @section Choosing Target Byte Order
17773 @cindex choosing target byte order
17774 @cindex target byte order
17776 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17777 offer the ability to run either big-endian or little-endian byte
17778 orders. Usually the executable or symbol will include a bit to
17779 designate the endian-ness, and you will not need to worry about
17780 which to use. However, you may still find it useful to adjust
17781 @value{GDBN}'s idea of processor endian-ness manually.
17785 @item set endian big
17786 Instruct @value{GDBN} to assume the target is big-endian.
17788 @item set endian little
17789 Instruct @value{GDBN} to assume the target is little-endian.
17791 @item set endian auto
17792 Instruct @value{GDBN} to use the byte order associated with the
17796 Display @value{GDBN}'s current idea of the target byte order.
17800 Note that these commands merely adjust interpretation of symbolic
17801 data on the host, and that they have absolutely no effect on the
17805 @node Remote Debugging
17806 @chapter Debugging Remote Programs
17807 @cindex remote debugging
17809 If you are trying to debug a program running on a machine that cannot run
17810 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17811 For example, you might use remote debugging on an operating system kernel,
17812 or on a small system which does not have a general purpose operating system
17813 powerful enough to run a full-featured debugger.
17815 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17816 to make this work with particular debugging targets. In addition,
17817 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17818 but not specific to any particular target system) which you can use if you
17819 write the remote stubs---the code that runs on the remote system to
17820 communicate with @value{GDBN}.
17822 Other remote targets may be available in your
17823 configuration of @value{GDBN}; use @code{help target} to list them.
17826 * Connecting:: Connecting to a remote target
17827 * File Transfer:: Sending files to a remote system
17828 * Server:: Using the gdbserver program
17829 * Remote Configuration:: Remote configuration
17830 * Remote Stub:: Implementing a remote stub
17834 @section Connecting to a Remote Target
17836 On the @value{GDBN} host machine, you will need an unstripped copy of
17837 your program, since @value{GDBN} needs symbol and debugging information.
17838 Start up @value{GDBN} as usual, using the name of the local copy of your
17839 program as the first argument.
17841 @cindex @code{target remote}
17842 @value{GDBN} can communicate with the target over a serial line, or
17843 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17844 each case, @value{GDBN} uses the same protocol for debugging your
17845 program; only the medium carrying the debugging packets varies. The
17846 @code{target remote} command establishes a connection to the target.
17847 Its arguments indicate which medium to use:
17851 @item target remote @var{serial-device}
17852 @cindex serial line, @code{target remote}
17853 Use @var{serial-device} to communicate with the target. For example,
17854 to use a serial line connected to the device named @file{/dev/ttyb}:
17857 target remote /dev/ttyb
17860 If you're using a serial line, you may want to give @value{GDBN} the
17861 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17862 (@pxref{Remote Configuration, set remotebaud}) before the
17863 @code{target} command.
17865 @item target remote @code{@var{host}:@var{port}}
17866 @itemx target remote @code{tcp:@var{host}:@var{port}}
17867 @cindex @acronym{TCP} port, @code{target remote}
17868 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17869 The @var{host} may be either a host name or a numeric @acronym{IP}
17870 address; @var{port} must be a decimal number. The @var{host} could be
17871 the target machine itself, if it is directly connected to the net, or
17872 it might be a terminal server which in turn has a serial line to the
17875 For example, to connect to port 2828 on a terminal server named
17879 target remote manyfarms:2828
17882 If your remote target is actually running on the same machine as your
17883 debugger session (e.g.@: a simulator for your target running on the
17884 same host), you can omit the hostname. For example, to connect to
17885 port 1234 on your local machine:
17888 target remote :1234
17892 Note that the colon is still required here.
17894 @item target remote @code{udp:@var{host}:@var{port}}
17895 @cindex @acronym{UDP} port, @code{target remote}
17896 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17897 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17900 target remote udp:manyfarms:2828
17903 When using a @acronym{UDP} connection for remote debugging, you should
17904 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17905 can silently drop packets on busy or unreliable networks, which will
17906 cause havoc with your debugging session.
17908 @item target remote | @var{command}
17909 @cindex pipe, @code{target remote} to
17910 Run @var{command} in the background and communicate with it using a
17911 pipe. The @var{command} is a shell command, to be parsed and expanded
17912 by the system's command shell, @code{/bin/sh}; it should expect remote
17913 protocol packets on its standard input, and send replies on its
17914 standard output. You could use this to run a stand-alone simulator
17915 that speaks the remote debugging protocol, to make net connections
17916 using programs like @code{ssh}, or for other similar tricks.
17918 If @var{command} closes its standard output (perhaps by exiting),
17919 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17920 program has already exited, this will have no effect.)
17924 Once the connection has been established, you can use all the usual
17925 commands to examine and change data. The remote program is already
17926 running; you can use @kbd{step} and @kbd{continue}, and you do not
17927 need to use @kbd{run}.
17929 @cindex interrupting remote programs
17930 @cindex remote programs, interrupting
17931 Whenever @value{GDBN} is waiting for the remote program, if you type the
17932 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17933 program. This may or may not succeed, depending in part on the hardware
17934 and the serial drivers the remote system uses. If you type the
17935 interrupt character once again, @value{GDBN} displays this prompt:
17938 Interrupted while waiting for the program.
17939 Give up (and stop debugging it)? (y or n)
17942 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17943 (If you decide you want to try again later, you can use @samp{target
17944 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17945 goes back to waiting.
17948 @kindex detach (remote)
17950 When you have finished debugging the remote program, you can use the
17951 @code{detach} command to release it from @value{GDBN} control.
17952 Detaching from the target normally resumes its execution, but the results
17953 will depend on your particular remote stub. After the @code{detach}
17954 command, @value{GDBN} is free to connect to another target.
17958 The @code{disconnect} command behaves like @code{detach}, except that
17959 the target is generally not resumed. It will wait for @value{GDBN}
17960 (this instance or another one) to connect and continue debugging. After
17961 the @code{disconnect} command, @value{GDBN} is again free to connect to
17964 @cindex send command to remote monitor
17965 @cindex extend @value{GDBN} for remote targets
17966 @cindex add new commands for external monitor
17968 @item monitor @var{cmd}
17969 This command allows you to send arbitrary commands directly to the
17970 remote monitor. Since @value{GDBN} doesn't care about the commands it
17971 sends like this, this command is the way to extend @value{GDBN}---you
17972 can add new commands that only the external monitor will understand
17976 @node File Transfer
17977 @section Sending files to a remote system
17978 @cindex remote target, file transfer
17979 @cindex file transfer
17980 @cindex sending files to remote systems
17982 Some remote targets offer the ability to transfer files over the same
17983 connection used to communicate with @value{GDBN}. This is convenient
17984 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17985 running @code{gdbserver} over a network interface. For other targets,
17986 e.g.@: embedded devices with only a single serial port, this may be
17987 the only way to upload or download files.
17989 Not all remote targets support these commands.
17993 @item remote put @var{hostfile} @var{targetfile}
17994 Copy file @var{hostfile} from the host system (the machine running
17995 @value{GDBN}) to @var{targetfile} on the target system.
17998 @item remote get @var{targetfile} @var{hostfile}
17999 Copy file @var{targetfile} from the target system to @var{hostfile}
18000 on the host system.
18002 @kindex remote delete
18003 @item remote delete @var{targetfile}
18004 Delete @var{targetfile} from the target system.
18009 @section Using the @code{gdbserver} Program
18012 @cindex remote connection without stubs
18013 @code{gdbserver} is a control program for Unix-like systems, which
18014 allows you to connect your program with a remote @value{GDBN} via
18015 @code{target remote}---but without linking in the usual debugging stub.
18017 @code{gdbserver} is not a complete replacement for the debugging stubs,
18018 because it requires essentially the same operating-system facilities
18019 that @value{GDBN} itself does. In fact, a system that can run
18020 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18021 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18022 because it is a much smaller program than @value{GDBN} itself. It is
18023 also easier to port than all of @value{GDBN}, so you may be able to get
18024 started more quickly on a new system by using @code{gdbserver}.
18025 Finally, if you develop code for real-time systems, you may find that
18026 the tradeoffs involved in real-time operation make it more convenient to
18027 do as much development work as possible on another system, for example
18028 by cross-compiling. You can use @code{gdbserver} to make a similar
18029 choice for debugging.
18031 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18032 or a TCP connection, using the standard @value{GDBN} remote serial
18036 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18037 Do not run @code{gdbserver} connected to any public network; a
18038 @value{GDBN} connection to @code{gdbserver} provides access to the
18039 target system with the same privileges as the user running
18043 @subsection Running @code{gdbserver}
18044 @cindex arguments, to @code{gdbserver}
18045 @cindex @code{gdbserver}, command-line arguments
18047 Run @code{gdbserver} on the target system. You need a copy of the
18048 program you want to debug, including any libraries it requires.
18049 @code{gdbserver} does not need your program's symbol table, so you can
18050 strip the program if necessary to save space. @value{GDBN} on the host
18051 system does all the symbol handling.
18053 To use the server, you must tell it how to communicate with @value{GDBN};
18054 the name of your program; and the arguments for your program. The usual
18058 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18061 @var{comm} is either a device name (to use a serial line), or a TCP
18062 hostname and portnumber, or @code{-} or @code{stdio} to use
18063 stdin/stdout of @code{gdbserver}.
18064 For example, to debug Emacs with the argument
18065 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18069 target> gdbserver /dev/com1 emacs foo.txt
18072 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18075 To use a TCP connection instead of a serial line:
18078 target> gdbserver host:2345 emacs foo.txt
18081 The only difference from the previous example is the first argument,
18082 specifying that you are communicating with the host @value{GDBN} via
18083 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18084 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18085 (Currently, the @samp{host} part is ignored.) You can choose any number
18086 you want for the port number as long as it does not conflict with any
18087 TCP ports already in use on the target system (for example, @code{23} is
18088 reserved for @code{telnet}).@footnote{If you choose a port number that
18089 conflicts with another service, @code{gdbserver} prints an error message
18090 and exits.} You must use the same port number with the host @value{GDBN}
18091 @code{target remote} command.
18093 The @code{stdio} connection is useful when starting @code{gdbserver}
18097 (gdb) target remote | ssh -T hostname gdbserver - hello
18100 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18101 and we don't want escape-character handling. Ssh does this by default when
18102 a command is provided, the flag is provided to make it explicit.
18103 You could elide it if you want to.
18105 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18106 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18107 display through a pipe connected to gdbserver.
18108 Both @code{stdout} and @code{stderr} use the same pipe.
18110 @subsubsection Attaching to a Running Program
18111 @cindex attach to a program, @code{gdbserver}
18112 @cindex @option{--attach}, @code{gdbserver} option
18114 On some targets, @code{gdbserver} can also attach to running programs.
18115 This is accomplished via the @code{--attach} argument. The syntax is:
18118 target> gdbserver --attach @var{comm} @var{pid}
18121 @var{pid} is the process ID of a currently running process. It isn't necessary
18122 to point @code{gdbserver} at a binary for the running process.
18125 You can debug processes by name instead of process ID if your target has the
18126 @code{pidof} utility:
18129 target> gdbserver --attach @var{comm} `pidof @var{program}`
18132 In case more than one copy of @var{program} is running, or @var{program}
18133 has multiple threads, most versions of @code{pidof} support the
18134 @code{-s} option to only return the first process ID.
18136 @subsubsection Multi-Process Mode for @code{gdbserver}
18137 @cindex @code{gdbserver}, multiple processes
18138 @cindex multiple processes with @code{gdbserver}
18140 When you connect to @code{gdbserver} using @code{target remote},
18141 @code{gdbserver} debugs the specified program only once. When the
18142 program exits, or you detach from it, @value{GDBN} closes the connection
18143 and @code{gdbserver} exits.
18145 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18146 enters multi-process mode. When the debugged program exits, or you
18147 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18148 though no program is running. The @code{run} and @code{attach}
18149 commands instruct @code{gdbserver} to run or attach to a new program.
18150 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18151 remote exec-file}) to select the program to run. Command line
18152 arguments are supported, except for wildcard expansion and I/O
18153 redirection (@pxref{Arguments}).
18155 @cindex @option{--multi}, @code{gdbserver} option
18156 To start @code{gdbserver} without supplying an initial command to run
18157 or process ID to attach, use the @option{--multi} command line option.
18158 Then you can connect using @kbd{target extended-remote} and start
18159 the program you want to debug.
18161 In multi-process mode @code{gdbserver} does not automatically exit unless you
18162 use the option @option{--once}. You can terminate it by using
18163 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18164 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18165 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18166 @option{--multi} option to @code{gdbserver} has no influence on that.
18168 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18170 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18172 @code{gdbserver} normally terminates after all of its debugged processes have
18173 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18174 extended-remote}, @code{gdbserver} stays running even with no processes left.
18175 @value{GDBN} normally terminates the spawned debugged process on its exit,
18176 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18177 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18178 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18179 stays running even in the @kbd{target remote} mode.
18181 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18182 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18183 completeness, at most one @value{GDBN} can be connected at a time.
18185 @cindex @option{--once}, @code{gdbserver} option
18186 By default, @code{gdbserver} keeps the listening TCP port open, so that
18187 subsequent connections are possible. However, if you start @code{gdbserver}
18188 with the @option{--once} option, it will stop listening for any further
18189 connection attempts after connecting to the first @value{GDBN} session. This
18190 means no further connections to @code{gdbserver} will be possible after the
18191 first one. It also means @code{gdbserver} will terminate after the first
18192 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18193 connections and even in the @kbd{target extended-remote} mode. The
18194 @option{--once} option allows reusing the same port number for connecting to
18195 multiple instances of @code{gdbserver} running on the same host, since each
18196 instance closes its port after the first connection.
18198 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18200 @cindex @option{--debug}, @code{gdbserver} option
18201 The @option{--debug} option tells @code{gdbserver} to display extra
18202 status information about the debugging process.
18203 @cindex @option{--remote-debug}, @code{gdbserver} option
18204 The @option{--remote-debug} option tells @code{gdbserver} to display
18205 remote protocol debug output. These options are intended for
18206 @code{gdbserver} development and for bug reports to the developers.
18208 @cindex @option{--wrapper}, @code{gdbserver} option
18209 The @option{--wrapper} option specifies a wrapper to launch programs
18210 for debugging. The option should be followed by the name of the
18211 wrapper, then any command-line arguments to pass to the wrapper, then
18212 @kbd{--} indicating the end of the wrapper arguments.
18214 @code{gdbserver} runs the specified wrapper program with a combined
18215 command line including the wrapper arguments, then the name of the
18216 program to debug, then any arguments to the program. The wrapper
18217 runs until it executes your program, and then @value{GDBN} gains control.
18219 You can use any program that eventually calls @code{execve} with
18220 its arguments as a wrapper. Several standard Unix utilities do
18221 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18222 with @code{exec "$@@"} will also work.
18224 For example, you can use @code{env} to pass an environment variable to
18225 the debugged program, without setting the variable in @code{gdbserver}'s
18229 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18232 @subsection Connecting to @code{gdbserver}
18234 Run @value{GDBN} on the host system.
18236 First make sure you have the necessary symbol files. Load symbols for
18237 your application using the @code{file} command before you connect. Use
18238 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18239 was compiled with the correct sysroot using @code{--with-sysroot}).
18241 The symbol file and target libraries must exactly match the executable
18242 and libraries on the target, with one exception: the files on the host
18243 system should not be stripped, even if the files on the target system
18244 are. Mismatched or missing files will lead to confusing results
18245 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18246 files may also prevent @code{gdbserver} from debugging multi-threaded
18249 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18250 For TCP connections, you must start up @code{gdbserver} prior to using
18251 the @code{target remote} command. Otherwise you may get an error whose
18252 text depends on the host system, but which usually looks something like
18253 @samp{Connection refused}. Don't use the @code{load}
18254 command in @value{GDBN} when using @code{gdbserver}, since the program is
18255 already on the target.
18257 @subsection Monitor Commands for @code{gdbserver}
18258 @cindex monitor commands, for @code{gdbserver}
18259 @anchor{Monitor Commands for gdbserver}
18261 During a @value{GDBN} session using @code{gdbserver}, you can use the
18262 @code{monitor} command to send special requests to @code{gdbserver}.
18263 Here are the available commands.
18267 List the available monitor commands.
18269 @item monitor set debug 0
18270 @itemx monitor set debug 1
18271 Disable or enable general debugging messages.
18273 @item monitor set remote-debug 0
18274 @itemx monitor set remote-debug 1
18275 Disable or enable specific debugging messages associated with the remote
18276 protocol (@pxref{Remote Protocol}).
18278 @item monitor set libthread-db-search-path [PATH]
18279 @cindex gdbserver, search path for @code{libthread_db}
18280 When this command is issued, @var{path} is a colon-separated list of
18281 directories to search for @code{libthread_db} (@pxref{Threads,,set
18282 libthread-db-search-path}). If you omit @var{path},
18283 @samp{libthread-db-search-path} will be reset to its default value.
18285 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18286 not supported in @code{gdbserver}.
18289 Tell gdbserver to exit immediately. This command should be followed by
18290 @code{disconnect} to close the debugging session. @code{gdbserver} will
18291 detach from any attached processes and kill any processes it created.
18292 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18293 of a multi-process mode debug session.
18297 @subsection Tracepoints support in @code{gdbserver}
18298 @cindex tracepoints support in @code{gdbserver}
18300 On some targets, @code{gdbserver} supports tracepoints, fast
18301 tracepoints and static tracepoints.
18303 For fast or static tracepoints to work, a special library called the
18304 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18305 This library is built and distributed as an integral part of
18306 @code{gdbserver}. In addition, support for static tracepoints
18307 requires building the in-process agent library with static tracepoints
18308 support. At present, the UST (LTTng Userspace Tracer,
18309 @url{http://lttng.org/ust}) tracing engine is supported. This support
18310 is automatically available if UST development headers are found in the
18311 standard include path when @code{gdbserver} is built, or if
18312 @code{gdbserver} was explicitly configured using @option{--with-ust}
18313 to point at such headers. You can explicitly disable the support
18314 using @option{--with-ust=no}.
18316 There are several ways to load the in-process agent in your program:
18319 @item Specifying it as dependency at link time
18321 You can link your program dynamically with the in-process agent
18322 library. On most systems, this is accomplished by adding
18323 @code{-linproctrace} to the link command.
18325 @item Using the system's preloading mechanisms
18327 You can force loading the in-process agent at startup time by using
18328 your system's support for preloading shared libraries. Many Unixes
18329 support the concept of preloading user defined libraries. In most
18330 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18331 in the environment. See also the description of @code{gdbserver}'s
18332 @option{--wrapper} command line option.
18334 @item Using @value{GDBN} to force loading the agent at run time
18336 On some systems, you can force the inferior to load a shared library,
18337 by calling a dynamic loader function in the inferior that takes care
18338 of dynamically looking up and loading a shared library. On most Unix
18339 systems, the function is @code{dlopen}. You'll use the @code{call}
18340 command for that. For example:
18343 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18346 Note that on most Unix systems, for the @code{dlopen} function to be
18347 available, the program needs to be linked with @code{-ldl}.
18350 On systems that have a userspace dynamic loader, like most Unix
18351 systems, when you connect to @code{gdbserver} using @code{target
18352 remote}, you'll find that the program is stopped at the dynamic
18353 loader's entry point, and no shared library has been loaded in the
18354 program's address space yet, including the in-process agent. In that
18355 case, before being able to use any of the fast or static tracepoints
18356 features, you need to let the loader run and load the shared
18357 libraries. The simplest way to do that is to run the program to the
18358 main procedure. E.g., if debugging a C or C@t{++} program, start
18359 @code{gdbserver} like so:
18362 $ gdbserver :9999 myprogram
18365 Start GDB and connect to @code{gdbserver} like so, and run to main:
18369 (@value{GDBP}) target remote myhost:9999
18370 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18371 (@value{GDBP}) b main
18372 (@value{GDBP}) continue
18375 The in-process tracing agent library should now be loaded into the
18376 process; you can confirm it with the @code{info sharedlibrary}
18377 command, which will list @file{libinproctrace.so} as loaded in the
18378 process. You are now ready to install fast tracepoints, list static
18379 tracepoint markers, probe static tracepoints markers, and start
18382 @node Remote Configuration
18383 @section Remote Configuration
18386 @kindex show remote
18387 This section documents the configuration options available when
18388 debugging remote programs. For the options related to the File I/O
18389 extensions of the remote protocol, see @ref{system,
18390 system-call-allowed}.
18393 @item set remoteaddresssize @var{bits}
18394 @cindex address size for remote targets
18395 @cindex bits in remote address
18396 Set the maximum size of address in a memory packet to the specified
18397 number of bits. @value{GDBN} will mask off the address bits above
18398 that number, when it passes addresses to the remote target. The
18399 default value is the number of bits in the target's address.
18401 @item show remoteaddresssize
18402 Show the current value of remote address size in bits.
18404 @item set remotebaud @var{n}
18405 @cindex baud rate for remote targets
18406 Set the baud rate for the remote serial I/O to @var{n} baud. The
18407 value is used to set the speed of the serial port used for debugging
18410 @item show remotebaud
18411 Show the current speed of the remote connection.
18413 @item set remotebreak
18414 @cindex interrupt remote programs
18415 @cindex BREAK signal instead of Ctrl-C
18416 @anchor{set remotebreak}
18417 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18418 when you type @kbd{Ctrl-c} to interrupt the program running
18419 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18420 character instead. The default is off, since most remote systems
18421 expect to see @samp{Ctrl-C} as the interrupt signal.
18423 @item show remotebreak
18424 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18425 interrupt the remote program.
18427 @item set remoteflow on
18428 @itemx set remoteflow off
18429 @kindex set remoteflow
18430 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18431 on the serial port used to communicate to the remote target.
18433 @item show remoteflow
18434 @kindex show remoteflow
18435 Show the current setting of hardware flow control.
18437 @item set remotelogbase @var{base}
18438 Set the base (a.k.a.@: radix) of logging serial protocol
18439 communications to @var{base}. Supported values of @var{base} are:
18440 @code{ascii}, @code{octal}, and @code{hex}. The default is
18443 @item show remotelogbase
18444 Show the current setting of the radix for logging remote serial
18447 @item set remotelogfile @var{file}
18448 @cindex record serial communications on file
18449 Record remote serial communications on the named @var{file}. The
18450 default is not to record at all.
18452 @item show remotelogfile.
18453 Show the current setting of the file name on which to record the
18454 serial communications.
18456 @item set remotetimeout @var{num}
18457 @cindex timeout for serial communications
18458 @cindex remote timeout
18459 Set the timeout limit to wait for the remote target to respond to
18460 @var{num} seconds. The default is 2 seconds.
18462 @item show remotetimeout
18463 Show the current number of seconds to wait for the remote target
18466 @cindex limit hardware breakpoints and watchpoints
18467 @cindex remote target, limit break- and watchpoints
18468 @anchor{set remote hardware-watchpoint-limit}
18469 @anchor{set remote hardware-breakpoint-limit}
18470 @item set remote hardware-watchpoint-limit @var{limit}
18471 @itemx set remote hardware-breakpoint-limit @var{limit}
18472 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18473 watchpoints. A limit of -1, the default, is treated as unlimited.
18475 @cindex limit hardware watchpoints length
18476 @cindex remote target, limit watchpoints length
18477 @anchor{set remote hardware-watchpoint-length-limit}
18478 @item set remote hardware-watchpoint-length-limit @var{limit}
18479 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18480 a remote hardware watchpoint. A limit of -1, the default, is treated
18483 @item show remote hardware-watchpoint-length-limit
18484 Show the current limit (in bytes) of the maximum length of
18485 a remote hardware watchpoint.
18487 @item set remote exec-file @var{filename}
18488 @itemx show remote exec-file
18489 @anchor{set remote exec-file}
18490 @cindex executable file, for remote target
18491 Select the file used for @code{run} with @code{target
18492 extended-remote}. This should be set to a filename valid on the
18493 target system. If it is not set, the target will use a default
18494 filename (e.g.@: the last program run).
18496 @item set remote interrupt-sequence
18497 @cindex interrupt remote programs
18498 @cindex select Ctrl-C, BREAK or BREAK-g
18499 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18500 @samp{BREAK-g} as the
18501 sequence to the remote target in order to interrupt the execution.
18502 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18503 is high level of serial line for some certain time.
18504 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18505 It is @code{BREAK} signal followed by character @code{g}.
18507 @item show interrupt-sequence
18508 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18509 is sent by @value{GDBN} to interrupt the remote program.
18510 @code{BREAK-g} is BREAK signal followed by @code{g} and
18511 also known as Magic SysRq g.
18513 @item set remote interrupt-on-connect
18514 @cindex send interrupt-sequence on start
18515 Specify whether interrupt-sequence is sent to remote target when
18516 @value{GDBN} connects to it. This is mostly needed when you debug
18517 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18518 which is known as Magic SysRq g in order to connect @value{GDBN}.
18520 @item show interrupt-on-connect
18521 Show whether interrupt-sequence is sent
18522 to remote target when @value{GDBN} connects to it.
18526 @item set tcp auto-retry on
18527 @cindex auto-retry, for remote TCP target
18528 Enable auto-retry for remote TCP connections. This is useful if the remote
18529 debugging agent is launched in parallel with @value{GDBN}; there is a race
18530 condition because the agent may not become ready to accept the connection
18531 before @value{GDBN} attempts to connect. When auto-retry is
18532 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18533 to establish the connection using the timeout specified by
18534 @code{set tcp connect-timeout}.
18536 @item set tcp auto-retry off
18537 Do not auto-retry failed TCP connections.
18539 @item show tcp auto-retry
18540 Show the current auto-retry setting.
18542 @item set tcp connect-timeout @var{seconds}
18543 @itemx set tcp connect-timeout unlimited
18544 @cindex connection timeout, for remote TCP target
18545 @cindex timeout, for remote target connection
18546 Set the timeout for establishing a TCP connection to the remote target to
18547 @var{seconds}. The timeout affects both polling to retry failed connections
18548 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18549 that are merely slow to complete, and represents an approximate cumulative
18550 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18551 @value{GDBN} will keep attempting to establish a connection forever,
18552 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18554 @item show tcp connect-timeout
18555 Show the current connection timeout setting.
18558 @cindex remote packets, enabling and disabling
18559 The @value{GDBN} remote protocol autodetects the packets supported by
18560 your debugging stub. If you need to override the autodetection, you
18561 can use these commands to enable or disable individual packets. Each
18562 packet can be set to @samp{on} (the remote target supports this
18563 packet), @samp{off} (the remote target does not support this packet),
18564 or @samp{auto} (detect remote target support for this packet). They
18565 all default to @samp{auto}. For more information about each packet,
18566 see @ref{Remote Protocol}.
18568 During normal use, you should not have to use any of these commands.
18569 If you do, that may be a bug in your remote debugging stub, or a bug
18570 in @value{GDBN}. You may want to report the problem to the
18571 @value{GDBN} developers.
18573 For each packet @var{name}, the command to enable or disable the
18574 packet is @code{set remote @var{name}-packet}. The available settings
18577 @multitable @columnfractions 0.28 0.32 0.25
18580 @tab Related Features
18582 @item @code{fetch-register}
18584 @tab @code{info registers}
18586 @item @code{set-register}
18590 @item @code{binary-download}
18592 @tab @code{load}, @code{set}
18594 @item @code{read-aux-vector}
18595 @tab @code{qXfer:auxv:read}
18596 @tab @code{info auxv}
18598 @item @code{symbol-lookup}
18599 @tab @code{qSymbol}
18600 @tab Detecting multiple threads
18602 @item @code{attach}
18603 @tab @code{vAttach}
18606 @item @code{verbose-resume}
18608 @tab Stepping or resuming multiple threads
18614 @item @code{software-breakpoint}
18618 @item @code{hardware-breakpoint}
18622 @item @code{write-watchpoint}
18626 @item @code{read-watchpoint}
18630 @item @code{access-watchpoint}
18634 @item @code{target-features}
18635 @tab @code{qXfer:features:read}
18636 @tab @code{set architecture}
18638 @item @code{library-info}
18639 @tab @code{qXfer:libraries:read}
18640 @tab @code{info sharedlibrary}
18642 @item @code{memory-map}
18643 @tab @code{qXfer:memory-map:read}
18644 @tab @code{info mem}
18646 @item @code{read-sdata-object}
18647 @tab @code{qXfer:sdata:read}
18648 @tab @code{print $_sdata}
18650 @item @code{read-spu-object}
18651 @tab @code{qXfer:spu:read}
18652 @tab @code{info spu}
18654 @item @code{write-spu-object}
18655 @tab @code{qXfer:spu:write}
18656 @tab @code{info spu}
18658 @item @code{read-siginfo-object}
18659 @tab @code{qXfer:siginfo:read}
18660 @tab @code{print $_siginfo}
18662 @item @code{write-siginfo-object}
18663 @tab @code{qXfer:siginfo:write}
18664 @tab @code{set $_siginfo}
18666 @item @code{threads}
18667 @tab @code{qXfer:threads:read}
18668 @tab @code{info threads}
18670 @item @code{get-thread-local-@*storage-address}
18671 @tab @code{qGetTLSAddr}
18672 @tab Displaying @code{__thread} variables
18674 @item @code{get-thread-information-block-address}
18675 @tab @code{qGetTIBAddr}
18676 @tab Display MS-Windows Thread Information Block.
18678 @item @code{search-memory}
18679 @tab @code{qSearch:memory}
18682 @item @code{supported-packets}
18683 @tab @code{qSupported}
18684 @tab Remote communications parameters
18686 @item @code{pass-signals}
18687 @tab @code{QPassSignals}
18688 @tab @code{handle @var{signal}}
18690 @item @code{program-signals}
18691 @tab @code{QProgramSignals}
18692 @tab @code{handle @var{signal}}
18694 @item @code{hostio-close-packet}
18695 @tab @code{vFile:close}
18696 @tab @code{remote get}, @code{remote put}
18698 @item @code{hostio-open-packet}
18699 @tab @code{vFile:open}
18700 @tab @code{remote get}, @code{remote put}
18702 @item @code{hostio-pread-packet}
18703 @tab @code{vFile:pread}
18704 @tab @code{remote get}, @code{remote put}
18706 @item @code{hostio-pwrite-packet}
18707 @tab @code{vFile:pwrite}
18708 @tab @code{remote get}, @code{remote put}
18710 @item @code{hostio-unlink-packet}
18711 @tab @code{vFile:unlink}
18712 @tab @code{remote delete}
18714 @item @code{hostio-readlink-packet}
18715 @tab @code{vFile:readlink}
18718 @item @code{noack-packet}
18719 @tab @code{QStartNoAckMode}
18720 @tab Packet acknowledgment
18722 @item @code{osdata}
18723 @tab @code{qXfer:osdata:read}
18724 @tab @code{info os}
18726 @item @code{query-attached}
18727 @tab @code{qAttached}
18728 @tab Querying remote process attach state.
18730 @item @code{trace-buffer-size}
18731 @tab @code{QTBuffer:size}
18732 @tab @code{set trace-buffer-size}
18734 @item @code{trace-status}
18735 @tab @code{qTStatus}
18736 @tab @code{tstatus}
18738 @item @code{traceframe-info}
18739 @tab @code{qXfer:traceframe-info:read}
18740 @tab Traceframe info
18742 @item @code{install-in-trace}
18743 @tab @code{InstallInTrace}
18744 @tab Install tracepoint in tracing
18746 @item @code{disable-randomization}
18747 @tab @code{QDisableRandomization}
18748 @tab @code{set disable-randomization}
18750 @item @code{conditional-breakpoints-packet}
18751 @tab @code{Z0 and Z1}
18752 @tab @code{Support for target-side breakpoint condition evaluation}
18756 @section Implementing a Remote Stub
18758 @cindex debugging stub, example
18759 @cindex remote stub, example
18760 @cindex stub example, remote debugging
18761 The stub files provided with @value{GDBN} implement the target side of the
18762 communication protocol, and the @value{GDBN} side is implemented in the
18763 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18764 these subroutines to communicate, and ignore the details. (If you're
18765 implementing your own stub file, you can still ignore the details: start
18766 with one of the existing stub files. @file{sparc-stub.c} is the best
18767 organized, and therefore the easiest to read.)
18769 @cindex remote serial debugging, overview
18770 To debug a program running on another machine (the debugging
18771 @dfn{target} machine), you must first arrange for all the usual
18772 prerequisites for the program to run by itself. For example, for a C
18777 A startup routine to set up the C runtime environment; these usually
18778 have a name like @file{crt0}. The startup routine may be supplied by
18779 your hardware supplier, or you may have to write your own.
18782 A C subroutine library to support your program's
18783 subroutine calls, notably managing input and output.
18786 A way of getting your program to the other machine---for example, a
18787 download program. These are often supplied by the hardware
18788 manufacturer, but you may have to write your own from hardware
18792 The next step is to arrange for your program to use a serial port to
18793 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18794 machine). In general terms, the scheme looks like this:
18798 @value{GDBN} already understands how to use this protocol; when everything
18799 else is set up, you can simply use the @samp{target remote} command
18800 (@pxref{Targets,,Specifying a Debugging Target}).
18802 @item On the target,
18803 you must link with your program a few special-purpose subroutines that
18804 implement the @value{GDBN} remote serial protocol. The file containing these
18805 subroutines is called a @dfn{debugging stub}.
18807 On certain remote targets, you can use an auxiliary program
18808 @code{gdbserver} instead of linking a stub into your program.
18809 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18812 The debugging stub is specific to the architecture of the remote
18813 machine; for example, use @file{sparc-stub.c} to debug programs on
18816 @cindex remote serial stub list
18817 These working remote stubs are distributed with @value{GDBN}:
18822 @cindex @file{i386-stub.c}
18825 For Intel 386 and compatible architectures.
18828 @cindex @file{m68k-stub.c}
18829 @cindex Motorola 680x0
18831 For Motorola 680x0 architectures.
18834 @cindex @file{sh-stub.c}
18837 For Renesas SH architectures.
18840 @cindex @file{sparc-stub.c}
18842 For @sc{sparc} architectures.
18844 @item sparcl-stub.c
18845 @cindex @file{sparcl-stub.c}
18848 For Fujitsu @sc{sparclite} architectures.
18852 The @file{README} file in the @value{GDBN} distribution may list other
18853 recently added stubs.
18856 * Stub Contents:: What the stub can do for you
18857 * Bootstrapping:: What you must do for the stub
18858 * Debug Session:: Putting it all together
18861 @node Stub Contents
18862 @subsection What the Stub Can Do for You
18864 @cindex remote serial stub
18865 The debugging stub for your architecture supplies these three
18869 @item set_debug_traps
18870 @findex set_debug_traps
18871 @cindex remote serial stub, initialization
18872 This routine arranges for @code{handle_exception} to run when your
18873 program stops. You must call this subroutine explicitly in your
18874 program's startup code.
18876 @item handle_exception
18877 @findex handle_exception
18878 @cindex remote serial stub, main routine
18879 This is the central workhorse, but your program never calls it
18880 explicitly---the setup code arranges for @code{handle_exception} to
18881 run when a trap is triggered.
18883 @code{handle_exception} takes control when your program stops during
18884 execution (for example, on a breakpoint), and mediates communications
18885 with @value{GDBN} on the host machine. This is where the communications
18886 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18887 representative on the target machine. It begins by sending summary
18888 information on the state of your program, then continues to execute,
18889 retrieving and transmitting any information @value{GDBN} needs, until you
18890 execute a @value{GDBN} command that makes your program resume; at that point,
18891 @code{handle_exception} returns control to your own code on the target
18895 @cindex @code{breakpoint} subroutine, remote
18896 Use this auxiliary subroutine to make your program contain a
18897 breakpoint. Depending on the particular situation, this may be the only
18898 way for @value{GDBN} to get control. For instance, if your target
18899 machine has some sort of interrupt button, you won't need to call this;
18900 pressing the interrupt button transfers control to
18901 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18902 simply receiving characters on the serial port may also trigger a trap;
18903 again, in that situation, you don't need to call @code{breakpoint} from
18904 your own program---simply running @samp{target remote} from the host
18905 @value{GDBN} session gets control.
18907 Call @code{breakpoint} if none of these is true, or if you simply want
18908 to make certain your program stops at a predetermined point for the
18909 start of your debugging session.
18912 @node Bootstrapping
18913 @subsection What You Must Do for the Stub
18915 @cindex remote stub, support routines
18916 The debugging stubs that come with @value{GDBN} are set up for a particular
18917 chip architecture, but they have no information about the rest of your
18918 debugging target machine.
18920 First of all you need to tell the stub how to communicate with the
18924 @item int getDebugChar()
18925 @findex getDebugChar
18926 Write this subroutine to read a single character from the serial port.
18927 It may be identical to @code{getchar} for your target system; a
18928 different name is used to allow you to distinguish the two if you wish.
18930 @item void putDebugChar(int)
18931 @findex putDebugChar
18932 Write this subroutine to write a single character to the serial port.
18933 It may be identical to @code{putchar} for your target system; a
18934 different name is used to allow you to distinguish the two if you wish.
18937 @cindex control C, and remote debugging
18938 @cindex interrupting remote targets
18939 If you want @value{GDBN} to be able to stop your program while it is
18940 running, you need to use an interrupt-driven serial driver, and arrange
18941 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18942 character). That is the character which @value{GDBN} uses to tell the
18943 remote system to stop.
18945 Getting the debugging target to return the proper status to @value{GDBN}
18946 probably requires changes to the standard stub; one quick and dirty way
18947 is to just execute a breakpoint instruction (the ``dirty'' part is that
18948 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18950 Other routines you need to supply are:
18953 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18954 @findex exceptionHandler
18955 Write this function to install @var{exception_address} in the exception
18956 handling tables. You need to do this because the stub does not have any
18957 way of knowing what the exception handling tables on your target system
18958 are like (for example, the processor's table might be in @sc{rom},
18959 containing entries which point to a table in @sc{ram}).
18960 @var{exception_number} is the exception number which should be changed;
18961 its meaning is architecture-dependent (for example, different numbers
18962 might represent divide by zero, misaligned access, etc). When this
18963 exception occurs, control should be transferred directly to
18964 @var{exception_address}, and the processor state (stack, registers,
18965 and so on) should be just as it is when a processor exception occurs. So if
18966 you want to use a jump instruction to reach @var{exception_address}, it
18967 should be a simple jump, not a jump to subroutine.
18969 For the 386, @var{exception_address} should be installed as an interrupt
18970 gate so that interrupts are masked while the handler runs. The gate
18971 should be at privilege level 0 (the most privileged level). The
18972 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18973 help from @code{exceptionHandler}.
18975 @item void flush_i_cache()
18976 @findex flush_i_cache
18977 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18978 instruction cache, if any, on your target machine. If there is no
18979 instruction cache, this subroutine may be a no-op.
18981 On target machines that have instruction caches, @value{GDBN} requires this
18982 function to make certain that the state of your program is stable.
18986 You must also make sure this library routine is available:
18989 @item void *memset(void *, int, int)
18991 This is the standard library function @code{memset} that sets an area of
18992 memory to a known value. If you have one of the free versions of
18993 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18994 either obtain it from your hardware manufacturer, or write your own.
18997 If you do not use the GNU C compiler, you may need other standard
18998 library subroutines as well; this varies from one stub to another,
18999 but in general the stubs are likely to use any of the common library
19000 subroutines which @code{@value{NGCC}} generates as inline code.
19003 @node Debug Session
19004 @subsection Putting it All Together
19006 @cindex remote serial debugging summary
19007 In summary, when your program is ready to debug, you must follow these
19012 Make sure you have defined the supporting low-level routines
19013 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19015 @code{getDebugChar}, @code{putDebugChar},
19016 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19020 Insert these lines in your program's startup code, before the main
19021 procedure is called:
19028 On some machines, when a breakpoint trap is raised, the hardware
19029 automatically makes the PC point to the instruction after the
19030 breakpoint. If your machine doesn't do that, you may need to adjust
19031 @code{handle_exception} to arrange for it to return to the instruction
19032 after the breakpoint on this first invocation, so that your program
19033 doesn't keep hitting the initial breakpoint instead of making
19037 For the 680x0 stub only, you need to provide a variable called
19038 @code{exceptionHook}. Normally you just use:
19041 void (*exceptionHook)() = 0;
19045 but if before calling @code{set_debug_traps}, you set it to point to a
19046 function in your program, that function is called when
19047 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19048 error). The function indicated by @code{exceptionHook} is called with
19049 one parameter: an @code{int} which is the exception number.
19052 Compile and link together: your program, the @value{GDBN} debugging stub for
19053 your target architecture, and the supporting subroutines.
19056 Make sure you have a serial connection between your target machine and
19057 the @value{GDBN} host, and identify the serial port on the host.
19060 @c The "remote" target now provides a `load' command, so we should
19061 @c document that. FIXME.
19062 Download your program to your target machine (or get it there by
19063 whatever means the manufacturer provides), and start it.
19066 Start @value{GDBN} on the host, and connect to the target
19067 (@pxref{Connecting,,Connecting to a Remote Target}).
19071 @node Configurations
19072 @chapter Configuration-Specific Information
19074 While nearly all @value{GDBN} commands are available for all native and
19075 cross versions of the debugger, there are some exceptions. This chapter
19076 describes things that are only available in certain configurations.
19078 There are three major categories of configurations: native
19079 configurations, where the host and target are the same, embedded
19080 operating system configurations, which are usually the same for several
19081 different processor architectures, and bare embedded processors, which
19082 are quite different from each other.
19087 * Embedded Processors::
19094 This section describes details specific to particular native
19099 * BSD libkvm Interface:: Debugging BSD kernel memory images
19100 * SVR4 Process Information:: SVR4 process information
19101 * DJGPP Native:: Features specific to the DJGPP port
19102 * Cygwin Native:: Features specific to the Cygwin port
19103 * Hurd Native:: Features specific to @sc{gnu} Hurd
19104 * Darwin:: Features specific to Darwin
19110 On HP-UX systems, if you refer to a function or variable name that
19111 begins with a dollar sign, @value{GDBN} searches for a user or system
19112 name first, before it searches for a convenience variable.
19115 @node BSD libkvm Interface
19116 @subsection BSD libkvm Interface
19119 @cindex kernel memory image
19120 @cindex kernel crash dump
19122 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19123 interface that provides a uniform interface for accessing kernel virtual
19124 memory images, including live systems and crash dumps. @value{GDBN}
19125 uses this interface to allow you to debug live kernels and kernel crash
19126 dumps on many native BSD configurations. This is implemented as a
19127 special @code{kvm} debugging target. For debugging a live system, load
19128 the currently running kernel into @value{GDBN} and connect to the
19132 (@value{GDBP}) @b{target kvm}
19135 For debugging crash dumps, provide the file name of the crash dump as an
19139 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19142 Once connected to the @code{kvm} target, the following commands are
19148 Set current context from the @dfn{Process Control Block} (PCB) address.
19151 Set current context from proc address. This command isn't available on
19152 modern FreeBSD systems.
19155 @node SVR4 Process Information
19156 @subsection SVR4 Process Information
19158 @cindex examine process image
19159 @cindex process info via @file{/proc}
19161 Many versions of SVR4 and compatible systems provide a facility called
19162 @samp{/proc} that can be used to examine the image of a running
19163 process using file-system subroutines.
19165 If @value{GDBN} is configured for an operating system with this
19166 facility, the command @code{info proc} is available to report
19167 information about the process running your program, or about any
19168 process running on your system. This includes, as of this writing,
19169 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19170 not HP-UX, for example.
19172 This command may also work on core files that were created on a system
19173 that has the @samp{/proc} facility.
19179 @itemx info proc @var{process-id}
19180 Summarize available information about any running process. If a
19181 process ID is specified by @var{process-id}, display information about
19182 that process; otherwise display information about the program being
19183 debugged. The summary includes the debugged process ID, the command
19184 line used to invoke it, its current working directory, and its
19185 executable file's absolute file name.
19187 On some systems, @var{process-id} can be of the form
19188 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19189 within a process. If the optional @var{pid} part is missing, it means
19190 a thread from the process being debugged (the leading @samp{/} still
19191 needs to be present, or else @value{GDBN} will interpret the number as
19192 a process ID rather than a thread ID).
19194 @item info proc cmdline
19195 @cindex info proc cmdline
19196 Show the original command line of the process. This command is
19197 specific to @sc{gnu}/Linux.
19199 @item info proc cwd
19200 @cindex info proc cwd
19201 Show the current working directory of the process. This command is
19202 specific to @sc{gnu}/Linux.
19204 @item info proc exe
19205 @cindex info proc exe
19206 Show the name of executable of the process. This command is specific
19209 @item info proc mappings
19210 @cindex memory address space mappings
19211 Report the memory address space ranges accessible in the program, with
19212 information on whether the process has read, write, or execute access
19213 rights to each range. On @sc{gnu}/Linux systems, each memory range
19214 includes the object file which is mapped to that range, instead of the
19215 memory access rights to that range.
19217 @item info proc stat
19218 @itemx info proc status
19219 @cindex process detailed status information
19220 These subcommands are specific to @sc{gnu}/Linux systems. They show
19221 the process-related information, including the user ID and group ID;
19222 how many threads are there in the process; its virtual memory usage;
19223 the signals that are pending, blocked, and ignored; its TTY; its
19224 consumption of system and user time; its stack size; its @samp{nice}
19225 value; etc. For more information, see the @samp{proc} man page
19226 (type @kbd{man 5 proc} from your shell prompt).
19228 @item info proc all
19229 Show all the information about the process described under all of the
19230 above @code{info proc} subcommands.
19233 @comment These sub-options of 'info proc' were not included when
19234 @comment procfs.c was re-written. Keep their descriptions around
19235 @comment against the day when someone finds the time to put them back in.
19236 @kindex info proc times
19237 @item info proc times
19238 Starting time, user CPU time, and system CPU time for your program and
19241 @kindex info proc id
19243 Report on the process IDs related to your program: its own process ID,
19244 the ID of its parent, the process group ID, and the session ID.
19247 @item set procfs-trace
19248 @kindex set procfs-trace
19249 @cindex @code{procfs} API calls
19250 This command enables and disables tracing of @code{procfs} API calls.
19252 @item show procfs-trace
19253 @kindex show procfs-trace
19254 Show the current state of @code{procfs} API call tracing.
19256 @item set procfs-file @var{file}
19257 @kindex set procfs-file
19258 Tell @value{GDBN} to write @code{procfs} API trace to the named
19259 @var{file}. @value{GDBN} appends the trace info to the previous
19260 contents of the file. The default is to display the trace on the
19263 @item show procfs-file
19264 @kindex show procfs-file
19265 Show the file to which @code{procfs} API trace is written.
19267 @item proc-trace-entry
19268 @itemx proc-trace-exit
19269 @itemx proc-untrace-entry
19270 @itemx proc-untrace-exit
19271 @kindex proc-trace-entry
19272 @kindex proc-trace-exit
19273 @kindex proc-untrace-entry
19274 @kindex proc-untrace-exit
19275 These commands enable and disable tracing of entries into and exits
19276 from the @code{syscall} interface.
19279 @kindex info pidlist
19280 @cindex process list, QNX Neutrino
19281 For QNX Neutrino only, this command displays the list of all the
19282 processes and all the threads within each process.
19285 @kindex info meminfo
19286 @cindex mapinfo list, QNX Neutrino
19287 For QNX Neutrino only, this command displays the list of all mapinfos.
19291 @subsection Features for Debugging @sc{djgpp} Programs
19292 @cindex @sc{djgpp} debugging
19293 @cindex native @sc{djgpp} debugging
19294 @cindex MS-DOS-specific commands
19297 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19298 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19299 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19300 top of real-mode DOS systems and their emulations.
19302 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19303 defines a few commands specific to the @sc{djgpp} port. This
19304 subsection describes those commands.
19309 This is a prefix of @sc{djgpp}-specific commands which print
19310 information about the target system and important OS structures.
19313 @cindex MS-DOS system info
19314 @cindex free memory information (MS-DOS)
19315 @item info dos sysinfo
19316 This command displays assorted information about the underlying
19317 platform: the CPU type and features, the OS version and flavor, the
19318 DPMI version, and the available conventional and DPMI memory.
19323 @cindex segment descriptor tables
19324 @cindex descriptor tables display
19326 @itemx info dos ldt
19327 @itemx info dos idt
19328 These 3 commands display entries from, respectively, Global, Local,
19329 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19330 tables are data structures which store a descriptor for each segment
19331 that is currently in use. The segment's selector is an index into a
19332 descriptor table; the table entry for that index holds the
19333 descriptor's base address and limit, and its attributes and access
19336 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19337 segment (used for both data and the stack), and a DOS segment (which
19338 allows access to DOS/BIOS data structures and absolute addresses in
19339 conventional memory). However, the DPMI host will usually define
19340 additional segments in order to support the DPMI environment.
19342 @cindex garbled pointers
19343 These commands allow to display entries from the descriptor tables.
19344 Without an argument, all entries from the specified table are
19345 displayed. An argument, which should be an integer expression, means
19346 display a single entry whose index is given by the argument. For
19347 example, here's a convenient way to display information about the
19348 debugged program's data segment:
19351 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19352 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19356 This comes in handy when you want to see whether a pointer is outside
19357 the data segment's limit (i.e.@: @dfn{garbled}).
19359 @cindex page tables display (MS-DOS)
19361 @itemx info dos pte
19362 These two commands display entries from, respectively, the Page
19363 Directory and the Page Tables. Page Directories and Page Tables are
19364 data structures which control how virtual memory addresses are mapped
19365 into physical addresses. A Page Table includes an entry for every
19366 page of memory that is mapped into the program's address space; there
19367 may be several Page Tables, each one holding up to 4096 entries. A
19368 Page Directory has up to 4096 entries, one each for every Page Table
19369 that is currently in use.
19371 Without an argument, @kbd{info dos pde} displays the entire Page
19372 Directory, and @kbd{info dos pte} displays all the entries in all of
19373 the Page Tables. An argument, an integer expression, given to the
19374 @kbd{info dos pde} command means display only that entry from the Page
19375 Directory table. An argument given to the @kbd{info dos pte} command
19376 means display entries from a single Page Table, the one pointed to by
19377 the specified entry in the Page Directory.
19379 @cindex direct memory access (DMA) on MS-DOS
19380 These commands are useful when your program uses @dfn{DMA} (Direct
19381 Memory Access), which needs physical addresses to program the DMA
19384 These commands are supported only with some DPMI servers.
19386 @cindex physical address from linear address
19387 @item info dos address-pte @var{addr}
19388 This command displays the Page Table entry for a specified linear
19389 address. The argument @var{addr} is a linear address which should
19390 already have the appropriate segment's base address added to it,
19391 because this command accepts addresses which may belong to @emph{any}
19392 segment. For example, here's how to display the Page Table entry for
19393 the page where a variable @code{i} is stored:
19396 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19397 @exdent @code{Page Table entry for address 0x11a00d30:}
19398 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19402 This says that @code{i} is stored at offset @code{0xd30} from the page
19403 whose physical base address is @code{0x02698000}, and shows all the
19404 attributes of that page.
19406 Note that you must cast the addresses of variables to a @code{char *},
19407 since otherwise the value of @code{__djgpp_base_address}, the base
19408 address of all variables and functions in a @sc{djgpp} program, will
19409 be added using the rules of C pointer arithmetics: if @code{i} is
19410 declared an @code{int}, @value{GDBN} will add 4 times the value of
19411 @code{__djgpp_base_address} to the address of @code{i}.
19413 Here's another example, it displays the Page Table entry for the
19417 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19418 @exdent @code{Page Table entry for address 0x29110:}
19419 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19423 (The @code{+ 3} offset is because the transfer buffer's address is the
19424 3rd member of the @code{_go32_info_block} structure.) The output
19425 clearly shows that this DPMI server maps the addresses in conventional
19426 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19427 linear (@code{0x29110}) addresses are identical.
19429 This command is supported only with some DPMI servers.
19432 @cindex DOS serial data link, remote debugging
19433 In addition to native debugging, the DJGPP port supports remote
19434 debugging via a serial data link. The following commands are specific
19435 to remote serial debugging in the DJGPP port of @value{GDBN}.
19438 @kindex set com1base
19439 @kindex set com1irq
19440 @kindex set com2base
19441 @kindex set com2irq
19442 @kindex set com3base
19443 @kindex set com3irq
19444 @kindex set com4base
19445 @kindex set com4irq
19446 @item set com1base @var{addr}
19447 This command sets the base I/O port address of the @file{COM1} serial
19450 @item set com1irq @var{irq}
19451 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19452 for the @file{COM1} serial port.
19454 There are similar commands @samp{set com2base}, @samp{set com3irq},
19455 etc.@: for setting the port address and the @code{IRQ} lines for the
19458 @kindex show com1base
19459 @kindex show com1irq
19460 @kindex show com2base
19461 @kindex show com2irq
19462 @kindex show com3base
19463 @kindex show com3irq
19464 @kindex show com4base
19465 @kindex show com4irq
19466 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19467 display the current settings of the base address and the @code{IRQ}
19468 lines used by the COM ports.
19471 @kindex info serial
19472 @cindex DOS serial port status
19473 This command prints the status of the 4 DOS serial ports. For each
19474 port, it prints whether it's active or not, its I/O base address and
19475 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19476 counts of various errors encountered so far.
19480 @node Cygwin Native
19481 @subsection Features for Debugging MS Windows PE Executables
19482 @cindex MS Windows debugging
19483 @cindex native Cygwin debugging
19484 @cindex Cygwin-specific commands
19486 @value{GDBN} supports native debugging of MS Windows programs, including
19487 DLLs with and without symbolic debugging information.
19489 @cindex Ctrl-BREAK, MS-Windows
19490 @cindex interrupt debuggee on MS-Windows
19491 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19492 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19493 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19494 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19495 sequence, which can be used to interrupt the debuggee even if it
19498 There are various additional Cygwin-specific commands, described in
19499 this section. Working with DLLs that have no debugging symbols is
19500 described in @ref{Non-debug DLL Symbols}.
19505 This is a prefix of MS Windows-specific commands which print
19506 information about the target system and important OS structures.
19508 @item info w32 selector
19509 This command displays information returned by
19510 the Win32 API @code{GetThreadSelectorEntry} function.
19511 It takes an optional argument that is evaluated to
19512 a long value to give the information about this given selector.
19513 Without argument, this command displays information
19514 about the six segment registers.
19516 @item info w32 thread-information-block
19517 This command displays thread specific information stored in the
19518 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19519 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19523 This is a Cygwin-specific alias of @code{info shared}.
19525 @kindex dll-symbols
19527 This command loads symbols from a dll similarly to
19528 add-sym command but without the need to specify a base address.
19530 @kindex set cygwin-exceptions
19531 @cindex debugging the Cygwin DLL
19532 @cindex Cygwin DLL, debugging
19533 @item set cygwin-exceptions @var{mode}
19534 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19535 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19536 @value{GDBN} will delay recognition of exceptions, and may ignore some
19537 exceptions which seem to be caused by internal Cygwin DLL
19538 ``bookkeeping''. This option is meant primarily for debugging the
19539 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19540 @value{GDBN} users with false @code{SIGSEGV} signals.
19542 @kindex show cygwin-exceptions
19543 @item show cygwin-exceptions
19544 Displays whether @value{GDBN} will break on exceptions that happen
19545 inside the Cygwin DLL itself.
19547 @kindex set new-console
19548 @item set new-console @var{mode}
19549 If @var{mode} is @code{on} the debuggee will
19550 be started in a new console on next start.
19551 If @var{mode} is @code{off}, the debuggee will
19552 be started in the same console as the debugger.
19554 @kindex show new-console
19555 @item show new-console
19556 Displays whether a new console is used
19557 when the debuggee is started.
19559 @kindex set new-group
19560 @item set new-group @var{mode}
19561 This boolean value controls whether the debuggee should
19562 start a new group or stay in the same group as the debugger.
19563 This affects the way the Windows OS handles
19566 @kindex show new-group
19567 @item show new-group
19568 Displays current value of new-group boolean.
19570 @kindex set debugevents
19571 @item set debugevents
19572 This boolean value adds debug output concerning kernel events related
19573 to the debuggee seen by the debugger. This includes events that
19574 signal thread and process creation and exit, DLL loading and
19575 unloading, console interrupts, and debugging messages produced by the
19576 Windows @code{OutputDebugString} API call.
19578 @kindex set debugexec
19579 @item set debugexec
19580 This boolean value adds debug output concerning execute events
19581 (such as resume thread) seen by the debugger.
19583 @kindex set debugexceptions
19584 @item set debugexceptions
19585 This boolean value adds debug output concerning exceptions in the
19586 debuggee seen by the debugger.
19588 @kindex set debugmemory
19589 @item set debugmemory
19590 This boolean value adds debug output concerning debuggee memory reads
19591 and writes by the debugger.
19595 This boolean values specifies whether the debuggee is called
19596 via a shell or directly (default value is on).
19600 Displays if the debuggee will be started with a shell.
19605 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19608 @node Non-debug DLL Symbols
19609 @subsubsection Support for DLLs without Debugging Symbols
19610 @cindex DLLs with no debugging symbols
19611 @cindex Minimal symbols and DLLs
19613 Very often on windows, some of the DLLs that your program relies on do
19614 not include symbolic debugging information (for example,
19615 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19616 symbols in a DLL, it relies on the minimal amount of symbolic
19617 information contained in the DLL's export table. This section
19618 describes working with such symbols, known internally to @value{GDBN} as
19619 ``minimal symbols''.
19621 Note that before the debugged program has started execution, no DLLs
19622 will have been loaded. The easiest way around this problem is simply to
19623 start the program --- either by setting a breakpoint or letting the
19624 program run once to completion. It is also possible to force
19625 @value{GDBN} to load a particular DLL before starting the executable ---
19626 see the shared library information in @ref{Files}, or the
19627 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19628 explicitly loading symbols from a DLL with no debugging information will
19629 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19630 which may adversely affect symbol lookup performance.
19632 @subsubsection DLL Name Prefixes
19634 In keeping with the naming conventions used by the Microsoft debugging
19635 tools, DLL export symbols are made available with a prefix based on the
19636 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19637 also entered into the symbol table, so @code{CreateFileA} is often
19638 sufficient. In some cases there will be name clashes within a program
19639 (particularly if the executable itself includes full debugging symbols)
19640 necessitating the use of the fully qualified name when referring to the
19641 contents of the DLL. Use single-quotes around the name to avoid the
19642 exclamation mark (``!'') being interpreted as a language operator.
19644 Note that the internal name of the DLL may be all upper-case, even
19645 though the file name of the DLL is lower-case, or vice-versa. Since
19646 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19647 some confusion. If in doubt, try the @code{info functions} and
19648 @code{info variables} commands or even @code{maint print msymbols}
19649 (@pxref{Symbols}). Here's an example:
19652 (@value{GDBP}) info function CreateFileA
19653 All functions matching regular expression "CreateFileA":
19655 Non-debugging symbols:
19656 0x77e885f4 CreateFileA
19657 0x77e885f4 KERNEL32!CreateFileA
19661 (@value{GDBP}) info function !
19662 All functions matching regular expression "!":
19664 Non-debugging symbols:
19665 0x6100114c cygwin1!__assert
19666 0x61004034 cygwin1!_dll_crt0@@0
19667 0x61004240 cygwin1!dll_crt0(per_process *)
19671 @subsubsection Working with Minimal Symbols
19673 Symbols extracted from a DLL's export table do not contain very much
19674 type information. All that @value{GDBN} can do is guess whether a symbol
19675 refers to a function or variable depending on the linker section that
19676 contains the symbol. Also note that the actual contents of the memory
19677 contained in a DLL are not available unless the program is running. This
19678 means that you cannot examine the contents of a variable or disassemble
19679 a function within a DLL without a running program.
19681 Variables are generally treated as pointers and dereferenced
19682 automatically. For this reason, it is often necessary to prefix a
19683 variable name with the address-of operator (``&'') and provide explicit
19684 type information in the command. Here's an example of the type of
19688 (@value{GDBP}) print 'cygwin1!__argv'
19693 (@value{GDBP}) x 'cygwin1!__argv'
19694 0x10021610: "\230y\""
19697 And two possible solutions:
19700 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19701 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19705 (@value{GDBP}) x/2x &'cygwin1!__argv'
19706 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19707 (@value{GDBP}) x/x 0x10021608
19708 0x10021608: 0x0022fd98
19709 (@value{GDBP}) x/s 0x0022fd98
19710 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19713 Setting a break point within a DLL is possible even before the program
19714 starts execution. However, under these circumstances, @value{GDBN} can't
19715 examine the initial instructions of the function in order to skip the
19716 function's frame set-up code. You can work around this by using ``*&''
19717 to set the breakpoint at a raw memory address:
19720 (@value{GDBP}) break *&'python22!PyOS_Readline'
19721 Breakpoint 1 at 0x1e04eff0
19724 The author of these extensions is not entirely convinced that setting a
19725 break point within a shared DLL like @file{kernel32.dll} is completely
19729 @subsection Commands Specific to @sc{gnu} Hurd Systems
19730 @cindex @sc{gnu} Hurd debugging
19732 This subsection describes @value{GDBN} commands specific to the
19733 @sc{gnu} Hurd native debugging.
19738 @kindex set signals@r{, Hurd command}
19739 @kindex set sigs@r{, Hurd command}
19740 This command toggles the state of inferior signal interception by
19741 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19742 affected by this command. @code{sigs} is a shorthand alias for
19747 @kindex show signals@r{, Hurd command}
19748 @kindex show sigs@r{, Hurd command}
19749 Show the current state of intercepting inferior's signals.
19751 @item set signal-thread
19752 @itemx set sigthread
19753 @kindex set signal-thread
19754 @kindex set sigthread
19755 This command tells @value{GDBN} which thread is the @code{libc} signal
19756 thread. That thread is run when a signal is delivered to a running
19757 process. @code{set sigthread} is the shorthand alias of @code{set
19760 @item show signal-thread
19761 @itemx show sigthread
19762 @kindex show signal-thread
19763 @kindex show sigthread
19764 These two commands show which thread will run when the inferior is
19765 delivered a signal.
19768 @kindex set stopped@r{, Hurd command}
19769 This commands tells @value{GDBN} that the inferior process is stopped,
19770 as with the @code{SIGSTOP} signal. The stopped process can be
19771 continued by delivering a signal to it.
19774 @kindex show stopped@r{, Hurd command}
19775 This command shows whether @value{GDBN} thinks the debuggee is
19778 @item set exceptions
19779 @kindex set exceptions@r{, Hurd command}
19780 Use this command to turn off trapping of exceptions in the inferior.
19781 When exception trapping is off, neither breakpoints nor
19782 single-stepping will work. To restore the default, set exception
19785 @item show exceptions
19786 @kindex show exceptions@r{, Hurd command}
19787 Show the current state of trapping exceptions in the inferior.
19789 @item set task pause
19790 @kindex set task@r{, Hurd commands}
19791 @cindex task attributes (@sc{gnu} Hurd)
19792 @cindex pause current task (@sc{gnu} Hurd)
19793 This command toggles task suspension when @value{GDBN} has control.
19794 Setting it to on takes effect immediately, and the task is suspended
19795 whenever @value{GDBN} gets control. Setting it to off will take
19796 effect the next time the inferior is continued. If this option is set
19797 to off, you can use @code{set thread default pause on} or @code{set
19798 thread pause on} (see below) to pause individual threads.
19800 @item show task pause
19801 @kindex show task@r{, Hurd commands}
19802 Show the current state of task suspension.
19804 @item set task detach-suspend-count
19805 @cindex task suspend count
19806 @cindex detach from task, @sc{gnu} Hurd
19807 This command sets the suspend count the task will be left with when
19808 @value{GDBN} detaches from it.
19810 @item show task detach-suspend-count
19811 Show the suspend count the task will be left with when detaching.
19813 @item set task exception-port
19814 @itemx set task excp
19815 @cindex task exception port, @sc{gnu} Hurd
19816 This command sets the task exception port to which @value{GDBN} will
19817 forward exceptions. The argument should be the value of the @dfn{send
19818 rights} of the task. @code{set task excp} is a shorthand alias.
19820 @item set noninvasive
19821 @cindex noninvasive task options
19822 This command switches @value{GDBN} to a mode that is the least
19823 invasive as far as interfering with the inferior is concerned. This
19824 is the same as using @code{set task pause}, @code{set exceptions}, and
19825 @code{set signals} to values opposite to the defaults.
19827 @item info send-rights
19828 @itemx info receive-rights
19829 @itemx info port-rights
19830 @itemx info port-sets
19831 @itemx info dead-names
19834 @cindex send rights, @sc{gnu} Hurd
19835 @cindex receive rights, @sc{gnu} Hurd
19836 @cindex port rights, @sc{gnu} Hurd
19837 @cindex port sets, @sc{gnu} Hurd
19838 @cindex dead names, @sc{gnu} Hurd
19839 These commands display information about, respectively, send rights,
19840 receive rights, port rights, port sets, and dead names of a task.
19841 There are also shorthand aliases: @code{info ports} for @code{info
19842 port-rights} and @code{info psets} for @code{info port-sets}.
19844 @item set thread pause
19845 @kindex set thread@r{, Hurd command}
19846 @cindex thread properties, @sc{gnu} Hurd
19847 @cindex pause current thread (@sc{gnu} Hurd)
19848 This command toggles current thread suspension when @value{GDBN} has
19849 control. Setting it to on takes effect immediately, and the current
19850 thread is suspended whenever @value{GDBN} gets control. Setting it to
19851 off will take effect the next time the inferior is continued.
19852 Normally, this command has no effect, since when @value{GDBN} has
19853 control, the whole task is suspended. However, if you used @code{set
19854 task pause off} (see above), this command comes in handy to suspend
19855 only the current thread.
19857 @item show thread pause
19858 @kindex show thread@r{, Hurd command}
19859 This command shows the state of current thread suspension.
19861 @item set thread run
19862 This command sets whether the current thread is allowed to run.
19864 @item show thread run
19865 Show whether the current thread is allowed to run.
19867 @item set thread detach-suspend-count
19868 @cindex thread suspend count, @sc{gnu} Hurd
19869 @cindex detach from thread, @sc{gnu} Hurd
19870 This command sets the suspend count @value{GDBN} will leave on a
19871 thread when detaching. This number is relative to the suspend count
19872 found by @value{GDBN} when it notices the thread; use @code{set thread
19873 takeover-suspend-count} to force it to an absolute value.
19875 @item show thread detach-suspend-count
19876 Show the suspend count @value{GDBN} will leave on the thread when
19879 @item set thread exception-port
19880 @itemx set thread excp
19881 Set the thread exception port to which to forward exceptions. This
19882 overrides the port set by @code{set task exception-port} (see above).
19883 @code{set thread excp} is the shorthand alias.
19885 @item set thread takeover-suspend-count
19886 Normally, @value{GDBN}'s thread suspend counts are relative to the
19887 value @value{GDBN} finds when it notices each thread. This command
19888 changes the suspend counts to be absolute instead.
19890 @item set thread default
19891 @itemx show thread default
19892 @cindex thread default settings, @sc{gnu} Hurd
19893 Each of the above @code{set thread} commands has a @code{set thread
19894 default} counterpart (e.g., @code{set thread default pause}, @code{set
19895 thread default exception-port}, etc.). The @code{thread default}
19896 variety of commands sets the default thread properties for all
19897 threads; you can then change the properties of individual threads with
19898 the non-default commands.
19905 @value{GDBN} provides the following commands specific to the Darwin target:
19908 @item set debug darwin @var{num}
19909 @kindex set debug darwin
19910 When set to a non zero value, enables debugging messages specific to
19911 the Darwin support. Higher values produce more verbose output.
19913 @item show debug darwin
19914 @kindex show debug darwin
19915 Show the current state of Darwin messages.
19917 @item set debug mach-o @var{num}
19918 @kindex set debug mach-o
19919 When set to a non zero value, enables debugging messages while
19920 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19921 file format used on Darwin for object and executable files.) Higher
19922 values produce more verbose output. This is a command to diagnose
19923 problems internal to @value{GDBN} and should not be needed in normal
19926 @item show debug mach-o
19927 @kindex show debug mach-o
19928 Show the current state of Mach-O file messages.
19930 @item set mach-exceptions on
19931 @itemx set mach-exceptions off
19932 @kindex set mach-exceptions
19933 On Darwin, faults are first reported as a Mach exception and are then
19934 mapped to a Posix signal. Use this command to turn on trapping of
19935 Mach exceptions in the inferior. This might be sometimes useful to
19936 better understand the cause of a fault. The default is off.
19938 @item show mach-exceptions
19939 @kindex show mach-exceptions
19940 Show the current state of exceptions trapping.
19945 @section Embedded Operating Systems
19947 This section describes configurations involving the debugging of
19948 embedded operating systems that are available for several different
19952 * VxWorks:: Using @value{GDBN} with VxWorks
19955 @value{GDBN} includes the ability to debug programs running on
19956 various real-time operating systems.
19959 @subsection Using @value{GDBN} with VxWorks
19965 @kindex target vxworks
19966 @item target vxworks @var{machinename}
19967 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19968 is the target system's machine name or IP address.
19972 On VxWorks, @code{load} links @var{filename} dynamically on the
19973 current target system as well as adding its symbols in @value{GDBN}.
19975 @value{GDBN} enables developers to spawn and debug tasks running on networked
19976 VxWorks targets from a Unix host. Already-running tasks spawned from
19977 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19978 both the Unix host and on the VxWorks target. The program
19979 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19980 installed with the name @code{vxgdb}, to distinguish it from a
19981 @value{GDBN} for debugging programs on the host itself.)
19984 @item VxWorks-timeout @var{args}
19985 @kindex vxworks-timeout
19986 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19987 This option is set by the user, and @var{args} represents the number of
19988 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19989 your VxWorks target is a slow software simulator or is on the far side
19990 of a thin network line.
19993 The following information on connecting to VxWorks was current when
19994 this manual was produced; newer releases of VxWorks may use revised
19997 @findex INCLUDE_RDB
19998 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19999 to include the remote debugging interface routines in the VxWorks
20000 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20001 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20002 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20003 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20004 information on configuring and remaking VxWorks, see the manufacturer's
20006 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20008 Once you have included @file{rdb.a} in your VxWorks system image and set
20009 your Unix execution search path to find @value{GDBN}, you are ready to
20010 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20011 @code{vxgdb}, depending on your installation).
20013 @value{GDBN} comes up showing the prompt:
20020 * VxWorks Connection:: Connecting to VxWorks
20021 * VxWorks Download:: VxWorks download
20022 * VxWorks Attach:: Running tasks
20025 @node VxWorks Connection
20026 @subsubsection Connecting to VxWorks
20028 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20029 network. To connect to a target whose host name is ``@code{tt}'', type:
20032 (vxgdb) target vxworks tt
20036 @value{GDBN} displays messages like these:
20039 Attaching remote machine across net...
20044 @value{GDBN} then attempts to read the symbol tables of any object modules
20045 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20046 these files by searching the directories listed in the command search
20047 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20048 to find an object file, it displays a message such as:
20051 prog.o: No such file or directory.
20054 When this happens, add the appropriate directory to the search path with
20055 the @value{GDBN} command @code{path}, and execute the @code{target}
20058 @node VxWorks Download
20059 @subsubsection VxWorks Download
20061 @cindex download to VxWorks
20062 If you have connected to the VxWorks target and you want to debug an
20063 object that has not yet been loaded, you can use the @value{GDBN}
20064 @code{load} command to download a file from Unix to VxWorks
20065 incrementally. The object file given as an argument to the @code{load}
20066 command is actually opened twice: first by the VxWorks target in order
20067 to download the code, then by @value{GDBN} in order to read the symbol
20068 table. This can lead to problems if the current working directories on
20069 the two systems differ. If both systems have NFS mounted the same
20070 filesystems, you can avoid these problems by using absolute paths.
20071 Otherwise, it is simplest to set the working directory on both systems
20072 to the directory in which the object file resides, and then to reference
20073 the file by its name, without any path. For instance, a program
20074 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20075 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20076 program, type this on VxWorks:
20079 -> cd "@var{vxpath}/vw/demo/rdb"
20083 Then, in @value{GDBN}, type:
20086 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20087 (vxgdb) load prog.o
20090 @value{GDBN} displays a response similar to this:
20093 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20096 You can also use the @code{load} command to reload an object module
20097 after editing and recompiling the corresponding source file. Note that
20098 this makes @value{GDBN} delete all currently-defined breakpoints,
20099 auto-displays, and convenience variables, and to clear the value
20100 history. (This is necessary in order to preserve the integrity of
20101 debugger's data structures that reference the target system's symbol
20104 @node VxWorks Attach
20105 @subsubsection Running Tasks
20107 @cindex running VxWorks tasks
20108 You can also attach to an existing task using the @code{attach} command as
20112 (vxgdb) attach @var{task}
20116 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20117 or suspended when you attach to it. Running tasks are suspended at
20118 the time of attachment.
20120 @node Embedded Processors
20121 @section Embedded Processors
20123 This section goes into details specific to particular embedded
20126 @cindex send command to simulator
20127 Whenever a specific embedded processor has a simulator, @value{GDBN}
20128 allows to send an arbitrary command to the simulator.
20131 @item sim @var{command}
20132 @kindex sim@r{, a command}
20133 Send an arbitrary @var{command} string to the simulator. Consult the
20134 documentation for the specific simulator in use for information about
20135 acceptable commands.
20141 * M32R/D:: Renesas M32R/D
20142 * M68K:: Motorola M68K
20143 * MicroBlaze:: Xilinx MicroBlaze
20144 * MIPS Embedded:: MIPS Embedded
20145 * PowerPC Embedded:: PowerPC Embedded
20146 * PA:: HP PA Embedded
20147 * Sparclet:: Tsqware Sparclet
20148 * Sparclite:: Fujitsu Sparclite
20149 * Z8000:: Zilog Z8000
20152 * Super-H:: Renesas Super-H
20161 @item target rdi @var{dev}
20162 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20163 use this target to communicate with both boards running the Angel
20164 monitor, or with the EmbeddedICE JTAG debug device.
20167 @item target rdp @var{dev}
20172 @value{GDBN} provides the following ARM-specific commands:
20175 @item set arm disassembler
20177 This commands selects from a list of disassembly styles. The
20178 @code{"std"} style is the standard style.
20180 @item show arm disassembler
20182 Show the current disassembly style.
20184 @item set arm apcs32
20185 @cindex ARM 32-bit mode
20186 This command toggles ARM operation mode between 32-bit and 26-bit.
20188 @item show arm apcs32
20189 Display the current usage of the ARM 32-bit mode.
20191 @item set arm fpu @var{fputype}
20192 This command sets the ARM floating-point unit (FPU) type. The
20193 argument @var{fputype} can be one of these:
20197 Determine the FPU type by querying the OS ABI.
20199 Software FPU, with mixed-endian doubles on little-endian ARM
20202 GCC-compiled FPA co-processor.
20204 Software FPU with pure-endian doubles.
20210 Show the current type of the FPU.
20213 This command forces @value{GDBN} to use the specified ABI.
20216 Show the currently used ABI.
20218 @item set arm fallback-mode (arm|thumb|auto)
20219 @value{GDBN} uses the symbol table, when available, to determine
20220 whether instructions are ARM or Thumb. This command controls
20221 @value{GDBN}'s default behavior when the symbol table is not
20222 available. The default is @samp{auto}, which causes @value{GDBN} to
20223 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20226 @item show arm fallback-mode
20227 Show the current fallback instruction mode.
20229 @item set arm force-mode (arm|thumb|auto)
20230 This command overrides use of the symbol table to determine whether
20231 instructions are ARM or Thumb. The default is @samp{auto}, which
20232 causes @value{GDBN} to use the symbol table and then the setting
20233 of @samp{set arm fallback-mode}.
20235 @item show arm force-mode
20236 Show the current forced instruction mode.
20238 @item set debug arm
20239 Toggle whether to display ARM-specific debugging messages from the ARM
20240 target support subsystem.
20242 @item show debug arm
20243 Show whether ARM-specific debugging messages are enabled.
20246 The following commands are available when an ARM target is debugged
20247 using the RDI interface:
20250 @item rdilogfile @r{[}@var{file}@r{]}
20252 @cindex ADP (Angel Debugger Protocol) logging
20253 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20254 With an argument, sets the log file to the specified @var{file}. With
20255 no argument, show the current log file name. The default log file is
20258 @item rdilogenable @r{[}@var{arg}@r{]}
20259 @kindex rdilogenable
20260 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20261 enables logging, with an argument 0 or @code{"no"} disables it. With
20262 no arguments displays the current setting. When logging is enabled,
20263 ADP packets exchanged between @value{GDBN} and the RDI target device
20264 are logged to a file.
20266 @item set rdiromatzero
20267 @kindex set rdiromatzero
20268 @cindex ROM at zero address, RDI
20269 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20270 vector catching is disabled, so that zero address can be used. If off
20271 (the default), vector catching is enabled. For this command to take
20272 effect, it needs to be invoked prior to the @code{target rdi} command.
20274 @item show rdiromatzero
20275 @kindex show rdiromatzero
20276 Show the current setting of ROM at zero address.
20278 @item set rdiheartbeat
20279 @kindex set rdiheartbeat
20280 @cindex RDI heartbeat
20281 Enable or disable RDI heartbeat packets. It is not recommended to
20282 turn on this option, since it confuses ARM and EPI JTAG interface, as
20283 well as the Angel monitor.
20285 @item show rdiheartbeat
20286 @kindex show rdiheartbeat
20287 Show the setting of RDI heartbeat packets.
20291 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20292 The @value{GDBN} ARM simulator accepts the following optional arguments.
20295 @item --swi-support=@var{type}
20296 Tell the simulator which SWI interfaces to support.
20297 @var{type} may be a comma separated list of the following values.
20298 The default value is @code{all}.
20311 @subsection Renesas M32R/D and M32R/SDI
20314 @kindex target m32r
20315 @item target m32r @var{dev}
20316 Renesas M32R/D ROM monitor.
20318 @kindex target m32rsdi
20319 @item target m32rsdi @var{dev}
20320 Renesas M32R SDI server, connected via parallel port to the board.
20323 The following @value{GDBN} commands are specific to the M32R monitor:
20326 @item set download-path @var{path}
20327 @kindex set download-path
20328 @cindex find downloadable @sc{srec} files (M32R)
20329 Set the default path for finding downloadable @sc{srec} files.
20331 @item show download-path
20332 @kindex show download-path
20333 Show the default path for downloadable @sc{srec} files.
20335 @item set board-address @var{addr}
20336 @kindex set board-address
20337 @cindex M32-EVA target board address
20338 Set the IP address for the M32R-EVA target board.
20340 @item show board-address
20341 @kindex show board-address
20342 Show the current IP address of the target board.
20344 @item set server-address @var{addr}
20345 @kindex set server-address
20346 @cindex download server address (M32R)
20347 Set the IP address for the download server, which is the @value{GDBN}'s
20350 @item show server-address
20351 @kindex show server-address
20352 Display the IP address of the download server.
20354 @item upload @r{[}@var{file}@r{]}
20355 @kindex upload@r{, M32R}
20356 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20357 upload capability. If no @var{file} argument is given, the current
20358 executable file is uploaded.
20360 @item tload @r{[}@var{file}@r{]}
20361 @kindex tload@r{, M32R}
20362 Test the @code{upload} command.
20365 The following commands are available for M32R/SDI:
20370 @cindex reset SDI connection, M32R
20371 This command resets the SDI connection.
20375 This command shows the SDI connection status.
20378 @kindex debug_chaos
20379 @cindex M32R/Chaos debugging
20380 Instructs the remote that M32R/Chaos debugging is to be used.
20382 @item use_debug_dma
20383 @kindex use_debug_dma
20384 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20387 @kindex use_mon_code
20388 Instructs the remote to use the MON_CODE method of accessing memory.
20391 @kindex use_ib_break
20392 Instructs the remote to set breakpoints by IB break.
20394 @item use_dbt_break
20395 @kindex use_dbt_break
20396 Instructs the remote to set breakpoints by DBT.
20402 The Motorola m68k configuration includes ColdFire support, and a
20403 target command for the following ROM monitor.
20407 @kindex target dbug
20408 @item target dbug @var{dev}
20409 dBUG ROM monitor for Motorola ColdFire.
20414 @subsection MicroBlaze
20415 @cindex Xilinx MicroBlaze
20416 @cindex XMD, Xilinx Microprocessor Debugger
20418 The MicroBlaze is a soft-core processor supported on various Xilinx
20419 FPGAs, such as Spartan or Virtex series. Boards with these processors
20420 usually have JTAG ports which connect to a host system running the Xilinx
20421 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20422 This host system is used to download the configuration bitstream to
20423 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20424 communicates with the target board using the JTAG interface and
20425 presents a @code{gdbserver} interface to the board. By default
20426 @code{xmd} uses port @code{1234}. (While it is possible to change
20427 this default port, it requires the use of undocumented @code{xmd}
20428 commands. Contact Xilinx support if you need to do this.)
20430 Use these GDB commands to connect to the MicroBlaze target processor.
20433 @item target remote :1234
20434 Use this command to connect to the target if you are running @value{GDBN}
20435 on the same system as @code{xmd}.
20437 @item target remote @var{xmd-host}:1234
20438 Use this command to connect to the target if it is connected to @code{xmd}
20439 running on a different system named @var{xmd-host}.
20442 Use this command to download a program to the MicroBlaze target.
20444 @item set debug microblaze @var{n}
20445 Enable MicroBlaze-specific debugging messages if non-zero.
20447 @item show debug microblaze @var{n}
20448 Show MicroBlaze-specific debugging level.
20451 @node MIPS Embedded
20452 @subsection @acronym{MIPS} Embedded
20454 @cindex @acronym{MIPS} boards
20455 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20456 @acronym{MIPS} board attached to a serial line. This is available when
20457 you configure @value{GDBN} with @samp{--target=mips-elf}.
20460 Use these @value{GDBN} commands to specify the connection to your target board:
20463 @item target mips @var{port}
20464 @kindex target mips @var{port}
20465 To run a program on the board, start up @code{@value{GDBP}} with the
20466 name of your program as the argument. To connect to the board, use the
20467 command @samp{target mips @var{port}}, where @var{port} is the name of
20468 the serial port connected to the board. If the program has not already
20469 been downloaded to the board, you may use the @code{load} command to
20470 download it. You can then use all the usual @value{GDBN} commands.
20472 For example, this sequence connects to the target board through a serial
20473 port, and loads and runs a program called @var{prog} through the
20477 host$ @value{GDBP} @var{prog}
20478 @value{GDBN} is free software and @dots{}
20479 (@value{GDBP}) target mips /dev/ttyb
20480 (@value{GDBP}) load @var{prog}
20484 @item target mips @var{hostname}:@var{portnumber}
20485 On some @value{GDBN} host configurations, you can specify a TCP
20486 connection (for instance, to a serial line managed by a terminal
20487 concentrator) instead of a serial port, using the syntax
20488 @samp{@var{hostname}:@var{portnumber}}.
20490 @item target pmon @var{port}
20491 @kindex target pmon @var{port}
20494 @item target ddb @var{port}
20495 @kindex target ddb @var{port}
20496 NEC's DDB variant of PMON for Vr4300.
20498 @item target lsi @var{port}
20499 @kindex target lsi @var{port}
20500 LSI variant of PMON.
20502 @kindex target r3900
20503 @item target r3900 @var{dev}
20504 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20506 @kindex target array
20507 @item target array @var{dev}
20508 Array Tech LSI33K RAID controller board.
20514 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20517 @item set mipsfpu double
20518 @itemx set mipsfpu single
20519 @itemx set mipsfpu none
20520 @itemx set mipsfpu auto
20521 @itemx show mipsfpu
20522 @kindex set mipsfpu
20523 @kindex show mipsfpu
20524 @cindex @acronym{MIPS} remote floating point
20525 @cindex floating point, @acronym{MIPS} remote
20526 If your target board does not support the @acronym{MIPS} floating point
20527 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20528 need this, you may wish to put the command in your @value{GDBN} init
20529 file). This tells @value{GDBN} how to find the return value of
20530 functions which return floating point values. It also allows
20531 @value{GDBN} to avoid saving the floating point registers when calling
20532 functions on the board. If you are using a floating point coprocessor
20533 with only single precision floating point support, as on the @sc{r4650}
20534 processor, use the command @samp{set mipsfpu single}. The default
20535 double precision floating point coprocessor may be selected using
20536 @samp{set mipsfpu double}.
20538 In previous versions the only choices were double precision or no
20539 floating point, so @samp{set mipsfpu on} will select double precision
20540 and @samp{set mipsfpu off} will select no floating point.
20542 As usual, you can inquire about the @code{mipsfpu} variable with
20543 @samp{show mipsfpu}.
20545 @item set timeout @var{seconds}
20546 @itemx set retransmit-timeout @var{seconds}
20547 @itemx show timeout
20548 @itemx show retransmit-timeout
20549 @cindex @code{timeout}, @acronym{MIPS} protocol
20550 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20551 @kindex set timeout
20552 @kindex show timeout
20553 @kindex set retransmit-timeout
20554 @kindex show retransmit-timeout
20555 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20556 remote protocol, with the @code{set timeout @var{seconds}} command. The
20557 default is 5 seconds. Similarly, you can control the timeout used while
20558 waiting for an acknowledgment of a packet with the @code{set
20559 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20560 You can inspect both values with @code{show timeout} and @code{show
20561 retransmit-timeout}. (These commands are @emph{only} available when
20562 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20564 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20565 is waiting for your program to stop. In that case, @value{GDBN} waits
20566 forever because it has no way of knowing how long the program is going
20567 to run before stopping.
20569 @item set syn-garbage-limit @var{num}
20570 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20571 @cindex synchronize with remote @acronym{MIPS} target
20572 Limit the maximum number of characters @value{GDBN} should ignore when
20573 it tries to synchronize with the remote target. The default is 10
20574 characters. Setting the limit to -1 means there's no limit.
20576 @item show syn-garbage-limit
20577 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20578 Show the current limit on the number of characters to ignore when
20579 trying to synchronize with the remote system.
20581 @item set monitor-prompt @var{prompt}
20582 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20583 @cindex remote monitor prompt
20584 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20585 remote monitor. The default depends on the target:
20595 @item show monitor-prompt
20596 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20597 Show the current strings @value{GDBN} expects as the prompt from the
20600 @item set monitor-warnings
20601 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20602 Enable or disable monitor warnings about hardware breakpoints. This
20603 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20604 display warning messages whose codes are returned by the @code{lsi}
20605 PMON monitor for breakpoint commands.
20607 @item show monitor-warnings
20608 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20609 Show the current setting of printing monitor warnings.
20611 @item pmon @var{command}
20612 @kindex pmon@r{, @acronym{MIPS} remote}
20613 @cindex send PMON command
20614 This command allows sending an arbitrary @var{command} string to the
20615 monitor. The monitor must be in debug mode for this to work.
20618 @node PowerPC Embedded
20619 @subsection PowerPC Embedded
20621 @cindex DVC register
20622 @value{GDBN} supports using the DVC (Data Value Compare) register to
20623 implement in hardware simple hardware watchpoint conditions of the form:
20626 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20627 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20630 The DVC register will be automatically used when @value{GDBN} detects
20631 such pattern in a condition expression, and the created watchpoint uses one
20632 debug register (either the @code{exact-watchpoints} option is on and the
20633 variable is scalar, or the variable has a length of one byte). This feature
20634 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20637 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20638 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20639 in which case watchpoints using only one debug register are created when
20640 watching variables of scalar types.
20642 You can create an artificial array to watch an arbitrary memory
20643 region using one of the following commands (@pxref{Expressions}):
20646 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20647 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20650 PowerPC embedded processors support masked watchpoints. See the discussion
20651 about the @code{mask} argument in @ref{Set Watchpoints}.
20653 @cindex ranged breakpoint
20654 PowerPC embedded processors support hardware accelerated
20655 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20656 the inferior whenever it executes an instruction at any address within
20657 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20658 use the @code{break-range} command.
20660 @value{GDBN} provides the following PowerPC-specific commands:
20663 @kindex break-range
20664 @item break-range @var{start-location}, @var{end-location}
20665 Set a breakpoint for an address range.
20666 @var{start-location} and @var{end-location} can specify a function name,
20667 a line number, an offset of lines from the current line or from the start
20668 location, or an address of an instruction (see @ref{Specify Location},
20669 for a list of all the possible ways to specify a @var{location}.)
20670 The breakpoint will stop execution of the inferior whenever it
20671 executes an instruction at any address within the specified range,
20672 (including @var{start-location} and @var{end-location}.)
20674 @kindex set powerpc
20675 @item set powerpc soft-float
20676 @itemx show powerpc soft-float
20677 Force @value{GDBN} to use (or not use) a software floating point calling
20678 convention. By default, @value{GDBN} selects the calling convention based
20679 on the selected architecture and the provided executable file.
20681 @item set powerpc vector-abi
20682 @itemx show powerpc vector-abi
20683 Force @value{GDBN} to use the specified calling convention for vector
20684 arguments and return values. The valid options are @samp{auto};
20685 @samp{generic}, to avoid vector registers even if they are present;
20686 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20687 registers. By default, @value{GDBN} selects the calling convention
20688 based on the selected architecture and the provided executable file.
20690 @item set powerpc exact-watchpoints
20691 @itemx show powerpc exact-watchpoints
20692 Allow @value{GDBN} to use only one debug register when watching a variable
20693 of scalar type, thus assuming that the variable is accessed through the
20694 address of its first byte.
20696 @kindex target dink32
20697 @item target dink32 @var{dev}
20698 DINK32 ROM monitor.
20700 @kindex target ppcbug
20701 @item target ppcbug @var{dev}
20702 @kindex target ppcbug1
20703 @item target ppcbug1 @var{dev}
20704 PPCBUG ROM monitor for PowerPC.
20707 @item target sds @var{dev}
20708 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20711 @cindex SDS protocol
20712 The following commands specific to the SDS protocol are supported
20716 @item set sdstimeout @var{nsec}
20717 @kindex set sdstimeout
20718 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20719 default is 2 seconds.
20721 @item show sdstimeout
20722 @kindex show sdstimeout
20723 Show the current value of the SDS timeout.
20725 @item sds @var{command}
20726 @kindex sds@r{, a command}
20727 Send the specified @var{command} string to the SDS monitor.
20732 @subsection HP PA Embedded
20736 @kindex target op50n
20737 @item target op50n @var{dev}
20738 OP50N monitor, running on an OKI HPPA board.
20740 @kindex target w89k
20741 @item target w89k @var{dev}
20742 W89K monitor, running on a Winbond HPPA board.
20747 @subsection Tsqware Sparclet
20751 @value{GDBN} enables developers to debug tasks running on
20752 Sparclet targets from a Unix host.
20753 @value{GDBN} uses code that runs on
20754 both the Unix host and on the Sparclet target. The program
20755 @code{@value{GDBP}} is installed and executed on the Unix host.
20758 @item remotetimeout @var{args}
20759 @kindex remotetimeout
20760 @value{GDBN} supports the option @code{remotetimeout}.
20761 This option is set by the user, and @var{args} represents the number of
20762 seconds @value{GDBN} waits for responses.
20765 @cindex compiling, on Sparclet
20766 When compiling for debugging, include the options @samp{-g} to get debug
20767 information and @samp{-Ttext} to relocate the program to where you wish to
20768 load it on the target. You may also want to add the options @samp{-n} or
20769 @samp{-N} in order to reduce the size of the sections. Example:
20772 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20775 You can use @code{objdump} to verify that the addresses are what you intended:
20778 sparclet-aout-objdump --headers --syms prog
20781 @cindex running, on Sparclet
20783 your Unix execution search path to find @value{GDBN}, you are ready to
20784 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20785 (or @code{sparclet-aout-gdb}, depending on your installation).
20787 @value{GDBN} comes up showing the prompt:
20794 * Sparclet File:: Setting the file to debug
20795 * Sparclet Connection:: Connecting to Sparclet
20796 * Sparclet Download:: Sparclet download
20797 * Sparclet Execution:: Running and debugging
20800 @node Sparclet File
20801 @subsubsection Setting File to Debug
20803 The @value{GDBN} command @code{file} lets you choose with program to debug.
20806 (gdbslet) file prog
20810 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20811 @value{GDBN} locates
20812 the file by searching the directories listed in the command search
20814 If the file was compiled with debug information (option @samp{-g}), source
20815 files will be searched as well.
20816 @value{GDBN} locates
20817 the source files by searching the directories listed in the directory search
20818 path (@pxref{Environment, ,Your Program's Environment}).
20820 to find a file, it displays a message such as:
20823 prog: No such file or directory.
20826 When this happens, add the appropriate directories to the search paths with
20827 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20828 @code{target} command again.
20830 @node Sparclet Connection
20831 @subsubsection Connecting to Sparclet
20833 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20834 To connect to a target on serial port ``@code{ttya}'', type:
20837 (gdbslet) target sparclet /dev/ttya
20838 Remote target sparclet connected to /dev/ttya
20839 main () at ../prog.c:3
20843 @value{GDBN} displays messages like these:
20849 @node Sparclet Download
20850 @subsubsection Sparclet Download
20852 @cindex download to Sparclet
20853 Once connected to the Sparclet target,
20854 you can use the @value{GDBN}
20855 @code{load} command to download the file from the host to the target.
20856 The file name and load offset should be given as arguments to the @code{load}
20858 Since the file format is aout, the program must be loaded to the starting
20859 address. You can use @code{objdump} to find out what this value is. The load
20860 offset is an offset which is added to the VMA (virtual memory address)
20861 of each of the file's sections.
20862 For instance, if the program
20863 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20864 and bss at 0x12010170, in @value{GDBN}, type:
20867 (gdbslet) load prog 0x12010000
20868 Loading section .text, size 0xdb0 vma 0x12010000
20871 If the code is loaded at a different address then what the program was linked
20872 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20873 to tell @value{GDBN} where to map the symbol table.
20875 @node Sparclet Execution
20876 @subsubsection Running and Debugging
20878 @cindex running and debugging Sparclet programs
20879 You can now begin debugging the task using @value{GDBN}'s execution control
20880 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20881 manual for the list of commands.
20885 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20887 Starting program: prog
20888 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20889 3 char *symarg = 0;
20891 4 char *execarg = "hello!";
20896 @subsection Fujitsu Sparclite
20900 @kindex target sparclite
20901 @item target sparclite @var{dev}
20902 Fujitsu sparclite boards, used only for the purpose of loading.
20903 You must use an additional command to debug the program.
20904 For example: target remote @var{dev} using @value{GDBN} standard
20910 @subsection Zilog Z8000
20913 @cindex simulator, Z8000
20914 @cindex Zilog Z8000 simulator
20916 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20919 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20920 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20921 segmented variant). The simulator recognizes which architecture is
20922 appropriate by inspecting the object code.
20925 @item target sim @var{args}
20927 @kindex target sim@r{, with Z8000}
20928 Debug programs on a simulated CPU. If the simulator supports setup
20929 options, specify them via @var{args}.
20933 After specifying this target, you can debug programs for the simulated
20934 CPU in the same style as programs for your host computer; use the
20935 @code{file} command to load a new program image, the @code{run} command
20936 to run your program, and so on.
20938 As well as making available all the usual machine registers
20939 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20940 additional items of information as specially named registers:
20945 Counts clock-ticks in the simulator.
20948 Counts instructions run in the simulator.
20951 Execution time in 60ths of a second.
20955 You can refer to these values in @value{GDBN} expressions with the usual
20956 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20957 conditional breakpoint that suspends only after at least 5000
20958 simulated clock ticks.
20961 @subsection Atmel AVR
20964 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20965 following AVR-specific commands:
20968 @item info io_registers
20969 @kindex info io_registers@r{, AVR}
20970 @cindex I/O registers (Atmel AVR)
20971 This command displays information about the AVR I/O registers. For
20972 each register, @value{GDBN} prints its number and value.
20979 When configured for debugging CRIS, @value{GDBN} provides the
20980 following CRIS-specific commands:
20983 @item set cris-version @var{ver}
20984 @cindex CRIS version
20985 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20986 The CRIS version affects register names and sizes. This command is useful in
20987 case autodetection of the CRIS version fails.
20989 @item show cris-version
20990 Show the current CRIS version.
20992 @item set cris-dwarf2-cfi
20993 @cindex DWARF-2 CFI and CRIS
20994 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20995 Change to @samp{off} when using @code{gcc-cris} whose version is below
20998 @item show cris-dwarf2-cfi
20999 Show the current state of using DWARF-2 CFI.
21001 @item set cris-mode @var{mode}
21003 Set the current CRIS mode to @var{mode}. It should only be changed when
21004 debugging in guru mode, in which case it should be set to
21005 @samp{guru} (the default is @samp{normal}).
21007 @item show cris-mode
21008 Show the current CRIS mode.
21012 @subsection Renesas Super-H
21015 For the Renesas Super-H processor, @value{GDBN} provides these
21019 @item set sh calling-convention @var{convention}
21020 @kindex set sh calling-convention
21021 Set the calling-convention used when calling functions from @value{GDBN}.
21022 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21023 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21024 convention. If the DWARF-2 information of the called function specifies
21025 that the function follows the Renesas calling convention, the function
21026 is called using the Renesas calling convention. If the calling convention
21027 is set to @samp{renesas}, the Renesas calling convention is always used,
21028 regardless of the DWARF-2 information. This can be used to override the
21029 default of @samp{gcc} if debug information is missing, or the compiler
21030 does not emit the DWARF-2 calling convention entry for a function.
21032 @item show sh calling-convention
21033 @kindex show sh calling-convention
21034 Show the current calling convention setting.
21039 @node Architectures
21040 @section Architectures
21042 This section describes characteristics of architectures that affect
21043 all uses of @value{GDBN} with the architecture, both native and cross.
21050 * HPPA:: HP PA architecture
21051 * SPU:: Cell Broadband Engine SPU architecture
21057 @subsection AArch64
21058 @cindex AArch64 support
21060 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21061 following special commands:
21064 @item set debug aarch64
21065 @kindex set debug aarch64
21066 This command determines whether AArch64 architecture-specific debugging
21067 messages are to be displayed.
21069 @item show debug aarch64
21070 Show whether AArch64 debugging messages are displayed.
21075 @subsection x86 Architecture-specific Issues
21078 @item set struct-convention @var{mode}
21079 @kindex set struct-convention
21080 @cindex struct return convention
21081 @cindex struct/union returned in registers
21082 Set the convention used by the inferior to return @code{struct}s and
21083 @code{union}s from functions to @var{mode}. Possible values of
21084 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21085 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21086 are returned on the stack, while @code{"reg"} means that a
21087 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21088 be returned in a register.
21090 @item show struct-convention
21091 @kindex show struct-convention
21092 Show the current setting of the convention to return @code{struct}s
21099 See the following section.
21102 @subsection @acronym{MIPS}
21104 @cindex stack on Alpha
21105 @cindex stack on @acronym{MIPS}
21106 @cindex Alpha stack
21107 @cindex @acronym{MIPS} stack
21108 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21109 sometimes requires @value{GDBN} to search backward in the object code to
21110 find the beginning of a function.
21112 @cindex response time, @acronym{MIPS} debugging
21113 To improve response time (especially for embedded applications, where
21114 @value{GDBN} may be restricted to a slow serial line for this search)
21115 you may want to limit the size of this search, using one of these
21119 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21120 @item set heuristic-fence-post @var{limit}
21121 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21122 search for the beginning of a function. A value of @var{0} (the
21123 default) means there is no limit. However, except for @var{0}, the
21124 larger the limit the more bytes @code{heuristic-fence-post} must search
21125 and therefore the longer it takes to run. You should only need to use
21126 this command when debugging a stripped executable.
21128 @item show heuristic-fence-post
21129 Display the current limit.
21133 These commands are available @emph{only} when @value{GDBN} is configured
21134 for debugging programs on Alpha or @acronym{MIPS} processors.
21136 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21140 @item set mips abi @var{arg}
21141 @kindex set mips abi
21142 @cindex set ABI for @acronym{MIPS}
21143 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21144 values of @var{arg} are:
21148 The default ABI associated with the current binary (this is the
21158 @item show mips abi
21159 @kindex show mips abi
21160 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21162 @item set mips compression @var{arg}
21163 @kindex set mips compression
21164 @cindex code compression, @acronym{MIPS}
21165 Tell @value{GDBN} which @acronym{MIPS} compressed
21166 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21167 inferior. @value{GDBN} uses this for code disassembly and other
21168 internal interpretation purposes. This setting is only referred to
21169 when no executable has been associated with the debugging session or
21170 the executable does not provide information about the encoding it uses.
21171 Otherwise this setting is automatically updated from information
21172 provided by the executable.
21174 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21175 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21176 executables containing @acronym{MIPS16} code frequently are not
21177 identified as such.
21179 This setting is ``sticky''; that is, it retains its value across
21180 debugging sessions until reset either explicitly with this command or
21181 implicitly from an executable.
21183 The compiler and/or assembler typically add symbol table annotations to
21184 identify functions compiled for the @acronym{MIPS16} or
21185 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21186 are present, @value{GDBN} uses them in preference to the global
21187 compressed @acronym{ISA} encoding setting.
21189 @item show mips compression
21190 @kindex show mips compression
21191 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21192 @value{GDBN} to debug the inferior.
21195 @itemx show mipsfpu
21196 @xref{MIPS Embedded, set mipsfpu}.
21198 @item set mips mask-address @var{arg}
21199 @kindex set mips mask-address
21200 @cindex @acronym{MIPS} addresses, masking
21201 This command determines whether the most-significant 32 bits of 64-bit
21202 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21203 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21204 setting, which lets @value{GDBN} determine the correct value.
21206 @item show mips mask-address
21207 @kindex show mips mask-address
21208 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21211 @item set remote-mips64-transfers-32bit-regs
21212 @kindex set remote-mips64-transfers-32bit-regs
21213 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21214 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21215 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21216 and 64 bits for other registers, set this option to @samp{on}.
21218 @item show remote-mips64-transfers-32bit-regs
21219 @kindex show remote-mips64-transfers-32bit-regs
21220 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21222 @item set debug mips
21223 @kindex set debug mips
21224 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21225 target code in @value{GDBN}.
21227 @item show debug mips
21228 @kindex show debug mips
21229 Show the current setting of @acronym{MIPS} debugging messages.
21235 @cindex HPPA support
21237 When @value{GDBN} is debugging the HP PA architecture, it provides the
21238 following special commands:
21241 @item set debug hppa
21242 @kindex set debug hppa
21243 This command determines whether HPPA architecture-specific debugging
21244 messages are to be displayed.
21246 @item show debug hppa
21247 Show whether HPPA debugging messages are displayed.
21249 @item maint print unwind @var{address}
21250 @kindex maint print unwind@r{, HPPA}
21251 This command displays the contents of the unwind table entry at the
21252 given @var{address}.
21258 @subsection Cell Broadband Engine SPU architecture
21259 @cindex Cell Broadband Engine
21262 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21263 it provides the following special commands:
21266 @item info spu event
21268 Display SPU event facility status. Shows current event mask
21269 and pending event status.
21271 @item info spu signal
21272 Display SPU signal notification facility status. Shows pending
21273 signal-control word and signal notification mode of both signal
21274 notification channels.
21276 @item info spu mailbox
21277 Display SPU mailbox facility status. Shows all pending entries,
21278 in order of processing, in each of the SPU Write Outbound,
21279 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21282 Display MFC DMA status. Shows all pending commands in the MFC
21283 DMA queue. For each entry, opcode, tag, class IDs, effective
21284 and local store addresses and transfer size are shown.
21286 @item info spu proxydma
21287 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21288 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21289 and local store addresses and transfer size are shown.
21293 When @value{GDBN} is debugging a combined PowerPC/SPU application
21294 on the Cell Broadband Engine, it provides in addition the following
21298 @item set spu stop-on-load @var{arg}
21300 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21301 will give control to the user when a new SPE thread enters its @code{main}
21302 function. The default is @code{off}.
21304 @item show spu stop-on-load
21306 Show whether to stop for new SPE threads.
21308 @item set spu auto-flush-cache @var{arg}
21309 Set whether to automatically flush the software-managed cache. When set to
21310 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21311 cache to be flushed whenever SPE execution stops. This provides a consistent
21312 view of PowerPC memory that is accessed via the cache. If an application
21313 does not use the software-managed cache, this option has no effect.
21315 @item show spu auto-flush-cache
21316 Show whether to automatically flush the software-managed cache.
21321 @subsection PowerPC
21322 @cindex PowerPC architecture
21324 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21325 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21326 numbers stored in the floating point registers. These values must be stored
21327 in two consecutive registers, always starting at an even register like
21328 @code{f0} or @code{f2}.
21330 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21331 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21332 @code{f2} and @code{f3} for @code{$dl1} and so on.
21334 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21335 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21338 @subsection Nios II
21339 @cindex Nios II architecture
21341 When @value{GDBN} is debugging the Nios II architecture,
21342 it provides the following special commands:
21346 @item set debug nios2
21347 @kindex set debug nios2
21348 This command turns on and off debugging messages for the Nios II
21349 target code in @value{GDBN}.
21351 @item show debug nios2
21352 @kindex show debug nios2
21353 Show the current setting of Nios II debugging messages.
21356 @node Controlling GDB
21357 @chapter Controlling @value{GDBN}
21359 You can alter the way @value{GDBN} interacts with you by using the
21360 @code{set} command. For commands controlling how @value{GDBN} displays
21361 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21366 * Editing:: Command editing
21367 * Command History:: Command history
21368 * Screen Size:: Screen size
21369 * Numbers:: Numbers
21370 * ABI:: Configuring the current ABI
21371 * Auto-loading:: Automatically loading associated files
21372 * Messages/Warnings:: Optional warnings and messages
21373 * Debugging Output:: Optional messages about internal happenings
21374 * Other Misc Settings:: Other Miscellaneous Settings
21382 @value{GDBN} indicates its readiness to read a command by printing a string
21383 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21384 can change the prompt string with the @code{set prompt} command. For
21385 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21386 the prompt in one of the @value{GDBN} sessions so that you can always tell
21387 which one you are talking to.
21389 @emph{Note:} @code{set prompt} does not add a space for you after the
21390 prompt you set. This allows you to set a prompt which ends in a space
21391 or a prompt that does not.
21395 @item set prompt @var{newprompt}
21396 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21398 @kindex show prompt
21400 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21403 Versions of @value{GDBN} that ship with Python scripting enabled have
21404 prompt extensions. The commands for interacting with these extensions
21408 @kindex set extended-prompt
21409 @item set extended-prompt @var{prompt}
21410 Set an extended prompt that allows for substitutions.
21411 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21412 substitution. Any escape sequences specified as part of the prompt
21413 string are replaced with the corresponding strings each time the prompt
21419 set extended-prompt Current working directory: \w (gdb)
21422 Note that when an extended-prompt is set, it takes control of the
21423 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21425 @kindex show extended-prompt
21426 @item show extended-prompt
21427 Prints the extended prompt. Any escape sequences specified as part of
21428 the prompt string with @code{set extended-prompt}, are replaced with the
21429 corresponding strings each time the prompt is displayed.
21433 @section Command Editing
21435 @cindex command line editing
21437 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21438 @sc{gnu} library provides consistent behavior for programs which provide a
21439 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21440 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21441 substitution, and a storage and recall of command history across
21442 debugging sessions.
21444 You may control the behavior of command line editing in @value{GDBN} with the
21445 command @code{set}.
21448 @kindex set editing
21451 @itemx set editing on
21452 Enable command line editing (enabled by default).
21454 @item set editing off
21455 Disable command line editing.
21457 @kindex show editing
21459 Show whether command line editing is enabled.
21462 @ifset SYSTEM_READLINE
21463 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21465 @ifclear SYSTEM_READLINE
21466 @xref{Command Line Editing},
21468 for more details about the Readline
21469 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21470 encouraged to read that chapter.
21472 @node Command History
21473 @section Command History
21474 @cindex command history
21476 @value{GDBN} can keep track of the commands you type during your
21477 debugging sessions, so that you can be certain of precisely what
21478 happened. Use these commands to manage the @value{GDBN} command
21481 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21482 package, to provide the history facility.
21483 @ifset SYSTEM_READLINE
21484 @xref{Using History Interactively, , , history, GNU History Library},
21486 @ifclear SYSTEM_READLINE
21487 @xref{Using History Interactively},
21489 for the detailed description of the History library.
21491 To issue a command to @value{GDBN} without affecting certain aspects of
21492 the state which is seen by users, prefix it with @samp{server }
21493 (@pxref{Server Prefix}). This
21494 means that this command will not affect the command history, nor will it
21495 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21496 pressed on a line by itself.
21498 @cindex @code{server}, command prefix
21499 The server prefix does not affect the recording of values into the value
21500 history; to print a value without recording it into the value history,
21501 use the @code{output} command instead of the @code{print} command.
21503 Here is the description of @value{GDBN} commands related to command
21507 @cindex history substitution
21508 @cindex history file
21509 @kindex set history filename
21510 @cindex @env{GDBHISTFILE}, environment variable
21511 @item set history filename @var{fname}
21512 Set the name of the @value{GDBN} command history file to @var{fname}.
21513 This is the file where @value{GDBN} reads an initial command history
21514 list, and where it writes the command history from this session when it
21515 exits. You can access this list through history expansion or through
21516 the history command editing characters listed below. This file defaults
21517 to the value of the environment variable @code{GDBHISTFILE}, or to
21518 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21521 @cindex save command history
21522 @kindex set history save
21523 @item set history save
21524 @itemx set history save on
21525 Record command history in a file, whose name may be specified with the
21526 @code{set history filename} command. By default, this option is disabled.
21528 @item set history save off
21529 Stop recording command history in a file.
21531 @cindex history size
21532 @kindex set history size
21533 @cindex @env{HISTSIZE}, environment variable
21534 @item set history size @var{size}
21535 @itemx set history size unlimited
21536 Set the number of commands which @value{GDBN} keeps in its history list.
21537 This defaults to the value of the environment variable
21538 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21539 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21540 history list is unlimited.
21543 History expansion assigns special meaning to the character @kbd{!}.
21544 @ifset SYSTEM_READLINE
21545 @xref{Event Designators, , , history, GNU History Library},
21547 @ifclear SYSTEM_READLINE
21548 @xref{Event Designators},
21552 @cindex history expansion, turn on/off
21553 Since @kbd{!} is also the logical not operator in C, history expansion
21554 is off by default. If you decide to enable history expansion with the
21555 @code{set history expansion on} command, you may sometimes need to
21556 follow @kbd{!} (when it is used as logical not, in an expression) with
21557 a space or a tab to prevent it from being expanded. The readline
21558 history facilities do not attempt substitution on the strings
21559 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21561 The commands to control history expansion are:
21564 @item set history expansion on
21565 @itemx set history expansion
21566 @kindex set history expansion
21567 Enable history expansion. History expansion is off by default.
21569 @item set history expansion off
21570 Disable history expansion.
21573 @kindex show history
21575 @itemx show history filename
21576 @itemx show history save
21577 @itemx show history size
21578 @itemx show history expansion
21579 These commands display the state of the @value{GDBN} history parameters.
21580 @code{show history} by itself displays all four states.
21585 @kindex show commands
21586 @cindex show last commands
21587 @cindex display command history
21588 @item show commands
21589 Display the last ten commands in the command history.
21591 @item show commands @var{n}
21592 Print ten commands centered on command number @var{n}.
21594 @item show commands +
21595 Print ten commands just after the commands last printed.
21599 @section Screen Size
21600 @cindex size of screen
21601 @cindex pauses in output
21603 Certain commands to @value{GDBN} may produce large amounts of
21604 information output to the screen. To help you read all of it,
21605 @value{GDBN} pauses and asks you for input at the end of each page of
21606 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21607 to discard the remaining output. Also, the screen width setting
21608 determines when to wrap lines of output. Depending on what is being
21609 printed, @value{GDBN} tries to break the line at a readable place,
21610 rather than simply letting it overflow onto the following line.
21612 Normally @value{GDBN} knows the size of the screen from the terminal
21613 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21614 together with the value of the @code{TERM} environment variable and the
21615 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21616 you can override it with the @code{set height} and @code{set
21623 @kindex show height
21624 @item set height @var{lpp}
21625 @itemx set height unlimited
21627 @itemx set width @var{cpl}
21628 @itemx set width unlimited
21630 These @code{set} commands specify a screen height of @var{lpp} lines and
21631 a screen width of @var{cpl} characters. The associated @code{show}
21632 commands display the current settings.
21634 If you specify a height of either @code{unlimited} or zero lines,
21635 @value{GDBN} does not pause during output no matter how long the
21636 output is. This is useful if output is to a file or to an editor
21639 Likewise, you can specify @samp{set width unlimited} or @samp{set
21640 width 0} to prevent @value{GDBN} from wrapping its output.
21642 @item set pagination on
21643 @itemx set pagination off
21644 @kindex set pagination
21645 Turn the output pagination on or off; the default is on. Turning
21646 pagination off is the alternative to @code{set height unlimited}. Note that
21647 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21648 Options, -batch}) also automatically disables pagination.
21650 @item show pagination
21651 @kindex show pagination
21652 Show the current pagination mode.
21657 @cindex number representation
21658 @cindex entering numbers
21660 You can always enter numbers in octal, decimal, or hexadecimal in
21661 @value{GDBN} by the usual conventions: octal numbers begin with
21662 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21663 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21664 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21665 10; likewise, the default display for numbers---when no particular
21666 format is specified---is base 10. You can change the default base for
21667 both input and output with the commands described below.
21670 @kindex set input-radix
21671 @item set input-radix @var{base}
21672 Set the default base for numeric input. Supported choices
21673 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21674 specified either unambiguously or using the current input radix; for
21678 set input-radix 012
21679 set input-radix 10.
21680 set input-radix 0xa
21684 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21685 leaves the input radix unchanged, no matter what it was, since
21686 @samp{10}, being without any leading or trailing signs of its base, is
21687 interpreted in the current radix. Thus, if the current radix is 16,
21688 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21691 @kindex set output-radix
21692 @item set output-radix @var{base}
21693 Set the default base for numeric display. Supported choices
21694 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21695 specified either unambiguously or using the current input radix.
21697 @kindex show input-radix
21698 @item show input-radix
21699 Display the current default base for numeric input.
21701 @kindex show output-radix
21702 @item show output-radix
21703 Display the current default base for numeric display.
21705 @item set radix @r{[}@var{base}@r{]}
21709 These commands set and show the default base for both input and output
21710 of numbers. @code{set radix} sets the radix of input and output to
21711 the same base; without an argument, it resets the radix back to its
21712 default value of 10.
21717 @section Configuring the Current ABI
21719 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21720 application automatically. However, sometimes you need to override its
21721 conclusions. Use these commands to manage @value{GDBN}'s view of the
21727 @cindex Newlib OS ABI and its influence on the longjmp handling
21729 One @value{GDBN} configuration can debug binaries for multiple operating
21730 system targets, either via remote debugging or native emulation.
21731 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21732 but you can override its conclusion using the @code{set osabi} command.
21733 One example where this is useful is in debugging of binaries which use
21734 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21735 not have the same identifying marks that the standard C library for your
21738 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21739 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21740 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21741 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21745 Show the OS ABI currently in use.
21748 With no argument, show the list of registered available OS ABI's.
21750 @item set osabi @var{abi}
21751 Set the current OS ABI to @var{abi}.
21754 @cindex float promotion
21756 Generally, the way that an argument of type @code{float} is passed to a
21757 function depends on whether the function is prototyped. For a prototyped
21758 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21759 according to the architecture's convention for @code{float}. For unprototyped
21760 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21761 @code{double} and then passed.
21763 Unfortunately, some forms of debug information do not reliably indicate whether
21764 a function is prototyped. If @value{GDBN} calls a function that is not marked
21765 as prototyped, it consults @kbd{set coerce-float-to-double}.
21768 @kindex set coerce-float-to-double
21769 @item set coerce-float-to-double
21770 @itemx set coerce-float-to-double on
21771 Arguments of type @code{float} will be promoted to @code{double} when passed
21772 to an unprototyped function. This is the default setting.
21774 @item set coerce-float-to-double off
21775 Arguments of type @code{float} will be passed directly to unprototyped
21778 @kindex show coerce-float-to-double
21779 @item show coerce-float-to-double
21780 Show the current setting of promoting @code{float} to @code{double}.
21784 @kindex show cp-abi
21785 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21786 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21787 used to build your application. @value{GDBN} only fully supports
21788 programs with a single C@t{++} ABI; if your program contains code using
21789 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21790 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21791 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21792 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21793 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21794 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21799 Show the C@t{++} ABI currently in use.
21802 With no argument, show the list of supported C@t{++} ABI's.
21804 @item set cp-abi @var{abi}
21805 @itemx set cp-abi auto
21806 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21810 @section Automatically loading associated files
21811 @cindex auto-loading
21813 @value{GDBN} sometimes reads files with commands and settings automatically,
21814 without being explicitly told so by the user. We call this feature
21815 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21816 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21817 results or introduce security risks (e.g., if the file comes from untrusted
21820 Note that loading of these associated files (including the local @file{.gdbinit}
21821 file) requires accordingly configured @code{auto-load safe-path}
21822 (@pxref{Auto-loading safe path}).
21824 For these reasons, @value{GDBN} includes commands and options to let you
21825 control when to auto-load files and which files should be auto-loaded.
21828 @anchor{set auto-load off}
21829 @kindex set auto-load off
21830 @item set auto-load off
21831 Globally disable loading of all auto-loaded files.
21832 You may want to use this command with the @samp{-iex} option
21833 (@pxref{Option -init-eval-command}) such as:
21835 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21838 Be aware that system init file (@pxref{System-wide configuration})
21839 and init files from your home directory (@pxref{Home Directory Init File})
21840 still get read (as they come from generally trusted directories).
21841 To prevent @value{GDBN} from auto-loading even those init files, use the
21842 @option{-nx} option (@pxref{Mode Options}), in addition to
21843 @code{set auto-load no}.
21845 @anchor{show auto-load}
21846 @kindex show auto-load
21847 @item show auto-load
21848 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21852 (gdb) show auto-load
21853 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21854 libthread-db: Auto-loading of inferior specific libthread_db is on.
21855 local-gdbinit: Auto-loading of .gdbinit script from current directory
21857 python-scripts: Auto-loading of Python scripts is on.
21858 safe-path: List of directories from which it is safe to auto-load files
21859 is $debugdir:$datadir/auto-load.
21860 scripts-directory: List of directories from which to load auto-loaded scripts
21861 is $debugdir:$datadir/auto-load.
21864 @anchor{info auto-load}
21865 @kindex info auto-load
21866 @item info auto-load
21867 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21871 (gdb) info auto-load
21874 Yes /home/user/gdb/gdb-gdb.gdb
21875 libthread-db: No auto-loaded libthread-db.
21876 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21880 Yes /home/user/gdb/gdb-gdb.py
21884 These are various kinds of files @value{GDBN} can automatically load:
21888 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21890 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21892 @xref{dotdebug_gdb_scripts section},
21893 controlled by @ref{set auto-load python-scripts}.
21895 @xref{Init File in the Current Directory},
21896 controlled by @ref{set auto-load local-gdbinit}.
21898 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21901 These are @value{GDBN} control commands for the auto-loading:
21903 @multitable @columnfractions .5 .5
21904 @item @xref{set auto-load off}.
21905 @tab Disable auto-loading globally.
21906 @item @xref{show auto-load}.
21907 @tab Show setting of all kinds of files.
21908 @item @xref{info auto-load}.
21909 @tab Show state of all kinds of files.
21910 @item @xref{set auto-load gdb-scripts}.
21911 @tab Control for @value{GDBN} command scripts.
21912 @item @xref{show auto-load gdb-scripts}.
21913 @tab Show setting of @value{GDBN} command scripts.
21914 @item @xref{info auto-load gdb-scripts}.
21915 @tab Show state of @value{GDBN} command scripts.
21916 @item @xref{set auto-load python-scripts}.
21917 @tab Control for @value{GDBN} Python scripts.
21918 @item @xref{show auto-load python-scripts}.
21919 @tab Show setting of @value{GDBN} Python scripts.
21920 @item @xref{info auto-load python-scripts}.
21921 @tab Show state of @value{GDBN} Python scripts.
21922 @item @xref{set auto-load scripts-directory}.
21923 @tab Control for @value{GDBN} auto-loaded scripts location.
21924 @item @xref{show auto-load scripts-directory}.
21925 @tab Show @value{GDBN} auto-loaded scripts location.
21926 @item @xref{set auto-load local-gdbinit}.
21927 @tab Control for init file in the current directory.
21928 @item @xref{show auto-load local-gdbinit}.
21929 @tab Show setting of init file in the current directory.
21930 @item @xref{info auto-load local-gdbinit}.
21931 @tab Show state of init file in the current directory.
21932 @item @xref{set auto-load libthread-db}.
21933 @tab Control for thread debugging library.
21934 @item @xref{show auto-load libthread-db}.
21935 @tab Show setting of thread debugging library.
21936 @item @xref{info auto-load libthread-db}.
21937 @tab Show state of thread debugging library.
21938 @item @xref{set auto-load safe-path}.
21939 @tab Control directories trusted for automatic loading.
21940 @item @xref{show auto-load safe-path}.
21941 @tab Show directories trusted for automatic loading.
21942 @item @xref{add-auto-load-safe-path}.
21943 @tab Add directory trusted for automatic loading.
21947 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21948 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21949 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21950 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21951 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21952 @xref{Python Auto-loading}.
21955 @node Init File in the Current Directory
21956 @subsection Automatically loading init file in the current directory
21957 @cindex auto-loading init file in the current directory
21959 By default, @value{GDBN} reads and executes the canned sequences of commands
21960 from init file (if any) in the current working directory,
21961 see @ref{Init File in the Current Directory during Startup}.
21963 Note that loading of this local @file{.gdbinit} file also requires accordingly
21964 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21967 @anchor{set auto-load local-gdbinit}
21968 @kindex set auto-load local-gdbinit
21969 @item set auto-load local-gdbinit [on|off]
21970 Enable or disable the auto-loading of canned sequences of commands
21971 (@pxref{Sequences}) found in init file in the current directory.
21973 @anchor{show auto-load local-gdbinit}
21974 @kindex show auto-load local-gdbinit
21975 @item show auto-load local-gdbinit
21976 Show whether auto-loading of canned sequences of commands from init file in the
21977 current directory is enabled or disabled.
21979 @anchor{info auto-load local-gdbinit}
21980 @kindex info auto-load local-gdbinit
21981 @item info auto-load local-gdbinit
21982 Print whether canned sequences of commands from init file in the
21983 current directory have been auto-loaded.
21986 @node libthread_db.so.1 file
21987 @subsection Automatically loading thread debugging library
21988 @cindex auto-loading libthread_db.so.1
21990 This feature is currently present only on @sc{gnu}/Linux native hosts.
21992 @value{GDBN} reads in some cases thread debugging library from places specific
21993 to the inferior (@pxref{set libthread-db-search-path}).
21995 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21996 without checking this @samp{set auto-load libthread-db} switch as system
21997 libraries have to be trusted in general. In all other cases of
21998 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21999 auto-load libthread-db} is enabled before trying to open such thread debugging
22002 Note that loading of this debugging library also requires accordingly configured
22003 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22006 @anchor{set auto-load libthread-db}
22007 @kindex set auto-load libthread-db
22008 @item set auto-load libthread-db [on|off]
22009 Enable or disable the auto-loading of inferior specific thread debugging library.
22011 @anchor{show auto-load libthread-db}
22012 @kindex show auto-load libthread-db
22013 @item show auto-load libthread-db
22014 Show whether auto-loading of inferior specific thread debugging library is
22015 enabled or disabled.
22017 @anchor{info auto-load libthread-db}
22018 @kindex info auto-load libthread-db
22019 @item info auto-load libthread-db
22020 Print the list of all loaded inferior specific thread debugging libraries and
22021 for each such library print list of inferior @var{pid}s using it.
22024 @node objfile-gdb.gdb file
22025 @subsection The @file{@var{objfile}-gdb.gdb} file
22026 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
22028 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
22029 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
22030 auto-load gdb-scripts} is set to @samp{on}.
22032 Note that loading of this script file also requires accordingly configured
22033 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22035 For more background refer to the similar Python scripts auto-loading
22036 description (@pxref{objfile-gdb.py file}).
22039 @anchor{set auto-load gdb-scripts}
22040 @kindex set auto-load gdb-scripts
22041 @item set auto-load gdb-scripts [on|off]
22042 Enable or disable the auto-loading of canned sequences of commands scripts.
22044 @anchor{show auto-load gdb-scripts}
22045 @kindex show auto-load gdb-scripts
22046 @item show auto-load gdb-scripts
22047 Show whether auto-loading of canned sequences of commands scripts is enabled or
22050 @anchor{info auto-load gdb-scripts}
22051 @kindex info auto-load gdb-scripts
22052 @cindex print list of auto-loaded canned sequences of commands scripts
22053 @item info auto-load gdb-scripts [@var{regexp}]
22054 Print the list of all canned sequences of commands scripts that @value{GDBN}
22058 If @var{regexp} is supplied only canned sequences of commands scripts with
22059 matching names are printed.
22061 @node Auto-loading safe path
22062 @subsection Security restriction for auto-loading
22063 @cindex auto-loading safe-path
22065 As the files of inferior can come from untrusted source (such as submitted by
22066 an application user) @value{GDBN} does not always load any files automatically.
22067 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22068 directories trusted for loading files not explicitly requested by user.
22069 Each directory can also be a shell wildcard pattern.
22071 If the path is not set properly you will see a warning and the file will not
22076 Reading symbols from /home/user/gdb/gdb...done.
22077 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22078 declined by your `auto-load safe-path' set
22079 to "$debugdir:$datadir/auto-load".
22080 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22081 declined by your `auto-load safe-path' set
22082 to "$debugdir:$datadir/auto-load".
22086 To instruct @value{GDBN} to go ahead and use the init files anyway,
22087 invoke @value{GDBN} like this:
22090 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22093 The list of trusted directories is controlled by the following commands:
22096 @anchor{set auto-load safe-path}
22097 @kindex set auto-load safe-path
22098 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22099 Set the list of directories (and their subdirectories) trusted for automatic
22100 loading and execution of scripts. You can also enter a specific trusted file.
22101 Each directory can also be a shell wildcard pattern; wildcards do not match
22102 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22103 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22104 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22105 its default value as specified during @value{GDBN} compilation.
22107 The list of directories uses path separator (@samp{:} on GNU and Unix
22108 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22109 to the @env{PATH} environment variable.
22111 @anchor{show auto-load safe-path}
22112 @kindex show auto-load safe-path
22113 @item show auto-load safe-path
22114 Show the list of directories trusted for automatic loading and execution of
22117 @anchor{add-auto-load-safe-path}
22118 @kindex add-auto-load-safe-path
22119 @item add-auto-load-safe-path
22120 Add an entry (or list of entries) the list of directories trusted for automatic
22121 loading and execution of scripts. Multiple entries may be delimited by the
22122 host platform path separator in use.
22125 This variable defaults to what @code{--with-auto-load-dir} has been configured
22126 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22127 substitution applies the same as for @ref{set auto-load scripts-directory}.
22128 The default @code{set auto-load safe-path} value can be also overriden by
22129 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22131 Setting this variable to @file{/} disables this security protection,
22132 corresponding @value{GDBN} configuration option is
22133 @option{--without-auto-load-safe-path}.
22134 This variable is supposed to be set to the system directories writable by the
22135 system superuser only. Users can add their source directories in init files in
22136 their home directories (@pxref{Home Directory Init File}). See also deprecated
22137 init file in the current directory
22138 (@pxref{Init File in the Current Directory during Startup}).
22140 To force @value{GDBN} to load the files it declined to load in the previous
22141 example, you could use one of the following ways:
22144 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22145 Specify this trusted directory (or a file) as additional component of the list.
22146 You have to specify also any existing directories displayed by
22147 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22149 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22150 Specify this directory as in the previous case but just for a single
22151 @value{GDBN} session.
22153 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22154 Disable auto-loading safety for a single @value{GDBN} session.
22155 This assumes all the files you debug during this @value{GDBN} session will come
22156 from trusted sources.
22158 @item @kbd{./configure --without-auto-load-safe-path}
22159 During compilation of @value{GDBN} you may disable any auto-loading safety.
22160 This assumes all the files you will ever debug with this @value{GDBN} come from
22164 On the other hand you can also explicitly forbid automatic files loading which
22165 also suppresses any such warning messages:
22168 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22169 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22171 @item @file{~/.gdbinit}: @samp{set auto-load no}
22172 Disable auto-loading globally for the user
22173 (@pxref{Home Directory Init File}). While it is improbable, you could also
22174 use system init file instead (@pxref{System-wide configuration}).
22177 This setting applies to the file names as entered by user. If no entry matches
22178 @value{GDBN} tries as a last resort to also resolve all the file names into
22179 their canonical form (typically resolving symbolic links) and compare the
22180 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22181 own before starting the comparison so a canonical form of directories is
22182 recommended to be entered.
22184 @node Auto-loading verbose mode
22185 @subsection Displaying files tried for auto-load
22186 @cindex auto-loading verbose mode
22188 For better visibility of all the file locations where you can place scripts to
22189 be auto-loaded with inferior --- or to protect yourself against accidental
22190 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22191 all the files attempted to be loaded. Both existing and non-existing files may
22194 For example the list of directories from which it is safe to auto-load files
22195 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22196 may not be too obvious while setting it up.
22199 (gdb) set debug auto-load on
22200 (gdb) file ~/src/t/true
22201 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22202 for objfile "/tmp/true".
22203 auto-load: Updating directories of "/usr:/opt".
22204 auto-load: Using directory "/usr".
22205 auto-load: Using directory "/opt".
22206 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22207 by your `auto-load safe-path' set to "/usr:/opt".
22211 @anchor{set debug auto-load}
22212 @kindex set debug auto-load
22213 @item set debug auto-load [on|off]
22214 Set whether to print the filenames attempted to be auto-loaded.
22216 @anchor{show debug auto-load}
22217 @kindex show debug auto-load
22218 @item show debug auto-load
22219 Show whether printing of the filenames attempted to be auto-loaded is turned
22223 @node Messages/Warnings
22224 @section Optional Warnings and Messages
22226 @cindex verbose operation
22227 @cindex optional warnings
22228 By default, @value{GDBN} is silent about its inner workings. If you are
22229 running on a slow machine, you may want to use the @code{set verbose}
22230 command. This makes @value{GDBN} tell you when it does a lengthy
22231 internal operation, so you will not think it has crashed.
22233 Currently, the messages controlled by @code{set verbose} are those
22234 which announce that the symbol table for a source file is being read;
22235 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22238 @kindex set verbose
22239 @item set verbose on
22240 Enables @value{GDBN} output of certain informational messages.
22242 @item set verbose off
22243 Disables @value{GDBN} output of certain informational messages.
22245 @kindex show verbose
22247 Displays whether @code{set verbose} is on or off.
22250 By default, if @value{GDBN} encounters bugs in the symbol table of an
22251 object file, it is silent; but if you are debugging a compiler, you may
22252 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22257 @kindex set complaints
22258 @item set complaints @var{limit}
22259 Permits @value{GDBN} to output @var{limit} complaints about each type of
22260 unusual symbols before becoming silent about the problem. Set
22261 @var{limit} to zero to suppress all complaints; set it to a large number
22262 to prevent complaints from being suppressed.
22264 @kindex show complaints
22265 @item show complaints
22266 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22270 @anchor{confirmation requests}
22271 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22272 lot of stupid questions to confirm certain commands. For example, if
22273 you try to run a program which is already running:
22277 The program being debugged has been started already.
22278 Start it from the beginning? (y or n)
22281 If you are willing to unflinchingly face the consequences of your own
22282 commands, you can disable this ``feature'':
22286 @kindex set confirm
22288 @cindex confirmation
22289 @cindex stupid questions
22290 @item set confirm off
22291 Disables confirmation requests. Note that running @value{GDBN} with
22292 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22293 automatically disables confirmation requests.
22295 @item set confirm on
22296 Enables confirmation requests (the default).
22298 @kindex show confirm
22300 Displays state of confirmation requests.
22304 @cindex command tracing
22305 If you need to debug user-defined commands or sourced files you may find it
22306 useful to enable @dfn{command tracing}. In this mode each command will be
22307 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22308 quantity denoting the call depth of each command.
22311 @kindex set trace-commands
22312 @cindex command scripts, debugging
22313 @item set trace-commands on
22314 Enable command tracing.
22315 @item set trace-commands off
22316 Disable command tracing.
22317 @item show trace-commands
22318 Display the current state of command tracing.
22321 @node Debugging Output
22322 @section Optional Messages about Internal Happenings
22323 @cindex optional debugging messages
22325 @value{GDBN} has commands that enable optional debugging messages from
22326 various @value{GDBN} subsystems; normally these commands are of
22327 interest to @value{GDBN} maintainers, or when reporting a bug. This
22328 section documents those commands.
22331 @kindex set exec-done-display
22332 @item set exec-done-display
22333 Turns on or off the notification of asynchronous commands'
22334 completion. When on, @value{GDBN} will print a message when an
22335 asynchronous command finishes its execution. The default is off.
22336 @kindex show exec-done-display
22337 @item show exec-done-display
22338 Displays the current setting of asynchronous command completion
22341 @cindex ARM AArch64
22342 @item set debug aarch64
22343 Turns on or off display of debugging messages related to ARM AArch64.
22344 The default is off.
22346 @item show debug aarch64
22347 Displays the current state of displaying debugging messages related to
22349 @cindex gdbarch debugging info
22350 @cindex architecture debugging info
22351 @item set debug arch
22352 Turns on or off display of gdbarch debugging info. The default is off
22353 @item show debug arch
22354 Displays the current state of displaying gdbarch debugging info.
22355 @item set debug aix-solib
22356 @cindex AIX shared library debugging
22357 Control display of debugging messages from the AIX shared library
22358 support module. The default is off.
22359 @item show debug aix-thread
22360 Show the current state of displaying AIX shared library debugging messages.
22361 @item set debug aix-thread
22362 @cindex AIX threads
22363 Display debugging messages about inner workings of the AIX thread
22365 @item show debug aix-thread
22366 Show the current state of AIX thread debugging info display.
22367 @item set debug check-physname
22369 Check the results of the ``physname'' computation. When reading DWARF
22370 debugging information for C@t{++}, @value{GDBN} attempts to compute
22371 each entity's name. @value{GDBN} can do this computation in two
22372 different ways, depending on exactly what information is present.
22373 When enabled, this setting causes @value{GDBN} to compute the names
22374 both ways and display any discrepancies.
22375 @item show debug check-physname
22376 Show the current state of ``physname'' checking.
22377 @item set debug coff-pe-read
22378 @cindex COFF/PE exported symbols
22379 Control display of debugging messages related to reading of COFF/PE
22380 exported symbols. The default is off.
22381 @item show debug coff-pe-read
22382 Displays the current state of displaying debugging messages related to
22383 reading of COFF/PE exported symbols.
22384 @item set debug dwarf2-die
22385 @cindex DWARF2 DIEs
22386 Dump DWARF2 DIEs after they are read in.
22387 The value is the number of nesting levels to print.
22388 A value of zero turns off the display.
22389 @item show debug dwarf2-die
22390 Show the current state of DWARF2 DIE debugging.
22391 @item set debug dwarf2-read
22392 @cindex DWARF2 Reading
22393 Turns on or off display of debugging messages related to reading
22394 DWARF debug info. The default is off.
22395 @item show debug dwarf2-read
22396 Show the current state of DWARF2 reader debugging.
22397 @item set debug displaced
22398 @cindex displaced stepping debugging info
22399 Turns on or off display of @value{GDBN} debugging info for the
22400 displaced stepping support. The default is off.
22401 @item show debug displaced
22402 Displays the current state of displaying @value{GDBN} debugging info
22403 related to displaced stepping.
22404 @item set debug event
22405 @cindex event debugging info
22406 Turns on or off display of @value{GDBN} event debugging info. The
22408 @item show debug event
22409 Displays the current state of displaying @value{GDBN} event debugging
22411 @item set debug expression
22412 @cindex expression debugging info
22413 Turns on or off display of debugging info about @value{GDBN}
22414 expression parsing. The default is off.
22415 @item show debug expression
22416 Displays the current state of displaying debugging info about
22417 @value{GDBN} expression parsing.
22418 @item set debug frame
22419 @cindex frame debugging info
22420 Turns on or off display of @value{GDBN} frame debugging info. The
22422 @item show debug frame
22423 Displays the current state of displaying @value{GDBN} frame debugging
22425 @item set debug gnu-nat
22426 @cindex @sc{gnu}/Hurd debug messages
22427 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22428 @item show debug gnu-nat
22429 Show the current state of @sc{gnu}/Hurd debugging messages.
22430 @item set debug infrun
22431 @cindex inferior debugging info
22432 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22433 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22434 for implementing operations such as single-stepping the inferior.
22435 @item show debug infrun
22436 Displays the current state of @value{GDBN} inferior debugging.
22437 @item set debug jit
22438 @cindex just-in-time compilation, debugging messages
22439 Turns on or off debugging messages from JIT debug support.
22440 @item show debug jit
22441 Displays the current state of @value{GDBN} JIT debugging.
22442 @item set debug lin-lwp
22443 @cindex @sc{gnu}/Linux LWP debug messages
22444 @cindex Linux lightweight processes
22445 Turns on or off debugging messages from the Linux LWP debug support.
22446 @item show debug lin-lwp
22447 Show the current state of Linux LWP debugging messages.
22448 @item set debug mach-o
22449 @cindex Mach-O symbols processing
22450 Control display of debugging messages related to Mach-O symbols
22451 processing. The default is off.
22452 @item show debug mach-o
22453 Displays the current state of displaying debugging messages related to
22454 reading of COFF/PE exported symbols.
22455 @item set debug notification
22456 @cindex remote async notification debugging info
22457 Turns on or off debugging messages about remote async notification.
22458 The default is off.
22459 @item show debug notification
22460 Displays the current state of remote async notification debugging messages.
22461 @item set debug observer
22462 @cindex observer debugging info
22463 Turns on or off display of @value{GDBN} observer debugging. This
22464 includes info such as the notification of observable events.
22465 @item show debug observer
22466 Displays the current state of observer debugging.
22467 @item set debug overload
22468 @cindex C@t{++} overload debugging info
22469 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22470 info. This includes info such as ranking of functions, etc. The default
22472 @item show debug overload
22473 Displays the current state of displaying @value{GDBN} C@t{++} overload
22475 @cindex expression parser, debugging info
22476 @cindex debug expression parser
22477 @item set debug parser
22478 Turns on or off the display of expression parser debugging output.
22479 Internally, this sets the @code{yydebug} variable in the expression
22480 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22481 details. The default is off.
22482 @item show debug parser
22483 Show the current state of expression parser debugging.
22484 @cindex packets, reporting on stdout
22485 @cindex serial connections, debugging
22486 @cindex debug remote protocol
22487 @cindex remote protocol debugging
22488 @cindex display remote packets
22489 @item set debug remote
22490 Turns on or off display of reports on all packets sent back and forth across
22491 the serial line to the remote machine. The info is printed on the
22492 @value{GDBN} standard output stream. The default is off.
22493 @item show debug remote
22494 Displays the state of display of remote packets.
22495 @item set debug serial
22496 Turns on or off display of @value{GDBN} serial debugging info. The
22498 @item show debug serial
22499 Displays the current state of displaying @value{GDBN} serial debugging
22501 @item set debug solib-frv
22502 @cindex FR-V shared-library debugging
22503 Turns on or off debugging messages for FR-V shared-library code.
22504 @item show debug solib-frv
22505 Display the current state of FR-V shared-library code debugging
22507 @item set debug symtab-create
22508 @cindex symbol table creation
22509 Turns on or off display of debugging messages related to symbol table creation.
22510 The default is off.
22511 @item show debug symtab-create
22512 Show the current state of symbol table creation debugging.
22513 @item set debug target
22514 @cindex target debugging info
22515 Turns on or off display of @value{GDBN} target debugging info. This info
22516 includes what is going on at the target level of GDB, as it happens. The
22517 default is 0. Set it to 1 to track events, and to 2 to also track the
22518 value of large memory transfers. Changes to this flag do not take effect
22519 until the next time you connect to a target or use the @code{run} command.
22520 @item show debug target
22521 Displays the current state of displaying @value{GDBN} target debugging
22523 @item set debug timestamp
22524 @cindex timestampping debugging info
22525 Turns on or off display of timestamps with @value{GDBN} debugging info.
22526 When enabled, seconds and microseconds are displayed before each debugging
22528 @item show debug timestamp
22529 Displays the current state of displaying timestamps with @value{GDBN}
22531 @item set debugvarobj
22532 @cindex variable object debugging info
22533 Turns on or off display of @value{GDBN} variable object debugging
22534 info. The default is off.
22535 @item show debugvarobj
22536 Displays the current state of displaying @value{GDBN} variable object
22538 @item set debug xml
22539 @cindex XML parser debugging
22540 Turns on or off debugging messages for built-in XML parsers.
22541 @item show debug xml
22542 Displays the current state of XML debugging messages.
22545 @node Other Misc Settings
22546 @section Other Miscellaneous Settings
22547 @cindex miscellaneous settings
22550 @kindex set interactive-mode
22551 @item set interactive-mode
22552 If @code{on}, forces @value{GDBN} to assume that GDB was started
22553 in a terminal. In practice, this means that @value{GDBN} should wait
22554 for the user to answer queries generated by commands entered at
22555 the command prompt. If @code{off}, forces @value{GDBN} to operate
22556 in the opposite mode, and it uses the default answers to all queries.
22557 If @code{auto} (the default), @value{GDBN} tries to determine whether
22558 its standard input is a terminal, and works in interactive-mode if it
22559 is, non-interactively otherwise.
22561 In the vast majority of cases, the debugger should be able to guess
22562 correctly which mode should be used. But this setting can be useful
22563 in certain specific cases, such as running a MinGW @value{GDBN}
22564 inside a cygwin window.
22566 @kindex show interactive-mode
22567 @item show interactive-mode
22568 Displays whether the debugger is operating in interactive mode or not.
22571 @node Extending GDB
22572 @chapter Extending @value{GDBN}
22573 @cindex extending GDB
22575 @value{GDBN} provides three mechanisms for extension. The first is based
22576 on composition of @value{GDBN} commands, the second is based on the
22577 Python scripting language, and the third is for defining new aliases of
22580 To facilitate the use of the first two extensions, @value{GDBN} is capable
22581 of evaluating the contents of a file. When doing so, @value{GDBN}
22582 can recognize which scripting language is being used by looking at
22583 the filename extension. Files with an unrecognized filename extension
22584 are always treated as a @value{GDBN} Command Files.
22585 @xref{Command Files,, Command files}.
22587 You can control how @value{GDBN} evaluates these files with the following
22591 @kindex set script-extension
22592 @kindex show script-extension
22593 @item set script-extension off
22594 All scripts are always evaluated as @value{GDBN} Command Files.
22596 @item set script-extension soft
22597 The debugger determines the scripting language based on filename
22598 extension. If this scripting language is supported, @value{GDBN}
22599 evaluates the script using that language. Otherwise, it evaluates
22600 the file as a @value{GDBN} Command File.
22602 @item set script-extension strict
22603 The debugger determines the scripting language based on filename
22604 extension, and evaluates the script using that language. If the
22605 language is not supported, then the evaluation fails.
22607 @item show script-extension
22608 Display the current value of the @code{script-extension} option.
22613 * Sequences:: Canned Sequences of Commands
22614 * Python:: Scripting @value{GDBN} using Python
22615 * Aliases:: Creating new spellings of existing commands
22619 @section Canned Sequences of Commands
22621 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22622 Command Lists}), @value{GDBN} provides two ways to store sequences of
22623 commands for execution as a unit: user-defined commands and command
22627 * Define:: How to define your own commands
22628 * Hooks:: Hooks for user-defined commands
22629 * Command Files:: How to write scripts of commands to be stored in a file
22630 * Output:: Commands for controlled output
22634 @subsection User-defined Commands
22636 @cindex user-defined command
22637 @cindex arguments, to user-defined commands
22638 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22639 which you assign a new name as a command. This is done with the
22640 @code{define} command. User commands may accept up to 10 arguments
22641 separated by whitespace. Arguments are accessed within the user command
22642 via @code{$arg0@dots{}$arg9}. A trivial example:
22646 print $arg0 + $arg1 + $arg2
22651 To execute the command use:
22658 This defines the command @code{adder}, which prints the sum of
22659 its three arguments. Note the arguments are text substitutions, so they may
22660 reference variables, use complex expressions, or even perform inferior
22663 @cindex argument count in user-defined commands
22664 @cindex how many arguments (user-defined commands)
22665 In addition, @code{$argc} may be used to find out how many arguments have
22666 been passed. This expands to a number in the range 0@dots{}10.
22671 print $arg0 + $arg1
22674 print $arg0 + $arg1 + $arg2
22682 @item define @var{commandname}
22683 Define a command named @var{commandname}. If there is already a command
22684 by that name, you are asked to confirm that you want to redefine it.
22685 @var{commandname} may be a bare command name consisting of letters,
22686 numbers, dashes, and underscores. It may also start with any predefined
22687 prefix command. For example, @samp{define target my-target} creates
22688 a user-defined @samp{target my-target} command.
22690 The definition of the command is made up of other @value{GDBN} command lines,
22691 which are given following the @code{define} command. The end of these
22692 commands is marked by a line containing @code{end}.
22695 @kindex end@r{ (user-defined commands)}
22696 @item document @var{commandname}
22697 Document the user-defined command @var{commandname}, so that it can be
22698 accessed by @code{help}. The command @var{commandname} must already be
22699 defined. This command reads lines of documentation just as @code{define}
22700 reads the lines of the command definition, ending with @code{end}.
22701 After the @code{document} command is finished, @code{help} on command
22702 @var{commandname} displays the documentation you have written.
22704 You may use the @code{document} command again to change the
22705 documentation of a command. Redefining the command with @code{define}
22706 does not change the documentation.
22708 @kindex dont-repeat
22709 @cindex don't repeat command
22711 Used inside a user-defined command, this tells @value{GDBN} that this
22712 command should not be repeated when the user hits @key{RET}
22713 (@pxref{Command Syntax, repeat last command}).
22715 @kindex help user-defined
22716 @item help user-defined
22717 List all user-defined commands and all python commands defined in class
22718 COMAND_USER. The first line of the documentation or docstring is
22723 @itemx show user @var{commandname}
22724 Display the @value{GDBN} commands used to define @var{commandname} (but
22725 not its documentation). If no @var{commandname} is given, display the
22726 definitions for all user-defined commands.
22727 This does not work for user-defined python commands.
22729 @cindex infinite recursion in user-defined commands
22730 @kindex show max-user-call-depth
22731 @kindex set max-user-call-depth
22732 @item show max-user-call-depth
22733 @itemx set max-user-call-depth
22734 The value of @code{max-user-call-depth} controls how many recursion
22735 levels are allowed in user-defined commands before @value{GDBN} suspects an
22736 infinite recursion and aborts the command.
22737 This does not apply to user-defined python commands.
22740 In addition to the above commands, user-defined commands frequently
22741 use control flow commands, described in @ref{Command Files}.
22743 When user-defined commands are executed, the
22744 commands of the definition are not printed. An error in any command
22745 stops execution of the user-defined command.
22747 If used interactively, commands that would ask for confirmation proceed
22748 without asking when used inside a user-defined command. Many @value{GDBN}
22749 commands that normally print messages to say what they are doing omit the
22750 messages when used in a user-defined command.
22753 @subsection User-defined Command Hooks
22754 @cindex command hooks
22755 @cindex hooks, for commands
22756 @cindex hooks, pre-command
22759 You may define @dfn{hooks}, which are a special kind of user-defined
22760 command. Whenever you run the command @samp{foo}, if the user-defined
22761 command @samp{hook-foo} exists, it is executed (with no arguments)
22762 before that command.
22764 @cindex hooks, post-command
22766 A hook may also be defined which is run after the command you executed.
22767 Whenever you run the command @samp{foo}, if the user-defined command
22768 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22769 that command. Post-execution hooks may exist simultaneously with
22770 pre-execution hooks, for the same command.
22772 It is valid for a hook to call the command which it hooks. If this
22773 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22775 @c It would be nice if hookpost could be passed a parameter indicating
22776 @c if the command it hooks executed properly or not. FIXME!
22778 @kindex stop@r{, a pseudo-command}
22779 In addition, a pseudo-command, @samp{stop} exists. Defining
22780 (@samp{hook-stop}) makes the associated commands execute every time
22781 execution stops in your program: before breakpoint commands are run,
22782 displays are printed, or the stack frame is printed.
22784 For example, to ignore @code{SIGALRM} signals while
22785 single-stepping, but treat them normally during normal execution,
22790 handle SIGALRM nopass
22794 handle SIGALRM pass
22797 define hook-continue
22798 handle SIGALRM pass
22802 As a further example, to hook at the beginning and end of the @code{echo}
22803 command, and to add extra text to the beginning and end of the message,
22811 define hookpost-echo
22815 (@value{GDBP}) echo Hello World
22816 <<<---Hello World--->>>
22821 You can define a hook for any single-word command in @value{GDBN}, but
22822 not for command aliases; you should define a hook for the basic command
22823 name, e.g.@: @code{backtrace} rather than @code{bt}.
22824 @c FIXME! So how does Joe User discover whether a command is an alias
22826 You can hook a multi-word command by adding @code{hook-} or
22827 @code{hookpost-} to the last word of the command, e.g.@:
22828 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22830 If an error occurs during the execution of your hook, execution of
22831 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22832 (before the command that you actually typed had a chance to run).
22834 If you try to define a hook which does not match any known command, you
22835 get a warning from the @code{define} command.
22837 @node Command Files
22838 @subsection Command Files
22840 @cindex command files
22841 @cindex scripting commands
22842 A command file for @value{GDBN} is a text file made of lines that are
22843 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22844 also be included. An empty line in a command file does nothing; it
22845 does not mean to repeat the last command, as it would from the
22848 You can request the execution of a command file with the @code{source}
22849 command. Note that the @code{source} command is also used to evaluate
22850 scripts that are not Command Files. The exact behavior can be configured
22851 using the @code{script-extension} setting.
22852 @xref{Extending GDB,, Extending GDB}.
22856 @cindex execute commands from a file
22857 @item source [-s] [-v] @var{filename}
22858 Execute the command file @var{filename}.
22861 The lines in a command file are generally executed sequentially,
22862 unless the order of execution is changed by one of the
22863 @emph{flow-control commands} described below. The commands are not
22864 printed as they are executed. An error in any command terminates
22865 execution of the command file and control is returned to the console.
22867 @value{GDBN} first searches for @var{filename} in the current directory.
22868 If the file is not found there, and @var{filename} does not specify a
22869 directory, then @value{GDBN} also looks for the file on the source search path
22870 (specified with the @samp{directory} command);
22871 except that @file{$cdir} is not searched because the compilation directory
22872 is not relevant to scripts.
22874 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22875 on the search path even if @var{filename} specifies a directory.
22876 The search is done by appending @var{filename} to each element of the
22877 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22878 and the search path contains @file{/home/user} then @value{GDBN} will
22879 look for the script @file{/home/user/mylib/myscript}.
22880 The search is also done if @var{filename} is an absolute path.
22881 For example, if @var{filename} is @file{/tmp/myscript} and
22882 the search path contains @file{/home/user} then @value{GDBN} will
22883 look for the script @file{/home/user/tmp/myscript}.
22884 For DOS-like systems, if @var{filename} contains a drive specification,
22885 it is stripped before concatenation. For example, if @var{filename} is
22886 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22887 will look for the script @file{c:/tmp/myscript}.
22889 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22890 each command as it is executed. The option must be given before
22891 @var{filename}, and is interpreted as part of the filename anywhere else.
22893 Commands that would ask for confirmation if used interactively proceed
22894 without asking when used in a command file. Many @value{GDBN} commands that
22895 normally print messages to say what they are doing omit the messages
22896 when called from command files.
22898 @value{GDBN} also accepts command input from standard input. In this
22899 mode, normal output goes to standard output and error output goes to
22900 standard error. Errors in a command file supplied on standard input do
22901 not terminate execution of the command file---execution continues with
22905 gdb < cmds > log 2>&1
22908 (The syntax above will vary depending on the shell used.) This example
22909 will execute commands from the file @file{cmds}. All output and errors
22910 would be directed to @file{log}.
22912 Since commands stored on command files tend to be more general than
22913 commands typed interactively, they frequently need to deal with
22914 complicated situations, such as different or unexpected values of
22915 variables and symbols, changes in how the program being debugged is
22916 built, etc. @value{GDBN} provides a set of flow-control commands to
22917 deal with these complexities. Using these commands, you can write
22918 complex scripts that loop over data structures, execute commands
22919 conditionally, etc.
22926 This command allows to include in your script conditionally executed
22927 commands. The @code{if} command takes a single argument, which is an
22928 expression to evaluate. It is followed by a series of commands that
22929 are executed only if the expression is true (its value is nonzero).
22930 There can then optionally be an @code{else} line, followed by a series
22931 of commands that are only executed if the expression was false. The
22932 end of the list is marked by a line containing @code{end}.
22936 This command allows to write loops. Its syntax is similar to
22937 @code{if}: the command takes a single argument, which is an expression
22938 to evaluate, and must be followed by the commands to execute, one per
22939 line, terminated by an @code{end}. These commands are called the
22940 @dfn{body} of the loop. The commands in the body of @code{while} are
22941 executed repeatedly as long as the expression evaluates to true.
22945 This command exits the @code{while} loop in whose body it is included.
22946 Execution of the script continues after that @code{while}s @code{end}
22949 @kindex loop_continue
22950 @item loop_continue
22951 This command skips the execution of the rest of the body of commands
22952 in the @code{while} loop in whose body it is included. Execution
22953 branches to the beginning of the @code{while} loop, where it evaluates
22954 the controlling expression.
22956 @kindex end@r{ (if/else/while commands)}
22958 Terminate the block of commands that are the body of @code{if},
22959 @code{else}, or @code{while} flow-control commands.
22964 @subsection Commands for Controlled Output
22966 During the execution of a command file or a user-defined command, normal
22967 @value{GDBN} output is suppressed; the only output that appears is what is
22968 explicitly printed by the commands in the definition. This section
22969 describes three commands useful for generating exactly the output you
22974 @item echo @var{text}
22975 @c I do not consider backslash-space a standard C escape sequence
22976 @c because it is not in ANSI.
22977 Print @var{text}. Nonprinting characters can be included in
22978 @var{text} using C escape sequences, such as @samp{\n} to print a
22979 newline. @strong{No newline is printed unless you specify one.}
22980 In addition to the standard C escape sequences, a backslash followed
22981 by a space stands for a space. This is useful for displaying a
22982 string with spaces at the beginning or the end, since leading and
22983 trailing spaces are otherwise trimmed from all arguments.
22984 To print @samp{@w{ }and foo =@w{ }}, use the command
22985 @samp{echo \@w{ }and foo = \@w{ }}.
22987 A backslash at the end of @var{text} can be used, as in C, to continue
22988 the command onto subsequent lines. For example,
22991 echo This is some text\n\
22992 which is continued\n\
22993 onto several lines.\n
22996 produces the same output as
22999 echo This is some text\n
23000 echo which is continued\n
23001 echo onto several lines.\n
23005 @item output @var{expression}
23006 Print the value of @var{expression} and nothing but that value: no
23007 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23008 value history either. @xref{Expressions, ,Expressions}, for more information
23011 @item output/@var{fmt} @var{expression}
23012 Print the value of @var{expression} in format @var{fmt}. You can use
23013 the same formats as for @code{print}. @xref{Output Formats,,Output
23014 Formats}, for more information.
23017 @item printf @var{template}, @var{expressions}@dots{}
23018 Print the values of one or more @var{expressions} under the control of
23019 the string @var{template}. To print several values, make
23020 @var{expressions} be a comma-separated list of individual expressions,
23021 which may be either numbers or pointers. Their values are printed as
23022 specified by @var{template}, exactly as a C program would do by
23023 executing the code below:
23026 printf (@var{template}, @var{expressions}@dots{});
23029 As in @code{C} @code{printf}, ordinary characters in @var{template}
23030 are printed verbatim, while @dfn{conversion specification} introduced
23031 by the @samp{%} character cause subsequent @var{expressions} to be
23032 evaluated, their values converted and formatted according to type and
23033 style information encoded in the conversion specifications, and then
23036 For example, you can print two values in hex like this:
23039 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23042 @code{printf} supports all the standard @code{C} conversion
23043 specifications, including the flags and modifiers between the @samp{%}
23044 character and the conversion letter, with the following exceptions:
23048 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23051 The modifier @samp{*} is not supported for specifying precision or
23055 The @samp{'} flag (for separation of digits into groups according to
23056 @code{LC_NUMERIC'}) is not supported.
23059 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23063 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23066 The conversion letters @samp{a} and @samp{A} are not supported.
23070 Note that the @samp{ll} type modifier is supported only if the
23071 underlying @code{C} implementation used to build @value{GDBN} supports
23072 the @code{long long int} type, and the @samp{L} type modifier is
23073 supported only if @code{long double} type is available.
23075 As in @code{C}, @code{printf} supports simple backslash-escape
23076 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23077 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23078 single character. Octal and hexadecimal escape sequences are not
23081 Additionally, @code{printf} supports conversion specifications for DFP
23082 (@dfn{Decimal Floating Point}) types using the following length modifiers
23083 together with a floating point specifier.
23088 @samp{H} for printing @code{Decimal32} types.
23091 @samp{D} for printing @code{Decimal64} types.
23094 @samp{DD} for printing @code{Decimal128} types.
23097 If the underlying @code{C} implementation used to build @value{GDBN} has
23098 support for the three length modifiers for DFP types, other modifiers
23099 such as width and precision will also be available for @value{GDBN} to use.
23101 In case there is no such @code{C} support, no additional modifiers will be
23102 available and the value will be printed in the standard way.
23104 Here's an example of printing DFP types using the above conversion letters:
23106 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23110 @item eval @var{template}, @var{expressions}@dots{}
23111 Convert the values of one or more @var{expressions} under the control of
23112 the string @var{template} to a command line, and call it.
23117 @section Scripting @value{GDBN} using Python
23118 @cindex python scripting
23119 @cindex scripting with python
23121 You can script @value{GDBN} using the @uref{http://www.python.org/,
23122 Python programming language}. This feature is available only if
23123 @value{GDBN} was configured using @option{--with-python}.
23125 @cindex python directory
23126 Python scripts used by @value{GDBN} should be installed in
23127 @file{@var{data-directory}/python}, where @var{data-directory} is
23128 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23129 This directory, known as the @dfn{python directory},
23130 is automatically added to the Python Search Path in order to allow
23131 the Python interpreter to locate all scripts installed at this location.
23133 Additionally, @value{GDBN} commands and convenience functions which
23134 are written in Python and are located in the
23135 @file{@var{data-directory}/python/gdb/command} or
23136 @file{@var{data-directory}/python/gdb/function} directories are
23137 automatically imported when @value{GDBN} starts.
23140 * Python Commands:: Accessing Python from @value{GDBN}.
23141 * Python API:: Accessing @value{GDBN} from Python.
23142 * Python Auto-loading:: Automatically loading Python code.
23143 * Python modules:: Python modules provided by @value{GDBN}.
23146 @node Python Commands
23147 @subsection Python Commands
23148 @cindex python commands
23149 @cindex commands to access python
23151 @value{GDBN} provides two commands for accessing the Python interpreter,
23152 and one related setting:
23155 @kindex python-interactive
23157 @item python-interactive @r{[}@var{command}@r{]}
23158 @itemx pi @r{[}@var{command}@r{]}
23159 Without an argument, the @code{python-interactive} command can be used
23160 to start an interactive Python prompt. To return to @value{GDBN},
23161 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23163 Alternatively, a single-line Python command can be given as an
23164 argument and evaluated. If the command is an expression, the result
23165 will be printed; otherwise, nothing will be printed. For example:
23168 (@value{GDBP}) python-interactive 2 + 3
23174 @item python @r{[}@var{command}@r{]}
23175 @itemx py @r{[}@var{command}@r{]}
23176 The @code{python} command can be used to evaluate Python code.
23178 If given an argument, the @code{python} command will evaluate the
23179 argument as a Python command. For example:
23182 (@value{GDBP}) python print 23
23186 If you do not provide an argument to @code{python}, it will act as a
23187 multi-line command, like @code{define}. In this case, the Python
23188 script is made up of subsequent command lines, given after the
23189 @code{python} command. This command list is terminated using a line
23190 containing @code{end}. For example:
23193 (@value{GDBP}) python
23195 End with a line saying just "end".
23201 @kindex set python print-stack
23202 @item set python print-stack
23203 By default, @value{GDBN} will print only the message component of a
23204 Python exception when an error occurs in a Python script. This can be
23205 controlled using @code{set python print-stack}: if @code{full}, then
23206 full Python stack printing is enabled; if @code{none}, then Python stack
23207 and message printing is disabled; if @code{message}, the default, only
23208 the message component of the error is printed.
23211 It is also possible to execute a Python script from the @value{GDBN}
23215 @item source @file{script-name}
23216 The script name must end with @samp{.py} and @value{GDBN} must be configured
23217 to recognize the script language based on filename extension using
23218 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23220 @item python execfile ("script-name")
23221 This method is based on the @code{execfile} Python built-in function,
23222 and thus is always available.
23226 @subsection Python API
23228 @cindex programming in python
23230 You can get quick online help for @value{GDBN}'s Python API by issuing
23231 the command @w{@kbd{python help (gdb)}}.
23233 Functions and methods which have two or more optional arguments allow
23234 them to be specified using keyword syntax. This allows passing some
23235 optional arguments while skipping others. Example:
23236 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23239 * Basic Python:: Basic Python Functions.
23240 * Exception Handling:: How Python exceptions are translated.
23241 * Values From Inferior:: Python representation of values.
23242 * Types In Python:: Python representation of types.
23243 * Pretty Printing API:: Pretty-printing values.
23244 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23245 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23246 * Type Printing API:: Pretty-printing types.
23247 * Frame Filter API:: Filtering Frames.
23248 * Frame Decorator API:: Decorating Frames.
23249 * Writing a Frame Filter:: Writing a Frame Filter.
23250 * Inferiors In Python:: Python representation of inferiors (processes)
23251 * Events In Python:: Listening for events from @value{GDBN}.
23252 * Threads In Python:: Accessing inferior threads from Python.
23253 * Commands In Python:: Implementing new commands in Python.
23254 * Parameters In Python:: Adding new @value{GDBN} parameters.
23255 * Functions In Python:: Writing new convenience functions.
23256 * Progspaces In Python:: Program spaces.
23257 * Objfiles In Python:: Object files.
23258 * Frames In Python:: Accessing inferior stack frames from Python.
23259 * Blocks In Python:: Accessing blocks from Python.
23260 * Symbols In Python:: Python representation of symbols.
23261 * Symbol Tables In Python:: Python representation of symbol tables.
23262 * Breakpoints In Python:: Manipulating breakpoints using Python.
23263 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23265 * Lazy Strings In Python:: Python representation of lazy strings.
23266 * Architectures In Python:: Python representation of architectures.
23270 @subsubsection Basic Python
23272 @cindex python stdout
23273 @cindex python pagination
23274 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23275 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23276 A Python program which outputs to one of these streams may have its
23277 output interrupted by the user (@pxref{Screen Size}). In this
23278 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23280 Some care must be taken when writing Python code to run in
23281 @value{GDBN}. Two things worth noting in particular:
23285 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23286 Python code must not override these, or even change the options using
23287 @code{sigaction}. If your program changes the handling of these
23288 signals, @value{GDBN} will most likely stop working correctly. Note
23289 that it is unfortunately common for GUI toolkits to install a
23290 @code{SIGCHLD} handler.
23293 @value{GDBN} takes care to mark its internal file descriptors as
23294 close-on-exec. However, this cannot be done in a thread-safe way on
23295 all platforms. Your Python programs should be aware of this and
23296 should both create new file descriptors with the close-on-exec flag
23297 set and arrange to close unneeded file descriptors before starting a
23301 @cindex python functions
23302 @cindex python module
23304 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23305 methods and classes added by @value{GDBN} are placed in this module.
23306 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23307 use in all scripts evaluated by the @code{python} command.
23309 @findex gdb.PYTHONDIR
23310 @defvar gdb.PYTHONDIR
23311 A string containing the python directory (@pxref{Python}).
23314 @findex gdb.execute
23315 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23316 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23317 If a GDB exception happens while @var{command} runs, it is
23318 translated as described in @ref{Exception Handling,,Exception Handling}.
23320 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23321 command as having originated from the user invoking it interactively.
23322 It must be a boolean value. If omitted, it defaults to @code{False}.
23324 By default, any output produced by @var{command} is sent to
23325 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23326 @code{True}, then output will be collected by @code{gdb.execute} and
23327 returned as a string. The default is @code{False}, in which case the
23328 return value is @code{None}. If @var{to_string} is @code{True}, the
23329 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23330 and height, and its pagination will be disabled; @pxref{Screen Size}.
23333 @findex gdb.breakpoints
23334 @defun gdb.breakpoints ()
23335 Return a sequence holding all of @value{GDBN}'s breakpoints.
23336 @xref{Breakpoints In Python}, for more information.
23339 @findex gdb.parameter
23340 @defun gdb.parameter (parameter)
23341 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23342 string naming the parameter to look up; @var{parameter} may contain
23343 spaces if the parameter has a multi-part name. For example,
23344 @samp{print object} is a valid parameter name.
23346 If the named parameter does not exist, this function throws a
23347 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23348 parameter's value is converted to a Python value of the appropriate
23349 type, and returned.
23352 @findex gdb.history
23353 @defun gdb.history (number)
23354 Return a value from @value{GDBN}'s value history (@pxref{Value
23355 History}). @var{number} indicates which history element to return.
23356 If @var{number} is negative, then @value{GDBN} will take its absolute value
23357 and count backward from the last element (i.e., the most recent element) to
23358 find the value to return. If @var{number} is zero, then @value{GDBN} will
23359 return the most recent element. If the element specified by @var{number}
23360 doesn't exist in the value history, a @code{gdb.error} exception will be
23363 If no exception is raised, the return value is always an instance of
23364 @code{gdb.Value} (@pxref{Values From Inferior}).
23367 @findex gdb.parse_and_eval
23368 @defun gdb.parse_and_eval (expression)
23369 Parse @var{expression} as an expression in the current language,
23370 evaluate it, and return the result as a @code{gdb.Value}.
23371 @var{expression} must be a string.
23373 This function can be useful when implementing a new command
23374 (@pxref{Commands In Python}), as it provides a way to parse the
23375 command's argument as an expression. It is also useful simply to
23376 compute values, for example, it is the only way to get the value of a
23377 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23380 @findex gdb.find_pc_line
23381 @defun gdb.find_pc_line (pc)
23382 Return the @code{gdb.Symtab_and_line} object corresponding to the
23383 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23384 value of @var{pc} is passed as an argument, then the @code{symtab} and
23385 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23386 will be @code{None} and 0 respectively.
23389 @findex gdb.post_event
23390 @defun gdb.post_event (event)
23391 Put @var{event}, a callable object taking no arguments, into
23392 @value{GDBN}'s internal event queue. This callable will be invoked at
23393 some later point, during @value{GDBN}'s event processing. Events
23394 posted using @code{post_event} will be run in the order in which they
23395 were posted; however, there is no way to know when they will be
23396 processed relative to other events inside @value{GDBN}.
23398 @value{GDBN} is not thread-safe. If your Python program uses multiple
23399 threads, you must be careful to only call @value{GDBN}-specific
23400 functions in the main @value{GDBN} thread. @code{post_event} ensures
23404 (@value{GDBP}) python
23408 > def __init__(self, message):
23409 > self.message = message;
23410 > def __call__(self):
23411 > gdb.write(self.message)
23413 >class MyThread1 (threading.Thread):
23415 > gdb.post_event(Writer("Hello "))
23417 >class MyThread2 (threading.Thread):
23419 > gdb.post_event(Writer("World\n"))
23421 >MyThread1().start()
23422 >MyThread2().start()
23424 (@value{GDBP}) Hello World
23429 @defun gdb.write (string @r{[}, stream{]})
23430 Print a string to @value{GDBN}'s paginated output stream. The
23431 optional @var{stream} determines the stream to print to. The default
23432 stream is @value{GDBN}'s standard output stream. Possible stream
23439 @value{GDBN}'s standard output stream.
23444 @value{GDBN}'s standard error stream.
23449 @value{GDBN}'s log stream (@pxref{Logging Output}).
23452 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23453 call this function and will automatically direct the output to the
23458 @defun gdb.flush ()
23459 Flush the buffer of a @value{GDBN} paginated stream so that the
23460 contents are displayed immediately. @value{GDBN} will flush the
23461 contents of a stream automatically when it encounters a newline in the
23462 buffer. The optional @var{stream} determines the stream to flush. The
23463 default stream is @value{GDBN}'s standard output stream. Possible
23470 @value{GDBN}'s standard output stream.
23475 @value{GDBN}'s standard error stream.
23480 @value{GDBN}'s log stream (@pxref{Logging Output}).
23484 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23485 call this function for the relevant stream.
23488 @findex gdb.target_charset
23489 @defun gdb.target_charset ()
23490 Return the name of the current target character set (@pxref{Character
23491 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23492 that @samp{auto} is never returned.
23495 @findex gdb.target_wide_charset
23496 @defun gdb.target_wide_charset ()
23497 Return the name of the current target wide character set
23498 (@pxref{Character Sets}). This differs from
23499 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23503 @findex gdb.solib_name
23504 @defun gdb.solib_name (address)
23505 Return the name of the shared library holding the given @var{address}
23506 as a string, or @code{None}.
23509 @findex gdb.decode_line
23510 @defun gdb.decode_line @r{[}expression@r{]}
23511 Return locations of the line specified by @var{expression}, or of the
23512 current line if no argument was given. This function returns a Python
23513 tuple containing two elements. The first element contains a string
23514 holding any unparsed section of @var{expression} (or @code{None} if
23515 the expression has been fully parsed). The second element contains
23516 either @code{None} or another tuple that contains all the locations
23517 that match the expression represented as @code{gdb.Symtab_and_line}
23518 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23519 provided, it is decoded the way that @value{GDBN}'s inbuilt
23520 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23523 @defun gdb.prompt_hook (current_prompt)
23524 @anchor{prompt_hook}
23526 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23527 assigned to this operation before a prompt is displayed by
23530 The parameter @code{current_prompt} contains the current @value{GDBN}
23531 prompt. This method must return a Python string, or @code{None}. If
23532 a string is returned, the @value{GDBN} prompt will be set to that
23533 string. If @code{None} is returned, @value{GDBN} will continue to use
23534 the current prompt.
23536 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23537 such as those used by readline for command input, and annotation
23538 related prompts are prohibited from being changed.
23541 @node Exception Handling
23542 @subsubsection Exception Handling
23543 @cindex python exceptions
23544 @cindex exceptions, python
23546 When executing the @code{python} command, Python exceptions
23547 uncaught within the Python code are translated to calls to
23548 @value{GDBN} error-reporting mechanism. If the command that called
23549 @code{python} does not handle the error, @value{GDBN} will
23550 terminate it and print an error message containing the Python
23551 exception name, the associated value, and the Python call stack
23552 backtrace at the point where the exception was raised. Example:
23555 (@value{GDBP}) python print foo
23556 Traceback (most recent call last):
23557 File "<string>", line 1, in <module>
23558 NameError: name 'foo' is not defined
23561 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23562 Python code are converted to Python exceptions. The type of the
23563 Python exception depends on the error.
23567 This is the base class for most exceptions generated by @value{GDBN}.
23568 It is derived from @code{RuntimeError}, for compatibility with earlier
23569 versions of @value{GDBN}.
23571 If an error occurring in @value{GDBN} does not fit into some more
23572 specific category, then the generated exception will have this type.
23574 @item gdb.MemoryError
23575 This is a subclass of @code{gdb.error} which is thrown when an
23576 operation tried to access invalid memory in the inferior.
23578 @item KeyboardInterrupt
23579 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23580 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23583 In all cases, your exception handler will see the @value{GDBN} error
23584 message as its value and the Python call stack backtrace at the Python
23585 statement closest to where the @value{GDBN} error occured as the
23588 @findex gdb.GdbError
23589 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23590 it is useful to be able to throw an exception that doesn't cause a
23591 traceback to be printed. For example, the user may have invoked the
23592 command incorrectly. Use the @code{gdb.GdbError} exception
23593 to handle this case. Example:
23597 >class HelloWorld (gdb.Command):
23598 > """Greet the whole world."""
23599 > def __init__ (self):
23600 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23601 > def invoke (self, args, from_tty):
23602 > argv = gdb.string_to_argv (args)
23603 > if len (argv) != 0:
23604 > raise gdb.GdbError ("hello-world takes no arguments")
23605 > print "Hello, World!"
23608 (gdb) hello-world 42
23609 hello-world takes no arguments
23612 @node Values From Inferior
23613 @subsubsection Values From Inferior
23614 @cindex values from inferior, with Python
23615 @cindex python, working with values from inferior
23617 @cindex @code{gdb.Value}
23618 @value{GDBN} provides values it obtains from the inferior program in
23619 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23620 for its internal bookkeeping of the inferior's values, and for
23621 fetching values when necessary.
23623 Inferior values that are simple scalars can be used directly in
23624 Python expressions that are valid for the value's data type. Here's
23625 an example for an integer or floating-point value @code{some_val}:
23632 As result of this, @code{bar} will also be a @code{gdb.Value} object
23633 whose values are of the same type as those of @code{some_val}.
23635 Inferior values that are structures or instances of some class can
23636 be accessed using the Python @dfn{dictionary syntax}. For example, if
23637 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23638 can access its @code{foo} element with:
23641 bar = some_val['foo']
23644 Again, @code{bar} will also be a @code{gdb.Value} object.
23646 A @code{gdb.Value} that represents a function can be executed via
23647 inferior function call. Any arguments provided to the call must match
23648 the function's prototype, and must be provided in the order specified
23651 For example, @code{some_val} is a @code{gdb.Value} instance
23652 representing a function that takes two integers as arguments. To
23653 execute this function, call it like so:
23656 result = some_val (10,20)
23659 Any values returned from a function call will be stored as a
23662 The following attributes are provided:
23664 @defvar Value.address
23665 If this object is addressable, this read-only attribute holds a
23666 @code{gdb.Value} object representing the address. Otherwise,
23667 this attribute holds @code{None}.
23670 @cindex optimized out value in Python
23671 @defvar Value.is_optimized_out
23672 This read-only boolean attribute is true if the compiler optimized out
23673 this value, thus it is not available for fetching from the inferior.
23677 The type of this @code{gdb.Value}. The value of this attribute is a
23678 @code{gdb.Type} object (@pxref{Types In Python}).
23681 @defvar Value.dynamic_type
23682 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23683 type information (@acronym{RTTI}) to determine the dynamic type of the
23684 value. If this value is of class type, it will return the class in
23685 which the value is embedded, if any. If this value is of pointer or
23686 reference to a class type, it will compute the dynamic type of the
23687 referenced object, and return a pointer or reference to that type,
23688 respectively. In all other cases, it will return the value's static
23691 Note that this feature will only work when debugging a C@t{++} program
23692 that includes @acronym{RTTI} for the object in question. Otherwise,
23693 it will just return the static type of the value as in @kbd{ptype foo}
23694 (@pxref{Symbols, ptype}).
23697 @defvar Value.is_lazy
23698 The value of this read-only boolean attribute is @code{True} if this
23699 @code{gdb.Value} has not yet been fetched from the inferior.
23700 @value{GDBN} does not fetch values until necessary, for efficiency.
23704 myval = gdb.parse_and_eval ('somevar')
23707 The value of @code{somevar} is not fetched at this time. It will be
23708 fetched when the value is needed, or when the @code{fetch_lazy}
23712 The following methods are provided:
23714 @defun Value.__init__ (@var{val})
23715 Many Python values can be converted directly to a @code{gdb.Value} via
23716 this object initializer. Specifically:
23719 @item Python boolean
23720 A Python boolean is converted to the boolean type from the current
23723 @item Python integer
23724 A Python integer is converted to the C @code{long} type for the
23725 current architecture.
23728 A Python long is converted to the C @code{long long} type for the
23729 current architecture.
23732 A Python float is converted to the C @code{double} type for the
23733 current architecture.
23735 @item Python string
23736 A Python string is converted to a target string, using the current
23739 @item @code{gdb.Value}
23740 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23742 @item @code{gdb.LazyString}
23743 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23744 Python}), then the lazy string's @code{value} method is called, and
23745 its result is used.
23749 @defun Value.cast (type)
23750 Return a new instance of @code{gdb.Value} that is the result of
23751 casting this instance to the type described by @var{type}, which must
23752 be a @code{gdb.Type} object. If the cast cannot be performed for some
23753 reason, this method throws an exception.
23756 @defun Value.dereference ()
23757 For pointer data types, this method returns a new @code{gdb.Value} object
23758 whose contents is the object pointed to by the pointer. For example, if
23759 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23766 then you can use the corresponding @code{gdb.Value} to access what
23767 @code{foo} points to like this:
23770 bar = foo.dereference ()
23773 The result @code{bar} will be a @code{gdb.Value} object holding the
23774 value pointed to by @code{foo}.
23776 A similar function @code{Value.referenced_value} exists which also
23777 returns @code{gdb.Value} objects corresonding to the values pointed to
23778 by pointer values (and additionally, values referenced by reference
23779 values). However, the behavior of @code{Value.dereference}
23780 differs from @code{Value.referenced_value} by the fact that the
23781 behavior of @code{Value.dereference} is identical to applying the C
23782 unary operator @code{*} on a given value. For example, consider a
23783 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23787 typedef int *intptr;
23791 intptr &ptrref = ptr;
23794 Though @code{ptrref} is a reference value, one can apply the method
23795 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23796 to it and obtain a @code{gdb.Value} which is identical to that
23797 corresponding to @code{val}. However, if you apply the method
23798 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23799 object identical to that corresponding to @code{ptr}.
23802 py_ptrref = gdb.parse_and_eval ("ptrref")
23803 py_val = py_ptrref.dereference ()
23804 py_ptr = py_ptrref.referenced_value ()
23807 The @code{gdb.Value} object @code{py_val} is identical to that
23808 corresponding to @code{val}, and @code{py_ptr} is identical to that
23809 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23810 be applied whenever the C unary operator @code{*} can be applied
23811 to the corresponding C value. For those cases where applying both
23812 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23813 the results obtained need not be identical (as we have seen in the above
23814 example). The results are however identical when applied on
23815 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23816 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23819 @defun Value.referenced_value ()
23820 For pointer or reference data types, this method returns a new
23821 @code{gdb.Value} object corresponding to the value referenced by the
23822 pointer/reference value. For pointer data types,
23823 @code{Value.dereference} and @code{Value.referenced_value} produce
23824 identical results. The difference between these methods is that
23825 @code{Value.dereference} cannot get the values referenced by reference
23826 values. For example, consider a reference to an @code{int}, declared
23827 in your C@t{++} program as
23835 then applying @code{Value.dereference} to the @code{gdb.Value} object
23836 corresponding to @code{ref} will result in an error, while applying
23837 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23838 identical to that corresponding to @code{val}.
23841 py_ref = gdb.parse_and_eval ("ref")
23842 er_ref = py_ref.dereference () # Results in error
23843 py_val = py_ref.referenced_value () # Returns the referenced value
23846 The @code{gdb.Value} object @code{py_val} is identical to that
23847 corresponding to @code{val}.
23850 @defun Value.dynamic_cast (type)
23851 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23852 operator were used. Consult a C@t{++} reference for details.
23855 @defun Value.reinterpret_cast (type)
23856 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23857 operator were used. Consult a C@t{++} reference for details.
23860 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23861 If this @code{gdb.Value} represents a string, then this method
23862 converts the contents to a Python string. Otherwise, this method will
23863 throw an exception.
23865 Strings are recognized in a language-specific way; whether a given
23866 @code{gdb.Value} represents a string is determined by the current
23869 For C-like languages, a value is a string if it is a pointer to or an
23870 array of characters or ints. The string is assumed to be terminated
23871 by a zero of the appropriate width. However if the optional length
23872 argument is given, the string will be converted to that given length,
23873 ignoring any embedded zeros that the string may contain.
23875 If the optional @var{encoding} argument is given, it must be a string
23876 naming the encoding of the string in the @code{gdb.Value}, such as
23877 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23878 the same encodings as the corresponding argument to Python's
23879 @code{string.decode} method, and the Python codec machinery will be used
23880 to convert the string. If @var{encoding} is not given, or if
23881 @var{encoding} is the empty string, then either the @code{target-charset}
23882 (@pxref{Character Sets}) will be used, or a language-specific encoding
23883 will be used, if the current language is able to supply one.
23885 The optional @var{errors} argument is the same as the corresponding
23886 argument to Python's @code{string.decode} method.
23888 If the optional @var{length} argument is given, the string will be
23889 fetched and converted to the given length.
23892 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23893 If this @code{gdb.Value} represents a string, then this method
23894 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23895 In Python}). Otherwise, this method will throw an exception.
23897 If the optional @var{encoding} argument is given, it must be a string
23898 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23899 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23900 @var{encoding} argument is an encoding that @value{GDBN} does
23901 recognize, @value{GDBN} will raise an error.
23903 When a lazy string is printed, the @value{GDBN} encoding machinery is
23904 used to convert the string during printing. If the optional
23905 @var{encoding} argument is not provided, or is an empty string,
23906 @value{GDBN} will automatically select the encoding most suitable for
23907 the string type. For further information on encoding in @value{GDBN}
23908 please see @ref{Character Sets}.
23910 If the optional @var{length} argument is given, the string will be
23911 fetched and encoded to the length of characters specified. If
23912 the @var{length} argument is not provided, the string will be fetched
23913 and encoded until a null of appropriate width is found.
23916 @defun Value.fetch_lazy ()
23917 If the @code{gdb.Value} object is currently a lazy value
23918 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23919 fetched from the inferior. Any errors that occur in the process
23920 will produce a Python exception.
23922 If the @code{gdb.Value} object is not a lazy value, this method
23925 This method does not return a value.
23929 @node Types In Python
23930 @subsubsection Types In Python
23931 @cindex types in Python
23932 @cindex Python, working with types
23935 @value{GDBN} represents types from the inferior using the class
23938 The following type-related functions are available in the @code{gdb}
23941 @findex gdb.lookup_type
23942 @defun gdb.lookup_type (name @r{[}, block@r{]})
23943 This function looks up a type by name. @var{name} is the name of the
23944 type to look up. It must be a string.
23946 If @var{block} is given, then @var{name} is looked up in that scope.
23947 Otherwise, it is searched for globally.
23949 Ordinarily, this function will return an instance of @code{gdb.Type}.
23950 If the named type cannot be found, it will throw an exception.
23953 If the type is a structure or class type, or an enum type, the fields
23954 of that type can be accessed using the Python @dfn{dictionary syntax}.
23955 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23956 a structure type, you can access its @code{foo} field with:
23959 bar = some_type['foo']
23962 @code{bar} will be a @code{gdb.Field} object; see below under the
23963 description of the @code{Type.fields} method for a description of the
23964 @code{gdb.Field} class.
23966 An instance of @code{Type} has the following attributes:
23969 The type code for this type. The type code will be one of the
23970 @code{TYPE_CODE_} constants defined below.
23973 @defvar Type.sizeof
23974 The size of this type, in target @code{char} units. Usually, a
23975 target's @code{char} type will be an 8-bit byte. However, on some
23976 unusual platforms, this type may have a different size.
23980 The tag name for this type. The tag name is the name after
23981 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23982 languages have this concept. If this type has no tag name, then
23983 @code{None} is returned.
23986 The following methods are provided:
23988 @defun Type.fields ()
23989 For structure and union types, this method returns the fields. Range
23990 types have two fields, the minimum and maximum values. Enum types
23991 have one field per enum constant. Function and method types have one
23992 field per parameter. The base types of C@t{++} classes are also
23993 represented as fields. If the type has no fields, or does not fit
23994 into one of these categories, an empty sequence will be returned.
23996 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23999 This attribute is not available for @code{static} fields (as in
24000 C@t{++} or Java). For non-@code{static} fields, the value is the bit
24001 position of the field. For @code{enum} fields, the value is the
24002 enumeration member's integer representation.
24005 The name of the field, or @code{None} for anonymous fields.
24008 This is @code{True} if the field is artificial, usually meaning that
24009 it was provided by the compiler and not the user. This attribute is
24010 always provided, and is @code{False} if the field is not artificial.
24012 @item is_base_class
24013 This is @code{True} if the field represents a base class of a C@t{++}
24014 structure. This attribute is always provided, and is @code{False}
24015 if the field is not a base class of the type that is the argument of
24016 @code{fields}, or if that type was not a C@t{++} class.
24019 If the field is packed, or is a bitfield, then this will have a
24020 non-zero value, which is the size of the field in bits. Otherwise,
24021 this will be zero; in this case the field's size is given by its type.
24024 The type of the field. This is usually an instance of @code{Type},
24025 but it can be @code{None} in some situations.
24029 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24030 Return a new @code{gdb.Type} object which represents an array of this
24031 type. If one argument is given, it is the inclusive upper bound of
24032 the array; in this case the lower bound is zero. If two arguments are
24033 given, the first argument is the lower bound of the array, and the
24034 second argument is the upper bound of the array. An array's length
24035 must not be negative, but the bounds can be.
24038 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24039 Return a new @code{gdb.Type} object which represents a vector of this
24040 type. If one argument is given, it is the inclusive upper bound of
24041 the vector; in this case the lower bound is zero. If two arguments are
24042 given, the first argument is the lower bound of the vector, and the
24043 second argument is the upper bound of the vector. A vector's length
24044 must not be negative, but the bounds can be.
24046 The difference between an @code{array} and a @code{vector} is that
24047 arrays behave like in C: when used in expressions they decay to a pointer
24048 to the first element whereas vectors are treated as first class values.
24051 @defun Type.const ()
24052 Return a new @code{gdb.Type} object which represents a
24053 @code{const}-qualified variant of this type.
24056 @defun Type.volatile ()
24057 Return a new @code{gdb.Type} object which represents a
24058 @code{volatile}-qualified variant of this type.
24061 @defun Type.unqualified ()
24062 Return a new @code{gdb.Type} object which represents an unqualified
24063 variant of this type. That is, the result is neither @code{const} nor
24067 @defun Type.range ()
24068 Return a Python @code{Tuple} object that contains two elements: the
24069 low bound of the argument type and the high bound of that type. If
24070 the type does not have a range, @value{GDBN} will raise a
24071 @code{gdb.error} exception (@pxref{Exception Handling}).
24074 @defun Type.reference ()
24075 Return a new @code{gdb.Type} object which represents a reference to this
24079 @defun Type.pointer ()
24080 Return a new @code{gdb.Type} object which represents a pointer to this
24084 @defun Type.strip_typedefs ()
24085 Return a new @code{gdb.Type} that represents the real type,
24086 after removing all layers of typedefs.
24089 @defun Type.target ()
24090 Return a new @code{gdb.Type} object which represents the target type
24093 For a pointer type, the target type is the type of the pointed-to
24094 object. For an array type (meaning C-like arrays), the target type is
24095 the type of the elements of the array. For a function or method type,
24096 the target type is the type of the return value. For a complex type,
24097 the target type is the type of the elements. For a typedef, the
24098 target type is the aliased type.
24100 If the type does not have a target, this method will throw an
24104 @defun Type.template_argument (n @r{[}, block@r{]})
24105 If this @code{gdb.Type} is an instantiation of a template, this will
24106 return a new @code{gdb.Type} which represents the type of the
24107 @var{n}th template argument.
24109 If this @code{gdb.Type} is not a template type, this will throw an
24110 exception. Ordinarily, only C@t{++} code will have template types.
24112 If @var{block} is given, then @var{name} is looked up in that scope.
24113 Otherwise, it is searched for globally.
24117 Each type has a code, which indicates what category this type falls
24118 into. The available type categories are represented by constants
24119 defined in the @code{gdb} module:
24122 @findex TYPE_CODE_PTR
24123 @findex gdb.TYPE_CODE_PTR
24124 @item gdb.TYPE_CODE_PTR
24125 The type is a pointer.
24127 @findex TYPE_CODE_ARRAY
24128 @findex gdb.TYPE_CODE_ARRAY
24129 @item gdb.TYPE_CODE_ARRAY
24130 The type is an array.
24132 @findex TYPE_CODE_STRUCT
24133 @findex gdb.TYPE_CODE_STRUCT
24134 @item gdb.TYPE_CODE_STRUCT
24135 The type is a structure.
24137 @findex TYPE_CODE_UNION
24138 @findex gdb.TYPE_CODE_UNION
24139 @item gdb.TYPE_CODE_UNION
24140 The type is a union.
24142 @findex TYPE_CODE_ENUM
24143 @findex gdb.TYPE_CODE_ENUM
24144 @item gdb.TYPE_CODE_ENUM
24145 The type is an enum.
24147 @findex TYPE_CODE_FLAGS
24148 @findex gdb.TYPE_CODE_FLAGS
24149 @item gdb.TYPE_CODE_FLAGS
24150 A bit flags type, used for things such as status registers.
24152 @findex TYPE_CODE_FUNC
24153 @findex gdb.TYPE_CODE_FUNC
24154 @item gdb.TYPE_CODE_FUNC
24155 The type is a function.
24157 @findex TYPE_CODE_INT
24158 @findex gdb.TYPE_CODE_INT
24159 @item gdb.TYPE_CODE_INT
24160 The type is an integer type.
24162 @findex TYPE_CODE_FLT
24163 @findex gdb.TYPE_CODE_FLT
24164 @item gdb.TYPE_CODE_FLT
24165 A floating point type.
24167 @findex TYPE_CODE_VOID
24168 @findex gdb.TYPE_CODE_VOID
24169 @item gdb.TYPE_CODE_VOID
24170 The special type @code{void}.
24172 @findex TYPE_CODE_SET
24173 @findex gdb.TYPE_CODE_SET
24174 @item gdb.TYPE_CODE_SET
24177 @findex TYPE_CODE_RANGE
24178 @findex gdb.TYPE_CODE_RANGE
24179 @item gdb.TYPE_CODE_RANGE
24180 A range type, that is, an integer type with bounds.
24182 @findex TYPE_CODE_STRING
24183 @findex gdb.TYPE_CODE_STRING
24184 @item gdb.TYPE_CODE_STRING
24185 A string type. Note that this is only used for certain languages with
24186 language-defined string types; C strings are not represented this way.
24188 @findex TYPE_CODE_BITSTRING
24189 @findex gdb.TYPE_CODE_BITSTRING
24190 @item gdb.TYPE_CODE_BITSTRING
24191 A string of bits. It is deprecated.
24193 @findex TYPE_CODE_ERROR
24194 @findex gdb.TYPE_CODE_ERROR
24195 @item gdb.TYPE_CODE_ERROR
24196 An unknown or erroneous type.
24198 @findex TYPE_CODE_METHOD
24199 @findex gdb.TYPE_CODE_METHOD
24200 @item gdb.TYPE_CODE_METHOD
24201 A method type, as found in C@t{++} or Java.
24203 @findex TYPE_CODE_METHODPTR
24204 @findex gdb.TYPE_CODE_METHODPTR
24205 @item gdb.TYPE_CODE_METHODPTR
24206 A pointer-to-member-function.
24208 @findex TYPE_CODE_MEMBERPTR
24209 @findex gdb.TYPE_CODE_MEMBERPTR
24210 @item gdb.TYPE_CODE_MEMBERPTR
24211 A pointer-to-member.
24213 @findex TYPE_CODE_REF
24214 @findex gdb.TYPE_CODE_REF
24215 @item gdb.TYPE_CODE_REF
24218 @findex TYPE_CODE_CHAR
24219 @findex gdb.TYPE_CODE_CHAR
24220 @item gdb.TYPE_CODE_CHAR
24223 @findex TYPE_CODE_BOOL
24224 @findex gdb.TYPE_CODE_BOOL
24225 @item gdb.TYPE_CODE_BOOL
24228 @findex TYPE_CODE_COMPLEX
24229 @findex gdb.TYPE_CODE_COMPLEX
24230 @item gdb.TYPE_CODE_COMPLEX
24231 A complex float type.
24233 @findex TYPE_CODE_TYPEDEF
24234 @findex gdb.TYPE_CODE_TYPEDEF
24235 @item gdb.TYPE_CODE_TYPEDEF
24236 A typedef to some other type.
24238 @findex TYPE_CODE_NAMESPACE
24239 @findex gdb.TYPE_CODE_NAMESPACE
24240 @item gdb.TYPE_CODE_NAMESPACE
24241 A C@t{++} namespace.
24243 @findex TYPE_CODE_DECFLOAT
24244 @findex gdb.TYPE_CODE_DECFLOAT
24245 @item gdb.TYPE_CODE_DECFLOAT
24246 A decimal floating point type.
24248 @findex TYPE_CODE_INTERNAL_FUNCTION
24249 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24250 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24251 A function internal to @value{GDBN}. This is the type used to represent
24252 convenience functions.
24255 Further support for types is provided in the @code{gdb.types}
24256 Python module (@pxref{gdb.types}).
24258 @node Pretty Printing API
24259 @subsubsection Pretty Printing API
24261 An example output is provided (@pxref{Pretty Printing}).
24263 A pretty-printer is just an object that holds a value and implements a
24264 specific interface, defined here.
24266 @defun pretty_printer.children (self)
24267 @value{GDBN} will call this method on a pretty-printer to compute the
24268 children of the pretty-printer's value.
24270 This method must return an object conforming to the Python iterator
24271 protocol. Each item returned by the iterator must be a tuple holding
24272 two elements. The first element is the ``name'' of the child; the
24273 second element is the child's value. The value can be any Python
24274 object which is convertible to a @value{GDBN} value.
24276 This method is optional. If it does not exist, @value{GDBN} will act
24277 as though the value has no children.
24280 @defun pretty_printer.display_hint (self)
24281 The CLI may call this method and use its result to change the
24282 formatting of a value. The result will also be supplied to an MI
24283 consumer as a @samp{displayhint} attribute of the variable being
24286 This method is optional. If it does exist, this method must return a
24289 Some display hints are predefined by @value{GDBN}:
24293 Indicate that the object being printed is ``array-like''. The CLI
24294 uses this to respect parameters such as @code{set print elements} and
24295 @code{set print array}.
24298 Indicate that the object being printed is ``map-like'', and that the
24299 children of this value can be assumed to alternate between keys and
24303 Indicate that the object being printed is ``string-like''. If the
24304 printer's @code{to_string} method returns a Python string of some
24305 kind, then @value{GDBN} will call its internal language-specific
24306 string-printing function to format the string. For the CLI this means
24307 adding quotation marks, possibly escaping some characters, respecting
24308 @code{set print elements}, and the like.
24312 @defun pretty_printer.to_string (self)
24313 @value{GDBN} will call this method to display the string
24314 representation of the value passed to the object's constructor.
24316 When printing from the CLI, if the @code{to_string} method exists,
24317 then @value{GDBN} will prepend its result to the values returned by
24318 @code{children}. Exactly how this formatting is done is dependent on
24319 the display hint, and may change as more hints are added. Also,
24320 depending on the print settings (@pxref{Print Settings}), the CLI may
24321 print just the result of @code{to_string} in a stack trace, omitting
24322 the result of @code{children}.
24324 If this method returns a string, it is printed verbatim.
24326 Otherwise, if this method returns an instance of @code{gdb.Value},
24327 then @value{GDBN} prints this value. This may result in a call to
24328 another pretty-printer.
24330 If instead the method returns a Python value which is convertible to a
24331 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24332 the resulting value. Again, this may result in a call to another
24333 pretty-printer. Python scalars (integers, floats, and booleans) and
24334 strings are convertible to @code{gdb.Value}; other types are not.
24336 Finally, if this method returns @code{None} then no further operations
24337 are peformed in this method and nothing is printed.
24339 If the result is not one of these types, an exception is raised.
24342 @value{GDBN} provides a function which can be used to look up the
24343 default pretty-printer for a @code{gdb.Value}:
24345 @findex gdb.default_visualizer
24346 @defun gdb.default_visualizer (value)
24347 This function takes a @code{gdb.Value} object as an argument. If a
24348 pretty-printer for this value exists, then it is returned. If no such
24349 printer exists, then this returns @code{None}.
24352 @node Selecting Pretty-Printers
24353 @subsubsection Selecting Pretty-Printers
24355 The Python list @code{gdb.pretty_printers} contains an array of
24356 functions or callable objects that have been registered via addition
24357 as a pretty-printer. Printers in this list are called @code{global}
24358 printers, they're available when debugging all inferiors.
24359 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24360 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24363 Each function on these lists is passed a single @code{gdb.Value}
24364 argument and should return a pretty-printer object conforming to the
24365 interface definition above (@pxref{Pretty Printing API}). If a function
24366 cannot create a pretty-printer for the value, it should return
24369 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24370 @code{gdb.Objfile} in the current program space and iteratively calls
24371 each enabled lookup routine in the list for that @code{gdb.Objfile}
24372 until it receives a pretty-printer object.
24373 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24374 searches the pretty-printer list of the current program space,
24375 calling each enabled function until an object is returned.
24376 After these lists have been exhausted, it tries the global
24377 @code{gdb.pretty_printers} list, again calling each enabled function until an
24378 object is returned.
24380 The order in which the objfiles are searched is not specified. For a
24381 given list, functions are always invoked from the head of the list,
24382 and iterated over sequentially until the end of the list, or a printer
24383 object is returned.
24385 For various reasons a pretty-printer may not work.
24386 For example, the underlying data structure may have changed and
24387 the pretty-printer is out of date.
24389 The consequences of a broken pretty-printer are severe enough that
24390 @value{GDBN} provides support for enabling and disabling individual
24391 printers. For example, if @code{print frame-arguments} is on,
24392 a backtrace can become highly illegible if any argument is printed
24393 with a broken printer.
24395 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24396 attribute to the registered function or callable object. If this attribute
24397 is present and its value is @code{False}, the printer is disabled, otherwise
24398 the printer is enabled.
24400 @node Writing a Pretty-Printer
24401 @subsubsection Writing a Pretty-Printer
24402 @cindex writing a pretty-printer
24404 A pretty-printer consists of two parts: a lookup function to detect
24405 if the type is supported, and the printer itself.
24407 Here is an example showing how a @code{std::string} printer might be
24408 written. @xref{Pretty Printing API}, for details on the API this class
24412 class StdStringPrinter(object):
24413 "Print a std::string"
24415 def __init__(self, val):
24418 def to_string(self):
24419 return self.val['_M_dataplus']['_M_p']
24421 def display_hint(self):
24425 And here is an example showing how a lookup function for the printer
24426 example above might be written.
24429 def str_lookup_function(val):
24430 lookup_tag = val.type.tag
24431 if lookup_tag == None:
24433 regex = re.compile("^std::basic_string<char,.*>$")
24434 if regex.match(lookup_tag):
24435 return StdStringPrinter(val)
24439 The example lookup function extracts the value's type, and attempts to
24440 match it to a type that it can pretty-print. If it is a type the
24441 printer can pretty-print, it will return a printer object. If not, it
24442 returns @code{None}.
24444 We recommend that you put your core pretty-printers into a Python
24445 package. If your pretty-printers are for use with a library, we
24446 further recommend embedding a version number into the package name.
24447 This practice will enable @value{GDBN} to load multiple versions of
24448 your pretty-printers at the same time, because they will have
24451 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24452 can be evaluated multiple times without changing its meaning. An
24453 ideal auto-load file will consist solely of @code{import}s of your
24454 printer modules, followed by a call to a register pretty-printers with
24455 the current objfile.
24457 Taken as a whole, this approach will scale nicely to multiple
24458 inferiors, each potentially using a different library version.
24459 Embedding a version number in the Python package name will ensure that
24460 @value{GDBN} is able to load both sets of printers simultaneously.
24461 Then, because the search for pretty-printers is done by objfile, and
24462 because your auto-loaded code took care to register your library's
24463 printers with a specific objfile, @value{GDBN} will find the correct
24464 printers for the specific version of the library used by each
24467 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24468 this code might appear in @code{gdb.libstdcxx.v6}:
24471 def register_printers(objfile):
24472 objfile.pretty_printers.append(str_lookup_function)
24476 And then the corresponding contents of the auto-load file would be:
24479 import gdb.libstdcxx.v6
24480 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24483 The previous example illustrates a basic pretty-printer.
24484 There are a few things that can be improved on.
24485 The printer doesn't have a name, making it hard to identify in a
24486 list of installed printers. The lookup function has a name, but
24487 lookup functions can have arbitrary, even identical, names.
24489 Second, the printer only handles one type, whereas a library typically has
24490 several types. One could install a lookup function for each desired type
24491 in the library, but one could also have a single lookup function recognize
24492 several types. The latter is the conventional way this is handled.
24493 If a pretty-printer can handle multiple data types, then its
24494 @dfn{subprinters} are the printers for the individual data types.
24496 The @code{gdb.printing} module provides a formal way of solving these
24497 problems (@pxref{gdb.printing}).
24498 Here is another example that handles multiple types.
24500 These are the types we are going to pretty-print:
24503 struct foo @{ int a, b; @};
24504 struct bar @{ struct foo x, y; @};
24507 Here are the printers:
24511 """Print a foo object."""
24513 def __init__(self, val):
24516 def to_string(self):
24517 return ("a=<" + str(self.val["a"]) +
24518 "> b=<" + str(self.val["b"]) + ">")
24521 """Print a bar object."""
24523 def __init__(self, val):
24526 def to_string(self):
24527 return ("x=<" + str(self.val["x"]) +
24528 "> y=<" + str(self.val["y"]) + ">")
24531 This example doesn't need a lookup function, that is handled by the
24532 @code{gdb.printing} module. Instead a function is provided to build up
24533 the object that handles the lookup.
24536 import gdb.printing
24538 def build_pretty_printer():
24539 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24541 pp.add_printer('foo', '^foo$', fooPrinter)
24542 pp.add_printer('bar', '^bar$', barPrinter)
24546 And here is the autoload support:
24549 import gdb.printing
24551 gdb.printing.register_pretty_printer(
24552 gdb.current_objfile(),
24553 my_library.build_pretty_printer())
24556 Finally, when this printer is loaded into @value{GDBN}, here is the
24557 corresponding output of @samp{info pretty-printer}:
24560 (gdb) info pretty-printer
24567 @node Type Printing API
24568 @subsubsection Type Printing API
24569 @cindex type printing API for Python
24571 @value{GDBN} provides a way for Python code to customize type display.
24572 This is mainly useful for substituting canonical typedef names for
24575 @cindex type printer
24576 A @dfn{type printer} is just a Python object conforming to a certain
24577 protocol. A simple base class implementing the protocol is provided;
24578 see @ref{gdb.types}. A type printer must supply at least:
24580 @defivar type_printer enabled
24581 A boolean which is True if the printer is enabled, and False
24582 otherwise. This is manipulated by the @code{enable type-printer}
24583 and @code{disable type-printer} commands.
24586 @defivar type_printer name
24587 The name of the type printer. This must be a string. This is used by
24588 the @code{enable type-printer} and @code{disable type-printer}
24592 @defmethod type_printer instantiate (self)
24593 This is called by @value{GDBN} at the start of type-printing. It is
24594 only called if the type printer is enabled. This method must return a
24595 new object that supplies a @code{recognize} method, as described below.
24599 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24600 will compute a list of type recognizers. This is done by iterating
24601 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24602 followed by the per-progspace type printers (@pxref{Progspaces In
24603 Python}), and finally the global type printers.
24605 @value{GDBN} will call the @code{instantiate} method of each enabled
24606 type printer. If this method returns @code{None}, then the result is
24607 ignored; otherwise, it is appended to the list of recognizers.
24609 Then, when @value{GDBN} is going to display a type name, it iterates
24610 over the list of recognizers. For each one, it calls the recognition
24611 function, stopping if the function returns a non-@code{None} value.
24612 The recognition function is defined as:
24614 @defmethod type_recognizer recognize (self, type)
24615 If @var{type} is not recognized, return @code{None}. Otherwise,
24616 return a string which is to be printed as the name of @var{type}.
24617 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24621 @value{GDBN} uses this two-pass approach so that type printers can
24622 efficiently cache information without holding on to it too long. For
24623 example, it can be convenient to look up type information in a type
24624 printer and hold it for a recognizer's lifetime; if a single pass were
24625 done then type printers would have to make use of the event system in
24626 order to avoid holding information that could become stale as the
24629 @node Frame Filter API
24630 @subsubsection Filtering Frames.
24631 @cindex frame filters api
24633 Frame filters are Python objects that manipulate the visibility of a
24634 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
24637 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
24638 commands (@pxref{GDB/MI}), those that return a collection of frames
24639 are affected. The commands that work with frame filters are:
24641 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
24642 @code{-stack-list-frames}
24643 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
24644 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
24645 -stack-list-variables command}), @code{-stack-list-arguments}
24646 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
24647 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
24648 -stack-list-locals command}).
24650 A frame filter works by taking an iterator as an argument, applying
24651 actions to the contents of that iterator, and returning another
24652 iterator (or, possibly, the same iterator it was provided in the case
24653 where the filter does not perform any operations). Typically, frame
24654 filters utilize tools such as the Python's @code{itertools} module to
24655 work with and create new iterators from the source iterator.
24656 Regardless of how a filter chooses to apply actions, it must not alter
24657 the underlying @value{GDBN} frame or frames, or attempt to alter the
24658 call-stack within @value{GDBN}. This preserves data integrity within
24659 @value{GDBN}. Frame filters are executed on a priority basis and care
24660 should be taken that some frame filters may have been executed before,
24661 and that some frame filters will be executed after.
24663 An important consideration when designing frame filters, and well
24664 worth reflecting upon, is that frame filters should avoid unwinding
24665 the call stack if possible. Some stacks can run very deep, into the
24666 tens of thousands in some cases. To search every frame when a frame
24667 filter executes may be too expensive at that step. The frame filter
24668 cannot know how many frames it has to iterate over, and it may have to
24669 iterate through them all. This ends up duplicating effort as
24670 @value{GDBN} performs this iteration when it prints the frames. If
24671 the filter can defer unwinding frames until frame decorators are
24672 executed, after the last filter has executed, it should. @xref{Frame
24673 Decorator API}, for more information on decorators. Also, there are
24674 examples for both frame decorators and filters in later chapters.
24675 @xref{Writing a Frame Filter}, for more information.
24677 The Python dictionary @code{gdb.frame_filters} contains key/object
24678 pairings that comprise a frame filter. Frame filters in this
24679 dictionary are called @code{global} frame filters, and they are
24680 available when debugging all inferiors. These frame filters must
24681 register with the dictionary directly. In addition to the
24682 @code{global} dictionary, there are other dictionaries that are loaded
24683 with different inferiors via auto-loading (@pxref{Python
24684 Auto-loading}). The two other areas where frame filter dictionaries
24685 can be found are: @code{gdb.Progspace} which contains a
24686 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
24687 object which also contains a @code{frame_filters} dictionary
24690 When a command is executed from @value{GDBN} that is compatible with
24691 frame filters, @value{GDBN} combines the @code{global},
24692 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
24693 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
24694 several frames, and thus several object files, might be in use.
24695 @value{GDBN} then prunes any frame filter whose @code{enabled}
24696 attribute is @code{False}. This pruned list is then sorted according
24697 to the @code{priority} attribute in each filter.
24699 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
24700 creates an iterator which wraps each frame in the call stack in a
24701 @code{FrameDecorator} object, and calls each filter in order. The
24702 output from the previous filter will always be the input to the next
24705 Frame filters have a mandatory interface which each frame filter must
24706 implement, defined here:
24708 @defun FrameFilter.filter (iterator)
24709 @value{GDBN} will call this method on a frame filter when it has
24710 reached the order in the priority list for that filter.
24712 For example, if there are four frame filters:
24723 The order that the frame filters will be called is:
24726 Filter3 -> Filter2 -> Filter1 -> Filter4
24729 Note that the output from @code{Filter3} is passed to the input of
24730 @code{Filter2}, and so on.
24732 This @code{filter} method is passed a Python iterator. This iterator
24733 contains a sequence of frame decorators that wrap each
24734 @code{gdb.Frame}, or a frame decorator that wraps another frame
24735 decorator. The first filter that is executed in the sequence of frame
24736 filters will receive an iterator entirely comprised of default
24737 @code{FrameDecorator} objects. However, after each frame filter is
24738 executed, the previous frame filter may have wrapped some or all of
24739 the frame decorators with their own frame decorator. As frame
24740 decorators must also conform to a mandatory interface, these
24741 decorators can be assumed to act in a uniform manner (@pxref{Frame
24744 This method must return an object conforming to the Python iterator
24745 protocol. Each item in the iterator must be an object conforming to
24746 the frame decorator interface. If a frame filter does not wish to
24747 perform any operations on this iterator, it should return that
24748 iterator untouched.
24750 This method is not optional. If it does not exist, @value{GDBN} will
24751 raise and print an error.
24754 @defvar FrameFilter.name
24755 The @code{name} attribute must be Python string which contains the
24756 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
24757 Management}). This attribute may contain any combination of letters
24758 or numbers. Care should be taken to ensure that it is unique. This
24759 attribute is mandatory.
24762 @defvar FrameFilter.enabled
24763 The @code{enabled} attribute must be Python boolean. This attribute
24764 indicates to @value{GDBN} whether the frame filter is enabled, and
24765 should be considered when frame filters are executed. If
24766 @code{enabled} is @code{True}, then the frame filter will be executed
24767 when any of the backtrace commands detailed earlier in this chapter
24768 are executed. If @code{enabled} is @code{False}, then the frame
24769 filter will not be executed. This attribute is mandatory.
24772 @defvar FrameFilter.priority
24773 The @code{priority} attribute must be Python integer. This attribute
24774 controls the order of execution in relation to other frame filters.
24775 There are no imposed limits on the range of @code{priority} other than
24776 it must be a valid integer. The higher the @code{priority} attribute,
24777 the sooner the frame filter will be executed in relation to other
24778 frame filters. Although @code{priority} can be negative, it is
24779 recommended practice to assume zero is the lowest priority that a
24780 frame filter can be assigned. Frame filters that have the same
24781 priority are executed in unsorted order in that priority slot. This
24782 attribute is mandatory.
24785 @node Frame Decorator API
24786 @subsubsection Decorating Frames.
24787 @cindex frame decorator api
24789 Frame decorators are sister objects to frame filters (@pxref{Frame
24790 Filter API}). Frame decorators are applied by a frame filter and can
24791 only be used in conjunction with frame filters.
24793 The purpose of a frame decorator is to customize the printed content
24794 of each @code{gdb.Frame} in commands where frame filters are executed.
24795 This concept is called decorating a frame. Frame decorators decorate
24796 a @code{gdb.Frame} with Python code contained within each API call.
24797 This separates the actual data contained in a @code{gdb.Frame} from
24798 the decorated data produced by a frame decorator. This abstraction is
24799 necessary to maintain integrity of the data contained in each
24802 Frame decorators have a mandatory interface, defined below.
24804 @value{GDBN} already contains a frame decorator called
24805 @code{FrameDecorator}. This contains substantial amounts of
24806 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
24807 recommended that other frame decorators inherit and extend this
24808 object, and only to override the methods needed.
24810 @defun FrameDecorator.elided (self)
24812 The @code{elided} method groups frames together in a hierarchical
24813 system. An example would be an interpreter, where multiple low-level
24814 frames make up a single call in the interpreted language. In this
24815 example, the frame filter would elide the low-level frames and present
24816 a single high-level frame, representing the call in the interpreted
24817 language, to the user.
24819 The @code{elided} function must return an iterable and this iterable
24820 must contain the frames that are being elided wrapped in a suitable
24821 frame decorator. If no frames are being elided this function may
24822 return an empty iterable, or @code{None}. Elided frames are indented
24823 from normal frames in a @code{CLI} backtrace, or in the case of
24824 @code{GDB/MI}, are placed in the @code{children} field of the eliding
24827 It is the frame filter's task to also filter out the elided frames from
24828 the source iterator. This will avoid printing the frame twice.
24831 @defun FrameDecorator.function (self)
24833 This method returns the name of the function in the frame that is to
24836 This method must return a Python string describing the function, or
24839 If this function returns @code{None}, @value{GDBN} will not print any
24840 data for this field.
24843 @defun FrameDecorator.address (self)
24845 This method returns the address of the frame that is to be printed.
24847 This method must return a Python numeric integer type of sufficient
24848 size to describe the address of the frame, or @code{None}.
24850 If this function returns a @code{None}, @value{GDBN} will not print
24851 any data for this field.
24854 @defun FrameDecorator.filename (self)
24856 This method returns the filename and path associated with this frame.
24858 This method must return a Python string containing the filename and
24859 the path to the object file backing the frame, or @code{None}.
24861 If this function returns a @code{None}, @value{GDBN} will not print
24862 any data for this field.
24865 @defun FrameDecorator.line (self):
24867 This method returns the line number associated with the current
24868 position within the function addressed by this frame.
24870 This method must return a Python integer type, or @code{None}.
24872 If this function returns a @code{None}, @value{GDBN} will not print
24873 any data for this field.
24876 @defun FrameDecorator.frame_args (self)
24877 @anchor{frame_args}
24879 This method must return an iterable, or @code{None}. Returning an
24880 empty iterable, or @code{None} means frame arguments will not be
24881 printed for this frame. This iterable must contain objects that
24882 implement two methods, described here.
24884 This object must implement a @code{argument} method which takes a
24885 single @code{self} parameter and must return a @code{gdb.Symbol}
24886 (@pxref{Symbols In Python}), or a Python string. The object must also
24887 implement a @code{value} method which takes a single @code{self}
24888 parameter and must return a @code{gdb.Value} (@pxref{Values From
24889 Inferior}), a Python value, or @code{None}. If the @code{value}
24890 method returns @code{None}, and the @code{argument} method returns a
24891 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
24892 the @code{gdb.Symbol} automatically.
24897 class SymValueWrapper():
24899 def __init__(self, symbol, value):
24909 class SomeFrameDecorator()
24912 def frame_args(self):
24915 block = self.inferior_frame.block()
24919 # Iterate over all symbols in a block. Only add
24920 # symbols that are arguments.
24922 if not sym.is_argument:
24924 args.append(SymValueWrapper(sym,None))
24926 # Add example synthetic argument.
24927 args.append(SymValueWrapper(``foo'', 42))
24933 @defun FrameDecorator.frame_locals (self)
24935 This method must return an iterable or @code{None}. Returning an
24936 empty iterable, or @code{None} means frame local arguments will not be
24937 printed for this frame.
24939 The object interface, the description of the various strategies for
24940 reading frame locals, and the example are largely similar to those
24941 described in the @code{frame_args} function, (@pxref{frame_args,,The
24942 frame filter frame_args function}). Below is a modified example:
24945 class SomeFrameDecorator()
24948 def frame_locals(self):
24951 block = self.inferior_frame.block()
24955 # Iterate over all symbols in a block. Add all
24956 # symbols, except arguments.
24958 if sym.is_argument:
24960 vars.append(SymValueWrapper(sym,None))
24962 # Add an example of a synthetic local variable.
24963 vars.append(SymValueWrapper(``bar'', 99))
24969 @defun FrameDecorator.inferior_frame (self):
24971 This method must return the underlying @code{gdb.Frame} that this
24972 frame decorator is decorating. @value{GDBN} requires the underlying
24973 frame for internal frame information to determine how to print certain
24974 values when printing a frame.
24977 @node Writing a Frame Filter
24978 @subsubsection Writing a Frame Filter
24979 @cindex writing a frame filter
24981 There are three basic elements that a frame filter must implement: it
24982 must correctly implement the documented interface (@pxref{Frame Filter
24983 API}), it must register itself with @value{GDBN}, and finally, it must
24984 decide if it is to work on the data provided by @value{GDBN}. In all
24985 cases, whether it works on the iterator or not, each frame filter must
24986 return an iterator. A bare-bones frame filter follows the pattern in
24987 the following example.
24992 class FrameFilter():
24994 def __init__(self):
24995 # Frame filter attribute creation.
24997 # 'name' is the name of the filter that GDB will display.
24999 # 'priority' is the priority of the filter relative to other
25002 # 'enabled' is a boolean that indicates whether this filter is
25003 # enabled and should be executed.
25006 self.priority = 100
25007 self.enabled = True
25009 # Register this frame filter with the global frame_filters
25011 gdb.frame_filters[self.name] = self
25013 def filter(self, frame_iter):
25014 # Just return the iterator.
25018 The frame filter in the example above implements the three
25019 requirements for all frame filters. It implements the API, self
25020 registers, and makes a decision on the iterator (in this case, it just
25021 returns the iterator untouched).
25023 The first step is attribute creation and assignment, and as shown in
25024 the comments the filter assigns the following attributes: @code{name},
25025 @code{priority} and whether the filter should be enabled with the
25026 @code{enabled} attribute.
25028 The second step is registering the frame filter with the dictionary or
25029 dictionaries that the frame filter has interest in. As shown in the
25030 comments, this filter just registers itself with the global dictionary
25031 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25032 is a dictionary that is initialized in the @code{gdb} module when
25033 @value{GDBN} starts. What dictionary a filter registers with is an
25034 important consideration. Generally, if a filter is specific to a set
25035 of code, it should be registered either in the @code{objfile} or
25036 @code{progspace} dictionaries as they are specific to the program
25037 currently loaded in @value{GDBN}. The global dictionary is always
25038 present in @value{GDBN} and is never unloaded. Any filters registered
25039 with the global dictionary will exist until @value{GDBN} exits. To
25040 avoid filters that may conflict, it is generally better to register
25041 frame filters against the dictionaries that more closely align with
25042 the usage of the filter currently in question. @xref{Python
25043 Auto-loading}, for further information on auto-loading Python scripts.
25045 @value{GDBN} takes a hands-off approach to frame filter registration,
25046 therefore it is the frame filter's responsibility to ensure
25047 registration has occurred, and that any exceptions are handled
25048 appropriately. In particular, you may wish to handle exceptions
25049 relating to Python dictionary key uniqueness. It is mandatory that
25050 the dictionary key is the same as frame filter's @code{name}
25051 attribute. When a user manages frame filters (@pxref{Frame Filter
25052 Management}), the names @value{GDBN} will display are those contained
25053 in the @code{name} attribute.
25055 The final step of this example is the implementation of the
25056 @code{filter} method. As shown in the example comments, we define the
25057 @code{filter} method and note that the method must take an iterator,
25058 and also must return an iterator. In this bare-bones example, the
25059 frame filter is not very useful as it just returns the iterator
25060 untouched. However this is a valid operation for frame filters that
25061 have the @code{enabled} attribute set, but decide not to operate on
25064 In the next example, the frame filter operates on all frames and
25065 utilizes a frame decorator to perform some work on the frames.
25066 @xref{Frame Decorator API}, for further information on the frame
25067 decorator interface.
25069 This example works on inlined frames. It highlights frames which are
25070 inlined by tagging them with an ``[inlined]'' tag. By applying a
25071 frame decorator to all frames with the Python @code{itertools imap}
25072 method, the example defers actions to the frame decorator. Frame
25073 decorators are only processed when @value{GDBN} prints the backtrace.
25075 This introduces a new decision making topic: whether to perform
25076 decision making operations at the filtering step, or at the printing
25077 step. In this example's approach, it does not perform any filtering
25078 decisions at the filtering step beyond mapping a frame decorator to
25079 each frame. This allows the actual decision making to be performed
25080 when each frame is printed. This is an important consideration, and
25081 well worth reflecting upon when designing a frame filter. An issue
25082 that frame filters should avoid is unwinding the stack if possible.
25083 Some stacks can run very deep, into the tens of thousands in some
25084 cases. To search every frame to determine if it is inlined ahead of
25085 time may be too expensive at the filtering step. The frame filter
25086 cannot know how many frames it has to iterate over, and it would have
25087 to iterate through them all. This ends up duplicating effort as
25088 @value{GDBN} performs this iteration when it prints the frames.
25090 In this example decision making can be deferred to the printing step.
25091 As each frame is printed, the frame decorator can examine each frame
25092 in turn when @value{GDBN} iterates. From a performance viewpoint,
25093 this is the most appropriate decision to make as it avoids duplicating
25094 the effort that the printing step would undertake anyway. Also, if
25095 there are many frame filters unwinding the stack during filtering, it
25096 can substantially delay the printing of the backtrace which will
25097 result in large memory usage, and a poor user experience.
25100 class InlineFilter():
25102 def __init__(self):
25103 self.name = "InlinedFrameFilter"
25104 self.priority = 100
25105 self.enabled = True
25106 gdb.frame_filters[self.name] = self
25108 def filter(self, frame_iter):
25109 frame_iter = itertools.imap(InlinedFrameDecorator,
25114 This frame filter is somewhat similar to the earlier example, except
25115 that the @code{filter} method applies a frame decorator object called
25116 @code{InlinedFrameDecorator} to each element in the iterator. The
25117 @code{imap} Python method is light-weight. It does not proactively
25118 iterate over the iterator, but rather creates a new iterator which
25119 wraps the existing one.
25121 Below is the frame decorator for this example.
25124 class InlinedFrameDecorator(FrameDecorator):
25126 def __init__(self, fobj):
25127 super(InlinedFrameDecorator, self).__init__(fobj)
25129 def function(self):
25130 frame = fobj.inferior_frame()
25131 name = str(frame.name())
25133 if frame.type() == gdb.INLINE_FRAME:
25134 name = name + " [inlined]"
25139 This frame decorator only defines and overrides the @code{function}
25140 method. It lets the supplied @code{FrameDecorator}, which is shipped
25141 with @value{GDBN}, perform the other work associated with printing
25144 The combination of these two objects create this output from a
25148 #0 0x004004e0 in bar () at inline.c:11
25149 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25150 #2 0x00400566 in main () at inline.c:31
25153 So in the case of this example, a frame decorator is applied to all
25154 frames, regardless of whether they may be inlined or not. As
25155 @value{GDBN} iterates over the iterator produced by the frame filters,
25156 @value{GDBN} executes each frame decorator which then makes a decision
25157 on what to print in the @code{function} callback. Using a strategy
25158 like this is a way to defer decisions on the frame content to printing
25161 @subheading Eliding Frames
25163 It might be that the above example is not desirable for representing
25164 inlined frames, and a hierarchical approach may be preferred. If we
25165 want to hierarchically represent frames, the @code{elided} frame
25166 decorator interface might be preferable.
25168 This example approaches the issue with the @code{elided} method. This
25169 example is quite long, but very simplistic. It is out-of-scope for
25170 this section to write a complete example that comprehensively covers
25171 all approaches of finding and printing inlined frames. However, this
25172 example illustrates the approach an author might use.
25174 This example comprises of three sections.
25177 class InlineFrameFilter():
25179 def __init__(self):
25180 self.name = "InlinedFrameFilter"
25181 self.priority = 100
25182 self.enabled = True
25183 gdb.frame_filters[self.name] = self
25185 def filter(self, frame_iter):
25186 return ElidingInlineIterator(frame_iter)
25189 This frame filter is very similar to the other examples. The only
25190 difference is this frame filter is wrapping the iterator provided to
25191 it (@code{frame_iter}) with a custom iterator called
25192 @code{ElidingInlineIterator}. This again defers actions to when
25193 @value{GDBN} prints the backtrace, as the iterator is not traversed
25196 The iterator for this example is as follows. It is in this section of
25197 the example where decisions are made on the content of the backtrace.
25200 class ElidingInlineIterator:
25201 def __init__(self, ii):
25202 self.input_iterator = ii
25204 def __iter__(self):
25208 frame = next(self.input_iterator)
25210 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25214 eliding_frame = next(self.input_iterator)
25215 except StopIteration:
25217 return ElidingFrameDecorator(eliding_frame, [frame])
25220 This iterator implements the Python iterator protocol. When the
25221 @code{next} function is called (when @value{GDBN} prints each frame),
25222 the iterator checks if this frame decorator, @code{frame}, is wrapping
25223 an inlined frame. If it is not, it returns the existing frame decorator
25224 untouched. If it is wrapping an inlined frame, it assumes that the
25225 inlined frame was contained within the next oldest frame,
25226 @code{eliding_frame}, which it fetches. It then creates and returns a
25227 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25228 elided frame, and the eliding frame.
25231 class ElidingInlineDecorator(FrameDecorator):
25233 def __init__(self, frame, elided_frames):
25234 super(ElidingInlineDecorator, self).__init__(frame)
25236 self.elided_frames = elided_frames
25239 return iter(self.elided_frames)
25242 This frame decorator overrides one function and returns the inlined
25243 frame in the @code{elided} method. As before it lets
25244 @code{FrameDecorator} do the rest of the work involved in printing
25245 this frame. This produces the following output.
25248 #0 0x004004e0 in bar () at inline.c:11
25249 #2 0x00400529 in main () at inline.c:25
25250 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25253 In that output, @code{max} which has been inlined into @code{main} is
25254 printed hierarchically. Another approach would be to combine the
25255 @code{function} method, and the @code{elided} method to both print a
25256 marker in the inlined frame, and also show the hierarchical
25259 @node Inferiors In Python
25260 @subsubsection Inferiors In Python
25261 @cindex inferiors in Python
25263 @findex gdb.Inferior
25264 Programs which are being run under @value{GDBN} are called inferiors
25265 (@pxref{Inferiors and Programs}). Python scripts can access
25266 information about and manipulate inferiors controlled by @value{GDBN}
25267 via objects of the @code{gdb.Inferior} class.
25269 The following inferior-related functions are available in the @code{gdb}
25272 @defun gdb.inferiors ()
25273 Return a tuple containing all inferior objects.
25276 @defun gdb.selected_inferior ()
25277 Return an object representing the current inferior.
25280 A @code{gdb.Inferior} object has the following attributes:
25282 @defvar Inferior.num
25283 ID of inferior, as assigned by GDB.
25286 @defvar Inferior.pid
25287 Process ID of the inferior, as assigned by the underlying operating
25291 @defvar Inferior.was_attached
25292 Boolean signaling whether the inferior was created using `attach', or
25293 started by @value{GDBN} itself.
25296 A @code{gdb.Inferior} object has the following methods:
25298 @defun Inferior.is_valid ()
25299 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25300 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25301 if the inferior no longer exists within @value{GDBN}. All other
25302 @code{gdb.Inferior} methods will throw an exception if it is invalid
25303 at the time the method is called.
25306 @defun Inferior.threads ()
25307 This method returns a tuple holding all the threads which are valid
25308 when it is called. If there are no valid threads, the method will
25309 return an empty tuple.
25312 @findex Inferior.read_memory
25313 @defun Inferior.read_memory (address, length)
25314 Read @var{length} bytes of memory from the inferior, starting at
25315 @var{address}. Returns a buffer object, which behaves much like an array
25316 or a string. It can be modified and given to the
25317 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25318 value is a @code{memoryview} object.
25321 @findex Inferior.write_memory
25322 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25323 Write the contents of @var{buffer} to the inferior, starting at
25324 @var{address}. The @var{buffer} parameter must be a Python object
25325 which supports the buffer protocol, i.e., a string, an array or the
25326 object returned from @code{Inferior.read_memory}. If given, @var{length}
25327 determines the number of bytes from @var{buffer} to be written.
25330 @findex gdb.search_memory
25331 @defun Inferior.search_memory (address, length, pattern)
25332 Search a region of the inferior memory starting at @var{address} with
25333 the given @var{length} using the search pattern supplied in
25334 @var{pattern}. The @var{pattern} parameter must be a Python object
25335 which supports the buffer protocol, i.e., a string, an array or the
25336 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25337 containing the address where the pattern was found, or @code{None} if
25338 the pattern could not be found.
25341 @node Events In Python
25342 @subsubsection Events In Python
25343 @cindex inferior events in Python
25345 @value{GDBN} provides a general event facility so that Python code can be
25346 notified of various state changes, particularly changes that occur in
25349 An @dfn{event} is just an object that describes some state change. The
25350 type of the object and its attributes will vary depending on the details
25351 of the change. All the existing events are described below.
25353 In order to be notified of an event, you must register an event handler
25354 with an @dfn{event registry}. An event registry is an object in the
25355 @code{gdb.events} module which dispatches particular events. A registry
25356 provides methods to register and unregister event handlers:
25358 @defun EventRegistry.connect (object)
25359 Add the given callable @var{object} to the registry. This object will be
25360 called when an event corresponding to this registry occurs.
25363 @defun EventRegistry.disconnect (object)
25364 Remove the given @var{object} from the registry. Once removed, the object
25365 will no longer receive notifications of events.
25368 Here is an example:
25371 def exit_handler (event):
25372 print "event type: exit"
25373 print "exit code: %d" % (event.exit_code)
25375 gdb.events.exited.connect (exit_handler)
25378 In the above example we connect our handler @code{exit_handler} to the
25379 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25380 called when the inferior exits. The argument @dfn{event} in this example is
25381 of type @code{gdb.ExitedEvent}. As you can see in the example the
25382 @code{ExitedEvent} object has an attribute which indicates the exit code of
25385 The following is a listing of the event registries that are available and
25386 details of the events they emit:
25391 Emits @code{gdb.ThreadEvent}.
25393 Some events can be thread specific when @value{GDBN} is running in non-stop
25394 mode. When represented in Python, these events all extend
25395 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25396 events which are emitted by this or other modules might extend this event.
25397 Examples of these events are @code{gdb.BreakpointEvent} and
25398 @code{gdb.ContinueEvent}.
25400 @defvar ThreadEvent.inferior_thread
25401 In non-stop mode this attribute will be set to the specific thread which was
25402 involved in the emitted event. Otherwise, it will be set to @code{None}.
25405 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25407 This event indicates that the inferior has been continued after a stop. For
25408 inherited attribute refer to @code{gdb.ThreadEvent} above.
25410 @item events.exited
25411 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25412 @code{events.ExitedEvent} has two attributes:
25413 @defvar ExitedEvent.exit_code
25414 An integer representing the exit code, if available, which the inferior
25415 has returned. (The exit code could be unavailable if, for example,
25416 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25417 the attribute does not exist.
25419 @defvar ExitedEvent inferior
25420 A reference to the inferior which triggered the @code{exited} event.
25424 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25426 Indicates that the inferior has stopped. All events emitted by this registry
25427 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25428 will indicate the stopped thread when @value{GDBN} is running in non-stop
25429 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25431 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25433 This event indicates that the inferior or one of its threads has received as
25434 signal. @code{gdb.SignalEvent} has the following attributes:
25436 @defvar SignalEvent.stop_signal
25437 A string representing the signal received by the inferior. A list of possible
25438 signal values can be obtained by running the command @code{info signals} in
25439 the @value{GDBN} command prompt.
25442 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25444 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25445 been hit, and has the following attributes:
25447 @defvar BreakpointEvent.breakpoints
25448 A sequence containing references to all the breakpoints (type
25449 @code{gdb.Breakpoint}) that were hit.
25450 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25452 @defvar BreakpointEvent.breakpoint
25453 A reference to the first breakpoint that was hit.
25454 This function is maintained for backward compatibility and is now deprecated
25455 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25458 @item events.new_objfile
25459 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25460 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25462 @defvar NewObjFileEvent.new_objfile
25463 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25464 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25469 @node Threads In Python
25470 @subsubsection Threads In Python
25471 @cindex threads in python
25473 @findex gdb.InferiorThread
25474 Python scripts can access information about, and manipulate inferior threads
25475 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25477 The following thread-related functions are available in the @code{gdb}
25480 @findex gdb.selected_thread
25481 @defun gdb.selected_thread ()
25482 This function returns the thread object for the selected thread. If there
25483 is no selected thread, this will return @code{None}.
25486 A @code{gdb.InferiorThread} object has the following attributes:
25488 @defvar InferiorThread.name
25489 The name of the thread. If the user specified a name using
25490 @code{thread name}, then this returns that name. Otherwise, if an
25491 OS-supplied name is available, then it is returned. Otherwise, this
25492 returns @code{None}.
25494 This attribute can be assigned to. The new value must be a string
25495 object, which sets the new name, or @code{None}, which removes any
25496 user-specified thread name.
25499 @defvar InferiorThread.num
25500 ID of the thread, as assigned by GDB.
25503 @defvar InferiorThread.ptid
25504 ID of the thread, as assigned by the operating system. This attribute is a
25505 tuple containing three integers. The first is the Process ID (PID); the second
25506 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25507 Either the LWPID or TID may be 0, which indicates that the operating system
25508 does not use that identifier.
25511 A @code{gdb.InferiorThread} object has the following methods:
25513 @defun InferiorThread.is_valid ()
25514 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25515 @code{False} if not. A @code{gdb.InferiorThread} object will become
25516 invalid if the thread exits, or the inferior that the thread belongs
25517 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25518 exception if it is invalid at the time the method is called.
25521 @defun InferiorThread.switch ()
25522 This changes @value{GDBN}'s currently selected thread to the one represented
25526 @defun InferiorThread.is_stopped ()
25527 Return a Boolean indicating whether the thread is stopped.
25530 @defun InferiorThread.is_running ()
25531 Return a Boolean indicating whether the thread is running.
25534 @defun InferiorThread.is_exited ()
25535 Return a Boolean indicating whether the thread is exited.
25538 @node Commands In Python
25539 @subsubsection Commands In Python
25541 @cindex commands in python
25542 @cindex python commands
25543 You can implement new @value{GDBN} CLI commands in Python. A CLI
25544 command is implemented using an instance of the @code{gdb.Command}
25545 class, most commonly using a subclass.
25547 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25548 The object initializer for @code{Command} registers the new command
25549 with @value{GDBN}. This initializer is normally invoked from the
25550 subclass' own @code{__init__} method.
25552 @var{name} is the name of the command. If @var{name} consists of
25553 multiple words, then the initial words are looked for as prefix
25554 commands. In this case, if one of the prefix commands does not exist,
25555 an exception is raised.
25557 There is no support for multi-line commands.
25559 @var{command_class} should be one of the @samp{COMMAND_} constants
25560 defined below. This argument tells @value{GDBN} how to categorize the
25561 new command in the help system.
25563 @var{completer_class} is an optional argument. If given, it should be
25564 one of the @samp{COMPLETE_} constants defined below. This argument
25565 tells @value{GDBN} how to perform completion for this command. If not
25566 given, @value{GDBN} will attempt to complete using the object's
25567 @code{complete} method (see below); if no such method is found, an
25568 error will occur when completion is attempted.
25570 @var{prefix} is an optional argument. If @code{True}, then the new
25571 command is a prefix command; sub-commands of this command may be
25574 The help text for the new command is taken from the Python
25575 documentation string for the command's class, if there is one. If no
25576 documentation string is provided, the default value ``This command is
25577 not documented.'' is used.
25580 @cindex don't repeat Python command
25581 @defun Command.dont_repeat ()
25582 By default, a @value{GDBN} command is repeated when the user enters a
25583 blank line at the command prompt. A command can suppress this
25584 behavior by invoking the @code{dont_repeat} method. This is similar
25585 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25588 @defun Command.invoke (argument, from_tty)
25589 This method is called by @value{GDBN} when this command is invoked.
25591 @var{argument} is a string. It is the argument to the command, after
25592 leading and trailing whitespace has been stripped.
25594 @var{from_tty} is a boolean argument. When true, this means that the
25595 command was entered by the user at the terminal; when false it means
25596 that the command came from elsewhere.
25598 If this method throws an exception, it is turned into a @value{GDBN}
25599 @code{error} call. Otherwise, the return value is ignored.
25601 @findex gdb.string_to_argv
25602 To break @var{argument} up into an argv-like string use
25603 @code{gdb.string_to_argv}. This function behaves identically to
25604 @value{GDBN}'s internal argument lexer @code{buildargv}.
25605 It is recommended to use this for consistency.
25606 Arguments are separated by spaces and may be quoted.
25610 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25611 ['1', '2 "3', '4 "5', "6 '7"]
25616 @cindex completion of Python commands
25617 @defun Command.complete (text, word)
25618 This method is called by @value{GDBN} when the user attempts
25619 completion on this command. All forms of completion are handled by
25620 this method, that is, the @key{TAB} and @key{M-?} key bindings
25621 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25624 The arguments @var{text} and @var{word} are both strings. @var{text}
25625 holds the complete command line up to the cursor's location.
25626 @var{word} holds the last word of the command line; this is computed
25627 using a word-breaking heuristic.
25629 The @code{complete} method can return several values:
25632 If the return value is a sequence, the contents of the sequence are
25633 used as the completions. It is up to @code{complete} to ensure that the
25634 contents actually do complete the word. A zero-length sequence is
25635 allowed, it means that there were no completions available. Only
25636 string elements of the sequence are used; other elements in the
25637 sequence are ignored.
25640 If the return value is one of the @samp{COMPLETE_} constants defined
25641 below, then the corresponding @value{GDBN}-internal completion
25642 function is invoked, and its result is used.
25645 All other results are treated as though there were no available
25650 When a new command is registered, it must be declared as a member of
25651 some general class of commands. This is used to classify top-level
25652 commands in the on-line help system; note that prefix commands are not
25653 listed under their own category but rather that of their top-level
25654 command. The available classifications are represented by constants
25655 defined in the @code{gdb} module:
25658 @findex COMMAND_NONE
25659 @findex gdb.COMMAND_NONE
25660 @item gdb.COMMAND_NONE
25661 The command does not belong to any particular class. A command in
25662 this category will not be displayed in any of the help categories.
25664 @findex COMMAND_RUNNING
25665 @findex gdb.COMMAND_RUNNING
25666 @item gdb.COMMAND_RUNNING
25667 The command is related to running the inferior. For example,
25668 @code{start}, @code{step}, and @code{continue} are in this category.
25669 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
25670 commands in this category.
25672 @findex COMMAND_DATA
25673 @findex gdb.COMMAND_DATA
25674 @item gdb.COMMAND_DATA
25675 The command is related to data or variables. For example,
25676 @code{call}, @code{find}, and @code{print} are in this category. Type
25677 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
25680 @findex COMMAND_STACK
25681 @findex gdb.COMMAND_STACK
25682 @item gdb.COMMAND_STACK
25683 The command has to do with manipulation of the stack. For example,
25684 @code{backtrace}, @code{frame}, and @code{return} are in this
25685 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
25686 list of commands in this category.
25688 @findex COMMAND_FILES
25689 @findex gdb.COMMAND_FILES
25690 @item gdb.COMMAND_FILES
25691 This class is used for file-related commands. For example,
25692 @code{file}, @code{list} and @code{section} are in this category.
25693 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
25694 commands in this category.
25696 @findex COMMAND_SUPPORT
25697 @findex gdb.COMMAND_SUPPORT
25698 @item gdb.COMMAND_SUPPORT
25699 This should be used for ``support facilities'', generally meaning
25700 things that are useful to the user when interacting with @value{GDBN},
25701 but not related to the state of the inferior. For example,
25702 @code{help}, @code{make}, and @code{shell} are in this category. Type
25703 @kbd{help support} at the @value{GDBN} prompt to see a list of
25704 commands in this category.
25706 @findex COMMAND_STATUS
25707 @findex gdb.COMMAND_STATUS
25708 @item gdb.COMMAND_STATUS
25709 The command is an @samp{info}-related command, that is, related to the
25710 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
25711 and @code{show} are in this category. Type @kbd{help status} at the
25712 @value{GDBN} prompt to see a list of commands in this category.
25714 @findex COMMAND_BREAKPOINTS
25715 @findex gdb.COMMAND_BREAKPOINTS
25716 @item gdb.COMMAND_BREAKPOINTS
25717 The command has to do with breakpoints. For example, @code{break},
25718 @code{clear}, and @code{delete} are in this category. Type @kbd{help
25719 breakpoints} at the @value{GDBN} prompt to see a list of commands in
25722 @findex COMMAND_TRACEPOINTS
25723 @findex gdb.COMMAND_TRACEPOINTS
25724 @item gdb.COMMAND_TRACEPOINTS
25725 The command has to do with tracepoints. For example, @code{trace},
25726 @code{actions}, and @code{tfind} are in this category. Type
25727 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
25728 commands in this category.
25730 @findex COMMAND_USER
25731 @findex gdb.COMMAND_USER
25732 @item gdb.COMMAND_USER
25733 The command is a general purpose command for the user, and typically
25734 does not fit in one of the other categories.
25735 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
25736 a list of commands in this category, as well as the list of gdb macros
25737 (@pxref{Sequences}).
25739 @findex COMMAND_OBSCURE
25740 @findex gdb.COMMAND_OBSCURE
25741 @item gdb.COMMAND_OBSCURE
25742 The command is only used in unusual circumstances, or is not of
25743 general interest to users. For example, @code{checkpoint},
25744 @code{fork}, and @code{stop} are in this category. Type @kbd{help
25745 obscure} at the @value{GDBN} prompt to see a list of commands in this
25748 @findex COMMAND_MAINTENANCE
25749 @findex gdb.COMMAND_MAINTENANCE
25750 @item gdb.COMMAND_MAINTENANCE
25751 The command is only useful to @value{GDBN} maintainers. The
25752 @code{maintenance} and @code{flushregs} commands are in this category.
25753 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
25754 commands in this category.
25757 A new command can use a predefined completion function, either by
25758 specifying it via an argument at initialization, or by returning it
25759 from the @code{complete} method. These predefined completion
25760 constants are all defined in the @code{gdb} module:
25763 @findex COMPLETE_NONE
25764 @findex gdb.COMPLETE_NONE
25765 @item gdb.COMPLETE_NONE
25766 This constant means that no completion should be done.
25768 @findex COMPLETE_FILENAME
25769 @findex gdb.COMPLETE_FILENAME
25770 @item gdb.COMPLETE_FILENAME
25771 This constant means that filename completion should be performed.
25773 @findex COMPLETE_LOCATION
25774 @findex gdb.COMPLETE_LOCATION
25775 @item gdb.COMPLETE_LOCATION
25776 This constant means that location completion should be done.
25777 @xref{Specify Location}.
25779 @findex COMPLETE_COMMAND
25780 @findex gdb.COMPLETE_COMMAND
25781 @item gdb.COMPLETE_COMMAND
25782 This constant means that completion should examine @value{GDBN}
25785 @findex COMPLETE_SYMBOL
25786 @findex gdb.COMPLETE_SYMBOL
25787 @item gdb.COMPLETE_SYMBOL
25788 This constant means that completion should be done using symbol names
25792 The following code snippet shows how a trivial CLI command can be
25793 implemented in Python:
25796 class HelloWorld (gdb.Command):
25797 """Greet the whole world."""
25799 def __init__ (self):
25800 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
25802 def invoke (self, arg, from_tty):
25803 print "Hello, World!"
25808 The last line instantiates the class, and is necessary to trigger the
25809 registration of the command with @value{GDBN}. Depending on how the
25810 Python code is read into @value{GDBN}, you may need to import the
25811 @code{gdb} module explicitly.
25813 @node Parameters In Python
25814 @subsubsection Parameters In Python
25816 @cindex parameters in python
25817 @cindex python parameters
25818 @tindex gdb.Parameter
25820 You can implement new @value{GDBN} parameters using Python. A new
25821 parameter is implemented as an instance of the @code{gdb.Parameter}
25824 Parameters are exposed to the user via the @code{set} and
25825 @code{show} commands. @xref{Help}.
25827 There are many parameters that already exist and can be set in
25828 @value{GDBN}. Two examples are: @code{set follow fork} and
25829 @code{set charset}. Setting these parameters influences certain
25830 behavior in @value{GDBN}. Similarly, you can define parameters that
25831 can be used to influence behavior in custom Python scripts and commands.
25833 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
25834 The object initializer for @code{Parameter} registers the new
25835 parameter with @value{GDBN}. This initializer is normally invoked
25836 from the subclass' own @code{__init__} method.
25838 @var{name} is the name of the new parameter. If @var{name} consists
25839 of multiple words, then the initial words are looked for as prefix
25840 parameters. An example of this can be illustrated with the
25841 @code{set print} set of parameters. If @var{name} is
25842 @code{print foo}, then @code{print} will be searched as the prefix
25843 parameter. In this case the parameter can subsequently be accessed in
25844 @value{GDBN} as @code{set print foo}.
25846 If @var{name} consists of multiple words, and no prefix parameter group
25847 can be found, an exception is raised.
25849 @var{command-class} should be one of the @samp{COMMAND_} constants
25850 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
25851 categorize the new parameter in the help system.
25853 @var{parameter-class} should be one of the @samp{PARAM_} constants
25854 defined below. This argument tells @value{GDBN} the type of the new
25855 parameter; this information is used for input validation and
25858 If @var{parameter-class} is @code{PARAM_ENUM}, then
25859 @var{enum-sequence} must be a sequence of strings. These strings
25860 represent the possible values for the parameter.
25862 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
25863 of a fourth argument will cause an exception to be thrown.
25865 The help text for the new parameter is taken from the Python
25866 documentation string for the parameter's class, if there is one. If
25867 there is no documentation string, a default value is used.
25870 @defvar Parameter.set_doc
25871 If this attribute exists, and is a string, then its value is used as
25872 the help text for this parameter's @code{set} command. The value is
25873 examined when @code{Parameter.__init__} is invoked; subsequent changes
25877 @defvar Parameter.show_doc
25878 If this attribute exists, and is a string, then its value is used as
25879 the help text for this parameter's @code{show} command. The value is
25880 examined when @code{Parameter.__init__} is invoked; subsequent changes
25884 @defvar Parameter.value
25885 The @code{value} attribute holds the underlying value of the
25886 parameter. It can be read and assigned to just as any other
25887 attribute. @value{GDBN} does validation when assignments are made.
25890 There are two methods that should be implemented in any
25891 @code{Parameter} class. These are:
25893 @defun Parameter.get_set_string (self)
25894 @value{GDBN} will call this method when a @var{parameter}'s value has
25895 been changed via the @code{set} API (for example, @kbd{set foo off}).
25896 The @code{value} attribute has already been populated with the new
25897 value and may be used in output. This method must return a string.
25900 @defun Parameter.get_show_string (self, svalue)
25901 @value{GDBN} will call this method when a @var{parameter}'s
25902 @code{show} API has been invoked (for example, @kbd{show foo}). The
25903 argument @code{svalue} receives the string representation of the
25904 current value. This method must return a string.
25907 When a new parameter is defined, its type must be specified. The
25908 available types are represented by constants defined in the @code{gdb}
25912 @findex PARAM_BOOLEAN
25913 @findex gdb.PARAM_BOOLEAN
25914 @item gdb.PARAM_BOOLEAN
25915 The value is a plain boolean. The Python boolean values, @code{True}
25916 and @code{False} are the only valid values.
25918 @findex PARAM_AUTO_BOOLEAN
25919 @findex gdb.PARAM_AUTO_BOOLEAN
25920 @item gdb.PARAM_AUTO_BOOLEAN
25921 The value has three possible states: true, false, and @samp{auto}. In
25922 Python, true and false are represented using boolean constants, and
25923 @samp{auto} is represented using @code{None}.
25925 @findex PARAM_UINTEGER
25926 @findex gdb.PARAM_UINTEGER
25927 @item gdb.PARAM_UINTEGER
25928 The value is an unsigned integer. The value of 0 should be
25929 interpreted to mean ``unlimited''.
25931 @findex PARAM_INTEGER
25932 @findex gdb.PARAM_INTEGER
25933 @item gdb.PARAM_INTEGER
25934 The value is a signed integer. The value of 0 should be interpreted
25935 to mean ``unlimited''.
25937 @findex PARAM_STRING
25938 @findex gdb.PARAM_STRING
25939 @item gdb.PARAM_STRING
25940 The value is a string. When the user modifies the string, any escape
25941 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
25942 translated into corresponding characters and encoded into the current
25945 @findex PARAM_STRING_NOESCAPE
25946 @findex gdb.PARAM_STRING_NOESCAPE
25947 @item gdb.PARAM_STRING_NOESCAPE
25948 The value is a string. When the user modifies the string, escapes are
25949 passed through untranslated.
25951 @findex PARAM_OPTIONAL_FILENAME
25952 @findex gdb.PARAM_OPTIONAL_FILENAME
25953 @item gdb.PARAM_OPTIONAL_FILENAME
25954 The value is a either a filename (a string), or @code{None}.
25956 @findex PARAM_FILENAME
25957 @findex gdb.PARAM_FILENAME
25958 @item gdb.PARAM_FILENAME
25959 The value is a filename. This is just like
25960 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
25962 @findex PARAM_ZINTEGER
25963 @findex gdb.PARAM_ZINTEGER
25964 @item gdb.PARAM_ZINTEGER
25965 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
25966 is interpreted as itself.
25969 @findex gdb.PARAM_ENUM
25970 @item gdb.PARAM_ENUM
25971 The value is a string, which must be one of a collection string
25972 constants provided when the parameter is created.
25975 @node Functions In Python
25976 @subsubsection Writing new convenience functions
25978 @cindex writing convenience functions
25979 @cindex convenience functions in python
25980 @cindex python convenience functions
25981 @tindex gdb.Function
25983 You can implement new convenience functions (@pxref{Convenience Vars})
25984 in Python. A convenience function is an instance of a subclass of the
25985 class @code{gdb.Function}.
25987 @defun Function.__init__ (name)
25988 The initializer for @code{Function} registers the new function with
25989 @value{GDBN}. The argument @var{name} is the name of the function,
25990 a string. The function will be visible to the user as a convenience
25991 variable of type @code{internal function}, whose name is the same as
25992 the given @var{name}.
25994 The documentation for the new function is taken from the documentation
25995 string for the new class.
25998 @defun Function.invoke (@var{*args})
25999 When a convenience function is evaluated, its arguments are converted
26000 to instances of @code{gdb.Value}, and then the function's
26001 @code{invoke} method is called. Note that @value{GDBN} does not
26002 predetermine the arity of convenience functions. Instead, all
26003 available arguments are passed to @code{invoke}, following the
26004 standard Python calling convention. In particular, a convenience
26005 function can have default values for parameters without ill effect.
26007 The return value of this method is used as its value in the enclosing
26008 expression. If an ordinary Python value is returned, it is converted
26009 to a @code{gdb.Value} following the usual rules.
26012 The following code snippet shows how a trivial convenience function can
26013 be implemented in Python:
26016 class Greet (gdb.Function):
26017 """Return string to greet someone.
26018 Takes a name as argument."""
26020 def __init__ (self):
26021 super (Greet, self).__init__ ("greet")
26023 def invoke (self, name):
26024 return "Hello, %s!" % name.string ()
26029 The last line instantiates the class, and is necessary to trigger the
26030 registration of the function with @value{GDBN}. Depending on how the
26031 Python code is read into @value{GDBN}, you may need to import the
26032 @code{gdb} module explicitly.
26034 Now you can use the function in an expression:
26037 (gdb) print $greet("Bob")
26041 @node Progspaces In Python
26042 @subsubsection Program Spaces In Python
26044 @cindex progspaces in python
26045 @tindex gdb.Progspace
26047 A program space, or @dfn{progspace}, represents a symbolic view
26048 of an address space.
26049 It consists of all of the objfiles of the program.
26050 @xref{Objfiles In Python}.
26051 @xref{Inferiors and Programs, program spaces}, for more details
26052 about program spaces.
26054 The following progspace-related functions are available in the
26057 @findex gdb.current_progspace
26058 @defun gdb.current_progspace ()
26059 This function returns the program space of the currently selected inferior.
26060 @xref{Inferiors and Programs}.
26063 @findex gdb.progspaces
26064 @defun gdb.progspaces ()
26065 Return a sequence of all the progspaces currently known to @value{GDBN}.
26068 Each progspace is represented by an instance of the @code{gdb.Progspace}
26071 @defvar Progspace.filename
26072 The file name of the progspace as a string.
26075 @defvar Progspace.pretty_printers
26076 The @code{pretty_printers} attribute is a list of functions. It is
26077 used to look up pretty-printers. A @code{Value} is passed to each
26078 function in order; if the function returns @code{None}, then the
26079 search continues. Otherwise, the return value should be an object
26080 which is used to format the value. @xref{Pretty Printing API}, for more
26084 @defvar Progspace.type_printers
26085 The @code{type_printers} attribute is a list of type printer objects.
26086 @xref{Type Printing API}, for more information.
26089 @defvar Progspace.frame_filters
26090 The @code{frame_filters} attribute is a dictionary of frame filter
26091 objects. @xref{Frame Filter API}, for more information.
26094 @node Objfiles In Python
26095 @subsubsection Objfiles In Python
26097 @cindex objfiles in python
26098 @tindex gdb.Objfile
26100 @value{GDBN} loads symbols for an inferior from various
26101 symbol-containing files (@pxref{Files}). These include the primary
26102 executable file, any shared libraries used by the inferior, and any
26103 separate debug info files (@pxref{Separate Debug Files}).
26104 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26106 The following objfile-related functions are available in the
26109 @findex gdb.current_objfile
26110 @defun gdb.current_objfile ()
26111 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26112 sets the ``current objfile'' to the corresponding objfile. This
26113 function returns the current objfile. If there is no current objfile,
26114 this function returns @code{None}.
26117 @findex gdb.objfiles
26118 @defun gdb.objfiles ()
26119 Return a sequence of all the objfiles current known to @value{GDBN}.
26120 @xref{Objfiles In Python}.
26123 Each objfile is represented by an instance of the @code{gdb.Objfile}
26126 @defvar Objfile.filename
26127 The file name of the objfile as a string.
26130 @defvar Objfile.pretty_printers
26131 The @code{pretty_printers} attribute is a list of functions. It is
26132 used to look up pretty-printers. A @code{Value} is passed to each
26133 function in order; if the function returns @code{None}, then the
26134 search continues. Otherwise, the return value should be an object
26135 which is used to format the value. @xref{Pretty Printing API}, for more
26139 @defvar Objfile.type_printers
26140 The @code{type_printers} attribute is a list of type printer objects.
26141 @xref{Type Printing API}, for more information.
26144 @defvar Objfile.frame_filters
26145 The @code{frame_filters} attribute is a dictionary of frame filter
26146 objects. @xref{Frame Filter API}, for more information.
26149 A @code{gdb.Objfile} object has the following methods:
26151 @defun Objfile.is_valid ()
26152 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26153 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26154 if the object file it refers to is not loaded in @value{GDBN} any
26155 longer. All other @code{gdb.Objfile} methods will throw an exception
26156 if it is invalid at the time the method is called.
26159 @node Frames In Python
26160 @subsubsection Accessing inferior stack frames from Python.
26162 @cindex frames in python
26163 When the debugged program stops, @value{GDBN} is able to analyze its call
26164 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26165 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26166 while its corresponding frame exists in the inferior's stack. If you try
26167 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26168 exception (@pxref{Exception Handling}).
26170 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26174 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26178 The following frame-related functions are available in the @code{gdb} module:
26180 @findex gdb.selected_frame
26181 @defun gdb.selected_frame ()
26182 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26185 @findex gdb.newest_frame
26186 @defun gdb.newest_frame ()
26187 Return the newest frame object for the selected thread.
26190 @defun gdb.frame_stop_reason_string (reason)
26191 Return a string explaining the reason why @value{GDBN} stopped unwinding
26192 frames, as expressed by the given @var{reason} code (an integer, see the
26193 @code{unwind_stop_reason} method further down in this section).
26196 A @code{gdb.Frame} object has the following methods:
26198 @defun Frame.is_valid ()
26199 Returns true if the @code{gdb.Frame} object is valid, false if not.
26200 A frame object can become invalid if the frame it refers to doesn't
26201 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26202 an exception if it is invalid at the time the method is called.
26205 @defun Frame.name ()
26206 Returns the function name of the frame, or @code{None} if it can't be
26210 @defun Frame.architecture ()
26211 Returns the @code{gdb.Architecture} object corresponding to the frame's
26212 architecture. @xref{Architectures In Python}.
26215 @defun Frame.type ()
26216 Returns the type of the frame. The value can be one of:
26218 @item gdb.NORMAL_FRAME
26219 An ordinary stack frame.
26221 @item gdb.DUMMY_FRAME
26222 A fake stack frame that was created by @value{GDBN} when performing an
26223 inferior function call.
26225 @item gdb.INLINE_FRAME
26226 A frame representing an inlined function. The function was inlined
26227 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26229 @item gdb.TAILCALL_FRAME
26230 A frame representing a tail call. @xref{Tail Call Frames}.
26232 @item gdb.SIGTRAMP_FRAME
26233 A signal trampoline frame. This is the frame created by the OS when
26234 it calls into a signal handler.
26236 @item gdb.ARCH_FRAME
26237 A fake stack frame representing a cross-architecture call.
26239 @item gdb.SENTINEL_FRAME
26240 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26245 @defun Frame.unwind_stop_reason ()
26246 Return an integer representing the reason why it's not possible to find
26247 more frames toward the outermost frame. Use
26248 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26249 function to a string. The value can be one of:
26252 @item gdb.FRAME_UNWIND_NO_REASON
26253 No particular reason (older frames should be available).
26255 @item gdb.FRAME_UNWIND_NULL_ID
26256 The previous frame's analyzer returns an invalid result.
26258 @item gdb.FRAME_UNWIND_OUTERMOST
26259 This frame is the outermost.
26261 @item gdb.FRAME_UNWIND_UNAVAILABLE
26262 Cannot unwind further, because that would require knowing the
26263 values of registers or memory that have not been collected.
26265 @item gdb.FRAME_UNWIND_INNER_ID
26266 This frame ID looks like it ought to belong to a NEXT frame,
26267 but we got it for a PREV frame. Normally, this is a sign of
26268 unwinder failure. It could also indicate stack corruption.
26270 @item gdb.FRAME_UNWIND_SAME_ID
26271 This frame has the same ID as the previous one. That means
26272 that unwinding further would almost certainly give us another
26273 frame with exactly the same ID, so break the chain. Normally,
26274 this is a sign of unwinder failure. It could also indicate
26277 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26278 The frame unwinder did not find any saved PC, but we needed
26279 one to unwind further.
26281 @item gdb.FRAME_UNWIND_FIRST_ERROR
26282 Any stop reason greater or equal to this value indicates some kind
26283 of error. This special value facilitates writing code that tests
26284 for errors in unwinding in a way that will work correctly even if
26285 the list of the other values is modified in future @value{GDBN}
26286 versions. Using it, you could write:
26288 reason = gdb.selected_frame().unwind_stop_reason ()
26289 reason_str = gdb.frame_stop_reason_string (reason)
26290 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26291 print "An error occured: %s" % reason_str
26298 Returns the frame's resume address.
26301 @defun Frame.block ()
26302 Return the frame's code block. @xref{Blocks In Python}.
26305 @defun Frame.function ()
26306 Return the symbol for the function corresponding to this frame.
26307 @xref{Symbols In Python}.
26310 @defun Frame.older ()
26311 Return the frame that called this frame.
26314 @defun Frame.newer ()
26315 Return the frame called by this frame.
26318 @defun Frame.find_sal ()
26319 Return the frame's symtab and line object.
26320 @xref{Symbol Tables In Python}.
26323 @defun Frame.read_var (variable @r{[}, block@r{]})
26324 Return the value of @var{variable} in this frame. If the optional
26325 argument @var{block} is provided, search for the variable from that
26326 block; otherwise start at the frame's current block (which is
26327 determined by the frame's current program counter). @var{variable}
26328 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26329 @code{gdb.Block} object.
26332 @defun Frame.select ()
26333 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26337 @node Blocks In Python
26338 @subsubsection Accessing blocks from Python.
26340 @cindex blocks in python
26343 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26344 roughly to a scope in the source code. Blocks are organized
26345 hierarchically, and are represented individually in Python as a
26346 @code{gdb.Block}. Blocks rely on debugging information being
26349 A frame has a block. Please see @ref{Frames In Python}, for a more
26350 in-depth discussion of frames.
26352 The outermost block is known as the @dfn{global block}. The global
26353 block typically holds public global variables and functions.
26355 The block nested just inside the global block is the @dfn{static
26356 block}. The static block typically holds file-scoped variables and
26359 @value{GDBN} provides a method to get a block's superblock, but there
26360 is currently no way to examine the sub-blocks of a block, or to
26361 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26364 Here is a short example that should help explain blocks:
26367 /* This is in the global block. */
26370 /* This is in the static block. */
26371 static int file_scope;
26373 /* 'function' is in the global block, and 'argument' is
26374 in a block nested inside of 'function'. */
26375 int function (int argument)
26377 /* 'local' is in a block inside 'function'. It may or may
26378 not be in the same block as 'argument'. */
26382 /* 'inner' is in a block whose superblock is the one holding
26386 /* If this call is expanded by the compiler, you may see
26387 a nested block here whose function is 'inline_function'
26388 and whose superblock is the one holding 'inner'. */
26389 inline_function ();
26394 A @code{gdb.Block} is iterable. The iterator returns the symbols
26395 (@pxref{Symbols In Python}) local to the block. Python programs
26396 should not assume that a specific block object will always contain a
26397 given symbol, since changes in @value{GDBN} features and
26398 infrastructure may cause symbols move across blocks in a symbol
26401 The following block-related functions are available in the @code{gdb}
26404 @findex gdb.block_for_pc
26405 @defun gdb.block_for_pc (pc)
26406 Return the innermost @code{gdb.Block} containing the given @var{pc}
26407 value. If the block cannot be found for the @var{pc} value specified,
26408 the function will return @code{None}.
26411 A @code{gdb.Block} object has the following methods:
26413 @defun Block.is_valid ()
26414 Returns @code{True} if the @code{gdb.Block} object is valid,
26415 @code{False} if not. A block object can become invalid if the block it
26416 refers to doesn't exist anymore in the inferior. All other
26417 @code{gdb.Block} methods will throw an exception if it is invalid at
26418 the time the method is called. The block's validity is also checked
26419 during iteration over symbols of the block.
26422 A @code{gdb.Block} object has the following attributes:
26424 @defvar Block.start
26425 The start address of the block. This attribute is not writable.
26429 The end address of the block. This attribute is not writable.
26432 @defvar Block.function
26433 The name of the block represented as a @code{gdb.Symbol}. If the
26434 block is not named, then this attribute holds @code{None}. This
26435 attribute is not writable.
26437 For ordinary function blocks, the superblock is the static block.
26438 However, you should note that it is possible for a function block to
26439 have a superblock that is not the static block -- for instance this
26440 happens for an inlined function.
26443 @defvar Block.superblock
26444 The block containing this block. If this parent block does not exist,
26445 this attribute holds @code{None}. This attribute is not writable.
26448 @defvar Block.global_block
26449 The global block associated with this block. This attribute is not
26453 @defvar Block.static_block
26454 The static block associated with this block. This attribute is not
26458 @defvar Block.is_global
26459 @code{True} if the @code{gdb.Block} object is a global block,
26460 @code{False} if not. This attribute is not
26464 @defvar Block.is_static
26465 @code{True} if the @code{gdb.Block} object is a static block,
26466 @code{False} if not. This attribute is not writable.
26469 @node Symbols In Python
26470 @subsubsection Python representation of Symbols.
26472 @cindex symbols in python
26475 @value{GDBN} represents every variable, function and type as an
26476 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26477 Similarly, Python represents these symbols in @value{GDBN} with the
26478 @code{gdb.Symbol} object.
26480 The following symbol-related functions are available in the @code{gdb}
26483 @findex gdb.lookup_symbol
26484 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26485 This function searches for a symbol by name. The search scope can be
26486 restricted to the parameters defined in the optional domain and block
26489 @var{name} is the name of the symbol. It must be a string. The
26490 optional @var{block} argument restricts the search to symbols visible
26491 in that @var{block}. The @var{block} argument must be a
26492 @code{gdb.Block} object. If omitted, the block for the current frame
26493 is used. The optional @var{domain} argument restricts
26494 the search to the domain type. The @var{domain} argument must be a
26495 domain constant defined in the @code{gdb} module and described later
26498 The result is a tuple of two elements.
26499 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26501 If the symbol is found, the second element is @code{True} if the symbol
26502 is a field of a method's object (e.g., @code{this} in C@t{++}),
26503 otherwise it is @code{False}.
26504 If the symbol is not found, the second element is @code{False}.
26507 @findex gdb.lookup_global_symbol
26508 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26509 This function searches for a global symbol by name.
26510 The search scope can be restricted to by the domain argument.
26512 @var{name} is the name of the symbol. It must be a string.
26513 The optional @var{domain} argument restricts the search to the domain type.
26514 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26515 module and described later in this chapter.
26517 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26521 A @code{gdb.Symbol} object has the following attributes:
26523 @defvar Symbol.type
26524 The type of the symbol or @code{None} if no type is recorded.
26525 This attribute is represented as a @code{gdb.Type} object.
26526 @xref{Types In Python}. This attribute is not writable.
26529 @defvar Symbol.symtab
26530 The symbol table in which the symbol appears. This attribute is
26531 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26532 Python}. This attribute is not writable.
26535 @defvar Symbol.line
26536 The line number in the source code at which the symbol was defined.
26537 This is an integer.
26540 @defvar Symbol.name
26541 The name of the symbol as a string. This attribute is not writable.
26544 @defvar Symbol.linkage_name
26545 The name of the symbol, as used by the linker (i.e., may be mangled).
26546 This attribute is not writable.
26549 @defvar Symbol.print_name
26550 The name of the symbol in a form suitable for output. This is either
26551 @code{name} or @code{linkage_name}, depending on whether the user
26552 asked @value{GDBN} to display demangled or mangled names.
26555 @defvar Symbol.addr_class
26556 The address class of the symbol. This classifies how to find the value
26557 of a symbol. Each address class is a constant defined in the
26558 @code{gdb} module and described later in this chapter.
26561 @defvar Symbol.needs_frame
26562 This is @code{True} if evaluating this symbol's value requires a frame
26563 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26564 local variables will require a frame, but other symbols will not.
26567 @defvar Symbol.is_argument
26568 @code{True} if the symbol is an argument of a function.
26571 @defvar Symbol.is_constant
26572 @code{True} if the symbol is a constant.
26575 @defvar Symbol.is_function
26576 @code{True} if the symbol is a function or a method.
26579 @defvar Symbol.is_variable
26580 @code{True} if the symbol is a variable.
26583 A @code{gdb.Symbol} object has the following methods:
26585 @defun Symbol.is_valid ()
26586 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26587 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26588 the symbol it refers to does not exist in @value{GDBN} any longer.
26589 All other @code{gdb.Symbol} methods will throw an exception if it is
26590 invalid at the time the method is called.
26593 @defun Symbol.value (@r{[}frame@r{]})
26594 Compute the value of the symbol, as a @code{gdb.Value}. For
26595 functions, this computes the address of the function, cast to the
26596 appropriate type. If the symbol requires a frame in order to compute
26597 its value, then @var{frame} must be given. If @var{frame} is not
26598 given, or if @var{frame} is invalid, then this method will throw an
26602 The available domain categories in @code{gdb.Symbol} are represented
26603 as constants in the @code{gdb} module:
26606 @findex SYMBOL_UNDEF_DOMAIN
26607 @findex gdb.SYMBOL_UNDEF_DOMAIN
26608 @item gdb.SYMBOL_UNDEF_DOMAIN
26609 This is used when a domain has not been discovered or none of the
26610 following domains apply. This usually indicates an error either
26611 in the symbol information or in @value{GDBN}'s handling of symbols.
26612 @findex SYMBOL_VAR_DOMAIN
26613 @findex gdb.SYMBOL_VAR_DOMAIN
26614 @item gdb.SYMBOL_VAR_DOMAIN
26615 This domain contains variables, function names, typedef names and enum
26617 @findex SYMBOL_STRUCT_DOMAIN
26618 @findex gdb.SYMBOL_STRUCT_DOMAIN
26619 @item gdb.SYMBOL_STRUCT_DOMAIN
26620 This domain holds struct, union and enum type names.
26621 @findex SYMBOL_LABEL_DOMAIN
26622 @findex gdb.SYMBOL_LABEL_DOMAIN
26623 @item gdb.SYMBOL_LABEL_DOMAIN
26624 This domain contains names of labels (for gotos).
26625 @findex SYMBOL_VARIABLES_DOMAIN
26626 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26627 @item gdb.SYMBOL_VARIABLES_DOMAIN
26628 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
26629 contains everything minus functions and types.
26630 @findex SYMBOL_FUNCTIONS_DOMAIN
26631 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
26632 @item gdb.SYMBOL_FUNCTION_DOMAIN
26633 This domain contains all functions.
26634 @findex SYMBOL_TYPES_DOMAIN
26635 @findex gdb.SYMBOL_TYPES_DOMAIN
26636 @item gdb.SYMBOL_TYPES_DOMAIN
26637 This domain contains all types.
26640 The available address class categories in @code{gdb.Symbol} are represented
26641 as constants in the @code{gdb} module:
26644 @findex SYMBOL_LOC_UNDEF
26645 @findex gdb.SYMBOL_LOC_UNDEF
26646 @item gdb.SYMBOL_LOC_UNDEF
26647 If this is returned by address class, it indicates an error either in
26648 the symbol information or in @value{GDBN}'s handling of symbols.
26649 @findex SYMBOL_LOC_CONST
26650 @findex gdb.SYMBOL_LOC_CONST
26651 @item gdb.SYMBOL_LOC_CONST
26652 Value is constant int.
26653 @findex SYMBOL_LOC_STATIC
26654 @findex gdb.SYMBOL_LOC_STATIC
26655 @item gdb.SYMBOL_LOC_STATIC
26656 Value is at a fixed address.
26657 @findex SYMBOL_LOC_REGISTER
26658 @findex gdb.SYMBOL_LOC_REGISTER
26659 @item gdb.SYMBOL_LOC_REGISTER
26660 Value is in a register.
26661 @findex SYMBOL_LOC_ARG
26662 @findex gdb.SYMBOL_LOC_ARG
26663 @item gdb.SYMBOL_LOC_ARG
26664 Value is an argument. This value is at the offset stored within the
26665 symbol inside the frame's argument list.
26666 @findex SYMBOL_LOC_REF_ARG
26667 @findex gdb.SYMBOL_LOC_REF_ARG
26668 @item gdb.SYMBOL_LOC_REF_ARG
26669 Value address is stored in the frame's argument list. Just like
26670 @code{LOC_ARG} except that the value's address is stored at the
26671 offset, not the value itself.
26672 @findex SYMBOL_LOC_REGPARM_ADDR
26673 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
26674 @item gdb.SYMBOL_LOC_REGPARM_ADDR
26675 Value is a specified register. Just like @code{LOC_REGISTER} except
26676 the register holds the address of the argument instead of the argument
26678 @findex SYMBOL_LOC_LOCAL
26679 @findex gdb.SYMBOL_LOC_LOCAL
26680 @item gdb.SYMBOL_LOC_LOCAL
26681 Value is a local variable.
26682 @findex SYMBOL_LOC_TYPEDEF
26683 @findex gdb.SYMBOL_LOC_TYPEDEF
26684 @item gdb.SYMBOL_LOC_TYPEDEF
26685 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
26687 @findex SYMBOL_LOC_BLOCK
26688 @findex gdb.SYMBOL_LOC_BLOCK
26689 @item gdb.SYMBOL_LOC_BLOCK
26691 @findex SYMBOL_LOC_CONST_BYTES
26692 @findex gdb.SYMBOL_LOC_CONST_BYTES
26693 @item gdb.SYMBOL_LOC_CONST_BYTES
26694 Value is a byte-sequence.
26695 @findex SYMBOL_LOC_UNRESOLVED
26696 @findex gdb.SYMBOL_LOC_UNRESOLVED
26697 @item gdb.SYMBOL_LOC_UNRESOLVED
26698 Value is at a fixed address, but the address of the variable has to be
26699 determined from the minimal symbol table whenever the variable is
26701 @findex SYMBOL_LOC_OPTIMIZED_OUT
26702 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
26703 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
26704 The value does not actually exist in the program.
26705 @findex SYMBOL_LOC_COMPUTED
26706 @findex gdb.SYMBOL_LOC_COMPUTED
26707 @item gdb.SYMBOL_LOC_COMPUTED
26708 The value's address is a computed location.
26711 @node Symbol Tables In Python
26712 @subsubsection Symbol table representation in Python.
26714 @cindex symbol tables in python
26716 @tindex gdb.Symtab_and_line
26718 Access to symbol table data maintained by @value{GDBN} on the inferior
26719 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
26720 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
26721 from the @code{find_sal} method in @code{gdb.Frame} object.
26722 @xref{Frames In Python}.
26724 For more information on @value{GDBN}'s symbol table management, see
26725 @ref{Symbols, ,Examining the Symbol Table}, for more information.
26727 A @code{gdb.Symtab_and_line} object has the following attributes:
26729 @defvar Symtab_and_line.symtab
26730 The symbol table object (@code{gdb.Symtab}) for this frame.
26731 This attribute is not writable.
26734 @defvar Symtab_and_line.pc
26735 Indicates the start of the address range occupied by code for the
26736 current source line. This attribute is not writable.
26739 @defvar Symtab_and_line.last
26740 Indicates the end of the address range occupied by code for the current
26741 source line. This attribute is not writable.
26744 @defvar Symtab_and_line.line
26745 Indicates the current line number for this object. This
26746 attribute is not writable.
26749 A @code{gdb.Symtab_and_line} object has the following methods:
26751 @defun Symtab_and_line.is_valid ()
26752 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
26753 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
26754 invalid if the Symbol table and line object it refers to does not
26755 exist in @value{GDBN} any longer. All other
26756 @code{gdb.Symtab_and_line} methods will throw an exception if it is
26757 invalid at the time the method is called.
26760 A @code{gdb.Symtab} object has the following attributes:
26762 @defvar Symtab.filename
26763 The symbol table's source filename. This attribute is not writable.
26766 @defvar Symtab.objfile
26767 The symbol table's backing object file. @xref{Objfiles In Python}.
26768 This attribute is not writable.
26771 A @code{gdb.Symtab} object has the following methods:
26773 @defun Symtab.is_valid ()
26774 Returns @code{True} if the @code{gdb.Symtab} object is valid,
26775 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
26776 the symbol table it refers to does not exist in @value{GDBN} any
26777 longer. All other @code{gdb.Symtab} methods will throw an exception
26778 if it is invalid at the time the method is called.
26781 @defun Symtab.fullname ()
26782 Return the symbol table's source absolute file name.
26785 @defun Symtab.global_block ()
26786 Return the global block of the underlying symbol table.
26787 @xref{Blocks In Python}.
26790 @defun Symtab.static_block ()
26791 Return the static block of the underlying symbol table.
26792 @xref{Blocks In Python}.
26795 @node Breakpoints In Python
26796 @subsubsection Manipulating breakpoints using Python
26798 @cindex breakpoints in python
26799 @tindex gdb.Breakpoint
26801 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
26804 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
26805 Create a new breakpoint. @var{spec} is a string naming the
26806 location of the breakpoint, or an expression that defines a
26807 watchpoint. The contents can be any location recognized by the
26808 @code{break} command, or in the case of a watchpoint, by the @code{watch}
26809 command. The optional @var{type} denotes the breakpoint to create
26810 from the types defined later in this chapter. This argument can be
26811 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
26812 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
26813 allows the breakpoint to become invisible to the user. The breakpoint
26814 will neither be reported when created, nor will it be listed in the
26815 output from @code{info breakpoints} (but will be listed with the
26816 @code{maint info breakpoints} command). The optional @var{wp_class}
26817 argument defines the class of watchpoint to create, if @var{type} is
26818 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
26819 assumed to be a @code{gdb.WP_WRITE} class.
26822 @defun Breakpoint.stop (self)
26823 The @code{gdb.Breakpoint} class can be sub-classed and, in
26824 particular, you may choose to implement the @code{stop} method.
26825 If this method is defined as a sub-class of @code{gdb.Breakpoint},
26826 it will be called when the inferior reaches any location of a
26827 breakpoint which instantiates that sub-class. If the method returns
26828 @code{True}, the inferior will be stopped at the location of the
26829 breakpoint, otherwise the inferior will continue.
26831 If there are multiple breakpoints at the same location with a
26832 @code{stop} method, each one will be called regardless of the
26833 return status of the previous. This ensures that all @code{stop}
26834 methods have a chance to execute at that location. In this scenario
26835 if one of the methods returns @code{True} but the others return
26836 @code{False}, the inferior will still be stopped.
26838 You should not alter the execution state of the inferior (i.e.@:, step,
26839 next, etc.), alter the current frame context (i.e.@:, change the current
26840 active frame), or alter, add or delete any breakpoint. As a general
26841 rule, you should not alter any data within @value{GDBN} or the inferior
26844 Example @code{stop} implementation:
26847 class MyBreakpoint (gdb.Breakpoint):
26849 inf_val = gdb.parse_and_eval("foo")
26856 The available watchpoint types represented by constants are defined in the
26861 @findex gdb.WP_READ
26863 Read only watchpoint.
26866 @findex gdb.WP_WRITE
26868 Write only watchpoint.
26871 @findex gdb.WP_ACCESS
26872 @item gdb.WP_ACCESS
26873 Read/Write watchpoint.
26876 @defun Breakpoint.is_valid ()
26877 Return @code{True} if this @code{Breakpoint} object is valid,
26878 @code{False} otherwise. A @code{Breakpoint} object can become invalid
26879 if the user deletes the breakpoint. In this case, the object still
26880 exists, but the underlying breakpoint does not. In the cases of
26881 watchpoint scope, the watchpoint remains valid even if execution of the
26882 inferior leaves the scope of that watchpoint.
26885 @defun Breakpoint.delete
26886 Permanently deletes the @value{GDBN} breakpoint. This also
26887 invalidates the Python @code{Breakpoint} object. Any further access
26888 to this object's attributes or methods will raise an error.
26891 @defvar Breakpoint.enabled
26892 This attribute is @code{True} if the breakpoint is enabled, and
26893 @code{False} otherwise. This attribute is writable.
26896 @defvar Breakpoint.silent
26897 This attribute is @code{True} if the breakpoint is silent, and
26898 @code{False} otherwise. This attribute is writable.
26900 Note that a breakpoint can also be silent if it has commands and the
26901 first command is @code{silent}. This is not reported by the
26902 @code{silent} attribute.
26905 @defvar Breakpoint.thread
26906 If the breakpoint is thread-specific, this attribute holds the thread
26907 id. If the breakpoint is not thread-specific, this attribute is
26908 @code{None}. This attribute is writable.
26911 @defvar Breakpoint.task
26912 If the breakpoint is Ada task-specific, this attribute holds the Ada task
26913 id. If the breakpoint is not task-specific (or the underlying
26914 language is not Ada), this attribute is @code{None}. This attribute
26918 @defvar Breakpoint.ignore_count
26919 This attribute holds the ignore count for the breakpoint, an integer.
26920 This attribute is writable.
26923 @defvar Breakpoint.number
26924 This attribute holds the breakpoint's number --- the identifier used by
26925 the user to manipulate the breakpoint. This attribute is not writable.
26928 @defvar Breakpoint.type
26929 This attribute holds the breakpoint's type --- the identifier used to
26930 determine the actual breakpoint type or use-case. This attribute is not
26934 @defvar Breakpoint.visible
26935 This attribute tells whether the breakpoint is visible to the user
26936 when set, or when the @samp{info breakpoints} command is run. This
26937 attribute is not writable.
26940 The available types are represented by constants defined in the @code{gdb}
26944 @findex BP_BREAKPOINT
26945 @findex gdb.BP_BREAKPOINT
26946 @item gdb.BP_BREAKPOINT
26947 Normal code breakpoint.
26949 @findex BP_WATCHPOINT
26950 @findex gdb.BP_WATCHPOINT
26951 @item gdb.BP_WATCHPOINT
26952 Watchpoint breakpoint.
26954 @findex BP_HARDWARE_WATCHPOINT
26955 @findex gdb.BP_HARDWARE_WATCHPOINT
26956 @item gdb.BP_HARDWARE_WATCHPOINT
26957 Hardware assisted watchpoint.
26959 @findex BP_READ_WATCHPOINT
26960 @findex gdb.BP_READ_WATCHPOINT
26961 @item gdb.BP_READ_WATCHPOINT
26962 Hardware assisted read watchpoint.
26964 @findex BP_ACCESS_WATCHPOINT
26965 @findex gdb.BP_ACCESS_WATCHPOINT
26966 @item gdb.BP_ACCESS_WATCHPOINT
26967 Hardware assisted access watchpoint.
26970 @defvar Breakpoint.hit_count
26971 This attribute holds the hit count for the breakpoint, an integer.
26972 This attribute is writable, but currently it can only be set to zero.
26975 @defvar Breakpoint.location
26976 This attribute holds the location of the breakpoint, as specified by
26977 the user. It is a string. If the breakpoint does not have a location
26978 (that is, it is a watchpoint) the attribute's value is @code{None}. This
26979 attribute is not writable.
26982 @defvar Breakpoint.expression
26983 This attribute holds a breakpoint expression, as specified by
26984 the user. It is a string. If the breakpoint does not have an
26985 expression (the breakpoint is not a watchpoint) the attribute's value
26986 is @code{None}. This attribute is not writable.
26989 @defvar Breakpoint.condition
26990 This attribute holds the condition of the breakpoint, as specified by
26991 the user. It is a string. If there is no condition, this attribute's
26992 value is @code{None}. This attribute is writable.
26995 @defvar Breakpoint.commands
26996 This attribute holds the commands attached to the breakpoint. If
26997 there are commands, this attribute's value is a string holding all the
26998 commands, separated by newlines. If there are no commands, this
26999 attribute is @code{None}. This attribute is not writable.
27002 @node Finish Breakpoints in Python
27003 @subsubsection Finish Breakpoints
27005 @cindex python finish breakpoints
27006 @tindex gdb.FinishBreakpoint
27008 A finish breakpoint is a temporary breakpoint set at the return address of
27009 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27010 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27011 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27012 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27013 Finish breakpoints are thread specific and must be create with the right
27016 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27017 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27018 object @var{frame}. If @var{frame} is not provided, this defaults to the
27019 newest frame. The optional @var{internal} argument allows the breakpoint to
27020 become invisible to the user. @xref{Breakpoints In Python}, for further
27021 details about this argument.
27024 @defun FinishBreakpoint.out_of_scope (self)
27025 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27026 @code{return} command, @dots{}), a function may not properly terminate, and
27027 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27028 situation, the @code{out_of_scope} callback will be triggered.
27030 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27034 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27036 print "normal finish"
27039 def out_of_scope ():
27040 print "abnormal finish"
27044 @defvar FinishBreakpoint.return_value
27045 When @value{GDBN} is stopped at a finish breakpoint and the frame
27046 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27047 attribute will contain a @code{gdb.Value} object corresponding to the return
27048 value of the function. The value will be @code{None} if the function return
27049 type is @code{void} or if the return value was not computable. This attribute
27053 @node Lazy Strings In Python
27054 @subsubsection Python representation of lazy strings.
27056 @cindex lazy strings in python
27057 @tindex gdb.LazyString
27059 A @dfn{lazy string} is a string whose contents is not retrieved or
27060 encoded until it is needed.
27062 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27063 @code{address} that points to a region of memory, an @code{encoding}
27064 that will be used to encode that region of memory, and a @code{length}
27065 to delimit the region of memory that represents the string. The
27066 difference between a @code{gdb.LazyString} and a string wrapped within
27067 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27068 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27069 retrieved and encoded during printing, while a @code{gdb.Value}
27070 wrapping a string is immediately retrieved and encoded on creation.
27072 A @code{gdb.LazyString} object has the following functions:
27074 @defun LazyString.value ()
27075 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27076 will point to the string in memory, but will lose all the delayed
27077 retrieval, encoding and handling that @value{GDBN} applies to a
27078 @code{gdb.LazyString}.
27081 @defvar LazyString.address
27082 This attribute holds the address of the string. This attribute is not
27086 @defvar LazyString.length
27087 This attribute holds the length of the string in characters. If the
27088 length is -1, then the string will be fetched and encoded up to the
27089 first null of appropriate width. This attribute is not writable.
27092 @defvar LazyString.encoding
27093 This attribute holds the encoding that will be applied to the string
27094 when the string is printed by @value{GDBN}. If the encoding is not
27095 set, or contains an empty string, then @value{GDBN} will select the
27096 most appropriate encoding when the string is printed. This attribute
27100 @defvar LazyString.type
27101 This attribute holds the type that is represented by the lazy string's
27102 type. For a lazy string this will always be a pointer type. To
27103 resolve this to the lazy string's character type, use the type's
27104 @code{target} method. @xref{Types In Python}. This attribute is not
27108 @node Architectures In Python
27109 @subsubsection Python representation of architectures
27110 @cindex Python architectures
27112 @value{GDBN} uses architecture specific parameters and artifacts in a
27113 number of its various computations. An architecture is represented
27114 by an instance of the @code{gdb.Architecture} class.
27116 A @code{gdb.Architecture} class has the following methods:
27118 @defun Architecture.name ()
27119 Return the name (string value) of the architecture.
27122 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27123 Return a list of disassembled instructions starting from the memory
27124 address @var{start_pc}. The optional arguments @var{end_pc} and
27125 @var{count} determine the number of instructions in the returned list.
27126 If both the optional arguments @var{end_pc} and @var{count} are
27127 specified, then a list of at most @var{count} disassembled instructions
27128 whose start address falls in the closed memory address interval from
27129 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27130 specified, but @var{count} is specified, then @var{count} number of
27131 instructions starting from the address @var{start_pc} are returned. If
27132 @var{count} is not specified but @var{end_pc} is specified, then all
27133 instructions whose start address falls in the closed memory address
27134 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27135 @var{end_pc} nor @var{count} are specified, then a single instruction at
27136 @var{start_pc} is returned. For all of these cases, each element of the
27137 returned list is a Python @code{dict} with the following string keys:
27142 The value corresponding to this key is a Python long integer capturing
27143 the memory address of the instruction.
27146 The value corresponding to this key is a string value which represents
27147 the instruction with assembly language mnemonics. The assembly
27148 language flavor used is the same as that specified by the current CLI
27149 variable @code{disassembly-flavor}. @xref{Machine Code}.
27152 The value corresponding to this key is the length (integer value) of the
27153 instruction in bytes.
27158 @node Python Auto-loading
27159 @subsection Python Auto-loading
27160 @cindex Python auto-loading
27162 When a new object file is read (for example, due to the @code{file}
27163 command, or because the inferior has loaded a shared library),
27164 @value{GDBN} will look for Python support scripts in several ways:
27165 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
27166 and @code{.debug_gdb_scripts} section
27167 (@pxref{dotdebug_gdb_scripts section}).
27169 The auto-loading feature is useful for supplying application-specific
27170 debugging commands and scripts.
27172 Auto-loading can be enabled or disabled,
27173 and the list of auto-loaded scripts can be printed.
27176 @anchor{set auto-load python-scripts}
27177 @kindex set auto-load python-scripts
27178 @item set auto-load python-scripts [on|off]
27179 Enable or disable the auto-loading of Python scripts.
27181 @anchor{show auto-load python-scripts}
27182 @kindex show auto-load python-scripts
27183 @item show auto-load python-scripts
27184 Show whether auto-loading of Python scripts is enabled or disabled.
27186 @anchor{info auto-load python-scripts}
27187 @kindex info auto-load python-scripts
27188 @cindex print list of auto-loaded Python scripts
27189 @item info auto-load python-scripts [@var{regexp}]
27190 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27192 Also printed is the list of Python scripts that were mentioned in
27193 the @code{.debug_gdb_scripts} section and were not found
27194 (@pxref{dotdebug_gdb_scripts section}).
27195 This is useful because their names are not printed when @value{GDBN}
27196 tries to load them and fails. There may be many of them, and printing
27197 an error message for each one is problematic.
27199 If @var{regexp} is supplied only Python scripts with matching names are printed.
27204 (gdb) info auto-load python-scripts
27206 Yes py-section-script.py
27207 full name: /tmp/py-section-script.py
27208 No my-foo-pretty-printers.py
27212 When reading an auto-loaded file, @value{GDBN} sets the
27213 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27214 function (@pxref{Objfiles In Python}). This can be useful for
27215 registering objfile-specific pretty-printers and frame-filters.
27218 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
27219 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
27220 * Which flavor to choose?::
27223 @node objfile-gdb.py file
27224 @subsubsection The @file{@var{objfile}-gdb.py} file
27225 @cindex @file{@var{objfile}-gdb.py}
27227 When a new object file is read, @value{GDBN} looks for
27228 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
27229 where @var{objfile} is the object file's real name, formed by ensuring
27230 that the file name is absolute, following all symlinks, and resolving
27231 @code{.} and @code{..} components. If this file exists and is
27232 readable, @value{GDBN} will evaluate it as a Python script.
27234 If this file does not exist, then @value{GDBN} will look for
27235 @var{script-name} file in all of the directories as specified below.
27237 Note that loading of this script file also requires accordingly configured
27238 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27240 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27241 scripts normally according to its @file{.exe} filename. But if no scripts are
27242 found @value{GDBN} also tries script filenames matching the object file without
27243 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27244 is attempted on any platform. This makes the script filenames compatible
27245 between Unix and MS-Windows hosts.
27248 @anchor{set auto-load scripts-directory}
27249 @kindex set auto-load scripts-directory
27250 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27251 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27252 may be delimited by the host platform path separator in use
27253 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27255 Each entry here needs to be covered also by the security setting
27256 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27258 @anchor{with-auto-load-dir}
27259 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27260 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27261 configuration option @option{--with-auto-load-dir}.
27263 Any reference to @file{$debugdir} will get replaced by
27264 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27265 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27266 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27267 @file{$datadir} must be placed as a directory component --- either alone or
27268 delimited by @file{/} or @file{\} directory separators, depending on the host
27271 The list of directories uses path separator (@samp{:} on GNU and Unix
27272 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27273 to the @env{PATH} environment variable.
27275 @anchor{show auto-load scripts-directory}
27276 @kindex show auto-load scripts-directory
27277 @item show auto-load scripts-directory
27278 Show @value{GDBN} auto-loaded scripts location.
27281 @value{GDBN} does not track which files it has already auto-loaded this way.
27282 @value{GDBN} will load the associated script every time the corresponding
27283 @var{objfile} is opened.
27284 So your @file{-gdb.py} file should be careful to avoid errors if it
27285 is evaluated more than once.
27287 @node dotdebug_gdb_scripts section
27288 @subsubsection The @code{.debug_gdb_scripts} section
27289 @cindex @code{.debug_gdb_scripts} section
27291 For systems using file formats like ELF and COFF,
27292 when @value{GDBN} loads a new object file
27293 it will look for a special section named @samp{.debug_gdb_scripts}.
27294 If this section exists, its contents is a list of names of scripts to load.
27296 @value{GDBN} will look for each specified script file first in the
27297 current directory and then along the source search path
27298 (@pxref{Source Path, ,Specifying Source Directories}),
27299 except that @file{$cdir} is not searched, since the compilation
27300 directory is not relevant to scripts.
27302 Entries can be placed in section @code{.debug_gdb_scripts} with,
27303 for example, this GCC macro:
27306 /* Note: The "MS" section flags are to remove duplicates. */
27307 #define DEFINE_GDB_SCRIPT(script_name) \
27309 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27311 .asciz \"" script_name "\"\n\
27317 Then one can reference the macro in a header or source file like this:
27320 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
27323 The script name may include directories if desired.
27325 Note that loading of this script file also requires accordingly configured
27326 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27328 If the macro is put in a header, any application or library
27329 using this header will get a reference to the specified script.
27331 @node Which flavor to choose?
27332 @subsubsection Which flavor to choose?
27334 Given the multiple ways of auto-loading Python scripts, it might not always
27335 be clear which one to choose. This section provides some guidance.
27337 Benefits of the @file{-gdb.py} way:
27341 Can be used with file formats that don't support multiple sections.
27344 Ease of finding scripts for public libraries.
27346 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27347 in the source search path.
27348 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27349 isn't a source directory in which to find the script.
27352 Doesn't require source code additions.
27355 Benefits of the @code{.debug_gdb_scripts} way:
27359 Works with static linking.
27361 Scripts for libraries done the @file{-gdb.py} way require an objfile to
27362 trigger their loading. When an application is statically linked the only
27363 objfile available is the executable, and it is cumbersome to attach all the
27364 scripts from all the input libraries to the executable's @file{-gdb.py} script.
27367 Works with classes that are entirely inlined.
27369 Some classes can be entirely inlined, and thus there may not be an associated
27370 shared library to attach a @file{-gdb.py} script to.
27373 Scripts needn't be copied out of the source tree.
27375 In some circumstances, apps can be built out of large collections of internal
27376 libraries, and the build infrastructure necessary to install the
27377 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
27378 cumbersome. It may be easier to specify the scripts in the
27379 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27380 top of the source tree to the source search path.
27383 @node Python modules
27384 @subsection Python modules
27385 @cindex python modules
27387 @value{GDBN} comes with several modules to assist writing Python code.
27390 * gdb.printing:: Building and registering pretty-printers.
27391 * gdb.types:: Utilities for working with types.
27392 * gdb.prompt:: Utilities for prompt value substitution.
27396 @subsubsection gdb.printing
27397 @cindex gdb.printing
27399 This module provides a collection of utilities for working with
27403 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27404 This class specifies the API that makes @samp{info pretty-printer},
27405 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27406 Pretty-printers should generally inherit from this class.
27408 @item SubPrettyPrinter (@var{name})
27409 For printers that handle multiple types, this class specifies the
27410 corresponding API for the subprinters.
27412 @item RegexpCollectionPrettyPrinter (@var{name})
27413 Utility class for handling multiple printers, all recognized via
27414 regular expressions.
27415 @xref{Writing a Pretty-Printer}, for an example.
27417 @item FlagEnumerationPrinter (@var{name})
27418 A pretty-printer which handles printing of @code{enum} values. Unlike
27419 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27420 work properly when there is some overlap between the enumeration
27421 constants. @var{name} is the name of the printer and also the name of
27422 the @code{enum} type to look up.
27424 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27425 Register @var{printer} with the pretty-printer list of @var{obj}.
27426 If @var{replace} is @code{True} then any existing copy of the printer
27427 is replaced. Otherwise a @code{RuntimeError} exception is raised
27428 if a printer with the same name already exists.
27432 @subsubsection gdb.types
27435 This module provides a collection of utilities for working with
27436 @code{gdb.Type} objects.
27439 @item get_basic_type (@var{type})
27440 Return @var{type} with const and volatile qualifiers stripped,
27441 and with typedefs and C@t{++} references converted to the underlying type.
27446 typedef const int const_int;
27448 const_int& foo_ref (foo);
27449 int main () @{ return 0; @}
27456 (gdb) python import gdb.types
27457 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27458 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27462 @item has_field (@var{type}, @var{field})
27463 Return @code{True} if @var{type}, assumed to be a type with fields
27464 (e.g., a structure or union), has field @var{field}.
27466 @item make_enum_dict (@var{enum_type})
27467 Return a Python @code{dictionary} type produced from @var{enum_type}.
27469 @item deep_items (@var{type})
27470 Returns a Python iterator similar to the standard
27471 @code{gdb.Type.iteritems} method, except that the iterator returned
27472 by @code{deep_items} will recursively traverse anonymous struct or
27473 union fields. For example:
27487 Then in @value{GDBN}:
27489 (@value{GDBP}) python import gdb.types
27490 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27491 (@value{GDBP}) python print struct_a.keys ()
27493 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27494 @{['a', 'b0', 'b1']@}
27497 @item get_type_recognizers ()
27498 Return a list of the enabled type recognizers for the current context.
27499 This is called by @value{GDBN} during the type-printing process
27500 (@pxref{Type Printing API}).
27502 @item apply_type_recognizers (recognizers, type_obj)
27503 Apply the type recognizers, @var{recognizers}, to the type object
27504 @var{type_obj}. If any recognizer returns a string, return that
27505 string. Otherwise, return @code{None}. This is called by
27506 @value{GDBN} during the type-printing process (@pxref{Type Printing
27509 @item register_type_printer (locus, printer)
27510 This is a convenience function to register a type printer.
27511 @var{printer} is the type printer to register. It must implement the
27512 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27513 which case the printer is registered with that objfile; a
27514 @code{gdb.Progspace}, in which case the printer is registered with
27515 that progspace; or @code{None}, in which case the printer is
27516 registered globally.
27519 This is a base class that implements the type printer protocol. Type
27520 printers are encouraged, but not required, to derive from this class.
27521 It defines a constructor:
27523 @defmethod TypePrinter __init__ (self, name)
27524 Initialize the type printer with the given name. The new printer
27525 starts in the enabled state.
27531 @subsubsection gdb.prompt
27534 This module provides a method for prompt value-substitution.
27537 @item substitute_prompt (@var{string})
27538 Return @var{string} with escape sequences substituted by values. Some
27539 escape sequences take arguments. You can specify arguments inside
27540 ``@{@}'' immediately following the escape sequence.
27542 The escape sequences you can pass to this function are:
27546 Substitute a backslash.
27548 Substitute an ESC character.
27550 Substitute the selected frame; an argument names a frame parameter.
27552 Substitute a newline.
27554 Substitute a parameter's value; the argument names the parameter.
27556 Substitute a carriage return.
27558 Substitute the selected thread; an argument names a thread parameter.
27560 Substitute the version of GDB.
27562 Substitute the current working directory.
27564 Begin a sequence of non-printing characters. These sequences are
27565 typically used with the ESC character, and are not counted in the string
27566 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27567 blue-colored ``(gdb)'' prompt where the length is five.
27569 End a sequence of non-printing characters.
27575 substitute_prompt (``frame: \f,
27576 print arguments: \p@{print frame-arguments@}'')
27579 @exdent will return the string:
27582 "frame: main, print arguments: scalars"
27587 @section Creating new spellings of existing commands
27588 @cindex aliases for commands
27590 It is often useful to define alternate spellings of existing commands.
27591 For example, if a new @value{GDBN} command defined in Python has
27592 a long name to type, it is handy to have an abbreviated version of it
27593 that involves less typing.
27595 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27596 of the @samp{step} command even though it is otherwise an ambiguous
27597 abbreviation of other commands like @samp{set} and @samp{show}.
27599 Aliases are also used to provide shortened or more common versions
27600 of multi-word commands. For example, @value{GDBN} provides the
27601 @samp{tty} alias of the @samp{set inferior-tty} command.
27603 You can define a new alias with the @samp{alias} command.
27608 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
27612 @var{ALIAS} specifies the name of the new alias.
27613 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
27616 @var{COMMAND} specifies the name of an existing command
27617 that is being aliased.
27619 The @samp{-a} option specifies that the new alias is an abbreviation
27620 of the command. Abbreviations are not shown in command
27621 lists displayed by the @samp{help} command.
27623 The @samp{--} option specifies the end of options,
27624 and is useful when @var{ALIAS} begins with a dash.
27626 Here is a simple example showing how to make an abbreviation
27627 of a command so that there is less to type.
27628 Suppose you were tired of typing @samp{disas}, the current
27629 shortest unambiguous abbreviation of the @samp{disassemble} command
27630 and you wanted an even shorter version named @samp{di}.
27631 The following will accomplish this.
27634 (gdb) alias -a di = disas
27637 Note that aliases are different from user-defined commands.
27638 With a user-defined command, you also need to write documentation
27639 for it with the @samp{document} command.
27640 An alias automatically picks up the documentation of the existing command.
27642 Here is an example where we make @samp{elms} an abbreviation of
27643 @samp{elements} in the @samp{set print elements} command.
27644 This is to show that you can make an abbreviation of any part
27648 (gdb) alias -a set print elms = set print elements
27649 (gdb) alias -a show print elms = show print elements
27650 (gdb) set p elms 20
27652 Limit on string chars or array elements to print is 200.
27655 Note that if you are defining an alias of a @samp{set} command,
27656 and you want to have an alias for the corresponding @samp{show}
27657 command, then you need to define the latter separately.
27659 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
27660 @var{ALIAS}, just as they are normally.
27663 (gdb) alias -a set pr elms = set p ele
27666 Finally, here is an example showing the creation of a one word
27667 alias for a more complex command.
27668 This creates alias @samp{spe} of the command @samp{set print elements}.
27671 (gdb) alias spe = set print elements
27676 @chapter Command Interpreters
27677 @cindex command interpreters
27679 @value{GDBN} supports multiple command interpreters, and some command
27680 infrastructure to allow users or user interface writers to switch
27681 between interpreters or run commands in other interpreters.
27683 @value{GDBN} currently supports two command interpreters, the console
27684 interpreter (sometimes called the command-line interpreter or @sc{cli})
27685 and the machine interface interpreter (or @sc{gdb/mi}). This manual
27686 describes both of these interfaces in great detail.
27688 By default, @value{GDBN} will start with the console interpreter.
27689 However, the user may choose to start @value{GDBN} with another
27690 interpreter by specifying the @option{-i} or @option{--interpreter}
27691 startup options. Defined interpreters include:
27695 @cindex console interpreter
27696 The traditional console or command-line interpreter. This is the most often
27697 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
27698 @value{GDBN} will use this interpreter.
27701 @cindex mi interpreter
27702 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
27703 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
27704 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
27708 @cindex mi2 interpreter
27709 The current @sc{gdb/mi} interface.
27712 @cindex mi1 interpreter
27713 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
27717 @cindex invoke another interpreter
27718 The interpreter being used by @value{GDBN} may not be dynamically
27719 switched at runtime. Although possible, this could lead to a very
27720 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
27721 enters the command "interpreter-set console" in a console view,
27722 @value{GDBN} would switch to using the console interpreter, rendering
27723 the IDE inoperable!
27725 @kindex interpreter-exec
27726 Although you may only choose a single interpreter at startup, you may execute
27727 commands in any interpreter from the current interpreter using the appropriate
27728 command. If you are running the console interpreter, simply use the
27729 @code{interpreter-exec} command:
27732 interpreter-exec mi "-data-list-register-names"
27735 @sc{gdb/mi} has a similar command, although it is only available in versions of
27736 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
27739 @chapter @value{GDBN} Text User Interface
27741 @cindex Text User Interface
27744 * TUI Overview:: TUI overview
27745 * TUI Keys:: TUI key bindings
27746 * TUI Single Key Mode:: TUI single key mode
27747 * TUI Commands:: TUI-specific commands
27748 * TUI Configuration:: TUI configuration variables
27751 The @value{GDBN} Text User Interface (TUI) is a terminal
27752 interface which uses the @code{curses} library to show the source
27753 file, the assembly output, the program registers and @value{GDBN}
27754 commands in separate text windows. The TUI mode is supported only
27755 on platforms where a suitable version of the @code{curses} library
27758 The TUI mode is enabled by default when you invoke @value{GDBN} as
27759 @samp{@value{GDBP} -tui}.
27760 You can also switch in and out of TUI mode while @value{GDBN} runs by
27761 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
27762 @xref{TUI Keys, ,TUI Key Bindings}.
27765 @section TUI Overview
27767 In TUI mode, @value{GDBN} can display several text windows:
27771 This window is the @value{GDBN} command window with the @value{GDBN}
27772 prompt and the @value{GDBN} output. The @value{GDBN} input is still
27773 managed using readline.
27776 The source window shows the source file of the program. The current
27777 line and active breakpoints are displayed in this window.
27780 The assembly window shows the disassembly output of the program.
27783 This window shows the processor registers. Registers are highlighted
27784 when their values change.
27787 The source and assembly windows show the current program position
27788 by highlighting the current line and marking it with a @samp{>} marker.
27789 Breakpoints are indicated with two markers. The first marker
27790 indicates the breakpoint type:
27794 Breakpoint which was hit at least once.
27797 Breakpoint which was never hit.
27800 Hardware breakpoint which was hit at least once.
27803 Hardware breakpoint which was never hit.
27806 The second marker indicates whether the breakpoint is enabled or not:
27810 Breakpoint is enabled.
27813 Breakpoint is disabled.
27816 The source, assembly and register windows are updated when the current
27817 thread changes, when the frame changes, or when the program counter
27820 These windows are not all visible at the same time. The command
27821 window is always visible. The others can be arranged in several
27832 source and assembly,
27835 source and registers, or
27838 assembly and registers.
27841 A status line above the command window shows the following information:
27845 Indicates the current @value{GDBN} target.
27846 (@pxref{Targets, ,Specifying a Debugging Target}).
27849 Gives the current process or thread number.
27850 When no process is being debugged, this field is set to @code{No process}.
27853 Gives the current function name for the selected frame.
27854 The name is demangled if demangling is turned on (@pxref{Print Settings}).
27855 When there is no symbol corresponding to the current program counter,
27856 the string @code{??} is displayed.
27859 Indicates the current line number for the selected frame.
27860 When the current line number is not known, the string @code{??} is displayed.
27863 Indicates the current program counter address.
27867 @section TUI Key Bindings
27868 @cindex TUI key bindings
27870 The TUI installs several key bindings in the readline keymaps
27871 @ifset SYSTEM_READLINE
27872 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
27874 @ifclear SYSTEM_READLINE
27875 (@pxref{Command Line Editing}).
27877 The following key bindings are installed for both TUI mode and the
27878 @value{GDBN} standard mode.
27887 Enter or leave the TUI mode. When leaving the TUI mode,
27888 the curses window management stops and @value{GDBN} operates using
27889 its standard mode, writing on the terminal directly. When reentering
27890 the TUI mode, control is given back to the curses windows.
27891 The screen is then refreshed.
27895 Use a TUI layout with only one window. The layout will
27896 either be @samp{source} or @samp{assembly}. When the TUI mode
27897 is not active, it will switch to the TUI mode.
27899 Think of this key binding as the Emacs @kbd{C-x 1} binding.
27903 Use a TUI layout with at least two windows. When the current
27904 layout already has two windows, the next layout with two windows is used.
27905 When a new layout is chosen, one window will always be common to the
27906 previous layout and the new one.
27908 Think of it as the Emacs @kbd{C-x 2} binding.
27912 Change the active window. The TUI associates several key bindings
27913 (like scrolling and arrow keys) with the active window. This command
27914 gives the focus to the next TUI window.
27916 Think of it as the Emacs @kbd{C-x o} binding.
27920 Switch in and out of the TUI SingleKey mode that binds single
27921 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
27924 The following key bindings only work in the TUI mode:
27929 Scroll the active window one page up.
27933 Scroll the active window one page down.
27937 Scroll the active window one line up.
27941 Scroll the active window one line down.
27945 Scroll the active window one column left.
27949 Scroll the active window one column right.
27953 Refresh the screen.
27956 Because the arrow keys scroll the active window in the TUI mode, they
27957 are not available for their normal use by readline unless the command
27958 window has the focus. When another window is active, you must use
27959 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
27960 and @kbd{C-f} to control the command window.
27962 @node TUI Single Key Mode
27963 @section TUI Single Key Mode
27964 @cindex TUI single key mode
27966 The TUI also provides a @dfn{SingleKey} mode, which binds several
27967 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
27968 switch into this mode, where the following key bindings are used:
27971 @kindex c @r{(SingleKey TUI key)}
27975 @kindex d @r{(SingleKey TUI key)}
27979 @kindex f @r{(SingleKey TUI key)}
27983 @kindex n @r{(SingleKey TUI key)}
27987 @kindex q @r{(SingleKey TUI key)}
27989 exit the SingleKey mode.
27991 @kindex r @r{(SingleKey TUI key)}
27995 @kindex s @r{(SingleKey TUI key)}
27999 @kindex u @r{(SingleKey TUI key)}
28003 @kindex v @r{(SingleKey TUI key)}
28007 @kindex w @r{(SingleKey TUI key)}
28012 Other keys temporarily switch to the @value{GDBN} command prompt.
28013 The key that was pressed is inserted in the editing buffer so that
28014 it is possible to type most @value{GDBN} commands without interaction
28015 with the TUI SingleKey mode. Once the command is entered the TUI
28016 SingleKey mode is restored. The only way to permanently leave
28017 this mode is by typing @kbd{q} or @kbd{C-x s}.
28021 @section TUI-specific Commands
28022 @cindex TUI commands
28024 The TUI has specific commands to control the text windows.
28025 These commands are always available, even when @value{GDBN} is not in
28026 the TUI mode. When @value{GDBN} is in the standard mode, most
28027 of these commands will automatically switch to the TUI mode.
28029 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28030 terminal, or @value{GDBN} has been started with the machine interface
28031 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28032 these commands will fail with an error, because it would not be
28033 possible or desirable to enable curses window management.
28038 List and give the size of all displayed windows.
28042 Display the next layout.
28045 Display the previous layout.
28048 Display the source window only.
28051 Display the assembly window only.
28054 Display the source and assembly window.
28057 Display the register window together with the source or assembly window.
28061 Make the next window active for scrolling.
28064 Make the previous window active for scrolling.
28067 Make the source window active for scrolling.
28070 Make the assembly window active for scrolling.
28073 Make the register window active for scrolling.
28076 Make the command window active for scrolling.
28080 Refresh the screen. This is similar to typing @kbd{C-L}.
28082 @item tui reg float
28084 Show the floating point registers in the register window.
28086 @item tui reg general
28087 Show the general registers in the register window.
28090 Show the next register group. The list of register groups as well as
28091 their order is target specific. The predefined register groups are the
28092 following: @code{general}, @code{float}, @code{system}, @code{vector},
28093 @code{all}, @code{save}, @code{restore}.
28095 @item tui reg system
28096 Show the system registers in the register window.
28100 Update the source window and the current execution point.
28102 @item winheight @var{name} +@var{count}
28103 @itemx winheight @var{name} -@var{count}
28105 Change the height of the window @var{name} by @var{count}
28106 lines. Positive counts increase the height, while negative counts
28109 @item tabset @var{nchars}
28111 Set the width of tab stops to be @var{nchars} characters.
28114 @node TUI Configuration
28115 @section TUI Configuration Variables
28116 @cindex TUI configuration variables
28118 Several configuration variables control the appearance of TUI windows.
28121 @item set tui border-kind @var{kind}
28122 @kindex set tui border-kind
28123 Select the border appearance for the source, assembly and register windows.
28124 The possible values are the following:
28127 Use a space character to draw the border.
28130 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28133 Use the Alternate Character Set to draw the border. The border is
28134 drawn using character line graphics if the terminal supports them.
28137 @item set tui border-mode @var{mode}
28138 @kindex set tui border-mode
28139 @itemx set tui active-border-mode @var{mode}
28140 @kindex set tui active-border-mode
28141 Select the display attributes for the borders of the inactive windows
28142 or the active window. The @var{mode} can be one of the following:
28145 Use normal attributes to display the border.
28151 Use reverse video mode.
28154 Use half bright mode.
28156 @item half-standout
28157 Use half bright and standout mode.
28160 Use extra bright or bold mode.
28162 @item bold-standout
28163 Use extra bright or bold and standout mode.
28168 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28171 @cindex @sc{gnu} Emacs
28172 A special interface allows you to use @sc{gnu} Emacs to view (and
28173 edit) the source files for the program you are debugging with
28176 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28177 executable file you want to debug as an argument. This command starts
28178 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28179 created Emacs buffer.
28180 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28182 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28187 All ``terminal'' input and output goes through an Emacs buffer, called
28190 This applies both to @value{GDBN} commands and their output, and to the input
28191 and output done by the program you are debugging.
28193 This is useful because it means that you can copy the text of previous
28194 commands and input them again; you can even use parts of the output
28197 All the facilities of Emacs' Shell mode are available for interacting
28198 with your program. In particular, you can send signals the usual
28199 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28203 @value{GDBN} displays source code through Emacs.
28205 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28206 source file for that frame and puts an arrow (@samp{=>}) at the
28207 left margin of the current line. Emacs uses a separate buffer for
28208 source display, and splits the screen to show both your @value{GDBN} session
28211 Explicit @value{GDBN} @code{list} or search commands still produce output as
28212 usual, but you probably have no reason to use them from Emacs.
28215 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28216 a graphical mode, enabled by default, which provides further buffers
28217 that can control the execution and describe the state of your program.
28218 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28220 If you specify an absolute file name when prompted for the @kbd{M-x
28221 gdb} argument, then Emacs sets your current working directory to where
28222 your program resides. If you only specify the file name, then Emacs
28223 sets your current working directory to the directory associated
28224 with the previous buffer. In this case, @value{GDBN} may find your
28225 program by searching your environment's @code{PATH} variable, but on
28226 some operating systems it might not find the source. So, although the
28227 @value{GDBN} input and output session proceeds normally, the auxiliary
28228 buffer does not display the current source and line of execution.
28230 The initial working directory of @value{GDBN} is printed on the top
28231 line of the GUD buffer and this serves as a default for the commands
28232 that specify files for @value{GDBN} to operate on. @xref{Files,
28233 ,Commands to Specify Files}.
28235 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28236 need to call @value{GDBN} by a different name (for example, if you
28237 keep several configurations around, with different names) you can
28238 customize the Emacs variable @code{gud-gdb-command-name} to run the
28241 In the GUD buffer, you can use these special Emacs commands in
28242 addition to the standard Shell mode commands:
28246 Describe the features of Emacs' GUD Mode.
28249 Execute to another source line, like the @value{GDBN} @code{step} command; also
28250 update the display window to show the current file and location.
28253 Execute to next source line in this function, skipping all function
28254 calls, like the @value{GDBN} @code{next} command. Then update the display window
28255 to show the current file and location.
28258 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28259 display window accordingly.
28262 Execute until exit from the selected stack frame, like the @value{GDBN}
28263 @code{finish} command.
28266 Continue execution of your program, like the @value{GDBN} @code{continue}
28270 Go up the number of frames indicated by the numeric argument
28271 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28272 like the @value{GDBN} @code{up} command.
28275 Go down the number of frames indicated by the numeric argument, like the
28276 @value{GDBN} @code{down} command.
28279 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28280 tells @value{GDBN} to set a breakpoint on the source line point is on.
28282 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28283 separate frame which shows a backtrace when the GUD buffer is current.
28284 Move point to any frame in the stack and type @key{RET} to make it
28285 become the current frame and display the associated source in the
28286 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28287 selected frame become the current one. In graphical mode, the
28288 speedbar displays watch expressions.
28290 If you accidentally delete the source-display buffer, an easy way to get
28291 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28292 request a frame display; when you run under Emacs, this recreates
28293 the source buffer if necessary to show you the context of the current
28296 The source files displayed in Emacs are in ordinary Emacs buffers
28297 which are visiting the source files in the usual way. You can edit
28298 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28299 communicates with Emacs in terms of line numbers. If you add or
28300 delete lines from the text, the line numbers that @value{GDBN} knows cease
28301 to correspond properly with the code.
28303 A more detailed description of Emacs' interaction with @value{GDBN} is
28304 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28308 @chapter The @sc{gdb/mi} Interface
28310 @unnumberedsec Function and Purpose
28312 @cindex @sc{gdb/mi}, its purpose
28313 @sc{gdb/mi} is a line based machine oriented text interface to
28314 @value{GDBN} and is activated by specifying using the
28315 @option{--interpreter} command line option (@pxref{Mode Options}). It
28316 is specifically intended to support the development of systems which
28317 use the debugger as just one small component of a larger system.
28319 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28320 in the form of a reference manual.
28322 Note that @sc{gdb/mi} is still under construction, so some of the
28323 features described below are incomplete and subject to change
28324 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28326 @unnumberedsec Notation and Terminology
28328 @cindex notational conventions, for @sc{gdb/mi}
28329 This chapter uses the following notation:
28333 @code{|} separates two alternatives.
28336 @code{[ @var{something} ]} indicates that @var{something} is optional:
28337 it may or may not be given.
28340 @code{( @var{group} )*} means that @var{group} inside the parentheses
28341 may repeat zero or more times.
28344 @code{( @var{group} )+} means that @var{group} inside the parentheses
28345 may repeat one or more times.
28348 @code{"@var{string}"} means a literal @var{string}.
28352 @heading Dependencies
28356 * GDB/MI General Design::
28357 * GDB/MI Command Syntax::
28358 * GDB/MI Compatibility with CLI::
28359 * GDB/MI Development and Front Ends::
28360 * GDB/MI Output Records::
28361 * GDB/MI Simple Examples::
28362 * GDB/MI Command Description Format::
28363 * GDB/MI Breakpoint Commands::
28364 * GDB/MI Catchpoint Commands::
28365 * GDB/MI Program Context::
28366 * GDB/MI Thread Commands::
28367 * GDB/MI Ada Tasking Commands::
28368 * GDB/MI Program Execution::
28369 * GDB/MI Stack Manipulation::
28370 * GDB/MI Variable Objects::
28371 * GDB/MI Data Manipulation::
28372 * GDB/MI Tracepoint Commands::
28373 * GDB/MI Symbol Query::
28374 * GDB/MI File Commands::
28376 * GDB/MI Kod Commands::
28377 * GDB/MI Memory Overlay Commands::
28378 * GDB/MI Signal Handling Commands::
28380 * GDB/MI Target Manipulation::
28381 * GDB/MI File Transfer Commands::
28382 * GDB/MI Miscellaneous Commands::
28385 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28386 @node GDB/MI General Design
28387 @section @sc{gdb/mi} General Design
28388 @cindex GDB/MI General Design
28390 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28391 parts---commands sent to @value{GDBN}, responses to those commands
28392 and notifications. Each command results in exactly one response,
28393 indicating either successful completion of the command, or an error.
28394 For the commands that do not resume the target, the response contains the
28395 requested information. For the commands that resume the target, the
28396 response only indicates whether the target was successfully resumed.
28397 Notifications is the mechanism for reporting changes in the state of the
28398 target, or in @value{GDBN} state, that cannot conveniently be associated with
28399 a command and reported as part of that command response.
28401 The important examples of notifications are:
28405 Exec notifications. These are used to report changes in
28406 target state---when a target is resumed, or stopped. It would not
28407 be feasible to include this information in response of resuming
28408 commands, because one resume commands can result in multiple events in
28409 different threads. Also, quite some time may pass before any event
28410 happens in the target, while a frontend needs to know whether the resuming
28411 command itself was successfully executed.
28414 Console output, and status notifications. Console output
28415 notifications are used to report output of CLI commands, as well as
28416 diagnostics for other commands. Status notifications are used to
28417 report the progress of a long-running operation. Naturally, including
28418 this information in command response would mean no output is produced
28419 until the command is finished, which is undesirable.
28422 General notifications. Commands may have various side effects on
28423 the @value{GDBN} or target state beyond their official purpose. For example,
28424 a command may change the selected thread. Although such changes can
28425 be included in command response, using notification allows for more
28426 orthogonal frontend design.
28430 There's no guarantee that whenever an MI command reports an error,
28431 @value{GDBN} or the target are in any specific state, and especially,
28432 the state is not reverted to the state before the MI command was
28433 processed. Therefore, whenever an MI command results in an error,
28434 we recommend that the frontend refreshes all the information shown in
28435 the user interface.
28439 * Context management::
28440 * Asynchronous and non-stop modes::
28444 @node Context management
28445 @subsection Context management
28447 In most cases when @value{GDBN} accesses the target, this access is
28448 done in context of a specific thread and frame (@pxref{Frames}).
28449 Often, even when accessing global data, the target requires that a thread
28450 be specified. The CLI interface maintains the selected thread and frame,
28451 and supplies them to target on each command. This is convenient,
28452 because a command line user would not want to specify that information
28453 explicitly on each command, and because user interacts with
28454 @value{GDBN} via a single terminal, so no confusion is possible as
28455 to what thread and frame are the current ones.
28457 In the case of MI, the concept of selected thread and frame is less
28458 useful. First, a frontend can easily remember this information
28459 itself. Second, a graphical frontend can have more than one window,
28460 each one used for debugging a different thread, and the frontend might
28461 want to access additional threads for internal purposes. This
28462 increases the risk that by relying on implicitly selected thread, the
28463 frontend may be operating on a wrong one. Therefore, each MI command
28464 should explicitly specify which thread and frame to operate on. To
28465 make it possible, each MI command accepts the @samp{--thread} and
28466 @samp{--frame} options, the value to each is @value{GDBN} identifier
28467 for thread and frame to operate on.
28469 Usually, each top-level window in a frontend allows the user to select
28470 a thread and a frame, and remembers the user selection for further
28471 operations. However, in some cases @value{GDBN} may suggest that the
28472 current thread be changed. For example, when stopping on a breakpoint
28473 it is reasonable to switch to the thread where breakpoint is hit. For
28474 another example, if the user issues the CLI @samp{thread} command via
28475 the frontend, it is desirable to change the frontend's selected thread to the
28476 one specified by user. @value{GDBN} communicates the suggestion to
28477 change current thread using the @samp{=thread-selected} notification.
28478 No such notification is available for the selected frame at the moment.
28480 Note that historically, MI shares the selected thread with CLI, so
28481 frontends used the @code{-thread-select} to execute commands in the
28482 right context. However, getting this to work right is cumbersome. The
28483 simplest way is for frontend to emit @code{-thread-select} command
28484 before every command. This doubles the number of commands that need
28485 to be sent. The alternative approach is to suppress @code{-thread-select}
28486 if the selected thread in @value{GDBN} is supposed to be identical to the
28487 thread the frontend wants to operate on. However, getting this
28488 optimization right can be tricky. In particular, if the frontend
28489 sends several commands to @value{GDBN}, and one of the commands changes the
28490 selected thread, then the behaviour of subsequent commands will
28491 change. So, a frontend should either wait for response from such
28492 problematic commands, or explicitly add @code{-thread-select} for
28493 all subsequent commands. No frontend is known to do this exactly
28494 right, so it is suggested to just always pass the @samp{--thread} and
28495 @samp{--frame} options.
28497 @node Asynchronous and non-stop modes
28498 @subsection Asynchronous command execution and non-stop mode
28500 On some targets, @value{GDBN} is capable of processing MI commands
28501 even while the target is running. This is called @dfn{asynchronous
28502 command execution} (@pxref{Background Execution}). The frontend may
28503 specify a preferrence for asynchronous execution using the
28504 @code{-gdb-set target-async 1} command, which should be emitted before
28505 either running the executable or attaching to the target. After the
28506 frontend has started the executable or attached to the target, it can
28507 find if asynchronous execution is enabled using the
28508 @code{-list-target-features} command.
28510 Even if @value{GDBN} can accept a command while target is running,
28511 many commands that access the target do not work when the target is
28512 running. Therefore, asynchronous command execution is most useful
28513 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28514 it is possible to examine the state of one thread, while other threads
28517 When a given thread is running, MI commands that try to access the
28518 target in the context of that thread may not work, or may work only on
28519 some targets. In particular, commands that try to operate on thread's
28520 stack will not work, on any target. Commands that read memory, or
28521 modify breakpoints, may work or not work, depending on the target. Note
28522 that even commands that operate on global state, such as @code{print},
28523 @code{set}, and breakpoint commands, still access the target in the
28524 context of a specific thread, so frontend should try to find a
28525 stopped thread and perform the operation on that thread (using the
28526 @samp{--thread} option).
28528 Which commands will work in the context of a running thread is
28529 highly target dependent. However, the two commands
28530 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28531 to find the state of a thread, will always work.
28533 @node Thread groups
28534 @subsection Thread groups
28535 @value{GDBN} may be used to debug several processes at the same time.
28536 On some platfroms, @value{GDBN} may support debugging of several
28537 hardware systems, each one having several cores with several different
28538 processes running on each core. This section describes the MI
28539 mechanism to support such debugging scenarios.
28541 The key observation is that regardless of the structure of the
28542 target, MI can have a global list of threads, because most commands that
28543 accept the @samp{--thread} option do not need to know what process that
28544 thread belongs to. Therefore, it is not necessary to introduce
28545 neither additional @samp{--process} option, nor an notion of the
28546 current process in the MI interface. The only strictly new feature
28547 that is required is the ability to find how the threads are grouped
28550 To allow the user to discover such grouping, and to support arbitrary
28551 hierarchy of machines/cores/processes, MI introduces the concept of a
28552 @dfn{thread group}. Thread group is a collection of threads and other
28553 thread groups. A thread group always has a string identifier, a type,
28554 and may have additional attributes specific to the type. A new
28555 command, @code{-list-thread-groups}, returns the list of top-level
28556 thread groups, which correspond to processes that @value{GDBN} is
28557 debugging at the moment. By passing an identifier of a thread group
28558 to the @code{-list-thread-groups} command, it is possible to obtain
28559 the members of specific thread group.
28561 To allow the user to easily discover processes, and other objects, he
28562 wishes to debug, a concept of @dfn{available thread group} is
28563 introduced. Available thread group is an thread group that
28564 @value{GDBN} is not debugging, but that can be attached to, using the
28565 @code{-target-attach} command. The list of available top-level thread
28566 groups can be obtained using @samp{-list-thread-groups --available}.
28567 In general, the content of a thread group may be only retrieved only
28568 after attaching to that thread group.
28570 Thread groups are related to inferiors (@pxref{Inferiors and
28571 Programs}). Each inferior corresponds to a thread group of a special
28572 type @samp{process}, and some additional operations are permitted on
28573 such thread groups.
28575 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28576 @node GDB/MI Command Syntax
28577 @section @sc{gdb/mi} Command Syntax
28580 * GDB/MI Input Syntax::
28581 * GDB/MI Output Syntax::
28584 @node GDB/MI Input Syntax
28585 @subsection @sc{gdb/mi} Input Syntax
28587 @cindex input syntax for @sc{gdb/mi}
28588 @cindex @sc{gdb/mi}, input syntax
28590 @item @var{command} @expansion{}
28591 @code{@var{cli-command} | @var{mi-command}}
28593 @item @var{cli-command} @expansion{}
28594 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
28595 @var{cli-command} is any existing @value{GDBN} CLI command.
28597 @item @var{mi-command} @expansion{}
28598 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
28599 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
28601 @item @var{token} @expansion{}
28602 "any sequence of digits"
28604 @item @var{option} @expansion{}
28605 @code{"-" @var{parameter} [ " " @var{parameter} ]}
28607 @item @var{parameter} @expansion{}
28608 @code{@var{non-blank-sequence} | @var{c-string}}
28610 @item @var{operation} @expansion{}
28611 @emph{any of the operations described in this chapter}
28613 @item @var{non-blank-sequence} @expansion{}
28614 @emph{anything, provided it doesn't contain special characters such as
28615 "-", @var{nl}, """ and of course " "}
28617 @item @var{c-string} @expansion{}
28618 @code{""" @var{seven-bit-iso-c-string-content} """}
28620 @item @var{nl} @expansion{}
28629 The CLI commands are still handled by the @sc{mi} interpreter; their
28630 output is described below.
28633 The @code{@var{token}}, when present, is passed back when the command
28637 Some @sc{mi} commands accept optional arguments as part of the parameter
28638 list. Each option is identified by a leading @samp{-} (dash) and may be
28639 followed by an optional argument parameter. Options occur first in the
28640 parameter list and can be delimited from normal parameters using
28641 @samp{--} (this is useful when some parameters begin with a dash).
28648 We want easy access to the existing CLI syntax (for debugging).
28651 We want it to be easy to spot a @sc{mi} operation.
28654 @node GDB/MI Output Syntax
28655 @subsection @sc{gdb/mi} Output Syntax
28657 @cindex output syntax of @sc{gdb/mi}
28658 @cindex @sc{gdb/mi}, output syntax
28659 The output from @sc{gdb/mi} consists of zero or more out-of-band records
28660 followed, optionally, by a single result record. This result record
28661 is for the most recent command. The sequence of output records is
28662 terminated by @samp{(gdb)}.
28664 If an input command was prefixed with a @code{@var{token}} then the
28665 corresponding output for that command will also be prefixed by that same
28669 @item @var{output} @expansion{}
28670 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
28672 @item @var{result-record} @expansion{}
28673 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
28675 @item @var{out-of-band-record} @expansion{}
28676 @code{@var{async-record} | @var{stream-record}}
28678 @item @var{async-record} @expansion{}
28679 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
28681 @item @var{exec-async-output} @expansion{}
28682 @code{[ @var{token} ] "*" @var{async-output}}
28684 @item @var{status-async-output} @expansion{}
28685 @code{[ @var{token} ] "+" @var{async-output}}
28687 @item @var{notify-async-output} @expansion{}
28688 @code{[ @var{token} ] "=" @var{async-output}}
28690 @item @var{async-output} @expansion{}
28691 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
28693 @item @var{result-class} @expansion{}
28694 @code{"done" | "running" | "connected" | "error" | "exit"}
28696 @item @var{async-class} @expansion{}
28697 @code{"stopped" | @var{others}} (where @var{others} will be added
28698 depending on the needs---this is still in development).
28700 @item @var{result} @expansion{}
28701 @code{ @var{variable} "=" @var{value}}
28703 @item @var{variable} @expansion{}
28704 @code{ @var{string} }
28706 @item @var{value} @expansion{}
28707 @code{ @var{const} | @var{tuple} | @var{list} }
28709 @item @var{const} @expansion{}
28710 @code{@var{c-string}}
28712 @item @var{tuple} @expansion{}
28713 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
28715 @item @var{list} @expansion{}
28716 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
28717 @var{result} ( "," @var{result} )* "]" }
28719 @item @var{stream-record} @expansion{}
28720 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
28722 @item @var{console-stream-output} @expansion{}
28723 @code{"~" @var{c-string}}
28725 @item @var{target-stream-output} @expansion{}
28726 @code{"@@" @var{c-string}}
28728 @item @var{log-stream-output} @expansion{}
28729 @code{"&" @var{c-string}}
28731 @item @var{nl} @expansion{}
28734 @item @var{token} @expansion{}
28735 @emph{any sequence of digits}.
28743 All output sequences end in a single line containing a period.
28746 The @code{@var{token}} is from the corresponding request. Note that
28747 for all async output, while the token is allowed by the grammar and
28748 may be output by future versions of @value{GDBN} for select async
28749 output messages, it is generally omitted. Frontends should treat
28750 all async output as reporting general changes in the state of the
28751 target and there should be no need to associate async output to any
28755 @cindex status output in @sc{gdb/mi}
28756 @var{status-async-output} contains on-going status information about the
28757 progress of a slow operation. It can be discarded. All status output is
28758 prefixed by @samp{+}.
28761 @cindex async output in @sc{gdb/mi}
28762 @var{exec-async-output} contains asynchronous state change on the target
28763 (stopped, started, disappeared). All async output is prefixed by
28767 @cindex notify output in @sc{gdb/mi}
28768 @var{notify-async-output} contains supplementary information that the
28769 client should handle (e.g., a new breakpoint information). All notify
28770 output is prefixed by @samp{=}.
28773 @cindex console output in @sc{gdb/mi}
28774 @var{console-stream-output} is output that should be displayed as is in the
28775 console. It is the textual response to a CLI command. All the console
28776 output is prefixed by @samp{~}.
28779 @cindex target output in @sc{gdb/mi}
28780 @var{target-stream-output} is the output produced by the target program.
28781 All the target output is prefixed by @samp{@@}.
28784 @cindex log output in @sc{gdb/mi}
28785 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
28786 instance messages that should be displayed as part of an error log. All
28787 the log output is prefixed by @samp{&}.
28790 @cindex list output in @sc{gdb/mi}
28791 New @sc{gdb/mi} commands should only output @var{lists} containing
28797 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
28798 details about the various output records.
28800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28801 @node GDB/MI Compatibility with CLI
28802 @section @sc{gdb/mi} Compatibility with CLI
28804 @cindex compatibility, @sc{gdb/mi} and CLI
28805 @cindex @sc{gdb/mi}, compatibility with CLI
28807 For the developers convenience CLI commands can be entered directly,
28808 but there may be some unexpected behaviour. For example, commands
28809 that query the user will behave as if the user replied yes, breakpoint
28810 command lists are not executed and some CLI commands, such as
28811 @code{if}, @code{when} and @code{define}, prompt for further input with
28812 @samp{>}, which is not valid MI output.
28814 This feature may be removed at some stage in the future and it is
28815 recommended that front ends use the @code{-interpreter-exec} command
28816 (@pxref{-interpreter-exec}).
28818 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28819 @node GDB/MI Development and Front Ends
28820 @section @sc{gdb/mi} Development and Front Ends
28821 @cindex @sc{gdb/mi} development
28823 The application which takes the MI output and presents the state of the
28824 program being debugged to the user is called a @dfn{front end}.
28826 Although @sc{gdb/mi} is still incomplete, it is currently being used
28827 by a variety of front ends to @value{GDBN}. This makes it difficult
28828 to introduce new functionality without breaking existing usage. This
28829 section tries to minimize the problems by describing how the protocol
28832 Some changes in MI need not break a carefully designed front end, and
28833 for these the MI version will remain unchanged. The following is a
28834 list of changes that may occur within one level, so front ends should
28835 parse MI output in a way that can handle them:
28839 New MI commands may be added.
28842 New fields may be added to the output of any MI command.
28845 The range of values for fields with specified values, e.g.,
28846 @code{in_scope} (@pxref{-var-update}) may be extended.
28848 @c The format of field's content e.g type prefix, may change so parse it
28849 @c at your own risk. Yes, in general?
28851 @c The order of fields may change? Shouldn't really matter but it might
28852 @c resolve inconsistencies.
28855 If the changes are likely to break front ends, the MI version level
28856 will be increased by one. This will allow the front end to parse the
28857 output according to the MI version. Apart from mi0, new versions of
28858 @value{GDBN} will not support old versions of MI and it will be the
28859 responsibility of the front end to work with the new one.
28861 @c Starting with mi3, add a new command -mi-version that prints the MI
28864 The best way to avoid unexpected changes in MI that might break your front
28865 end is to make your project known to @value{GDBN} developers and
28866 follow development on @email{gdb@@sourceware.org} and
28867 @email{gdb-patches@@sourceware.org}.
28868 @cindex mailing lists
28870 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28871 @node GDB/MI Output Records
28872 @section @sc{gdb/mi} Output Records
28875 * GDB/MI Result Records::
28876 * GDB/MI Stream Records::
28877 * GDB/MI Async Records::
28878 * GDB/MI Breakpoint Information::
28879 * GDB/MI Frame Information::
28880 * GDB/MI Thread Information::
28881 * GDB/MI Ada Exception Information::
28884 @node GDB/MI Result Records
28885 @subsection @sc{gdb/mi} Result Records
28887 @cindex result records in @sc{gdb/mi}
28888 @cindex @sc{gdb/mi}, result records
28889 In addition to a number of out-of-band notifications, the response to a
28890 @sc{gdb/mi} command includes one of the following result indications:
28894 @item "^done" [ "," @var{results} ]
28895 The synchronous operation was successful, @code{@var{results}} are the return
28900 This result record is equivalent to @samp{^done}. Historically, it
28901 was output instead of @samp{^done} if the command has resumed the
28902 target. This behaviour is maintained for backward compatibility, but
28903 all frontends should treat @samp{^done} and @samp{^running}
28904 identically and rely on the @samp{*running} output record to determine
28905 which threads are resumed.
28909 @value{GDBN} has connected to a remote target.
28911 @item "^error" "," @var{c-string}
28913 The operation failed. The @code{@var{c-string}} contains the corresponding
28918 @value{GDBN} has terminated.
28922 @node GDB/MI Stream Records
28923 @subsection @sc{gdb/mi} Stream Records
28925 @cindex @sc{gdb/mi}, stream records
28926 @cindex stream records in @sc{gdb/mi}
28927 @value{GDBN} internally maintains a number of output streams: the console, the
28928 target, and the log. The output intended for each of these streams is
28929 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
28931 Each stream record begins with a unique @dfn{prefix character} which
28932 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
28933 Syntax}). In addition to the prefix, each stream record contains a
28934 @code{@var{string-output}}. This is either raw text (with an implicit new
28935 line) or a quoted C string (which does not contain an implicit newline).
28938 @item "~" @var{string-output}
28939 The console output stream contains text that should be displayed in the
28940 CLI console window. It contains the textual responses to CLI commands.
28942 @item "@@" @var{string-output}
28943 The target output stream contains any textual output from the running
28944 target. This is only present when GDB's event loop is truly
28945 asynchronous, which is currently only the case for remote targets.
28947 @item "&" @var{string-output}
28948 The log stream contains debugging messages being produced by @value{GDBN}'s
28952 @node GDB/MI Async Records
28953 @subsection @sc{gdb/mi} Async Records
28955 @cindex async records in @sc{gdb/mi}
28956 @cindex @sc{gdb/mi}, async records
28957 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
28958 additional changes that have occurred. Those changes can either be a
28959 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28960 target activity (e.g., target stopped).
28962 The following is the list of possible async records:
28966 @item *running,thread-id="@var{thread}"
28967 The target is now running. The @var{thread} field tells which
28968 specific thread is now running, and can be @samp{all} if all threads
28969 are running. The frontend should assume that no interaction with a
28970 running thread is possible after this notification is produced.
28971 The frontend should not assume that this notification is output
28972 only once for any command. @value{GDBN} may emit this notification
28973 several times, either for different threads, because it cannot resume
28974 all threads together, or even for a single thread, if the thread must
28975 be stepped though some code before letting it run freely.
28977 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28978 The target has stopped. The @var{reason} field can have one of the
28982 @item breakpoint-hit
28983 A breakpoint was reached.
28984 @item watchpoint-trigger
28985 A watchpoint was triggered.
28986 @item read-watchpoint-trigger
28987 A read watchpoint was triggered.
28988 @item access-watchpoint-trigger
28989 An access watchpoint was triggered.
28990 @item function-finished
28991 An -exec-finish or similar CLI command was accomplished.
28992 @item location-reached
28993 An -exec-until or similar CLI command was accomplished.
28994 @item watchpoint-scope
28995 A watchpoint has gone out of scope.
28996 @item end-stepping-range
28997 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28998 similar CLI command was accomplished.
28999 @item exited-signalled
29000 The inferior exited because of a signal.
29002 The inferior exited.
29003 @item exited-normally
29004 The inferior exited normally.
29005 @item signal-received
29006 A signal was received by the inferior.
29008 The inferior has stopped due to a library being loaded or unloaded.
29009 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29010 set or when a @code{catch load} or @code{catch unload} catchpoint is
29011 in use (@pxref{Set Catchpoints}).
29013 The inferior has forked. This is reported when @code{catch fork}
29014 (@pxref{Set Catchpoints}) has been used.
29016 The inferior has vforked. This is reported in when @code{catch vfork}
29017 (@pxref{Set Catchpoints}) has been used.
29018 @item syscall-entry
29019 The inferior entered a system call. This is reported when @code{catch
29020 syscall} (@pxref{Set Catchpoints}) has been used.
29021 @item syscall-entry
29022 The inferior returned from a system call. This is reported when
29023 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29025 The inferior called @code{exec}. This is reported when @code{catch exec}
29026 (@pxref{Set Catchpoints}) has been used.
29029 The @var{id} field identifies the thread that directly caused the stop
29030 -- for example by hitting a breakpoint. Depending on whether all-stop
29031 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29032 stop all threads, or only the thread that directly triggered the stop.
29033 If all threads are stopped, the @var{stopped} field will have the
29034 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29035 field will be a list of thread identifiers. Presently, this list will
29036 always include a single thread, but frontend should be prepared to see
29037 several threads in the list. The @var{core} field reports the
29038 processor core on which the stop event has happened. This field may be absent
29039 if such information is not available.
29041 @item =thread-group-added,id="@var{id}"
29042 @itemx =thread-group-removed,id="@var{id}"
29043 A thread group was either added or removed. The @var{id} field
29044 contains the @value{GDBN} identifier of the thread group. When a thread
29045 group is added, it generally might not be associated with a running
29046 process. When a thread group is removed, its id becomes invalid and
29047 cannot be used in any way.
29049 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29050 A thread group became associated with a running program,
29051 either because the program was just started or the thread group
29052 was attached to a program. The @var{id} field contains the
29053 @value{GDBN} identifier of the thread group. The @var{pid} field
29054 contains process identifier, specific to the operating system.
29056 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29057 A thread group is no longer associated with a running program,
29058 either because the program has exited, or because it was detached
29059 from. The @var{id} field contains the @value{GDBN} identifier of the
29060 thread group. @var{code} is the exit code of the inferior; it exists
29061 only when the inferior exited with some code.
29063 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29064 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29065 A thread either was created, or has exited. The @var{id} field
29066 contains the @value{GDBN} identifier of the thread. The @var{gid}
29067 field identifies the thread group this thread belongs to.
29069 @item =thread-selected,id="@var{id}"
29070 Informs that the selected thread was changed as result of the last
29071 command. This notification is not emitted as result of @code{-thread-select}
29072 command but is emitted whenever an MI command that is not documented
29073 to change the selected thread actually changes it. In particular,
29074 invoking, directly or indirectly (via user-defined command), the CLI
29075 @code{thread} command, will generate this notification.
29077 We suggest that in response to this notification, front ends
29078 highlight the selected thread and cause subsequent commands to apply to
29081 @item =library-loaded,...
29082 Reports that a new library file was loaded by the program. This
29083 notification has 4 fields---@var{id}, @var{target-name},
29084 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29085 opaque identifier of the library. For remote debugging case,
29086 @var{target-name} and @var{host-name} fields give the name of the
29087 library file on the target, and on the host respectively. For native
29088 debugging, both those fields have the same value. The
29089 @var{symbols-loaded} field is emitted only for backward compatibility
29090 and should not be relied on to convey any useful information. The
29091 @var{thread-group} field, if present, specifies the id of the thread
29092 group in whose context the library was loaded. If the field is
29093 absent, it means the library was loaded in the context of all present
29096 @item =library-unloaded,...
29097 Reports that a library was unloaded by the program. This notification
29098 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29099 the same meaning as for the @code{=library-loaded} notification.
29100 The @var{thread-group} field, if present, specifies the id of the
29101 thread group in whose context the library was unloaded. If the field is
29102 absent, it means the library was unloaded in the context of all present
29105 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29106 @itemx =traceframe-changed,end
29107 Reports that the trace frame was changed and its new number is
29108 @var{tfnum}. The number of the tracepoint associated with this trace
29109 frame is @var{tpnum}.
29111 @item =tsv-created,name=@var{name},initial=@var{initial}
29112 Reports that the new trace state variable @var{name} is created with
29113 initial value @var{initial}.
29115 @item =tsv-deleted,name=@var{name}
29116 @itemx =tsv-deleted
29117 Reports that the trace state variable @var{name} is deleted or all
29118 trace state variables are deleted.
29120 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29121 Reports that the trace state variable @var{name} is modified with
29122 the initial value @var{initial}. The current value @var{current} of
29123 trace state variable is optional and is reported if the current
29124 value of trace state variable is known.
29126 @item =breakpoint-created,bkpt=@{...@}
29127 @itemx =breakpoint-modified,bkpt=@{...@}
29128 @itemx =breakpoint-deleted,id=@var{number}
29129 Reports that a breakpoint was created, modified, or deleted,
29130 respectively. Only user-visible breakpoints are reported to the MI
29133 The @var{bkpt} argument is of the same form as returned by the various
29134 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29135 @var{number} is the ordinal number of the breakpoint.
29137 Note that if a breakpoint is emitted in the result record of a
29138 command, then it will not also be emitted in an async record.
29140 @item =record-started,thread-group="@var{id}"
29141 @itemx =record-stopped,thread-group="@var{id}"
29142 Execution log recording was either started or stopped on an
29143 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29144 group corresponding to the affected inferior.
29146 @item =cmd-param-changed,param=@var{param},value=@var{value}
29147 Reports that a parameter of the command @code{set @var{param}} is
29148 changed to @var{value}. In the multi-word @code{set} command,
29149 the @var{param} is the whole parameter list to @code{set} command.
29150 For example, In command @code{set check type on}, @var{param}
29151 is @code{check type} and @var{value} is @code{on}.
29153 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29154 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29155 written in an inferior. The @var{id} is the identifier of the
29156 thread group corresponding to the affected inferior. The optional
29157 @code{type="code"} part is reported if the memory written to holds
29161 @node GDB/MI Breakpoint Information
29162 @subsection @sc{gdb/mi} Breakpoint Information
29164 When @value{GDBN} reports information about a breakpoint, a
29165 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29170 The breakpoint number. For a breakpoint that represents one location
29171 of a multi-location breakpoint, this will be a dotted pair, like
29175 The type of the breakpoint. For ordinary breakpoints this will be
29176 @samp{breakpoint}, but many values are possible.
29179 If the type of the breakpoint is @samp{catchpoint}, then this
29180 indicates the exact type of catchpoint.
29183 This is the breakpoint disposition---either @samp{del}, meaning that
29184 the breakpoint will be deleted at the next stop, or @samp{keep},
29185 meaning that the breakpoint will not be deleted.
29188 This indicates whether the breakpoint is enabled, in which case the
29189 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29190 Note that this is not the same as the field @code{enable}.
29193 The address of the breakpoint. This may be a hexidecimal number,
29194 giving the address; or the string @samp{<PENDING>}, for a pending
29195 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29196 multiple locations. This field will not be present if no address can
29197 be determined. For example, a watchpoint does not have an address.
29200 If known, the function in which the breakpoint appears.
29201 If not known, this field is not present.
29204 The name of the source file which contains this function, if known.
29205 If not known, this field is not present.
29208 The full file name of the source file which contains this function, if
29209 known. If not known, this field is not present.
29212 The line number at which this breakpoint appears, if known.
29213 If not known, this field is not present.
29216 If the source file is not known, this field may be provided. If
29217 provided, this holds the address of the breakpoint, possibly followed
29221 If this breakpoint is pending, this field is present and holds the
29222 text used to set the breakpoint, as entered by the user.
29225 Where this breakpoint's condition is evaluated, either @samp{host} or
29229 If this is a thread-specific breakpoint, then this identifies the
29230 thread in which the breakpoint can trigger.
29233 If this breakpoint is restricted to a particular Ada task, then this
29234 field will hold the task identifier.
29237 If the breakpoint is conditional, this is the condition expression.
29240 The ignore count of the breakpoint.
29243 The enable count of the breakpoint.
29245 @item traceframe-usage
29248 @item static-tracepoint-marker-string-id
29249 For a static tracepoint, the name of the static tracepoint marker.
29252 For a masked watchpoint, this is the mask.
29255 A tracepoint's pass count.
29257 @item original-location
29258 The location of the breakpoint as originally specified by the user.
29259 This field is optional.
29262 The number of times the breakpoint has been hit.
29265 This field is only given for tracepoints. This is either @samp{y},
29266 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29270 Some extra data, the exact contents of which are type-dependent.
29274 For example, here is what the output of @code{-break-insert}
29275 (@pxref{GDB/MI Breakpoint Commands}) might be:
29278 -> -break-insert main
29279 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29280 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29281 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29286 @node GDB/MI Frame Information
29287 @subsection @sc{gdb/mi} Frame Information
29289 Response from many MI commands includes an information about stack
29290 frame. This information is a tuple that may have the following
29295 The level of the stack frame. The innermost frame has the level of
29296 zero. This field is always present.
29299 The name of the function corresponding to the frame. This field may
29300 be absent if @value{GDBN} is unable to determine the function name.
29303 The code address for the frame. This field is always present.
29306 The name of the source files that correspond to the frame's code
29307 address. This field may be absent.
29310 The source line corresponding to the frames' code address. This field
29314 The name of the binary file (either executable or shared library) the
29315 corresponds to the frame's code address. This field may be absent.
29319 @node GDB/MI Thread Information
29320 @subsection @sc{gdb/mi} Thread Information
29322 Whenever @value{GDBN} has to report an information about a thread, it
29323 uses a tuple with the following fields:
29327 The numeric id assigned to the thread by @value{GDBN}. This field is
29331 Target-specific string identifying the thread. This field is always present.
29334 Additional information about the thread provided by the target.
29335 It is supposed to be human-readable and not interpreted by the
29336 frontend. This field is optional.
29339 Either @samp{stopped} or @samp{running}, depending on whether the
29340 thread is presently running. This field is always present.
29343 The value of this field is an integer number of the processor core the
29344 thread was last seen on. This field is optional.
29347 @node GDB/MI Ada Exception Information
29348 @subsection @sc{gdb/mi} Ada Exception Information
29350 Whenever a @code{*stopped} record is emitted because the program
29351 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29352 @value{GDBN} provides the name of the exception that was raised via
29353 the @code{exception-name} field.
29355 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29356 @node GDB/MI Simple Examples
29357 @section Simple Examples of @sc{gdb/mi} Interaction
29358 @cindex @sc{gdb/mi}, simple examples
29360 This subsection presents several simple examples of interaction using
29361 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29362 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29363 the output received from @sc{gdb/mi}.
29365 Note the line breaks shown in the examples are here only for
29366 readability, they don't appear in the real output.
29368 @subheading Setting a Breakpoint
29370 Setting a breakpoint generates synchronous output which contains detailed
29371 information of the breakpoint.
29374 -> -break-insert main
29375 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29376 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29377 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29382 @subheading Program Execution
29384 Program execution generates asynchronous records and MI gives the
29385 reason that execution stopped.
29391 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29392 frame=@{addr="0x08048564",func="main",
29393 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29394 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29399 <- *stopped,reason="exited-normally"
29403 @subheading Quitting @value{GDBN}
29405 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29413 Please note that @samp{^exit} is printed immediately, but it might
29414 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29415 performs necessary cleanups, including killing programs being debugged
29416 or disconnecting from debug hardware, so the frontend should wait till
29417 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29418 fails to exit in reasonable time.
29420 @subheading A Bad Command
29422 Here's what happens if you pass a non-existent command:
29426 <- ^error,msg="Undefined MI command: rubbish"
29431 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29432 @node GDB/MI Command Description Format
29433 @section @sc{gdb/mi} Command Description Format
29435 The remaining sections describe blocks of commands. Each block of
29436 commands is laid out in a fashion similar to this section.
29438 @subheading Motivation
29440 The motivation for this collection of commands.
29442 @subheading Introduction
29444 A brief introduction to this collection of commands as a whole.
29446 @subheading Commands
29448 For each command in the block, the following is described:
29450 @subsubheading Synopsis
29453 -command @var{args}@dots{}
29456 @subsubheading Result
29458 @subsubheading @value{GDBN} Command
29460 The corresponding @value{GDBN} CLI command(s), if any.
29462 @subsubheading Example
29464 Example(s) formatted for readability. Some of the described commands have
29465 not been implemented yet and these are labeled N.A.@: (not available).
29468 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29469 @node GDB/MI Breakpoint Commands
29470 @section @sc{gdb/mi} Breakpoint Commands
29472 @cindex breakpoint commands for @sc{gdb/mi}
29473 @cindex @sc{gdb/mi}, breakpoint commands
29474 This section documents @sc{gdb/mi} commands for manipulating
29477 @subheading The @code{-break-after} Command
29478 @findex -break-after
29480 @subsubheading Synopsis
29483 -break-after @var{number} @var{count}
29486 The breakpoint number @var{number} is not in effect until it has been
29487 hit @var{count} times. To see how this is reflected in the output of
29488 the @samp{-break-list} command, see the description of the
29489 @samp{-break-list} command below.
29491 @subsubheading @value{GDBN} Command
29493 The corresponding @value{GDBN} command is @samp{ignore}.
29495 @subsubheading Example
29500 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29501 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29502 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29510 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29511 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29512 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29513 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29514 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29515 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29516 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29517 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29518 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29519 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29524 @subheading The @code{-break-catch} Command
29525 @findex -break-catch
29528 @subheading The @code{-break-commands} Command
29529 @findex -break-commands
29531 @subsubheading Synopsis
29534 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29537 Specifies the CLI commands that should be executed when breakpoint
29538 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29539 are the commands. If no command is specified, any previously-set
29540 commands are cleared. @xref{Break Commands}. Typical use of this
29541 functionality is tracing a program, that is, printing of values of
29542 some variables whenever breakpoint is hit and then continuing.
29544 @subsubheading @value{GDBN} Command
29546 The corresponding @value{GDBN} command is @samp{commands}.
29548 @subsubheading Example
29553 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29554 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29555 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29558 -break-commands 1 "print v" "continue"
29563 @subheading The @code{-break-condition} Command
29564 @findex -break-condition
29566 @subsubheading Synopsis
29569 -break-condition @var{number} @var{expr}
29572 Breakpoint @var{number} will stop the program only if the condition in
29573 @var{expr} is true. The condition becomes part of the
29574 @samp{-break-list} output (see the description of the @samp{-break-list}
29577 @subsubheading @value{GDBN} Command
29579 The corresponding @value{GDBN} command is @samp{condition}.
29581 @subsubheading Example
29585 -break-condition 1 1
29589 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29590 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29591 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29592 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29593 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29594 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29595 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29596 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29597 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29598 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
29602 @subheading The @code{-break-delete} Command
29603 @findex -break-delete
29605 @subsubheading Synopsis
29608 -break-delete ( @var{breakpoint} )+
29611 Delete the breakpoint(s) whose number(s) are specified in the argument
29612 list. This is obviously reflected in the breakpoint list.
29614 @subsubheading @value{GDBN} Command
29616 The corresponding @value{GDBN} command is @samp{delete}.
29618 @subsubheading Example
29626 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29627 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29628 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29629 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29630 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29631 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29632 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29637 @subheading The @code{-break-disable} Command
29638 @findex -break-disable
29640 @subsubheading Synopsis
29643 -break-disable ( @var{breakpoint} )+
29646 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
29647 break list is now set to @samp{n} for the named @var{breakpoint}(s).
29649 @subsubheading @value{GDBN} Command
29651 The corresponding @value{GDBN} command is @samp{disable}.
29653 @subsubheading Example
29661 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29662 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29663 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29664 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29665 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29666 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29667 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29668 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
29669 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29670 line="5",thread-groups=["i1"],times="0"@}]@}
29674 @subheading The @code{-break-enable} Command
29675 @findex -break-enable
29677 @subsubheading Synopsis
29680 -break-enable ( @var{breakpoint} )+
29683 Enable (previously disabled) @var{breakpoint}(s).
29685 @subsubheading @value{GDBN} Command
29687 The corresponding @value{GDBN} command is @samp{enable}.
29689 @subsubheading Example
29697 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29698 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29699 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29700 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29701 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29702 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29703 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29704 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29705 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29706 line="5",thread-groups=["i1"],times="0"@}]@}
29710 @subheading The @code{-break-info} Command
29711 @findex -break-info
29713 @subsubheading Synopsis
29716 -break-info @var{breakpoint}
29720 Get information about a single breakpoint.
29722 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
29723 Information}, for details on the format of each breakpoint in the
29726 @subsubheading @value{GDBN} Command
29728 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
29730 @subsubheading Example
29733 @subheading The @code{-break-insert} Command
29734 @findex -break-insert
29736 @subsubheading Synopsis
29739 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
29740 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29741 [ -p @var{thread-id} ] [ @var{location} ]
29745 If specified, @var{location}, can be one of:
29752 @item filename:linenum
29753 @item filename:function
29757 The possible optional parameters of this command are:
29761 Insert a temporary breakpoint.
29763 Insert a hardware breakpoint.
29765 If @var{location} cannot be parsed (for example if it
29766 refers to unknown files or functions), create a pending
29767 breakpoint. Without this flag, @value{GDBN} will report
29768 an error, and won't create a breakpoint, if @var{location}
29771 Create a disabled breakpoint.
29773 Create a tracepoint. @xref{Tracepoints}. When this parameter
29774 is used together with @samp{-h}, a fast tracepoint is created.
29775 @item -c @var{condition}
29776 Make the breakpoint conditional on @var{condition}.
29777 @item -i @var{ignore-count}
29778 Initialize the @var{ignore-count}.
29779 @item -p @var{thread-id}
29780 Restrict the breakpoint to the specified @var{thread-id}.
29783 @subsubheading Result
29785 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29786 resulting breakpoint.
29788 Note: this format is open to change.
29789 @c An out-of-band breakpoint instead of part of the result?
29791 @subsubheading @value{GDBN} Command
29793 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
29794 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
29796 @subsubheading Example
29801 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
29802 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
29805 -break-insert -t foo
29806 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
29807 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
29811 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29812 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29813 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29814 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29815 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29816 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29817 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29818 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29819 addr="0x0001072c", func="main",file="recursive2.c",
29820 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
29822 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
29823 addr="0x00010774",func="foo",file="recursive2.c",
29824 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29827 @c -break-insert -r foo.*
29828 @c ~int foo(int, int);
29829 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
29830 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29835 @subheading The @code{-dprintf-insert} Command
29836 @findex -dprintf-insert
29838 @subsubheading Synopsis
29841 -dprintf-insert [ -t ] [ -f ] [ -d ]
29842 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29843 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
29848 If specified, @var{location}, can be one of:
29851 @item @var{function}
29854 @c @item @var{linenum}
29855 @item @var{filename}:@var{linenum}
29856 @item @var{filename}:function
29857 @item *@var{address}
29860 The possible optional parameters of this command are:
29864 Insert a temporary breakpoint.
29866 If @var{location} cannot be parsed (for example, if it
29867 refers to unknown files or functions), create a pending
29868 breakpoint. Without this flag, @value{GDBN} will report
29869 an error, and won't create a breakpoint, if @var{location}
29872 Create a disabled breakpoint.
29873 @item -c @var{condition}
29874 Make the breakpoint conditional on @var{condition}.
29875 @item -i @var{ignore-count}
29876 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
29877 to @var{ignore-count}.
29878 @item -p @var{thread-id}
29879 Restrict the breakpoint to the specified @var{thread-id}.
29882 @subsubheading Result
29884 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29885 resulting breakpoint.
29887 @c An out-of-band breakpoint instead of part of the result?
29889 @subsubheading @value{GDBN} Command
29891 The corresponding @value{GDBN} command is @samp{dprintf}.
29893 @subsubheading Example
29897 4-dprintf-insert foo "At foo entry\n"
29898 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
29899 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
29900 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
29901 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
29902 original-location="foo"@}
29904 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
29905 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
29906 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
29907 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
29908 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
29909 original-location="mi-dprintf.c:26"@}
29913 @subheading The @code{-break-list} Command
29914 @findex -break-list
29916 @subsubheading Synopsis
29922 Displays the list of inserted breakpoints, showing the following fields:
29926 number of the breakpoint
29928 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
29930 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
29933 is the breakpoint enabled or no: @samp{y} or @samp{n}
29935 memory location at which the breakpoint is set
29937 logical location of the breakpoint, expressed by function name, file
29939 @item Thread-groups
29940 list of thread groups to which this breakpoint applies
29942 number of times the breakpoint has been hit
29945 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
29946 @code{body} field is an empty list.
29948 @subsubheading @value{GDBN} Command
29950 The corresponding @value{GDBN} command is @samp{info break}.
29952 @subsubheading Example
29957 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29958 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29959 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29960 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29961 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29962 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29963 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29964 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29965 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
29967 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29968 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
29969 line="13",thread-groups=["i1"],times="0"@}]@}
29973 Here's an example of the result when there are no breakpoints:
29978 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29979 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29980 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29981 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29982 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29983 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29984 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29989 @subheading The @code{-break-passcount} Command
29990 @findex -break-passcount
29992 @subsubheading Synopsis
29995 -break-passcount @var{tracepoint-number} @var{passcount}
29998 Set the passcount for tracepoint @var{tracepoint-number} to
29999 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30000 is not a tracepoint, error is emitted. This corresponds to CLI
30001 command @samp{passcount}.
30003 @subheading The @code{-break-watch} Command
30004 @findex -break-watch
30006 @subsubheading Synopsis
30009 -break-watch [ -a | -r ]
30012 Create a watchpoint. With the @samp{-a} option it will create an
30013 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30014 read from or on a write to the memory location. With the @samp{-r}
30015 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30016 trigger only when the memory location is accessed for reading. Without
30017 either of the options, the watchpoint created is a regular watchpoint,
30018 i.e., it will trigger when the memory location is accessed for writing.
30019 @xref{Set Watchpoints, , Setting Watchpoints}.
30021 Note that @samp{-break-list} will report a single list of watchpoints and
30022 breakpoints inserted.
30024 @subsubheading @value{GDBN} Command
30026 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30029 @subsubheading Example
30031 Setting a watchpoint on a variable in the @code{main} function:
30036 ^done,wpt=@{number="2",exp="x"@}
30041 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30042 value=@{old="-268439212",new="55"@},
30043 frame=@{func="main",args=[],file="recursive2.c",
30044 fullname="/home/foo/bar/recursive2.c",line="5"@}
30048 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30049 the program execution twice: first for the variable changing value, then
30050 for the watchpoint going out of scope.
30055 ^done,wpt=@{number="5",exp="C"@}
30060 *stopped,reason="watchpoint-trigger",
30061 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30062 frame=@{func="callee4",args=[],
30063 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30064 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30069 *stopped,reason="watchpoint-scope",wpnum="5",
30070 frame=@{func="callee3",args=[@{name="strarg",
30071 value="0x11940 \"A string argument.\""@}],
30072 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30073 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30077 Listing breakpoints and watchpoints, at different points in the program
30078 execution. Note that once the watchpoint goes out of scope, it is
30084 ^done,wpt=@{number="2",exp="C"@}
30087 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30088 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30089 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30090 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30091 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30092 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30093 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30094 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30095 addr="0x00010734",func="callee4",
30096 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30097 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30099 bkpt=@{number="2",type="watchpoint",disp="keep",
30100 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30105 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30106 value=@{old="-276895068",new="3"@},
30107 frame=@{func="callee4",args=[],
30108 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30109 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30112 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30113 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30114 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30115 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30116 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30117 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30118 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30119 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30120 addr="0x00010734",func="callee4",
30121 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30122 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30124 bkpt=@{number="2",type="watchpoint",disp="keep",
30125 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30129 ^done,reason="watchpoint-scope",wpnum="2",
30130 frame=@{func="callee3",args=[@{name="strarg",
30131 value="0x11940 \"A string argument.\""@}],
30132 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30133 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30136 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30137 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30138 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30139 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30140 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30141 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30142 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30143 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30144 addr="0x00010734",func="callee4",
30145 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30146 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30147 thread-groups=["i1"],times="1"@}]@}
30152 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30153 @node GDB/MI Catchpoint Commands
30154 @section @sc{gdb/mi} Catchpoint Commands
30156 This section documents @sc{gdb/mi} commands for manipulating
30159 @subheading The @code{-catch-load} Command
30160 @findex -catch-load
30162 @subsubheading Synopsis
30165 -catch-load [ -t ] [ -d ] @var{regexp}
30168 Add a catchpoint for library load events. If the @samp{-t} option is used,
30169 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30170 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30171 in a disabled state. The @samp{regexp} argument is a regular
30172 expression used to match the name of the loaded library.
30175 @subsubheading @value{GDBN} Command
30177 The corresponding @value{GDBN} command is @samp{catch load}.
30179 @subsubheading Example
30182 -catch-load -t foo.so
30183 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30184 what="load of library matching foo.so",catch-type="load",times="0"@}
30189 @subheading The @code{-catch-unload} Command
30190 @findex -catch-unload
30192 @subsubheading Synopsis
30195 -catch-unload [ -t ] [ -d ] @var{regexp}
30198 Add a catchpoint for library unload events. If the @samp{-t} option is
30199 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30200 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30201 created in a disabled state. The @samp{regexp} argument is a regular
30202 expression used to match the name of the unloaded library.
30204 @subsubheading @value{GDBN} Command
30206 The corresponding @value{GDBN} command is @samp{catch unload}.
30208 @subsubheading Example
30211 -catch-unload -d bar.so
30212 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30213 what="load of library matching bar.so",catch-type="unload",times="0"@}
30218 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30219 @node GDB/MI Program Context
30220 @section @sc{gdb/mi} Program Context
30222 @subheading The @code{-exec-arguments} Command
30223 @findex -exec-arguments
30226 @subsubheading Synopsis
30229 -exec-arguments @var{args}
30232 Set the inferior program arguments, to be used in the next
30235 @subsubheading @value{GDBN} Command
30237 The corresponding @value{GDBN} command is @samp{set args}.
30239 @subsubheading Example
30243 -exec-arguments -v word
30250 @subheading The @code{-exec-show-arguments} Command
30251 @findex -exec-show-arguments
30253 @subsubheading Synopsis
30256 -exec-show-arguments
30259 Print the arguments of the program.
30261 @subsubheading @value{GDBN} Command
30263 The corresponding @value{GDBN} command is @samp{show args}.
30265 @subsubheading Example
30270 @subheading The @code{-environment-cd} Command
30271 @findex -environment-cd
30273 @subsubheading Synopsis
30276 -environment-cd @var{pathdir}
30279 Set @value{GDBN}'s working directory.
30281 @subsubheading @value{GDBN} Command
30283 The corresponding @value{GDBN} command is @samp{cd}.
30285 @subsubheading Example
30289 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30295 @subheading The @code{-environment-directory} Command
30296 @findex -environment-directory
30298 @subsubheading Synopsis
30301 -environment-directory [ -r ] [ @var{pathdir} ]+
30304 Add directories @var{pathdir} to beginning of search path for source files.
30305 If the @samp{-r} option is used, the search path is reset to the default
30306 search path. If directories @var{pathdir} are supplied in addition to the
30307 @samp{-r} option, the search path is first reset and then addition
30309 Multiple directories may be specified, separated by blanks. Specifying
30310 multiple directories in a single command
30311 results in the directories added to the beginning of the
30312 search path in the same order they were presented in the command.
30313 If blanks are needed as
30314 part of a directory name, double-quotes should be used around
30315 the name. In the command output, the path will show up separated
30316 by the system directory-separator character. The directory-separator
30317 character must not be used
30318 in any directory name.
30319 If no directories are specified, the current search path is displayed.
30321 @subsubheading @value{GDBN} Command
30323 The corresponding @value{GDBN} command is @samp{dir}.
30325 @subsubheading Example
30329 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30330 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30332 -environment-directory ""
30333 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30335 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30336 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30338 -environment-directory -r
30339 ^done,source-path="$cdir:$cwd"
30344 @subheading The @code{-environment-path} Command
30345 @findex -environment-path
30347 @subsubheading Synopsis
30350 -environment-path [ -r ] [ @var{pathdir} ]+
30353 Add directories @var{pathdir} to beginning of search path for object files.
30354 If the @samp{-r} option is used, the search path is reset to the original
30355 search path that existed at gdb start-up. If directories @var{pathdir} are
30356 supplied in addition to the
30357 @samp{-r} option, the search path is first reset and then addition
30359 Multiple directories may be specified, separated by blanks. Specifying
30360 multiple directories in a single command
30361 results in the directories added to the beginning of the
30362 search path in the same order they were presented in the command.
30363 If blanks are needed as
30364 part of a directory name, double-quotes should be used around
30365 the name. In the command output, the path will show up separated
30366 by the system directory-separator character. The directory-separator
30367 character must not be used
30368 in any directory name.
30369 If no directories are specified, the current path is displayed.
30372 @subsubheading @value{GDBN} Command
30374 The corresponding @value{GDBN} command is @samp{path}.
30376 @subsubheading Example
30381 ^done,path="/usr/bin"
30383 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30384 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30386 -environment-path -r /usr/local/bin
30387 ^done,path="/usr/local/bin:/usr/bin"
30392 @subheading The @code{-environment-pwd} Command
30393 @findex -environment-pwd
30395 @subsubheading Synopsis
30401 Show the current working directory.
30403 @subsubheading @value{GDBN} Command
30405 The corresponding @value{GDBN} command is @samp{pwd}.
30407 @subsubheading Example
30412 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30416 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30417 @node GDB/MI Thread Commands
30418 @section @sc{gdb/mi} Thread Commands
30421 @subheading The @code{-thread-info} Command
30422 @findex -thread-info
30424 @subsubheading Synopsis
30427 -thread-info [ @var{thread-id} ]
30430 Reports information about either a specific thread, if
30431 the @var{thread-id} parameter is present, or about all
30432 threads. When printing information about all threads,
30433 also reports the current thread.
30435 @subsubheading @value{GDBN} Command
30437 The @samp{info thread} command prints the same information
30440 @subsubheading Result
30442 The result is a list of threads. The following attributes are
30443 defined for a given thread:
30447 This field exists only for the current thread. It has the value @samp{*}.
30450 The identifier that @value{GDBN} uses to refer to the thread.
30453 The identifier that the target uses to refer to the thread.
30456 Extra information about the thread, in a target-specific format. This
30460 The name of the thread. If the user specified a name using the
30461 @code{thread name} command, then this name is given. Otherwise, if
30462 @value{GDBN} can extract the thread name from the target, then that
30463 name is given. If @value{GDBN} cannot find the thread name, then this
30467 The stack frame currently executing in the thread.
30470 The thread's state. The @samp{state} field may have the following
30475 The thread is stopped. Frame information is available for stopped
30479 The thread is running. There's no frame information for running
30485 If @value{GDBN} can find the CPU core on which this thread is running,
30486 then this field is the core identifier. This field is optional.
30490 @subsubheading Example
30495 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30496 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
30497 args=[]@},state="running"@},
30498 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30499 frame=@{level="0",addr="0x0804891f",func="foo",
30500 args=[@{name="i",value="10"@}],
30501 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
30502 state="running"@}],
30503 current-thread-id="1"
30507 @subheading The @code{-thread-list-ids} Command
30508 @findex -thread-list-ids
30510 @subsubheading Synopsis
30516 Produces a list of the currently known @value{GDBN} thread ids. At the
30517 end of the list it also prints the total number of such threads.
30519 This command is retained for historical reasons, the
30520 @code{-thread-info} command should be used instead.
30522 @subsubheading @value{GDBN} Command
30524 Part of @samp{info threads} supplies the same information.
30526 @subsubheading Example
30531 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30532 current-thread-id="1",number-of-threads="3"
30537 @subheading The @code{-thread-select} Command
30538 @findex -thread-select
30540 @subsubheading Synopsis
30543 -thread-select @var{threadnum}
30546 Make @var{threadnum} the current thread. It prints the number of the new
30547 current thread, and the topmost frame for that thread.
30549 This command is deprecated in favor of explicitly using the
30550 @samp{--thread} option to each command.
30552 @subsubheading @value{GDBN} Command
30554 The corresponding @value{GDBN} command is @samp{thread}.
30556 @subsubheading Example
30563 *stopped,reason="end-stepping-range",thread-id="2",line="187",
30564 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
30568 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30569 number-of-threads="3"
30572 ^done,new-thread-id="3",
30573 frame=@{level="0",func="vprintf",
30574 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
30575 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
30579 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30580 @node GDB/MI Ada Tasking Commands
30581 @section @sc{gdb/mi} Ada Tasking Commands
30583 @subheading The @code{-ada-task-info} Command
30584 @findex -ada-task-info
30586 @subsubheading Synopsis
30589 -ada-task-info [ @var{task-id} ]
30592 Reports information about either a specific Ada task, if the
30593 @var{task-id} parameter is present, or about all Ada tasks.
30595 @subsubheading @value{GDBN} Command
30597 The @samp{info tasks} command prints the same information
30598 about all Ada tasks (@pxref{Ada Tasks}).
30600 @subsubheading Result
30602 The result is a table of Ada tasks. The following columns are
30603 defined for each Ada task:
30607 This field exists only for the current thread. It has the value @samp{*}.
30610 The identifier that @value{GDBN} uses to refer to the Ada task.
30613 The identifier that the target uses to refer to the Ada task.
30616 The identifier of the thread corresponding to the Ada task.
30618 This field should always exist, as Ada tasks are always implemented
30619 on top of a thread. But if @value{GDBN} cannot find this corresponding
30620 thread for any reason, the field is omitted.
30623 This field exists only when the task was created by another task.
30624 In this case, it provides the ID of the parent task.
30627 The base priority of the task.
30630 The current state of the task. For a detailed description of the
30631 possible states, see @ref{Ada Tasks}.
30634 The name of the task.
30638 @subsubheading Example
30642 ^done,tasks=@{nr_rows="3",nr_cols="8",
30643 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
30644 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
30645 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
30646 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
30647 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
30648 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
30649 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
30650 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
30651 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
30652 state="Child Termination Wait",name="main_task"@}]@}
30656 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30657 @node GDB/MI Program Execution
30658 @section @sc{gdb/mi} Program Execution
30660 These are the asynchronous commands which generate the out-of-band
30661 record @samp{*stopped}. Currently @value{GDBN} only really executes
30662 asynchronously with remote targets and this interaction is mimicked in
30665 @subheading The @code{-exec-continue} Command
30666 @findex -exec-continue
30668 @subsubheading Synopsis
30671 -exec-continue [--reverse] [--all|--thread-group N]
30674 Resumes the execution of the inferior program, which will continue
30675 to execute until it reaches a debugger stop event. If the
30676 @samp{--reverse} option is specified, execution resumes in reverse until
30677 it reaches a stop event. Stop events may include
30680 breakpoints or watchpoints
30682 signals or exceptions
30684 the end of the process (or its beginning under @samp{--reverse})
30686 the end or beginning of a replay log if one is being used.
30688 In all-stop mode (@pxref{All-Stop
30689 Mode}), may resume only one thread, or all threads, depending on the
30690 value of the @samp{scheduler-locking} variable. If @samp{--all} is
30691 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
30692 ignored in all-stop mode. If the @samp{--thread-group} options is
30693 specified, then all threads in that thread group are resumed.
30695 @subsubheading @value{GDBN} Command
30697 The corresponding @value{GDBN} corresponding is @samp{continue}.
30699 @subsubheading Example
30706 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
30707 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
30713 @subheading The @code{-exec-finish} Command
30714 @findex -exec-finish
30716 @subsubheading Synopsis
30719 -exec-finish [--reverse]
30722 Resumes the execution of the inferior program until the current
30723 function is exited. Displays the results returned by the function.
30724 If the @samp{--reverse} option is specified, resumes the reverse
30725 execution of the inferior program until the point where current
30726 function was called.
30728 @subsubheading @value{GDBN} Command
30730 The corresponding @value{GDBN} command is @samp{finish}.
30732 @subsubheading Example
30734 Function returning @code{void}.
30741 *stopped,reason="function-finished",frame=@{func="main",args=[],
30742 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
30746 Function returning other than @code{void}. The name of the internal
30747 @value{GDBN} variable storing the result is printed, together with the
30754 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
30755 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
30756 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30757 gdb-result-var="$1",return-value="0"
30762 @subheading The @code{-exec-interrupt} Command
30763 @findex -exec-interrupt
30765 @subsubheading Synopsis
30768 -exec-interrupt [--all|--thread-group N]
30771 Interrupts the background execution of the target. Note how the token
30772 associated with the stop message is the one for the execution command
30773 that has been interrupted. The token for the interrupt itself only
30774 appears in the @samp{^done} output. If the user is trying to
30775 interrupt a non-running program, an error message will be printed.
30777 Note that when asynchronous execution is enabled, this command is
30778 asynchronous just like other execution commands. That is, first the
30779 @samp{^done} response will be printed, and the target stop will be
30780 reported after that using the @samp{*stopped} notification.
30782 In non-stop mode, only the context thread is interrupted by default.
30783 All threads (in all inferiors) will be interrupted if the
30784 @samp{--all} option is specified. If the @samp{--thread-group}
30785 option is specified, all threads in that group will be interrupted.
30787 @subsubheading @value{GDBN} Command
30789 The corresponding @value{GDBN} command is @samp{interrupt}.
30791 @subsubheading Example
30802 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
30803 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
30804 fullname="/home/foo/bar/try.c",line="13"@}
30809 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
30813 @subheading The @code{-exec-jump} Command
30816 @subsubheading Synopsis
30819 -exec-jump @var{location}
30822 Resumes execution of the inferior program at the location specified by
30823 parameter. @xref{Specify Location}, for a description of the
30824 different forms of @var{location}.
30826 @subsubheading @value{GDBN} Command
30828 The corresponding @value{GDBN} command is @samp{jump}.
30830 @subsubheading Example
30833 -exec-jump foo.c:10
30834 *running,thread-id="all"
30839 @subheading The @code{-exec-next} Command
30842 @subsubheading Synopsis
30845 -exec-next [--reverse]
30848 Resumes execution of the inferior program, stopping when the beginning
30849 of the next source line is reached.
30851 If the @samp{--reverse} option is specified, resumes reverse execution
30852 of the inferior program, stopping at the beginning of the previous
30853 source line. If you issue this command on the first line of a
30854 function, it will take you back to the caller of that function, to the
30855 source line where the function was called.
30858 @subsubheading @value{GDBN} Command
30860 The corresponding @value{GDBN} command is @samp{next}.
30862 @subsubheading Example
30868 *stopped,reason="end-stepping-range",line="8",file="hello.c"
30873 @subheading The @code{-exec-next-instruction} Command
30874 @findex -exec-next-instruction
30876 @subsubheading Synopsis
30879 -exec-next-instruction [--reverse]
30882 Executes one machine instruction. If the instruction is a function
30883 call, continues until the function returns. If the program stops at an
30884 instruction in the middle of a source line, the address will be
30887 If the @samp{--reverse} option is specified, resumes reverse execution
30888 of the inferior program, stopping at the previous instruction. If the
30889 previously executed instruction was a return from another function,
30890 it will continue to execute in reverse until the call to that function
30891 (from the current stack frame) is reached.
30893 @subsubheading @value{GDBN} Command
30895 The corresponding @value{GDBN} command is @samp{nexti}.
30897 @subsubheading Example
30901 -exec-next-instruction
30905 *stopped,reason="end-stepping-range",
30906 addr="0x000100d4",line="5",file="hello.c"
30911 @subheading The @code{-exec-return} Command
30912 @findex -exec-return
30914 @subsubheading Synopsis
30920 Makes current function return immediately. Doesn't execute the inferior.
30921 Displays the new current frame.
30923 @subsubheading @value{GDBN} Command
30925 The corresponding @value{GDBN} command is @samp{return}.
30927 @subsubheading Example
30931 200-break-insert callee4
30932 200^done,bkpt=@{number="1",addr="0x00010734",
30933 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
30938 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30939 frame=@{func="callee4",args=[],
30940 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30941 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
30947 111^done,frame=@{level="0",func="callee3",
30948 args=[@{name="strarg",
30949 value="0x11940 \"A string argument.\""@}],
30950 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30951 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30956 @subheading The @code{-exec-run} Command
30959 @subsubheading Synopsis
30962 -exec-run [--all | --thread-group N]
30965 Starts execution of the inferior from the beginning. The inferior
30966 executes until either a breakpoint is encountered or the program
30967 exits. In the latter case the output will include an exit code, if
30968 the program has exited exceptionally.
30970 When no option is specified, the current inferior is started. If the
30971 @samp{--thread-group} option is specified, it should refer to a thread
30972 group of type @samp{process}, and that thread group will be started.
30973 If the @samp{--all} option is specified, then all inferiors will be started.
30975 @subsubheading @value{GDBN} Command
30977 The corresponding @value{GDBN} command is @samp{run}.
30979 @subsubheading Examples
30984 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30989 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30990 frame=@{func="main",args=[],file="recursive2.c",
30991 fullname="/home/foo/bar/recursive2.c",line="4"@}
30996 Program exited normally:
31004 *stopped,reason="exited-normally"
31009 Program exited exceptionally:
31017 *stopped,reason="exited",exit-code="01"
31021 Another way the program can terminate is if it receives a signal such as
31022 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31026 *stopped,reason="exited-signalled",signal-name="SIGINT",
31027 signal-meaning="Interrupt"
31031 @c @subheading -exec-signal
31034 @subheading The @code{-exec-step} Command
31037 @subsubheading Synopsis
31040 -exec-step [--reverse]
31043 Resumes execution of the inferior program, stopping when the beginning
31044 of the next source line is reached, if the next source line is not a
31045 function call. If it is, stop at the first instruction of the called
31046 function. If the @samp{--reverse} option is specified, resumes reverse
31047 execution of the inferior program, stopping at the beginning of the
31048 previously executed source line.
31050 @subsubheading @value{GDBN} Command
31052 The corresponding @value{GDBN} command is @samp{step}.
31054 @subsubheading Example
31056 Stepping into a function:
31062 *stopped,reason="end-stepping-range",
31063 frame=@{func="foo",args=[@{name="a",value="10"@},
31064 @{name="b",value="0"@}],file="recursive2.c",
31065 fullname="/home/foo/bar/recursive2.c",line="11"@}
31075 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31080 @subheading The @code{-exec-step-instruction} Command
31081 @findex -exec-step-instruction
31083 @subsubheading Synopsis
31086 -exec-step-instruction [--reverse]
31089 Resumes the inferior which executes one machine instruction. If the
31090 @samp{--reverse} option is specified, resumes reverse execution of the
31091 inferior program, stopping at the previously executed instruction.
31092 The output, once @value{GDBN} has stopped, will vary depending on
31093 whether we have stopped in the middle of a source line or not. In the
31094 former case, the address at which the program stopped will be printed
31097 @subsubheading @value{GDBN} Command
31099 The corresponding @value{GDBN} command is @samp{stepi}.
31101 @subsubheading Example
31105 -exec-step-instruction
31109 *stopped,reason="end-stepping-range",
31110 frame=@{func="foo",args=[],file="try.c",
31111 fullname="/home/foo/bar/try.c",line="10"@}
31113 -exec-step-instruction
31117 *stopped,reason="end-stepping-range",
31118 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31119 fullname="/home/foo/bar/try.c",line="10"@}
31124 @subheading The @code{-exec-until} Command
31125 @findex -exec-until
31127 @subsubheading Synopsis
31130 -exec-until [ @var{location} ]
31133 Executes the inferior until the @var{location} specified in the
31134 argument is reached. If there is no argument, the inferior executes
31135 until a source line greater than the current one is reached. The
31136 reason for stopping in this case will be @samp{location-reached}.
31138 @subsubheading @value{GDBN} Command
31140 The corresponding @value{GDBN} command is @samp{until}.
31142 @subsubheading Example
31146 -exec-until recursive2.c:6
31150 *stopped,reason="location-reached",frame=@{func="main",args=[],
31151 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31156 @subheading -file-clear
31157 Is this going away????
31160 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31161 @node GDB/MI Stack Manipulation
31162 @section @sc{gdb/mi} Stack Manipulation Commands
31164 @subheading The @code{-enable-frame-filters} Command
31165 @findex -enable-frame-filters
31168 -enable-frame-filters
31171 @value{GDBN} allows Python-based frame filters to affect the output of
31172 the MI commands relating to stack traces. As there is no way to
31173 implement this in a fully backward-compatible way, a front end must
31174 request that this functionality be enabled.
31176 Once enabled, this feature cannot be disabled.
31178 Note that if Python support has not been compiled into @value{GDBN},
31179 this command will still succeed (and do nothing).
31181 @subheading The @code{-stack-info-frame} Command
31182 @findex -stack-info-frame
31184 @subsubheading Synopsis
31190 Get info on the selected frame.
31192 @subsubheading @value{GDBN} Command
31194 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31195 (without arguments).
31197 @subsubheading Example
31202 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31203 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31204 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31208 @subheading The @code{-stack-info-depth} Command
31209 @findex -stack-info-depth
31211 @subsubheading Synopsis
31214 -stack-info-depth [ @var{max-depth} ]
31217 Return the depth of the stack. If the integer argument @var{max-depth}
31218 is specified, do not count beyond @var{max-depth} frames.
31220 @subsubheading @value{GDBN} Command
31222 There's no equivalent @value{GDBN} command.
31224 @subsubheading Example
31226 For a stack with frame levels 0 through 11:
31233 -stack-info-depth 4
31236 -stack-info-depth 12
31239 -stack-info-depth 11
31242 -stack-info-depth 13
31247 @anchor{-stack-list-arguments}
31248 @subheading The @code{-stack-list-arguments} Command
31249 @findex -stack-list-arguments
31251 @subsubheading Synopsis
31254 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31255 [ @var{low-frame} @var{high-frame} ]
31258 Display a list of the arguments for the frames between @var{low-frame}
31259 and @var{high-frame} (inclusive). If @var{low-frame} and
31260 @var{high-frame} are not provided, list the arguments for the whole
31261 call stack. If the two arguments are equal, show the single frame
31262 at the corresponding level. It is an error if @var{low-frame} is
31263 larger than the actual number of frames. On the other hand,
31264 @var{high-frame} may be larger than the actual number of frames, in
31265 which case only existing frames will be returned.
31267 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31268 the variables; if it is 1 or @code{--all-values}, print also their
31269 values; and if it is 2 or @code{--simple-values}, print the name,
31270 type and value for simple data types, and the name and type for arrays,
31271 structures and unions. If the option @code{--no-frame-filters} is
31272 supplied, then Python frame filters will not be executed.
31274 If the @code{--skip-unavailable} option is specified, arguments that
31275 are not available are not listed. Partially available arguments
31276 are still displayed, however.
31278 Use of this command to obtain arguments in a single frame is
31279 deprecated in favor of the @samp{-stack-list-variables} command.
31281 @subsubheading @value{GDBN} Command
31283 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31284 @samp{gdb_get_args} command which partially overlaps with the
31285 functionality of @samp{-stack-list-arguments}.
31287 @subsubheading Example
31294 frame=@{level="0",addr="0x00010734",func="callee4",
31295 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31296 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31297 frame=@{level="1",addr="0x0001076c",func="callee3",
31298 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31299 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31300 frame=@{level="2",addr="0x0001078c",func="callee2",
31301 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31302 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31303 frame=@{level="3",addr="0x000107b4",func="callee1",
31304 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31305 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31306 frame=@{level="4",addr="0x000107e0",func="main",
31307 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31308 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31310 -stack-list-arguments 0
31313 frame=@{level="0",args=[]@},
31314 frame=@{level="1",args=[name="strarg"]@},
31315 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31316 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31317 frame=@{level="4",args=[]@}]
31319 -stack-list-arguments 1
31322 frame=@{level="0",args=[]@},
31324 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31325 frame=@{level="2",args=[
31326 @{name="intarg",value="2"@},
31327 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31328 @{frame=@{level="3",args=[
31329 @{name="intarg",value="2"@},
31330 @{name="strarg",value="0x11940 \"A string argument.\""@},
31331 @{name="fltarg",value="3.5"@}]@},
31332 frame=@{level="4",args=[]@}]
31334 -stack-list-arguments 0 2 2
31335 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31337 -stack-list-arguments 1 2 2
31338 ^done,stack-args=[frame=@{level="2",
31339 args=[@{name="intarg",value="2"@},
31340 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31344 @c @subheading -stack-list-exception-handlers
31347 @anchor{-stack-list-frames}
31348 @subheading The @code{-stack-list-frames} Command
31349 @findex -stack-list-frames
31351 @subsubheading Synopsis
31354 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31357 List the frames currently on the stack. For each frame it displays the
31362 The frame number, 0 being the topmost frame, i.e., the innermost function.
31364 The @code{$pc} value for that frame.
31368 File name of the source file where the function lives.
31369 @item @var{fullname}
31370 The full file name of the source file where the function lives.
31372 Line number corresponding to the @code{$pc}.
31374 The shared library where this function is defined. This is only given
31375 if the frame's function is not known.
31378 If invoked without arguments, this command prints a backtrace for the
31379 whole stack. If given two integer arguments, it shows the frames whose
31380 levels are between the two arguments (inclusive). If the two arguments
31381 are equal, it shows the single frame at the corresponding level. It is
31382 an error if @var{low-frame} is larger than the actual number of
31383 frames. On the other hand, @var{high-frame} may be larger than the
31384 actual number of frames, in which case only existing frames will be
31385 returned. If the option @code{--no-frame-filters} is supplied, then
31386 Python frame filters will not be executed.
31388 @subsubheading @value{GDBN} Command
31390 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31392 @subsubheading Example
31394 Full stack backtrace:
31400 [frame=@{level="0",addr="0x0001076c",func="foo",
31401 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
31402 frame=@{level="1",addr="0x000107a4",func="foo",
31403 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31404 frame=@{level="2",addr="0x000107a4",func="foo",
31405 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31406 frame=@{level="3",addr="0x000107a4",func="foo",
31407 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31408 frame=@{level="4",addr="0x000107a4",func="foo",
31409 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31410 frame=@{level="5",addr="0x000107a4",func="foo",
31411 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31412 frame=@{level="6",addr="0x000107a4",func="foo",
31413 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31414 frame=@{level="7",addr="0x000107a4",func="foo",
31415 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31416 frame=@{level="8",addr="0x000107a4",func="foo",
31417 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31418 frame=@{level="9",addr="0x000107a4",func="foo",
31419 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31420 frame=@{level="10",addr="0x000107a4",func="foo",
31421 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31422 frame=@{level="11",addr="0x00010738",func="main",
31423 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
31427 Show frames between @var{low_frame} and @var{high_frame}:
31431 -stack-list-frames 3 5
31433 [frame=@{level="3",addr="0x000107a4",func="foo",
31434 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31435 frame=@{level="4",addr="0x000107a4",func="foo",
31436 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31437 frame=@{level="5",addr="0x000107a4",func="foo",
31438 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31442 Show a single frame:
31446 -stack-list-frames 3 3
31448 [frame=@{level="3",addr="0x000107a4",func="foo",
31449 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31454 @subheading The @code{-stack-list-locals} Command
31455 @findex -stack-list-locals
31456 @anchor{-stack-list-locals}
31458 @subsubheading Synopsis
31461 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31464 Display the local variable names for the selected frame. If
31465 @var{print-values} is 0 or @code{--no-values}, print only the names of
31466 the variables; if it is 1 or @code{--all-values}, print also their
31467 values; and if it is 2 or @code{--simple-values}, print the name,
31468 type and value for simple data types, and the name and type for arrays,
31469 structures and unions. In this last case, a frontend can immediately
31470 display the value of simple data types and create variable objects for
31471 other data types when the user wishes to explore their values in
31472 more detail. If the option @code{--no-frame-filters} is supplied, then
31473 Python frame filters will not be executed.
31475 If the @code{--skip-unavailable} option is specified, local variables
31476 that are not available are not listed. Partially available local
31477 variables are still displayed, however.
31479 This command is deprecated in favor of the
31480 @samp{-stack-list-variables} command.
31482 @subsubheading @value{GDBN} Command
31484 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
31486 @subsubheading Example
31490 -stack-list-locals 0
31491 ^done,locals=[name="A",name="B",name="C"]
31493 -stack-list-locals --all-values
31494 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
31495 @{name="C",value="@{1, 2, 3@}"@}]
31496 -stack-list-locals --simple-values
31497 ^done,locals=[@{name="A",type="int",value="1"@},
31498 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
31502 @anchor{-stack-list-variables}
31503 @subheading The @code{-stack-list-variables} Command
31504 @findex -stack-list-variables
31506 @subsubheading Synopsis
31509 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31512 Display the names of local variables and function arguments for the selected frame. If
31513 @var{print-values} is 0 or @code{--no-values}, print only the names of
31514 the variables; if it is 1 or @code{--all-values}, print also their
31515 values; and if it is 2 or @code{--simple-values}, print the name,
31516 type and value for simple data types, and the name and type for arrays,
31517 structures and unions. If the option @code{--no-frame-filters} is
31518 supplied, then Python frame filters will not be executed.
31520 If the @code{--skip-unavailable} option is specified, local variables
31521 and arguments that are not available are not listed. Partially
31522 available arguments and local variables are still displayed, however.
31524 @subsubheading Example
31528 -stack-list-variables --thread 1 --frame 0 --all-values
31529 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
31534 @subheading The @code{-stack-select-frame} Command
31535 @findex -stack-select-frame
31537 @subsubheading Synopsis
31540 -stack-select-frame @var{framenum}
31543 Change the selected frame. Select a different frame @var{framenum} on
31546 This command in deprecated in favor of passing the @samp{--frame}
31547 option to every command.
31549 @subsubheading @value{GDBN} Command
31551 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
31552 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
31554 @subsubheading Example
31558 -stack-select-frame 2
31563 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31564 @node GDB/MI Variable Objects
31565 @section @sc{gdb/mi} Variable Objects
31569 @subheading Motivation for Variable Objects in @sc{gdb/mi}
31571 For the implementation of a variable debugger window (locals, watched
31572 expressions, etc.), we are proposing the adaptation of the existing code
31573 used by @code{Insight}.
31575 The two main reasons for that are:
31579 It has been proven in practice (it is already on its second generation).
31582 It will shorten development time (needless to say how important it is
31586 The original interface was designed to be used by Tcl code, so it was
31587 slightly changed so it could be used through @sc{gdb/mi}. This section
31588 describes the @sc{gdb/mi} operations that will be available and gives some
31589 hints about their use.
31591 @emph{Note}: In addition to the set of operations described here, we
31592 expect the @sc{gui} implementation of a variable window to require, at
31593 least, the following operations:
31596 @item @code{-gdb-show} @code{output-radix}
31597 @item @code{-stack-list-arguments}
31598 @item @code{-stack-list-locals}
31599 @item @code{-stack-select-frame}
31604 @subheading Introduction to Variable Objects
31606 @cindex variable objects in @sc{gdb/mi}
31608 Variable objects are "object-oriented" MI interface for examining and
31609 changing values of expressions. Unlike some other MI interfaces that
31610 work with expressions, variable objects are specifically designed for
31611 simple and efficient presentation in the frontend. A variable object
31612 is identified by string name. When a variable object is created, the
31613 frontend specifies the expression for that variable object. The
31614 expression can be a simple variable, or it can be an arbitrary complex
31615 expression, and can even involve CPU registers. After creating a
31616 variable object, the frontend can invoke other variable object
31617 operations---for example to obtain or change the value of a variable
31618 object, or to change display format.
31620 Variable objects have hierarchical tree structure. Any variable object
31621 that corresponds to a composite type, such as structure in C, has
31622 a number of child variable objects, for example corresponding to each
31623 element of a structure. A child variable object can itself have
31624 children, recursively. Recursion ends when we reach
31625 leaf variable objects, which always have built-in types. Child variable
31626 objects are created only by explicit request, so if a frontend
31627 is not interested in the children of a particular variable object, no
31628 child will be created.
31630 For a leaf variable object it is possible to obtain its value as a
31631 string, or set the value from a string. String value can be also
31632 obtained for a non-leaf variable object, but it's generally a string
31633 that only indicates the type of the object, and does not list its
31634 contents. Assignment to a non-leaf variable object is not allowed.
31636 A frontend does not need to read the values of all variable objects each time
31637 the program stops. Instead, MI provides an update command that lists all
31638 variable objects whose values has changed since the last update
31639 operation. This considerably reduces the amount of data that must
31640 be transferred to the frontend. As noted above, children variable
31641 objects are created on demand, and only leaf variable objects have a
31642 real value. As result, gdb will read target memory only for leaf
31643 variables that frontend has created.
31645 The automatic update is not always desirable. For example, a frontend
31646 might want to keep a value of some expression for future reference,
31647 and never update it. For another example, fetching memory is
31648 relatively slow for embedded targets, so a frontend might want
31649 to disable automatic update for the variables that are either not
31650 visible on the screen, or ``closed''. This is possible using so
31651 called ``frozen variable objects''. Such variable objects are never
31652 implicitly updated.
31654 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
31655 fixed variable object, the expression is parsed when the variable
31656 object is created, including associating identifiers to specific
31657 variables. The meaning of expression never changes. For a floating
31658 variable object the values of variables whose names appear in the
31659 expressions are re-evaluated every time in the context of the current
31660 frame. Consider this example:
31665 struct work_state state;
31672 If a fixed variable object for the @code{state} variable is created in
31673 this function, and we enter the recursive call, the variable
31674 object will report the value of @code{state} in the top-level
31675 @code{do_work} invocation. On the other hand, a floating variable
31676 object will report the value of @code{state} in the current frame.
31678 If an expression specified when creating a fixed variable object
31679 refers to a local variable, the variable object becomes bound to the
31680 thread and frame in which the variable object is created. When such
31681 variable object is updated, @value{GDBN} makes sure that the
31682 thread/frame combination the variable object is bound to still exists,
31683 and re-evaluates the variable object in context of that thread/frame.
31685 The following is the complete set of @sc{gdb/mi} operations defined to
31686 access this functionality:
31688 @multitable @columnfractions .4 .6
31689 @item @strong{Operation}
31690 @tab @strong{Description}
31692 @item @code{-enable-pretty-printing}
31693 @tab enable Python-based pretty-printing
31694 @item @code{-var-create}
31695 @tab create a variable object
31696 @item @code{-var-delete}
31697 @tab delete the variable object and/or its children
31698 @item @code{-var-set-format}
31699 @tab set the display format of this variable
31700 @item @code{-var-show-format}
31701 @tab show the display format of this variable
31702 @item @code{-var-info-num-children}
31703 @tab tells how many children this object has
31704 @item @code{-var-list-children}
31705 @tab return a list of the object's children
31706 @item @code{-var-info-type}
31707 @tab show the type of this variable object
31708 @item @code{-var-info-expression}
31709 @tab print parent-relative expression that this variable object represents
31710 @item @code{-var-info-path-expression}
31711 @tab print full expression that this variable object represents
31712 @item @code{-var-show-attributes}
31713 @tab is this variable editable? does it exist here?
31714 @item @code{-var-evaluate-expression}
31715 @tab get the value of this variable
31716 @item @code{-var-assign}
31717 @tab set the value of this variable
31718 @item @code{-var-update}
31719 @tab update the variable and its children
31720 @item @code{-var-set-frozen}
31721 @tab set frozeness attribute
31722 @item @code{-var-set-update-range}
31723 @tab set range of children to display on update
31726 In the next subsection we describe each operation in detail and suggest
31727 how it can be used.
31729 @subheading Description And Use of Operations on Variable Objects
31731 @subheading The @code{-enable-pretty-printing} Command
31732 @findex -enable-pretty-printing
31735 -enable-pretty-printing
31738 @value{GDBN} allows Python-based visualizers to affect the output of the
31739 MI variable object commands. However, because there was no way to
31740 implement this in a fully backward-compatible way, a front end must
31741 request that this functionality be enabled.
31743 Once enabled, this feature cannot be disabled.
31745 Note that if Python support has not been compiled into @value{GDBN},
31746 this command will still succeed (and do nothing).
31748 This feature is currently (as of @value{GDBN} 7.0) experimental, and
31749 may work differently in future versions of @value{GDBN}.
31751 @subheading The @code{-var-create} Command
31752 @findex -var-create
31754 @subsubheading Synopsis
31757 -var-create @{@var{name} | "-"@}
31758 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
31761 This operation creates a variable object, which allows the monitoring of
31762 a variable, the result of an expression, a memory cell or a CPU
31765 The @var{name} parameter is the string by which the object can be
31766 referenced. It must be unique. If @samp{-} is specified, the varobj
31767 system will generate a string ``varNNNNNN'' automatically. It will be
31768 unique provided that one does not specify @var{name} of that format.
31769 The command fails if a duplicate name is found.
31771 The frame under which the expression should be evaluated can be
31772 specified by @var{frame-addr}. A @samp{*} indicates that the current
31773 frame should be used. A @samp{@@} indicates that a floating variable
31774 object must be created.
31776 @var{expression} is any expression valid on the current language set (must not
31777 begin with a @samp{*}), or one of the following:
31781 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
31784 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
31787 @samp{$@var{regname}} --- a CPU register name
31790 @cindex dynamic varobj
31791 A varobj's contents may be provided by a Python-based pretty-printer. In this
31792 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
31793 have slightly different semantics in some cases. If the
31794 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
31795 will never create a dynamic varobj. This ensures backward
31796 compatibility for existing clients.
31798 @subsubheading Result
31800 This operation returns attributes of the newly-created varobj. These
31805 The name of the varobj.
31808 The number of children of the varobj. This number is not necessarily
31809 reliable for a dynamic varobj. Instead, you must examine the
31810 @samp{has_more} attribute.
31813 The varobj's scalar value. For a varobj whose type is some sort of
31814 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
31815 will not be interesting.
31818 The varobj's type. This is a string representation of the type, as
31819 would be printed by the @value{GDBN} CLI. If @samp{print object}
31820 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31821 @emph{actual} (derived) type of the object is shown rather than the
31822 @emph{declared} one.
31825 If a variable object is bound to a specific thread, then this is the
31826 thread's identifier.
31829 For a dynamic varobj, this indicates whether there appear to be any
31830 children available. For a non-dynamic varobj, this will be 0.
31833 This attribute will be present and have the value @samp{1} if the
31834 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31835 then this attribute will not be present.
31838 A dynamic varobj can supply a display hint to the front end. The
31839 value comes directly from the Python pretty-printer object's
31840 @code{display_hint} method. @xref{Pretty Printing API}.
31843 Typical output will look like this:
31846 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
31847 has_more="@var{has_more}"
31851 @subheading The @code{-var-delete} Command
31852 @findex -var-delete
31854 @subsubheading Synopsis
31857 -var-delete [ -c ] @var{name}
31860 Deletes a previously created variable object and all of its children.
31861 With the @samp{-c} option, just deletes the children.
31863 Returns an error if the object @var{name} is not found.
31866 @subheading The @code{-var-set-format} Command
31867 @findex -var-set-format
31869 @subsubheading Synopsis
31872 -var-set-format @var{name} @var{format-spec}
31875 Sets the output format for the value of the object @var{name} to be
31878 @anchor{-var-set-format}
31879 The syntax for the @var{format-spec} is as follows:
31882 @var{format-spec} @expansion{}
31883 @{binary | decimal | hexadecimal | octal | natural@}
31886 The natural format is the default format choosen automatically
31887 based on the variable type (like decimal for an @code{int}, hex
31888 for pointers, etc.).
31890 For a variable with children, the format is set only on the
31891 variable itself, and the children are not affected.
31893 @subheading The @code{-var-show-format} Command
31894 @findex -var-show-format
31896 @subsubheading Synopsis
31899 -var-show-format @var{name}
31902 Returns the format used to display the value of the object @var{name}.
31905 @var{format} @expansion{}
31910 @subheading The @code{-var-info-num-children} Command
31911 @findex -var-info-num-children
31913 @subsubheading Synopsis
31916 -var-info-num-children @var{name}
31919 Returns the number of children of a variable object @var{name}:
31925 Note that this number is not completely reliable for a dynamic varobj.
31926 It will return the current number of children, but more children may
31930 @subheading The @code{-var-list-children} Command
31931 @findex -var-list-children
31933 @subsubheading Synopsis
31936 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31938 @anchor{-var-list-children}
31940 Return a list of the children of the specified variable object and
31941 create variable objects for them, if they do not already exist. With
31942 a single argument or if @var{print-values} has a value of 0 or
31943 @code{--no-values}, print only the names of the variables; if
31944 @var{print-values} is 1 or @code{--all-values}, also print their
31945 values; and if it is 2 or @code{--simple-values} print the name and
31946 value for simple data types and just the name for arrays, structures
31949 @var{from} and @var{to}, if specified, indicate the range of children
31950 to report. If @var{from} or @var{to} is less than zero, the range is
31951 reset and all children will be reported. Otherwise, children starting
31952 at @var{from} (zero-based) and up to and excluding @var{to} will be
31955 If a child range is requested, it will only affect the current call to
31956 @code{-var-list-children}, but not future calls to @code{-var-update}.
31957 For this, you must instead use @code{-var-set-update-range}. The
31958 intent of this approach is to enable a front end to implement any
31959 update approach it likes; for example, scrolling a view may cause the
31960 front end to request more children with @code{-var-list-children}, and
31961 then the front end could call @code{-var-set-update-range} with a
31962 different range to ensure that future updates are restricted to just
31965 For each child the following results are returned:
31970 Name of the variable object created for this child.
31973 The expression to be shown to the user by the front end to designate this child.
31974 For example this may be the name of a structure member.
31976 For a dynamic varobj, this value cannot be used to form an
31977 expression. There is no way to do this at all with a dynamic varobj.
31979 For C/C@t{++} structures there are several pseudo children returned to
31980 designate access qualifiers. For these pseudo children @var{exp} is
31981 @samp{public}, @samp{private}, or @samp{protected}. In this case the
31982 type and value are not present.
31984 A dynamic varobj will not report the access qualifying
31985 pseudo-children, regardless of the language. This information is not
31986 available at all with a dynamic varobj.
31989 Number of children this child has. For a dynamic varobj, this will be
31993 The type of the child. If @samp{print object}
31994 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31995 @emph{actual} (derived) type of the object is shown rather than the
31996 @emph{declared} one.
31999 If values were requested, this is the value.
32002 If this variable object is associated with a thread, this is the thread id.
32003 Otherwise this result is not present.
32006 If the variable object is frozen, this variable will be present with a value of 1.
32009 The result may have its own attributes:
32013 A dynamic varobj can supply a display hint to the front end. The
32014 value comes directly from the Python pretty-printer object's
32015 @code{display_hint} method. @xref{Pretty Printing API}.
32018 This is an integer attribute which is nonzero if there are children
32019 remaining after the end of the selected range.
32022 @subsubheading Example
32026 -var-list-children n
32027 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32028 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32030 -var-list-children --all-values n
32031 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32032 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32036 @subheading The @code{-var-info-type} Command
32037 @findex -var-info-type
32039 @subsubheading Synopsis
32042 -var-info-type @var{name}
32045 Returns the type of the specified variable @var{name}. The type is
32046 returned as a string in the same format as it is output by the
32050 type=@var{typename}
32054 @subheading The @code{-var-info-expression} Command
32055 @findex -var-info-expression
32057 @subsubheading Synopsis
32060 -var-info-expression @var{name}
32063 Returns a string that is suitable for presenting this
32064 variable object in user interface. The string is generally
32065 not valid expression in the current language, and cannot be evaluated.
32067 For example, if @code{a} is an array, and variable object
32068 @code{A} was created for @code{a}, then we'll get this output:
32071 (gdb) -var-info-expression A.1
32072 ^done,lang="C",exp="1"
32076 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
32078 Note that the output of the @code{-var-list-children} command also
32079 includes those expressions, so the @code{-var-info-expression} command
32082 @subheading The @code{-var-info-path-expression} Command
32083 @findex -var-info-path-expression
32085 @subsubheading Synopsis
32088 -var-info-path-expression @var{name}
32091 Returns an expression that can be evaluated in the current
32092 context and will yield the same value that a variable object has.
32093 Compare this with the @code{-var-info-expression} command, which
32094 result can be used only for UI presentation. Typical use of
32095 the @code{-var-info-path-expression} command is creating a
32096 watchpoint from a variable object.
32098 This command is currently not valid for children of a dynamic varobj,
32099 and will give an error when invoked on one.
32101 For example, suppose @code{C} is a C@t{++} class, derived from class
32102 @code{Base}, and that the @code{Base} class has a member called
32103 @code{m_size}. Assume a variable @code{c} is has the type of
32104 @code{C} and a variable object @code{C} was created for variable
32105 @code{c}. Then, we'll get this output:
32107 (gdb) -var-info-path-expression C.Base.public.m_size
32108 ^done,path_expr=((Base)c).m_size)
32111 @subheading The @code{-var-show-attributes} Command
32112 @findex -var-show-attributes
32114 @subsubheading Synopsis
32117 -var-show-attributes @var{name}
32120 List attributes of the specified variable object @var{name}:
32123 status=@var{attr} [ ( ,@var{attr} )* ]
32127 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32129 @subheading The @code{-var-evaluate-expression} Command
32130 @findex -var-evaluate-expression
32132 @subsubheading Synopsis
32135 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32138 Evaluates the expression that is represented by the specified variable
32139 object and returns its value as a string. The format of the string
32140 can be specified with the @samp{-f} option. The possible values of
32141 this option are the same as for @code{-var-set-format}
32142 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32143 the current display format will be used. The current display format
32144 can be changed using the @code{-var-set-format} command.
32150 Note that one must invoke @code{-var-list-children} for a variable
32151 before the value of a child variable can be evaluated.
32153 @subheading The @code{-var-assign} Command
32154 @findex -var-assign
32156 @subsubheading Synopsis
32159 -var-assign @var{name} @var{expression}
32162 Assigns the value of @var{expression} to the variable object specified
32163 by @var{name}. The object must be @samp{editable}. If the variable's
32164 value is altered by the assign, the variable will show up in any
32165 subsequent @code{-var-update} list.
32167 @subsubheading Example
32175 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32179 @subheading The @code{-var-update} Command
32180 @findex -var-update
32182 @subsubheading Synopsis
32185 -var-update [@var{print-values}] @{@var{name} | "*"@}
32188 Reevaluate the expressions corresponding to the variable object
32189 @var{name} and all its direct and indirect children, and return the
32190 list of variable objects whose values have changed; @var{name} must
32191 be a root variable object. Here, ``changed'' means that the result of
32192 @code{-var-evaluate-expression} before and after the
32193 @code{-var-update} is different. If @samp{*} is used as the variable
32194 object names, all existing variable objects are updated, except
32195 for frozen ones (@pxref{-var-set-frozen}). The option
32196 @var{print-values} determines whether both names and values, or just
32197 names are printed. The possible values of this option are the same
32198 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32199 recommended to use the @samp{--all-values} option, to reduce the
32200 number of MI commands needed on each program stop.
32202 With the @samp{*} parameter, if a variable object is bound to a
32203 currently running thread, it will not be updated, without any
32206 If @code{-var-set-update-range} was previously used on a varobj, then
32207 only the selected range of children will be reported.
32209 @code{-var-update} reports all the changed varobjs in a tuple named
32212 Each item in the change list is itself a tuple holding:
32216 The name of the varobj.
32219 If values were requested for this update, then this field will be
32220 present and will hold the value of the varobj.
32223 @anchor{-var-update}
32224 This field is a string which may take one of three values:
32228 The variable object's current value is valid.
32231 The variable object does not currently hold a valid value but it may
32232 hold one in the future if its associated expression comes back into
32236 The variable object no longer holds a valid value.
32237 This can occur when the executable file being debugged has changed,
32238 either through recompilation or by using the @value{GDBN} @code{file}
32239 command. The front end should normally choose to delete these variable
32243 In the future new values may be added to this list so the front should
32244 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32247 This is only present if the varobj is still valid. If the type
32248 changed, then this will be the string @samp{true}; otherwise it will
32251 When a varobj's type changes, its children are also likely to have
32252 become incorrect. Therefore, the varobj's children are automatically
32253 deleted when this attribute is @samp{true}. Also, the varobj's update
32254 range, when set using the @code{-var-set-update-range} command, is
32258 If the varobj's type changed, then this field will be present and will
32261 @item new_num_children
32262 For a dynamic varobj, if the number of children changed, or if the
32263 type changed, this will be the new number of children.
32265 The @samp{numchild} field in other varobj responses is generally not
32266 valid for a dynamic varobj -- it will show the number of children that
32267 @value{GDBN} knows about, but because dynamic varobjs lazily
32268 instantiate their children, this will not reflect the number of
32269 children which may be available.
32271 The @samp{new_num_children} attribute only reports changes to the
32272 number of children known by @value{GDBN}. This is the only way to
32273 detect whether an update has removed children (which necessarily can
32274 only happen at the end of the update range).
32277 The display hint, if any.
32280 This is an integer value, which will be 1 if there are more children
32281 available outside the varobj's update range.
32284 This attribute will be present and have the value @samp{1} if the
32285 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32286 then this attribute will not be present.
32289 If new children were added to a dynamic varobj within the selected
32290 update range (as set by @code{-var-set-update-range}), then they will
32291 be listed in this attribute.
32294 @subsubheading Example
32301 -var-update --all-values var1
32302 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32303 type_changed="false"@}]
32307 @subheading The @code{-var-set-frozen} Command
32308 @findex -var-set-frozen
32309 @anchor{-var-set-frozen}
32311 @subsubheading Synopsis
32314 -var-set-frozen @var{name} @var{flag}
32317 Set the frozenness flag on the variable object @var{name}. The
32318 @var{flag} parameter should be either @samp{1} to make the variable
32319 frozen or @samp{0} to make it unfrozen. If a variable object is
32320 frozen, then neither itself, nor any of its children, are
32321 implicitly updated by @code{-var-update} of
32322 a parent variable or by @code{-var-update *}. Only
32323 @code{-var-update} of the variable itself will update its value and
32324 values of its children. After a variable object is unfrozen, it is
32325 implicitly updated by all subsequent @code{-var-update} operations.
32326 Unfreezing a variable does not update it, only subsequent
32327 @code{-var-update} does.
32329 @subsubheading Example
32333 -var-set-frozen V 1
32338 @subheading The @code{-var-set-update-range} command
32339 @findex -var-set-update-range
32340 @anchor{-var-set-update-range}
32342 @subsubheading Synopsis
32345 -var-set-update-range @var{name} @var{from} @var{to}
32348 Set the range of children to be returned by future invocations of
32349 @code{-var-update}.
32351 @var{from} and @var{to} indicate the range of children to report. If
32352 @var{from} or @var{to} is less than zero, the range is reset and all
32353 children will be reported. Otherwise, children starting at @var{from}
32354 (zero-based) and up to and excluding @var{to} will be reported.
32356 @subsubheading Example
32360 -var-set-update-range V 1 2
32364 @subheading The @code{-var-set-visualizer} command
32365 @findex -var-set-visualizer
32366 @anchor{-var-set-visualizer}
32368 @subsubheading Synopsis
32371 -var-set-visualizer @var{name} @var{visualizer}
32374 Set a visualizer for the variable object @var{name}.
32376 @var{visualizer} is the visualizer to use. The special value
32377 @samp{None} means to disable any visualizer in use.
32379 If not @samp{None}, @var{visualizer} must be a Python expression.
32380 This expression must evaluate to a callable object which accepts a
32381 single argument. @value{GDBN} will call this object with the value of
32382 the varobj @var{name} as an argument (this is done so that the same
32383 Python pretty-printing code can be used for both the CLI and MI).
32384 When called, this object must return an object which conforms to the
32385 pretty-printing interface (@pxref{Pretty Printing API}).
32387 The pre-defined function @code{gdb.default_visualizer} may be used to
32388 select a visualizer by following the built-in process
32389 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32390 a varobj is created, and so ordinarily is not needed.
32392 This feature is only available if Python support is enabled. The MI
32393 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
32394 can be used to check this.
32396 @subsubheading Example
32398 Resetting the visualizer:
32402 -var-set-visualizer V None
32406 Reselecting the default (type-based) visualizer:
32410 -var-set-visualizer V gdb.default_visualizer
32414 Suppose @code{SomeClass} is a visualizer class. A lambda expression
32415 can be used to instantiate this class for a varobj:
32419 -var-set-visualizer V "lambda val: SomeClass()"
32423 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32424 @node GDB/MI Data Manipulation
32425 @section @sc{gdb/mi} Data Manipulation
32427 @cindex data manipulation, in @sc{gdb/mi}
32428 @cindex @sc{gdb/mi}, data manipulation
32429 This section describes the @sc{gdb/mi} commands that manipulate data:
32430 examine memory and registers, evaluate expressions, etc.
32432 @c REMOVED FROM THE INTERFACE.
32433 @c @subheading -data-assign
32434 @c Change the value of a program variable. Plenty of side effects.
32435 @c @subsubheading GDB Command
32437 @c @subsubheading Example
32440 @subheading The @code{-data-disassemble} Command
32441 @findex -data-disassemble
32443 @subsubheading Synopsis
32447 [ -s @var{start-addr} -e @var{end-addr} ]
32448 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
32456 @item @var{start-addr}
32457 is the beginning address (or @code{$pc})
32458 @item @var{end-addr}
32460 @item @var{filename}
32461 is the name of the file to disassemble
32462 @item @var{linenum}
32463 is the line number to disassemble around
32465 is the number of disassembly lines to be produced. If it is -1,
32466 the whole function will be disassembled, in case no @var{end-addr} is
32467 specified. If @var{end-addr} is specified as a non-zero value, and
32468 @var{lines} is lower than the number of disassembly lines between
32469 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
32470 displayed; if @var{lines} is higher than the number of lines between
32471 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
32474 is either 0 (meaning only disassembly), 1 (meaning mixed source and
32475 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
32476 mixed source and disassembly with raw opcodes).
32479 @subsubheading Result
32481 The result of the @code{-data-disassemble} command will be a list named
32482 @samp{asm_insns}, the contents of this list depend on the @var{mode}
32483 used with the @code{-data-disassemble} command.
32485 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
32490 The address at which this instruction was disassembled.
32493 The name of the function this instruction is within.
32496 The decimal offset in bytes from the start of @samp{func-name}.
32499 The text disassembly for this @samp{address}.
32502 This field is only present for mode 2. This contains the raw opcode
32503 bytes for the @samp{inst} field.
32507 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
32508 @samp{src_and_asm_line}, each of which has the following fields:
32512 The line number within @samp{file}.
32515 The file name from the compilation unit. This might be an absolute
32516 file name or a relative file name depending on the compile command
32520 Absolute file name of @samp{file}. It is converted to a canonical form
32521 using the source file search path
32522 (@pxref{Source Path, ,Specifying Source Directories})
32523 and after resolving all the symbolic links.
32525 If the source file is not found this field will contain the path as
32526 present in the debug information.
32528 @item line_asm_insn
32529 This is a list of tuples containing the disassembly for @samp{line} in
32530 @samp{file}. The fields of each tuple are the same as for
32531 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
32532 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
32537 Note that whatever included in the @samp{inst} field, is not
32538 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
32541 @subsubheading @value{GDBN} Command
32543 The corresponding @value{GDBN} command is @samp{disassemble}.
32545 @subsubheading Example
32547 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
32551 -data-disassemble -s $pc -e "$pc + 20" -- 0
32554 @{address="0x000107c0",func-name="main",offset="4",
32555 inst="mov 2, %o0"@},
32556 @{address="0x000107c4",func-name="main",offset="8",
32557 inst="sethi %hi(0x11800), %o2"@},
32558 @{address="0x000107c8",func-name="main",offset="12",
32559 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
32560 @{address="0x000107cc",func-name="main",offset="16",
32561 inst="sethi %hi(0x11800), %o2"@},
32562 @{address="0x000107d0",func-name="main",offset="20",
32563 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
32567 Disassemble the whole @code{main} function. Line 32 is part of
32571 -data-disassemble -f basics.c -l 32 -- 0
32573 @{address="0x000107bc",func-name="main",offset="0",
32574 inst="save %sp, -112, %sp"@},
32575 @{address="0x000107c0",func-name="main",offset="4",
32576 inst="mov 2, %o0"@},
32577 @{address="0x000107c4",func-name="main",offset="8",
32578 inst="sethi %hi(0x11800), %o2"@},
32580 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
32581 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
32585 Disassemble 3 instructions from the start of @code{main}:
32589 -data-disassemble -f basics.c -l 32 -n 3 -- 0
32591 @{address="0x000107bc",func-name="main",offset="0",
32592 inst="save %sp, -112, %sp"@},
32593 @{address="0x000107c0",func-name="main",offset="4",
32594 inst="mov 2, %o0"@},
32595 @{address="0x000107c4",func-name="main",offset="8",
32596 inst="sethi %hi(0x11800), %o2"@}]
32600 Disassemble 3 instructions from the start of @code{main} in mixed mode:
32604 -data-disassemble -f basics.c -l 32 -n 3 -- 1
32606 src_and_asm_line=@{line="31",
32607 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32608 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32609 line_asm_insn=[@{address="0x000107bc",
32610 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
32611 src_and_asm_line=@{line="32",
32612 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32613 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32614 line_asm_insn=[@{address="0x000107c0",
32615 func-name="main",offset="4",inst="mov 2, %o0"@},
32616 @{address="0x000107c4",func-name="main",offset="8",
32617 inst="sethi %hi(0x11800), %o2"@}]@}]
32622 @subheading The @code{-data-evaluate-expression} Command
32623 @findex -data-evaluate-expression
32625 @subsubheading Synopsis
32628 -data-evaluate-expression @var{expr}
32631 Evaluate @var{expr} as an expression. The expression could contain an
32632 inferior function call. The function call will execute synchronously.
32633 If the expression contains spaces, it must be enclosed in double quotes.
32635 @subsubheading @value{GDBN} Command
32637 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
32638 @samp{call}. In @code{gdbtk} only, there's a corresponding
32639 @samp{gdb_eval} command.
32641 @subsubheading Example
32643 In the following example, the numbers that precede the commands are the
32644 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
32645 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
32649 211-data-evaluate-expression A
32652 311-data-evaluate-expression &A
32653 311^done,value="0xefffeb7c"
32655 411-data-evaluate-expression A+3
32658 511-data-evaluate-expression "A + 3"
32664 @subheading The @code{-data-list-changed-registers} Command
32665 @findex -data-list-changed-registers
32667 @subsubheading Synopsis
32670 -data-list-changed-registers
32673 Display a list of the registers that have changed.
32675 @subsubheading @value{GDBN} Command
32677 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
32678 has the corresponding command @samp{gdb_changed_register_list}.
32680 @subsubheading Example
32682 On a PPC MBX board:
32690 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
32691 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
32694 -data-list-changed-registers
32695 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32696 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32697 "24","25","26","27","28","30","31","64","65","66","67","69"]
32702 @subheading The @code{-data-list-register-names} Command
32703 @findex -data-list-register-names
32705 @subsubheading Synopsis
32708 -data-list-register-names [ ( @var{regno} )+ ]
32711 Show a list of register names for the current target. If no arguments
32712 are given, it shows a list of the names of all the registers. If
32713 integer numbers are given as arguments, it will print a list of the
32714 names of the registers corresponding to the arguments. To ensure
32715 consistency between a register name and its number, the output list may
32716 include empty register names.
32718 @subsubheading @value{GDBN} Command
32720 @value{GDBN} does not have a command which corresponds to
32721 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32722 corresponding command @samp{gdb_regnames}.
32724 @subsubheading Example
32726 For the PPC MBX board:
32729 -data-list-register-names
32730 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
32731 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
32732 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
32733 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
32734 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
32735 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
32736 "", "pc","ps","cr","lr","ctr","xer"]
32738 -data-list-register-names 1 2 3
32739 ^done,register-names=["r1","r2","r3"]
32743 @subheading The @code{-data-list-register-values} Command
32744 @findex -data-list-register-values
32746 @subsubheading Synopsis
32749 -data-list-register-values
32750 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
32753 Display the registers' contents. @var{fmt} is the format according to
32754 which the registers' contents are to be returned, followed by an optional
32755 list of numbers specifying the registers to display. A missing list of
32756 numbers indicates that the contents of all the registers must be
32757 returned. The @code{--skip-unavailable} option indicates that only
32758 the available registers are to be returned.
32760 Allowed formats for @var{fmt} are:
32777 @subsubheading @value{GDBN} Command
32779 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
32780 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
32782 @subsubheading Example
32784 For a PPC MBX board (note: line breaks are for readability only, they
32785 don't appear in the actual output):
32789 -data-list-register-values r 64 65
32790 ^done,register-values=[@{number="64",value="0xfe00a300"@},
32791 @{number="65",value="0x00029002"@}]
32793 -data-list-register-values x
32794 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
32795 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
32796 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
32797 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
32798 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
32799 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
32800 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
32801 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
32802 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
32803 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
32804 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
32805 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
32806 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
32807 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
32808 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
32809 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
32810 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
32811 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
32812 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
32813 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
32814 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
32815 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
32816 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
32817 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
32818 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
32819 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
32820 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
32821 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
32822 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
32823 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
32824 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
32825 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
32826 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
32827 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
32828 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
32829 @{number="69",value="0x20002b03"@}]
32834 @subheading The @code{-data-read-memory} Command
32835 @findex -data-read-memory
32837 This command is deprecated, use @code{-data-read-memory-bytes} instead.
32839 @subsubheading Synopsis
32842 -data-read-memory [ -o @var{byte-offset} ]
32843 @var{address} @var{word-format} @var{word-size}
32844 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
32851 @item @var{address}
32852 An expression specifying the address of the first memory word to be
32853 read. Complex expressions containing embedded white space should be
32854 quoted using the C convention.
32856 @item @var{word-format}
32857 The format to be used to print the memory words. The notation is the
32858 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
32861 @item @var{word-size}
32862 The size of each memory word in bytes.
32864 @item @var{nr-rows}
32865 The number of rows in the output table.
32867 @item @var{nr-cols}
32868 The number of columns in the output table.
32871 If present, indicates that each row should include an @sc{ascii} dump. The
32872 value of @var{aschar} is used as a padding character when a byte is not a
32873 member of the printable @sc{ascii} character set (printable @sc{ascii}
32874 characters are those whose code is between 32 and 126, inclusively).
32876 @item @var{byte-offset}
32877 An offset to add to the @var{address} before fetching memory.
32880 This command displays memory contents as a table of @var{nr-rows} by
32881 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
32882 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
32883 (returned as @samp{total-bytes}). Should less than the requested number
32884 of bytes be returned by the target, the missing words are identified
32885 using @samp{N/A}. The number of bytes read from the target is returned
32886 in @samp{nr-bytes} and the starting address used to read memory in
32889 The address of the next/previous row or page is available in
32890 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32893 @subsubheading @value{GDBN} Command
32895 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32896 @samp{gdb_get_mem} memory read command.
32898 @subsubheading Example
32900 Read six bytes of memory starting at @code{bytes+6} but then offset by
32901 @code{-6} bytes. Format as three rows of two columns. One byte per
32902 word. Display each word in hex.
32906 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32907 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32908 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32909 prev-page="0x0000138a",memory=[
32910 @{addr="0x00001390",data=["0x00","0x01"]@},
32911 @{addr="0x00001392",data=["0x02","0x03"]@},
32912 @{addr="0x00001394",data=["0x04","0x05"]@}]
32916 Read two bytes of memory starting at address @code{shorts + 64} and
32917 display as a single word formatted in decimal.
32921 5-data-read-memory shorts+64 d 2 1 1
32922 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32923 next-row="0x00001512",prev-row="0x0000150e",
32924 next-page="0x00001512",prev-page="0x0000150e",memory=[
32925 @{addr="0x00001510",data=["128"]@}]
32929 Read thirty two bytes of memory starting at @code{bytes+16} and format
32930 as eight rows of four columns. Include a string encoding with @samp{x}
32931 used as the non-printable character.
32935 4-data-read-memory bytes+16 x 1 8 4 x
32936 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32937 next-row="0x000013c0",prev-row="0x0000139c",
32938 next-page="0x000013c0",prev-page="0x00001380",memory=[
32939 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32940 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32941 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32942 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32943 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32944 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32945 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32946 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
32950 @subheading The @code{-data-read-memory-bytes} Command
32951 @findex -data-read-memory-bytes
32953 @subsubheading Synopsis
32956 -data-read-memory-bytes [ -o @var{byte-offset} ]
32957 @var{address} @var{count}
32964 @item @var{address}
32965 An expression specifying the address of the first memory word to be
32966 read. Complex expressions containing embedded white space should be
32967 quoted using the C convention.
32970 The number of bytes to read. This should be an integer literal.
32972 @item @var{byte-offset}
32973 The offsets in bytes relative to @var{address} at which to start
32974 reading. This should be an integer literal. This option is provided
32975 so that a frontend is not required to first evaluate address and then
32976 perform address arithmetics itself.
32980 This command attempts to read all accessible memory regions in the
32981 specified range. First, all regions marked as unreadable in the memory
32982 map (if one is defined) will be skipped. @xref{Memory Region
32983 Attributes}. Second, @value{GDBN} will attempt to read the remaining
32984 regions. For each one, if reading full region results in an errors,
32985 @value{GDBN} will try to read a subset of the region.
32987 In general, every single byte in the region may be readable or not,
32988 and the only way to read every readable byte is to try a read at
32989 every address, which is not practical. Therefore, @value{GDBN} will
32990 attempt to read all accessible bytes at either beginning or the end
32991 of the region, using a binary division scheme. This heuristic works
32992 well for reading accross a memory map boundary. Note that if a region
32993 has a readable range that is neither at the beginning or the end,
32994 @value{GDBN} will not read it.
32996 The result record (@pxref{GDB/MI Result Records}) that is output of
32997 the command includes a field named @samp{memory} whose content is a
32998 list of tuples. Each tuple represent a successfully read memory block
32999 and has the following fields:
33003 The start address of the memory block, as hexadecimal literal.
33006 The end address of the memory block, as hexadecimal literal.
33009 The offset of the memory block, as hexadecimal literal, relative to
33010 the start address passed to @code{-data-read-memory-bytes}.
33013 The contents of the memory block, in hex.
33019 @subsubheading @value{GDBN} Command
33021 The corresponding @value{GDBN} command is @samp{x}.
33023 @subsubheading Example
33027 -data-read-memory-bytes &a 10
33028 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33030 contents="01000000020000000300"@}]
33035 @subheading The @code{-data-write-memory-bytes} Command
33036 @findex -data-write-memory-bytes
33038 @subsubheading Synopsis
33041 -data-write-memory-bytes @var{address} @var{contents}
33042 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33049 @item @var{address}
33050 An expression specifying the address of the first memory word to be
33051 read. Complex expressions containing embedded white space should be
33052 quoted using the C convention.
33054 @item @var{contents}
33055 The hex-encoded bytes to write.
33058 Optional argument indicating the number of bytes to be written. If @var{count}
33059 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33060 write @var{contents} until it fills @var{count} bytes.
33064 @subsubheading @value{GDBN} Command
33066 There's no corresponding @value{GDBN} command.
33068 @subsubheading Example
33072 -data-write-memory-bytes &a "aabbccdd"
33079 -data-write-memory-bytes &a "aabbccdd" 16e
33084 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33085 @node GDB/MI Tracepoint Commands
33086 @section @sc{gdb/mi} Tracepoint Commands
33088 The commands defined in this section implement MI support for
33089 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33091 @subheading The @code{-trace-find} Command
33092 @findex -trace-find
33094 @subsubheading Synopsis
33097 -trace-find @var{mode} [@var{parameters}@dots{}]
33100 Find a trace frame using criteria defined by @var{mode} and
33101 @var{parameters}. The following table lists permissible
33102 modes and their parameters. For details of operation, see @ref{tfind}.
33107 No parameters are required. Stops examining trace frames.
33110 An integer is required as parameter. Selects tracepoint frame with
33113 @item tracepoint-number
33114 An integer is required as parameter. Finds next
33115 trace frame that corresponds to tracepoint with the specified number.
33118 An address is required as parameter. Finds
33119 next trace frame that corresponds to any tracepoint at the specified
33122 @item pc-inside-range
33123 Two addresses are required as parameters. Finds next trace
33124 frame that corresponds to a tracepoint at an address inside the
33125 specified range. Both bounds are considered to be inside the range.
33127 @item pc-outside-range
33128 Two addresses are required as parameters. Finds
33129 next trace frame that corresponds to a tracepoint at an address outside
33130 the specified range. Both bounds are considered to be inside the range.
33133 Line specification is required as parameter. @xref{Specify Location}.
33134 Finds next trace frame that corresponds to a tracepoint at
33135 the specified location.
33139 If @samp{none} was passed as @var{mode}, the response does not
33140 have fields. Otherwise, the response may have the following fields:
33144 This field has either @samp{0} or @samp{1} as the value, depending
33145 on whether a matching tracepoint was found.
33148 The index of the found traceframe. This field is present iff
33149 the @samp{found} field has value of @samp{1}.
33152 The index of the found tracepoint. This field is present iff
33153 the @samp{found} field has value of @samp{1}.
33156 The information about the frame corresponding to the found trace
33157 frame. This field is present only if a trace frame was found.
33158 @xref{GDB/MI Frame Information}, for description of this field.
33162 @subsubheading @value{GDBN} Command
33164 The corresponding @value{GDBN} command is @samp{tfind}.
33166 @subheading -trace-define-variable
33167 @findex -trace-define-variable
33169 @subsubheading Synopsis
33172 -trace-define-variable @var{name} [ @var{value} ]
33175 Create trace variable @var{name} if it does not exist. If
33176 @var{value} is specified, sets the initial value of the specified
33177 trace variable to that value. Note that the @var{name} should start
33178 with the @samp{$} character.
33180 @subsubheading @value{GDBN} Command
33182 The corresponding @value{GDBN} command is @samp{tvariable}.
33184 @subheading The @code{-trace-frame-collected} Command
33185 @findex -trace-frame-collected
33187 @subsubheading Synopsis
33190 -trace-frame-collected
33191 [--var-print-values @var{var_pval}]
33192 [--comp-print-values @var{comp_pval}]
33193 [--registers-format @var{regformat}]
33194 [--memory-contents]
33197 This command returns the set of collected objects, register names,
33198 trace state variable names, memory ranges and computed expressions
33199 that have been collected at a particular trace frame. The optional
33200 parameters to the command affect the output format in different ways.
33201 See the output description table below for more details.
33203 The reported names can be used in the normal manner to create
33204 varobjs and inspect the objects themselves. The items returned by
33205 this command are categorized so that it is clear which is a variable,
33206 which is a register, which is a trace state variable, which is a
33207 memory range and which is a computed expression.
33209 For instance, if the actions were
33211 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33212 collect *(int*)0xaf02bef0@@40
33216 the object collected in its entirety would be @code{myVar}. The
33217 object @code{myArray} would be partially collected, because only the
33218 element at index @code{myIndex} would be collected. The remaining
33219 objects would be computed expressions.
33221 An example output would be:
33225 -trace-frame-collected
33227 explicit-variables=[@{name="myVar",value="1"@}],
33228 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33229 @{name="myObj.field",value="0"@},
33230 @{name="myPtr->field",value="1"@},
33231 @{name="myCount + 2",value="3"@},
33232 @{name="$tvar1 + 1",value="43970027"@}],
33233 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33234 @{number="1",value="0x0"@},
33235 @{number="2",value="0x4"@},
33237 @{number="125",value="0x0"@}],
33238 tvars=[@{name="$tvar1",current="43970026"@}],
33239 memory=[@{address="0x0000000000602264",length="4"@},
33240 @{address="0x0000000000615bc0",length="4"@}]
33247 @item explicit-variables
33248 The set of objects that have been collected in their entirety (as
33249 opposed to collecting just a few elements of an array or a few struct
33250 members). For each object, its name and value are printed.
33251 The @code{--var-print-values} option affects how or whether the value
33252 field is output. If @var{var_pval} is 0, then print only the names;
33253 if it is 1, print also their values; and if it is 2, print the name,
33254 type and value for simple data types, and the name and type for
33255 arrays, structures and unions.
33257 @item computed-expressions
33258 The set of computed expressions that have been collected at the
33259 current trace frame. The @code{--comp-print-values} option affects
33260 this set like the @code{--var-print-values} option affects the
33261 @code{explicit-variables} set. See above.
33264 The registers that have been collected at the current trace frame.
33265 For each register collected, the name and current value are returned.
33266 The value is formatted according to the @code{--registers-format}
33267 option. See the @command{-data-list-register-values} command for a
33268 list of the allowed formats. The default is @samp{x}.
33271 The trace state variables that have been collected at the current
33272 trace frame. For each trace state variable collected, the name and
33273 current value are returned.
33276 The set of memory ranges that have been collected at the current trace
33277 frame. Its content is a list of tuples. Each tuple represents a
33278 collected memory range and has the following fields:
33282 The start address of the memory range, as hexadecimal literal.
33285 The length of the memory range, as decimal literal.
33288 The contents of the memory block, in hex. This field is only present
33289 if the @code{--memory-contents} option is specified.
33295 @subsubheading @value{GDBN} Command
33297 There is no corresponding @value{GDBN} command.
33299 @subsubheading Example
33301 @subheading -trace-list-variables
33302 @findex -trace-list-variables
33304 @subsubheading Synopsis
33307 -trace-list-variables
33310 Return a table of all defined trace variables. Each element of the
33311 table has the following fields:
33315 The name of the trace variable. This field is always present.
33318 The initial value. This is a 64-bit signed integer. This
33319 field is always present.
33322 The value the trace variable has at the moment. This is a 64-bit
33323 signed integer. This field is absent iff current value is
33324 not defined, for example if the trace was never run, or is
33329 @subsubheading @value{GDBN} Command
33331 The corresponding @value{GDBN} command is @samp{tvariables}.
33333 @subsubheading Example
33337 -trace-list-variables
33338 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33339 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33340 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33341 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33342 body=[variable=@{name="$trace_timestamp",initial="0"@}
33343 variable=@{name="$foo",initial="10",current="15"@}]@}
33347 @subheading -trace-save
33348 @findex -trace-save
33350 @subsubheading Synopsis
33353 -trace-save [-r ] @var{filename}
33356 Saves the collected trace data to @var{filename}. Without the
33357 @samp{-r} option, the data is downloaded from the target and saved
33358 in a local file. With the @samp{-r} option the target is asked
33359 to perform the save.
33361 @subsubheading @value{GDBN} Command
33363 The corresponding @value{GDBN} command is @samp{tsave}.
33366 @subheading -trace-start
33367 @findex -trace-start
33369 @subsubheading Synopsis
33375 Starts a tracing experiments. The result of this command does not
33378 @subsubheading @value{GDBN} Command
33380 The corresponding @value{GDBN} command is @samp{tstart}.
33382 @subheading -trace-status
33383 @findex -trace-status
33385 @subsubheading Synopsis
33391 Obtains the status of a tracing experiment. The result may include
33392 the following fields:
33397 May have a value of either @samp{0}, when no tracing operations are
33398 supported, @samp{1}, when all tracing operations are supported, or
33399 @samp{file} when examining trace file. In the latter case, examining
33400 of trace frame is possible but new tracing experiement cannot be
33401 started. This field is always present.
33404 May have a value of either @samp{0} or @samp{1} depending on whether
33405 tracing experiement is in progress on target. This field is present
33406 if @samp{supported} field is not @samp{0}.
33409 Report the reason why the tracing was stopped last time. This field
33410 may be absent iff tracing was never stopped on target yet. The
33411 value of @samp{request} means the tracing was stopped as result of
33412 the @code{-trace-stop} command. The value of @samp{overflow} means
33413 the tracing buffer is full. The value of @samp{disconnection} means
33414 tracing was automatically stopped when @value{GDBN} has disconnected.
33415 The value of @samp{passcount} means tracing was stopped when a
33416 tracepoint was passed a maximal number of times for that tracepoint.
33417 This field is present if @samp{supported} field is not @samp{0}.
33419 @item stopping-tracepoint
33420 The number of tracepoint whose passcount as exceeded. This field is
33421 present iff the @samp{stop-reason} field has the value of
33425 @itemx frames-created
33426 The @samp{frames} field is a count of the total number of trace frames
33427 in the trace buffer, while @samp{frames-created} is the total created
33428 during the run, including ones that were discarded, such as when a
33429 circular trace buffer filled up. Both fields are optional.
33433 These fields tell the current size of the tracing buffer and the
33434 remaining space. These fields are optional.
33437 The value of the circular trace buffer flag. @code{1} means that the
33438 trace buffer is circular and old trace frames will be discarded if
33439 necessary to make room, @code{0} means that the trace buffer is linear
33443 The value of the disconnected tracing flag. @code{1} means that
33444 tracing will continue after @value{GDBN} disconnects, @code{0} means
33445 that the trace run will stop.
33448 The filename of the trace file being examined. This field is
33449 optional, and only present when examining a trace file.
33453 @subsubheading @value{GDBN} Command
33455 The corresponding @value{GDBN} command is @samp{tstatus}.
33457 @subheading -trace-stop
33458 @findex -trace-stop
33460 @subsubheading Synopsis
33466 Stops a tracing experiment. The result of this command has the same
33467 fields as @code{-trace-status}, except that the @samp{supported} and
33468 @samp{running} fields are not output.
33470 @subsubheading @value{GDBN} Command
33472 The corresponding @value{GDBN} command is @samp{tstop}.
33475 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33476 @node GDB/MI Symbol Query
33477 @section @sc{gdb/mi} Symbol Query Commands
33481 @subheading The @code{-symbol-info-address} Command
33482 @findex -symbol-info-address
33484 @subsubheading Synopsis
33487 -symbol-info-address @var{symbol}
33490 Describe where @var{symbol} is stored.
33492 @subsubheading @value{GDBN} Command
33494 The corresponding @value{GDBN} command is @samp{info address}.
33496 @subsubheading Example
33500 @subheading The @code{-symbol-info-file} Command
33501 @findex -symbol-info-file
33503 @subsubheading Synopsis
33509 Show the file for the symbol.
33511 @subsubheading @value{GDBN} Command
33513 There's no equivalent @value{GDBN} command. @code{gdbtk} has
33514 @samp{gdb_find_file}.
33516 @subsubheading Example
33520 @subheading The @code{-symbol-info-function} Command
33521 @findex -symbol-info-function
33523 @subsubheading Synopsis
33526 -symbol-info-function
33529 Show which function the symbol lives in.
33531 @subsubheading @value{GDBN} Command
33533 @samp{gdb_get_function} in @code{gdbtk}.
33535 @subsubheading Example
33539 @subheading The @code{-symbol-info-line} Command
33540 @findex -symbol-info-line
33542 @subsubheading Synopsis
33548 Show the core addresses of the code for a source line.
33550 @subsubheading @value{GDBN} Command
33552 The corresponding @value{GDBN} command is @samp{info line}.
33553 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
33555 @subsubheading Example
33559 @subheading The @code{-symbol-info-symbol} Command
33560 @findex -symbol-info-symbol
33562 @subsubheading Synopsis
33565 -symbol-info-symbol @var{addr}
33568 Describe what symbol is at location @var{addr}.
33570 @subsubheading @value{GDBN} Command
33572 The corresponding @value{GDBN} command is @samp{info symbol}.
33574 @subsubheading Example
33578 @subheading The @code{-symbol-list-functions} Command
33579 @findex -symbol-list-functions
33581 @subsubheading Synopsis
33584 -symbol-list-functions
33587 List the functions in the executable.
33589 @subsubheading @value{GDBN} Command
33591 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
33592 @samp{gdb_search} in @code{gdbtk}.
33594 @subsubheading Example
33599 @subheading The @code{-symbol-list-lines} Command
33600 @findex -symbol-list-lines
33602 @subsubheading Synopsis
33605 -symbol-list-lines @var{filename}
33608 Print the list of lines that contain code and their associated program
33609 addresses for the given source filename. The entries are sorted in
33610 ascending PC order.
33612 @subsubheading @value{GDBN} Command
33614 There is no corresponding @value{GDBN} command.
33616 @subsubheading Example
33619 -symbol-list-lines basics.c
33620 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
33626 @subheading The @code{-symbol-list-types} Command
33627 @findex -symbol-list-types
33629 @subsubheading Synopsis
33635 List all the type names.
33637 @subsubheading @value{GDBN} Command
33639 The corresponding commands are @samp{info types} in @value{GDBN},
33640 @samp{gdb_search} in @code{gdbtk}.
33642 @subsubheading Example
33646 @subheading The @code{-symbol-list-variables} Command
33647 @findex -symbol-list-variables
33649 @subsubheading Synopsis
33652 -symbol-list-variables
33655 List all the global and static variable names.
33657 @subsubheading @value{GDBN} Command
33659 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
33661 @subsubheading Example
33665 @subheading The @code{-symbol-locate} Command
33666 @findex -symbol-locate
33668 @subsubheading Synopsis
33674 @subsubheading @value{GDBN} Command
33676 @samp{gdb_loc} in @code{gdbtk}.
33678 @subsubheading Example
33682 @subheading The @code{-symbol-type} Command
33683 @findex -symbol-type
33685 @subsubheading Synopsis
33688 -symbol-type @var{variable}
33691 Show type of @var{variable}.
33693 @subsubheading @value{GDBN} Command
33695 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33696 @samp{gdb_obj_variable}.
33698 @subsubheading Example
33703 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33704 @node GDB/MI File Commands
33705 @section @sc{gdb/mi} File Commands
33707 This section describes the GDB/MI commands to specify executable file names
33708 and to read in and obtain symbol table information.
33710 @subheading The @code{-file-exec-and-symbols} Command
33711 @findex -file-exec-and-symbols
33713 @subsubheading Synopsis
33716 -file-exec-and-symbols @var{file}
33719 Specify the executable file to be debugged. This file is the one from
33720 which the symbol table is also read. If no file is specified, the
33721 command clears the executable and symbol information. If breakpoints
33722 are set when using this command with no arguments, @value{GDBN} will produce
33723 error messages. Otherwise, no output is produced, except a completion
33726 @subsubheading @value{GDBN} Command
33728 The corresponding @value{GDBN} command is @samp{file}.
33730 @subsubheading Example
33734 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33740 @subheading The @code{-file-exec-file} Command
33741 @findex -file-exec-file
33743 @subsubheading Synopsis
33746 -file-exec-file @var{file}
33749 Specify the executable file to be debugged. Unlike
33750 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
33751 from this file. If used without argument, @value{GDBN} clears the information
33752 about the executable file. No output is produced, except a completion
33755 @subsubheading @value{GDBN} Command
33757 The corresponding @value{GDBN} command is @samp{exec-file}.
33759 @subsubheading Example
33763 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33770 @subheading The @code{-file-list-exec-sections} Command
33771 @findex -file-list-exec-sections
33773 @subsubheading Synopsis
33776 -file-list-exec-sections
33779 List the sections of the current executable file.
33781 @subsubheading @value{GDBN} Command
33783 The @value{GDBN} command @samp{info file} shows, among the rest, the same
33784 information as this command. @code{gdbtk} has a corresponding command
33785 @samp{gdb_load_info}.
33787 @subsubheading Example
33792 @subheading The @code{-file-list-exec-source-file} Command
33793 @findex -file-list-exec-source-file
33795 @subsubheading Synopsis
33798 -file-list-exec-source-file
33801 List the line number, the current source file, and the absolute path
33802 to the current source file for the current executable. The macro
33803 information field has a value of @samp{1} or @samp{0} depending on
33804 whether or not the file includes preprocessor macro information.
33806 @subsubheading @value{GDBN} Command
33808 The @value{GDBN} equivalent is @samp{info source}
33810 @subsubheading Example
33814 123-file-list-exec-source-file
33815 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
33820 @subheading The @code{-file-list-exec-source-files} Command
33821 @findex -file-list-exec-source-files
33823 @subsubheading Synopsis
33826 -file-list-exec-source-files
33829 List the source files for the current executable.
33831 It will always output both the filename and fullname (absolute file
33832 name) of a source file.
33834 @subsubheading @value{GDBN} Command
33836 The @value{GDBN} equivalent is @samp{info sources}.
33837 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
33839 @subsubheading Example
33842 -file-list-exec-source-files
33844 @{file=foo.c,fullname=/home/foo.c@},
33845 @{file=/home/bar.c,fullname=/home/bar.c@},
33846 @{file=gdb_could_not_find_fullpath.c@}]
33851 @subheading The @code{-file-list-shared-libraries} Command
33852 @findex -file-list-shared-libraries
33854 @subsubheading Synopsis
33857 -file-list-shared-libraries
33860 List the shared libraries in the program.
33862 @subsubheading @value{GDBN} Command
33864 The corresponding @value{GDBN} command is @samp{info shared}.
33866 @subsubheading Example
33870 @subheading The @code{-file-list-symbol-files} Command
33871 @findex -file-list-symbol-files
33873 @subsubheading Synopsis
33876 -file-list-symbol-files
33881 @subsubheading @value{GDBN} Command
33883 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33885 @subsubheading Example
33890 @subheading The @code{-file-symbol-file} Command
33891 @findex -file-symbol-file
33893 @subsubheading Synopsis
33896 -file-symbol-file @var{file}
33899 Read symbol table info from the specified @var{file} argument. When
33900 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33901 produced, except for a completion notification.
33903 @subsubheading @value{GDBN} Command
33905 The corresponding @value{GDBN} command is @samp{symbol-file}.
33907 @subsubheading Example
33911 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33917 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33918 @node GDB/MI Memory Overlay Commands
33919 @section @sc{gdb/mi} Memory Overlay Commands
33921 The memory overlay commands are not implemented.
33923 @c @subheading -overlay-auto
33925 @c @subheading -overlay-list-mapping-state
33927 @c @subheading -overlay-list-overlays
33929 @c @subheading -overlay-map
33931 @c @subheading -overlay-off
33933 @c @subheading -overlay-on
33935 @c @subheading -overlay-unmap
33937 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33938 @node GDB/MI Signal Handling Commands
33939 @section @sc{gdb/mi} Signal Handling Commands
33941 Signal handling commands are not implemented.
33943 @c @subheading -signal-handle
33945 @c @subheading -signal-list-handle-actions
33947 @c @subheading -signal-list-signal-types
33951 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33952 @node GDB/MI Target Manipulation
33953 @section @sc{gdb/mi} Target Manipulation Commands
33956 @subheading The @code{-target-attach} Command
33957 @findex -target-attach
33959 @subsubheading Synopsis
33962 -target-attach @var{pid} | @var{gid} | @var{file}
33965 Attach to a process @var{pid} or a file @var{file} outside of
33966 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
33967 group, the id previously returned by
33968 @samp{-list-thread-groups --available} must be used.
33970 @subsubheading @value{GDBN} Command
33972 The corresponding @value{GDBN} command is @samp{attach}.
33974 @subsubheading Example
33978 =thread-created,id="1"
33979 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
33985 @subheading The @code{-target-compare-sections} Command
33986 @findex -target-compare-sections
33988 @subsubheading Synopsis
33991 -target-compare-sections [ @var{section} ]
33994 Compare data of section @var{section} on target to the exec file.
33995 Without the argument, all sections are compared.
33997 @subsubheading @value{GDBN} Command
33999 The @value{GDBN} equivalent is @samp{compare-sections}.
34001 @subsubheading Example
34006 @subheading The @code{-target-detach} Command
34007 @findex -target-detach
34009 @subsubheading Synopsis
34012 -target-detach [ @var{pid} | @var{gid} ]
34015 Detach from the remote target which normally resumes its execution.
34016 If either @var{pid} or @var{gid} is specified, detaches from either
34017 the specified process, or specified thread group. There's no output.
34019 @subsubheading @value{GDBN} Command
34021 The corresponding @value{GDBN} command is @samp{detach}.
34023 @subsubheading Example
34033 @subheading The @code{-target-disconnect} Command
34034 @findex -target-disconnect
34036 @subsubheading Synopsis
34042 Disconnect from the remote target. There's no output and the target is
34043 generally not resumed.
34045 @subsubheading @value{GDBN} Command
34047 The corresponding @value{GDBN} command is @samp{disconnect}.
34049 @subsubheading Example
34059 @subheading The @code{-target-download} Command
34060 @findex -target-download
34062 @subsubheading Synopsis
34068 Loads the executable onto the remote target.
34069 It prints out an update message every half second, which includes the fields:
34073 The name of the section.
34075 The size of what has been sent so far for that section.
34077 The size of the section.
34079 The total size of what was sent so far (the current and the previous sections).
34081 The size of the overall executable to download.
34085 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34086 @sc{gdb/mi} Output Syntax}).
34088 In addition, it prints the name and size of the sections, as they are
34089 downloaded. These messages include the following fields:
34093 The name of the section.
34095 The size of the section.
34097 The size of the overall executable to download.
34101 At the end, a summary is printed.
34103 @subsubheading @value{GDBN} Command
34105 The corresponding @value{GDBN} command is @samp{load}.
34107 @subsubheading Example
34109 Note: each status message appears on a single line. Here the messages
34110 have been broken down so that they can fit onto a page.
34115 +download,@{section=".text",section-size="6668",total-size="9880"@}
34116 +download,@{section=".text",section-sent="512",section-size="6668",
34117 total-sent="512",total-size="9880"@}
34118 +download,@{section=".text",section-sent="1024",section-size="6668",
34119 total-sent="1024",total-size="9880"@}
34120 +download,@{section=".text",section-sent="1536",section-size="6668",
34121 total-sent="1536",total-size="9880"@}
34122 +download,@{section=".text",section-sent="2048",section-size="6668",
34123 total-sent="2048",total-size="9880"@}
34124 +download,@{section=".text",section-sent="2560",section-size="6668",
34125 total-sent="2560",total-size="9880"@}
34126 +download,@{section=".text",section-sent="3072",section-size="6668",
34127 total-sent="3072",total-size="9880"@}
34128 +download,@{section=".text",section-sent="3584",section-size="6668",
34129 total-sent="3584",total-size="9880"@}
34130 +download,@{section=".text",section-sent="4096",section-size="6668",
34131 total-sent="4096",total-size="9880"@}
34132 +download,@{section=".text",section-sent="4608",section-size="6668",
34133 total-sent="4608",total-size="9880"@}
34134 +download,@{section=".text",section-sent="5120",section-size="6668",
34135 total-sent="5120",total-size="9880"@}
34136 +download,@{section=".text",section-sent="5632",section-size="6668",
34137 total-sent="5632",total-size="9880"@}
34138 +download,@{section=".text",section-sent="6144",section-size="6668",
34139 total-sent="6144",total-size="9880"@}
34140 +download,@{section=".text",section-sent="6656",section-size="6668",
34141 total-sent="6656",total-size="9880"@}
34142 +download,@{section=".init",section-size="28",total-size="9880"@}
34143 +download,@{section=".fini",section-size="28",total-size="9880"@}
34144 +download,@{section=".data",section-size="3156",total-size="9880"@}
34145 +download,@{section=".data",section-sent="512",section-size="3156",
34146 total-sent="7236",total-size="9880"@}
34147 +download,@{section=".data",section-sent="1024",section-size="3156",
34148 total-sent="7748",total-size="9880"@}
34149 +download,@{section=".data",section-sent="1536",section-size="3156",
34150 total-sent="8260",total-size="9880"@}
34151 +download,@{section=".data",section-sent="2048",section-size="3156",
34152 total-sent="8772",total-size="9880"@}
34153 +download,@{section=".data",section-sent="2560",section-size="3156",
34154 total-sent="9284",total-size="9880"@}
34155 +download,@{section=".data",section-sent="3072",section-size="3156",
34156 total-sent="9796",total-size="9880"@}
34157 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34164 @subheading The @code{-target-exec-status} Command
34165 @findex -target-exec-status
34167 @subsubheading Synopsis
34170 -target-exec-status
34173 Provide information on the state of the target (whether it is running or
34174 not, for instance).
34176 @subsubheading @value{GDBN} Command
34178 There's no equivalent @value{GDBN} command.
34180 @subsubheading Example
34184 @subheading The @code{-target-list-available-targets} Command
34185 @findex -target-list-available-targets
34187 @subsubheading Synopsis
34190 -target-list-available-targets
34193 List the possible targets to connect to.
34195 @subsubheading @value{GDBN} Command
34197 The corresponding @value{GDBN} command is @samp{help target}.
34199 @subsubheading Example
34203 @subheading The @code{-target-list-current-targets} Command
34204 @findex -target-list-current-targets
34206 @subsubheading Synopsis
34209 -target-list-current-targets
34212 Describe the current target.
34214 @subsubheading @value{GDBN} Command
34216 The corresponding information is printed by @samp{info file} (among
34219 @subsubheading Example
34223 @subheading The @code{-target-list-parameters} Command
34224 @findex -target-list-parameters
34226 @subsubheading Synopsis
34229 -target-list-parameters
34235 @subsubheading @value{GDBN} Command
34239 @subsubheading Example
34243 @subheading The @code{-target-select} Command
34244 @findex -target-select
34246 @subsubheading Synopsis
34249 -target-select @var{type} @var{parameters @dots{}}
34252 Connect @value{GDBN} to the remote target. This command takes two args:
34256 The type of target, for instance @samp{remote}, etc.
34257 @item @var{parameters}
34258 Device names, host names and the like. @xref{Target Commands, ,
34259 Commands for Managing Targets}, for more details.
34262 The output is a connection notification, followed by the address at
34263 which the target program is, in the following form:
34266 ^connected,addr="@var{address}",func="@var{function name}",
34267 args=[@var{arg list}]
34270 @subsubheading @value{GDBN} Command
34272 The corresponding @value{GDBN} command is @samp{target}.
34274 @subsubheading Example
34278 -target-select remote /dev/ttya
34279 ^connected,addr="0xfe00a300",func="??",args=[]
34283 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34284 @node GDB/MI File Transfer Commands
34285 @section @sc{gdb/mi} File Transfer Commands
34288 @subheading The @code{-target-file-put} Command
34289 @findex -target-file-put
34291 @subsubheading Synopsis
34294 -target-file-put @var{hostfile} @var{targetfile}
34297 Copy file @var{hostfile} from the host system (the machine running
34298 @value{GDBN}) to @var{targetfile} on the target system.
34300 @subsubheading @value{GDBN} Command
34302 The corresponding @value{GDBN} command is @samp{remote put}.
34304 @subsubheading Example
34308 -target-file-put localfile remotefile
34314 @subheading The @code{-target-file-get} Command
34315 @findex -target-file-get
34317 @subsubheading Synopsis
34320 -target-file-get @var{targetfile} @var{hostfile}
34323 Copy file @var{targetfile} from the target system to @var{hostfile}
34324 on the host system.
34326 @subsubheading @value{GDBN} Command
34328 The corresponding @value{GDBN} command is @samp{remote get}.
34330 @subsubheading Example
34334 -target-file-get remotefile localfile
34340 @subheading The @code{-target-file-delete} Command
34341 @findex -target-file-delete
34343 @subsubheading Synopsis
34346 -target-file-delete @var{targetfile}
34349 Delete @var{targetfile} from the target system.
34351 @subsubheading @value{GDBN} Command
34353 The corresponding @value{GDBN} command is @samp{remote delete}.
34355 @subsubheading Example
34359 -target-file-delete remotefile
34365 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34366 @node GDB/MI Miscellaneous Commands
34367 @section Miscellaneous @sc{gdb/mi} Commands
34369 @c @subheading -gdb-complete
34371 @subheading The @code{-gdb-exit} Command
34374 @subsubheading Synopsis
34380 Exit @value{GDBN} immediately.
34382 @subsubheading @value{GDBN} Command
34384 Approximately corresponds to @samp{quit}.
34386 @subsubheading Example
34396 @subheading The @code{-exec-abort} Command
34397 @findex -exec-abort
34399 @subsubheading Synopsis
34405 Kill the inferior running program.
34407 @subsubheading @value{GDBN} Command
34409 The corresponding @value{GDBN} command is @samp{kill}.
34411 @subsubheading Example
34416 @subheading The @code{-gdb-set} Command
34419 @subsubheading Synopsis
34425 Set an internal @value{GDBN} variable.
34426 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34428 @subsubheading @value{GDBN} Command
34430 The corresponding @value{GDBN} command is @samp{set}.
34432 @subsubheading Example
34442 @subheading The @code{-gdb-show} Command
34445 @subsubheading Synopsis
34451 Show the current value of a @value{GDBN} variable.
34453 @subsubheading @value{GDBN} Command
34455 The corresponding @value{GDBN} command is @samp{show}.
34457 @subsubheading Example
34466 @c @subheading -gdb-source
34469 @subheading The @code{-gdb-version} Command
34470 @findex -gdb-version
34472 @subsubheading Synopsis
34478 Show version information for @value{GDBN}. Used mostly in testing.
34480 @subsubheading @value{GDBN} Command
34482 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34483 default shows this information when you start an interactive session.
34485 @subsubheading Example
34487 @c This example modifies the actual output from GDB to avoid overfull
34493 ~Copyright 2000 Free Software Foundation, Inc.
34494 ~GDB is free software, covered by the GNU General Public License, and
34495 ~you are welcome to change it and/or distribute copies of it under
34496 ~ certain conditions.
34497 ~Type "show copying" to see the conditions.
34498 ~There is absolutely no warranty for GDB. Type "show warranty" for
34500 ~This GDB was configured as
34501 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34506 @subheading The @code{-list-features} Command
34507 @findex -list-features
34509 Returns a list of particular features of the MI protocol that
34510 this version of gdb implements. A feature can be a command,
34511 or a new field in an output of some command, or even an
34512 important bugfix. While a frontend can sometimes detect presence
34513 of a feature at runtime, it is easier to perform detection at debugger
34516 The command returns a list of strings, with each string naming an
34517 available feature. Each returned string is just a name, it does not
34518 have any internal structure. The list of possible feature names
34524 (gdb) -list-features
34525 ^done,result=["feature1","feature2"]
34528 The current list of features is:
34531 @item frozen-varobjs
34532 Indicates support for the @code{-var-set-frozen} command, as well
34533 as possible presense of the @code{frozen} field in the output
34534 of @code{-varobj-create}.
34535 @item pending-breakpoints
34536 Indicates support for the @option{-f} option to the @code{-break-insert}
34539 Indicates Python scripting support, Python-based
34540 pretty-printing commands, and possible presence of the
34541 @samp{display_hint} field in the output of @code{-var-list-children}
34543 Indicates support for the @code{-thread-info} command.
34544 @item data-read-memory-bytes
34545 Indicates support for the @code{-data-read-memory-bytes} and the
34546 @code{-data-write-memory-bytes} commands.
34547 @item breakpoint-notifications
34548 Indicates that changes to breakpoints and breakpoints created via the
34549 CLI will be announced via async records.
34550 @item ada-task-info
34551 Indicates support for the @code{-ada-task-info} command.
34554 @subheading The @code{-list-target-features} Command
34555 @findex -list-target-features
34557 Returns a list of particular features that are supported by the
34558 target. Those features affect the permitted MI commands, but
34559 unlike the features reported by the @code{-list-features} command, the
34560 features depend on which target GDB is using at the moment. Whenever
34561 a target can change, due to commands such as @code{-target-select},
34562 @code{-target-attach} or @code{-exec-run}, the list of target features
34563 may change, and the frontend should obtain it again.
34567 (gdb) -list-features
34568 ^done,result=["async"]
34571 The current list of features is:
34575 Indicates that the target is capable of asynchronous command
34576 execution, which means that @value{GDBN} will accept further commands
34577 while the target is running.
34580 Indicates that the target is capable of reverse execution.
34581 @xref{Reverse Execution}, for more information.
34585 @subheading The @code{-list-thread-groups} Command
34586 @findex -list-thread-groups
34588 @subheading Synopsis
34591 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34594 Lists thread groups (@pxref{Thread groups}). When a single thread
34595 group is passed as the argument, lists the children of that group.
34596 When several thread group are passed, lists information about those
34597 thread groups. Without any parameters, lists information about all
34598 top-level thread groups.
34600 Normally, thread groups that are being debugged are reported.
34601 With the @samp{--available} option, @value{GDBN} reports thread groups
34602 available on the target.
34604 The output of this command may have either a @samp{threads} result or
34605 a @samp{groups} result. The @samp{thread} result has a list of tuples
34606 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34607 Information}). The @samp{groups} result has a list of tuples as value,
34608 each tuple describing a thread group. If top-level groups are
34609 requested (that is, no parameter is passed), or when several groups
34610 are passed, the output always has a @samp{groups} result. The format
34611 of the @samp{group} result is described below.
34613 To reduce the number of roundtrips it's possible to list thread groups
34614 together with their children, by passing the @samp{--recurse} option
34615 and the recursion depth. Presently, only recursion depth of 1 is
34616 permitted. If this option is present, then every reported thread group
34617 will also include its children, either as @samp{group} or
34618 @samp{threads} field.
34620 In general, any combination of option and parameters is permitted, with
34621 the following caveats:
34625 When a single thread group is passed, the output will typically
34626 be the @samp{threads} result. Because threads may not contain
34627 anything, the @samp{recurse} option will be ignored.
34630 When the @samp{--available} option is passed, limited information may
34631 be available. In particular, the list of threads of a process might
34632 be inaccessible. Further, specifying specific thread groups might
34633 not give any performance advantage over listing all thread groups.
34634 The frontend should assume that @samp{-list-thread-groups --available}
34635 is always an expensive operation and cache the results.
34639 The @samp{groups} result is a list of tuples, where each tuple may
34640 have the following fields:
34644 Identifier of the thread group. This field is always present.
34645 The identifier is an opaque string; frontends should not try to
34646 convert it to an integer, even though it might look like one.
34649 The type of the thread group. At present, only @samp{process} is a
34653 The target-specific process identifier. This field is only present
34654 for thread groups of type @samp{process} and only if the process exists.
34657 The number of children this thread group has. This field may be
34658 absent for an available thread group.
34661 This field has a list of tuples as value, each tuple describing a
34662 thread. It may be present if the @samp{--recurse} option is
34663 specified, and it's actually possible to obtain the threads.
34666 This field is a list of integers, each identifying a core that one
34667 thread of the group is running on. This field may be absent if
34668 such information is not available.
34671 The name of the executable file that corresponds to this thread group.
34672 The field is only present for thread groups of type @samp{process},
34673 and only if there is a corresponding executable file.
34677 @subheading Example
34681 -list-thread-groups
34682 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
34683 -list-thread-groups 17
34684 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
34685 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
34686 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34687 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34688 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
34689 -list-thread-groups --available
34690 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34691 -list-thread-groups --available --recurse 1
34692 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34693 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34694 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34695 -list-thread-groups --available --recurse 1 17 18
34696 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34697 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34698 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34701 @subheading The @code{-info-os} Command
34704 @subsubheading Synopsis
34707 -info-os [ @var{type} ]
34710 If no argument is supplied, the command returns a table of available
34711 operating-system-specific information types. If one of these types is
34712 supplied as an argument @var{type}, then the command returns a table
34713 of data of that type.
34715 The types of information available depend on the target operating
34718 @subsubheading @value{GDBN} Command
34720 The corresponding @value{GDBN} command is @samp{info os}.
34722 @subsubheading Example
34724 When run on a @sc{gnu}/Linux system, the output will look something
34730 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
34731 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34732 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34733 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34734 body=[item=@{col0="processes",col1="Listing of all processes",
34735 col2="Processes"@},
34736 item=@{col0="procgroups",col1="Listing of all process groups",
34737 col2="Process groups"@},
34738 item=@{col0="threads",col1="Listing of all threads",
34740 item=@{col0="files",col1="Listing of all file descriptors",
34741 col2="File descriptors"@},
34742 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34744 item=@{col0="shm",col1="Listing of all shared-memory regions",
34745 col2="Shared-memory regions"@},
34746 item=@{col0="semaphores",col1="Listing of all semaphores",
34747 col2="Semaphores"@},
34748 item=@{col0="msg",col1="Listing of all message queues",
34749 col2="Message queues"@},
34750 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34751 col2="Kernel modules"@}]@}
34754 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34755 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34756 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34757 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34758 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34759 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34760 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34761 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34763 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34764 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34768 (Note that the MI output here includes a @code{"Title"} column that
34769 does not appear in command-line @code{info os}; this column is useful
34770 for MI clients that want to enumerate the types of data, such as in a
34771 popup menu, but is needless clutter on the command line, and
34772 @code{info os} omits it.)
34774 @subheading The @code{-add-inferior} Command
34775 @findex -add-inferior
34777 @subheading Synopsis
34783 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34784 inferior is not associated with any executable. Such association may
34785 be established with the @samp{-file-exec-and-symbols} command
34786 (@pxref{GDB/MI File Commands}). The command response has a single
34787 field, @samp{inferior}, whose value is the identifier of the
34788 thread group corresponding to the new inferior.
34790 @subheading Example
34795 ^done,inferior="i3"
34798 @subheading The @code{-interpreter-exec} Command
34799 @findex -interpreter-exec
34801 @subheading Synopsis
34804 -interpreter-exec @var{interpreter} @var{command}
34806 @anchor{-interpreter-exec}
34808 Execute the specified @var{command} in the given @var{interpreter}.
34810 @subheading @value{GDBN} Command
34812 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34814 @subheading Example
34818 -interpreter-exec console "break main"
34819 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34820 &"During symbol reading, bad structure-type format.\n"
34821 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34826 @subheading The @code{-inferior-tty-set} Command
34827 @findex -inferior-tty-set
34829 @subheading Synopsis
34832 -inferior-tty-set /dev/pts/1
34835 Set terminal for future runs of the program being debugged.
34837 @subheading @value{GDBN} Command
34839 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34841 @subheading Example
34845 -inferior-tty-set /dev/pts/1
34850 @subheading The @code{-inferior-tty-show} Command
34851 @findex -inferior-tty-show
34853 @subheading Synopsis
34859 Show terminal for future runs of program being debugged.
34861 @subheading @value{GDBN} Command
34863 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34865 @subheading Example
34869 -inferior-tty-set /dev/pts/1
34873 ^done,inferior_tty_terminal="/dev/pts/1"
34877 @subheading The @code{-enable-timings} Command
34878 @findex -enable-timings
34880 @subheading Synopsis
34883 -enable-timings [yes | no]
34886 Toggle the printing of the wallclock, user and system times for an MI
34887 command as a field in its output. This command is to help frontend
34888 developers optimize the performance of their code. No argument is
34889 equivalent to @samp{yes}.
34891 @subheading @value{GDBN} Command
34895 @subheading Example
34903 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34904 addr="0x080484ed",func="main",file="myprog.c",
34905 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34907 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34915 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34916 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34917 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34918 fullname="/home/nickrob/myprog.c",line="73"@}
34923 @chapter @value{GDBN} Annotations
34925 This chapter describes annotations in @value{GDBN}. Annotations were
34926 designed to interface @value{GDBN} to graphical user interfaces or other
34927 similar programs which want to interact with @value{GDBN} at a
34928 relatively high level.
34930 The annotation mechanism has largely been superseded by @sc{gdb/mi}
34934 This is Edition @value{EDITION}, @value{DATE}.
34938 * Annotations Overview:: What annotations are; the general syntax.
34939 * Server Prefix:: Issuing a command without affecting user state.
34940 * Prompting:: Annotations marking @value{GDBN}'s need for input.
34941 * Errors:: Annotations for error messages.
34942 * Invalidation:: Some annotations describe things now invalid.
34943 * Annotations for Running::
34944 Whether the program is running, how it stopped, etc.
34945 * Source Annotations:: Annotations describing source code.
34948 @node Annotations Overview
34949 @section What is an Annotation?
34950 @cindex annotations
34952 Annotations start with a newline character, two @samp{control-z}
34953 characters, and the name of the annotation. If there is no additional
34954 information associated with this annotation, the name of the annotation
34955 is followed immediately by a newline. If there is additional
34956 information, the name of the annotation is followed by a space, the
34957 additional information, and a newline. The additional information
34958 cannot contain newline characters.
34960 Any output not beginning with a newline and two @samp{control-z}
34961 characters denotes literal output from @value{GDBN}. Currently there is
34962 no need for @value{GDBN} to output a newline followed by two
34963 @samp{control-z} characters, but if there was such a need, the
34964 annotations could be extended with an @samp{escape} annotation which
34965 means those three characters as output.
34967 The annotation @var{level}, which is specified using the
34968 @option{--annotate} command line option (@pxref{Mode Options}), controls
34969 how much information @value{GDBN} prints together with its prompt,
34970 values of expressions, source lines, and other types of output. Level 0
34971 is for no annotations, level 1 is for use when @value{GDBN} is run as a
34972 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
34973 for programs that control @value{GDBN}, and level 2 annotations have
34974 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
34975 Interface, annotate, GDB's Obsolete Annotations}).
34978 @kindex set annotate
34979 @item set annotate @var{level}
34980 The @value{GDBN} command @code{set annotate} sets the level of
34981 annotations to the specified @var{level}.
34983 @item show annotate
34984 @kindex show annotate
34985 Show the current annotation level.
34988 This chapter describes level 3 annotations.
34990 A simple example of starting up @value{GDBN} with annotations is:
34993 $ @kbd{gdb --annotate=3}
34995 Copyright 2003 Free Software Foundation, Inc.
34996 GDB is free software, covered by the GNU General Public License,
34997 and you are welcome to change it and/or distribute copies of it
34998 under certain conditions.
34999 Type "show copying" to see the conditions.
35000 There is absolutely no warranty for GDB. Type "show warranty"
35002 This GDB was configured as "i386-pc-linux-gnu"
35013 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35014 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35015 denotes a @samp{control-z} character) are annotations; the rest is
35016 output from @value{GDBN}.
35018 @node Server Prefix
35019 @section The Server Prefix
35020 @cindex server prefix
35022 If you prefix a command with @samp{server } then it will not affect
35023 the command history, nor will it affect @value{GDBN}'s notion of which
35024 command to repeat if @key{RET} is pressed on a line by itself. This
35025 means that commands can be run behind a user's back by a front-end in
35026 a transparent manner.
35028 The @code{server } prefix does not affect the recording of values into
35029 the value history; to print a value without recording it into the
35030 value history, use the @code{output} command instead of the
35031 @code{print} command.
35033 Using this prefix also disables confirmation requests
35034 (@pxref{confirmation requests}).
35037 @section Annotation for @value{GDBN} Input
35039 @cindex annotations for prompts
35040 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35041 to know when to send output, when the output from a given command is
35044 Different kinds of input each have a different @dfn{input type}. Each
35045 input type has three annotations: a @code{pre-} annotation, which
35046 denotes the beginning of any prompt which is being output, a plain
35047 annotation, which denotes the end of the prompt, and then a @code{post-}
35048 annotation which denotes the end of any echo which may (or may not) be
35049 associated with the input. For example, the @code{prompt} input type
35050 features the following annotations:
35058 The input types are
35061 @findex pre-prompt annotation
35062 @findex prompt annotation
35063 @findex post-prompt annotation
35065 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35067 @findex pre-commands annotation
35068 @findex commands annotation
35069 @findex post-commands annotation
35071 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35072 command. The annotations are repeated for each command which is input.
35074 @findex pre-overload-choice annotation
35075 @findex overload-choice annotation
35076 @findex post-overload-choice annotation
35077 @item overload-choice
35078 When @value{GDBN} wants the user to select between various overloaded functions.
35080 @findex pre-query annotation
35081 @findex query annotation
35082 @findex post-query annotation
35084 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35086 @findex pre-prompt-for-continue annotation
35087 @findex prompt-for-continue annotation
35088 @findex post-prompt-for-continue annotation
35089 @item prompt-for-continue
35090 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35091 expect this to work well; instead use @code{set height 0} to disable
35092 prompting. This is because the counting of lines is buggy in the
35093 presence of annotations.
35098 @cindex annotations for errors, warnings and interrupts
35100 @findex quit annotation
35105 This annotation occurs right before @value{GDBN} responds to an interrupt.
35107 @findex error annotation
35112 This annotation occurs right before @value{GDBN} responds to an error.
35114 Quit and error annotations indicate that any annotations which @value{GDBN} was
35115 in the middle of may end abruptly. For example, if a
35116 @code{value-history-begin} annotation is followed by a @code{error}, one
35117 cannot expect to receive the matching @code{value-history-end}. One
35118 cannot expect not to receive it either, however; an error annotation
35119 does not necessarily mean that @value{GDBN} is immediately returning all the way
35122 @findex error-begin annotation
35123 A quit or error annotation may be preceded by
35129 Any output between that and the quit or error annotation is the error
35132 Warning messages are not yet annotated.
35133 @c If we want to change that, need to fix warning(), type_error(),
35134 @c range_error(), and possibly other places.
35137 @section Invalidation Notices
35139 @cindex annotations for invalidation messages
35140 The following annotations say that certain pieces of state may have
35144 @findex frames-invalid annotation
35145 @item ^Z^Zframes-invalid
35147 The frames (for example, output from the @code{backtrace} command) may
35150 @findex breakpoints-invalid annotation
35151 @item ^Z^Zbreakpoints-invalid
35153 The breakpoints may have changed. For example, the user just added or
35154 deleted a breakpoint.
35157 @node Annotations for Running
35158 @section Running the Program
35159 @cindex annotations for running programs
35161 @findex starting annotation
35162 @findex stopping annotation
35163 When the program starts executing due to a @value{GDBN} command such as
35164 @code{step} or @code{continue},
35170 is output. When the program stops,
35176 is output. Before the @code{stopped} annotation, a variety of
35177 annotations describe how the program stopped.
35180 @findex exited annotation
35181 @item ^Z^Zexited @var{exit-status}
35182 The program exited, and @var{exit-status} is the exit status (zero for
35183 successful exit, otherwise nonzero).
35185 @findex signalled annotation
35186 @findex signal-name annotation
35187 @findex signal-name-end annotation
35188 @findex signal-string annotation
35189 @findex signal-string-end annotation
35190 @item ^Z^Zsignalled
35191 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35192 annotation continues:
35198 ^Z^Zsignal-name-end
35202 ^Z^Zsignal-string-end
35207 where @var{name} is the name of the signal, such as @code{SIGILL} or
35208 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35209 as @code{Illegal Instruction} or @code{Segmentation fault}.
35210 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35211 user's benefit and have no particular format.
35213 @findex signal annotation
35215 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35216 just saying that the program received the signal, not that it was
35217 terminated with it.
35219 @findex breakpoint annotation
35220 @item ^Z^Zbreakpoint @var{number}
35221 The program hit breakpoint number @var{number}.
35223 @findex watchpoint annotation
35224 @item ^Z^Zwatchpoint @var{number}
35225 The program hit watchpoint number @var{number}.
35228 @node Source Annotations
35229 @section Displaying Source
35230 @cindex annotations for source display
35232 @findex source annotation
35233 The following annotation is used instead of displaying source code:
35236 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
35239 where @var{filename} is an absolute file name indicating which source
35240 file, @var{line} is the line number within that file (where 1 is the
35241 first line in the file), @var{character} is the character position
35242 within the file (where 0 is the first character in the file) (for most
35243 debug formats this will necessarily point to the beginning of a line),
35244 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
35245 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
35246 @var{addr} is the address in the target program associated with the
35247 source which is being displayed. @var{addr} is in the form @samp{0x}
35248 followed by one or more lowercase hex digits (note that this does not
35249 depend on the language).
35251 @node JIT Interface
35252 @chapter JIT Compilation Interface
35253 @cindex just-in-time compilation
35254 @cindex JIT compilation interface
35256 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
35257 interface. A JIT compiler is a program or library that generates native
35258 executable code at runtime and executes it, usually in order to achieve good
35259 performance while maintaining platform independence.
35261 Programs that use JIT compilation are normally difficult to debug because
35262 portions of their code are generated at runtime, instead of being loaded from
35263 object files, which is where @value{GDBN} normally finds the program's symbols
35264 and debug information. In order to debug programs that use JIT compilation,
35265 @value{GDBN} has an interface that allows the program to register in-memory
35266 symbol files with @value{GDBN} at runtime.
35268 If you are using @value{GDBN} to debug a program that uses this interface, then
35269 it should work transparently so long as you have not stripped the binary. If
35270 you are developing a JIT compiler, then the interface is documented in the rest
35271 of this chapter. At this time, the only known client of this interface is the
35274 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
35275 JIT compiler communicates with @value{GDBN} by writing data into a global
35276 variable and calling a fuction at a well-known symbol. When @value{GDBN}
35277 attaches, it reads a linked list of symbol files from the global variable to
35278 find existing code, and puts a breakpoint in the function so that it can find
35279 out about additional code.
35282 * Declarations:: Relevant C struct declarations
35283 * Registering Code:: Steps to register code
35284 * Unregistering Code:: Steps to unregister code
35285 * Custom Debug Info:: Emit debug information in a custom format
35289 @section JIT Declarations
35291 These are the relevant struct declarations that a C program should include to
35292 implement the interface:
35302 struct jit_code_entry
35304 struct jit_code_entry *next_entry;
35305 struct jit_code_entry *prev_entry;
35306 const char *symfile_addr;
35307 uint64_t symfile_size;
35310 struct jit_descriptor
35313 /* This type should be jit_actions_t, but we use uint32_t
35314 to be explicit about the bitwidth. */
35315 uint32_t action_flag;
35316 struct jit_code_entry *relevant_entry;
35317 struct jit_code_entry *first_entry;
35320 /* GDB puts a breakpoint in this function. */
35321 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
35323 /* Make sure to specify the version statically, because the
35324 debugger may check the version before we can set it. */
35325 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
35328 If the JIT is multi-threaded, then it is important that the JIT synchronize any
35329 modifications to this global data properly, which can easily be done by putting
35330 a global mutex around modifications to these structures.
35332 @node Registering Code
35333 @section Registering Code
35335 To register code with @value{GDBN}, the JIT should follow this protocol:
35339 Generate an object file in memory with symbols and other desired debug
35340 information. The file must include the virtual addresses of the sections.
35343 Create a code entry for the file, which gives the start and size of the symbol
35347 Add it to the linked list in the JIT descriptor.
35350 Point the relevant_entry field of the descriptor at the entry.
35353 Set @code{action_flag} to @code{JIT_REGISTER} and call
35354 @code{__jit_debug_register_code}.
35357 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
35358 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
35359 new code. However, the linked list must still be maintained in order to allow
35360 @value{GDBN} to attach to a running process and still find the symbol files.
35362 @node Unregistering Code
35363 @section Unregistering Code
35365 If code is freed, then the JIT should use the following protocol:
35369 Remove the code entry corresponding to the code from the linked list.
35372 Point the @code{relevant_entry} field of the descriptor at the code entry.
35375 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
35376 @code{__jit_debug_register_code}.
35379 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
35380 and the JIT will leak the memory used for the associated symbol files.
35382 @node Custom Debug Info
35383 @section Custom Debug Info
35384 @cindex custom JIT debug info
35385 @cindex JIT debug info reader
35387 Generating debug information in platform-native file formats (like ELF
35388 or COFF) may be an overkill for JIT compilers; especially if all the
35389 debug info is used for is displaying a meaningful backtrace. The
35390 issue can be resolved by having the JIT writers decide on a debug info
35391 format and also provide a reader that parses the debug info generated
35392 by the JIT compiler. This section gives a brief overview on writing
35393 such a parser. More specific details can be found in the source file
35394 @file{gdb/jit-reader.in}, which is also installed as a header at
35395 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35397 The reader is implemented as a shared object (so this functionality is
35398 not available on platforms which don't allow loading shared objects at
35399 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
35400 @code{jit-reader-unload} are provided, to be used to load and unload
35401 the readers from a preconfigured directory. Once loaded, the shared
35402 object is used the parse the debug information emitted by the JIT
35406 * Using JIT Debug Info Readers:: How to use supplied readers correctly
35407 * Writing JIT Debug Info Readers:: Creating a debug-info reader
35410 @node Using JIT Debug Info Readers
35411 @subsection Using JIT Debug Info Readers
35412 @kindex jit-reader-load
35413 @kindex jit-reader-unload
35415 Readers can be loaded and unloaded using the @code{jit-reader-load}
35416 and @code{jit-reader-unload} commands.
35419 @item jit-reader-load @var{reader}
35420 Load the JIT reader named @var{reader}. @var{reader} is a shared
35421 object specified as either an absolute or a relative file name. In
35422 the latter case, @value{GDBN} will try to load the reader from a
35423 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
35424 system (here @var{libdir} is the system library directory, often
35425 @file{/usr/local/lib}).
35427 Only one reader can be active at a time; trying to load a second
35428 reader when one is already loaded will result in @value{GDBN}
35429 reporting an error. A new JIT reader can be loaded by first unloading
35430 the current one using @code{jit-reader-unload} and then invoking
35431 @code{jit-reader-load}.
35433 @item jit-reader-unload
35434 Unload the currently loaded JIT reader.
35438 @node Writing JIT Debug Info Readers
35439 @subsection Writing JIT Debug Info Readers
35440 @cindex writing JIT debug info readers
35442 As mentioned, a reader is essentially a shared object conforming to a
35443 certain ABI. This ABI is described in @file{jit-reader.h}.
35445 @file{jit-reader.h} defines the structures, macros and functions
35446 required to write a reader. It is installed (along with
35447 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
35448 the system include directory.
35450 Readers need to be released under a GPL compatible license. A reader
35451 can be declared as released under such a license by placing the macro
35452 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
35454 The entry point for readers is the symbol @code{gdb_init_reader},
35455 which is expected to be a function with the prototype
35457 @findex gdb_init_reader
35459 extern struct gdb_reader_funcs *gdb_init_reader (void);
35462 @cindex @code{struct gdb_reader_funcs}
35464 @code{struct gdb_reader_funcs} contains a set of pointers to callback
35465 functions. These functions are executed to read the debug info
35466 generated by the JIT compiler (@code{read}), to unwind stack frames
35467 (@code{unwind}) and to create canonical frame IDs
35468 (@code{get_Frame_id}). It also has a callback that is called when the
35469 reader is being unloaded (@code{destroy}). The struct looks like this
35472 struct gdb_reader_funcs
35474 /* Must be set to GDB_READER_INTERFACE_VERSION. */
35475 int reader_version;
35477 /* For use by the reader. */
35480 gdb_read_debug_info *read;
35481 gdb_unwind_frame *unwind;
35482 gdb_get_frame_id *get_frame_id;
35483 gdb_destroy_reader *destroy;
35487 @cindex @code{struct gdb_symbol_callbacks}
35488 @cindex @code{struct gdb_unwind_callbacks}
35490 The callbacks are provided with another set of callbacks by
35491 @value{GDBN} to do their job. For @code{read}, these callbacks are
35492 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
35493 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
35494 @code{struct gdb_symbol_callbacks} has callbacks to create new object
35495 files and new symbol tables inside those object files. @code{struct
35496 gdb_unwind_callbacks} has callbacks to read registers off the current
35497 frame and to write out the values of the registers in the previous
35498 frame. Both have a callback (@code{target_read}) to read bytes off the
35499 target's address space.
35501 @node In-Process Agent
35502 @chapter In-Process Agent
35503 @cindex debugging agent
35504 The traditional debugging model is conceptually low-speed, but works fine,
35505 because most bugs can be reproduced in debugging-mode execution. However,
35506 as multi-core or many-core processors are becoming mainstream, and
35507 multi-threaded programs become more and more popular, there should be more
35508 and more bugs that only manifest themselves at normal-mode execution, for
35509 example, thread races, because debugger's interference with the program's
35510 timing may conceal the bugs. On the other hand, in some applications,
35511 it is not feasible for the debugger to interrupt the program's execution
35512 long enough for the developer to learn anything helpful about its behavior.
35513 If the program's correctness depends on its real-time behavior, delays
35514 introduced by a debugger might cause the program to fail, even when the
35515 code itself is correct. It is useful to be able to observe the program's
35516 behavior without interrupting it.
35518 Therefore, traditional debugging model is too intrusive to reproduce
35519 some bugs. In order to reduce the interference with the program, we can
35520 reduce the number of operations performed by debugger. The
35521 @dfn{In-Process Agent}, a shared library, is running within the same
35522 process with inferior, and is able to perform some debugging operations
35523 itself. As a result, debugger is only involved when necessary, and
35524 performance of debugging can be improved accordingly. Note that
35525 interference with program can be reduced but can't be removed completely,
35526 because the in-process agent will still stop or slow down the program.
35528 The in-process agent can interpret and execute Agent Expressions
35529 (@pxref{Agent Expressions}) during performing debugging operations. The
35530 agent expressions can be used for different purposes, such as collecting
35531 data in tracepoints, and condition evaluation in breakpoints.
35533 @anchor{Control Agent}
35534 You can control whether the in-process agent is used as an aid for
35535 debugging with the following commands:
35538 @kindex set agent on
35540 Causes the in-process agent to perform some operations on behalf of the
35541 debugger. Just which operations requested by the user will be done
35542 by the in-process agent depends on the its capabilities. For example,
35543 if you request to evaluate breakpoint conditions in the in-process agent,
35544 and the in-process agent has such capability as well, then breakpoint
35545 conditions will be evaluated in the in-process agent.
35547 @kindex set agent off
35548 @item set agent off
35549 Disables execution of debugging operations by the in-process agent. All
35550 of the operations will be performed by @value{GDBN}.
35554 Display the current setting of execution of debugging operations by
35555 the in-process agent.
35559 * In-Process Agent Protocol::
35562 @node In-Process Agent Protocol
35563 @section In-Process Agent Protocol
35564 @cindex in-process agent protocol
35566 The in-process agent is able to communicate with both @value{GDBN} and
35567 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
35568 used for communications between @value{GDBN} or GDBserver and the IPA.
35569 In general, @value{GDBN} or GDBserver sends commands
35570 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
35571 in-process agent replies back with the return result of the command, or
35572 some other information. The data sent to in-process agent is composed
35573 of primitive data types, such as 4-byte or 8-byte type, and composite
35574 types, which are called objects (@pxref{IPA Protocol Objects}).
35577 * IPA Protocol Objects::
35578 * IPA Protocol Commands::
35581 @node IPA Protocol Objects
35582 @subsection IPA Protocol Objects
35583 @cindex ipa protocol objects
35585 The commands sent to and results received from agent may contain some
35586 complex data types called @dfn{objects}.
35588 The in-process agent is running on the same machine with @value{GDBN}
35589 or GDBserver, so it doesn't have to handle as much differences between
35590 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
35591 However, there are still some differences of two ends in two processes:
35595 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
35596 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
35598 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
35599 GDBserver is compiled with one, and in-process agent is compiled with
35603 Here are the IPA Protocol Objects:
35607 agent expression object. It represents an agent expression
35608 (@pxref{Agent Expressions}).
35609 @anchor{agent expression object}
35611 tracepoint action object. It represents a tracepoint action
35612 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
35613 memory, static trace data and to evaluate expression.
35614 @anchor{tracepoint action object}
35616 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
35617 @anchor{tracepoint object}
35621 The following table describes important attributes of each IPA protocol
35624 @multitable @columnfractions .30 .20 .50
35625 @headitem Name @tab Size @tab Description
35626 @item @emph{agent expression object} @tab @tab
35627 @item length @tab 4 @tab length of bytes code
35628 @item byte code @tab @var{length} @tab contents of byte code
35629 @item @emph{tracepoint action for collecting memory} @tab @tab
35630 @item 'M' @tab 1 @tab type of tracepoint action
35631 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
35632 address of the lowest byte to collect, otherwise @var{addr} is the offset
35633 of @var{basereg} for memory collecting.
35634 @item len @tab 8 @tab length of memory for collecting
35635 @item basereg @tab 4 @tab the register number containing the starting
35636 memory address for collecting.
35637 @item @emph{tracepoint action for collecting registers} @tab @tab
35638 @item 'R' @tab 1 @tab type of tracepoint action
35639 @item @emph{tracepoint action for collecting static trace data} @tab @tab
35640 @item 'L' @tab 1 @tab type of tracepoint action
35641 @item @emph{tracepoint action for expression evaluation} @tab @tab
35642 @item 'X' @tab 1 @tab type of tracepoint action
35643 @item agent expression @tab length of @tab @ref{agent expression object}
35644 @item @emph{tracepoint object} @tab @tab
35645 @item number @tab 4 @tab number of tracepoint
35646 @item address @tab 8 @tab address of tracepoint inserted on
35647 @item type @tab 4 @tab type of tracepoint
35648 @item enabled @tab 1 @tab enable or disable of tracepoint
35649 @item step_count @tab 8 @tab step
35650 @item pass_count @tab 8 @tab pass
35651 @item numactions @tab 4 @tab number of tracepoint actions
35652 @item hit count @tab 8 @tab hit count
35653 @item trace frame usage @tab 8 @tab trace frame usage
35654 @item compiled_cond @tab 8 @tab compiled condition
35655 @item orig_size @tab 8 @tab orig size
35656 @item condition @tab 4 if condition is NULL otherwise length of
35657 @ref{agent expression object}
35658 @tab zero if condition is NULL, otherwise is
35659 @ref{agent expression object}
35660 @item actions @tab variable
35661 @tab numactions number of @ref{tracepoint action object}
35664 @node IPA Protocol Commands
35665 @subsection IPA Protocol Commands
35666 @cindex ipa protocol commands
35668 The spaces in each command are delimiters to ease reading this commands
35669 specification. They don't exist in real commands.
35673 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
35674 Installs a new fast tracepoint described by @var{tracepoint_object}
35675 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
35676 head of @dfn{jumppad}, which is used to jump to data collection routine
35681 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
35682 @var{target_address} is address of tracepoint in the inferior.
35683 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
35684 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35685 @var{fjump} contains a sequence of instructions jump to jumppad entry.
35686 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35693 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35694 is about to kill inferiors.
35702 @item probe_marker_at:@var{address}
35703 Asks in-process agent to probe the marker at @var{address}.
35710 @item unprobe_marker_at:@var{address}
35711 Asks in-process agent to unprobe the marker at @var{address}.
35715 @chapter Reporting Bugs in @value{GDBN}
35716 @cindex bugs in @value{GDBN}
35717 @cindex reporting bugs in @value{GDBN}
35719 Your bug reports play an essential role in making @value{GDBN} reliable.
35721 Reporting a bug may help you by bringing a solution to your problem, or it
35722 may not. But in any case the principal function of a bug report is to help
35723 the entire community by making the next version of @value{GDBN} work better. Bug
35724 reports are your contribution to the maintenance of @value{GDBN}.
35726 In order for a bug report to serve its purpose, you must include the
35727 information that enables us to fix the bug.
35730 * Bug Criteria:: Have you found a bug?
35731 * Bug Reporting:: How to report bugs
35735 @section Have You Found a Bug?
35736 @cindex bug criteria
35738 If you are not sure whether you have found a bug, here are some guidelines:
35741 @cindex fatal signal
35742 @cindex debugger crash
35743 @cindex crash of debugger
35745 If the debugger gets a fatal signal, for any input whatever, that is a
35746 @value{GDBN} bug. Reliable debuggers never crash.
35748 @cindex error on valid input
35750 If @value{GDBN} produces an error message for valid input, that is a
35751 bug. (Note that if you're cross debugging, the problem may also be
35752 somewhere in the connection to the target.)
35754 @cindex invalid input
35756 If @value{GDBN} does not produce an error message for invalid input,
35757 that is a bug. However, you should note that your idea of
35758 ``invalid input'' might be our idea of ``an extension'' or ``support
35759 for traditional practice''.
35762 If you are an experienced user of debugging tools, your suggestions
35763 for improvement of @value{GDBN} are welcome in any case.
35766 @node Bug Reporting
35767 @section How to Report Bugs
35768 @cindex bug reports
35769 @cindex @value{GDBN} bugs, reporting
35771 A number of companies and individuals offer support for @sc{gnu} products.
35772 If you obtained @value{GDBN} from a support organization, we recommend you
35773 contact that organization first.
35775 You can find contact information for many support companies and
35776 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35778 @c should add a web page ref...
35781 @ifset BUGURL_DEFAULT
35782 In any event, we also recommend that you submit bug reports for
35783 @value{GDBN}. The preferred method is to submit them directly using
35784 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35785 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35788 @strong{Do not send bug reports to @samp{info-gdb}, or to
35789 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35790 not want to receive bug reports. Those that do have arranged to receive
35793 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35794 serves as a repeater. The mailing list and the newsgroup carry exactly
35795 the same messages. Often people think of posting bug reports to the
35796 newsgroup instead of mailing them. This appears to work, but it has one
35797 problem which can be crucial: a newsgroup posting often lacks a mail
35798 path back to the sender. Thus, if we need to ask for more information,
35799 we may be unable to reach you. For this reason, it is better to send
35800 bug reports to the mailing list.
35802 @ifclear BUGURL_DEFAULT
35803 In any event, we also recommend that you submit bug reports for
35804 @value{GDBN} to @value{BUGURL}.
35808 The fundamental principle of reporting bugs usefully is this:
35809 @strong{report all the facts}. If you are not sure whether to state a
35810 fact or leave it out, state it!
35812 Often people omit facts because they think they know what causes the
35813 problem and assume that some details do not matter. Thus, you might
35814 assume that the name of the variable you use in an example does not matter.
35815 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35816 stray memory reference which happens to fetch from the location where that
35817 name is stored in memory; perhaps, if the name were different, the contents
35818 of that location would fool the debugger into doing the right thing despite
35819 the bug. Play it safe and give a specific, complete example. That is the
35820 easiest thing for you to do, and the most helpful.
35822 Keep in mind that the purpose of a bug report is to enable us to fix the
35823 bug. It may be that the bug has been reported previously, but neither
35824 you nor we can know that unless your bug report is complete and
35827 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35828 bell?'' Those bug reports are useless, and we urge everyone to
35829 @emph{refuse to respond to them} except to chide the sender to report
35832 To enable us to fix the bug, you should include all these things:
35836 The version of @value{GDBN}. @value{GDBN} announces it if you start
35837 with no arguments; you can also print it at any time using @code{show
35840 Without this, we will not know whether there is any point in looking for
35841 the bug in the current version of @value{GDBN}.
35844 The type of machine you are using, and the operating system name and
35848 The details of the @value{GDBN} build-time configuration.
35849 @value{GDBN} shows these details if you invoke it with the
35850 @option{--configuration} command-line option, or if you type
35851 @code{show configuration} at @value{GDBN}'s prompt.
35854 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35855 ``@value{GCC}--2.8.1''.
35858 What compiler (and its version) was used to compile the program you are
35859 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35860 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35861 to get this information; for other compilers, see the documentation for
35865 The command arguments you gave the compiler to compile your example and
35866 observe the bug. For example, did you use @samp{-O}? To guarantee
35867 you will not omit something important, list them all. A copy of the
35868 Makefile (or the output from make) is sufficient.
35870 If we were to try to guess the arguments, we would probably guess wrong
35871 and then we might not encounter the bug.
35874 A complete input script, and all necessary source files, that will
35878 A description of what behavior you observe that you believe is
35879 incorrect. For example, ``It gets a fatal signal.''
35881 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35882 will certainly notice it. But if the bug is incorrect output, we might
35883 not notice unless it is glaringly wrong. You might as well not give us
35884 a chance to make a mistake.
35886 Even if the problem you experience is a fatal signal, you should still
35887 say so explicitly. Suppose something strange is going on, such as, your
35888 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35889 the C library on your system. (This has happened!) Your copy might
35890 crash and ours would not. If you told us to expect a crash, then when
35891 ours fails to crash, we would know that the bug was not happening for
35892 us. If you had not told us to expect a crash, then we would not be able
35893 to draw any conclusion from our observations.
35896 @cindex recording a session script
35897 To collect all this information, you can use a session recording program
35898 such as @command{script}, which is available on many Unix systems.
35899 Just run your @value{GDBN} session inside @command{script} and then
35900 include the @file{typescript} file with your bug report.
35902 Another way to record a @value{GDBN} session is to run @value{GDBN}
35903 inside Emacs and then save the entire buffer to a file.
35906 If you wish to suggest changes to the @value{GDBN} source, send us context
35907 diffs. If you even discuss something in the @value{GDBN} source, refer to
35908 it by context, not by line number.
35910 The line numbers in our development sources will not match those in your
35911 sources. Your line numbers would convey no useful information to us.
35915 Here are some things that are not necessary:
35919 A description of the envelope of the bug.
35921 Often people who encounter a bug spend a lot of time investigating
35922 which changes to the input file will make the bug go away and which
35923 changes will not affect it.
35925 This is often time consuming and not very useful, because the way we
35926 will find the bug is by running a single example under the debugger
35927 with breakpoints, not by pure deduction from a series of examples.
35928 We recommend that you save your time for something else.
35930 Of course, if you can find a simpler example to report @emph{instead}
35931 of the original one, that is a convenience for us. Errors in the
35932 output will be easier to spot, running under the debugger will take
35933 less time, and so on.
35935 However, simplification is not vital; if you do not want to do this,
35936 report the bug anyway and send us the entire test case you used.
35939 A patch for the bug.
35941 A patch for the bug does help us if it is a good one. But do not omit
35942 the necessary information, such as the test case, on the assumption that
35943 a patch is all we need. We might see problems with your patch and decide
35944 to fix the problem another way, or we might not understand it at all.
35946 Sometimes with a program as complicated as @value{GDBN} it is very hard to
35947 construct an example that will make the program follow a certain path
35948 through the code. If you do not send us the example, we will not be able
35949 to construct one, so we will not be able to verify that the bug is fixed.
35951 And if we cannot understand what bug you are trying to fix, or why your
35952 patch should be an improvement, we will not install it. A test case will
35953 help us to understand.
35956 A guess about what the bug is or what it depends on.
35958 Such guesses are usually wrong. Even we cannot guess right about such
35959 things without first using the debugger to find the facts.
35962 @c The readline documentation is distributed with the readline code
35963 @c and consists of the two following files:
35966 @c Use -I with makeinfo to point to the appropriate directory,
35967 @c environment var TEXINPUTS with TeX.
35968 @ifclear SYSTEM_READLINE
35969 @include rluser.texi
35970 @include hsuser.texi
35974 @appendix In Memoriam
35976 The @value{GDBN} project mourns the loss of the following long-time
35981 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
35982 to Free Software in general. Outside of @value{GDBN}, he was known in
35983 the Amiga world for his series of Fish Disks, and the GeekGadget project.
35985 @item Michael Snyder
35986 Michael was one of the Global Maintainers of the @value{GDBN} project,
35987 with contributions recorded as early as 1996, until 2011. In addition
35988 to his day to day participation, he was a large driving force behind
35989 adding Reverse Debugging to @value{GDBN}.
35992 Beyond their technical contributions to the project, they were also
35993 enjoyable members of the Free Software Community. We will miss them.
35995 @node Formatting Documentation
35996 @appendix Formatting Documentation
35998 @cindex @value{GDBN} reference card
35999 @cindex reference card
36000 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36001 for printing with PostScript or Ghostscript, in the @file{gdb}
36002 subdirectory of the main source directory@footnote{In
36003 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36004 release.}. If you can use PostScript or Ghostscript with your printer,
36005 you can print the reference card immediately with @file{refcard.ps}.
36007 The release also includes the source for the reference card. You
36008 can format it, using @TeX{}, by typing:
36014 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36015 mode on US ``letter'' size paper;
36016 that is, on a sheet 11 inches wide by 8.5 inches
36017 high. You will need to specify this form of printing as an option to
36018 your @sc{dvi} output program.
36020 @cindex documentation
36022 All the documentation for @value{GDBN} comes as part of the machine-readable
36023 distribution. The documentation is written in Texinfo format, which is
36024 a documentation system that uses a single source file to produce both
36025 on-line information and a printed manual. You can use one of the Info
36026 formatting commands to create the on-line version of the documentation
36027 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36029 @value{GDBN} includes an already formatted copy of the on-line Info
36030 version of this manual in the @file{gdb} subdirectory. The main Info
36031 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36032 subordinate files matching @samp{gdb.info*} in the same directory. If
36033 necessary, you can print out these files, or read them with any editor;
36034 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36035 Emacs or the standalone @code{info} program, available as part of the
36036 @sc{gnu} Texinfo distribution.
36038 If you want to format these Info files yourself, you need one of the
36039 Info formatting programs, such as @code{texinfo-format-buffer} or
36042 If you have @code{makeinfo} installed, and are in the top level
36043 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36044 version @value{GDBVN}), you can make the Info file by typing:
36051 If you want to typeset and print copies of this manual, you need @TeX{},
36052 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36053 Texinfo definitions file.
36055 @TeX{} is a typesetting program; it does not print files directly, but
36056 produces output files called @sc{dvi} files. To print a typeset
36057 document, you need a program to print @sc{dvi} files. If your system
36058 has @TeX{} installed, chances are it has such a program. The precise
36059 command to use depends on your system; @kbd{lpr -d} is common; another
36060 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36061 require a file name without any extension or a @samp{.dvi} extension.
36063 @TeX{} also requires a macro definitions file called
36064 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36065 written in Texinfo format. On its own, @TeX{} cannot either read or
36066 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36067 and is located in the @file{gdb-@var{version-number}/texinfo}
36070 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36071 typeset and print this manual. First switch to the @file{gdb}
36072 subdirectory of the main source directory (for example, to
36073 @file{gdb-@value{GDBVN}/gdb}) and type:
36079 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36081 @node Installing GDB
36082 @appendix Installing @value{GDBN}
36083 @cindex installation
36086 * Requirements:: Requirements for building @value{GDBN}
36087 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36088 * Separate Objdir:: Compiling @value{GDBN} in another directory
36089 * Config Names:: Specifying names for hosts and targets
36090 * Configure Options:: Summary of options for configure
36091 * System-wide configuration:: Having a system-wide init file
36095 @section Requirements for Building @value{GDBN}
36096 @cindex building @value{GDBN}, requirements for
36098 Building @value{GDBN} requires various tools and packages to be available.
36099 Other packages will be used only if they are found.
36101 @heading Tools/Packages Necessary for Building @value{GDBN}
36103 @item ISO C90 compiler
36104 @value{GDBN} is written in ISO C90. It should be buildable with any
36105 working C90 compiler, e.g.@: GCC.
36109 @heading Tools/Packages Optional for Building @value{GDBN}
36113 @value{GDBN} can use the Expat XML parsing library. This library may be
36114 included with your operating system distribution; if it is not, you
36115 can get the latest version from @url{http://expat.sourceforge.net}.
36116 The @file{configure} script will search for this library in several
36117 standard locations; if it is installed in an unusual path, you can
36118 use the @option{--with-libexpat-prefix} option to specify its location.
36124 Remote protocol memory maps (@pxref{Memory Map Format})
36126 Target descriptions (@pxref{Target Descriptions})
36128 Remote shared library lists (@xref{Library List Format},
36129 or alternatively @pxref{Library List Format for SVR4 Targets})
36131 MS-Windows shared libraries (@pxref{Shared Libraries})
36133 Traceframe info (@pxref{Traceframe Info Format})
36135 Branch trace (@pxref{Branch Trace Format})
36139 @cindex compressed debug sections
36140 @value{GDBN} will use the @samp{zlib} library, if available, to read
36141 compressed debug sections. Some linkers, such as GNU gold, are capable
36142 of producing binaries with compressed debug sections. If @value{GDBN}
36143 is compiled with @samp{zlib}, it will be able to read the debug
36144 information in such binaries.
36146 The @samp{zlib} library is likely included with your operating system
36147 distribution; if it is not, you can get the latest version from
36148 @url{http://zlib.net}.
36151 @value{GDBN}'s features related to character sets (@pxref{Character
36152 Sets}) require a functioning @code{iconv} implementation. If you are
36153 on a GNU system, then this is provided by the GNU C Library. Some
36154 other systems also provide a working @code{iconv}.
36156 If @value{GDBN} is using the @code{iconv} program which is installed
36157 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36158 This is done with @option{--with-iconv-bin} which specifies the
36159 directory that contains the @code{iconv} program.
36161 On systems without @code{iconv}, you can install GNU Libiconv. If you
36162 have previously installed Libiconv, you can use the
36163 @option{--with-libiconv-prefix} option to configure.
36165 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36166 arrange to build Libiconv if a directory named @file{libiconv} appears
36167 in the top-most source directory. If Libiconv is built this way, and
36168 if the operating system does not provide a suitable @code{iconv}
36169 implementation, then the just-built library will automatically be used
36170 by @value{GDBN}. One easy way to set this up is to download GNU
36171 Libiconv, unpack it, and then rename the directory holding the
36172 Libiconv source code to @samp{libiconv}.
36175 @node Running Configure
36176 @section Invoking the @value{GDBN} @file{configure} Script
36177 @cindex configuring @value{GDBN}
36178 @value{GDBN} comes with a @file{configure} script that automates the process
36179 of preparing @value{GDBN} for installation; you can then use @code{make} to
36180 build the @code{gdb} program.
36182 @c irrelevant in info file; it's as current as the code it lives with.
36183 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36184 look at the @file{README} file in the sources; we may have improved the
36185 installation procedures since publishing this manual.}
36188 The @value{GDBN} distribution includes all the source code you need for
36189 @value{GDBN} in a single directory, whose name is usually composed by
36190 appending the version number to @samp{gdb}.
36192 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36193 @file{gdb-@value{GDBVN}} directory. That directory contains:
36196 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36197 script for configuring @value{GDBN} and all its supporting libraries
36199 @item gdb-@value{GDBVN}/gdb
36200 the source specific to @value{GDBN} itself
36202 @item gdb-@value{GDBVN}/bfd
36203 source for the Binary File Descriptor library
36205 @item gdb-@value{GDBVN}/include
36206 @sc{gnu} include files
36208 @item gdb-@value{GDBVN}/libiberty
36209 source for the @samp{-liberty} free software library
36211 @item gdb-@value{GDBVN}/opcodes
36212 source for the library of opcode tables and disassemblers
36214 @item gdb-@value{GDBVN}/readline
36215 source for the @sc{gnu} command-line interface
36217 @item gdb-@value{GDBVN}/glob
36218 source for the @sc{gnu} filename pattern-matching subroutine
36220 @item gdb-@value{GDBVN}/mmalloc
36221 source for the @sc{gnu} memory-mapped malloc package
36224 The simplest way to configure and build @value{GDBN} is to run @file{configure}
36225 from the @file{gdb-@var{version-number}} source directory, which in
36226 this example is the @file{gdb-@value{GDBVN}} directory.
36228 First switch to the @file{gdb-@var{version-number}} source directory
36229 if you are not already in it; then run @file{configure}. Pass the
36230 identifier for the platform on which @value{GDBN} will run as an
36236 cd gdb-@value{GDBVN}
36237 ./configure @var{host}
36242 where @var{host} is an identifier such as @samp{sun4} or
36243 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
36244 (You can often leave off @var{host}; @file{configure} tries to guess the
36245 correct value by examining your system.)
36247 Running @samp{configure @var{host}} and then running @code{make} builds the
36248 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
36249 libraries, then @code{gdb} itself. The configured source files, and the
36250 binaries, are left in the corresponding source directories.
36253 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
36254 system does not recognize this automatically when you run a different
36255 shell, you may need to run @code{sh} on it explicitly:
36258 sh configure @var{host}
36261 If you run @file{configure} from a directory that contains source
36262 directories for multiple libraries or programs, such as the
36263 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
36265 creates configuration files for every directory level underneath (unless
36266 you tell it not to, with the @samp{--norecursion} option).
36268 You should run the @file{configure} script from the top directory in the
36269 source tree, the @file{gdb-@var{version-number}} directory. If you run
36270 @file{configure} from one of the subdirectories, you will configure only
36271 that subdirectory. That is usually not what you want. In particular,
36272 if you run the first @file{configure} from the @file{gdb} subdirectory
36273 of the @file{gdb-@var{version-number}} directory, you will omit the
36274 configuration of @file{bfd}, @file{readline}, and other sibling
36275 directories of the @file{gdb} subdirectory. This leads to build errors
36276 about missing include files such as @file{bfd/bfd.h}.
36278 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
36279 However, you should make sure that the shell on your path (named by
36280 the @samp{SHELL} environment variable) is publicly readable. Remember
36281 that @value{GDBN} uses the shell to start your program---some systems refuse to
36282 let @value{GDBN} debug child processes whose programs are not readable.
36284 @node Separate Objdir
36285 @section Compiling @value{GDBN} in Another Directory
36287 If you want to run @value{GDBN} versions for several host or target machines,
36288 you need a different @code{gdb} compiled for each combination of
36289 host and target. @file{configure} is designed to make this easy by
36290 allowing you to generate each configuration in a separate subdirectory,
36291 rather than in the source directory. If your @code{make} program
36292 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36293 @code{make} in each of these directories builds the @code{gdb}
36294 program specified there.
36296 To build @code{gdb} in a separate directory, run @file{configure}
36297 with the @samp{--srcdir} option to specify where to find the source.
36298 (You also need to specify a path to find @file{configure}
36299 itself from your working directory. If the path to @file{configure}
36300 would be the same as the argument to @samp{--srcdir}, you can leave out
36301 the @samp{--srcdir} option; it is assumed.)
36303 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
36304 separate directory for a Sun 4 like this:
36308 cd gdb-@value{GDBVN}
36311 ../gdb-@value{GDBVN}/configure sun4
36316 When @file{configure} builds a configuration using a remote source
36317 directory, it creates a tree for the binaries with the same structure
36318 (and using the same names) as the tree under the source directory. In
36319 the example, you'd find the Sun 4 library @file{libiberty.a} in the
36320 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
36321 @file{gdb-sun4/gdb}.
36323 Make sure that your path to the @file{configure} script has just one
36324 instance of @file{gdb} in it. If your path to @file{configure} looks
36325 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
36326 one subdirectory of @value{GDBN}, not the whole package. This leads to
36327 build errors about missing include files such as @file{bfd/bfd.h}.
36329 One popular reason to build several @value{GDBN} configurations in separate
36330 directories is to configure @value{GDBN} for cross-compiling (where
36331 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
36332 programs that run on another machine---the @dfn{target}).
36333 You specify a cross-debugging target by
36334 giving the @samp{--target=@var{target}} option to @file{configure}.
36336 When you run @code{make} to build a program or library, you must run
36337 it in a configured directory---whatever directory you were in when you
36338 called @file{configure} (or one of its subdirectories).
36340 The @code{Makefile} that @file{configure} generates in each source
36341 directory also runs recursively. If you type @code{make} in a source
36342 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
36343 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
36344 will build all the required libraries, and then build GDB.
36346 When you have multiple hosts or targets configured in separate
36347 directories, you can run @code{make} on them in parallel (for example,
36348 if they are NFS-mounted on each of the hosts); they will not interfere
36352 @section Specifying Names for Hosts and Targets
36354 The specifications used for hosts and targets in the @file{configure}
36355 script are based on a three-part naming scheme, but some short predefined
36356 aliases are also supported. The full naming scheme encodes three pieces
36357 of information in the following pattern:
36360 @var{architecture}-@var{vendor}-@var{os}
36363 For example, you can use the alias @code{sun4} as a @var{host} argument,
36364 or as the value for @var{target} in a @code{--target=@var{target}}
36365 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36367 The @file{configure} script accompanying @value{GDBN} does not provide
36368 any query facility to list all supported host and target names or
36369 aliases. @file{configure} calls the Bourne shell script
36370 @code{config.sub} to map abbreviations to full names; you can read the
36371 script, if you wish, or you can use it to test your guesses on
36372 abbreviations---for example:
36375 % sh config.sub i386-linux
36377 % sh config.sub alpha-linux
36378 alpha-unknown-linux-gnu
36379 % sh config.sub hp9k700
36381 % sh config.sub sun4
36382 sparc-sun-sunos4.1.1
36383 % sh config.sub sun3
36384 m68k-sun-sunos4.1.1
36385 % sh config.sub i986v
36386 Invalid configuration `i986v': machine `i986v' not recognized
36390 @code{config.sub} is also distributed in the @value{GDBN} source
36391 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36393 @node Configure Options
36394 @section @file{configure} Options
36396 Here is a summary of the @file{configure} options and arguments that
36397 are most often useful for building @value{GDBN}. @file{configure} also has
36398 several other options not listed here. @inforef{What Configure
36399 Does,,configure.info}, for a full explanation of @file{configure}.
36402 configure @r{[}--help@r{]}
36403 @r{[}--prefix=@var{dir}@r{]}
36404 @r{[}--exec-prefix=@var{dir}@r{]}
36405 @r{[}--srcdir=@var{dirname}@r{]}
36406 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
36407 @r{[}--target=@var{target}@r{]}
36412 You may introduce options with a single @samp{-} rather than
36413 @samp{--} if you prefer; but you may abbreviate option names if you use
36418 Display a quick summary of how to invoke @file{configure}.
36420 @item --prefix=@var{dir}
36421 Configure the source to install programs and files under directory
36424 @item --exec-prefix=@var{dir}
36425 Configure the source to install programs under directory
36428 @c avoid splitting the warning from the explanation:
36430 @item --srcdir=@var{dirname}
36431 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
36432 @code{make} that implements the @code{VPATH} feature.}@*
36433 Use this option to make configurations in directories separate from the
36434 @value{GDBN} source directories. Among other things, you can use this to
36435 build (or maintain) several configurations simultaneously, in separate
36436 directories. @file{configure} writes configuration-specific files in
36437 the current directory, but arranges for them to use the source in the
36438 directory @var{dirname}. @file{configure} creates directories under
36439 the working directory in parallel to the source directories below
36442 @item --norecursion
36443 Configure only the directory level where @file{configure} is executed; do not
36444 propagate configuration to subdirectories.
36446 @item --target=@var{target}
36447 Configure @value{GDBN} for cross-debugging programs running on the specified
36448 @var{target}. Without this option, @value{GDBN} is configured to debug
36449 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
36451 There is no convenient way to generate a list of all available targets.
36453 @item @var{host} @dots{}
36454 Configure @value{GDBN} to run on the specified @var{host}.
36456 There is no convenient way to generate a list of all available hosts.
36459 There are many other options available as well, but they are generally
36460 needed for special purposes only.
36462 @node System-wide configuration
36463 @section System-wide configuration and settings
36464 @cindex system-wide init file
36466 @value{GDBN} can be configured to have a system-wide init file;
36467 this file will be read and executed at startup (@pxref{Startup, , What
36468 @value{GDBN} does during startup}).
36470 Here is the corresponding configure option:
36473 @item --with-system-gdbinit=@var{file}
36474 Specify that the default location of the system-wide init file is
36478 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
36479 it may be subject to relocation. Two possible cases:
36483 If the default location of this init file contains @file{$prefix},
36484 it will be subject to relocation. Suppose that the configure options
36485 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
36486 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
36487 init file is looked for as @file{$install/etc/gdbinit} instead of
36488 @file{$prefix/etc/gdbinit}.
36491 By contrast, if the default location does not contain the prefix,
36492 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
36493 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
36494 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
36495 wherever @value{GDBN} is installed.
36498 If the configured location of the system-wide init file (as given by the
36499 @option{--with-system-gdbinit} option at configure time) is in the
36500 data-directory (as specified by @option{--with-gdb-datadir} at configure
36501 time) or in one of its subdirectories, then @value{GDBN} will look for the
36502 system-wide init file in the directory specified by the
36503 @option{--data-directory} command-line option.
36504 Note that the system-wide init file is only read once, during @value{GDBN}
36505 initialization. If the data-directory is changed after @value{GDBN} has
36506 started with the @code{set data-directory} command, the file will not be
36510 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36513 @node System-wide Configuration Scripts
36514 @subsection Installed System-wide Configuration Scripts
36515 @cindex system-wide configuration scripts
36517 The @file{system-gdbinit} directory, located inside the data-directory
36518 (as specified by @option{--with-gdb-datadir} at configure time) contains
36519 a number of scripts which can be used as system-wide init files. To
36520 automatically source those scripts at startup, @value{GDBN} should be
36521 configured with @option{--with-system-gdbinit}. Otherwise, any user
36522 should be able to source them by hand as needed.
36524 The following scripts are currently available:
36527 @item @file{elinos.py}
36529 @cindex ELinOS system-wide configuration script
36530 This script is useful when debugging a program on an ELinOS target.
36531 It takes advantage of the environment variables defined in a standard
36532 ELinOS environment in order to determine the location of the system
36533 shared libraries, and then sets the @samp{solib-absolute-prefix}
36534 and @samp{solib-search-path} variables appropriately.
36536 @item @file{wrs-linux.py}
36537 @pindex wrs-linux.py
36538 @cindex Wind River Linux system-wide configuration script
36539 This script is useful when debugging a program on a target running
36540 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36541 the host-side sysroot used by the target system.
36545 @node Maintenance Commands
36546 @appendix Maintenance Commands
36547 @cindex maintenance commands
36548 @cindex internal commands
36550 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36551 includes a number of commands intended for @value{GDBN} developers,
36552 that are not documented elsewhere in this manual. These commands are
36553 provided here for reference. (For commands that turn on debugging
36554 messages, see @ref{Debugging Output}.)
36557 @kindex maint agent
36558 @kindex maint agent-eval
36559 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36560 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36561 Translate the given @var{expression} into remote agent bytecodes.
36562 This command is useful for debugging the Agent Expression mechanism
36563 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36564 expression useful for data collection, such as by tracepoints, while
36565 @samp{maint agent-eval} produces an expression that evaluates directly
36566 to a result. For instance, a collection expression for @code{globa +
36567 globb} will include bytecodes to record four bytes of memory at each
36568 of the addresses of @code{globa} and @code{globb}, while discarding
36569 the result of the addition, while an evaluation expression will do the
36570 addition and return the sum.
36571 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36572 If not, generate remote agent bytecode for current frame PC address.
36574 @kindex maint agent-printf
36575 @item maint agent-printf @var{format},@var{expr},...
36576 Translate the given format string and list of argument expressions
36577 into remote agent bytecodes and display them as a disassembled list.
36578 This command is useful for debugging the agent version of dynamic
36579 printf (@pxref{Dynamic Printf}).
36581 @kindex maint info breakpoints
36582 @item @anchor{maint info breakpoints}maint info breakpoints
36583 Using the same format as @samp{info breakpoints}, display both the
36584 breakpoints you've set explicitly, and those @value{GDBN} is using for
36585 internal purposes. Internal breakpoints are shown with negative
36586 breakpoint numbers. The type column identifies what kind of breakpoint
36591 Normal, explicitly set breakpoint.
36594 Normal, explicitly set watchpoint.
36597 Internal breakpoint, used to handle correctly stepping through
36598 @code{longjmp} calls.
36600 @item longjmp resume
36601 Internal breakpoint at the target of a @code{longjmp}.
36604 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36607 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36610 Shared library events.
36614 @kindex maint info bfds
36615 @item maint info bfds
36616 This prints information about each @code{bfd} object that is known to
36617 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
36619 @kindex set displaced-stepping
36620 @kindex show displaced-stepping
36621 @cindex displaced stepping support
36622 @cindex out-of-line single-stepping
36623 @item set displaced-stepping
36624 @itemx show displaced-stepping
36625 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36626 if the target supports it. Displaced stepping is a way to single-step
36627 over breakpoints without removing them from the inferior, by executing
36628 an out-of-line copy of the instruction that was originally at the
36629 breakpoint location. It is also known as out-of-line single-stepping.
36632 @item set displaced-stepping on
36633 If the target architecture supports it, @value{GDBN} will use
36634 displaced stepping to step over breakpoints.
36636 @item set displaced-stepping off
36637 @value{GDBN} will not use displaced stepping to step over breakpoints,
36638 even if such is supported by the target architecture.
36640 @cindex non-stop mode, and @samp{set displaced-stepping}
36641 @item set displaced-stepping auto
36642 This is the default mode. @value{GDBN} will use displaced stepping
36643 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36644 architecture supports displaced stepping.
36647 @kindex maint check-psymtabs
36648 @item maint check-psymtabs
36649 Check the consistency of currently expanded psymtabs versus symtabs.
36650 Use this to check, for example, whether a symbol is in one but not the other.
36652 @kindex maint check-symtabs
36653 @item maint check-symtabs
36654 Check the consistency of currently expanded symtabs.
36656 @kindex maint expand-symtabs
36657 @item maint expand-symtabs [@var{regexp}]
36658 Expand symbol tables.
36659 If @var{regexp} is specified, only expand symbol tables for file
36660 names matching @var{regexp}.
36662 @kindex maint cplus first_component
36663 @item maint cplus first_component @var{name}
36664 Print the first C@t{++} class/namespace component of @var{name}.
36666 @kindex maint cplus namespace
36667 @item maint cplus namespace
36668 Print the list of possible C@t{++} namespaces.
36670 @kindex maint demangle
36671 @item maint demangle @var{name}
36672 Demangle a C@t{++} or Objective-C mangled @var{name}.
36674 @kindex maint deprecate
36675 @kindex maint undeprecate
36676 @cindex deprecated commands
36677 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36678 @itemx maint undeprecate @var{command}
36679 Deprecate or undeprecate the named @var{command}. Deprecated commands
36680 cause @value{GDBN} to issue a warning when you use them. The optional
36681 argument @var{replacement} says which newer command should be used in
36682 favor of the deprecated one; if it is given, @value{GDBN} will mention
36683 the replacement as part of the warning.
36685 @kindex maint dump-me
36686 @item maint dump-me
36687 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36688 Cause a fatal signal in the debugger and force it to dump its core.
36689 This is supported only on systems which support aborting a program
36690 with the @code{SIGQUIT} signal.
36692 @kindex maint internal-error
36693 @kindex maint internal-warning
36694 @item maint internal-error @r{[}@var{message-text}@r{]}
36695 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36696 Cause @value{GDBN} to call the internal function @code{internal_error}
36697 or @code{internal_warning} and hence behave as though an internal error
36698 or internal warning has been detected. In addition to reporting the
36699 internal problem, these functions give the user the opportunity to
36700 either quit @value{GDBN} or create a core file of the current
36701 @value{GDBN} session.
36703 These commands take an optional parameter @var{message-text} that is
36704 used as the text of the error or warning message.
36706 Here's an example of using @code{internal-error}:
36709 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36710 @dots{}/maint.c:121: internal-error: testing, 1, 2
36711 A problem internal to GDB has been detected. Further
36712 debugging may prove unreliable.
36713 Quit this debugging session? (y or n) @kbd{n}
36714 Create a core file? (y or n) @kbd{n}
36718 @cindex @value{GDBN} internal error
36719 @cindex internal errors, control of @value{GDBN} behavior
36721 @kindex maint set internal-error
36722 @kindex maint show internal-error
36723 @kindex maint set internal-warning
36724 @kindex maint show internal-warning
36725 @item maint set internal-error @var{action} [ask|yes|no]
36726 @itemx maint show internal-error @var{action}
36727 @itemx maint set internal-warning @var{action} [ask|yes|no]
36728 @itemx maint show internal-warning @var{action}
36729 When @value{GDBN} reports an internal problem (error or warning) it
36730 gives the user the opportunity to both quit @value{GDBN} and create a
36731 core file of the current @value{GDBN} session. These commands let you
36732 override the default behaviour for each particular @var{action},
36733 described in the table below.
36737 You can specify that @value{GDBN} should always (yes) or never (no)
36738 quit. The default is to ask the user what to do.
36741 You can specify that @value{GDBN} should always (yes) or never (no)
36742 create a core file. The default is to ask the user what to do.
36745 @kindex maint packet
36746 @item maint packet @var{text}
36747 If @value{GDBN} is talking to an inferior via the serial protocol,
36748 then this command sends the string @var{text} to the inferior, and
36749 displays the response packet. @value{GDBN} supplies the initial
36750 @samp{$} character, the terminating @samp{#} character, and the
36753 @kindex maint print architecture
36754 @item maint print architecture @r{[}@var{file}@r{]}
36755 Print the entire architecture configuration. The optional argument
36756 @var{file} names the file where the output goes.
36758 @kindex maint print c-tdesc
36759 @item maint print c-tdesc
36760 Print the current target description (@pxref{Target Descriptions}) as
36761 a C source file. The created source file can be used in @value{GDBN}
36762 when an XML parser is not available to parse the description.
36764 @kindex maint print dummy-frames
36765 @item maint print dummy-frames
36766 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36769 (@value{GDBP}) @kbd{b add}
36771 (@value{GDBP}) @kbd{print add(2,3)}
36772 Breakpoint 2, add (a=2, b=3) at @dots{}
36774 The program being debugged stopped while in a function called from GDB.
36776 (@value{GDBP}) @kbd{maint print dummy-frames}
36777 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
36778 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
36779 call_lo=0x01014000 call_hi=0x01014001
36783 Takes an optional file parameter.
36785 @kindex maint print registers
36786 @kindex maint print raw-registers
36787 @kindex maint print cooked-registers
36788 @kindex maint print register-groups
36789 @kindex maint print remote-registers
36790 @item maint print registers @r{[}@var{file}@r{]}
36791 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36792 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36793 @itemx maint print register-groups @r{[}@var{file}@r{]}
36794 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36795 Print @value{GDBN}'s internal register data structures.
36797 The command @code{maint print raw-registers} includes the contents of
36798 the raw register cache; the command @code{maint print
36799 cooked-registers} includes the (cooked) value of all registers,
36800 including registers which aren't available on the target nor visible
36801 to user; the command @code{maint print register-groups} includes the
36802 groups that each register is a member of; and the command @code{maint
36803 print remote-registers} includes the remote target's register numbers
36804 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
36805 @value{GDBN} Internals}.
36807 These commands take an optional parameter, a file name to which to
36808 write the information.
36810 @kindex maint print reggroups
36811 @item maint print reggroups @r{[}@var{file}@r{]}
36812 Print @value{GDBN}'s internal register group data structures. The
36813 optional argument @var{file} tells to what file to write the
36816 The register groups info looks like this:
36819 (@value{GDBP}) @kbd{maint print reggroups}
36832 This command forces @value{GDBN} to flush its internal register cache.
36834 @kindex maint print objfiles
36835 @cindex info for known object files
36836 @item maint print objfiles @r{[}@var{regexp}@r{]}
36837 Print a dump of all known object files.
36838 If @var{regexp} is specified, only print object files whose names
36839 match @var{regexp}. For each object file, this command prints its name,
36840 address in memory, and all of its psymtabs and symtabs.
36842 @kindex maint print section-scripts
36843 @cindex info for known .debug_gdb_scripts-loaded scripts
36844 @item maint print section-scripts [@var{regexp}]
36845 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36846 If @var{regexp} is specified, only print scripts loaded by object files
36847 matching @var{regexp}.
36848 For each script, this command prints its name as specified in the objfile,
36849 and the full path if known.
36850 @xref{dotdebug_gdb_scripts section}.
36852 @kindex maint print statistics
36853 @cindex bcache statistics
36854 @item maint print statistics
36855 This command prints, for each object file in the program, various data
36856 about that object file followed by the byte cache (@dfn{bcache})
36857 statistics for the object file. The objfile data includes the number
36858 of minimal, partial, full, and stabs symbols, the number of types
36859 defined by the objfile, the number of as yet unexpanded psym tables,
36860 the number of line tables and string tables, and the amount of memory
36861 used by the various tables. The bcache statistics include the counts,
36862 sizes, and counts of duplicates of all and unique objects, max,
36863 average, and median entry size, total memory used and its overhead and
36864 savings, and various measures of the hash table size and chain
36867 @kindex maint print target-stack
36868 @cindex target stack description
36869 @item maint print target-stack
36870 A @dfn{target} is an interface between the debugger and a particular
36871 kind of file or process. Targets can be stacked in @dfn{strata},
36872 so that more than one target can potentially respond to a request.
36873 In particular, memory accesses will walk down the stack of targets
36874 until they find a target that is interested in handling that particular
36877 This command prints a short description of each layer that was pushed on
36878 the @dfn{target stack}, starting from the top layer down to the bottom one.
36880 @kindex maint print type
36881 @cindex type chain of a data type
36882 @item maint print type @var{expr}
36883 Print the type chain for a type specified by @var{expr}. The argument
36884 can be either a type name or a symbol. If it is a symbol, the type of
36885 that symbol is described. The type chain produced by this command is
36886 a recursive definition of the data type as stored in @value{GDBN}'s
36887 data structures, including its flags and contained types.
36889 @kindex maint set dwarf2 always-disassemble
36890 @kindex maint show dwarf2 always-disassemble
36891 @item maint set dwarf2 always-disassemble
36892 @item maint show dwarf2 always-disassemble
36893 Control the behavior of @code{info address} when using DWARF debugging
36896 The default is @code{off}, which means that @value{GDBN} should try to
36897 describe a variable's location in an easily readable format. When
36898 @code{on}, @value{GDBN} will instead display the DWARF location
36899 expression in an assembly-like format. Note that some locations are
36900 too complex for @value{GDBN} to describe simply; in this case you will
36901 always see the disassembly form.
36903 Here is an example of the resulting disassembly:
36906 (gdb) info addr argc
36907 Symbol "argc" is a complex DWARF expression:
36911 For more information on these expressions, see
36912 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36914 @kindex maint set dwarf2 max-cache-age
36915 @kindex maint show dwarf2 max-cache-age
36916 @item maint set dwarf2 max-cache-age
36917 @itemx maint show dwarf2 max-cache-age
36918 Control the DWARF 2 compilation unit cache.
36920 @cindex DWARF 2 compilation units cache
36921 In object files with inter-compilation-unit references, such as those
36922 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
36923 reader needs to frequently refer to previously read compilation units.
36924 This setting controls how long a compilation unit will remain in the
36925 cache if it is not referenced. A higher limit means that cached
36926 compilation units will be stored in memory longer, and more total
36927 memory will be used. Setting it to zero disables caching, which will
36928 slow down @value{GDBN} startup, but reduce memory consumption.
36930 @kindex maint set profile
36931 @kindex maint show profile
36932 @cindex profiling GDB
36933 @item maint set profile
36934 @itemx maint show profile
36935 Control profiling of @value{GDBN}.
36937 Profiling will be disabled until you use the @samp{maint set profile}
36938 command to enable it. When you enable profiling, the system will begin
36939 collecting timing and execution count data; when you disable profiling or
36940 exit @value{GDBN}, the results will be written to a log file. Remember that
36941 if you use profiling, @value{GDBN} will overwrite the profiling log file
36942 (often called @file{gmon.out}). If you have a record of important profiling
36943 data in a @file{gmon.out} file, be sure to move it to a safe location.
36945 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36946 compiled with the @samp{-pg} compiler option.
36948 @kindex maint set show-debug-regs
36949 @kindex maint show show-debug-regs
36950 @cindex hardware debug registers
36951 @item maint set show-debug-regs
36952 @itemx maint show show-debug-regs
36953 Control whether to show variables that mirror the hardware debug
36954 registers. Use @code{ON} to enable, @code{OFF} to disable. If
36955 enabled, the debug registers values are shown when @value{GDBN} inserts or
36956 removes a hardware breakpoint or watchpoint, and when the inferior
36957 triggers a hardware-assisted breakpoint or watchpoint.
36959 @kindex maint set show-all-tib
36960 @kindex maint show show-all-tib
36961 @item maint set show-all-tib
36962 @itemx maint show show-all-tib
36963 Control whether to show all non zero areas within a 1k block starting
36964 at thread local base, when using the @samp{info w32 thread-information-block}
36967 @kindex maint set per-command
36968 @kindex maint show per-command
36969 @item maint set per-command
36970 @itemx maint show per-command
36971 @cindex resources used by commands
36973 @value{GDBN} can display the resources used by each command.
36974 This is useful in debugging performance problems.
36977 @item maint set per-command space [on|off]
36978 @itemx maint show per-command space
36979 Enable or disable the printing of the memory used by GDB for each command.
36980 If enabled, @value{GDBN} will display how much memory each command
36981 took, following the command's own output.
36982 This can also be requested by invoking @value{GDBN} with the
36983 @option{--statistics} command-line switch (@pxref{Mode Options}).
36985 @item maint set per-command time [on|off]
36986 @itemx maint show per-command time
36987 Enable or disable the printing of the execution time of @value{GDBN}
36989 If enabled, @value{GDBN} will display how much time it
36990 took to execute each command, following the command's own output.
36991 Both CPU time and wallclock time are printed.
36992 Printing both is useful when trying to determine whether the cost is
36993 CPU or, e.g., disk/network latency.
36994 Note that the CPU time printed is for @value{GDBN} only, it does not include
36995 the execution time of the inferior because there's no mechanism currently
36996 to compute how much time was spent by @value{GDBN} and how much time was
36997 spent by the program been debugged.
36998 This can also be requested by invoking @value{GDBN} with the
36999 @option{--statistics} command-line switch (@pxref{Mode Options}).
37001 @item maint set per-command symtab [on|off]
37002 @itemx maint show per-command symtab
37003 Enable or disable the printing of basic symbol table statistics
37005 If enabled, @value{GDBN} will display the following information:
37009 number of symbol tables
37011 number of primary symbol tables
37013 number of blocks in the blockvector
37017 @kindex maint space
37018 @cindex memory used by commands
37019 @item maint space @var{value}
37020 An alias for @code{maint set per-command space}.
37021 A non-zero value enables it, zero disables it.
37024 @cindex time of command execution
37025 @item maint time @var{value}
37026 An alias for @code{maint set per-command time}.
37027 A non-zero value enables it, zero disables it.
37029 @kindex maint translate-address
37030 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37031 Find the symbol stored at the location specified by the address
37032 @var{addr} and an optional section name @var{section}. If found,
37033 @value{GDBN} prints the name of the closest symbol and an offset from
37034 the symbol's location to the specified address. This is similar to
37035 the @code{info address} command (@pxref{Symbols}), except that this
37036 command also allows to find symbols in other sections.
37038 If section was not specified, the section in which the symbol was found
37039 is also printed. For dynamically linked executables, the name of
37040 executable or shared library containing the symbol is printed as well.
37044 The following command is useful for non-interactive invocations of
37045 @value{GDBN}, such as in the test suite.
37048 @item set watchdog @var{nsec}
37049 @kindex set watchdog
37050 @cindex watchdog timer
37051 @cindex timeout for commands
37052 Set the maximum number of seconds @value{GDBN} will wait for the
37053 target operation to finish. If this time expires, @value{GDBN}
37054 reports and error and the command is aborted.
37056 @item show watchdog
37057 Show the current setting of the target wait timeout.
37060 @node Remote Protocol
37061 @appendix @value{GDBN} Remote Serial Protocol
37066 * Stop Reply Packets::
37067 * General Query Packets::
37068 * Architecture-Specific Protocol Details::
37069 * Tracepoint Packets::
37070 * Host I/O Packets::
37072 * Notification Packets::
37073 * Remote Non-Stop::
37074 * Packet Acknowledgment::
37076 * File-I/O Remote Protocol Extension::
37077 * Library List Format::
37078 * Library List Format for SVR4 Targets::
37079 * Memory Map Format::
37080 * Thread List Format::
37081 * Traceframe Info Format::
37082 * Branch Trace Format::
37088 There may be occasions when you need to know something about the
37089 protocol---for example, if there is only one serial port to your target
37090 machine, you might want your program to do something special if it
37091 recognizes a packet meant for @value{GDBN}.
37093 In the examples below, @samp{->} and @samp{<-} are used to indicate
37094 transmitted and received data, respectively.
37096 @cindex protocol, @value{GDBN} remote serial
37097 @cindex serial protocol, @value{GDBN} remote
37098 @cindex remote serial protocol
37099 All @value{GDBN} commands and responses (other than acknowledgments
37100 and notifications, see @ref{Notification Packets}) are sent as a
37101 @var{packet}. A @var{packet} is introduced with the character
37102 @samp{$}, the actual @var{packet-data}, and the terminating character
37103 @samp{#} followed by a two-digit @var{checksum}:
37106 @code{$}@var{packet-data}@code{#}@var{checksum}
37110 @cindex checksum, for @value{GDBN} remote
37112 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37113 characters between the leading @samp{$} and the trailing @samp{#} (an
37114 eight bit unsigned checksum).
37116 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37117 specification also included an optional two-digit @var{sequence-id}:
37120 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37123 @cindex sequence-id, for @value{GDBN} remote
37125 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37126 has never output @var{sequence-id}s. Stubs that handle packets added
37127 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37129 When either the host or the target machine receives a packet, the first
37130 response expected is an acknowledgment: either @samp{+} (to indicate
37131 the package was received correctly) or @samp{-} (to request
37135 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37140 The @samp{+}/@samp{-} acknowledgments can be disabled
37141 once a connection is established.
37142 @xref{Packet Acknowledgment}, for details.
37144 The host (@value{GDBN}) sends @var{command}s, and the target (the
37145 debugging stub incorporated in your program) sends a @var{response}. In
37146 the case of step and continue @var{command}s, the response is only sent
37147 when the operation has completed, and the target has again stopped all
37148 threads in all attached processes. This is the default all-stop mode
37149 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37150 execution mode; see @ref{Remote Non-Stop}, for details.
37152 @var{packet-data} consists of a sequence of characters with the
37153 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37156 @cindex remote protocol, field separator
37157 Fields within the packet should be separated using @samp{,} @samp{;} or
37158 @samp{:}. Except where otherwise noted all numbers are represented in
37159 @sc{hex} with leading zeros suppressed.
37161 Implementors should note that prior to @value{GDBN} 5.0, the character
37162 @samp{:} could not appear as the third character in a packet (as it
37163 would potentially conflict with the @var{sequence-id}).
37165 @cindex remote protocol, binary data
37166 @anchor{Binary Data}
37167 Binary data in most packets is encoded either as two hexadecimal
37168 digits per byte of binary data. This allowed the traditional remote
37169 protocol to work over connections which were only seven-bit clean.
37170 Some packets designed more recently assume an eight-bit clean
37171 connection, and use a more efficient encoding to send and receive
37174 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37175 as an escape character. Any escaped byte is transmitted as the escape
37176 character followed by the original character XORed with @code{0x20}.
37177 For example, the byte @code{0x7d} would be transmitted as the two
37178 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37179 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37180 @samp{@}}) must always be escaped. Responses sent by the stub
37181 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37182 is not interpreted as the start of a run-length encoded sequence
37185 Response @var{data} can be run-length encoded to save space.
37186 Run-length encoding replaces runs of identical characters with one
37187 instance of the repeated character, followed by a @samp{*} and a
37188 repeat count. The repeat count is itself sent encoded, to avoid
37189 binary characters in @var{data}: a value of @var{n} is sent as
37190 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37191 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37192 code 32) for a repeat count of 3. (This is because run-length
37193 encoding starts to win for counts 3 or more.) Thus, for example,
37194 @samp{0* } is a run-length encoding of ``0000'': the space character
37195 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37198 The printable characters @samp{#} and @samp{$} or with a numeric value
37199 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37200 seven repeats (@samp{$}) can be expanded using a repeat count of only
37201 five (@samp{"}). For example, @samp{00000000} can be encoded as
37204 The error response returned for some packets includes a two character
37205 error number. That number is not well defined.
37207 @cindex empty response, for unsupported packets
37208 For any @var{command} not supported by the stub, an empty response
37209 (@samp{$#00}) should be returned. That way it is possible to extend the
37210 protocol. A newer @value{GDBN} can tell if a packet is supported based
37213 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37214 commands for register access, and the @samp{m} and @samp{M} commands
37215 for memory access. Stubs that only control single-threaded targets
37216 can implement run control with the @samp{c} (continue), and @samp{s}
37217 (step) commands. Stubs that support multi-threading targets should
37218 support the @samp{vCont} command. All other commands are optional.
37223 The following table provides a complete list of all currently defined
37224 @var{command}s and their corresponding response @var{data}.
37225 @xref{File-I/O Remote Protocol Extension}, for details about the File
37226 I/O extension of the remote protocol.
37228 Each packet's description has a template showing the packet's overall
37229 syntax, followed by an explanation of the packet's meaning. We
37230 include spaces in some of the templates for clarity; these are not
37231 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37232 separate its components. For example, a template like @samp{foo
37233 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37234 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37235 @var{baz}. @value{GDBN} does not transmit a space character between the
37236 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37239 @cindex @var{thread-id}, in remote protocol
37240 @anchor{thread-id syntax}
37241 Several packets and replies include a @var{thread-id} field to identify
37242 a thread. Normally these are positive numbers with a target-specific
37243 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37244 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37247 In addition, the remote protocol supports a multiprocess feature in
37248 which the @var{thread-id} syntax is extended to optionally include both
37249 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37250 The @var{pid} (process) and @var{tid} (thread) components each have the
37251 format described above: a positive number with target-specific
37252 interpretation formatted as a big-endian hex string, literal @samp{-1}
37253 to indicate all processes or threads (respectively), or @samp{0} to
37254 indicate an arbitrary process or thread. Specifying just a process, as
37255 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37256 error to specify all processes but a specific thread, such as
37257 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37258 for those packets and replies explicitly documented to include a process
37259 ID, rather than a @var{thread-id}.
37261 The multiprocess @var{thread-id} syntax extensions are only used if both
37262 @value{GDBN} and the stub report support for the @samp{multiprocess}
37263 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37266 Note that all packet forms beginning with an upper- or lower-case
37267 letter, other than those described here, are reserved for future use.
37269 Here are the packet descriptions.
37274 @cindex @samp{!} packet
37275 @anchor{extended mode}
37276 Enable extended mode. In extended mode, the remote server is made
37277 persistent. The @samp{R} packet is used to restart the program being
37283 The remote target both supports and has enabled extended mode.
37287 @cindex @samp{?} packet
37288 Indicate the reason the target halted. The reply is the same as for
37289 step and continue. This packet has a special interpretation when the
37290 target is in non-stop mode; see @ref{Remote Non-Stop}.
37293 @xref{Stop Reply Packets}, for the reply specifications.
37295 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37296 @cindex @samp{A} packet
37297 Initialized @code{argv[]} array passed into program. @var{arglen}
37298 specifies the number of bytes in the hex encoded byte stream
37299 @var{arg}. See @code{gdbserver} for more details.
37304 The arguments were set.
37310 @cindex @samp{b} packet
37311 (Don't use this packet; its behavior is not well-defined.)
37312 Change the serial line speed to @var{baud}.
37314 JTC: @emph{When does the transport layer state change? When it's
37315 received, or after the ACK is transmitted. In either case, there are
37316 problems if the command or the acknowledgment packet is dropped.}
37318 Stan: @emph{If people really wanted to add something like this, and get
37319 it working for the first time, they ought to modify ser-unix.c to send
37320 some kind of out-of-band message to a specially-setup stub and have the
37321 switch happen "in between" packets, so that from remote protocol's point
37322 of view, nothing actually happened.}
37324 @item B @var{addr},@var{mode}
37325 @cindex @samp{B} packet
37326 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37327 breakpoint at @var{addr}.
37329 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37330 (@pxref{insert breakpoint or watchpoint packet}).
37332 @cindex @samp{bc} packet
37335 Backward continue. Execute the target system in reverse. No parameter.
37336 @xref{Reverse Execution}, for more information.
37339 @xref{Stop Reply Packets}, for the reply specifications.
37341 @cindex @samp{bs} packet
37344 Backward single step. Execute one instruction in reverse. No parameter.
37345 @xref{Reverse Execution}, for more information.
37348 @xref{Stop Reply Packets}, for the reply specifications.
37350 @item c @r{[}@var{addr}@r{]}
37351 @cindex @samp{c} packet
37352 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
37353 resume at current address.
37355 This packet is deprecated for multi-threading support. @xref{vCont
37359 @xref{Stop Reply Packets}, for the reply specifications.
37361 @item C @var{sig}@r{[};@var{addr}@r{]}
37362 @cindex @samp{C} packet
37363 Continue with signal @var{sig} (hex signal number). If
37364 @samp{;@var{addr}} is omitted, resume at same address.
37366 This packet is deprecated for multi-threading support. @xref{vCont
37370 @xref{Stop Reply Packets}, for the reply specifications.
37373 @cindex @samp{d} packet
37376 Don't use this packet; instead, define a general set packet
37377 (@pxref{General Query Packets}).
37381 @cindex @samp{D} packet
37382 The first form of the packet is used to detach @value{GDBN} from the
37383 remote system. It is sent to the remote target
37384 before @value{GDBN} disconnects via the @code{detach} command.
37386 The second form, including a process ID, is used when multiprocess
37387 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37388 detach only a specific process. The @var{pid} is specified as a
37389 big-endian hex string.
37399 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37400 @cindex @samp{F} packet
37401 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37402 This is part of the File-I/O protocol extension. @xref{File-I/O
37403 Remote Protocol Extension}, for the specification.
37406 @anchor{read registers packet}
37407 @cindex @samp{g} packet
37408 Read general registers.
37412 @item @var{XX@dots{}}
37413 Each byte of register data is described by two hex digits. The bytes
37414 with the register are transmitted in target byte order. The size of
37415 each register and their position within the @samp{g} packet are
37416 determined by the @value{GDBN} internal gdbarch functions
37417 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
37418 specification of several standard @samp{g} packets is specified below.
37420 When reading registers from a trace frame (@pxref{Analyze Collected
37421 Data,,Using the Collected Data}), the stub may also return a string of
37422 literal @samp{x}'s in place of the register data digits, to indicate
37423 that the corresponding register has not been collected, thus its value
37424 is unavailable. For example, for an architecture with 4 registers of
37425 4 bytes each, the following reply indicates to @value{GDBN} that
37426 registers 0 and 2 have not been collected, while registers 1 and 3
37427 have been collected, and both have zero value:
37431 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37438 @item G @var{XX@dots{}}
37439 @cindex @samp{G} packet
37440 Write general registers. @xref{read registers packet}, for a
37441 description of the @var{XX@dots{}} data.
37451 @item H @var{op} @var{thread-id}
37452 @cindex @samp{H} packet
37453 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37454 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
37455 it should be @samp{c} for step and continue operations (note that this
37456 is deprecated, supporting the @samp{vCont} command is a better
37457 option), @samp{g} for other operations. The thread designator
37458 @var{thread-id} has the format and interpretation described in
37459 @ref{thread-id syntax}.
37470 @c 'H': How restrictive (or permissive) is the thread model. If a
37471 @c thread is selected and stopped, are other threads allowed
37472 @c to continue to execute? As I mentioned above, I think the
37473 @c semantics of each command when a thread is selected must be
37474 @c described. For example:
37476 @c 'g': If the stub supports threads and a specific thread is
37477 @c selected, returns the register block from that thread;
37478 @c otherwise returns current registers.
37480 @c 'G' If the stub supports threads and a specific thread is
37481 @c selected, sets the registers of the register block of
37482 @c that thread; otherwise sets current registers.
37484 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37485 @anchor{cycle step packet}
37486 @cindex @samp{i} packet
37487 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37488 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37489 step starting at that address.
37492 @cindex @samp{I} packet
37493 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37497 @cindex @samp{k} packet
37500 FIXME: @emph{There is no description of how to operate when a specific
37501 thread context has been selected (i.e.@: does 'k' kill only that
37504 @item m @var{addr},@var{length}
37505 @cindex @samp{m} packet
37506 Read @var{length} bytes of memory starting at address @var{addr}.
37507 Note that @var{addr} may not be aligned to any particular boundary.
37509 The stub need not use any particular size or alignment when gathering
37510 data from memory for the response; even if @var{addr} is word-aligned
37511 and @var{length} is a multiple of the word size, the stub is free to
37512 use byte accesses, or not. For this reason, this packet may not be
37513 suitable for accessing memory-mapped I/O devices.
37514 @cindex alignment of remote memory accesses
37515 @cindex size of remote memory accesses
37516 @cindex memory, alignment and size of remote accesses
37520 @item @var{XX@dots{}}
37521 Memory contents; each byte is transmitted as a two-digit hexadecimal
37522 number. The reply may contain fewer bytes than requested if the
37523 server was able to read only part of the region of memory.
37528 @item M @var{addr},@var{length}:@var{XX@dots{}}
37529 @cindex @samp{M} packet
37530 Write @var{length} bytes of memory starting at address @var{addr}.
37531 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
37532 hexadecimal number.
37539 for an error (this includes the case where only part of the data was
37544 @cindex @samp{p} packet
37545 Read the value of register @var{n}; @var{n} is in hex.
37546 @xref{read registers packet}, for a description of how the returned
37547 register value is encoded.
37551 @item @var{XX@dots{}}
37552 the register's value
37556 Indicating an unrecognized @var{query}.
37559 @item P @var{n@dots{}}=@var{r@dots{}}
37560 @anchor{write register packet}
37561 @cindex @samp{P} packet
37562 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37563 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37564 digits for each byte in the register (target byte order).
37574 @item q @var{name} @var{params}@dots{}
37575 @itemx Q @var{name} @var{params}@dots{}
37576 @cindex @samp{q} packet
37577 @cindex @samp{Q} packet
37578 General query (@samp{q}) and set (@samp{Q}). These packets are
37579 described fully in @ref{General Query Packets}.
37582 @cindex @samp{r} packet
37583 Reset the entire system.
37585 Don't use this packet; use the @samp{R} packet instead.
37588 @cindex @samp{R} packet
37589 Restart the program being debugged. @var{XX}, while needed, is ignored.
37590 This packet is only available in extended mode (@pxref{extended mode}).
37592 The @samp{R} packet has no reply.
37594 @item s @r{[}@var{addr}@r{]}
37595 @cindex @samp{s} packet
37596 Single step. @var{addr} is the address at which to resume. If
37597 @var{addr} is omitted, resume at same address.
37599 This packet is deprecated for multi-threading support. @xref{vCont
37603 @xref{Stop Reply Packets}, for the reply specifications.
37605 @item S @var{sig}@r{[};@var{addr}@r{]}
37606 @anchor{step with signal packet}
37607 @cindex @samp{S} packet
37608 Step with signal. This is analogous to the @samp{C} packet, but
37609 requests a single-step, rather than a normal resumption of execution.
37611 This packet is deprecated for multi-threading support. @xref{vCont
37615 @xref{Stop Reply Packets}, for the reply specifications.
37617 @item t @var{addr}:@var{PP},@var{MM}
37618 @cindex @samp{t} packet
37619 Search backwards starting at address @var{addr} for a match with pattern
37620 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
37621 @var{addr} must be at least 3 digits.
37623 @item T @var{thread-id}
37624 @cindex @samp{T} packet
37625 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37630 thread is still alive
37636 Packets starting with @samp{v} are identified by a multi-letter name,
37637 up to the first @samp{;} or @samp{?} (or the end of the packet).
37639 @item vAttach;@var{pid}
37640 @cindex @samp{vAttach} packet
37641 Attach to a new process with the specified process ID @var{pid}.
37642 The process ID is a
37643 hexadecimal integer identifying the process. In all-stop mode, all
37644 threads in the attached process are stopped; in non-stop mode, it may be
37645 attached without being stopped if that is supported by the target.
37647 @c In non-stop mode, on a successful vAttach, the stub should set the
37648 @c current thread to a thread of the newly-attached process. After
37649 @c attaching, GDB queries for the attached process's thread ID with qC.
37650 @c Also note that, from a user perspective, whether or not the
37651 @c target is stopped on attach in non-stop mode depends on whether you
37652 @c use the foreground or background version of the attach command, not
37653 @c on what vAttach does; GDB does the right thing with respect to either
37654 @c stopping or restarting threads.
37656 This packet is only available in extended mode (@pxref{extended mode}).
37662 @item @r{Any stop packet}
37663 for success in all-stop mode (@pxref{Stop Reply Packets})
37665 for success in non-stop mode (@pxref{Remote Non-Stop})
37668 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37669 @cindex @samp{vCont} packet
37670 @anchor{vCont packet}
37671 Resume the inferior, specifying different actions for each thread.
37672 If an action is specified with no @var{thread-id}, then it is applied to any
37673 threads that don't have a specific action specified; if no default action is
37674 specified then other threads should remain stopped in all-stop mode and
37675 in their current state in non-stop mode.
37676 Specifying multiple
37677 default actions is an error; specifying no actions is also an error.
37678 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
37680 Currently supported actions are:
37686 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37690 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37693 @item r @var{start},@var{end}
37694 Step once, and then keep stepping as long as the thread stops at
37695 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37696 The remote stub reports a stop reply when either the thread goes out
37697 of the range or is stopped due to an unrelated reason, such as hitting
37698 a breakpoint. @xref{range stepping}.
37700 If the range is empty (@var{start} == @var{end}), then the action
37701 becomes equivalent to the @samp{s} action. In other words,
37702 single-step once, and report the stop (even if the stepped instruction
37703 jumps to @var{start}).
37705 (A stop reply may be sent at any point even if the PC is still within
37706 the stepping range; for example, it is valid to implement this packet
37707 in a degenerate way as a single instruction step operation.)
37711 The optional argument @var{addr} normally associated with the
37712 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37713 not supported in @samp{vCont}.
37715 The @samp{t} action is only relevant in non-stop mode
37716 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37717 A stop reply should be generated for any affected thread not already stopped.
37718 When a thread is stopped by means of a @samp{t} action,
37719 the corresponding stop reply should indicate that the thread has stopped with
37720 signal @samp{0}, regardless of whether the target uses some other signal
37721 as an implementation detail.
37723 The stub must support @samp{vCont} if it reports support for
37724 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
37725 this case @samp{vCont} actions can be specified to apply to all threads
37726 in a process by using the @samp{p@var{pid}.-1} form of the
37730 @xref{Stop Reply Packets}, for the reply specifications.
37733 @cindex @samp{vCont?} packet
37734 Request a list of actions supported by the @samp{vCont} packet.
37738 @item vCont@r{[};@var{action}@dots{}@r{]}
37739 The @samp{vCont} packet is supported. Each @var{action} is a supported
37740 command in the @samp{vCont} packet.
37742 The @samp{vCont} packet is not supported.
37745 @item vFile:@var{operation}:@var{parameter}@dots{}
37746 @cindex @samp{vFile} packet
37747 Perform a file operation on the target system. For details,
37748 see @ref{Host I/O Packets}.
37750 @item vFlashErase:@var{addr},@var{length}
37751 @cindex @samp{vFlashErase} packet
37752 Direct the stub to erase @var{length} bytes of flash starting at
37753 @var{addr}. The region may enclose any number of flash blocks, but
37754 its start and end must fall on block boundaries, as indicated by the
37755 flash block size appearing in the memory map (@pxref{Memory Map
37756 Format}). @value{GDBN} groups flash memory programming operations
37757 together, and sends a @samp{vFlashDone} request after each group; the
37758 stub is allowed to delay erase operation until the @samp{vFlashDone}
37759 packet is received.
37769 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37770 @cindex @samp{vFlashWrite} packet
37771 Direct the stub to write data to flash address @var{addr}. The data
37772 is passed in binary form using the same encoding as for the @samp{X}
37773 packet (@pxref{Binary Data}). The memory ranges specified by
37774 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37775 not overlap, and must appear in order of increasing addresses
37776 (although @samp{vFlashErase} packets for higher addresses may already
37777 have been received; the ordering is guaranteed only between
37778 @samp{vFlashWrite} packets). If a packet writes to an address that was
37779 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37780 target-specific method, the results are unpredictable.
37788 for vFlashWrite addressing non-flash memory
37794 @cindex @samp{vFlashDone} packet
37795 Indicate to the stub that flash programming operation is finished.
37796 The stub is permitted to delay or batch the effects of a group of
37797 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37798 @samp{vFlashDone} packet is received. The contents of the affected
37799 regions of flash memory are unpredictable until the @samp{vFlashDone}
37800 request is completed.
37802 @item vKill;@var{pid}
37803 @cindex @samp{vKill} packet
37804 Kill the process with the specified process ID. @var{pid} is a
37805 hexadecimal integer identifying the process. This packet is used in
37806 preference to @samp{k} when multiprocess protocol extensions are
37807 supported; see @ref{multiprocess extensions}.
37817 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37818 @cindex @samp{vRun} packet
37819 Run the program @var{filename}, passing it each @var{argument} on its
37820 command line. The file and arguments are hex-encoded strings. If
37821 @var{filename} is an empty string, the stub may use a default program
37822 (e.g.@: the last program run). The program is created in the stopped
37825 @c FIXME: What about non-stop mode?
37827 This packet is only available in extended mode (@pxref{extended mode}).
37833 @item @r{Any stop packet}
37834 for success (@pxref{Stop Reply Packets})
37838 @cindex @samp{vStopped} packet
37839 @xref{Notification Packets}.
37841 @item X @var{addr},@var{length}:@var{XX@dots{}}
37843 @cindex @samp{X} packet
37844 Write data to memory, where the data is transmitted in binary.
37845 @var{addr} is address, @var{length} is number of bytes,
37846 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37856 @item z @var{type},@var{addr},@var{kind}
37857 @itemx Z @var{type},@var{addr},@var{kind}
37858 @anchor{insert breakpoint or watchpoint packet}
37859 @cindex @samp{z} packet
37860 @cindex @samp{Z} packets
37861 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37862 watchpoint starting at address @var{address} of kind @var{kind}.
37864 Each breakpoint and watchpoint packet @var{type} is documented
37867 @emph{Implementation notes: A remote target shall return an empty string
37868 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37869 remote target shall support either both or neither of a given
37870 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37871 avoid potential problems with duplicate packets, the operations should
37872 be implemented in an idempotent way.}
37874 @item z0,@var{addr},@var{kind}
37875 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37876 @cindex @samp{z0} packet
37877 @cindex @samp{Z0} packet
37878 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
37879 @var{addr} of type @var{kind}.
37881 A memory breakpoint is implemented by replacing the instruction at
37882 @var{addr} with a software breakpoint or trap instruction. The
37883 @var{kind} is target-specific and typically indicates the size of
37884 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
37885 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37886 architectures have additional meanings for @var{kind};
37887 @var{cond_list} is an optional list of conditional expressions in bytecode
37888 form that should be evaluated on the target's side. These are the
37889 conditions that should be taken into consideration when deciding if
37890 the breakpoint trigger should be reported back to @var{GDBN}.
37892 The @var{cond_list} parameter is comprised of a series of expressions,
37893 concatenated without separators. Each expression has the following form:
37897 @item X @var{len},@var{expr}
37898 @var{len} is the length of the bytecode expression and @var{expr} is the
37899 actual conditional expression in bytecode form.
37903 The optional @var{cmd_list} parameter introduces commands that may be
37904 run on the target, rather than being reported back to @value{GDBN}.
37905 The parameter starts with a numeric flag @var{persist}; if the flag is
37906 nonzero, then the breakpoint may remain active and the commands
37907 continue to be run even when @value{GDBN} disconnects from the target.
37908 Following this flag is a series of expressions concatenated with no
37909 separators. Each expression has the following form:
37913 @item X @var{len},@var{expr}
37914 @var{len} is the length of the bytecode expression and @var{expr} is the
37915 actual conditional expression in bytecode form.
37919 see @ref{Architecture-Specific Protocol Details}.
37921 @emph{Implementation note: It is possible for a target to copy or move
37922 code that contains memory breakpoints (e.g., when implementing
37923 overlays). The behavior of this packet, in the presence of such a
37924 target, is not defined.}
37936 @item z1,@var{addr},@var{kind}
37937 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
37938 @cindex @samp{z1} packet
37939 @cindex @samp{Z1} packet
37940 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
37941 address @var{addr}.
37943 A hardware breakpoint is implemented using a mechanism that is not
37944 dependant on being able to modify the target's memory. @var{kind}
37945 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
37947 @emph{Implementation note: A hardware breakpoint is not affected by code
37960 @item z2,@var{addr},@var{kind}
37961 @itemx Z2,@var{addr},@var{kind}
37962 @cindex @samp{z2} packet
37963 @cindex @samp{Z2} packet
37964 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
37965 @var{kind} is interpreted as the number of bytes to watch.
37977 @item z3,@var{addr},@var{kind}
37978 @itemx Z3,@var{addr},@var{kind}
37979 @cindex @samp{z3} packet
37980 @cindex @samp{Z3} packet
37981 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
37982 @var{kind} is interpreted as the number of bytes to watch.
37994 @item z4,@var{addr},@var{kind}
37995 @itemx Z4,@var{addr},@var{kind}
37996 @cindex @samp{z4} packet
37997 @cindex @samp{Z4} packet
37998 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
37999 @var{kind} is interpreted as the number of bytes to watch.
38013 @node Stop Reply Packets
38014 @section Stop Reply Packets
38015 @cindex stop reply packets
38017 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38018 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38019 receive any of the below as a reply. Except for @samp{?}
38020 and @samp{vStopped}, that reply is only returned
38021 when the target halts. In the below the exact meaning of @dfn{signal
38022 number} is defined by the header @file{include/gdb/signals.h} in the
38023 @value{GDBN} source code.
38025 As in the description of request packets, we include spaces in the
38026 reply templates for clarity; these are not part of the reply packet's
38027 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38033 The program received signal number @var{AA} (a two-digit hexadecimal
38034 number). This is equivalent to a @samp{T} response with no
38035 @var{n}:@var{r} pairs.
38037 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38038 @cindex @samp{T} packet reply
38039 The program received signal number @var{AA} (a two-digit hexadecimal
38040 number). This is equivalent to an @samp{S} response, except that the
38041 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38042 and other information directly in the stop reply packet, reducing
38043 round-trip latency. Single-step and breakpoint traps are reported
38044 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38048 If @var{n} is a hexadecimal number, it is a register number, and the
38049 corresponding @var{r} gives that register's value. @var{r} is a
38050 series of bytes in target byte order, with each byte given by a
38051 two-digit hex number.
38054 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38055 the stopped thread, as specified in @ref{thread-id syntax}.
38058 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38059 the core on which the stop event was detected.
38062 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38063 specific event that stopped the target. The currently defined stop
38064 reasons are listed below. @var{aa} should be @samp{05}, the trap
38065 signal. At most one stop reason should be present.
38068 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38069 and go on to the next; this allows us to extend the protocol in the
38073 The currently defined stop reasons are:
38079 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38082 @cindex shared library events, remote reply
38084 The packet indicates that the loaded libraries have changed.
38085 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38086 list of loaded libraries. @var{r} is ignored.
38088 @cindex replay log events, remote reply
38090 The packet indicates that the target cannot continue replaying
38091 logged execution events, because it has reached the end (or the
38092 beginning when executing backward) of the log. The value of @var{r}
38093 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38094 for more information.
38098 @itemx W @var{AA} ; process:@var{pid}
38099 The process exited, and @var{AA} is the exit status. This is only
38100 applicable to certain targets.
38102 The second form of the response, including the process ID of the exited
38103 process, can be used only when @value{GDBN} has reported support for
38104 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38105 The @var{pid} is formatted as a big-endian hex string.
38108 @itemx X @var{AA} ; process:@var{pid}
38109 The process terminated with signal @var{AA}.
38111 The second form of the response, including the process ID of the
38112 terminated process, can be used only when @value{GDBN} has reported
38113 support for multiprocess protocol extensions; see @ref{multiprocess
38114 extensions}. The @var{pid} is formatted as a big-endian hex string.
38116 @item O @var{XX}@dots{}
38117 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38118 written as the program's console output. This can happen at any time
38119 while the program is running and the debugger should continue to wait
38120 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38122 @item F @var{call-id},@var{parameter}@dots{}
38123 @var{call-id} is the identifier which says which host system call should
38124 be called. This is just the name of the function. Translation into the
38125 correct system call is only applicable as it's defined in @value{GDBN}.
38126 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38129 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38130 this very system call.
38132 The target replies with this packet when it expects @value{GDBN} to
38133 call a host system call on behalf of the target. @value{GDBN} replies
38134 with an appropriate @samp{F} packet and keeps up waiting for the next
38135 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38136 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38137 Protocol Extension}, for more details.
38141 @node General Query Packets
38142 @section General Query Packets
38143 @cindex remote query requests
38145 Packets starting with @samp{q} are @dfn{general query packets};
38146 packets starting with @samp{Q} are @dfn{general set packets}. General
38147 query and set packets are a semi-unified form for retrieving and
38148 sending information to and from the stub.
38150 The initial letter of a query or set packet is followed by a name
38151 indicating what sort of thing the packet applies to. For example,
38152 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38153 definitions with the stub. These packet names follow some
38158 The name must not contain commas, colons or semicolons.
38160 Most @value{GDBN} query and set packets have a leading upper case
38163 The names of custom vendor packets should use a company prefix, in
38164 lower case, followed by a period. For example, packets designed at
38165 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38166 foos) or @samp{Qacme.bar} (for setting bars).
38169 The name of a query or set packet should be separated from any
38170 parameters by a @samp{:}; the parameters themselves should be
38171 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38172 full packet name, and check for a separator or the end of the packet,
38173 in case two packet names share a common prefix. New packets should not begin
38174 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38175 packets predate these conventions, and have arguments without any terminator
38176 for the packet name; we suspect they are in widespread use in places that
38177 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38178 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38181 Like the descriptions of the other packets, each description here
38182 has a template showing the packet's overall syntax, followed by an
38183 explanation of the packet's meaning. We include spaces in some of the
38184 templates for clarity; these are not part of the packet's syntax. No
38185 @value{GDBN} packet uses spaces to separate its components.
38187 Here are the currently defined query and set packets:
38193 Turn on or off the agent as a helper to perform some debugging operations
38194 delegated from @value{GDBN} (@pxref{Control Agent}).
38196 @item QAllow:@var{op}:@var{val}@dots{}
38197 @cindex @samp{QAllow} packet
38198 Specify which operations @value{GDBN} expects to request of the
38199 target, as a semicolon-separated list of operation name and value
38200 pairs. Possible values for @var{op} include @samp{WriteReg},
38201 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38202 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38203 indicating that @value{GDBN} will not request the operation, or 1,
38204 indicating that it may. (The target can then use this to set up its
38205 own internals optimally, for instance if the debugger never expects to
38206 insert breakpoints, it may not need to install its own trap handler.)
38209 @cindex current thread, remote request
38210 @cindex @samp{qC} packet
38211 Return the current thread ID.
38215 @item QC @var{thread-id}
38216 Where @var{thread-id} is a thread ID as documented in
38217 @ref{thread-id syntax}.
38218 @item @r{(anything else)}
38219 Any other reply implies the old thread ID.
38222 @item qCRC:@var{addr},@var{length}
38223 @cindex CRC of memory block, remote request
38224 @cindex @samp{qCRC} packet
38225 Compute the CRC checksum of a block of memory using CRC-32 defined in
38226 IEEE 802.3. The CRC is computed byte at a time, taking the most
38227 significant bit of each byte first. The initial pattern code
38228 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38230 @emph{Note:} This is the same CRC used in validating separate debug
38231 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38232 Files}). However the algorithm is slightly different. When validating
38233 separate debug files, the CRC is computed taking the @emph{least}
38234 significant bit of each byte first, and the final result is inverted to
38235 detect trailing zeros.
38240 An error (such as memory fault)
38241 @item C @var{crc32}
38242 The specified memory region's checksum is @var{crc32}.
38245 @item QDisableRandomization:@var{value}
38246 @cindex disable address space randomization, remote request
38247 @cindex @samp{QDisableRandomization} packet
38248 Some target operating systems will randomize the virtual address space
38249 of the inferior process as a security feature, but provide a feature
38250 to disable such randomization, e.g.@: to allow for a more deterministic
38251 debugging experience. On such systems, this packet with a @var{value}
38252 of 1 directs the target to disable address space randomization for
38253 processes subsequently started via @samp{vRun} packets, while a packet
38254 with a @var{value} of 0 tells the target to enable address space
38257 This packet is only available in extended mode (@pxref{extended mode}).
38262 The request succeeded.
38265 An error occurred. @var{nn} are hex digits.
38268 An empty reply indicates that @samp{QDisableRandomization} is not supported
38272 This packet is not probed by default; the remote stub must request it,
38273 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38274 This should only be done on targets that actually support disabling
38275 address space randomization.
38278 @itemx qsThreadInfo
38279 @cindex list active threads, remote request
38280 @cindex @samp{qfThreadInfo} packet
38281 @cindex @samp{qsThreadInfo} packet
38282 Obtain a list of all active thread IDs from the target (OS). Since there
38283 may be too many active threads to fit into one reply packet, this query
38284 works iteratively: it may require more than one query/reply sequence to
38285 obtain the entire list of threads. The first query of the sequence will
38286 be the @samp{qfThreadInfo} query; subsequent queries in the
38287 sequence will be the @samp{qsThreadInfo} query.
38289 NOTE: This packet replaces the @samp{qL} query (see below).
38293 @item m @var{thread-id}
38295 @item m @var{thread-id},@var{thread-id}@dots{}
38296 a comma-separated list of thread IDs
38298 (lower case letter @samp{L}) denotes end of list.
38301 In response to each query, the target will reply with a list of one or
38302 more thread IDs, separated by commas.
38303 @value{GDBN} will respond to each reply with a request for more thread
38304 ids (using the @samp{qs} form of the query), until the target responds
38305 with @samp{l} (lower-case ell, for @dfn{last}).
38306 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38309 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38310 @cindex get thread-local storage address, remote request
38311 @cindex @samp{qGetTLSAddr} packet
38312 Fetch the address associated with thread local storage specified
38313 by @var{thread-id}, @var{offset}, and @var{lm}.
38315 @var{thread-id} is the thread ID associated with the
38316 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38318 @var{offset} is the (big endian, hex encoded) offset associated with the
38319 thread local variable. (This offset is obtained from the debug
38320 information associated with the variable.)
38322 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38323 load module associated with the thread local storage. For example,
38324 a @sc{gnu}/Linux system will pass the link map address of the shared
38325 object associated with the thread local storage under consideration.
38326 Other operating environments may choose to represent the load module
38327 differently, so the precise meaning of this parameter will vary.
38331 @item @var{XX}@dots{}
38332 Hex encoded (big endian) bytes representing the address of the thread
38333 local storage requested.
38336 An error occurred. @var{nn} are hex digits.
38339 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38342 @item qGetTIBAddr:@var{thread-id}
38343 @cindex get thread information block address
38344 @cindex @samp{qGetTIBAddr} packet
38345 Fetch address of the Windows OS specific Thread Information Block.
38347 @var{thread-id} is the thread ID associated with the thread.
38351 @item @var{XX}@dots{}
38352 Hex encoded (big endian) bytes representing the linear address of the
38353 thread information block.
38356 An error occured. This means that either the thread was not found, or the
38357 address could not be retrieved.
38360 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38363 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38364 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38365 digit) is one to indicate the first query and zero to indicate a
38366 subsequent query; @var{threadcount} (two hex digits) is the maximum
38367 number of threads the response packet can contain; and @var{nextthread}
38368 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38369 returned in the response as @var{argthread}.
38371 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38375 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38376 Where: @var{count} (two hex digits) is the number of threads being
38377 returned; @var{done} (one hex digit) is zero to indicate more threads
38378 and one indicates no further threads; @var{argthreadid} (eight hex
38379 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38380 is a sequence of thread IDs from the target. @var{threadid} (eight hex
38381 digits). See @code{remote.c:parse_threadlist_response()}.
38385 @cindex section offsets, remote request
38386 @cindex @samp{qOffsets} packet
38387 Get section offsets that the target used when relocating the downloaded
38392 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38393 Relocate the @code{Text} section by @var{xxx} from its original address.
38394 Relocate the @code{Data} section by @var{yyy} from its original address.
38395 If the object file format provides segment information (e.g.@: @sc{elf}
38396 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38397 segments by the supplied offsets.
38399 @emph{Note: while a @code{Bss} offset may be included in the response,
38400 @value{GDBN} ignores this and instead applies the @code{Data} offset
38401 to the @code{Bss} section.}
38403 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38404 Relocate the first segment of the object file, which conventionally
38405 contains program code, to a starting address of @var{xxx}. If
38406 @samp{DataSeg} is specified, relocate the second segment, which
38407 conventionally contains modifiable data, to a starting address of
38408 @var{yyy}. @value{GDBN} will report an error if the object file
38409 does not contain segment information, or does not contain at least
38410 as many segments as mentioned in the reply. Extra segments are
38411 kept at fixed offsets relative to the last relocated segment.
38414 @item qP @var{mode} @var{thread-id}
38415 @cindex thread information, remote request
38416 @cindex @samp{qP} packet
38417 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38418 encoded 32 bit mode; @var{thread-id} is a thread ID
38419 (@pxref{thread-id syntax}).
38421 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38424 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38428 @cindex non-stop mode, remote request
38429 @cindex @samp{QNonStop} packet
38431 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38432 @xref{Remote Non-Stop}, for more information.
38437 The request succeeded.
38440 An error occurred. @var{nn} are hex digits.
38443 An empty reply indicates that @samp{QNonStop} is not supported by
38447 This packet is not probed by default; the remote stub must request it,
38448 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38449 Use of this packet is controlled by the @code{set non-stop} command;
38450 @pxref{Non-Stop Mode}.
38452 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38453 @cindex pass signals to inferior, remote request
38454 @cindex @samp{QPassSignals} packet
38455 @anchor{QPassSignals}
38456 Each listed @var{signal} should be passed directly to the inferior process.
38457 Signals are numbered identically to continue packets and stop replies
38458 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38459 strictly greater than the previous item. These signals do not need to stop
38460 the inferior, or be reported to @value{GDBN}. All other signals should be
38461 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38462 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38463 new list. This packet improves performance when using @samp{handle
38464 @var{signal} nostop noprint pass}.
38469 The request succeeded.
38472 An error occurred. @var{nn} are hex digits.
38475 An empty reply indicates that @samp{QPassSignals} is not supported by
38479 Use of this packet is controlled by the @code{set remote pass-signals}
38480 command (@pxref{Remote Configuration, set remote pass-signals}).
38481 This packet is not probed by default; the remote stub must request it,
38482 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38484 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38485 @cindex signals the inferior may see, remote request
38486 @cindex @samp{QProgramSignals} packet
38487 @anchor{QProgramSignals}
38488 Each listed @var{signal} may be delivered to the inferior process.
38489 Others should be silently discarded.
38491 In some cases, the remote stub may need to decide whether to deliver a
38492 signal to the program or not without @value{GDBN} involvement. One
38493 example of that is while detaching --- the program's threads may have
38494 stopped for signals that haven't yet had a chance of being reported to
38495 @value{GDBN}, and so the remote stub can use the signal list specified
38496 by this packet to know whether to deliver or ignore those pending
38499 This does not influence whether to deliver a signal as requested by a
38500 resumption packet (@pxref{vCont packet}).
38502 Signals are numbered identically to continue packets and stop replies
38503 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38504 strictly greater than the previous item. Multiple
38505 @samp{QProgramSignals} packets do not combine; any earlier
38506 @samp{QProgramSignals} list is completely replaced by the new list.
38511 The request succeeded.
38514 An error occurred. @var{nn} are hex digits.
38517 An empty reply indicates that @samp{QProgramSignals} is not supported
38521 Use of this packet is controlled by the @code{set remote program-signals}
38522 command (@pxref{Remote Configuration, set remote program-signals}).
38523 This packet is not probed by default; the remote stub must request it,
38524 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38526 @item qRcmd,@var{command}
38527 @cindex execute remote command, remote request
38528 @cindex @samp{qRcmd} packet
38529 @var{command} (hex encoded) is passed to the local interpreter for
38530 execution. Invalid commands should be reported using the output
38531 string. Before the final result packet, the target may also respond
38532 with a number of intermediate @samp{O@var{output}} console output
38533 packets. @emph{Implementors should note that providing access to a
38534 stubs's interpreter may have security implications}.
38539 A command response with no output.
38541 A command response with the hex encoded output string @var{OUTPUT}.
38543 Indicate a badly formed request.
38545 An empty reply indicates that @samp{qRcmd} is not recognized.
38548 (Note that the @code{qRcmd} packet's name is separated from the
38549 command by a @samp{,}, not a @samp{:}, contrary to the naming
38550 conventions above. Please don't use this packet as a model for new
38553 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38554 @cindex searching memory, in remote debugging
38556 @cindex @samp{qSearch:memory} packet
38558 @cindex @samp{qSearch memory} packet
38559 @anchor{qSearch memory}
38560 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38561 @var{address} and @var{length} are encoded in hex.
38562 @var{search-pattern} is a sequence of bytes, hex encoded.
38567 The pattern was not found.
38569 The pattern was found at @var{address}.
38571 A badly formed request or an error was encountered while searching memory.
38573 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38576 @item QStartNoAckMode
38577 @cindex @samp{QStartNoAckMode} packet
38578 @anchor{QStartNoAckMode}
38579 Request that the remote stub disable the normal @samp{+}/@samp{-}
38580 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38585 The stub has switched to no-acknowledgment mode.
38586 @value{GDBN} acknowledges this reponse,
38587 but neither the stub nor @value{GDBN} shall send or expect further
38588 @samp{+}/@samp{-} acknowledgments in the current connection.
38590 An empty reply indicates that the stub does not support no-acknowledgment mode.
38593 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38594 @cindex supported packets, remote query
38595 @cindex features of the remote protocol
38596 @cindex @samp{qSupported} packet
38597 @anchor{qSupported}
38598 Tell the remote stub about features supported by @value{GDBN}, and
38599 query the stub for features it supports. This packet allows
38600 @value{GDBN} and the remote stub to take advantage of each others'
38601 features. @samp{qSupported} also consolidates multiple feature probes
38602 at startup, to improve @value{GDBN} performance---a single larger
38603 packet performs better than multiple smaller probe packets on
38604 high-latency links. Some features may enable behavior which must not
38605 be on by default, e.g.@: because it would confuse older clients or
38606 stubs. Other features may describe packets which could be
38607 automatically probed for, but are not. These features must be
38608 reported before @value{GDBN} will use them. This ``default
38609 unsupported'' behavior is not appropriate for all packets, but it
38610 helps to keep the initial connection time under control with new
38611 versions of @value{GDBN} which support increasing numbers of packets.
38615 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38616 The stub supports or does not support each returned @var{stubfeature},
38617 depending on the form of each @var{stubfeature} (see below for the
38620 An empty reply indicates that @samp{qSupported} is not recognized,
38621 or that no features needed to be reported to @value{GDBN}.
38624 The allowed forms for each feature (either a @var{gdbfeature} in the
38625 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38629 @item @var{name}=@var{value}
38630 The remote protocol feature @var{name} is supported, and associated
38631 with the specified @var{value}. The format of @var{value} depends
38632 on the feature, but it must not include a semicolon.
38634 The remote protocol feature @var{name} is supported, and does not
38635 need an associated value.
38637 The remote protocol feature @var{name} is not supported.
38639 The remote protocol feature @var{name} may be supported, and
38640 @value{GDBN} should auto-detect support in some other way when it is
38641 needed. This form will not be used for @var{gdbfeature} notifications,
38642 but may be used for @var{stubfeature} responses.
38645 Whenever the stub receives a @samp{qSupported} request, the
38646 supplied set of @value{GDBN} features should override any previous
38647 request. This allows @value{GDBN} to put the stub in a known
38648 state, even if the stub had previously been communicating with
38649 a different version of @value{GDBN}.
38651 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38656 This feature indicates whether @value{GDBN} supports multiprocess
38657 extensions to the remote protocol. @value{GDBN} does not use such
38658 extensions unless the stub also reports that it supports them by
38659 including @samp{multiprocess+} in its @samp{qSupported} reply.
38660 @xref{multiprocess extensions}, for details.
38663 This feature indicates that @value{GDBN} supports the XML target
38664 description. If the stub sees @samp{xmlRegisters=} with target
38665 specific strings separated by a comma, it will report register
38669 This feature indicates whether @value{GDBN} supports the
38670 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
38671 instruction reply packet}).
38674 Stubs should ignore any unknown values for
38675 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
38676 packet supports receiving packets of unlimited length (earlier
38677 versions of @value{GDBN} may reject overly long responses). Additional values
38678 for @var{gdbfeature} may be defined in the future to let the stub take
38679 advantage of new features in @value{GDBN}, e.g.@: incompatible
38680 improvements in the remote protocol---the @samp{multiprocess} feature is
38681 an example of such a feature. The stub's reply should be independent
38682 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
38683 describes all the features it supports, and then the stub replies with
38684 all the features it supports.
38686 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
38687 responses, as long as each response uses one of the standard forms.
38689 Some features are flags. A stub which supports a flag feature
38690 should respond with a @samp{+} form response. Other features
38691 require values, and the stub should respond with an @samp{=}
38694 Each feature has a default value, which @value{GDBN} will use if
38695 @samp{qSupported} is not available or if the feature is not mentioned
38696 in the @samp{qSupported} response. The default values are fixed; a
38697 stub is free to omit any feature responses that match the defaults.
38699 Not all features can be probed, but for those which can, the probing
38700 mechanism is useful: in some cases, a stub's internal
38701 architecture may not allow the protocol layer to know some information
38702 about the underlying target in advance. This is especially common in
38703 stubs which may be configured for multiple targets.
38705 These are the currently defined stub features and their properties:
38707 @multitable @columnfractions 0.35 0.2 0.12 0.2
38708 @c NOTE: The first row should be @headitem, but we do not yet require
38709 @c a new enough version of Texinfo (4.7) to use @headitem.
38711 @tab Value Required
38715 @item @samp{PacketSize}
38720 @item @samp{qXfer:auxv:read}
38725 @item @samp{qXfer:btrace:read}
38730 @item @samp{qXfer:features:read}
38735 @item @samp{qXfer:libraries:read}
38740 @item @samp{qXfer:libraries-svr4:read}
38745 @item @samp{augmented-libraries-svr4-read}
38750 @item @samp{qXfer:memory-map:read}
38755 @item @samp{qXfer:sdata:read}
38760 @item @samp{qXfer:spu:read}
38765 @item @samp{qXfer:spu:write}
38770 @item @samp{qXfer:siginfo:read}
38775 @item @samp{qXfer:siginfo:write}
38780 @item @samp{qXfer:threads:read}
38785 @item @samp{qXfer:traceframe-info:read}
38790 @item @samp{qXfer:uib:read}
38795 @item @samp{qXfer:fdpic:read}
38800 @item @samp{Qbtrace:off}
38805 @item @samp{Qbtrace:bts}
38810 @item @samp{QNonStop}
38815 @item @samp{QPassSignals}
38820 @item @samp{QStartNoAckMode}
38825 @item @samp{multiprocess}
38830 @item @samp{ConditionalBreakpoints}
38835 @item @samp{ConditionalTracepoints}
38840 @item @samp{ReverseContinue}
38845 @item @samp{ReverseStep}
38850 @item @samp{TracepointSource}
38855 @item @samp{QAgent}
38860 @item @samp{QAllow}
38865 @item @samp{QDisableRandomization}
38870 @item @samp{EnableDisableTracepoints}
38875 @item @samp{QTBuffer:size}
38880 @item @samp{tracenz}
38885 @item @samp{BreakpointCommands}
38892 These are the currently defined stub features, in more detail:
38895 @cindex packet size, remote protocol
38896 @item PacketSize=@var{bytes}
38897 The remote stub can accept packets up to at least @var{bytes} in
38898 length. @value{GDBN} will send packets up to this size for bulk
38899 transfers, and will never send larger packets. This is a limit on the
38900 data characters in the packet, including the frame and checksum.
38901 There is no trailing NUL byte in a remote protocol packet; if the stub
38902 stores packets in a NUL-terminated format, it should allow an extra
38903 byte in its buffer for the NUL. If this stub feature is not supported,
38904 @value{GDBN} guesses based on the size of the @samp{g} packet response.
38906 @item qXfer:auxv:read
38907 The remote stub understands the @samp{qXfer:auxv:read} packet
38908 (@pxref{qXfer auxiliary vector read}).
38910 @item qXfer:btrace:read
38911 The remote stub understands the @samp{qXfer:btrace:read}
38912 packet (@pxref{qXfer btrace read}).
38914 @item qXfer:features:read
38915 The remote stub understands the @samp{qXfer:features:read} packet
38916 (@pxref{qXfer target description read}).
38918 @item qXfer:libraries:read
38919 The remote stub understands the @samp{qXfer:libraries:read} packet
38920 (@pxref{qXfer library list read}).
38922 @item qXfer:libraries-svr4:read
38923 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
38924 (@pxref{qXfer svr4 library list read}).
38926 @item augmented-libraries-svr4-read
38927 The remote stub understands the augmented form of the
38928 @samp{qXfer:libraries-svr4:read} packet
38929 (@pxref{qXfer svr4 library list read}).
38931 @item qXfer:memory-map:read
38932 The remote stub understands the @samp{qXfer:memory-map:read} packet
38933 (@pxref{qXfer memory map read}).
38935 @item qXfer:sdata:read
38936 The remote stub understands the @samp{qXfer:sdata:read} packet
38937 (@pxref{qXfer sdata read}).
38939 @item qXfer:spu:read
38940 The remote stub understands the @samp{qXfer:spu:read} packet
38941 (@pxref{qXfer spu read}).
38943 @item qXfer:spu:write
38944 The remote stub understands the @samp{qXfer:spu:write} packet
38945 (@pxref{qXfer spu write}).
38947 @item qXfer:siginfo:read
38948 The remote stub understands the @samp{qXfer:siginfo:read} packet
38949 (@pxref{qXfer siginfo read}).
38951 @item qXfer:siginfo:write
38952 The remote stub understands the @samp{qXfer:siginfo:write} packet
38953 (@pxref{qXfer siginfo write}).
38955 @item qXfer:threads:read
38956 The remote stub understands the @samp{qXfer:threads:read} packet
38957 (@pxref{qXfer threads read}).
38959 @item qXfer:traceframe-info:read
38960 The remote stub understands the @samp{qXfer:traceframe-info:read}
38961 packet (@pxref{qXfer traceframe info read}).
38963 @item qXfer:uib:read
38964 The remote stub understands the @samp{qXfer:uib:read}
38965 packet (@pxref{qXfer unwind info block}).
38967 @item qXfer:fdpic:read
38968 The remote stub understands the @samp{qXfer:fdpic:read}
38969 packet (@pxref{qXfer fdpic loadmap read}).
38972 The remote stub understands the @samp{QNonStop} packet
38973 (@pxref{QNonStop}).
38976 The remote stub understands the @samp{QPassSignals} packet
38977 (@pxref{QPassSignals}).
38979 @item QStartNoAckMode
38980 The remote stub understands the @samp{QStartNoAckMode} packet and
38981 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
38984 @anchor{multiprocess extensions}
38985 @cindex multiprocess extensions, in remote protocol
38986 The remote stub understands the multiprocess extensions to the remote
38987 protocol syntax. The multiprocess extensions affect the syntax of
38988 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
38989 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
38990 replies. Note that reporting this feature indicates support for the
38991 syntactic extensions only, not that the stub necessarily supports
38992 debugging of more than one process at a time. The stub must not use
38993 multiprocess extensions in packet replies unless @value{GDBN} has also
38994 indicated it supports them in its @samp{qSupported} request.
38996 @item qXfer:osdata:read
38997 The remote stub understands the @samp{qXfer:osdata:read} packet
38998 ((@pxref{qXfer osdata read}).
39000 @item ConditionalBreakpoints
39001 The target accepts and implements evaluation of conditional expressions
39002 defined for breakpoints. The target will only report breakpoint triggers
39003 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39005 @item ConditionalTracepoints
39006 The remote stub accepts and implements conditional expressions defined
39007 for tracepoints (@pxref{Tracepoint Conditions}).
39009 @item ReverseContinue
39010 The remote stub accepts and implements the reverse continue packet
39014 The remote stub accepts and implements the reverse step packet
39017 @item TracepointSource
39018 The remote stub understands the @samp{QTDPsrc} packet that supplies
39019 the source form of tracepoint definitions.
39022 The remote stub understands the @samp{QAgent} packet.
39025 The remote stub understands the @samp{QAllow} packet.
39027 @item QDisableRandomization
39028 The remote stub understands the @samp{QDisableRandomization} packet.
39030 @item StaticTracepoint
39031 @cindex static tracepoints, in remote protocol
39032 The remote stub supports static tracepoints.
39034 @item InstallInTrace
39035 @anchor{install tracepoint in tracing}
39036 The remote stub supports installing tracepoint in tracing.
39038 @item EnableDisableTracepoints
39039 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39040 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39041 to be enabled and disabled while a trace experiment is running.
39043 @item QTBuffer:size
39044 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39045 packet that allows to change the size of the trace buffer.
39048 @cindex string tracing, in remote protocol
39049 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39050 See @ref{Bytecode Descriptions} for details about the bytecode.
39052 @item BreakpointCommands
39053 @cindex breakpoint commands, in remote protocol
39054 The remote stub supports running a breakpoint's command list itself,
39055 rather than reporting the hit to @value{GDBN}.
39058 The remote stub understands the @samp{Qbtrace:off} packet.
39061 The remote stub understands the @samp{Qbtrace:bts} packet.
39066 @cindex symbol lookup, remote request
39067 @cindex @samp{qSymbol} packet
39068 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39069 requests. Accept requests from the target for the values of symbols.
39074 The target does not need to look up any (more) symbols.
39075 @item qSymbol:@var{sym_name}
39076 The target requests the value of symbol @var{sym_name} (hex encoded).
39077 @value{GDBN} may provide the value by using the
39078 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39082 @item qSymbol:@var{sym_value}:@var{sym_name}
39083 Set the value of @var{sym_name} to @var{sym_value}.
39085 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39086 target has previously requested.
39088 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39089 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39095 The target does not need to look up any (more) symbols.
39096 @item qSymbol:@var{sym_name}
39097 The target requests the value of a new symbol @var{sym_name} (hex
39098 encoded). @value{GDBN} will continue to supply the values of symbols
39099 (if available), until the target ceases to request them.
39104 @itemx QTDisconnected
39111 @itemx qTMinFTPILen
39113 @xref{Tracepoint Packets}.
39115 @item qThreadExtraInfo,@var{thread-id}
39116 @cindex thread attributes info, remote request
39117 @cindex @samp{qThreadExtraInfo} packet
39118 Obtain a printable string description of a thread's attributes from
39119 the target OS. @var{thread-id} is a thread ID;
39120 see @ref{thread-id syntax}. This
39121 string may contain anything that the target OS thinks is interesting
39122 for @value{GDBN} to tell the user about the thread. The string is
39123 displayed in @value{GDBN}'s @code{info threads} display. Some
39124 examples of possible thread extra info strings are @samp{Runnable}, or
39125 @samp{Blocked on Mutex}.
39129 @item @var{XX}@dots{}
39130 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39131 comprising the printable string containing the extra information about
39132 the thread's attributes.
39135 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39136 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39137 conventions above. Please don't use this packet as a model for new
39156 @xref{Tracepoint Packets}.
39158 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39159 @cindex read special object, remote request
39160 @cindex @samp{qXfer} packet
39161 @anchor{qXfer read}
39162 Read uninterpreted bytes from the target's special data area
39163 identified by the keyword @var{object}. Request @var{length} bytes
39164 starting at @var{offset} bytes into the data. The content and
39165 encoding of @var{annex} is specific to @var{object}; it can supply
39166 additional details about what data to access.
39168 Here are the specific requests of this form defined so far. All
39169 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39170 formats, listed below.
39173 @item qXfer:auxv:read::@var{offset},@var{length}
39174 @anchor{qXfer auxiliary vector read}
39175 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39176 auxiliary vector}. Note @var{annex} must be empty.
39178 This packet is not probed by default; the remote stub must request it,
39179 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39181 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39182 @anchor{qXfer btrace read}
39184 Return a description of the current branch trace.
39185 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39186 packet may have one of the following values:
39190 Returns all available branch trace.
39193 Returns all available branch trace if the branch trace changed since
39194 the last read request.
39197 This packet is not probed by default; the remote stub must request it
39198 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39200 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39201 @anchor{qXfer target description read}
39202 Access the @dfn{target description}. @xref{Target Descriptions}. The
39203 annex specifies which XML document to access. The main description is
39204 always loaded from the @samp{target.xml} annex.
39206 This packet is not probed by default; the remote stub must request it,
39207 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39209 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39210 @anchor{qXfer library list read}
39211 Access the target's list of loaded libraries. @xref{Library List Format}.
39212 The annex part of the generic @samp{qXfer} packet must be empty
39213 (@pxref{qXfer read}).
39215 Targets which maintain a list of libraries in the program's memory do
39216 not need to implement this packet; it is designed for platforms where
39217 the operating system manages the list of loaded libraries.
39219 This packet is not probed by default; the remote stub must request it,
39220 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39222 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39223 @anchor{qXfer svr4 library list read}
39224 Access the target's list of loaded libraries when the target is an SVR4
39225 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39226 of the generic @samp{qXfer} packet must be empty unless the remote
39227 stub indicated it supports the augmented form of this packet
39228 by supplying an appropriate @samp{qSupported} response
39229 (@pxref{qXfer read}, @ref{qSupported}).
39231 This packet is optional for better performance on SVR4 targets.
39232 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39234 This packet is not probed by default; the remote stub must request it,
39235 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39237 If the remote stub indicates it supports the augmented form of this
39238 packet then the annex part of the generic @samp{qXfer} packet may
39239 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39240 arguments. The currently supported arguments are:
39243 @item start=@var{address}
39244 A hexadecimal number specifying the address of the @samp{struct
39245 link_map} to start reading the library list from. If unset or zero
39246 then the first @samp{struct link_map} in the library list will be
39247 chosen as the starting point.
39249 @item prev=@var{address}
39250 A hexadecimal number specifying the address of the @samp{struct
39251 link_map} immediately preceding the @samp{struct link_map}
39252 specified by the @samp{start} argument. If unset or zero then
39253 the remote stub will expect that no @samp{struct link_map}
39254 exists prior to the starting point.
39258 Arguments that are not understood by the remote stub will be silently
39261 @item qXfer:memory-map:read::@var{offset},@var{length}
39262 @anchor{qXfer memory map read}
39263 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39264 annex part of the generic @samp{qXfer} packet must be empty
39265 (@pxref{qXfer read}).
39267 This packet is not probed by default; the remote stub must request it,
39268 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39270 @item qXfer:sdata:read::@var{offset},@var{length}
39271 @anchor{qXfer sdata read}
39273 Read contents of the extra collected static tracepoint marker
39274 information. The annex part of the generic @samp{qXfer} packet must
39275 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39278 This packet is not probed by default; the remote stub must request it,
39279 by supplying an appropriate @samp{qSupported} response
39280 (@pxref{qSupported}).
39282 @item qXfer:siginfo:read::@var{offset},@var{length}
39283 @anchor{qXfer siginfo read}
39284 Read contents of the extra signal information on the target
39285 system. The annex part of the generic @samp{qXfer} packet must be
39286 empty (@pxref{qXfer read}).
39288 This packet is not probed by default; the remote stub must request it,
39289 by supplying an appropriate @samp{qSupported} response
39290 (@pxref{qSupported}).
39292 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39293 @anchor{qXfer spu read}
39294 Read contents of an @code{spufs} file on the target system. The
39295 annex specifies which file to read; it must be of the form
39296 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39297 in the target process, and @var{name} identifes the @code{spufs} file
39298 in that context to be accessed.
39300 This packet is not probed by default; the remote stub must request it,
39301 by supplying an appropriate @samp{qSupported} response
39302 (@pxref{qSupported}).
39304 @item qXfer:threads:read::@var{offset},@var{length}
39305 @anchor{qXfer threads read}
39306 Access the list of threads on target. @xref{Thread List Format}. The
39307 annex part of the generic @samp{qXfer} packet must be empty
39308 (@pxref{qXfer read}).
39310 This packet is not probed by default; the remote stub must request it,
39311 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39313 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39314 @anchor{qXfer traceframe info read}
39316 Return a description of the current traceframe's contents.
39317 @xref{Traceframe Info Format}. The annex part of the generic
39318 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39320 This packet is not probed by default; the remote stub must request it,
39321 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39323 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39324 @anchor{qXfer unwind info block}
39326 Return the unwind information block for @var{pc}. This packet is used
39327 on OpenVMS/ia64 to ask the kernel unwind information.
39329 This packet is not probed by default.
39331 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39332 @anchor{qXfer fdpic loadmap read}
39333 Read contents of @code{loadmap}s on the target system. The
39334 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39335 executable @code{loadmap} or interpreter @code{loadmap} to read.
39337 This packet is not probed by default; the remote stub must request it,
39338 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39340 @item qXfer:osdata:read::@var{offset},@var{length}
39341 @anchor{qXfer osdata read}
39342 Access the target's @dfn{operating system information}.
39343 @xref{Operating System Information}.
39350 Data @var{data} (@pxref{Binary Data}) has been read from the
39351 target. There may be more data at a higher address (although
39352 it is permitted to return @samp{m} even for the last valid
39353 block of data, as long as at least one byte of data was read).
39354 @var{data} may have fewer bytes than the @var{length} in the
39358 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39359 There is no more data to be read. @var{data} may have fewer bytes
39360 than the @var{length} in the request.
39363 The @var{offset} in the request is at the end of the data.
39364 There is no more data to be read.
39367 The request was malformed, or @var{annex} was invalid.
39370 The offset was invalid, or there was an error encountered reading the data.
39371 @var{nn} is a hex-encoded @code{errno} value.
39374 An empty reply indicates the @var{object} string was not recognized by
39375 the stub, or that the object does not support reading.
39378 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39379 @cindex write data into object, remote request
39380 @anchor{qXfer write}
39381 Write uninterpreted bytes into the target's special data area
39382 identified by the keyword @var{object}, starting at @var{offset} bytes
39383 into the data. @var{data}@dots{} is the binary-encoded data
39384 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
39385 is specific to @var{object}; it can supply additional details about what data
39388 Here are the specific requests of this form defined so far. All
39389 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39390 formats, listed below.
39393 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39394 @anchor{qXfer siginfo write}
39395 Write @var{data} to the extra signal information on the target system.
39396 The annex part of the generic @samp{qXfer} packet must be
39397 empty (@pxref{qXfer write}).
39399 This packet is not probed by default; the remote stub must request it,
39400 by supplying an appropriate @samp{qSupported} response
39401 (@pxref{qSupported}).
39403 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39404 @anchor{qXfer spu write}
39405 Write @var{data} to an @code{spufs} file on the target system. The
39406 annex specifies which file to write; it must be of the form
39407 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39408 in the target process, and @var{name} identifes the @code{spufs} file
39409 in that context to be accessed.
39411 This packet is not probed by default; the remote stub must request it,
39412 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39418 @var{nn} (hex encoded) is the number of bytes written.
39419 This may be fewer bytes than supplied in the request.
39422 The request was malformed, or @var{annex} was invalid.
39425 The offset was invalid, or there was an error encountered writing the data.
39426 @var{nn} is a hex-encoded @code{errno} value.
39429 An empty reply indicates the @var{object} string was not
39430 recognized by the stub, or that the object does not support writing.
39433 @item qXfer:@var{object}:@var{operation}:@dots{}
39434 Requests of this form may be added in the future. When a stub does
39435 not recognize the @var{object} keyword, or its support for
39436 @var{object} does not recognize the @var{operation} keyword, the stub
39437 must respond with an empty packet.
39439 @item qAttached:@var{pid}
39440 @cindex query attached, remote request
39441 @cindex @samp{qAttached} packet
39442 Return an indication of whether the remote server attached to an
39443 existing process or created a new process. When the multiprocess
39444 protocol extensions are supported (@pxref{multiprocess extensions}),
39445 @var{pid} is an integer in hexadecimal format identifying the target
39446 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39447 the query packet will be simplified as @samp{qAttached}.
39449 This query is used, for example, to know whether the remote process
39450 should be detached or killed when a @value{GDBN} session is ended with
39451 the @code{quit} command.
39456 The remote server attached to an existing process.
39458 The remote server created a new process.
39460 A badly formed request or an error was encountered.
39464 Enable branch tracing for the current thread using bts tracing.
39469 Branch tracing has been enabled.
39471 A badly formed request or an error was encountered.
39475 Disable branch tracing for the current thread.
39480 Branch tracing has been disabled.
39482 A badly formed request or an error was encountered.
39487 @node Architecture-Specific Protocol Details
39488 @section Architecture-Specific Protocol Details
39490 This section describes how the remote protocol is applied to specific
39491 target architectures. Also see @ref{Standard Target Features}, for
39492 details of XML target descriptions for each architecture.
39495 * ARM-Specific Protocol Details::
39496 * MIPS-Specific Protocol Details::
39499 @node ARM-Specific Protocol Details
39500 @subsection @acronym{ARM}-specific Protocol Details
39503 * ARM Breakpoint Kinds::
39506 @node ARM Breakpoint Kinds
39507 @subsubsection @acronym{ARM} Breakpoint Kinds
39508 @cindex breakpoint kinds, @acronym{ARM}
39510 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39515 16-bit Thumb mode breakpoint.
39518 32-bit Thumb mode (Thumb-2) breakpoint.
39521 32-bit @acronym{ARM} mode breakpoint.
39525 @node MIPS-Specific Protocol Details
39526 @subsection @acronym{MIPS}-specific Protocol Details
39529 * MIPS Register packet Format::
39530 * MIPS Breakpoint Kinds::
39533 @node MIPS Register packet Format
39534 @subsubsection @acronym{MIPS} Register Packet Format
39535 @cindex register packet format, @acronym{MIPS}
39537 The following @code{g}/@code{G} packets have previously been defined.
39538 In the below, some thirty-two bit registers are transferred as
39539 sixty-four bits. Those registers should be zero/sign extended (which?)
39540 to fill the space allocated. Register bytes are transferred in target
39541 byte order. The two nibbles within a register byte are transferred
39542 most-significant -- least-significant.
39547 All registers are transferred as thirty-two bit quantities in the order:
39548 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
39549 registers; fsr; fir; fp.
39552 All registers are transferred as sixty-four bit quantities (including
39553 thirty-two bit registers such as @code{sr}). The ordering is the same
39558 @node MIPS Breakpoint Kinds
39559 @subsubsection @acronym{MIPS} Breakpoint Kinds
39560 @cindex breakpoint kinds, @acronym{MIPS}
39562 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39567 16-bit @acronym{MIPS16} mode breakpoint.
39570 16-bit @acronym{microMIPS} mode breakpoint.
39573 32-bit standard @acronym{MIPS} mode breakpoint.
39576 32-bit @acronym{microMIPS} mode breakpoint.
39580 @node Tracepoint Packets
39581 @section Tracepoint Packets
39582 @cindex tracepoint packets
39583 @cindex packets, tracepoint
39585 Here we describe the packets @value{GDBN} uses to implement
39586 tracepoints (@pxref{Tracepoints}).
39590 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
39591 @cindex @samp{QTDP} packet
39592 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
39593 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
39594 the tracepoint is disabled. @var{step} is the tracepoint's step
39595 count, and @var{pass} is its pass count. If an @samp{F} is present,
39596 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
39597 the number of bytes that the target should copy elsewhere to make room
39598 for the tracepoint. If an @samp{X} is present, it introduces a
39599 tracepoint condition, which consists of a hexadecimal length, followed
39600 by a comma and hex-encoded bytes, in a manner similar to action
39601 encodings as described below. If the trailing @samp{-} is present,
39602 further @samp{QTDP} packets will follow to specify this tracepoint's
39608 The packet was understood and carried out.
39610 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39612 The packet was not recognized.
39615 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
39616 Define actions to be taken when a tracepoint is hit. @var{n} and
39617 @var{addr} must be the same as in the initial @samp{QTDP} packet for
39618 this tracepoint. This packet may only be sent immediately after
39619 another @samp{QTDP} packet that ended with a @samp{-}. If the
39620 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
39621 specifying more actions for this tracepoint.
39623 In the series of action packets for a given tracepoint, at most one
39624 can have an @samp{S} before its first @var{action}. If such a packet
39625 is sent, it and the following packets define ``while-stepping''
39626 actions. Any prior packets define ordinary actions --- that is, those
39627 taken when the tracepoint is first hit. If no action packet has an
39628 @samp{S}, then all the packets in the series specify ordinary
39629 tracepoint actions.
39631 The @samp{@var{action}@dots{}} portion of the packet is a series of
39632 actions, concatenated without separators. Each action has one of the
39638 Collect the registers whose bits are set in @var{mask}. @var{mask} is
39639 a hexadecimal number whose @var{i}'th bit is set if register number
39640 @var{i} should be collected. (The least significant bit is numbered
39641 zero.) Note that @var{mask} may be any number of digits long; it may
39642 not fit in a 32-bit word.
39644 @item M @var{basereg},@var{offset},@var{len}
39645 Collect @var{len} bytes of memory starting at the address in register
39646 number @var{basereg}, plus @var{offset}. If @var{basereg} is
39647 @samp{-1}, then the range has a fixed address: @var{offset} is the
39648 address of the lowest byte to collect. The @var{basereg},
39649 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
39650 values (the @samp{-1} value for @var{basereg} is a special case).
39652 @item X @var{len},@var{expr}
39653 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
39654 it directs. @var{expr} is an agent expression, as described in
39655 @ref{Agent Expressions}. Each byte of the expression is encoded as a
39656 two-digit hex number in the packet; @var{len} is the number of bytes
39657 in the expression (and thus one-half the number of hex digits in the
39662 Any number of actions may be packed together in a single @samp{QTDP}
39663 packet, as long as the packet does not exceed the maximum packet
39664 length (400 bytes, for many stubs). There may be only one @samp{R}
39665 action per tracepoint, and it must precede any @samp{M} or @samp{X}
39666 actions. Any registers referred to by @samp{M} and @samp{X} actions
39667 must be collected by a preceding @samp{R} action. (The
39668 ``while-stepping'' actions are treated as if they were attached to a
39669 separate tracepoint, as far as these restrictions are concerned.)
39674 The packet was understood and carried out.
39676 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39678 The packet was not recognized.
39681 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
39682 @cindex @samp{QTDPsrc} packet
39683 Specify a source string of tracepoint @var{n} at address @var{addr}.
39684 This is useful to get accurate reproduction of the tracepoints
39685 originally downloaded at the beginning of the trace run. @var{type}
39686 is the name of the tracepoint part, such as @samp{cond} for the
39687 tracepoint's conditional expression (see below for a list of types), while
39688 @var{bytes} is the string, encoded in hexadecimal.
39690 @var{start} is the offset of the @var{bytes} within the overall source
39691 string, while @var{slen} is the total length of the source string.
39692 This is intended for handling source strings that are longer than will
39693 fit in a single packet.
39694 @c Add detailed example when this info is moved into a dedicated
39695 @c tracepoint descriptions section.
39697 The available string types are @samp{at} for the location,
39698 @samp{cond} for the conditional, and @samp{cmd} for an action command.
39699 @value{GDBN} sends a separate packet for each command in the action
39700 list, in the same order in which the commands are stored in the list.
39702 The target does not need to do anything with source strings except
39703 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
39706 Although this packet is optional, and @value{GDBN} will only send it
39707 if the target replies with @samp{TracepointSource} @xref{General
39708 Query Packets}, it makes both disconnected tracing and trace files
39709 much easier to use. Otherwise the user must be careful that the
39710 tracepoints in effect while looking at trace frames are identical to
39711 the ones in effect during the trace run; even a small discrepancy
39712 could cause @samp{tdump} not to work, or a particular trace frame not
39715 @item QTDV:@var{n}:@var{value}
39716 @cindex define trace state variable, remote request
39717 @cindex @samp{QTDV} packet
39718 Create a new trace state variable, number @var{n}, with an initial
39719 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
39720 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
39721 the option of not using this packet for initial values of zero; the
39722 target should simply create the trace state variables as they are
39723 mentioned in expressions.
39725 @item QTFrame:@var{n}
39726 @cindex @samp{QTFrame} packet
39727 Select the @var{n}'th tracepoint frame from the buffer, and use the
39728 register and memory contents recorded there to answer subsequent
39729 request packets from @value{GDBN}.
39731 A successful reply from the stub indicates that the stub has found the
39732 requested frame. The response is a series of parts, concatenated
39733 without separators, describing the frame we selected. Each part has
39734 one of the following forms:
39738 The selected frame is number @var{n} in the trace frame buffer;
39739 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
39740 was no frame matching the criteria in the request packet.
39743 The selected trace frame records a hit of tracepoint number @var{t};
39744 @var{t} is a hexadecimal number.
39748 @item QTFrame:pc:@var{addr}
39749 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39750 currently selected frame whose PC is @var{addr};
39751 @var{addr} is a hexadecimal number.
39753 @item QTFrame:tdp:@var{t}
39754 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39755 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
39756 is a hexadecimal number.
39758 @item QTFrame:range:@var{start}:@var{end}
39759 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39760 currently selected frame whose PC is between @var{start} (inclusive)
39761 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
39764 @item QTFrame:outside:@var{start}:@var{end}
39765 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
39766 frame @emph{outside} the given range of addresses (exclusive).
39769 @cindex @samp{qTMinFTPILen} packet
39770 This packet requests the minimum length of instruction at which a fast
39771 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
39772 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
39773 it depends on the target system being able to create trampolines in
39774 the first 64K of memory, which might or might not be possible for that
39775 system. So the reply to this packet will be 4 if it is able to
39782 The minimum instruction length is currently unknown.
39784 The minimum instruction length is @var{length}, where @var{length} is greater
39785 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
39786 that a fast tracepoint may be placed on any instruction regardless of size.
39788 An error has occurred.
39790 An empty reply indicates that the request is not supported by the stub.
39794 @cindex @samp{QTStart} packet
39795 Begin the tracepoint experiment. Begin collecting data from
39796 tracepoint hits in the trace frame buffer. This packet supports the
39797 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
39798 instruction reply packet}).
39801 @cindex @samp{QTStop} packet
39802 End the tracepoint experiment. Stop collecting trace frames.
39804 @item QTEnable:@var{n}:@var{addr}
39806 @cindex @samp{QTEnable} packet
39807 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
39808 experiment. If the tracepoint was previously disabled, then collection
39809 of data from it will resume.
39811 @item QTDisable:@var{n}:@var{addr}
39813 @cindex @samp{QTDisable} packet
39814 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
39815 experiment. No more data will be collected from the tracepoint unless
39816 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
39819 @cindex @samp{QTinit} packet
39820 Clear the table of tracepoints, and empty the trace frame buffer.
39822 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
39823 @cindex @samp{QTro} packet
39824 Establish the given ranges of memory as ``transparent''. The stub
39825 will answer requests for these ranges from memory's current contents,
39826 if they were not collected as part of the tracepoint hit.
39828 @value{GDBN} uses this to mark read-only regions of memory, like those
39829 containing program code. Since these areas never change, they should
39830 still have the same contents they did when the tracepoint was hit, so
39831 there's no reason for the stub to refuse to provide their contents.
39833 @item QTDisconnected:@var{value}
39834 @cindex @samp{QTDisconnected} packet
39835 Set the choice to what to do with the tracing run when @value{GDBN}
39836 disconnects from the target. A @var{value} of 1 directs the target to
39837 continue the tracing run, while 0 tells the target to stop tracing if
39838 @value{GDBN} is no longer in the picture.
39841 @cindex @samp{qTStatus} packet
39842 Ask the stub if there is a trace experiment running right now.
39844 The reply has the form:
39848 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
39849 @var{running} is a single digit @code{1} if the trace is presently
39850 running, or @code{0} if not. It is followed by semicolon-separated
39851 optional fields that an agent may use to report additional status.
39855 If the trace is not running, the agent may report any of several
39856 explanations as one of the optional fields:
39861 No trace has been run yet.
39863 @item tstop[:@var{text}]:0
39864 The trace was stopped by a user-originated stop command. The optional
39865 @var{text} field is a user-supplied string supplied as part of the
39866 stop command (for instance, an explanation of why the trace was
39867 stopped manually). It is hex-encoded.
39870 The trace stopped because the trace buffer filled up.
39872 @item tdisconnected:0
39873 The trace stopped because @value{GDBN} disconnected from the target.
39875 @item tpasscount:@var{tpnum}
39876 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
39878 @item terror:@var{text}:@var{tpnum}
39879 The trace stopped because tracepoint @var{tpnum} had an error. The
39880 string @var{text} is available to describe the nature of the error
39881 (for instance, a divide by zero in the condition expression).
39882 @var{text} is hex encoded.
39885 The trace stopped for some other reason.
39889 Additional optional fields supply statistical and other information.
39890 Although not required, they are extremely useful for users monitoring
39891 the progress of a trace run. If a trace has stopped, and these
39892 numbers are reported, they must reflect the state of the just-stopped
39897 @item tframes:@var{n}
39898 The number of trace frames in the buffer.
39900 @item tcreated:@var{n}
39901 The total number of trace frames created during the run. This may
39902 be larger than the trace frame count, if the buffer is circular.
39904 @item tsize:@var{n}
39905 The total size of the trace buffer, in bytes.
39907 @item tfree:@var{n}
39908 The number of bytes still unused in the buffer.
39910 @item circular:@var{n}
39911 The value of the circular trace buffer flag. @code{1} means that the
39912 trace buffer is circular and old trace frames will be discarded if
39913 necessary to make room, @code{0} means that the trace buffer is linear
39916 @item disconn:@var{n}
39917 The value of the disconnected tracing flag. @code{1} means that
39918 tracing will continue after @value{GDBN} disconnects, @code{0} means
39919 that the trace run will stop.
39923 @item qTP:@var{tp}:@var{addr}
39924 @cindex tracepoint status, remote request
39925 @cindex @samp{qTP} packet
39926 Ask the stub for the current state of tracepoint number @var{tp} at
39927 address @var{addr}.
39931 @item V@var{hits}:@var{usage}
39932 The tracepoint has been hit @var{hits} times so far during the trace
39933 run, and accounts for @var{usage} in the trace buffer. Note that
39934 @code{while-stepping} steps are not counted as separate hits, but the
39935 steps' space consumption is added into the usage number.
39939 @item qTV:@var{var}
39940 @cindex trace state variable value, remote request
39941 @cindex @samp{qTV} packet
39942 Ask the stub for the value of the trace state variable number @var{var}.
39947 The value of the variable is @var{value}. This will be the current
39948 value of the variable if the user is examining a running target, or a
39949 saved value if the variable was collected in the trace frame that the
39950 user is looking at. Note that multiple requests may result in
39951 different reply values, such as when requesting values while the
39952 program is running.
39955 The value of the variable is unknown. This would occur, for example,
39956 if the user is examining a trace frame in which the requested variable
39961 @cindex @samp{qTfP} packet
39963 @cindex @samp{qTsP} packet
39964 These packets request data about tracepoints that are being used by
39965 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39966 of data, and multiple @code{qTsP} to get additional pieces. Replies
39967 to these packets generally take the form of the @code{QTDP} packets
39968 that define tracepoints. (FIXME add detailed syntax)
39971 @cindex @samp{qTfV} packet
39973 @cindex @samp{qTsV} packet
39974 These packets request data about trace state variables that are on the
39975 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39976 and multiple @code{qTsV} to get additional variables. Replies to
39977 these packets follow the syntax of the @code{QTDV} packets that define
39978 trace state variables.
39984 @cindex @samp{qTfSTM} packet
39985 @cindex @samp{qTsSTM} packet
39986 These packets request data about static tracepoint markers that exist
39987 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39988 first piece of data, and multiple @code{qTsSTM} to get additional
39989 pieces. Replies to these packets take the following form:
39993 @item m @var{address}:@var{id}:@var{extra}
39995 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39996 a comma-separated list of markers
39998 (lower case letter @samp{L}) denotes end of list.
40000 An error occurred. @var{nn} are hex digits.
40002 An empty reply indicates that the request is not supported by the
40006 @var{address} is encoded in hex.
40007 @var{id} and @var{extra} are strings encoded in hex.
40009 In response to each query, the target will reply with a list of one or
40010 more markers, separated by commas. @value{GDBN} will respond to each
40011 reply with a request for more markers (using the @samp{qs} form of the
40012 query), until the target responds with @samp{l} (lower-case ell, for
40015 @item qTSTMat:@var{address}
40017 @cindex @samp{qTSTMat} packet
40018 This packets requests data about static tracepoint markers in the
40019 target program at @var{address}. Replies to this packet follow the
40020 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40021 tracepoint markers.
40023 @item QTSave:@var{filename}
40024 @cindex @samp{QTSave} packet
40025 This packet directs the target to save trace data to the file name
40026 @var{filename} in the target's filesystem. @var{filename} is encoded
40027 as a hex string; the interpretation of the file name (relative vs
40028 absolute, wild cards, etc) is up to the target.
40030 @item qTBuffer:@var{offset},@var{len}
40031 @cindex @samp{qTBuffer} packet
40032 Return up to @var{len} bytes of the current contents of trace buffer,
40033 starting at @var{offset}. The trace buffer is treated as if it were
40034 a contiguous collection of traceframes, as per the trace file format.
40035 The reply consists as many hex-encoded bytes as the target can deliver
40036 in a packet; it is not an error to return fewer than were asked for.
40037 A reply consisting of just @code{l} indicates that no bytes are
40040 @item QTBuffer:circular:@var{value}
40041 This packet directs the target to use a circular trace buffer if
40042 @var{value} is 1, or a linear buffer if the value is 0.
40044 @item QTBuffer:size:@var{size}
40045 @anchor{QTBuffer-size}
40046 @cindex @samp{QTBuffer size} packet
40047 This packet directs the target to make the trace buffer be of size
40048 @var{size} if possible. A value of @code{-1} tells the target to
40049 use whatever size it prefers.
40051 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40052 @cindex @samp{QTNotes} packet
40053 This packet adds optional textual notes to the trace run. Allowable
40054 types include @code{user}, @code{notes}, and @code{tstop}, the
40055 @var{text} fields are arbitrary strings, hex-encoded.
40059 @subsection Relocate instruction reply packet
40060 When installing fast tracepoints in memory, the target may need to
40061 relocate the instruction currently at the tracepoint address to a
40062 different address in memory. For most instructions, a simple copy is
40063 enough, but, for example, call instructions that implicitly push the
40064 return address on the stack, and relative branches or other
40065 PC-relative instructions require offset adjustment, so that the effect
40066 of executing the instruction at a different address is the same as if
40067 it had executed in the original location.
40069 In response to several of the tracepoint packets, the target may also
40070 respond with a number of intermediate @samp{qRelocInsn} request
40071 packets before the final result packet, to have @value{GDBN} handle
40072 this relocation operation. If a packet supports this mechanism, its
40073 documentation will explicitly say so. See for example the above
40074 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40075 format of the request is:
40078 @item qRelocInsn:@var{from};@var{to}
40080 This requests @value{GDBN} to copy instruction at address @var{from}
40081 to address @var{to}, possibly adjusted so that executing the
40082 instruction at @var{to} has the same effect as executing it at
40083 @var{from}. @value{GDBN} writes the adjusted instruction to target
40084 memory starting at @var{to}.
40089 @item qRelocInsn:@var{adjusted_size}
40090 Informs the stub the relocation is complete. @var{adjusted_size} is
40091 the length in bytes of resulting relocated instruction sequence.
40093 A badly formed request was detected, or an error was encountered while
40094 relocating the instruction.
40097 @node Host I/O Packets
40098 @section Host I/O Packets
40099 @cindex Host I/O, remote protocol
40100 @cindex file transfer, remote protocol
40102 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40103 operations on the far side of a remote link. For example, Host I/O is
40104 used to upload and download files to a remote target with its own
40105 filesystem. Host I/O uses the same constant values and data structure
40106 layout as the target-initiated File-I/O protocol. However, the
40107 Host I/O packets are structured differently. The target-initiated
40108 protocol relies on target memory to store parameters and buffers.
40109 Host I/O requests are initiated by @value{GDBN}, and the
40110 target's memory is not involved. @xref{File-I/O Remote Protocol
40111 Extension}, for more details on the target-initiated protocol.
40113 The Host I/O request packets all encode a single operation along with
40114 its arguments. They have this format:
40118 @item vFile:@var{operation}: @var{parameter}@dots{}
40119 @var{operation} is the name of the particular request; the target
40120 should compare the entire packet name up to the second colon when checking
40121 for a supported operation. The format of @var{parameter} depends on
40122 the operation. Numbers are always passed in hexadecimal. Negative
40123 numbers have an explicit minus sign (i.e.@: two's complement is not
40124 used). Strings (e.g.@: filenames) are encoded as a series of
40125 hexadecimal bytes. The last argument to a system call may be a
40126 buffer of escaped binary data (@pxref{Binary Data}).
40130 The valid responses to Host I/O packets are:
40134 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40135 @var{result} is the integer value returned by this operation, usually
40136 non-negative for success and -1 for errors. If an error has occured,
40137 @var{errno} will be included in the result. @var{errno} will have a
40138 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40139 operations which return data, @var{attachment} supplies the data as a
40140 binary buffer. Binary buffers in response packets are escaped in the
40141 normal way (@pxref{Binary Data}). See the individual packet
40142 documentation for the interpretation of @var{result} and
40146 An empty response indicates that this operation is not recognized.
40150 These are the supported Host I/O operations:
40153 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40154 Open a file at @var{pathname} and return a file descriptor for it, or
40155 return -1 if an error occurs. @var{pathname} is a string,
40156 @var{flags} is an integer indicating a mask of open flags
40157 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40158 of mode bits to use if the file is created (@pxref{mode_t Values}).
40159 @xref{open}, for details of the open flags and mode values.
40161 @item vFile:close: @var{fd}
40162 Close the open file corresponding to @var{fd} and return 0, or
40163 -1 if an error occurs.
40165 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40166 Read data from the open file corresponding to @var{fd}. Up to
40167 @var{count} bytes will be read from the file, starting at @var{offset}
40168 relative to the start of the file. The target may read fewer bytes;
40169 common reasons include packet size limits and an end-of-file
40170 condition. The number of bytes read is returned. Zero should only be
40171 returned for a successful read at the end of the file, or if
40172 @var{count} was zero.
40174 The data read should be returned as a binary attachment on success.
40175 If zero bytes were read, the response should include an empty binary
40176 attachment (i.e.@: a trailing semicolon). The return value is the
40177 number of target bytes read; the binary attachment may be longer if
40178 some characters were escaped.
40180 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40181 Write @var{data} (a binary buffer) to the open file corresponding
40182 to @var{fd}. Start the write at @var{offset} from the start of the
40183 file. Unlike many @code{write} system calls, there is no
40184 separate @var{count} argument; the length of @var{data} in the
40185 packet is used. @samp{vFile:write} returns the number of bytes written,
40186 which may be shorter than the length of @var{data}, or -1 if an
40189 @item vFile:unlink: @var{pathname}
40190 Delete the file at @var{pathname} on the target. Return 0,
40191 or -1 if an error occurs. @var{pathname} is a string.
40193 @item vFile:readlink: @var{filename}
40194 Read value of symbolic link @var{filename} on the target. Return
40195 the number of bytes read, or -1 if an error occurs.
40197 The data read should be returned as a binary attachment on success.
40198 If zero bytes were read, the response should include an empty binary
40199 attachment (i.e.@: a trailing semicolon). The return value is the
40200 number of target bytes read; the binary attachment may be longer if
40201 some characters were escaped.
40206 @section Interrupts
40207 @cindex interrupts (remote protocol)
40209 When a program on the remote target is running, @value{GDBN} may
40210 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
40211 a @code{BREAK} followed by @code{g},
40212 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40214 The precise meaning of @code{BREAK} is defined by the transport
40215 mechanism and may, in fact, be undefined. @value{GDBN} does not
40216 currently define a @code{BREAK} mechanism for any of the network
40217 interfaces except for TCP, in which case @value{GDBN} sends the
40218 @code{telnet} BREAK sequence.
40220 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40221 transport mechanisms. It is represented by sending the single byte
40222 @code{0x03} without any of the usual packet overhead described in
40223 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40224 transmitted as part of a packet, it is considered to be packet data
40225 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40226 (@pxref{X packet}), used for binary downloads, may include an unescaped
40227 @code{0x03} as part of its packet.
40229 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40230 When Linux kernel receives this sequence from serial port,
40231 it stops execution and connects to gdb.
40233 Stubs are not required to recognize these interrupt mechanisms and the
40234 precise meaning associated with receipt of the interrupt is
40235 implementation defined. If the target supports debugging of multiple
40236 threads and/or processes, it should attempt to interrupt all
40237 currently-executing threads and processes.
40238 If the stub is successful at interrupting the
40239 running program, it should send one of the stop
40240 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40241 of successfully stopping the program in all-stop mode, and a stop reply
40242 for each stopped thread in non-stop mode.
40243 Interrupts received while the
40244 program is stopped are discarded.
40246 @node Notification Packets
40247 @section Notification Packets
40248 @cindex notification packets
40249 @cindex packets, notification
40251 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40252 packets that require no acknowledgment. Both the GDB and the stub
40253 may send notifications (although the only notifications defined at
40254 present are sent by the stub). Notifications carry information
40255 without incurring the round-trip latency of an acknowledgment, and so
40256 are useful for low-impact communications where occasional packet loss
40259 A notification packet has the form @samp{% @var{data} #
40260 @var{checksum}}, where @var{data} is the content of the notification,
40261 and @var{checksum} is a checksum of @var{data}, computed and formatted
40262 as for ordinary @value{GDBN} packets. A notification's @var{data}
40263 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40264 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40265 to acknowledge the notification's receipt or to report its corruption.
40267 Every notification's @var{data} begins with a name, which contains no
40268 colon characters, followed by a colon character.
40270 Recipients should silently ignore corrupted notifications and
40271 notifications they do not understand. Recipients should restart
40272 timeout periods on receipt of a well-formed notification, whether or
40273 not they understand it.
40275 Senders should only send the notifications described here when this
40276 protocol description specifies that they are permitted. In the
40277 future, we may extend the protocol to permit existing notifications in
40278 new contexts; this rule helps older senders avoid confusing newer
40281 (Older versions of @value{GDBN} ignore bytes received until they see
40282 the @samp{$} byte that begins an ordinary packet, so new stubs may
40283 transmit notifications without fear of confusing older clients. There
40284 are no notifications defined for @value{GDBN} to send at the moment, but we
40285 assume that most older stubs would ignore them, as well.)
40287 Each notification is comprised of three parts:
40289 @item @var{name}:@var{event}
40290 The notification packet is sent by the side that initiates the
40291 exchange (currently, only the stub does that), with @var{event}
40292 carrying the specific information about the notification.
40293 @var{name} is the name of the notification.
40295 The acknowledge sent by the other side, usually @value{GDBN}, to
40296 acknowledge the exchange and request the event.
40299 The purpose of an asynchronous notification mechanism is to report to
40300 @value{GDBN} that something interesting happened in the remote stub.
40302 The remote stub may send notification @var{name}:@var{event}
40303 at any time, but @value{GDBN} acknowledges the notification when
40304 appropriate. The notification event is pending before @value{GDBN}
40305 acknowledges. Only one notification at a time may be pending; if
40306 additional events occur before @value{GDBN} has acknowledged the
40307 previous notification, they must be queued by the stub for later
40308 synchronous transmission in response to @var{ack} packets from
40309 @value{GDBN}. Because the notification mechanism is unreliable,
40310 the stub is permitted to resend a notification if it believes
40311 @value{GDBN} may not have received it.
40313 Specifically, notifications may appear when @value{GDBN} is not
40314 otherwise reading input from the stub, or when @value{GDBN} is
40315 expecting to read a normal synchronous response or a
40316 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40317 Notification packets are distinct from any other communication from
40318 the stub so there is no ambiguity.
40320 After receiving a notification, @value{GDBN} shall acknowledge it by
40321 sending a @var{ack} packet as a regular, synchronous request to the
40322 stub. Such acknowledgment is not required to happen immediately, as
40323 @value{GDBN} is permitted to send other, unrelated packets to the
40324 stub first, which the stub should process normally.
40326 Upon receiving a @var{ack} packet, if the stub has other queued
40327 events to report to @value{GDBN}, it shall respond by sending a
40328 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40329 packet to solicit further responses; again, it is permitted to send
40330 other, unrelated packets as well which the stub should process
40333 If the stub receives a @var{ack} packet and there are no additional
40334 @var{event} to report, the stub shall return an @samp{OK} response.
40335 At this point, @value{GDBN} has finished processing a notification
40336 and the stub has completed sending any queued events. @value{GDBN}
40337 won't accept any new notifications until the final @samp{OK} is
40338 received . If further notification events occur, the stub shall send
40339 a new notification, @value{GDBN} shall accept the notification, and
40340 the process shall be repeated.
40342 The process of asynchronous notification can be illustrated by the
40345 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40348 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40350 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40355 The following notifications are defined:
40356 @multitable @columnfractions 0.12 0.12 0.38 0.38
40365 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40366 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40367 for information on how these notifications are acknowledged by
40369 @tab Report an asynchronous stop event in non-stop mode.
40373 @node Remote Non-Stop
40374 @section Remote Protocol Support for Non-Stop Mode
40376 @value{GDBN}'s remote protocol supports non-stop debugging of
40377 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40378 supports non-stop mode, it should report that to @value{GDBN} by including
40379 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40381 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40382 establishing a new connection with the stub. Entering non-stop mode
40383 does not alter the state of any currently-running threads, but targets
40384 must stop all threads in any already-attached processes when entering
40385 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40386 probe the target state after a mode change.
40388 In non-stop mode, when an attached process encounters an event that
40389 would otherwise be reported with a stop reply, it uses the
40390 asynchronous notification mechanism (@pxref{Notification Packets}) to
40391 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40392 in all processes are stopped when a stop reply is sent, in non-stop
40393 mode only the thread reporting the stop event is stopped. That is,
40394 when reporting a @samp{S} or @samp{T} response to indicate completion
40395 of a step operation, hitting a breakpoint, or a fault, only the
40396 affected thread is stopped; any other still-running threads continue
40397 to run. When reporting a @samp{W} or @samp{X} response, all running
40398 threads belonging to other attached processes continue to run.
40400 In non-stop mode, the target shall respond to the @samp{?} packet as
40401 follows. First, any incomplete stop reply notification/@samp{vStopped}
40402 sequence in progress is abandoned. The target must begin a new
40403 sequence reporting stop events for all stopped threads, whether or not
40404 it has previously reported those events to @value{GDBN}. The first
40405 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40406 subsequent stop replies are sent as responses to @samp{vStopped} packets
40407 using the mechanism described above. The target must not send
40408 asynchronous stop reply notifications until the sequence is complete.
40409 If all threads are running when the target receives the @samp{?} packet,
40410 or if the target is not attached to any process, it shall respond
40413 @node Packet Acknowledgment
40414 @section Packet Acknowledgment
40416 @cindex acknowledgment, for @value{GDBN} remote
40417 @cindex packet acknowledgment, for @value{GDBN} remote
40418 By default, when either the host or the target machine receives a packet,
40419 the first response expected is an acknowledgment: either @samp{+} (to indicate
40420 the package was received correctly) or @samp{-} (to request retransmission).
40421 This mechanism allows the @value{GDBN} remote protocol to operate over
40422 unreliable transport mechanisms, such as a serial line.
40424 In cases where the transport mechanism is itself reliable (such as a pipe or
40425 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40426 It may be desirable to disable them in that case to reduce communication
40427 overhead, or for other reasons. This can be accomplished by means of the
40428 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40430 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
40431 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
40432 and response format still includes the normal checksum, as described in
40433 @ref{Overview}, but the checksum may be ignored by the receiver.
40435 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
40436 no-acknowledgment mode, it should report that to @value{GDBN}
40437 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
40438 @pxref{qSupported}.
40439 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40440 disabled via the @code{set remote noack-packet off} command
40441 (@pxref{Remote Configuration}),
40442 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40443 Only then may the stub actually turn off packet acknowledgments.
40444 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
40445 response, which can be safely ignored by the stub.
40447 Note that @code{set remote noack-packet} command only affects negotiation
40448 between @value{GDBN} and the stub when subsequent connections are made;
40449 it does not affect the protocol acknowledgment state for any current
40451 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
40452 new connection is established,
40453 there is also no protocol request to re-enable the acknowledgments
40454 for the current connection, once disabled.
40459 Example sequence of a target being re-started. Notice how the restart
40460 does not get any direct output:
40465 @emph{target restarts}
40468 <- @code{T001:1234123412341234}
40472 Example sequence of a target being stepped by a single instruction:
40475 -> @code{G1445@dots{}}
40480 <- @code{T001:1234123412341234}
40484 <- @code{1455@dots{}}
40488 @node File-I/O Remote Protocol Extension
40489 @section File-I/O Remote Protocol Extension
40490 @cindex File-I/O remote protocol extension
40493 * File-I/O Overview::
40494 * Protocol Basics::
40495 * The F Request Packet::
40496 * The F Reply Packet::
40497 * The Ctrl-C Message::
40499 * List of Supported Calls::
40500 * Protocol-specific Representation of Datatypes::
40502 * File-I/O Examples::
40505 @node File-I/O Overview
40506 @subsection File-I/O Overview
40507 @cindex file-i/o overview
40509 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
40510 target to use the host's file system and console I/O to perform various
40511 system calls. System calls on the target system are translated into a
40512 remote protocol packet to the host system, which then performs the needed
40513 actions and returns a response packet to the target system.
40514 This simulates file system operations even on targets that lack file systems.
40516 The protocol is defined to be independent of both the host and target systems.
40517 It uses its own internal representation of datatypes and values. Both
40518 @value{GDBN} and the target's @value{GDBN} stub are responsible for
40519 translating the system-dependent value representations into the internal
40520 protocol representations when data is transmitted.
40522 The communication is synchronous. A system call is possible only when
40523 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
40524 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
40525 the target is stopped to allow deterministic access to the target's
40526 memory. Therefore File-I/O is not interruptible by target signals. On
40527 the other hand, it is possible to interrupt File-I/O by a user interrupt
40528 (@samp{Ctrl-C}) within @value{GDBN}.
40530 The target's request to perform a host system call does not finish
40531 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
40532 after finishing the system call, the target returns to continuing the
40533 previous activity (continue, step). No additional continue or step
40534 request from @value{GDBN} is required.
40537 (@value{GDBP}) continue
40538 <- target requests 'system call X'
40539 target is stopped, @value{GDBN} executes system call
40540 -> @value{GDBN} returns result
40541 ... target continues, @value{GDBN} returns to wait for the target
40542 <- target hits breakpoint and sends a Txx packet
40545 The protocol only supports I/O on the console and to regular files on
40546 the host file system. Character or block special devices, pipes,
40547 named pipes, sockets or any other communication method on the host
40548 system are not supported by this protocol.
40550 File I/O is not supported in non-stop mode.
40552 @node Protocol Basics
40553 @subsection Protocol Basics
40554 @cindex protocol basics, file-i/o
40556 The File-I/O protocol uses the @code{F} packet as the request as well
40557 as reply packet. Since a File-I/O system call can only occur when
40558 @value{GDBN} is waiting for a response from the continuing or stepping target,
40559 the File-I/O request is a reply that @value{GDBN} has to expect as a result
40560 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
40561 This @code{F} packet contains all information needed to allow @value{GDBN}
40562 to call the appropriate host system call:
40566 A unique identifier for the requested system call.
40569 All parameters to the system call. Pointers are given as addresses
40570 in the target memory address space. Pointers to strings are given as
40571 pointer/length pair. Numerical values are given as they are.
40572 Numerical control flags are given in a protocol-specific representation.
40576 At this point, @value{GDBN} has to perform the following actions.
40580 If the parameters include pointer values to data needed as input to a
40581 system call, @value{GDBN} requests this data from the target with a
40582 standard @code{m} packet request. This additional communication has to be
40583 expected by the target implementation and is handled as any other @code{m}
40587 @value{GDBN} translates all value from protocol representation to host
40588 representation as needed. Datatypes are coerced into the host types.
40591 @value{GDBN} calls the system call.
40594 It then coerces datatypes back to protocol representation.
40597 If the system call is expected to return data in buffer space specified
40598 by pointer parameters to the call, the data is transmitted to the
40599 target using a @code{M} or @code{X} packet. This packet has to be expected
40600 by the target implementation and is handled as any other @code{M} or @code{X}
40605 Eventually @value{GDBN} replies with another @code{F} packet which contains all
40606 necessary information for the target to continue. This at least contains
40613 @code{errno}, if has been changed by the system call.
40620 After having done the needed type and value coercion, the target continues
40621 the latest continue or step action.
40623 @node The F Request Packet
40624 @subsection The @code{F} Request Packet
40625 @cindex file-i/o request packet
40626 @cindex @code{F} request packet
40628 The @code{F} request packet has the following format:
40631 @item F@var{call-id},@var{parameter@dots{}}
40633 @var{call-id} is the identifier to indicate the host system call to be called.
40634 This is just the name of the function.
40636 @var{parameter@dots{}} are the parameters to the system call.
40637 Parameters are hexadecimal integer values, either the actual values in case
40638 of scalar datatypes, pointers to target buffer space in case of compound
40639 datatypes and unspecified memory areas, or pointer/length pairs in case
40640 of string parameters. These are appended to the @var{call-id} as a
40641 comma-delimited list. All values are transmitted in ASCII
40642 string representation, pointer/length pairs separated by a slash.
40648 @node The F Reply Packet
40649 @subsection The @code{F} Reply Packet
40650 @cindex file-i/o reply packet
40651 @cindex @code{F} reply packet
40653 The @code{F} reply packet has the following format:
40657 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
40659 @var{retcode} is the return code of the system call as hexadecimal value.
40661 @var{errno} is the @code{errno} set by the call, in protocol-specific
40663 This parameter can be omitted if the call was successful.
40665 @var{Ctrl-C flag} is only sent if the user requested a break. In this
40666 case, @var{errno} must be sent as well, even if the call was successful.
40667 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
40674 or, if the call was interrupted before the host call has been performed:
40681 assuming 4 is the protocol-specific representation of @code{EINTR}.
40686 @node The Ctrl-C Message
40687 @subsection The @samp{Ctrl-C} Message
40688 @cindex ctrl-c message, in file-i/o protocol
40690 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
40691 reply packet (@pxref{The F Reply Packet}),
40692 the target should behave as if it had
40693 gotten a break message. The meaning for the target is ``system call
40694 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
40695 (as with a break message) and return to @value{GDBN} with a @code{T02}
40698 It's important for the target to know in which
40699 state the system call was interrupted. There are two possible cases:
40703 The system call hasn't been performed on the host yet.
40706 The system call on the host has been finished.
40710 These two states can be distinguished by the target by the value of the
40711 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
40712 call hasn't been performed. This is equivalent to the @code{EINTR} handling
40713 on POSIX systems. In any other case, the target may presume that the
40714 system call has been finished --- successfully or not --- and should behave
40715 as if the break message arrived right after the system call.
40717 @value{GDBN} must behave reliably. If the system call has not been called
40718 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
40719 @code{errno} in the packet. If the system call on the host has been finished
40720 before the user requests a break, the full action must be finished by
40721 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
40722 The @code{F} packet may only be sent when either nothing has happened
40723 or the full action has been completed.
40726 @subsection Console I/O
40727 @cindex console i/o as part of file-i/o
40729 By default and if not explicitly closed by the target system, the file
40730 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
40731 on the @value{GDBN} console is handled as any other file output operation
40732 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
40733 by @value{GDBN} so that after the target read request from file descriptor
40734 0 all following typing is buffered until either one of the following
40739 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
40741 system call is treated as finished.
40744 The user presses @key{RET}. This is treated as end of input with a trailing
40748 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
40749 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
40753 If the user has typed more characters than fit in the buffer given to
40754 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
40755 either another @code{read(0, @dots{})} is requested by the target, or debugging
40756 is stopped at the user's request.
40759 @node List of Supported Calls
40760 @subsection List of Supported Calls
40761 @cindex list of supported file-i/o calls
40778 @unnumberedsubsubsec open
40779 @cindex open, file-i/o system call
40784 int open(const char *pathname, int flags);
40785 int open(const char *pathname, int flags, mode_t mode);
40789 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
40792 @var{flags} is the bitwise @code{OR} of the following values:
40796 If the file does not exist it will be created. The host
40797 rules apply as far as file ownership and time stamps
40801 When used with @code{O_CREAT}, if the file already exists it is
40802 an error and open() fails.
40805 If the file already exists and the open mode allows
40806 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
40807 truncated to zero length.
40810 The file is opened in append mode.
40813 The file is opened for reading only.
40816 The file is opened for writing only.
40819 The file is opened for reading and writing.
40823 Other bits are silently ignored.
40827 @var{mode} is the bitwise @code{OR} of the following values:
40831 User has read permission.
40834 User has write permission.
40837 Group has read permission.
40840 Group has write permission.
40843 Others have read permission.
40846 Others have write permission.
40850 Other bits are silently ignored.
40853 @item Return value:
40854 @code{open} returns the new file descriptor or -1 if an error
40861 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40864 @var{pathname} refers to a directory.
40867 The requested access is not allowed.
40870 @var{pathname} was too long.
40873 A directory component in @var{pathname} does not exist.
40876 @var{pathname} refers to a device, pipe, named pipe or socket.
40879 @var{pathname} refers to a file on a read-only filesystem and
40880 write access was requested.
40883 @var{pathname} is an invalid pointer value.
40886 No space on device to create the file.
40889 The process already has the maximum number of files open.
40892 The limit on the total number of files open on the system
40896 The call was interrupted by the user.
40902 @unnumberedsubsubsec close
40903 @cindex close, file-i/o system call
40912 @samp{Fclose,@var{fd}}
40914 @item Return value:
40915 @code{close} returns zero on success, or -1 if an error occurred.
40921 @var{fd} isn't a valid open file descriptor.
40924 The call was interrupted by the user.
40930 @unnumberedsubsubsec read
40931 @cindex read, file-i/o system call
40936 int read(int fd, void *buf, unsigned int count);
40940 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40942 @item Return value:
40943 On success, the number of bytes read is returned.
40944 Zero indicates end of file. If count is zero, read
40945 returns zero as well. On error, -1 is returned.
40951 @var{fd} is not a valid file descriptor or is not open for
40955 @var{bufptr} is an invalid pointer value.
40958 The call was interrupted by the user.
40964 @unnumberedsubsubsec write
40965 @cindex write, file-i/o system call
40970 int write(int fd, const void *buf, unsigned int count);
40974 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40976 @item Return value:
40977 On success, the number of bytes written are returned.
40978 Zero indicates nothing was written. On error, -1
40985 @var{fd} is not a valid file descriptor or is not open for
40989 @var{bufptr} is an invalid pointer value.
40992 An attempt was made to write a file that exceeds the
40993 host-specific maximum file size allowed.
40996 No space on device to write the data.
40999 The call was interrupted by the user.
41005 @unnumberedsubsubsec lseek
41006 @cindex lseek, file-i/o system call
41011 long lseek (int fd, long offset, int flag);
41015 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41017 @var{flag} is one of:
41021 The offset is set to @var{offset} bytes.
41024 The offset is set to its current location plus @var{offset}
41028 The offset is set to the size of the file plus @var{offset}
41032 @item Return value:
41033 On success, the resulting unsigned offset in bytes from
41034 the beginning of the file is returned. Otherwise, a
41035 value of -1 is returned.
41041 @var{fd} is not a valid open file descriptor.
41044 @var{fd} is associated with the @value{GDBN} console.
41047 @var{flag} is not a proper value.
41050 The call was interrupted by the user.
41056 @unnumberedsubsubsec rename
41057 @cindex rename, file-i/o system call
41062 int rename(const char *oldpath, const char *newpath);
41066 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41068 @item Return value:
41069 On success, zero is returned. On error, -1 is returned.
41075 @var{newpath} is an existing directory, but @var{oldpath} is not a
41079 @var{newpath} is a non-empty directory.
41082 @var{oldpath} or @var{newpath} is a directory that is in use by some
41086 An attempt was made to make a directory a subdirectory
41090 A component used as a directory in @var{oldpath} or new
41091 path is not a directory. Or @var{oldpath} is a directory
41092 and @var{newpath} exists but is not a directory.
41095 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41098 No access to the file or the path of the file.
41102 @var{oldpath} or @var{newpath} was too long.
41105 A directory component in @var{oldpath} or @var{newpath} does not exist.
41108 The file is on a read-only filesystem.
41111 The device containing the file has no room for the new
41115 The call was interrupted by the user.
41121 @unnumberedsubsubsec unlink
41122 @cindex unlink, file-i/o system call
41127 int unlink(const char *pathname);
41131 @samp{Funlink,@var{pathnameptr}/@var{len}}
41133 @item Return value:
41134 On success, zero is returned. On error, -1 is returned.
41140 No access to the file or the path of the file.
41143 The system does not allow unlinking of directories.
41146 The file @var{pathname} cannot be unlinked because it's
41147 being used by another process.
41150 @var{pathnameptr} is an invalid pointer value.
41153 @var{pathname} was too long.
41156 A directory component in @var{pathname} does not exist.
41159 A component of the path is not a directory.
41162 The file is on a read-only filesystem.
41165 The call was interrupted by the user.
41171 @unnumberedsubsubsec stat/fstat
41172 @cindex fstat, file-i/o system call
41173 @cindex stat, file-i/o system call
41178 int stat(const char *pathname, struct stat *buf);
41179 int fstat(int fd, struct stat *buf);
41183 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41184 @samp{Ffstat,@var{fd},@var{bufptr}}
41186 @item Return value:
41187 On success, zero is returned. On error, -1 is returned.
41193 @var{fd} is not a valid open file.
41196 A directory component in @var{pathname} does not exist or the
41197 path is an empty string.
41200 A component of the path is not a directory.
41203 @var{pathnameptr} is an invalid pointer value.
41206 No access to the file or the path of the file.
41209 @var{pathname} was too long.
41212 The call was interrupted by the user.
41218 @unnumberedsubsubsec gettimeofday
41219 @cindex gettimeofday, file-i/o system call
41224 int gettimeofday(struct timeval *tv, void *tz);
41228 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41230 @item Return value:
41231 On success, 0 is returned, -1 otherwise.
41237 @var{tz} is a non-NULL pointer.
41240 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41246 @unnumberedsubsubsec isatty
41247 @cindex isatty, file-i/o system call
41252 int isatty(int fd);
41256 @samp{Fisatty,@var{fd}}
41258 @item Return value:
41259 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41265 The call was interrupted by the user.
41270 Note that the @code{isatty} call is treated as a special case: it returns
41271 1 to the target if the file descriptor is attached
41272 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41273 would require implementing @code{ioctl} and would be more complex than
41278 @unnumberedsubsubsec system
41279 @cindex system, file-i/o system call
41284 int system(const char *command);
41288 @samp{Fsystem,@var{commandptr}/@var{len}}
41290 @item Return value:
41291 If @var{len} is zero, the return value indicates whether a shell is
41292 available. A zero return value indicates a shell is not available.
41293 For non-zero @var{len}, the value returned is -1 on error and the
41294 return status of the command otherwise. Only the exit status of the
41295 command is returned, which is extracted from the host's @code{system}
41296 return value by calling @code{WEXITSTATUS(retval)}. In case
41297 @file{/bin/sh} could not be executed, 127 is returned.
41303 The call was interrupted by the user.
41308 @value{GDBN} takes over the full task of calling the necessary host calls
41309 to perform the @code{system} call. The return value of @code{system} on
41310 the host is simplified before it's returned
41311 to the target. Any termination signal information from the child process
41312 is discarded, and the return value consists
41313 entirely of the exit status of the called command.
41315 Due to security concerns, the @code{system} call is by default refused
41316 by @value{GDBN}. The user has to allow this call explicitly with the
41317 @code{set remote system-call-allowed 1} command.
41320 @item set remote system-call-allowed
41321 @kindex set remote system-call-allowed
41322 Control whether to allow the @code{system} calls in the File I/O
41323 protocol for the remote target. The default is zero (disabled).
41325 @item show remote system-call-allowed
41326 @kindex show remote system-call-allowed
41327 Show whether the @code{system} calls are allowed in the File I/O
41331 @node Protocol-specific Representation of Datatypes
41332 @subsection Protocol-specific Representation of Datatypes
41333 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41336 * Integral Datatypes::
41338 * Memory Transfer::
41343 @node Integral Datatypes
41344 @unnumberedsubsubsec Integral Datatypes
41345 @cindex integral datatypes, in file-i/o protocol
41347 The integral datatypes used in the system calls are @code{int},
41348 @code{unsigned int}, @code{long}, @code{unsigned long},
41349 @code{mode_t}, and @code{time_t}.
41351 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41352 implemented as 32 bit values in this protocol.
41354 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41356 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41357 in @file{limits.h}) to allow range checking on host and target.
41359 @code{time_t} datatypes are defined as seconds since the Epoch.
41361 All integral datatypes transferred as part of a memory read or write of a
41362 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41365 @node Pointer Values
41366 @unnumberedsubsubsec Pointer Values
41367 @cindex pointer values, in file-i/o protocol
41369 Pointers to target data are transmitted as they are. An exception
41370 is made for pointers to buffers for which the length isn't
41371 transmitted as part of the function call, namely strings. Strings
41372 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41379 which is a pointer to data of length 18 bytes at position 0x1aaf.
41380 The length is defined as the full string length in bytes, including
41381 the trailing null byte. For example, the string @code{"hello world"}
41382 at address 0x123456 is transmitted as
41388 @node Memory Transfer
41389 @unnumberedsubsubsec Memory Transfer
41390 @cindex memory transfer, in file-i/o protocol
41392 Structured data which is transferred using a memory read or write (for
41393 example, a @code{struct stat}) is expected to be in a protocol-specific format
41394 with all scalar multibyte datatypes being big endian. Translation to
41395 this representation needs to be done both by the target before the @code{F}
41396 packet is sent, and by @value{GDBN} before
41397 it transfers memory to the target. Transferred pointers to structured
41398 data should point to the already-coerced data at any time.
41402 @unnumberedsubsubsec struct stat
41403 @cindex struct stat, in file-i/o protocol
41405 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41406 is defined as follows:
41410 unsigned int st_dev; /* device */
41411 unsigned int st_ino; /* inode */
41412 mode_t st_mode; /* protection */
41413 unsigned int st_nlink; /* number of hard links */
41414 unsigned int st_uid; /* user ID of owner */
41415 unsigned int st_gid; /* group ID of owner */
41416 unsigned int st_rdev; /* device type (if inode device) */
41417 unsigned long st_size; /* total size, in bytes */
41418 unsigned long st_blksize; /* blocksize for filesystem I/O */
41419 unsigned long st_blocks; /* number of blocks allocated */
41420 time_t st_atime; /* time of last access */
41421 time_t st_mtime; /* time of last modification */
41422 time_t st_ctime; /* time of last change */
41426 The integral datatypes conform to the definitions given in the
41427 appropriate section (see @ref{Integral Datatypes}, for details) so this
41428 structure is of size 64 bytes.
41430 The values of several fields have a restricted meaning and/or
41436 A value of 0 represents a file, 1 the console.
41439 No valid meaning for the target. Transmitted unchanged.
41442 Valid mode bits are described in @ref{Constants}. Any other
41443 bits have currently no meaning for the target.
41448 No valid meaning for the target. Transmitted unchanged.
41453 These values have a host and file system dependent
41454 accuracy. Especially on Windows hosts, the file system may not
41455 support exact timing values.
41458 The target gets a @code{struct stat} of the above representation and is
41459 responsible for coercing it to the target representation before
41462 Note that due to size differences between the host, target, and protocol
41463 representations of @code{struct stat} members, these members could eventually
41464 get truncated on the target.
41466 @node struct timeval
41467 @unnumberedsubsubsec struct timeval
41468 @cindex struct timeval, in file-i/o protocol
41470 The buffer of type @code{struct timeval} used by the File-I/O protocol
41471 is defined as follows:
41475 time_t tv_sec; /* second */
41476 long tv_usec; /* microsecond */
41480 The integral datatypes conform to the definitions given in the
41481 appropriate section (see @ref{Integral Datatypes}, for details) so this
41482 structure is of size 8 bytes.
41485 @subsection Constants
41486 @cindex constants, in file-i/o protocol
41488 The following values are used for the constants inside of the
41489 protocol. @value{GDBN} and target are responsible for translating these
41490 values before and after the call as needed.
41501 @unnumberedsubsubsec Open Flags
41502 @cindex open flags, in file-i/o protocol
41504 All values are given in hexadecimal representation.
41516 @node mode_t Values
41517 @unnumberedsubsubsec mode_t Values
41518 @cindex mode_t values, in file-i/o protocol
41520 All values are given in octal representation.
41537 @unnumberedsubsubsec Errno Values
41538 @cindex errno values, in file-i/o protocol
41540 All values are given in decimal representation.
41565 @code{EUNKNOWN} is used as a fallback error value if a host system returns
41566 any error value not in the list of supported error numbers.
41569 @unnumberedsubsubsec Lseek Flags
41570 @cindex lseek flags, in file-i/o protocol
41579 @unnumberedsubsubsec Limits
41580 @cindex limits, in file-i/o protocol
41582 All values are given in decimal representation.
41585 INT_MIN -2147483648
41587 UINT_MAX 4294967295
41588 LONG_MIN -9223372036854775808
41589 LONG_MAX 9223372036854775807
41590 ULONG_MAX 18446744073709551615
41593 @node File-I/O Examples
41594 @subsection File-I/O Examples
41595 @cindex file-i/o examples
41597 Example sequence of a write call, file descriptor 3, buffer is at target
41598 address 0x1234, 6 bytes should be written:
41601 <- @code{Fwrite,3,1234,6}
41602 @emph{request memory read from target}
41605 @emph{return "6 bytes written"}
41609 Example sequence of a read call, file descriptor 3, buffer is at target
41610 address 0x1234, 6 bytes should be read:
41613 <- @code{Fread,3,1234,6}
41614 @emph{request memory write to target}
41615 -> @code{X1234,6:XXXXXX}
41616 @emph{return "6 bytes read"}
41620 Example sequence of a read call, call fails on the host due to invalid
41621 file descriptor (@code{EBADF}):
41624 <- @code{Fread,3,1234,6}
41628 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
41632 <- @code{Fread,3,1234,6}
41637 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
41641 <- @code{Fread,3,1234,6}
41642 -> @code{X1234,6:XXXXXX}
41646 @node Library List Format
41647 @section Library List Format
41648 @cindex library list format, remote protocol
41650 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
41651 same process as your application to manage libraries. In this case,
41652 @value{GDBN} can use the loader's symbol table and normal memory
41653 operations to maintain a list of shared libraries. On other
41654 platforms, the operating system manages loaded libraries.
41655 @value{GDBN} can not retrieve the list of currently loaded libraries
41656 through memory operations, so it uses the @samp{qXfer:libraries:read}
41657 packet (@pxref{qXfer library list read}) instead. The remote stub
41658 queries the target's operating system and reports which libraries
41661 The @samp{qXfer:libraries:read} packet returns an XML document which
41662 lists loaded libraries and their offsets. Each library has an
41663 associated name and one or more segment or section base addresses,
41664 which report where the library was loaded in memory.
41666 For the common case of libraries that are fully linked binaries, the
41667 library should have a list of segments. If the target supports
41668 dynamic linking of a relocatable object file, its library XML element
41669 should instead include a list of allocated sections. The segment or
41670 section bases are start addresses, not relocation offsets; they do not
41671 depend on the library's link-time base addresses.
41673 @value{GDBN} must be linked with the Expat library to support XML
41674 library lists. @xref{Expat}.
41676 A simple memory map, with one loaded library relocated by a single
41677 offset, looks like this:
41681 <library name="/lib/libc.so.6">
41682 <segment address="0x10000000"/>
41687 Another simple memory map, with one loaded library with three
41688 allocated sections (.text, .data, .bss), looks like this:
41692 <library name="sharedlib.o">
41693 <section address="0x10000000"/>
41694 <section address="0x20000000"/>
41695 <section address="0x30000000"/>
41700 The format of a library list is described by this DTD:
41703 <!-- library-list: Root element with versioning -->
41704 <!ELEMENT library-list (library)*>
41705 <!ATTLIST library-list version CDATA #FIXED "1.0">
41706 <!ELEMENT library (segment*, section*)>
41707 <!ATTLIST library name CDATA #REQUIRED>
41708 <!ELEMENT segment EMPTY>
41709 <!ATTLIST segment address CDATA #REQUIRED>
41710 <!ELEMENT section EMPTY>
41711 <!ATTLIST section address CDATA #REQUIRED>
41714 In addition, segments and section descriptors cannot be mixed within a
41715 single library element, and you must supply at least one segment or
41716 section for each library.
41718 @node Library List Format for SVR4 Targets
41719 @section Library List Format for SVR4 Targets
41720 @cindex library list format, remote protocol
41722 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
41723 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
41724 shared libraries. Still a special library list provided by this packet is
41725 more efficient for the @value{GDBN} remote protocol.
41727 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
41728 loaded libraries and their SVR4 linker parameters. For each library on SVR4
41729 target, the following parameters are reported:
41733 @code{name}, the absolute file name from the @code{l_name} field of
41734 @code{struct link_map}.
41736 @code{lm} with address of @code{struct link_map} used for TLS
41737 (Thread Local Storage) access.
41739 @code{l_addr}, the displacement as read from the field @code{l_addr} of
41740 @code{struct link_map}. For prelinked libraries this is not an absolute
41741 memory address. It is a displacement of absolute memory address against
41742 address the file was prelinked to during the library load.
41744 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
41747 Additionally the single @code{main-lm} attribute specifies address of
41748 @code{struct link_map} used for the main executable. This parameter is used
41749 for TLS access and its presence is optional.
41751 @value{GDBN} must be linked with the Expat library to support XML
41752 SVR4 library lists. @xref{Expat}.
41754 A simple memory map, with two loaded libraries (which do not use prelink),
41758 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
41759 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
41761 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
41763 </library-list-svr>
41766 The format of an SVR4 library list is described by this DTD:
41769 <!-- library-list-svr4: Root element with versioning -->
41770 <!ELEMENT library-list-svr4 (library)*>
41771 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
41772 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
41773 <!ELEMENT library EMPTY>
41774 <!ATTLIST library name CDATA #REQUIRED>
41775 <!ATTLIST library lm CDATA #REQUIRED>
41776 <!ATTLIST library l_addr CDATA #REQUIRED>
41777 <!ATTLIST library l_ld CDATA #REQUIRED>
41780 @node Memory Map Format
41781 @section Memory Map Format
41782 @cindex memory map format
41784 To be able to write into flash memory, @value{GDBN} needs to obtain a
41785 memory map from the target. This section describes the format of the
41788 The memory map is obtained using the @samp{qXfer:memory-map:read}
41789 (@pxref{qXfer memory map read}) packet and is an XML document that
41790 lists memory regions.
41792 @value{GDBN} must be linked with the Expat library to support XML
41793 memory maps. @xref{Expat}.
41795 The top-level structure of the document is shown below:
41798 <?xml version="1.0"?>
41799 <!DOCTYPE memory-map
41800 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41801 "http://sourceware.org/gdb/gdb-memory-map.dtd">
41807 Each region can be either:
41812 A region of RAM starting at @var{addr} and extending for @var{length}
41816 <memory type="ram" start="@var{addr}" length="@var{length}"/>
41821 A region of read-only memory:
41824 <memory type="rom" start="@var{addr}" length="@var{length}"/>
41829 A region of flash memory, with erasure blocks @var{blocksize}
41833 <memory type="flash" start="@var{addr}" length="@var{length}">
41834 <property name="blocksize">@var{blocksize}</property>
41840 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
41841 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
41842 packets to write to addresses in such ranges.
41844 The formal DTD for memory map format is given below:
41847 <!-- ................................................... -->
41848 <!-- Memory Map XML DTD ................................ -->
41849 <!-- File: memory-map.dtd .............................. -->
41850 <!-- .................................... .............. -->
41851 <!-- memory-map.dtd -->
41852 <!-- memory-map: Root element with versioning -->
41853 <!ELEMENT memory-map (memory | property)>
41854 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
41855 <!ELEMENT memory (property)>
41856 <!-- memory: Specifies a memory region,
41857 and its type, or device. -->
41858 <!ATTLIST memory type CDATA #REQUIRED
41859 start CDATA #REQUIRED
41860 length CDATA #REQUIRED
41861 device CDATA #IMPLIED>
41862 <!-- property: Generic attribute tag -->
41863 <!ELEMENT property (#PCDATA | property)*>
41864 <!ATTLIST property name CDATA #REQUIRED>
41867 @node Thread List Format
41868 @section Thread List Format
41869 @cindex thread list format
41871 To efficiently update the list of threads and their attributes,
41872 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41873 (@pxref{qXfer threads read}) and obtains the XML document with
41874 the following structure:
41877 <?xml version="1.0"?>
41879 <thread id="id" core="0">
41880 ... description ...
41885 Each @samp{thread} element must have the @samp{id} attribute that
41886 identifies the thread (@pxref{thread-id syntax}). The
41887 @samp{core} attribute, if present, specifies which processor core
41888 the thread was last executing on. The content of the of @samp{thread}
41889 element is interpreted as human-readable auxilliary information.
41891 @node Traceframe Info Format
41892 @section Traceframe Info Format
41893 @cindex traceframe info format
41895 To be able to know which objects in the inferior can be examined when
41896 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41897 memory ranges, registers and trace state variables that have been
41898 collected in a traceframe.
41900 This list is obtained using the @samp{qXfer:traceframe-info:read}
41901 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41903 @value{GDBN} must be linked with the Expat library to support XML
41904 traceframe info discovery. @xref{Expat}.
41906 The top-level structure of the document is shown below:
41909 <?xml version="1.0"?>
41910 <!DOCTYPE traceframe-info
41911 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41912 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41918 Each traceframe block can be either:
41923 A region of collected memory starting at @var{addr} and extending for
41924 @var{length} bytes from there:
41927 <memory start="@var{addr}" length="@var{length}"/>
41931 A block indicating trace state variable numbered @var{number} has been
41935 <tvar id="@var{number}"/>
41940 The formal DTD for the traceframe info format is given below:
41943 <!ELEMENT traceframe-info (memory | tvar)* >
41944 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41946 <!ELEMENT memory EMPTY>
41947 <!ATTLIST memory start CDATA #REQUIRED
41948 length CDATA #REQUIRED>
41950 <!ATTLIST tvar id CDATA #REQUIRED>
41953 @node Branch Trace Format
41954 @section Branch Trace Format
41955 @cindex branch trace format
41957 In order to display the branch trace of an inferior thread,
41958 @value{GDBN} needs to obtain the list of branches. This list is
41959 represented as list of sequential code blocks that are connected via
41960 branches. The code in each block has been executed sequentially.
41962 This list is obtained using the @samp{qXfer:btrace:read}
41963 (@pxref{qXfer btrace read}) packet and is an XML document.
41965 @value{GDBN} must be linked with the Expat library to support XML
41966 traceframe info discovery. @xref{Expat}.
41968 The top-level structure of the document is shown below:
41971 <?xml version="1.0"?>
41973 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41974 "http://sourceware.org/gdb/gdb-btrace.dtd">
41983 A block of sequentially executed instructions starting at @var{begin}
41984 and ending at @var{end}:
41987 <block begin="@var{begin}" end="@var{end}"/>
41992 The formal DTD for the branch trace format is given below:
41995 <!ELEMENT btrace (block)* >
41996 <!ATTLIST btrace version CDATA #FIXED "1.0">
41998 <!ELEMENT block EMPTY>
41999 <!ATTLIST block begin CDATA #REQUIRED
42000 end CDATA #REQUIRED>
42003 @include agentexpr.texi
42005 @node Target Descriptions
42006 @appendix Target Descriptions
42007 @cindex target descriptions
42009 One of the challenges of using @value{GDBN} to debug embedded systems
42010 is that there are so many minor variants of each processor
42011 architecture in use. It is common practice for vendors to start with
42012 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42013 and then make changes to adapt it to a particular market niche. Some
42014 architectures have hundreds of variants, available from dozens of
42015 vendors. This leads to a number of problems:
42019 With so many different customized processors, it is difficult for
42020 the @value{GDBN} maintainers to keep up with the changes.
42022 Since individual variants may have short lifetimes or limited
42023 audiences, it may not be worthwhile to carry information about every
42024 variant in the @value{GDBN} source tree.
42026 When @value{GDBN} does support the architecture of the embedded system
42027 at hand, the task of finding the correct architecture name to give the
42028 @command{set architecture} command can be error-prone.
42031 To address these problems, the @value{GDBN} remote protocol allows a
42032 target system to not only identify itself to @value{GDBN}, but to
42033 actually describe its own features. This lets @value{GDBN} support
42034 processor variants it has never seen before --- to the extent that the
42035 descriptions are accurate, and that @value{GDBN} understands them.
42037 @value{GDBN} must be linked with the Expat library to support XML
42038 target descriptions. @xref{Expat}.
42041 * Retrieving Descriptions:: How descriptions are fetched from a target.
42042 * Target Description Format:: The contents of a target description.
42043 * Predefined Target Types:: Standard types available for target
42045 * Standard Target Features:: Features @value{GDBN} knows about.
42048 @node Retrieving Descriptions
42049 @section Retrieving Descriptions
42051 Target descriptions can be read from the target automatically, or
42052 specified by the user manually. The default behavior is to read the
42053 description from the target. @value{GDBN} retrieves it via the remote
42054 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42055 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42056 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42057 XML document, of the form described in @ref{Target Description
42060 Alternatively, you can specify a file to read for the target description.
42061 If a file is set, the target will not be queried. The commands to
42062 specify a file are:
42065 @cindex set tdesc filename
42066 @item set tdesc filename @var{path}
42067 Read the target description from @var{path}.
42069 @cindex unset tdesc filename
42070 @item unset tdesc filename
42071 Do not read the XML target description from a file. @value{GDBN}
42072 will use the description supplied by the current target.
42074 @cindex show tdesc filename
42075 @item show tdesc filename
42076 Show the filename to read for a target description, if any.
42080 @node Target Description Format
42081 @section Target Description Format
42082 @cindex target descriptions, XML format
42084 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42085 document which complies with the Document Type Definition provided in
42086 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42087 means you can use generally available tools like @command{xmllint} to
42088 check that your feature descriptions are well-formed and valid.
42089 However, to help people unfamiliar with XML write descriptions for
42090 their targets, we also describe the grammar here.
42092 Target descriptions can identify the architecture of the remote target
42093 and (for some architectures) provide information about custom register
42094 sets. They can also identify the OS ABI of the remote target.
42095 @value{GDBN} can use this information to autoconfigure for your
42096 target, or to warn you if you connect to an unsupported target.
42098 Here is a simple target description:
42101 <target version="1.0">
42102 <architecture>i386:x86-64</architecture>
42107 This minimal description only says that the target uses
42108 the x86-64 architecture.
42110 A target description has the following overall form, with [ ] marking
42111 optional elements and @dots{} marking repeatable elements. The elements
42112 are explained further below.
42115 <?xml version="1.0"?>
42116 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42117 <target version="1.0">
42118 @r{[}@var{architecture}@r{]}
42119 @r{[}@var{osabi}@r{]}
42120 @r{[}@var{compatible}@r{]}
42121 @r{[}@var{feature}@dots{}@r{]}
42126 The description is generally insensitive to whitespace and line
42127 breaks, under the usual common-sense rules. The XML version
42128 declaration and document type declaration can generally be omitted
42129 (@value{GDBN} does not require them), but specifying them may be
42130 useful for XML validation tools. The @samp{version} attribute for
42131 @samp{<target>} may also be omitted, but we recommend
42132 including it; if future versions of @value{GDBN} use an incompatible
42133 revision of @file{gdb-target.dtd}, they will detect and report
42134 the version mismatch.
42136 @subsection Inclusion
42137 @cindex target descriptions, inclusion
42140 @cindex <xi:include>
42143 It can sometimes be valuable to split a target description up into
42144 several different annexes, either for organizational purposes, or to
42145 share files between different possible target descriptions. You can
42146 divide a description into multiple files by replacing any element of
42147 the target description with an inclusion directive of the form:
42150 <xi:include href="@var{document}"/>
42154 When @value{GDBN} encounters an element of this form, it will retrieve
42155 the named XML @var{document}, and replace the inclusion directive with
42156 the contents of that document. If the current description was read
42157 using @samp{qXfer}, then so will be the included document;
42158 @var{document} will be interpreted as the name of an annex. If the
42159 current description was read from a file, @value{GDBN} will look for
42160 @var{document} as a file in the same directory where it found the
42161 original description.
42163 @subsection Architecture
42164 @cindex <architecture>
42166 An @samp{<architecture>} element has this form:
42169 <architecture>@var{arch}</architecture>
42172 @var{arch} is one of the architectures from the set accepted by
42173 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42176 @cindex @code{<osabi>}
42178 This optional field was introduced in @value{GDBN} version 7.0.
42179 Previous versions of @value{GDBN} ignore it.
42181 An @samp{<osabi>} element has this form:
42184 <osabi>@var{abi-name}</osabi>
42187 @var{abi-name} is an OS ABI name from the same selection accepted by
42188 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42190 @subsection Compatible Architecture
42191 @cindex @code{<compatible>}
42193 This optional field was introduced in @value{GDBN} version 7.0.
42194 Previous versions of @value{GDBN} ignore it.
42196 A @samp{<compatible>} element has this form:
42199 <compatible>@var{arch}</compatible>
42202 @var{arch} is one of the architectures from the set accepted by
42203 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42205 A @samp{<compatible>} element is used to specify that the target
42206 is able to run binaries in some other than the main target architecture
42207 given by the @samp{<architecture>} element. For example, on the
42208 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42209 or @code{powerpc:common64}, but the system is able to run binaries
42210 in the @code{spu} architecture as well. The way to describe this
42211 capability with @samp{<compatible>} is as follows:
42214 <architecture>powerpc:common</architecture>
42215 <compatible>spu</compatible>
42218 @subsection Features
42221 Each @samp{<feature>} describes some logical portion of the target
42222 system. Features are currently used to describe available CPU
42223 registers and the types of their contents. A @samp{<feature>} element
42227 <feature name="@var{name}">
42228 @r{[}@var{type}@dots{}@r{]}
42234 Each feature's name should be unique within the description. The name
42235 of a feature does not matter unless @value{GDBN} has some special
42236 knowledge of the contents of that feature; if it does, the feature
42237 should have its standard name. @xref{Standard Target Features}.
42241 Any register's value is a collection of bits which @value{GDBN} must
42242 interpret. The default interpretation is a two's complement integer,
42243 but other types can be requested by name in the register description.
42244 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42245 Target Types}), and the description can define additional composite types.
42247 Each type element must have an @samp{id} attribute, which gives
42248 a unique (within the containing @samp{<feature>}) name to the type.
42249 Types must be defined before they are used.
42252 Some targets offer vector registers, which can be treated as arrays
42253 of scalar elements. These types are written as @samp{<vector>} elements,
42254 specifying the array element type, @var{type}, and the number of elements,
42258 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42262 If a register's value is usefully viewed in multiple ways, define it
42263 with a union type containing the useful representations. The
42264 @samp{<union>} element contains one or more @samp{<field>} elements,
42265 each of which has a @var{name} and a @var{type}:
42268 <union id="@var{id}">
42269 <field name="@var{name}" type="@var{type}"/>
42275 If a register's value is composed from several separate values, define
42276 it with a structure type. There are two forms of the @samp{<struct>}
42277 element; a @samp{<struct>} element must either contain only bitfields
42278 or contain no bitfields. If the structure contains only bitfields,
42279 its total size in bytes must be specified, each bitfield must have an
42280 explicit start and end, and bitfields are automatically assigned an
42281 integer type. The field's @var{start} should be less than or
42282 equal to its @var{end}, and zero represents the least significant bit.
42285 <struct id="@var{id}" size="@var{size}">
42286 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42291 If the structure contains no bitfields, then each field has an
42292 explicit type, and no implicit padding is added.
42295 <struct id="@var{id}">
42296 <field name="@var{name}" type="@var{type}"/>
42302 If a register's value is a series of single-bit flags, define it with
42303 a flags type. The @samp{<flags>} element has an explicit @var{size}
42304 and contains one or more @samp{<field>} elements. Each field has a
42305 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
42309 <flags id="@var{id}" size="@var{size}">
42310 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42315 @subsection Registers
42318 Each register is represented as an element with this form:
42321 <reg name="@var{name}"
42322 bitsize="@var{size}"
42323 @r{[}regnum="@var{num}"@r{]}
42324 @r{[}save-restore="@var{save-restore}"@r{]}
42325 @r{[}type="@var{type}"@r{]}
42326 @r{[}group="@var{group}"@r{]}/>
42330 The components are as follows:
42335 The register's name; it must be unique within the target description.
42338 The register's size, in bits.
42341 The register's number. If omitted, a register's number is one greater
42342 than that of the previous register (either in the current feature or in
42343 a preceding feature); the first register in the target description
42344 defaults to zero. This register number is used to read or write
42345 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42346 packets, and registers appear in the @code{g} and @code{G} packets
42347 in order of increasing register number.
42350 Whether the register should be preserved across inferior function
42351 calls; this must be either @code{yes} or @code{no}. The default is
42352 @code{yes}, which is appropriate for most registers except for
42353 some system control registers; this is not related to the target's
42357 The type of the register. @var{type} may be a predefined type, a type
42358 defined in the current feature, or one of the special types @code{int}
42359 and @code{float}. @code{int} is an integer type of the correct size
42360 for @var{bitsize}, and @code{float} is a floating point type (in the
42361 architecture's normal floating point format) of the correct size for
42362 @var{bitsize}. The default is @code{int}.
42365 The register group to which this register belongs. @var{group} must
42366 be either @code{general}, @code{float}, or @code{vector}. If no
42367 @var{group} is specified, @value{GDBN} will not display the register
42368 in @code{info registers}.
42372 @node Predefined Target Types
42373 @section Predefined Target Types
42374 @cindex target descriptions, predefined types
42376 Type definitions in the self-description can build up composite types
42377 from basic building blocks, but can not define fundamental types. Instead,
42378 standard identifiers are provided by @value{GDBN} for the fundamental
42379 types. The currently supported types are:
42388 Signed integer types holding the specified number of bits.
42395 Unsigned integer types holding the specified number of bits.
42399 Pointers to unspecified code and data. The program counter and
42400 any dedicated return address register may be marked as code
42401 pointers; printing a code pointer converts it into a symbolic
42402 address. The stack pointer and any dedicated address registers
42403 may be marked as data pointers.
42406 Single precision IEEE floating point.
42409 Double precision IEEE floating point.
42412 The 12-byte extended precision format used by ARM FPA registers.
42415 The 10-byte extended precision format used by x87 registers.
42418 32bit @sc{eflags} register used by x86.
42421 32bit @sc{mxcsr} register used by x86.
42425 @node Standard Target Features
42426 @section Standard Target Features
42427 @cindex target descriptions, standard features
42429 A target description must contain either no registers or all the
42430 target's registers. If the description contains no registers, then
42431 @value{GDBN} will assume a default register layout, selected based on
42432 the architecture. If the description contains any registers, the
42433 default layout will not be used; the standard registers must be
42434 described in the target description, in such a way that @value{GDBN}
42435 can recognize them.
42437 This is accomplished by giving specific names to feature elements
42438 which contain standard registers. @value{GDBN} will look for features
42439 with those names and verify that they contain the expected registers;
42440 if any known feature is missing required registers, or if any required
42441 feature is missing, @value{GDBN} will reject the target
42442 description. You can add additional registers to any of the
42443 standard features --- @value{GDBN} will display them just as if
42444 they were added to an unrecognized feature.
42446 This section lists the known features and their expected contents.
42447 Sample XML documents for these features are included in the
42448 @value{GDBN} source tree, in the directory @file{gdb/features}.
42450 Names recognized by @value{GDBN} should include the name of the
42451 company or organization which selected the name, and the overall
42452 architecture to which the feature applies; so e.g.@: the feature
42453 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
42455 The names of registers are not case sensitive for the purpose
42456 of recognizing standard features, but @value{GDBN} will only display
42457 registers using the capitalization used in the description.
42460 * AArch64 Features::
42465 * Nios II Features::
42466 * PowerPC Features::
42471 @node AArch64 Features
42472 @subsection AArch64 Features
42473 @cindex target descriptions, AArch64 features
42475 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
42476 targets. It should contain registers @samp{x0} through @samp{x30},
42477 @samp{sp}, @samp{pc}, and @samp{cpsr}.
42479 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
42480 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
42484 @subsection ARM Features
42485 @cindex target descriptions, ARM features
42487 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
42489 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
42490 @samp{lr}, @samp{pc}, and @samp{cpsr}.
42492 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
42493 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
42494 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
42497 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
42498 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
42500 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
42501 it should contain at least registers @samp{wR0} through @samp{wR15} and
42502 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
42503 @samp{wCSSF}, and @samp{wCASF} registers are optional.
42505 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
42506 should contain at least registers @samp{d0} through @samp{d15}. If
42507 they are present, @samp{d16} through @samp{d31} should also be included.
42508 @value{GDBN} will synthesize the single-precision registers from
42509 halves of the double-precision registers.
42511 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
42512 need to contain registers; it instructs @value{GDBN} to display the
42513 VFP double-precision registers as vectors and to synthesize the
42514 quad-precision registers from pairs of double-precision registers.
42515 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
42516 be present and include 32 double-precision registers.
42518 @node i386 Features
42519 @subsection i386 Features
42520 @cindex target descriptions, i386 features
42522 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
42523 targets. It should describe the following registers:
42527 @samp{eax} through @samp{edi} plus @samp{eip} for i386
42529 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
42531 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
42532 @samp{fs}, @samp{gs}
42534 @samp{st0} through @samp{st7}
42536 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
42537 @samp{foseg}, @samp{fooff} and @samp{fop}
42540 The register sets may be different, depending on the target.
42542 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
42543 describe registers:
42547 @samp{xmm0} through @samp{xmm7} for i386
42549 @samp{xmm0} through @samp{xmm15} for amd64
42554 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
42555 @samp{org.gnu.gdb.i386.sse} feature. It should
42556 describe the upper 128 bits of @sc{ymm} registers:
42560 @samp{ymm0h} through @samp{ymm7h} for i386
42562 @samp{ymm0h} through @samp{ymm15h} for amd64
42565 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
42566 describe a single register, @samp{orig_eax}.
42568 @node MIPS Features
42569 @subsection @acronym{MIPS} Features
42570 @cindex target descriptions, @acronym{MIPS} features
42572 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
42573 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
42574 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
42577 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
42578 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
42579 registers. They may be 32-bit or 64-bit depending on the target.
42581 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42582 it may be optional in a future version of @value{GDBN}. It should
42583 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42584 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42586 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42587 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42588 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42589 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42591 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42592 contain a single register, @samp{restart}, which is used by the
42593 Linux kernel to control restartable syscalls.
42595 @node M68K Features
42596 @subsection M68K Features
42597 @cindex target descriptions, M68K features
42600 @item @samp{org.gnu.gdb.m68k.core}
42601 @itemx @samp{org.gnu.gdb.coldfire.core}
42602 @itemx @samp{org.gnu.gdb.fido.core}
42603 One of those features must be always present.
42604 The feature that is present determines which flavor of m68k is
42605 used. The feature that is present should contain registers
42606 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42607 @samp{sp}, @samp{ps} and @samp{pc}.
42609 @item @samp{org.gnu.gdb.coldfire.fp}
42610 This feature is optional. If present, it should contain registers
42611 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42615 @node Nios II Features
42616 @subsection Nios II Features
42617 @cindex target descriptions, Nios II features
42619 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42620 targets. It should contain the 32 core registers (@samp{zero},
42621 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42622 @samp{pc}, and the 16 control registers (@samp{status} through
42625 @node PowerPC Features
42626 @subsection PowerPC Features
42627 @cindex target descriptions, PowerPC features
42629 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42630 targets. It should contain registers @samp{r0} through @samp{r31},
42631 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42632 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42634 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42635 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42637 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42638 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42641 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42642 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42643 will combine these registers with the floating point registers
42644 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42645 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42646 through @samp{vs63}, the set of vector registers for POWER7.
42648 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42649 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42650 @samp{spefscr}. SPE targets should provide 32-bit registers in
42651 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42652 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42653 these to present registers @samp{ev0} through @samp{ev31} to the
42656 @node TIC6x Features
42657 @subsection TMS320C6x Features
42658 @cindex target descriptions, TIC6x features
42659 @cindex target descriptions, TMS320C6x features
42660 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42661 targets. It should contain registers @samp{A0} through @samp{A15},
42662 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42664 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42665 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42666 through @samp{B31}.
42668 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42669 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42671 @node Operating System Information
42672 @appendix Operating System Information
42673 @cindex operating system information
42679 Users of @value{GDBN} often wish to obtain information about the state of
42680 the operating system running on the target---for example the list of
42681 processes, or the list of open files. This section describes the
42682 mechanism that makes it possible. This mechanism is similar to the
42683 target features mechanism (@pxref{Target Descriptions}), but focuses
42684 on a different aspect of target.
42686 Operating system information is retrived from the target via the
42687 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42688 read}). The object name in the request should be @samp{osdata}, and
42689 the @var{annex} identifies the data to be fetched.
42692 @appendixsection Process list
42693 @cindex operating system information, process list
42695 When requesting the process list, the @var{annex} field in the
42696 @samp{qXfer} request should be @samp{processes}. The returned data is
42697 an XML document. The formal syntax of this document is defined in
42698 @file{gdb/features/osdata.dtd}.
42700 An example document is:
42703 <?xml version="1.0"?>
42704 <!DOCTYPE target SYSTEM "osdata.dtd">
42705 <osdata type="processes">
42707 <column name="pid">1</column>
42708 <column name="user">root</column>
42709 <column name="command">/sbin/init</column>
42710 <column name="cores">1,2,3</column>
42715 Each item should include a column whose name is @samp{pid}. The value
42716 of that column should identify the process on the target. The
42717 @samp{user} and @samp{command} columns are optional, and will be
42718 displayed by @value{GDBN}. The @samp{cores} column, if present,
42719 should contain a comma-separated list of cores that this process
42720 is running on. Target may provide additional columns,
42721 which @value{GDBN} currently ignores.
42723 @node Trace File Format
42724 @appendix Trace File Format
42725 @cindex trace file format
42727 The trace file comes in three parts: a header, a textual description
42728 section, and a trace frame section with binary data.
42730 The header has the form @code{\x7fTRACE0\n}. The first byte is
42731 @code{0x7f} so as to indicate that the file contains binary data,
42732 while the @code{0} is a version number that may have different values
42735 The description section consists of multiple lines of @sc{ascii} text
42736 separated by newline characters (@code{0xa}). The lines may include a
42737 variety of optional descriptive or context-setting information, such
42738 as tracepoint definitions or register set size. @value{GDBN} will
42739 ignore any line that it does not recognize. An empty line marks the end
42742 @c FIXME add some specific types of data
42744 The trace frame section consists of a number of consecutive frames.
42745 Each frame begins with a two-byte tracepoint number, followed by a
42746 four-byte size giving the amount of data in the frame. The data in
42747 the frame consists of a number of blocks, each introduced by a
42748 character indicating its type (at least register, memory, and trace
42749 state variable). The data in this section is raw binary, not a
42750 hexadecimal or other encoding; its endianness matches the target's
42753 @c FIXME bi-arch may require endianness/arch info in description section
42756 @item R @var{bytes}
42757 Register block. The number and ordering of bytes matches that of a
42758 @code{g} packet in the remote protocol. Note that these are the
42759 actual bytes, in target order and @value{GDBN} register order, not a
42760 hexadecimal encoding.
42762 @item M @var{address} @var{length} @var{bytes}...
42763 Memory block. This is a contiguous block of memory, at the 8-byte
42764 address @var{address}, with a 2-byte length @var{length}, followed by
42765 @var{length} bytes.
42767 @item V @var{number} @var{value}
42768 Trace state variable block. This records the 8-byte signed value
42769 @var{value} of trace state variable numbered @var{number}.
42773 Future enhancements of the trace file format may include additional types
42776 @node Index Section Format
42777 @appendix @code{.gdb_index} section format
42778 @cindex .gdb_index section format
42779 @cindex index section format
42781 This section documents the index section that is created by @code{save
42782 gdb-index} (@pxref{Index Files}). The index section is
42783 DWARF-specific; some knowledge of DWARF is assumed in this
42786 The mapped index file format is designed to be directly
42787 @code{mmap}able on any architecture. In most cases, a datum is
42788 represented using a little-endian 32-bit integer value, called an
42789 @code{offset_type}. Big endian machines must byte-swap the values
42790 before using them. Exceptions to this rule are noted. The data is
42791 laid out such that alignment is always respected.
42793 A mapped index consists of several areas, laid out in order.
42797 The file header. This is a sequence of values, of @code{offset_type}
42798 unless otherwise noted:
42802 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42803 Version 4 uses a different hashing function from versions 5 and 6.
42804 Version 6 includes symbols for inlined functions, whereas versions 4
42805 and 5 do not. Version 7 adds attributes to the CU indices in the
42806 symbol table. Version 8 specifies that symbols from DWARF type units
42807 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42808 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42810 @value{GDBN} will only read version 4, 5, or 6 indices
42811 by specifying @code{set use-deprecated-index-sections on}.
42812 GDB has a workaround for potentially broken version 7 indices so it is
42813 currently not flagged as deprecated.
42816 The offset, from the start of the file, of the CU list.
42819 The offset, from the start of the file, of the types CU list. Note
42820 that this area can be empty, in which case this offset will be equal
42821 to the next offset.
42824 The offset, from the start of the file, of the address area.
42827 The offset, from the start of the file, of the symbol table.
42830 The offset, from the start of the file, of the constant pool.
42834 The CU list. This is a sequence of pairs of 64-bit little-endian
42835 values, sorted by the CU offset. The first element in each pair is
42836 the offset of a CU in the @code{.debug_info} section. The second
42837 element in each pair is the length of that CU. References to a CU
42838 elsewhere in the map are done using a CU index, which is just the
42839 0-based index into this table. Note that if there are type CUs, then
42840 conceptually CUs and type CUs form a single list for the purposes of
42844 The types CU list. This is a sequence of triplets of 64-bit
42845 little-endian values. In a triplet, the first value is the CU offset,
42846 the second value is the type offset in the CU, and the third value is
42847 the type signature. The types CU list is not sorted.
42850 The address area. The address area consists of a sequence of address
42851 entries. Each address entry has three elements:
42855 The low address. This is a 64-bit little-endian value.
42858 The high address. This is a 64-bit little-endian value. Like
42859 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42862 The CU index. This is an @code{offset_type} value.
42866 The symbol table. This is an open-addressed hash table. The size of
42867 the hash table is always a power of 2.
42869 Each slot in the hash table consists of a pair of @code{offset_type}
42870 values. The first value is the offset of the symbol's name in the
42871 constant pool. The second value is the offset of the CU vector in the
42874 If both values are 0, then this slot in the hash table is empty. This
42875 is ok because while 0 is a valid constant pool index, it cannot be a
42876 valid index for both a string and a CU vector.
42878 The hash value for a table entry is computed by applying an
42879 iterative hash function to the symbol's name. Starting with an
42880 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42881 the string is incorporated into the hash using the formula depending on the
42886 The formula is @code{r = r * 67 + c - 113}.
42888 @item Versions 5 to 7
42889 The formula is @code{r = r * 67 + tolower (c) - 113}.
42892 The terminating @samp{\0} is not incorporated into the hash.
42894 The step size used in the hash table is computed via
42895 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42896 value, and @samp{size} is the size of the hash table. The step size
42897 is used to find the next candidate slot when handling a hash
42900 The names of C@t{++} symbols in the hash table are canonicalized. We
42901 don't currently have a simple description of the canonicalization
42902 algorithm; if you intend to create new index sections, you must read
42906 The constant pool. This is simply a bunch of bytes. It is organized
42907 so that alignment is correct: CU vectors are stored first, followed by
42910 A CU vector in the constant pool is a sequence of @code{offset_type}
42911 values. The first value is the number of CU indices in the vector.
42912 Each subsequent value is the index and symbol attributes of a CU in
42913 the CU list. This element in the hash table is used to indicate which
42914 CUs define the symbol and how the symbol is used.
42915 See below for the format of each CU index+attributes entry.
42917 A string in the constant pool is zero-terminated.
42920 Attributes were added to CU index values in @code{.gdb_index} version 7.
42921 If a symbol has multiple uses within a CU then there is one
42922 CU index+attributes value for each use.
42924 The format of each CU index+attributes entry is as follows
42930 This is the index of the CU in the CU list.
42932 These bits are reserved for future purposes and must be zero.
42934 The kind of the symbol in the CU.
42938 This value is reserved and should not be used.
42939 By reserving zero the full @code{offset_type} value is backwards compatible
42940 with previous versions of the index.
42942 The symbol is a type.
42944 The symbol is a variable or an enum value.
42946 The symbol is a function.
42948 Any other kind of symbol.
42950 These values are reserved.
42954 This bit is zero if the value is global and one if it is static.
42956 The determination of whether a symbol is global or static is complicated.
42957 The authorative reference is the file @file{dwarf2read.c} in
42958 @value{GDBN} sources.
42962 This pseudo-code describes the computation of a symbol's kind and
42963 global/static attributes in the index.
42966 is_external = get_attribute (die, DW_AT_external);
42967 language = get_attribute (cu_die, DW_AT_language);
42970 case DW_TAG_typedef:
42971 case DW_TAG_base_type:
42972 case DW_TAG_subrange_type:
42976 case DW_TAG_enumerator:
42978 is_static = (language != CPLUS && language != JAVA);
42980 case DW_TAG_subprogram:
42982 is_static = ! (is_external || language == ADA);
42984 case DW_TAG_constant:
42986 is_static = ! is_external;
42988 case DW_TAG_variable:
42990 is_static = ! is_external;
42992 case DW_TAG_namespace:
42996 case DW_TAG_class_type:
42997 case DW_TAG_interface_type:
42998 case DW_TAG_structure_type:
42999 case DW_TAG_union_type:
43000 case DW_TAG_enumeration_type:
43002 is_static = (language != CPLUS && language != JAVA);
43010 @appendix Manual pages
43014 * gdb man:: The GNU Debugger man page
43015 * gdbserver man:: Remote Server for the GNU Debugger man page
43016 * gcore man:: Generate a core file of a running program
43017 * gdbinit man:: gdbinit scripts
43023 @c man title gdb The GNU Debugger
43025 @c man begin SYNOPSIS gdb
43026 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43027 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43028 [@option{-b}@w{ }@var{bps}]
43029 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43030 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43031 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43032 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43033 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43036 @c man begin DESCRIPTION gdb
43037 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43038 going on ``inside'' another program while it executes -- or what another
43039 program was doing at the moment it crashed.
43041 @value{GDBN} can do four main kinds of things (plus other things in support of
43042 these) to help you catch bugs in the act:
43046 Start your program, specifying anything that might affect its behavior.
43049 Make your program stop on specified conditions.
43052 Examine what has happened, when your program has stopped.
43055 Change things in your program, so you can experiment with correcting the
43056 effects of one bug and go on to learn about another.
43059 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43062 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43063 commands from the terminal until you tell it to exit with the @value{GDBN}
43064 command @code{quit}. You can get online help from @value{GDBN} itself
43065 by using the command @code{help}.
43067 You can run @code{gdb} with no arguments or options; but the most
43068 usual way to start @value{GDBN} is with one argument or two, specifying an
43069 executable program as the argument:
43075 You can also start with both an executable program and a core file specified:
43081 You can, instead, specify a process ID as a second argument, if you want
43082 to debug a running process:
43090 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43091 named @file{1234}; @value{GDBN} does check for a core file first).
43092 With option @option{-p} you can omit the @var{program} filename.
43094 Here are some of the most frequently needed @value{GDBN} commands:
43096 @c pod2man highlights the right hand side of the @item lines.
43098 @item break [@var{file}:]@var{functiop}
43099 Set a breakpoint at @var{function} (in @var{file}).
43101 @item run [@var{arglist}]
43102 Start your program (with @var{arglist}, if specified).
43105 Backtrace: display the program stack.
43107 @item print @var{expr}
43108 Display the value of an expression.
43111 Continue running your program (after stopping, e.g. at a breakpoint).
43114 Execute next program line (after stopping); step @emph{over} any
43115 function calls in the line.
43117 @item edit [@var{file}:]@var{function}
43118 look at the program line where it is presently stopped.
43120 @item list [@var{file}:]@var{function}
43121 type the text of the program in the vicinity of where it is presently stopped.
43124 Execute next program line (after stopping); step @emph{into} any
43125 function calls in the line.
43127 @item help [@var{name}]
43128 Show information about @value{GDBN} command @var{name}, or general information
43129 about using @value{GDBN}.
43132 Exit from @value{GDBN}.
43136 For full details on @value{GDBN},
43137 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43138 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43139 as the @code{gdb} entry in the @code{info} program.
43143 @c man begin OPTIONS gdb
43144 Any arguments other than options specify an executable
43145 file and core file (or process ID); that is, the first argument
43146 encountered with no
43147 associated option flag is equivalent to a @option{-se} option, and the second,
43148 if any, is equivalent to a @option{-c} option if it's the name of a file.
43150 both long and short forms; both are shown here. The long forms are also
43151 recognized if you truncate them, so long as enough of the option is
43152 present to be unambiguous. (If you prefer, you can flag option
43153 arguments with @option{+} rather than @option{-}, though we illustrate the
43154 more usual convention.)
43156 All the options and command line arguments you give are processed
43157 in sequential order. The order makes a difference when the @option{-x}
43163 List all options, with brief explanations.
43165 @item -symbols=@var{file}
43166 @itemx -s @var{file}
43167 Read symbol table from file @var{file}.
43170 Enable writing into executable and core files.
43172 @item -exec=@var{file}
43173 @itemx -e @var{file}
43174 Use file @var{file} as the executable file to execute when
43175 appropriate, and for examining pure data in conjunction with a core
43178 @item -se=@var{file}
43179 Read symbol table from file @var{file} and use it as the executable
43182 @item -core=@var{file}
43183 @itemx -c @var{file}
43184 Use file @var{file} as a core dump to examine.
43186 @item -command=@var{file}
43187 @itemx -x @var{file}
43188 Execute @value{GDBN} commands from file @var{file}.
43190 @item -ex @var{command}
43191 Execute given @value{GDBN} @var{command}.
43193 @item -directory=@var{directory}
43194 @itemx -d @var{directory}
43195 Add @var{directory} to the path to search for source files.
43198 Do not execute commands from @file{~/.gdbinit}.
43202 Do not execute commands from any @file{.gdbinit} initialization files.
43206 ``Quiet''. Do not print the introductory and copyright messages. These
43207 messages are also suppressed in batch mode.
43210 Run in batch mode. Exit with status @code{0} after processing all the command
43211 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43212 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43213 commands in the command files.
43215 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43216 download and run a program on another computer; in order to make this
43217 more useful, the message
43220 Program exited normally.
43224 (which is ordinarily issued whenever a program running under @value{GDBN} control
43225 terminates) is not issued when running in batch mode.
43227 @item -cd=@var{directory}
43228 Run @value{GDBN} using @var{directory} as its working directory,
43229 instead of the current directory.
43233 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43234 @value{GDBN} to output the full file name and line number in a standard,
43235 recognizable fashion each time a stack frame is displayed (which
43236 includes each time the program stops). This recognizable format looks
43237 like two @samp{\032} characters, followed by the file name, line number
43238 and character position separated by colons, and a newline. The
43239 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43240 characters as a signal to display the source code for the frame.
43243 Set the line speed (baud rate or bits per second) of any serial
43244 interface used by @value{GDBN} for remote debugging.
43246 @item -tty=@var{device}
43247 Run using @var{device} for your program's standard input and output.
43251 @c man begin SEEALSO gdb
43253 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43254 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43255 documentation are properly installed at your site, the command
43262 should give you access to the complete manual.
43264 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43265 Richard M. Stallman and Roland H. Pesch, July 1991.
43269 @node gdbserver man
43270 @heading gdbserver man
43272 @c man title gdbserver Remote Server for the GNU Debugger
43274 @c man begin SYNOPSIS gdbserver
43275 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43277 gdbserver --attach @var{comm} @var{pid}
43279 gdbserver --multi @var{comm}
43283 @c man begin DESCRIPTION gdbserver
43284 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43285 than the one which is running the program being debugged.
43288 @subheading Usage (server (target) side)
43291 Usage (server (target) side):
43294 First, you need to have a copy of the program you want to debug put onto
43295 the target system. The program can be stripped to save space if needed, as
43296 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43297 the @value{GDBN} running on the host system.
43299 To use the server, you log on to the target system, and run the @command{gdbserver}
43300 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43301 your program, and (c) its arguments. The general syntax is:
43304 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43307 For example, using a serial port, you might say:
43311 @c @file would wrap it as F</dev/com1>.
43312 target> gdbserver /dev/com1 emacs foo.txt
43315 target> gdbserver @file{/dev/com1} emacs foo.txt
43319 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43320 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43321 waits patiently for the host @value{GDBN} to communicate with it.
43323 To use a TCP connection, you could say:
43326 target> gdbserver host:2345 emacs foo.txt
43329 This says pretty much the same thing as the last example, except that we are
43330 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43331 that we are expecting to see a TCP connection from @code{host} to local TCP port
43332 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43333 want for the port number as long as it does not conflict with any existing TCP
43334 ports on the target system. This same port number must be used in the host
43335 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43336 you chose a port number that conflicts with another service, @command{gdbserver} will
43337 print an error message and exit.
43339 @command{gdbserver} can also attach to running programs.
43340 This is accomplished via the @option{--attach} argument. The syntax is:
43343 target> gdbserver --attach @var{comm} @var{pid}
43346 @var{pid} is the process ID of a currently running process. It isn't
43347 necessary to point @command{gdbserver} at a binary for the running process.
43349 To start @code{gdbserver} without supplying an initial command to run
43350 or process ID to attach, use the @option{--multi} command line option.
43351 In such case you should connect using @kbd{target extended-remote} to start
43352 the program you want to debug.
43355 target> gdbserver --multi @var{comm}
43359 @subheading Usage (host side)
43365 You need an unstripped copy of the target program on your host system, since
43366 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43367 would, with the target program as the first argument. (You may need to use the
43368 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43369 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43370 new command you need to know about is @code{target remote}
43371 (or @code{target extended-remote}). Its argument is either
43372 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43373 descriptor. For example:
43377 @c @file would wrap it as F</dev/ttyb>.
43378 (gdb) target remote /dev/ttyb
43381 (gdb) target remote @file{/dev/ttyb}
43386 communicates with the server via serial line @file{/dev/ttyb}, and:
43389 (gdb) target remote the-target:2345
43393 communicates via a TCP connection to port 2345 on host `the-target', where
43394 you previously started up @command{gdbserver} with the same port number. Note that for
43395 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43396 command, otherwise you may get an error that looks something like
43397 `Connection refused'.
43399 @command{gdbserver} can also debug multiple inferiors at once,
43402 the @value{GDBN} manual in node @code{Inferiors and Programs}
43403 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43406 @ref{Inferiors and Programs}.
43408 In such case use the @code{extended-remote} @value{GDBN} command variant:
43411 (gdb) target extended-remote the-target:2345
43414 The @command{gdbserver} option @option{--multi} may or may not be used in such
43418 @c man begin OPTIONS gdbserver
43419 There are three different modes for invoking @command{gdbserver}:
43424 Debug a specific program specified by its program name:
43427 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43430 The @var{comm} parameter specifies how should the server communicate
43431 with @value{GDBN}; it is either a device name (to use a serial line),
43432 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43433 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43434 debug in @var{prog}. Any remaining arguments will be passed to the
43435 program verbatim. When the program exits, @value{GDBN} will close the
43436 connection, and @code{gdbserver} will exit.
43439 Debug a specific program by specifying the process ID of a running
43443 gdbserver --attach @var{comm} @var{pid}
43446 The @var{comm} parameter is as described above. Supply the process ID
43447 of a running program in @var{pid}; @value{GDBN} will do everything
43448 else. Like with the previous mode, when the process @var{pid} exits,
43449 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43452 Multi-process mode -- debug more than one program/process:
43455 gdbserver --multi @var{comm}
43458 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43459 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43460 close the connection when a process being debugged exits, so you can
43461 debug several processes in the same session.
43464 In each of the modes you may specify these options:
43469 List all options, with brief explanations.
43472 This option causes @command{gdbserver} to print its version number and exit.
43475 @command{gdbserver} will attach to a running program. The syntax is:
43478 target> gdbserver --attach @var{comm} @var{pid}
43481 @var{pid} is the process ID of a currently running process. It isn't
43482 necessary to point @command{gdbserver} at a binary for the running process.
43485 To start @code{gdbserver} without supplying an initial command to run
43486 or process ID to attach, use this command line option.
43487 Then you can connect using @kbd{target extended-remote} and start
43488 the program you want to debug. The syntax is:
43491 target> gdbserver --multi @var{comm}
43495 Instruct @code{gdbserver} to display extra status information about the debugging
43497 This option is intended for @code{gdbserver} development and for bug reports to
43500 @item --remote-debug
43501 Instruct @code{gdbserver} to display remote protocol debug output.
43502 This option is intended for @code{gdbserver} development and for bug reports to
43506 Specify a wrapper to launch programs
43507 for debugging. The option should be followed by the name of the
43508 wrapper, then any command-line arguments to pass to the wrapper, then
43509 @kbd{--} indicating the end of the wrapper arguments.
43512 By default, @command{gdbserver} keeps the listening TCP port open, so that
43513 additional connections are possible. However, if you start @code{gdbserver}
43514 with the @option{--once} option, it will stop listening for any further
43515 connection attempts after connecting to the first @value{GDBN} session.
43517 @c --disable-packet is not documented for users.
43519 @c --disable-randomization and --no-disable-randomization are superseded by
43520 @c QDisableRandomization.
43525 @c man begin SEEALSO gdbserver
43527 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43528 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43529 documentation are properly installed at your site, the command
43535 should give you access to the complete manual.
43537 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43538 Richard M. Stallman and Roland H. Pesch, July 1991.
43545 @c man title gcore Generate a core file of a running program
43548 @c man begin SYNOPSIS gcore
43549 gcore [-o @var{filename}] @var{pid}
43553 @c man begin DESCRIPTION gcore
43554 Generate a core dump of a running program with process ID @var{pid}.
43555 Produced file is equivalent to a kernel produced core file as if the process
43556 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43557 limit). Unlike after a crash, after @command{gcore} the program remains
43558 running without any change.
43561 @c man begin OPTIONS gcore
43563 @item -o @var{filename}
43564 The optional argument
43565 @var{filename} specifies the file name where to put the core dump.
43566 If not specified, the file name defaults to @file{core.@var{pid}},
43567 where @var{pid} is the running program process ID.
43571 @c man begin SEEALSO gcore
43573 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43574 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43575 documentation are properly installed at your site, the command
43582 should give you access to the complete manual.
43584 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43585 Richard M. Stallman and Roland H. Pesch, July 1991.
43592 @c man title gdbinit GDB initialization scripts
43595 @c man begin SYNOPSIS gdbinit
43596 @ifset SYSTEM_GDBINIT
43597 @value{SYSTEM_GDBINIT}
43606 @c man begin DESCRIPTION gdbinit
43607 These files contain @value{GDBN} commands to automatically execute during
43608 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43611 the @value{GDBN} manual in node @code{Sequences}
43612 -- shell command @code{info -f gdb -n Sequences}.
43618 Please read more in
43620 the @value{GDBN} manual in node @code{Startup}
43621 -- shell command @code{info -f gdb -n Startup}.
43628 @ifset SYSTEM_GDBINIT
43629 @item @value{SYSTEM_GDBINIT}
43631 @ifclear SYSTEM_GDBINIT
43632 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43634 System-wide initialization file. It is executed unless user specified
43635 @value{GDBN} option @code{-nx} or @code{-n}.
43638 the @value{GDBN} manual in node @code{System-wide configuration}
43639 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43642 @ref{System-wide configuration}.
43646 User initialization file. It is executed unless user specified
43647 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43650 Initialization file for current directory. It may need to be enabled with
43651 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43654 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43655 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43658 @ref{Init File in the Current Directory}.
43663 @c man begin SEEALSO gdbinit
43665 gdb(1), @code{info -f gdb -n Startup}
43667 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43668 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43669 documentation are properly installed at your site, the command
43675 should give you access to the complete manual.
43677 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43678 Richard M. Stallman and Roland H. Pesch, July 1991.
43684 @node GNU Free Documentation License
43685 @appendix GNU Free Documentation License
43688 @node Concept Index
43689 @unnumbered Concept Index
43693 @node Command and Variable Index
43694 @unnumbered Command, Variable, and Function Index
43699 % I think something like @@colophon should be in texinfo. In the
43701 \long\def\colophon{\hbox to0pt{}\vfill
43702 \centerline{The body of this manual is set in}
43703 \centerline{\fontname\tenrm,}
43704 \centerline{with headings in {\bf\fontname\tenbf}}
43705 \centerline{and examples in {\tt\fontname\tentt}.}
43706 \centerline{{\it\fontname\tenit\/},}
43707 \centerline{{\bf\fontname\tenbf}, and}
43708 \centerline{{\sl\fontname\tensl\/}}
43709 \centerline{are used for emphasis.}\vfill}
43711 % Blame: doc@@cygnus.com, 1991.