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. If you do not define @code{SHELL},
2015 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2016 use of any shell with the @code{set startup-with-shell} command (see
2019 @item The @emph{environment.}
2020 Your program normally inherits its environment from @value{GDBN}, but you can
2021 use the @value{GDBN} commands @code{set environment} and @code{unset
2022 environment} to change parts of the environment that affect
2023 your program. @xref{Environment, ,Your Program's Environment}.
2025 @item The @emph{working directory.}
2026 Your program inherits its working directory from @value{GDBN}. You can set
2027 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2028 @xref{Working Directory, ,Your Program's Working Directory}.
2030 @item The @emph{standard input and output.}
2031 Your program normally uses the same device for standard input and
2032 standard output as @value{GDBN} is using. You can redirect input and output
2033 in the @code{run} command line, or you can use the @code{tty} command to
2034 set a different device for your program.
2035 @xref{Input/Output, ,Your Program's Input and Output}.
2038 @emph{Warning:} While input and output redirection work, you cannot use
2039 pipes to pass the output of the program you are debugging to another
2040 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2044 When you issue the @code{run} command, your program begins to execute
2045 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2046 of how to arrange for your program to stop. Once your program has
2047 stopped, you may call functions in your program, using the @code{print}
2048 or @code{call} commands. @xref{Data, ,Examining Data}.
2050 If the modification time of your symbol file has changed since the last
2051 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2052 table, and reads it again. When it does this, @value{GDBN} tries to retain
2053 your current breakpoints.
2058 @cindex run to main procedure
2059 The name of the main procedure can vary from language to language.
2060 With C or C@t{++}, the main procedure name is always @code{main}, but
2061 other languages such as Ada do not require a specific name for their
2062 main procedure. The debugger provides a convenient way to start the
2063 execution of the program and to stop at the beginning of the main
2064 procedure, depending on the language used.
2066 The @samp{start} command does the equivalent of setting a temporary
2067 breakpoint at the beginning of the main procedure and then invoking
2068 the @samp{run} command.
2070 @cindex elaboration phase
2071 Some programs contain an @dfn{elaboration} phase where some startup code is
2072 executed before the main procedure is called. This depends on the
2073 languages used to write your program. In C@t{++}, for instance,
2074 constructors for static and global objects are executed before
2075 @code{main} is called. It is therefore possible that the debugger stops
2076 before reaching the main procedure. However, the temporary breakpoint
2077 will remain to halt execution.
2079 Specify the arguments to give to your program as arguments to the
2080 @samp{start} command. These arguments will be given verbatim to the
2081 underlying @samp{run} command. Note that the same arguments will be
2082 reused if no argument is provided during subsequent calls to
2083 @samp{start} or @samp{run}.
2085 It is sometimes necessary to debug the program during elaboration. In
2086 these cases, using the @code{start} command would stop the execution of
2087 your program too late, as the program would have already completed the
2088 elaboration phase. Under these circumstances, insert breakpoints in your
2089 elaboration code before running your program.
2091 @kindex set exec-wrapper
2092 @item set exec-wrapper @var{wrapper}
2093 @itemx show exec-wrapper
2094 @itemx unset exec-wrapper
2095 When @samp{exec-wrapper} is set, the specified wrapper is used to
2096 launch programs for debugging. @value{GDBN} starts your program
2097 with a shell command of the form @kbd{exec @var{wrapper}
2098 @var{program}}. Quoting is added to @var{program} and its
2099 arguments, but not to @var{wrapper}, so you should add quotes if
2100 appropriate for your shell. The wrapper runs until it executes
2101 your program, and then @value{GDBN} takes control.
2103 You can use any program that eventually calls @code{execve} with
2104 its arguments as a wrapper. Several standard Unix utilities do
2105 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2106 with @code{exec "$@@"} will also work.
2108 For example, you can use @code{env} to pass an environment variable to
2109 the debugged program, without setting the variable in your shell's
2113 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2117 This command is available when debugging locally on most targets, excluding
2118 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2120 @kindex set startup-with-shell
2121 @item set startup-with-shell
2122 @itemx set startup-with-shell on
2123 @itemx set startup-with-shell off
2124 @itemx show set startup-with-shell
2125 On Unix systems, by default, if a shell is available on your target,
2126 @value{GDBN}) uses it to start your program. Arguments of the
2127 @code{run} command are passed to the shell, which does variable
2128 substitution, expands wildcard characters and performs redirection of
2129 I/O. In some circumstances, it may be useful to disable such use of a
2130 shell, for example, when debugging the shell itself or diagnosing
2131 startup failures such as:
2135 Starting program: ./a.out
2136 During startup program terminated with signal SIGSEGV, Segmentation fault.
2140 which indicates the shell or the wrapper specified with
2141 @samp{exec-wrapper} crashed, not your program. Most often, this is
2142 caused by something odd in your shell's non-interactive mode
2143 initialization file---such as @file{.cshrc} for C-shell,
2144 $@file{.zshenv} for the Z shell, or the file specified in the
2145 @samp{BASH_ENV} environment variable for BASH.
2147 @kindex set disable-randomization
2148 @item set disable-randomization
2149 @itemx set disable-randomization on
2150 This option (enabled by default in @value{GDBN}) will turn off the native
2151 randomization of the virtual address space of the started program. This option
2152 is useful for multiple debugging sessions to make the execution better
2153 reproducible and memory addresses reusable across debugging sessions.
2155 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2156 On @sc{gnu}/Linux you can get the same behavior using
2159 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2162 @item set disable-randomization off
2163 Leave the behavior of the started executable unchanged. Some bugs rear their
2164 ugly heads only when the program is loaded at certain addresses. If your bug
2165 disappears when you run the program under @value{GDBN}, that might be because
2166 @value{GDBN} by default disables the address randomization on platforms, such
2167 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2168 disable-randomization off} to try to reproduce such elusive bugs.
2170 On targets where it is available, virtual address space randomization
2171 protects the programs against certain kinds of security attacks. In these
2172 cases the attacker needs to know the exact location of a concrete executable
2173 code. Randomizing its location makes it impossible to inject jumps misusing
2174 a code at its expected addresses.
2176 Prelinking shared libraries provides a startup performance advantage but it
2177 makes addresses in these libraries predictable for privileged processes by
2178 having just unprivileged access at the target system. Reading the shared
2179 library binary gives enough information for assembling the malicious code
2180 misusing it. Still even a prelinked shared library can get loaded at a new
2181 random address just requiring the regular relocation process during the
2182 startup. Shared libraries not already prelinked are always loaded at
2183 a randomly chosen address.
2185 Position independent executables (PIE) contain position independent code
2186 similar to the shared libraries and therefore such executables get loaded at
2187 a randomly chosen address upon startup. PIE executables always load even
2188 already prelinked shared libraries at a random address. You can build such
2189 executable using @command{gcc -fPIE -pie}.
2191 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2192 (as long as the randomization is enabled).
2194 @item show disable-randomization
2195 Show the current setting of the explicit disable of the native randomization of
2196 the virtual address space of the started program.
2201 @section Your Program's Arguments
2203 @cindex arguments (to your program)
2204 The arguments to your program can be specified by the arguments of the
2206 They are passed to a shell, which expands wildcard characters and
2207 performs redirection of I/O, and thence to your program. Your
2208 @code{SHELL} environment variable (if it exists) specifies what shell
2209 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2210 the default shell (@file{/bin/sh} on Unix).
2212 On non-Unix systems, the program is usually invoked directly by
2213 @value{GDBN}, which emulates I/O redirection via the appropriate system
2214 calls, and the wildcard characters are expanded by the startup code of
2215 the program, not by the shell.
2217 @code{run} with no arguments uses the same arguments used by the previous
2218 @code{run}, or those set by the @code{set args} command.
2223 Specify the arguments to be used the next time your program is run. If
2224 @code{set args} has no arguments, @code{run} executes your program
2225 with no arguments. Once you have run your program with arguments,
2226 using @code{set args} before the next @code{run} is the only way to run
2227 it again without arguments.
2231 Show the arguments to give your program when it is started.
2235 @section Your Program's Environment
2237 @cindex environment (of your program)
2238 The @dfn{environment} consists of a set of environment variables and
2239 their values. Environment variables conventionally record such things as
2240 your user name, your home directory, your terminal type, and your search
2241 path for programs to run. Usually you set up environment variables with
2242 the shell and they are inherited by all the other programs you run. When
2243 debugging, it can be useful to try running your program with a modified
2244 environment without having to start @value{GDBN} over again.
2248 @item path @var{directory}
2249 Add @var{directory} to the front of the @code{PATH} environment variable
2250 (the search path for executables) that will be passed to your program.
2251 The value of @code{PATH} used by @value{GDBN} does not change.
2252 You may specify several directory names, separated by whitespace or by a
2253 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2254 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2255 is moved to the front, so it is searched sooner.
2257 You can use the string @samp{$cwd} to refer to whatever is the current
2258 working directory at the time @value{GDBN} searches the path. If you
2259 use @samp{.} instead, it refers to the directory where you executed the
2260 @code{path} command. @value{GDBN} replaces @samp{.} in the
2261 @var{directory} argument (with the current path) before adding
2262 @var{directory} to the search path.
2263 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2264 @c document that, since repeating it would be a no-op.
2268 Display the list of search paths for executables (the @code{PATH}
2269 environment variable).
2271 @kindex show environment
2272 @item show environment @r{[}@var{varname}@r{]}
2273 Print the value of environment variable @var{varname} to be given to
2274 your program when it starts. If you do not supply @var{varname},
2275 print the names and values of all environment variables to be given to
2276 your program. You can abbreviate @code{environment} as @code{env}.
2278 @kindex set environment
2279 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2280 Set environment variable @var{varname} to @var{value}. The value
2281 changes for your program only, not for @value{GDBN} itself. @var{value} may
2282 be any string; the values of environment variables are just strings, and
2283 any interpretation is supplied by your program itself. The @var{value}
2284 parameter is optional; if it is eliminated, the variable is set to a
2286 @c "any string" here does not include leading, trailing
2287 @c blanks. Gnu asks: does anyone care?
2289 For example, this command:
2296 tells the debugged program, when subsequently run, that its user is named
2297 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2298 are not actually required.)
2300 @kindex unset environment
2301 @item unset environment @var{varname}
2302 Remove variable @var{varname} from the environment to be passed to your
2303 program. This is different from @samp{set env @var{varname} =};
2304 @code{unset environment} removes the variable from the environment,
2305 rather than assigning it an empty value.
2308 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2309 the shell indicated by your @code{SHELL} environment variable if it
2310 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2311 names a shell that runs an initialization file when started
2312 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2313 for the Z shell, or the file specified in the @samp{BASH_ENV}
2314 environment variable for BASH---any variables you set in that file
2315 affect your program. You may wish to move setting of environment
2316 variables to files that are only run when you sign on, such as
2317 @file{.login} or @file{.profile}.
2319 @node Working Directory
2320 @section Your Program's Working Directory
2322 @cindex working directory (of your program)
2323 Each time you start your program with @code{run}, it inherits its
2324 working directory from the current working directory of @value{GDBN}.
2325 The @value{GDBN} working directory is initially whatever it inherited
2326 from its parent process (typically the shell), but you can specify a new
2327 working directory in @value{GDBN} with the @code{cd} command.
2329 The @value{GDBN} working directory also serves as a default for the commands
2330 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2335 @cindex change working directory
2336 @item cd @r{[}@var{directory}@r{]}
2337 Set the @value{GDBN} working directory to @var{directory}. If not
2338 given, @var{directory} uses @file{'~'}.
2342 Print the @value{GDBN} working directory.
2345 It is generally impossible to find the current working directory of
2346 the process being debugged (since a program can change its directory
2347 during its run). If you work on a system where @value{GDBN} is
2348 configured with the @file{/proc} support, you can use the @code{info
2349 proc} command (@pxref{SVR4 Process Information}) to find out the
2350 current working directory of the debuggee.
2353 @section Your Program's Input and Output
2358 By default, the program you run under @value{GDBN} does input and output to
2359 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2360 to its own terminal modes to interact with you, but it records the terminal
2361 modes your program was using and switches back to them when you continue
2362 running your program.
2365 @kindex info terminal
2367 Displays information recorded by @value{GDBN} about the terminal modes your
2371 You can redirect your program's input and/or output using shell
2372 redirection with the @code{run} command. For example,
2379 starts your program, diverting its output to the file @file{outfile}.
2382 @cindex controlling terminal
2383 Another way to specify where your program should do input and output is
2384 with the @code{tty} command. This command accepts a file name as
2385 argument, and causes this file to be the default for future @code{run}
2386 commands. It also resets the controlling terminal for the child
2387 process, for future @code{run} commands. For example,
2394 directs that processes started with subsequent @code{run} commands
2395 default to do input and output on the terminal @file{/dev/ttyb} and have
2396 that as their controlling terminal.
2398 An explicit redirection in @code{run} overrides the @code{tty} command's
2399 effect on the input/output device, but not its effect on the controlling
2402 When you use the @code{tty} command or redirect input in the @code{run}
2403 command, only the input @emph{for your program} is affected. The input
2404 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2405 for @code{set inferior-tty}.
2407 @cindex inferior tty
2408 @cindex set inferior controlling terminal
2409 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2410 display the name of the terminal that will be used for future runs of your
2414 @item set inferior-tty /dev/ttyb
2415 @kindex set inferior-tty
2416 Set the tty for the program being debugged to /dev/ttyb.
2418 @item show inferior-tty
2419 @kindex show inferior-tty
2420 Show the current tty for the program being debugged.
2424 @section Debugging an Already-running Process
2429 @item attach @var{process-id}
2430 This command attaches to a running process---one that was started
2431 outside @value{GDBN}. (@code{info files} shows your active
2432 targets.) The command takes as argument a process ID. The usual way to
2433 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2434 or with the @samp{jobs -l} shell command.
2436 @code{attach} does not repeat if you press @key{RET} a second time after
2437 executing the command.
2440 To use @code{attach}, your program must be running in an environment
2441 which supports processes; for example, @code{attach} does not work for
2442 programs on bare-board targets that lack an operating system. You must
2443 also have permission to send the process a signal.
2445 When you use @code{attach}, the debugger finds the program running in
2446 the process first by looking in the current working directory, then (if
2447 the program is not found) by using the source file search path
2448 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2449 the @code{file} command to load the program. @xref{Files, ,Commands to
2452 The first thing @value{GDBN} does after arranging to debug the specified
2453 process is to stop it. You can examine and modify an attached process
2454 with all the @value{GDBN} commands that are ordinarily available when
2455 you start processes with @code{run}. You can insert breakpoints; you
2456 can step and continue; you can modify storage. If you would rather the
2457 process continue running, you may use the @code{continue} command after
2458 attaching @value{GDBN} to the process.
2463 When you have finished debugging the attached process, you can use the
2464 @code{detach} command to release it from @value{GDBN} control. Detaching
2465 the process continues its execution. After the @code{detach} command,
2466 that process and @value{GDBN} become completely independent once more, and you
2467 are ready to @code{attach} another process or start one with @code{run}.
2468 @code{detach} does not repeat if you press @key{RET} again after
2469 executing the command.
2472 If you exit @value{GDBN} while you have an attached process, you detach
2473 that process. If you use the @code{run} command, you kill that process.
2474 By default, @value{GDBN} asks for confirmation if you try to do either of these
2475 things; you can control whether or not you need to confirm by using the
2476 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2480 @section Killing the Child Process
2485 Kill the child process in which your program is running under @value{GDBN}.
2488 This command is useful if you wish to debug a core dump instead of a
2489 running process. @value{GDBN} ignores any core dump file while your program
2492 On some operating systems, a program cannot be executed outside @value{GDBN}
2493 while you have breakpoints set on it inside @value{GDBN}. You can use the
2494 @code{kill} command in this situation to permit running your program
2495 outside the debugger.
2497 The @code{kill} command is also useful if you wish to recompile and
2498 relink your program, since on many systems it is impossible to modify an
2499 executable file while it is running in a process. In this case, when you
2500 next type @code{run}, @value{GDBN} notices that the file has changed, and
2501 reads the symbol table again (while trying to preserve your current
2502 breakpoint settings).
2504 @node Inferiors and Programs
2505 @section Debugging Multiple Inferiors and Programs
2507 @value{GDBN} lets you run and debug multiple programs in a single
2508 session. In addition, @value{GDBN} on some systems may let you run
2509 several programs simultaneously (otherwise you have to exit from one
2510 before starting another). In the most general case, you can have
2511 multiple threads of execution in each of multiple processes, launched
2512 from multiple executables.
2515 @value{GDBN} represents the state of each program execution with an
2516 object called an @dfn{inferior}. An inferior typically corresponds to
2517 a process, but is more general and applies also to targets that do not
2518 have processes. Inferiors may be created before a process runs, and
2519 may be retained after a process exits. Inferiors have unique
2520 identifiers that are different from process ids. Usually each
2521 inferior will also have its own distinct address space, although some
2522 embedded targets may have several inferiors running in different parts
2523 of a single address space. Each inferior may in turn have multiple
2524 threads running in it.
2526 To find out what inferiors exist at any moment, use @w{@code{info
2530 @kindex info inferiors
2531 @item info inferiors
2532 Print a list of all inferiors currently being managed by @value{GDBN}.
2534 @value{GDBN} displays for each inferior (in this order):
2538 the inferior number assigned by @value{GDBN}
2541 the target system's inferior identifier
2544 the name of the executable the inferior is running.
2549 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2550 indicates the current inferior.
2554 @c end table here to get a little more width for example
2557 (@value{GDBP}) info inferiors
2558 Num Description Executable
2559 2 process 2307 hello
2560 * 1 process 3401 goodbye
2563 To switch focus between inferiors, use the @code{inferior} command:
2566 @kindex inferior @var{infno}
2567 @item inferior @var{infno}
2568 Make inferior number @var{infno} the current inferior. The argument
2569 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2570 in the first field of the @samp{info inferiors} display.
2574 You can get multiple executables into a debugging session via the
2575 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2576 systems @value{GDBN} can add inferiors to the debug session
2577 automatically by following calls to @code{fork} and @code{exec}. To
2578 remove inferiors from the debugging session use the
2579 @w{@code{remove-inferiors}} command.
2582 @kindex add-inferior
2583 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2584 Adds @var{n} inferiors to be run using @var{executable} as the
2585 executable. @var{n} defaults to 1. If no executable is specified,
2586 the inferiors begins empty, with no program. You can still assign or
2587 change the program assigned to the inferior at any time by using the
2588 @code{file} command with the executable name as its argument.
2590 @kindex clone-inferior
2591 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2592 Adds @var{n} inferiors ready to execute the same program as inferior
2593 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2594 number of the current inferior. This is a convenient command when you
2595 want to run another instance of the inferior you are debugging.
2598 (@value{GDBP}) info inferiors
2599 Num Description Executable
2600 * 1 process 29964 helloworld
2601 (@value{GDBP}) clone-inferior
2604 (@value{GDBP}) info inferiors
2605 Num Description Executable
2607 * 1 process 29964 helloworld
2610 You can now simply switch focus to inferior 2 and run it.
2612 @kindex remove-inferiors
2613 @item remove-inferiors @var{infno}@dots{}
2614 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2615 possible to remove an inferior that is running with this command. For
2616 those, use the @code{kill} or @code{detach} command first.
2620 To quit debugging one of the running inferiors that is not the current
2621 inferior, you can either detach from it by using the @w{@code{detach
2622 inferior}} command (allowing it to run independently), or kill it
2623 using the @w{@code{kill inferiors}} command:
2626 @kindex detach inferiors @var{infno}@dots{}
2627 @item detach inferior @var{infno}@dots{}
2628 Detach from the inferior or inferiors identified by @value{GDBN}
2629 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2630 still stays on the list of inferiors shown by @code{info inferiors},
2631 but its Description will show @samp{<null>}.
2633 @kindex kill inferiors @var{infno}@dots{}
2634 @item kill inferiors @var{infno}@dots{}
2635 Kill the inferior or inferiors identified by @value{GDBN} inferior
2636 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2637 stays on the list of inferiors shown by @code{info inferiors}, but its
2638 Description will show @samp{<null>}.
2641 After the successful completion of a command such as @code{detach},
2642 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2643 a normal process exit, the inferior is still valid and listed with
2644 @code{info inferiors}, ready to be restarted.
2647 To be notified when inferiors are started or exit under @value{GDBN}'s
2648 control use @w{@code{set print inferior-events}}:
2651 @kindex set print inferior-events
2652 @cindex print messages on inferior start and exit
2653 @item set print inferior-events
2654 @itemx set print inferior-events on
2655 @itemx set print inferior-events off
2656 The @code{set print inferior-events} command allows you to enable or
2657 disable printing of messages when @value{GDBN} notices that new
2658 inferiors have started or that inferiors have exited or have been
2659 detached. By default, these messages will not be printed.
2661 @kindex show print inferior-events
2662 @item show print inferior-events
2663 Show whether messages will be printed when @value{GDBN} detects that
2664 inferiors have started, exited or have been detached.
2667 Many commands will work the same with multiple programs as with a
2668 single program: e.g., @code{print myglobal} will simply display the
2669 value of @code{myglobal} in the current inferior.
2672 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2673 get more info about the relationship of inferiors, programs, address
2674 spaces in a debug session. You can do that with the @w{@code{maint
2675 info program-spaces}} command.
2678 @kindex maint info program-spaces
2679 @item maint info program-spaces
2680 Print a list of all program spaces currently being managed by
2683 @value{GDBN} displays for each program space (in this order):
2687 the program space number assigned by @value{GDBN}
2690 the name of the executable loaded into the program space, with e.g.,
2691 the @code{file} command.
2696 An asterisk @samp{*} preceding the @value{GDBN} program space number
2697 indicates the current program space.
2699 In addition, below each program space line, @value{GDBN} prints extra
2700 information that isn't suitable to display in tabular form. For
2701 example, the list of inferiors bound to the program space.
2704 (@value{GDBP}) maint info program-spaces
2707 Bound inferiors: ID 1 (process 21561)
2711 Here we can see that no inferior is running the program @code{hello},
2712 while @code{process 21561} is running the program @code{goodbye}. On
2713 some targets, it is possible that multiple inferiors are bound to the
2714 same program space. The most common example is that of debugging both
2715 the parent and child processes of a @code{vfork} call. For example,
2718 (@value{GDBP}) maint info program-spaces
2721 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2724 Here, both inferior 2 and inferior 1 are running in the same program
2725 space as a result of inferior 1 having executed a @code{vfork} call.
2729 @section Debugging Programs with Multiple Threads
2731 @cindex threads of execution
2732 @cindex multiple threads
2733 @cindex switching threads
2734 In some operating systems, such as HP-UX and Solaris, a single program
2735 may have more than one @dfn{thread} of execution. The precise semantics
2736 of threads differ from one operating system to another, but in general
2737 the threads of a single program are akin to multiple processes---except
2738 that they share one address space (that is, they can all examine and
2739 modify the same variables). On the other hand, each thread has its own
2740 registers and execution stack, and perhaps private memory.
2742 @value{GDBN} provides these facilities for debugging multi-thread
2746 @item automatic notification of new threads
2747 @item @samp{thread @var{threadno}}, a command to switch among threads
2748 @item @samp{info threads}, a command to inquire about existing threads
2749 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2750 a command to apply a command to a list of threads
2751 @item thread-specific breakpoints
2752 @item @samp{set print thread-events}, which controls printing of
2753 messages on thread start and exit.
2754 @item @samp{set libthread-db-search-path @var{path}}, which lets
2755 the user specify which @code{libthread_db} to use if the default choice
2756 isn't compatible with the program.
2760 @emph{Warning:} These facilities are not yet available on every
2761 @value{GDBN} configuration where the operating system supports threads.
2762 If your @value{GDBN} does not support threads, these commands have no
2763 effect. For example, a system without thread support shows no output
2764 from @samp{info threads}, and always rejects the @code{thread} command,
2768 (@value{GDBP}) info threads
2769 (@value{GDBP}) thread 1
2770 Thread ID 1 not known. Use the "info threads" command to
2771 see the IDs of currently known threads.
2773 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2774 @c doesn't support threads"?
2777 @cindex focus of debugging
2778 @cindex current thread
2779 The @value{GDBN} thread debugging facility allows you to observe all
2780 threads while your program runs---but whenever @value{GDBN} takes
2781 control, one thread in particular is always the focus of debugging.
2782 This thread is called the @dfn{current thread}. Debugging commands show
2783 program information from the perspective of the current thread.
2785 @cindex @code{New} @var{systag} message
2786 @cindex thread identifier (system)
2787 @c FIXME-implementors!! It would be more helpful if the [New...] message
2788 @c included GDB's numeric thread handle, so you could just go to that
2789 @c thread without first checking `info threads'.
2790 Whenever @value{GDBN} detects a new thread in your program, it displays
2791 the target system's identification for the thread with a message in the
2792 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2793 whose form varies depending on the particular system. For example, on
2794 @sc{gnu}/Linux, you might see
2797 [New Thread 0x41e02940 (LWP 25582)]
2801 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2802 the @var{systag} is simply something like @samp{process 368}, with no
2805 @c FIXME!! (1) Does the [New...] message appear even for the very first
2806 @c thread of a program, or does it only appear for the
2807 @c second---i.e.@: when it becomes obvious we have a multithread
2809 @c (2) *Is* there necessarily a first thread always? Or do some
2810 @c multithread systems permit starting a program with multiple
2811 @c threads ab initio?
2813 @cindex thread number
2814 @cindex thread identifier (GDB)
2815 For debugging purposes, @value{GDBN} associates its own thread
2816 number---always a single integer---with each thread in your program.
2819 @kindex info threads
2820 @item info threads @r{[}@var{id}@dots{}@r{]}
2821 Display a summary of all threads currently in your program. Optional
2822 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2823 means to print information only about the specified thread or threads.
2824 @value{GDBN} displays for each thread (in this order):
2828 the thread number assigned by @value{GDBN}
2831 the target system's thread identifier (@var{systag})
2834 the thread's name, if one is known. A thread can either be named by
2835 the user (see @code{thread name}, below), or, in some cases, by the
2839 the current stack frame summary for that thread
2843 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2844 indicates the current thread.
2848 @c end table here to get a little more width for example
2851 (@value{GDBP}) info threads
2853 3 process 35 thread 27 0x34e5 in sigpause ()
2854 2 process 35 thread 23 0x34e5 in sigpause ()
2855 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2859 On Solaris, you can display more information about user threads with a
2860 Solaris-specific command:
2863 @item maint info sol-threads
2864 @kindex maint info sol-threads
2865 @cindex thread info (Solaris)
2866 Display info on Solaris user threads.
2870 @kindex thread @var{threadno}
2871 @item thread @var{threadno}
2872 Make thread number @var{threadno} the current thread. The command
2873 argument @var{threadno} is the internal @value{GDBN} thread number, as
2874 shown in the first field of the @samp{info threads} display.
2875 @value{GDBN} responds by displaying the system identifier of the thread
2876 you selected, and its current stack frame summary:
2879 (@value{GDBP}) thread 2
2880 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2881 #0 some_function (ignore=0x0) at example.c:8
2882 8 printf ("hello\n");
2886 As with the @samp{[New @dots{}]} message, the form of the text after
2887 @samp{Switching to} depends on your system's conventions for identifying
2890 @vindex $_thread@r{, convenience variable}
2891 The debugger convenience variable @samp{$_thread} contains the number
2892 of the current thread. You may find this useful in writing breakpoint
2893 conditional expressions, command scripts, and so forth. See
2894 @xref{Convenience Vars,, Convenience Variables}, for general
2895 information on convenience variables.
2897 @kindex thread apply
2898 @cindex apply command to several threads
2899 @item thread apply [@var{threadno} | all] @var{command}
2900 The @code{thread apply} command allows you to apply the named
2901 @var{command} to one or more threads. Specify the numbers of the
2902 threads that you want affected with the command argument
2903 @var{threadno}. It can be a single thread number, one of the numbers
2904 shown in the first field of the @samp{info threads} display; or it
2905 could be a range of thread numbers, as in @code{2-4}. To apply a
2906 command to all threads, type @kbd{thread apply all @var{command}}.
2909 @cindex name a thread
2910 @item thread name [@var{name}]
2911 This command assigns a name to the current thread. If no argument is
2912 given, any existing user-specified name is removed. The thread name
2913 appears in the @samp{info threads} display.
2915 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2916 determine the name of the thread as given by the OS. On these
2917 systems, a name specified with @samp{thread name} will override the
2918 system-give name, and removing the user-specified name will cause
2919 @value{GDBN} to once again display the system-specified name.
2922 @cindex search for a thread
2923 @item thread find [@var{regexp}]
2924 Search for and display thread ids whose name or @var{systag}
2925 matches the supplied regular expression.
2927 As well as being the complement to the @samp{thread name} command,
2928 this command also allows you to identify a thread by its target
2929 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2933 (@value{GDBN}) thread find 26688
2934 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2935 (@value{GDBN}) info thread 4
2937 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2940 @kindex set print thread-events
2941 @cindex print messages on thread start and exit
2942 @item set print thread-events
2943 @itemx set print thread-events on
2944 @itemx set print thread-events off
2945 The @code{set print thread-events} command allows you to enable or
2946 disable printing of messages when @value{GDBN} notices that new threads have
2947 started or that threads have exited. By default, these messages will
2948 be printed if detection of these events is supported by the target.
2949 Note that these messages cannot be disabled on all targets.
2951 @kindex show print thread-events
2952 @item show print thread-events
2953 Show whether messages will be printed when @value{GDBN} detects that threads
2954 have started and exited.
2957 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2958 more information about how @value{GDBN} behaves when you stop and start
2959 programs with multiple threads.
2961 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2962 watchpoints in programs with multiple threads.
2964 @anchor{set libthread-db-search-path}
2966 @kindex set libthread-db-search-path
2967 @cindex search path for @code{libthread_db}
2968 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2969 If this variable is set, @var{path} is a colon-separated list of
2970 directories @value{GDBN} will use to search for @code{libthread_db}.
2971 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2972 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2973 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2976 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2977 @code{libthread_db} library to obtain information about threads in the
2978 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2979 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2980 specific thread debugging library loading is enabled
2981 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2983 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2984 refers to the default system directories that are
2985 normally searched for loading shared libraries. The @samp{$sdir} entry
2986 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2987 (@pxref{libthread_db.so.1 file}).
2989 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2990 refers to the directory from which @code{libpthread}
2991 was loaded in the inferior process.
2993 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2994 @value{GDBN} attempts to initialize it with the current inferior process.
2995 If this initialization fails (which could happen because of a version
2996 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2997 will unload @code{libthread_db}, and continue with the next directory.
2998 If none of @code{libthread_db} libraries initialize successfully,
2999 @value{GDBN} will issue a warning and thread debugging will be disabled.
3001 Setting @code{libthread-db-search-path} is currently implemented
3002 only on some platforms.
3004 @kindex show libthread-db-search-path
3005 @item show libthread-db-search-path
3006 Display current libthread_db search path.
3008 @kindex set debug libthread-db
3009 @kindex show debug libthread-db
3010 @cindex debugging @code{libthread_db}
3011 @item set debug libthread-db
3012 @itemx show debug libthread-db
3013 Turns on or off display of @code{libthread_db}-related events.
3014 Use @code{1} to enable, @code{0} to disable.
3018 @section Debugging Forks
3020 @cindex fork, debugging programs which call
3021 @cindex multiple processes
3022 @cindex processes, multiple
3023 On most systems, @value{GDBN} has no special support for debugging
3024 programs which create additional processes using the @code{fork}
3025 function. When a program forks, @value{GDBN} will continue to debug the
3026 parent process and the child process will run unimpeded. If you have
3027 set a breakpoint in any code which the child then executes, the child
3028 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3029 will cause it to terminate.
3031 However, if you want to debug the child process there is a workaround
3032 which isn't too painful. Put a call to @code{sleep} in the code which
3033 the child process executes after the fork. It may be useful to sleep
3034 only if a certain environment variable is set, or a certain file exists,
3035 so that the delay need not occur when you don't want to run @value{GDBN}
3036 on the child. While the child is sleeping, use the @code{ps} program to
3037 get its process ID. Then tell @value{GDBN} (a new invocation of
3038 @value{GDBN} if you are also debugging the parent process) to attach to
3039 the child process (@pxref{Attach}). From that point on you can debug
3040 the child process just like any other process which you attached to.
3042 On some systems, @value{GDBN} provides support for debugging programs that
3043 create additional processes using the @code{fork} or @code{vfork} functions.
3044 Currently, the only platforms with this feature are HP-UX (11.x and later
3045 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3047 By default, when a program forks, @value{GDBN} will continue to debug
3048 the parent process and the child process will run unimpeded.
3050 If you want to follow the child process instead of the parent process,
3051 use the command @w{@code{set follow-fork-mode}}.
3054 @kindex set follow-fork-mode
3055 @item set follow-fork-mode @var{mode}
3056 Set the debugger response to a program call of @code{fork} or
3057 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3058 process. The @var{mode} argument can be:
3062 The original process is debugged after a fork. The child process runs
3063 unimpeded. This is the default.
3066 The new process is debugged after a fork. The parent process runs
3071 @kindex show follow-fork-mode
3072 @item show follow-fork-mode
3073 Display the current debugger response to a @code{fork} or @code{vfork} call.
3076 @cindex debugging multiple processes
3077 On Linux, if you want to debug both the parent and child processes, use the
3078 command @w{@code{set detach-on-fork}}.
3081 @kindex set detach-on-fork
3082 @item set detach-on-fork @var{mode}
3083 Tells gdb whether to detach one of the processes after a fork, or
3084 retain debugger control over them both.
3088 The child process (or parent process, depending on the value of
3089 @code{follow-fork-mode}) will be detached and allowed to run
3090 independently. This is the default.
3093 Both processes will be held under the control of @value{GDBN}.
3094 One process (child or parent, depending on the value of
3095 @code{follow-fork-mode}) is debugged as usual, while the other
3100 @kindex show detach-on-fork
3101 @item show detach-on-fork
3102 Show whether detach-on-fork mode is on/off.
3105 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3106 will retain control of all forked processes (including nested forks).
3107 You can list the forked processes under the control of @value{GDBN} by
3108 using the @w{@code{info inferiors}} command, and switch from one fork
3109 to another by using the @code{inferior} command (@pxref{Inferiors and
3110 Programs, ,Debugging Multiple Inferiors and Programs}).
3112 To quit debugging one of the forked processes, you can either detach
3113 from it by using the @w{@code{detach inferiors}} command (allowing it
3114 to run independently), or kill it using the @w{@code{kill inferiors}}
3115 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3118 If you ask to debug a child process and a @code{vfork} is followed by an
3119 @code{exec}, @value{GDBN} executes the new target up to the first
3120 breakpoint in the new target. If you have a breakpoint set on
3121 @code{main} in your original program, the breakpoint will also be set on
3122 the child process's @code{main}.
3124 On some systems, when a child process is spawned by @code{vfork}, you
3125 cannot debug the child or parent until an @code{exec} call completes.
3127 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3128 call executes, the new target restarts. To restart the parent
3129 process, use the @code{file} command with the parent executable name
3130 as its argument. By default, after an @code{exec} call executes,
3131 @value{GDBN} discards the symbols of the previous executable image.
3132 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3136 @kindex set follow-exec-mode
3137 @item set follow-exec-mode @var{mode}
3139 Set debugger response to a program call of @code{exec}. An
3140 @code{exec} call replaces the program image of a process.
3142 @code{follow-exec-mode} can be:
3146 @value{GDBN} creates a new inferior and rebinds the process to this
3147 new inferior. The program the process was running before the
3148 @code{exec} call can be restarted afterwards by restarting the
3154 (@value{GDBP}) info inferiors
3156 Id Description Executable
3159 process 12020 is executing new program: prog2
3160 Program exited normally.
3161 (@value{GDBP}) info inferiors
3162 Id Description Executable
3168 @value{GDBN} keeps the process bound to the same inferior. The new
3169 executable image replaces the previous executable loaded in the
3170 inferior. Restarting the inferior after the @code{exec} call, with
3171 e.g., the @code{run} command, restarts the executable the process was
3172 running after the @code{exec} call. This is the default mode.
3177 (@value{GDBP}) info inferiors
3178 Id Description Executable
3181 process 12020 is executing new program: prog2
3182 Program exited normally.
3183 (@value{GDBP}) info inferiors
3184 Id Description Executable
3191 You can use the @code{catch} command to make @value{GDBN} stop whenever
3192 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3193 Catchpoints, ,Setting Catchpoints}.
3195 @node Checkpoint/Restart
3196 @section Setting a @emph{Bookmark} to Return to Later
3201 @cindex snapshot of a process
3202 @cindex rewind program state
3204 On certain operating systems@footnote{Currently, only
3205 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3206 program's state, called a @dfn{checkpoint}, and come back to it
3209 Returning to a checkpoint effectively undoes everything that has
3210 happened in the program since the @code{checkpoint} was saved. This
3211 includes changes in memory, registers, and even (within some limits)
3212 system state. Effectively, it is like going back in time to the
3213 moment when the checkpoint was saved.
3215 Thus, if you're stepping thru a program and you think you're
3216 getting close to the point where things go wrong, you can save
3217 a checkpoint. Then, if you accidentally go too far and miss
3218 the critical statement, instead of having to restart your program
3219 from the beginning, you can just go back to the checkpoint and
3220 start again from there.
3222 This can be especially useful if it takes a lot of time or
3223 steps to reach the point where you think the bug occurs.
3225 To use the @code{checkpoint}/@code{restart} method of debugging:
3230 Save a snapshot of the debugged program's current execution state.
3231 The @code{checkpoint} command takes no arguments, but each checkpoint
3232 is assigned a small integer id, similar to a breakpoint id.
3234 @kindex info checkpoints
3235 @item info checkpoints
3236 List the checkpoints that have been saved in the current debugging
3237 session. For each checkpoint, the following information will be
3244 @item Source line, or label
3247 @kindex restart @var{checkpoint-id}
3248 @item restart @var{checkpoint-id}
3249 Restore the program state that was saved as checkpoint number
3250 @var{checkpoint-id}. All program variables, registers, stack frames
3251 etc.@: will be returned to the values that they had when the checkpoint
3252 was saved. In essence, gdb will ``wind back the clock'' to the point
3253 in time when the checkpoint was saved.
3255 Note that breakpoints, @value{GDBN} variables, command history etc.
3256 are not affected by restoring a checkpoint. In general, a checkpoint
3257 only restores things that reside in the program being debugged, not in
3260 @kindex delete checkpoint @var{checkpoint-id}
3261 @item delete checkpoint @var{checkpoint-id}
3262 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3266 Returning to a previously saved checkpoint will restore the user state
3267 of the program being debugged, plus a significant subset of the system
3268 (OS) state, including file pointers. It won't ``un-write'' data from
3269 a file, but it will rewind the file pointer to the previous location,
3270 so that the previously written data can be overwritten. For files
3271 opened in read mode, the pointer will also be restored so that the
3272 previously read data can be read again.
3274 Of course, characters that have been sent to a printer (or other
3275 external device) cannot be ``snatched back'', and characters received
3276 from eg.@: a serial device can be removed from internal program buffers,
3277 but they cannot be ``pushed back'' into the serial pipeline, ready to
3278 be received again. Similarly, the actual contents of files that have
3279 been changed cannot be restored (at this time).
3281 However, within those constraints, you actually can ``rewind'' your
3282 program to a previously saved point in time, and begin debugging it
3283 again --- and you can change the course of events so as to debug a
3284 different execution path this time.
3286 @cindex checkpoints and process id
3287 Finally, there is one bit of internal program state that will be
3288 different when you return to a checkpoint --- the program's process
3289 id. Each checkpoint will have a unique process id (or @var{pid}),
3290 and each will be different from the program's original @var{pid}.
3291 If your program has saved a local copy of its process id, this could
3292 potentially pose a problem.
3294 @subsection A Non-obvious Benefit of Using Checkpoints
3296 On some systems such as @sc{gnu}/Linux, address space randomization
3297 is performed on new processes for security reasons. This makes it
3298 difficult or impossible to set a breakpoint, or watchpoint, on an
3299 absolute address if you have to restart the program, since the
3300 absolute location of a symbol will change from one execution to the
3303 A checkpoint, however, is an @emph{identical} copy of a process.
3304 Therefore if you create a checkpoint at (eg.@:) the start of main,
3305 and simply return to that checkpoint instead of restarting the
3306 process, you can avoid the effects of address randomization and
3307 your symbols will all stay in the same place.
3310 @chapter Stopping and Continuing
3312 The principal purposes of using a debugger are so that you can stop your
3313 program before it terminates; or so that, if your program runs into
3314 trouble, you can investigate and find out why.
3316 Inside @value{GDBN}, your program may stop for any of several reasons,
3317 such as a signal, a breakpoint, or reaching a new line after a
3318 @value{GDBN} command such as @code{step}. You may then examine and
3319 change variables, set new breakpoints or remove old ones, and then
3320 continue execution. Usually, the messages shown by @value{GDBN} provide
3321 ample explanation of the status of your program---but you can also
3322 explicitly request this information at any time.
3325 @kindex info program
3327 Display information about the status of your program: whether it is
3328 running or not, what process it is, and why it stopped.
3332 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3333 * Continuing and Stepping:: Resuming execution
3334 * Skipping Over Functions and Files::
3335 Skipping over functions and files
3337 * Thread Stops:: Stopping and starting multi-thread programs
3341 @section Breakpoints, Watchpoints, and Catchpoints
3344 A @dfn{breakpoint} makes your program stop whenever a certain point in
3345 the program is reached. For each breakpoint, you can add conditions to
3346 control in finer detail whether your program stops. You can set
3347 breakpoints with the @code{break} command and its variants (@pxref{Set
3348 Breaks, ,Setting Breakpoints}), to specify the place where your program
3349 should stop by line number, function name or exact address in the
3352 On some systems, you can set breakpoints in shared libraries before
3353 the executable is run. There is a minor limitation on HP-UX systems:
3354 you must wait until the executable is run in order to set breakpoints
3355 in shared library routines that are not called directly by the program
3356 (for example, routines that are arguments in a @code{pthread_create}
3360 @cindex data breakpoints
3361 @cindex memory tracing
3362 @cindex breakpoint on memory address
3363 @cindex breakpoint on variable modification
3364 A @dfn{watchpoint} is a special breakpoint that stops your program
3365 when the value of an expression changes. The expression may be a value
3366 of a variable, or it could involve values of one or more variables
3367 combined by operators, such as @samp{a + b}. This is sometimes called
3368 @dfn{data breakpoints}. You must use a different command to set
3369 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3370 from that, you can manage a watchpoint like any other breakpoint: you
3371 enable, disable, and delete both breakpoints and watchpoints using the
3374 You can arrange to have values from your program displayed automatically
3375 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3379 @cindex breakpoint on events
3380 A @dfn{catchpoint} is another special breakpoint that stops your program
3381 when a certain kind of event occurs, such as the throwing of a C@t{++}
3382 exception or the loading of a library. As with watchpoints, you use a
3383 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3384 Catchpoints}), but aside from that, you can manage a catchpoint like any
3385 other breakpoint. (To stop when your program receives a signal, use the
3386 @code{handle} command; see @ref{Signals, ,Signals}.)
3388 @cindex breakpoint numbers
3389 @cindex numbers for breakpoints
3390 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3391 catchpoint when you create it; these numbers are successive integers
3392 starting with one. In many of the commands for controlling various
3393 features of breakpoints you use the breakpoint number to say which
3394 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3395 @dfn{disabled}; if disabled, it has no effect on your program until you
3398 @cindex breakpoint ranges
3399 @cindex ranges of breakpoints
3400 Some @value{GDBN} commands accept a range of breakpoints on which to
3401 operate. A breakpoint range is either a single breakpoint number, like
3402 @samp{5}, or two such numbers, in increasing order, separated by a
3403 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3404 all breakpoints in that range are operated on.
3407 * Set Breaks:: Setting breakpoints
3408 * Set Watchpoints:: Setting watchpoints
3409 * Set Catchpoints:: Setting catchpoints
3410 * Delete Breaks:: Deleting breakpoints
3411 * Disabling:: Disabling breakpoints
3412 * Conditions:: Break conditions
3413 * Break Commands:: Breakpoint command lists
3414 * Dynamic Printf:: Dynamic printf
3415 * Save Breakpoints:: How to save breakpoints in a file
3416 * Static Probe Points:: Listing static probe points
3417 * Error in Breakpoints:: ``Cannot insert breakpoints''
3418 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3422 @subsection Setting Breakpoints
3424 @c FIXME LMB what does GDB do if no code on line of breakpt?
3425 @c consider in particular declaration with/without initialization.
3427 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3430 @kindex b @r{(@code{break})}
3431 @vindex $bpnum@r{, convenience variable}
3432 @cindex latest breakpoint
3433 Breakpoints are set with the @code{break} command (abbreviated
3434 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3435 number of the breakpoint you've set most recently; see @ref{Convenience
3436 Vars,, Convenience Variables}, for a discussion of what you can do with
3437 convenience variables.
3440 @item break @var{location}
3441 Set a breakpoint at the given @var{location}, which can specify a
3442 function name, a line number, or an address of an instruction.
3443 (@xref{Specify Location}, for a list of all the possible ways to
3444 specify a @var{location}.) The breakpoint will stop your program just
3445 before it executes any of the code in the specified @var{location}.
3447 When using source languages that permit overloading of symbols, such as
3448 C@t{++}, a function name may refer to more than one possible place to break.
3449 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3452 It is also possible to insert a breakpoint that will stop the program
3453 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3454 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3457 When called without any arguments, @code{break} sets a breakpoint at
3458 the next instruction to be executed in the selected stack frame
3459 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3460 innermost, this makes your program stop as soon as control
3461 returns to that frame. This is similar to the effect of a
3462 @code{finish} command in the frame inside the selected frame---except
3463 that @code{finish} does not leave an active breakpoint. If you use
3464 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3465 the next time it reaches the current location; this may be useful
3468 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3469 least one instruction has been executed. If it did not do this, you
3470 would be unable to proceed past a breakpoint without first disabling the
3471 breakpoint. This rule applies whether or not the breakpoint already
3472 existed when your program stopped.
3474 @item break @dots{} if @var{cond}
3475 Set a breakpoint with condition @var{cond}; evaluate the expression
3476 @var{cond} each time the breakpoint is reached, and stop only if the
3477 value is nonzero---that is, if @var{cond} evaluates as true.
3478 @samp{@dots{}} stands for one of the possible arguments described
3479 above (or no argument) specifying where to break. @xref{Conditions,
3480 ,Break Conditions}, for more information on breakpoint conditions.
3483 @item tbreak @var{args}
3484 Set a breakpoint enabled only for one stop. @var{args} are the
3485 same as for the @code{break} command, and the breakpoint is set in the same
3486 way, but the breakpoint is automatically deleted after the first time your
3487 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3490 @cindex hardware breakpoints
3491 @item hbreak @var{args}
3492 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3493 @code{break} command and the breakpoint is set in the same way, but the
3494 breakpoint requires hardware support and some target hardware may not
3495 have this support. The main purpose of this is EPROM/ROM code
3496 debugging, so you can set a breakpoint at an instruction without
3497 changing the instruction. This can be used with the new trap-generation
3498 provided by SPARClite DSU and most x86-based targets. These targets
3499 will generate traps when a program accesses some data or instruction
3500 address that is assigned to the debug registers. However the hardware
3501 breakpoint registers can take a limited number of breakpoints. For
3502 example, on the DSU, only two data breakpoints can be set at a time, and
3503 @value{GDBN} will reject this command if more than two are used. Delete
3504 or disable unused hardware breakpoints before setting new ones
3505 (@pxref{Disabling, ,Disabling Breakpoints}).
3506 @xref{Conditions, ,Break Conditions}.
3507 For remote targets, you can restrict the number of hardware
3508 breakpoints @value{GDBN} will use, see @ref{set remote
3509 hardware-breakpoint-limit}.
3512 @item thbreak @var{args}
3513 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3514 are the same as for the @code{hbreak} command and the breakpoint is set in
3515 the same way. However, like the @code{tbreak} command,
3516 the breakpoint is automatically deleted after the
3517 first time your program stops there. Also, like the @code{hbreak}
3518 command, the breakpoint requires hardware support and some target hardware
3519 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3520 See also @ref{Conditions, ,Break Conditions}.
3523 @cindex regular expression
3524 @cindex breakpoints at functions matching a regexp
3525 @cindex set breakpoints in many functions
3526 @item rbreak @var{regex}
3527 Set breakpoints on all functions matching the regular expression
3528 @var{regex}. This command sets an unconditional breakpoint on all
3529 matches, printing a list of all breakpoints it set. Once these
3530 breakpoints are set, they are treated just like the breakpoints set with
3531 the @code{break} command. You can delete them, disable them, or make
3532 them conditional the same way as any other breakpoint.
3534 The syntax of the regular expression is the standard one used with tools
3535 like @file{grep}. Note that this is different from the syntax used by
3536 shells, so for instance @code{foo*} matches all functions that include
3537 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3538 @code{.*} leading and trailing the regular expression you supply, so to
3539 match only functions that begin with @code{foo}, use @code{^foo}.
3541 @cindex non-member C@t{++} functions, set breakpoint in
3542 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3543 breakpoints on overloaded functions that are not members of any special
3546 @cindex set breakpoints on all functions
3547 The @code{rbreak} command can be used to set breakpoints in
3548 @strong{all} the functions in a program, like this:
3551 (@value{GDBP}) rbreak .
3554 @item rbreak @var{file}:@var{regex}
3555 If @code{rbreak} is called with a filename qualification, it limits
3556 the search for functions matching the given regular expression to the
3557 specified @var{file}. This can be used, for example, to set breakpoints on
3558 every function in a given file:
3561 (@value{GDBP}) rbreak file.c:.
3564 The colon separating the filename qualifier from the regex may
3565 optionally be surrounded by spaces.
3567 @kindex info breakpoints
3568 @cindex @code{$_} and @code{info breakpoints}
3569 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3570 @itemx info break @r{[}@var{n}@dots{}@r{]}
3571 Print a table of all breakpoints, watchpoints, and catchpoints set and
3572 not deleted. Optional argument @var{n} means print information only
3573 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3574 For each breakpoint, following columns are printed:
3577 @item Breakpoint Numbers
3579 Breakpoint, watchpoint, or catchpoint.
3581 Whether the breakpoint is marked to be disabled or deleted when hit.
3582 @item Enabled or Disabled
3583 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3584 that are not enabled.
3586 Where the breakpoint is in your program, as a memory address. For a
3587 pending breakpoint whose address is not yet known, this field will
3588 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3589 library that has the symbol or line referred by breakpoint is loaded.
3590 See below for details. A breakpoint with several locations will
3591 have @samp{<MULTIPLE>} in this field---see below for details.
3593 Where the breakpoint is in the source for your program, as a file and
3594 line number. For a pending breakpoint, the original string passed to
3595 the breakpoint command will be listed as it cannot be resolved until
3596 the appropriate shared library is loaded in the future.
3600 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3601 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3602 @value{GDBN} on the host's side. If it is ``target'', then the condition
3603 is evaluated by the target. The @code{info break} command shows
3604 the condition on the line following the affected breakpoint, together with
3605 its condition evaluation mode in between parentheses.
3607 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3608 allowed to have a condition specified for it. The condition is not parsed for
3609 validity until a shared library is loaded that allows the pending
3610 breakpoint to resolve to a valid location.
3613 @code{info break} with a breakpoint
3614 number @var{n} as argument lists only that breakpoint. The
3615 convenience variable @code{$_} and the default examining-address for
3616 the @code{x} command are set to the address of the last breakpoint
3617 listed (@pxref{Memory, ,Examining Memory}).
3620 @code{info break} displays a count of the number of times the breakpoint
3621 has been hit. This is especially useful in conjunction with the
3622 @code{ignore} command. You can ignore a large number of breakpoint
3623 hits, look at the breakpoint info to see how many times the breakpoint
3624 was hit, and then run again, ignoring one less than that number. This
3625 will get you quickly to the last hit of that breakpoint.
3628 For a breakpoints with an enable count (xref) greater than 1,
3629 @code{info break} also displays that count.
3633 @value{GDBN} allows you to set any number of breakpoints at the same place in
3634 your program. There is nothing silly or meaningless about this. When
3635 the breakpoints are conditional, this is even useful
3636 (@pxref{Conditions, ,Break Conditions}).
3638 @cindex multiple locations, breakpoints
3639 @cindex breakpoints, multiple locations
3640 It is possible that a breakpoint corresponds to several locations
3641 in your program. Examples of this situation are:
3645 Multiple functions in the program may have the same name.
3648 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3649 instances of the function body, used in different cases.
3652 For a C@t{++} template function, a given line in the function can
3653 correspond to any number of instantiations.
3656 For an inlined function, a given source line can correspond to
3657 several places where that function is inlined.
3660 In all those cases, @value{GDBN} will insert a breakpoint at all
3661 the relevant locations.
3663 A breakpoint with multiple locations is displayed in the breakpoint
3664 table using several rows---one header row, followed by one row for
3665 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3666 address column. The rows for individual locations contain the actual
3667 addresses for locations, and show the functions to which those
3668 locations belong. The number column for a location is of the form
3669 @var{breakpoint-number}.@var{location-number}.
3674 Num Type Disp Enb Address What
3675 1 breakpoint keep y <MULTIPLE>
3677 breakpoint already hit 1 time
3678 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3679 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3682 Each location can be individually enabled or disabled by passing
3683 @var{breakpoint-number}.@var{location-number} as argument to the
3684 @code{enable} and @code{disable} commands. Note that you cannot
3685 delete the individual locations from the list, you can only delete the
3686 entire list of locations that belong to their parent breakpoint (with
3687 the @kbd{delete @var{num}} command, where @var{num} is the number of
3688 the parent breakpoint, 1 in the above example). Disabling or enabling
3689 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3690 that belong to that breakpoint.
3692 @cindex pending breakpoints
3693 It's quite common to have a breakpoint inside a shared library.
3694 Shared libraries can be loaded and unloaded explicitly,
3695 and possibly repeatedly, as the program is executed. To support
3696 this use case, @value{GDBN} updates breakpoint locations whenever
3697 any shared library is loaded or unloaded. Typically, you would
3698 set a breakpoint in a shared library at the beginning of your
3699 debugging session, when the library is not loaded, and when the
3700 symbols from the library are not available. When you try to set
3701 breakpoint, @value{GDBN} will ask you if you want to set
3702 a so called @dfn{pending breakpoint}---breakpoint whose address
3703 is not yet resolved.
3705 After the program is run, whenever a new shared library is loaded,
3706 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3707 shared library contains the symbol or line referred to by some
3708 pending breakpoint, that breakpoint is resolved and becomes an
3709 ordinary breakpoint. When a library is unloaded, all breakpoints
3710 that refer to its symbols or source lines become pending again.
3712 This logic works for breakpoints with multiple locations, too. For
3713 example, if you have a breakpoint in a C@t{++} template function, and
3714 a newly loaded shared library has an instantiation of that template,
3715 a new location is added to the list of locations for the breakpoint.
3717 Except for having unresolved address, pending breakpoints do not
3718 differ from regular breakpoints. You can set conditions or commands,
3719 enable and disable them and perform other breakpoint operations.
3721 @value{GDBN} provides some additional commands for controlling what
3722 happens when the @samp{break} command cannot resolve breakpoint
3723 address specification to an address:
3725 @kindex set breakpoint pending
3726 @kindex show breakpoint pending
3728 @item set breakpoint pending auto
3729 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3730 location, it queries you whether a pending breakpoint should be created.
3732 @item set breakpoint pending on
3733 This indicates that an unrecognized breakpoint location should automatically
3734 result in a pending breakpoint being created.
3736 @item set breakpoint pending off
3737 This indicates that pending breakpoints are not to be created. Any
3738 unrecognized breakpoint location results in an error. This setting does
3739 not affect any pending breakpoints previously created.
3741 @item show breakpoint pending
3742 Show the current behavior setting for creating pending breakpoints.
3745 The settings above only affect the @code{break} command and its
3746 variants. Once breakpoint is set, it will be automatically updated
3747 as shared libraries are loaded and unloaded.
3749 @cindex automatic hardware breakpoints
3750 For some targets, @value{GDBN} can automatically decide if hardware or
3751 software breakpoints should be used, depending on whether the
3752 breakpoint address is read-only or read-write. This applies to
3753 breakpoints set with the @code{break} command as well as to internal
3754 breakpoints set by commands like @code{next} and @code{finish}. For
3755 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3758 You can control this automatic behaviour with the following commands::
3760 @kindex set breakpoint auto-hw
3761 @kindex show breakpoint auto-hw
3763 @item set breakpoint auto-hw on
3764 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3765 will try to use the target memory map to decide if software or hardware
3766 breakpoint must be used.
3768 @item set breakpoint auto-hw off
3769 This indicates @value{GDBN} should not automatically select breakpoint
3770 type. If the target provides a memory map, @value{GDBN} will warn when
3771 trying to set software breakpoint at a read-only address.
3774 @value{GDBN} normally implements breakpoints by replacing the program code
3775 at the breakpoint address with a special instruction, which, when
3776 executed, given control to the debugger. By default, the program
3777 code is so modified only when the program is resumed. As soon as
3778 the program stops, @value{GDBN} restores the original instructions. This
3779 behaviour guards against leaving breakpoints inserted in the
3780 target should gdb abrubptly disconnect. However, with slow remote
3781 targets, inserting and removing breakpoint can reduce the performance.
3782 This behavior can be controlled with the following commands::
3784 @kindex set breakpoint always-inserted
3785 @kindex show breakpoint always-inserted
3787 @item set breakpoint always-inserted off
3788 All breakpoints, including newly added by the user, are inserted in
3789 the target only when the target is resumed. All breakpoints are
3790 removed from the target when it stops.
3792 @item set breakpoint always-inserted on
3793 Causes all breakpoints to be inserted in the target at all times. If
3794 the user adds a new breakpoint, or changes an existing breakpoint, the
3795 breakpoints in the target are updated immediately. A breakpoint is
3796 removed from the target only when breakpoint itself is removed.
3798 @cindex non-stop mode, and @code{breakpoint always-inserted}
3799 @item set breakpoint always-inserted auto
3800 This is the default mode. If @value{GDBN} is controlling the inferior
3801 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3802 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3803 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3804 @code{breakpoint always-inserted} mode is off.
3807 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3808 when a breakpoint breaks. If the condition is true, then the process being
3809 debugged stops, otherwise the process is resumed.
3811 If the target supports evaluating conditions on its end, @value{GDBN} may
3812 download the breakpoint, together with its conditions, to it.
3814 This feature can be controlled via the following commands:
3816 @kindex set breakpoint condition-evaluation
3817 @kindex show breakpoint condition-evaluation
3819 @item set breakpoint condition-evaluation host
3820 This option commands @value{GDBN} to evaluate the breakpoint
3821 conditions on the host's side. Unconditional breakpoints are sent to
3822 the target which in turn receives the triggers and reports them back to GDB
3823 for condition evaluation. This is the standard evaluation mode.
3825 @item set breakpoint condition-evaluation target
3826 This option commands @value{GDBN} to download breakpoint conditions
3827 to the target at the moment of their insertion. The target
3828 is responsible for evaluating the conditional expression and reporting
3829 breakpoint stop events back to @value{GDBN} whenever the condition
3830 is true. Due to limitations of target-side evaluation, some conditions
3831 cannot be evaluated there, e.g., conditions that depend on local data
3832 that is only known to the host. Examples include
3833 conditional expressions involving convenience variables, complex types
3834 that cannot be handled by the agent expression parser and expressions
3835 that are too long to be sent over to the target, specially when the
3836 target is a remote system. In these cases, the conditions will be
3837 evaluated by @value{GDBN}.
3839 @item set breakpoint condition-evaluation auto
3840 This is the default mode. If the target supports evaluating breakpoint
3841 conditions on its end, @value{GDBN} will download breakpoint conditions to
3842 the target (limitations mentioned previously apply). If the target does
3843 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3844 to evaluating all these conditions on the host's side.
3848 @cindex negative breakpoint numbers
3849 @cindex internal @value{GDBN} breakpoints
3850 @value{GDBN} itself sometimes sets breakpoints in your program for
3851 special purposes, such as proper handling of @code{longjmp} (in C
3852 programs). These internal breakpoints are assigned negative numbers,
3853 starting with @code{-1}; @samp{info breakpoints} does not display them.
3854 You can see these breakpoints with the @value{GDBN} maintenance command
3855 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3858 @node Set Watchpoints
3859 @subsection Setting Watchpoints
3861 @cindex setting watchpoints
3862 You can use a watchpoint to stop execution whenever the value of an
3863 expression changes, without having to predict a particular place where
3864 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3865 The expression may be as simple as the value of a single variable, or
3866 as complex as many variables combined by operators. Examples include:
3870 A reference to the value of a single variable.
3873 An address cast to an appropriate data type. For example,
3874 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3875 address (assuming an @code{int} occupies 4 bytes).
3878 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3879 expression can use any operators valid in the program's native
3880 language (@pxref{Languages}).
3883 You can set a watchpoint on an expression even if the expression can
3884 not be evaluated yet. For instance, you can set a watchpoint on
3885 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3886 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3887 the expression produces a valid value. If the expression becomes
3888 valid in some other way than changing a variable (e.g.@: if the memory
3889 pointed to by @samp{*global_ptr} becomes readable as the result of a
3890 @code{malloc} call), @value{GDBN} may not stop until the next time
3891 the expression changes.
3893 @cindex software watchpoints
3894 @cindex hardware watchpoints
3895 Depending on your system, watchpoints may be implemented in software or
3896 hardware. @value{GDBN} does software watchpointing by single-stepping your
3897 program and testing the variable's value each time, which is hundreds of
3898 times slower than normal execution. (But this may still be worth it, to
3899 catch errors where you have no clue what part of your program is the
3902 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3903 x86-based targets, @value{GDBN} includes support for hardware
3904 watchpoints, which do not slow down the running of your program.
3908 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3909 Set a watchpoint for an expression. @value{GDBN} will break when the
3910 expression @var{expr} is written into by the program and its value
3911 changes. The simplest (and the most popular) use of this command is
3912 to watch the value of a single variable:
3915 (@value{GDBP}) watch foo
3918 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3919 argument, @value{GDBN} breaks only when the thread identified by
3920 @var{threadnum} changes the value of @var{expr}. If any other threads
3921 change the value of @var{expr}, @value{GDBN} will not break. Note
3922 that watchpoints restricted to a single thread in this way only work
3923 with Hardware Watchpoints.
3925 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3926 (see below). The @code{-location} argument tells @value{GDBN} to
3927 instead watch the memory referred to by @var{expr}. In this case,
3928 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3929 and watch the memory at that address. The type of the result is used
3930 to determine the size of the watched memory. If the expression's
3931 result does not have an address, then @value{GDBN} will print an
3934 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3935 of masked watchpoints, if the current architecture supports this
3936 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3937 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3938 to an address to watch. The mask specifies that some bits of an address
3939 (the bits which are reset in the mask) should be ignored when matching
3940 the address accessed by the inferior against the watchpoint address.
3941 Thus, a masked watchpoint watches many addresses simultaneously---those
3942 addresses whose unmasked bits are identical to the unmasked bits in the
3943 watchpoint address. The @code{mask} argument implies @code{-location}.
3947 (@value{GDBP}) watch foo mask 0xffff00ff
3948 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3952 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3953 Set a watchpoint that will break when the value of @var{expr} is read
3957 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3958 Set a watchpoint that will break when @var{expr} is either read from
3959 or written into by the program.
3961 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3962 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3963 This command prints a list of watchpoints, using the same format as
3964 @code{info break} (@pxref{Set Breaks}).
3967 If you watch for a change in a numerically entered address you need to
3968 dereference it, as the address itself is just a constant number which will
3969 never change. @value{GDBN} refuses to create a watchpoint that watches
3970 a never-changing value:
3973 (@value{GDBP}) watch 0x600850
3974 Cannot watch constant value 0x600850.
3975 (@value{GDBP}) watch *(int *) 0x600850
3976 Watchpoint 1: *(int *) 6293584
3979 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3980 watchpoints execute very quickly, and the debugger reports a change in
3981 value at the exact instruction where the change occurs. If @value{GDBN}
3982 cannot set a hardware watchpoint, it sets a software watchpoint, which
3983 executes more slowly and reports the change in value at the next
3984 @emph{statement}, not the instruction, after the change occurs.
3986 @cindex use only software watchpoints
3987 You can force @value{GDBN} to use only software watchpoints with the
3988 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3989 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3990 the underlying system supports them. (Note that hardware-assisted
3991 watchpoints that were set @emph{before} setting
3992 @code{can-use-hw-watchpoints} to zero will still use the hardware
3993 mechanism of watching expression values.)
3996 @item set can-use-hw-watchpoints
3997 @kindex set can-use-hw-watchpoints
3998 Set whether or not to use hardware watchpoints.
4000 @item show can-use-hw-watchpoints
4001 @kindex show can-use-hw-watchpoints
4002 Show the current mode of using hardware watchpoints.
4005 For remote targets, you can restrict the number of hardware
4006 watchpoints @value{GDBN} will use, see @ref{set remote
4007 hardware-breakpoint-limit}.
4009 When you issue the @code{watch} command, @value{GDBN} reports
4012 Hardware watchpoint @var{num}: @var{expr}
4016 if it was able to set a hardware watchpoint.
4018 Currently, the @code{awatch} and @code{rwatch} commands can only set
4019 hardware watchpoints, because accesses to data that don't change the
4020 value of the watched expression cannot be detected without examining
4021 every instruction as it is being executed, and @value{GDBN} does not do
4022 that currently. If @value{GDBN} finds that it is unable to set a
4023 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4024 will print a message like this:
4027 Expression cannot be implemented with read/access watchpoint.
4030 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4031 data type of the watched expression is wider than what a hardware
4032 watchpoint on the target machine can handle. For example, some systems
4033 can only watch regions that are up to 4 bytes wide; on such systems you
4034 cannot set hardware watchpoints for an expression that yields a
4035 double-precision floating-point number (which is typically 8 bytes
4036 wide). As a work-around, it might be possible to break the large region
4037 into a series of smaller ones and watch them with separate watchpoints.
4039 If you set too many hardware watchpoints, @value{GDBN} might be unable
4040 to insert all of them when you resume the execution of your program.
4041 Since the precise number of active watchpoints is unknown until such
4042 time as the program is about to be resumed, @value{GDBN} might not be
4043 able to warn you about this when you set the watchpoints, and the
4044 warning will be printed only when the program is resumed:
4047 Hardware watchpoint @var{num}: Could not insert watchpoint
4051 If this happens, delete or disable some of the watchpoints.
4053 Watching complex expressions that reference many variables can also
4054 exhaust the resources available for hardware-assisted watchpoints.
4055 That's because @value{GDBN} needs to watch every variable in the
4056 expression with separately allocated resources.
4058 If you call a function interactively using @code{print} or @code{call},
4059 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4060 kind of breakpoint or the call completes.
4062 @value{GDBN} automatically deletes watchpoints that watch local
4063 (automatic) variables, or expressions that involve such variables, when
4064 they go out of scope, that is, when the execution leaves the block in
4065 which these variables were defined. In particular, when the program
4066 being debugged terminates, @emph{all} local variables go out of scope,
4067 and so only watchpoints that watch global variables remain set. If you
4068 rerun the program, you will need to set all such watchpoints again. One
4069 way of doing that would be to set a code breakpoint at the entry to the
4070 @code{main} function and when it breaks, set all the watchpoints.
4072 @cindex watchpoints and threads
4073 @cindex threads and watchpoints
4074 In multi-threaded programs, watchpoints will detect changes to the
4075 watched expression from every thread.
4078 @emph{Warning:} In multi-threaded programs, software watchpoints
4079 have only limited usefulness. If @value{GDBN} creates a software
4080 watchpoint, it can only watch the value of an expression @emph{in a
4081 single thread}. If you are confident that the expression can only
4082 change due to the current thread's activity (and if you are also
4083 confident that no other thread can become current), then you can use
4084 software watchpoints as usual. However, @value{GDBN} may not notice
4085 when a non-current thread's activity changes the expression. (Hardware
4086 watchpoints, in contrast, watch an expression in all threads.)
4089 @xref{set remote hardware-watchpoint-limit}.
4091 @node Set Catchpoints
4092 @subsection Setting Catchpoints
4093 @cindex catchpoints, setting
4094 @cindex exception handlers
4095 @cindex event handling
4097 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4098 kinds of program events, such as C@t{++} exceptions or the loading of a
4099 shared library. Use the @code{catch} command to set a catchpoint.
4103 @item catch @var{event}
4104 Stop when @var{event} occurs. @var{event} can be any of the following:
4107 @item throw @r{[}@var{regexp}@r{]}
4108 @itemx rethrow @r{[}@var{regexp}@r{]}
4109 @itemx catch @r{[}@var{regexp}@r{]}
4110 @cindex stop on C@t{++} exceptions
4111 The throwing, re-throwing, or catching of a C@t{++} exception.
4113 If @var{regexp} is given, then only exceptions whose type matches the
4114 regular expression will be caught.
4116 @vindex $_exception@r{, convenience variable}
4117 The convenience variable @code{$_exception} is available at an
4118 exception-related catchpoint, on some systems. This holds the
4119 exception being thrown.
4121 There are currently some limitations to C@t{++} exception handling in
4126 The support for these commands is system-dependent. Currently, only
4127 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4131 The regular expression feature and the @code{$_exception} convenience
4132 variable rely on the presence of some SDT probes in @code{libstdc++}.
4133 If these probes are not present, then these features cannot be used.
4134 These probes were first available in the GCC 4.8 release, but whether
4135 or not they are available in your GCC also depends on how it was
4139 The @code{$_exception} convenience variable is only valid at the
4140 instruction at which an exception-related catchpoint is set.
4143 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4144 location in the system library which implements runtime exception
4145 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4146 (@pxref{Selection}) to get to your code.
4149 If you call a function interactively, @value{GDBN} normally returns
4150 control to you when the function has finished executing. If the call
4151 raises an exception, however, the call may bypass the mechanism that
4152 returns control to you and cause your program either to abort or to
4153 simply continue running until it hits a breakpoint, catches a signal
4154 that @value{GDBN} is listening for, or exits. This is the case even if
4155 you set a catchpoint for the exception; catchpoints on exceptions are
4156 disabled within interactive calls. @xref{Calling}, for information on
4157 controlling this with @code{set unwind-on-terminating-exception}.
4160 You cannot raise an exception interactively.
4163 You cannot install an exception handler interactively.
4167 @cindex Ada exception catching
4168 @cindex catch Ada exceptions
4169 An Ada exception being raised. If an exception name is specified
4170 at the end of the command (eg @code{catch exception Program_Error}),
4171 the debugger will stop only when this specific exception is raised.
4172 Otherwise, the debugger stops execution when any Ada exception is raised.
4174 When inserting an exception catchpoint on a user-defined exception whose
4175 name is identical to one of the exceptions defined by the language, the
4176 fully qualified name must be used as the exception name. Otherwise,
4177 @value{GDBN} will assume that it should stop on the pre-defined exception
4178 rather than the user-defined one. For instance, assuming an exception
4179 called @code{Constraint_Error} is defined in package @code{Pck}, then
4180 the command to use to catch such exceptions is @kbd{catch exception
4181 Pck.Constraint_Error}.
4183 @item exception unhandled
4184 An exception that was raised but is not handled by the program.
4187 A failed Ada assertion.
4190 @cindex break on fork/exec
4191 A call to @code{exec}. This is currently only available for HP-UX
4195 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4196 @cindex break on a system call.
4197 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4198 syscall is a mechanism for application programs to request a service
4199 from the operating system (OS) or one of the OS system services.
4200 @value{GDBN} can catch some or all of the syscalls issued by the
4201 debuggee, and show the related information for each syscall. If no
4202 argument is specified, calls to and returns from all system calls
4205 @var{name} can be any system call name that is valid for the
4206 underlying OS. Just what syscalls are valid depends on the OS. On
4207 GNU and Unix systems, you can find the full list of valid syscall
4208 names on @file{/usr/include/asm/unistd.h}.
4210 @c For MS-Windows, the syscall names and the corresponding numbers
4211 @c can be found, e.g., on this URL:
4212 @c http://www.metasploit.com/users/opcode/syscalls.html
4213 @c but we don't support Windows syscalls yet.
4215 Normally, @value{GDBN} knows in advance which syscalls are valid for
4216 each OS, so you can use the @value{GDBN} command-line completion
4217 facilities (@pxref{Completion,, command completion}) to list the
4220 You may also specify the system call numerically. A syscall's
4221 number is the value passed to the OS's syscall dispatcher to
4222 identify the requested service. When you specify the syscall by its
4223 name, @value{GDBN} uses its database of syscalls to convert the name
4224 into the corresponding numeric code, but using the number directly
4225 may be useful if @value{GDBN}'s database does not have the complete
4226 list of syscalls on your system (e.g., because @value{GDBN} lags
4227 behind the OS upgrades).
4229 The example below illustrates how this command works if you don't provide
4233 (@value{GDBP}) catch syscall
4234 Catchpoint 1 (syscall)
4236 Starting program: /tmp/catch-syscall
4238 Catchpoint 1 (call to syscall 'close'), \
4239 0xffffe424 in __kernel_vsyscall ()
4243 Catchpoint 1 (returned from syscall 'close'), \
4244 0xffffe424 in __kernel_vsyscall ()
4248 Here is an example of catching a system call by name:
4251 (@value{GDBP}) catch syscall chroot
4252 Catchpoint 1 (syscall 'chroot' [61])
4254 Starting program: /tmp/catch-syscall
4256 Catchpoint 1 (call to syscall 'chroot'), \
4257 0xffffe424 in __kernel_vsyscall ()
4261 Catchpoint 1 (returned from syscall 'chroot'), \
4262 0xffffe424 in __kernel_vsyscall ()
4266 An example of specifying a system call numerically. In the case
4267 below, the syscall number has a corresponding entry in the XML
4268 file, so @value{GDBN} finds its name and prints it:
4271 (@value{GDBP}) catch syscall 252
4272 Catchpoint 1 (syscall(s) 'exit_group')
4274 Starting program: /tmp/catch-syscall
4276 Catchpoint 1 (call to syscall 'exit_group'), \
4277 0xffffe424 in __kernel_vsyscall ()
4281 Program exited normally.
4285 However, there can be situations when there is no corresponding name
4286 in XML file for that syscall number. In this case, @value{GDBN} prints
4287 a warning message saying that it was not able to find the syscall name,
4288 but the catchpoint will be set anyway. See the example below:
4291 (@value{GDBP}) catch syscall 764
4292 warning: The number '764' does not represent a known syscall.
4293 Catchpoint 2 (syscall 764)
4297 If you configure @value{GDBN} using the @samp{--without-expat} option,
4298 it will not be able to display syscall names. Also, if your
4299 architecture does not have an XML file describing its system calls,
4300 you will not be able to see the syscall names. It is important to
4301 notice that these two features are used for accessing the syscall
4302 name database. In either case, you will see a warning like this:
4305 (@value{GDBP}) catch syscall
4306 warning: Could not open "syscalls/i386-linux.xml"
4307 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4308 GDB will not be able to display syscall names.
4309 Catchpoint 1 (syscall)
4313 Of course, the file name will change depending on your architecture and system.
4315 Still using the example above, you can also try to catch a syscall by its
4316 number. In this case, you would see something like:
4319 (@value{GDBP}) catch syscall 252
4320 Catchpoint 1 (syscall(s) 252)
4323 Again, in this case @value{GDBN} would not be able to display syscall's names.
4326 A call to @code{fork}. This is currently only available for HP-UX
4330 A call to @code{vfork}. This is currently only available for HP-UX
4333 @item load @r{[}regexp@r{]}
4334 @itemx unload @r{[}regexp@r{]}
4335 The loading or unloading of a shared library. If @var{regexp} is
4336 given, then the catchpoint will stop only if the regular expression
4337 matches one of the affected libraries.
4339 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4340 The delivery of a signal.
4342 With no arguments, this catchpoint will catch any signal that is not
4343 used internally by @value{GDBN}, specifically, all signals except
4344 @samp{SIGTRAP} and @samp{SIGINT}.
4346 With the argument @samp{all}, all signals, including those used by
4347 @value{GDBN}, will be caught. This argument cannot be used with other
4350 Otherwise, the arguments are a list of signal names as given to
4351 @code{handle} (@pxref{Signals}). Only signals specified in this list
4354 One reason that @code{catch signal} can be more useful than
4355 @code{handle} is that you can attach commands and conditions to the
4358 When a signal is caught by a catchpoint, the signal's @code{stop} and
4359 @code{print} settings, as specified by @code{handle}, are ignored.
4360 However, whether the signal is still delivered to the inferior depends
4361 on the @code{pass} setting; this can be changed in the catchpoint's
4366 @item tcatch @var{event}
4367 Set a catchpoint that is enabled only for one stop. The catchpoint is
4368 automatically deleted after the first time the event is caught.
4372 Use the @code{info break} command to list the current catchpoints.
4376 @subsection Deleting Breakpoints
4378 @cindex clearing breakpoints, watchpoints, catchpoints
4379 @cindex deleting breakpoints, watchpoints, catchpoints
4380 It is often necessary to eliminate a breakpoint, watchpoint, or
4381 catchpoint once it has done its job and you no longer want your program
4382 to stop there. This is called @dfn{deleting} the breakpoint. A
4383 breakpoint that has been deleted no longer exists; it is forgotten.
4385 With the @code{clear} command you can delete breakpoints according to
4386 where they are in your program. With the @code{delete} command you can
4387 delete individual breakpoints, watchpoints, or catchpoints by specifying
4388 their breakpoint numbers.
4390 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4391 automatically ignores breakpoints on the first instruction to be executed
4392 when you continue execution without changing the execution address.
4397 Delete any breakpoints at the next instruction to be executed in the
4398 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4399 the innermost frame is selected, this is a good way to delete a
4400 breakpoint where your program just stopped.
4402 @item clear @var{location}
4403 Delete any breakpoints set at the specified @var{location}.
4404 @xref{Specify Location}, for the various forms of @var{location}; the
4405 most useful ones are listed below:
4408 @item clear @var{function}
4409 @itemx clear @var{filename}:@var{function}
4410 Delete any breakpoints set at entry to the named @var{function}.
4412 @item clear @var{linenum}
4413 @itemx clear @var{filename}:@var{linenum}
4414 Delete any breakpoints set at or within the code of the specified
4415 @var{linenum} of the specified @var{filename}.
4418 @cindex delete breakpoints
4420 @kindex d @r{(@code{delete})}
4421 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4422 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4423 ranges specified as arguments. If no argument is specified, delete all
4424 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4425 confirm off}). You can abbreviate this command as @code{d}.
4429 @subsection Disabling Breakpoints
4431 @cindex enable/disable a breakpoint
4432 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4433 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4434 it had been deleted, but remembers the information on the breakpoint so
4435 that you can @dfn{enable} it again later.
4437 You disable and enable breakpoints, watchpoints, and catchpoints with
4438 the @code{enable} and @code{disable} commands, optionally specifying
4439 one or more breakpoint numbers as arguments. Use @code{info break} to
4440 print a list of all breakpoints, watchpoints, and catchpoints if you
4441 do not know which numbers to use.
4443 Disabling and enabling a breakpoint that has multiple locations
4444 affects all of its locations.
4446 A breakpoint, watchpoint, or catchpoint can have any of several
4447 different states of enablement:
4451 Enabled. The breakpoint stops your program. A breakpoint set
4452 with the @code{break} command starts out in this state.
4454 Disabled. The breakpoint has no effect on your program.
4456 Enabled once. The breakpoint stops your program, but then becomes
4459 Enabled for a count. The breakpoint stops your program for the next
4460 N times, then becomes disabled.
4462 Enabled for deletion. The breakpoint stops your program, but
4463 immediately after it does so it is deleted permanently. A breakpoint
4464 set with the @code{tbreak} command starts out in this state.
4467 You can use the following commands to enable or disable breakpoints,
4468 watchpoints, and catchpoints:
4472 @kindex dis @r{(@code{disable})}
4473 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4474 Disable the specified breakpoints---or all breakpoints, if none are
4475 listed. A disabled breakpoint has no effect but is not forgotten. All
4476 options such as ignore-counts, conditions and commands are remembered in
4477 case the breakpoint is enabled again later. You may abbreviate
4478 @code{disable} as @code{dis}.
4481 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4482 Enable the specified breakpoints (or all defined breakpoints). They
4483 become effective once again in stopping your program.
4485 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4486 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4487 of these breakpoints immediately after stopping your program.
4489 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4490 Enable the specified breakpoints temporarily. @value{GDBN} records
4491 @var{count} with each of the specified breakpoints, and decrements a
4492 breakpoint's count when it is hit. When any count reaches 0,
4493 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4494 count (@pxref{Conditions, ,Break Conditions}), that will be
4495 decremented to 0 before @var{count} is affected.
4497 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4498 Enable the specified breakpoints to work once, then die. @value{GDBN}
4499 deletes any of these breakpoints as soon as your program stops there.
4500 Breakpoints set by the @code{tbreak} command start out in this state.
4503 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4504 @c confusing: tbreak is also initially enabled.
4505 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4506 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4507 subsequently, they become disabled or enabled only when you use one of
4508 the commands above. (The command @code{until} can set and delete a
4509 breakpoint of its own, but it does not change the state of your other
4510 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4514 @subsection Break Conditions
4515 @cindex conditional breakpoints
4516 @cindex breakpoint conditions
4518 @c FIXME what is scope of break condition expr? Context where wanted?
4519 @c in particular for a watchpoint?
4520 The simplest sort of breakpoint breaks every time your program reaches a
4521 specified place. You can also specify a @dfn{condition} for a
4522 breakpoint. A condition is just a Boolean expression in your
4523 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4524 a condition evaluates the expression each time your program reaches it,
4525 and your program stops only if the condition is @emph{true}.
4527 This is the converse of using assertions for program validation; in that
4528 situation, you want to stop when the assertion is violated---that is,
4529 when the condition is false. In C, if you want to test an assertion expressed
4530 by the condition @var{assert}, you should set the condition
4531 @samp{! @var{assert}} on the appropriate breakpoint.
4533 Conditions are also accepted for watchpoints; you may not need them,
4534 since a watchpoint is inspecting the value of an expression anyhow---but
4535 it might be simpler, say, to just set a watchpoint on a variable name,
4536 and specify a condition that tests whether the new value is an interesting
4539 Break conditions can have side effects, and may even call functions in
4540 your program. This can be useful, for example, to activate functions
4541 that log program progress, or to use your own print functions to
4542 format special data structures. The effects are completely predictable
4543 unless there is another enabled breakpoint at the same address. (In
4544 that case, @value{GDBN} might see the other breakpoint first and stop your
4545 program without checking the condition of this one.) Note that
4546 breakpoint commands are usually more convenient and flexible than break
4548 purpose of performing side effects when a breakpoint is reached
4549 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4551 Breakpoint conditions can also be evaluated on the target's side if
4552 the target supports it. Instead of evaluating the conditions locally,
4553 @value{GDBN} encodes the expression into an agent expression
4554 (@pxref{Agent Expressions}) suitable for execution on the target,
4555 independently of @value{GDBN}. Global variables become raw memory
4556 locations, locals become stack accesses, and so forth.
4558 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4559 when its condition evaluates to true. This mechanism may provide faster
4560 response times depending on the performance characteristics of the target
4561 since it does not need to keep @value{GDBN} informed about
4562 every breakpoint trigger, even those with false conditions.
4564 Break conditions can be specified when a breakpoint is set, by using
4565 @samp{if} in the arguments to the @code{break} command. @xref{Set
4566 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4567 with the @code{condition} command.
4569 You can also use the @code{if} keyword with the @code{watch} command.
4570 The @code{catch} command does not recognize the @code{if} keyword;
4571 @code{condition} is the only way to impose a further condition on a
4576 @item condition @var{bnum} @var{expression}
4577 Specify @var{expression} as the break condition for breakpoint,
4578 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4579 breakpoint @var{bnum} stops your program only if the value of
4580 @var{expression} is true (nonzero, in C). When you use
4581 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4582 syntactic correctness, and to determine whether symbols in it have
4583 referents in the context of your breakpoint. If @var{expression} uses
4584 symbols not referenced in the context of the breakpoint, @value{GDBN}
4585 prints an error message:
4588 No symbol "foo" in current context.
4593 not actually evaluate @var{expression} at the time the @code{condition}
4594 command (or a command that sets a breakpoint with a condition, like
4595 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4597 @item condition @var{bnum}
4598 Remove the condition from breakpoint number @var{bnum}. It becomes
4599 an ordinary unconditional breakpoint.
4602 @cindex ignore count (of breakpoint)
4603 A special case of a breakpoint condition is to stop only when the
4604 breakpoint has been reached a certain number of times. This is so
4605 useful that there is a special way to do it, using the @dfn{ignore
4606 count} of the breakpoint. Every breakpoint has an ignore count, which
4607 is an integer. Most of the time, the ignore count is zero, and
4608 therefore has no effect. But if your program reaches a breakpoint whose
4609 ignore count is positive, then instead of stopping, it just decrements
4610 the ignore count by one and continues. As a result, if the ignore count
4611 value is @var{n}, the breakpoint does not stop the next @var{n} times
4612 your program reaches it.
4616 @item ignore @var{bnum} @var{count}
4617 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4618 The next @var{count} times the breakpoint is reached, your program's
4619 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4622 To make the breakpoint stop the next time it is reached, specify
4625 When you use @code{continue} to resume execution of your program from a
4626 breakpoint, you can specify an ignore count directly as an argument to
4627 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4628 Stepping,,Continuing and Stepping}.
4630 If a breakpoint has a positive ignore count and a condition, the
4631 condition is not checked. Once the ignore count reaches zero,
4632 @value{GDBN} resumes checking the condition.
4634 You could achieve the effect of the ignore count with a condition such
4635 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4636 is decremented each time. @xref{Convenience Vars, ,Convenience
4640 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4643 @node Break Commands
4644 @subsection Breakpoint Command Lists
4646 @cindex breakpoint commands
4647 You can give any breakpoint (or watchpoint or catchpoint) a series of
4648 commands to execute when your program stops due to that breakpoint. For
4649 example, you might want to print the values of certain expressions, or
4650 enable other breakpoints.
4654 @kindex end@r{ (breakpoint commands)}
4655 @item commands @r{[}@var{range}@dots{}@r{]}
4656 @itemx @dots{} @var{command-list} @dots{}
4658 Specify a list of commands for the given breakpoints. The commands
4659 themselves appear on the following lines. Type a line containing just
4660 @code{end} to terminate the commands.
4662 To remove all commands from a breakpoint, type @code{commands} and
4663 follow it immediately with @code{end}; that is, give no commands.
4665 With no argument, @code{commands} refers to the last breakpoint,
4666 watchpoint, or catchpoint set (not to the breakpoint most recently
4667 encountered). If the most recent breakpoints were set with a single
4668 command, then the @code{commands} will apply to all the breakpoints
4669 set by that command. This applies to breakpoints set by
4670 @code{rbreak}, and also applies when a single @code{break} command
4671 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4675 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4676 disabled within a @var{command-list}.
4678 You can use breakpoint commands to start your program up again. Simply
4679 use the @code{continue} command, or @code{step}, or any other command
4680 that resumes execution.
4682 Any other commands in the command list, after a command that resumes
4683 execution, are ignored. This is because any time you resume execution
4684 (even with a simple @code{next} or @code{step}), you may encounter
4685 another breakpoint---which could have its own command list, leading to
4686 ambiguities about which list to execute.
4689 If the first command you specify in a command list is @code{silent}, the
4690 usual message about stopping at a breakpoint is not printed. This may
4691 be desirable for breakpoints that are to print a specific message and
4692 then continue. If none of the remaining commands print anything, you
4693 see no sign that the breakpoint was reached. @code{silent} is
4694 meaningful only at the beginning of a breakpoint command list.
4696 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4697 print precisely controlled output, and are often useful in silent
4698 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4700 For example, here is how you could use breakpoint commands to print the
4701 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4707 printf "x is %d\n",x
4712 One application for breakpoint commands is to compensate for one bug so
4713 you can test for another. Put a breakpoint just after the erroneous line
4714 of code, give it a condition to detect the case in which something
4715 erroneous has been done, and give it commands to assign correct values
4716 to any variables that need them. End with the @code{continue} command
4717 so that your program does not stop, and start with the @code{silent}
4718 command so that no output is produced. Here is an example:
4729 @node Dynamic Printf
4730 @subsection Dynamic Printf
4732 @cindex dynamic printf
4734 The dynamic printf command @code{dprintf} combines a breakpoint with
4735 formatted printing of your program's data to give you the effect of
4736 inserting @code{printf} calls into your program on-the-fly, without
4737 having to recompile it.
4739 In its most basic form, the output goes to the GDB console. However,
4740 you can set the variable @code{dprintf-style} for alternate handling.
4741 For instance, you can ask to format the output by calling your
4742 program's @code{printf} function. This has the advantage that the
4743 characters go to the program's output device, so they can recorded in
4744 redirects to files and so forth.
4746 If you are doing remote debugging with a stub or agent, you can also
4747 ask to have the printf handled by the remote agent. In addition to
4748 ensuring that the output goes to the remote program's device along
4749 with any other output the program might produce, you can also ask that
4750 the dprintf remain active even after disconnecting from the remote
4751 target. Using the stub/agent is also more efficient, as it can do
4752 everything without needing to communicate with @value{GDBN}.
4756 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4757 Whenever execution reaches @var{location}, print the values of one or
4758 more @var{expressions} under the control of the string @var{template}.
4759 To print several values, separate them with commas.
4761 @item set dprintf-style @var{style}
4762 Set the dprintf output to be handled in one of several different
4763 styles enumerated below. A change of style affects all existing
4764 dynamic printfs immediately. (If you need individual control over the
4765 print commands, simply define normal breakpoints with
4766 explicitly-supplied command lists.)
4769 @kindex dprintf-style gdb
4770 Handle the output using the @value{GDBN} @code{printf} command.
4773 @kindex dprintf-style call
4774 Handle the output by calling a function in your program (normally
4778 @kindex dprintf-style agent
4779 Have the remote debugging agent (such as @code{gdbserver}) handle
4780 the output itself. This style is only available for agents that
4781 support running commands on the target.
4783 @item set dprintf-function @var{function}
4784 Set the function to call if the dprintf style is @code{call}. By
4785 default its value is @code{printf}. You may set it to any expression.
4786 that @value{GDBN} can evaluate to a function, as per the @code{call}
4789 @item set dprintf-channel @var{channel}
4790 Set a ``channel'' for dprintf. If set to a non-empty value,
4791 @value{GDBN} will evaluate it as an expression and pass the result as
4792 a first argument to the @code{dprintf-function}, in the manner of
4793 @code{fprintf} and similar functions. Otherwise, the dprintf format
4794 string will be the first argument, in the manner of @code{printf}.
4796 As an example, if you wanted @code{dprintf} output to go to a logfile
4797 that is a standard I/O stream assigned to the variable @code{mylog},
4798 you could do the following:
4801 (gdb) set dprintf-style call
4802 (gdb) set dprintf-function fprintf
4803 (gdb) set dprintf-channel mylog
4804 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4805 Dprintf 1 at 0x123456: file main.c, line 25.
4807 1 dprintf keep y 0x00123456 in main at main.c:25
4808 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4813 Note that the @code{info break} displays the dynamic printf commands
4814 as normal breakpoint commands; you can thus easily see the effect of
4815 the variable settings.
4817 @item set disconnected-dprintf on
4818 @itemx set disconnected-dprintf off
4819 @kindex set disconnected-dprintf
4820 Choose whether @code{dprintf} commands should continue to run if
4821 @value{GDBN} has disconnected from the target. This only applies
4822 if the @code{dprintf-style} is @code{agent}.
4824 @item show disconnected-dprintf off
4825 @kindex show disconnected-dprintf
4826 Show the current choice for disconnected @code{dprintf}.
4830 @value{GDBN} does not check the validity of function and channel,
4831 relying on you to supply values that are meaningful for the contexts
4832 in which they are being used. For instance, the function and channel
4833 may be the values of local variables, but if that is the case, then
4834 all enabled dynamic prints must be at locations within the scope of
4835 those locals. If evaluation fails, @value{GDBN} will report an error.
4837 @node Save Breakpoints
4838 @subsection How to save breakpoints to a file
4840 To save breakpoint definitions to a file use the @w{@code{save
4841 breakpoints}} command.
4844 @kindex save breakpoints
4845 @cindex save breakpoints to a file for future sessions
4846 @item save breakpoints [@var{filename}]
4847 This command saves all current breakpoint definitions together with
4848 their commands and ignore counts, into a file @file{@var{filename}}
4849 suitable for use in a later debugging session. This includes all
4850 types of breakpoints (breakpoints, watchpoints, catchpoints,
4851 tracepoints). To read the saved breakpoint definitions, use the
4852 @code{source} command (@pxref{Command Files}). Note that watchpoints
4853 with expressions involving local variables may fail to be recreated
4854 because it may not be possible to access the context where the
4855 watchpoint is valid anymore. Because the saved breakpoint definitions
4856 are simply a sequence of @value{GDBN} commands that recreate the
4857 breakpoints, you can edit the file in your favorite editing program,
4858 and remove the breakpoint definitions you're not interested in, or
4859 that can no longer be recreated.
4862 @node Static Probe Points
4863 @subsection Static Probe Points
4865 @cindex static probe point, SystemTap
4866 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4867 for Statically Defined Tracing, and the probes are designed to have a tiny
4868 runtime code and data footprint, and no dynamic relocations. They are
4869 usable from assembly, C and C@t{++} languages. See
4870 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4871 for a good reference on how the @acronym{SDT} probes are implemented.
4873 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4874 @acronym{SDT} probes are supported on ELF-compatible systems. See
4875 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4876 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4877 in your applications.
4879 @cindex semaphores on static probe points
4880 Some probes have an associated semaphore variable; for instance, this
4881 happens automatically if you defined your probe using a DTrace-style
4882 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4883 automatically enable it when you specify a breakpoint using the
4884 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4885 location by some other method (e.g., @code{break file:line}), then
4886 @value{GDBN} will not automatically set the semaphore.
4888 You can examine the available static static probes using @code{info
4889 probes}, with optional arguments:
4893 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4894 If given, @var{provider} is a regular expression used to match against provider
4895 names when selecting which probes to list. If omitted, probes by all
4896 probes from all providers are listed.
4898 If given, @var{name} is a regular expression to match against probe names
4899 when selecting which probes to list. If omitted, probe names are not
4900 considered when deciding whether to display them.
4902 If given, @var{objfile} is a regular expression used to select which
4903 object files (executable or shared libraries) to examine. If not
4904 given, all object files are considered.
4906 @item info probes all
4907 List the available static probes, from all types.
4910 @vindex $_probe_arg@r{, convenience variable}
4911 A probe may specify up to twelve arguments. These are available at the
4912 point at which the probe is defined---that is, when the current PC is
4913 at the probe's location. The arguments are available using the
4914 convenience variables (@pxref{Convenience Vars})
4915 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4916 an integer of the appropriate size; types are not preserved. The
4917 convenience variable @code{$_probe_argc} holds the number of arguments
4918 at the current probe point.
4920 These variables are always available, but attempts to access them at
4921 any location other than a probe point will cause @value{GDBN} to give
4925 @c @ifclear BARETARGET
4926 @node Error in Breakpoints
4927 @subsection ``Cannot insert breakpoints''
4929 If you request too many active hardware-assisted breakpoints and
4930 watchpoints, you will see this error message:
4932 @c FIXME: the precise wording of this message may change; the relevant
4933 @c source change is not committed yet (Sep 3, 1999).
4935 Stopped; cannot insert breakpoints.
4936 You may have requested too many hardware breakpoints and watchpoints.
4940 This message is printed when you attempt to resume the program, since
4941 only then @value{GDBN} knows exactly how many hardware breakpoints and
4942 watchpoints it needs to insert.
4944 When this message is printed, you need to disable or remove some of the
4945 hardware-assisted breakpoints and watchpoints, and then continue.
4947 @node Breakpoint-related Warnings
4948 @subsection ``Breakpoint address adjusted...''
4949 @cindex breakpoint address adjusted
4951 Some processor architectures place constraints on the addresses at
4952 which breakpoints may be placed. For architectures thus constrained,
4953 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4954 with the constraints dictated by the architecture.
4956 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4957 a VLIW architecture in which a number of RISC-like instructions may be
4958 bundled together for parallel execution. The FR-V architecture
4959 constrains the location of a breakpoint instruction within such a
4960 bundle to the instruction with the lowest address. @value{GDBN}
4961 honors this constraint by adjusting a breakpoint's address to the
4962 first in the bundle.
4964 It is not uncommon for optimized code to have bundles which contain
4965 instructions from different source statements, thus it may happen that
4966 a breakpoint's address will be adjusted from one source statement to
4967 another. Since this adjustment may significantly alter @value{GDBN}'s
4968 breakpoint related behavior from what the user expects, a warning is
4969 printed when the breakpoint is first set and also when the breakpoint
4972 A warning like the one below is printed when setting a breakpoint
4973 that's been subject to address adjustment:
4976 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4979 Such warnings are printed both for user settable and @value{GDBN}'s
4980 internal breakpoints. If you see one of these warnings, you should
4981 verify that a breakpoint set at the adjusted address will have the
4982 desired affect. If not, the breakpoint in question may be removed and
4983 other breakpoints may be set which will have the desired behavior.
4984 E.g., it may be sufficient to place the breakpoint at a later
4985 instruction. A conditional breakpoint may also be useful in some
4986 cases to prevent the breakpoint from triggering too often.
4988 @value{GDBN} will also issue a warning when stopping at one of these
4989 adjusted breakpoints:
4992 warning: Breakpoint 1 address previously adjusted from 0x00010414
4996 When this warning is encountered, it may be too late to take remedial
4997 action except in cases where the breakpoint is hit earlier or more
4998 frequently than expected.
5000 @node Continuing and Stepping
5001 @section Continuing and Stepping
5005 @cindex resuming execution
5006 @dfn{Continuing} means resuming program execution until your program
5007 completes normally. In contrast, @dfn{stepping} means executing just
5008 one more ``step'' of your program, where ``step'' may mean either one
5009 line of source code, or one machine instruction (depending on what
5010 particular command you use). Either when continuing or when stepping,
5011 your program may stop even sooner, due to a breakpoint or a signal. (If
5012 it stops due to a signal, you may want to use @code{handle}, or use
5013 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
5017 @kindex c @r{(@code{continue})}
5018 @kindex fg @r{(resume foreground execution)}
5019 @item continue @r{[}@var{ignore-count}@r{]}
5020 @itemx c @r{[}@var{ignore-count}@r{]}
5021 @itemx fg @r{[}@var{ignore-count}@r{]}
5022 Resume program execution, at the address where your program last stopped;
5023 any breakpoints set at that address are bypassed. The optional argument
5024 @var{ignore-count} allows you to specify a further number of times to
5025 ignore a breakpoint at this location; its effect is like that of
5026 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5028 The argument @var{ignore-count} is meaningful only when your program
5029 stopped due to a breakpoint. At other times, the argument to
5030 @code{continue} is ignored.
5032 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5033 debugged program is deemed to be the foreground program) are provided
5034 purely for convenience, and have exactly the same behavior as
5038 To resume execution at a different place, you can use @code{return}
5039 (@pxref{Returning, ,Returning from a Function}) to go back to the
5040 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5041 Different Address}) to go to an arbitrary location in your program.
5043 A typical technique for using stepping is to set a breakpoint
5044 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5045 beginning of the function or the section of your program where a problem
5046 is believed to lie, run your program until it stops at that breakpoint,
5047 and then step through the suspect area, examining the variables that are
5048 interesting, until you see the problem happen.
5052 @kindex s @r{(@code{step})}
5054 Continue running your program until control reaches a different source
5055 line, then stop it and return control to @value{GDBN}. This command is
5056 abbreviated @code{s}.
5059 @c "without debugging information" is imprecise; actually "without line
5060 @c numbers in the debugging information". (gcc -g1 has debugging info but
5061 @c not line numbers). But it seems complex to try to make that
5062 @c distinction here.
5063 @emph{Warning:} If you use the @code{step} command while control is
5064 within a function that was compiled without debugging information,
5065 execution proceeds until control reaches a function that does have
5066 debugging information. Likewise, it will not step into a function which
5067 is compiled without debugging information. To step through functions
5068 without debugging information, use the @code{stepi} command, described
5072 The @code{step} command only stops at the first instruction of a source
5073 line. This prevents the multiple stops that could otherwise occur in
5074 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5075 to stop if a function that has debugging information is called within
5076 the line. In other words, @code{step} @emph{steps inside} any functions
5077 called within the line.
5079 Also, the @code{step} command only enters a function if there is line
5080 number information for the function. Otherwise it acts like the
5081 @code{next} command. This avoids problems when using @code{cc -gl}
5082 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5083 was any debugging information about the routine.
5085 @item step @var{count}
5086 Continue running as in @code{step}, but do so @var{count} times. If a
5087 breakpoint is reached, or a signal not related to stepping occurs before
5088 @var{count} steps, stepping stops right away.
5091 @kindex n @r{(@code{next})}
5092 @item next @r{[}@var{count}@r{]}
5093 Continue to the next source line in the current (innermost) stack frame.
5094 This is similar to @code{step}, but function calls that appear within
5095 the line of code are executed without stopping. Execution stops when
5096 control reaches a different line of code at the original stack level
5097 that was executing when you gave the @code{next} command. This command
5098 is abbreviated @code{n}.
5100 An argument @var{count} is a repeat count, as for @code{step}.
5103 @c FIX ME!! Do we delete this, or is there a way it fits in with
5104 @c the following paragraph? --- Vctoria
5106 @c @code{next} within a function that lacks debugging information acts like
5107 @c @code{step}, but any function calls appearing within the code of the
5108 @c function are executed without stopping.
5110 The @code{next} command only stops at the first instruction of a
5111 source line. This prevents multiple stops that could otherwise occur in
5112 @code{switch} statements, @code{for} loops, etc.
5114 @kindex set step-mode
5116 @cindex functions without line info, and stepping
5117 @cindex stepping into functions with no line info
5118 @itemx set step-mode on
5119 The @code{set step-mode on} command causes the @code{step} command to
5120 stop at the first instruction of a function which contains no debug line
5121 information rather than stepping over it.
5123 This is useful in cases where you may be interested in inspecting the
5124 machine instructions of a function which has no symbolic info and do not
5125 want @value{GDBN} to automatically skip over this function.
5127 @item set step-mode off
5128 Causes the @code{step} command to step over any functions which contains no
5129 debug information. This is the default.
5131 @item show step-mode
5132 Show whether @value{GDBN} will stop in or step over functions without
5133 source line debug information.
5136 @kindex fin @r{(@code{finish})}
5138 Continue running until just after function in the selected stack frame
5139 returns. Print the returned value (if any). This command can be
5140 abbreviated as @code{fin}.
5142 Contrast this with the @code{return} command (@pxref{Returning,
5143 ,Returning from a Function}).
5146 @kindex u @r{(@code{until})}
5147 @cindex run until specified location
5150 Continue running until a source line past the current line, in the
5151 current stack frame, is reached. This command is used to avoid single
5152 stepping through a loop more than once. It is like the @code{next}
5153 command, except that when @code{until} encounters a jump, it
5154 automatically continues execution until the program counter is greater
5155 than the address of the jump.
5157 This means that when you reach the end of a loop after single stepping
5158 though it, @code{until} makes your program continue execution until it
5159 exits the loop. In contrast, a @code{next} command at the end of a loop
5160 simply steps back to the beginning of the loop, which forces you to step
5161 through the next iteration.
5163 @code{until} always stops your program if it attempts to exit the current
5166 @code{until} may produce somewhat counterintuitive results if the order
5167 of machine code does not match the order of the source lines. For
5168 example, in the following excerpt from a debugging session, the @code{f}
5169 (@code{frame}) command shows that execution is stopped at line
5170 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5174 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5176 (@value{GDBP}) until
5177 195 for ( ; argc > 0; NEXTARG) @{
5180 This happened because, for execution efficiency, the compiler had
5181 generated code for the loop closure test at the end, rather than the
5182 start, of the loop---even though the test in a C @code{for}-loop is
5183 written before the body of the loop. The @code{until} command appeared
5184 to step back to the beginning of the loop when it advanced to this
5185 expression; however, it has not really gone to an earlier
5186 statement---not in terms of the actual machine code.
5188 @code{until} with no argument works by means of single
5189 instruction stepping, and hence is slower than @code{until} with an
5192 @item until @var{location}
5193 @itemx u @var{location}
5194 Continue running your program until either the specified location is
5195 reached, or the current stack frame returns. @var{location} is any of
5196 the forms described in @ref{Specify Location}.
5197 This form of the command uses temporary breakpoints, and
5198 hence is quicker than @code{until} without an argument. The specified
5199 location is actually reached only if it is in the current frame. This
5200 implies that @code{until} can be used to skip over recursive function
5201 invocations. For instance in the code below, if the current location is
5202 line @code{96}, issuing @code{until 99} will execute the program up to
5203 line @code{99} in the same invocation of factorial, i.e., after the inner
5204 invocations have returned.
5207 94 int factorial (int value)
5209 96 if (value > 1) @{
5210 97 value *= factorial (value - 1);
5217 @kindex advance @var{location}
5218 @item advance @var{location}
5219 Continue running the program up to the given @var{location}. An argument is
5220 required, which should be of one of the forms described in
5221 @ref{Specify Location}.
5222 Execution will also stop upon exit from the current stack
5223 frame. This command is similar to @code{until}, but @code{advance} will
5224 not skip over recursive function calls, and the target location doesn't
5225 have to be in the same frame as the current one.
5229 @kindex si @r{(@code{stepi})}
5231 @itemx stepi @var{arg}
5233 Execute one machine instruction, then stop and return to the debugger.
5235 It is often useful to do @samp{display/i $pc} when stepping by machine
5236 instructions. This makes @value{GDBN} automatically display the next
5237 instruction to be executed, each time your program stops. @xref{Auto
5238 Display,, Automatic Display}.
5240 An argument is a repeat count, as in @code{step}.
5244 @kindex ni @r{(@code{nexti})}
5246 @itemx nexti @var{arg}
5248 Execute one machine instruction, but if it is a function call,
5249 proceed until the function returns.
5251 An argument is a repeat count, as in @code{next}.
5255 @anchor{range stepping}
5256 @cindex range stepping
5257 @cindex target-assisted range stepping
5258 By default, and if available, @value{GDBN} makes use of
5259 target-assisted @dfn{range stepping}. In other words, whenever you
5260 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5261 tells the target to step the corresponding range of instruction
5262 addresses instead of issuing multiple single-steps. This speeds up
5263 line stepping, particularly for remote targets. Ideally, there should
5264 be no reason you would want to turn range stepping off. However, it's
5265 possible that a bug in the debug info, a bug in the remote stub (for
5266 remote targets), or even a bug in @value{GDBN} could make line
5267 stepping behave incorrectly when target-assisted range stepping is
5268 enabled. You can use the following command to turn off range stepping
5272 @kindex set range-stepping
5273 @kindex show range-stepping
5274 @item set range-stepping
5275 @itemx show range-stepping
5276 Control whether range stepping is enabled.
5278 If @code{on}, and the target supports it, @value{GDBN} tells the
5279 target to step a range of addresses itself, instead of issuing
5280 multiple single-steps. If @code{off}, @value{GDBN} always issues
5281 single-steps, even if range stepping is supported by the target. The
5282 default is @code{on}.
5286 @node Skipping Over Functions and Files
5287 @section Skipping Over Functions and Files
5288 @cindex skipping over functions and files
5290 The program you are debugging may contain some functions which are
5291 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5292 skip a function or all functions in a file when stepping.
5294 For example, consider the following C function:
5305 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5306 are not interested in stepping through @code{boring}. If you run @code{step}
5307 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5308 step over both @code{foo} and @code{boring}!
5310 One solution is to @code{step} into @code{boring} and use the @code{finish}
5311 command to immediately exit it. But this can become tedious if @code{boring}
5312 is called from many places.
5314 A more flexible solution is to execute @kbd{skip boring}. This instructs
5315 @value{GDBN} never to step into @code{boring}. Now when you execute
5316 @code{step} at line 103, you'll step over @code{boring} and directly into
5319 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5320 example, @code{skip file boring.c}.
5323 @kindex skip function
5324 @item skip @r{[}@var{linespec}@r{]}
5325 @itemx skip function @r{[}@var{linespec}@r{]}
5326 After running this command, the function named by @var{linespec} or the
5327 function containing the line named by @var{linespec} will be skipped over when
5328 stepping. @xref{Specify Location}.
5330 If you do not specify @var{linespec}, the function you're currently debugging
5333 (If you have a function called @code{file} that you want to skip, use
5334 @kbd{skip function file}.)
5337 @item skip file @r{[}@var{filename}@r{]}
5338 After running this command, any function whose source lives in @var{filename}
5339 will be skipped over when stepping.
5341 If you do not specify @var{filename}, functions whose source lives in the file
5342 you're currently debugging will be skipped.
5345 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5346 These are the commands for managing your list of skips:
5350 @item info skip @r{[}@var{range}@r{]}
5351 Print details about the specified skip(s). If @var{range} is not specified,
5352 print a table with details about all functions and files marked for skipping.
5353 @code{info skip} prints the following information about each skip:
5357 A number identifying this skip.
5359 The type of this skip, either @samp{function} or @samp{file}.
5360 @item Enabled or Disabled
5361 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5363 For function skips, this column indicates the address in memory of the function
5364 being skipped. If you've set a function skip on a function which has not yet
5365 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5366 which has the function is loaded, @code{info skip} will show the function's
5369 For file skips, this field contains the filename being skipped. For functions
5370 skips, this field contains the function name and its line number in the file
5371 where it is defined.
5375 @item skip delete @r{[}@var{range}@r{]}
5376 Delete the specified skip(s). If @var{range} is not specified, delete all
5380 @item skip enable @r{[}@var{range}@r{]}
5381 Enable the specified skip(s). If @var{range} is not specified, enable all
5384 @kindex skip disable
5385 @item skip disable @r{[}@var{range}@r{]}
5386 Disable the specified skip(s). If @var{range} is not specified, disable all
5395 A signal is an asynchronous event that can happen in a program. The
5396 operating system defines the possible kinds of signals, and gives each
5397 kind a name and a number. For example, in Unix @code{SIGINT} is the
5398 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5399 @code{SIGSEGV} is the signal a program gets from referencing a place in
5400 memory far away from all the areas in use; @code{SIGALRM} occurs when
5401 the alarm clock timer goes off (which happens only if your program has
5402 requested an alarm).
5404 @cindex fatal signals
5405 Some signals, including @code{SIGALRM}, are a normal part of the
5406 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5407 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5408 program has not specified in advance some other way to handle the signal.
5409 @code{SIGINT} does not indicate an error in your program, but it is normally
5410 fatal so it can carry out the purpose of the interrupt: to kill the program.
5412 @value{GDBN} has the ability to detect any occurrence of a signal in your
5413 program. You can tell @value{GDBN} in advance what to do for each kind of
5416 @cindex handling signals
5417 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5418 @code{SIGALRM} be silently passed to your program
5419 (so as not to interfere with their role in the program's functioning)
5420 but to stop your program immediately whenever an error signal happens.
5421 You can change these settings with the @code{handle} command.
5424 @kindex info signals
5428 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5429 handle each one. You can use this to see the signal numbers of all
5430 the defined types of signals.
5432 @item info signals @var{sig}
5433 Similar, but print information only about the specified signal number.
5435 @code{info handle} is an alias for @code{info signals}.
5437 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5438 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5439 for details about this command.
5442 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5443 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5444 can be the number of a signal or its name (with or without the
5445 @samp{SIG} at the beginning); a list of signal numbers of the form
5446 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5447 known signals. Optional arguments @var{keywords}, described below,
5448 say what change to make.
5452 The keywords allowed by the @code{handle} command can be abbreviated.
5453 Their full names are:
5457 @value{GDBN} should not stop your program when this signal happens. It may
5458 still print a message telling you that the signal has come in.
5461 @value{GDBN} should stop your program when this signal happens. This implies
5462 the @code{print} keyword as well.
5465 @value{GDBN} should print a message when this signal happens.
5468 @value{GDBN} should not mention the occurrence of the signal at all. This
5469 implies the @code{nostop} keyword as well.
5473 @value{GDBN} should allow your program to see this signal; your program
5474 can handle the signal, or else it may terminate if the signal is fatal
5475 and not handled. @code{pass} and @code{noignore} are synonyms.
5479 @value{GDBN} should not allow your program to see this signal.
5480 @code{nopass} and @code{ignore} are synonyms.
5484 When a signal stops your program, the signal is not visible to the
5486 continue. Your program sees the signal then, if @code{pass} is in
5487 effect for the signal in question @emph{at that time}. In other words,
5488 after @value{GDBN} reports a signal, you can use the @code{handle}
5489 command with @code{pass} or @code{nopass} to control whether your
5490 program sees that signal when you continue.
5492 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5493 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5494 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5497 You can also use the @code{signal} command to prevent your program from
5498 seeing a signal, or cause it to see a signal it normally would not see,
5499 or to give it any signal at any time. For example, if your program stopped
5500 due to some sort of memory reference error, you might store correct
5501 values into the erroneous variables and continue, hoping to see more
5502 execution; but your program would probably terminate immediately as
5503 a result of the fatal signal once it saw the signal. To prevent this,
5504 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5507 @cindex extra signal information
5508 @anchor{extra signal information}
5510 On some targets, @value{GDBN} can inspect extra signal information
5511 associated with the intercepted signal, before it is actually
5512 delivered to the program being debugged. This information is exported
5513 by the convenience variable @code{$_siginfo}, and consists of data
5514 that is passed by the kernel to the signal handler at the time of the
5515 receipt of a signal. The data type of the information itself is
5516 target dependent. You can see the data type using the @code{ptype
5517 $_siginfo} command. On Unix systems, it typically corresponds to the
5518 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5521 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5522 referenced address that raised a segmentation fault.
5526 (@value{GDBP}) continue
5527 Program received signal SIGSEGV, Segmentation fault.
5528 0x0000000000400766 in main ()
5530 (@value{GDBP}) ptype $_siginfo
5537 struct @{...@} _kill;
5538 struct @{...@} _timer;
5540 struct @{...@} _sigchld;
5541 struct @{...@} _sigfault;
5542 struct @{...@} _sigpoll;
5545 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5549 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5550 $1 = (void *) 0x7ffff7ff7000
5554 Depending on target support, @code{$_siginfo} may also be writable.
5557 @section Stopping and Starting Multi-thread Programs
5559 @cindex stopped threads
5560 @cindex threads, stopped
5562 @cindex continuing threads
5563 @cindex threads, continuing
5565 @value{GDBN} supports debugging programs with multiple threads
5566 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5567 are two modes of controlling execution of your program within the
5568 debugger. In the default mode, referred to as @dfn{all-stop mode},
5569 when any thread in your program stops (for example, at a breakpoint
5570 or while being stepped), all other threads in the program are also stopped by
5571 @value{GDBN}. On some targets, @value{GDBN} also supports
5572 @dfn{non-stop mode}, in which other threads can continue to run freely while
5573 you examine the stopped thread in the debugger.
5576 * All-Stop Mode:: All threads stop when GDB takes control
5577 * Non-Stop Mode:: Other threads continue to execute
5578 * Background Execution:: Running your program asynchronously
5579 * Thread-Specific Breakpoints:: Controlling breakpoints
5580 * Interrupted System Calls:: GDB may interfere with system calls
5581 * Observer Mode:: GDB does not alter program behavior
5585 @subsection All-Stop Mode
5587 @cindex all-stop mode
5589 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5590 @emph{all} threads of execution stop, not just the current thread. This
5591 allows you to examine the overall state of the program, including
5592 switching between threads, without worrying that things may change
5595 Conversely, whenever you restart the program, @emph{all} threads start
5596 executing. @emph{This is true even when single-stepping} with commands
5597 like @code{step} or @code{next}.
5599 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5600 Since thread scheduling is up to your debugging target's operating
5601 system (not controlled by @value{GDBN}), other threads may
5602 execute more than one statement while the current thread completes a
5603 single step. Moreover, in general other threads stop in the middle of a
5604 statement, rather than at a clean statement boundary, when the program
5607 You might even find your program stopped in another thread after
5608 continuing or even single-stepping. This happens whenever some other
5609 thread runs into a breakpoint, a signal, or an exception before the
5610 first thread completes whatever you requested.
5612 @cindex automatic thread selection
5613 @cindex switching threads automatically
5614 @cindex threads, automatic switching
5615 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5616 signal, it automatically selects the thread where that breakpoint or
5617 signal happened. @value{GDBN} alerts you to the context switch with a
5618 message such as @samp{[Switching to Thread @var{n}]} to identify the
5621 On some OSes, you can modify @value{GDBN}'s default behavior by
5622 locking the OS scheduler to allow only a single thread to run.
5625 @item set scheduler-locking @var{mode}
5626 @cindex scheduler locking mode
5627 @cindex lock scheduler
5628 Set the scheduler locking mode. If it is @code{off}, then there is no
5629 locking and any thread may run at any time. If @code{on}, then only the
5630 current thread may run when the inferior is resumed. The @code{step}
5631 mode optimizes for single-stepping; it prevents other threads
5632 from preempting the current thread while you are stepping, so that
5633 the focus of debugging does not change unexpectedly.
5634 Other threads only rarely (or never) get a chance to run
5635 when you step. They are more likely to run when you @samp{next} over a
5636 function call, and they are completely free to run when you use commands
5637 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5638 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5639 the current thread away from the thread that you are debugging.
5641 @item show scheduler-locking
5642 Display the current scheduler locking mode.
5645 @cindex resume threads of multiple processes simultaneously
5646 By default, when you issue one of the execution commands such as
5647 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5648 threads of the current inferior to run. For example, if @value{GDBN}
5649 is attached to two inferiors, each with two threads, the
5650 @code{continue} command resumes only the two threads of the current
5651 inferior. This is useful, for example, when you debug a program that
5652 forks and you want to hold the parent stopped (so that, for instance,
5653 it doesn't run to exit), while you debug the child. In other
5654 situations, you may not be interested in inspecting the current state
5655 of any of the processes @value{GDBN} is attached to, and you may want
5656 to resume them all until some breakpoint is hit. In the latter case,
5657 you can instruct @value{GDBN} to allow all threads of all the
5658 inferiors to run with the @w{@code{set schedule-multiple}} command.
5661 @kindex set schedule-multiple
5662 @item set schedule-multiple
5663 Set the mode for allowing threads of multiple processes to be resumed
5664 when an execution command is issued. When @code{on}, all threads of
5665 all processes are allowed to run. When @code{off}, only the threads
5666 of the current process are resumed. The default is @code{off}. The
5667 @code{scheduler-locking} mode takes precedence when set to @code{on},
5668 or while you are stepping and set to @code{step}.
5670 @item show schedule-multiple
5671 Display the current mode for resuming the execution of threads of
5676 @subsection Non-Stop Mode
5678 @cindex non-stop mode
5680 @c This section is really only a place-holder, and needs to be expanded
5681 @c with more details.
5683 For some multi-threaded targets, @value{GDBN} supports an optional
5684 mode of operation in which you can examine stopped program threads in
5685 the debugger while other threads continue to execute freely. This
5686 minimizes intrusion when debugging live systems, such as programs
5687 where some threads have real-time constraints or must continue to
5688 respond to external events. This is referred to as @dfn{non-stop} mode.
5690 In non-stop mode, when a thread stops to report a debugging event,
5691 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5692 threads as well, in contrast to the all-stop mode behavior. Additionally,
5693 execution commands such as @code{continue} and @code{step} apply by default
5694 only to the current thread in non-stop mode, rather than all threads as
5695 in all-stop mode. This allows you to control threads explicitly in
5696 ways that are not possible in all-stop mode --- for example, stepping
5697 one thread while allowing others to run freely, stepping
5698 one thread while holding all others stopped, or stepping several threads
5699 independently and simultaneously.
5701 To enter non-stop mode, use this sequence of commands before you run
5702 or attach to your program:
5705 # Enable the async interface.
5708 # If using the CLI, pagination breaks non-stop.
5711 # Finally, turn it on!
5715 You can use these commands to manipulate the non-stop mode setting:
5718 @kindex set non-stop
5719 @item set non-stop on
5720 Enable selection of non-stop mode.
5721 @item set non-stop off
5722 Disable selection of non-stop mode.
5723 @kindex show non-stop
5725 Show the current non-stop enablement setting.
5728 Note these commands only reflect whether non-stop mode is enabled,
5729 not whether the currently-executing program is being run in non-stop mode.
5730 In particular, the @code{set non-stop} preference is only consulted when
5731 @value{GDBN} starts or connects to the target program, and it is generally
5732 not possible to switch modes once debugging has started. Furthermore,
5733 since not all targets support non-stop mode, even when you have enabled
5734 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5737 In non-stop mode, all execution commands apply only to the current thread
5738 by default. That is, @code{continue} only continues one thread.
5739 To continue all threads, issue @code{continue -a} or @code{c -a}.
5741 You can use @value{GDBN}'s background execution commands
5742 (@pxref{Background Execution}) to run some threads in the background
5743 while you continue to examine or step others from @value{GDBN}.
5744 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5745 always executed asynchronously in non-stop mode.
5747 Suspending execution is done with the @code{interrupt} command when
5748 running in the background, or @kbd{Ctrl-c} during foreground execution.
5749 In all-stop mode, this stops the whole process;
5750 but in non-stop mode the interrupt applies only to the current thread.
5751 To stop the whole program, use @code{interrupt -a}.
5753 Other execution commands do not currently support the @code{-a} option.
5755 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5756 that thread current, as it does in all-stop mode. This is because the
5757 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5758 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5759 changed to a different thread just as you entered a command to operate on the
5760 previously current thread.
5762 @node Background Execution
5763 @subsection Background Execution
5765 @cindex foreground execution
5766 @cindex background execution
5767 @cindex asynchronous execution
5768 @cindex execution, foreground, background and asynchronous
5770 @value{GDBN}'s execution commands have two variants: the normal
5771 foreground (synchronous) behavior, and a background
5772 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5773 the program to report that some thread has stopped before prompting for
5774 another command. In background execution, @value{GDBN} immediately gives
5775 a command prompt so that you can issue other commands while your program runs.
5777 You need to explicitly enable asynchronous mode before you can use
5778 background execution commands. You can use these commands to
5779 manipulate the asynchronous mode setting:
5782 @kindex set target-async
5783 @item set target-async on
5784 Enable asynchronous mode.
5785 @item set target-async off
5786 Disable asynchronous mode.
5787 @kindex show target-async
5788 @item show target-async
5789 Show the current target-async setting.
5792 If the target doesn't support async mode, @value{GDBN} issues an error
5793 message if you attempt to use the background execution commands.
5795 To specify background execution, add a @code{&} to the command. For example,
5796 the background form of the @code{continue} command is @code{continue&}, or
5797 just @code{c&}. The execution commands that accept background execution
5803 @xref{Starting, , Starting your Program}.
5807 @xref{Attach, , Debugging an Already-running Process}.
5811 @xref{Continuing and Stepping, step}.
5815 @xref{Continuing and Stepping, stepi}.
5819 @xref{Continuing and Stepping, next}.
5823 @xref{Continuing and Stepping, nexti}.
5827 @xref{Continuing and Stepping, continue}.
5831 @xref{Continuing and Stepping, finish}.
5835 @xref{Continuing and Stepping, until}.
5839 Background execution is especially useful in conjunction with non-stop
5840 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5841 However, you can also use these commands in the normal all-stop mode with
5842 the restriction that you cannot issue another execution command until the
5843 previous one finishes. Examples of commands that are valid in all-stop
5844 mode while the program is running include @code{help} and @code{info break}.
5846 You can interrupt your program while it is running in the background by
5847 using the @code{interrupt} command.
5854 Suspend execution of the running program. In all-stop mode,
5855 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5856 only the current thread. To stop the whole program in non-stop mode,
5857 use @code{interrupt -a}.
5860 @node Thread-Specific Breakpoints
5861 @subsection Thread-Specific Breakpoints
5863 When your program has multiple threads (@pxref{Threads,, Debugging
5864 Programs with Multiple Threads}), you can choose whether to set
5865 breakpoints on all threads, or on a particular thread.
5868 @cindex breakpoints and threads
5869 @cindex thread breakpoints
5870 @kindex break @dots{} thread @var{threadno}
5871 @item break @var{linespec} thread @var{threadno}
5872 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5873 @var{linespec} specifies source lines; there are several ways of
5874 writing them (@pxref{Specify Location}), but the effect is always to
5875 specify some source line.
5877 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5878 to specify that you only want @value{GDBN} to stop the program when a
5879 particular thread reaches this breakpoint. @var{threadno} is one of the
5880 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5881 column of the @samp{info threads} display.
5883 If you do not specify @samp{thread @var{threadno}} when you set a
5884 breakpoint, the breakpoint applies to @emph{all} threads of your
5887 You can use the @code{thread} qualifier on conditional breakpoints as
5888 well; in this case, place @samp{thread @var{threadno}} before or
5889 after the breakpoint condition, like this:
5892 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5897 Thread-specific breakpoints are automatically deleted when
5898 @value{GDBN} detects the corresponding thread is no longer in the
5899 thread list. For example:
5903 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
5906 There are several ways for a thread to disappear, such as a regular
5907 thread exit, but also when you detach from the process with the
5908 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
5909 Process}), or if @value{GDBN} loses the remote connection
5910 (@pxref{Remote Debugging}), etc. Note that with some targets,
5911 @value{GDBN} is only able to detect a thread has exited when the user
5912 explictly asks for the thread list with the @code{info threads}
5915 @node Interrupted System Calls
5916 @subsection Interrupted System Calls
5918 @cindex thread breakpoints and system calls
5919 @cindex system calls and thread breakpoints
5920 @cindex premature return from system calls
5921 There is an unfortunate side effect when using @value{GDBN} to debug
5922 multi-threaded programs. If one thread stops for a
5923 breakpoint, or for some other reason, and another thread is blocked in a
5924 system call, then the system call may return prematurely. This is a
5925 consequence of the interaction between multiple threads and the signals
5926 that @value{GDBN} uses to implement breakpoints and other events that
5929 To handle this problem, your program should check the return value of
5930 each system call and react appropriately. This is good programming
5933 For example, do not write code like this:
5939 The call to @code{sleep} will return early if a different thread stops
5940 at a breakpoint or for some other reason.
5942 Instead, write this:
5947 unslept = sleep (unslept);
5950 A system call is allowed to return early, so the system is still
5951 conforming to its specification. But @value{GDBN} does cause your
5952 multi-threaded program to behave differently than it would without
5955 Also, @value{GDBN} uses internal breakpoints in the thread library to
5956 monitor certain events such as thread creation and thread destruction.
5957 When such an event happens, a system call in another thread may return
5958 prematurely, even though your program does not appear to stop.
5961 @subsection Observer Mode
5963 If you want to build on non-stop mode and observe program behavior
5964 without any chance of disruption by @value{GDBN}, you can set
5965 variables to disable all of the debugger's attempts to modify state,
5966 whether by writing memory, inserting breakpoints, etc. These operate
5967 at a low level, intercepting operations from all commands.
5969 When all of these are set to @code{off}, then @value{GDBN} is said to
5970 be @dfn{observer mode}. As a convenience, the variable
5971 @code{observer} can be set to disable these, plus enable non-stop
5974 Note that @value{GDBN} will not prevent you from making nonsensical
5975 combinations of these settings. For instance, if you have enabled
5976 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5977 then breakpoints that work by writing trap instructions into the code
5978 stream will still not be able to be placed.
5983 @item set observer on
5984 @itemx set observer off
5985 When set to @code{on}, this disables all the permission variables
5986 below (except for @code{insert-fast-tracepoints}), plus enables
5987 non-stop debugging. Setting this to @code{off} switches back to
5988 normal debugging, though remaining in non-stop mode.
5991 Show whether observer mode is on or off.
5993 @kindex may-write-registers
5994 @item set may-write-registers on
5995 @itemx set may-write-registers off
5996 This controls whether @value{GDBN} will attempt to alter the values of
5997 registers, such as with assignment expressions in @code{print}, or the
5998 @code{jump} command. It defaults to @code{on}.
6000 @item show may-write-registers
6001 Show the current permission to write registers.
6003 @kindex may-write-memory
6004 @item set may-write-memory on
6005 @itemx set may-write-memory off
6006 This controls whether @value{GDBN} will attempt to alter the contents
6007 of memory, such as with assignment expressions in @code{print}. It
6008 defaults to @code{on}.
6010 @item show may-write-memory
6011 Show the current permission to write memory.
6013 @kindex may-insert-breakpoints
6014 @item set may-insert-breakpoints on
6015 @itemx set may-insert-breakpoints off
6016 This controls whether @value{GDBN} will attempt to insert breakpoints.
6017 This affects all breakpoints, including internal breakpoints defined
6018 by @value{GDBN}. It defaults to @code{on}.
6020 @item show may-insert-breakpoints
6021 Show the current permission to insert breakpoints.
6023 @kindex may-insert-tracepoints
6024 @item set may-insert-tracepoints on
6025 @itemx set may-insert-tracepoints off
6026 This controls whether @value{GDBN} will attempt to insert (regular)
6027 tracepoints at the beginning of a tracing experiment. It affects only
6028 non-fast tracepoints, fast tracepoints being under the control of
6029 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6031 @item show may-insert-tracepoints
6032 Show the current permission to insert tracepoints.
6034 @kindex may-insert-fast-tracepoints
6035 @item set may-insert-fast-tracepoints on
6036 @itemx set may-insert-fast-tracepoints off
6037 This controls whether @value{GDBN} will attempt to insert fast
6038 tracepoints at the beginning of a tracing experiment. It affects only
6039 fast tracepoints, regular (non-fast) tracepoints being under the
6040 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6042 @item show may-insert-fast-tracepoints
6043 Show the current permission to insert fast tracepoints.
6045 @kindex may-interrupt
6046 @item set may-interrupt on
6047 @itemx set may-interrupt off
6048 This controls whether @value{GDBN} will attempt to interrupt or stop
6049 program execution. When this variable is @code{off}, the
6050 @code{interrupt} command will have no effect, nor will
6051 @kbd{Ctrl-c}. It defaults to @code{on}.
6053 @item show may-interrupt
6054 Show the current permission to interrupt or stop the program.
6058 @node Reverse Execution
6059 @chapter Running programs backward
6060 @cindex reverse execution
6061 @cindex running programs backward
6063 When you are debugging a program, it is not unusual to realize that
6064 you have gone too far, and some event of interest has already happened.
6065 If the target environment supports it, @value{GDBN} can allow you to
6066 ``rewind'' the program by running it backward.
6068 A target environment that supports reverse execution should be able
6069 to ``undo'' the changes in machine state that have taken place as the
6070 program was executing normally. Variables, registers etc.@: should
6071 revert to their previous values. Obviously this requires a great
6072 deal of sophistication on the part of the target environment; not
6073 all target environments can support reverse execution.
6075 When a program is executed in reverse, the instructions that
6076 have most recently been executed are ``un-executed'', in reverse
6077 order. The program counter runs backward, following the previous
6078 thread of execution in reverse. As each instruction is ``un-executed'',
6079 the values of memory and/or registers that were changed by that
6080 instruction are reverted to their previous states. After executing
6081 a piece of source code in reverse, all side effects of that code
6082 should be ``undone'', and all variables should be returned to their
6083 prior values@footnote{
6084 Note that some side effects are easier to undo than others. For instance,
6085 memory and registers are relatively easy, but device I/O is hard. Some
6086 targets may be able undo things like device I/O, and some may not.
6088 The contract between @value{GDBN} and the reverse executing target
6089 requires only that the target do something reasonable when
6090 @value{GDBN} tells it to execute backwards, and then report the
6091 results back to @value{GDBN}. Whatever the target reports back to
6092 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6093 assumes that the memory and registers that the target reports are in a
6094 consistant state, but @value{GDBN} accepts whatever it is given.
6097 If you are debugging in a target environment that supports
6098 reverse execution, @value{GDBN} provides the following commands.
6101 @kindex reverse-continue
6102 @kindex rc @r{(@code{reverse-continue})}
6103 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6104 @itemx rc @r{[}@var{ignore-count}@r{]}
6105 Beginning at the point where your program last stopped, start executing
6106 in reverse. Reverse execution will stop for breakpoints and synchronous
6107 exceptions (signals), just like normal execution. Behavior of
6108 asynchronous signals depends on the target environment.
6110 @kindex reverse-step
6111 @kindex rs @r{(@code{step})}
6112 @item reverse-step @r{[}@var{count}@r{]}
6113 Run the program backward until control reaches the start of a
6114 different source line; then stop it, and return control to @value{GDBN}.
6116 Like the @code{step} command, @code{reverse-step} will only stop
6117 at the beginning of a source line. It ``un-executes'' the previously
6118 executed source line. If the previous source line included calls to
6119 debuggable functions, @code{reverse-step} will step (backward) into
6120 the called function, stopping at the beginning of the @emph{last}
6121 statement in the called function (typically a return statement).
6123 Also, as with the @code{step} command, if non-debuggable functions are
6124 called, @code{reverse-step} will run thru them backward without stopping.
6126 @kindex reverse-stepi
6127 @kindex rsi @r{(@code{reverse-stepi})}
6128 @item reverse-stepi @r{[}@var{count}@r{]}
6129 Reverse-execute one machine instruction. Note that the instruction
6130 to be reverse-executed is @emph{not} the one pointed to by the program
6131 counter, but the instruction executed prior to that one. For instance,
6132 if the last instruction was a jump, @code{reverse-stepi} will take you
6133 back from the destination of the jump to the jump instruction itself.
6135 @kindex reverse-next
6136 @kindex rn @r{(@code{reverse-next})}
6137 @item reverse-next @r{[}@var{count}@r{]}
6138 Run backward to the beginning of the previous line executed in
6139 the current (innermost) stack frame. If the line contains function
6140 calls, they will be ``un-executed'' without stopping. Starting from
6141 the first line of a function, @code{reverse-next} will take you back
6142 to the caller of that function, @emph{before} the function was called,
6143 just as the normal @code{next} command would take you from the last
6144 line of a function back to its return to its caller
6145 @footnote{Unless the code is too heavily optimized.}.
6147 @kindex reverse-nexti
6148 @kindex rni @r{(@code{reverse-nexti})}
6149 @item reverse-nexti @r{[}@var{count}@r{]}
6150 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6151 in reverse, except that called functions are ``un-executed'' atomically.
6152 That is, if the previously executed instruction was a return from
6153 another function, @code{reverse-nexti} will continue to execute
6154 in reverse until the call to that function (from the current stack
6157 @kindex reverse-finish
6158 @item reverse-finish
6159 Just as the @code{finish} command takes you to the point where the
6160 current function returns, @code{reverse-finish} takes you to the point
6161 where it was called. Instead of ending up at the end of the current
6162 function invocation, you end up at the beginning.
6164 @kindex set exec-direction
6165 @item set exec-direction
6166 Set the direction of target execution.
6167 @item set exec-direction reverse
6168 @cindex execute forward or backward in time
6169 @value{GDBN} will perform all execution commands in reverse, until the
6170 exec-direction mode is changed to ``forward''. Affected commands include
6171 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6172 command cannot be used in reverse mode.
6173 @item set exec-direction forward
6174 @value{GDBN} will perform all execution commands in the normal fashion.
6175 This is the default.
6179 @node Process Record and Replay
6180 @chapter Recording Inferior's Execution and Replaying It
6181 @cindex process record and replay
6182 @cindex recording inferior's execution and replaying it
6184 On some platforms, @value{GDBN} provides a special @dfn{process record
6185 and replay} target that can record a log of the process execution, and
6186 replay it later with both forward and reverse execution commands.
6189 When this target is in use, if the execution log includes the record
6190 for the next instruction, @value{GDBN} will debug in @dfn{replay
6191 mode}. In the replay mode, the inferior does not really execute code
6192 instructions. Instead, all the events that normally happen during
6193 code execution are taken from the execution log. While code is not
6194 really executed in replay mode, the values of registers (including the
6195 program counter register) and the memory of the inferior are still
6196 changed as they normally would. Their contents are taken from the
6200 If the record for the next instruction is not in the execution log,
6201 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6202 inferior executes normally, and @value{GDBN} records the execution log
6205 The process record and replay target supports reverse execution
6206 (@pxref{Reverse Execution}), even if the platform on which the
6207 inferior runs does not. However, the reverse execution is limited in
6208 this case by the range of the instructions recorded in the execution
6209 log. In other words, reverse execution on platforms that don't
6210 support it directly can only be done in the replay mode.
6212 When debugging in the reverse direction, @value{GDBN} will work in
6213 replay mode as long as the execution log includes the record for the
6214 previous instruction; otherwise, it will work in record mode, if the
6215 platform supports reverse execution, or stop if not.
6217 For architecture environments that support process record and replay,
6218 @value{GDBN} provides the following commands:
6221 @kindex target record
6222 @kindex target record-full
6223 @kindex target record-btrace
6226 @kindex record btrace
6230 @item record @var{method}
6231 This command starts the process record and replay target. The
6232 recording method can be specified as parameter. Without a parameter
6233 the command uses the @code{full} recording method. The following
6234 recording methods are available:
6238 Full record/replay recording using @value{GDBN}'s software record and
6239 replay implementation. This method allows replaying and reverse
6243 Hardware-supported instruction recording. This method does not allow
6244 replaying and reverse execution.
6246 This recording method may not be available on all processors.
6249 The process record and replay target can only debug a process that is
6250 already running. Therefore, you need first to start the process with
6251 the @kbd{run} or @kbd{start} commands, and then start the recording
6252 with the @kbd{record @var{method}} command.
6254 Both @code{record @var{method}} and @code{rec @var{method}} are
6255 aliases of @code{target record-@var{method}}.
6257 @cindex displaced stepping, and process record and replay
6258 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6259 will be automatically disabled when process record and replay target
6260 is started. That's because the process record and replay target
6261 doesn't support displaced stepping.
6263 @cindex non-stop mode, and process record and replay
6264 @cindex asynchronous execution, and process record and replay
6265 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6266 the asynchronous execution mode (@pxref{Background Execution}), not
6267 all recording methods are available. The @code{full} recording method
6268 does not support these two modes.
6273 Stop the process record and replay target. When process record and
6274 replay target stops, the entire execution log will be deleted and the
6275 inferior will either be terminated, or will remain in its final state.
6277 When you stop the process record and replay target in record mode (at
6278 the end of the execution log), the inferior will be stopped at the
6279 next instruction that would have been recorded. In other words, if
6280 you record for a while and then stop recording, the inferior process
6281 will be left in the same state as if the recording never happened.
6283 On the other hand, if the process record and replay target is stopped
6284 while in replay mode (that is, not at the end of the execution log,
6285 but at some earlier point), the inferior process will become ``live''
6286 at that earlier state, and it will then be possible to continue the
6287 usual ``live'' debugging of the process from that state.
6289 When the inferior process exits, or @value{GDBN} detaches from it,
6290 process record and replay target will automatically stop itself.
6294 Go to a specific location in the execution log. There are several
6295 ways to specify the location to go to:
6298 @item record goto begin
6299 @itemx record goto start
6300 Go to the beginning of the execution log.
6302 @item record goto end
6303 Go to the end of the execution log.
6305 @item record goto @var{n}
6306 Go to instruction number @var{n} in the execution log.
6310 @item record save @var{filename}
6311 Save the execution log to a file @file{@var{filename}}.
6312 Default filename is @file{gdb_record.@var{process_id}}, where
6313 @var{process_id} is the process ID of the inferior.
6315 This command may not be available for all recording methods.
6317 @kindex record restore
6318 @item record restore @var{filename}
6319 Restore the execution log from a file @file{@var{filename}}.
6320 File must have been created with @code{record save}.
6322 @kindex set record full
6323 @item set record full insn-number-max @var{limit}
6324 @itemx set record full insn-number-max unlimited
6325 Set the limit of instructions to be recorded for the @code{full}
6326 recording method. Default value is 200000.
6328 If @var{limit} is a positive number, then @value{GDBN} will start
6329 deleting instructions from the log once the number of the record
6330 instructions becomes greater than @var{limit}. For every new recorded
6331 instruction, @value{GDBN} will delete the earliest recorded
6332 instruction to keep the number of recorded instructions at the limit.
6333 (Since deleting recorded instructions loses information, @value{GDBN}
6334 lets you control what happens when the limit is reached, by means of
6335 the @code{stop-at-limit} option, described below.)
6337 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6338 delete recorded instructions from the execution log. The number of
6339 recorded instructions is limited only by the available memory.
6341 @kindex show record full
6342 @item show record full insn-number-max
6343 Show the limit of instructions to be recorded with the @code{full}
6346 @item set record full stop-at-limit
6347 Control the behavior of the @code{full} recording method when the
6348 number of recorded instructions reaches the limit. If ON (the
6349 default), @value{GDBN} will stop when the limit is reached for the
6350 first time and ask you whether you want to stop the inferior or
6351 continue running it and recording the execution log. If you decide
6352 to continue recording, each new recorded instruction will cause the
6353 oldest one to be deleted.
6355 If this option is OFF, @value{GDBN} will automatically delete the
6356 oldest record to make room for each new one, without asking.
6358 @item show record full stop-at-limit
6359 Show the current setting of @code{stop-at-limit}.
6361 @item set record full memory-query
6362 Control the behavior when @value{GDBN} is unable to record memory
6363 changes caused by an instruction for the @code{full} recording method.
6364 If ON, @value{GDBN} will query whether to stop the inferior in that
6367 If this option is OFF (the default), @value{GDBN} will automatically
6368 ignore the effect of such instructions on memory. Later, when
6369 @value{GDBN} replays this execution log, it will mark the log of this
6370 instruction as not accessible, and it will not affect the replay
6373 @item show record full memory-query
6374 Show the current setting of @code{memory-query}.
6378 Show various statistics about the recording depending on the recording
6383 For the @code{full} recording method, it shows the state of process
6384 record and its in-memory execution log buffer, including:
6388 Whether in record mode or replay mode.
6390 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6392 Highest recorded instruction number.
6394 Current instruction about to be replayed (if in replay mode).
6396 Number of instructions contained in the execution log.
6398 Maximum number of instructions that may be contained in the execution log.
6402 For the @code{btrace} recording method, it shows the number of
6403 instructions that have been recorded and the number of blocks of
6404 sequential control-flow that is formed by the recorded instructions.
6407 @kindex record delete
6410 When record target runs in replay mode (``in the past''), delete the
6411 subsequent execution log and begin to record a new execution log starting
6412 from the current address. This means you will abandon the previously
6413 recorded ``future'' and begin recording a new ``future''.
6415 @kindex record instruction-history
6416 @kindex rec instruction-history
6417 @item record instruction-history
6418 Disassembles instructions from the recorded execution log. By
6419 default, ten instructions are disassembled. This can be changed using
6420 the @code{set record instruction-history-size} command. Instructions
6421 are printed in execution order. There are several ways to specify
6422 what part of the execution log to disassemble:
6425 @item record instruction-history @var{insn}
6426 Disassembles ten instructions starting from instruction number
6429 @item record instruction-history @var{insn}, +/-@var{n}
6430 Disassembles @var{n} instructions around instruction number
6431 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6432 @var{n} instructions after instruction number @var{insn}. If
6433 @var{n} is preceded with @code{-}, disassembles @var{n}
6434 instructions before instruction number @var{insn}.
6436 @item record instruction-history
6437 Disassembles ten more instructions after the last disassembly.
6439 @item record instruction-history -
6440 Disassembles ten more instructions before the last disassembly.
6442 @item record instruction-history @var{begin} @var{end}
6443 Disassembles instructions beginning with instruction number
6444 @var{begin} until instruction number @var{end}. The instruction
6445 number @var{end} is not included.
6448 This command may not be available for all recording methods.
6451 @item set record instruction-history-size @var{size}
6452 @itemx set record instruction-history-size unlimited
6453 Define how many instructions to disassemble in the @code{record
6454 instruction-history} command. The default value is 10.
6455 A @var{size} of @code{unlimited} means unlimited instructions.
6458 @item show record instruction-history-size
6459 Show how many instructions to disassemble in the @code{record
6460 instruction-history} command.
6462 @kindex record function-call-history
6463 @kindex rec function-call-history
6464 @item record function-call-history
6465 Prints the execution history at function granularity. It prints one
6466 line for each sequence of instructions that belong to the same
6467 function giving the name of that function, the source lines
6468 for this instruction sequence (if the @code{/l} modifier is
6469 specified), and the instructions numbers that form the sequence (if
6470 the @code{/i} modifier is specified).
6473 (@value{GDBP}) @b{list 1, 10}
6484 (@value{GDBP}) @b{record function-call-history /l}
6490 By default, ten lines are printed. This can be changed using the
6491 @code{set record function-call-history-size} command. Functions are
6492 printed in execution order. There are several ways to specify what
6496 @item record function-call-history @var{func}
6497 Prints ten functions starting from function number @var{func}.
6499 @item record function-call-history @var{func}, +/-@var{n}
6500 Prints @var{n} functions around function number @var{func}. If
6501 @var{n} is preceded with @code{+}, prints @var{n} functions after
6502 function number @var{func}. If @var{n} is preceded with @code{-},
6503 prints @var{n} functions before function number @var{func}.
6505 @item record function-call-history
6506 Prints ten more functions after the last ten-line print.
6508 @item record function-call-history -
6509 Prints ten more functions before the last ten-line print.
6511 @item record function-call-history @var{begin} @var{end}
6512 Prints functions beginning with function number @var{begin} until
6513 function number @var{end}. The function number @var{end} is not
6517 This command may not be available for all recording methods.
6519 @item set record function-call-history-size @var{size}
6520 @itemx set record function-call-history-size unlimited
6521 Define how many lines to print in the
6522 @code{record function-call-history} command. The default value is 10.
6523 A size of @code{unlimited} means unlimited lines.
6525 @item show record function-call-history-size
6526 Show how many lines to print in the
6527 @code{record function-call-history} command.
6532 @chapter Examining the Stack
6534 When your program has stopped, the first thing you need to know is where it
6535 stopped and how it got there.
6538 Each time your program performs a function call, information about the call
6540 That information includes the location of the call in your program,
6541 the arguments of the call,
6542 and the local variables of the function being called.
6543 The information is saved in a block of data called a @dfn{stack frame}.
6544 The stack frames are allocated in a region of memory called the @dfn{call
6547 When your program stops, the @value{GDBN} commands for examining the
6548 stack allow you to see all of this information.
6550 @cindex selected frame
6551 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6552 @value{GDBN} commands refer implicitly to the selected frame. In
6553 particular, whenever you ask @value{GDBN} for the value of a variable in
6554 your program, the value is found in the selected frame. There are
6555 special @value{GDBN} commands to select whichever frame you are
6556 interested in. @xref{Selection, ,Selecting a Frame}.
6558 When your program stops, @value{GDBN} automatically selects the
6559 currently executing frame and describes it briefly, similar to the
6560 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6563 * Frames:: Stack frames
6564 * Backtrace:: Backtraces
6565 * Frame Filter Management:: Managing frame filters
6566 * Selection:: Selecting a frame
6567 * Frame Info:: Information on a frame
6572 @section Stack Frames
6574 @cindex frame, definition
6576 The call stack is divided up into contiguous pieces called @dfn{stack
6577 frames}, or @dfn{frames} for short; each frame is the data associated
6578 with one call to one function. The frame contains the arguments given
6579 to the function, the function's local variables, and the address at
6580 which the function is executing.
6582 @cindex initial frame
6583 @cindex outermost frame
6584 @cindex innermost frame
6585 When your program is started, the stack has only one frame, that of the
6586 function @code{main}. This is called the @dfn{initial} frame or the
6587 @dfn{outermost} frame. Each time a function is called, a new frame is
6588 made. Each time a function returns, the frame for that function invocation
6589 is eliminated. If a function is recursive, there can be many frames for
6590 the same function. The frame for the function in which execution is
6591 actually occurring is called the @dfn{innermost} frame. This is the most
6592 recently created of all the stack frames that still exist.
6594 @cindex frame pointer
6595 Inside your program, stack frames are identified by their addresses. A
6596 stack frame consists of many bytes, each of which has its own address; each
6597 kind of computer has a convention for choosing one byte whose
6598 address serves as the address of the frame. Usually this address is kept
6599 in a register called the @dfn{frame pointer register}
6600 (@pxref{Registers, $fp}) while execution is going on in that frame.
6602 @cindex frame number
6603 @value{GDBN} assigns numbers to all existing stack frames, starting with
6604 zero for the innermost frame, one for the frame that called it,
6605 and so on upward. These numbers do not really exist in your program;
6606 they are assigned by @value{GDBN} to give you a way of designating stack
6607 frames in @value{GDBN} commands.
6609 @c The -fomit-frame-pointer below perennially causes hbox overflow
6610 @c underflow problems.
6611 @cindex frameless execution
6612 Some compilers provide a way to compile functions so that they operate
6613 without stack frames. (For example, the @value{NGCC} option
6615 @samp{-fomit-frame-pointer}
6617 generates functions without a frame.)
6618 This is occasionally done with heavily used library functions to save
6619 the frame setup time. @value{GDBN} has limited facilities for dealing
6620 with these function invocations. If the innermost function invocation
6621 has no stack frame, @value{GDBN} nevertheless regards it as though
6622 it had a separate frame, which is numbered zero as usual, allowing
6623 correct tracing of the function call chain. However, @value{GDBN} has
6624 no provision for frameless functions elsewhere in the stack.
6627 @kindex frame@r{, command}
6628 @cindex current stack frame
6629 @item frame @var{args}
6630 The @code{frame} command allows you to move from one stack frame to another,
6631 and to print the stack frame you select. @var{args} may be either the
6632 address of the frame or the stack frame number. Without an argument,
6633 @code{frame} prints the current stack frame.
6635 @kindex select-frame
6636 @cindex selecting frame silently
6638 The @code{select-frame} command allows you to move from one stack frame
6639 to another without printing the frame. This is the silent version of
6647 @cindex call stack traces
6648 A backtrace is a summary of how your program got where it is. It shows one
6649 line per frame, for many frames, starting with the currently executing
6650 frame (frame zero), followed by its caller (frame one), and on up the
6653 @anchor{backtrace-command}
6656 @kindex bt @r{(@code{backtrace})}
6659 Print a backtrace of the entire stack: one line per frame for all
6660 frames in the stack.
6662 You can stop the backtrace at any time by typing the system interrupt
6663 character, normally @kbd{Ctrl-c}.
6665 @item backtrace @var{n}
6667 Similar, but print only the innermost @var{n} frames.
6669 @item backtrace -@var{n}
6671 Similar, but print only the outermost @var{n} frames.
6673 @item backtrace full
6675 @itemx bt full @var{n}
6676 @itemx bt full -@var{n}
6677 Print the values of the local variables also. @var{n} specifies the
6678 number of frames to print, as described above.
6680 @item backtrace no-filters
6681 @itemx bt no-filters
6682 @itemx bt no-filters @var{n}
6683 @itemx bt no-filters -@var{n}
6684 @itemx bt no-filters full
6685 @itemx bt no-filters full @var{n}
6686 @itemx bt no-filters full -@var{n}
6687 Do not run Python frame filters on this backtrace. @xref{Frame
6688 Filter API}, for more information. Additionally use @ref{disable
6689 frame-filter all} to turn off all frame filters. This is only
6690 relevant when @value{GDBN} has been configured with @code{Python}
6696 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6697 are additional aliases for @code{backtrace}.
6699 @cindex multiple threads, backtrace
6700 In a multi-threaded program, @value{GDBN} by default shows the
6701 backtrace only for the current thread. To display the backtrace for
6702 several or all of the threads, use the command @code{thread apply}
6703 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6704 apply all backtrace}, @value{GDBN} will display the backtrace for all
6705 the threads; this is handy when you debug a core dump of a
6706 multi-threaded program.
6708 Each line in the backtrace shows the frame number and the function name.
6709 The program counter value is also shown---unless you use @code{set
6710 print address off}. The backtrace also shows the source file name and
6711 line number, as well as the arguments to the function. The program
6712 counter value is omitted if it is at the beginning of the code for that
6715 Here is an example of a backtrace. It was made with the command
6716 @samp{bt 3}, so it shows the innermost three frames.
6720 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6722 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6723 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6725 (More stack frames follow...)
6730 The display for frame zero does not begin with a program counter
6731 value, indicating that your program has stopped at the beginning of the
6732 code for line @code{993} of @code{builtin.c}.
6735 The value of parameter @code{data} in frame 1 has been replaced by
6736 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6737 only if it is a scalar (integer, pointer, enumeration, etc). See command
6738 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6739 on how to configure the way function parameter values are printed.
6741 @cindex optimized out, in backtrace
6742 @cindex function call arguments, optimized out
6743 If your program was compiled with optimizations, some compilers will
6744 optimize away arguments passed to functions if those arguments are
6745 never used after the call. Such optimizations generate code that
6746 passes arguments through registers, but doesn't store those arguments
6747 in the stack frame. @value{GDBN} has no way of displaying such
6748 arguments in stack frames other than the innermost one. Here's what
6749 such a backtrace might look like:
6753 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6755 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6756 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6758 (More stack frames follow...)
6763 The values of arguments that were not saved in their stack frames are
6764 shown as @samp{<optimized out>}.
6766 If you need to display the values of such optimized-out arguments,
6767 either deduce that from other variables whose values depend on the one
6768 you are interested in, or recompile without optimizations.
6770 @cindex backtrace beyond @code{main} function
6771 @cindex program entry point
6772 @cindex startup code, and backtrace
6773 Most programs have a standard user entry point---a place where system
6774 libraries and startup code transition into user code. For C this is
6775 @code{main}@footnote{
6776 Note that embedded programs (the so-called ``free-standing''
6777 environment) are not required to have a @code{main} function as the
6778 entry point. They could even have multiple entry points.}.
6779 When @value{GDBN} finds the entry function in a backtrace
6780 it will terminate the backtrace, to avoid tracing into highly
6781 system-specific (and generally uninteresting) code.
6783 If you need to examine the startup code, or limit the number of levels
6784 in a backtrace, you can change this behavior:
6787 @item set backtrace past-main
6788 @itemx set backtrace past-main on
6789 @kindex set backtrace
6790 Backtraces will continue past the user entry point.
6792 @item set backtrace past-main off
6793 Backtraces will stop when they encounter the user entry point. This is the
6796 @item show backtrace past-main
6797 @kindex show backtrace
6798 Display the current user entry point backtrace policy.
6800 @item set backtrace past-entry
6801 @itemx set backtrace past-entry on
6802 Backtraces will continue past the internal entry point of an application.
6803 This entry point is encoded by the linker when the application is built,
6804 and is likely before the user entry point @code{main} (or equivalent) is called.
6806 @item set backtrace past-entry off
6807 Backtraces will stop when they encounter the internal entry point of an
6808 application. This is the default.
6810 @item show backtrace past-entry
6811 Display the current internal entry point backtrace policy.
6813 @item set backtrace limit @var{n}
6814 @itemx set backtrace limit 0
6815 @itemx set backtrace limit unlimited
6816 @cindex backtrace limit
6817 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6818 or zero means unlimited levels.
6820 @item show backtrace limit
6821 Display the current limit on backtrace levels.
6824 You can control how file names are displayed.
6827 @item set filename-display
6828 @itemx set filename-display relative
6829 @cindex filename-display
6830 Display file names relative to the compilation directory. This is the default.
6832 @item set filename-display basename
6833 Display only basename of a filename.
6835 @item set filename-display absolute
6836 Display an absolute filename.
6838 @item show filename-display
6839 Show the current way to display filenames.
6842 @node Frame Filter Management
6843 @section Management of Frame Filters.
6844 @cindex managing frame filters
6846 Frame filters are Python based utilities to manage and decorate the
6847 output of frames. @xref{Frame Filter API}, for further information.
6849 Managing frame filters is performed by several commands available
6850 within @value{GDBN}, detailed here.
6853 @kindex info frame-filter
6854 @item info frame-filter
6855 Print a list of installed frame filters from all dictionaries, showing
6856 their name, priority and enabled status.
6858 @kindex disable frame-filter
6859 @anchor{disable frame-filter all}
6860 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6861 Disable a frame filter in the dictionary matching
6862 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6863 @var{filter-dictionary} may be @code{all}, @code{global},
6864 @code{progspace} or the name of the object file where the frame filter
6865 dictionary resides. When @code{all} is specified, all frame filters
6866 across all dictionaries are disabled. @var{filter-name} is the name
6867 of the frame filter and is used when @code{all} is not the option for
6868 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6869 may be enabled again later.
6871 @kindex enable frame-filter
6872 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6873 Enable a frame filter in the dictionary matching
6874 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6875 @var{filter-dictionary} may be @code{all}, @code{global},
6876 @code{progspace} or the name of the object file where the frame filter
6877 dictionary resides. When @code{all} is specified, all frame filters across
6878 all dictionaries are enabled. @var{filter-name} is the name of the frame
6879 filter and is used when @code{all} is not the option for
6880 @var{filter-dictionary}.
6885 (gdb) info frame-filter
6887 global frame-filters:
6888 Priority Enabled Name
6889 1000 No PrimaryFunctionFilter
6892 progspace /build/test frame-filters:
6893 Priority Enabled Name
6894 100 Yes ProgspaceFilter
6896 objfile /build/test frame-filters:
6897 Priority Enabled Name
6898 999 Yes BuildProgra Filter
6900 (gdb) disable frame-filter /build/test BuildProgramFilter
6901 (gdb) info frame-filter
6903 global frame-filters:
6904 Priority Enabled Name
6905 1000 No PrimaryFunctionFilter
6908 progspace /build/test frame-filters:
6909 Priority Enabled Name
6910 100 Yes ProgspaceFilter
6912 objfile /build/test frame-filters:
6913 Priority Enabled Name
6914 999 No BuildProgramFilter
6916 (gdb) enable frame-filter global PrimaryFunctionFilter
6917 (gdb) info frame-filter
6919 global frame-filters:
6920 Priority Enabled Name
6921 1000 Yes PrimaryFunctionFilter
6924 progspace /build/test frame-filters:
6925 Priority Enabled Name
6926 100 Yes ProgspaceFilter
6928 objfile /build/test frame-filters:
6929 Priority Enabled Name
6930 999 No BuildProgramFilter
6933 @kindex set frame-filter priority
6934 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
6935 Set the @var{priority} of a frame filter in the dictionary matching
6936 @var{filter-dictionary}, and the frame filter name matching
6937 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6938 @code{progspace} or the name of the object file where the frame filter
6939 dictionary resides. @var{priority} is an integer.
6941 @kindex show frame-filter priority
6942 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
6943 Show the @var{priority} of a frame filter in the dictionary matching
6944 @var{filter-dictionary}, and the frame filter name matching
6945 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6946 @code{progspace} or the name of the object file where the frame filter
6952 (gdb) info frame-filter
6954 global frame-filters:
6955 Priority Enabled Name
6956 1000 Yes PrimaryFunctionFilter
6959 progspace /build/test frame-filters:
6960 Priority Enabled Name
6961 100 Yes ProgspaceFilter
6963 objfile /build/test frame-filters:
6964 Priority Enabled Name
6965 999 No BuildProgramFilter
6967 (gdb) set frame-filter priority global Reverse 50
6968 (gdb) info frame-filter
6970 global frame-filters:
6971 Priority Enabled Name
6972 1000 Yes PrimaryFunctionFilter
6975 progspace /build/test frame-filters:
6976 Priority Enabled Name
6977 100 Yes ProgspaceFilter
6979 objfile /build/test frame-filters:
6980 Priority Enabled Name
6981 999 No BuildProgramFilter
6986 @section Selecting a Frame
6988 Most commands for examining the stack and other data in your program work on
6989 whichever stack frame is selected at the moment. Here are the commands for
6990 selecting a stack frame; all of them finish by printing a brief description
6991 of the stack frame just selected.
6994 @kindex frame@r{, selecting}
6995 @kindex f @r{(@code{frame})}
6998 Select frame number @var{n}. Recall that frame zero is the innermost
6999 (currently executing) frame, frame one is the frame that called the
7000 innermost one, and so on. The highest-numbered frame is the one for
7003 @item frame @var{addr}
7005 Select the frame at address @var{addr}. This is useful mainly if the
7006 chaining of stack frames has been damaged by a bug, making it
7007 impossible for @value{GDBN} to assign numbers properly to all frames. In
7008 addition, this can be useful when your program has multiple stacks and
7009 switches between them.
7011 On the SPARC architecture, @code{frame} needs two addresses to
7012 select an arbitrary frame: a frame pointer and a stack pointer.
7014 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7015 pointer and a program counter.
7017 On the 29k architecture, it needs three addresses: a register stack
7018 pointer, a program counter, and a memory stack pointer.
7022 Move @var{n} frames up the stack. For positive numbers @var{n}, this
7023 advances toward the outermost frame, to higher frame numbers, to frames
7024 that have existed longer. @var{n} defaults to one.
7027 @kindex do @r{(@code{down})}
7029 Move @var{n} frames down the stack. For positive numbers @var{n}, this
7030 advances toward the innermost frame, to lower frame numbers, to frames
7031 that were created more recently. @var{n} defaults to one. You may
7032 abbreviate @code{down} as @code{do}.
7035 All of these commands end by printing two lines of output describing the
7036 frame. The first line shows the frame number, the function name, the
7037 arguments, and the source file and line number of execution in that
7038 frame. The second line shows the text of that source line.
7046 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7048 10 read_input_file (argv[i]);
7052 After such a printout, the @code{list} command with no arguments
7053 prints ten lines centered on the point of execution in the frame.
7054 You can also edit the program at the point of execution with your favorite
7055 editing program by typing @code{edit}.
7056 @xref{List, ,Printing Source Lines},
7060 @kindex down-silently
7062 @item up-silently @var{n}
7063 @itemx down-silently @var{n}
7064 These two commands are variants of @code{up} and @code{down},
7065 respectively; they differ in that they do their work silently, without
7066 causing display of the new frame. They are intended primarily for use
7067 in @value{GDBN} command scripts, where the output might be unnecessary and
7072 @section Information About a Frame
7074 There are several other commands to print information about the selected
7080 When used without any argument, this command does not change which
7081 frame is selected, but prints a brief description of the currently
7082 selected stack frame. It can be abbreviated @code{f}. With an
7083 argument, this command is used to select a stack frame.
7084 @xref{Selection, ,Selecting a Frame}.
7087 @kindex info f @r{(@code{info frame})}
7090 This command prints a verbose description of the selected stack frame,
7095 the address of the frame
7097 the address of the next frame down (called by this frame)
7099 the address of the next frame up (caller of this frame)
7101 the language in which the source code corresponding to this frame is written
7103 the address of the frame's arguments
7105 the address of the frame's local variables
7107 the program counter saved in it (the address of execution in the caller frame)
7109 which registers were saved in the frame
7112 @noindent The verbose description is useful when
7113 something has gone wrong that has made the stack format fail to fit
7114 the usual conventions.
7116 @item info frame @var{addr}
7117 @itemx info f @var{addr}
7118 Print a verbose description of the frame at address @var{addr}, without
7119 selecting that frame. The selected frame remains unchanged by this
7120 command. This requires the same kind of address (more than one for some
7121 architectures) that you specify in the @code{frame} command.
7122 @xref{Selection, ,Selecting a Frame}.
7126 Print the arguments of the selected frame, each on a separate line.
7130 Print the local variables of the selected frame, each on a separate
7131 line. These are all variables (declared either static or automatic)
7132 accessible at the point of execution of the selected frame.
7138 @chapter Examining Source Files
7140 @value{GDBN} can print parts of your program's source, since the debugging
7141 information recorded in the program tells @value{GDBN} what source files were
7142 used to build it. When your program stops, @value{GDBN} spontaneously prints
7143 the line where it stopped. Likewise, when you select a stack frame
7144 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7145 execution in that frame has stopped. You can print other portions of
7146 source files by explicit command.
7148 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7149 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7150 @value{GDBN} under @sc{gnu} Emacs}.
7153 * List:: Printing source lines
7154 * Specify Location:: How to specify code locations
7155 * Edit:: Editing source files
7156 * Search:: Searching source files
7157 * Source Path:: Specifying source directories
7158 * Machine Code:: Source and machine code
7162 @section Printing Source Lines
7165 @kindex l @r{(@code{list})}
7166 To print lines from a source file, use the @code{list} command
7167 (abbreviated @code{l}). By default, ten lines are printed.
7168 There are several ways to specify what part of the file you want to
7169 print; see @ref{Specify Location}, for the full list.
7171 Here are the forms of the @code{list} command most commonly used:
7174 @item list @var{linenum}
7175 Print lines centered around line number @var{linenum} in the
7176 current source file.
7178 @item list @var{function}
7179 Print lines centered around the beginning of function
7183 Print more lines. If the last lines printed were printed with a
7184 @code{list} command, this prints lines following the last lines
7185 printed; however, if the last line printed was a solitary line printed
7186 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7187 Stack}), this prints lines centered around that line.
7190 Print lines just before the lines last printed.
7193 @cindex @code{list}, how many lines to display
7194 By default, @value{GDBN} prints ten source lines with any of these forms of
7195 the @code{list} command. You can change this using @code{set listsize}:
7198 @kindex set listsize
7199 @item set listsize @var{count}
7200 @itemx set listsize unlimited
7201 Make the @code{list} command display @var{count} source lines (unless
7202 the @code{list} argument explicitly specifies some other number).
7203 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7205 @kindex show listsize
7207 Display the number of lines that @code{list} prints.
7210 Repeating a @code{list} command with @key{RET} discards the argument,
7211 so it is equivalent to typing just @code{list}. This is more useful
7212 than listing the same lines again. An exception is made for an
7213 argument of @samp{-}; that argument is preserved in repetition so that
7214 each repetition moves up in the source file.
7216 In general, the @code{list} command expects you to supply zero, one or two
7217 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7218 of writing them (@pxref{Specify Location}), but the effect is always
7219 to specify some source line.
7221 Here is a complete description of the possible arguments for @code{list}:
7224 @item list @var{linespec}
7225 Print lines centered around the line specified by @var{linespec}.
7227 @item list @var{first},@var{last}
7228 Print lines from @var{first} to @var{last}. Both arguments are
7229 linespecs. When a @code{list} command has two linespecs, and the
7230 source file of the second linespec is omitted, this refers to
7231 the same source file as the first linespec.
7233 @item list ,@var{last}
7234 Print lines ending with @var{last}.
7236 @item list @var{first},
7237 Print lines starting with @var{first}.
7240 Print lines just after the lines last printed.
7243 Print lines just before the lines last printed.
7246 As described in the preceding table.
7249 @node Specify Location
7250 @section Specifying a Location
7251 @cindex specifying location
7254 Several @value{GDBN} commands accept arguments that specify a location
7255 of your program's code. Since @value{GDBN} is a source-level
7256 debugger, a location usually specifies some line in the source code;
7257 for that reason, locations are also known as @dfn{linespecs}.
7259 Here are all the different ways of specifying a code location that
7260 @value{GDBN} understands:
7264 Specifies the line number @var{linenum} of the current source file.
7267 @itemx +@var{offset}
7268 Specifies the line @var{offset} lines before or after the @dfn{current
7269 line}. For the @code{list} command, the current line is the last one
7270 printed; for the breakpoint commands, this is the line at which
7271 execution stopped in the currently selected @dfn{stack frame}
7272 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7273 used as the second of the two linespecs in a @code{list} command,
7274 this specifies the line @var{offset} lines up or down from the first
7277 @item @var{filename}:@var{linenum}
7278 Specifies the line @var{linenum} in the source file @var{filename}.
7279 If @var{filename} is a relative file name, then it will match any
7280 source file name with the same trailing components. For example, if
7281 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7282 name of @file{/build/trunk/gcc/expr.c}, but not
7283 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7285 @item @var{function}
7286 Specifies the line that begins the body of the function @var{function}.
7287 For example, in C, this is the line with the open brace.
7289 @item @var{function}:@var{label}
7290 Specifies the line where @var{label} appears in @var{function}.
7292 @item @var{filename}:@var{function}
7293 Specifies the line that begins the body of the function @var{function}
7294 in the file @var{filename}. You only need the file name with a
7295 function name to avoid ambiguity when there are identically named
7296 functions in different source files.
7299 Specifies the line at which the label named @var{label} appears.
7300 @value{GDBN} searches for the label in the function corresponding to
7301 the currently selected stack frame. If there is no current selected
7302 stack frame (for instance, if the inferior is not running), then
7303 @value{GDBN} will not search for a label.
7305 @item *@var{address}
7306 Specifies the program address @var{address}. For line-oriented
7307 commands, such as @code{list} and @code{edit}, this specifies a source
7308 line that contains @var{address}. For @code{break} and other
7309 breakpoint oriented commands, this can be used to set breakpoints in
7310 parts of your program which do not have debugging information or
7313 Here @var{address} may be any expression valid in the current working
7314 language (@pxref{Languages, working language}) that specifies a code
7315 address. In addition, as a convenience, @value{GDBN} extends the
7316 semantics of expressions used in locations to cover the situations
7317 that frequently happen during debugging. Here are the various forms
7321 @item @var{expression}
7322 Any expression valid in the current working language.
7324 @item @var{funcaddr}
7325 An address of a function or procedure derived from its name. In C,
7326 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7327 simply the function's name @var{function} (and actually a special case
7328 of a valid expression). In Pascal and Modula-2, this is
7329 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7330 (although the Pascal form also works).
7332 This form specifies the address of the function's first instruction,
7333 before the stack frame and arguments have been set up.
7335 @item '@var{filename}'::@var{funcaddr}
7336 Like @var{funcaddr} above, but also specifies the name of the source
7337 file explicitly. This is useful if the name of the function does not
7338 specify the function unambiguously, e.g., if there are several
7339 functions with identical names in different source files.
7342 @cindex breakpoint at static probe point
7343 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7344 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7345 applications to embed static probes. @xref{Static Probe Points}, for more
7346 information on finding and using static probes. This form of linespec
7347 specifies the location of such a static probe.
7349 If @var{objfile} is given, only probes coming from that shared library
7350 or executable matching @var{objfile} as a regular expression are considered.
7351 If @var{provider} is given, then only probes from that provider are considered.
7352 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7353 each one of those probes.
7359 @section Editing Source Files
7360 @cindex editing source files
7363 @kindex e @r{(@code{edit})}
7364 To edit the lines in a source file, use the @code{edit} command.
7365 The editing program of your choice
7366 is invoked with the current line set to
7367 the active line in the program.
7368 Alternatively, there are several ways to specify what part of the file you
7369 want to print if you want to see other parts of the program:
7372 @item edit @var{location}
7373 Edit the source file specified by @code{location}. Editing starts at
7374 that @var{location}, e.g., at the specified source line of the
7375 specified file. @xref{Specify Location}, for all the possible forms
7376 of the @var{location} argument; here are the forms of the @code{edit}
7377 command most commonly used:
7380 @item edit @var{number}
7381 Edit the current source file with @var{number} as the active line number.
7383 @item edit @var{function}
7384 Edit the file containing @var{function} at the beginning of its definition.
7389 @subsection Choosing your Editor
7390 You can customize @value{GDBN} to use any editor you want
7392 The only restriction is that your editor (say @code{ex}), recognizes the
7393 following command-line syntax:
7395 ex +@var{number} file
7397 The optional numeric value +@var{number} specifies the number of the line in
7398 the file where to start editing.}.
7399 By default, it is @file{@value{EDITOR}}, but you can change this
7400 by setting the environment variable @code{EDITOR} before using
7401 @value{GDBN}. For example, to configure @value{GDBN} to use the
7402 @code{vi} editor, you could use these commands with the @code{sh} shell:
7408 or in the @code{csh} shell,
7410 setenv EDITOR /usr/bin/vi
7415 @section Searching Source Files
7416 @cindex searching source files
7418 There are two commands for searching through the current source file for a
7423 @kindex forward-search
7424 @kindex fo @r{(@code{forward-search})}
7425 @item forward-search @var{regexp}
7426 @itemx search @var{regexp}
7427 The command @samp{forward-search @var{regexp}} checks each line,
7428 starting with the one following the last line listed, for a match for
7429 @var{regexp}. It lists the line that is found. You can use the
7430 synonym @samp{search @var{regexp}} or abbreviate the command name as
7433 @kindex reverse-search
7434 @item reverse-search @var{regexp}
7435 The command @samp{reverse-search @var{regexp}} checks each line, starting
7436 with the one before the last line listed and going backward, for a match
7437 for @var{regexp}. It lists the line that is found. You can abbreviate
7438 this command as @code{rev}.
7442 @section Specifying Source Directories
7445 @cindex directories for source files
7446 Executable programs sometimes do not record the directories of the source
7447 files from which they were compiled, just the names. Even when they do,
7448 the directories could be moved between the compilation and your debugging
7449 session. @value{GDBN} has a list of directories to search for source files;
7450 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7451 it tries all the directories in the list, in the order they are present
7452 in the list, until it finds a file with the desired name.
7454 For example, suppose an executable references the file
7455 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7456 @file{/mnt/cross}. The file is first looked up literally; if this
7457 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7458 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7459 message is printed. @value{GDBN} does not look up the parts of the
7460 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7461 Likewise, the subdirectories of the source path are not searched: if
7462 the source path is @file{/mnt/cross}, and the binary refers to
7463 @file{foo.c}, @value{GDBN} would not find it under
7464 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7466 Plain file names, relative file names with leading directories, file
7467 names containing dots, etc.@: are all treated as described above; for
7468 instance, if the source path is @file{/mnt/cross}, and the source file
7469 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7470 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7471 that---@file{/mnt/cross/foo.c}.
7473 Note that the executable search path is @emph{not} used to locate the
7476 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7477 any information it has cached about where source files are found and where
7478 each line is in the file.
7482 When you start @value{GDBN}, its source path includes only @samp{cdir}
7483 and @samp{cwd}, in that order.
7484 To add other directories, use the @code{directory} command.
7486 The search path is used to find both program source files and @value{GDBN}
7487 script files (read using the @samp{-command} option and @samp{source} command).
7489 In addition to the source path, @value{GDBN} provides a set of commands
7490 that manage a list of source path substitution rules. A @dfn{substitution
7491 rule} specifies how to rewrite source directories stored in the program's
7492 debug information in case the sources were moved to a different
7493 directory between compilation and debugging. A rule is made of
7494 two strings, the first specifying what needs to be rewritten in
7495 the path, and the second specifying how it should be rewritten.
7496 In @ref{set substitute-path}, we name these two parts @var{from} and
7497 @var{to} respectively. @value{GDBN} does a simple string replacement
7498 of @var{from} with @var{to} at the start of the directory part of the
7499 source file name, and uses that result instead of the original file
7500 name to look up the sources.
7502 Using the previous example, suppose the @file{foo-1.0} tree has been
7503 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7504 @value{GDBN} to replace @file{/usr/src} in all source path names with
7505 @file{/mnt/cross}. The first lookup will then be
7506 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7507 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7508 substitution rule, use the @code{set substitute-path} command
7509 (@pxref{set substitute-path}).
7511 To avoid unexpected substitution results, a rule is applied only if the
7512 @var{from} part of the directory name ends at a directory separator.
7513 For instance, a rule substituting @file{/usr/source} into
7514 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7515 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7516 is applied only at the beginning of the directory name, this rule will
7517 not be applied to @file{/root/usr/source/baz.c} either.
7519 In many cases, you can achieve the same result using the @code{directory}
7520 command. However, @code{set substitute-path} can be more efficient in
7521 the case where the sources are organized in a complex tree with multiple
7522 subdirectories. With the @code{directory} command, you need to add each
7523 subdirectory of your project. If you moved the entire tree while
7524 preserving its internal organization, then @code{set substitute-path}
7525 allows you to direct the debugger to all the sources with one single
7528 @code{set substitute-path} is also more than just a shortcut command.
7529 The source path is only used if the file at the original location no
7530 longer exists. On the other hand, @code{set substitute-path} modifies
7531 the debugger behavior to look at the rewritten location instead. So, if
7532 for any reason a source file that is not relevant to your executable is
7533 located at the original location, a substitution rule is the only
7534 method available to point @value{GDBN} at the new location.
7536 @cindex @samp{--with-relocated-sources}
7537 @cindex default source path substitution
7538 You can configure a default source path substitution rule by
7539 configuring @value{GDBN} with the
7540 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7541 should be the name of a directory under @value{GDBN}'s configured
7542 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7543 directory names in debug information under @var{dir} will be adjusted
7544 automatically if the installed @value{GDBN} is moved to a new
7545 location. This is useful if @value{GDBN}, libraries or executables
7546 with debug information and corresponding source code are being moved
7550 @item directory @var{dirname} @dots{}
7551 @item dir @var{dirname} @dots{}
7552 Add directory @var{dirname} to the front of the source path. Several
7553 directory names may be given to this command, separated by @samp{:}
7554 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7555 part of absolute file names) or
7556 whitespace. You may specify a directory that is already in the source
7557 path; this moves it forward, so @value{GDBN} searches it sooner.
7561 @vindex $cdir@r{, convenience variable}
7562 @vindex $cwd@r{, convenience variable}
7563 @cindex compilation directory
7564 @cindex current directory
7565 @cindex working directory
7566 @cindex directory, current
7567 @cindex directory, compilation
7568 You can use the string @samp{$cdir} to refer to the compilation
7569 directory (if one is recorded), and @samp{$cwd} to refer to the current
7570 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7571 tracks the current working directory as it changes during your @value{GDBN}
7572 session, while the latter is immediately expanded to the current
7573 directory at the time you add an entry to the source path.
7576 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7578 @c RET-repeat for @code{directory} is explicitly disabled, but since
7579 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7581 @item set directories @var{path-list}
7582 @kindex set directories
7583 Set the source path to @var{path-list}.
7584 @samp{$cdir:$cwd} are added if missing.
7586 @item show directories
7587 @kindex show directories
7588 Print the source path: show which directories it contains.
7590 @anchor{set substitute-path}
7591 @item set substitute-path @var{from} @var{to}
7592 @kindex set substitute-path
7593 Define a source path substitution rule, and add it at the end of the
7594 current list of existing substitution rules. If a rule with the same
7595 @var{from} was already defined, then the old rule is also deleted.
7597 For example, if the file @file{/foo/bar/baz.c} was moved to
7598 @file{/mnt/cross/baz.c}, then the command
7601 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7605 will tell @value{GDBN} to replace @samp{/usr/src} with
7606 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7607 @file{baz.c} even though it was moved.
7609 In the case when more than one substitution rule have been defined,
7610 the rules are evaluated one by one in the order where they have been
7611 defined. The first one matching, if any, is selected to perform
7614 For instance, if we had entered the following commands:
7617 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7618 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7622 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7623 @file{/mnt/include/defs.h} by using the first rule. However, it would
7624 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7625 @file{/mnt/src/lib/foo.c}.
7628 @item unset substitute-path [path]
7629 @kindex unset substitute-path
7630 If a path is specified, search the current list of substitution rules
7631 for a rule that would rewrite that path. Delete that rule if found.
7632 A warning is emitted by the debugger if no rule could be found.
7634 If no path is specified, then all substitution rules are deleted.
7636 @item show substitute-path [path]
7637 @kindex show substitute-path
7638 If a path is specified, then print the source path substitution rule
7639 which would rewrite that path, if any.
7641 If no path is specified, then print all existing source path substitution
7646 If your source path is cluttered with directories that are no longer of
7647 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7648 versions of source. You can correct the situation as follows:
7652 Use @code{directory} with no argument to reset the source path to its default value.
7655 Use @code{directory} with suitable arguments to reinstall the
7656 directories you want in the source path. You can add all the
7657 directories in one command.
7661 @section Source and Machine Code
7662 @cindex source line and its code address
7664 You can use the command @code{info line} to map source lines to program
7665 addresses (and vice versa), and the command @code{disassemble} to display
7666 a range of addresses as machine instructions. You can use the command
7667 @code{set disassemble-next-line} to set whether to disassemble next
7668 source line when execution stops. When run under @sc{gnu} Emacs
7669 mode, the @code{info line} command causes the arrow to point to the
7670 line specified. Also, @code{info line} prints addresses in symbolic form as
7675 @item info line @var{linespec}
7676 Print the starting and ending addresses of the compiled code for
7677 source line @var{linespec}. You can specify source lines in any of
7678 the ways documented in @ref{Specify Location}.
7681 For example, we can use @code{info line} to discover the location of
7682 the object code for the first line of function
7683 @code{m4_changequote}:
7685 @c FIXME: I think this example should also show the addresses in
7686 @c symbolic form, as they usually would be displayed.
7688 (@value{GDBP}) info line m4_changequote
7689 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7693 @cindex code address and its source line
7694 We can also inquire (using @code{*@var{addr}} as the form for
7695 @var{linespec}) what source line covers a particular address:
7697 (@value{GDBP}) info line *0x63ff
7698 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7701 @cindex @code{$_} and @code{info line}
7702 @cindex @code{x} command, default address
7703 @kindex x@r{(examine), and} info line
7704 After @code{info line}, the default address for the @code{x} command
7705 is changed to the starting address of the line, so that @samp{x/i} is
7706 sufficient to begin examining the machine code (@pxref{Memory,
7707 ,Examining Memory}). Also, this address is saved as the value of the
7708 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7713 @cindex assembly instructions
7714 @cindex instructions, assembly
7715 @cindex machine instructions
7716 @cindex listing machine instructions
7718 @itemx disassemble /m
7719 @itemx disassemble /r
7720 This specialized command dumps a range of memory as machine
7721 instructions. It can also print mixed source+disassembly by specifying
7722 the @code{/m} modifier and print the raw instructions in hex as well as
7723 in symbolic form by specifying the @code{/r}.
7724 The default memory range is the function surrounding the
7725 program counter of the selected frame. A single argument to this
7726 command is a program counter value; @value{GDBN} dumps the function
7727 surrounding this value. When two arguments are given, they should
7728 be separated by a comma, possibly surrounded by whitespace. The
7729 arguments specify a range of addresses to dump, in one of two forms:
7732 @item @var{start},@var{end}
7733 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7734 @item @var{start},+@var{length}
7735 the addresses from @var{start} (inclusive) to
7736 @code{@var{start}+@var{length}} (exclusive).
7740 When 2 arguments are specified, the name of the function is also
7741 printed (since there could be several functions in the given range).
7743 The argument(s) can be any expression yielding a numeric value, such as
7744 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7746 If the range of memory being disassembled contains current program counter,
7747 the instruction at that location is shown with a @code{=>} marker.
7750 The following example shows the disassembly of a range of addresses of
7751 HP PA-RISC 2.0 code:
7754 (@value{GDBP}) disas 0x32c4, 0x32e4
7755 Dump of assembler code from 0x32c4 to 0x32e4:
7756 0x32c4 <main+204>: addil 0,dp
7757 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7758 0x32cc <main+212>: ldil 0x3000,r31
7759 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7760 0x32d4 <main+220>: ldo 0(r31),rp
7761 0x32d8 <main+224>: addil -0x800,dp
7762 0x32dc <main+228>: ldo 0x588(r1),r26
7763 0x32e0 <main+232>: ldil 0x3000,r31
7764 End of assembler dump.
7767 Here is an example showing mixed source+assembly for Intel x86, when the
7768 program is stopped just after function prologue:
7771 (@value{GDBP}) disas /m main
7772 Dump of assembler code for function main:
7774 0x08048330 <+0>: push %ebp
7775 0x08048331 <+1>: mov %esp,%ebp
7776 0x08048333 <+3>: sub $0x8,%esp
7777 0x08048336 <+6>: and $0xfffffff0,%esp
7778 0x08048339 <+9>: sub $0x10,%esp
7780 6 printf ("Hello.\n");
7781 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7782 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7786 0x08048348 <+24>: mov $0x0,%eax
7787 0x0804834d <+29>: leave
7788 0x0804834e <+30>: ret
7790 End of assembler dump.
7793 Here is another example showing raw instructions in hex for AMD x86-64,
7796 (gdb) disas /r 0x400281,+10
7797 Dump of assembler code from 0x400281 to 0x40028b:
7798 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7799 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7800 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7801 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7802 End of assembler dump.
7805 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7806 So, for example, if you want to disassemble function @code{bar}
7807 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7808 and not @samp{disassemble foo.c:bar}.
7810 Some architectures have more than one commonly-used set of instruction
7811 mnemonics or other syntax.
7813 For programs that were dynamically linked and use shared libraries,
7814 instructions that call functions or branch to locations in the shared
7815 libraries might show a seemingly bogus location---it's actually a
7816 location of the relocation table. On some architectures, @value{GDBN}
7817 might be able to resolve these to actual function names.
7820 @kindex set disassembly-flavor
7821 @cindex Intel disassembly flavor
7822 @cindex AT&T disassembly flavor
7823 @item set disassembly-flavor @var{instruction-set}
7824 Select the instruction set to use when disassembling the
7825 program via the @code{disassemble} or @code{x/i} commands.
7827 Currently this command is only defined for the Intel x86 family. You
7828 can set @var{instruction-set} to either @code{intel} or @code{att}.
7829 The default is @code{att}, the AT&T flavor used by default by Unix
7830 assemblers for x86-based targets.
7832 @kindex show disassembly-flavor
7833 @item show disassembly-flavor
7834 Show the current setting of the disassembly flavor.
7838 @kindex set disassemble-next-line
7839 @kindex show disassemble-next-line
7840 @item set disassemble-next-line
7841 @itemx show disassemble-next-line
7842 Control whether or not @value{GDBN} will disassemble the next source
7843 line or instruction when execution stops. If ON, @value{GDBN} will
7844 display disassembly of the next source line when execution of the
7845 program being debugged stops. This is @emph{in addition} to
7846 displaying the source line itself, which @value{GDBN} always does if
7847 possible. If the next source line cannot be displayed for some reason
7848 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7849 info in the debug info), @value{GDBN} will display disassembly of the
7850 next @emph{instruction} instead of showing the next source line. If
7851 AUTO, @value{GDBN} will display disassembly of next instruction only
7852 if the source line cannot be displayed. This setting causes
7853 @value{GDBN} to display some feedback when you step through a function
7854 with no line info or whose source file is unavailable. The default is
7855 OFF, which means never display the disassembly of the next line or
7861 @chapter Examining Data
7863 @cindex printing data
7864 @cindex examining data
7867 The usual way to examine data in your program is with the @code{print}
7868 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7869 evaluates and prints the value of an expression of the language your
7870 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7871 Different Languages}). It may also print the expression using a
7872 Python-based pretty-printer (@pxref{Pretty Printing}).
7875 @item print @var{expr}
7876 @itemx print /@var{f} @var{expr}
7877 @var{expr} is an expression (in the source language). By default the
7878 value of @var{expr} is printed in a format appropriate to its data type;
7879 you can choose a different format by specifying @samp{/@var{f}}, where
7880 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7884 @itemx print /@var{f}
7885 @cindex reprint the last value
7886 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7887 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7888 conveniently inspect the same value in an alternative format.
7891 A more low-level way of examining data is with the @code{x} command.
7892 It examines data in memory at a specified address and prints it in a
7893 specified format. @xref{Memory, ,Examining Memory}.
7895 If you are interested in information about types, or about how the
7896 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7897 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7900 @cindex exploring hierarchical data structures
7902 Another way of examining values of expressions and type information is
7903 through the Python extension command @code{explore} (available only if
7904 the @value{GDBN} build is configured with @code{--with-python}). It
7905 offers an interactive way to start at the highest level (or, the most
7906 abstract level) of the data type of an expression (or, the data type
7907 itself) and explore all the way down to leaf scalar values/fields
7908 embedded in the higher level data types.
7911 @item explore @var{arg}
7912 @var{arg} is either an expression (in the source language), or a type
7913 visible in the current context of the program being debugged.
7916 The working of the @code{explore} command can be illustrated with an
7917 example. If a data type @code{struct ComplexStruct} is defined in your
7927 struct ComplexStruct
7929 struct SimpleStruct *ss_p;
7935 followed by variable declarations as
7938 struct SimpleStruct ss = @{ 10, 1.11 @};
7939 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7943 then, the value of the variable @code{cs} can be explored using the
7944 @code{explore} command as follows.
7948 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7949 the following fields:
7951 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7952 arr = <Enter 1 to explore this field of type `int [10]'>
7954 Enter the field number of choice:
7958 Since the fields of @code{cs} are not scalar values, you are being
7959 prompted to chose the field you want to explore. Let's say you choose
7960 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7961 pointer, you will be asked if it is pointing to a single value. From
7962 the declaration of @code{cs} above, it is indeed pointing to a single
7963 value, hence you enter @code{y}. If you enter @code{n}, then you will
7964 be asked if it were pointing to an array of values, in which case this
7965 field will be explored as if it were an array.
7968 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7969 Continue exploring it as a pointer to a single value [y/n]: y
7970 The value of `*(cs.ss_p)' is a struct/class of type `struct
7971 SimpleStruct' with the following fields:
7973 i = 10 .. (Value of type `int')
7974 d = 1.1100000000000001 .. (Value of type `double')
7976 Press enter to return to parent value:
7980 If the field @code{arr} of @code{cs} was chosen for exploration by
7981 entering @code{1} earlier, then since it is as array, you will be
7982 prompted to enter the index of the element in the array that you want
7986 `cs.arr' is an array of `int'.
7987 Enter the index of the element you want to explore in `cs.arr': 5
7989 `(cs.arr)[5]' is a scalar value of type `int'.
7993 Press enter to return to parent value:
7996 In general, at any stage of exploration, you can go deeper towards the
7997 leaf values by responding to the prompts appropriately, or hit the
7998 return key to return to the enclosing data structure (the @i{higher}
7999 level data structure).
8001 Similar to exploring values, you can use the @code{explore} command to
8002 explore types. Instead of specifying a value (which is typically a
8003 variable name or an expression valid in the current context of the
8004 program being debugged), you specify a type name. If you consider the
8005 same example as above, your can explore the type
8006 @code{struct ComplexStruct} by passing the argument
8007 @code{struct ComplexStruct} to the @code{explore} command.
8010 (gdb) explore struct ComplexStruct
8014 By responding to the prompts appropriately in the subsequent interactive
8015 session, you can explore the type @code{struct ComplexStruct} in a
8016 manner similar to how the value @code{cs} was explored in the above
8019 The @code{explore} command also has two sub-commands,
8020 @code{explore value} and @code{explore type}. The former sub-command is
8021 a way to explicitly specify that value exploration of the argument is
8022 being invoked, while the latter is a way to explicitly specify that type
8023 exploration of the argument is being invoked.
8026 @item explore value @var{expr}
8027 @cindex explore value
8028 This sub-command of @code{explore} explores the value of the
8029 expression @var{expr} (if @var{expr} is an expression valid in the
8030 current context of the program being debugged). The behavior of this
8031 command is identical to that of the behavior of the @code{explore}
8032 command being passed the argument @var{expr}.
8034 @item explore type @var{arg}
8035 @cindex explore type
8036 This sub-command of @code{explore} explores the type of @var{arg} (if
8037 @var{arg} is a type visible in the current context of program being
8038 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8039 is an expression valid in the current context of the program being
8040 debugged). If @var{arg} is a type, then the behavior of this command is
8041 identical to that of the @code{explore} command being passed the
8042 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8043 this command will be identical to that of the @code{explore} command
8044 being passed the type of @var{arg} as the argument.
8048 * Expressions:: Expressions
8049 * Ambiguous Expressions:: Ambiguous Expressions
8050 * Variables:: Program variables
8051 * Arrays:: Artificial arrays
8052 * Output Formats:: Output formats
8053 * Memory:: Examining memory
8054 * Auto Display:: Automatic display
8055 * Print Settings:: Print settings
8056 * Pretty Printing:: Python pretty printing
8057 * Value History:: Value history
8058 * Convenience Vars:: Convenience variables
8059 * Convenience Funs:: Convenience functions
8060 * Registers:: Registers
8061 * Floating Point Hardware:: Floating point hardware
8062 * Vector Unit:: Vector Unit
8063 * OS Information:: Auxiliary data provided by operating system
8064 * Memory Region Attributes:: Memory region attributes
8065 * Dump/Restore Files:: Copy between memory and a file
8066 * Core File Generation:: Cause a program dump its core
8067 * Character Sets:: Debugging programs that use a different
8068 character set than GDB does
8069 * Caching Target Data:: Data caching for targets
8070 * Searching Memory:: Searching memory for a sequence of bytes
8074 @section Expressions
8077 @code{print} and many other @value{GDBN} commands accept an expression and
8078 compute its value. Any kind of constant, variable or operator defined
8079 by the programming language you are using is valid in an expression in
8080 @value{GDBN}. This includes conditional expressions, function calls,
8081 casts, and string constants. It also includes preprocessor macros, if
8082 you compiled your program to include this information; see
8085 @cindex arrays in expressions
8086 @value{GDBN} supports array constants in expressions input by
8087 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8088 you can use the command @code{print @{1, 2, 3@}} to create an array
8089 of three integers. If you pass an array to a function or assign it
8090 to a program variable, @value{GDBN} copies the array to memory that
8091 is @code{malloc}ed in the target program.
8093 Because C is so widespread, most of the expressions shown in examples in
8094 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8095 Languages}, for information on how to use expressions in other
8098 In this section, we discuss operators that you can use in @value{GDBN}
8099 expressions regardless of your programming language.
8101 @cindex casts, in expressions
8102 Casts are supported in all languages, not just in C, because it is so
8103 useful to cast a number into a pointer in order to examine a structure
8104 at that address in memory.
8105 @c FIXME: casts supported---Mod2 true?
8107 @value{GDBN} supports these operators, in addition to those common
8108 to programming languages:
8112 @samp{@@} is a binary operator for treating parts of memory as arrays.
8113 @xref{Arrays, ,Artificial Arrays}, for more information.
8116 @samp{::} allows you to specify a variable in terms of the file or
8117 function where it is defined. @xref{Variables, ,Program Variables}.
8119 @cindex @{@var{type}@}
8120 @cindex type casting memory
8121 @cindex memory, viewing as typed object
8122 @cindex casts, to view memory
8123 @item @{@var{type}@} @var{addr}
8124 Refers to an object of type @var{type} stored at address @var{addr} in
8125 memory. @var{addr} may be any expression whose value is an integer or
8126 pointer (but parentheses are required around binary operators, just as in
8127 a cast). This construct is allowed regardless of what kind of data is
8128 normally supposed to reside at @var{addr}.
8131 @node Ambiguous Expressions
8132 @section Ambiguous Expressions
8133 @cindex ambiguous expressions
8135 Expressions can sometimes contain some ambiguous elements. For instance,
8136 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8137 a single function name to be defined several times, for application in
8138 different contexts. This is called @dfn{overloading}. Another example
8139 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8140 templates and is typically instantiated several times, resulting in
8141 the same function name being defined in different contexts.
8143 In some cases and depending on the language, it is possible to adjust
8144 the expression to remove the ambiguity. For instance in C@t{++}, you
8145 can specify the signature of the function you want to break on, as in
8146 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8147 qualified name of your function often makes the expression unambiguous
8150 When an ambiguity that needs to be resolved is detected, the debugger
8151 has the capability to display a menu of numbered choices for each
8152 possibility, and then waits for the selection with the prompt @samp{>}.
8153 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8154 aborts the current command. If the command in which the expression was
8155 used allows more than one choice to be selected, the next option in the
8156 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8159 For example, the following session excerpt shows an attempt to set a
8160 breakpoint at the overloaded symbol @code{String::after}.
8161 We choose three particular definitions of that function name:
8163 @c FIXME! This is likely to change to show arg type lists, at least
8166 (@value{GDBP}) b String::after
8169 [2] file:String.cc; line number:867
8170 [3] file:String.cc; line number:860
8171 [4] file:String.cc; line number:875
8172 [5] file:String.cc; line number:853
8173 [6] file:String.cc; line number:846
8174 [7] file:String.cc; line number:735
8176 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8177 Breakpoint 2 at 0xb344: file String.cc, line 875.
8178 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8179 Multiple breakpoints were set.
8180 Use the "delete" command to delete unwanted
8187 @kindex set multiple-symbols
8188 @item set multiple-symbols @var{mode}
8189 @cindex multiple-symbols menu
8191 This option allows you to adjust the debugger behavior when an expression
8194 By default, @var{mode} is set to @code{all}. If the command with which
8195 the expression is used allows more than one choice, then @value{GDBN}
8196 automatically selects all possible choices. For instance, inserting
8197 a breakpoint on a function using an ambiguous name results in a breakpoint
8198 inserted on each possible match. However, if a unique choice must be made,
8199 then @value{GDBN} uses the menu to help you disambiguate the expression.
8200 For instance, printing the address of an overloaded function will result
8201 in the use of the menu.
8203 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8204 when an ambiguity is detected.
8206 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8207 an error due to the ambiguity and the command is aborted.
8209 @kindex show multiple-symbols
8210 @item show multiple-symbols
8211 Show the current value of the @code{multiple-symbols} setting.
8215 @section Program Variables
8217 The most common kind of expression to use is the name of a variable
8220 Variables in expressions are understood in the selected stack frame
8221 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8225 global (or file-static)
8232 visible according to the scope rules of the
8233 programming language from the point of execution in that frame
8236 @noindent This means that in the function
8251 you can examine and use the variable @code{a} whenever your program is
8252 executing within the function @code{foo}, but you can only use or
8253 examine the variable @code{b} while your program is executing inside
8254 the block where @code{b} is declared.
8256 @cindex variable name conflict
8257 There is an exception: you can refer to a variable or function whose
8258 scope is a single source file even if the current execution point is not
8259 in this file. But it is possible to have more than one such variable or
8260 function with the same name (in different source files). If that
8261 happens, referring to that name has unpredictable effects. If you wish,
8262 you can specify a static variable in a particular function or file by
8263 using the colon-colon (@code{::}) notation:
8265 @cindex colon-colon, context for variables/functions
8267 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8268 @cindex @code{::}, context for variables/functions
8271 @var{file}::@var{variable}
8272 @var{function}::@var{variable}
8276 Here @var{file} or @var{function} is the name of the context for the
8277 static @var{variable}. In the case of file names, you can use quotes to
8278 make sure @value{GDBN} parses the file name as a single word---for example,
8279 to print a global value of @code{x} defined in @file{f2.c}:
8282 (@value{GDBP}) p 'f2.c'::x
8285 The @code{::} notation is normally used for referring to
8286 static variables, since you typically disambiguate uses of local variables
8287 in functions by selecting the appropriate frame and using the
8288 simple name of the variable. However, you may also use this notation
8289 to refer to local variables in frames enclosing the selected frame:
8298 process (a); /* Stop here */
8309 For example, if there is a breakpoint at the commented line,
8310 here is what you might see
8311 when the program stops after executing the call @code{bar(0)}:
8316 (@value{GDBP}) p bar::a
8319 #2 0x080483d0 in foo (a=5) at foobar.c:12
8322 (@value{GDBP}) p bar::a
8326 @cindex C@t{++} scope resolution
8327 These uses of @samp{::} are very rarely in conflict with the very
8328 similar use of the same notation in C@t{++}. When they are in
8329 conflict, the C@t{++} meaning takes precedence; however, this can be
8330 overridden by quoting the file or function name with single quotes.
8332 For example, suppose the program is stopped in a method of a class
8333 that has a field named @code{includefile}, and there is also an
8334 include file named @file{includefile} that defines a variable,
8338 (@value{GDBP}) p includefile
8340 (@value{GDBP}) p includefile::some_global
8341 A syntax error in expression, near `'.
8342 (@value{GDBP}) p 'includefile'::some_global
8346 @cindex wrong values
8347 @cindex variable values, wrong
8348 @cindex function entry/exit, wrong values of variables
8349 @cindex optimized code, wrong values of variables
8351 @emph{Warning:} Occasionally, a local variable may appear to have the
8352 wrong value at certain points in a function---just after entry to a new
8353 scope, and just before exit.
8355 You may see this problem when you are stepping by machine instructions.
8356 This is because, on most machines, it takes more than one instruction to
8357 set up a stack frame (including local variable definitions); if you are
8358 stepping by machine instructions, variables may appear to have the wrong
8359 values until the stack frame is completely built. On exit, it usually
8360 also takes more than one machine instruction to destroy a stack frame;
8361 after you begin stepping through that group of instructions, local
8362 variable definitions may be gone.
8364 This may also happen when the compiler does significant optimizations.
8365 To be sure of always seeing accurate values, turn off all optimization
8368 @cindex ``No symbol "foo" in current context''
8369 Another possible effect of compiler optimizations is to optimize
8370 unused variables out of existence, or assign variables to registers (as
8371 opposed to memory addresses). Depending on the support for such cases
8372 offered by the debug info format used by the compiler, @value{GDBN}
8373 might not be able to display values for such local variables. If that
8374 happens, @value{GDBN} will print a message like this:
8377 No symbol "foo" in current context.
8380 To solve such problems, either recompile without optimizations, or use a
8381 different debug info format, if the compiler supports several such
8382 formats. @xref{Compilation}, for more information on choosing compiler
8383 options. @xref{C, ,C and C@t{++}}, for more information about debug
8384 info formats that are best suited to C@t{++} programs.
8386 If you ask to print an object whose contents are unknown to
8387 @value{GDBN}, e.g., because its data type is not completely specified
8388 by the debug information, @value{GDBN} will say @samp{<incomplete
8389 type>}. @xref{Symbols, incomplete type}, for more about this.
8391 If you append @kbd{@@entry} string to a function parameter name you get its
8392 value at the time the function got called. If the value is not available an
8393 error message is printed. Entry values are available only with some compilers.
8394 Entry values are normally also printed at the function parameter list according
8395 to @ref{set print entry-values}.
8398 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8404 (gdb) print i@@entry
8408 Strings are identified as arrays of @code{char} values without specified
8409 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8410 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8411 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8412 defines literal string type @code{"char"} as @code{char} without a sign.
8417 signed char var1[] = "A";
8420 You get during debugging
8425 $2 = @{65 'A', 0 '\0'@}
8429 @section Artificial Arrays
8431 @cindex artificial array
8433 @kindex @@@r{, referencing memory as an array}
8434 It is often useful to print out several successive objects of the
8435 same type in memory; a section of an array, or an array of
8436 dynamically determined size for which only a pointer exists in the
8439 You can do this by referring to a contiguous span of memory as an
8440 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8441 operand of @samp{@@} should be the first element of the desired array
8442 and be an individual object. The right operand should be the desired length
8443 of the array. The result is an array value whose elements are all of
8444 the type of the left argument. The first element is actually the left
8445 argument; the second element comes from bytes of memory immediately
8446 following those that hold the first element, and so on. Here is an
8447 example. If a program says
8450 int *array = (int *) malloc (len * sizeof (int));
8454 you can print the contents of @code{array} with
8460 The left operand of @samp{@@} must reside in memory. Array values made
8461 with @samp{@@} in this way behave just like other arrays in terms of
8462 subscripting, and are coerced to pointers when used in expressions.
8463 Artificial arrays most often appear in expressions via the value history
8464 (@pxref{Value History, ,Value History}), after printing one out.
8466 Another way to create an artificial array is to use a cast.
8467 This re-interprets a value as if it were an array.
8468 The value need not be in memory:
8470 (@value{GDBP}) p/x (short[2])0x12345678
8471 $1 = @{0x1234, 0x5678@}
8474 As a convenience, if you leave the array length out (as in
8475 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8476 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8478 (@value{GDBP}) p/x (short[])0x12345678
8479 $2 = @{0x1234, 0x5678@}
8482 Sometimes the artificial array mechanism is not quite enough; in
8483 moderately complex data structures, the elements of interest may not
8484 actually be adjacent---for example, if you are interested in the values
8485 of pointers in an array. One useful work-around in this situation is
8486 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8487 Variables}) as a counter in an expression that prints the first
8488 interesting value, and then repeat that expression via @key{RET}. For
8489 instance, suppose you have an array @code{dtab} of pointers to
8490 structures, and you are interested in the values of a field @code{fv}
8491 in each structure. Here is an example of what you might type:
8501 @node Output Formats
8502 @section Output Formats
8504 @cindex formatted output
8505 @cindex output formats
8506 By default, @value{GDBN} prints a value according to its data type. Sometimes
8507 this is not what you want. For example, you might want to print a number
8508 in hex, or a pointer in decimal. Or you might want to view data in memory
8509 at a certain address as a character string or as an instruction. To do
8510 these things, specify an @dfn{output format} when you print a value.
8512 The simplest use of output formats is to say how to print a value
8513 already computed. This is done by starting the arguments of the
8514 @code{print} command with a slash and a format letter. The format
8515 letters supported are:
8519 Regard the bits of the value as an integer, and print the integer in
8523 Print as integer in signed decimal.
8526 Print as integer in unsigned decimal.
8529 Print as integer in octal.
8532 Print as integer in binary. The letter @samp{t} stands for ``two''.
8533 @footnote{@samp{b} cannot be used because these format letters are also
8534 used with the @code{x} command, where @samp{b} stands for ``byte'';
8535 see @ref{Memory,,Examining Memory}.}
8538 @cindex unknown address, locating
8539 @cindex locate address
8540 Print as an address, both absolute in hexadecimal and as an offset from
8541 the nearest preceding symbol. You can use this format used to discover
8542 where (in what function) an unknown address is located:
8545 (@value{GDBP}) p/a 0x54320
8546 $3 = 0x54320 <_initialize_vx+396>
8550 The command @code{info symbol 0x54320} yields similar results.
8551 @xref{Symbols, info symbol}.
8554 Regard as an integer and print it as a character constant. This
8555 prints both the numerical value and its character representation. The
8556 character representation is replaced with the octal escape @samp{\nnn}
8557 for characters outside the 7-bit @sc{ascii} range.
8559 Without this format, @value{GDBN} displays @code{char},
8560 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8561 constants. Single-byte members of vectors are displayed as integer
8565 Regard the bits of the value as a floating point number and print
8566 using typical floating point syntax.
8569 @cindex printing strings
8570 @cindex printing byte arrays
8571 Regard as a string, if possible. With this format, pointers to single-byte
8572 data are displayed as null-terminated strings and arrays of single-byte data
8573 are displayed as fixed-length strings. Other values are displayed in their
8576 Without this format, @value{GDBN} displays pointers to and arrays of
8577 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8578 strings. Single-byte members of a vector are displayed as an integer
8582 Like @samp{x} formatting, the value is treated as an integer and
8583 printed as hexadecimal, but leading zeros are printed to pad the value
8584 to the size of the integer type.
8587 @cindex raw printing
8588 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8589 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8590 Printing}). This typically results in a higher-level display of the
8591 value's contents. The @samp{r} format bypasses any Python
8592 pretty-printer which might exist.
8595 For example, to print the program counter in hex (@pxref{Registers}), type
8602 Note that no space is required before the slash; this is because command
8603 names in @value{GDBN} cannot contain a slash.
8605 To reprint the last value in the value history with a different format,
8606 you can use the @code{print} command with just a format and no
8607 expression. For example, @samp{p/x} reprints the last value in hex.
8610 @section Examining Memory
8612 You can use the command @code{x} (for ``examine'') to examine memory in
8613 any of several formats, independently of your program's data types.
8615 @cindex examining memory
8617 @kindex x @r{(examine memory)}
8618 @item x/@var{nfu} @var{addr}
8621 Use the @code{x} command to examine memory.
8624 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8625 much memory to display and how to format it; @var{addr} is an
8626 expression giving the address where you want to start displaying memory.
8627 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8628 Several commands set convenient defaults for @var{addr}.
8631 @item @var{n}, the repeat count
8632 The repeat count is a decimal integer; the default is 1. It specifies
8633 how much memory (counting by units @var{u}) to display.
8634 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8637 @item @var{f}, the display format
8638 The display format is one of the formats used by @code{print}
8639 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8640 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8641 The default is @samp{x} (hexadecimal) initially. The default changes
8642 each time you use either @code{x} or @code{print}.
8644 @item @var{u}, the unit size
8645 The unit size is any of
8651 Halfwords (two bytes).
8653 Words (four bytes). This is the initial default.
8655 Giant words (eight bytes).
8658 Each time you specify a unit size with @code{x}, that size becomes the
8659 default unit the next time you use @code{x}. For the @samp{i} format,
8660 the unit size is ignored and is normally not written. For the @samp{s} format,
8661 the unit size defaults to @samp{b}, unless it is explicitly given.
8662 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8663 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8664 Note that the results depend on the programming language of the
8665 current compilation unit. If the language is C, the @samp{s}
8666 modifier will use the UTF-16 encoding while @samp{w} will use
8667 UTF-32. The encoding is set by the programming language and cannot
8670 @item @var{addr}, starting display address
8671 @var{addr} is the address where you want @value{GDBN} to begin displaying
8672 memory. The expression need not have a pointer value (though it may);
8673 it is always interpreted as an integer address of a byte of memory.
8674 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8675 @var{addr} is usually just after the last address examined---but several
8676 other commands also set the default address: @code{info breakpoints} (to
8677 the address of the last breakpoint listed), @code{info line} (to the
8678 starting address of a line), and @code{print} (if you use it to display
8679 a value from memory).
8682 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8683 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8684 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8685 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8686 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8688 Since the letters indicating unit sizes are all distinct from the
8689 letters specifying output formats, you do not have to remember whether
8690 unit size or format comes first; either order works. The output
8691 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8692 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8694 Even though the unit size @var{u} is ignored for the formats @samp{s}
8695 and @samp{i}, you might still want to use a count @var{n}; for example,
8696 @samp{3i} specifies that you want to see three machine instructions,
8697 including any operands. For convenience, especially when used with
8698 the @code{display} command, the @samp{i} format also prints branch delay
8699 slot instructions, if any, beyond the count specified, which immediately
8700 follow the last instruction that is within the count. The command
8701 @code{disassemble} gives an alternative way of inspecting machine
8702 instructions; see @ref{Machine Code,,Source and Machine Code}.
8704 All the defaults for the arguments to @code{x} are designed to make it
8705 easy to continue scanning memory with minimal specifications each time
8706 you use @code{x}. For example, after you have inspected three machine
8707 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8708 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8709 the repeat count @var{n} is used again; the other arguments default as
8710 for successive uses of @code{x}.
8712 When examining machine instructions, the instruction at current program
8713 counter is shown with a @code{=>} marker. For example:
8716 (@value{GDBP}) x/5i $pc-6
8717 0x804837f <main+11>: mov %esp,%ebp
8718 0x8048381 <main+13>: push %ecx
8719 0x8048382 <main+14>: sub $0x4,%esp
8720 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8721 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8724 @cindex @code{$_}, @code{$__}, and value history
8725 The addresses and contents printed by the @code{x} command are not saved
8726 in the value history because there is often too much of them and they
8727 would get in the way. Instead, @value{GDBN} makes these values available for
8728 subsequent use in expressions as values of the convenience variables
8729 @code{$_} and @code{$__}. After an @code{x} command, the last address
8730 examined is available for use in expressions in the convenience variable
8731 @code{$_}. The contents of that address, as examined, are available in
8732 the convenience variable @code{$__}.
8734 If the @code{x} command has a repeat count, the address and contents saved
8735 are from the last memory unit printed; this is not the same as the last
8736 address printed if several units were printed on the last line of output.
8738 @cindex remote memory comparison
8739 @cindex verify remote memory image
8740 When you are debugging a program running on a remote target machine
8741 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8742 remote machine's memory against the executable file you downloaded to
8743 the target. The @code{compare-sections} command is provided for such
8747 @kindex compare-sections
8748 @item compare-sections @r{[}@var{section-name}@r{]}
8749 Compare the data of a loadable section @var{section-name} in the
8750 executable file of the program being debugged with the same section in
8751 the remote machine's memory, and report any mismatches. With no
8752 arguments, compares all loadable sections. This command's
8753 availability depends on the target's support for the @code{"qCRC"}
8758 @section Automatic Display
8759 @cindex automatic display
8760 @cindex display of expressions
8762 If you find that you want to print the value of an expression frequently
8763 (to see how it changes), you might want to add it to the @dfn{automatic
8764 display list} so that @value{GDBN} prints its value each time your program stops.
8765 Each expression added to the list is given a number to identify it;
8766 to remove an expression from the list, you specify that number.
8767 The automatic display looks like this:
8771 3: bar[5] = (struct hack *) 0x3804
8775 This display shows item numbers, expressions and their current values. As with
8776 displays you request manually using @code{x} or @code{print}, you can
8777 specify the output format you prefer; in fact, @code{display} decides
8778 whether to use @code{print} or @code{x} depending your format
8779 specification---it uses @code{x} if you specify either the @samp{i}
8780 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8784 @item display @var{expr}
8785 Add the expression @var{expr} to the list of expressions to display
8786 each time your program stops. @xref{Expressions, ,Expressions}.
8788 @code{display} does not repeat if you press @key{RET} again after using it.
8790 @item display/@var{fmt} @var{expr}
8791 For @var{fmt} specifying only a display format and not a size or
8792 count, add the expression @var{expr} to the auto-display list but
8793 arrange to display it each time in the specified format @var{fmt}.
8794 @xref{Output Formats,,Output Formats}.
8796 @item display/@var{fmt} @var{addr}
8797 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8798 number of units, add the expression @var{addr} as a memory address to
8799 be examined each time your program stops. Examining means in effect
8800 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8803 For example, @samp{display/i $pc} can be helpful, to see the machine
8804 instruction about to be executed each time execution stops (@samp{$pc}
8805 is a common name for the program counter; @pxref{Registers, ,Registers}).
8808 @kindex delete display
8810 @item undisplay @var{dnums}@dots{}
8811 @itemx delete display @var{dnums}@dots{}
8812 Remove items from the list of expressions to display. Specify the
8813 numbers of the displays that you want affected with the command
8814 argument @var{dnums}. It can be a single display number, one of the
8815 numbers shown in the first field of the @samp{info display} display;
8816 or it could be a range of display numbers, as in @code{2-4}.
8818 @code{undisplay} does not repeat if you press @key{RET} after using it.
8819 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8821 @kindex disable display
8822 @item disable display @var{dnums}@dots{}
8823 Disable the display of item numbers @var{dnums}. A disabled display
8824 item is not printed automatically, but is not forgotten. It may be
8825 enabled again later. Specify the numbers of the displays that you
8826 want affected with the command argument @var{dnums}. It can be a
8827 single display number, one of the numbers shown in the first field of
8828 the @samp{info display} display; or it could be a range of display
8829 numbers, as in @code{2-4}.
8831 @kindex enable display
8832 @item enable display @var{dnums}@dots{}
8833 Enable display of item numbers @var{dnums}. It becomes effective once
8834 again in auto display of its expression, until you specify otherwise.
8835 Specify the numbers of the displays that you want affected with the
8836 command argument @var{dnums}. It can be a single display number, one
8837 of the numbers shown in the first field of the @samp{info display}
8838 display; or it could be a range of display numbers, as in @code{2-4}.
8841 Display the current values of the expressions on the list, just as is
8842 done when your program stops.
8844 @kindex info display
8846 Print the list of expressions previously set up to display
8847 automatically, each one with its item number, but without showing the
8848 values. This includes disabled expressions, which are marked as such.
8849 It also includes expressions which would not be displayed right now
8850 because they refer to automatic variables not currently available.
8853 @cindex display disabled out of scope
8854 If a display expression refers to local variables, then it does not make
8855 sense outside the lexical context for which it was set up. Such an
8856 expression is disabled when execution enters a context where one of its
8857 variables is not defined. For example, if you give the command
8858 @code{display last_char} while inside a function with an argument
8859 @code{last_char}, @value{GDBN} displays this argument while your program
8860 continues to stop inside that function. When it stops elsewhere---where
8861 there is no variable @code{last_char}---the display is disabled
8862 automatically. The next time your program stops where @code{last_char}
8863 is meaningful, you can enable the display expression once again.
8865 @node Print Settings
8866 @section Print Settings
8868 @cindex format options
8869 @cindex print settings
8870 @value{GDBN} provides the following ways to control how arrays, structures,
8871 and symbols are printed.
8874 These settings are useful for debugging programs in any language:
8878 @item set print address
8879 @itemx set print address on
8880 @cindex print/don't print memory addresses
8881 @value{GDBN} prints memory addresses showing the location of stack
8882 traces, structure values, pointer values, breakpoints, and so forth,
8883 even when it also displays the contents of those addresses. The default
8884 is @code{on}. For example, this is what a stack frame display looks like with
8885 @code{set print address on}:
8890 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8892 530 if (lquote != def_lquote)
8896 @item set print address off
8897 Do not print addresses when displaying their contents. For example,
8898 this is the same stack frame displayed with @code{set print address off}:
8902 (@value{GDBP}) set print addr off
8904 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8905 530 if (lquote != def_lquote)
8909 You can use @samp{set print address off} to eliminate all machine
8910 dependent displays from the @value{GDBN} interface. For example, with
8911 @code{print address off}, you should get the same text for backtraces on
8912 all machines---whether or not they involve pointer arguments.
8915 @item show print address
8916 Show whether or not addresses are to be printed.
8919 When @value{GDBN} prints a symbolic address, it normally prints the
8920 closest earlier symbol plus an offset. If that symbol does not uniquely
8921 identify the address (for example, it is a name whose scope is a single
8922 source file), you may need to clarify. One way to do this is with
8923 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8924 you can set @value{GDBN} to print the source file and line number when
8925 it prints a symbolic address:
8928 @item set print symbol-filename on
8929 @cindex source file and line of a symbol
8930 @cindex symbol, source file and line
8931 Tell @value{GDBN} to print the source file name and line number of a
8932 symbol in the symbolic form of an address.
8934 @item set print symbol-filename off
8935 Do not print source file name and line number of a symbol. This is the
8938 @item show print symbol-filename
8939 Show whether or not @value{GDBN} will print the source file name and
8940 line number of a symbol in the symbolic form of an address.
8943 Another situation where it is helpful to show symbol filenames and line
8944 numbers is when disassembling code; @value{GDBN} shows you the line
8945 number and source file that corresponds to each instruction.
8947 Also, you may wish to see the symbolic form only if the address being
8948 printed is reasonably close to the closest earlier symbol:
8951 @item set print max-symbolic-offset @var{max-offset}
8952 @itemx set print max-symbolic-offset unlimited
8953 @cindex maximum value for offset of closest symbol
8954 Tell @value{GDBN} to only display the symbolic form of an address if the
8955 offset between the closest earlier symbol and the address is less than
8956 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8957 to always print the symbolic form of an address if any symbol precedes
8958 it. Zero is equivalent to @code{unlimited}.
8960 @item show print max-symbolic-offset
8961 Ask how large the maximum offset is that @value{GDBN} prints in a
8965 @cindex wild pointer, interpreting
8966 @cindex pointer, finding referent
8967 If you have a pointer and you are not sure where it points, try
8968 @samp{set print symbol-filename on}. Then you can determine the name
8969 and source file location of the variable where it points, using
8970 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8971 For example, here @value{GDBN} shows that a variable @code{ptt} points
8972 at another variable @code{t}, defined in @file{hi2.c}:
8975 (@value{GDBP}) set print symbol-filename on
8976 (@value{GDBP}) p/a ptt
8977 $4 = 0xe008 <t in hi2.c>
8981 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8982 does not show the symbol name and filename of the referent, even with
8983 the appropriate @code{set print} options turned on.
8986 You can also enable @samp{/a}-like formatting all the time using
8987 @samp{set print symbol on}:
8990 @item set print symbol on
8991 Tell @value{GDBN} to print the symbol corresponding to an address, if
8994 @item set print symbol off
8995 Tell @value{GDBN} not to print the symbol corresponding to an
8996 address. In this mode, @value{GDBN} will still print the symbol
8997 corresponding to pointers to functions. This is the default.
8999 @item show print symbol
9000 Show whether @value{GDBN} will display the symbol corresponding to an
9004 Other settings control how different kinds of objects are printed:
9007 @item set print array
9008 @itemx set print array on
9009 @cindex pretty print arrays
9010 Pretty print arrays. This format is more convenient to read,
9011 but uses more space. The default is off.
9013 @item set print array off
9014 Return to compressed format for arrays.
9016 @item show print array
9017 Show whether compressed or pretty format is selected for displaying
9020 @cindex print array indexes
9021 @item set print array-indexes
9022 @itemx set print array-indexes on
9023 Print the index of each element when displaying arrays. May be more
9024 convenient to locate a given element in the array or quickly find the
9025 index of a given element in that printed array. The default is off.
9027 @item set print array-indexes off
9028 Stop printing element indexes when displaying arrays.
9030 @item show print array-indexes
9031 Show whether the index of each element is printed when displaying
9034 @item set print elements @var{number-of-elements}
9035 @itemx set print elements unlimited
9036 @cindex number of array elements to print
9037 @cindex limit on number of printed array elements
9038 Set a limit on how many elements of an array @value{GDBN} will print.
9039 If @value{GDBN} is printing a large array, it stops printing after it has
9040 printed the number of elements set by the @code{set print elements} command.
9041 This limit also applies to the display of strings.
9042 When @value{GDBN} starts, this limit is set to 200.
9043 Setting @var{number-of-elements} to @code{unlimited} or zero means
9044 that the number of elements to print is unlimited.
9046 @item show print elements
9047 Display the number of elements of a large array that @value{GDBN} will print.
9048 If the number is 0, then the printing is unlimited.
9050 @item set print frame-arguments @var{value}
9051 @kindex set print frame-arguments
9052 @cindex printing frame argument values
9053 @cindex print all frame argument values
9054 @cindex print frame argument values for scalars only
9055 @cindex do not print frame argument values
9056 This command allows to control how the values of arguments are printed
9057 when the debugger prints a frame (@pxref{Frames}). The possible
9062 The values of all arguments are printed.
9065 Print the value of an argument only if it is a scalar. The value of more
9066 complex arguments such as arrays, structures, unions, etc, is replaced
9067 by @code{@dots{}}. This is the default. Here is an example where
9068 only scalar arguments are shown:
9071 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9076 None of the argument values are printed. Instead, the value of each argument
9077 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9080 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9085 By default, only scalar arguments are printed. This command can be used
9086 to configure the debugger to print the value of all arguments, regardless
9087 of their type. However, it is often advantageous to not print the value
9088 of more complex parameters. For instance, it reduces the amount of
9089 information printed in each frame, making the backtrace more readable.
9090 Also, it improves performance when displaying Ada frames, because
9091 the computation of large arguments can sometimes be CPU-intensive,
9092 especially in large applications. Setting @code{print frame-arguments}
9093 to @code{scalars} (the default) or @code{none} avoids this computation,
9094 thus speeding up the display of each Ada frame.
9096 @item show print frame-arguments
9097 Show how the value of arguments should be displayed when printing a frame.
9099 @item set print raw frame-arguments on
9100 Print frame arguments in raw, non pretty-printed, form.
9102 @item set print raw frame-arguments off
9103 Print frame arguments in pretty-printed form, if there is a pretty-printer
9104 for the value (@pxref{Pretty Printing}),
9105 otherwise print the value in raw form.
9106 This is the default.
9108 @item show print raw frame-arguments
9109 Show whether to print frame arguments in raw form.
9111 @anchor{set print entry-values}
9112 @item set print entry-values @var{value}
9113 @kindex set print entry-values
9114 Set printing of frame argument values at function entry. In some cases
9115 @value{GDBN} can determine the value of function argument which was passed by
9116 the function caller, even if the value was modified inside the called function
9117 and therefore is different. With optimized code, the current value could be
9118 unavailable, but the entry value may still be known.
9120 The default value is @code{default} (see below for its description). Older
9121 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9122 this feature will behave in the @code{default} setting the same way as with the
9125 This functionality is currently supported only by DWARF 2 debugging format and
9126 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9127 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9130 The @var{value} parameter can be one of the following:
9134 Print only actual parameter values, never print values from function entry
9138 #0 different (val=6)
9139 #0 lost (val=<optimized out>)
9141 #0 invalid (val=<optimized out>)
9145 Print only parameter values from function entry point. The actual parameter
9146 values are never printed.
9148 #0 equal (val@@entry=5)
9149 #0 different (val@@entry=5)
9150 #0 lost (val@@entry=5)
9151 #0 born (val@@entry=<optimized out>)
9152 #0 invalid (val@@entry=<optimized out>)
9156 Print only parameter values from function entry point. If value from function
9157 entry point is not known while the actual value is known, print the actual
9158 value for such parameter.
9160 #0 equal (val@@entry=5)
9161 #0 different (val@@entry=5)
9162 #0 lost (val@@entry=5)
9164 #0 invalid (val@@entry=<optimized out>)
9168 Print actual parameter values. If actual parameter value is not known while
9169 value from function entry point is known, print the entry point value for such
9173 #0 different (val=6)
9174 #0 lost (val@@entry=5)
9176 #0 invalid (val=<optimized out>)
9180 Always print both the actual parameter value and its value from function entry
9181 point, even if values of one or both are not available due to compiler
9184 #0 equal (val=5, val@@entry=5)
9185 #0 different (val=6, val@@entry=5)
9186 #0 lost (val=<optimized out>, val@@entry=5)
9187 #0 born (val=10, val@@entry=<optimized out>)
9188 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9192 Print the actual parameter value if it is known and also its value from
9193 function entry point if it is known. If neither is known, print for the actual
9194 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9195 values are known and identical, print the shortened
9196 @code{param=param@@entry=VALUE} notation.
9198 #0 equal (val=val@@entry=5)
9199 #0 different (val=6, val@@entry=5)
9200 #0 lost (val@@entry=5)
9202 #0 invalid (val=<optimized out>)
9206 Always print the actual parameter value. Print also its value from function
9207 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9208 if both values are known and identical, print the shortened
9209 @code{param=param@@entry=VALUE} notation.
9211 #0 equal (val=val@@entry=5)
9212 #0 different (val=6, val@@entry=5)
9213 #0 lost (val=<optimized out>, val@@entry=5)
9215 #0 invalid (val=<optimized out>)
9219 For analysis messages on possible failures of frame argument values at function
9220 entry resolution see @ref{set debug entry-values}.
9222 @item show print entry-values
9223 Show the method being used for printing of frame argument values at function
9226 @item set print repeats @var{number-of-repeats}
9227 @itemx set print repeats unlimited
9228 @cindex repeated array elements
9229 Set the threshold for suppressing display of repeated array
9230 elements. When the number of consecutive identical elements of an
9231 array exceeds the threshold, @value{GDBN} prints the string
9232 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9233 identical repetitions, instead of displaying the identical elements
9234 themselves. Setting the threshold to @code{unlimited} or zero will
9235 cause all elements to be individually printed. The default threshold
9238 @item show print repeats
9239 Display the current threshold for printing repeated identical
9242 @item set print null-stop
9243 @cindex @sc{null} elements in arrays
9244 Cause @value{GDBN} to stop printing the characters of an array when the first
9245 @sc{null} is encountered. This is useful when large arrays actually
9246 contain only short strings.
9249 @item show print null-stop
9250 Show whether @value{GDBN} stops printing an array on the first
9251 @sc{null} character.
9253 @item set print pretty on
9254 @cindex print structures in indented form
9255 @cindex indentation in structure display
9256 Cause @value{GDBN} to print structures in an indented format with one member
9257 per line, like this:
9272 @item set print pretty off
9273 Cause @value{GDBN} to print structures in a compact format, like this:
9277 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9278 meat = 0x54 "Pork"@}
9283 This is the default format.
9285 @item show print pretty
9286 Show which format @value{GDBN} is using to print structures.
9288 @item set print sevenbit-strings on
9289 @cindex eight-bit characters in strings
9290 @cindex octal escapes in strings
9291 Print using only seven-bit characters; if this option is set,
9292 @value{GDBN} displays any eight-bit characters (in strings or
9293 character values) using the notation @code{\}@var{nnn}. This setting is
9294 best if you are working in English (@sc{ascii}) and you use the
9295 high-order bit of characters as a marker or ``meta'' bit.
9297 @item set print sevenbit-strings off
9298 Print full eight-bit characters. This allows the use of more
9299 international character sets, and is the default.
9301 @item show print sevenbit-strings
9302 Show whether or not @value{GDBN} is printing only seven-bit characters.
9304 @item set print union on
9305 @cindex unions in structures, printing
9306 Tell @value{GDBN} to print unions which are contained in structures
9307 and other unions. This is the default setting.
9309 @item set print union off
9310 Tell @value{GDBN} not to print unions which are contained in
9311 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9314 @item show print union
9315 Ask @value{GDBN} whether or not it will print unions which are contained in
9316 structures and other unions.
9318 For example, given the declarations
9321 typedef enum @{Tree, Bug@} Species;
9322 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9323 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9334 struct thing foo = @{Tree, @{Acorn@}@};
9338 with @code{set print union on} in effect @samp{p foo} would print
9341 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9345 and with @code{set print union off} in effect it would print
9348 $1 = @{it = Tree, form = @{...@}@}
9352 @code{set print union} affects programs written in C-like languages
9358 These settings are of interest when debugging C@t{++} programs:
9361 @cindex demangling C@t{++} names
9362 @item set print demangle
9363 @itemx set print demangle on
9364 Print C@t{++} names in their source form rather than in the encoded
9365 (``mangled'') form passed to the assembler and linker for type-safe
9366 linkage. The default is on.
9368 @item show print demangle
9369 Show whether C@t{++} names are printed in mangled or demangled form.
9371 @item set print asm-demangle
9372 @itemx set print asm-demangle on
9373 Print C@t{++} names in their source form rather than their mangled form, even
9374 in assembler code printouts such as instruction disassemblies.
9377 @item show print asm-demangle
9378 Show whether C@t{++} names in assembly listings are printed in mangled
9381 @cindex C@t{++} symbol decoding style
9382 @cindex symbol decoding style, C@t{++}
9383 @kindex set demangle-style
9384 @item set demangle-style @var{style}
9385 Choose among several encoding schemes used by different compilers to
9386 represent C@t{++} names. The choices for @var{style} are currently:
9390 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9391 This is the default.
9394 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9397 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9400 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9403 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9404 @strong{Warning:} this setting alone is not sufficient to allow
9405 debugging @code{cfront}-generated executables. @value{GDBN} would
9406 require further enhancement to permit that.
9409 If you omit @var{style}, you will see a list of possible formats.
9411 @item show demangle-style
9412 Display the encoding style currently in use for decoding C@t{++} symbols.
9414 @item set print object
9415 @itemx set print object on
9416 @cindex derived type of an object, printing
9417 @cindex display derived types
9418 When displaying a pointer to an object, identify the @emph{actual}
9419 (derived) type of the object rather than the @emph{declared} type, using
9420 the virtual function table. Note that the virtual function table is
9421 required---this feature can only work for objects that have run-time
9422 type identification; a single virtual method in the object's declared
9423 type is sufficient. Note that this setting is also taken into account when
9424 working with variable objects via MI (@pxref{GDB/MI}).
9426 @item set print object off
9427 Display only the declared type of objects, without reference to the
9428 virtual function table. This is the default setting.
9430 @item show print object
9431 Show whether actual, or declared, object types are displayed.
9433 @item set print static-members
9434 @itemx set print static-members on
9435 @cindex static members of C@t{++} objects
9436 Print static members when displaying a C@t{++} object. The default is on.
9438 @item set print static-members off
9439 Do not print static members when displaying a C@t{++} object.
9441 @item show print static-members
9442 Show whether C@t{++} static members are printed or not.
9444 @item set print pascal_static-members
9445 @itemx set print pascal_static-members on
9446 @cindex static members of Pascal objects
9447 @cindex Pascal objects, static members display
9448 Print static members when displaying a Pascal object. The default is on.
9450 @item set print pascal_static-members off
9451 Do not print static members when displaying a Pascal object.
9453 @item show print pascal_static-members
9454 Show whether Pascal static members are printed or not.
9456 @c These don't work with HP ANSI C++ yet.
9457 @item set print vtbl
9458 @itemx set print vtbl on
9459 @cindex pretty print C@t{++} virtual function tables
9460 @cindex virtual functions (C@t{++}) display
9461 @cindex VTBL display
9462 Pretty print C@t{++} virtual function tables. The default is off.
9463 (The @code{vtbl} commands do not work on programs compiled with the HP
9464 ANSI C@t{++} compiler (@code{aCC}).)
9466 @item set print vtbl off
9467 Do not pretty print C@t{++} virtual function tables.
9469 @item show print vtbl
9470 Show whether C@t{++} virtual function tables are pretty printed, or not.
9473 @node Pretty Printing
9474 @section Pretty Printing
9476 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9477 Python code. It greatly simplifies the display of complex objects. This
9478 mechanism works for both MI and the CLI.
9481 * Pretty-Printer Introduction:: Introduction to pretty-printers
9482 * Pretty-Printer Example:: An example pretty-printer
9483 * Pretty-Printer Commands:: Pretty-printer commands
9486 @node Pretty-Printer Introduction
9487 @subsection Pretty-Printer Introduction
9489 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9490 registered for the value. If there is then @value{GDBN} invokes the
9491 pretty-printer to print the value. Otherwise the value is printed normally.
9493 Pretty-printers are normally named. This makes them easy to manage.
9494 The @samp{info pretty-printer} command will list all the installed
9495 pretty-printers with their names.
9496 If a pretty-printer can handle multiple data types, then its
9497 @dfn{subprinters} are the printers for the individual data types.
9498 Each such subprinter has its own name.
9499 The format of the name is @var{printer-name};@var{subprinter-name}.
9501 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9502 Typically they are automatically loaded and registered when the corresponding
9503 debug information is loaded, thus making them available without having to
9504 do anything special.
9506 There are three places where a pretty-printer can be registered.
9510 Pretty-printers registered globally are available when debugging
9514 Pretty-printers registered with a program space are available only
9515 when debugging that program.
9516 @xref{Progspaces In Python}, for more details on program spaces in Python.
9519 Pretty-printers registered with an objfile are loaded and unloaded
9520 with the corresponding objfile (e.g., shared library).
9521 @xref{Objfiles In Python}, for more details on objfiles in Python.
9524 @xref{Selecting Pretty-Printers}, for further information on how
9525 pretty-printers are selected,
9527 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9530 @node Pretty-Printer Example
9531 @subsection Pretty-Printer Example
9533 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9536 (@value{GDBP}) print s
9538 static npos = 4294967295,
9540 <std::allocator<char>> = @{
9541 <__gnu_cxx::new_allocator<char>> = @{
9542 <No data fields>@}, <No data fields>
9544 members of std::basic_string<char, std::char_traits<char>,
9545 std::allocator<char> >::_Alloc_hider:
9546 _M_p = 0x804a014 "abcd"
9551 With a pretty-printer for @code{std::string} only the contents are printed:
9554 (@value{GDBP}) print s
9558 @node Pretty-Printer Commands
9559 @subsection Pretty-Printer Commands
9560 @cindex pretty-printer commands
9563 @kindex info pretty-printer
9564 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9565 Print the list of installed pretty-printers.
9566 This includes disabled pretty-printers, which are marked as such.
9568 @var{object-regexp} is a regular expression matching the objects
9569 whose pretty-printers to list.
9570 Objects can be @code{global}, the program space's file
9571 (@pxref{Progspaces In Python}),
9572 and the object files within that program space (@pxref{Objfiles In Python}).
9573 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9574 looks up a printer from these three objects.
9576 @var{name-regexp} is a regular expression matching the name of the printers
9579 @kindex disable pretty-printer
9580 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9581 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9582 A disabled pretty-printer is not forgotten, it may be enabled again later.
9584 @kindex enable pretty-printer
9585 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9586 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9591 Suppose we have three pretty-printers installed: one from library1.so
9592 named @code{foo} that prints objects of type @code{foo}, and
9593 another from library2.so named @code{bar} that prints two types of objects,
9594 @code{bar1} and @code{bar2}.
9597 (gdb) info pretty-printer
9604 (gdb) info pretty-printer library2
9609 (gdb) disable pretty-printer library1
9611 2 of 3 printers enabled
9612 (gdb) info pretty-printer
9619 (gdb) disable pretty-printer library2 bar:bar1
9621 1 of 3 printers enabled
9622 (gdb) info pretty-printer library2
9629 (gdb) disable pretty-printer library2 bar
9631 0 of 3 printers enabled
9632 (gdb) info pretty-printer library2
9641 Note that for @code{bar} the entire printer can be disabled,
9642 as can each individual subprinter.
9645 @section Value History
9647 @cindex value history
9648 @cindex history of values printed by @value{GDBN}
9649 Values printed by the @code{print} command are saved in the @value{GDBN}
9650 @dfn{value history}. This allows you to refer to them in other expressions.
9651 Values are kept until the symbol table is re-read or discarded
9652 (for example with the @code{file} or @code{symbol-file} commands).
9653 When the symbol table changes, the value history is discarded,
9654 since the values may contain pointers back to the types defined in the
9659 @cindex history number
9660 The values printed are given @dfn{history numbers} by which you can
9661 refer to them. These are successive integers starting with one.
9662 @code{print} shows you the history number assigned to a value by
9663 printing @samp{$@var{num} = } before the value; here @var{num} is the
9666 To refer to any previous value, use @samp{$} followed by the value's
9667 history number. The way @code{print} labels its output is designed to
9668 remind you of this. Just @code{$} refers to the most recent value in
9669 the history, and @code{$$} refers to the value before that.
9670 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9671 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9672 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9674 For example, suppose you have just printed a pointer to a structure and
9675 want to see the contents of the structure. It suffices to type
9681 If you have a chain of structures where the component @code{next} points
9682 to the next one, you can print the contents of the next one with this:
9689 You can print successive links in the chain by repeating this
9690 command---which you can do by just typing @key{RET}.
9692 Note that the history records values, not expressions. If the value of
9693 @code{x} is 4 and you type these commands:
9701 then the value recorded in the value history by the @code{print} command
9702 remains 4 even though the value of @code{x} has changed.
9707 Print the last ten values in the value history, with their item numbers.
9708 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9709 values} does not change the history.
9711 @item show values @var{n}
9712 Print ten history values centered on history item number @var{n}.
9715 Print ten history values just after the values last printed. If no more
9716 values are available, @code{show values +} produces no display.
9719 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9720 same effect as @samp{show values +}.
9722 @node Convenience Vars
9723 @section Convenience Variables
9725 @cindex convenience variables
9726 @cindex user-defined variables
9727 @value{GDBN} provides @dfn{convenience variables} that you can use within
9728 @value{GDBN} to hold on to a value and refer to it later. These variables
9729 exist entirely within @value{GDBN}; they are not part of your program, and
9730 setting a convenience variable has no direct effect on further execution
9731 of your program. That is why you can use them freely.
9733 Convenience variables are prefixed with @samp{$}. Any name preceded by
9734 @samp{$} can be used for a convenience variable, unless it is one of
9735 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9736 (Value history references, in contrast, are @emph{numbers} preceded
9737 by @samp{$}. @xref{Value History, ,Value History}.)
9739 You can save a value in a convenience variable with an assignment
9740 expression, just as you would set a variable in your program.
9744 set $foo = *object_ptr
9748 would save in @code{$foo} the value contained in the object pointed to by
9751 Using a convenience variable for the first time creates it, but its
9752 value is @code{void} until you assign a new value. You can alter the
9753 value with another assignment at any time.
9755 Convenience variables have no fixed types. You can assign a convenience
9756 variable any type of value, including structures and arrays, even if
9757 that variable already has a value of a different type. The convenience
9758 variable, when used as an expression, has the type of its current value.
9761 @kindex show convenience
9762 @cindex show all user variables and functions
9763 @item show convenience
9764 Print a list of convenience variables used so far, and their values,
9765 as well as a list of the convenience functions.
9766 Abbreviated @code{show conv}.
9768 @kindex init-if-undefined
9769 @cindex convenience variables, initializing
9770 @item init-if-undefined $@var{variable} = @var{expression}
9771 Set a convenience variable if it has not already been set. This is useful
9772 for user-defined commands that keep some state. It is similar, in concept,
9773 to using local static variables with initializers in C (except that
9774 convenience variables are global). It can also be used to allow users to
9775 override default values used in a command script.
9777 If the variable is already defined then the expression is not evaluated so
9778 any side-effects do not occur.
9781 One of the ways to use a convenience variable is as a counter to be
9782 incremented or a pointer to be advanced. For example, to print
9783 a field from successive elements of an array of structures:
9787 print bar[$i++]->contents
9791 Repeat that command by typing @key{RET}.
9793 Some convenience variables are created automatically by @value{GDBN} and given
9794 values likely to be useful.
9797 @vindex $_@r{, convenience variable}
9799 The variable @code{$_} is automatically set by the @code{x} command to
9800 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9801 commands which provide a default address for @code{x} to examine also
9802 set @code{$_} to that address; these commands include @code{info line}
9803 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9804 except when set by the @code{x} command, in which case it is a pointer
9805 to the type of @code{$__}.
9807 @vindex $__@r{, convenience variable}
9809 The variable @code{$__} is automatically set by the @code{x} command
9810 to the value found in the last address examined. Its type is chosen
9811 to match the format in which the data was printed.
9814 @vindex $_exitcode@r{, convenience variable}
9815 When the program being debugged terminates normally, @value{GDBN}
9816 automatically sets this variable to the exit code of the program, and
9817 resets @code{$_exitsignal} to @code{void}.
9820 @vindex $_exitsignal@r{, convenience variable}
9821 When the program being debugged dies due to an uncaught signal,
9822 @value{GDBN} automatically sets this variable to that signal's number,
9823 and resets @code{$_exitcode} to @code{void}.
9825 To distinguish between whether the program being debugged has exited
9826 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9827 @code{$_exitsignal} is not @code{void}), the convenience function
9828 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9829 Functions}). For example, considering the following source code:
9835 main (int argc, char *argv[])
9842 A valid way of telling whether the program being debugged has exited
9843 or signalled would be:
9846 (@value{GDBP}) define has_exited_or_signalled
9847 Type commands for definition of ``has_exited_or_signalled''.
9848 End with a line saying just ``end''.
9849 >if $_isvoid ($_exitsignal)
9850 >echo The program has exited\n
9852 >echo The program has signalled\n
9858 Program terminated with signal SIGALRM, Alarm clock.
9859 The program no longer exists.
9860 (@value{GDBP}) has_exited_or_signalled
9861 The program has signalled
9864 As can be seen, @value{GDBN} correctly informs that the program being
9865 debugged has signalled, since it calls @code{raise} and raises a
9866 @code{SIGALRM} signal. If the program being debugged had not called
9867 @code{raise}, then @value{GDBN} would report a normal exit:
9870 (@value{GDBP}) has_exited_or_signalled
9871 The program has exited
9875 The variable @code{$_exception} is set to the exception object being
9876 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9879 @itemx $_probe_arg0@dots{}$_probe_arg11
9880 Arguments to a static probe. @xref{Static Probe Points}.
9883 @vindex $_sdata@r{, inspect, convenience variable}
9884 The variable @code{$_sdata} contains extra collected static tracepoint
9885 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9886 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9887 if extra static tracepoint data has not been collected.
9890 @vindex $_siginfo@r{, convenience variable}
9891 The variable @code{$_siginfo} contains extra signal information
9892 (@pxref{extra signal information}). Note that @code{$_siginfo}
9893 could be empty, if the application has not yet received any signals.
9894 For example, it will be empty before you execute the @code{run} command.
9897 @vindex $_tlb@r{, convenience variable}
9898 The variable @code{$_tlb} is automatically set when debugging
9899 applications running on MS-Windows in native mode or connected to
9900 gdbserver that supports the @code{qGetTIBAddr} request.
9901 @xref{General Query Packets}.
9902 This variable contains the address of the thread information block.
9906 On HP-UX systems, if you refer to a function or variable name that
9907 begins with a dollar sign, @value{GDBN} searches for a user or system
9908 name first, before it searches for a convenience variable.
9910 @node Convenience Funs
9911 @section Convenience Functions
9913 @cindex convenience functions
9914 @value{GDBN} also supplies some @dfn{convenience functions}. These
9915 have a syntax similar to convenience variables. A convenience
9916 function can be used in an expression just like an ordinary function;
9917 however, a convenience function is implemented internally to
9920 These functions do not require @value{GDBN} to be configured with
9921 @code{Python} support, which means that they are always available.
9925 @item $_isvoid (@var{expr})
9926 @findex $_isvoid@r{, convenience function}
9927 Return one if the expression @var{expr} is @code{void}. Otherwise it
9930 A @code{void} expression is an expression where the type of the result
9931 is @code{void}. For example, you can examine a convenience variable
9932 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
9936 (@value{GDBP}) print $_exitcode
9938 (@value{GDBP}) print $_isvoid ($_exitcode)
9941 Starting program: ./a.out
9942 [Inferior 1 (process 29572) exited normally]
9943 (@value{GDBP}) print $_exitcode
9945 (@value{GDBP}) print $_isvoid ($_exitcode)
9949 In the example above, we used @code{$_isvoid} to check whether
9950 @code{$_exitcode} is @code{void} before and after the execution of the
9951 program being debugged. Before the execution there is no exit code to
9952 be examined, therefore @code{$_exitcode} is @code{void}. After the
9953 execution the program being debugged returned zero, therefore
9954 @code{$_exitcode} is zero, which means that it is not @code{void}
9957 The @code{void} expression can also be a call of a function from the
9958 program being debugged. For example, given the following function:
9967 The result of calling it inside @value{GDBN} is @code{void}:
9970 (@value{GDBP}) print foo ()
9972 (@value{GDBP}) print $_isvoid (foo ())
9974 (@value{GDBP}) set $v = foo ()
9975 (@value{GDBP}) print $v
9977 (@value{GDBP}) print $_isvoid ($v)
9983 These functions require @value{GDBN} to be configured with
9984 @code{Python} support.
9988 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9989 @findex $_memeq@r{, convenience function}
9990 Returns one if the @var{length} bytes at the addresses given by
9991 @var{buf1} and @var{buf2} are equal.
9992 Otherwise it returns zero.
9994 @item $_regex(@var{str}, @var{regex})
9995 @findex $_regex@r{, convenience function}
9996 Returns one if the string @var{str} matches the regular expression
9997 @var{regex}. Otherwise it returns zero.
9998 The syntax of the regular expression is that specified by @code{Python}'s
9999 regular expression support.
10001 @item $_streq(@var{str1}, @var{str2})
10002 @findex $_streq@r{, convenience function}
10003 Returns one if the strings @var{str1} and @var{str2} are equal.
10004 Otherwise it returns zero.
10006 @item $_strlen(@var{str})
10007 @findex $_strlen@r{, convenience function}
10008 Returns the length of string @var{str}.
10012 @value{GDBN} provides the ability to list and get help on
10013 convenience functions.
10016 @item help function
10017 @kindex help function
10018 @cindex show all convenience functions
10019 Print a list of all convenience functions.
10026 You can refer to machine register contents, in expressions, as variables
10027 with names starting with @samp{$}. The names of registers are different
10028 for each machine; use @code{info registers} to see the names used on
10032 @kindex info registers
10033 @item info registers
10034 Print the names and values of all registers except floating-point
10035 and vector registers (in the selected stack frame).
10037 @kindex info all-registers
10038 @cindex floating point registers
10039 @item info all-registers
10040 Print the names and values of all registers, including floating-point
10041 and vector registers (in the selected stack frame).
10043 @item info registers @var{regname} @dots{}
10044 Print the @dfn{relativized} value of each specified register @var{regname}.
10045 As discussed in detail below, register values are normally relative to
10046 the selected stack frame. @var{regname} may be any register name valid on
10047 the machine you are using, with or without the initial @samp{$}.
10050 @cindex stack pointer register
10051 @cindex program counter register
10052 @cindex process status register
10053 @cindex frame pointer register
10054 @cindex standard registers
10055 @value{GDBN} has four ``standard'' register names that are available (in
10056 expressions) on most machines---whenever they do not conflict with an
10057 architecture's canonical mnemonics for registers. The register names
10058 @code{$pc} and @code{$sp} are used for the program counter register and
10059 the stack pointer. @code{$fp} is used for a register that contains a
10060 pointer to the current stack frame, and @code{$ps} is used for a
10061 register that contains the processor status. For example,
10062 you could print the program counter in hex with
10069 or print the instruction to be executed next with
10076 or add four to the stack pointer@footnote{This is a way of removing
10077 one word from the stack, on machines where stacks grow downward in
10078 memory (most machines, nowadays). This assumes that the innermost
10079 stack frame is selected; setting @code{$sp} is not allowed when other
10080 stack frames are selected. To pop entire frames off the stack,
10081 regardless of machine architecture, use @code{return};
10082 see @ref{Returning, ,Returning from a Function}.} with
10088 Whenever possible, these four standard register names are available on
10089 your machine even though the machine has different canonical mnemonics,
10090 so long as there is no conflict. The @code{info registers} command
10091 shows the canonical names. For example, on the SPARC, @code{info
10092 registers} displays the processor status register as @code{$psr} but you
10093 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10094 is an alias for the @sc{eflags} register.
10096 @value{GDBN} always considers the contents of an ordinary register as an
10097 integer when the register is examined in this way. Some machines have
10098 special registers which can hold nothing but floating point; these
10099 registers are considered to have floating point values. There is no way
10100 to refer to the contents of an ordinary register as floating point value
10101 (although you can @emph{print} it as a floating point value with
10102 @samp{print/f $@var{regname}}).
10104 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10105 means that the data format in which the register contents are saved by
10106 the operating system is not the same one that your program normally
10107 sees. For example, the registers of the 68881 floating point
10108 coprocessor are always saved in ``extended'' (raw) format, but all C
10109 programs expect to work with ``double'' (virtual) format. In such
10110 cases, @value{GDBN} normally works with the virtual format only (the format
10111 that makes sense for your program), but the @code{info registers} command
10112 prints the data in both formats.
10114 @cindex SSE registers (x86)
10115 @cindex MMX registers (x86)
10116 Some machines have special registers whose contents can be interpreted
10117 in several different ways. For example, modern x86-based machines
10118 have SSE and MMX registers that can hold several values packed
10119 together in several different formats. @value{GDBN} refers to such
10120 registers in @code{struct} notation:
10123 (@value{GDBP}) print $xmm1
10125 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10126 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10127 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10128 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10129 v4_int32 = @{0, 20657912, 11, 13@},
10130 v2_int64 = @{88725056443645952, 55834574859@},
10131 uint128 = 0x0000000d0000000b013b36f800000000
10136 To set values of such registers, you need to tell @value{GDBN} which
10137 view of the register you wish to change, as if you were assigning
10138 value to a @code{struct} member:
10141 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10144 Normally, register values are relative to the selected stack frame
10145 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10146 value that the register would contain if all stack frames farther in
10147 were exited and their saved registers restored. In order to see the
10148 true contents of hardware registers, you must select the innermost
10149 frame (with @samp{frame 0}).
10151 @cindex caller-saved registers
10152 @cindex call-clobbered registers
10153 @cindex volatile registers
10154 @cindex <not saved> values
10155 Usually ABIs reserve some registers as not needed to be saved by the
10156 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10157 registers). It may therefore not be possible for @value{GDBN} to know
10158 the value a register had before the call (in other words, in the outer
10159 frame), if the register value has since been changed by the callee.
10160 @value{GDBN} tries to deduce where the inner frame saved
10161 (``callee-saved'') registers, from the debug info, unwind info, or the
10162 machine code generated by your compiler. If some register is not
10163 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10164 its own knowledge of the ABI, or because the debug/unwind info
10165 explicitly says the register's value is undefined), @value{GDBN}
10166 displays @w{@samp{<not saved>}} as the register's value. With targets
10167 that @value{GDBN} has no knowledge of the register saving convention,
10168 if a register was not saved by the callee, then its value and location
10169 in the outer frame are assumed to be the same of the inner frame.
10170 This is usually harmless, because if the register is call-clobbered,
10171 the caller either does not care what is in the register after the
10172 call, or has code to restore the value that it does care about. Note,
10173 however, that if you change such a register in the outer frame, you
10174 may also be affecting the inner frame. Also, the more ``outer'' the
10175 frame is you're looking at, the more likely a call-clobbered
10176 register's value is to be wrong, in the sense that it doesn't actually
10177 represent the value the register had just before the call.
10179 @node Floating Point Hardware
10180 @section Floating Point Hardware
10181 @cindex floating point
10183 Depending on the configuration, @value{GDBN} may be able to give
10184 you more information about the status of the floating point hardware.
10189 Display hardware-dependent information about the floating
10190 point unit. The exact contents and layout vary depending on the
10191 floating point chip. Currently, @samp{info float} is supported on
10192 the ARM and x86 machines.
10196 @section Vector Unit
10197 @cindex vector unit
10199 Depending on the configuration, @value{GDBN} may be able to give you
10200 more information about the status of the vector unit.
10203 @kindex info vector
10205 Display information about the vector unit. The exact contents and
10206 layout vary depending on the hardware.
10209 @node OS Information
10210 @section Operating System Auxiliary Information
10211 @cindex OS information
10213 @value{GDBN} provides interfaces to useful OS facilities that can help
10214 you debug your program.
10216 @cindex auxiliary vector
10217 @cindex vector, auxiliary
10218 Some operating systems supply an @dfn{auxiliary vector} to programs at
10219 startup. This is akin to the arguments and environment that you
10220 specify for a program, but contains a system-dependent variety of
10221 binary values that tell system libraries important details about the
10222 hardware, operating system, and process. Each value's purpose is
10223 identified by an integer tag; the meanings are well-known but system-specific.
10224 Depending on the configuration and operating system facilities,
10225 @value{GDBN} may be able to show you this information. For remote
10226 targets, this functionality may further depend on the remote stub's
10227 support of the @samp{qXfer:auxv:read} packet, see
10228 @ref{qXfer auxiliary vector read}.
10233 Display the auxiliary vector of the inferior, which can be either a
10234 live process or a core dump file. @value{GDBN} prints each tag value
10235 numerically, and also shows names and text descriptions for recognized
10236 tags. Some values in the vector are numbers, some bit masks, and some
10237 pointers to strings or other data. @value{GDBN} displays each value in the
10238 most appropriate form for a recognized tag, and in hexadecimal for
10239 an unrecognized tag.
10242 On some targets, @value{GDBN} can access operating system-specific
10243 information and show it to you. The types of information available
10244 will differ depending on the type of operating system running on the
10245 target. The mechanism used to fetch the data is described in
10246 @ref{Operating System Information}. For remote targets, this
10247 functionality depends on the remote stub's support of the
10248 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10252 @item info os @var{infotype}
10254 Display OS information of the requested type.
10256 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10258 @anchor{linux info os infotypes}
10260 @kindex info os processes
10262 Display the list of processes on the target. For each process,
10263 @value{GDBN} prints the process identifier, the name of the user, the
10264 command corresponding to the process, and the list of processor cores
10265 that the process is currently running on. (To understand what these
10266 properties mean, for this and the following info types, please consult
10267 the general @sc{gnu}/Linux documentation.)
10269 @kindex info os procgroups
10271 Display the list of process groups on the target. For each process,
10272 @value{GDBN} prints the identifier of the process group that it belongs
10273 to, the command corresponding to the process group leader, the process
10274 identifier, and the command line of the process. The list is sorted
10275 first by the process group identifier, then by the process identifier,
10276 so that processes belonging to the same process group are grouped together
10277 and the process group leader is listed first.
10279 @kindex info os threads
10281 Display the list of threads running on the target. For each thread,
10282 @value{GDBN} prints the identifier of the process that the thread
10283 belongs to, the command of the process, the thread identifier, and the
10284 processor core that it is currently running on. The main thread of a
10285 process is not listed.
10287 @kindex info os files
10289 Display the list of open file descriptors on the target. For each
10290 file descriptor, @value{GDBN} prints the identifier of the process
10291 owning the descriptor, the command of the owning process, the value
10292 of the descriptor, and the target of the descriptor.
10294 @kindex info os sockets
10296 Display the list of Internet-domain sockets on the target. For each
10297 socket, @value{GDBN} prints the address and port of the local and
10298 remote endpoints, the current state of the connection, the creator of
10299 the socket, the IP address family of the socket, and the type of the
10302 @kindex info os shm
10304 Display the list of all System V shared-memory regions on the target.
10305 For each shared-memory region, @value{GDBN} prints the region key,
10306 the shared-memory identifier, the access permissions, the size of the
10307 region, the process that created the region, the process that last
10308 attached to or detached from the region, the current number of live
10309 attaches to the region, and the times at which the region was last
10310 attached to, detach from, and changed.
10312 @kindex info os semaphores
10314 Display the list of all System V semaphore sets on the target. For each
10315 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10316 set identifier, the access permissions, the number of semaphores in the
10317 set, the user and group of the owner and creator of the semaphore set,
10318 and the times at which the semaphore set was operated upon and changed.
10320 @kindex info os msg
10322 Display the list of all System V message queues on the target. For each
10323 message queue, @value{GDBN} prints the message queue key, the message
10324 queue identifier, the access permissions, the current number of bytes
10325 on the queue, the current number of messages on the queue, the processes
10326 that last sent and received a message on the queue, the user and group
10327 of the owner and creator of the message queue, the times at which a
10328 message was last sent and received on the queue, and the time at which
10329 the message queue was last changed.
10331 @kindex info os modules
10333 Display the list of all loaded kernel modules on the target. For each
10334 module, @value{GDBN} prints the module name, the size of the module in
10335 bytes, the number of times the module is used, the dependencies of the
10336 module, the status of the module, and the address of the loaded module
10341 If @var{infotype} is omitted, then list the possible values for
10342 @var{infotype} and the kind of OS information available for each
10343 @var{infotype}. If the target does not return a list of possible
10344 types, this command will report an error.
10347 @node Memory Region Attributes
10348 @section Memory Region Attributes
10349 @cindex memory region attributes
10351 @dfn{Memory region attributes} allow you to describe special handling
10352 required by regions of your target's memory. @value{GDBN} uses
10353 attributes to determine whether to allow certain types of memory
10354 accesses; whether to use specific width accesses; and whether to cache
10355 target memory. By default the description of memory regions is
10356 fetched from the target (if the current target supports this), but the
10357 user can override the fetched regions.
10359 Defined memory regions can be individually enabled and disabled. When a
10360 memory region is disabled, @value{GDBN} uses the default attributes when
10361 accessing memory in that region. Similarly, if no memory regions have
10362 been defined, @value{GDBN} uses the default attributes when accessing
10365 When a memory region is defined, it is given a number to identify it;
10366 to enable, disable, or remove a memory region, you specify that number.
10370 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10371 Define a memory region bounded by @var{lower} and @var{upper} with
10372 attributes @var{attributes}@dots{}, and add it to the list of regions
10373 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10374 case: it is treated as the target's maximum memory address.
10375 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10378 Discard any user changes to the memory regions and use target-supplied
10379 regions, if available, or no regions if the target does not support.
10382 @item delete mem @var{nums}@dots{}
10383 Remove memory regions @var{nums}@dots{} from the list of regions
10384 monitored by @value{GDBN}.
10386 @kindex disable mem
10387 @item disable mem @var{nums}@dots{}
10388 Disable monitoring of memory regions @var{nums}@dots{}.
10389 A disabled memory region is not forgotten.
10390 It may be enabled again later.
10393 @item enable mem @var{nums}@dots{}
10394 Enable monitoring of memory regions @var{nums}@dots{}.
10398 Print a table of all defined memory regions, with the following columns
10402 @item Memory Region Number
10403 @item Enabled or Disabled.
10404 Enabled memory regions are marked with @samp{y}.
10405 Disabled memory regions are marked with @samp{n}.
10408 The address defining the inclusive lower bound of the memory region.
10411 The address defining the exclusive upper bound of the memory region.
10414 The list of attributes set for this memory region.
10419 @subsection Attributes
10421 @subsubsection Memory Access Mode
10422 The access mode attributes set whether @value{GDBN} may make read or
10423 write accesses to a memory region.
10425 While these attributes prevent @value{GDBN} from performing invalid
10426 memory accesses, they do nothing to prevent the target system, I/O DMA,
10427 etc.@: from accessing memory.
10431 Memory is read only.
10433 Memory is write only.
10435 Memory is read/write. This is the default.
10438 @subsubsection Memory Access Size
10439 The access size attribute tells @value{GDBN} to use specific sized
10440 accesses in the memory region. Often memory mapped device registers
10441 require specific sized accesses. If no access size attribute is
10442 specified, @value{GDBN} may use accesses of any size.
10446 Use 8 bit memory accesses.
10448 Use 16 bit memory accesses.
10450 Use 32 bit memory accesses.
10452 Use 64 bit memory accesses.
10455 @c @subsubsection Hardware/Software Breakpoints
10456 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10457 @c will use hardware or software breakpoints for the internal breakpoints
10458 @c used by the step, next, finish, until, etc. commands.
10462 @c Always use hardware breakpoints
10463 @c @item swbreak (default)
10466 @subsubsection Data Cache
10467 The data cache attributes set whether @value{GDBN} will cache target
10468 memory. While this generally improves performance by reducing debug
10469 protocol overhead, it can lead to incorrect results because @value{GDBN}
10470 does not know about volatile variables or memory mapped device
10475 Enable @value{GDBN} to cache target memory.
10477 Disable @value{GDBN} from caching target memory. This is the default.
10480 @subsection Memory Access Checking
10481 @value{GDBN} can be instructed to refuse accesses to memory that is
10482 not explicitly described. This can be useful if accessing such
10483 regions has undesired effects for a specific target, or to provide
10484 better error checking. The following commands control this behaviour.
10487 @kindex set mem inaccessible-by-default
10488 @item set mem inaccessible-by-default [on|off]
10489 If @code{on} is specified, make @value{GDBN} treat memory not
10490 explicitly described by the memory ranges as non-existent and refuse accesses
10491 to such memory. The checks are only performed if there's at least one
10492 memory range defined. If @code{off} is specified, make @value{GDBN}
10493 treat the memory not explicitly described by the memory ranges as RAM.
10494 The default value is @code{on}.
10495 @kindex show mem inaccessible-by-default
10496 @item show mem inaccessible-by-default
10497 Show the current handling of accesses to unknown memory.
10501 @c @subsubsection Memory Write Verification
10502 @c The memory write verification attributes set whether @value{GDBN}
10503 @c will re-reads data after each write to verify the write was successful.
10507 @c @item noverify (default)
10510 @node Dump/Restore Files
10511 @section Copy Between Memory and a File
10512 @cindex dump/restore files
10513 @cindex append data to a file
10514 @cindex dump data to a file
10515 @cindex restore data from a file
10517 You can use the commands @code{dump}, @code{append}, and
10518 @code{restore} to copy data between target memory and a file. The
10519 @code{dump} and @code{append} commands write data to a file, and the
10520 @code{restore} command reads data from a file back into the inferior's
10521 memory. Files may be in binary, Motorola S-record, Intel hex, or
10522 Tektronix Hex format; however, @value{GDBN} can only append to binary
10528 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10529 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10530 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10531 or the value of @var{expr}, to @var{filename} in the given format.
10533 The @var{format} parameter may be any one of:
10540 Motorola S-record format.
10542 Tektronix Hex format.
10545 @value{GDBN} uses the same definitions of these formats as the
10546 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10547 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10551 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10552 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10553 Append the contents of memory from @var{start_addr} to @var{end_addr},
10554 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10555 (@value{GDBN} can only append data to files in raw binary form.)
10558 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10559 Restore the contents of file @var{filename} into memory. The
10560 @code{restore} command can automatically recognize any known @sc{bfd}
10561 file format, except for raw binary. To restore a raw binary file you
10562 must specify the optional keyword @code{binary} after the filename.
10564 If @var{bias} is non-zero, its value will be added to the addresses
10565 contained in the file. Binary files always start at address zero, so
10566 they will be restored at address @var{bias}. Other bfd files have
10567 a built-in location; they will be restored at offset @var{bias}
10568 from that location.
10570 If @var{start} and/or @var{end} are non-zero, then only data between
10571 file offset @var{start} and file offset @var{end} will be restored.
10572 These offsets are relative to the addresses in the file, before
10573 the @var{bias} argument is applied.
10577 @node Core File Generation
10578 @section How to Produce a Core File from Your Program
10579 @cindex dump core from inferior
10581 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10582 image of a running process and its process status (register values
10583 etc.). Its primary use is post-mortem debugging of a program that
10584 crashed while it ran outside a debugger. A program that crashes
10585 automatically produces a core file, unless this feature is disabled by
10586 the user. @xref{Files}, for information on invoking @value{GDBN} in
10587 the post-mortem debugging mode.
10589 Occasionally, you may wish to produce a core file of the program you
10590 are debugging in order to preserve a snapshot of its state.
10591 @value{GDBN} has a special command for that.
10595 @kindex generate-core-file
10596 @item generate-core-file [@var{file}]
10597 @itemx gcore [@var{file}]
10598 Produce a core dump of the inferior process. The optional argument
10599 @var{file} specifies the file name where to put the core dump. If not
10600 specified, the file name defaults to @file{core.@var{pid}}, where
10601 @var{pid} is the inferior process ID.
10603 Note that this command is implemented only for some systems (as of
10604 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10607 @node Character Sets
10608 @section Character Sets
10609 @cindex character sets
10611 @cindex translating between character sets
10612 @cindex host character set
10613 @cindex target character set
10615 If the program you are debugging uses a different character set to
10616 represent characters and strings than the one @value{GDBN} uses itself,
10617 @value{GDBN} can automatically translate between the character sets for
10618 you. The character set @value{GDBN} uses we call the @dfn{host
10619 character set}; the one the inferior program uses we call the
10620 @dfn{target character set}.
10622 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10623 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10624 remote protocol (@pxref{Remote Debugging}) to debug a program
10625 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10626 then the host character set is Latin-1, and the target character set is
10627 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10628 target-charset EBCDIC-US}, then @value{GDBN} translates between
10629 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10630 character and string literals in expressions.
10632 @value{GDBN} has no way to automatically recognize which character set
10633 the inferior program uses; you must tell it, using the @code{set
10634 target-charset} command, described below.
10636 Here are the commands for controlling @value{GDBN}'s character set
10640 @item set target-charset @var{charset}
10641 @kindex set target-charset
10642 Set the current target character set to @var{charset}. To display the
10643 list of supported target character sets, type
10644 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10646 @item set host-charset @var{charset}
10647 @kindex set host-charset
10648 Set the current host character set to @var{charset}.
10650 By default, @value{GDBN} uses a host character set appropriate to the
10651 system it is running on; you can override that default using the
10652 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10653 automatically determine the appropriate host character set. In this
10654 case, @value{GDBN} uses @samp{UTF-8}.
10656 @value{GDBN} can only use certain character sets as its host character
10657 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10658 @value{GDBN} will list the host character sets it supports.
10660 @item set charset @var{charset}
10661 @kindex set charset
10662 Set the current host and target character sets to @var{charset}. As
10663 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10664 @value{GDBN} will list the names of the character sets that can be used
10665 for both host and target.
10668 @kindex show charset
10669 Show the names of the current host and target character sets.
10671 @item show host-charset
10672 @kindex show host-charset
10673 Show the name of the current host character set.
10675 @item show target-charset
10676 @kindex show target-charset
10677 Show the name of the current target character set.
10679 @item set target-wide-charset @var{charset}
10680 @kindex set target-wide-charset
10681 Set the current target's wide character set to @var{charset}. This is
10682 the character set used by the target's @code{wchar_t} type. To
10683 display the list of supported wide character sets, type
10684 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10686 @item show target-wide-charset
10687 @kindex show target-wide-charset
10688 Show the name of the current target's wide character set.
10691 Here is an example of @value{GDBN}'s character set support in action.
10692 Assume that the following source code has been placed in the file
10693 @file{charset-test.c}:
10699 = @{72, 101, 108, 108, 111, 44, 32, 119,
10700 111, 114, 108, 100, 33, 10, 0@};
10701 char ibm1047_hello[]
10702 = @{200, 133, 147, 147, 150, 107, 64, 166,
10703 150, 153, 147, 132, 90, 37, 0@};
10707 printf ("Hello, world!\n");
10711 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10712 containing the string @samp{Hello, world!} followed by a newline,
10713 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10715 We compile the program, and invoke the debugger on it:
10718 $ gcc -g charset-test.c -o charset-test
10719 $ gdb -nw charset-test
10720 GNU gdb 2001-12-19-cvs
10721 Copyright 2001 Free Software Foundation, Inc.
10726 We can use the @code{show charset} command to see what character sets
10727 @value{GDBN} is currently using to interpret and display characters and
10731 (@value{GDBP}) show charset
10732 The current host and target character set is `ISO-8859-1'.
10736 For the sake of printing this manual, let's use @sc{ascii} as our
10737 initial character set:
10739 (@value{GDBP}) set charset ASCII
10740 (@value{GDBP}) show charset
10741 The current host and target character set is `ASCII'.
10745 Let's assume that @sc{ascii} is indeed the correct character set for our
10746 host system --- in other words, let's assume that if @value{GDBN} prints
10747 characters using the @sc{ascii} character set, our terminal will display
10748 them properly. Since our current target character set is also
10749 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10752 (@value{GDBP}) print ascii_hello
10753 $1 = 0x401698 "Hello, world!\n"
10754 (@value{GDBP}) print ascii_hello[0]
10759 @value{GDBN} uses the target character set for character and string
10760 literals you use in expressions:
10763 (@value{GDBP}) print '+'
10768 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10771 @value{GDBN} relies on the user to tell it which character set the
10772 target program uses. If we print @code{ibm1047_hello} while our target
10773 character set is still @sc{ascii}, we get jibberish:
10776 (@value{GDBP}) print ibm1047_hello
10777 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10778 (@value{GDBP}) print ibm1047_hello[0]
10783 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10784 @value{GDBN} tells us the character sets it supports:
10787 (@value{GDBP}) set target-charset
10788 ASCII EBCDIC-US IBM1047 ISO-8859-1
10789 (@value{GDBP}) set target-charset
10792 We can select @sc{ibm1047} as our target character set, and examine the
10793 program's strings again. Now the @sc{ascii} string is wrong, but
10794 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10795 target character set, @sc{ibm1047}, to the host character set,
10796 @sc{ascii}, and they display correctly:
10799 (@value{GDBP}) set target-charset IBM1047
10800 (@value{GDBP}) show charset
10801 The current host character set is `ASCII'.
10802 The current target character set is `IBM1047'.
10803 (@value{GDBP}) print ascii_hello
10804 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10805 (@value{GDBP}) print ascii_hello[0]
10807 (@value{GDBP}) print ibm1047_hello
10808 $8 = 0x4016a8 "Hello, world!\n"
10809 (@value{GDBP}) print ibm1047_hello[0]
10814 As above, @value{GDBN} uses the target character set for character and
10815 string literals you use in expressions:
10818 (@value{GDBP}) print '+'
10823 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10826 @node Caching Target Data
10827 @section Caching Data of Targets
10828 @cindex caching data of targets
10830 @value{GDBN} caches data exchanged between the debugger and a target.
10831 Each cache is associated with the address space of the inferior.
10832 @xref{Inferiors and Programs}, about inferior and address space.
10833 Such caching generally improves performance in remote debugging
10834 (@pxref{Remote Debugging}), because it reduces the overhead of the
10835 remote protocol by bundling memory reads and writes into large chunks.
10836 Unfortunately, simply caching everything would lead to incorrect results,
10837 since @value{GDBN} does not necessarily know anything about volatile
10838 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
10839 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
10841 Therefore, by default, @value{GDBN} only caches data
10842 known to be on the stack@footnote{In non-stop mode, it is moderately
10843 rare for a running thread to modify the stack of a stopped thread
10844 in a way that would interfere with a backtrace, and caching of
10845 stack reads provides a significant speed up of remote backtraces.} or
10846 in the code segment.
10847 Other regions of memory can be explicitly marked as
10848 cacheable; @pxref{Memory Region Attributes}.
10851 @kindex set remotecache
10852 @item set remotecache on
10853 @itemx set remotecache off
10854 This option no longer does anything; it exists for compatibility
10857 @kindex show remotecache
10858 @item show remotecache
10859 Show the current state of the obsolete remotecache flag.
10861 @kindex set stack-cache
10862 @item set stack-cache on
10863 @itemx set stack-cache off
10864 Enable or disable caching of stack accesses. When @code{on}, use
10865 caching. By default, this option is @code{on}.
10867 @kindex show stack-cache
10868 @item show stack-cache
10869 Show the current state of data caching for memory accesses.
10871 @kindex set code-cache
10872 @item set code-cache on
10873 @itemx set code-cache off
10874 Enable or disable caching of code segment accesses. When @code{on},
10875 use caching. By default, this option is @code{on}. This improves
10876 performance of disassembly in remote debugging.
10878 @kindex show code-cache
10879 @item show code-cache
10880 Show the current state of target memory cache for code segment
10883 @kindex info dcache
10884 @item info dcache @r{[}line@r{]}
10885 Print the information about the performance of data cache of the
10886 current inferior's address space. The information displayed
10887 includes the dcache width and depth, and for each cache line, its
10888 number, address, and how many times it was referenced. This
10889 command is useful for debugging the data cache operation.
10891 If a line number is specified, the contents of that line will be
10894 @item set dcache size @var{size}
10895 @cindex dcache size
10896 @kindex set dcache size
10897 Set maximum number of entries in dcache (dcache depth above).
10899 @item set dcache line-size @var{line-size}
10900 @cindex dcache line-size
10901 @kindex set dcache line-size
10902 Set number of bytes each dcache entry caches (dcache width above).
10903 Must be a power of 2.
10905 @item show dcache size
10906 @kindex show dcache size
10907 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
10909 @item show dcache line-size
10910 @kindex show dcache line-size
10911 Show default size of dcache lines.
10915 @node Searching Memory
10916 @section Search Memory
10917 @cindex searching memory
10919 Memory can be searched for a particular sequence of bytes with the
10920 @code{find} command.
10924 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10925 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10926 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10927 etc. The search begins at address @var{start_addr} and continues for either
10928 @var{len} bytes or through to @var{end_addr} inclusive.
10931 @var{s} and @var{n} are optional parameters.
10932 They may be specified in either order, apart or together.
10935 @item @var{s}, search query size
10936 The size of each search query value.
10942 halfwords (two bytes)
10946 giant words (eight bytes)
10949 All values are interpreted in the current language.
10950 This means, for example, that if the current source language is C/C@t{++}
10951 then searching for the string ``hello'' includes the trailing '\0'.
10953 If the value size is not specified, it is taken from the
10954 value's type in the current language.
10955 This is useful when one wants to specify the search
10956 pattern as a mixture of types.
10957 Note that this means, for example, that in the case of C-like languages
10958 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10959 which is typically four bytes.
10961 @item @var{n}, maximum number of finds
10962 The maximum number of matches to print. The default is to print all finds.
10965 You can use strings as search values. Quote them with double-quotes
10967 The string value is copied into the search pattern byte by byte,
10968 regardless of the endianness of the target and the size specification.
10970 The address of each match found is printed as well as a count of the
10971 number of matches found.
10973 The address of the last value found is stored in convenience variable
10975 A count of the number of matches is stored in @samp{$numfound}.
10977 For example, if stopped at the @code{printf} in this function:
10983 static char hello[] = "hello-hello";
10984 static struct @{ char c; short s; int i; @}
10985 __attribute__ ((packed)) mixed
10986 = @{ 'c', 0x1234, 0x87654321 @};
10987 printf ("%s\n", hello);
10992 you get during debugging:
10995 (gdb) find &hello[0], +sizeof(hello), "hello"
10996 0x804956d <hello.1620+6>
10998 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10999 0x8049567 <hello.1620>
11000 0x804956d <hello.1620+6>
11002 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11003 0x8049567 <hello.1620>
11005 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11006 0x8049560 <mixed.1625>
11008 (gdb) print $numfound
11011 $2 = (void *) 0x8049560
11014 @node Optimized Code
11015 @chapter Debugging Optimized Code
11016 @cindex optimized code, debugging
11017 @cindex debugging optimized code
11019 Almost all compilers support optimization. With optimization
11020 disabled, the compiler generates assembly code that corresponds
11021 directly to your source code, in a simplistic way. As the compiler
11022 applies more powerful optimizations, the generated assembly code
11023 diverges from your original source code. With help from debugging
11024 information generated by the compiler, @value{GDBN} can map from
11025 the running program back to constructs from your original source.
11027 @value{GDBN} is more accurate with optimization disabled. If you
11028 can recompile without optimization, it is easier to follow the
11029 progress of your program during debugging. But, there are many cases
11030 where you may need to debug an optimized version.
11032 When you debug a program compiled with @samp{-g -O}, remember that the
11033 optimizer has rearranged your code; the debugger shows you what is
11034 really there. Do not be too surprised when the execution path does not
11035 exactly match your source file! An extreme example: if you define a
11036 variable, but never use it, @value{GDBN} never sees that
11037 variable---because the compiler optimizes it out of existence.
11039 Some things do not work as well with @samp{-g -O} as with just
11040 @samp{-g}, particularly on machines with instruction scheduling. If in
11041 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11042 please report it to us as a bug (including a test case!).
11043 @xref{Variables}, for more information about debugging optimized code.
11046 * Inline Functions:: How @value{GDBN} presents inlining
11047 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11050 @node Inline Functions
11051 @section Inline Functions
11052 @cindex inline functions, debugging
11054 @dfn{Inlining} is an optimization that inserts a copy of the function
11055 body directly at each call site, instead of jumping to a shared
11056 routine. @value{GDBN} displays inlined functions just like
11057 non-inlined functions. They appear in backtraces. You can view their
11058 arguments and local variables, step into them with @code{step}, skip
11059 them with @code{next}, and escape from them with @code{finish}.
11060 You can check whether a function was inlined by using the
11061 @code{info frame} command.
11063 For @value{GDBN} to support inlined functions, the compiler must
11064 record information about inlining in the debug information ---
11065 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11066 other compilers do also. @value{GDBN} only supports inlined functions
11067 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11068 do not emit two required attributes (@samp{DW_AT_call_file} and
11069 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11070 function calls with earlier versions of @value{NGCC}. It instead
11071 displays the arguments and local variables of inlined functions as
11072 local variables in the caller.
11074 The body of an inlined function is directly included at its call site;
11075 unlike a non-inlined function, there are no instructions devoted to
11076 the call. @value{GDBN} still pretends that the call site and the
11077 start of the inlined function are different instructions. Stepping to
11078 the call site shows the call site, and then stepping again shows
11079 the first line of the inlined function, even though no additional
11080 instructions are executed.
11082 This makes source-level debugging much clearer; you can see both the
11083 context of the call and then the effect of the call. Only stepping by
11084 a single instruction using @code{stepi} or @code{nexti} does not do
11085 this; single instruction steps always show the inlined body.
11087 There are some ways that @value{GDBN} does not pretend that inlined
11088 function calls are the same as normal calls:
11092 Setting breakpoints at the call site of an inlined function may not
11093 work, because the call site does not contain any code. @value{GDBN}
11094 may incorrectly move the breakpoint to the next line of the enclosing
11095 function, after the call. This limitation will be removed in a future
11096 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11097 or inside the inlined function instead.
11100 @value{GDBN} cannot locate the return value of inlined calls after
11101 using the @code{finish} command. This is a limitation of compiler-generated
11102 debugging information; after @code{finish}, you can step to the next line
11103 and print a variable where your program stored the return value.
11107 @node Tail Call Frames
11108 @section Tail Call Frames
11109 @cindex tail call frames, debugging
11111 Function @code{B} can call function @code{C} in its very last statement. In
11112 unoptimized compilation the call of @code{C} is immediately followed by return
11113 instruction at the end of @code{B} code. Optimizing compiler may replace the
11114 call and return in function @code{B} into one jump to function @code{C}
11115 instead. Such use of a jump instruction is called @dfn{tail call}.
11117 During execution of function @code{C}, there will be no indication in the
11118 function call stack frames that it was tail-called from @code{B}. If function
11119 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11120 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11121 some cases @value{GDBN} can determine that @code{C} was tail-called from
11122 @code{B}, and it will then create fictitious call frame for that, with the
11123 return address set up as if @code{B} called @code{C} normally.
11125 This functionality is currently supported only by DWARF 2 debugging format and
11126 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11127 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11130 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11131 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11135 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11137 Stack level 1, frame at 0x7fffffffda30:
11138 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11139 tail call frame, caller of frame at 0x7fffffffda30
11140 source language c++.
11141 Arglist at unknown address.
11142 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11145 The detection of all the possible code path executions can find them ambiguous.
11146 There is no execution history stored (possible @ref{Reverse Execution} is never
11147 used for this purpose) and the last known caller could have reached the known
11148 callee by multiple different jump sequences. In such case @value{GDBN} still
11149 tries to show at least all the unambiguous top tail callers and all the
11150 unambiguous bottom tail calees, if any.
11153 @anchor{set debug entry-values}
11154 @item set debug entry-values
11155 @kindex set debug entry-values
11156 When set to on, enables printing of analysis messages for both frame argument
11157 values at function entry and tail calls. It will show all the possible valid
11158 tail calls code paths it has considered. It will also print the intersection
11159 of them with the final unambiguous (possibly partial or even empty) code path
11162 @item show debug entry-values
11163 @kindex show debug entry-values
11164 Show the current state of analysis messages printing for both frame argument
11165 values at function entry and tail calls.
11168 The analysis messages for tail calls can for example show why the virtual tail
11169 call frame for function @code{c} has not been recognized (due to the indirect
11170 reference by variable @code{x}):
11173 static void __attribute__((noinline, noclone)) c (void);
11174 void (*x) (void) = c;
11175 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11176 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11177 int main (void) @{ x (); return 0; @}
11179 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11180 DW_TAG_GNU_call_site 0x40039a in main
11182 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11185 #1 0x000000000040039a in main () at t.c:5
11188 Another possibility is an ambiguous virtual tail call frames resolution:
11192 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11193 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11194 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11195 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11196 static void __attribute__((noinline, noclone)) b (void)
11197 @{ if (i) c (); else e (); @}
11198 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11199 int main (void) @{ a (); return 0; @}
11201 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11202 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11203 tailcall: reduced: 0x4004d2(a) |
11206 #1 0x00000000004004d2 in a () at t.c:8
11207 #2 0x0000000000400395 in main () at t.c:9
11210 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11211 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11213 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11214 @ifset HAVE_MAKEINFO_CLICK
11215 @set ARROW @click{}
11216 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11217 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11219 @ifclear HAVE_MAKEINFO_CLICK
11221 @set CALLSEQ1B @value{CALLSEQ1A}
11222 @set CALLSEQ2B @value{CALLSEQ2A}
11225 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11226 The code can have possible execution paths @value{CALLSEQ1B} or
11227 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11229 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11230 has found. It then finds another possible calling sequcen - that one is
11231 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11232 printed as the @code{reduced:} calling sequence. That one could have many
11233 futher @code{compare:} and @code{reduced:} statements as long as there remain
11234 any non-ambiguous sequence entries.
11236 For the frame of function @code{b} in both cases there are different possible
11237 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11238 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11239 therefore this one is displayed to the user while the ambiguous frames are
11242 There can be also reasons why printing of frame argument values at function
11247 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11248 static void __attribute__((noinline, noclone)) a (int i);
11249 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11250 static void __attribute__((noinline, noclone)) a (int i)
11251 @{ if (i) b (i - 1); else c (0); @}
11252 int main (void) @{ a (5); return 0; @}
11255 #0 c (i=i@@entry=0) at t.c:2
11256 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11257 function "a" at 0x400420 can call itself via tail calls
11258 i=<optimized out>) at t.c:6
11259 #2 0x000000000040036e in main () at t.c:7
11262 @value{GDBN} cannot find out from the inferior state if and how many times did
11263 function @code{a} call itself (via function @code{b}) as these calls would be
11264 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11265 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11266 prints @code{<optimized out>} instead.
11269 @chapter C Preprocessor Macros
11271 Some languages, such as C and C@t{++}, provide a way to define and invoke
11272 ``preprocessor macros'' which expand into strings of tokens.
11273 @value{GDBN} can evaluate expressions containing macro invocations, show
11274 the result of macro expansion, and show a macro's definition, including
11275 where it was defined.
11277 You may need to compile your program specially to provide @value{GDBN}
11278 with information about preprocessor macros. Most compilers do not
11279 include macros in their debugging information, even when you compile
11280 with the @option{-g} flag. @xref{Compilation}.
11282 A program may define a macro at one point, remove that definition later,
11283 and then provide a different definition after that. Thus, at different
11284 points in the program, a macro may have different definitions, or have
11285 no definition at all. If there is a current stack frame, @value{GDBN}
11286 uses the macros in scope at that frame's source code line. Otherwise,
11287 @value{GDBN} uses the macros in scope at the current listing location;
11290 Whenever @value{GDBN} evaluates an expression, it always expands any
11291 macro invocations present in the expression. @value{GDBN} also provides
11292 the following commands for working with macros explicitly.
11296 @kindex macro expand
11297 @cindex macro expansion, showing the results of preprocessor
11298 @cindex preprocessor macro expansion, showing the results of
11299 @cindex expanding preprocessor macros
11300 @item macro expand @var{expression}
11301 @itemx macro exp @var{expression}
11302 Show the results of expanding all preprocessor macro invocations in
11303 @var{expression}. Since @value{GDBN} simply expands macros, but does
11304 not parse the result, @var{expression} need not be a valid expression;
11305 it can be any string of tokens.
11308 @item macro expand-once @var{expression}
11309 @itemx macro exp1 @var{expression}
11310 @cindex expand macro once
11311 @i{(This command is not yet implemented.)} Show the results of
11312 expanding those preprocessor macro invocations that appear explicitly in
11313 @var{expression}. Macro invocations appearing in that expansion are
11314 left unchanged. This command allows you to see the effect of a
11315 particular macro more clearly, without being confused by further
11316 expansions. Since @value{GDBN} simply expands macros, but does not
11317 parse the result, @var{expression} need not be a valid expression; it
11318 can be any string of tokens.
11321 @cindex macro definition, showing
11322 @cindex definition of a macro, showing
11323 @cindex macros, from debug info
11324 @item info macro [-a|-all] [--] @var{macro}
11325 Show the current definition or all definitions of the named @var{macro},
11326 and describe the source location or compiler command-line where that
11327 definition was established. The optional double dash is to signify the end of
11328 argument processing and the beginning of @var{macro} for non C-like macros where
11329 the macro may begin with a hyphen.
11331 @kindex info macros
11332 @item info macros @var{linespec}
11333 Show all macro definitions that are in effect at the location specified
11334 by @var{linespec}, and describe the source location or compiler
11335 command-line where those definitions were established.
11337 @kindex macro define
11338 @cindex user-defined macros
11339 @cindex defining macros interactively
11340 @cindex macros, user-defined
11341 @item macro define @var{macro} @var{replacement-list}
11342 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11343 Introduce a definition for a preprocessor macro named @var{macro},
11344 invocations of which are replaced by the tokens given in
11345 @var{replacement-list}. The first form of this command defines an
11346 ``object-like'' macro, which takes no arguments; the second form
11347 defines a ``function-like'' macro, which takes the arguments given in
11350 A definition introduced by this command is in scope in every
11351 expression evaluated in @value{GDBN}, until it is removed with the
11352 @code{macro undef} command, described below. The definition overrides
11353 all definitions for @var{macro} present in the program being debugged,
11354 as well as any previous user-supplied definition.
11356 @kindex macro undef
11357 @item macro undef @var{macro}
11358 Remove any user-supplied definition for the macro named @var{macro}.
11359 This command only affects definitions provided with the @code{macro
11360 define} command, described above; it cannot remove definitions present
11361 in the program being debugged.
11365 List all the macros defined using the @code{macro define} command.
11368 @cindex macros, example of debugging with
11369 Here is a transcript showing the above commands in action. First, we
11370 show our source files:
11375 #include "sample.h"
11378 #define ADD(x) (M + x)
11383 printf ("Hello, world!\n");
11385 printf ("We're so creative.\n");
11387 printf ("Goodbye, world!\n");
11394 Now, we compile the program using the @sc{gnu} C compiler,
11395 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11396 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11397 and @option{-gdwarf-4}; we recommend always choosing the most recent
11398 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11399 includes information about preprocessor macros in the debugging
11403 $ gcc -gdwarf-2 -g3 sample.c -o sample
11407 Now, we start @value{GDBN} on our sample program:
11411 GNU gdb 2002-05-06-cvs
11412 Copyright 2002 Free Software Foundation, Inc.
11413 GDB is free software, @dots{}
11417 We can expand macros and examine their definitions, even when the
11418 program is not running. @value{GDBN} uses the current listing position
11419 to decide which macro definitions are in scope:
11422 (@value{GDBP}) list main
11425 5 #define ADD(x) (M + x)
11430 10 printf ("Hello, world!\n");
11432 12 printf ("We're so creative.\n");
11433 (@value{GDBP}) info macro ADD
11434 Defined at /home/jimb/gdb/macros/play/sample.c:5
11435 #define ADD(x) (M + x)
11436 (@value{GDBP}) info macro Q
11437 Defined at /home/jimb/gdb/macros/play/sample.h:1
11438 included at /home/jimb/gdb/macros/play/sample.c:2
11440 (@value{GDBP}) macro expand ADD(1)
11441 expands to: (42 + 1)
11442 (@value{GDBP}) macro expand-once ADD(1)
11443 expands to: once (M + 1)
11447 In the example above, note that @code{macro expand-once} expands only
11448 the macro invocation explicit in the original text --- the invocation of
11449 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11450 which was introduced by @code{ADD}.
11452 Once the program is running, @value{GDBN} uses the macro definitions in
11453 force at the source line of the current stack frame:
11456 (@value{GDBP}) break main
11457 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11459 Starting program: /home/jimb/gdb/macros/play/sample
11461 Breakpoint 1, main () at sample.c:10
11462 10 printf ("Hello, world!\n");
11466 At line 10, the definition of the macro @code{N} at line 9 is in force:
11469 (@value{GDBP}) info macro N
11470 Defined at /home/jimb/gdb/macros/play/sample.c:9
11472 (@value{GDBP}) macro expand N Q M
11473 expands to: 28 < 42
11474 (@value{GDBP}) print N Q M
11479 As we step over directives that remove @code{N}'s definition, and then
11480 give it a new definition, @value{GDBN} finds the definition (or lack
11481 thereof) in force at each point:
11484 (@value{GDBP}) next
11486 12 printf ("We're so creative.\n");
11487 (@value{GDBP}) info macro N
11488 The symbol `N' has no definition as a C/C++ preprocessor macro
11489 at /home/jimb/gdb/macros/play/sample.c:12
11490 (@value{GDBP}) next
11492 14 printf ("Goodbye, world!\n");
11493 (@value{GDBP}) info macro N
11494 Defined at /home/jimb/gdb/macros/play/sample.c:13
11496 (@value{GDBP}) macro expand N Q M
11497 expands to: 1729 < 42
11498 (@value{GDBP}) print N Q M
11503 In addition to source files, macros can be defined on the compilation command
11504 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11505 such a way, @value{GDBN} displays the location of their definition as line zero
11506 of the source file submitted to the compiler.
11509 (@value{GDBP}) info macro __STDC__
11510 Defined at /home/jimb/gdb/macros/play/sample.c:0
11517 @chapter Tracepoints
11518 @c This chapter is based on the documentation written by Michael
11519 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11521 @cindex tracepoints
11522 In some applications, it is not feasible for the debugger to interrupt
11523 the program's execution long enough for the developer to learn
11524 anything helpful about its behavior. If the program's correctness
11525 depends on its real-time behavior, delays introduced by a debugger
11526 might cause the program to change its behavior drastically, or perhaps
11527 fail, even when the code itself is correct. It is useful to be able
11528 to observe the program's behavior without interrupting it.
11530 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11531 specify locations in the program, called @dfn{tracepoints}, and
11532 arbitrary expressions to evaluate when those tracepoints are reached.
11533 Later, using the @code{tfind} command, you can examine the values
11534 those expressions had when the program hit the tracepoints. The
11535 expressions may also denote objects in memory---structures or arrays,
11536 for example---whose values @value{GDBN} should record; while visiting
11537 a particular tracepoint, you may inspect those objects as if they were
11538 in memory at that moment. However, because @value{GDBN} records these
11539 values without interacting with you, it can do so quickly and
11540 unobtrusively, hopefully not disturbing the program's behavior.
11542 The tracepoint facility is currently available only for remote
11543 targets. @xref{Targets}. In addition, your remote target must know
11544 how to collect trace data. This functionality is implemented in the
11545 remote stub; however, none of the stubs distributed with @value{GDBN}
11546 support tracepoints as of this writing. The format of the remote
11547 packets used to implement tracepoints are described in @ref{Tracepoint
11550 It is also possible to get trace data from a file, in a manner reminiscent
11551 of corefiles; you specify the filename, and use @code{tfind} to search
11552 through the file. @xref{Trace Files}, for more details.
11554 This chapter describes the tracepoint commands and features.
11557 * Set Tracepoints::
11558 * Analyze Collected Data::
11559 * Tracepoint Variables::
11563 @node Set Tracepoints
11564 @section Commands to Set Tracepoints
11566 Before running such a @dfn{trace experiment}, an arbitrary number of
11567 tracepoints can be set. A tracepoint is actually a special type of
11568 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11569 standard breakpoint commands. For instance, as with breakpoints,
11570 tracepoint numbers are successive integers starting from one, and many
11571 of the commands associated with tracepoints take the tracepoint number
11572 as their argument, to identify which tracepoint to work on.
11574 For each tracepoint, you can specify, in advance, some arbitrary set
11575 of data that you want the target to collect in the trace buffer when
11576 it hits that tracepoint. The collected data can include registers,
11577 local variables, or global data. Later, you can use @value{GDBN}
11578 commands to examine the values these data had at the time the
11579 tracepoint was hit.
11581 Tracepoints do not support every breakpoint feature. Ignore counts on
11582 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11583 commands when they are hit. Tracepoints may not be thread-specific
11586 @cindex fast tracepoints
11587 Some targets may support @dfn{fast tracepoints}, which are inserted in
11588 a different way (such as with a jump instead of a trap), that is
11589 faster but possibly restricted in where they may be installed.
11591 @cindex static tracepoints
11592 @cindex markers, static tracepoints
11593 @cindex probing markers, static tracepoints
11594 Regular and fast tracepoints are dynamic tracing facilities, meaning
11595 that they can be used to insert tracepoints at (almost) any location
11596 in the target. Some targets may also support controlling @dfn{static
11597 tracepoints} from @value{GDBN}. With static tracing, a set of
11598 instrumentation points, also known as @dfn{markers}, are embedded in
11599 the target program, and can be activated or deactivated by name or
11600 address. These are usually placed at locations which facilitate
11601 investigating what the target is actually doing. @value{GDBN}'s
11602 support for static tracing includes being able to list instrumentation
11603 points, and attach them with @value{GDBN} defined high level
11604 tracepoints that expose the whole range of convenience of
11605 @value{GDBN}'s tracepoints support. Namely, support for collecting
11606 registers values and values of global or local (to the instrumentation
11607 point) variables; tracepoint conditions and trace state variables.
11608 The act of installing a @value{GDBN} static tracepoint on an
11609 instrumentation point, or marker, is referred to as @dfn{probing} a
11610 static tracepoint marker.
11612 @code{gdbserver} supports tracepoints on some target systems.
11613 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11615 This section describes commands to set tracepoints and associated
11616 conditions and actions.
11619 * Create and Delete Tracepoints::
11620 * Enable and Disable Tracepoints::
11621 * Tracepoint Passcounts::
11622 * Tracepoint Conditions::
11623 * Trace State Variables::
11624 * Tracepoint Actions::
11625 * Listing Tracepoints::
11626 * Listing Static Tracepoint Markers::
11627 * Starting and Stopping Trace Experiments::
11628 * Tracepoint Restrictions::
11631 @node Create and Delete Tracepoints
11632 @subsection Create and Delete Tracepoints
11635 @cindex set tracepoint
11637 @item trace @var{location}
11638 The @code{trace} command is very similar to the @code{break} command.
11639 Its argument @var{location} can be a source line, a function name, or
11640 an address in the target program. @xref{Specify Location}. The
11641 @code{trace} command defines a tracepoint, which is a point in the
11642 target program where the debugger will briefly stop, collect some
11643 data, and then allow the program to continue. Setting a tracepoint or
11644 changing its actions takes effect immediately if the remote stub
11645 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11647 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11648 these changes don't take effect until the next @code{tstart}
11649 command, and once a trace experiment is running, further changes will
11650 not have any effect until the next trace experiment starts. In addition,
11651 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11652 address is not yet resolved. (This is similar to pending breakpoints.)
11653 Pending tracepoints are not downloaded to the target and not installed
11654 until they are resolved. The resolution of pending tracepoints requires
11655 @value{GDBN} support---when debugging with the remote target, and
11656 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11657 tracing}), pending tracepoints can not be resolved (and downloaded to
11658 the remote stub) while @value{GDBN} is disconnected.
11660 Here are some examples of using the @code{trace} command:
11663 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11665 (@value{GDBP}) @b{trace +2} // 2 lines forward
11667 (@value{GDBP}) @b{trace my_function} // first source line of function
11669 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11671 (@value{GDBP}) @b{trace *0x2117c4} // an address
11675 You can abbreviate @code{trace} as @code{tr}.
11677 @item trace @var{location} if @var{cond}
11678 Set a tracepoint with condition @var{cond}; evaluate the expression
11679 @var{cond} each time the tracepoint is reached, and collect data only
11680 if the value is nonzero---that is, if @var{cond} evaluates as true.
11681 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11682 information on tracepoint conditions.
11684 @item ftrace @var{location} [ if @var{cond} ]
11685 @cindex set fast tracepoint
11686 @cindex fast tracepoints, setting
11688 The @code{ftrace} command sets a fast tracepoint. For targets that
11689 support them, fast tracepoints will use a more efficient but possibly
11690 less general technique to trigger data collection, such as a jump
11691 instruction instead of a trap, or some sort of hardware support. It
11692 may not be possible to create a fast tracepoint at the desired
11693 location, in which case the command will exit with an explanatory
11696 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11699 On 32-bit x86-architecture systems, fast tracepoints normally need to
11700 be placed at an instruction that is 5 bytes or longer, but can be
11701 placed at 4-byte instructions if the low 64K of memory of the target
11702 program is available to install trampolines. Some Unix-type systems,
11703 such as @sc{gnu}/Linux, exclude low addresses from the program's
11704 address space; but for instance with the Linux kernel it is possible
11705 to let @value{GDBN} use this area by doing a @command{sysctl} command
11706 to set the @code{mmap_min_addr} kernel parameter, as in
11709 sudo sysctl -w vm.mmap_min_addr=32768
11713 which sets the low address to 32K, which leaves plenty of room for
11714 trampolines. The minimum address should be set to a page boundary.
11716 @item strace @var{location} [ if @var{cond} ]
11717 @cindex set static tracepoint
11718 @cindex static tracepoints, setting
11719 @cindex probe static tracepoint marker
11721 The @code{strace} command sets a static tracepoint. For targets that
11722 support it, setting a static tracepoint probes a static
11723 instrumentation point, or marker, found at @var{location}. It may not
11724 be possible to set a static tracepoint at the desired location, in
11725 which case the command will exit with an explanatory message.
11727 @value{GDBN} handles arguments to @code{strace} exactly as for
11728 @code{trace}, with the addition that the user can also specify
11729 @code{-m @var{marker}} as @var{location}. This probes the marker
11730 identified by the @var{marker} string identifier. This identifier
11731 depends on the static tracepoint backend library your program is
11732 using. You can find all the marker identifiers in the @samp{ID} field
11733 of the @code{info static-tracepoint-markers} command output.
11734 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11735 Markers}. For example, in the following small program using the UST
11741 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11746 the marker id is composed of joining the first two arguments to the
11747 @code{trace_mark} call with a slash, which translates to:
11750 (@value{GDBP}) info static-tracepoint-markers
11751 Cnt Enb ID Address What
11752 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11758 so you may probe the marker above with:
11761 (@value{GDBP}) strace -m ust/bar33
11764 Static tracepoints accept an extra collect action --- @code{collect
11765 $_sdata}. This collects arbitrary user data passed in the probe point
11766 call to the tracing library. In the UST example above, you'll see
11767 that the third argument to @code{trace_mark} is a printf-like format
11768 string. The user data is then the result of running that formating
11769 string against the following arguments. Note that @code{info
11770 static-tracepoint-markers} command output lists that format string in
11771 the @samp{Data:} field.
11773 You can inspect this data when analyzing the trace buffer, by printing
11774 the $_sdata variable like any other variable available to
11775 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11778 @cindex last tracepoint number
11779 @cindex recent tracepoint number
11780 @cindex tracepoint number
11781 The convenience variable @code{$tpnum} records the tracepoint number
11782 of the most recently set tracepoint.
11784 @kindex delete tracepoint
11785 @cindex tracepoint deletion
11786 @item delete tracepoint @r{[}@var{num}@r{]}
11787 Permanently delete one or more tracepoints. With no argument, the
11788 default is to delete all tracepoints. Note that the regular
11789 @code{delete} command can remove tracepoints also.
11794 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11796 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11800 You can abbreviate this command as @code{del tr}.
11803 @node Enable and Disable Tracepoints
11804 @subsection Enable and Disable Tracepoints
11806 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11809 @kindex disable tracepoint
11810 @item disable tracepoint @r{[}@var{num}@r{]}
11811 Disable tracepoint @var{num}, or all tracepoints if no argument
11812 @var{num} is given. A disabled tracepoint will have no effect during
11813 a trace experiment, but it is not forgotten. You can re-enable
11814 a disabled tracepoint using the @code{enable tracepoint} command.
11815 If the command is issued during a trace experiment and the debug target
11816 has support for disabling tracepoints during a trace experiment, then the
11817 change will be effective immediately. Otherwise, it will be applied to the
11818 next trace experiment.
11820 @kindex enable tracepoint
11821 @item enable tracepoint @r{[}@var{num}@r{]}
11822 Enable tracepoint @var{num}, or all tracepoints. If this command is
11823 issued during a trace experiment and the debug target supports enabling
11824 tracepoints during a trace experiment, then the enabled tracepoints will
11825 become effective immediately. Otherwise, they will become effective the
11826 next time a trace experiment is run.
11829 @node Tracepoint Passcounts
11830 @subsection Tracepoint Passcounts
11834 @cindex tracepoint pass count
11835 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11836 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11837 automatically stop a trace experiment. If a tracepoint's passcount is
11838 @var{n}, then the trace experiment will be automatically stopped on
11839 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11840 @var{num} is not specified, the @code{passcount} command sets the
11841 passcount of the most recently defined tracepoint. If no passcount is
11842 given, the trace experiment will run until stopped explicitly by the
11848 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11849 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11851 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11852 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11853 (@value{GDBP}) @b{trace foo}
11854 (@value{GDBP}) @b{pass 3}
11855 (@value{GDBP}) @b{trace bar}
11856 (@value{GDBP}) @b{pass 2}
11857 (@value{GDBP}) @b{trace baz}
11858 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11859 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11860 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11861 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11865 @node Tracepoint Conditions
11866 @subsection Tracepoint Conditions
11867 @cindex conditional tracepoints
11868 @cindex tracepoint conditions
11870 The simplest sort of tracepoint collects data every time your program
11871 reaches a specified place. You can also specify a @dfn{condition} for
11872 a tracepoint. A condition is just a Boolean expression in your
11873 programming language (@pxref{Expressions, ,Expressions}). A
11874 tracepoint with a condition evaluates the expression each time your
11875 program reaches it, and data collection happens only if the condition
11878 Tracepoint conditions can be specified when a tracepoint is set, by
11879 using @samp{if} in the arguments to the @code{trace} command.
11880 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11881 also be set or changed at any time with the @code{condition} command,
11882 just as with breakpoints.
11884 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11885 the conditional expression itself. Instead, @value{GDBN} encodes the
11886 expression into an agent expression (@pxref{Agent Expressions})
11887 suitable for execution on the target, independently of @value{GDBN}.
11888 Global variables become raw memory locations, locals become stack
11889 accesses, and so forth.
11891 For instance, suppose you have a function that is usually called
11892 frequently, but should not be called after an error has occurred. You
11893 could use the following tracepoint command to collect data about calls
11894 of that function that happen while the error code is propagating
11895 through the program; an unconditional tracepoint could end up
11896 collecting thousands of useless trace frames that you would have to
11900 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11903 @node Trace State Variables
11904 @subsection Trace State Variables
11905 @cindex trace state variables
11907 A @dfn{trace state variable} is a special type of variable that is
11908 created and managed by target-side code. The syntax is the same as
11909 that for GDB's convenience variables (a string prefixed with ``$''),
11910 but they are stored on the target. They must be created explicitly,
11911 using a @code{tvariable} command. They are always 64-bit signed
11914 Trace state variables are remembered by @value{GDBN}, and downloaded
11915 to the target along with tracepoint information when the trace
11916 experiment starts. There are no intrinsic limits on the number of
11917 trace state variables, beyond memory limitations of the target.
11919 @cindex convenience variables, and trace state variables
11920 Although trace state variables are managed by the target, you can use
11921 them in print commands and expressions as if they were convenience
11922 variables; @value{GDBN} will get the current value from the target
11923 while the trace experiment is running. Trace state variables share
11924 the same namespace as other ``$'' variables, which means that you
11925 cannot have trace state variables with names like @code{$23} or
11926 @code{$pc}, nor can you have a trace state variable and a convenience
11927 variable with the same name.
11931 @item tvariable $@var{name} [ = @var{expression} ]
11933 The @code{tvariable} command creates a new trace state variable named
11934 @code{$@var{name}}, and optionally gives it an initial value of
11935 @var{expression}. @var{expression} is evaluated when this command is
11936 entered; the result will be converted to an integer if possible,
11937 otherwise @value{GDBN} will report an error. A subsequent
11938 @code{tvariable} command specifying the same name does not create a
11939 variable, but instead assigns the supplied initial value to the
11940 existing variable of that name, overwriting any previous initial
11941 value. The default initial value is 0.
11943 @item info tvariables
11944 @kindex info tvariables
11945 List all the trace state variables along with their initial values.
11946 Their current values may also be displayed, if the trace experiment is
11949 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11950 @kindex delete tvariable
11951 Delete the given trace state variables, or all of them if no arguments
11956 @node Tracepoint Actions
11957 @subsection Tracepoint Action Lists
11961 @cindex tracepoint actions
11962 @item actions @r{[}@var{num}@r{]}
11963 This command will prompt for a list of actions to be taken when the
11964 tracepoint is hit. If the tracepoint number @var{num} is not
11965 specified, this command sets the actions for the one that was most
11966 recently defined (so that you can define a tracepoint and then say
11967 @code{actions} without bothering about its number). You specify the
11968 actions themselves on the following lines, one action at a time, and
11969 terminate the actions list with a line containing just @code{end}. So
11970 far, the only defined actions are @code{collect}, @code{teval}, and
11971 @code{while-stepping}.
11973 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11974 Commands, ,Breakpoint Command Lists}), except that only the defined
11975 actions are allowed; any other @value{GDBN} command is rejected.
11977 @cindex remove actions from a tracepoint
11978 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11979 and follow it immediately with @samp{end}.
11982 (@value{GDBP}) @b{collect @var{data}} // collect some data
11984 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11986 (@value{GDBP}) @b{end} // signals the end of actions.
11989 In the following example, the action list begins with @code{collect}
11990 commands indicating the things to be collected when the tracepoint is
11991 hit. Then, in order to single-step and collect additional data
11992 following the tracepoint, a @code{while-stepping} command is used,
11993 followed by the list of things to be collected after each step in a
11994 sequence of single steps. The @code{while-stepping} command is
11995 terminated by its own separate @code{end} command. Lastly, the action
11996 list is terminated by an @code{end} command.
11999 (@value{GDBP}) @b{trace foo}
12000 (@value{GDBP}) @b{actions}
12001 Enter actions for tracepoint 1, one per line:
12004 > while-stepping 12
12005 > collect $pc, arr[i]
12010 @kindex collect @r{(tracepoints)}
12011 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12012 Collect values of the given expressions when the tracepoint is hit.
12013 This command accepts a comma-separated list of any valid expressions.
12014 In addition to global, static, or local variables, the following
12015 special arguments are supported:
12019 Collect all registers.
12022 Collect all function arguments.
12025 Collect all local variables.
12028 Collect the return address. This is helpful if you want to see more
12032 Collects the number of arguments from the static probe at which the
12033 tracepoint is located.
12034 @xref{Static Probe Points}.
12036 @item $_probe_arg@var{n}
12037 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12038 from the static probe at which the tracepoint is located.
12039 @xref{Static Probe Points}.
12042 @vindex $_sdata@r{, collect}
12043 Collect static tracepoint marker specific data. Only available for
12044 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12045 Lists}. On the UST static tracepoints library backend, an
12046 instrumentation point resembles a @code{printf} function call. The
12047 tracing library is able to collect user specified data formatted to a
12048 character string using the format provided by the programmer that
12049 instrumented the program. Other backends have similar mechanisms.
12050 Here's an example of a UST marker call:
12053 const char master_name[] = "$your_name";
12054 trace_mark(channel1, marker1, "hello %s", master_name)
12057 In this case, collecting @code{$_sdata} collects the string
12058 @samp{hello $yourname}. When analyzing the trace buffer, you can
12059 inspect @samp{$_sdata} like any other variable available to
12063 You can give several consecutive @code{collect} commands, each one
12064 with a single argument, or one @code{collect} command with several
12065 arguments separated by commas; the effect is the same.
12067 The optional @var{mods} changes the usual handling of the arguments.
12068 @code{s} requests that pointers to chars be handled as strings, in
12069 particular collecting the contents of the memory being pointed at, up
12070 to the first zero. The upper bound is by default the value of the
12071 @code{print elements} variable; if @code{s} is followed by a decimal
12072 number, that is the upper bound instead. So for instance
12073 @samp{collect/s25 mystr} collects as many as 25 characters at
12076 The command @code{info scope} (@pxref{Symbols, info scope}) is
12077 particularly useful for figuring out what data to collect.
12079 @kindex teval @r{(tracepoints)}
12080 @item teval @var{expr1}, @var{expr2}, @dots{}
12081 Evaluate the given expressions when the tracepoint is hit. This
12082 command accepts a comma-separated list of expressions. The results
12083 are discarded, so this is mainly useful for assigning values to trace
12084 state variables (@pxref{Trace State Variables}) without adding those
12085 values to the trace buffer, as would be the case if the @code{collect}
12088 @kindex while-stepping @r{(tracepoints)}
12089 @item while-stepping @var{n}
12090 Perform @var{n} single-step instruction traces after the tracepoint,
12091 collecting new data after each step. The @code{while-stepping}
12092 command is followed by the list of what to collect while stepping
12093 (followed by its own @code{end} command):
12096 > while-stepping 12
12097 > collect $regs, myglobal
12103 Note that @code{$pc} is not automatically collected by
12104 @code{while-stepping}; you need to explicitly collect that register if
12105 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12108 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12109 @kindex set default-collect
12110 @cindex default collection action
12111 This variable is a list of expressions to collect at each tracepoint
12112 hit. It is effectively an additional @code{collect} action prepended
12113 to every tracepoint action list. The expressions are parsed
12114 individually for each tracepoint, so for instance a variable named
12115 @code{xyz} may be interpreted as a global for one tracepoint, and a
12116 local for another, as appropriate to the tracepoint's location.
12118 @item show default-collect
12119 @kindex show default-collect
12120 Show the list of expressions that are collected by default at each
12125 @node Listing Tracepoints
12126 @subsection Listing Tracepoints
12129 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12130 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12131 @cindex information about tracepoints
12132 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12133 Display information about the tracepoint @var{num}. If you don't
12134 specify a tracepoint number, displays information about all the
12135 tracepoints defined so far. The format is similar to that used for
12136 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12137 command, simply restricting itself to tracepoints.
12139 A tracepoint's listing may include additional information specific to
12144 its passcount as given by the @code{passcount @var{n}} command
12147 the state about installed on target of each location
12151 (@value{GDBP}) @b{info trace}
12152 Num Type Disp Enb Address What
12153 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12155 collect globfoo, $regs
12160 2 tracepoint keep y <MULTIPLE>
12162 2.1 y 0x0804859c in func4 at change-loc.h:35
12163 installed on target
12164 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12165 installed on target
12166 2.3 y <PENDING> set_tracepoint
12167 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12168 not installed on target
12173 This command can be abbreviated @code{info tp}.
12176 @node Listing Static Tracepoint Markers
12177 @subsection Listing Static Tracepoint Markers
12180 @kindex info static-tracepoint-markers
12181 @cindex information about static tracepoint markers
12182 @item info static-tracepoint-markers
12183 Display information about all static tracepoint markers defined in the
12186 For each marker, the following columns are printed:
12190 An incrementing counter, output to help readability. This is not a
12193 The marker ID, as reported by the target.
12194 @item Enabled or Disabled
12195 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12196 that are not enabled.
12198 Where the marker is in your program, as a memory address.
12200 Where the marker is in the source for your program, as a file and line
12201 number. If the debug information included in the program does not
12202 allow @value{GDBN} to locate the source of the marker, this column
12203 will be left blank.
12207 In addition, the following information may be printed for each marker:
12211 User data passed to the tracing library by the marker call. In the
12212 UST backend, this is the format string passed as argument to the
12214 @item Static tracepoints probing the marker
12215 The list of static tracepoints attached to the marker.
12219 (@value{GDBP}) info static-tracepoint-markers
12220 Cnt ID Enb Address What
12221 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12222 Data: number1 %d number2 %d
12223 Probed by static tracepoints: #2
12224 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12230 @node Starting and Stopping Trace Experiments
12231 @subsection Starting and Stopping Trace Experiments
12234 @kindex tstart [ @var{notes} ]
12235 @cindex start a new trace experiment
12236 @cindex collected data discarded
12238 This command starts the trace experiment, and begins collecting data.
12239 It has the side effect of discarding all the data collected in the
12240 trace buffer during the previous trace experiment. If any arguments
12241 are supplied, they are taken as a note and stored with the trace
12242 experiment's state. The notes may be arbitrary text, and are
12243 especially useful with disconnected tracing in a multi-user context;
12244 the notes can explain what the trace is doing, supply user contact
12245 information, and so forth.
12247 @kindex tstop [ @var{notes} ]
12248 @cindex stop a running trace experiment
12250 This command stops the trace experiment. If any arguments are
12251 supplied, they are recorded with the experiment as a note. This is
12252 useful if you are stopping a trace started by someone else, for
12253 instance if the trace is interfering with the system's behavior and
12254 needs to be stopped quickly.
12256 @strong{Note}: a trace experiment and data collection may stop
12257 automatically if any tracepoint's passcount is reached
12258 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12261 @cindex status of trace data collection
12262 @cindex trace experiment, status of
12264 This command displays the status of the current trace data
12268 Here is an example of the commands we described so far:
12271 (@value{GDBP}) @b{trace gdb_c_test}
12272 (@value{GDBP}) @b{actions}
12273 Enter actions for tracepoint #1, one per line.
12274 > collect $regs,$locals,$args
12275 > while-stepping 11
12279 (@value{GDBP}) @b{tstart}
12280 [time passes @dots{}]
12281 (@value{GDBP}) @b{tstop}
12284 @anchor{disconnected tracing}
12285 @cindex disconnected tracing
12286 You can choose to continue running the trace experiment even if
12287 @value{GDBN} disconnects from the target, voluntarily or
12288 involuntarily. For commands such as @code{detach}, the debugger will
12289 ask what you want to do with the trace. But for unexpected
12290 terminations (@value{GDBN} crash, network outage), it would be
12291 unfortunate to lose hard-won trace data, so the variable
12292 @code{disconnected-tracing} lets you decide whether the trace should
12293 continue running without @value{GDBN}.
12296 @item set disconnected-tracing on
12297 @itemx set disconnected-tracing off
12298 @kindex set disconnected-tracing
12299 Choose whether a tracing run should continue to run if @value{GDBN}
12300 has disconnected from the target. Note that @code{detach} or
12301 @code{quit} will ask you directly what to do about a running trace no
12302 matter what this variable's setting, so the variable is mainly useful
12303 for handling unexpected situations, such as loss of the network.
12305 @item show disconnected-tracing
12306 @kindex show disconnected-tracing
12307 Show the current choice for disconnected tracing.
12311 When you reconnect to the target, the trace experiment may or may not
12312 still be running; it might have filled the trace buffer in the
12313 meantime, or stopped for one of the other reasons. If it is running,
12314 it will continue after reconnection.
12316 Upon reconnection, the target will upload information about the
12317 tracepoints in effect. @value{GDBN} will then compare that
12318 information to the set of tracepoints currently defined, and attempt
12319 to match them up, allowing for the possibility that the numbers may
12320 have changed due to creation and deletion in the meantime. If one of
12321 the target's tracepoints does not match any in @value{GDBN}, the
12322 debugger will create a new tracepoint, so that you have a number with
12323 which to specify that tracepoint. This matching-up process is
12324 necessarily heuristic, and it may result in useless tracepoints being
12325 created; you may simply delete them if they are of no use.
12327 @cindex circular trace buffer
12328 If your target agent supports a @dfn{circular trace buffer}, then you
12329 can run a trace experiment indefinitely without filling the trace
12330 buffer; when space runs out, the agent deletes already-collected trace
12331 frames, oldest first, until there is enough room to continue
12332 collecting. This is especially useful if your tracepoints are being
12333 hit too often, and your trace gets terminated prematurely because the
12334 buffer is full. To ask for a circular trace buffer, simply set
12335 @samp{circular-trace-buffer} to on. You can set this at any time,
12336 including during tracing; if the agent can do it, it will change
12337 buffer handling on the fly, otherwise it will not take effect until
12341 @item set circular-trace-buffer on
12342 @itemx set circular-trace-buffer off
12343 @kindex set circular-trace-buffer
12344 Choose whether a tracing run should use a linear or circular buffer
12345 for trace data. A linear buffer will not lose any trace data, but may
12346 fill up prematurely, while a circular buffer will discard old trace
12347 data, but it will have always room for the latest tracepoint hits.
12349 @item show circular-trace-buffer
12350 @kindex show circular-trace-buffer
12351 Show the current choice for the trace buffer. Note that this may not
12352 match the agent's current buffer handling, nor is it guaranteed to
12353 match the setting that might have been in effect during a past run,
12354 for instance if you are looking at frames from a trace file.
12359 @item set trace-buffer-size @var{n}
12360 @itemx set trace-buffer-size unlimited
12361 @kindex set trace-buffer-size
12362 Request that the target use a trace buffer of @var{n} bytes. Not all
12363 targets will honor the request; they may have a compiled-in size for
12364 the trace buffer, or some other limitation. Set to a value of
12365 @code{unlimited} or @code{-1} to let the target use whatever size it
12366 likes. This is also the default.
12368 @item show trace-buffer-size
12369 @kindex show trace-buffer-size
12370 Show the current requested size for the trace buffer. Note that this
12371 will only match the actual size if the target supports size-setting,
12372 and was able to handle the requested size. For instance, if the
12373 target can only change buffer size between runs, this variable will
12374 not reflect the change until the next run starts. Use @code{tstatus}
12375 to get a report of the actual buffer size.
12379 @item set trace-user @var{text}
12380 @kindex set trace-user
12382 @item show trace-user
12383 @kindex show trace-user
12385 @item set trace-notes @var{text}
12386 @kindex set trace-notes
12387 Set the trace run's notes.
12389 @item show trace-notes
12390 @kindex show trace-notes
12391 Show the trace run's notes.
12393 @item set trace-stop-notes @var{text}
12394 @kindex set trace-stop-notes
12395 Set the trace run's stop notes. The handling of the note is as for
12396 @code{tstop} arguments; the set command is convenient way to fix a
12397 stop note that is mistaken or incomplete.
12399 @item show trace-stop-notes
12400 @kindex show trace-stop-notes
12401 Show the trace run's stop notes.
12405 @node Tracepoint Restrictions
12406 @subsection Tracepoint Restrictions
12408 @cindex tracepoint restrictions
12409 There are a number of restrictions on the use of tracepoints. As
12410 described above, tracepoint data gathering occurs on the target
12411 without interaction from @value{GDBN}. Thus the full capabilities of
12412 the debugger are not available during data gathering, and then at data
12413 examination time, you will be limited by only having what was
12414 collected. The following items describe some common problems, but it
12415 is not exhaustive, and you may run into additional difficulties not
12421 Tracepoint expressions are intended to gather objects (lvalues). Thus
12422 the full flexibility of GDB's expression evaluator is not available.
12423 You cannot call functions, cast objects to aggregate types, access
12424 convenience variables or modify values (except by assignment to trace
12425 state variables). Some language features may implicitly call
12426 functions (for instance Objective-C fields with accessors), and therefore
12427 cannot be collected either.
12430 Collection of local variables, either individually or in bulk with
12431 @code{$locals} or @code{$args}, during @code{while-stepping} may
12432 behave erratically. The stepping action may enter a new scope (for
12433 instance by stepping into a function), or the location of the variable
12434 may change (for instance it is loaded into a register). The
12435 tracepoint data recorded uses the location information for the
12436 variables that is correct for the tracepoint location. When the
12437 tracepoint is created, it is not possible, in general, to determine
12438 where the steps of a @code{while-stepping} sequence will advance the
12439 program---particularly if a conditional branch is stepped.
12442 Collection of an incompletely-initialized or partially-destroyed object
12443 may result in something that @value{GDBN} cannot display, or displays
12444 in a misleading way.
12447 When @value{GDBN} displays a pointer to character it automatically
12448 dereferences the pointer to also display characters of the string
12449 being pointed to. However, collecting the pointer during tracing does
12450 not automatically collect the string. You need to explicitly
12451 dereference the pointer and provide size information if you want to
12452 collect not only the pointer, but the memory pointed to. For example,
12453 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12457 It is not possible to collect a complete stack backtrace at a
12458 tracepoint. Instead, you may collect the registers and a few hundred
12459 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12460 (adjust to use the name of the actual stack pointer register on your
12461 target architecture, and the amount of stack you wish to capture).
12462 Then the @code{backtrace} command will show a partial backtrace when
12463 using a trace frame. The number of stack frames that can be examined
12464 depends on the sizes of the frames in the collected stack. Note that
12465 if you ask for a block so large that it goes past the bottom of the
12466 stack, the target agent may report an error trying to read from an
12470 If you do not collect registers at a tracepoint, @value{GDBN} can
12471 infer that the value of @code{$pc} must be the same as the address of
12472 the tracepoint and use that when you are looking at a trace frame
12473 for that tracepoint. However, this cannot work if the tracepoint has
12474 multiple locations (for instance if it was set in a function that was
12475 inlined), or if it has a @code{while-stepping} loop. In those cases
12476 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12481 @node Analyze Collected Data
12482 @section Using the Collected Data
12484 After the tracepoint experiment ends, you use @value{GDBN} commands
12485 for examining the trace data. The basic idea is that each tracepoint
12486 collects a trace @dfn{snapshot} every time it is hit and another
12487 snapshot every time it single-steps. All these snapshots are
12488 consecutively numbered from zero and go into a buffer, and you can
12489 examine them later. The way you examine them is to @dfn{focus} on a
12490 specific trace snapshot. When the remote stub is focused on a trace
12491 snapshot, it will respond to all @value{GDBN} requests for memory and
12492 registers by reading from the buffer which belongs to that snapshot,
12493 rather than from @emph{real} memory or registers of the program being
12494 debugged. This means that @strong{all} @value{GDBN} commands
12495 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12496 behave as if we were currently debugging the program state as it was
12497 when the tracepoint occurred. Any requests for data that are not in
12498 the buffer will fail.
12501 * tfind:: How to select a trace snapshot
12502 * tdump:: How to display all data for a snapshot
12503 * save tracepoints:: How to save tracepoints for a future run
12507 @subsection @code{tfind @var{n}}
12510 @cindex select trace snapshot
12511 @cindex find trace snapshot
12512 The basic command for selecting a trace snapshot from the buffer is
12513 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12514 counting from zero. If no argument @var{n} is given, the next
12515 snapshot is selected.
12517 Here are the various forms of using the @code{tfind} command.
12521 Find the first snapshot in the buffer. This is a synonym for
12522 @code{tfind 0} (since 0 is the number of the first snapshot).
12525 Stop debugging trace snapshots, resume @emph{live} debugging.
12528 Same as @samp{tfind none}.
12531 No argument means find the next trace snapshot.
12534 Find the previous trace snapshot before the current one. This permits
12535 retracing earlier steps.
12537 @item tfind tracepoint @var{num}
12538 Find the next snapshot associated with tracepoint @var{num}. Search
12539 proceeds forward from the last examined trace snapshot. If no
12540 argument @var{num} is given, it means find the next snapshot collected
12541 for the same tracepoint as the current snapshot.
12543 @item tfind pc @var{addr}
12544 Find the next snapshot associated with the value @var{addr} of the
12545 program counter. Search proceeds forward from the last examined trace
12546 snapshot. If no argument @var{addr} is given, it means find the next
12547 snapshot with the same value of PC as the current snapshot.
12549 @item tfind outside @var{addr1}, @var{addr2}
12550 Find the next snapshot whose PC is outside the given range of
12551 addresses (exclusive).
12553 @item tfind range @var{addr1}, @var{addr2}
12554 Find the next snapshot whose PC is between @var{addr1} and
12555 @var{addr2} (inclusive).
12557 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12558 Find the next snapshot associated with the source line @var{n}. If
12559 the optional argument @var{file} is given, refer to line @var{n} in
12560 that source file. Search proceeds forward from the last examined
12561 trace snapshot. If no argument @var{n} is given, it means find the
12562 next line other than the one currently being examined; thus saying
12563 @code{tfind line} repeatedly can appear to have the same effect as
12564 stepping from line to line in a @emph{live} debugging session.
12567 The default arguments for the @code{tfind} commands are specifically
12568 designed to make it easy to scan through the trace buffer. For
12569 instance, @code{tfind} with no argument selects the next trace
12570 snapshot, and @code{tfind -} with no argument selects the previous
12571 trace snapshot. So, by giving one @code{tfind} command, and then
12572 simply hitting @key{RET} repeatedly you can examine all the trace
12573 snapshots in order. Or, by saying @code{tfind -} and then hitting
12574 @key{RET} repeatedly you can examine the snapshots in reverse order.
12575 The @code{tfind line} command with no argument selects the snapshot
12576 for the next source line executed. The @code{tfind pc} command with
12577 no argument selects the next snapshot with the same program counter
12578 (PC) as the current frame. The @code{tfind tracepoint} command with
12579 no argument selects the next trace snapshot collected by the same
12580 tracepoint as the current one.
12582 In addition to letting you scan through the trace buffer manually,
12583 these commands make it easy to construct @value{GDBN} scripts that
12584 scan through the trace buffer and print out whatever collected data
12585 you are interested in. Thus, if we want to examine the PC, FP, and SP
12586 registers from each trace frame in the buffer, we can say this:
12589 (@value{GDBP}) @b{tfind start}
12590 (@value{GDBP}) @b{while ($trace_frame != -1)}
12591 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12592 $trace_frame, $pc, $sp, $fp
12596 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12597 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12598 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12599 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12600 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12601 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12602 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12603 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12604 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12605 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12606 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12609 Or, if we want to examine the variable @code{X} at each source line in
12613 (@value{GDBP}) @b{tfind start}
12614 (@value{GDBP}) @b{while ($trace_frame != -1)}
12615 > printf "Frame %d, X == %d\n", $trace_frame, X
12625 @subsection @code{tdump}
12627 @cindex dump all data collected at tracepoint
12628 @cindex tracepoint data, display
12630 This command takes no arguments. It prints all the data collected at
12631 the current trace snapshot.
12634 (@value{GDBP}) @b{trace 444}
12635 (@value{GDBP}) @b{actions}
12636 Enter actions for tracepoint #2, one per line:
12637 > collect $regs, $locals, $args, gdb_long_test
12640 (@value{GDBP}) @b{tstart}
12642 (@value{GDBP}) @b{tfind line 444}
12643 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12645 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12647 (@value{GDBP}) @b{tdump}
12648 Data collected at tracepoint 2, trace frame 1:
12649 d0 0xc4aa0085 -995491707
12653 d4 0x71aea3d 119204413
12656 d7 0x380035 3670069
12657 a0 0x19e24a 1696330
12658 a1 0x3000668 50333288
12660 a3 0x322000 3284992
12661 a4 0x3000698 50333336
12662 a5 0x1ad3cc 1758156
12663 fp 0x30bf3c 0x30bf3c
12664 sp 0x30bf34 0x30bf34
12666 pc 0x20b2c8 0x20b2c8
12670 p = 0x20e5b4 "gdb-test"
12677 gdb_long_test = 17 '\021'
12682 @code{tdump} works by scanning the tracepoint's current collection
12683 actions and printing the value of each expression listed. So
12684 @code{tdump} can fail, if after a run, you change the tracepoint's
12685 actions to mention variables that were not collected during the run.
12687 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12688 uses the collected value of @code{$pc} to distinguish between trace
12689 frames that were collected at the tracepoint hit, and frames that were
12690 collected while stepping. This allows it to correctly choose whether
12691 to display the basic list of collections, or the collections from the
12692 body of the while-stepping loop. However, if @code{$pc} was not collected,
12693 then @code{tdump} will always attempt to dump using the basic collection
12694 list, and may fail if a while-stepping frame does not include all the
12695 same data that is collected at the tracepoint hit.
12696 @c This is getting pretty arcane, example would be good.
12698 @node save tracepoints
12699 @subsection @code{save tracepoints @var{filename}}
12700 @kindex save tracepoints
12701 @kindex save-tracepoints
12702 @cindex save tracepoints for future sessions
12704 This command saves all current tracepoint definitions together with
12705 their actions and passcounts, into a file @file{@var{filename}}
12706 suitable for use in a later debugging session. To read the saved
12707 tracepoint definitions, use the @code{source} command (@pxref{Command
12708 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12709 alias for @w{@code{save tracepoints}}
12711 @node Tracepoint Variables
12712 @section Convenience Variables for Tracepoints
12713 @cindex tracepoint variables
12714 @cindex convenience variables for tracepoints
12717 @vindex $trace_frame
12718 @item (int) $trace_frame
12719 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12720 snapshot is selected.
12722 @vindex $tracepoint
12723 @item (int) $tracepoint
12724 The tracepoint for the current trace snapshot.
12726 @vindex $trace_line
12727 @item (int) $trace_line
12728 The line number for the current trace snapshot.
12730 @vindex $trace_file
12731 @item (char []) $trace_file
12732 The source file for the current trace snapshot.
12734 @vindex $trace_func
12735 @item (char []) $trace_func
12736 The name of the function containing @code{$tracepoint}.
12739 Note: @code{$trace_file} is not suitable for use in @code{printf},
12740 use @code{output} instead.
12742 Here's a simple example of using these convenience variables for
12743 stepping through all the trace snapshots and printing some of their
12744 data. Note that these are not the same as trace state variables,
12745 which are managed by the target.
12748 (@value{GDBP}) @b{tfind start}
12750 (@value{GDBP}) @b{while $trace_frame != -1}
12751 > output $trace_file
12752 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12758 @section Using Trace Files
12759 @cindex trace files
12761 In some situations, the target running a trace experiment may no
12762 longer be available; perhaps it crashed, or the hardware was needed
12763 for a different activity. To handle these cases, you can arrange to
12764 dump the trace data into a file, and later use that file as a source
12765 of trace data, via the @code{target tfile} command.
12770 @item tsave [ -r ] @var{filename}
12771 @itemx tsave [-ctf] @var{dirname}
12772 Save the trace data to @var{filename}. By default, this command
12773 assumes that @var{filename} refers to the host filesystem, so if
12774 necessary @value{GDBN} will copy raw trace data up from the target and
12775 then save it. If the target supports it, you can also supply the
12776 optional argument @code{-r} (``remote'') to direct the target to save
12777 the data directly into @var{filename} in its own filesystem, which may be
12778 more efficient if the trace buffer is very large. (Note, however, that
12779 @code{target tfile} can only read from files accessible to the host.)
12780 By default, this command will save trace frame in tfile format.
12781 You can supply the optional argument @code{-ctf} to save date in CTF
12782 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12783 that can be shared by multiple debugging and tracing tools. Please go to
12784 @indicateurl{http://www.efficios.com/ctf} to get more information.
12786 @kindex target tfile
12790 @item target tfile @var{filename}
12791 @itemx target ctf @var{dirname}
12792 Use the file named @var{filename} or directory named @var{dirname} as
12793 a source of trace data. Commands that examine data work as they do with
12794 a live target, but it is not possible to run any new trace experiments.
12795 @code{tstatus} will report the state of the trace run at the moment
12796 the data was saved, as well as the current trace frame you are examining.
12797 @var{filename} or @var{dirname} must be on a filesystem accessible to
12801 (@value{GDBP}) target ctf ctf.ctf
12802 (@value{GDBP}) tfind
12803 Found trace frame 0, tracepoint 2
12804 39 ++a; /* set tracepoint 1 here */
12805 (@value{GDBP}) tdump
12806 Data collected at tracepoint 2, trace frame 0:
12810 c = @{"123", "456", "789", "123", "456", "789"@}
12811 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12819 @chapter Debugging Programs That Use Overlays
12822 If your program is too large to fit completely in your target system's
12823 memory, you can sometimes use @dfn{overlays} to work around this
12824 problem. @value{GDBN} provides some support for debugging programs that
12828 * How Overlays Work:: A general explanation of overlays.
12829 * Overlay Commands:: Managing overlays in @value{GDBN}.
12830 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12831 mapped by asking the inferior.
12832 * Overlay Sample Program:: A sample program using overlays.
12835 @node How Overlays Work
12836 @section How Overlays Work
12837 @cindex mapped overlays
12838 @cindex unmapped overlays
12839 @cindex load address, overlay's
12840 @cindex mapped address
12841 @cindex overlay area
12843 Suppose you have a computer whose instruction address space is only 64
12844 kilobytes long, but which has much more memory which can be accessed by
12845 other means: special instructions, segment registers, or memory
12846 management hardware, for example. Suppose further that you want to
12847 adapt a program which is larger than 64 kilobytes to run on this system.
12849 One solution is to identify modules of your program which are relatively
12850 independent, and need not call each other directly; call these modules
12851 @dfn{overlays}. Separate the overlays from the main program, and place
12852 their machine code in the larger memory. Place your main program in
12853 instruction memory, but leave at least enough space there to hold the
12854 largest overlay as well.
12856 Now, to call a function located in an overlay, you must first copy that
12857 overlay's machine code from the large memory into the space set aside
12858 for it in the instruction memory, and then jump to its entry point
12861 @c NB: In the below the mapped area's size is greater or equal to the
12862 @c size of all overlays. This is intentional to remind the developer
12863 @c that overlays don't necessarily need to be the same size.
12867 Data Instruction Larger
12868 Address Space Address Space Address Space
12869 +-----------+ +-----------+ +-----------+
12871 +-----------+ +-----------+ +-----------+<-- overlay 1
12872 | program | | main | .----| overlay 1 | load address
12873 | variables | | program | | +-----------+
12874 | and heap | | | | | |
12875 +-----------+ | | | +-----------+<-- overlay 2
12876 | | +-----------+ | | | load address
12877 +-----------+ | | | .-| overlay 2 |
12879 mapped --->+-----------+ | | +-----------+
12880 address | | | | | |
12881 | overlay | <-' | | |
12882 | area | <---' +-----------+<-- overlay 3
12883 | | <---. | | load address
12884 +-----------+ `--| overlay 3 |
12891 @anchor{A code overlay}A code overlay
12895 The diagram (@pxref{A code overlay}) shows a system with separate data
12896 and instruction address spaces. To map an overlay, the program copies
12897 its code from the larger address space to the instruction address space.
12898 Since the overlays shown here all use the same mapped address, only one
12899 may be mapped at a time. For a system with a single address space for
12900 data and instructions, the diagram would be similar, except that the
12901 program variables and heap would share an address space with the main
12902 program and the overlay area.
12904 An overlay loaded into instruction memory and ready for use is called a
12905 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12906 instruction memory. An overlay not present (or only partially present)
12907 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12908 is its address in the larger memory. The mapped address is also called
12909 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12910 called the @dfn{load memory address}, or @dfn{LMA}.
12912 Unfortunately, overlays are not a completely transparent way to adapt a
12913 program to limited instruction memory. They introduce a new set of
12914 global constraints you must keep in mind as you design your program:
12919 Before calling or returning to a function in an overlay, your program
12920 must make sure that overlay is actually mapped. Otherwise, the call or
12921 return will transfer control to the right address, but in the wrong
12922 overlay, and your program will probably crash.
12925 If the process of mapping an overlay is expensive on your system, you
12926 will need to choose your overlays carefully to minimize their effect on
12927 your program's performance.
12930 The executable file you load onto your system must contain each
12931 overlay's instructions, appearing at the overlay's load address, not its
12932 mapped address. However, each overlay's instructions must be relocated
12933 and its symbols defined as if the overlay were at its mapped address.
12934 You can use GNU linker scripts to specify different load and relocation
12935 addresses for pieces of your program; see @ref{Overlay Description,,,
12936 ld.info, Using ld: the GNU linker}.
12939 The procedure for loading executable files onto your system must be able
12940 to load their contents into the larger address space as well as the
12941 instruction and data spaces.
12945 The overlay system described above is rather simple, and could be
12946 improved in many ways:
12951 If your system has suitable bank switch registers or memory management
12952 hardware, you could use those facilities to make an overlay's load area
12953 contents simply appear at their mapped address in instruction space.
12954 This would probably be faster than copying the overlay to its mapped
12955 area in the usual way.
12958 If your overlays are small enough, you could set aside more than one
12959 overlay area, and have more than one overlay mapped at a time.
12962 You can use overlays to manage data, as well as instructions. In
12963 general, data overlays are even less transparent to your design than
12964 code overlays: whereas code overlays only require care when you call or
12965 return to functions, data overlays require care every time you access
12966 the data. Also, if you change the contents of a data overlay, you
12967 must copy its contents back out to its load address before you can copy a
12968 different data overlay into the same mapped area.
12973 @node Overlay Commands
12974 @section Overlay Commands
12976 To use @value{GDBN}'s overlay support, each overlay in your program must
12977 correspond to a separate section of the executable file. The section's
12978 virtual memory address and load memory address must be the overlay's
12979 mapped and load addresses. Identifying overlays with sections allows
12980 @value{GDBN} to determine the appropriate address of a function or
12981 variable, depending on whether the overlay is mapped or not.
12983 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12984 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12989 Disable @value{GDBN}'s overlay support. When overlay support is
12990 disabled, @value{GDBN} assumes that all functions and variables are
12991 always present at their mapped addresses. By default, @value{GDBN}'s
12992 overlay support is disabled.
12994 @item overlay manual
12995 @cindex manual overlay debugging
12996 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12997 relies on you to tell it which overlays are mapped, and which are not,
12998 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12999 commands described below.
13001 @item overlay map-overlay @var{overlay}
13002 @itemx overlay map @var{overlay}
13003 @cindex map an overlay
13004 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13005 be the name of the object file section containing the overlay. When an
13006 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13007 functions and variables at their mapped addresses. @value{GDBN} assumes
13008 that any other overlays whose mapped ranges overlap that of
13009 @var{overlay} are now unmapped.
13011 @item overlay unmap-overlay @var{overlay}
13012 @itemx overlay unmap @var{overlay}
13013 @cindex unmap an overlay
13014 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13015 must be the name of the object file section containing the overlay.
13016 When an overlay is unmapped, @value{GDBN} assumes it can find the
13017 overlay's functions and variables at their load addresses.
13020 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13021 consults a data structure the overlay manager maintains in the inferior
13022 to see which overlays are mapped. For details, see @ref{Automatic
13023 Overlay Debugging}.
13025 @item overlay load-target
13026 @itemx overlay load
13027 @cindex reloading the overlay table
13028 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13029 re-reads the table @value{GDBN} automatically each time the inferior
13030 stops, so this command should only be necessary if you have changed the
13031 overlay mapping yourself using @value{GDBN}. This command is only
13032 useful when using automatic overlay debugging.
13034 @item overlay list-overlays
13035 @itemx overlay list
13036 @cindex listing mapped overlays
13037 Display a list of the overlays currently mapped, along with their mapped
13038 addresses, load addresses, and sizes.
13042 Normally, when @value{GDBN} prints a code address, it includes the name
13043 of the function the address falls in:
13046 (@value{GDBP}) print main
13047 $3 = @{int ()@} 0x11a0 <main>
13050 When overlay debugging is enabled, @value{GDBN} recognizes code in
13051 unmapped overlays, and prints the names of unmapped functions with
13052 asterisks around them. For example, if @code{foo} is a function in an
13053 unmapped overlay, @value{GDBN} prints it this way:
13056 (@value{GDBP}) overlay list
13057 No sections are mapped.
13058 (@value{GDBP}) print foo
13059 $5 = @{int (int)@} 0x100000 <*foo*>
13062 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13066 (@value{GDBP}) overlay list
13067 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13068 mapped at 0x1016 - 0x104a
13069 (@value{GDBP}) print foo
13070 $6 = @{int (int)@} 0x1016 <foo>
13073 When overlay debugging is enabled, @value{GDBN} can find the correct
13074 address for functions and variables in an overlay, whether or not the
13075 overlay is mapped. This allows most @value{GDBN} commands, like
13076 @code{break} and @code{disassemble}, to work normally, even on unmapped
13077 code. However, @value{GDBN}'s breakpoint support has some limitations:
13081 @cindex breakpoints in overlays
13082 @cindex overlays, setting breakpoints in
13083 You can set breakpoints in functions in unmapped overlays, as long as
13084 @value{GDBN} can write to the overlay at its load address.
13086 @value{GDBN} can not set hardware or simulator-based breakpoints in
13087 unmapped overlays. However, if you set a breakpoint at the end of your
13088 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13089 you are using manual overlay management), @value{GDBN} will re-set its
13090 breakpoints properly.
13094 @node Automatic Overlay Debugging
13095 @section Automatic Overlay Debugging
13096 @cindex automatic overlay debugging
13098 @value{GDBN} can automatically track which overlays are mapped and which
13099 are not, given some simple co-operation from the overlay manager in the
13100 inferior. If you enable automatic overlay debugging with the
13101 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13102 looks in the inferior's memory for certain variables describing the
13103 current state of the overlays.
13105 Here are the variables your overlay manager must define to support
13106 @value{GDBN}'s automatic overlay debugging:
13110 @item @code{_ovly_table}:
13111 This variable must be an array of the following structures:
13116 /* The overlay's mapped address. */
13119 /* The size of the overlay, in bytes. */
13120 unsigned long size;
13122 /* The overlay's load address. */
13125 /* Non-zero if the overlay is currently mapped;
13127 unsigned long mapped;
13131 @item @code{_novlys}:
13132 This variable must be a four-byte signed integer, holding the total
13133 number of elements in @code{_ovly_table}.
13137 To decide whether a particular overlay is mapped or not, @value{GDBN}
13138 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13139 @code{lma} members equal the VMA and LMA of the overlay's section in the
13140 executable file. When @value{GDBN} finds a matching entry, it consults
13141 the entry's @code{mapped} member to determine whether the overlay is
13144 In addition, your overlay manager may define a function called
13145 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13146 will silently set a breakpoint there. If the overlay manager then
13147 calls this function whenever it has changed the overlay table, this
13148 will enable @value{GDBN} to accurately keep track of which overlays
13149 are in program memory, and update any breakpoints that may be set
13150 in overlays. This will allow breakpoints to work even if the
13151 overlays are kept in ROM or other non-writable memory while they
13152 are not being executed.
13154 @node Overlay Sample Program
13155 @section Overlay Sample Program
13156 @cindex overlay example program
13158 When linking a program which uses overlays, you must place the overlays
13159 at their load addresses, while relocating them to run at their mapped
13160 addresses. To do this, you must write a linker script (@pxref{Overlay
13161 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13162 since linker scripts are specific to a particular host system, target
13163 architecture, and target memory layout, this manual cannot provide
13164 portable sample code demonstrating @value{GDBN}'s overlay support.
13166 However, the @value{GDBN} source distribution does contain an overlaid
13167 program, with linker scripts for a few systems, as part of its test
13168 suite. The program consists of the following files from
13169 @file{gdb/testsuite/gdb.base}:
13173 The main program file.
13175 A simple overlay manager, used by @file{overlays.c}.
13180 Overlay modules, loaded and used by @file{overlays.c}.
13183 Linker scripts for linking the test program on the @code{d10v-elf}
13184 and @code{m32r-elf} targets.
13187 You can build the test program using the @code{d10v-elf} GCC
13188 cross-compiler like this:
13191 $ d10v-elf-gcc -g -c overlays.c
13192 $ d10v-elf-gcc -g -c ovlymgr.c
13193 $ d10v-elf-gcc -g -c foo.c
13194 $ d10v-elf-gcc -g -c bar.c
13195 $ d10v-elf-gcc -g -c baz.c
13196 $ d10v-elf-gcc -g -c grbx.c
13197 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13198 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13201 The build process is identical for any other architecture, except that
13202 you must substitute the appropriate compiler and linker script for the
13203 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13207 @chapter Using @value{GDBN} with Different Languages
13210 Although programming languages generally have common aspects, they are
13211 rarely expressed in the same manner. For instance, in ANSI C,
13212 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13213 Modula-2, it is accomplished by @code{p^}. Values can also be
13214 represented (and displayed) differently. Hex numbers in C appear as
13215 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13217 @cindex working language
13218 Language-specific information is built into @value{GDBN} for some languages,
13219 allowing you to express operations like the above in your program's
13220 native language, and allowing @value{GDBN} to output values in a manner
13221 consistent with the syntax of your program's native language. The
13222 language you use to build expressions is called the @dfn{working
13226 * Setting:: Switching between source languages
13227 * Show:: Displaying the language
13228 * Checks:: Type and range checks
13229 * Supported Languages:: Supported languages
13230 * Unsupported Languages:: Unsupported languages
13234 @section Switching Between Source Languages
13236 There are two ways to control the working language---either have @value{GDBN}
13237 set it automatically, or select it manually yourself. You can use the
13238 @code{set language} command for either purpose. On startup, @value{GDBN}
13239 defaults to setting the language automatically. The working language is
13240 used to determine how expressions you type are interpreted, how values
13243 In addition to the working language, every source file that
13244 @value{GDBN} knows about has its own working language. For some object
13245 file formats, the compiler might indicate which language a particular
13246 source file is in. However, most of the time @value{GDBN} infers the
13247 language from the name of the file. The language of a source file
13248 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13249 show each frame appropriately for its own language. There is no way to
13250 set the language of a source file from within @value{GDBN}, but you can
13251 set the language associated with a filename extension. @xref{Show, ,
13252 Displaying the Language}.
13254 This is most commonly a problem when you use a program, such
13255 as @code{cfront} or @code{f2c}, that generates C but is written in
13256 another language. In that case, make the
13257 program use @code{#line} directives in its C output; that way
13258 @value{GDBN} will know the correct language of the source code of the original
13259 program, and will display that source code, not the generated C code.
13262 * Filenames:: Filename extensions and languages.
13263 * Manually:: Setting the working language manually
13264 * Automatically:: Having @value{GDBN} infer the source language
13268 @subsection List of Filename Extensions and Languages
13270 If a source file name ends in one of the following extensions, then
13271 @value{GDBN} infers that its language is the one indicated.
13289 C@t{++} source file
13295 Objective-C source file
13299 Fortran source file
13302 Modula-2 source file
13306 Assembler source file. This actually behaves almost like C, but
13307 @value{GDBN} does not skip over function prologues when stepping.
13310 In addition, you may set the language associated with a filename
13311 extension. @xref{Show, , Displaying the Language}.
13314 @subsection Setting the Working Language
13316 If you allow @value{GDBN} to set the language automatically,
13317 expressions are interpreted the same way in your debugging session and
13320 @kindex set language
13321 If you wish, you may set the language manually. To do this, issue the
13322 command @samp{set language @var{lang}}, where @var{lang} is the name of
13323 a language, such as
13324 @code{c} or @code{modula-2}.
13325 For a list of the supported languages, type @samp{set language}.
13327 Setting the language manually prevents @value{GDBN} from updating the working
13328 language automatically. This can lead to confusion if you try
13329 to debug a program when the working language is not the same as the
13330 source language, when an expression is acceptable to both
13331 languages---but means different things. For instance, if the current
13332 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13340 might not have the effect you intended. In C, this means to add
13341 @code{b} and @code{c} and place the result in @code{a}. The result
13342 printed would be the value of @code{a}. In Modula-2, this means to compare
13343 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13345 @node Automatically
13346 @subsection Having @value{GDBN} Infer the Source Language
13348 To have @value{GDBN} set the working language automatically, use
13349 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13350 then infers the working language. That is, when your program stops in a
13351 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13352 working language to the language recorded for the function in that
13353 frame. If the language for a frame is unknown (that is, if the function
13354 or block corresponding to the frame was defined in a source file that
13355 does not have a recognized extension), the current working language is
13356 not changed, and @value{GDBN} issues a warning.
13358 This may not seem necessary for most programs, which are written
13359 entirely in one source language. However, program modules and libraries
13360 written in one source language can be used by a main program written in
13361 a different source language. Using @samp{set language auto} in this
13362 case frees you from having to set the working language manually.
13365 @section Displaying the Language
13367 The following commands help you find out which language is the
13368 working language, and also what language source files were written in.
13371 @item show language
13372 @anchor{show language}
13373 @kindex show language
13374 Display the current working language. This is the
13375 language you can use with commands such as @code{print} to
13376 build and compute expressions that may involve variables in your program.
13379 @kindex info frame@r{, show the source language}
13380 Display the source language for this frame. This language becomes the
13381 working language if you use an identifier from this frame.
13382 @xref{Frame Info, ,Information about a Frame}, to identify the other
13383 information listed here.
13386 @kindex info source@r{, show the source language}
13387 Display the source language of this source file.
13388 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13389 information listed here.
13392 In unusual circumstances, you may have source files with extensions
13393 not in the standard list. You can then set the extension associated
13394 with a language explicitly:
13397 @item set extension-language @var{ext} @var{language}
13398 @kindex set extension-language
13399 Tell @value{GDBN} that source files with extension @var{ext} are to be
13400 assumed as written in the source language @var{language}.
13402 @item info extensions
13403 @kindex info extensions
13404 List all the filename extensions and the associated languages.
13408 @section Type and Range Checking
13410 Some languages are designed to guard you against making seemingly common
13411 errors through a series of compile- and run-time checks. These include
13412 checking the type of arguments to functions and operators and making
13413 sure mathematical overflows are caught at run time. Checks such as
13414 these help to ensure a program's correctness once it has been compiled
13415 by eliminating type mismatches and providing active checks for range
13416 errors when your program is running.
13418 By default @value{GDBN} checks for these errors according to the
13419 rules of the current source language. Although @value{GDBN} does not check
13420 the statements in your program, it can check expressions entered directly
13421 into @value{GDBN} for evaluation via the @code{print} command, for example.
13424 * Type Checking:: An overview of type checking
13425 * Range Checking:: An overview of range checking
13428 @cindex type checking
13429 @cindex checks, type
13430 @node Type Checking
13431 @subsection An Overview of Type Checking
13433 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13434 arguments to operators and functions have to be of the correct type,
13435 otherwise an error occurs. These checks prevent type mismatch
13436 errors from ever causing any run-time problems. For example,
13439 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13441 (@value{GDBP}) print obj.my_method (0)
13444 (@value{GDBP}) print obj.my_method (0x1234)
13445 Cannot resolve method klass::my_method to any overloaded instance
13448 The second example fails because in C@t{++} the integer constant
13449 @samp{0x1234} is not type-compatible with the pointer parameter type.
13451 For the expressions you use in @value{GDBN} commands, you can tell
13452 @value{GDBN} to not enforce strict type checking or
13453 to treat any mismatches as errors and abandon the expression;
13454 When type checking is disabled, @value{GDBN} successfully evaluates
13455 expressions like the second example above.
13457 Even if type checking is off, there may be other reasons
13458 related to type that prevent @value{GDBN} from evaluating an expression.
13459 For instance, @value{GDBN} does not know how to add an @code{int} and
13460 a @code{struct foo}. These particular type errors have nothing to do
13461 with the language in use and usually arise from expressions which make
13462 little sense to evaluate anyway.
13464 @value{GDBN} provides some additional commands for controlling type checking:
13466 @kindex set check type
13467 @kindex show check type
13469 @item set check type on
13470 @itemx set check type off
13471 Set strict type checking on or off. If any type mismatches occur in
13472 evaluating an expression while type checking is on, @value{GDBN} prints a
13473 message and aborts evaluation of the expression.
13475 @item show check type
13476 Show the current setting of type checking and whether @value{GDBN}
13477 is enforcing strict type checking rules.
13480 @cindex range checking
13481 @cindex checks, range
13482 @node Range Checking
13483 @subsection An Overview of Range Checking
13485 In some languages (such as Modula-2), it is an error to exceed the
13486 bounds of a type; this is enforced with run-time checks. Such range
13487 checking is meant to ensure program correctness by making sure
13488 computations do not overflow, or indices on an array element access do
13489 not exceed the bounds of the array.
13491 For expressions you use in @value{GDBN} commands, you can tell
13492 @value{GDBN} to treat range errors in one of three ways: ignore them,
13493 always treat them as errors and abandon the expression, or issue
13494 warnings but evaluate the expression anyway.
13496 A range error can result from numerical overflow, from exceeding an
13497 array index bound, or when you type a constant that is not a member
13498 of any type. Some languages, however, do not treat overflows as an
13499 error. In many implementations of C, mathematical overflow causes the
13500 result to ``wrap around'' to lower values---for example, if @var{m} is
13501 the largest integer value, and @var{s} is the smallest, then
13504 @var{m} + 1 @result{} @var{s}
13507 This, too, is specific to individual languages, and in some cases
13508 specific to individual compilers or machines. @xref{Supported Languages, ,
13509 Supported Languages}, for further details on specific languages.
13511 @value{GDBN} provides some additional commands for controlling the range checker:
13513 @kindex set check range
13514 @kindex show check range
13516 @item set check range auto
13517 Set range checking on or off based on the current working language.
13518 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13521 @item set check range on
13522 @itemx set check range off
13523 Set range checking on or off, overriding the default setting for the
13524 current working language. A warning is issued if the setting does not
13525 match the language default. If a range error occurs and range checking is on,
13526 then a message is printed and evaluation of the expression is aborted.
13528 @item set check range warn
13529 Output messages when the @value{GDBN} range checker detects a range error,
13530 but attempt to evaluate the expression anyway. Evaluating the
13531 expression may still be impossible for other reasons, such as accessing
13532 memory that the process does not own (a typical example from many Unix
13536 Show the current setting of the range checker, and whether or not it is
13537 being set automatically by @value{GDBN}.
13540 @node Supported Languages
13541 @section Supported Languages
13543 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13544 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13545 @c This is false ...
13546 Some @value{GDBN} features may be used in expressions regardless of the
13547 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13548 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13549 ,Expressions}) can be used with the constructs of any supported
13552 The following sections detail to what degree each source language is
13553 supported by @value{GDBN}. These sections are not meant to be language
13554 tutorials or references, but serve only as a reference guide to what the
13555 @value{GDBN} expression parser accepts, and what input and output
13556 formats should look like for different languages. There are many good
13557 books written on each of these languages; please look to these for a
13558 language reference or tutorial.
13561 * C:: C and C@t{++}
13564 * Objective-C:: Objective-C
13565 * OpenCL C:: OpenCL C
13566 * Fortran:: Fortran
13568 * Modula-2:: Modula-2
13573 @subsection C and C@t{++}
13575 @cindex C and C@t{++}
13576 @cindex expressions in C or C@t{++}
13578 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13579 to both languages. Whenever this is the case, we discuss those languages
13583 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13584 @cindex @sc{gnu} C@t{++}
13585 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13586 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13587 effectively, you must compile your C@t{++} programs with a supported
13588 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13589 compiler (@code{aCC}).
13592 * C Operators:: C and C@t{++} operators
13593 * C Constants:: C and C@t{++} constants
13594 * C Plus Plus Expressions:: C@t{++} expressions
13595 * C Defaults:: Default settings for C and C@t{++}
13596 * C Checks:: C and C@t{++} type and range checks
13597 * Debugging C:: @value{GDBN} and C
13598 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13599 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13603 @subsubsection C and C@t{++} Operators
13605 @cindex C and C@t{++} operators
13607 Operators must be defined on values of specific types. For instance,
13608 @code{+} is defined on numbers, but not on structures. Operators are
13609 often defined on groups of types.
13611 For the purposes of C and C@t{++}, the following definitions hold:
13616 @emph{Integral types} include @code{int} with any of its storage-class
13617 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13620 @emph{Floating-point types} include @code{float}, @code{double}, and
13621 @code{long double} (if supported by the target platform).
13624 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13627 @emph{Scalar types} include all of the above.
13632 The following operators are supported. They are listed here
13633 in order of increasing precedence:
13637 The comma or sequencing operator. Expressions in a comma-separated list
13638 are evaluated from left to right, with the result of the entire
13639 expression being the last expression evaluated.
13642 Assignment. The value of an assignment expression is the value
13643 assigned. Defined on scalar types.
13646 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13647 and translated to @w{@code{@var{a} = @var{a op b}}}.
13648 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13649 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13650 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13653 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13654 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13658 Logical @sc{or}. Defined on integral types.
13661 Logical @sc{and}. Defined on integral types.
13664 Bitwise @sc{or}. Defined on integral types.
13667 Bitwise exclusive-@sc{or}. Defined on integral types.
13670 Bitwise @sc{and}. Defined on integral types.
13673 Equality and inequality. Defined on scalar types. The value of these
13674 expressions is 0 for false and non-zero for true.
13676 @item <@r{, }>@r{, }<=@r{, }>=
13677 Less than, greater than, less than or equal, greater than or equal.
13678 Defined on scalar types. The value of these expressions is 0 for false
13679 and non-zero for true.
13682 left shift, and right shift. Defined on integral types.
13685 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13688 Addition and subtraction. Defined on integral types, floating-point types and
13691 @item *@r{, }/@r{, }%
13692 Multiplication, division, and modulus. Multiplication and division are
13693 defined on integral and floating-point types. Modulus is defined on
13697 Increment and decrement. When appearing before a variable, the
13698 operation is performed before the variable is used in an expression;
13699 when appearing after it, the variable's value is used before the
13700 operation takes place.
13703 Pointer dereferencing. Defined on pointer types. Same precedence as
13707 Address operator. Defined on variables. Same precedence as @code{++}.
13709 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13710 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13711 to examine the address
13712 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13716 Negative. Defined on integral and floating-point types. Same
13717 precedence as @code{++}.
13720 Logical negation. Defined on integral types. Same precedence as
13724 Bitwise complement operator. Defined on integral types. Same precedence as
13729 Structure member, and pointer-to-structure member. For convenience,
13730 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13731 pointer based on the stored type information.
13732 Defined on @code{struct} and @code{union} data.
13735 Dereferences of pointers to members.
13738 Array indexing. @code{@var{a}[@var{i}]} is defined as
13739 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13742 Function parameter list. Same precedence as @code{->}.
13745 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13746 and @code{class} types.
13749 Doubled colons also represent the @value{GDBN} scope operator
13750 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13754 If an operator is redefined in the user code, @value{GDBN} usually
13755 attempts to invoke the redefined version instead of using the operator's
13756 predefined meaning.
13759 @subsubsection C and C@t{++} Constants
13761 @cindex C and C@t{++} constants
13763 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13768 Integer constants are a sequence of digits. Octal constants are
13769 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13770 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13771 @samp{l}, specifying that the constant should be treated as a
13775 Floating point constants are a sequence of digits, followed by a decimal
13776 point, followed by a sequence of digits, and optionally followed by an
13777 exponent. An exponent is of the form:
13778 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13779 sequence of digits. The @samp{+} is optional for positive exponents.
13780 A floating-point constant may also end with a letter @samp{f} or
13781 @samp{F}, specifying that the constant should be treated as being of
13782 the @code{float} (as opposed to the default @code{double}) type; or with
13783 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13787 Enumerated constants consist of enumerated identifiers, or their
13788 integral equivalents.
13791 Character constants are a single character surrounded by single quotes
13792 (@code{'}), or a number---the ordinal value of the corresponding character
13793 (usually its @sc{ascii} value). Within quotes, the single character may
13794 be represented by a letter or by @dfn{escape sequences}, which are of
13795 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13796 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13797 @samp{@var{x}} is a predefined special character---for example,
13798 @samp{\n} for newline.
13800 Wide character constants can be written by prefixing a character
13801 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13802 form of @samp{x}. The target wide character set is used when
13803 computing the value of this constant (@pxref{Character Sets}).
13806 String constants are a sequence of character constants surrounded by
13807 double quotes (@code{"}). Any valid character constant (as described
13808 above) may appear. Double quotes within the string must be preceded by
13809 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13812 Wide string constants can be written by prefixing a string constant
13813 with @samp{L}, as in C. The target wide character set is used when
13814 computing the value of this constant (@pxref{Character Sets}).
13817 Pointer constants are an integral value. You can also write pointers
13818 to constants using the C operator @samp{&}.
13821 Array constants are comma-separated lists surrounded by braces @samp{@{}
13822 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13823 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13824 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13827 @node C Plus Plus Expressions
13828 @subsubsection C@t{++} Expressions
13830 @cindex expressions in C@t{++}
13831 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13833 @cindex debugging C@t{++} programs
13834 @cindex C@t{++} compilers
13835 @cindex debug formats and C@t{++}
13836 @cindex @value{NGCC} and C@t{++}
13838 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13839 the proper compiler and the proper debug format. Currently,
13840 @value{GDBN} works best when debugging C@t{++} code that is compiled
13841 with the most recent version of @value{NGCC} possible. The DWARF
13842 debugging format is preferred; @value{NGCC} defaults to this on most
13843 popular platforms. Other compilers and/or debug formats are likely to
13844 work badly or not at all when using @value{GDBN} to debug C@t{++}
13845 code. @xref{Compilation}.
13850 @cindex member functions
13852 Member function calls are allowed; you can use expressions like
13855 count = aml->GetOriginal(x, y)
13858 @vindex this@r{, inside C@t{++} member functions}
13859 @cindex namespace in C@t{++}
13861 While a member function is active (in the selected stack frame), your
13862 expressions have the same namespace available as the member function;
13863 that is, @value{GDBN} allows implicit references to the class instance
13864 pointer @code{this} following the same rules as C@t{++}. @code{using}
13865 declarations in the current scope are also respected by @value{GDBN}.
13867 @cindex call overloaded functions
13868 @cindex overloaded functions, calling
13869 @cindex type conversions in C@t{++}
13871 You can call overloaded functions; @value{GDBN} resolves the function
13872 call to the right definition, with some restrictions. @value{GDBN} does not
13873 perform overload resolution involving user-defined type conversions,
13874 calls to constructors, or instantiations of templates that do not exist
13875 in the program. It also cannot handle ellipsis argument lists or
13878 It does perform integral conversions and promotions, floating-point
13879 promotions, arithmetic conversions, pointer conversions, conversions of
13880 class objects to base classes, and standard conversions such as those of
13881 functions or arrays to pointers; it requires an exact match on the
13882 number of function arguments.
13884 Overload resolution is always performed, unless you have specified
13885 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13886 ,@value{GDBN} Features for C@t{++}}.
13888 You must specify @code{set overload-resolution off} in order to use an
13889 explicit function signature to call an overloaded function, as in
13891 p 'foo(char,int)'('x', 13)
13894 The @value{GDBN} command-completion facility can simplify this;
13895 see @ref{Completion, ,Command Completion}.
13897 @cindex reference declarations
13899 @value{GDBN} understands variables declared as C@t{++} references; you can use
13900 them in expressions just as you do in C@t{++} source---they are automatically
13903 In the parameter list shown when @value{GDBN} displays a frame, the values of
13904 reference variables are not displayed (unlike other variables); this
13905 avoids clutter, since references are often used for large structures.
13906 The @emph{address} of a reference variable is always shown, unless
13907 you have specified @samp{set print address off}.
13910 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13911 expressions can use it just as expressions in your program do. Since
13912 one scope may be defined in another, you can use @code{::} repeatedly if
13913 necessary, for example in an expression like
13914 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13915 resolving name scope by reference to source files, in both C and C@t{++}
13916 debugging (@pxref{Variables, ,Program Variables}).
13919 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13924 @subsubsection C and C@t{++} Defaults
13926 @cindex C and C@t{++} defaults
13928 If you allow @value{GDBN} to set range checking automatically, it
13929 defaults to @code{off} whenever the working language changes to
13930 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13931 selects the working language.
13933 If you allow @value{GDBN} to set the language automatically, it
13934 recognizes source files whose names end with @file{.c}, @file{.C}, or
13935 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13936 these files, it sets the working language to C or C@t{++}.
13937 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13938 for further details.
13941 @subsubsection C and C@t{++} Type and Range Checks
13943 @cindex C and C@t{++} checks
13945 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13946 checking is used. However, if you turn type checking off, @value{GDBN}
13947 will allow certain non-standard conversions, such as promoting integer
13948 constants to pointers.
13950 Range checking, if turned on, is done on mathematical operations. Array
13951 indices are not checked, since they are often used to index a pointer
13952 that is not itself an array.
13955 @subsubsection @value{GDBN} and C
13957 The @code{set print union} and @code{show print union} commands apply to
13958 the @code{union} type. When set to @samp{on}, any @code{union} that is
13959 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13960 appears as @samp{@{...@}}.
13962 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13963 with pointers and a memory allocation function. @xref{Expressions,
13966 @node Debugging C Plus Plus
13967 @subsubsection @value{GDBN} Features for C@t{++}
13969 @cindex commands for C@t{++}
13971 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13972 designed specifically for use with C@t{++}. Here is a summary:
13975 @cindex break in overloaded functions
13976 @item @r{breakpoint menus}
13977 When you want a breakpoint in a function whose name is overloaded,
13978 @value{GDBN} has the capability to display a menu of possible breakpoint
13979 locations to help you specify which function definition you want.
13980 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13982 @cindex overloading in C@t{++}
13983 @item rbreak @var{regex}
13984 Setting breakpoints using regular expressions is helpful for setting
13985 breakpoints on overloaded functions that are not members of any special
13987 @xref{Set Breaks, ,Setting Breakpoints}.
13989 @cindex C@t{++} exception handling
13991 @itemx catch rethrow
13993 Debug C@t{++} exception handling using these commands. @xref{Set
13994 Catchpoints, , Setting Catchpoints}.
13996 @cindex inheritance
13997 @item ptype @var{typename}
13998 Print inheritance relationships as well as other information for type
14000 @xref{Symbols, ,Examining the Symbol Table}.
14002 @item info vtbl @var{expression}.
14003 The @code{info vtbl} command can be used to display the virtual
14004 method tables of the object computed by @var{expression}. This shows
14005 one entry per virtual table; there may be multiple virtual tables when
14006 multiple inheritance is in use.
14008 @cindex C@t{++} symbol display
14009 @item set print demangle
14010 @itemx show print demangle
14011 @itemx set print asm-demangle
14012 @itemx show print asm-demangle
14013 Control whether C@t{++} symbols display in their source form, both when
14014 displaying code as C@t{++} source and when displaying disassemblies.
14015 @xref{Print Settings, ,Print Settings}.
14017 @item set print object
14018 @itemx show print object
14019 Choose whether to print derived (actual) or declared types of objects.
14020 @xref{Print Settings, ,Print Settings}.
14022 @item set print vtbl
14023 @itemx show print vtbl
14024 Control the format for printing virtual function tables.
14025 @xref{Print Settings, ,Print Settings}.
14026 (The @code{vtbl} commands do not work on programs compiled with the HP
14027 ANSI C@t{++} compiler (@code{aCC}).)
14029 @kindex set overload-resolution
14030 @cindex overloaded functions, overload resolution
14031 @item set overload-resolution on
14032 Enable overload resolution for C@t{++} expression evaluation. The default
14033 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14034 and searches for a function whose signature matches the argument types,
14035 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14036 Expressions, ,C@t{++} Expressions}, for details).
14037 If it cannot find a match, it emits a message.
14039 @item set overload-resolution off
14040 Disable overload resolution for C@t{++} expression evaluation. For
14041 overloaded functions that are not class member functions, @value{GDBN}
14042 chooses the first function of the specified name that it finds in the
14043 symbol table, whether or not its arguments are of the correct type. For
14044 overloaded functions that are class member functions, @value{GDBN}
14045 searches for a function whose signature @emph{exactly} matches the
14048 @kindex show overload-resolution
14049 @item show overload-resolution
14050 Show the current setting of overload resolution.
14052 @item @r{Overloaded symbol names}
14053 You can specify a particular definition of an overloaded symbol, using
14054 the same notation that is used to declare such symbols in C@t{++}: type
14055 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14056 also use the @value{GDBN} command-line word completion facilities to list the
14057 available choices, or to finish the type list for you.
14058 @xref{Completion,, Command Completion}, for details on how to do this.
14061 @node Decimal Floating Point
14062 @subsubsection Decimal Floating Point format
14063 @cindex decimal floating point format
14065 @value{GDBN} can examine, set and perform computations with numbers in
14066 decimal floating point format, which in the C language correspond to the
14067 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14068 specified by the extension to support decimal floating-point arithmetic.
14070 There are two encodings in use, depending on the architecture: BID (Binary
14071 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14072 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14075 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14076 to manipulate decimal floating point numbers, it is not possible to convert
14077 (using a cast, for example) integers wider than 32-bit to decimal float.
14079 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14080 point computations, error checking in decimal float operations ignores
14081 underflow, overflow and divide by zero exceptions.
14083 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14084 to inspect @code{_Decimal128} values stored in floating point registers.
14085 See @ref{PowerPC,,PowerPC} for more details.
14091 @value{GDBN} can be used to debug programs written in D and compiled with
14092 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14093 specific feature --- dynamic arrays.
14098 @cindex Go (programming language)
14099 @value{GDBN} can be used to debug programs written in Go and compiled with
14100 @file{gccgo} or @file{6g} compilers.
14102 Here is a summary of the Go-specific features and restrictions:
14105 @cindex current Go package
14106 @item The current Go package
14107 The name of the current package does not need to be specified when
14108 specifying global variables and functions.
14110 For example, given the program:
14114 var myglob = "Shall we?"
14120 When stopped inside @code{main} either of these work:
14124 (gdb) p main.myglob
14127 @cindex builtin Go types
14128 @item Builtin Go types
14129 The @code{string} type is recognized by @value{GDBN} and is printed
14132 @cindex builtin Go functions
14133 @item Builtin Go functions
14134 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14135 function and handles it internally.
14137 @cindex restrictions on Go expressions
14138 @item Restrictions on Go expressions
14139 All Go operators are supported except @code{&^}.
14140 The Go @code{_} ``blank identifier'' is not supported.
14141 Automatic dereferencing of pointers is not supported.
14145 @subsection Objective-C
14147 @cindex Objective-C
14148 This section provides information about some commands and command
14149 options that are useful for debugging Objective-C code. See also
14150 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14151 few more commands specific to Objective-C support.
14154 * Method Names in Commands::
14155 * The Print Command with Objective-C::
14158 @node Method Names in Commands
14159 @subsubsection Method Names in Commands
14161 The following commands have been extended to accept Objective-C method
14162 names as line specifications:
14164 @kindex clear@r{, and Objective-C}
14165 @kindex break@r{, and Objective-C}
14166 @kindex info line@r{, and Objective-C}
14167 @kindex jump@r{, and Objective-C}
14168 @kindex list@r{, and Objective-C}
14172 @item @code{info line}
14177 A fully qualified Objective-C method name is specified as
14180 -[@var{Class} @var{methodName}]
14183 where the minus sign is used to indicate an instance method and a
14184 plus sign (not shown) is used to indicate a class method. The class
14185 name @var{Class} and method name @var{methodName} are enclosed in
14186 brackets, similar to the way messages are specified in Objective-C
14187 source code. For example, to set a breakpoint at the @code{create}
14188 instance method of class @code{Fruit} in the program currently being
14192 break -[Fruit create]
14195 To list ten program lines around the @code{initialize} class method,
14199 list +[NSText initialize]
14202 In the current version of @value{GDBN}, the plus or minus sign is
14203 required. In future versions of @value{GDBN}, the plus or minus
14204 sign will be optional, but you can use it to narrow the search. It
14205 is also possible to specify just a method name:
14211 You must specify the complete method name, including any colons. If
14212 your program's source files contain more than one @code{create} method,
14213 you'll be presented with a numbered list of classes that implement that
14214 method. Indicate your choice by number, or type @samp{0} to exit if
14217 As another example, to clear a breakpoint established at the
14218 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14221 clear -[NSWindow makeKeyAndOrderFront:]
14224 @node The Print Command with Objective-C
14225 @subsubsection The Print Command With Objective-C
14226 @cindex Objective-C, print objects
14227 @kindex print-object
14228 @kindex po @r{(@code{print-object})}
14230 The print command has also been extended to accept methods. For example:
14233 print -[@var{object} hash]
14236 @cindex print an Objective-C object description
14237 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14239 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14240 and print the result. Also, an additional command has been added,
14241 @code{print-object} or @code{po} for short, which is meant to print
14242 the description of an object. However, this command may only work
14243 with certain Objective-C libraries that have a particular hook
14244 function, @code{_NSPrintForDebugger}, defined.
14247 @subsection OpenCL C
14250 This section provides information about @value{GDBN}s OpenCL C support.
14253 * OpenCL C Datatypes::
14254 * OpenCL C Expressions::
14255 * OpenCL C Operators::
14258 @node OpenCL C Datatypes
14259 @subsubsection OpenCL C Datatypes
14261 @cindex OpenCL C Datatypes
14262 @value{GDBN} supports the builtin scalar and vector datatypes specified
14263 by OpenCL 1.1. In addition the half- and double-precision floating point
14264 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14265 extensions are also known to @value{GDBN}.
14267 @node OpenCL C Expressions
14268 @subsubsection OpenCL C Expressions
14270 @cindex OpenCL C Expressions
14271 @value{GDBN} supports accesses to vector components including the access as
14272 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14273 supported by @value{GDBN} can be used as well.
14275 @node OpenCL C Operators
14276 @subsubsection OpenCL C Operators
14278 @cindex OpenCL C Operators
14279 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14283 @subsection Fortran
14284 @cindex Fortran-specific support in @value{GDBN}
14286 @value{GDBN} can be used to debug programs written in Fortran, but it
14287 currently supports only the features of Fortran 77 language.
14289 @cindex trailing underscore, in Fortran symbols
14290 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14291 among them) append an underscore to the names of variables and
14292 functions. When you debug programs compiled by those compilers, you
14293 will need to refer to variables and functions with a trailing
14297 * Fortran Operators:: Fortran operators and expressions
14298 * Fortran Defaults:: Default settings for Fortran
14299 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14302 @node Fortran Operators
14303 @subsubsection Fortran Operators and Expressions
14305 @cindex Fortran operators and expressions
14307 Operators must be defined on values of specific types. For instance,
14308 @code{+} is defined on numbers, but not on characters or other non-
14309 arithmetic types. Operators are often defined on groups of types.
14313 The exponentiation operator. It raises the first operand to the power
14317 The range operator. Normally used in the form of array(low:high) to
14318 represent a section of array.
14321 The access component operator. Normally used to access elements in derived
14322 types. Also suitable for unions. As unions aren't part of regular Fortran,
14323 this can only happen when accessing a register that uses a gdbarch-defined
14327 @node Fortran Defaults
14328 @subsubsection Fortran Defaults
14330 @cindex Fortran Defaults
14332 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14333 default uses case-insensitive matches for Fortran symbols. You can
14334 change that with the @samp{set case-insensitive} command, see
14335 @ref{Symbols}, for the details.
14337 @node Special Fortran Commands
14338 @subsubsection Special Fortran Commands
14340 @cindex Special Fortran commands
14342 @value{GDBN} has some commands to support Fortran-specific features,
14343 such as displaying common blocks.
14346 @cindex @code{COMMON} blocks, Fortran
14347 @kindex info common
14348 @item info common @r{[}@var{common-name}@r{]}
14349 This command prints the values contained in the Fortran @code{COMMON}
14350 block whose name is @var{common-name}. With no argument, the names of
14351 all @code{COMMON} blocks visible at the current program location are
14358 @cindex Pascal support in @value{GDBN}, limitations
14359 Debugging Pascal programs which use sets, subranges, file variables, or
14360 nested functions does not currently work. @value{GDBN} does not support
14361 entering expressions, printing values, or similar features using Pascal
14364 The Pascal-specific command @code{set print pascal_static-members}
14365 controls whether static members of Pascal objects are displayed.
14366 @xref{Print Settings, pascal_static-members}.
14369 @subsection Modula-2
14371 @cindex Modula-2, @value{GDBN} support
14373 The extensions made to @value{GDBN} to support Modula-2 only support
14374 output from the @sc{gnu} Modula-2 compiler (which is currently being
14375 developed). Other Modula-2 compilers are not currently supported, and
14376 attempting to debug executables produced by them is most likely
14377 to give an error as @value{GDBN} reads in the executable's symbol
14380 @cindex expressions in Modula-2
14382 * M2 Operators:: Built-in operators
14383 * Built-In Func/Proc:: Built-in functions and procedures
14384 * M2 Constants:: Modula-2 constants
14385 * M2 Types:: Modula-2 types
14386 * M2 Defaults:: Default settings for Modula-2
14387 * Deviations:: Deviations from standard Modula-2
14388 * M2 Checks:: Modula-2 type and range checks
14389 * M2 Scope:: The scope operators @code{::} and @code{.}
14390 * GDB/M2:: @value{GDBN} and Modula-2
14394 @subsubsection Operators
14395 @cindex Modula-2 operators
14397 Operators must be defined on values of specific types. For instance,
14398 @code{+} is defined on numbers, but not on structures. Operators are
14399 often defined on groups of types. For the purposes of Modula-2, the
14400 following definitions hold:
14405 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14409 @emph{Character types} consist of @code{CHAR} and its subranges.
14412 @emph{Floating-point types} consist of @code{REAL}.
14415 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14419 @emph{Scalar types} consist of all of the above.
14422 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14425 @emph{Boolean types} consist of @code{BOOLEAN}.
14429 The following operators are supported, and appear in order of
14430 increasing precedence:
14434 Function argument or array index separator.
14437 Assignment. The value of @var{var} @code{:=} @var{value} is
14441 Less than, greater than on integral, floating-point, or enumerated
14445 Less than or equal to, greater than or equal to
14446 on integral, floating-point and enumerated types, or set inclusion on
14447 set types. Same precedence as @code{<}.
14449 @item =@r{, }<>@r{, }#
14450 Equality and two ways of expressing inequality, valid on scalar types.
14451 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14452 available for inequality, since @code{#} conflicts with the script
14456 Set membership. Defined on set types and the types of their members.
14457 Same precedence as @code{<}.
14460 Boolean disjunction. Defined on boolean types.
14463 Boolean conjunction. Defined on boolean types.
14466 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14469 Addition and subtraction on integral and floating-point types, or union
14470 and difference on set types.
14473 Multiplication on integral and floating-point types, or set intersection
14477 Division on floating-point types, or symmetric set difference on set
14478 types. Same precedence as @code{*}.
14481 Integer division and remainder. Defined on integral types. Same
14482 precedence as @code{*}.
14485 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14488 Pointer dereferencing. Defined on pointer types.
14491 Boolean negation. Defined on boolean types. Same precedence as
14495 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14496 precedence as @code{^}.
14499 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14502 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14506 @value{GDBN} and Modula-2 scope operators.
14510 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14511 treats the use of the operator @code{IN}, or the use of operators
14512 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14513 @code{<=}, and @code{>=} on sets as an error.
14517 @node Built-In Func/Proc
14518 @subsubsection Built-in Functions and Procedures
14519 @cindex Modula-2 built-ins
14521 Modula-2 also makes available several built-in procedures and functions.
14522 In describing these, the following metavariables are used:
14527 represents an @code{ARRAY} variable.
14530 represents a @code{CHAR} constant or variable.
14533 represents a variable or constant of integral type.
14536 represents an identifier that belongs to a set. Generally used in the
14537 same function with the metavariable @var{s}. The type of @var{s} should
14538 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14541 represents a variable or constant of integral or floating-point type.
14544 represents a variable or constant of floating-point type.
14550 represents a variable.
14553 represents a variable or constant of one of many types. See the
14554 explanation of the function for details.
14557 All Modula-2 built-in procedures also return a result, described below.
14561 Returns the absolute value of @var{n}.
14564 If @var{c} is a lower case letter, it returns its upper case
14565 equivalent, otherwise it returns its argument.
14568 Returns the character whose ordinal value is @var{i}.
14571 Decrements the value in the variable @var{v} by one. Returns the new value.
14573 @item DEC(@var{v},@var{i})
14574 Decrements the value in the variable @var{v} by @var{i}. Returns the
14577 @item EXCL(@var{m},@var{s})
14578 Removes the element @var{m} from the set @var{s}. Returns the new
14581 @item FLOAT(@var{i})
14582 Returns the floating point equivalent of the integer @var{i}.
14584 @item HIGH(@var{a})
14585 Returns the index of the last member of @var{a}.
14588 Increments the value in the variable @var{v} by one. Returns the new value.
14590 @item INC(@var{v},@var{i})
14591 Increments the value in the variable @var{v} by @var{i}. Returns the
14594 @item INCL(@var{m},@var{s})
14595 Adds the element @var{m} to the set @var{s} if it is not already
14596 there. Returns the new set.
14599 Returns the maximum value of the type @var{t}.
14602 Returns the minimum value of the type @var{t}.
14605 Returns boolean TRUE if @var{i} is an odd number.
14608 Returns the ordinal value of its argument. For example, the ordinal
14609 value of a character is its @sc{ascii} value (on machines supporting the
14610 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14611 integral, character and enumerated types.
14613 @item SIZE(@var{x})
14614 Returns the size of its argument. @var{x} can be a variable or a type.
14616 @item TRUNC(@var{r})
14617 Returns the integral part of @var{r}.
14619 @item TSIZE(@var{x})
14620 Returns the size of its argument. @var{x} can be a variable or a type.
14622 @item VAL(@var{t},@var{i})
14623 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14627 @emph{Warning:} Sets and their operations are not yet supported, so
14628 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14632 @cindex Modula-2 constants
14634 @subsubsection Constants
14636 @value{GDBN} allows you to express the constants of Modula-2 in the following
14642 Integer constants are simply a sequence of digits. When used in an
14643 expression, a constant is interpreted to be type-compatible with the
14644 rest of the expression. Hexadecimal integers are specified by a
14645 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14648 Floating point constants appear as a sequence of digits, followed by a
14649 decimal point and another sequence of digits. An optional exponent can
14650 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14651 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14652 digits of the floating point constant must be valid decimal (base 10)
14656 Character constants consist of a single character enclosed by a pair of
14657 like quotes, either single (@code{'}) or double (@code{"}). They may
14658 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14659 followed by a @samp{C}.
14662 String constants consist of a sequence of characters enclosed by a
14663 pair of like quotes, either single (@code{'}) or double (@code{"}).
14664 Escape sequences in the style of C are also allowed. @xref{C
14665 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14669 Enumerated constants consist of an enumerated identifier.
14672 Boolean constants consist of the identifiers @code{TRUE} and
14676 Pointer constants consist of integral values only.
14679 Set constants are not yet supported.
14683 @subsubsection Modula-2 Types
14684 @cindex Modula-2 types
14686 Currently @value{GDBN} can print the following data types in Modula-2
14687 syntax: array types, record types, set types, pointer types, procedure
14688 types, enumerated types, subrange types and base types. You can also
14689 print the contents of variables declared using these type.
14690 This section gives a number of simple source code examples together with
14691 sample @value{GDBN} sessions.
14693 The first example contains the following section of code:
14702 and you can request @value{GDBN} to interrogate the type and value of
14703 @code{r} and @code{s}.
14706 (@value{GDBP}) print s
14708 (@value{GDBP}) ptype s
14710 (@value{GDBP}) print r
14712 (@value{GDBP}) ptype r
14717 Likewise if your source code declares @code{s} as:
14721 s: SET ['A'..'Z'] ;
14725 then you may query the type of @code{s} by:
14728 (@value{GDBP}) ptype s
14729 type = SET ['A'..'Z']
14733 Note that at present you cannot interactively manipulate set
14734 expressions using the debugger.
14736 The following example shows how you might declare an array in Modula-2
14737 and how you can interact with @value{GDBN} to print its type and contents:
14741 s: ARRAY [-10..10] OF CHAR ;
14745 (@value{GDBP}) ptype s
14746 ARRAY [-10..10] OF CHAR
14749 Note that the array handling is not yet complete and although the type
14750 is printed correctly, expression handling still assumes that all
14751 arrays have a lower bound of zero and not @code{-10} as in the example
14754 Here are some more type related Modula-2 examples:
14758 colour = (blue, red, yellow, green) ;
14759 t = [blue..yellow] ;
14767 The @value{GDBN} interaction shows how you can query the data type
14768 and value of a variable.
14771 (@value{GDBP}) print s
14773 (@value{GDBP}) ptype t
14774 type = [blue..yellow]
14778 In this example a Modula-2 array is declared and its contents
14779 displayed. Observe that the contents are written in the same way as
14780 their @code{C} counterparts.
14784 s: ARRAY [1..5] OF CARDINAL ;
14790 (@value{GDBP}) print s
14791 $1 = @{1, 0, 0, 0, 0@}
14792 (@value{GDBP}) ptype s
14793 type = ARRAY [1..5] OF CARDINAL
14796 The Modula-2 language interface to @value{GDBN} also understands
14797 pointer types as shown in this example:
14801 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14808 and you can request that @value{GDBN} describes the type of @code{s}.
14811 (@value{GDBP}) ptype s
14812 type = POINTER TO ARRAY [1..5] OF CARDINAL
14815 @value{GDBN} handles compound types as we can see in this example.
14816 Here we combine array types, record types, pointer types and subrange
14827 myarray = ARRAY myrange OF CARDINAL ;
14828 myrange = [-2..2] ;
14830 s: POINTER TO ARRAY myrange OF foo ;
14834 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14838 (@value{GDBP}) ptype s
14839 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14842 f3 : ARRAY [-2..2] OF CARDINAL;
14847 @subsubsection Modula-2 Defaults
14848 @cindex Modula-2 defaults
14850 If type and range checking are set automatically by @value{GDBN}, they
14851 both default to @code{on} whenever the working language changes to
14852 Modula-2. This happens regardless of whether you or @value{GDBN}
14853 selected the working language.
14855 If you allow @value{GDBN} to set the language automatically, then entering
14856 code compiled from a file whose name ends with @file{.mod} sets the
14857 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14858 Infer the Source Language}, for further details.
14861 @subsubsection Deviations from Standard Modula-2
14862 @cindex Modula-2, deviations from
14864 A few changes have been made to make Modula-2 programs easier to debug.
14865 This is done primarily via loosening its type strictness:
14869 Unlike in standard Modula-2, pointer constants can be formed by
14870 integers. This allows you to modify pointer variables during
14871 debugging. (In standard Modula-2, the actual address contained in a
14872 pointer variable is hidden from you; it can only be modified
14873 through direct assignment to another pointer variable or expression that
14874 returned a pointer.)
14877 C escape sequences can be used in strings and characters to represent
14878 non-printable characters. @value{GDBN} prints out strings with these
14879 escape sequences embedded. Single non-printable characters are
14880 printed using the @samp{CHR(@var{nnn})} format.
14883 The assignment operator (@code{:=}) returns the value of its right-hand
14887 All built-in procedures both modify @emph{and} return their argument.
14891 @subsubsection Modula-2 Type and Range Checks
14892 @cindex Modula-2 checks
14895 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14898 @c FIXME remove warning when type/range checks added
14900 @value{GDBN} considers two Modula-2 variables type equivalent if:
14904 They are of types that have been declared equivalent via a @code{TYPE
14905 @var{t1} = @var{t2}} statement
14908 They have been declared on the same line. (Note: This is true of the
14909 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14912 As long as type checking is enabled, any attempt to combine variables
14913 whose types are not equivalent is an error.
14915 Range checking is done on all mathematical operations, assignment, array
14916 index bounds, and all built-in functions and procedures.
14919 @subsubsection The Scope Operators @code{::} and @code{.}
14921 @cindex @code{.}, Modula-2 scope operator
14922 @cindex colon, doubled as scope operator
14924 @vindex colon-colon@r{, in Modula-2}
14925 @c Info cannot handle :: but TeX can.
14928 @vindex ::@r{, in Modula-2}
14931 There are a few subtle differences between the Modula-2 scope operator
14932 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14937 @var{module} . @var{id}
14938 @var{scope} :: @var{id}
14942 where @var{scope} is the name of a module or a procedure,
14943 @var{module} the name of a module, and @var{id} is any declared
14944 identifier within your program, except another module.
14946 Using the @code{::} operator makes @value{GDBN} search the scope
14947 specified by @var{scope} for the identifier @var{id}. If it is not
14948 found in the specified scope, then @value{GDBN} searches all scopes
14949 enclosing the one specified by @var{scope}.
14951 Using the @code{.} operator makes @value{GDBN} search the current scope for
14952 the identifier specified by @var{id} that was imported from the
14953 definition module specified by @var{module}. With this operator, it is
14954 an error if the identifier @var{id} was not imported from definition
14955 module @var{module}, or if @var{id} is not an identifier in
14959 @subsubsection @value{GDBN} and Modula-2
14961 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14962 Five subcommands of @code{set print} and @code{show print} apply
14963 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14964 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14965 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14966 analogue in Modula-2.
14968 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14969 with any language, is not useful with Modula-2. Its
14970 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14971 created in Modula-2 as they can in C or C@t{++}. However, because an
14972 address can be specified by an integral constant, the construct
14973 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14975 @cindex @code{#} in Modula-2
14976 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14977 interpreted as the beginning of a comment. Use @code{<>} instead.
14983 The extensions made to @value{GDBN} for Ada only support
14984 output from the @sc{gnu} Ada (GNAT) compiler.
14985 Other Ada compilers are not currently supported, and
14986 attempting to debug executables produced by them is most likely
14990 @cindex expressions in Ada
14992 * Ada Mode Intro:: General remarks on the Ada syntax
14993 and semantics supported by Ada mode
14995 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14996 * Additions to Ada:: Extensions of the Ada expression syntax.
14997 * Stopping Before Main Program:: Debugging the program during elaboration.
14998 * Ada Exceptions:: Ada Exceptions
14999 * Ada Tasks:: Listing and setting breakpoints in tasks.
15000 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15001 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15003 * Ada Glitches:: Known peculiarities of Ada mode.
15006 @node Ada Mode Intro
15007 @subsubsection Introduction
15008 @cindex Ada mode, general
15010 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15011 syntax, with some extensions.
15012 The philosophy behind the design of this subset is
15016 That @value{GDBN} should provide basic literals and access to operations for
15017 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15018 leaving more sophisticated computations to subprograms written into the
15019 program (which therefore may be called from @value{GDBN}).
15022 That type safety and strict adherence to Ada language restrictions
15023 are not particularly important to the @value{GDBN} user.
15026 That brevity is important to the @value{GDBN} user.
15029 Thus, for brevity, the debugger acts as if all names declared in
15030 user-written packages are directly visible, even if they are not visible
15031 according to Ada rules, thus making it unnecessary to fully qualify most
15032 names with their packages, regardless of context. Where this causes
15033 ambiguity, @value{GDBN} asks the user's intent.
15035 The debugger will start in Ada mode if it detects an Ada main program.
15036 As for other languages, it will enter Ada mode when stopped in a program that
15037 was translated from an Ada source file.
15039 While in Ada mode, you may use `@t{--}' for comments. This is useful
15040 mostly for documenting command files. The standard @value{GDBN} comment
15041 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15042 middle (to allow based literals).
15044 The debugger supports limited overloading. Given a subprogram call in which
15045 the function symbol has multiple definitions, it will use the number of
15046 actual parameters and some information about their types to attempt to narrow
15047 the set of definitions. It also makes very limited use of context, preferring
15048 procedures to functions in the context of the @code{call} command, and
15049 functions to procedures elsewhere.
15051 @node Omissions from Ada
15052 @subsubsection Omissions from Ada
15053 @cindex Ada, omissions from
15055 Here are the notable omissions from the subset:
15059 Only a subset of the attributes are supported:
15063 @t{'First}, @t{'Last}, and @t{'Length}
15064 on array objects (not on types and subtypes).
15067 @t{'Min} and @t{'Max}.
15070 @t{'Pos} and @t{'Val}.
15076 @t{'Range} on array objects (not subtypes), but only as the right
15077 operand of the membership (@code{in}) operator.
15080 @t{'Access}, @t{'Unchecked_Access}, and
15081 @t{'Unrestricted_Access} (a GNAT extension).
15089 @code{Characters.Latin_1} are not available and
15090 concatenation is not implemented. Thus, escape characters in strings are
15091 not currently available.
15094 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15095 equality of representations. They will generally work correctly
15096 for strings and arrays whose elements have integer or enumeration types.
15097 They may not work correctly for arrays whose element
15098 types have user-defined equality, for arrays of real values
15099 (in particular, IEEE-conformant floating point, because of negative
15100 zeroes and NaNs), and for arrays whose elements contain unused bits with
15101 indeterminate values.
15104 The other component-by-component array operations (@code{and}, @code{or},
15105 @code{xor}, @code{not}, and relational tests other than equality)
15106 are not implemented.
15109 @cindex array aggregates (Ada)
15110 @cindex record aggregates (Ada)
15111 @cindex aggregates (Ada)
15112 There is limited support for array and record aggregates. They are
15113 permitted only on the right sides of assignments, as in these examples:
15116 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15117 (@value{GDBP}) set An_Array := (1, others => 0)
15118 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15119 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15120 (@value{GDBP}) set A_Record := (1, "Peter", True);
15121 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15125 discriminant's value by assigning an aggregate has an
15126 undefined effect if that discriminant is used within the record.
15127 However, you can first modify discriminants by directly assigning to
15128 them (which normally would not be allowed in Ada), and then performing an
15129 aggregate assignment. For example, given a variable @code{A_Rec}
15130 declared to have a type such as:
15133 type Rec (Len : Small_Integer := 0) is record
15135 Vals : IntArray (1 .. Len);
15139 you can assign a value with a different size of @code{Vals} with two
15143 (@value{GDBP}) set A_Rec.Len := 4
15144 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15147 As this example also illustrates, @value{GDBN} is very loose about the usual
15148 rules concerning aggregates. You may leave out some of the
15149 components of an array or record aggregate (such as the @code{Len}
15150 component in the assignment to @code{A_Rec} above); they will retain their
15151 original values upon assignment. You may freely use dynamic values as
15152 indices in component associations. You may even use overlapping or
15153 redundant component associations, although which component values are
15154 assigned in such cases is not defined.
15157 Calls to dispatching subprograms are not implemented.
15160 The overloading algorithm is much more limited (i.e., less selective)
15161 than that of real Ada. It makes only limited use of the context in
15162 which a subexpression appears to resolve its meaning, and it is much
15163 looser in its rules for allowing type matches. As a result, some
15164 function calls will be ambiguous, and the user will be asked to choose
15165 the proper resolution.
15168 The @code{new} operator is not implemented.
15171 Entry calls are not implemented.
15174 Aside from printing, arithmetic operations on the native VAX floating-point
15175 formats are not supported.
15178 It is not possible to slice a packed array.
15181 The names @code{True} and @code{False}, when not part of a qualified name,
15182 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15184 Should your program
15185 redefine these names in a package or procedure (at best a dubious practice),
15186 you will have to use fully qualified names to access their new definitions.
15189 @node Additions to Ada
15190 @subsubsection Additions to Ada
15191 @cindex Ada, deviations from
15193 As it does for other languages, @value{GDBN} makes certain generic
15194 extensions to Ada (@pxref{Expressions}):
15198 If the expression @var{E} is a variable residing in memory (typically
15199 a local variable or array element) and @var{N} is a positive integer,
15200 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15201 @var{N}-1 adjacent variables following it in memory as an array. In
15202 Ada, this operator is generally not necessary, since its prime use is
15203 in displaying parts of an array, and slicing will usually do this in
15204 Ada. However, there are occasional uses when debugging programs in
15205 which certain debugging information has been optimized away.
15208 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15209 appears in function or file @var{B}.'' When @var{B} is a file name,
15210 you must typically surround it in single quotes.
15213 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15214 @var{type} that appears at address @var{addr}.''
15217 A name starting with @samp{$} is a convenience variable
15218 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15221 In addition, @value{GDBN} provides a few other shortcuts and outright
15222 additions specific to Ada:
15226 The assignment statement is allowed as an expression, returning
15227 its right-hand operand as its value. Thus, you may enter
15230 (@value{GDBP}) set x := y + 3
15231 (@value{GDBP}) print A(tmp := y + 1)
15235 The semicolon is allowed as an ``operator,'' returning as its value
15236 the value of its right-hand operand.
15237 This allows, for example,
15238 complex conditional breaks:
15241 (@value{GDBP}) break f
15242 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15246 Rather than use catenation and symbolic character names to introduce special
15247 characters into strings, one may instead use a special bracket notation,
15248 which is also used to print strings. A sequence of characters of the form
15249 @samp{["@var{XX}"]} within a string or character literal denotes the
15250 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15251 sequence of characters @samp{["""]} also denotes a single quotation mark
15252 in strings. For example,
15254 "One line.["0a"]Next line.["0a"]"
15257 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15261 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15262 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15266 (@value{GDBP}) print 'max(x, y)
15270 When printing arrays, @value{GDBN} uses positional notation when the
15271 array has a lower bound of 1, and uses a modified named notation otherwise.
15272 For example, a one-dimensional array of three integers with a lower bound
15273 of 3 might print as
15280 That is, in contrast to valid Ada, only the first component has a @code{=>}
15284 You may abbreviate attributes in expressions with any unique,
15285 multi-character subsequence of
15286 their names (an exact match gets preference).
15287 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15288 in place of @t{a'length}.
15291 @cindex quoting Ada internal identifiers
15292 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15293 to lower case. The GNAT compiler uses upper-case characters for
15294 some of its internal identifiers, which are normally of no interest to users.
15295 For the rare occasions when you actually have to look at them,
15296 enclose them in angle brackets to avoid the lower-case mapping.
15299 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15303 Printing an object of class-wide type or dereferencing an
15304 access-to-class-wide value will display all the components of the object's
15305 specific type (as indicated by its run-time tag). Likewise, component
15306 selection on such a value will operate on the specific type of the
15311 @node Stopping Before Main Program
15312 @subsubsection Stopping at the Very Beginning
15314 @cindex breakpointing Ada elaboration code
15315 It is sometimes necessary to debug the program during elaboration, and
15316 before reaching the main procedure.
15317 As defined in the Ada Reference
15318 Manual, the elaboration code is invoked from a procedure called
15319 @code{adainit}. To run your program up to the beginning of
15320 elaboration, simply use the following two commands:
15321 @code{tbreak adainit} and @code{run}.
15323 @node Ada Exceptions
15324 @subsubsection Ada Exceptions
15326 A command is provided to list all Ada exceptions:
15329 @kindex info exceptions
15330 @item info exceptions
15331 @itemx info exceptions @var{regexp}
15332 The @code{info exceptions} command allows you to list all Ada exceptions
15333 defined within the program being debugged, as well as their addresses.
15334 With a regular expression, @var{regexp}, as argument, only those exceptions
15335 whose names match @var{regexp} are listed.
15338 Below is a small example, showing how the command can be used, first
15339 without argument, and next with a regular expression passed as an
15343 (@value{GDBP}) info exceptions
15344 All defined Ada exceptions:
15345 constraint_error: 0x613da0
15346 program_error: 0x613d20
15347 storage_error: 0x613ce0
15348 tasking_error: 0x613ca0
15349 const.aint_global_e: 0x613b00
15350 (@value{GDBP}) info exceptions const.aint
15351 All Ada exceptions matching regular expression "const.aint":
15352 constraint_error: 0x613da0
15353 const.aint_global_e: 0x613b00
15356 It is also possible to ask @value{GDBN} to stop your program's execution
15357 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15360 @subsubsection Extensions for Ada Tasks
15361 @cindex Ada, tasking
15363 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15364 @value{GDBN} provides the following task-related commands:
15369 This command shows a list of current Ada tasks, as in the following example:
15376 (@value{GDBP}) info tasks
15377 ID TID P-ID Pri State Name
15378 1 8088000 0 15 Child Activation Wait main_task
15379 2 80a4000 1 15 Accept Statement b
15380 3 809a800 1 15 Child Activation Wait a
15381 * 4 80ae800 3 15 Runnable c
15386 In this listing, the asterisk before the last task indicates it to be the
15387 task currently being inspected.
15391 Represents @value{GDBN}'s internal task number.
15397 The parent's task ID (@value{GDBN}'s internal task number).
15400 The base priority of the task.
15403 Current state of the task.
15407 The task has been created but has not been activated. It cannot be
15411 The task is not blocked for any reason known to Ada. (It may be waiting
15412 for a mutex, though.) It is conceptually "executing" in normal mode.
15415 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15416 that were waiting on terminate alternatives have been awakened and have
15417 terminated themselves.
15419 @item Child Activation Wait
15420 The task is waiting for created tasks to complete activation.
15422 @item Accept Statement
15423 The task is waiting on an accept or selective wait statement.
15425 @item Waiting on entry call
15426 The task is waiting on an entry call.
15428 @item Async Select Wait
15429 The task is waiting to start the abortable part of an asynchronous
15433 The task is waiting on a select statement with only a delay
15436 @item Child Termination Wait
15437 The task is sleeping having completed a master within itself, and is
15438 waiting for the tasks dependent on that master to become terminated or
15439 waiting on a terminate Phase.
15441 @item Wait Child in Term Alt
15442 The task is sleeping waiting for tasks on terminate alternatives to
15443 finish terminating.
15445 @item Accepting RV with @var{taskno}
15446 The task is accepting a rendez-vous with the task @var{taskno}.
15450 Name of the task in the program.
15454 @kindex info task @var{taskno}
15455 @item info task @var{taskno}
15456 This command shows detailled informations on the specified task, as in
15457 the following example:
15462 (@value{GDBP}) info tasks
15463 ID TID P-ID Pri State Name
15464 1 8077880 0 15 Child Activation Wait main_task
15465 * 2 807c468 1 15 Runnable task_1
15466 (@value{GDBP}) info task 2
15467 Ada Task: 0x807c468
15470 Parent: 1 (main_task)
15476 @kindex task@r{ (Ada)}
15477 @cindex current Ada task ID
15478 This command prints the ID of the current task.
15484 (@value{GDBP}) info tasks
15485 ID TID P-ID Pri State Name
15486 1 8077870 0 15 Child Activation Wait main_task
15487 * 2 807c458 1 15 Runnable t
15488 (@value{GDBP}) task
15489 [Current task is 2]
15492 @item task @var{taskno}
15493 @cindex Ada task switching
15494 This command is like the @code{thread @var{threadno}}
15495 command (@pxref{Threads}). It switches the context of debugging
15496 from the current task to the given task.
15502 (@value{GDBP}) info tasks
15503 ID TID P-ID Pri State Name
15504 1 8077870 0 15 Child Activation Wait main_task
15505 * 2 807c458 1 15 Runnable t
15506 (@value{GDBP}) task 1
15507 [Switching to task 1]
15508 #0 0x8067726 in pthread_cond_wait ()
15510 #0 0x8067726 in pthread_cond_wait ()
15511 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15512 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15513 #3 0x806153e in system.tasking.stages.activate_tasks ()
15514 #4 0x804aacc in un () at un.adb:5
15517 @item break @var{linespec} task @var{taskno}
15518 @itemx break @var{linespec} task @var{taskno} if @dots{}
15519 @cindex breakpoints and tasks, in Ada
15520 @cindex task breakpoints, in Ada
15521 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15522 These commands are like the @code{break @dots{} thread @dots{}}
15523 command (@pxref{Thread Stops}).
15524 @var{linespec} specifies source lines, as described
15525 in @ref{Specify Location}.
15527 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15528 to specify that you only want @value{GDBN} to stop the program when a
15529 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15530 numeric task identifiers assigned by @value{GDBN}, shown in the first
15531 column of the @samp{info tasks} display.
15533 If you do not specify @samp{task @var{taskno}} when you set a
15534 breakpoint, the breakpoint applies to @emph{all} tasks of your
15537 You can use the @code{task} qualifier on conditional breakpoints as
15538 well; in this case, place @samp{task @var{taskno}} before the
15539 breakpoint condition (before the @code{if}).
15547 (@value{GDBP}) info tasks
15548 ID TID P-ID Pri State Name
15549 1 140022020 0 15 Child Activation Wait main_task
15550 2 140045060 1 15 Accept/Select Wait t2
15551 3 140044840 1 15 Runnable t1
15552 * 4 140056040 1 15 Runnable t3
15553 (@value{GDBP}) b 15 task 2
15554 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15555 (@value{GDBP}) cont
15560 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15562 (@value{GDBP}) info tasks
15563 ID TID P-ID Pri State Name
15564 1 140022020 0 15 Child Activation Wait main_task
15565 * 2 140045060 1 15 Runnable t2
15566 3 140044840 1 15 Runnable t1
15567 4 140056040 1 15 Delay Sleep t3
15571 @node Ada Tasks and Core Files
15572 @subsubsection Tasking Support when Debugging Core Files
15573 @cindex Ada tasking and core file debugging
15575 When inspecting a core file, as opposed to debugging a live program,
15576 tasking support may be limited or even unavailable, depending on
15577 the platform being used.
15578 For instance, on x86-linux, the list of tasks is available, but task
15579 switching is not supported. On Tru64, however, task switching will work
15582 On certain platforms, including Tru64, the debugger needs to perform some
15583 memory writes in order to provide Ada tasking support. When inspecting
15584 a core file, this means that the core file must be opened with read-write
15585 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15586 Under these circumstances, you should make a backup copy of the core
15587 file before inspecting it with @value{GDBN}.
15589 @node Ravenscar Profile
15590 @subsubsection Tasking Support when using the Ravenscar Profile
15591 @cindex Ravenscar Profile
15593 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15594 specifically designed for systems with safety-critical real-time
15598 @kindex set ravenscar task-switching on
15599 @cindex task switching with program using Ravenscar Profile
15600 @item set ravenscar task-switching on
15601 Allows task switching when debugging a program that uses the Ravenscar
15602 Profile. This is the default.
15604 @kindex set ravenscar task-switching off
15605 @item set ravenscar task-switching off
15606 Turn off task switching when debugging a program that uses the Ravenscar
15607 Profile. This is mostly intended to disable the code that adds support
15608 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15609 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15610 To be effective, this command should be run before the program is started.
15612 @kindex show ravenscar task-switching
15613 @item show ravenscar task-switching
15614 Show whether it is possible to switch from task to task in a program
15615 using the Ravenscar Profile.
15620 @subsubsection Known Peculiarities of Ada Mode
15621 @cindex Ada, problems
15623 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15624 we know of several problems with and limitations of Ada mode in
15626 some of which will be fixed with planned future releases of the debugger
15627 and the GNU Ada compiler.
15631 Static constants that the compiler chooses not to materialize as objects in
15632 storage are invisible to the debugger.
15635 Named parameter associations in function argument lists are ignored (the
15636 argument lists are treated as positional).
15639 Many useful library packages are currently invisible to the debugger.
15642 Fixed-point arithmetic, conversions, input, and output is carried out using
15643 floating-point arithmetic, and may give results that only approximate those on
15647 The GNAT compiler never generates the prefix @code{Standard} for any of
15648 the standard symbols defined by the Ada language. @value{GDBN} knows about
15649 this: it will strip the prefix from names when you use it, and will never
15650 look for a name you have so qualified among local symbols, nor match against
15651 symbols in other packages or subprograms. If you have
15652 defined entities anywhere in your program other than parameters and
15653 local variables whose simple names match names in @code{Standard},
15654 GNAT's lack of qualification here can cause confusion. When this happens,
15655 you can usually resolve the confusion
15656 by qualifying the problematic names with package
15657 @code{Standard} explicitly.
15660 Older versions of the compiler sometimes generate erroneous debugging
15661 information, resulting in the debugger incorrectly printing the value
15662 of affected entities. In some cases, the debugger is able to work
15663 around an issue automatically. In other cases, the debugger is able
15664 to work around the issue, but the work-around has to be specifically
15667 @kindex set ada trust-PAD-over-XVS
15668 @kindex show ada trust-PAD-over-XVS
15671 @item set ada trust-PAD-over-XVS on
15672 Configure GDB to strictly follow the GNAT encoding when computing the
15673 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15674 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15675 a complete description of the encoding used by the GNAT compiler).
15676 This is the default.
15678 @item set ada trust-PAD-over-XVS off
15679 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15680 sometimes prints the wrong value for certain entities, changing @code{ada
15681 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15682 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15683 @code{off}, but this incurs a slight performance penalty, so it is
15684 recommended to leave this setting to @code{on} unless necessary.
15688 @node Unsupported Languages
15689 @section Unsupported Languages
15691 @cindex unsupported languages
15692 @cindex minimal language
15693 In addition to the other fully-supported programming languages,
15694 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15695 It does not represent a real programming language, but provides a set
15696 of capabilities close to what the C or assembly languages provide.
15697 This should allow most simple operations to be performed while debugging
15698 an application that uses a language currently not supported by @value{GDBN}.
15700 If the language is set to @code{auto}, @value{GDBN} will automatically
15701 select this language if the current frame corresponds to an unsupported
15705 @chapter Examining the Symbol Table
15707 The commands described in this chapter allow you to inquire about the
15708 symbols (names of variables, functions and types) defined in your
15709 program. This information is inherent in the text of your program and
15710 does not change as your program executes. @value{GDBN} finds it in your
15711 program's symbol table, in the file indicated when you started @value{GDBN}
15712 (@pxref{File Options, ,Choosing Files}), or by one of the
15713 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15715 @cindex symbol names
15716 @cindex names of symbols
15717 @cindex quoting names
15718 Occasionally, you may need to refer to symbols that contain unusual
15719 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15720 most frequent case is in referring to static variables in other
15721 source files (@pxref{Variables,,Program Variables}). File names
15722 are recorded in object files as debugging symbols, but @value{GDBN} would
15723 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15724 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15725 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15732 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15735 @cindex case-insensitive symbol names
15736 @cindex case sensitivity in symbol names
15737 @kindex set case-sensitive
15738 @item set case-sensitive on
15739 @itemx set case-sensitive off
15740 @itemx set case-sensitive auto
15741 Normally, when @value{GDBN} looks up symbols, it matches their names
15742 with case sensitivity determined by the current source language.
15743 Occasionally, you may wish to control that. The command @code{set
15744 case-sensitive} lets you do that by specifying @code{on} for
15745 case-sensitive matches or @code{off} for case-insensitive ones. If
15746 you specify @code{auto}, case sensitivity is reset to the default
15747 suitable for the source language. The default is case-sensitive
15748 matches for all languages except for Fortran, for which the default is
15749 case-insensitive matches.
15751 @kindex show case-sensitive
15752 @item show case-sensitive
15753 This command shows the current setting of case sensitivity for symbols
15756 @kindex set print type methods
15757 @item set print type methods
15758 @itemx set print type methods on
15759 @itemx set print type methods off
15760 Normally, when @value{GDBN} prints a class, it displays any methods
15761 declared in that class. You can control this behavior either by
15762 passing the appropriate flag to @code{ptype}, or using @command{set
15763 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15764 display the methods; this is the default. Specifying @code{off} will
15765 cause @value{GDBN} to omit the methods.
15767 @kindex show print type methods
15768 @item show print type methods
15769 This command shows the current setting of method display when printing
15772 @kindex set print type typedefs
15773 @item set print type typedefs
15774 @itemx set print type typedefs on
15775 @itemx set print type typedefs off
15777 Normally, when @value{GDBN} prints a class, it displays any typedefs
15778 defined in that class. You can control this behavior either by
15779 passing the appropriate flag to @code{ptype}, or using @command{set
15780 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15781 display the typedef definitions; this is the default. Specifying
15782 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15783 Note that this controls whether the typedef definition itself is
15784 printed, not whether typedef names are substituted when printing other
15787 @kindex show print type typedefs
15788 @item show print type typedefs
15789 This command shows the current setting of typedef display when
15792 @kindex info address
15793 @cindex address of a symbol
15794 @item info address @var{symbol}
15795 Describe where the data for @var{symbol} is stored. For a register
15796 variable, this says which register it is kept in. For a non-register
15797 local variable, this prints the stack-frame offset at which the variable
15800 Note the contrast with @samp{print &@var{symbol}}, which does not work
15801 at all for a register variable, and for a stack local variable prints
15802 the exact address of the current instantiation of the variable.
15804 @kindex info symbol
15805 @cindex symbol from address
15806 @cindex closest symbol and offset for an address
15807 @item info symbol @var{addr}
15808 Print the name of a symbol which is stored at the address @var{addr}.
15809 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15810 nearest symbol and an offset from it:
15813 (@value{GDBP}) info symbol 0x54320
15814 _initialize_vx + 396 in section .text
15818 This is the opposite of the @code{info address} command. You can use
15819 it to find out the name of a variable or a function given its address.
15821 For dynamically linked executables, the name of executable or shared
15822 library containing the symbol is also printed:
15825 (@value{GDBP}) info symbol 0x400225
15826 _start + 5 in section .text of /tmp/a.out
15827 (@value{GDBP}) info symbol 0x2aaaac2811cf
15828 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15832 @item whatis[/@var{flags}] [@var{arg}]
15833 Print the data type of @var{arg}, which can be either an expression
15834 or a name of a data type. With no argument, print the data type of
15835 @code{$}, the last value in the value history.
15837 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15838 is not actually evaluated, and any side-effecting operations (such as
15839 assignments or function calls) inside it do not take place.
15841 If @var{arg} is a variable or an expression, @code{whatis} prints its
15842 literal type as it is used in the source code. If the type was
15843 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15844 the data type underlying the @code{typedef}. If the type of the
15845 variable or the expression is a compound data type, such as
15846 @code{struct} or @code{class}, @code{whatis} never prints their
15847 fields or methods. It just prints the @code{struct}/@code{class}
15848 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15849 such a compound data type, use @code{ptype}.
15851 If @var{arg} is a type name that was defined using @code{typedef},
15852 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15853 Unrolling means that @code{whatis} will show the underlying type used
15854 in the @code{typedef} declaration of @var{arg}. However, if that
15855 underlying type is also a @code{typedef}, @code{whatis} will not
15858 For C code, the type names may also have the form @samp{class
15859 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15860 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15862 @var{flags} can be used to modify how the type is displayed.
15863 Available flags are:
15867 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15868 parameters and typedefs defined in a class when printing the class'
15869 members. The @code{/r} flag disables this.
15872 Do not print methods defined in the class.
15875 Print methods defined in the class. This is the default, but the flag
15876 exists in case you change the default with @command{set print type methods}.
15879 Do not print typedefs defined in the class. Note that this controls
15880 whether the typedef definition itself is printed, not whether typedef
15881 names are substituted when printing other types.
15884 Print typedefs defined in the class. This is the default, but the flag
15885 exists in case you change the default with @command{set print type typedefs}.
15889 @item ptype[/@var{flags}] [@var{arg}]
15890 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15891 detailed description of the type, instead of just the name of the type.
15892 @xref{Expressions, ,Expressions}.
15894 Contrary to @code{whatis}, @code{ptype} always unrolls any
15895 @code{typedef}s in its argument declaration, whether the argument is
15896 a variable, expression, or a data type. This means that @code{ptype}
15897 of a variable or an expression will not print literally its type as
15898 present in the source code---use @code{whatis} for that. @code{typedef}s at
15899 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15900 fields, methods and inner @code{class typedef}s of @code{struct}s,
15901 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15903 For example, for this variable declaration:
15906 typedef double real_t;
15907 struct complex @{ real_t real; double imag; @};
15908 typedef struct complex complex_t;
15910 real_t *real_pointer_var;
15914 the two commands give this output:
15918 (@value{GDBP}) whatis var
15920 (@value{GDBP}) ptype var
15921 type = struct complex @{
15925 (@value{GDBP}) whatis complex_t
15926 type = struct complex
15927 (@value{GDBP}) whatis struct complex
15928 type = struct complex
15929 (@value{GDBP}) ptype struct complex
15930 type = struct complex @{
15934 (@value{GDBP}) whatis real_pointer_var
15936 (@value{GDBP}) ptype real_pointer_var
15942 As with @code{whatis}, using @code{ptype} without an argument refers to
15943 the type of @code{$}, the last value in the value history.
15945 @cindex incomplete type
15946 Sometimes, programs use opaque data types or incomplete specifications
15947 of complex data structure. If the debug information included in the
15948 program does not allow @value{GDBN} to display a full declaration of
15949 the data type, it will say @samp{<incomplete type>}. For example,
15950 given these declarations:
15954 struct foo *fooptr;
15958 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15961 (@value{GDBP}) ptype foo
15962 $1 = <incomplete type>
15966 ``Incomplete type'' is C terminology for data types that are not
15967 completely specified.
15970 @item info types @var{regexp}
15972 Print a brief description of all types whose names match the regular
15973 expression @var{regexp} (or all types in your program, if you supply
15974 no argument). Each complete typename is matched as though it were a
15975 complete line; thus, @samp{i type value} gives information on all
15976 types in your program whose names include the string @code{value}, but
15977 @samp{i type ^value$} gives information only on types whose complete
15978 name is @code{value}.
15980 This command differs from @code{ptype} in two ways: first, like
15981 @code{whatis}, it does not print a detailed description; second, it
15982 lists all source files where a type is defined.
15984 @kindex info type-printers
15985 @item info type-printers
15986 Versions of @value{GDBN} that ship with Python scripting enabled may
15987 have ``type printers'' available. When using @command{ptype} or
15988 @command{whatis}, these printers are consulted when the name of a type
15989 is needed. @xref{Type Printing API}, for more information on writing
15992 @code{info type-printers} displays all the available type printers.
15994 @kindex enable type-printer
15995 @kindex disable type-printer
15996 @item enable type-printer @var{name}@dots{}
15997 @item disable type-printer @var{name}@dots{}
15998 These commands can be used to enable or disable type printers.
16001 @cindex local variables
16002 @item info scope @var{location}
16003 List all the variables local to a particular scope. This command
16004 accepts a @var{location} argument---a function name, a source line, or
16005 an address preceded by a @samp{*}, and prints all the variables local
16006 to the scope defined by that location. (@xref{Specify Location}, for
16007 details about supported forms of @var{location}.) For example:
16010 (@value{GDBP}) @b{info scope command_line_handler}
16011 Scope for command_line_handler:
16012 Symbol rl is an argument at stack/frame offset 8, length 4.
16013 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16014 Symbol linelength is in static storage at address 0x150a1c, length 4.
16015 Symbol p is a local variable in register $esi, length 4.
16016 Symbol p1 is a local variable in register $ebx, length 4.
16017 Symbol nline is a local variable in register $edx, length 4.
16018 Symbol repeat is a local variable at frame offset -8, length 4.
16022 This command is especially useful for determining what data to collect
16023 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16026 @kindex info source
16028 Show information about the current source file---that is, the source file for
16029 the function containing the current point of execution:
16032 the name of the source file, and the directory containing it,
16034 the directory it was compiled in,
16036 its length, in lines,
16038 which programming language it is written in,
16040 whether the executable includes debugging information for that file, and
16041 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16043 whether the debugging information includes information about
16044 preprocessor macros.
16048 @kindex info sources
16050 Print the names of all source files in your program for which there is
16051 debugging information, organized into two lists: files whose symbols
16052 have already been read, and files whose symbols will be read when needed.
16054 @kindex info functions
16055 @item info functions
16056 Print the names and data types of all defined functions.
16058 @item info functions @var{regexp}
16059 Print the names and data types of all defined functions
16060 whose names contain a match for regular expression @var{regexp}.
16061 Thus, @samp{info fun step} finds all functions whose names
16062 include @code{step}; @samp{info fun ^step} finds those whose names
16063 start with @code{step}. If a function name contains characters
16064 that conflict with the regular expression language (e.g.@:
16065 @samp{operator*()}), they may be quoted with a backslash.
16067 @kindex info variables
16068 @item info variables
16069 Print the names and data types of all variables that are defined
16070 outside of functions (i.e.@: excluding local variables).
16072 @item info variables @var{regexp}
16073 Print the names and data types of all variables (except for local
16074 variables) whose names contain a match for regular expression
16077 @kindex info classes
16078 @cindex Objective-C, classes and selectors
16080 @itemx info classes @var{regexp}
16081 Display all Objective-C classes in your program, or
16082 (with the @var{regexp} argument) all those matching a particular regular
16085 @kindex info selectors
16086 @item info selectors
16087 @itemx info selectors @var{regexp}
16088 Display all Objective-C selectors in your program, or
16089 (with the @var{regexp} argument) all those matching a particular regular
16093 This was never implemented.
16094 @kindex info methods
16096 @itemx info methods @var{regexp}
16097 The @code{info methods} command permits the user to examine all defined
16098 methods within C@t{++} program, or (with the @var{regexp} argument) a
16099 specific set of methods found in the various C@t{++} classes. Many
16100 C@t{++} classes provide a large number of methods. Thus, the output
16101 from the @code{ptype} command can be overwhelming and hard to use. The
16102 @code{info-methods} command filters the methods, printing only those
16103 which match the regular-expression @var{regexp}.
16106 @cindex opaque data types
16107 @kindex set opaque-type-resolution
16108 @item set opaque-type-resolution on
16109 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16110 declared as a pointer to a @code{struct}, @code{class}, or
16111 @code{union}---for example, @code{struct MyType *}---that is used in one
16112 source file although the full declaration of @code{struct MyType} is in
16113 another source file. The default is on.
16115 A change in the setting of this subcommand will not take effect until
16116 the next time symbols for a file are loaded.
16118 @item set opaque-type-resolution off
16119 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16120 is printed as follows:
16122 @{<no data fields>@}
16125 @kindex show opaque-type-resolution
16126 @item show opaque-type-resolution
16127 Show whether opaque types are resolved or not.
16129 @kindex maint print symbols
16130 @cindex symbol dump
16131 @kindex maint print psymbols
16132 @cindex partial symbol dump
16133 @kindex maint print msymbols
16134 @cindex minimal symbol dump
16135 @item maint print symbols @var{filename}
16136 @itemx maint print psymbols @var{filename}
16137 @itemx maint print msymbols @var{filename}
16138 Write a dump of debugging symbol data into the file @var{filename}.
16139 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16140 symbols with debugging data are included. If you use @samp{maint print
16141 symbols}, @value{GDBN} includes all the symbols for which it has already
16142 collected full details: that is, @var{filename} reflects symbols for
16143 only those files whose symbols @value{GDBN} has read. You can use the
16144 command @code{info sources} to find out which files these are. If you
16145 use @samp{maint print psymbols} instead, the dump shows information about
16146 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16147 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16148 @samp{maint print msymbols} dumps just the minimal symbol information
16149 required for each object file from which @value{GDBN} has read some symbols.
16150 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16151 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16153 @kindex maint info symtabs
16154 @kindex maint info psymtabs
16155 @cindex listing @value{GDBN}'s internal symbol tables
16156 @cindex symbol tables, listing @value{GDBN}'s internal
16157 @cindex full symbol tables, listing @value{GDBN}'s internal
16158 @cindex partial symbol tables, listing @value{GDBN}'s internal
16159 @item maint info symtabs @r{[} @var{regexp} @r{]}
16160 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16162 List the @code{struct symtab} or @code{struct partial_symtab}
16163 structures whose names match @var{regexp}. If @var{regexp} is not
16164 given, list them all. The output includes expressions which you can
16165 copy into a @value{GDBN} debugging this one to examine a particular
16166 structure in more detail. For example:
16169 (@value{GDBP}) maint info psymtabs dwarf2read
16170 @{ objfile /home/gnu/build/gdb/gdb
16171 ((struct objfile *) 0x82e69d0)
16172 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16173 ((struct partial_symtab *) 0x8474b10)
16176 text addresses 0x814d3c8 -- 0x8158074
16177 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16178 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16179 dependencies (none)
16182 (@value{GDBP}) maint info symtabs
16186 We see that there is one partial symbol table whose filename contains
16187 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16188 and we see that @value{GDBN} has not read in any symtabs yet at all.
16189 If we set a breakpoint on a function, that will cause @value{GDBN} to
16190 read the symtab for the compilation unit containing that function:
16193 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16194 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16196 (@value{GDBP}) maint info symtabs
16197 @{ objfile /home/gnu/build/gdb/gdb
16198 ((struct objfile *) 0x82e69d0)
16199 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16200 ((struct symtab *) 0x86c1f38)
16203 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16204 linetable ((struct linetable *) 0x8370fa0)
16205 debugformat DWARF 2
16214 @chapter Altering Execution
16216 Once you think you have found an error in your program, you might want to
16217 find out for certain whether correcting the apparent error would lead to
16218 correct results in the rest of the run. You can find the answer by
16219 experiment, using the @value{GDBN} features for altering execution of the
16222 For example, you can store new values into variables or memory
16223 locations, give your program a signal, restart it at a different
16224 address, or even return prematurely from a function.
16227 * Assignment:: Assignment to variables
16228 * Jumping:: Continuing at a different address
16229 * Signaling:: Giving your program a signal
16230 * Returning:: Returning from a function
16231 * Calling:: Calling your program's functions
16232 * Patching:: Patching your program
16236 @section Assignment to Variables
16239 @cindex setting variables
16240 To alter the value of a variable, evaluate an assignment expression.
16241 @xref{Expressions, ,Expressions}. For example,
16248 stores the value 4 into the variable @code{x}, and then prints the
16249 value of the assignment expression (which is 4).
16250 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16251 information on operators in supported languages.
16253 @kindex set variable
16254 @cindex variables, setting
16255 If you are not interested in seeing the value of the assignment, use the
16256 @code{set} command instead of the @code{print} command. @code{set} is
16257 really the same as @code{print} except that the expression's value is
16258 not printed and is not put in the value history (@pxref{Value History,
16259 ,Value History}). The expression is evaluated only for its effects.
16261 If the beginning of the argument string of the @code{set} command
16262 appears identical to a @code{set} subcommand, use the @code{set
16263 variable} command instead of just @code{set}. This command is identical
16264 to @code{set} except for its lack of subcommands. For example, if your
16265 program has a variable @code{width}, you get an error if you try to set
16266 a new value with just @samp{set width=13}, because @value{GDBN} has the
16267 command @code{set width}:
16270 (@value{GDBP}) whatis width
16272 (@value{GDBP}) p width
16274 (@value{GDBP}) set width=47
16275 Invalid syntax in expression.
16279 The invalid expression, of course, is @samp{=47}. In
16280 order to actually set the program's variable @code{width}, use
16283 (@value{GDBP}) set var width=47
16286 Because the @code{set} command has many subcommands that can conflict
16287 with the names of program variables, it is a good idea to use the
16288 @code{set variable} command instead of just @code{set}. For example, if
16289 your program has a variable @code{g}, you run into problems if you try
16290 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16291 the command @code{set gnutarget}, abbreviated @code{set g}:
16295 (@value{GDBP}) whatis g
16299 (@value{GDBP}) set g=4
16303 The program being debugged has been started already.
16304 Start it from the beginning? (y or n) y
16305 Starting program: /home/smith/cc_progs/a.out
16306 "/home/smith/cc_progs/a.out": can't open to read symbols:
16307 Invalid bfd target.
16308 (@value{GDBP}) show g
16309 The current BFD target is "=4".
16314 The program variable @code{g} did not change, and you silently set the
16315 @code{gnutarget} to an invalid value. In order to set the variable
16319 (@value{GDBP}) set var g=4
16322 @value{GDBN} allows more implicit conversions in assignments than C; you can
16323 freely store an integer value into a pointer variable or vice versa,
16324 and you can convert any structure to any other structure that is the
16325 same length or shorter.
16326 @comment FIXME: how do structs align/pad in these conversions?
16327 @comment /doc@cygnus.com 18dec1990
16329 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16330 construct to generate a value of specified type at a specified address
16331 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16332 to memory location @code{0x83040} as an integer (which implies a certain size
16333 and representation in memory), and
16336 set @{int@}0x83040 = 4
16340 stores the value 4 into that memory location.
16343 @section Continuing at a Different Address
16345 Ordinarily, when you continue your program, you do so at the place where
16346 it stopped, with the @code{continue} command. You can instead continue at
16347 an address of your own choosing, with the following commands:
16351 @kindex j @r{(@code{jump})}
16352 @item jump @var{linespec}
16353 @itemx j @var{linespec}
16354 @itemx jump @var{location}
16355 @itemx j @var{location}
16356 Resume execution at line @var{linespec} or at address given by
16357 @var{location}. Execution stops again immediately if there is a
16358 breakpoint there. @xref{Specify Location}, for a description of the
16359 different forms of @var{linespec} and @var{location}. It is common
16360 practice to use the @code{tbreak} command in conjunction with
16361 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16363 The @code{jump} command does not change the current stack frame, or
16364 the stack pointer, or the contents of any memory location or any
16365 register other than the program counter. If line @var{linespec} is in
16366 a different function from the one currently executing, the results may
16367 be bizarre if the two functions expect different patterns of arguments or
16368 of local variables. For this reason, the @code{jump} command requests
16369 confirmation if the specified line is not in the function currently
16370 executing. However, even bizarre results are predictable if you are
16371 well acquainted with the machine-language code of your program.
16374 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16375 On many systems, you can get much the same effect as the @code{jump}
16376 command by storing a new value into the register @code{$pc}. The
16377 difference is that this does not start your program running; it only
16378 changes the address of where it @emph{will} run when you continue. For
16386 makes the next @code{continue} command or stepping command execute at
16387 address @code{0x485}, rather than at the address where your program stopped.
16388 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16390 The most common occasion to use the @code{jump} command is to back
16391 up---perhaps with more breakpoints set---over a portion of a program
16392 that has already executed, in order to examine its execution in more
16397 @section Giving your Program a Signal
16398 @cindex deliver a signal to a program
16402 @item signal @var{signal}
16403 Resume execution where your program stopped, but immediately give it the
16404 signal @var{signal}. @var{signal} can be the name or the number of a
16405 signal. For example, on many systems @code{signal 2} and @code{signal
16406 SIGINT} are both ways of sending an interrupt signal.
16408 Alternatively, if @var{signal} is zero, continue execution without
16409 giving a signal. This is useful when your program stopped on account of
16410 a signal and would ordinarily see the signal when resumed with the
16411 @code{continue} command; @samp{signal 0} causes it to resume without a
16414 @code{signal} does not repeat when you press @key{RET} a second time
16415 after executing the command.
16419 Invoking the @code{signal} command is not the same as invoking the
16420 @code{kill} utility from the shell. Sending a signal with @code{kill}
16421 causes @value{GDBN} to decide what to do with the signal depending on
16422 the signal handling tables (@pxref{Signals}). The @code{signal} command
16423 passes the signal directly to your program.
16427 @section Returning from a Function
16430 @cindex returning from a function
16433 @itemx return @var{expression}
16434 You can cancel execution of a function call with the @code{return}
16435 command. If you give an
16436 @var{expression} argument, its value is used as the function's return
16440 When you use @code{return}, @value{GDBN} discards the selected stack frame
16441 (and all frames within it). You can think of this as making the
16442 discarded frame return prematurely. If you wish to specify a value to
16443 be returned, give that value as the argument to @code{return}.
16445 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16446 Frame}), and any other frames inside of it, leaving its caller as the
16447 innermost remaining frame. That frame becomes selected. The
16448 specified value is stored in the registers used for returning values
16451 The @code{return} command does not resume execution; it leaves the
16452 program stopped in the state that would exist if the function had just
16453 returned. In contrast, the @code{finish} command (@pxref{Continuing
16454 and Stepping, ,Continuing and Stepping}) resumes execution until the
16455 selected stack frame returns naturally.
16457 @value{GDBN} needs to know how the @var{expression} argument should be set for
16458 the inferior. The concrete registers assignment depends on the OS ABI and the
16459 type being returned by the selected stack frame. For example it is common for
16460 OS ABI to return floating point values in FPU registers while integer values in
16461 CPU registers. Still some ABIs return even floating point values in CPU
16462 registers. Larger integer widths (such as @code{long long int}) also have
16463 specific placement rules. @value{GDBN} already knows the OS ABI from its
16464 current target so it needs to find out also the type being returned to make the
16465 assignment into the right register(s).
16467 Normally, the selected stack frame has debug info. @value{GDBN} will always
16468 use the debug info instead of the implicit type of @var{expression} when the
16469 debug info is available. For example, if you type @kbd{return -1}, and the
16470 function in the current stack frame is declared to return a @code{long long
16471 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16472 into a @code{long long int}:
16475 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16477 (@value{GDBP}) return -1
16478 Make func return now? (y or n) y
16479 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16480 43 printf ("result=%lld\n", func ());
16484 However, if the selected stack frame does not have a debug info, e.g., if the
16485 function was compiled without debug info, @value{GDBN} has to find out the type
16486 to return from user. Specifying a different type by mistake may set the value
16487 in different inferior registers than the caller code expects. For example,
16488 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16489 of a @code{long long int} result for a debug info less function (on 32-bit
16490 architectures). Therefore the user is required to specify the return type by
16491 an appropriate cast explicitly:
16494 Breakpoint 2, 0x0040050b in func ()
16495 (@value{GDBP}) return -1
16496 Return value type not available for selected stack frame.
16497 Please use an explicit cast of the value to return.
16498 (@value{GDBP}) return (long long int) -1
16499 Make selected stack frame return now? (y or n) y
16500 #0 0x00400526 in main ()
16505 @section Calling Program Functions
16508 @cindex calling functions
16509 @cindex inferior functions, calling
16510 @item print @var{expr}
16511 Evaluate the expression @var{expr} and display the resulting value.
16512 @var{expr} may include calls to functions in the program being
16516 @item call @var{expr}
16517 Evaluate the expression @var{expr} without displaying @code{void}
16520 You can use this variant of the @code{print} command if you want to
16521 execute a function from your program that does not return anything
16522 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16523 with @code{void} returned values that @value{GDBN} will otherwise
16524 print. If the result is not void, it is printed and saved in the
16528 It is possible for the function you call via the @code{print} or
16529 @code{call} command to generate a signal (e.g., if there's a bug in
16530 the function, or if you passed it incorrect arguments). What happens
16531 in that case is controlled by the @code{set unwindonsignal} command.
16533 Similarly, with a C@t{++} program it is possible for the function you
16534 call via the @code{print} or @code{call} command to generate an
16535 exception that is not handled due to the constraints of the dummy
16536 frame. In this case, any exception that is raised in the frame, but has
16537 an out-of-frame exception handler will not be found. GDB builds a
16538 dummy-frame for the inferior function call, and the unwinder cannot
16539 seek for exception handlers outside of this dummy-frame. What happens
16540 in that case is controlled by the
16541 @code{set unwind-on-terminating-exception} command.
16544 @item set unwindonsignal
16545 @kindex set unwindonsignal
16546 @cindex unwind stack in called functions
16547 @cindex call dummy stack unwinding
16548 Set unwinding of the stack if a signal is received while in a function
16549 that @value{GDBN} called in the program being debugged. If set to on,
16550 @value{GDBN} unwinds the stack it created for the call and restores
16551 the context to what it was before the call. If set to off (the
16552 default), @value{GDBN} stops in the frame where the signal was
16555 @item show unwindonsignal
16556 @kindex show unwindonsignal
16557 Show the current setting of stack unwinding in the functions called by
16560 @item set unwind-on-terminating-exception
16561 @kindex set unwind-on-terminating-exception
16562 @cindex unwind stack in called functions with unhandled exceptions
16563 @cindex call dummy stack unwinding on unhandled exception.
16564 Set unwinding of the stack if a C@t{++} exception is raised, but left
16565 unhandled while in a function that @value{GDBN} called in the program being
16566 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16567 it created for the call and restores the context to what it was before
16568 the call. If set to off, @value{GDBN} the exception is delivered to
16569 the default C@t{++} exception handler and the inferior terminated.
16571 @item show unwind-on-terminating-exception
16572 @kindex show unwind-on-terminating-exception
16573 Show the current setting of stack unwinding in the functions called by
16578 @cindex weak alias functions
16579 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16580 for another function. In such case, @value{GDBN} might not pick up
16581 the type information, including the types of the function arguments,
16582 which causes @value{GDBN} to call the inferior function incorrectly.
16583 As a result, the called function will function erroneously and may
16584 even crash. A solution to that is to use the name of the aliased
16588 @section Patching Programs
16590 @cindex patching binaries
16591 @cindex writing into executables
16592 @cindex writing into corefiles
16594 By default, @value{GDBN} opens the file containing your program's
16595 executable code (or the corefile) read-only. This prevents accidental
16596 alterations to machine code; but it also prevents you from intentionally
16597 patching your program's binary.
16599 If you'd like to be able to patch the binary, you can specify that
16600 explicitly with the @code{set write} command. For example, you might
16601 want to turn on internal debugging flags, or even to make emergency
16607 @itemx set write off
16608 If you specify @samp{set write on}, @value{GDBN} opens executable and
16609 core files for both reading and writing; if you specify @kbd{set write
16610 off} (the default), @value{GDBN} opens them read-only.
16612 If you have already loaded a file, you must load it again (using the
16613 @code{exec-file} or @code{core-file} command) after changing @code{set
16614 write}, for your new setting to take effect.
16618 Display whether executable files and core files are opened for writing
16619 as well as reading.
16623 @chapter @value{GDBN} Files
16625 @value{GDBN} needs to know the file name of the program to be debugged,
16626 both in order to read its symbol table and in order to start your
16627 program. To debug a core dump of a previous run, you must also tell
16628 @value{GDBN} the name of the core dump file.
16631 * Files:: Commands to specify files
16632 * Separate Debug Files:: Debugging information in separate files
16633 * MiniDebugInfo:: Debugging information in a special section
16634 * Index Files:: Index files speed up GDB
16635 * Symbol Errors:: Errors reading symbol files
16636 * Data Files:: GDB data files
16640 @section Commands to Specify Files
16642 @cindex symbol table
16643 @cindex core dump file
16645 You may want to specify executable and core dump file names. The usual
16646 way to do this is at start-up time, using the arguments to
16647 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16648 Out of @value{GDBN}}).
16650 Occasionally it is necessary to change to a different file during a
16651 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16652 specify a file you want to use. Or you are debugging a remote target
16653 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16654 Program}). In these situations the @value{GDBN} commands to specify
16655 new files are useful.
16658 @cindex executable file
16660 @item file @var{filename}
16661 Use @var{filename} as the program to be debugged. It is read for its
16662 symbols and for the contents of pure memory. It is also the program
16663 executed when you use the @code{run} command. If you do not specify a
16664 directory and the file is not found in the @value{GDBN} working directory,
16665 @value{GDBN} uses the environment variable @code{PATH} as a list of
16666 directories to search, just as the shell does when looking for a program
16667 to run. You can change the value of this variable, for both @value{GDBN}
16668 and your program, using the @code{path} command.
16670 @cindex unlinked object files
16671 @cindex patching object files
16672 You can load unlinked object @file{.o} files into @value{GDBN} using
16673 the @code{file} command. You will not be able to ``run'' an object
16674 file, but you can disassemble functions and inspect variables. Also,
16675 if the underlying BFD functionality supports it, you could use
16676 @kbd{gdb -write} to patch object files using this technique. Note
16677 that @value{GDBN} can neither interpret nor modify relocations in this
16678 case, so branches and some initialized variables will appear to go to
16679 the wrong place. But this feature is still handy from time to time.
16682 @code{file} with no argument makes @value{GDBN} discard any information it
16683 has on both executable file and the symbol table.
16686 @item exec-file @r{[} @var{filename} @r{]}
16687 Specify that the program to be run (but not the symbol table) is found
16688 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16689 if necessary to locate your program. Omitting @var{filename} means to
16690 discard information on the executable file.
16692 @kindex symbol-file
16693 @item symbol-file @r{[} @var{filename} @r{]}
16694 Read symbol table information from file @var{filename}. @code{PATH} is
16695 searched when necessary. Use the @code{file} command to get both symbol
16696 table and program to run from the same file.
16698 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16699 program's symbol table.
16701 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16702 some breakpoints and auto-display expressions. This is because they may
16703 contain pointers to the internal data recording symbols and data types,
16704 which are part of the old symbol table data being discarded inside
16707 @code{symbol-file} does not repeat if you press @key{RET} again after
16710 When @value{GDBN} is configured for a particular environment, it
16711 understands debugging information in whatever format is the standard
16712 generated for that environment; you may use either a @sc{gnu} compiler, or
16713 other compilers that adhere to the local conventions.
16714 Best results are usually obtained from @sc{gnu} compilers; for example,
16715 using @code{@value{NGCC}} you can generate debugging information for
16718 For most kinds of object files, with the exception of old SVR3 systems
16719 using COFF, the @code{symbol-file} command does not normally read the
16720 symbol table in full right away. Instead, it scans the symbol table
16721 quickly to find which source files and which symbols are present. The
16722 details are read later, one source file at a time, as they are needed.
16724 The purpose of this two-stage reading strategy is to make @value{GDBN}
16725 start up faster. For the most part, it is invisible except for
16726 occasional pauses while the symbol table details for a particular source
16727 file are being read. (The @code{set verbose} command can turn these
16728 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16729 Warnings and Messages}.)
16731 We have not implemented the two-stage strategy for COFF yet. When the
16732 symbol table is stored in COFF format, @code{symbol-file} reads the
16733 symbol table data in full right away. Note that ``stabs-in-COFF''
16734 still does the two-stage strategy, since the debug info is actually
16738 @cindex reading symbols immediately
16739 @cindex symbols, reading immediately
16740 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16741 @itemx file @r{[} -readnow @r{]} @var{filename}
16742 You can override the @value{GDBN} two-stage strategy for reading symbol
16743 tables by using the @samp{-readnow} option with any of the commands that
16744 load symbol table information, if you want to be sure @value{GDBN} has the
16745 entire symbol table available.
16747 @c FIXME: for now no mention of directories, since this seems to be in
16748 @c flux. 13mar1992 status is that in theory GDB would look either in
16749 @c current dir or in same dir as myprog; but issues like competing
16750 @c GDB's, or clutter in system dirs, mean that in practice right now
16751 @c only current dir is used. FFish says maybe a special GDB hierarchy
16752 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16756 @item core-file @r{[}@var{filename}@r{]}
16758 Specify the whereabouts of a core dump file to be used as the ``contents
16759 of memory''. Traditionally, core files contain only some parts of the
16760 address space of the process that generated them; @value{GDBN} can access the
16761 executable file itself for other parts.
16763 @code{core-file} with no argument specifies that no core file is
16766 Note that the core file is ignored when your program is actually running
16767 under @value{GDBN}. So, if you have been running your program and you
16768 wish to debug a core file instead, you must kill the subprocess in which
16769 the program is running. To do this, use the @code{kill} command
16770 (@pxref{Kill Process, ,Killing the Child Process}).
16772 @kindex add-symbol-file
16773 @cindex dynamic linking
16774 @item add-symbol-file @var{filename} @var{address}
16775 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16776 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16777 The @code{add-symbol-file} command reads additional symbol table
16778 information from the file @var{filename}. You would use this command
16779 when @var{filename} has been dynamically loaded (by some other means)
16780 into the program that is running. @var{address} should be the memory
16781 address at which the file has been loaded; @value{GDBN} cannot figure
16782 this out for itself. You can additionally specify an arbitrary number
16783 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16784 section name and base address for that section. You can specify any
16785 @var{address} as an expression.
16787 The symbol table of the file @var{filename} is added to the symbol table
16788 originally read with the @code{symbol-file} command. You can use the
16789 @code{add-symbol-file} command any number of times; the new symbol data
16790 thus read is kept in addition to the old.
16792 Changes can be reverted using the command @code{remove-symbol-file}.
16794 @cindex relocatable object files, reading symbols from
16795 @cindex object files, relocatable, reading symbols from
16796 @cindex reading symbols from relocatable object files
16797 @cindex symbols, reading from relocatable object files
16798 @cindex @file{.o} files, reading symbols from
16799 Although @var{filename} is typically a shared library file, an
16800 executable file, or some other object file which has been fully
16801 relocated for loading into a process, you can also load symbolic
16802 information from relocatable @file{.o} files, as long as:
16806 the file's symbolic information refers only to linker symbols defined in
16807 that file, not to symbols defined by other object files,
16809 every section the file's symbolic information refers to has actually
16810 been loaded into the inferior, as it appears in the file, and
16812 you can determine the address at which every section was loaded, and
16813 provide these to the @code{add-symbol-file} command.
16817 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16818 relocatable files into an already running program; such systems
16819 typically make the requirements above easy to meet. However, it's
16820 important to recognize that many native systems use complex link
16821 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16822 assembly, for example) that make the requirements difficult to meet. In
16823 general, one cannot assume that using @code{add-symbol-file} to read a
16824 relocatable object file's symbolic information will have the same effect
16825 as linking the relocatable object file into the program in the normal
16828 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16830 @kindex remove-symbol-file
16831 @item remove-symbol-file @var{filename}
16832 @item remove-symbol-file -a @var{address}
16833 Remove a symbol file added via the @code{add-symbol-file} command. The
16834 file to remove can be identified by its @var{filename} or by an @var{address}
16835 that lies within the boundaries of this symbol file in memory. Example:
16838 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16839 add symbol table from file "/home/user/gdb/mylib.so" at
16840 .text_addr = 0x7ffff7ff9480
16842 Reading symbols from /home/user/gdb/mylib.so...done.
16843 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16844 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16849 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16851 @kindex add-symbol-file-from-memory
16852 @cindex @code{syscall DSO}
16853 @cindex load symbols from memory
16854 @item add-symbol-file-from-memory @var{address}
16855 Load symbols from the given @var{address} in a dynamically loaded
16856 object file whose image is mapped directly into the inferior's memory.
16857 For example, the Linux kernel maps a @code{syscall DSO} into each
16858 process's address space; this DSO provides kernel-specific code for
16859 some system calls. The argument can be any expression whose
16860 evaluation yields the address of the file's shared object file header.
16861 For this command to work, you must have used @code{symbol-file} or
16862 @code{exec-file} commands in advance.
16864 @kindex add-shared-symbol-files
16866 @item add-shared-symbol-files @var{library-file}
16867 @itemx assf @var{library-file}
16868 The @code{add-shared-symbol-files} command can currently be used only
16869 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16870 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16871 @value{GDBN} automatically looks for shared libraries, however if
16872 @value{GDBN} does not find yours, you can invoke
16873 @code{add-shared-symbol-files}. It takes one argument: the shared
16874 library's file name. @code{assf} is a shorthand alias for
16875 @code{add-shared-symbol-files}.
16878 @item section @var{section} @var{addr}
16879 The @code{section} command changes the base address of the named
16880 @var{section} of the exec file to @var{addr}. This can be used if the
16881 exec file does not contain section addresses, (such as in the
16882 @code{a.out} format), or when the addresses specified in the file
16883 itself are wrong. Each section must be changed separately. The
16884 @code{info files} command, described below, lists all the sections and
16888 @kindex info target
16891 @code{info files} and @code{info target} are synonymous; both print the
16892 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16893 including the names of the executable and core dump files currently in
16894 use by @value{GDBN}, and the files from which symbols were loaded. The
16895 command @code{help target} lists all possible targets rather than
16898 @kindex maint info sections
16899 @item maint info sections
16900 Another command that can give you extra information about program sections
16901 is @code{maint info sections}. In addition to the section information
16902 displayed by @code{info files}, this command displays the flags and file
16903 offset of each section in the executable and core dump files. In addition,
16904 @code{maint info sections} provides the following command options (which
16905 may be arbitrarily combined):
16909 Display sections for all loaded object files, including shared libraries.
16910 @item @var{sections}
16911 Display info only for named @var{sections}.
16912 @item @var{section-flags}
16913 Display info only for sections for which @var{section-flags} are true.
16914 The section flags that @value{GDBN} currently knows about are:
16917 Section will have space allocated in the process when loaded.
16918 Set for all sections except those containing debug information.
16920 Section will be loaded from the file into the child process memory.
16921 Set for pre-initialized code and data, clear for @code{.bss} sections.
16923 Section needs to be relocated before loading.
16925 Section cannot be modified by the child process.
16927 Section contains executable code only.
16929 Section contains data only (no executable code).
16931 Section will reside in ROM.
16933 Section contains data for constructor/destructor lists.
16935 Section is not empty.
16937 An instruction to the linker to not output the section.
16938 @item COFF_SHARED_LIBRARY
16939 A notification to the linker that the section contains
16940 COFF shared library information.
16942 Section contains common symbols.
16945 @kindex set trust-readonly-sections
16946 @cindex read-only sections
16947 @item set trust-readonly-sections on
16948 Tell @value{GDBN} that readonly sections in your object file
16949 really are read-only (i.e.@: that their contents will not change).
16950 In that case, @value{GDBN} can fetch values from these sections
16951 out of the object file, rather than from the target program.
16952 For some targets (notably embedded ones), this can be a significant
16953 enhancement to debugging performance.
16955 The default is off.
16957 @item set trust-readonly-sections off
16958 Tell @value{GDBN} not to trust readonly sections. This means that
16959 the contents of the section might change while the program is running,
16960 and must therefore be fetched from the target when needed.
16962 @item show trust-readonly-sections
16963 Show the current setting of trusting readonly sections.
16966 All file-specifying commands allow both absolute and relative file names
16967 as arguments. @value{GDBN} always converts the file name to an absolute file
16968 name and remembers it that way.
16970 @cindex shared libraries
16971 @anchor{Shared Libraries}
16972 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16973 and IBM RS/6000 AIX shared libraries.
16975 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16976 shared libraries. @xref{Expat}.
16978 @value{GDBN} automatically loads symbol definitions from shared libraries
16979 when you use the @code{run} command, or when you examine a core file.
16980 (Before you issue the @code{run} command, @value{GDBN} does not understand
16981 references to a function in a shared library, however---unless you are
16982 debugging a core file).
16984 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16985 automatically loads the symbols at the time of the @code{shl_load} call.
16987 @c FIXME: some @value{GDBN} release may permit some refs to undef
16988 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16989 @c FIXME...lib; check this from time to time when updating manual
16991 There are times, however, when you may wish to not automatically load
16992 symbol definitions from shared libraries, such as when they are
16993 particularly large or there are many of them.
16995 To control the automatic loading of shared library symbols, use the
16999 @kindex set auto-solib-add
17000 @item set auto-solib-add @var{mode}
17001 If @var{mode} is @code{on}, symbols from all shared object libraries
17002 will be loaded automatically when the inferior begins execution, you
17003 attach to an independently started inferior, or when the dynamic linker
17004 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17005 is @code{off}, symbols must be loaded manually, using the
17006 @code{sharedlibrary} command. The default value is @code{on}.
17008 @cindex memory used for symbol tables
17009 If your program uses lots of shared libraries with debug info that
17010 takes large amounts of memory, you can decrease the @value{GDBN}
17011 memory footprint by preventing it from automatically loading the
17012 symbols from shared libraries. To that end, type @kbd{set
17013 auto-solib-add off} before running the inferior, then load each
17014 library whose debug symbols you do need with @kbd{sharedlibrary
17015 @var{regexp}}, where @var{regexp} is a regular expression that matches
17016 the libraries whose symbols you want to be loaded.
17018 @kindex show auto-solib-add
17019 @item show auto-solib-add
17020 Display the current autoloading mode.
17023 @cindex load shared library
17024 To explicitly load shared library symbols, use the @code{sharedlibrary}
17028 @kindex info sharedlibrary
17030 @item info share @var{regex}
17031 @itemx info sharedlibrary @var{regex}
17032 Print the names of the shared libraries which are currently loaded
17033 that match @var{regex}. If @var{regex} is omitted then print
17034 all shared libraries that are loaded.
17036 @kindex sharedlibrary
17038 @item sharedlibrary @var{regex}
17039 @itemx share @var{regex}
17040 Load shared object library symbols for files matching a
17041 Unix regular expression.
17042 As with files loaded automatically, it only loads shared libraries
17043 required by your program for a core file or after typing @code{run}. If
17044 @var{regex} is omitted all shared libraries required by your program are
17047 @item nosharedlibrary
17048 @kindex nosharedlibrary
17049 @cindex unload symbols from shared libraries
17050 Unload all shared object library symbols. This discards all symbols
17051 that have been loaded from all shared libraries. Symbols from shared
17052 libraries that were loaded by explicit user requests are not
17056 Sometimes you may wish that @value{GDBN} stops and gives you control
17057 when any of shared library events happen. The best way to do this is
17058 to use @code{catch load} and @code{catch unload} (@pxref{Set
17061 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17062 command for this. This command exists for historical reasons. It is
17063 less useful than setting a catchpoint, because it does not allow for
17064 conditions or commands as a catchpoint does.
17067 @item set stop-on-solib-events
17068 @kindex set stop-on-solib-events
17069 This command controls whether @value{GDBN} should give you control
17070 when the dynamic linker notifies it about some shared library event.
17071 The most common event of interest is loading or unloading of a new
17074 @item show stop-on-solib-events
17075 @kindex show stop-on-solib-events
17076 Show whether @value{GDBN} stops and gives you control when shared
17077 library events happen.
17080 Shared libraries are also supported in many cross or remote debugging
17081 configurations. @value{GDBN} needs to have access to the target's libraries;
17082 this can be accomplished either by providing copies of the libraries
17083 on the host system, or by asking @value{GDBN} to automatically retrieve the
17084 libraries from the target. If copies of the target libraries are
17085 provided, they need to be the same as the target libraries, although the
17086 copies on the target can be stripped as long as the copies on the host are
17089 @cindex where to look for shared libraries
17090 For remote debugging, you need to tell @value{GDBN} where the target
17091 libraries are, so that it can load the correct copies---otherwise, it
17092 may try to load the host's libraries. @value{GDBN} has two variables
17093 to specify the search directories for target libraries.
17096 @cindex prefix for shared library file names
17097 @cindex system root, alternate
17098 @kindex set solib-absolute-prefix
17099 @kindex set sysroot
17100 @item set sysroot @var{path}
17101 Use @var{path} as the system root for the program being debugged. Any
17102 absolute shared library paths will be prefixed with @var{path}; many
17103 runtime loaders store the absolute paths to the shared library in the
17104 target program's memory. If you use @code{set sysroot} to find shared
17105 libraries, they need to be laid out in the same way that they are on
17106 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17109 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17110 retrieve the target libraries from the remote system. This is only
17111 supported when using a remote target that supports the @code{remote get}
17112 command (@pxref{File Transfer,,Sending files to a remote system}).
17113 The part of @var{path} following the initial @file{remote:}
17114 (if present) is used as system root prefix on the remote file system.
17115 @footnote{If you want to specify a local system root using a directory
17116 that happens to be named @file{remote:}, you need to use some equivalent
17117 variant of the name like @file{./remote:}.}
17119 For targets with an MS-DOS based filesystem, such as MS-Windows and
17120 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17121 absolute file name with @var{path}. But first, on Unix hosts,
17122 @value{GDBN} converts all backslash directory separators into forward
17123 slashes, because the backslash is not a directory separator on Unix:
17126 c:\foo\bar.dll @result{} c:/foo/bar.dll
17129 Then, @value{GDBN} attempts prefixing the target file name with
17130 @var{path}, and looks for the resulting file name in the host file
17134 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17137 If that does not find the shared library, @value{GDBN} tries removing
17138 the @samp{:} character from the drive spec, both for convenience, and,
17139 for the case of the host file system not supporting file names with
17143 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17146 This makes it possible to have a system root that mirrors a target
17147 with more than one drive. E.g., you may want to setup your local
17148 copies of the target system shared libraries like so (note @samp{c} vs
17152 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17153 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17154 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17158 and point the system root at @file{/path/to/sysroot}, so that
17159 @value{GDBN} can find the correct copies of both
17160 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17162 If that still does not find the shared library, @value{GDBN} tries
17163 removing the whole drive spec from the target file name:
17166 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17169 This last lookup makes it possible to not care about the drive name,
17170 if you don't want or need to.
17172 The @code{set solib-absolute-prefix} command is an alias for @code{set
17175 @cindex default system root
17176 @cindex @samp{--with-sysroot}
17177 You can set the default system root by using the configure-time
17178 @samp{--with-sysroot} option. If the system root is inside
17179 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17180 @samp{--exec-prefix}), then the default system root will be updated
17181 automatically if the installed @value{GDBN} is moved to a new
17184 @kindex show sysroot
17186 Display the current shared library prefix.
17188 @kindex set solib-search-path
17189 @item set solib-search-path @var{path}
17190 If this variable is set, @var{path} is a colon-separated list of
17191 directories to search for shared libraries. @samp{solib-search-path}
17192 is used after @samp{sysroot} fails to locate the library, or if the
17193 path to the library is relative instead of absolute. If you want to
17194 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17195 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17196 finding your host's libraries. @samp{sysroot} is preferred; setting
17197 it to a nonexistent directory may interfere with automatic loading
17198 of shared library symbols.
17200 @kindex show solib-search-path
17201 @item show solib-search-path
17202 Display the current shared library search path.
17204 @cindex DOS file-name semantics of file names.
17205 @kindex set target-file-system-kind (unix|dos-based|auto)
17206 @kindex show target-file-system-kind
17207 @item set target-file-system-kind @var{kind}
17208 Set assumed file system kind for target reported file names.
17210 Shared library file names as reported by the target system may not
17211 make sense as is on the system @value{GDBN} is running on. For
17212 example, when remote debugging a target that has MS-DOS based file
17213 system semantics, from a Unix host, the target may be reporting to
17214 @value{GDBN} a list of loaded shared libraries with file names such as
17215 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17216 drive letters, so the @samp{c:\} prefix is not normally understood as
17217 indicating an absolute file name, and neither is the backslash
17218 normally considered a directory separator character. In that case,
17219 the native file system would interpret this whole absolute file name
17220 as a relative file name with no directory components. This would make
17221 it impossible to point @value{GDBN} at a copy of the remote target's
17222 shared libraries on the host using @code{set sysroot}, and impractical
17223 with @code{set solib-search-path}. Setting
17224 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17225 to interpret such file names similarly to how the target would, and to
17226 map them to file names valid on @value{GDBN}'s native file system
17227 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17228 to one of the supported file system kinds. In that case, @value{GDBN}
17229 tries to determine the appropriate file system variant based on the
17230 current target's operating system (@pxref{ABI, ,Configuring the
17231 Current ABI}). The supported file system settings are:
17235 Instruct @value{GDBN} to assume the target file system is of Unix
17236 kind. Only file names starting the forward slash (@samp{/}) character
17237 are considered absolute, and the directory separator character is also
17241 Instruct @value{GDBN} to assume the target file system is DOS based.
17242 File names starting with either a forward slash, or a drive letter
17243 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17244 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17245 considered directory separators.
17248 Instruct @value{GDBN} to use the file system kind associated with the
17249 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17250 This is the default.
17254 @cindex file name canonicalization
17255 @cindex base name differences
17256 When processing file names provided by the user, @value{GDBN}
17257 frequently needs to compare them to the file names recorded in the
17258 program's debug info. Normally, @value{GDBN} compares just the
17259 @dfn{base names} of the files as strings, which is reasonably fast
17260 even for very large programs. (The base name of a file is the last
17261 portion of its name, after stripping all the leading directories.)
17262 This shortcut in comparison is based upon the assumption that files
17263 cannot have more than one base name. This is usually true, but
17264 references to files that use symlinks or similar filesystem
17265 facilities violate that assumption. If your program records files
17266 using such facilities, or if you provide file names to @value{GDBN}
17267 using symlinks etc., you can set @code{basenames-may-differ} to
17268 @code{true} to instruct @value{GDBN} to completely canonicalize each
17269 pair of file names it needs to compare. This will make file-name
17270 comparisons accurate, but at a price of a significant slowdown.
17273 @item set basenames-may-differ
17274 @kindex set basenames-may-differ
17275 Set whether a source file may have multiple base names.
17277 @item show basenames-may-differ
17278 @kindex show basenames-may-differ
17279 Show whether a source file may have multiple base names.
17282 @node Separate Debug Files
17283 @section Debugging Information in Separate Files
17284 @cindex separate debugging information files
17285 @cindex debugging information in separate files
17286 @cindex @file{.debug} subdirectories
17287 @cindex debugging information directory, global
17288 @cindex global debugging information directories
17289 @cindex build ID, and separate debugging files
17290 @cindex @file{.build-id} directory
17292 @value{GDBN} allows you to put a program's debugging information in a
17293 file separate from the executable itself, in a way that allows
17294 @value{GDBN} to find and load the debugging information automatically.
17295 Since debugging information can be very large---sometimes larger
17296 than the executable code itself---some systems distribute debugging
17297 information for their executables in separate files, which users can
17298 install only when they need to debug a problem.
17300 @value{GDBN} supports two ways of specifying the separate debug info
17305 The executable contains a @dfn{debug link} that specifies the name of
17306 the separate debug info file. The separate debug file's name is
17307 usually @file{@var{executable}.debug}, where @var{executable} is the
17308 name of the corresponding executable file without leading directories
17309 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17310 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17311 checksum for the debug file, which @value{GDBN} uses to validate that
17312 the executable and the debug file came from the same build.
17315 The executable contains a @dfn{build ID}, a unique bit string that is
17316 also present in the corresponding debug info file. (This is supported
17317 only on some operating systems, notably those which use the ELF format
17318 for binary files and the @sc{gnu} Binutils.) For more details about
17319 this feature, see the description of the @option{--build-id}
17320 command-line option in @ref{Options, , Command Line Options, ld.info,
17321 The GNU Linker}. The debug info file's name is not specified
17322 explicitly by the build ID, but can be computed from the build ID, see
17326 Depending on the way the debug info file is specified, @value{GDBN}
17327 uses two different methods of looking for the debug file:
17331 For the ``debug link'' method, @value{GDBN} looks up the named file in
17332 the directory of the executable file, then in a subdirectory of that
17333 directory named @file{.debug}, and finally under each one of the global debug
17334 directories, in a subdirectory whose name is identical to the leading
17335 directories of the executable's absolute file name.
17338 For the ``build ID'' method, @value{GDBN} looks in the
17339 @file{.build-id} subdirectory of each one of the global debug directories for
17340 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17341 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17342 are the rest of the bit string. (Real build ID strings are 32 or more
17343 hex characters, not 10.)
17346 So, for example, suppose you ask @value{GDBN} to debug
17347 @file{/usr/bin/ls}, which has a debug link that specifies the
17348 file @file{ls.debug}, and a build ID whose value in hex is
17349 @code{abcdef1234}. If the list of the global debug directories includes
17350 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17351 debug information files, in the indicated order:
17355 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17357 @file{/usr/bin/ls.debug}
17359 @file{/usr/bin/.debug/ls.debug}
17361 @file{/usr/lib/debug/usr/bin/ls.debug}.
17364 @anchor{debug-file-directory}
17365 Global debugging info directories default to what is set by @value{GDBN}
17366 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17367 you can also set the global debugging info directories, and view the list
17368 @value{GDBN} is currently using.
17372 @kindex set debug-file-directory
17373 @item set debug-file-directory @var{directories}
17374 Set the directories which @value{GDBN} searches for separate debugging
17375 information files to @var{directory}. Multiple path components can be set
17376 concatenating them by a path separator.
17378 @kindex show debug-file-directory
17379 @item show debug-file-directory
17380 Show the directories @value{GDBN} searches for separate debugging
17385 @cindex @code{.gnu_debuglink} sections
17386 @cindex debug link sections
17387 A debug link is a special section of the executable file named
17388 @code{.gnu_debuglink}. The section must contain:
17392 A filename, with any leading directory components removed, followed by
17395 zero to three bytes of padding, as needed to reach the next four-byte
17396 boundary within the section, and
17398 a four-byte CRC checksum, stored in the same endianness used for the
17399 executable file itself. The checksum is computed on the debugging
17400 information file's full contents by the function given below, passing
17401 zero as the @var{crc} argument.
17404 Any executable file format can carry a debug link, as long as it can
17405 contain a section named @code{.gnu_debuglink} with the contents
17408 @cindex @code{.note.gnu.build-id} sections
17409 @cindex build ID sections
17410 The build ID is a special section in the executable file (and in other
17411 ELF binary files that @value{GDBN} may consider). This section is
17412 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17413 It contains unique identification for the built files---the ID remains
17414 the same across multiple builds of the same build tree. The default
17415 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17416 content for the build ID string. The same section with an identical
17417 value is present in the original built binary with symbols, in its
17418 stripped variant, and in the separate debugging information file.
17420 The debugging information file itself should be an ordinary
17421 executable, containing a full set of linker symbols, sections, and
17422 debugging information. The sections of the debugging information file
17423 should have the same names, addresses, and sizes as the original file,
17424 but they need not contain any data---much like a @code{.bss} section
17425 in an ordinary executable.
17427 The @sc{gnu} binary utilities (Binutils) package includes the
17428 @samp{objcopy} utility that can produce
17429 the separated executable / debugging information file pairs using the
17430 following commands:
17433 @kbd{objcopy --only-keep-debug foo foo.debug}
17438 These commands remove the debugging
17439 information from the executable file @file{foo} and place it in the file
17440 @file{foo.debug}. You can use the first, second or both methods to link the
17445 The debug link method needs the following additional command to also leave
17446 behind a debug link in @file{foo}:
17449 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17452 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17453 a version of the @code{strip} command such that the command @kbd{strip foo -f
17454 foo.debug} has the same functionality as the two @code{objcopy} commands and
17455 the @code{ln -s} command above, together.
17458 Build ID gets embedded into the main executable using @code{ld --build-id} or
17459 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17460 compatibility fixes for debug files separation are present in @sc{gnu} binary
17461 utilities (Binutils) package since version 2.18.
17466 @cindex CRC algorithm definition
17467 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17468 IEEE 802.3 using the polynomial:
17470 @c TexInfo requires naked braces for multi-digit exponents for Tex
17471 @c output, but this causes HTML output to barf. HTML has to be set using
17472 @c raw commands. So we end up having to specify this equation in 2
17477 <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>
17478 + <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
17484 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17485 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17489 The function is computed byte at a time, taking the least
17490 significant bit of each byte first. The initial pattern
17491 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17492 the final result is inverted to ensure trailing zeros also affect the
17495 @emph{Note:} This is the same CRC polynomial as used in handling the
17496 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17497 , @value{GDBN} Remote Serial Protocol}). However in the
17498 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17499 significant bit first, and the result is not inverted, so trailing
17500 zeros have no effect on the CRC value.
17502 To complete the description, we show below the code of the function
17503 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17504 initially supplied @code{crc} argument means that an initial call to
17505 this function passing in zero will start computing the CRC using
17508 @kindex gnu_debuglink_crc32
17511 gnu_debuglink_crc32 (unsigned long crc,
17512 unsigned char *buf, size_t len)
17514 static const unsigned long crc32_table[256] =
17516 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17517 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17518 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17519 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17520 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17521 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17522 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17523 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17524 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17525 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17526 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17527 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17528 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17529 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17530 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17531 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17532 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17533 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17534 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17535 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17536 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17537 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17538 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17539 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17540 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17541 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17542 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17543 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17544 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17545 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17546 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17547 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17548 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17549 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17550 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17551 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17552 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17553 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17554 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17555 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17556 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17557 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17558 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17559 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17560 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17561 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17562 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17563 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17564 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17565 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17566 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17569 unsigned char *end;
17571 crc = ~crc & 0xffffffff;
17572 for (end = buf + len; buf < end; ++buf)
17573 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17574 return ~crc & 0xffffffff;
17579 This computation does not apply to the ``build ID'' method.
17581 @node MiniDebugInfo
17582 @section Debugging information in a special section
17583 @cindex separate debug sections
17584 @cindex @samp{.gnu_debugdata} section
17586 Some systems ship pre-built executables and libraries that have a
17587 special @samp{.gnu_debugdata} section. This feature is called
17588 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17589 is used to supply extra symbols for backtraces.
17591 The intent of this section is to provide extra minimal debugging
17592 information for use in simple backtraces. It is not intended to be a
17593 replacement for full separate debugging information (@pxref{Separate
17594 Debug Files}). The example below shows the intended use; however,
17595 @value{GDBN} does not currently put restrictions on what sort of
17596 debugging information might be included in the section.
17598 @value{GDBN} has support for this extension. If the section exists,
17599 then it is used provided that no other source of debugging information
17600 can be found, and that @value{GDBN} was configured with LZMA support.
17602 This section can be easily created using @command{objcopy} and other
17603 standard utilities:
17606 # Extract the dynamic symbols from the main binary, there is no need
17607 # to also have these in the normal symbol table.
17608 nm -D @var{binary} --format=posix --defined-only \
17609 | awk '@{ print $1 @}' | sort > dynsyms
17611 # Extract all the text (i.e. function) symbols from the debuginfo.
17612 # (Note that we actually also accept "D" symbols, for the benefit
17613 # of platforms like PowerPC64 that use function descriptors.)
17614 nm @var{binary} --format=posix --defined-only \
17615 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17618 # Keep all the function symbols not already in the dynamic symbol
17620 comm -13 dynsyms funcsyms > keep_symbols
17622 # Separate full debug info into debug binary.
17623 objcopy --only-keep-debug @var{binary} debug
17625 # Copy the full debuginfo, keeping only a minimal set of symbols and
17626 # removing some unnecessary sections.
17627 objcopy -S --remove-section .gdb_index --remove-section .comment \
17628 --keep-symbols=keep_symbols debug mini_debuginfo
17630 # Drop the full debug info from the original binary.
17631 strip --strip-all -R .comment @var{binary}
17633 # Inject the compressed data into the .gnu_debugdata section of the
17636 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17640 @section Index Files Speed Up @value{GDBN}
17641 @cindex index files
17642 @cindex @samp{.gdb_index} section
17644 When @value{GDBN} finds a symbol file, it scans the symbols in the
17645 file in order to construct an internal symbol table. This lets most
17646 @value{GDBN} operations work quickly---at the cost of a delay early
17647 on. For large programs, this delay can be quite lengthy, so
17648 @value{GDBN} provides a way to build an index, which speeds up
17651 The index is stored as a section in the symbol file. @value{GDBN} can
17652 write the index to a file, then you can put it into the symbol file
17653 using @command{objcopy}.
17655 To create an index file, use the @code{save gdb-index} command:
17658 @item save gdb-index @var{directory}
17659 @kindex save gdb-index
17660 Create an index file for each symbol file currently known by
17661 @value{GDBN}. Each file is named after its corresponding symbol file,
17662 with @samp{.gdb-index} appended, and is written into the given
17666 Once you have created an index file you can merge it into your symbol
17667 file, here named @file{symfile}, using @command{objcopy}:
17670 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17671 --set-section-flags .gdb_index=readonly symfile symfile
17674 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17675 sections that have been deprecated. Usually they are deprecated because
17676 they are missing a new feature or have performance issues.
17677 To tell @value{GDBN} to use a deprecated index section anyway
17678 specify @code{set use-deprecated-index-sections on}.
17679 The default is @code{off}.
17680 This can speed up startup, but may result in some functionality being lost.
17681 @xref{Index Section Format}.
17683 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17684 must be done before gdb reads the file. The following will not work:
17687 $ gdb -ex "set use-deprecated-index-sections on" <program>
17690 Instead you must do, for example,
17693 $ gdb -iex "set use-deprecated-index-sections on" <program>
17696 There are currently some limitation on indices. They only work when
17697 for DWARF debugging information, not stabs. And, they do not
17698 currently work for programs using Ada.
17700 @node Symbol Errors
17701 @section Errors Reading Symbol Files
17703 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17704 such as symbol types it does not recognize, or known bugs in compiler
17705 output. By default, @value{GDBN} does not notify you of such problems, since
17706 they are relatively common and primarily of interest to people
17707 debugging compilers. If you are interested in seeing information
17708 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17709 only one message about each such type of problem, no matter how many
17710 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17711 to see how many times the problems occur, with the @code{set
17712 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17715 The messages currently printed, and their meanings, include:
17718 @item inner block not inside outer block in @var{symbol}
17720 The symbol information shows where symbol scopes begin and end
17721 (such as at the start of a function or a block of statements). This
17722 error indicates that an inner scope block is not fully contained
17723 in its outer scope blocks.
17725 @value{GDBN} circumvents the problem by treating the inner block as if it had
17726 the same scope as the outer block. In the error message, @var{symbol}
17727 may be shown as ``@code{(don't know)}'' if the outer block is not a
17730 @item block at @var{address} out of order
17732 The symbol information for symbol scope blocks should occur in
17733 order of increasing addresses. This error indicates that it does not
17736 @value{GDBN} does not circumvent this problem, and has trouble
17737 locating symbols in the source file whose symbols it is reading. (You
17738 can often determine what source file is affected by specifying
17739 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17742 @item bad block start address patched
17744 The symbol information for a symbol scope block has a start address
17745 smaller than the address of the preceding source line. This is known
17746 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17748 @value{GDBN} circumvents the problem by treating the symbol scope block as
17749 starting on the previous source line.
17751 @item bad string table offset in symbol @var{n}
17754 Symbol number @var{n} contains a pointer into the string table which is
17755 larger than the size of the string table.
17757 @value{GDBN} circumvents the problem by considering the symbol to have the
17758 name @code{foo}, which may cause other problems if many symbols end up
17761 @item unknown symbol type @code{0x@var{nn}}
17763 The symbol information contains new data types that @value{GDBN} does
17764 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17765 uncomprehended information, in hexadecimal.
17767 @value{GDBN} circumvents the error by ignoring this symbol information.
17768 This usually allows you to debug your program, though certain symbols
17769 are not accessible. If you encounter such a problem and feel like
17770 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17771 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17772 and examine @code{*bufp} to see the symbol.
17774 @item stub type has NULL name
17776 @value{GDBN} could not find the full definition for a struct or class.
17778 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17779 The symbol information for a C@t{++} member function is missing some
17780 information that recent versions of the compiler should have output for
17783 @item info mismatch between compiler and debugger
17785 @value{GDBN} could not parse a type specification output by the compiler.
17790 @section GDB Data Files
17792 @cindex prefix for data files
17793 @value{GDBN} will sometimes read an auxiliary data file. These files
17794 are kept in a directory known as the @dfn{data directory}.
17796 You can set the data directory's name, and view the name @value{GDBN}
17797 is currently using.
17800 @kindex set data-directory
17801 @item set data-directory @var{directory}
17802 Set the directory which @value{GDBN} searches for auxiliary data files
17803 to @var{directory}.
17805 @kindex show data-directory
17806 @item show data-directory
17807 Show the directory @value{GDBN} searches for auxiliary data files.
17810 @cindex default data directory
17811 @cindex @samp{--with-gdb-datadir}
17812 You can set the default data directory by using the configure-time
17813 @samp{--with-gdb-datadir} option. If the data directory is inside
17814 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17815 @samp{--exec-prefix}), then the default data directory will be updated
17816 automatically if the installed @value{GDBN} is moved to a new
17819 The data directory may also be specified with the
17820 @code{--data-directory} command line option.
17821 @xref{Mode Options}.
17824 @chapter Specifying a Debugging Target
17826 @cindex debugging target
17827 A @dfn{target} is the execution environment occupied by your program.
17829 Often, @value{GDBN} runs in the same host environment as your program;
17830 in that case, the debugging target is specified as a side effect when
17831 you use the @code{file} or @code{core} commands. When you need more
17832 flexibility---for example, running @value{GDBN} on a physically separate
17833 host, or controlling a standalone system over a serial port or a
17834 realtime system over a TCP/IP connection---you can use the @code{target}
17835 command to specify one of the target types configured for @value{GDBN}
17836 (@pxref{Target Commands, ,Commands for Managing Targets}).
17838 @cindex target architecture
17839 It is possible to build @value{GDBN} for several different @dfn{target
17840 architectures}. When @value{GDBN} is built like that, you can choose
17841 one of the available architectures with the @kbd{set architecture}
17845 @kindex set architecture
17846 @kindex show architecture
17847 @item set architecture @var{arch}
17848 This command sets the current target architecture to @var{arch}. The
17849 value of @var{arch} can be @code{"auto"}, in addition to one of the
17850 supported architectures.
17852 @item show architecture
17853 Show the current target architecture.
17855 @item set processor
17857 @kindex set processor
17858 @kindex show processor
17859 These are alias commands for, respectively, @code{set architecture}
17860 and @code{show architecture}.
17864 * Active Targets:: Active targets
17865 * Target Commands:: Commands for managing targets
17866 * Byte Order:: Choosing target byte order
17869 @node Active Targets
17870 @section Active Targets
17872 @cindex stacking targets
17873 @cindex active targets
17874 @cindex multiple targets
17876 There are multiple classes of targets such as: processes, executable files or
17877 recording sessions. Core files belong to the process class, making core file
17878 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17879 on multiple active targets, one in each class. This allows you to (for
17880 example) start a process and inspect its activity, while still having access to
17881 the executable file after the process finishes. Or if you start process
17882 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17883 presented a virtual layer of the recording target, while the process target
17884 remains stopped at the chronologically last point of the process execution.
17886 Use the @code{core-file} and @code{exec-file} commands to select a new core
17887 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17888 specify as a target a process that is already running, use the @code{attach}
17889 command (@pxref{Attach, ,Debugging an Already-running Process}).
17891 @node Target Commands
17892 @section Commands for Managing Targets
17895 @item target @var{type} @var{parameters}
17896 Connects the @value{GDBN} host environment to a target machine or
17897 process. A target is typically a protocol for talking to debugging
17898 facilities. You use the argument @var{type} to specify the type or
17899 protocol of the target machine.
17901 Further @var{parameters} are interpreted by the target protocol, but
17902 typically include things like device names or host names to connect
17903 with, process numbers, and baud rates.
17905 The @code{target} command does not repeat if you press @key{RET} again
17906 after executing the command.
17908 @kindex help target
17910 Displays the names of all targets available. To display targets
17911 currently selected, use either @code{info target} or @code{info files}
17912 (@pxref{Files, ,Commands to Specify Files}).
17914 @item help target @var{name}
17915 Describe a particular target, including any parameters necessary to
17918 @kindex set gnutarget
17919 @item set gnutarget @var{args}
17920 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17921 knows whether it is reading an @dfn{executable},
17922 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17923 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17924 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17927 @emph{Warning:} To specify a file format with @code{set gnutarget},
17928 you must know the actual BFD name.
17932 @xref{Files, , Commands to Specify Files}.
17934 @kindex show gnutarget
17935 @item show gnutarget
17936 Use the @code{show gnutarget} command to display what file format
17937 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17938 @value{GDBN} will determine the file format for each file automatically,
17939 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17942 @cindex common targets
17943 Here are some common targets (available, or not, depending on the GDB
17948 @item target exec @var{program}
17949 @cindex executable file target
17950 An executable file. @samp{target exec @var{program}} is the same as
17951 @samp{exec-file @var{program}}.
17953 @item target core @var{filename}
17954 @cindex core dump file target
17955 A core dump file. @samp{target core @var{filename}} is the same as
17956 @samp{core-file @var{filename}}.
17958 @item target remote @var{medium}
17959 @cindex remote target
17960 A remote system connected to @value{GDBN} via a serial line or network
17961 connection. This command tells @value{GDBN} to use its own remote
17962 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17964 For example, if you have a board connected to @file{/dev/ttya} on the
17965 machine running @value{GDBN}, you could say:
17968 target remote /dev/ttya
17971 @code{target remote} supports the @code{load} command. This is only
17972 useful if you have some other way of getting the stub to the target
17973 system, and you can put it somewhere in memory where it won't get
17974 clobbered by the download.
17976 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17977 @cindex built-in simulator target
17978 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17986 works; however, you cannot assume that a specific memory map, device
17987 drivers, or even basic I/O is available, although some simulators do
17988 provide these. For info about any processor-specific simulator details,
17989 see the appropriate section in @ref{Embedded Processors, ,Embedded
17994 Different targets are available on different configurations of @value{GDBN};
17995 your configuration may have more or fewer targets.
17997 Many remote targets require you to download the executable's code once
17998 you've successfully established a connection. You may wish to control
17999 various aspects of this process.
18004 @kindex set hash@r{, for remote monitors}
18005 @cindex hash mark while downloading
18006 This command controls whether a hash mark @samp{#} is displayed while
18007 downloading a file to the remote monitor. If on, a hash mark is
18008 displayed after each S-record is successfully downloaded to the
18012 @kindex show hash@r{, for remote monitors}
18013 Show the current status of displaying the hash mark.
18015 @item set debug monitor
18016 @kindex set debug monitor
18017 @cindex display remote monitor communications
18018 Enable or disable display of communications messages between
18019 @value{GDBN} and the remote monitor.
18021 @item show debug monitor
18022 @kindex show debug monitor
18023 Show the current status of displaying communications between
18024 @value{GDBN} and the remote monitor.
18029 @kindex load @var{filename}
18030 @item load @var{filename}
18032 Depending on what remote debugging facilities are configured into
18033 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18034 is meant to make @var{filename} (an executable) available for debugging
18035 on the remote system---by downloading, or dynamic linking, for example.
18036 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18037 the @code{add-symbol-file} command.
18039 If your @value{GDBN} does not have a @code{load} command, attempting to
18040 execute it gets the error message ``@code{You can't do that when your
18041 target is @dots{}}''
18043 The file is loaded at whatever address is specified in the executable.
18044 For some object file formats, you can specify the load address when you
18045 link the program; for other formats, like a.out, the object file format
18046 specifies a fixed address.
18047 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18049 Depending on the remote side capabilities, @value{GDBN} may be able to
18050 load programs into flash memory.
18052 @code{load} does not repeat if you press @key{RET} again after using it.
18056 @section Choosing Target Byte Order
18058 @cindex choosing target byte order
18059 @cindex target byte order
18061 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18062 offer the ability to run either big-endian or little-endian byte
18063 orders. Usually the executable or symbol will include a bit to
18064 designate the endian-ness, and you will not need to worry about
18065 which to use. However, you may still find it useful to adjust
18066 @value{GDBN}'s idea of processor endian-ness manually.
18070 @item set endian big
18071 Instruct @value{GDBN} to assume the target is big-endian.
18073 @item set endian little
18074 Instruct @value{GDBN} to assume the target is little-endian.
18076 @item set endian auto
18077 Instruct @value{GDBN} to use the byte order associated with the
18081 Display @value{GDBN}'s current idea of the target byte order.
18085 Note that these commands merely adjust interpretation of symbolic
18086 data on the host, and that they have absolutely no effect on the
18090 @node Remote Debugging
18091 @chapter Debugging Remote Programs
18092 @cindex remote debugging
18094 If you are trying to debug a program running on a machine that cannot run
18095 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18096 For example, you might use remote debugging on an operating system kernel,
18097 or on a small system which does not have a general purpose operating system
18098 powerful enough to run a full-featured debugger.
18100 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18101 to make this work with particular debugging targets. In addition,
18102 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18103 but not specific to any particular target system) which you can use if you
18104 write the remote stubs---the code that runs on the remote system to
18105 communicate with @value{GDBN}.
18107 Other remote targets may be available in your
18108 configuration of @value{GDBN}; use @code{help target} to list them.
18111 * Connecting:: Connecting to a remote target
18112 * File Transfer:: Sending files to a remote system
18113 * Server:: Using the gdbserver program
18114 * Remote Configuration:: Remote configuration
18115 * Remote Stub:: Implementing a remote stub
18119 @section Connecting to a Remote Target
18121 On the @value{GDBN} host machine, you will need an unstripped copy of
18122 your program, since @value{GDBN} needs symbol and debugging information.
18123 Start up @value{GDBN} as usual, using the name of the local copy of your
18124 program as the first argument.
18126 @cindex @code{target remote}
18127 @value{GDBN} can communicate with the target over a serial line, or
18128 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18129 each case, @value{GDBN} uses the same protocol for debugging your
18130 program; only the medium carrying the debugging packets varies. The
18131 @code{target remote} command establishes a connection to the target.
18132 Its arguments indicate which medium to use:
18136 @item target remote @var{serial-device}
18137 @cindex serial line, @code{target remote}
18138 Use @var{serial-device} to communicate with the target. For example,
18139 to use a serial line connected to the device named @file{/dev/ttyb}:
18142 target remote /dev/ttyb
18145 If you're using a serial line, you may want to give @value{GDBN} the
18146 @samp{--baud} option, or use the @code{set serial baud} command
18147 (@pxref{Remote Configuration, set serial baud}) before the
18148 @code{target} command.
18150 @item target remote @code{@var{host}:@var{port}}
18151 @itemx target remote @code{tcp:@var{host}:@var{port}}
18152 @cindex @acronym{TCP} port, @code{target remote}
18153 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18154 The @var{host} may be either a host name or a numeric @acronym{IP}
18155 address; @var{port} must be a decimal number. The @var{host} could be
18156 the target machine itself, if it is directly connected to the net, or
18157 it might be a terminal server which in turn has a serial line to the
18160 For example, to connect to port 2828 on a terminal server named
18164 target remote manyfarms:2828
18167 If your remote target is actually running on the same machine as your
18168 debugger session (e.g.@: a simulator for your target running on the
18169 same host), you can omit the hostname. For example, to connect to
18170 port 1234 on your local machine:
18173 target remote :1234
18177 Note that the colon is still required here.
18179 @item target remote @code{udp:@var{host}:@var{port}}
18180 @cindex @acronym{UDP} port, @code{target remote}
18181 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18182 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18185 target remote udp:manyfarms:2828
18188 When using a @acronym{UDP} connection for remote debugging, you should
18189 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18190 can silently drop packets on busy or unreliable networks, which will
18191 cause havoc with your debugging session.
18193 @item target remote | @var{command}
18194 @cindex pipe, @code{target remote} to
18195 Run @var{command} in the background and communicate with it using a
18196 pipe. The @var{command} is a shell command, to be parsed and expanded
18197 by the system's command shell, @code{/bin/sh}; it should expect remote
18198 protocol packets on its standard input, and send replies on its
18199 standard output. You could use this to run a stand-alone simulator
18200 that speaks the remote debugging protocol, to make net connections
18201 using programs like @code{ssh}, or for other similar tricks.
18203 If @var{command} closes its standard output (perhaps by exiting),
18204 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18205 program has already exited, this will have no effect.)
18209 Once the connection has been established, you can use all the usual
18210 commands to examine and change data. The remote program is already
18211 running; you can use @kbd{step} and @kbd{continue}, and you do not
18212 need to use @kbd{run}.
18214 @cindex interrupting remote programs
18215 @cindex remote programs, interrupting
18216 Whenever @value{GDBN} is waiting for the remote program, if you type the
18217 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18218 program. This may or may not succeed, depending in part on the hardware
18219 and the serial drivers the remote system uses. If you type the
18220 interrupt character once again, @value{GDBN} displays this prompt:
18223 Interrupted while waiting for the program.
18224 Give up (and stop debugging it)? (y or n)
18227 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18228 (If you decide you want to try again later, you can use @samp{target
18229 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18230 goes back to waiting.
18233 @kindex detach (remote)
18235 When you have finished debugging the remote program, you can use the
18236 @code{detach} command to release it from @value{GDBN} control.
18237 Detaching from the target normally resumes its execution, but the results
18238 will depend on your particular remote stub. After the @code{detach}
18239 command, @value{GDBN} is free to connect to another target.
18243 The @code{disconnect} command behaves like @code{detach}, except that
18244 the target is generally not resumed. It will wait for @value{GDBN}
18245 (this instance or another one) to connect and continue debugging. After
18246 the @code{disconnect} command, @value{GDBN} is again free to connect to
18249 @cindex send command to remote monitor
18250 @cindex extend @value{GDBN} for remote targets
18251 @cindex add new commands for external monitor
18253 @item monitor @var{cmd}
18254 This command allows you to send arbitrary commands directly to the
18255 remote monitor. Since @value{GDBN} doesn't care about the commands it
18256 sends like this, this command is the way to extend @value{GDBN}---you
18257 can add new commands that only the external monitor will understand
18261 @node File Transfer
18262 @section Sending files to a remote system
18263 @cindex remote target, file transfer
18264 @cindex file transfer
18265 @cindex sending files to remote systems
18267 Some remote targets offer the ability to transfer files over the same
18268 connection used to communicate with @value{GDBN}. This is convenient
18269 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18270 running @code{gdbserver} over a network interface. For other targets,
18271 e.g.@: embedded devices with only a single serial port, this may be
18272 the only way to upload or download files.
18274 Not all remote targets support these commands.
18278 @item remote put @var{hostfile} @var{targetfile}
18279 Copy file @var{hostfile} from the host system (the machine running
18280 @value{GDBN}) to @var{targetfile} on the target system.
18283 @item remote get @var{targetfile} @var{hostfile}
18284 Copy file @var{targetfile} from the target system to @var{hostfile}
18285 on the host system.
18287 @kindex remote delete
18288 @item remote delete @var{targetfile}
18289 Delete @var{targetfile} from the target system.
18294 @section Using the @code{gdbserver} Program
18297 @cindex remote connection without stubs
18298 @code{gdbserver} is a control program for Unix-like systems, which
18299 allows you to connect your program with a remote @value{GDBN} via
18300 @code{target remote}---but without linking in the usual debugging stub.
18302 @code{gdbserver} is not a complete replacement for the debugging stubs,
18303 because it requires essentially the same operating-system facilities
18304 that @value{GDBN} itself does. In fact, a system that can run
18305 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18306 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18307 because it is a much smaller program than @value{GDBN} itself. It is
18308 also easier to port than all of @value{GDBN}, so you may be able to get
18309 started more quickly on a new system by using @code{gdbserver}.
18310 Finally, if you develop code for real-time systems, you may find that
18311 the tradeoffs involved in real-time operation make it more convenient to
18312 do as much development work as possible on another system, for example
18313 by cross-compiling. You can use @code{gdbserver} to make a similar
18314 choice for debugging.
18316 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18317 or a TCP connection, using the standard @value{GDBN} remote serial
18321 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18322 Do not run @code{gdbserver} connected to any public network; a
18323 @value{GDBN} connection to @code{gdbserver} provides access to the
18324 target system with the same privileges as the user running
18328 @subsection Running @code{gdbserver}
18329 @cindex arguments, to @code{gdbserver}
18330 @cindex @code{gdbserver}, command-line arguments
18332 Run @code{gdbserver} on the target system. You need a copy of the
18333 program you want to debug, including any libraries it requires.
18334 @code{gdbserver} does not need your program's symbol table, so you can
18335 strip the program if necessary to save space. @value{GDBN} on the host
18336 system does all the symbol handling.
18338 To use the server, you must tell it how to communicate with @value{GDBN};
18339 the name of your program; and the arguments for your program. The usual
18343 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18346 @var{comm} is either a device name (to use a serial line), or a TCP
18347 hostname and portnumber, or @code{-} or @code{stdio} to use
18348 stdin/stdout of @code{gdbserver}.
18349 For example, to debug Emacs with the argument
18350 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18354 target> gdbserver /dev/com1 emacs foo.txt
18357 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18360 To use a TCP connection instead of a serial line:
18363 target> gdbserver host:2345 emacs foo.txt
18366 The only difference from the previous example is the first argument,
18367 specifying that you are communicating with the host @value{GDBN} via
18368 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18369 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18370 (Currently, the @samp{host} part is ignored.) You can choose any number
18371 you want for the port number as long as it does not conflict with any
18372 TCP ports already in use on the target system (for example, @code{23} is
18373 reserved for @code{telnet}).@footnote{If you choose a port number that
18374 conflicts with another service, @code{gdbserver} prints an error message
18375 and exits.} You must use the same port number with the host @value{GDBN}
18376 @code{target remote} command.
18378 The @code{stdio} connection is useful when starting @code{gdbserver}
18382 (gdb) target remote | ssh -T hostname gdbserver - hello
18385 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18386 and we don't want escape-character handling. Ssh does this by default when
18387 a command is provided, the flag is provided to make it explicit.
18388 You could elide it if you want to.
18390 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18391 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18392 display through a pipe connected to gdbserver.
18393 Both @code{stdout} and @code{stderr} use the same pipe.
18395 @subsubsection Attaching to a Running Program
18396 @cindex attach to a program, @code{gdbserver}
18397 @cindex @option{--attach}, @code{gdbserver} option
18399 On some targets, @code{gdbserver} can also attach to running programs.
18400 This is accomplished via the @code{--attach} argument. The syntax is:
18403 target> gdbserver --attach @var{comm} @var{pid}
18406 @var{pid} is the process ID of a currently running process. It isn't necessary
18407 to point @code{gdbserver} at a binary for the running process.
18410 You can debug processes by name instead of process ID if your target has the
18411 @code{pidof} utility:
18414 target> gdbserver --attach @var{comm} `pidof @var{program}`
18417 In case more than one copy of @var{program} is running, or @var{program}
18418 has multiple threads, most versions of @code{pidof} support the
18419 @code{-s} option to only return the first process ID.
18421 @subsubsection Multi-Process Mode for @code{gdbserver}
18422 @cindex @code{gdbserver}, multiple processes
18423 @cindex multiple processes with @code{gdbserver}
18425 When you connect to @code{gdbserver} using @code{target remote},
18426 @code{gdbserver} debugs the specified program only once. When the
18427 program exits, or you detach from it, @value{GDBN} closes the connection
18428 and @code{gdbserver} exits.
18430 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18431 enters multi-process mode. When the debugged program exits, or you
18432 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18433 though no program is running. The @code{run} and @code{attach}
18434 commands instruct @code{gdbserver} to run or attach to a new program.
18435 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18436 remote exec-file}) to select the program to run. Command line
18437 arguments are supported, except for wildcard expansion and I/O
18438 redirection (@pxref{Arguments}).
18440 @cindex @option{--multi}, @code{gdbserver} option
18441 To start @code{gdbserver} without supplying an initial command to run
18442 or process ID to attach, use the @option{--multi} command line option.
18443 Then you can connect using @kbd{target extended-remote} and start
18444 the program you want to debug.
18446 In multi-process mode @code{gdbserver} does not automatically exit unless you
18447 use the option @option{--once}. You can terminate it by using
18448 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18449 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18450 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18451 @option{--multi} option to @code{gdbserver} has no influence on that.
18453 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18455 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18457 @code{gdbserver} normally terminates after all of its debugged processes have
18458 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18459 extended-remote}, @code{gdbserver} stays running even with no processes left.
18460 @value{GDBN} normally terminates the spawned debugged process on its exit,
18461 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18462 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18463 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18464 stays running even in the @kbd{target remote} mode.
18466 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18467 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18468 completeness, at most one @value{GDBN} can be connected at a time.
18470 @cindex @option{--once}, @code{gdbserver} option
18471 By default, @code{gdbserver} keeps the listening TCP port open, so that
18472 subsequent connections are possible. However, if you start @code{gdbserver}
18473 with the @option{--once} option, it will stop listening for any further
18474 connection attempts after connecting to the first @value{GDBN} session. This
18475 means no further connections to @code{gdbserver} will be possible after the
18476 first one. It also means @code{gdbserver} will terminate after the first
18477 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18478 connections and even in the @kbd{target extended-remote} mode. The
18479 @option{--once} option allows reusing the same port number for connecting to
18480 multiple instances of @code{gdbserver} running on the same host, since each
18481 instance closes its port after the first connection.
18483 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18485 @cindex @option{--debug}, @code{gdbserver} option
18486 The @option{--debug} option tells @code{gdbserver} to display extra
18487 status information about the debugging process.
18488 @cindex @option{--remote-debug}, @code{gdbserver} option
18489 The @option{--remote-debug} option tells @code{gdbserver} to display
18490 remote protocol debug output. These options are intended for
18491 @code{gdbserver} development and for bug reports to the developers.
18493 @cindex @option{--wrapper}, @code{gdbserver} option
18494 The @option{--wrapper} option specifies a wrapper to launch programs
18495 for debugging. The option should be followed by the name of the
18496 wrapper, then any command-line arguments to pass to the wrapper, then
18497 @kbd{--} indicating the end of the wrapper arguments.
18499 @code{gdbserver} runs the specified wrapper program with a combined
18500 command line including the wrapper arguments, then the name of the
18501 program to debug, then any arguments to the program. The wrapper
18502 runs until it executes your program, and then @value{GDBN} gains control.
18504 You can use any program that eventually calls @code{execve} with
18505 its arguments as a wrapper. Several standard Unix utilities do
18506 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18507 with @code{exec "$@@"} will also work.
18509 For example, you can use @code{env} to pass an environment variable to
18510 the debugged program, without setting the variable in @code{gdbserver}'s
18514 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18517 @subsection Connecting to @code{gdbserver}
18519 Run @value{GDBN} on the host system.
18521 First make sure you have the necessary symbol files. Load symbols for
18522 your application using the @code{file} command before you connect. Use
18523 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18524 was compiled with the correct sysroot using @code{--with-sysroot}).
18526 The symbol file and target libraries must exactly match the executable
18527 and libraries on the target, with one exception: the files on the host
18528 system should not be stripped, even if the files on the target system
18529 are. Mismatched or missing files will lead to confusing results
18530 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18531 files may also prevent @code{gdbserver} from debugging multi-threaded
18534 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18535 For TCP connections, you must start up @code{gdbserver} prior to using
18536 the @code{target remote} command. Otherwise you may get an error whose
18537 text depends on the host system, but which usually looks something like
18538 @samp{Connection refused}. Don't use the @code{load}
18539 command in @value{GDBN} when using @code{gdbserver}, since the program is
18540 already on the target.
18542 @subsection Monitor Commands for @code{gdbserver}
18543 @cindex monitor commands, for @code{gdbserver}
18544 @anchor{Monitor Commands for gdbserver}
18546 During a @value{GDBN} session using @code{gdbserver}, you can use the
18547 @code{monitor} command to send special requests to @code{gdbserver}.
18548 Here are the available commands.
18552 List the available monitor commands.
18554 @item monitor set debug 0
18555 @itemx monitor set debug 1
18556 Disable or enable general debugging messages.
18558 @item monitor set remote-debug 0
18559 @itemx monitor set remote-debug 1
18560 Disable or enable specific debugging messages associated with the remote
18561 protocol (@pxref{Remote Protocol}).
18563 @item monitor set libthread-db-search-path [PATH]
18564 @cindex gdbserver, search path for @code{libthread_db}
18565 When this command is issued, @var{path} is a colon-separated list of
18566 directories to search for @code{libthread_db} (@pxref{Threads,,set
18567 libthread-db-search-path}). If you omit @var{path},
18568 @samp{libthread-db-search-path} will be reset to its default value.
18570 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18571 not supported in @code{gdbserver}.
18574 Tell gdbserver to exit immediately. This command should be followed by
18575 @code{disconnect} to close the debugging session. @code{gdbserver} will
18576 detach from any attached processes and kill any processes it created.
18577 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18578 of a multi-process mode debug session.
18582 @subsection Tracepoints support in @code{gdbserver}
18583 @cindex tracepoints support in @code{gdbserver}
18585 On some targets, @code{gdbserver} supports tracepoints, fast
18586 tracepoints and static tracepoints.
18588 For fast or static tracepoints to work, a special library called the
18589 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18590 This library is built and distributed as an integral part of
18591 @code{gdbserver}. In addition, support for static tracepoints
18592 requires building the in-process agent library with static tracepoints
18593 support. At present, the UST (LTTng Userspace Tracer,
18594 @url{http://lttng.org/ust}) tracing engine is supported. This support
18595 is automatically available if UST development headers are found in the
18596 standard include path when @code{gdbserver} is built, or if
18597 @code{gdbserver} was explicitly configured using @option{--with-ust}
18598 to point at such headers. You can explicitly disable the support
18599 using @option{--with-ust=no}.
18601 There are several ways to load the in-process agent in your program:
18604 @item Specifying it as dependency at link time
18606 You can link your program dynamically with the in-process agent
18607 library. On most systems, this is accomplished by adding
18608 @code{-linproctrace} to the link command.
18610 @item Using the system's preloading mechanisms
18612 You can force loading the in-process agent at startup time by using
18613 your system's support for preloading shared libraries. Many Unixes
18614 support the concept of preloading user defined libraries. In most
18615 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18616 in the environment. See also the description of @code{gdbserver}'s
18617 @option{--wrapper} command line option.
18619 @item Using @value{GDBN} to force loading the agent at run time
18621 On some systems, you can force the inferior to load a shared library,
18622 by calling a dynamic loader function in the inferior that takes care
18623 of dynamically looking up and loading a shared library. On most Unix
18624 systems, the function is @code{dlopen}. You'll use the @code{call}
18625 command for that. For example:
18628 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18631 Note that on most Unix systems, for the @code{dlopen} function to be
18632 available, the program needs to be linked with @code{-ldl}.
18635 On systems that have a userspace dynamic loader, like most Unix
18636 systems, when you connect to @code{gdbserver} using @code{target
18637 remote}, you'll find that the program is stopped at the dynamic
18638 loader's entry point, and no shared library has been loaded in the
18639 program's address space yet, including the in-process agent. In that
18640 case, before being able to use any of the fast or static tracepoints
18641 features, you need to let the loader run and load the shared
18642 libraries. The simplest way to do that is to run the program to the
18643 main procedure. E.g., if debugging a C or C@t{++} program, start
18644 @code{gdbserver} like so:
18647 $ gdbserver :9999 myprogram
18650 Start GDB and connect to @code{gdbserver} like so, and run to main:
18654 (@value{GDBP}) target remote myhost:9999
18655 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18656 (@value{GDBP}) b main
18657 (@value{GDBP}) continue
18660 The in-process tracing agent library should now be loaded into the
18661 process; you can confirm it with the @code{info sharedlibrary}
18662 command, which will list @file{libinproctrace.so} as loaded in the
18663 process. You are now ready to install fast tracepoints, list static
18664 tracepoint markers, probe static tracepoints markers, and start
18667 @node Remote Configuration
18668 @section Remote Configuration
18671 @kindex show remote
18672 This section documents the configuration options available when
18673 debugging remote programs. For the options related to the File I/O
18674 extensions of the remote protocol, see @ref{system,
18675 system-call-allowed}.
18678 @item set remoteaddresssize @var{bits}
18679 @cindex address size for remote targets
18680 @cindex bits in remote address
18681 Set the maximum size of address in a memory packet to the specified
18682 number of bits. @value{GDBN} will mask off the address bits above
18683 that number, when it passes addresses to the remote target. The
18684 default value is the number of bits in the target's address.
18686 @item show remoteaddresssize
18687 Show the current value of remote address size in bits.
18689 @item set serial baud @var{n}
18690 @cindex baud rate for remote targets
18691 Set the baud rate for the remote serial I/O to @var{n} baud. The
18692 value is used to set the speed of the serial port used for debugging
18695 @item show serial baud
18696 Show the current speed of the remote connection.
18698 @item set remotebreak
18699 @cindex interrupt remote programs
18700 @cindex BREAK signal instead of Ctrl-C
18701 @anchor{set remotebreak}
18702 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18703 when you type @kbd{Ctrl-c} to interrupt the program running
18704 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18705 character instead. The default is off, since most remote systems
18706 expect to see @samp{Ctrl-C} as the interrupt signal.
18708 @item show remotebreak
18709 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18710 interrupt the remote program.
18712 @item set remoteflow on
18713 @itemx set remoteflow off
18714 @kindex set remoteflow
18715 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18716 on the serial port used to communicate to the remote target.
18718 @item show remoteflow
18719 @kindex show remoteflow
18720 Show the current setting of hardware flow control.
18722 @item set remotelogbase @var{base}
18723 Set the base (a.k.a.@: radix) of logging serial protocol
18724 communications to @var{base}. Supported values of @var{base} are:
18725 @code{ascii}, @code{octal}, and @code{hex}. The default is
18728 @item show remotelogbase
18729 Show the current setting of the radix for logging remote serial
18732 @item set remotelogfile @var{file}
18733 @cindex record serial communications on file
18734 Record remote serial communications on the named @var{file}. The
18735 default is not to record at all.
18737 @item show remotelogfile.
18738 Show the current setting of the file name on which to record the
18739 serial communications.
18741 @item set remotetimeout @var{num}
18742 @cindex timeout for serial communications
18743 @cindex remote timeout
18744 Set the timeout limit to wait for the remote target to respond to
18745 @var{num} seconds. The default is 2 seconds.
18747 @item show remotetimeout
18748 Show the current number of seconds to wait for the remote target
18751 @cindex limit hardware breakpoints and watchpoints
18752 @cindex remote target, limit break- and watchpoints
18753 @anchor{set remote hardware-watchpoint-limit}
18754 @anchor{set remote hardware-breakpoint-limit}
18755 @item set remote hardware-watchpoint-limit @var{limit}
18756 @itemx set remote hardware-breakpoint-limit @var{limit}
18757 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18758 watchpoints. A limit of -1, the default, is treated as unlimited.
18760 @cindex limit hardware watchpoints length
18761 @cindex remote target, limit watchpoints length
18762 @anchor{set remote hardware-watchpoint-length-limit}
18763 @item set remote hardware-watchpoint-length-limit @var{limit}
18764 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18765 a remote hardware watchpoint. A limit of -1, the default, is treated
18768 @item show remote hardware-watchpoint-length-limit
18769 Show the current limit (in bytes) of the maximum length of
18770 a remote hardware watchpoint.
18772 @item set remote exec-file @var{filename}
18773 @itemx show remote exec-file
18774 @anchor{set remote exec-file}
18775 @cindex executable file, for remote target
18776 Select the file used for @code{run} with @code{target
18777 extended-remote}. This should be set to a filename valid on the
18778 target system. If it is not set, the target will use a default
18779 filename (e.g.@: the last program run).
18781 @item set remote interrupt-sequence
18782 @cindex interrupt remote programs
18783 @cindex select Ctrl-C, BREAK or BREAK-g
18784 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18785 @samp{BREAK-g} as the
18786 sequence to the remote target in order to interrupt the execution.
18787 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18788 is high level of serial line for some certain time.
18789 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18790 It is @code{BREAK} signal followed by character @code{g}.
18792 @item show interrupt-sequence
18793 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18794 is sent by @value{GDBN} to interrupt the remote program.
18795 @code{BREAK-g} is BREAK signal followed by @code{g} and
18796 also known as Magic SysRq g.
18798 @item set remote interrupt-on-connect
18799 @cindex send interrupt-sequence on start
18800 Specify whether interrupt-sequence is sent to remote target when
18801 @value{GDBN} connects to it. This is mostly needed when you debug
18802 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18803 which is known as Magic SysRq g in order to connect @value{GDBN}.
18805 @item show interrupt-on-connect
18806 Show whether interrupt-sequence is sent
18807 to remote target when @value{GDBN} connects to it.
18811 @item set tcp auto-retry on
18812 @cindex auto-retry, for remote TCP target
18813 Enable auto-retry for remote TCP connections. This is useful if the remote
18814 debugging agent is launched in parallel with @value{GDBN}; there is a race
18815 condition because the agent may not become ready to accept the connection
18816 before @value{GDBN} attempts to connect. When auto-retry is
18817 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18818 to establish the connection using the timeout specified by
18819 @code{set tcp connect-timeout}.
18821 @item set tcp auto-retry off
18822 Do not auto-retry failed TCP connections.
18824 @item show tcp auto-retry
18825 Show the current auto-retry setting.
18827 @item set tcp connect-timeout @var{seconds}
18828 @itemx set tcp connect-timeout unlimited
18829 @cindex connection timeout, for remote TCP target
18830 @cindex timeout, for remote target connection
18831 Set the timeout for establishing a TCP connection to the remote target to
18832 @var{seconds}. The timeout affects both polling to retry failed connections
18833 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18834 that are merely slow to complete, and represents an approximate cumulative
18835 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18836 @value{GDBN} will keep attempting to establish a connection forever,
18837 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18839 @item show tcp connect-timeout
18840 Show the current connection timeout setting.
18843 @cindex remote packets, enabling and disabling
18844 The @value{GDBN} remote protocol autodetects the packets supported by
18845 your debugging stub. If you need to override the autodetection, you
18846 can use these commands to enable or disable individual packets. Each
18847 packet can be set to @samp{on} (the remote target supports this
18848 packet), @samp{off} (the remote target does not support this packet),
18849 or @samp{auto} (detect remote target support for this packet). They
18850 all default to @samp{auto}. For more information about each packet,
18851 see @ref{Remote Protocol}.
18853 During normal use, you should not have to use any of these commands.
18854 If you do, that may be a bug in your remote debugging stub, or a bug
18855 in @value{GDBN}. You may want to report the problem to the
18856 @value{GDBN} developers.
18858 For each packet @var{name}, the command to enable or disable the
18859 packet is @code{set remote @var{name}-packet}. The available settings
18862 @multitable @columnfractions 0.28 0.32 0.25
18865 @tab Related Features
18867 @item @code{fetch-register}
18869 @tab @code{info registers}
18871 @item @code{set-register}
18875 @item @code{binary-download}
18877 @tab @code{load}, @code{set}
18879 @item @code{read-aux-vector}
18880 @tab @code{qXfer:auxv:read}
18881 @tab @code{info auxv}
18883 @item @code{symbol-lookup}
18884 @tab @code{qSymbol}
18885 @tab Detecting multiple threads
18887 @item @code{attach}
18888 @tab @code{vAttach}
18891 @item @code{verbose-resume}
18893 @tab Stepping or resuming multiple threads
18899 @item @code{software-breakpoint}
18903 @item @code{hardware-breakpoint}
18907 @item @code{write-watchpoint}
18911 @item @code{read-watchpoint}
18915 @item @code{access-watchpoint}
18919 @item @code{target-features}
18920 @tab @code{qXfer:features:read}
18921 @tab @code{set architecture}
18923 @item @code{library-info}
18924 @tab @code{qXfer:libraries:read}
18925 @tab @code{info sharedlibrary}
18927 @item @code{memory-map}
18928 @tab @code{qXfer:memory-map:read}
18929 @tab @code{info mem}
18931 @item @code{read-sdata-object}
18932 @tab @code{qXfer:sdata:read}
18933 @tab @code{print $_sdata}
18935 @item @code{read-spu-object}
18936 @tab @code{qXfer:spu:read}
18937 @tab @code{info spu}
18939 @item @code{write-spu-object}
18940 @tab @code{qXfer:spu:write}
18941 @tab @code{info spu}
18943 @item @code{read-siginfo-object}
18944 @tab @code{qXfer:siginfo:read}
18945 @tab @code{print $_siginfo}
18947 @item @code{write-siginfo-object}
18948 @tab @code{qXfer:siginfo:write}
18949 @tab @code{set $_siginfo}
18951 @item @code{threads}
18952 @tab @code{qXfer:threads:read}
18953 @tab @code{info threads}
18955 @item @code{get-thread-local-@*storage-address}
18956 @tab @code{qGetTLSAddr}
18957 @tab Displaying @code{__thread} variables
18959 @item @code{get-thread-information-block-address}
18960 @tab @code{qGetTIBAddr}
18961 @tab Display MS-Windows Thread Information Block.
18963 @item @code{search-memory}
18964 @tab @code{qSearch:memory}
18967 @item @code{supported-packets}
18968 @tab @code{qSupported}
18969 @tab Remote communications parameters
18971 @item @code{pass-signals}
18972 @tab @code{QPassSignals}
18973 @tab @code{handle @var{signal}}
18975 @item @code{program-signals}
18976 @tab @code{QProgramSignals}
18977 @tab @code{handle @var{signal}}
18979 @item @code{hostio-close-packet}
18980 @tab @code{vFile:close}
18981 @tab @code{remote get}, @code{remote put}
18983 @item @code{hostio-open-packet}
18984 @tab @code{vFile:open}
18985 @tab @code{remote get}, @code{remote put}
18987 @item @code{hostio-pread-packet}
18988 @tab @code{vFile:pread}
18989 @tab @code{remote get}, @code{remote put}
18991 @item @code{hostio-pwrite-packet}
18992 @tab @code{vFile:pwrite}
18993 @tab @code{remote get}, @code{remote put}
18995 @item @code{hostio-unlink-packet}
18996 @tab @code{vFile:unlink}
18997 @tab @code{remote delete}
18999 @item @code{hostio-readlink-packet}
19000 @tab @code{vFile:readlink}
19003 @item @code{noack-packet}
19004 @tab @code{QStartNoAckMode}
19005 @tab Packet acknowledgment
19007 @item @code{osdata}
19008 @tab @code{qXfer:osdata:read}
19009 @tab @code{info os}
19011 @item @code{query-attached}
19012 @tab @code{qAttached}
19013 @tab Querying remote process attach state.
19015 @item @code{trace-buffer-size}
19016 @tab @code{QTBuffer:size}
19017 @tab @code{set trace-buffer-size}
19019 @item @code{trace-status}
19020 @tab @code{qTStatus}
19021 @tab @code{tstatus}
19023 @item @code{traceframe-info}
19024 @tab @code{qXfer:traceframe-info:read}
19025 @tab Traceframe info
19027 @item @code{install-in-trace}
19028 @tab @code{InstallInTrace}
19029 @tab Install tracepoint in tracing
19031 @item @code{disable-randomization}
19032 @tab @code{QDisableRandomization}
19033 @tab @code{set disable-randomization}
19035 @item @code{conditional-breakpoints-packet}
19036 @tab @code{Z0 and Z1}
19037 @tab @code{Support for target-side breakpoint condition evaluation}
19041 @section Implementing a Remote Stub
19043 @cindex debugging stub, example
19044 @cindex remote stub, example
19045 @cindex stub example, remote debugging
19046 The stub files provided with @value{GDBN} implement the target side of the
19047 communication protocol, and the @value{GDBN} side is implemented in the
19048 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19049 these subroutines to communicate, and ignore the details. (If you're
19050 implementing your own stub file, you can still ignore the details: start
19051 with one of the existing stub files. @file{sparc-stub.c} is the best
19052 organized, and therefore the easiest to read.)
19054 @cindex remote serial debugging, overview
19055 To debug a program running on another machine (the debugging
19056 @dfn{target} machine), you must first arrange for all the usual
19057 prerequisites for the program to run by itself. For example, for a C
19062 A startup routine to set up the C runtime environment; these usually
19063 have a name like @file{crt0}. The startup routine may be supplied by
19064 your hardware supplier, or you may have to write your own.
19067 A C subroutine library to support your program's
19068 subroutine calls, notably managing input and output.
19071 A way of getting your program to the other machine---for example, a
19072 download program. These are often supplied by the hardware
19073 manufacturer, but you may have to write your own from hardware
19077 The next step is to arrange for your program to use a serial port to
19078 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19079 machine). In general terms, the scheme looks like this:
19083 @value{GDBN} already understands how to use this protocol; when everything
19084 else is set up, you can simply use the @samp{target remote} command
19085 (@pxref{Targets,,Specifying a Debugging Target}).
19087 @item On the target,
19088 you must link with your program a few special-purpose subroutines that
19089 implement the @value{GDBN} remote serial protocol. The file containing these
19090 subroutines is called a @dfn{debugging stub}.
19092 On certain remote targets, you can use an auxiliary program
19093 @code{gdbserver} instead of linking a stub into your program.
19094 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19097 The debugging stub is specific to the architecture of the remote
19098 machine; for example, use @file{sparc-stub.c} to debug programs on
19101 @cindex remote serial stub list
19102 These working remote stubs are distributed with @value{GDBN}:
19107 @cindex @file{i386-stub.c}
19110 For Intel 386 and compatible architectures.
19113 @cindex @file{m68k-stub.c}
19114 @cindex Motorola 680x0
19116 For Motorola 680x0 architectures.
19119 @cindex @file{sh-stub.c}
19122 For Renesas SH architectures.
19125 @cindex @file{sparc-stub.c}
19127 For @sc{sparc} architectures.
19129 @item sparcl-stub.c
19130 @cindex @file{sparcl-stub.c}
19133 For Fujitsu @sc{sparclite} architectures.
19137 The @file{README} file in the @value{GDBN} distribution may list other
19138 recently added stubs.
19141 * Stub Contents:: What the stub can do for you
19142 * Bootstrapping:: What you must do for the stub
19143 * Debug Session:: Putting it all together
19146 @node Stub Contents
19147 @subsection What the Stub Can Do for You
19149 @cindex remote serial stub
19150 The debugging stub for your architecture supplies these three
19154 @item set_debug_traps
19155 @findex set_debug_traps
19156 @cindex remote serial stub, initialization
19157 This routine arranges for @code{handle_exception} to run when your
19158 program stops. You must call this subroutine explicitly in your
19159 program's startup code.
19161 @item handle_exception
19162 @findex handle_exception
19163 @cindex remote serial stub, main routine
19164 This is the central workhorse, but your program never calls it
19165 explicitly---the setup code arranges for @code{handle_exception} to
19166 run when a trap is triggered.
19168 @code{handle_exception} takes control when your program stops during
19169 execution (for example, on a breakpoint), and mediates communications
19170 with @value{GDBN} on the host machine. This is where the communications
19171 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19172 representative on the target machine. It begins by sending summary
19173 information on the state of your program, then continues to execute,
19174 retrieving and transmitting any information @value{GDBN} needs, until you
19175 execute a @value{GDBN} command that makes your program resume; at that point,
19176 @code{handle_exception} returns control to your own code on the target
19180 @cindex @code{breakpoint} subroutine, remote
19181 Use this auxiliary subroutine to make your program contain a
19182 breakpoint. Depending on the particular situation, this may be the only
19183 way for @value{GDBN} to get control. For instance, if your target
19184 machine has some sort of interrupt button, you won't need to call this;
19185 pressing the interrupt button transfers control to
19186 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19187 simply receiving characters on the serial port may also trigger a trap;
19188 again, in that situation, you don't need to call @code{breakpoint} from
19189 your own program---simply running @samp{target remote} from the host
19190 @value{GDBN} session gets control.
19192 Call @code{breakpoint} if none of these is true, or if you simply want
19193 to make certain your program stops at a predetermined point for the
19194 start of your debugging session.
19197 @node Bootstrapping
19198 @subsection What You Must Do for the Stub
19200 @cindex remote stub, support routines
19201 The debugging stubs that come with @value{GDBN} are set up for a particular
19202 chip architecture, but they have no information about the rest of your
19203 debugging target machine.
19205 First of all you need to tell the stub how to communicate with the
19209 @item int getDebugChar()
19210 @findex getDebugChar
19211 Write this subroutine to read a single character from the serial port.
19212 It may be identical to @code{getchar} for your target system; a
19213 different name is used to allow you to distinguish the two if you wish.
19215 @item void putDebugChar(int)
19216 @findex putDebugChar
19217 Write this subroutine to write a single character to the serial port.
19218 It may be identical to @code{putchar} for your target system; a
19219 different name is used to allow you to distinguish the two if you wish.
19222 @cindex control C, and remote debugging
19223 @cindex interrupting remote targets
19224 If you want @value{GDBN} to be able to stop your program while it is
19225 running, you need to use an interrupt-driven serial driver, and arrange
19226 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19227 character). That is the character which @value{GDBN} uses to tell the
19228 remote system to stop.
19230 Getting the debugging target to return the proper status to @value{GDBN}
19231 probably requires changes to the standard stub; one quick and dirty way
19232 is to just execute a breakpoint instruction (the ``dirty'' part is that
19233 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19235 Other routines you need to supply are:
19238 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19239 @findex exceptionHandler
19240 Write this function to install @var{exception_address} in the exception
19241 handling tables. You need to do this because the stub does not have any
19242 way of knowing what the exception handling tables on your target system
19243 are like (for example, the processor's table might be in @sc{rom},
19244 containing entries which point to a table in @sc{ram}).
19245 @var{exception_number} is the exception number which should be changed;
19246 its meaning is architecture-dependent (for example, different numbers
19247 might represent divide by zero, misaligned access, etc). When this
19248 exception occurs, control should be transferred directly to
19249 @var{exception_address}, and the processor state (stack, registers,
19250 and so on) should be just as it is when a processor exception occurs. So if
19251 you want to use a jump instruction to reach @var{exception_address}, it
19252 should be a simple jump, not a jump to subroutine.
19254 For the 386, @var{exception_address} should be installed as an interrupt
19255 gate so that interrupts are masked while the handler runs. The gate
19256 should be at privilege level 0 (the most privileged level). The
19257 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19258 help from @code{exceptionHandler}.
19260 @item void flush_i_cache()
19261 @findex flush_i_cache
19262 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19263 instruction cache, if any, on your target machine. If there is no
19264 instruction cache, this subroutine may be a no-op.
19266 On target machines that have instruction caches, @value{GDBN} requires this
19267 function to make certain that the state of your program is stable.
19271 You must also make sure this library routine is available:
19274 @item void *memset(void *, int, int)
19276 This is the standard library function @code{memset} that sets an area of
19277 memory to a known value. If you have one of the free versions of
19278 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19279 either obtain it from your hardware manufacturer, or write your own.
19282 If you do not use the GNU C compiler, you may need other standard
19283 library subroutines as well; this varies from one stub to another,
19284 but in general the stubs are likely to use any of the common library
19285 subroutines which @code{@value{NGCC}} generates as inline code.
19288 @node Debug Session
19289 @subsection Putting it All Together
19291 @cindex remote serial debugging summary
19292 In summary, when your program is ready to debug, you must follow these
19297 Make sure you have defined the supporting low-level routines
19298 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19300 @code{getDebugChar}, @code{putDebugChar},
19301 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19305 Insert these lines in your program's startup code, before the main
19306 procedure is called:
19313 On some machines, when a breakpoint trap is raised, the hardware
19314 automatically makes the PC point to the instruction after the
19315 breakpoint. If your machine doesn't do that, you may need to adjust
19316 @code{handle_exception} to arrange for it to return to the instruction
19317 after the breakpoint on this first invocation, so that your program
19318 doesn't keep hitting the initial breakpoint instead of making
19322 For the 680x0 stub only, you need to provide a variable called
19323 @code{exceptionHook}. Normally you just use:
19326 void (*exceptionHook)() = 0;
19330 but if before calling @code{set_debug_traps}, you set it to point to a
19331 function in your program, that function is called when
19332 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19333 error). The function indicated by @code{exceptionHook} is called with
19334 one parameter: an @code{int} which is the exception number.
19337 Compile and link together: your program, the @value{GDBN} debugging stub for
19338 your target architecture, and the supporting subroutines.
19341 Make sure you have a serial connection between your target machine and
19342 the @value{GDBN} host, and identify the serial port on the host.
19345 @c The "remote" target now provides a `load' command, so we should
19346 @c document that. FIXME.
19347 Download your program to your target machine (or get it there by
19348 whatever means the manufacturer provides), and start it.
19351 Start @value{GDBN} on the host, and connect to the target
19352 (@pxref{Connecting,,Connecting to a Remote Target}).
19356 @node Configurations
19357 @chapter Configuration-Specific Information
19359 While nearly all @value{GDBN} commands are available for all native and
19360 cross versions of the debugger, there are some exceptions. This chapter
19361 describes things that are only available in certain configurations.
19363 There are three major categories of configurations: native
19364 configurations, where the host and target are the same, embedded
19365 operating system configurations, which are usually the same for several
19366 different processor architectures, and bare embedded processors, which
19367 are quite different from each other.
19372 * Embedded Processors::
19379 This section describes details specific to particular native
19384 * BSD libkvm Interface:: Debugging BSD kernel memory images
19385 * SVR4 Process Information:: SVR4 process information
19386 * DJGPP Native:: Features specific to the DJGPP port
19387 * Cygwin Native:: Features specific to the Cygwin port
19388 * Hurd Native:: Features specific to @sc{gnu} Hurd
19389 * Darwin:: Features specific to Darwin
19395 On HP-UX systems, if you refer to a function or variable name that
19396 begins with a dollar sign, @value{GDBN} searches for a user or system
19397 name first, before it searches for a convenience variable.
19400 @node BSD libkvm Interface
19401 @subsection BSD libkvm Interface
19404 @cindex kernel memory image
19405 @cindex kernel crash dump
19407 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19408 interface that provides a uniform interface for accessing kernel virtual
19409 memory images, including live systems and crash dumps. @value{GDBN}
19410 uses this interface to allow you to debug live kernels and kernel crash
19411 dumps on many native BSD configurations. This is implemented as a
19412 special @code{kvm} debugging target. For debugging a live system, load
19413 the currently running kernel into @value{GDBN} and connect to the
19417 (@value{GDBP}) @b{target kvm}
19420 For debugging crash dumps, provide the file name of the crash dump as an
19424 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19427 Once connected to the @code{kvm} target, the following commands are
19433 Set current context from the @dfn{Process Control Block} (PCB) address.
19436 Set current context from proc address. This command isn't available on
19437 modern FreeBSD systems.
19440 @node SVR4 Process Information
19441 @subsection SVR4 Process Information
19443 @cindex examine process image
19444 @cindex process info via @file{/proc}
19446 Many versions of SVR4 and compatible systems provide a facility called
19447 @samp{/proc} that can be used to examine the image of a running
19448 process using file-system subroutines.
19450 If @value{GDBN} is configured for an operating system with this
19451 facility, the command @code{info proc} is available to report
19452 information about the process running your program, or about any
19453 process running on your system. This includes, as of this writing,
19454 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19455 not HP-UX, for example.
19457 This command may also work on core files that were created on a system
19458 that has the @samp{/proc} facility.
19464 @itemx info proc @var{process-id}
19465 Summarize available information about any running process. If a
19466 process ID is specified by @var{process-id}, display information about
19467 that process; otherwise display information about the program being
19468 debugged. The summary includes the debugged process ID, the command
19469 line used to invoke it, its current working directory, and its
19470 executable file's absolute file name.
19472 On some systems, @var{process-id} can be of the form
19473 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19474 within a process. If the optional @var{pid} part is missing, it means
19475 a thread from the process being debugged (the leading @samp{/} still
19476 needs to be present, or else @value{GDBN} will interpret the number as
19477 a process ID rather than a thread ID).
19479 @item info proc cmdline
19480 @cindex info proc cmdline
19481 Show the original command line of the process. This command is
19482 specific to @sc{gnu}/Linux.
19484 @item info proc cwd
19485 @cindex info proc cwd
19486 Show the current working directory of the process. This command is
19487 specific to @sc{gnu}/Linux.
19489 @item info proc exe
19490 @cindex info proc exe
19491 Show the name of executable of the process. This command is specific
19494 @item info proc mappings
19495 @cindex memory address space mappings
19496 Report the memory address space ranges accessible in the program, with
19497 information on whether the process has read, write, or execute access
19498 rights to each range. On @sc{gnu}/Linux systems, each memory range
19499 includes the object file which is mapped to that range, instead of the
19500 memory access rights to that range.
19502 @item info proc stat
19503 @itemx info proc status
19504 @cindex process detailed status information
19505 These subcommands are specific to @sc{gnu}/Linux systems. They show
19506 the process-related information, including the user ID and group ID;
19507 how many threads are there in the process; its virtual memory usage;
19508 the signals that are pending, blocked, and ignored; its TTY; its
19509 consumption of system and user time; its stack size; its @samp{nice}
19510 value; etc. For more information, see the @samp{proc} man page
19511 (type @kbd{man 5 proc} from your shell prompt).
19513 @item info proc all
19514 Show all the information about the process described under all of the
19515 above @code{info proc} subcommands.
19518 @comment These sub-options of 'info proc' were not included when
19519 @comment procfs.c was re-written. Keep their descriptions around
19520 @comment against the day when someone finds the time to put them back in.
19521 @kindex info proc times
19522 @item info proc times
19523 Starting time, user CPU time, and system CPU time for your program and
19526 @kindex info proc id
19528 Report on the process IDs related to your program: its own process ID,
19529 the ID of its parent, the process group ID, and the session ID.
19532 @item set procfs-trace
19533 @kindex set procfs-trace
19534 @cindex @code{procfs} API calls
19535 This command enables and disables tracing of @code{procfs} API calls.
19537 @item show procfs-trace
19538 @kindex show procfs-trace
19539 Show the current state of @code{procfs} API call tracing.
19541 @item set procfs-file @var{file}
19542 @kindex set procfs-file
19543 Tell @value{GDBN} to write @code{procfs} API trace to the named
19544 @var{file}. @value{GDBN} appends the trace info to the previous
19545 contents of the file. The default is to display the trace on the
19548 @item show procfs-file
19549 @kindex show procfs-file
19550 Show the file to which @code{procfs} API trace is written.
19552 @item proc-trace-entry
19553 @itemx proc-trace-exit
19554 @itemx proc-untrace-entry
19555 @itemx proc-untrace-exit
19556 @kindex proc-trace-entry
19557 @kindex proc-trace-exit
19558 @kindex proc-untrace-entry
19559 @kindex proc-untrace-exit
19560 These commands enable and disable tracing of entries into and exits
19561 from the @code{syscall} interface.
19564 @kindex info pidlist
19565 @cindex process list, QNX Neutrino
19566 For QNX Neutrino only, this command displays the list of all the
19567 processes and all the threads within each process.
19570 @kindex info meminfo
19571 @cindex mapinfo list, QNX Neutrino
19572 For QNX Neutrino only, this command displays the list of all mapinfos.
19576 @subsection Features for Debugging @sc{djgpp} Programs
19577 @cindex @sc{djgpp} debugging
19578 @cindex native @sc{djgpp} debugging
19579 @cindex MS-DOS-specific commands
19582 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19583 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19584 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19585 top of real-mode DOS systems and their emulations.
19587 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19588 defines a few commands specific to the @sc{djgpp} port. This
19589 subsection describes those commands.
19594 This is a prefix of @sc{djgpp}-specific commands which print
19595 information about the target system and important OS structures.
19598 @cindex MS-DOS system info
19599 @cindex free memory information (MS-DOS)
19600 @item info dos sysinfo
19601 This command displays assorted information about the underlying
19602 platform: the CPU type and features, the OS version and flavor, the
19603 DPMI version, and the available conventional and DPMI memory.
19608 @cindex segment descriptor tables
19609 @cindex descriptor tables display
19611 @itemx info dos ldt
19612 @itemx info dos idt
19613 These 3 commands display entries from, respectively, Global, Local,
19614 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19615 tables are data structures which store a descriptor for each segment
19616 that is currently in use. The segment's selector is an index into a
19617 descriptor table; the table entry for that index holds the
19618 descriptor's base address and limit, and its attributes and access
19621 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19622 segment (used for both data and the stack), and a DOS segment (which
19623 allows access to DOS/BIOS data structures and absolute addresses in
19624 conventional memory). However, the DPMI host will usually define
19625 additional segments in order to support the DPMI environment.
19627 @cindex garbled pointers
19628 These commands allow to display entries from the descriptor tables.
19629 Without an argument, all entries from the specified table are
19630 displayed. An argument, which should be an integer expression, means
19631 display a single entry whose index is given by the argument. For
19632 example, here's a convenient way to display information about the
19633 debugged program's data segment:
19636 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19637 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19641 This comes in handy when you want to see whether a pointer is outside
19642 the data segment's limit (i.e.@: @dfn{garbled}).
19644 @cindex page tables display (MS-DOS)
19646 @itemx info dos pte
19647 These two commands display entries from, respectively, the Page
19648 Directory and the Page Tables. Page Directories and Page Tables are
19649 data structures which control how virtual memory addresses are mapped
19650 into physical addresses. A Page Table includes an entry for every
19651 page of memory that is mapped into the program's address space; there
19652 may be several Page Tables, each one holding up to 4096 entries. A
19653 Page Directory has up to 4096 entries, one each for every Page Table
19654 that is currently in use.
19656 Without an argument, @kbd{info dos pde} displays the entire Page
19657 Directory, and @kbd{info dos pte} displays all the entries in all of
19658 the Page Tables. An argument, an integer expression, given to the
19659 @kbd{info dos pde} command means display only that entry from the Page
19660 Directory table. An argument given to the @kbd{info dos pte} command
19661 means display entries from a single Page Table, the one pointed to by
19662 the specified entry in the Page Directory.
19664 @cindex direct memory access (DMA) on MS-DOS
19665 These commands are useful when your program uses @dfn{DMA} (Direct
19666 Memory Access), which needs physical addresses to program the DMA
19669 These commands are supported only with some DPMI servers.
19671 @cindex physical address from linear address
19672 @item info dos address-pte @var{addr}
19673 This command displays the Page Table entry for a specified linear
19674 address. The argument @var{addr} is a linear address which should
19675 already have the appropriate segment's base address added to it,
19676 because this command accepts addresses which may belong to @emph{any}
19677 segment. For example, here's how to display the Page Table entry for
19678 the page where a variable @code{i} is stored:
19681 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19682 @exdent @code{Page Table entry for address 0x11a00d30:}
19683 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19687 This says that @code{i} is stored at offset @code{0xd30} from the page
19688 whose physical base address is @code{0x02698000}, and shows all the
19689 attributes of that page.
19691 Note that you must cast the addresses of variables to a @code{char *},
19692 since otherwise the value of @code{__djgpp_base_address}, the base
19693 address of all variables and functions in a @sc{djgpp} program, will
19694 be added using the rules of C pointer arithmetics: if @code{i} is
19695 declared an @code{int}, @value{GDBN} will add 4 times the value of
19696 @code{__djgpp_base_address} to the address of @code{i}.
19698 Here's another example, it displays the Page Table entry for the
19702 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19703 @exdent @code{Page Table entry for address 0x29110:}
19704 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19708 (The @code{+ 3} offset is because the transfer buffer's address is the
19709 3rd member of the @code{_go32_info_block} structure.) The output
19710 clearly shows that this DPMI server maps the addresses in conventional
19711 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19712 linear (@code{0x29110}) addresses are identical.
19714 This command is supported only with some DPMI servers.
19717 @cindex DOS serial data link, remote debugging
19718 In addition to native debugging, the DJGPP port supports remote
19719 debugging via a serial data link. The following commands are specific
19720 to remote serial debugging in the DJGPP port of @value{GDBN}.
19723 @kindex set com1base
19724 @kindex set com1irq
19725 @kindex set com2base
19726 @kindex set com2irq
19727 @kindex set com3base
19728 @kindex set com3irq
19729 @kindex set com4base
19730 @kindex set com4irq
19731 @item set com1base @var{addr}
19732 This command sets the base I/O port address of the @file{COM1} serial
19735 @item set com1irq @var{irq}
19736 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19737 for the @file{COM1} serial port.
19739 There are similar commands @samp{set com2base}, @samp{set com3irq},
19740 etc.@: for setting the port address and the @code{IRQ} lines for the
19743 @kindex show com1base
19744 @kindex show com1irq
19745 @kindex show com2base
19746 @kindex show com2irq
19747 @kindex show com3base
19748 @kindex show com3irq
19749 @kindex show com4base
19750 @kindex show com4irq
19751 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19752 display the current settings of the base address and the @code{IRQ}
19753 lines used by the COM ports.
19756 @kindex info serial
19757 @cindex DOS serial port status
19758 This command prints the status of the 4 DOS serial ports. For each
19759 port, it prints whether it's active or not, its I/O base address and
19760 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19761 counts of various errors encountered so far.
19765 @node Cygwin Native
19766 @subsection Features for Debugging MS Windows PE Executables
19767 @cindex MS Windows debugging
19768 @cindex native Cygwin debugging
19769 @cindex Cygwin-specific commands
19771 @value{GDBN} supports native debugging of MS Windows programs, including
19772 DLLs with and without symbolic debugging information.
19774 @cindex Ctrl-BREAK, MS-Windows
19775 @cindex interrupt debuggee on MS-Windows
19776 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19777 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19778 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19779 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19780 sequence, which can be used to interrupt the debuggee even if it
19783 There are various additional Cygwin-specific commands, described in
19784 this section. Working with DLLs that have no debugging symbols is
19785 described in @ref{Non-debug DLL Symbols}.
19790 This is a prefix of MS Windows-specific commands which print
19791 information about the target system and important OS structures.
19793 @item info w32 selector
19794 This command displays information returned by
19795 the Win32 API @code{GetThreadSelectorEntry} function.
19796 It takes an optional argument that is evaluated to
19797 a long value to give the information about this given selector.
19798 Without argument, this command displays information
19799 about the six segment registers.
19801 @item info w32 thread-information-block
19802 This command displays thread specific information stored in the
19803 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19804 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19808 This is a Cygwin-specific alias of @code{info shared}.
19810 @kindex dll-symbols
19812 This command loads symbols from a dll similarly to
19813 add-sym command but without the need to specify a base address.
19815 @kindex set cygwin-exceptions
19816 @cindex debugging the Cygwin DLL
19817 @cindex Cygwin DLL, debugging
19818 @item set cygwin-exceptions @var{mode}
19819 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19820 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19821 @value{GDBN} will delay recognition of exceptions, and may ignore some
19822 exceptions which seem to be caused by internal Cygwin DLL
19823 ``bookkeeping''. This option is meant primarily for debugging the
19824 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19825 @value{GDBN} users with false @code{SIGSEGV} signals.
19827 @kindex show cygwin-exceptions
19828 @item show cygwin-exceptions
19829 Displays whether @value{GDBN} will break on exceptions that happen
19830 inside the Cygwin DLL itself.
19832 @kindex set new-console
19833 @item set new-console @var{mode}
19834 If @var{mode} is @code{on} the debuggee will
19835 be started in a new console on next start.
19836 If @var{mode} is @code{off}, the debuggee will
19837 be started in the same console as the debugger.
19839 @kindex show new-console
19840 @item show new-console
19841 Displays whether a new console is used
19842 when the debuggee is started.
19844 @kindex set new-group
19845 @item set new-group @var{mode}
19846 This boolean value controls whether the debuggee should
19847 start a new group or stay in the same group as the debugger.
19848 This affects the way the Windows OS handles
19851 @kindex show new-group
19852 @item show new-group
19853 Displays current value of new-group boolean.
19855 @kindex set debugevents
19856 @item set debugevents
19857 This boolean value adds debug output concerning kernel events related
19858 to the debuggee seen by the debugger. This includes events that
19859 signal thread and process creation and exit, DLL loading and
19860 unloading, console interrupts, and debugging messages produced by the
19861 Windows @code{OutputDebugString} API call.
19863 @kindex set debugexec
19864 @item set debugexec
19865 This boolean value adds debug output concerning execute events
19866 (such as resume thread) seen by the debugger.
19868 @kindex set debugexceptions
19869 @item set debugexceptions
19870 This boolean value adds debug output concerning exceptions in the
19871 debuggee seen by the debugger.
19873 @kindex set debugmemory
19874 @item set debugmemory
19875 This boolean value adds debug output concerning debuggee memory reads
19876 and writes by the debugger.
19880 This boolean values specifies whether the debuggee is called
19881 via a shell or directly (default value is on).
19885 Displays if the debuggee will be started with a shell.
19890 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19893 @node Non-debug DLL Symbols
19894 @subsubsection Support for DLLs without Debugging Symbols
19895 @cindex DLLs with no debugging symbols
19896 @cindex Minimal symbols and DLLs
19898 Very often on windows, some of the DLLs that your program relies on do
19899 not include symbolic debugging information (for example,
19900 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19901 symbols in a DLL, it relies on the minimal amount of symbolic
19902 information contained in the DLL's export table. This section
19903 describes working with such symbols, known internally to @value{GDBN} as
19904 ``minimal symbols''.
19906 Note that before the debugged program has started execution, no DLLs
19907 will have been loaded. The easiest way around this problem is simply to
19908 start the program --- either by setting a breakpoint or letting the
19909 program run once to completion. It is also possible to force
19910 @value{GDBN} to load a particular DLL before starting the executable ---
19911 see the shared library information in @ref{Files}, or the
19912 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19913 explicitly loading symbols from a DLL with no debugging information will
19914 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19915 which may adversely affect symbol lookup performance.
19917 @subsubsection DLL Name Prefixes
19919 In keeping with the naming conventions used by the Microsoft debugging
19920 tools, DLL export symbols are made available with a prefix based on the
19921 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19922 also entered into the symbol table, so @code{CreateFileA} is often
19923 sufficient. In some cases there will be name clashes within a program
19924 (particularly if the executable itself includes full debugging symbols)
19925 necessitating the use of the fully qualified name when referring to the
19926 contents of the DLL. Use single-quotes around the name to avoid the
19927 exclamation mark (``!'') being interpreted as a language operator.
19929 Note that the internal name of the DLL may be all upper-case, even
19930 though the file name of the DLL is lower-case, or vice-versa. Since
19931 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19932 some confusion. If in doubt, try the @code{info functions} and
19933 @code{info variables} commands or even @code{maint print msymbols}
19934 (@pxref{Symbols}). Here's an example:
19937 (@value{GDBP}) info function CreateFileA
19938 All functions matching regular expression "CreateFileA":
19940 Non-debugging symbols:
19941 0x77e885f4 CreateFileA
19942 0x77e885f4 KERNEL32!CreateFileA
19946 (@value{GDBP}) info function !
19947 All functions matching regular expression "!":
19949 Non-debugging symbols:
19950 0x6100114c cygwin1!__assert
19951 0x61004034 cygwin1!_dll_crt0@@0
19952 0x61004240 cygwin1!dll_crt0(per_process *)
19956 @subsubsection Working with Minimal Symbols
19958 Symbols extracted from a DLL's export table do not contain very much
19959 type information. All that @value{GDBN} can do is guess whether a symbol
19960 refers to a function or variable depending on the linker section that
19961 contains the symbol. Also note that the actual contents of the memory
19962 contained in a DLL are not available unless the program is running. This
19963 means that you cannot examine the contents of a variable or disassemble
19964 a function within a DLL without a running program.
19966 Variables are generally treated as pointers and dereferenced
19967 automatically. For this reason, it is often necessary to prefix a
19968 variable name with the address-of operator (``&'') and provide explicit
19969 type information in the command. Here's an example of the type of
19973 (@value{GDBP}) print 'cygwin1!__argv'
19978 (@value{GDBP}) x 'cygwin1!__argv'
19979 0x10021610: "\230y\""
19982 And two possible solutions:
19985 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19986 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19990 (@value{GDBP}) x/2x &'cygwin1!__argv'
19991 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19992 (@value{GDBP}) x/x 0x10021608
19993 0x10021608: 0x0022fd98
19994 (@value{GDBP}) x/s 0x0022fd98
19995 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19998 Setting a break point within a DLL is possible even before the program
19999 starts execution. However, under these circumstances, @value{GDBN} can't
20000 examine the initial instructions of the function in order to skip the
20001 function's frame set-up code. You can work around this by using ``*&''
20002 to set the breakpoint at a raw memory address:
20005 (@value{GDBP}) break *&'python22!PyOS_Readline'
20006 Breakpoint 1 at 0x1e04eff0
20009 The author of these extensions is not entirely convinced that setting a
20010 break point within a shared DLL like @file{kernel32.dll} is completely
20014 @subsection Commands Specific to @sc{gnu} Hurd Systems
20015 @cindex @sc{gnu} Hurd debugging
20017 This subsection describes @value{GDBN} commands specific to the
20018 @sc{gnu} Hurd native debugging.
20023 @kindex set signals@r{, Hurd command}
20024 @kindex set sigs@r{, Hurd command}
20025 This command toggles the state of inferior signal interception by
20026 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20027 affected by this command. @code{sigs} is a shorthand alias for
20032 @kindex show signals@r{, Hurd command}
20033 @kindex show sigs@r{, Hurd command}
20034 Show the current state of intercepting inferior's signals.
20036 @item set signal-thread
20037 @itemx set sigthread
20038 @kindex set signal-thread
20039 @kindex set sigthread
20040 This command tells @value{GDBN} which thread is the @code{libc} signal
20041 thread. That thread is run when a signal is delivered to a running
20042 process. @code{set sigthread} is the shorthand alias of @code{set
20045 @item show signal-thread
20046 @itemx show sigthread
20047 @kindex show signal-thread
20048 @kindex show sigthread
20049 These two commands show which thread will run when the inferior is
20050 delivered a signal.
20053 @kindex set stopped@r{, Hurd command}
20054 This commands tells @value{GDBN} that the inferior process is stopped,
20055 as with the @code{SIGSTOP} signal. The stopped process can be
20056 continued by delivering a signal to it.
20059 @kindex show stopped@r{, Hurd command}
20060 This command shows whether @value{GDBN} thinks the debuggee is
20063 @item set exceptions
20064 @kindex set exceptions@r{, Hurd command}
20065 Use this command to turn off trapping of exceptions in the inferior.
20066 When exception trapping is off, neither breakpoints nor
20067 single-stepping will work. To restore the default, set exception
20070 @item show exceptions
20071 @kindex show exceptions@r{, Hurd command}
20072 Show the current state of trapping exceptions in the inferior.
20074 @item set task pause
20075 @kindex set task@r{, Hurd commands}
20076 @cindex task attributes (@sc{gnu} Hurd)
20077 @cindex pause current task (@sc{gnu} Hurd)
20078 This command toggles task suspension when @value{GDBN} has control.
20079 Setting it to on takes effect immediately, and the task is suspended
20080 whenever @value{GDBN} gets control. Setting it to off will take
20081 effect the next time the inferior is continued. If this option is set
20082 to off, you can use @code{set thread default pause on} or @code{set
20083 thread pause on} (see below) to pause individual threads.
20085 @item show task pause
20086 @kindex show task@r{, Hurd commands}
20087 Show the current state of task suspension.
20089 @item set task detach-suspend-count
20090 @cindex task suspend count
20091 @cindex detach from task, @sc{gnu} Hurd
20092 This command sets the suspend count the task will be left with when
20093 @value{GDBN} detaches from it.
20095 @item show task detach-suspend-count
20096 Show the suspend count the task will be left with when detaching.
20098 @item set task exception-port
20099 @itemx set task excp
20100 @cindex task exception port, @sc{gnu} Hurd
20101 This command sets the task exception port to which @value{GDBN} will
20102 forward exceptions. The argument should be the value of the @dfn{send
20103 rights} of the task. @code{set task excp} is a shorthand alias.
20105 @item set noninvasive
20106 @cindex noninvasive task options
20107 This command switches @value{GDBN} to a mode that is the least
20108 invasive as far as interfering with the inferior is concerned. This
20109 is the same as using @code{set task pause}, @code{set exceptions}, and
20110 @code{set signals} to values opposite to the defaults.
20112 @item info send-rights
20113 @itemx info receive-rights
20114 @itemx info port-rights
20115 @itemx info port-sets
20116 @itemx info dead-names
20119 @cindex send rights, @sc{gnu} Hurd
20120 @cindex receive rights, @sc{gnu} Hurd
20121 @cindex port rights, @sc{gnu} Hurd
20122 @cindex port sets, @sc{gnu} Hurd
20123 @cindex dead names, @sc{gnu} Hurd
20124 These commands display information about, respectively, send rights,
20125 receive rights, port rights, port sets, and dead names of a task.
20126 There are also shorthand aliases: @code{info ports} for @code{info
20127 port-rights} and @code{info psets} for @code{info port-sets}.
20129 @item set thread pause
20130 @kindex set thread@r{, Hurd command}
20131 @cindex thread properties, @sc{gnu} Hurd
20132 @cindex pause current thread (@sc{gnu} Hurd)
20133 This command toggles current thread suspension when @value{GDBN} has
20134 control. Setting it to on takes effect immediately, and the current
20135 thread is suspended whenever @value{GDBN} gets control. Setting it to
20136 off will take effect the next time the inferior is continued.
20137 Normally, this command has no effect, since when @value{GDBN} has
20138 control, the whole task is suspended. However, if you used @code{set
20139 task pause off} (see above), this command comes in handy to suspend
20140 only the current thread.
20142 @item show thread pause
20143 @kindex show thread@r{, Hurd command}
20144 This command shows the state of current thread suspension.
20146 @item set thread run
20147 This command sets whether the current thread is allowed to run.
20149 @item show thread run
20150 Show whether the current thread is allowed to run.
20152 @item set thread detach-suspend-count
20153 @cindex thread suspend count, @sc{gnu} Hurd
20154 @cindex detach from thread, @sc{gnu} Hurd
20155 This command sets the suspend count @value{GDBN} will leave on a
20156 thread when detaching. This number is relative to the suspend count
20157 found by @value{GDBN} when it notices the thread; use @code{set thread
20158 takeover-suspend-count} to force it to an absolute value.
20160 @item show thread detach-suspend-count
20161 Show the suspend count @value{GDBN} will leave on the thread when
20164 @item set thread exception-port
20165 @itemx set thread excp
20166 Set the thread exception port to which to forward exceptions. This
20167 overrides the port set by @code{set task exception-port} (see above).
20168 @code{set thread excp} is the shorthand alias.
20170 @item set thread takeover-suspend-count
20171 Normally, @value{GDBN}'s thread suspend counts are relative to the
20172 value @value{GDBN} finds when it notices each thread. This command
20173 changes the suspend counts to be absolute instead.
20175 @item set thread default
20176 @itemx show thread default
20177 @cindex thread default settings, @sc{gnu} Hurd
20178 Each of the above @code{set thread} commands has a @code{set thread
20179 default} counterpart (e.g., @code{set thread default pause}, @code{set
20180 thread default exception-port}, etc.). The @code{thread default}
20181 variety of commands sets the default thread properties for all
20182 threads; you can then change the properties of individual threads with
20183 the non-default commands.
20190 @value{GDBN} provides the following commands specific to the Darwin target:
20193 @item set debug darwin @var{num}
20194 @kindex set debug darwin
20195 When set to a non zero value, enables debugging messages specific to
20196 the Darwin support. Higher values produce more verbose output.
20198 @item show debug darwin
20199 @kindex show debug darwin
20200 Show the current state of Darwin messages.
20202 @item set debug mach-o @var{num}
20203 @kindex set debug mach-o
20204 When set to a non zero value, enables debugging messages while
20205 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20206 file format used on Darwin for object and executable files.) Higher
20207 values produce more verbose output. This is a command to diagnose
20208 problems internal to @value{GDBN} and should not be needed in normal
20211 @item show debug mach-o
20212 @kindex show debug mach-o
20213 Show the current state of Mach-O file messages.
20215 @item set mach-exceptions on
20216 @itemx set mach-exceptions off
20217 @kindex set mach-exceptions
20218 On Darwin, faults are first reported as a Mach exception and are then
20219 mapped to a Posix signal. Use this command to turn on trapping of
20220 Mach exceptions in the inferior. This might be sometimes useful to
20221 better understand the cause of a fault. The default is off.
20223 @item show mach-exceptions
20224 @kindex show mach-exceptions
20225 Show the current state of exceptions trapping.
20230 @section Embedded Operating Systems
20232 This section describes configurations involving the debugging of
20233 embedded operating systems that are available for several different
20237 * VxWorks:: Using @value{GDBN} with VxWorks
20240 @value{GDBN} includes the ability to debug programs running on
20241 various real-time operating systems.
20244 @subsection Using @value{GDBN} with VxWorks
20250 @kindex target vxworks
20251 @item target vxworks @var{machinename}
20252 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20253 is the target system's machine name or IP address.
20257 On VxWorks, @code{load} links @var{filename} dynamically on the
20258 current target system as well as adding its symbols in @value{GDBN}.
20260 @value{GDBN} enables developers to spawn and debug tasks running on networked
20261 VxWorks targets from a Unix host. Already-running tasks spawned from
20262 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20263 both the Unix host and on the VxWorks target. The program
20264 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20265 installed with the name @code{vxgdb}, to distinguish it from a
20266 @value{GDBN} for debugging programs on the host itself.)
20269 @item VxWorks-timeout @var{args}
20270 @kindex vxworks-timeout
20271 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20272 This option is set by the user, and @var{args} represents the number of
20273 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20274 your VxWorks target is a slow software simulator or is on the far side
20275 of a thin network line.
20278 The following information on connecting to VxWorks was current when
20279 this manual was produced; newer releases of VxWorks may use revised
20282 @findex INCLUDE_RDB
20283 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20284 to include the remote debugging interface routines in the VxWorks
20285 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20286 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20287 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20288 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20289 information on configuring and remaking VxWorks, see the manufacturer's
20291 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20293 Once you have included @file{rdb.a} in your VxWorks system image and set
20294 your Unix execution search path to find @value{GDBN}, you are ready to
20295 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20296 @code{vxgdb}, depending on your installation).
20298 @value{GDBN} comes up showing the prompt:
20305 * VxWorks Connection:: Connecting to VxWorks
20306 * VxWorks Download:: VxWorks download
20307 * VxWorks Attach:: Running tasks
20310 @node VxWorks Connection
20311 @subsubsection Connecting to VxWorks
20313 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20314 network. To connect to a target whose host name is ``@code{tt}'', type:
20317 (vxgdb) target vxworks tt
20321 @value{GDBN} displays messages like these:
20324 Attaching remote machine across net...
20329 @value{GDBN} then attempts to read the symbol tables of any object modules
20330 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20331 these files by searching the directories listed in the command search
20332 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20333 to find an object file, it displays a message such as:
20336 prog.o: No such file or directory.
20339 When this happens, add the appropriate directory to the search path with
20340 the @value{GDBN} command @code{path}, and execute the @code{target}
20343 @node VxWorks Download
20344 @subsubsection VxWorks Download
20346 @cindex download to VxWorks
20347 If you have connected to the VxWorks target and you want to debug an
20348 object that has not yet been loaded, you can use the @value{GDBN}
20349 @code{load} command to download a file from Unix to VxWorks
20350 incrementally. The object file given as an argument to the @code{load}
20351 command is actually opened twice: first by the VxWorks target in order
20352 to download the code, then by @value{GDBN} in order to read the symbol
20353 table. This can lead to problems if the current working directories on
20354 the two systems differ. If both systems have NFS mounted the same
20355 filesystems, you can avoid these problems by using absolute paths.
20356 Otherwise, it is simplest to set the working directory on both systems
20357 to the directory in which the object file resides, and then to reference
20358 the file by its name, without any path. For instance, a program
20359 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20360 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20361 program, type this on VxWorks:
20364 -> cd "@var{vxpath}/vw/demo/rdb"
20368 Then, in @value{GDBN}, type:
20371 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20372 (vxgdb) load prog.o
20375 @value{GDBN} displays a response similar to this:
20378 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20381 You can also use the @code{load} command to reload an object module
20382 after editing and recompiling the corresponding source file. Note that
20383 this makes @value{GDBN} delete all currently-defined breakpoints,
20384 auto-displays, and convenience variables, and to clear the value
20385 history. (This is necessary in order to preserve the integrity of
20386 debugger's data structures that reference the target system's symbol
20389 @node VxWorks Attach
20390 @subsubsection Running Tasks
20392 @cindex running VxWorks tasks
20393 You can also attach to an existing task using the @code{attach} command as
20397 (vxgdb) attach @var{task}
20401 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20402 or suspended when you attach to it. Running tasks are suspended at
20403 the time of attachment.
20405 @node Embedded Processors
20406 @section Embedded Processors
20408 This section goes into details specific to particular embedded
20411 @cindex send command to simulator
20412 Whenever a specific embedded processor has a simulator, @value{GDBN}
20413 allows to send an arbitrary command to the simulator.
20416 @item sim @var{command}
20417 @kindex sim@r{, a command}
20418 Send an arbitrary @var{command} string to the simulator. Consult the
20419 documentation for the specific simulator in use for information about
20420 acceptable commands.
20426 * M32R/D:: Renesas M32R/D
20427 * M68K:: Motorola M68K
20428 * MicroBlaze:: Xilinx MicroBlaze
20429 * MIPS Embedded:: MIPS Embedded
20430 * PowerPC Embedded:: PowerPC Embedded
20431 * PA:: HP PA Embedded
20432 * Sparclet:: Tsqware Sparclet
20433 * Sparclite:: Fujitsu Sparclite
20434 * Z8000:: Zilog Z8000
20437 * Super-H:: Renesas Super-H
20446 @item target rdi @var{dev}
20447 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20448 use this target to communicate with both boards running the Angel
20449 monitor, or with the EmbeddedICE JTAG debug device.
20452 @item target rdp @var{dev}
20457 @value{GDBN} provides the following ARM-specific commands:
20460 @item set arm disassembler
20462 This commands selects from a list of disassembly styles. The
20463 @code{"std"} style is the standard style.
20465 @item show arm disassembler
20467 Show the current disassembly style.
20469 @item set arm apcs32
20470 @cindex ARM 32-bit mode
20471 This command toggles ARM operation mode between 32-bit and 26-bit.
20473 @item show arm apcs32
20474 Display the current usage of the ARM 32-bit mode.
20476 @item set arm fpu @var{fputype}
20477 This command sets the ARM floating-point unit (FPU) type. The
20478 argument @var{fputype} can be one of these:
20482 Determine the FPU type by querying the OS ABI.
20484 Software FPU, with mixed-endian doubles on little-endian ARM
20487 GCC-compiled FPA co-processor.
20489 Software FPU with pure-endian doubles.
20495 Show the current type of the FPU.
20498 This command forces @value{GDBN} to use the specified ABI.
20501 Show the currently used ABI.
20503 @item set arm fallback-mode (arm|thumb|auto)
20504 @value{GDBN} uses the symbol table, when available, to determine
20505 whether instructions are ARM or Thumb. This command controls
20506 @value{GDBN}'s default behavior when the symbol table is not
20507 available. The default is @samp{auto}, which causes @value{GDBN} to
20508 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20511 @item show arm fallback-mode
20512 Show the current fallback instruction mode.
20514 @item set arm force-mode (arm|thumb|auto)
20515 This command overrides use of the symbol table to determine whether
20516 instructions are ARM or Thumb. The default is @samp{auto}, which
20517 causes @value{GDBN} to use the symbol table and then the setting
20518 of @samp{set arm fallback-mode}.
20520 @item show arm force-mode
20521 Show the current forced instruction mode.
20523 @item set debug arm
20524 Toggle whether to display ARM-specific debugging messages from the ARM
20525 target support subsystem.
20527 @item show debug arm
20528 Show whether ARM-specific debugging messages are enabled.
20531 The following commands are available when an ARM target is debugged
20532 using the RDI interface:
20535 @item rdilogfile @r{[}@var{file}@r{]}
20537 @cindex ADP (Angel Debugger Protocol) logging
20538 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20539 With an argument, sets the log file to the specified @var{file}. With
20540 no argument, show the current log file name. The default log file is
20543 @item rdilogenable @r{[}@var{arg}@r{]}
20544 @kindex rdilogenable
20545 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20546 enables logging, with an argument 0 or @code{"no"} disables it. With
20547 no arguments displays the current setting. When logging is enabled,
20548 ADP packets exchanged between @value{GDBN} and the RDI target device
20549 are logged to a file.
20551 @item set rdiromatzero
20552 @kindex set rdiromatzero
20553 @cindex ROM at zero address, RDI
20554 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20555 vector catching is disabled, so that zero address can be used. If off
20556 (the default), vector catching is enabled. For this command to take
20557 effect, it needs to be invoked prior to the @code{target rdi} command.
20559 @item show rdiromatzero
20560 @kindex show rdiromatzero
20561 Show the current setting of ROM at zero address.
20563 @item set rdiheartbeat
20564 @kindex set rdiheartbeat
20565 @cindex RDI heartbeat
20566 Enable or disable RDI heartbeat packets. It is not recommended to
20567 turn on this option, since it confuses ARM and EPI JTAG interface, as
20568 well as the Angel monitor.
20570 @item show rdiheartbeat
20571 @kindex show rdiheartbeat
20572 Show the setting of RDI heartbeat packets.
20576 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20577 The @value{GDBN} ARM simulator accepts the following optional arguments.
20580 @item --swi-support=@var{type}
20581 Tell the simulator which SWI interfaces to support.
20582 @var{type} may be a comma separated list of the following values.
20583 The default value is @code{all}.
20596 @subsection Renesas M32R/D and M32R/SDI
20599 @kindex target m32r
20600 @item target m32r @var{dev}
20601 Renesas M32R/D ROM monitor.
20603 @kindex target m32rsdi
20604 @item target m32rsdi @var{dev}
20605 Renesas M32R SDI server, connected via parallel port to the board.
20608 The following @value{GDBN} commands are specific to the M32R monitor:
20611 @item set download-path @var{path}
20612 @kindex set download-path
20613 @cindex find downloadable @sc{srec} files (M32R)
20614 Set the default path for finding downloadable @sc{srec} files.
20616 @item show download-path
20617 @kindex show download-path
20618 Show the default path for downloadable @sc{srec} files.
20620 @item set board-address @var{addr}
20621 @kindex set board-address
20622 @cindex M32-EVA target board address
20623 Set the IP address for the M32R-EVA target board.
20625 @item show board-address
20626 @kindex show board-address
20627 Show the current IP address of the target board.
20629 @item set server-address @var{addr}
20630 @kindex set server-address
20631 @cindex download server address (M32R)
20632 Set the IP address for the download server, which is the @value{GDBN}'s
20635 @item show server-address
20636 @kindex show server-address
20637 Display the IP address of the download server.
20639 @item upload @r{[}@var{file}@r{]}
20640 @kindex upload@r{, M32R}
20641 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20642 upload capability. If no @var{file} argument is given, the current
20643 executable file is uploaded.
20645 @item tload @r{[}@var{file}@r{]}
20646 @kindex tload@r{, M32R}
20647 Test the @code{upload} command.
20650 The following commands are available for M32R/SDI:
20655 @cindex reset SDI connection, M32R
20656 This command resets the SDI connection.
20660 This command shows the SDI connection status.
20663 @kindex debug_chaos
20664 @cindex M32R/Chaos debugging
20665 Instructs the remote that M32R/Chaos debugging is to be used.
20667 @item use_debug_dma
20668 @kindex use_debug_dma
20669 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20672 @kindex use_mon_code
20673 Instructs the remote to use the MON_CODE method of accessing memory.
20676 @kindex use_ib_break
20677 Instructs the remote to set breakpoints by IB break.
20679 @item use_dbt_break
20680 @kindex use_dbt_break
20681 Instructs the remote to set breakpoints by DBT.
20687 The Motorola m68k configuration includes ColdFire support, and a
20688 target command for the following ROM monitor.
20692 @kindex target dbug
20693 @item target dbug @var{dev}
20694 dBUG ROM monitor for Motorola ColdFire.
20699 @subsection MicroBlaze
20700 @cindex Xilinx MicroBlaze
20701 @cindex XMD, Xilinx Microprocessor Debugger
20703 The MicroBlaze is a soft-core processor supported on various Xilinx
20704 FPGAs, such as Spartan or Virtex series. Boards with these processors
20705 usually have JTAG ports which connect to a host system running the Xilinx
20706 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20707 This host system is used to download the configuration bitstream to
20708 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20709 communicates with the target board using the JTAG interface and
20710 presents a @code{gdbserver} interface to the board. By default
20711 @code{xmd} uses port @code{1234}. (While it is possible to change
20712 this default port, it requires the use of undocumented @code{xmd}
20713 commands. Contact Xilinx support if you need to do this.)
20715 Use these GDB commands to connect to the MicroBlaze target processor.
20718 @item target remote :1234
20719 Use this command to connect to the target if you are running @value{GDBN}
20720 on the same system as @code{xmd}.
20722 @item target remote @var{xmd-host}:1234
20723 Use this command to connect to the target if it is connected to @code{xmd}
20724 running on a different system named @var{xmd-host}.
20727 Use this command to download a program to the MicroBlaze target.
20729 @item set debug microblaze @var{n}
20730 Enable MicroBlaze-specific debugging messages if non-zero.
20732 @item show debug microblaze @var{n}
20733 Show MicroBlaze-specific debugging level.
20736 @node MIPS Embedded
20737 @subsection @acronym{MIPS} Embedded
20739 @cindex @acronym{MIPS} boards
20740 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20741 @acronym{MIPS} board attached to a serial line. This is available when
20742 you configure @value{GDBN} with @samp{--target=mips-elf}.
20745 Use these @value{GDBN} commands to specify the connection to your target board:
20748 @item target mips @var{port}
20749 @kindex target mips @var{port}
20750 To run a program on the board, start up @code{@value{GDBP}} with the
20751 name of your program as the argument. To connect to the board, use the
20752 command @samp{target mips @var{port}}, where @var{port} is the name of
20753 the serial port connected to the board. If the program has not already
20754 been downloaded to the board, you may use the @code{load} command to
20755 download it. You can then use all the usual @value{GDBN} commands.
20757 For example, this sequence connects to the target board through a serial
20758 port, and loads and runs a program called @var{prog} through the
20762 host$ @value{GDBP} @var{prog}
20763 @value{GDBN} is free software and @dots{}
20764 (@value{GDBP}) target mips /dev/ttyb
20765 (@value{GDBP}) load @var{prog}
20769 @item target mips @var{hostname}:@var{portnumber}
20770 On some @value{GDBN} host configurations, you can specify a TCP
20771 connection (for instance, to a serial line managed by a terminal
20772 concentrator) instead of a serial port, using the syntax
20773 @samp{@var{hostname}:@var{portnumber}}.
20775 @item target pmon @var{port}
20776 @kindex target pmon @var{port}
20779 @item target ddb @var{port}
20780 @kindex target ddb @var{port}
20781 NEC's DDB variant of PMON for Vr4300.
20783 @item target lsi @var{port}
20784 @kindex target lsi @var{port}
20785 LSI variant of PMON.
20787 @kindex target r3900
20788 @item target r3900 @var{dev}
20789 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20791 @kindex target array
20792 @item target array @var{dev}
20793 Array Tech LSI33K RAID controller board.
20799 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20802 @item set mipsfpu double
20803 @itemx set mipsfpu single
20804 @itemx set mipsfpu none
20805 @itemx set mipsfpu auto
20806 @itemx show mipsfpu
20807 @kindex set mipsfpu
20808 @kindex show mipsfpu
20809 @cindex @acronym{MIPS} remote floating point
20810 @cindex floating point, @acronym{MIPS} remote
20811 If your target board does not support the @acronym{MIPS} floating point
20812 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20813 need this, you may wish to put the command in your @value{GDBN} init
20814 file). This tells @value{GDBN} how to find the return value of
20815 functions which return floating point values. It also allows
20816 @value{GDBN} to avoid saving the floating point registers when calling
20817 functions on the board. If you are using a floating point coprocessor
20818 with only single precision floating point support, as on the @sc{r4650}
20819 processor, use the command @samp{set mipsfpu single}. The default
20820 double precision floating point coprocessor may be selected using
20821 @samp{set mipsfpu double}.
20823 In previous versions the only choices were double precision or no
20824 floating point, so @samp{set mipsfpu on} will select double precision
20825 and @samp{set mipsfpu off} will select no floating point.
20827 As usual, you can inquire about the @code{mipsfpu} variable with
20828 @samp{show mipsfpu}.
20830 @item set timeout @var{seconds}
20831 @itemx set retransmit-timeout @var{seconds}
20832 @itemx show timeout
20833 @itemx show retransmit-timeout
20834 @cindex @code{timeout}, @acronym{MIPS} protocol
20835 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20836 @kindex set timeout
20837 @kindex show timeout
20838 @kindex set retransmit-timeout
20839 @kindex show retransmit-timeout
20840 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20841 remote protocol, with the @code{set timeout @var{seconds}} command. The
20842 default is 5 seconds. Similarly, you can control the timeout used while
20843 waiting for an acknowledgment of a packet with the @code{set
20844 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20845 You can inspect both values with @code{show timeout} and @code{show
20846 retransmit-timeout}. (These commands are @emph{only} available when
20847 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20849 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20850 is waiting for your program to stop. In that case, @value{GDBN} waits
20851 forever because it has no way of knowing how long the program is going
20852 to run before stopping.
20854 @item set syn-garbage-limit @var{num}
20855 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20856 @cindex synchronize with remote @acronym{MIPS} target
20857 Limit the maximum number of characters @value{GDBN} should ignore when
20858 it tries to synchronize with the remote target. The default is 10
20859 characters. Setting the limit to -1 means there's no limit.
20861 @item show syn-garbage-limit
20862 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20863 Show the current limit on the number of characters to ignore when
20864 trying to synchronize with the remote system.
20866 @item set monitor-prompt @var{prompt}
20867 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20868 @cindex remote monitor prompt
20869 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20870 remote monitor. The default depends on the target:
20880 @item show monitor-prompt
20881 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20882 Show the current strings @value{GDBN} expects as the prompt from the
20885 @item set monitor-warnings
20886 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20887 Enable or disable monitor warnings about hardware breakpoints. This
20888 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20889 display warning messages whose codes are returned by the @code{lsi}
20890 PMON monitor for breakpoint commands.
20892 @item show monitor-warnings
20893 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20894 Show the current setting of printing monitor warnings.
20896 @item pmon @var{command}
20897 @kindex pmon@r{, @acronym{MIPS} remote}
20898 @cindex send PMON command
20899 This command allows sending an arbitrary @var{command} string to the
20900 monitor. The monitor must be in debug mode for this to work.
20903 @node PowerPC Embedded
20904 @subsection PowerPC Embedded
20906 @cindex DVC register
20907 @value{GDBN} supports using the DVC (Data Value Compare) register to
20908 implement in hardware simple hardware watchpoint conditions of the form:
20911 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20912 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20915 The DVC register will be automatically used when @value{GDBN} detects
20916 such pattern in a condition expression, and the created watchpoint uses one
20917 debug register (either the @code{exact-watchpoints} option is on and the
20918 variable is scalar, or the variable has a length of one byte). This feature
20919 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20922 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20923 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20924 in which case watchpoints using only one debug register are created when
20925 watching variables of scalar types.
20927 You can create an artificial array to watch an arbitrary memory
20928 region using one of the following commands (@pxref{Expressions}):
20931 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20932 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20935 PowerPC embedded processors support masked watchpoints. See the discussion
20936 about the @code{mask} argument in @ref{Set Watchpoints}.
20938 @cindex ranged breakpoint
20939 PowerPC embedded processors support hardware accelerated
20940 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20941 the inferior whenever it executes an instruction at any address within
20942 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20943 use the @code{break-range} command.
20945 @value{GDBN} provides the following PowerPC-specific commands:
20948 @kindex break-range
20949 @item break-range @var{start-location}, @var{end-location}
20950 Set a breakpoint for an address range.
20951 @var{start-location} and @var{end-location} can specify a function name,
20952 a line number, an offset of lines from the current line or from the start
20953 location, or an address of an instruction (see @ref{Specify Location},
20954 for a list of all the possible ways to specify a @var{location}.)
20955 The breakpoint will stop execution of the inferior whenever it
20956 executes an instruction at any address within the specified range,
20957 (including @var{start-location} and @var{end-location}.)
20959 @kindex set powerpc
20960 @item set powerpc soft-float
20961 @itemx show powerpc soft-float
20962 Force @value{GDBN} to use (or not use) a software floating point calling
20963 convention. By default, @value{GDBN} selects the calling convention based
20964 on the selected architecture and the provided executable file.
20966 @item set powerpc vector-abi
20967 @itemx show powerpc vector-abi
20968 Force @value{GDBN} to use the specified calling convention for vector
20969 arguments and return values. The valid options are @samp{auto};
20970 @samp{generic}, to avoid vector registers even if they are present;
20971 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20972 registers. By default, @value{GDBN} selects the calling convention
20973 based on the selected architecture and the provided executable file.
20975 @item set powerpc exact-watchpoints
20976 @itemx show powerpc exact-watchpoints
20977 Allow @value{GDBN} to use only one debug register when watching a variable
20978 of scalar type, thus assuming that the variable is accessed through the
20979 address of its first byte.
20981 @kindex target dink32
20982 @item target dink32 @var{dev}
20983 DINK32 ROM monitor.
20985 @kindex target ppcbug
20986 @item target ppcbug @var{dev}
20987 @kindex target ppcbug1
20988 @item target ppcbug1 @var{dev}
20989 PPCBUG ROM monitor for PowerPC.
20992 @item target sds @var{dev}
20993 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20996 @cindex SDS protocol
20997 The following commands specific to the SDS protocol are supported
21001 @item set sdstimeout @var{nsec}
21002 @kindex set sdstimeout
21003 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21004 default is 2 seconds.
21006 @item show sdstimeout
21007 @kindex show sdstimeout
21008 Show the current value of the SDS timeout.
21010 @item sds @var{command}
21011 @kindex sds@r{, a command}
21012 Send the specified @var{command} string to the SDS monitor.
21017 @subsection HP PA Embedded
21021 @kindex target op50n
21022 @item target op50n @var{dev}
21023 OP50N monitor, running on an OKI HPPA board.
21025 @kindex target w89k
21026 @item target w89k @var{dev}
21027 W89K monitor, running on a Winbond HPPA board.
21032 @subsection Tsqware Sparclet
21036 @value{GDBN} enables developers to debug tasks running on
21037 Sparclet targets from a Unix host.
21038 @value{GDBN} uses code that runs on
21039 both the Unix host and on the Sparclet target. The program
21040 @code{@value{GDBP}} is installed and executed on the Unix host.
21043 @item remotetimeout @var{args}
21044 @kindex remotetimeout
21045 @value{GDBN} supports the option @code{remotetimeout}.
21046 This option is set by the user, and @var{args} represents the number of
21047 seconds @value{GDBN} waits for responses.
21050 @cindex compiling, on Sparclet
21051 When compiling for debugging, include the options @samp{-g} to get debug
21052 information and @samp{-Ttext} to relocate the program to where you wish to
21053 load it on the target. You may also want to add the options @samp{-n} or
21054 @samp{-N} in order to reduce the size of the sections. Example:
21057 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21060 You can use @code{objdump} to verify that the addresses are what you intended:
21063 sparclet-aout-objdump --headers --syms prog
21066 @cindex running, on Sparclet
21068 your Unix execution search path to find @value{GDBN}, you are ready to
21069 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21070 (or @code{sparclet-aout-gdb}, depending on your installation).
21072 @value{GDBN} comes up showing the prompt:
21079 * Sparclet File:: Setting the file to debug
21080 * Sparclet Connection:: Connecting to Sparclet
21081 * Sparclet Download:: Sparclet download
21082 * Sparclet Execution:: Running and debugging
21085 @node Sparclet File
21086 @subsubsection Setting File to Debug
21088 The @value{GDBN} command @code{file} lets you choose with program to debug.
21091 (gdbslet) file prog
21095 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21096 @value{GDBN} locates
21097 the file by searching the directories listed in the command search
21099 If the file was compiled with debug information (option @samp{-g}), source
21100 files will be searched as well.
21101 @value{GDBN} locates
21102 the source files by searching the directories listed in the directory search
21103 path (@pxref{Environment, ,Your Program's Environment}).
21105 to find a file, it displays a message such as:
21108 prog: No such file or directory.
21111 When this happens, add the appropriate directories to the search paths with
21112 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21113 @code{target} command again.
21115 @node Sparclet Connection
21116 @subsubsection Connecting to Sparclet
21118 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21119 To connect to a target on serial port ``@code{ttya}'', type:
21122 (gdbslet) target sparclet /dev/ttya
21123 Remote target sparclet connected to /dev/ttya
21124 main () at ../prog.c:3
21128 @value{GDBN} displays messages like these:
21134 @node Sparclet Download
21135 @subsubsection Sparclet Download
21137 @cindex download to Sparclet
21138 Once connected to the Sparclet target,
21139 you can use the @value{GDBN}
21140 @code{load} command to download the file from the host to the target.
21141 The file name and load offset should be given as arguments to the @code{load}
21143 Since the file format is aout, the program must be loaded to the starting
21144 address. You can use @code{objdump} to find out what this value is. The load
21145 offset is an offset which is added to the VMA (virtual memory address)
21146 of each of the file's sections.
21147 For instance, if the program
21148 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21149 and bss at 0x12010170, in @value{GDBN}, type:
21152 (gdbslet) load prog 0x12010000
21153 Loading section .text, size 0xdb0 vma 0x12010000
21156 If the code is loaded at a different address then what the program was linked
21157 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21158 to tell @value{GDBN} where to map the symbol table.
21160 @node Sparclet Execution
21161 @subsubsection Running and Debugging
21163 @cindex running and debugging Sparclet programs
21164 You can now begin debugging the task using @value{GDBN}'s execution control
21165 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21166 manual for the list of commands.
21170 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21172 Starting program: prog
21173 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21174 3 char *symarg = 0;
21176 4 char *execarg = "hello!";
21181 @subsection Fujitsu Sparclite
21185 @kindex target sparclite
21186 @item target sparclite @var{dev}
21187 Fujitsu sparclite boards, used only for the purpose of loading.
21188 You must use an additional command to debug the program.
21189 For example: target remote @var{dev} using @value{GDBN} standard
21195 @subsection Zilog Z8000
21198 @cindex simulator, Z8000
21199 @cindex Zilog Z8000 simulator
21201 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21204 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21205 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21206 segmented variant). The simulator recognizes which architecture is
21207 appropriate by inspecting the object code.
21210 @item target sim @var{args}
21212 @kindex target sim@r{, with Z8000}
21213 Debug programs on a simulated CPU. If the simulator supports setup
21214 options, specify them via @var{args}.
21218 After specifying this target, you can debug programs for the simulated
21219 CPU in the same style as programs for your host computer; use the
21220 @code{file} command to load a new program image, the @code{run} command
21221 to run your program, and so on.
21223 As well as making available all the usual machine registers
21224 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21225 additional items of information as specially named registers:
21230 Counts clock-ticks in the simulator.
21233 Counts instructions run in the simulator.
21236 Execution time in 60ths of a second.
21240 You can refer to these values in @value{GDBN} expressions with the usual
21241 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21242 conditional breakpoint that suspends only after at least 5000
21243 simulated clock ticks.
21246 @subsection Atmel AVR
21249 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21250 following AVR-specific commands:
21253 @item info io_registers
21254 @kindex info io_registers@r{, AVR}
21255 @cindex I/O registers (Atmel AVR)
21256 This command displays information about the AVR I/O registers. For
21257 each register, @value{GDBN} prints its number and value.
21264 When configured for debugging CRIS, @value{GDBN} provides the
21265 following CRIS-specific commands:
21268 @item set cris-version @var{ver}
21269 @cindex CRIS version
21270 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21271 The CRIS version affects register names and sizes. This command is useful in
21272 case autodetection of the CRIS version fails.
21274 @item show cris-version
21275 Show the current CRIS version.
21277 @item set cris-dwarf2-cfi
21278 @cindex DWARF-2 CFI and CRIS
21279 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21280 Change to @samp{off} when using @code{gcc-cris} whose version is below
21283 @item show cris-dwarf2-cfi
21284 Show the current state of using DWARF-2 CFI.
21286 @item set cris-mode @var{mode}
21288 Set the current CRIS mode to @var{mode}. It should only be changed when
21289 debugging in guru mode, in which case it should be set to
21290 @samp{guru} (the default is @samp{normal}).
21292 @item show cris-mode
21293 Show the current CRIS mode.
21297 @subsection Renesas Super-H
21300 For the Renesas Super-H processor, @value{GDBN} provides these
21304 @item set sh calling-convention @var{convention}
21305 @kindex set sh calling-convention
21306 Set the calling-convention used when calling functions from @value{GDBN}.
21307 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21308 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21309 convention. If the DWARF-2 information of the called function specifies
21310 that the function follows the Renesas calling convention, the function
21311 is called using the Renesas calling convention. If the calling convention
21312 is set to @samp{renesas}, the Renesas calling convention is always used,
21313 regardless of the DWARF-2 information. This can be used to override the
21314 default of @samp{gcc} if debug information is missing, or the compiler
21315 does not emit the DWARF-2 calling convention entry for a function.
21317 @item show sh calling-convention
21318 @kindex show sh calling-convention
21319 Show the current calling convention setting.
21324 @node Architectures
21325 @section Architectures
21327 This section describes characteristics of architectures that affect
21328 all uses of @value{GDBN} with the architecture, both native and cross.
21335 * HPPA:: HP PA architecture
21336 * SPU:: Cell Broadband Engine SPU architecture
21342 @subsection AArch64
21343 @cindex AArch64 support
21345 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21346 following special commands:
21349 @item set debug aarch64
21350 @kindex set debug aarch64
21351 This command determines whether AArch64 architecture-specific debugging
21352 messages are to be displayed.
21354 @item show debug aarch64
21355 Show whether AArch64 debugging messages are displayed.
21360 @subsection x86 Architecture-specific Issues
21363 @item set struct-convention @var{mode}
21364 @kindex set struct-convention
21365 @cindex struct return convention
21366 @cindex struct/union returned in registers
21367 Set the convention used by the inferior to return @code{struct}s and
21368 @code{union}s from functions to @var{mode}. Possible values of
21369 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21370 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21371 are returned on the stack, while @code{"reg"} means that a
21372 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21373 be returned in a register.
21375 @item show struct-convention
21376 @kindex show struct-convention
21377 Show the current setting of the convention to return @code{struct}s
21384 See the following section.
21387 @subsection @acronym{MIPS}
21389 @cindex stack on Alpha
21390 @cindex stack on @acronym{MIPS}
21391 @cindex Alpha stack
21392 @cindex @acronym{MIPS} stack
21393 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21394 sometimes requires @value{GDBN} to search backward in the object code to
21395 find the beginning of a function.
21397 @cindex response time, @acronym{MIPS} debugging
21398 To improve response time (especially for embedded applications, where
21399 @value{GDBN} may be restricted to a slow serial line for this search)
21400 you may want to limit the size of this search, using one of these
21404 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21405 @item set heuristic-fence-post @var{limit}
21406 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21407 search for the beginning of a function. A value of @var{0} (the
21408 default) means there is no limit. However, except for @var{0}, the
21409 larger the limit the more bytes @code{heuristic-fence-post} must search
21410 and therefore the longer it takes to run. You should only need to use
21411 this command when debugging a stripped executable.
21413 @item show heuristic-fence-post
21414 Display the current limit.
21418 These commands are available @emph{only} when @value{GDBN} is configured
21419 for debugging programs on Alpha or @acronym{MIPS} processors.
21421 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21425 @item set mips abi @var{arg}
21426 @kindex set mips abi
21427 @cindex set ABI for @acronym{MIPS}
21428 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21429 values of @var{arg} are:
21433 The default ABI associated with the current binary (this is the
21443 @item show mips abi
21444 @kindex show mips abi
21445 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21447 @item set mips compression @var{arg}
21448 @kindex set mips compression
21449 @cindex code compression, @acronym{MIPS}
21450 Tell @value{GDBN} which @acronym{MIPS} compressed
21451 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21452 inferior. @value{GDBN} uses this for code disassembly and other
21453 internal interpretation purposes. This setting is only referred to
21454 when no executable has been associated with the debugging session or
21455 the executable does not provide information about the encoding it uses.
21456 Otherwise this setting is automatically updated from information
21457 provided by the executable.
21459 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21460 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21461 executables containing @acronym{MIPS16} code frequently are not
21462 identified as such.
21464 This setting is ``sticky''; that is, it retains its value across
21465 debugging sessions until reset either explicitly with this command or
21466 implicitly from an executable.
21468 The compiler and/or assembler typically add symbol table annotations to
21469 identify functions compiled for the @acronym{MIPS16} or
21470 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21471 are present, @value{GDBN} uses them in preference to the global
21472 compressed @acronym{ISA} encoding setting.
21474 @item show mips compression
21475 @kindex show mips compression
21476 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21477 @value{GDBN} to debug the inferior.
21480 @itemx show mipsfpu
21481 @xref{MIPS Embedded, set mipsfpu}.
21483 @item set mips mask-address @var{arg}
21484 @kindex set mips mask-address
21485 @cindex @acronym{MIPS} addresses, masking
21486 This command determines whether the most-significant 32 bits of 64-bit
21487 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21488 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21489 setting, which lets @value{GDBN} determine the correct value.
21491 @item show mips mask-address
21492 @kindex show mips mask-address
21493 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21496 @item set remote-mips64-transfers-32bit-regs
21497 @kindex set remote-mips64-transfers-32bit-regs
21498 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21499 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21500 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21501 and 64 bits for other registers, set this option to @samp{on}.
21503 @item show remote-mips64-transfers-32bit-regs
21504 @kindex show remote-mips64-transfers-32bit-regs
21505 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21507 @item set debug mips
21508 @kindex set debug mips
21509 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21510 target code in @value{GDBN}.
21512 @item show debug mips
21513 @kindex show debug mips
21514 Show the current setting of @acronym{MIPS} debugging messages.
21520 @cindex HPPA support
21522 When @value{GDBN} is debugging the HP PA architecture, it provides the
21523 following special commands:
21526 @item set debug hppa
21527 @kindex set debug hppa
21528 This command determines whether HPPA architecture-specific debugging
21529 messages are to be displayed.
21531 @item show debug hppa
21532 Show whether HPPA debugging messages are displayed.
21534 @item maint print unwind @var{address}
21535 @kindex maint print unwind@r{, HPPA}
21536 This command displays the contents of the unwind table entry at the
21537 given @var{address}.
21543 @subsection Cell Broadband Engine SPU architecture
21544 @cindex Cell Broadband Engine
21547 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21548 it provides the following special commands:
21551 @item info spu event
21553 Display SPU event facility status. Shows current event mask
21554 and pending event status.
21556 @item info spu signal
21557 Display SPU signal notification facility status. Shows pending
21558 signal-control word and signal notification mode of both signal
21559 notification channels.
21561 @item info spu mailbox
21562 Display SPU mailbox facility status. Shows all pending entries,
21563 in order of processing, in each of the SPU Write Outbound,
21564 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21567 Display MFC DMA status. Shows all pending commands in the MFC
21568 DMA queue. For each entry, opcode, tag, class IDs, effective
21569 and local store addresses and transfer size are shown.
21571 @item info spu proxydma
21572 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21573 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21574 and local store addresses and transfer size are shown.
21578 When @value{GDBN} is debugging a combined PowerPC/SPU application
21579 on the Cell Broadband Engine, it provides in addition the following
21583 @item set spu stop-on-load @var{arg}
21585 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21586 will give control to the user when a new SPE thread enters its @code{main}
21587 function. The default is @code{off}.
21589 @item show spu stop-on-load
21591 Show whether to stop for new SPE threads.
21593 @item set spu auto-flush-cache @var{arg}
21594 Set whether to automatically flush the software-managed cache. When set to
21595 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21596 cache to be flushed whenever SPE execution stops. This provides a consistent
21597 view of PowerPC memory that is accessed via the cache. If an application
21598 does not use the software-managed cache, this option has no effect.
21600 @item show spu auto-flush-cache
21601 Show whether to automatically flush the software-managed cache.
21606 @subsection PowerPC
21607 @cindex PowerPC architecture
21609 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21610 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21611 numbers stored in the floating point registers. These values must be stored
21612 in two consecutive registers, always starting at an even register like
21613 @code{f0} or @code{f2}.
21615 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21616 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21617 @code{f2} and @code{f3} for @code{$dl1} and so on.
21619 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21620 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21623 @subsection Nios II
21624 @cindex Nios II architecture
21626 When @value{GDBN} is debugging the Nios II architecture,
21627 it provides the following special commands:
21631 @item set debug nios2
21632 @kindex set debug nios2
21633 This command turns on and off debugging messages for the Nios II
21634 target code in @value{GDBN}.
21636 @item show debug nios2
21637 @kindex show debug nios2
21638 Show the current setting of Nios II debugging messages.
21641 @node Controlling GDB
21642 @chapter Controlling @value{GDBN}
21644 You can alter the way @value{GDBN} interacts with you by using the
21645 @code{set} command. For commands controlling how @value{GDBN} displays
21646 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21651 * Editing:: Command editing
21652 * Command History:: Command history
21653 * Screen Size:: Screen size
21654 * Numbers:: Numbers
21655 * ABI:: Configuring the current ABI
21656 * Auto-loading:: Automatically loading associated files
21657 * Messages/Warnings:: Optional warnings and messages
21658 * Debugging Output:: Optional messages about internal happenings
21659 * Other Misc Settings:: Other Miscellaneous Settings
21667 @value{GDBN} indicates its readiness to read a command by printing a string
21668 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21669 can change the prompt string with the @code{set prompt} command. For
21670 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21671 the prompt in one of the @value{GDBN} sessions so that you can always tell
21672 which one you are talking to.
21674 @emph{Note:} @code{set prompt} does not add a space for you after the
21675 prompt you set. This allows you to set a prompt which ends in a space
21676 or a prompt that does not.
21680 @item set prompt @var{newprompt}
21681 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21683 @kindex show prompt
21685 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21688 Versions of @value{GDBN} that ship with Python scripting enabled have
21689 prompt extensions. The commands for interacting with these extensions
21693 @kindex set extended-prompt
21694 @item set extended-prompt @var{prompt}
21695 Set an extended prompt that allows for substitutions.
21696 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21697 substitution. Any escape sequences specified as part of the prompt
21698 string are replaced with the corresponding strings each time the prompt
21704 set extended-prompt Current working directory: \w (gdb)
21707 Note that when an extended-prompt is set, it takes control of the
21708 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21710 @kindex show extended-prompt
21711 @item show extended-prompt
21712 Prints the extended prompt. Any escape sequences specified as part of
21713 the prompt string with @code{set extended-prompt}, are replaced with the
21714 corresponding strings each time the prompt is displayed.
21718 @section Command Editing
21720 @cindex command line editing
21722 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21723 @sc{gnu} library provides consistent behavior for programs which provide a
21724 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21725 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21726 substitution, and a storage and recall of command history across
21727 debugging sessions.
21729 You may control the behavior of command line editing in @value{GDBN} with the
21730 command @code{set}.
21733 @kindex set editing
21736 @itemx set editing on
21737 Enable command line editing (enabled by default).
21739 @item set editing off
21740 Disable command line editing.
21742 @kindex show editing
21744 Show whether command line editing is enabled.
21747 @ifset SYSTEM_READLINE
21748 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21750 @ifclear SYSTEM_READLINE
21751 @xref{Command Line Editing},
21753 for more details about the Readline
21754 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21755 encouraged to read that chapter.
21757 @node Command History
21758 @section Command History
21759 @cindex command history
21761 @value{GDBN} can keep track of the commands you type during your
21762 debugging sessions, so that you can be certain of precisely what
21763 happened. Use these commands to manage the @value{GDBN} command
21766 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21767 package, to provide the history facility.
21768 @ifset SYSTEM_READLINE
21769 @xref{Using History Interactively, , , history, GNU History Library},
21771 @ifclear SYSTEM_READLINE
21772 @xref{Using History Interactively},
21774 for the detailed description of the History library.
21776 To issue a command to @value{GDBN} without affecting certain aspects of
21777 the state which is seen by users, prefix it with @samp{server }
21778 (@pxref{Server Prefix}). This
21779 means that this command will not affect the command history, nor will it
21780 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21781 pressed on a line by itself.
21783 @cindex @code{server}, command prefix
21784 The server prefix does not affect the recording of values into the value
21785 history; to print a value without recording it into the value history,
21786 use the @code{output} command instead of the @code{print} command.
21788 Here is the description of @value{GDBN} commands related to command
21792 @cindex history substitution
21793 @cindex history file
21794 @kindex set history filename
21795 @cindex @env{GDBHISTFILE}, environment variable
21796 @item set history filename @var{fname}
21797 Set the name of the @value{GDBN} command history file to @var{fname}.
21798 This is the file where @value{GDBN} reads an initial command history
21799 list, and where it writes the command history from this session when it
21800 exits. You can access this list through history expansion or through
21801 the history command editing characters listed below. This file defaults
21802 to the value of the environment variable @code{GDBHISTFILE}, or to
21803 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21806 @cindex save command history
21807 @kindex set history save
21808 @item set history save
21809 @itemx set history save on
21810 Record command history in a file, whose name may be specified with the
21811 @code{set history filename} command. By default, this option is disabled.
21813 @item set history save off
21814 Stop recording command history in a file.
21816 @cindex history size
21817 @kindex set history size
21818 @cindex @env{HISTSIZE}, environment variable
21819 @item set history size @var{size}
21820 @itemx set history size unlimited
21821 Set the number of commands which @value{GDBN} keeps in its history list.
21822 This defaults to the value of the environment variable
21823 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21824 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21825 history list is unlimited.
21828 History expansion assigns special meaning to the character @kbd{!}.
21829 @ifset SYSTEM_READLINE
21830 @xref{Event Designators, , , history, GNU History Library},
21832 @ifclear SYSTEM_READLINE
21833 @xref{Event Designators},
21837 @cindex history expansion, turn on/off
21838 Since @kbd{!} is also the logical not operator in C, history expansion
21839 is off by default. If you decide to enable history expansion with the
21840 @code{set history expansion on} command, you may sometimes need to
21841 follow @kbd{!} (when it is used as logical not, in an expression) with
21842 a space or a tab to prevent it from being expanded. The readline
21843 history facilities do not attempt substitution on the strings
21844 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21846 The commands to control history expansion are:
21849 @item set history expansion on
21850 @itemx set history expansion
21851 @kindex set history expansion
21852 Enable history expansion. History expansion is off by default.
21854 @item set history expansion off
21855 Disable history expansion.
21858 @kindex show history
21860 @itemx show history filename
21861 @itemx show history save
21862 @itemx show history size
21863 @itemx show history expansion
21864 These commands display the state of the @value{GDBN} history parameters.
21865 @code{show history} by itself displays all four states.
21870 @kindex show commands
21871 @cindex show last commands
21872 @cindex display command history
21873 @item show commands
21874 Display the last ten commands in the command history.
21876 @item show commands @var{n}
21877 Print ten commands centered on command number @var{n}.
21879 @item show commands +
21880 Print ten commands just after the commands last printed.
21884 @section Screen Size
21885 @cindex size of screen
21886 @cindex pauses in output
21888 Certain commands to @value{GDBN} may produce large amounts of
21889 information output to the screen. To help you read all of it,
21890 @value{GDBN} pauses and asks you for input at the end of each page of
21891 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21892 to discard the remaining output. Also, the screen width setting
21893 determines when to wrap lines of output. Depending on what is being
21894 printed, @value{GDBN} tries to break the line at a readable place,
21895 rather than simply letting it overflow onto the following line.
21897 Normally @value{GDBN} knows the size of the screen from the terminal
21898 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21899 together with the value of the @code{TERM} environment variable and the
21900 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21901 you can override it with the @code{set height} and @code{set
21908 @kindex show height
21909 @item set height @var{lpp}
21910 @itemx set height unlimited
21912 @itemx set width @var{cpl}
21913 @itemx set width unlimited
21915 These @code{set} commands specify a screen height of @var{lpp} lines and
21916 a screen width of @var{cpl} characters. The associated @code{show}
21917 commands display the current settings.
21919 If you specify a height of either @code{unlimited} or zero lines,
21920 @value{GDBN} does not pause during output no matter how long the
21921 output is. This is useful if output is to a file or to an editor
21924 Likewise, you can specify @samp{set width unlimited} or @samp{set
21925 width 0} to prevent @value{GDBN} from wrapping its output.
21927 @item set pagination on
21928 @itemx set pagination off
21929 @kindex set pagination
21930 Turn the output pagination on or off; the default is on. Turning
21931 pagination off is the alternative to @code{set height unlimited}. Note that
21932 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21933 Options, -batch}) also automatically disables pagination.
21935 @item show pagination
21936 @kindex show pagination
21937 Show the current pagination mode.
21942 @cindex number representation
21943 @cindex entering numbers
21945 You can always enter numbers in octal, decimal, or hexadecimal in
21946 @value{GDBN} by the usual conventions: octal numbers begin with
21947 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21948 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21949 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21950 10; likewise, the default display for numbers---when no particular
21951 format is specified---is base 10. You can change the default base for
21952 both input and output with the commands described below.
21955 @kindex set input-radix
21956 @item set input-radix @var{base}
21957 Set the default base for numeric input. Supported choices
21958 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21959 specified either unambiguously or using the current input radix; for
21963 set input-radix 012
21964 set input-radix 10.
21965 set input-radix 0xa
21969 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21970 leaves the input radix unchanged, no matter what it was, since
21971 @samp{10}, being without any leading or trailing signs of its base, is
21972 interpreted in the current radix. Thus, if the current radix is 16,
21973 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21976 @kindex set output-radix
21977 @item set output-radix @var{base}
21978 Set the default base for numeric display. Supported choices
21979 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21980 specified either unambiguously or using the current input radix.
21982 @kindex show input-radix
21983 @item show input-radix
21984 Display the current default base for numeric input.
21986 @kindex show output-radix
21987 @item show output-radix
21988 Display the current default base for numeric display.
21990 @item set radix @r{[}@var{base}@r{]}
21994 These commands set and show the default base for both input and output
21995 of numbers. @code{set radix} sets the radix of input and output to
21996 the same base; without an argument, it resets the radix back to its
21997 default value of 10.
22002 @section Configuring the Current ABI
22004 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22005 application automatically. However, sometimes you need to override its
22006 conclusions. Use these commands to manage @value{GDBN}'s view of the
22012 @cindex Newlib OS ABI and its influence on the longjmp handling
22014 One @value{GDBN} configuration can debug binaries for multiple operating
22015 system targets, either via remote debugging or native emulation.
22016 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22017 but you can override its conclusion using the @code{set osabi} command.
22018 One example where this is useful is in debugging of binaries which use
22019 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22020 not have the same identifying marks that the standard C library for your
22023 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22024 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22025 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22026 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22030 Show the OS ABI currently in use.
22033 With no argument, show the list of registered available OS ABI's.
22035 @item set osabi @var{abi}
22036 Set the current OS ABI to @var{abi}.
22039 @cindex float promotion
22041 Generally, the way that an argument of type @code{float} is passed to a
22042 function depends on whether the function is prototyped. For a prototyped
22043 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22044 according to the architecture's convention for @code{float}. For unprototyped
22045 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22046 @code{double} and then passed.
22048 Unfortunately, some forms of debug information do not reliably indicate whether
22049 a function is prototyped. If @value{GDBN} calls a function that is not marked
22050 as prototyped, it consults @kbd{set coerce-float-to-double}.
22053 @kindex set coerce-float-to-double
22054 @item set coerce-float-to-double
22055 @itemx set coerce-float-to-double on
22056 Arguments of type @code{float} will be promoted to @code{double} when passed
22057 to an unprototyped function. This is the default setting.
22059 @item set coerce-float-to-double off
22060 Arguments of type @code{float} will be passed directly to unprototyped
22063 @kindex show coerce-float-to-double
22064 @item show coerce-float-to-double
22065 Show the current setting of promoting @code{float} to @code{double}.
22069 @kindex show cp-abi
22070 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22071 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22072 used to build your application. @value{GDBN} only fully supports
22073 programs with a single C@t{++} ABI; if your program contains code using
22074 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22075 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22076 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22077 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22078 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22079 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22084 Show the C@t{++} ABI currently in use.
22087 With no argument, show the list of supported C@t{++} ABI's.
22089 @item set cp-abi @var{abi}
22090 @itemx set cp-abi auto
22091 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22095 @section Automatically loading associated files
22096 @cindex auto-loading
22098 @value{GDBN} sometimes reads files with commands and settings automatically,
22099 without being explicitly told so by the user. We call this feature
22100 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22101 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22102 results or introduce security risks (e.g., if the file comes from untrusted
22105 Note that loading of these associated files (including the local @file{.gdbinit}
22106 file) requires accordingly configured @code{auto-load safe-path}
22107 (@pxref{Auto-loading safe path}).
22109 For these reasons, @value{GDBN} includes commands and options to let you
22110 control when to auto-load files and which files should be auto-loaded.
22113 @anchor{set auto-load off}
22114 @kindex set auto-load off
22115 @item set auto-load off
22116 Globally disable loading of all auto-loaded files.
22117 You may want to use this command with the @samp{-iex} option
22118 (@pxref{Option -init-eval-command}) such as:
22120 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22123 Be aware that system init file (@pxref{System-wide configuration})
22124 and init files from your home directory (@pxref{Home Directory Init File})
22125 still get read (as they come from generally trusted directories).
22126 To prevent @value{GDBN} from auto-loading even those init files, use the
22127 @option{-nx} option (@pxref{Mode Options}), in addition to
22128 @code{set auto-load no}.
22130 @anchor{show auto-load}
22131 @kindex show auto-load
22132 @item show auto-load
22133 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22137 (gdb) show auto-load
22138 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22139 libthread-db: Auto-loading of inferior specific libthread_db is on.
22140 local-gdbinit: Auto-loading of .gdbinit script from current directory
22142 python-scripts: Auto-loading of Python scripts is on.
22143 safe-path: List of directories from which it is safe to auto-load files
22144 is $debugdir:$datadir/auto-load.
22145 scripts-directory: List of directories from which to load auto-loaded scripts
22146 is $debugdir:$datadir/auto-load.
22149 @anchor{info auto-load}
22150 @kindex info auto-load
22151 @item info auto-load
22152 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22156 (gdb) info auto-load
22159 Yes /home/user/gdb/gdb-gdb.gdb
22160 libthread-db: No auto-loaded libthread-db.
22161 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22165 Yes /home/user/gdb/gdb-gdb.py
22169 These are various kinds of files @value{GDBN} can automatically load:
22173 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
22175 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
22177 @xref{dotdebug_gdb_scripts section},
22178 controlled by @ref{set auto-load python-scripts}.
22180 @xref{Init File in the Current Directory},
22181 controlled by @ref{set auto-load local-gdbinit}.
22183 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
22186 These are @value{GDBN} control commands for the auto-loading:
22188 @multitable @columnfractions .5 .5
22189 @item @xref{set auto-load off}.
22190 @tab Disable auto-loading globally.
22191 @item @xref{show auto-load}.
22192 @tab Show setting of all kinds of files.
22193 @item @xref{info auto-load}.
22194 @tab Show state of all kinds of files.
22195 @item @xref{set auto-load gdb-scripts}.
22196 @tab Control for @value{GDBN} command scripts.
22197 @item @xref{show auto-load gdb-scripts}.
22198 @tab Show setting of @value{GDBN} command scripts.
22199 @item @xref{info auto-load gdb-scripts}.
22200 @tab Show state of @value{GDBN} command scripts.
22201 @item @xref{set auto-load python-scripts}.
22202 @tab Control for @value{GDBN} Python scripts.
22203 @item @xref{show auto-load python-scripts}.
22204 @tab Show setting of @value{GDBN} Python scripts.
22205 @item @xref{info auto-load python-scripts}.
22206 @tab Show state of @value{GDBN} Python scripts.
22207 @item @xref{set auto-load scripts-directory}.
22208 @tab Control for @value{GDBN} auto-loaded scripts location.
22209 @item @xref{show auto-load scripts-directory}.
22210 @tab Show @value{GDBN} auto-loaded scripts location.
22211 @item @xref{set auto-load local-gdbinit}.
22212 @tab Control for init file in the current directory.
22213 @item @xref{show auto-load local-gdbinit}.
22214 @tab Show setting of init file in the current directory.
22215 @item @xref{info auto-load local-gdbinit}.
22216 @tab Show state of init file in the current directory.
22217 @item @xref{set auto-load libthread-db}.
22218 @tab Control for thread debugging library.
22219 @item @xref{show auto-load libthread-db}.
22220 @tab Show setting of thread debugging library.
22221 @item @xref{info auto-load libthread-db}.
22222 @tab Show state of thread debugging library.
22223 @item @xref{set auto-load safe-path}.
22224 @tab Control directories trusted for automatic loading.
22225 @item @xref{show auto-load safe-path}.
22226 @tab Show directories trusted for automatic loading.
22227 @item @xref{add-auto-load-safe-path}.
22228 @tab Add directory trusted for automatic loading.
22232 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22233 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22234 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
22235 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22236 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22237 @xref{Python Auto-loading}.
22240 @node Init File in the Current Directory
22241 @subsection Automatically loading init file in the current directory
22242 @cindex auto-loading init file in the current directory
22244 By default, @value{GDBN} reads and executes the canned sequences of commands
22245 from init file (if any) in the current working directory,
22246 see @ref{Init File in the Current Directory during Startup}.
22248 Note that loading of this local @file{.gdbinit} file also requires accordingly
22249 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22252 @anchor{set auto-load local-gdbinit}
22253 @kindex set auto-load local-gdbinit
22254 @item set auto-load local-gdbinit [on|off]
22255 Enable or disable the auto-loading of canned sequences of commands
22256 (@pxref{Sequences}) found in init file in the current directory.
22258 @anchor{show auto-load local-gdbinit}
22259 @kindex show auto-load local-gdbinit
22260 @item show auto-load local-gdbinit
22261 Show whether auto-loading of canned sequences of commands from init file in the
22262 current directory is enabled or disabled.
22264 @anchor{info auto-load local-gdbinit}
22265 @kindex info auto-load local-gdbinit
22266 @item info auto-load local-gdbinit
22267 Print whether canned sequences of commands from init file in the
22268 current directory have been auto-loaded.
22271 @node libthread_db.so.1 file
22272 @subsection Automatically loading thread debugging library
22273 @cindex auto-loading libthread_db.so.1
22275 This feature is currently present only on @sc{gnu}/Linux native hosts.
22277 @value{GDBN} reads in some cases thread debugging library from places specific
22278 to the inferior (@pxref{set libthread-db-search-path}).
22280 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22281 without checking this @samp{set auto-load libthread-db} switch as system
22282 libraries have to be trusted in general. In all other cases of
22283 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22284 auto-load libthread-db} is enabled before trying to open such thread debugging
22287 Note that loading of this debugging library also requires accordingly configured
22288 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22291 @anchor{set auto-load libthread-db}
22292 @kindex set auto-load libthread-db
22293 @item set auto-load libthread-db [on|off]
22294 Enable or disable the auto-loading of inferior specific thread debugging library.
22296 @anchor{show auto-load libthread-db}
22297 @kindex show auto-load libthread-db
22298 @item show auto-load libthread-db
22299 Show whether auto-loading of inferior specific thread debugging library is
22300 enabled or disabled.
22302 @anchor{info auto-load libthread-db}
22303 @kindex info auto-load libthread-db
22304 @item info auto-load libthread-db
22305 Print the list of all loaded inferior specific thread debugging libraries and
22306 for each such library print list of inferior @var{pid}s using it.
22309 @node objfile-gdb.gdb file
22310 @subsection The @file{@var{objfile}-gdb.gdb} file
22311 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
22313 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
22314 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
22315 auto-load gdb-scripts} is set to @samp{on}.
22317 Note that loading of this script file also requires accordingly configured
22318 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22320 For more background refer to the similar Python scripts auto-loading
22321 description (@pxref{objfile-gdb.py file}).
22324 @anchor{set auto-load gdb-scripts}
22325 @kindex set auto-load gdb-scripts
22326 @item set auto-load gdb-scripts [on|off]
22327 Enable or disable the auto-loading of canned sequences of commands scripts.
22329 @anchor{show auto-load gdb-scripts}
22330 @kindex show auto-load gdb-scripts
22331 @item show auto-load gdb-scripts
22332 Show whether auto-loading of canned sequences of commands scripts is enabled or
22335 @anchor{info auto-load gdb-scripts}
22336 @kindex info auto-load gdb-scripts
22337 @cindex print list of auto-loaded canned sequences of commands scripts
22338 @item info auto-load gdb-scripts [@var{regexp}]
22339 Print the list of all canned sequences of commands scripts that @value{GDBN}
22343 If @var{regexp} is supplied only canned sequences of commands scripts with
22344 matching names are printed.
22346 @node Auto-loading safe path
22347 @subsection Security restriction for auto-loading
22348 @cindex auto-loading safe-path
22350 As the files of inferior can come from untrusted source (such as submitted by
22351 an application user) @value{GDBN} does not always load any files automatically.
22352 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22353 directories trusted for loading files not explicitly requested by user.
22354 Each directory can also be a shell wildcard pattern.
22356 If the path is not set properly you will see a warning and the file will not
22361 Reading symbols from /home/user/gdb/gdb...done.
22362 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22363 declined by your `auto-load safe-path' set
22364 to "$debugdir:$datadir/auto-load".
22365 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22366 declined by your `auto-load safe-path' set
22367 to "$debugdir:$datadir/auto-load".
22371 To instruct @value{GDBN} to go ahead and use the init files anyway,
22372 invoke @value{GDBN} like this:
22375 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22378 The list of trusted directories is controlled by the following commands:
22381 @anchor{set auto-load safe-path}
22382 @kindex set auto-load safe-path
22383 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22384 Set the list of directories (and their subdirectories) trusted for automatic
22385 loading and execution of scripts. You can also enter a specific trusted file.
22386 Each directory can also be a shell wildcard pattern; wildcards do not match
22387 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22388 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22389 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22390 its default value as specified during @value{GDBN} compilation.
22392 The list of directories uses path separator (@samp{:} on GNU and Unix
22393 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22394 to the @env{PATH} environment variable.
22396 @anchor{show auto-load safe-path}
22397 @kindex show auto-load safe-path
22398 @item show auto-load safe-path
22399 Show the list of directories trusted for automatic loading and execution of
22402 @anchor{add-auto-load-safe-path}
22403 @kindex add-auto-load-safe-path
22404 @item add-auto-load-safe-path
22405 Add an entry (or list of entries) the list of directories trusted for automatic
22406 loading and execution of scripts. Multiple entries may be delimited by the
22407 host platform path separator in use.
22410 This variable defaults to what @code{--with-auto-load-dir} has been configured
22411 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22412 substitution applies the same as for @ref{set auto-load scripts-directory}.
22413 The default @code{set auto-load safe-path} value can be also overriden by
22414 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22416 Setting this variable to @file{/} disables this security protection,
22417 corresponding @value{GDBN} configuration option is
22418 @option{--without-auto-load-safe-path}.
22419 This variable is supposed to be set to the system directories writable by the
22420 system superuser only. Users can add their source directories in init files in
22421 their home directories (@pxref{Home Directory Init File}). See also deprecated
22422 init file in the current directory
22423 (@pxref{Init File in the Current Directory during Startup}).
22425 To force @value{GDBN} to load the files it declined to load in the previous
22426 example, you could use one of the following ways:
22429 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22430 Specify this trusted directory (or a file) as additional component of the list.
22431 You have to specify also any existing directories displayed by
22432 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22434 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22435 Specify this directory as in the previous case but just for a single
22436 @value{GDBN} session.
22438 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22439 Disable auto-loading safety for a single @value{GDBN} session.
22440 This assumes all the files you debug during this @value{GDBN} session will come
22441 from trusted sources.
22443 @item @kbd{./configure --without-auto-load-safe-path}
22444 During compilation of @value{GDBN} you may disable any auto-loading safety.
22445 This assumes all the files you will ever debug with this @value{GDBN} come from
22449 On the other hand you can also explicitly forbid automatic files loading which
22450 also suppresses any such warning messages:
22453 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22454 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22456 @item @file{~/.gdbinit}: @samp{set auto-load no}
22457 Disable auto-loading globally for the user
22458 (@pxref{Home Directory Init File}). While it is improbable, you could also
22459 use system init file instead (@pxref{System-wide configuration}).
22462 This setting applies to the file names as entered by user. If no entry matches
22463 @value{GDBN} tries as a last resort to also resolve all the file names into
22464 their canonical form (typically resolving symbolic links) and compare the
22465 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22466 own before starting the comparison so a canonical form of directories is
22467 recommended to be entered.
22469 @node Auto-loading verbose mode
22470 @subsection Displaying files tried for auto-load
22471 @cindex auto-loading verbose mode
22473 For better visibility of all the file locations where you can place scripts to
22474 be auto-loaded with inferior --- or to protect yourself against accidental
22475 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22476 all the files attempted to be loaded. Both existing and non-existing files may
22479 For example the list of directories from which it is safe to auto-load files
22480 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22481 may not be too obvious while setting it up.
22484 (gdb) set debug auto-load on
22485 (gdb) file ~/src/t/true
22486 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22487 for objfile "/tmp/true".
22488 auto-load: Updating directories of "/usr:/opt".
22489 auto-load: Using directory "/usr".
22490 auto-load: Using directory "/opt".
22491 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22492 by your `auto-load safe-path' set to "/usr:/opt".
22496 @anchor{set debug auto-load}
22497 @kindex set debug auto-load
22498 @item set debug auto-load [on|off]
22499 Set whether to print the filenames attempted to be auto-loaded.
22501 @anchor{show debug auto-load}
22502 @kindex show debug auto-load
22503 @item show debug auto-load
22504 Show whether printing of the filenames attempted to be auto-loaded is turned
22508 @node Messages/Warnings
22509 @section Optional Warnings and Messages
22511 @cindex verbose operation
22512 @cindex optional warnings
22513 By default, @value{GDBN} is silent about its inner workings. If you are
22514 running on a slow machine, you may want to use the @code{set verbose}
22515 command. This makes @value{GDBN} tell you when it does a lengthy
22516 internal operation, so you will not think it has crashed.
22518 Currently, the messages controlled by @code{set verbose} are those
22519 which announce that the symbol table for a source file is being read;
22520 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22523 @kindex set verbose
22524 @item set verbose on
22525 Enables @value{GDBN} output of certain informational messages.
22527 @item set verbose off
22528 Disables @value{GDBN} output of certain informational messages.
22530 @kindex show verbose
22532 Displays whether @code{set verbose} is on or off.
22535 By default, if @value{GDBN} encounters bugs in the symbol table of an
22536 object file, it is silent; but if you are debugging a compiler, you may
22537 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22542 @kindex set complaints
22543 @item set complaints @var{limit}
22544 Permits @value{GDBN} to output @var{limit} complaints about each type of
22545 unusual symbols before becoming silent about the problem. Set
22546 @var{limit} to zero to suppress all complaints; set it to a large number
22547 to prevent complaints from being suppressed.
22549 @kindex show complaints
22550 @item show complaints
22551 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22555 @anchor{confirmation requests}
22556 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22557 lot of stupid questions to confirm certain commands. For example, if
22558 you try to run a program which is already running:
22562 The program being debugged has been started already.
22563 Start it from the beginning? (y or n)
22566 If you are willing to unflinchingly face the consequences of your own
22567 commands, you can disable this ``feature'':
22571 @kindex set confirm
22573 @cindex confirmation
22574 @cindex stupid questions
22575 @item set confirm off
22576 Disables confirmation requests. Note that running @value{GDBN} with
22577 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22578 automatically disables confirmation requests.
22580 @item set confirm on
22581 Enables confirmation requests (the default).
22583 @kindex show confirm
22585 Displays state of confirmation requests.
22589 @cindex command tracing
22590 If you need to debug user-defined commands or sourced files you may find it
22591 useful to enable @dfn{command tracing}. In this mode each command will be
22592 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22593 quantity denoting the call depth of each command.
22596 @kindex set trace-commands
22597 @cindex command scripts, debugging
22598 @item set trace-commands on
22599 Enable command tracing.
22600 @item set trace-commands off
22601 Disable command tracing.
22602 @item show trace-commands
22603 Display the current state of command tracing.
22606 @node Debugging Output
22607 @section Optional Messages about Internal Happenings
22608 @cindex optional debugging messages
22610 @value{GDBN} has commands that enable optional debugging messages from
22611 various @value{GDBN} subsystems; normally these commands are of
22612 interest to @value{GDBN} maintainers, or when reporting a bug. This
22613 section documents those commands.
22616 @kindex set exec-done-display
22617 @item set exec-done-display
22618 Turns on or off the notification of asynchronous commands'
22619 completion. When on, @value{GDBN} will print a message when an
22620 asynchronous command finishes its execution. The default is off.
22621 @kindex show exec-done-display
22622 @item show exec-done-display
22623 Displays the current setting of asynchronous command completion
22626 @cindex ARM AArch64
22627 @item set debug aarch64
22628 Turns on or off display of debugging messages related to ARM AArch64.
22629 The default is off.
22631 @item show debug aarch64
22632 Displays the current state of displaying debugging messages related to
22634 @cindex gdbarch debugging info
22635 @cindex architecture debugging info
22636 @item set debug arch
22637 Turns on or off display of gdbarch debugging info. The default is off
22638 @item show debug arch
22639 Displays the current state of displaying gdbarch debugging info.
22640 @item set debug aix-solib
22641 @cindex AIX shared library debugging
22642 Control display of debugging messages from the AIX shared library
22643 support module. The default is off.
22644 @item show debug aix-thread
22645 Show the current state of displaying AIX shared library debugging messages.
22646 @item set debug aix-thread
22647 @cindex AIX threads
22648 Display debugging messages about inner workings of the AIX thread
22650 @item show debug aix-thread
22651 Show the current state of AIX thread debugging info display.
22652 @item set debug check-physname
22654 Check the results of the ``physname'' computation. When reading DWARF
22655 debugging information for C@t{++}, @value{GDBN} attempts to compute
22656 each entity's name. @value{GDBN} can do this computation in two
22657 different ways, depending on exactly what information is present.
22658 When enabled, this setting causes @value{GDBN} to compute the names
22659 both ways and display any discrepancies.
22660 @item show debug check-physname
22661 Show the current state of ``physname'' checking.
22662 @item set debug coff-pe-read
22663 @cindex COFF/PE exported symbols
22664 Control display of debugging messages related to reading of COFF/PE
22665 exported symbols. The default is off.
22666 @item show debug coff-pe-read
22667 Displays the current state of displaying debugging messages related to
22668 reading of COFF/PE exported symbols.
22669 @item set debug dwarf2-die
22670 @cindex DWARF2 DIEs
22671 Dump DWARF2 DIEs after they are read in.
22672 The value is the number of nesting levels to print.
22673 A value of zero turns off the display.
22674 @item show debug dwarf2-die
22675 Show the current state of DWARF2 DIE debugging.
22676 @item set debug dwarf2-read
22677 @cindex DWARF2 Reading
22678 Turns on or off display of debugging messages related to reading
22679 DWARF debug info. The default is 0 (off).
22680 A value of 1 provides basic information.
22681 A value greater than 1 provides more verbose information.
22682 @item show debug dwarf2-read
22683 Show the current state of DWARF2 reader debugging.
22684 @item set debug displaced
22685 @cindex displaced stepping debugging info
22686 Turns on or off display of @value{GDBN} debugging info for the
22687 displaced stepping support. The default is off.
22688 @item show debug displaced
22689 Displays the current state of displaying @value{GDBN} debugging info
22690 related to displaced stepping.
22691 @item set debug event
22692 @cindex event debugging info
22693 Turns on or off display of @value{GDBN} event debugging info. The
22695 @item show debug event
22696 Displays the current state of displaying @value{GDBN} event debugging
22698 @item set debug expression
22699 @cindex expression debugging info
22700 Turns on or off display of debugging info about @value{GDBN}
22701 expression parsing. The default is off.
22702 @item show debug expression
22703 Displays the current state of displaying debugging info about
22704 @value{GDBN} expression parsing.
22705 @item set debug frame
22706 @cindex frame debugging info
22707 Turns on or off display of @value{GDBN} frame debugging info. The
22709 @item show debug frame
22710 Displays the current state of displaying @value{GDBN} frame debugging
22712 @item set debug gnu-nat
22713 @cindex @sc{gnu}/Hurd debug messages
22714 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22715 @item show debug gnu-nat
22716 Show the current state of @sc{gnu}/Hurd debugging messages.
22717 @item set debug infrun
22718 @cindex inferior debugging info
22719 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22720 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22721 for implementing operations such as single-stepping the inferior.
22722 @item show debug infrun
22723 Displays the current state of @value{GDBN} inferior debugging.
22724 @item set debug jit
22725 @cindex just-in-time compilation, debugging messages
22726 Turns on or off debugging messages from JIT debug support.
22727 @item show debug jit
22728 Displays the current state of @value{GDBN} JIT debugging.
22729 @item set debug lin-lwp
22730 @cindex @sc{gnu}/Linux LWP debug messages
22731 @cindex Linux lightweight processes
22732 Turns on or off debugging messages from the Linux LWP debug support.
22733 @item show debug lin-lwp
22734 Show the current state of Linux LWP debugging messages.
22735 @item set debug mach-o
22736 @cindex Mach-O symbols processing
22737 Control display of debugging messages related to Mach-O symbols
22738 processing. The default is off.
22739 @item show debug mach-o
22740 Displays the current state of displaying debugging messages related to
22741 reading of COFF/PE exported symbols.
22742 @item set debug notification
22743 @cindex remote async notification debugging info
22744 Turns on or off debugging messages about remote async notification.
22745 The default is off.
22746 @item show debug notification
22747 Displays the current state of remote async notification debugging messages.
22748 @item set debug observer
22749 @cindex observer debugging info
22750 Turns on or off display of @value{GDBN} observer debugging. This
22751 includes info such as the notification of observable events.
22752 @item show debug observer
22753 Displays the current state of observer debugging.
22754 @item set debug overload
22755 @cindex C@t{++} overload debugging info
22756 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22757 info. This includes info such as ranking of functions, etc. The default
22759 @item show debug overload
22760 Displays the current state of displaying @value{GDBN} C@t{++} overload
22762 @cindex expression parser, debugging info
22763 @cindex debug expression parser
22764 @item set debug parser
22765 Turns on or off the display of expression parser debugging output.
22766 Internally, this sets the @code{yydebug} variable in the expression
22767 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22768 details. The default is off.
22769 @item show debug parser
22770 Show the current state of expression parser debugging.
22771 @cindex packets, reporting on stdout
22772 @cindex serial connections, debugging
22773 @cindex debug remote protocol
22774 @cindex remote protocol debugging
22775 @cindex display remote packets
22776 @item set debug remote
22777 Turns on or off display of reports on all packets sent back and forth across
22778 the serial line to the remote machine. The info is printed on the
22779 @value{GDBN} standard output stream. The default is off.
22780 @item show debug remote
22781 Displays the state of display of remote packets.
22782 @item set debug serial
22783 Turns on or off display of @value{GDBN} serial debugging info. The
22785 @item show debug serial
22786 Displays the current state of displaying @value{GDBN} serial debugging
22788 @item set debug solib-frv
22789 @cindex FR-V shared-library debugging
22790 Turns on or off debugging messages for FR-V shared-library code.
22791 @item show debug solib-frv
22792 Display the current state of FR-V shared-library code debugging
22794 @item set debug symfile
22795 @cindex symbol file functions
22796 Turns on or off display of debugging messages related to symbol file functions.
22797 The default is off. @xref{Files}.
22798 @item show debug symfile
22799 Show the current state of symbol file debugging messages.
22800 @item set debug symtab-create
22801 @cindex symbol table creation
22802 Turns on or off display of debugging messages related to symbol table creation.
22803 The default is 0 (off).
22804 A value of 1 provides basic information.
22805 A value greater than 1 provides more verbose information.
22806 @item show debug symtab-create
22807 Show the current state of symbol table creation debugging.
22808 @item set debug target
22809 @cindex target debugging info
22810 Turns on or off display of @value{GDBN} target debugging info. This info
22811 includes what is going on at the target level of GDB, as it happens. The
22812 default is 0. Set it to 1 to track events, and to 2 to also track the
22813 value of large memory transfers. Changes to this flag do not take effect
22814 until the next time you connect to a target or use the @code{run} command.
22815 @item show debug target
22816 Displays the current state of displaying @value{GDBN} target debugging
22818 @item set debug timestamp
22819 @cindex timestampping debugging info
22820 Turns on or off display of timestamps with @value{GDBN} debugging info.
22821 When enabled, seconds and microseconds are displayed before each debugging
22823 @item show debug timestamp
22824 Displays the current state of displaying timestamps with @value{GDBN}
22826 @item set debugvarobj
22827 @cindex variable object debugging info
22828 Turns on or off display of @value{GDBN} variable object debugging
22829 info. The default is off.
22830 @item show debugvarobj
22831 Displays the current state of displaying @value{GDBN} variable object
22833 @item set debug xml
22834 @cindex XML parser debugging
22835 Turns on or off debugging messages for built-in XML parsers.
22836 @item show debug xml
22837 Displays the current state of XML debugging messages.
22840 @node Other Misc Settings
22841 @section Other Miscellaneous Settings
22842 @cindex miscellaneous settings
22845 @kindex set interactive-mode
22846 @item set interactive-mode
22847 If @code{on}, forces @value{GDBN} to assume that GDB was started
22848 in a terminal. In practice, this means that @value{GDBN} should wait
22849 for the user to answer queries generated by commands entered at
22850 the command prompt. If @code{off}, forces @value{GDBN} to operate
22851 in the opposite mode, and it uses the default answers to all queries.
22852 If @code{auto} (the default), @value{GDBN} tries to determine whether
22853 its standard input is a terminal, and works in interactive-mode if it
22854 is, non-interactively otherwise.
22856 In the vast majority of cases, the debugger should be able to guess
22857 correctly which mode should be used. But this setting can be useful
22858 in certain specific cases, such as running a MinGW @value{GDBN}
22859 inside a cygwin window.
22861 @kindex show interactive-mode
22862 @item show interactive-mode
22863 Displays whether the debugger is operating in interactive mode or not.
22866 @node Extending GDB
22867 @chapter Extending @value{GDBN}
22868 @cindex extending GDB
22870 @value{GDBN} provides three mechanisms for extension. The first is based
22871 on composition of @value{GDBN} commands, the second is based on the
22872 Python scripting language, and the third is for defining new aliases of
22875 To facilitate the use of the first two extensions, @value{GDBN} is capable
22876 of evaluating the contents of a file. When doing so, @value{GDBN}
22877 can recognize which scripting language is being used by looking at
22878 the filename extension. Files with an unrecognized filename extension
22879 are always treated as a @value{GDBN} Command Files.
22880 @xref{Command Files,, Command files}.
22882 You can control how @value{GDBN} evaluates these files with the following
22886 @kindex set script-extension
22887 @kindex show script-extension
22888 @item set script-extension off
22889 All scripts are always evaluated as @value{GDBN} Command Files.
22891 @item set script-extension soft
22892 The debugger determines the scripting language based on filename
22893 extension. If this scripting language is supported, @value{GDBN}
22894 evaluates the script using that language. Otherwise, it evaluates
22895 the file as a @value{GDBN} Command File.
22897 @item set script-extension strict
22898 The debugger determines the scripting language based on filename
22899 extension, and evaluates the script using that language. If the
22900 language is not supported, then the evaluation fails.
22902 @item show script-extension
22903 Display the current value of the @code{script-extension} option.
22908 * Sequences:: Canned Sequences of Commands
22909 * Python:: Scripting @value{GDBN} using Python
22910 * Aliases:: Creating new spellings of existing commands
22914 @section Canned Sequences of Commands
22916 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22917 Command Lists}), @value{GDBN} provides two ways to store sequences of
22918 commands for execution as a unit: user-defined commands and command
22922 * Define:: How to define your own commands
22923 * Hooks:: Hooks for user-defined commands
22924 * Command Files:: How to write scripts of commands to be stored in a file
22925 * Output:: Commands for controlled output
22929 @subsection User-defined Commands
22931 @cindex user-defined command
22932 @cindex arguments, to user-defined commands
22933 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22934 which you assign a new name as a command. This is done with the
22935 @code{define} command. User commands may accept up to 10 arguments
22936 separated by whitespace. Arguments are accessed within the user command
22937 via @code{$arg0@dots{}$arg9}. A trivial example:
22941 print $arg0 + $arg1 + $arg2
22946 To execute the command use:
22953 This defines the command @code{adder}, which prints the sum of
22954 its three arguments. Note the arguments are text substitutions, so they may
22955 reference variables, use complex expressions, or even perform inferior
22958 @cindex argument count in user-defined commands
22959 @cindex how many arguments (user-defined commands)
22960 In addition, @code{$argc} may be used to find out how many arguments have
22961 been passed. This expands to a number in the range 0@dots{}10.
22966 print $arg0 + $arg1
22969 print $arg0 + $arg1 + $arg2
22977 @item define @var{commandname}
22978 Define a command named @var{commandname}. If there is already a command
22979 by that name, you are asked to confirm that you want to redefine it.
22980 @var{commandname} may be a bare command name consisting of letters,
22981 numbers, dashes, and underscores. It may also start with any predefined
22982 prefix command. For example, @samp{define target my-target} creates
22983 a user-defined @samp{target my-target} command.
22985 The definition of the command is made up of other @value{GDBN} command lines,
22986 which are given following the @code{define} command. The end of these
22987 commands is marked by a line containing @code{end}.
22990 @kindex end@r{ (user-defined commands)}
22991 @item document @var{commandname}
22992 Document the user-defined command @var{commandname}, so that it can be
22993 accessed by @code{help}. The command @var{commandname} must already be
22994 defined. This command reads lines of documentation just as @code{define}
22995 reads the lines of the command definition, ending with @code{end}.
22996 After the @code{document} command is finished, @code{help} on command
22997 @var{commandname} displays the documentation you have written.
22999 You may use the @code{document} command again to change the
23000 documentation of a command. Redefining the command with @code{define}
23001 does not change the documentation.
23003 @kindex dont-repeat
23004 @cindex don't repeat command
23006 Used inside a user-defined command, this tells @value{GDBN} that this
23007 command should not be repeated when the user hits @key{RET}
23008 (@pxref{Command Syntax, repeat last command}).
23010 @kindex help user-defined
23011 @item help user-defined
23012 List all user-defined commands and all python commands defined in class
23013 COMAND_USER. The first line of the documentation or docstring is
23018 @itemx show user @var{commandname}
23019 Display the @value{GDBN} commands used to define @var{commandname} (but
23020 not its documentation). If no @var{commandname} is given, display the
23021 definitions for all user-defined commands.
23022 This does not work for user-defined python commands.
23024 @cindex infinite recursion in user-defined commands
23025 @kindex show max-user-call-depth
23026 @kindex set max-user-call-depth
23027 @item show max-user-call-depth
23028 @itemx set max-user-call-depth
23029 The value of @code{max-user-call-depth} controls how many recursion
23030 levels are allowed in user-defined commands before @value{GDBN} suspects an
23031 infinite recursion and aborts the command.
23032 This does not apply to user-defined python commands.
23035 In addition to the above commands, user-defined commands frequently
23036 use control flow commands, described in @ref{Command Files}.
23038 When user-defined commands are executed, the
23039 commands of the definition are not printed. An error in any command
23040 stops execution of the user-defined command.
23042 If used interactively, commands that would ask for confirmation proceed
23043 without asking when used inside a user-defined command. Many @value{GDBN}
23044 commands that normally print messages to say what they are doing omit the
23045 messages when used in a user-defined command.
23048 @subsection User-defined Command Hooks
23049 @cindex command hooks
23050 @cindex hooks, for commands
23051 @cindex hooks, pre-command
23054 You may define @dfn{hooks}, which are a special kind of user-defined
23055 command. Whenever you run the command @samp{foo}, if the user-defined
23056 command @samp{hook-foo} exists, it is executed (with no arguments)
23057 before that command.
23059 @cindex hooks, post-command
23061 A hook may also be defined which is run after the command you executed.
23062 Whenever you run the command @samp{foo}, if the user-defined command
23063 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23064 that command. Post-execution hooks may exist simultaneously with
23065 pre-execution hooks, for the same command.
23067 It is valid for a hook to call the command which it hooks. If this
23068 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23070 @c It would be nice if hookpost could be passed a parameter indicating
23071 @c if the command it hooks executed properly or not. FIXME!
23073 @kindex stop@r{, a pseudo-command}
23074 In addition, a pseudo-command, @samp{stop} exists. Defining
23075 (@samp{hook-stop}) makes the associated commands execute every time
23076 execution stops in your program: before breakpoint commands are run,
23077 displays are printed, or the stack frame is printed.
23079 For example, to ignore @code{SIGALRM} signals while
23080 single-stepping, but treat them normally during normal execution,
23085 handle SIGALRM nopass
23089 handle SIGALRM pass
23092 define hook-continue
23093 handle SIGALRM pass
23097 As a further example, to hook at the beginning and end of the @code{echo}
23098 command, and to add extra text to the beginning and end of the message,
23106 define hookpost-echo
23110 (@value{GDBP}) echo Hello World
23111 <<<---Hello World--->>>
23116 You can define a hook for any single-word command in @value{GDBN}, but
23117 not for command aliases; you should define a hook for the basic command
23118 name, e.g.@: @code{backtrace} rather than @code{bt}.
23119 @c FIXME! So how does Joe User discover whether a command is an alias
23121 You can hook a multi-word command by adding @code{hook-} or
23122 @code{hookpost-} to the last word of the command, e.g.@:
23123 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23125 If an error occurs during the execution of your hook, execution of
23126 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23127 (before the command that you actually typed had a chance to run).
23129 If you try to define a hook which does not match any known command, you
23130 get a warning from the @code{define} command.
23132 @node Command Files
23133 @subsection Command Files
23135 @cindex command files
23136 @cindex scripting commands
23137 A command file for @value{GDBN} is a text file made of lines that are
23138 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23139 also be included. An empty line in a command file does nothing; it
23140 does not mean to repeat the last command, as it would from the
23143 You can request the execution of a command file with the @code{source}
23144 command. Note that the @code{source} command is also used to evaluate
23145 scripts that are not Command Files. The exact behavior can be configured
23146 using the @code{script-extension} setting.
23147 @xref{Extending GDB,, Extending GDB}.
23151 @cindex execute commands from a file
23152 @item source [-s] [-v] @var{filename}
23153 Execute the command file @var{filename}.
23156 The lines in a command file are generally executed sequentially,
23157 unless the order of execution is changed by one of the
23158 @emph{flow-control commands} described below. The commands are not
23159 printed as they are executed. An error in any command terminates
23160 execution of the command file and control is returned to the console.
23162 @value{GDBN} first searches for @var{filename} in the current directory.
23163 If the file is not found there, and @var{filename} does not specify a
23164 directory, then @value{GDBN} also looks for the file on the source search path
23165 (specified with the @samp{directory} command);
23166 except that @file{$cdir} is not searched because the compilation directory
23167 is not relevant to scripts.
23169 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23170 on the search path even if @var{filename} specifies a directory.
23171 The search is done by appending @var{filename} to each element of the
23172 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23173 and the search path contains @file{/home/user} then @value{GDBN} will
23174 look for the script @file{/home/user/mylib/myscript}.
23175 The search is also done if @var{filename} is an absolute path.
23176 For example, if @var{filename} is @file{/tmp/myscript} and
23177 the search path contains @file{/home/user} then @value{GDBN} will
23178 look for the script @file{/home/user/tmp/myscript}.
23179 For DOS-like systems, if @var{filename} contains a drive specification,
23180 it is stripped before concatenation. For example, if @var{filename} is
23181 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23182 will look for the script @file{c:/tmp/myscript}.
23184 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23185 each command as it is executed. The option must be given before
23186 @var{filename}, and is interpreted as part of the filename anywhere else.
23188 Commands that would ask for confirmation if used interactively proceed
23189 without asking when used in a command file. Many @value{GDBN} commands that
23190 normally print messages to say what they are doing omit the messages
23191 when called from command files.
23193 @value{GDBN} also accepts command input from standard input. In this
23194 mode, normal output goes to standard output and error output goes to
23195 standard error. Errors in a command file supplied on standard input do
23196 not terminate execution of the command file---execution continues with
23200 gdb < cmds > log 2>&1
23203 (The syntax above will vary depending on the shell used.) This example
23204 will execute commands from the file @file{cmds}. All output and errors
23205 would be directed to @file{log}.
23207 Since commands stored on command files tend to be more general than
23208 commands typed interactively, they frequently need to deal with
23209 complicated situations, such as different or unexpected values of
23210 variables and symbols, changes in how the program being debugged is
23211 built, etc. @value{GDBN} provides a set of flow-control commands to
23212 deal with these complexities. Using these commands, you can write
23213 complex scripts that loop over data structures, execute commands
23214 conditionally, etc.
23221 This command allows to include in your script conditionally executed
23222 commands. The @code{if} command takes a single argument, which is an
23223 expression to evaluate. It is followed by a series of commands that
23224 are executed only if the expression is true (its value is nonzero).
23225 There can then optionally be an @code{else} line, followed by a series
23226 of commands that are only executed if the expression was false. The
23227 end of the list is marked by a line containing @code{end}.
23231 This command allows to write loops. Its syntax is similar to
23232 @code{if}: the command takes a single argument, which is an expression
23233 to evaluate, and must be followed by the commands to execute, one per
23234 line, terminated by an @code{end}. These commands are called the
23235 @dfn{body} of the loop. The commands in the body of @code{while} are
23236 executed repeatedly as long as the expression evaluates to true.
23240 This command exits the @code{while} loop in whose body it is included.
23241 Execution of the script continues after that @code{while}s @code{end}
23244 @kindex loop_continue
23245 @item loop_continue
23246 This command skips the execution of the rest of the body of commands
23247 in the @code{while} loop in whose body it is included. Execution
23248 branches to the beginning of the @code{while} loop, where it evaluates
23249 the controlling expression.
23251 @kindex end@r{ (if/else/while commands)}
23253 Terminate the block of commands that are the body of @code{if},
23254 @code{else}, or @code{while} flow-control commands.
23259 @subsection Commands for Controlled Output
23261 During the execution of a command file or a user-defined command, normal
23262 @value{GDBN} output is suppressed; the only output that appears is what is
23263 explicitly printed by the commands in the definition. This section
23264 describes three commands useful for generating exactly the output you
23269 @item echo @var{text}
23270 @c I do not consider backslash-space a standard C escape sequence
23271 @c because it is not in ANSI.
23272 Print @var{text}. Nonprinting characters can be included in
23273 @var{text} using C escape sequences, such as @samp{\n} to print a
23274 newline. @strong{No newline is printed unless you specify one.}
23275 In addition to the standard C escape sequences, a backslash followed
23276 by a space stands for a space. This is useful for displaying a
23277 string with spaces at the beginning or the end, since leading and
23278 trailing spaces are otherwise trimmed from all arguments.
23279 To print @samp{@w{ }and foo =@w{ }}, use the command
23280 @samp{echo \@w{ }and foo = \@w{ }}.
23282 A backslash at the end of @var{text} can be used, as in C, to continue
23283 the command onto subsequent lines. For example,
23286 echo This is some text\n\
23287 which is continued\n\
23288 onto several lines.\n
23291 produces the same output as
23294 echo This is some text\n
23295 echo which is continued\n
23296 echo onto several lines.\n
23300 @item output @var{expression}
23301 Print the value of @var{expression} and nothing but that value: no
23302 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23303 value history either. @xref{Expressions, ,Expressions}, for more information
23306 @item output/@var{fmt} @var{expression}
23307 Print the value of @var{expression} in format @var{fmt}. You can use
23308 the same formats as for @code{print}. @xref{Output Formats,,Output
23309 Formats}, for more information.
23312 @item printf @var{template}, @var{expressions}@dots{}
23313 Print the values of one or more @var{expressions} under the control of
23314 the string @var{template}. To print several values, make
23315 @var{expressions} be a comma-separated list of individual expressions,
23316 which may be either numbers or pointers. Their values are printed as
23317 specified by @var{template}, exactly as a C program would do by
23318 executing the code below:
23321 printf (@var{template}, @var{expressions}@dots{});
23324 As in @code{C} @code{printf}, ordinary characters in @var{template}
23325 are printed verbatim, while @dfn{conversion specification} introduced
23326 by the @samp{%} character cause subsequent @var{expressions} to be
23327 evaluated, their values converted and formatted according to type and
23328 style information encoded in the conversion specifications, and then
23331 For example, you can print two values in hex like this:
23334 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23337 @code{printf} supports all the standard @code{C} conversion
23338 specifications, including the flags and modifiers between the @samp{%}
23339 character and the conversion letter, with the following exceptions:
23343 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23346 The modifier @samp{*} is not supported for specifying precision or
23350 The @samp{'} flag (for separation of digits into groups according to
23351 @code{LC_NUMERIC'}) is not supported.
23354 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23358 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23361 The conversion letters @samp{a} and @samp{A} are not supported.
23365 Note that the @samp{ll} type modifier is supported only if the
23366 underlying @code{C} implementation used to build @value{GDBN} supports
23367 the @code{long long int} type, and the @samp{L} type modifier is
23368 supported only if @code{long double} type is available.
23370 As in @code{C}, @code{printf} supports simple backslash-escape
23371 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23372 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23373 single character. Octal and hexadecimal escape sequences are not
23376 Additionally, @code{printf} supports conversion specifications for DFP
23377 (@dfn{Decimal Floating Point}) types using the following length modifiers
23378 together with a floating point specifier.
23383 @samp{H} for printing @code{Decimal32} types.
23386 @samp{D} for printing @code{Decimal64} types.
23389 @samp{DD} for printing @code{Decimal128} types.
23392 If the underlying @code{C} implementation used to build @value{GDBN} has
23393 support for the three length modifiers for DFP types, other modifiers
23394 such as width and precision will also be available for @value{GDBN} to use.
23396 In case there is no such @code{C} support, no additional modifiers will be
23397 available and the value will be printed in the standard way.
23399 Here's an example of printing DFP types using the above conversion letters:
23401 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23405 @item eval @var{template}, @var{expressions}@dots{}
23406 Convert the values of one or more @var{expressions} under the control of
23407 the string @var{template} to a command line, and call it.
23412 @section Scripting @value{GDBN} using Python
23413 @cindex python scripting
23414 @cindex scripting with python
23416 You can script @value{GDBN} using the @uref{http://www.python.org/,
23417 Python programming language}. This feature is available only if
23418 @value{GDBN} was configured using @option{--with-python}.
23420 @cindex python directory
23421 Python scripts used by @value{GDBN} should be installed in
23422 @file{@var{data-directory}/python}, where @var{data-directory} is
23423 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23424 This directory, known as the @dfn{python directory},
23425 is automatically added to the Python Search Path in order to allow
23426 the Python interpreter to locate all scripts installed at this location.
23428 Additionally, @value{GDBN} commands and convenience functions which
23429 are written in Python and are located in the
23430 @file{@var{data-directory}/python/gdb/command} or
23431 @file{@var{data-directory}/python/gdb/function} directories are
23432 automatically imported when @value{GDBN} starts.
23435 * Python Commands:: Accessing Python from @value{GDBN}.
23436 * Python API:: Accessing @value{GDBN} from Python.
23437 * Python Auto-loading:: Automatically loading Python code.
23438 * Python modules:: Python modules provided by @value{GDBN}.
23441 @node Python Commands
23442 @subsection Python Commands
23443 @cindex python commands
23444 @cindex commands to access python
23446 @value{GDBN} provides two commands for accessing the Python interpreter,
23447 and one related setting:
23450 @kindex python-interactive
23452 @item python-interactive @r{[}@var{command}@r{]}
23453 @itemx pi @r{[}@var{command}@r{]}
23454 Without an argument, the @code{python-interactive} command can be used
23455 to start an interactive Python prompt. To return to @value{GDBN},
23456 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23458 Alternatively, a single-line Python command can be given as an
23459 argument and evaluated. If the command is an expression, the result
23460 will be printed; otherwise, nothing will be printed. For example:
23463 (@value{GDBP}) python-interactive 2 + 3
23469 @item python @r{[}@var{command}@r{]}
23470 @itemx py @r{[}@var{command}@r{]}
23471 The @code{python} command can be used to evaluate Python code.
23473 If given an argument, the @code{python} command will evaluate the
23474 argument as a Python command. For example:
23477 (@value{GDBP}) python print 23
23481 If you do not provide an argument to @code{python}, it will act as a
23482 multi-line command, like @code{define}. In this case, the Python
23483 script is made up of subsequent command lines, given after the
23484 @code{python} command. This command list is terminated using a line
23485 containing @code{end}. For example:
23488 (@value{GDBP}) python
23490 End with a line saying just "end".
23496 @kindex set python print-stack
23497 @item set python print-stack
23498 By default, @value{GDBN} will print only the message component of a
23499 Python exception when an error occurs in a Python script. This can be
23500 controlled using @code{set python print-stack}: if @code{full}, then
23501 full Python stack printing is enabled; if @code{none}, then Python stack
23502 and message printing is disabled; if @code{message}, the default, only
23503 the message component of the error is printed.
23506 It is also possible to execute a Python script from the @value{GDBN}
23510 @item source @file{script-name}
23511 The script name must end with @samp{.py} and @value{GDBN} must be configured
23512 to recognize the script language based on filename extension using
23513 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23515 @item python execfile ("script-name")
23516 This method is based on the @code{execfile} Python built-in function,
23517 and thus is always available.
23521 @subsection Python API
23523 @cindex programming in python
23525 You can get quick online help for @value{GDBN}'s Python API by issuing
23526 the command @w{@kbd{python help (gdb)}}.
23528 Functions and methods which have two or more optional arguments allow
23529 them to be specified using keyword syntax. This allows passing some
23530 optional arguments while skipping others. Example:
23531 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23534 * Basic Python:: Basic Python Functions.
23535 * Exception Handling:: How Python exceptions are translated.
23536 * Values From Inferior:: Python representation of values.
23537 * Types In Python:: Python representation of types.
23538 * Pretty Printing API:: Pretty-printing values.
23539 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23540 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23541 * Type Printing API:: Pretty-printing types.
23542 * Frame Filter API:: Filtering Frames.
23543 * Frame Decorator API:: Decorating Frames.
23544 * Writing a Frame Filter:: Writing a Frame Filter.
23545 * Inferiors In Python:: Python representation of inferiors (processes)
23546 * Events In Python:: Listening for events from @value{GDBN}.
23547 * Threads In Python:: Accessing inferior threads from Python.
23548 * Commands In Python:: Implementing new commands in Python.
23549 * Parameters In Python:: Adding new @value{GDBN} parameters.
23550 * Functions In Python:: Writing new convenience functions.
23551 * Progspaces In Python:: Program spaces.
23552 * Objfiles In Python:: Object files.
23553 * Frames In Python:: Accessing inferior stack frames from Python.
23554 * Blocks In Python:: Accessing blocks from Python.
23555 * Symbols In Python:: Python representation of symbols.
23556 * Symbol Tables In Python:: Python representation of symbol tables.
23557 * Line Tables In Python:: Python representation of line tables.
23558 * Breakpoints In Python:: Manipulating breakpoints using Python.
23559 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23561 * Lazy Strings In Python:: Python representation of lazy strings.
23562 * Architectures In Python:: Python representation of architectures.
23566 @subsubsection Basic Python
23568 @cindex python stdout
23569 @cindex python pagination
23570 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23571 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23572 A Python program which outputs to one of these streams may have its
23573 output interrupted by the user (@pxref{Screen Size}). In this
23574 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23576 Some care must be taken when writing Python code to run in
23577 @value{GDBN}. Two things worth noting in particular:
23581 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23582 Python code must not override these, or even change the options using
23583 @code{sigaction}. If your program changes the handling of these
23584 signals, @value{GDBN} will most likely stop working correctly. Note
23585 that it is unfortunately common for GUI toolkits to install a
23586 @code{SIGCHLD} handler.
23589 @value{GDBN} takes care to mark its internal file descriptors as
23590 close-on-exec. However, this cannot be done in a thread-safe way on
23591 all platforms. Your Python programs should be aware of this and
23592 should both create new file descriptors with the close-on-exec flag
23593 set and arrange to close unneeded file descriptors before starting a
23597 @cindex python functions
23598 @cindex python module
23600 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23601 methods and classes added by @value{GDBN} are placed in this module.
23602 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23603 use in all scripts evaluated by the @code{python} command.
23605 @findex gdb.PYTHONDIR
23606 @defvar gdb.PYTHONDIR
23607 A string containing the python directory (@pxref{Python}).
23610 @findex gdb.execute
23611 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23612 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23613 If a GDB exception happens while @var{command} runs, it is
23614 translated as described in @ref{Exception Handling,,Exception Handling}.
23616 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23617 command as having originated from the user invoking it interactively.
23618 It must be a boolean value. If omitted, it defaults to @code{False}.
23620 By default, any output produced by @var{command} is sent to
23621 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23622 @code{True}, then output will be collected by @code{gdb.execute} and
23623 returned as a string. The default is @code{False}, in which case the
23624 return value is @code{None}. If @var{to_string} is @code{True}, the
23625 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23626 and height, and its pagination will be disabled; @pxref{Screen Size}.
23629 @findex gdb.breakpoints
23630 @defun gdb.breakpoints ()
23631 Return a sequence holding all of @value{GDBN}'s breakpoints.
23632 @xref{Breakpoints In Python}, for more information.
23635 @findex gdb.parameter
23636 @defun gdb.parameter (parameter)
23637 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23638 string naming the parameter to look up; @var{parameter} may contain
23639 spaces if the parameter has a multi-part name. For example,
23640 @samp{print object} is a valid parameter name.
23642 If the named parameter does not exist, this function throws a
23643 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23644 parameter's value is converted to a Python value of the appropriate
23645 type, and returned.
23648 @findex gdb.history
23649 @defun gdb.history (number)
23650 Return a value from @value{GDBN}'s value history (@pxref{Value
23651 History}). @var{number} indicates which history element to return.
23652 If @var{number} is negative, then @value{GDBN} will take its absolute value
23653 and count backward from the last element (i.e., the most recent element) to
23654 find the value to return. If @var{number} is zero, then @value{GDBN} will
23655 return the most recent element. If the element specified by @var{number}
23656 doesn't exist in the value history, a @code{gdb.error} exception will be
23659 If no exception is raised, the return value is always an instance of
23660 @code{gdb.Value} (@pxref{Values From Inferior}).
23663 @findex gdb.parse_and_eval
23664 @defun gdb.parse_and_eval (expression)
23665 Parse @var{expression} as an expression in the current language,
23666 evaluate it, and return the result as a @code{gdb.Value}.
23667 @var{expression} must be a string.
23669 This function can be useful when implementing a new command
23670 (@pxref{Commands In Python}), as it provides a way to parse the
23671 command's argument as an expression. It is also useful simply to
23672 compute values, for example, it is the only way to get the value of a
23673 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23676 @findex gdb.find_pc_line
23677 @defun gdb.find_pc_line (pc)
23678 Return the @code{gdb.Symtab_and_line} object corresponding to the
23679 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23680 value of @var{pc} is passed as an argument, then the @code{symtab} and
23681 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23682 will be @code{None} and 0 respectively.
23685 @findex gdb.post_event
23686 @defun gdb.post_event (event)
23687 Put @var{event}, a callable object taking no arguments, into
23688 @value{GDBN}'s internal event queue. This callable will be invoked at
23689 some later point, during @value{GDBN}'s event processing. Events
23690 posted using @code{post_event} will be run in the order in which they
23691 were posted; however, there is no way to know when they will be
23692 processed relative to other events inside @value{GDBN}.
23694 @value{GDBN} is not thread-safe. If your Python program uses multiple
23695 threads, you must be careful to only call @value{GDBN}-specific
23696 functions in the main @value{GDBN} thread. @code{post_event} ensures
23700 (@value{GDBP}) python
23704 > def __init__(self, message):
23705 > self.message = message;
23706 > def __call__(self):
23707 > gdb.write(self.message)
23709 >class MyThread1 (threading.Thread):
23711 > gdb.post_event(Writer("Hello "))
23713 >class MyThread2 (threading.Thread):
23715 > gdb.post_event(Writer("World\n"))
23717 >MyThread1().start()
23718 >MyThread2().start()
23720 (@value{GDBP}) Hello World
23725 @defun gdb.write (string @r{[}, stream{]})
23726 Print a string to @value{GDBN}'s paginated output stream. The
23727 optional @var{stream} determines the stream to print to. The default
23728 stream is @value{GDBN}'s standard output stream. Possible stream
23735 @value{GDBN}'s standard output stream.
23740 @value{GDBN}'s standard error stream.
23745 @value{GDBN}'s log stream (@pxref{Logging Output}).
23748 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23749 call this function and will automatically direct the output to the
23754 @defun gdb.flush ()
23755 Flush the buffer of a @value{GDBN} paginated stream so that the
23756 contents are displayed immediately. @value{GDBN} will flush the
23757 contents of a stream automatically when it encounters a newline in the
23758 buffer. The optional @var{stream} determines the stream to flush. The
23759 default stream is @value{GDBN}'s standard output stream. Possible
23766 @value{GDBN}'s standard output stream.
23771 @value{GDBN}'s standard error stream.
23776 @value{GDBN}'s log stream (@pxref{Logging Output}).
23780 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23781 call this function for the relevant stream.
23784 @findex gdb.target_charset
23785 @defun gdb.target_charset ()
23786 Return the name of the current target character set (@pxref{Character
23787 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23788 that @samp{auto} is never returned.
23791 @findex gdb.target_wide_charset
23792 @defun gdb.target_wide_charset ()
23793 Return the name of the current target wide character set
23794 (@pxref{Character Sets}). This differs from
23795 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23799 @findex gdb.solib_name
23800 @defun gdb.solib_name (address)
23801 Return the name of the shared library holding the given @var{address}
23802 as a string, or @code{None}.
23805 @findex gdb.decode_line
23806 @defun gdb.decode_line @r{[}expression@r{]}
23807 Return locations of the line specified by @var{expression}, or of the
23808 current line if no argument was given. This function returns a Python
23809 tuple containing two elements. The first element contains a string
23810 holding any unparsed section of @var{expression} (or @code{None} if
23811 the expression has been fully parsed). The second element contains
23812 either @code{None} or another tuple that contains all the locations
23813 that match the expression represented as @code{gdb.Symtab_and_line}
23814 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23815 provided, it is decoded the way that @value{GDBN}'s inbuilt
23816 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23819 @defun gdb.prompt_hook (current_prompt)
23820 @anchor{prompt_hook}
23822 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23823 assigned to this operation before a prompt is displayed by
23826 The parameter @code{current_prompt} contains the current @value{GDBN}
23827 prompt. This method must return a Python string, or @code{None}. If
23828 a string is returned, the @value{GDBN} prompt will be set to that
23829 string. If @code{None} is returned, @value{GDBN} will continue to use
23830 the current prompt.
23832 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23833 such as those used by readline for command input, and annotation
23834 related prompts are prohibited from being changed.
23837 @node Exception Handling
23838 @subsubsection Exception Handling
23839 @cindex python exceptions
23840 @cindex exceptions, python
23842 When executing the @code{python} command, Python exceptions
23843 uncaught within the Python code are translated to calls to
23844 @value{GDBN} error-reporting mechanism. If the command that called
23845 @code{python} does not handle the error, @value{GDBN} will
23846 terminate it and print an error message containing the Python
23847 exception name, the associated value, and the Python call stack
23848 backtrace at the point where the exception was raised. Example:
23851 (@value{GDBP}) python print foo
23852 Traceback (most recent call last):
23853 File "<string>", line 1, in <module>
23854 NameError: name 'foo' is not defined
23857 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23858 Python code are converted to Python exceptions. The type of the
23859 Python exception depends on the error.
23863 This is the base class for most exceptions generated by @value{GDBN}.
23864 It is derived from @code{RuntimeError}, for compatibility with earlier
23865 versions of @value{GDBN}.
23867 If an error occurring in @value{GDBN} does not fit into some more
23868 specific category, then the generated exception will have this type.
23870 @item gdb.MemoryError
23871 This is a subclass of @code{gdb.error} which is thrown when an
23872 operation tried to access invalid memory in the inferior.
23874 @item KeyboardInterrupt
23875 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23876 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23879 In all cases, your exception handler will see the @value{GDBN} error
23880 message as its value and the Python call stack backtrace at the Python
23881 statement closest to where the @value{GDBN} error occured as the
23884 @findex gdb.GdbError
23885 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23886 it is useful to be able to throw an exception that doesn't cause a
23887 traceback to be printed. For example, the user may have invoked the
23888 command incorrectly. Use the @code{gdb.GdbError} exception
23889 to handle this case. Example:
23893 >class HelloWorld (gdb.Command):
23894 > """Greet the whole world."""
23895 > def __init__ (self):
23896 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23897 > def invoke (self, args, from_tty):
23898 > argv = gdb.string_to_argv (args)
23899 > if len (argv) != 0:
23900 > raise gdb.GdbError ("hello-world takes no arguments")
23901 > print "Hello, World!"
23904 (gdb) hello-world 42
23905 hello-world takes no arguments
23908 @node Values From Inferior
23909 @subsubsection Values From Inferior
23910 @cindex values from inferior, with Python
23911 @cindex python, working with values from inferior
23913 @cindex @code{gdb.Value}
23914 @value{GDBN} provides values it obtains from the inferior program in
23915 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23916 for its internal bookkeeping of the inferior's values, and for
23917 fetching values when necessary.
23919 Inferior values that are simple scalars can be used directly in
23920 Python expressions that are valid for the value's data type. Here's
23921 an example for an integer or floating-point value @code{some_val}:
23928 As result of this, @code{bar} will also be a @code{gdb.Value} object
23929 whose values are of the same type as those of @code{some_val}.
23931 Inferior values that are structures or instances of some class can
23932 be accessed using the Python @dfn{dictionary syntax}. For example, if
23933 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23934 can access its @code{foo} element with:
23937 bar = some_val['foo']
23940 Again, @code{bar} will also be a @code{gdb.Value} object.
23942 A @code{gdb.Value} that represents a function can be executed via
23943 inferior function call. Any arguments provided to the call must match
23944 the function's prototype, and must be provided in the order specified
23947 For example, @code{some_val} is a @code{gdb.Value} instance
23948 representing a function that takes two integers as arguments. To
23949 execute this function, call it like so:
23952 result = some_val (10,20)
23955 Any values returned from a function call will be stored as a
23958 The following attributes are provided:
23960 @defvar Value.address
23961 If this object is addressable, this read-only attribute holds a
23962 @code{gdb.Value} object representing the address. Otherwise,
23963 this attribute holds @code{None}.
23966 @cindex optimized out value in Python
23967 @defvar Value.is_optimized_out
23968 This read-only boolean attribute is true if the compiler optimized out
23969 this value, thus it is not available for fetching from the inferior.
23973 The type of this @code{gdb.Value}. The value of this attribute is a
23974 @code{gdb.Type} object (@pxref{Types In Python}).
23977 @defvar Value.dynamic_type
23978 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23979 type information (@acronym{RTTI}) to determine the dynamic type of the
23980 value. If this value is of class type, it will return the class in
23981 which the value is embedded, if any. If this value is of pointer or
23982 reference to a class type, it will compute the dynamic type of the
23983 referenced object, and return a pointer or reference to that type,
23984 respectively. In all other cases, it will return the value's static
23987 Note that this feature will only work when debugging a C@t{++} program
23988 that includes @acronym{RTTI} for the object in question. Otherwise,
23989 it will just return the static type of the value as in @kbd{ptype foo}
23990 (@pxref{Symbols, ptype}).
23993 @defvar Value.is_lazy
23994 The value of this read-only boolean attribute is @code{True} if this
23995 @code{gdb.Value} has not yet been fetched from the inferior.
23996 @value{GDBN} does not fetch values until necessary, for efficiency.
24000 myval = gdb.parse_and_eval ('somevar')
24003 The value of @code{somevar} is not fetched at this time. It will be
24004 fetched when the value is needed, or when the @code{fetch_lazy}
24008 The following methods are provided:
24010 @defun Value.__init__ (@var{val})
24011 Many Python values can be converted directly to a @code{gdb.Value} via
24012 this object initializer. Specifically:
24015 @item Python boolean
24016 A Python boolean is converted to the boolean type from the current
24019 @item Python integer
24020 A Python integer is converted to the C @code{long} type for the
24021 current architecture.
24024 A Python long is converted to the C @code{long long} type for the
24025 current architecture.
24028 A Python float is converted to the C @code{double} type for the
24029 current architecture.
24031 @item Python string
24032 A Python string is converted to a target string, using the current
24035 @item @code{gdb.Value}
24036 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
24038 @item @code{gdb.LazyString}
24039 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
24040 Python}), then the lazy string's @code{value} method is called, and
24041 its result is used.
24045 @defun Value.cast (type)
24046 Return a new instance of @code{gdb.Value} that is the result of
24047 casting this instance to the type described by @var{type}, which must
24048 be a @code{gdb.Type} object. If the cast cannot be performed for some
24049 reason, this method throws an exception.
24052 @defun Value.dereference ()
24053 For pointer data types, this method returns a new @code{gdb.Value} object
24054 whose contents is the object pointed to by the pointer. For example, if
24055 @code{foo} is a C pointer to an @code{int}, declared in your C program as
24062 then you can use the corresponding @code{gdb.Value} to access what
24063 @code{foo} points to like this:
24066 bar = foo.dereference ()
24069 The result @code{bar} will be a @code{gdb.Value} object holding the
24070 value pointed to by @code{foo}.
24072 A similar function @code{Value.referenced_value} exists which also
24073 returns @code{gdb.Value} objects corresonding to the values pointed to
24074 by pointer values (and additionally, values referenced by reference
24075 values). However, the behavior of @code{Value.dereference}
24076 differs from @code{Value.referenced_value} by the fact that the
24077 behavior of @code{Value.dereference} is identical to applying the C
24078 unary operator @code{*} on a given value. For example, consider a
24079 reference to a pointer @code{ptrref}, declared in your C@t{++} program
24083 typedef int *intptr;
24087 intptr &ptrref = ptr;
24090 Though @code{ptrref} is a reference value, one can apply the method
24091 @code{Value.dereference} to the @code{gdb.Value} object corresponding
24092 to it and obtain a @code{gdb.Value} which is identical to that
24093 corresponding to @code{val}. However, if you apply the method
24094 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
24095 object identical to that corresponding to @code{ptr}.
24098 py_ptrref = gdb.parse_and_eval ("ptrref")
24099 py_val = py_ptrref.dereference ()
24100 py_ptr = py_ptrref.referenced_value ()
24103 The @code{gdb.Value} object @code{py_val} is identical to that
24104 corresponding to @code{val}, and @code{py_ptr} is identical to that
24105 corresponding to @code{ptr}. In general, @code{Value.dereference} can
24106 be applied whenever the C unary operator @code{*} can be applied
24107 to the corresponding C value. For those cases where applying both
24108 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
24109 the results obtained need not be identical (as we have seen in the above
24110 example). The results are however identical when applied on
24111 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
24112 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
24115 @defun Value.referenced_value ()
24116 For pointer or reference data types, this method returns a new
24117 @code{gdb.Value} object corresponding to the value referenced by the
24118 pointer/reference value. For pointer data types,
24119 @code{Value.dereference} and @code{Value.referenced_value} produce
24120 identical results. The difference between these methods is that
24121 @code{Value.dereference} cannot get the values referenced by reference
24122 values. For example, consider a reference to an @code{int}, declared
24123 in your C@t{++} program as
24131 then applying @code{Value.dereference} to the @code{gdb.Value} object
24132 corresponding to @code{ref} will result in an error, while applying
24133 @code{Value.referenced_value} will result in a @code{gdb.Value} object
24134 identical to that corresponding to @code{val}.
24137 py_ref = gdb.parse_and_eval ("ref")
24138 er_ref = py_ref.dereference () # Results in error
24139 py_val = py_ref.referenced_value () # Returns the referenced value
24142 The @code{gdb.Value} object @code{py_val} is identical to that
24143 corresponding to @code{val}.
24146 @defun Value.dynamic_cast (type)
24147 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
24148 operator were used. Consult a C@t{++} reference for details.
24151 @defun Value.reinterpret_cast (type)
24152 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
24153 operator were used. Consult a C@t{++} reference for details.
24156 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
24157 If this @code{gdb.Value} represents a string, then this method
24158 converts the contents to a Python string. Otherwise, this method will
24159 throw an exception.
24161 Strings are recognized in a language-specific way; whether a given
24162 @code{gdb.Value} represents a string is determined by the current
24165 For C-like languages, a value is a string if it is a pointer to or an
24166 array of characters or ints. The string is assumed to be terminated
24167 by a zero of the appropriate width. However if the optional length
24168 argument is given, the string will be converted to that given length,
24169 ignoring any embedded zeros that the string may contain.
24171 If the optional @var{encoding} argument is given, it must be a string
24172 naming the encoding of the string in the @code{gdb.Value}, such as
24173 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
24174 the same encodings as the corresponding argument to Python's
24175 @code{string.decode} method, and the Python codec machinery will be used
24176 to convert the string. If @var{encoding} is not given, or if
24177 @var{encoding} is the empty string, then either the @code{target-charset}
24178 (@pxref{Character Sets}) will be used, or a language-specific encoding
24179 will be used, if the current language is able to supply one.
24181 The optional @var{errors} argument is the same as the corresponding
24182 argument to Python's @code{string.decode} method.
24184 If the optional @var{length} argument is given, the string will be
24185 fetched and converted to the given length.
24188 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
24189 If this @code{gdb.Value} represents a string, then this method
24190 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
24191 In Python}). Otherwise, this method will throw an exception.
24193 If the optional @var{encoding} argument is given, it must be a string
24194 naming the encoding of the @code{gdb.LazyString}. Some examples are:
24195 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
24196 @var{encoding} argument is an encoding that @value{GDBN} does
24197 recognize, @value{GDBN} will raise an error.
24199 When a lazy string is printed, the @value{GDBN} encoding machinery is
24200 used to convert the string during printing. If the optional
24201 @var{encoding} argument is not provided, or is an empty string,
24202 @value{GDBN} will automatically select the encoding most suitable for
24203 the string type. For further information on encoding in @value{GDBN}
24204 please see @ref{Character Sets}.
24206 If the optional @var{length} argument is given, the string will be
24207 fetched and encoded to the length of characters specified. If
24208 the @var{length} argument is not provided, the string will be fetched
24209 and encoded until a null of appropriate width is found.
24212 @defun Value.fetch_lazy ()
24213 If the @code{gdb.Value} object is currently a lazy value
24214 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
24215 fetched from the inferior. Any errors that occur in the process
24216 will produce a Python exception.
24218 If the @code{gdb.Value} object is not a lazy value, this method
24221 This method does not return a value.
24225 @node Types In Python
24226 @subsubsection Types In Python
24227 @cindex types in Python
24228 @cindex Python, working with types
24231 @value{GDBN} represents types from the inferior using the class
24234 The following type-related functions are available in the @code{gdb}
24237 @findex gdb.lookup_type
24238 @defun gdb.lookup_type (name @r{[}, block@r{]})
24239 This function looks up a type by name. @var{name} is the name of the
24240 type to look up. It must be a string.
24242 If @var{block} is given, then @var{name} is looked up in that scope.
24243 Otherwise, it is searched for globally.
24245 Ordinarily, this function will return an instance of @code{gdb.Type}.
24246 If the named type cannot be found, it will throw an exception.
24249 If the type is a structure or class type, or an enum type, the fields
24250 of that type can be accessed using the Python @dfn{dictionary syntax}.
24251 For example, if @code{some_type} is a @code{gdb.Type} instance holding
24252 a structure type, you can access its @code{foo} field with:
24255 bar = some_type['foo']
24258 @code{bar} will be a @code{gdb.Field} object; see below under the
24259 description of the @code{Type.fields} method for a description of the
24260 @code{gdb.Field} class.
24262 An instance of @code{Type} has the following attributes:
24265 The type code for this type. The type code will be one of the
24266 @code{TYPE_CODE_} constants defined below.
24269 @defvar Type.sizeof
24270 The size of this type, in target @code{char} units. Usually, a
24271 target's @code{char} type will be an 8-bit byte. However, on some
24272 unusual platforms, this type may have a different size.
24276 The tag name for this type. The tag name is the name after
24277 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
24278 languages have this concept. If this type has no tag name, then
24279 @code{None} is returned.
24282 The following methods are provided:
24284 @defun Type.fields ()
24285 For structure and union types, this method returns the fields. Range
24286 types have two fields, the minimum and maximum values. Enum types
24287 have one field per enum constant. Function and method types have one
24288 field per parameter. The base types of C@t{++} classes are also
24289 represented as fields. If the type has no fields, or does not fit
24290 into one of these categories, an empty sequence will be returned.
24292 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
24295 This attribute is not available for @code{static} fields (as in
24296 C@t{++} or Java). For non-@code{static} fields, the value is the bit
24297 position of the field. For @code{enum} fields, the value is the
24298 enumeration member's integer representation.
24301 The name of the field, or @code{None} for anonymous fields.
24304 This is @code{True} if the field is artificial, usually meaning that
24305 it was provided by the compiler and not the user. This attribute is
24306 always provided, and is @code{False} if the field is not artificial.
24308 @item is_base_class
24309 This is @code{True} if the field represents a base class of a C@t{++}
24310 structure. This attribute is always provided, and is @code{False}
24311 if the field is not a base class of the type that is the argument of
24312 @code{fields}, or if that type was not a C@t{++} class.
24315 If the field is packed, or is a bitfield, then this will have a
24316 non-zero value, which is the size of the field in bits. Otherwise,
24317 this will be zero; in this case the field's size is given by its type.
24320 The type of the field. This is usually an instance of @code{Type},
24321 but it can be @code{None} in some situations.
24325 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24326 Return a new @code{gdb.Type} object which represents an array of this
24327 type. If one argument is given, it is the inclusive upper bound of
24328 the array; in this case the lower bound is zero. If two arguments are
24329 given, the first argument is the lower bound of the array, and the
24330 second argument is the upper bound of the array. An array's length
24331 must not be negative, but the bounds can be.
24334 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24335 Return a new @code{gdb.Type} object which represents a vector of this
24336 type. If one argument is given, it is the inclusive upper bound of
24337 the vector; in this case the lower bound is zero. If two arguments are
24338 given, the first argument is the lower bound of the vector, and the
24339 second argument is the upper bound of the vector. A vector's length
24340 must not be negative, but the bounds can be.
24342 The difference between an @code{array} and a @code{vector} is that
24343 arrays behave like in C: when used in expressions they decay to a pointer
24344 to the first element whereas vectors are treated as first class values.
24347 @defun Type.const ()
24348 Return a new @code{gdb.Type} object which represents a
24349 @code{const}-qualified variant of this type.
24352 @defun Type.volatile ()
24353 Return a new @code{gdb.Type} object which represents a
24354 @code{volatile}-qualified variant of this type.
24357 @defun Type.unqualified ()
24358 Return a new @code{gdb.Type} object which represents an unqualified
24359 variant of this type. That is, the result is neither @code{const} nor
24363 @defun Type.range ()
24364 Return a Python @code{Tuple} object that contains two elements: the
24365 low bound of the argument type and the high bound of that type. If
24366 the type does not have a range, @value{GDBN} will raise a
24367 @code{gdb.error} exception (@pxref{Exception Handling}).
24370 @defun Type.reference ()
24371 Return a new @code{gdb.Type} object which represents a reference to this
24375 @defun Type.pointer ()
24376 Return a new @code{gdb.Type} object which represents a pointer to this
24380 @defun Type.strip_typedefs ()
24381 Return a new @code{gdb.Type} that represents the real type,
24382 after removing all layers of typedefs.
24385 @defun Type.target ()
24386 Return a new @code{gdb.Type} object which represents the target type
24389 For a pointer type, the target type is the type of the pointed-to
24390 object. For an array type (meaning C-like arrays), the target type is
24391 the type of the elements of the array. For a function or method type,
24392 the target type is the type of the return value. For a complex type,
24393 the target type is the type of the elements. For a typedef, the
24394 target type is the aliased type.
24396 If the type does not have a target, this method will throw an
24400 @defun Type.template_argument (n @r{[}, block@r{]})
24401 If this @code{gdb.Type} is an instantiation of a template, this will
24402 return a new @code{gdb.Type} which represents the type of the
24403 @var{n}th template argument.
24405 If this @code{gdb.Type} is not a template type, this will throw an
24406 exception. Ordinarily, only C@t{++} code will have template types.
24408 If @var{block} is given, then @var{name} is looked up in that scope.
24409 Otherwise, it is searched for globally.
24413 Each type has a code, which indicates what category this type falls
24414 into. The available type categories are represented by constants
24415 defined in the @code{gdb} module:
24418 @findex TYPE_CODE_PTR
24419 @findex gdb.TYPE_CODE_PTR
24420 @item gdb.TYPE_CODE_PTR
24421 The type is a pointer.
24423 @findex TYPE_CODE_ARRAY
24424 @findex gdb.TYPE_CODE_ARRAY
24425 @item gdb.TYPE_CODE_ARRAY
24426 The type is an array.
24428 @findex TYPE_CODE_STRUCT
24429 @findex gdb.TYPE_CODE_STRUCT
24430 @item gdb.TYPE_CODE_STRUCT
24431 The type is a structure.
24433 @findex TYPE_CODE_UNION
24434 @findex gdb.TYPE_CODE_UNION
24435 @item gdb.TYPE_CODE_UNION
24436 The type is a union.
24438 @findex TYPE_CODE_ENUM
24439 @findex gdb.TYPE_CODE_ENUM
24440 @item gdb.TYPE_CODE_ENUM
24441 The type is an enum.
24443 @findex TYPE_CODE_FLAGS
24444 @findex gdb.TYPE_CODE_FLAGS
24445 @item gdb.TYPE_CODE_FLAGS
24446 A bit flags type, used for things such as status registers.
24448 @findex TYPE_CODE_FUNC
24449 @findex gdb.TYPE_CODE_FUNC
24450 @item gdb.TYPE_CODE_FUNC
24451 The type is a function.
24453 @findex TYPE_CODE_INT
24454 @findex gdb.TYPE_CODE_INT
24455 @item gdb.TYPE_CODE_INT
24456 The type is an integer type.
24458 @findex TYPE_CODE_FLT
24459 @findex gdb.TYPE_CODE_FLT
24460 @item gdb.TYPE_CODE_FLT
24461 A floating point type.
24463 @findex TYPE_CODE_VOID
24464 @findex gdb.TYPE_CODE_VOID
24465 @item gdb.TYPE_CODE_VOID
24466 The special type @code{void}.
24468 @findex TYPE_CODE_SET
24469 @findex gdb.TYPE_CODE_SET
24470 @item gdb.TYPE_CODE_SET
24473 @findex TYPE_CODE_RANGE
24474 @findex gdb.TYPE_CODE_RANGE
24475 @item gdb.TYPE_CODE_RANGE
24476 A range type, that is, an integer type with bounds.
24478 @findex TYPE_CODE_STRING
24479 @findex gdb.TYPE_CODE_STRING
24480 @item gdb.TYPE_CODE_STRING
24481 A string type. Note that this is only used for certain languages with
24482 language-defined string types; C strings are not represented this way.
24484 @findex TYPE_CODE_BITSTRING
24485 @findex gdb.TYPE_CODE_BITSTRING
24486 @item gdb.TYPE_CODE_BITSTRING
24487 A string of bits. It is deprecated.
24489 @findex TYPE_CODE_ERROR
24490 @findex gdb.TYPE_CODE_ERROR
24491 @item gdb.TYPE_CODE_ERROR
24492 An unknown or erroneous type.
24494 @findex TYPE_CODE_METHOD
24495 @findex gdb.TYPE_CODE_METHOD
24496 @item gdb.TYPE_CODE_METHOD
24497 A method type, as found in C@t{++} or Java.
24499 @findex TYPE_CODE_METHODPTR
24500 @findex gdb.TYPE_CODE_METHODPTR
24501 @item gdb.TYPE_CODE_METHODPTR
24502 A pointer-to-member-function.
24504 @findex TYPE_CODE_MEMBERPTR
24505 @findex gdb.TYPE_CODE_MEMBERPTR
24506 @item gdb.TYPE_CODE_MEMBERPTR
24507 A pointer-to-member.
24509 @findex TYPE_CODE_REF
24510 @findex gdb.TYPE_CODE_REF
24511 @item gdb.TYPE_CODE_REF
24514 @findex TYPE_CODE_CHAR
24515 @findex gdb.TYPE_CODE_CHAR
24516 @item gdb.TYPE_CODE_CHAR
24519 @findex TYPE_CODE_BOOL
24520 @findex gdb.TYPE_CODE_BOOL
24521 @item gdb.TYPE_CODE_BOOL
24524 @findex TYPE_CODE_COMPLEX
24525 @findex gdb.TYPE_CODE_COMPLEX
24526 @item gdb.TYPE_CODE_COMPLEX
24527 A complex float type.
24529 @findex TYPE_CODE_TYPEDEF
24530 @findex gdb.TYPE_CODE_TYPEDEF
24531 @item gdb.TYPE_CODE_TYPEDEF
24532 A typedef to some other type.
24534 @findex TYPE_CODE_NAMESPACE
24535 @findex gdb.TYPE_CODE_NAMESPACE
24536 @item gdb.TYPE_CODE_NAMESPACE
24537 A C@t{++} namespace.
24539 @findex TYPE_CODE_DECFLOAT
24540 @findex gdb.TYPE_CODE_DECFLOAT
24541 @item gdb.TYPE_CODE_DECFLOAT
24542 A decimal floating point type.
24544 @findex TYPE_CODE_INTERNAL_FUNCTION
24545 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24546 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24547 A function internal to @value{GDBN}. This is the type used to represent
24548 convenience functions.
24551 Further support for types is provided in the @code{gdb.types}
24552 Python module (@pxref{gdb.types}).
24554 @node Pretty Printing API
24555 @subsubsection Pretty Printing API
24557 An example output is provided (@pxref{Pretty Printing}).
24559 A pretty-printer is just an object that holds a value and implements a
24560 specific interface, defined here.
24562 @defun pretty_printer.children (self)
24563 @value{GDBN} will call this method on a pretty-printer to compute the
24564 children of the pretty-printer's value.
24566 This method must return an object conforming to the Python iterator
24567 protocol. Each item returned by the iterator must be a tuple holding
24568 two elements. The first element is the ``name'' of the child; the
24569 second element is the child's value. The value can be any Python
24570 object which is convertible to a @value{GDBN} value.
24572 This method is optional. If it does not exist, @value{GDBN} will act
24573 as though the value has no children.
24576 @defun pretty_printer.display_hint (self)
24577 The CLI may call this method and use its result to change the
24578 formatting of a value. The result will also be supplied to an MI
24579 consumer as a @samp{displayhint} attribute of the variable being
24582 This method is optional. If it does exist, this method must return a
24585 Some display hints are predefined by @value{GDBN}:
24589 Indicate that the object being printed is ``array-like''. The CLI
24590 uses this to respect parameters such as @code{set print elements} and
24591 @code{set print array}.
24594 Indicate that the object being printed is ``map-like'', and that the
24595 children of this value can be assumed to alternate between keys and
24599 Indicate that the object being printed is ``string-like''. If the
24600 printer's @code{to_string} method returns a Python string of some
24601 kind, then @value{GDBN} will call its internal language-specific
24602 string-printing function to format the string. For the CLI this means
24603 adding quotation marks, possibly escaping some characters, respecting
24604 @code{set print elements}, and the like.
24608 @defun pretty_printer.to_string (self)
24609 @value{GDBN} will call this method to display the string
24610 representation of the value passed to the object's constructor.
24612 When printing from the CLI, if the @code{to_string} method exists,
24613 then @value{GDBN} will prepend its result to the values returned by
24614 @code{children}. Exactly how this formatting is done is dependent on
24615 the display hint, and may change as more hints are added. Also,
24616 depending on the print settings (@pxref{Print Settings}), the CLI may
24617 print just the result of @code{to_string} in a stack trace, omitting
24618 the result of @code{children}.
24620 If this method returns a string, it is printed verbatim.
24622 Otherwise, if this method returns an instance of @code{gdb.Value},
24623 then @value{GDBN} prints this value. This may result in a call to
24624 another pretty-printer.
24626 If instead the method returns a Python value which is convertible to a
24627 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24628 the resulting value. Again, this may result in a call to another
24629 pretty-printer. Python scalars (integers, floats, and booleans) and
24630 strings are convertible to @code{gdb.Value}; other types are not.
24632 Finally, if this method returns @code{None} then no further operations
24633 are peformed in this method and nothing is printed.
24635 If the result is not one of these types, an exception is raised.
24638 @value{GDBN} provides a function which can be used to look up the
24639 default pretty-printer for a @code{gdb.Value}:
24641 @findex gdb.default_visualizer
24642 @defun gdb.default_visualizer (value)
24643 This function takes a @code{gdb.Value} object as an argument. If a
24644 pretty-printer for this value exists, then it is returned. If no such
24645 printer exists, then this returns @code{None}.
24648 @node Selecting Pretty-Printers
24649 @subsubsection Selecting Pretty-Printers
24651 The Python list @code{gdb.pretty_printers} contains an array of
24652 functions or callable objects that have been registered via addition
24653 as a pretty-printer. Printers in this list are called @code{global}
24654 printers, they're available when debugging all inferiors.
24655 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24656 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24659 Each function on these lists is passed a single @code{gdb.Value}
24660 argument and should return a pretty-printer object conforming to the
24661 interface definition above (@pxref{Pretty Printing API}). If a function
24662 cannot create a pretty-printer for the value, it should return
24665 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24666 @code{gdb.Objfile} in the current program space and iteratively calls
24667 each enabled lookup routine in the list for that @code{gdb.Objfile}
24668 until it receives a pretty-printer object.
24669 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24670 searches the pretty-printer list of the current program space,
24671 calling each enabled function until an object is returned.
24672 After these lists have been exhausted, it tries the global
24673 @code{gdb.pretty_printers} list, again calling each enabled function until an
24674 object is returned.
24676 The order in which the objfiles are searched is not specified. For a
24677 given list, functions are always invoked from the head of the list,
24678 and iterated over sequentially until the end of the list, or a printer
24679 object is returned.
24681 For various reasons a pretty-printer may not work.
24682 For example, the underlying data structure may have changed and
24683 the pretty-printer is out of date.
24685 The consequences of a broken pretty-printer are severe enough that
24686 @value{GDBN} provides support for enabling and disabling individual
24687 printers. For example, if @code{print frame-arguments} is on,
24688 a backtrace can become highly illegible if any argument is printed
24689 with a broken printer.
24691 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24692 attribute to the registered function or callable object. If this attribute
24693 is present and its value is @code{False}, the printer is disabled, otherwise
24694 the printer is enabled.
24696 @node Writing a Pretty-Printer
24697 @subsubsection Writing a Pretty-Printer
24698 @cindex writing a pretty-printer
24700 A pretty-printer consists of two parts: a lookup function to detect
24701 if the type is supported, and the printer itself.
24703 Here is an example showing how a @code{std::string} printer might be
24704 written. @xref{Pretty Printing API}, for details on the API this class
24708 class StdStringPrinter(object):
24709 "Print a std::string"
24711 def __init__(self, val):
24714 def to_string(self):
24715 return self.val['_M_dataplus']['_M_p']
24717 def display_hint(self):
24721 And here is an example showing how a lookup function for the printer
24722 example above might be written.
24725 def str_lookup_function(val):
24726 lookup_tag = val.type.tag
24727 if lookup_tag == None:
24729 regex = re.compile("^std::basic_string<char,.*>$")
24730 if regex.match(lookup_tag):
24731 return StdStringPrinter(val)
24735 The example lookup function extracts the value's type, and attempts to
24736 match it to a type that it can pretty-print. If it is a type the
24737 printer can pretty-print, it will return a printer object. If not, it
24738 returns @code{None}.
24740 We recommend that you put your core pretty-printers into a Python
24741 package. If your pretty-printers are for use with a library, we
24742 further recommend embedding a version number into the package name.
24743 This practice will enable @value{GDBN} to load multiple versions of
24744 your pretty-printers at the same time, because they will have
24747 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24748 can be evaluated multiple times without changing its meaning. An
24749 ideal auto-load file will consist solely of @code{import}s of your
24750 printer modules, followed by a call to a register pretty-printers with
24751 the current objfile.
24753 Taken as a whole, this approach will scale nicely to multiple
24754 inferiors, each potentially using a different library version.
24755 Embedding a version number in the Python package name will ensure that
24756 @value{GDBN} is able to load both sets of printers simultaneously.
24757 Then, because the search for pretty-printers is done by objfile, and
24758 because your auto-loaded code took care to register your library's
24759 printers with a specific objfile, @value{GDBN} will find the correct
24760 printers for the specific version of the library used by each
24763 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24764 this code might appear in @code{gdb.libstdcxx.v6}:
24767 def register_printers(objfile):
24768 objfile.pretty_printers.append(str_lookup_function)
24772 And then the corresponding contents of the auto-load file would be:
24775 import gdb.libstdcxx.v6
24776 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24779 The previous example illustrates a basic pretty-printer.
24780 There are a few things that can be improved on.
24781 The printer doesn't have a name, making it hard to identify in a
24782 list of installed printers. The lookup function has a name, but
24783 lookup functions can have arbitrary, even identical, names.
24785 Second, the printer only handles one type, whereas a library typically has
24786 several types. One could install a lookup function for each desired type
24787 in the library, but one could also have a single lookup function recognize
24788 several types. The latter is the conventional way this is handled.
24789 If a pretty-printer can handle multiple data types, then its
24790 @dfn{subprinters} are the printers for the individual data types.
24792 The @code{gdb.printing} module provides a formal way of solving these
24793 problems (@pxref{gdb.printing}).
24794 Here is another example that handles multiple types.
24796 These are the types we are going to pretty-print:
24799 struct foo @{ int a, b; @};
24800 struct bar @{ struct foo x, y; @};
24803 Here are the printers:
24807 """Print a foo object."""
24809 def __init__(self, val):
24812 def to_string(self):
24813 return ("a=<" + str(self.val["a"]) +
24814 "> b=<" + str(self.val["b"]) + ">")
24817 """Print a bar object."""
24819 def __init__(self, val):
24822 def to_string(self):
24823 return ("x=<" + str(self.val["x"]) +
24824 "> y=<" + str(self.val["y"]) + ">")
24827 This example doesn't need a lookup function, that is handled by the
24828 @code{gdb.printing} module. Instead a function is provided to build up
24829 the object that handles the lookup.
24832 import gdb.printing
24834 def build_pretty_printer():
24835 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24837 pp.add_printer('foo', '^foo$', fooPrinter)
24838 pp.add_printer('bar', '^bar$', barPrinter)
24842 And here is the autoload support:
24845 import gdb.printing
24847 gdb.printing.register_pretty_printer(
24848 gdb.current_objfile(),
24849 my_library.build_pretty_printer())
24852 Finally, when this printer is loaded into @value{GDBN}, here is the
24853 corresponding output of @samp{info pretty-printer}:
24856 (gdb) info pretty-printer
24863 @node Type Printing API
24864 @subsubsection Type Printing API
24865 @cindex type printing API for Python
24867 @value{GDBN} provides a way for Python code to customize type display.
24868 This is mainly useful for substituting canonical typedef names for
24871 @cindex type printer
24872 A @dfn{type printer} is just a Python object conforming to a certain
24873 protocol. A simple base class implementing the protocol is provided;
24874 see @ref{gdb.types}. A type printer must supply at least:
24876 @defivar type_printer enabled
24877 A boolean which is True if the printer is enabled, and False
24878 otherwise. This is manipulated by the @code{enable type-printer}
24879 and @code{disable type-printer} commands.
24882 @defivar type_printer name
24883 The name of the type printer. This must be a string. This is used by
24884 the @code{enable type-printer} and @code{disable type-printer}
24888 @defmethod type_printer instantiate (self)
24889 This is called by @value{GDBN} at the start of type-printing. It is
24890 only called if the type printer is enabled. This method must return a
24891 new object that supplies a @code{recognize} method, as described below.
24895 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24896 will compute a list of type recognizers. This is done by iterating
24897 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24898 followed by the per-progspace type printers (@pxref{Progspaces In
24899 Python}), and finally the global type printers.
24901 @value{GDBN} will call the @code{instantiate} method of each enabled
24902 type printer. If this method returns @code{None}, then the result is
24903 ignored; otherwise, it is appended to the list of recognizers.
24905 Then, when @value{GDBN} is going to display a type name, it iterates
24906 over the list of recognizers. For each one, it calls the recognition
24907 function, stopping if the function returns a non-@code{None} value.
24908 The recognition function is defined as:
24910 @defmethod type_recognizer recognize (self, type)
24911 If @var{type} is not recognized, return @code{None}. Otherwise,
24912 return a string which is to be printed as the name of @var{type}.
24913 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24917 @value{GDBN} uses this two-pass approach so that type printers can
24918 efficiently cache information without holding on to it too long. For
24919 example, it can be convenient to look up type information in a type
24920 printer and hold it for a recognizer's lifetime; if a single pass were
24921 done then type printers would have to make use of the event system in
24922 order to avoid holding information that could become stale as the
24925 @node Frame Filter API
24926 @subsubsection Filtering Frames.
24927 @cindex frame filters api
24929 Frame filters are Python objects that manipulate the visibility of a
24930 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
24933 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
24934 commands (@pxref{GDB/MI}), those that return a collection of frames
24935 are affected. The commands that work with frame filters are:
24937 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
24938 @code{-stack-list-frames}
24939 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
24940 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
24941 -stack-list-variables command}), @code{-stack-list-arguments}
24942 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
24943 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
24944 -stack-list-locals command}).
24946 A frame filter works by taking an iterator as an argument, applying
24947 actions to the contents of that iterator, and returning another
24948 iterator (or, possibly, the same iterator it was provided in the case
24949 where the filter does not perform any operations). Typically, frame
24950 filters utilize tools such as the Python's @code{itertools} module to
24951 work with and create new iterators from the source iterator.
24952 Regardless of how a filter chooses to apply actions, it must not alter
24953 the underlying @value{GDBN} frame or frames, or attempt to alter the
24954 call-stack within @value{GDBN}. This preserves data integrity within
24955 @value{GDBN}. Frame filters are executed on a priority basis and care
24956 should be taken that some frame filters may have been executed before,
24957 and that some frame filters will be executed after.
24959 An important consideration when designing frame filters, and well
24960 worth reflecting upon, is that frame filters should avoid unwinding
24961 the call stack if possible. Some stacks can run very deep, into the
24962 tens of thousands in some cases. To search every frame when a frame
24963 filter executes may be too expensive at that step. The frame filter
24964 cannot know how many frames it has to iterate over, and it may have to
24965 iterate through them all. This ends up duplicating effort as
24966 @value{GDBN} performs this iteration when it prints the frames. If
24967 the filter can defer unwinding frames until frame decorators are
24968 executed, after the last filter has executed, it should. @xref{Frame
24969 Decorator API}, for more information on decorators. Also, there are
24970 examples for both frame decorators and filters in later chapters.
24971 @xref{Writing a Frame Filter}, for more information.
24973 The Python dictionary @code{gdb.frame_filters} contains key/object
24974 pairings that comprise a frame filter. Frame filters in this
24975 dictionary are called @code{global} frame filters, and they are
24976 available when debugging all inferiors. These frame filters must
24977 register with the dictionary directly. In addition to the
24978 @code{global} dictionary, there are other dictionaries that are loaded
24979 with different inferiors via auto-loading (@pxref{Python
24980 Auto-loading}). The two other areas where frame filter dictionaries
24981 can be found are: @code{gdb.Progspace} which contains a
24982 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
24983 object which also contains a @code{frame_filters} dictionary
24986 When a command is executed from @value{GDBN} that is compatible with
24987 frame filters, @value{GDBN} combines the @code{global},
24988 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
24989 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
24990 several frames, and thus several object files, might be in use.
24991 @value{GDBN} then prunes any frame filter whose @code{enabled}
24992 attribute is @code{False}. This pruned list is then sorted according
24993 to the @code{priority} attribute in each filter.
24995 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
24996 creates an iterator which wraps each frame in the call stack in a
24997 @code{FrameDecorator} object, and calls each filter in order. The
24998 output from the previous filter will always be the input to the next
25001 Frame filters have a mandatory interface which each frame filter must
25002 implement, defined here:
25004 @defun FrameFilter.filter (iterator)
25005 @value{GDBN} will call this method on a frame filter when it has
25006 reached the order in the priority list for that filter.
25008 For example, if there are four frame filters:
25019 The order that the frame filters will be called is:
25022 Filter3 -> Filter2 -> Filter1 -> Filter4
25025 Note that the output from @code{Filter3} is passed to the input of
25026 @code{Filter2}, and so on.
25028 This @code{filter} method is passed a Python iterator. This iterator
25029 contains a sequence of frame decorators that wrap each
25030 @code{gdb.Frame}, or a frame decorator that wraps another frame
25031 decorator. The first filter that is executed in the sequence of frame
25032 filters will receive an iterator entirely comprised of default
25033 @code{FrameDecorator} objects. However, after each frame filter is
25034 executed, the previous frame filter may have wrapped some or all of
25035 the frame decorators with their own frame decorator. As frame
25036 decorators must also conform to a mandatory interface, these
25037 decorators can be assumed to act in a uniform manner (@pxref{Frame
25040 This method must return an object conforming to the Python iterator
25041 protocol. Each item in the iterator must be an object conforming to
25042 the frame decorator interface. If a frame filter does not wish to
25043 perform any operations on this iterator, it should return that
25044 iterator untouched.
25046 This method is not optional. If it does not exist, @value{GDBN} will
25047 raise and print an error.
25050 @defvar FrameFilter.name
25051 The @code{name} attribute must be Python string which contains the
25052 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
25053 Management}). This attribute may contain any combination of letters
25054 or numbers. Care should be taken to ensure that it is unique. This
25055 attribute is mandatory.
25058 @defvar FrameFilter.enabled
25059 The @code{enabled} attribute must be Python boolean. This attribute
25060 indicates to @value{GDBN} whether the frame filter is enabled, and
25061 should be considered when frame filters are executed. If
25062 @code{enabled} is @code{True}, then the frame filter will be executed
25063 when any of the backtrace commands detailed earlier in this chapter
25064 are executed. If @code{enabled} is @code{False}, then the frame
25065 filter will not be executed. This attribute is mandatory.
25068 @defvar FrameFilter.priority
25069 The @code{priority} attribute must be Python integer. This attribute
25070 controls the order of execution in relation to other frame filters.
25071 There are no imposed limits on the range of @code{priority} other than
25072 it must be a valid integer. The higher the @code{priority} attribute,
25073 the sooner the frame filter will be executed in relation to other
25074 frame filters. Although @code{priority} can be negative, it is
25075 recommended practice to assume zero is the lowest priority that a
25076 frame filter can be assigned. Frame filters that have the same
25077 priority are executed in unsorted order in that priority slot. This
25078 attribute is mandatory.
25081 @node Frame Decorator API
25082 @subsubsection Decorating Frames.
25083 @cindex frame decorator api
25085 Frame decorators are sister objects to frame filters (@pxref{Frame
25086 Filter API}). Frame decorators are applied by a frame filter and can
25087 only be used in conjunction with frame filters.
25089 The purpose of a frame decorator is to customize the printed content
25090 of each @code{gdb.Frame} in commands where frame filters are executed.
25091 This concept is called decorating a frame. Frame decorators decorate
25092 a @code{gdb.Frame} with Python code contained within each API call.
25093 This separates the actual data contained in a @code{gdb.Frame} from
25094 the decorated data produced by a frame decorator. This abstraction is
25095 necessary to maintain integrity of the data contained in each
25098 Frame decorators have a mandatory interface, defined below.
25100 @value{GDBN} already contains a frame decorator called
25101 @code{FrameDecorator}. This contains substantial amounts of
25102 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
25103 recommended that other frame decorators inherit and extend this
25104 object, and only to override the methods needed.
25106 @defun FrameDecorator.elided (self)
25108 The @code{elided} method groups frames together in a hierarchical
25109 system. An example would be an interpreter, where multiple low-level
25110 frames make up a single call in the interpreted language. In this
25111 example, the frame filter would elide the low-level frames and present
25112 a single high-level frame, representing the call in the interpreted
25113 language, to the user.
25115 The @code{elided} function must return an iterable and this iterable
25116 must contain the frames that are being elided wrapped in a suitable
25117 frame decorator. If no frames are being elided this function may
25118 return an empty iterable, or @code{None}. Elided frames are indented
25119 from normal frames in a @code{CLI} backtrace, or in the case of
25120 @code{GDB/MI}, are placed in the @code{children} field of the eliding
25123 It is the frame filter's task to also filter out the elided frames from
25124 the source iterator. This will avoid printing the frame twice.
25127 @defun FrameDecorator.function (self)
25129 This method returns the name of the function in the frame that is to
25132 This method must return a Python string describing the function, or
25135 If this function returns @code{None}, @value{GDBN} will not print any
25136 data for this field.
25139 @defun FrameDecorator.address (self)
25141 This method returns the address of the frame that is to be printed.
25143 This method must return a Python numeric integer type of sufficient
25144 size to describe the address of the frame, or @code{None}.
25146 If this function returns a @code{None}, @value{GDBN} will not print
25147 any data for this field.
25150 @defun FrameDecorator.filename (self)
25152 This method returns the filename and path associated with this frame.
25154 This method must return a Python string containing the filename and
25155 the path to the object file backing the frame, or @code{None}.
25157 If this function returns a @code{None}, @value{GDBN} will not print
25158 any data for this field.
25161 @defun FrameDecorator.line (self):
25163 This method returns the line number associated with the current
25164 position within the function addressed by this frame.
25166 This method must return a Python integer type, or @code{None}.
25168 If this function returns a @code{None}, @value{GDBN} will not print
25169 any data for this field.
25172 @defun FrameDecorator.frame_args (self)
25173 @anchor{frame_args}
25175 This method must return an iterable, or @code{None}. Returning an
25176 empty iterable, or @code{None} means frame arguments will not be
25177 printed for this frame. This iterable must contain objects that
25178 implement two methods, described here.
25180 This object must implement a @code{argument} method which takes a
25181 single @code{self} parameter and must return a @code{gdb.Symbol}
25182 (@pxref{Symbols In Python}), or a Python string. The object must also
25183 implement a @code{value} method which takes a single @code{self}
25184 parameter and must return a @code{gdb.Value} (@pxref{Values From
25185 Inferior}), a Python value, or @code{None}. If the @code{value}
25186 method returns @code{None}, and the @code{argument} method returns a
25187 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
25188 the @code{gdb.Symbol} automatically.
25193 class SymValueWrapper():
25195 def __init__(self, symbol, value):
25205 class SomeFrameDecorator()
25208 def frame_args(self):
25211 block = self.inferior_frame.block()
25215 # Iterate over all symbols in a block. Only add
25216 # symbols that are arguments.
25218 if not sym.is_argument:
25220 args.append(SymValueWrapper(sym,None))
25222 # Add example synthetic argument.
25223 args.append(SymValueWrapper(``foo'', 42))
25229 @defun FrameDecorator.frame_locals (self)
25231 This method must return an iterable or @code{None}. Returning an
25232 empty iterable, or @code{None} means frame local arguments will not be
25233 printed for this frame.
25235 The object interface, the description of the various strategies for
25236 reading frame locals, and the example are largely similar to those
25237 described in the @code{frame_args} function, (@pxref{frame_args,,The
25238 frame filter frame_args function}). Below is a modified example:
25241 class SomeFrameDecorator()
25244 def frame_locals(self):
25247 block = self.inferior_frame.block()
25251 # Iterate over all symbols in a block. Add all
25252 # symbols, except arguments.
25254 if sym.is_argument:
25256 vars.append(SymValueWrapper(sym,None))
25258 # Add an example of a synthetic local variable.
25259 vars.append(SymValueWrapper(``bar'', 99))
25265 @defun FrameDecorator.inferior_frame (self):
25267 This method must return the underlying @code{gdb.Frame} that this
25268 frame decorator is decorating. @value{GDBN} requires the underlying
25269 frame for internal frame information to determine how to print certain
25270 values when printing a frame.
25273 @node Writing a Frame Filter
25274 @subsubsection Writing a Frame Filter
25275 @cindex writing a frame filter
25277 There are three basic elements that a frame filter must implement: it
25278 must correctly implement the documented interface (@pxref{Frame Filter
25279 API}), it must register itself with @value{GDBN}, and finally, it must
25280 decide if it is to work on the data provided by @value{GDBN}. In all
25281 cases, whether it works on the iterator or not, each frame filter must
25282 return an iterator. A bare-bones frame filter follows the pattern in
25283 the following example.
25288 class FrameFilter():
25290 def __init__(self):
25291 # Frame filter attribute creation.
25293 # 'name' is the name of the filter that GDB will display.
25295 # 'priority' is the priority of the filter relative to other
25298 # 'enabled' is a boolean that indicates whether this filter is
25299 # enabled and should be executed.
25302 self.priority = 100
25303 self.enabled = True
25305 # Register this frame filter with the global frame_filters
25307 gdb.frame_filters[self.name] = self
25309 def filter(self, frame_iter):
25310 # Just return the iterator.
25314 The frame filter in the example above implements the three
25315 requirements for all frame filters. It implements the API, self
25316 registers, and makes a decision on the iterator (in this case, it just
25317 returns the iterator untouched).
25319 The first step is attribute creation and assignment, and as shown in
25320 the comments the filter assigns the following attributes: @code{name},
25321 @code{priority} and whether the filter should be enabled with the
25322 @code{enabled} attribute.
25324 The second step is registering the frame filter with the dictionary or
25325 dictionaries that the frame filter has interest in. As shown in the
25326 comments, this filter just registers itself with the global dictionary
25327 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25328 is a dictionary that is initialized in the @code{gdb} module when
25329 @value{GDBN} starts. What dictionary a filter registers with is an
25330 important consideration. Generally, if a filter is specific to a set
25331 of code, it should be registered either in the @code{objfile} or
25332 @code{progspace} dictionaries as they are specific to the program
25333 currently loaded in @value{GDBN}. The global dictionary is always
25334 present in @value{GDBN} and is never unloaded. Any filters registered
25335 with the global dictionary will exist until @value{GDBN} exits. To
25336 avoid filters that may conflict, it is generally better to register
25337 frame filters against the dictionaries that more closely align with
25338 the usage of the filter currently in question. @xref{Python
25339 Auto-loading}, for further information on auto-loading Python scripts.
25341 @value{GDBN} takes a hands-off approach to frame filter registration,
25342 therefore it is the frame filter's responsibility to ensure
25343 registration has occurred, and that any exceptions are handled
25344 appropriately. In particular, you may wish to handle exceptions
25345 relating to Python dictionary key uniqueness. It is mandatory that
25346 the dictionary key is the same as frame filter's @code{name}
25347 attribute. When a user manages frame filters (@pxref{Frame Filter
25348 Management}), the names @value{GDBN} will display are those contained
25349 in the @code{name} attribute.
25351 The final step of this example is the implementation of the
25352 @code{filter} method. As shown in the example comments, we define the
25353 @code{filter} method and note that the method must take an iterator,
25354 and also must return an iterator. In this bare-bones example, the
25355 frame filter is not very useful as it just returns the iterator
25356 untouched. However this is a valid operation for frame filters that
25357 have the @code{enabled} attribute set, but decide not to operate on
25360 In the next example, the frame filter operates on all frames and
25361 utilizes a frame decorator to perform some work on the frames.
25362 @xref{Frame Decorator API}, for further information on the frame
25363 decorator interface.
25365 This example works on inlined frames. It highlights frames which are
25366 inlined by tagging them with an ``[inlined]'' tag. By applying a
25367 frame decorator to all frames with the Python @code{itertools imap}
25368 method, the example defers actions to the frame decorator. Frame
25369 decorators are only processed when @value{GDBN} prints the backtrace.
25371 This introduces a new decision making topic: whether to perform
25372 decision making operations at the filtering step, or at the printing
25373 step. In this example's approach, it does not perform any filtering
25374 decisions at the filtering step beyond mapping a frame decorator to
25375 each frame. This allows the actual decision making to be performed
25376 when each frame is printed. This is an important consideration, and
25377 well worth reflecting upon when designing a frame filter. An issue
25378 that frame filters should avoid is unwinding the stack if possible.
25379 Some stacks can run very deep, into the tens of thousands in some
25380 cases. To search every frame to determine if it is inlined ahead of
25381 time may be too expensive at the filtering step. The frame filter
25382 cannot know how many frames it has to iterate over, and it would have
25383 to iterate through them all. This ends up duplicating effort as
25384 @value{GDBN} performs this iteration when it prints the frames.
25386 In this example decision making can be deferred to the printing step.
25387 As each frame is printed, the frame decorator can examine each frame
25388 in turn when @value{GDBN} iterates. From a performance viewpoint,
25389 this is the most appropriate decision to make as it avoids duplicating
25390 the effort that the printing step would undertake anyway. Also, if
25391 there are many frame filters unwinding the stack during filtering, it
25392 can substantially delay the printing of the backtrace which will
25393 result in large memory usage, and a poor user experience.
25396 class InlineFilter():
25398 def __init__(self):
25399 self.name = "InlinedFrameFilter"
25400 self.priority = 100
25401 self.enabled = True
25402 gdb.frame_filters[self.name] = self
25404 def filter(self, frame_iter):
25405 frame_iter = itertools.imap(InlinedFrameDecorator,
25410 This frame filter is somewhat similar to the earlier example, except
25411 that the @code{filter} method applies a frame decorator object called
25412 @code{InlinedFrameDecorator} to each element in the iterator. The
25413 @code{imap} Python method is light-weight. It does not proactively
25414 iterate over the iterator, but rather creates a new iterator which
25415 wraps the existing one.
25417 Below is the frame decorator for this example.
25420 class InlinedFrameDecorator(FrameDecorator):
25422 def __init__(self, fobj):
25423 super(InlinedFrameDecorator, self).__init__(fobj)
25425 def function(self):
25426 frame = fobj.inferior_frame()
25427 name = str(frame.name())
25429 if frame.type() == gdb.INLINE_FRAME:
25430 name = name + " [inlined]"
25435 This frame decorator only defines and overrides the @code{function}
25436 method. It lets the supplied @code{FrameDecorator}, which is shipped
25437 with @value{GDBN}, perform the other work associated with printing
25440 The combination of these two objects create this output from a
25444 #0 0x004004e0 in bar () at inline.c:11
25445 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25446 #2 0x00400566 in main () at inline.c:31
25449 So in the case of this example, a frame decorator is applied to all
25450 frames, regardless of whether they may be inlined or not. As
25451 @value{GDBN} iterates over the iterator produced by the frame filters,
25452 @value{GDBN} executes each frame decorator which then makes a decision
25453 on what to print in the @code{function} callback. Using a strategy
25454 like this is a way to defer decisions on the frame content to printing
25457 @subheading Eliding Frames
25459 It might be that the above example is not desirable for representing
25460 inlined frames, and a hierarchical approach may be preferred. If we
25461 want to hierarchically represent frames, the @code{elided} frame
25462 decorator interface might be preferable.
25464 This example approaches the issue with the @code{elided} method. This
25465 example is quite long, but very simplistic. It is out-of-scope for
25466 this section to write a complete example that comprehensively covers
25467 all approaches of finding and printing inlined frames. However, this
25468 example illustrates the approach an author might use.
25470 This example comprises of three sections.
25473 class InlineFrameFilter():
25475 def __init__(self):
25476 self.name = "InlinedFrameFilter"
25477 self.priority = 100
25478 self.enabled = True
25479 gdb.frame_filters[self.name] = self
25481 def filter(self, frame_iter):
25482 return ElidingInlineIterator(frame_iter)
25485 This frame filter is very similar to the other examples. The only
25486 difference is this frame filter is wrapping the iterator provided to
25487 it (@code{frame_iter}) with a custom iterator called
25488 @code{ElidingInlineIterator}. This again defers actions to when
25489 @value{GDBN} prints the backtrace, as the iterator is not traversed
25492 The iterator for this example is as follows. It is in this section of
25493 the example where decisions are made on the content of the backtrace.
25496 class ElidingInlineIterator:
25497 def __init__(self, ii):
25498 self.input_iterator = ii
25500 def __iter__(self):
25504 frame = next(self.input_iterator)
25506 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25510 eliding_frame = next(self.input_iterator)
25511 except StopIteration:
25513 return ElidingFrameDecorator(eliding_frame, [frame])
25516 This iterator implements the Python iterator protocol. When the
25517 @code{next} function is called (when @value{GDBN} prints each frame),
25518 the iterator checks if this frame decorator, @code{frame}, is wrapping
25519 an inlined frame. If it is not, it returns the existing frame decorator
25520 untouched. If it is wrapping an inlined frame, it assumes that the
25521 inlined frame was contained within the next oldest frame,
25522 @code{eliding_frame}, which it fetches. It then creates and returns a
25523 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25524 elided frame, and the eliding frame.
25527 class ElidingInlineDecorator(FrameDecorator):
25529 def __init__(self, frame, elided_frames):
25530 super(ElidingInlineDecorator, self).__init__(frame)
25532 self.elided_frames = elided_frames
25535 return iter(self.elided_frames)
25538 This frame decorator overrides one function and returns the inlined
25539 frame in the @code{elided} method. As before it lets
25540 @code{FrameDecorator} do the rest of the work involved in printing
25541 this frame. This produces the following output.
25544 #0 0x004004e0 in bar () at inline.c:11
25545 #2 0x00400529 in main () at inline.c:25
25546 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25549 In that output, @code{max} which has been inlined into @code{main} is
25550 printed hierarchically. Another approach would be to combine the
25551 @code{function} method, and the @code{elided} method to both print a
25552 marker in the inlined frame, and also show the hierarchical
25555 @node Inferiors In Python
25556 @subsubsection Inferiors In Python
25557 @cindex inferiors in Python
25559 @findex gdb.Inferior
25560 Programs which are being run under @value{GDBN} are called inferiors
25561 (@pxref{Inferiors and Programs}). Python scripts can access
25562 information about and manipulate inferiors controlled by @value{GDBN}
25563 via objects of the @code{gdb.Inferior} class.
25565 The following inferior-related functions are available in the @code{gdb}
25568 @defun gdb.inferiors ()
25569 Return a tuple containing all inferior objects.
25572 @defun gdb.selected_inferior ()
25573 Return an object representing the current inferior.
25576 A @code{gdb.Inferior} object has the following attributes:
25578 @defvar Inferior.num
25579 ID of inferior, as assigned by GDB.
25582 @defvar Inferior.pid
25583 Process ID of the inferior, as assigned by the underlying operating
25587 @defvar Inferior.was_attached
25588 Boolean signaling whether the inferior was created using `attach', or
25589 started by @value{GDBN} itself.
25592 A @code{gdb.Inferior} object has the following methods:
25594 @defun Inferior.is_valid ()
25595 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25596 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25597 if the inferior no longer exists within @value{GDBN}. All other
25598 @code{gdb.Inferior} methods will throw an exception if it is invalid
25599 at the time the method is called.
25602 @defun Inferior.threads ()
25603 This method returns a tuple holding all the threads which are valid
25604 when it is called. If there are no valid threads, the method will
25605 return an empty tuple.
25608 @findex Inferior.read_memory
25609 @defun Inferior.read_memory (address, length)
25610 Read @var{length} bytes of memory from the inferior, starting at
25611 @var{address}. Returns a buffer object, which behaves much like an array
25612 or a string. It can be modified and given to the
25613 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25614 value is a @code{memoryview} object.
25617 @findex Inferior.write_memory
25618 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25619 Write the contents of @var{buffer} to the inferior, starting at
25620 @var{address}. The @var{buffer} parameter must be a Python object
25621 which supports the buffer protocol, i.e., a string, an array or the
25622 object returned from @code{Inferior.read_memory}. If given, @var{length}
25623 determines the number of bytes from @var{buffer} to be written.
25626 @findex gdb.search_memory
25627 @defun Inferior.search_memory (address, length, pattern)
25628 Search a region of the inferior memory starting at @var{address} with
25629 the given @var{length} using the search pattern supplied in
25630 @var{pattern}. The @var{pattern} parameter must be a Python object
25631 which supports the buffer protocol, i.e., a string, an array or the
25632 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25633 containing the address where the pattern was found, or @code{None} if
25634 the pattern could not be found.
25637 @node Events In Python
25638 @subsubsection Events In Python
25639 @cindex inferior events in Python
25641 @value{GDBN} provides a general event facility so that Python code can be
25642 notified of various state changes, particularly changes that occur in
25645 An @dfn{event} is just an object that describes some state change. The
25646 type of the object and its attributes will vary depending on the details
25647 of the change. All the existing events are described below.
25649 In order to be notified of an event, you must register an event handler
25650 with an @dfn{event registry}. An event registry is an object in the
25651 @code{gdb.events} module which dispatches particular events. A registry
25652 provides methods to register and unregister event handlers:
25654 @defun EventRegistry.connect (object)
25655 Add the given callable @var{object} to the registry. This object will be
25656 called when an event corresponding to this registry occurs.
25659 @defun EventRegistry.disconnect (object)
25660 Remove the given @var{object} from the registry. Once removed, the object
25661 will no longer receive notifications of events.
25664 Here is an example:
25667 def exit_handler (event):
25668 print "event type: exit"
25669 print "exit code: %d" % (event.exit_code)
25671 gdb.events.exited.connect (exit_handler)
25674 In the above example we connect our handler @code{exit_handler} to the
25675 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25676 called when the inferior exits. The argument @dfn{event} in this example is
25677 of type @code{gdb.ExitedEvent}. As you can see in the example the
25678 @code{ExitedEvent} object has an attribute which indicates the exit code of
25681 The following is a listing of the event registries that are available and
25682 details of the events they emit:
25687 Emits @code{gdb.ThreadEvent}.
25689 Some events can be thread specific when @value{GDBN} is running in non-stop
25690 mode. When represented in Python, these events all extend
25691 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25692 events which are emitted by this or other modules might extend this event.
25693 Examples of these events are @code{gdb.BreakpointEvent} and
25694 @code{gdb.ContinueEvent}.
25696 @defvar ThreadEvent.inferior_thread
25697 In non-stop mode this attribute will be set to the specific thread which was
25698 involved in the emitted event. Otherwise, it will be set to @code{None}.
25701 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25703 This event indicates that the inferior has been continued after a stop. For
25704 inherited attribute refer to @code{gdb.ThreadEvent} above.
25706 @item events.exited
25707 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25708 @code{events.ExitedEvent} has two attributes:
25709 @defvar ExitedEvent.exit_code
25710 An integer representing the exit code, if available, which the inferior
25711 has returned. (The exit code could be unavailable if, for example,
25712 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25713 the attribute does not exist.
25715 @defvar ExitedEvent inferior
25716 A reference to the inferior which triggered the @code{exited} event.
25720 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25722 Indicates that the inferior has stopped. All events emitted by this registry
25723 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25724 will indicate the stopped thread when @value{GDBN} is running in non-stop
25725 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25727 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25729 This event indicates that the inferior or one of its threads has received as
25730 signal. @code{gdb.SignalEvent} has the following attributes:
25732 @defvar SignalEvent.stop_signal
25733 A string representing the signal received by the inferior. A list of possible
25734 signal values can be obtained by running the command @code{info signals} in
25735 the @value{GDBN} command prompt.
25738 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25740 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25741 been hit, and has the following attributes:
25743 @defvar BreakpointEvent.breakpoints
25744 A sequence containing references to all the breakpoints (type
25745 @code{gdb.Breakpoint}) that were hit.
25746 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25748 @defvar BreakpointEvent.breakpoint
25749 A reference to the first breakpoint that was hit.
25750 This function is maintained for backward compatibility and is now deprecated
25751 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25754 @item events.new_objfile
25755 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25756 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25758 @defvar NewObjFileEvent.new_objfile
25759 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25760 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25765 @node Threads In Python
25766 @subsubsection Threads In Python
25767 @cindex threads in python
25769 @findex gdb.InferiorThread
25770 Python scripts can access information about, and manipulate inferior threads
25771 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25773 The following thread-related functions are available in the @code{gdb}
25776 @findex gdb.selected_thread
25777 @defun gdb.selected_thread ()
25778 This function returns the thread object for the selected thread. If there
25779 is no selected thread, this will return @code{None}.
25782 A @code{gdb.InferiorThread} object has the following attributes:
25784 @defvar InferiorThread.name
25785 The name of the thread. If the user specified a name using
25786 @code{thread name}, then this returns that name. Otherwise, if an
25787 OS-supplied name is available, then it is returned. Otherwise, this
25788 returns @code{None}.
25790 This attribute can be assigned to. The new value must be a string
25791 object, which sets the new name, or @code{None}, which removes any
25792 user-specified thread name.
25795 @defvar InferiorThread.num
25796 ID of the thread, as assigned by GDB.
25799 @defvar InferiorThread.ptid
25800 ID of the thread, as assigned by the operating system. This attribute is a
25801 tuple containing three integers. The first is the Process ID (PID); the second
25802 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25803 Either the LWPID or TID may be 0, which indicates that the operating system
25804 does not use that identifier.
25807 A @code{gdb.InferiorThread} object has the following methods:
25809 @defun InferiorThread.is_valid ()
25810 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25811 @code{False} if not. A @code{gdb.InferiorThread} object will become
25812 invalid if the thread exits, or the inferior that the thread belongs
25813 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25814 exception if it is invalid at the time the method is called.
25817 @defun InferiorThread.switch ()
25818 This changes @value{GDBN}'s currently selected thread to the one represented
25822 @defun InferiorThread.is_stopped ()
25823 Return a Boolean indicating whether the thread is stopped.
25826 @defun InferiorThread.is_running ()
25827 Return a Boolean indicating whether the thread is running.
25830 @defun InferiorThread.is_exited ()
25831 Return a Boolean indicating whether the thread is exited.
25834 @node Commands In Python
25835 @subsubsection Commands In Python
25837 @cindex commands in python
25838 @cindex python commands
25839 You can implement new @value{GDBN} CLI commands in Python. A CLI
25840 command is implemented using an instance of the @code{gdb.Command}
25841 class, most commonly using a subclass.
25843 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25844 The object initializer for @code{Command} registers the new command
25845 with @value{GDBN}. This initializer is normally invoked from the
25846 subclass' own @code{__init__} method.
25848 @var{name} is the name of the command. If @var{name} consists of
25849 multiple words, then the initial words are looked for as prefix
25850 commands. In this case, if one of the prefix commands does not exist,
25851 an exception is raised.
25853 There is no support for multi-line commands.
25855 @var{command_class} should be one of the @samp{COMMAND_} constants
25856 defined below. This argument tells @value{GDBN} how to categorize the
25857 new command in the help system.
25859 @var{completer_class} is an optional argument. If given, it should be
25860 one of the @samp{COMPLETE_} constants defined below. This argument
25861 tells @value{GDBN} how to perform completion for this command. If not
25862 given, @value{GDBN} will attempt to complete using the object's
25863 @code{complete} method (see below); if no such method is found, an
25864 error will occur when completion is attempted.
25866 @var{prefix} is an optional argument. If @code{True}, then the new
25867 command is a prefix command; sub-commands of this command may be
25870 The help text for the new command is taken from the Python
25871 documentation string for the command's class, if there is one. If no
25872 documentation string is provided, the default value ``This command is
25873 not documented.'' is used.
25876 @cindex don't repeat Python command
25877 @defun Command.dont_repeat ()
25878 By default, a @value{GDBN} command is repeated when the user enters a
25879 blank line at the command prompt. A command can suppress this
25880 behavior by invoking the @code{dont_repeat} method. This is similar
25881 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25884 @defun Command.invoke (argument, from_tty)
25885 This method is called by @value{GDBN} when this command is invoked.
25887 @var{argument} is a string. It is the argument to the command, after
25888 leading and trailing whitespace has been stripped.
25890 @var{from_tty} is a boolean argument. When true, this means that the
25891 command was entered by the user at the terminal; when false it means
25892 that the command came from elsewhere.
25894 If this method throws an exception, it is turned into a @value{GDBN}
25895 @code{error} call. Otherwise, the return value is ignored.
25897 @findex gdb.string_to_argv
25898 To break @var{argument} up into an argv-like string use
25899 @code{gdb.string_to_argv}. This function behaves identically to
25900 @value{GDBN}'s internal argument lexer @code{buildargv}.
25901 It is recommended to use this for consistency.
25902 Arguments are separated by spaces and may be quoted.
25906 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25907 ['1', '2 "3', '4 "5', "6 '7"]
25912 @cindex completion of Python commands
25913 @defun Command.complete (text, word)
25914 This method is called by @value{GDBN} when the user attempts
25915 completion on this command. All forms of completion are handled by
25916 this method, that is, the @key{TAB} and @key{M-?} key bindings
25917 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25920 The arguments @var{text} and @var{word} are both strings. @var{text}
25921 holds the complete command line up to the cursor's location.
25922 @var{word} holds the last word of the command line; this is computed
25923 using a word-breaking heuristic.
25925 The @code{complete} method can return several values:
25928 If the return value is a sequence, the contents of the sequence are
25929 used as the completions. It is up to @code{complete} to ensure that the
25930 contents actually do complete the word. A zero-length sequence is
25931 allowed, it means that there were no completions available. Only
25932 string elements of the sequence are used; other elements in the
25933 sequence are ignored.
25936 If the return value is one of the @samp{COMPLETE_} constants defined
25937 below, then the corresponding @value{GDBN}-internal completion
25938 function is invoked, and its result is used.
25941 All other results are treated as though there were no available
25946 When a new command is registered, it must be declared as a member of
25947 some general class of commands. This is used to classify top-level
25948 commands in the on-line help system; note that prefix commands are not
25949 listed under their own category but rather that of their top-level
25950 command. The available classifications are represented by constants
25951 defined in the @code{gdb} module:
25954 @findex COMMAND_NONE
25955 @findex gdb.COMMAND_NONE
25956 @item gdb.COMMAND_NONE
25957 The command does not belong to any particular class. A command in
25958 this category will not be displayed in any of the help categories.
25960 @findex COMMAND_RUNNING
25961 @findex gdb.COMMAND_RUNNING
25962 @item gdb.COMMAND_RUNNING
25963 The command is related to running the inferior. For example,
25964 @code{start}, @code{step}, and @code{continue} are in this category.
25965 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
25966 commands in this category.
25968 @findex COMMAND_DATA
25969 @findex gdb.COMMAND_DATA
25970 @item gdb.COMMAND_DATA
25971 The command is related to data or variables. For example,
25972 @code{call}, @code{find}, and @code{print} are in this category. Type
25973 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
25976 @findex COMMAND_STACK
25977 @findex gdb.COMMAND_STACK
25978 @item gdb.COMMAND_STACK
25979 The command has to do with manipulation of the stack. For example,
25980 @code{backtrace}, @code{frame}, and @code{return} are in this
25981 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
25982 list of commands in this category.
25984 @findex COMMAND_FILES
25985 @findex gdb.COMMAND_FILES
25986 @item gdb.COMMAND_FILES
25987 This class is used for file-related commands. For example,
25988 @code{file}, @code{list} and @code{section} are in this category.
25989 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
25990 commands in this category.
25992 @findex COMMAND_SUPPORT
25993 @findex gdb.COMMAND_SUPPORT
25994 @item gdb.COMMAND_SUPPORT
25995 This should be used for ``support facilities'', generally meaning
25996 things that are useful to the user when interacting with @value{GDBN},
25997 but not related to the state of the inferior. For example,
25998 @code{help}, @code{make}, and @code{shell} are in this category. Type
25999 @kbd{help support} at the @value{GDBN} prompt to see a list of
26000 commands in this category.
26002 @findex COMMAND_STATUS
26003 @findex gdb.COMMAND_STATUS
26004 @item gdb.COMMAND_STATUS
26005 The command is an @samp{info}-related command, that is, related to the
26006 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
26007 and @code{show} are in this category. Type @kbd{help status} at the
26008 @value{GDBN} prompt to see a list of commands in this category.
26010 @findex COMMAND_BREAKPOINTS
26011 @findex gdb.COMMAND_BREAKPOINTS
26012 @item gdb.COMMAND_BREAKPOINTS
26013 The command has to do with breakpoints. For example, @code{break},
26014 @code{clear}, and @code{delete} are in this category. Type @kbd{help
26015 breakpoints} at the @value{GDBN} prompt to see a list of commands in
26018 @findex COMMAND_TRACEPOINTS
26019 @findex gdb.COMMAND_TRACEPOINTS
26020 @item gdb.COMMAND_TRACEPOINTS
26021 The command has to do with tracepoints. For example, @code{trace},
26022 @code{actions}, and @code{tfind} are in this category. Type
26023 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
26024 commands in this category.
26026 @findex COMMAND_USER
26027 @findex gdb.COMMAND_USER
26028 @item gdb.COMMAND_USER
26029 The command is a general purpose command for the user, and typically
26030 does not fit in one of the other categories.
26031 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
26032 a list of commands in this category, as well as the list of gdb macros
26033 (@pxref{Sequences}).
26035 @findex COMMAND_OBSCURE
26036 @findex gdb.COMMAND_OBSCURE
26037 @item gdb.COMMAND_OBSCURE
26038 The command is only used in unusual circumstances, or is not of
26039 general interest to users. For example, @code{checkpoint},
26040 @code{fork}, and @code{stop} are in this category. Type @kbd{help
26041 obscure} at the @value{GDBN} prompt to see a list of commands in this
26044 @findex COMMAND_MAINTENANCE
26045 @findex gdb.COMMAND_MAINTENANCE
26046 @item gdb.COMMAND_MAINTENANCE
26047 The command is only useful to @value{GDBN} maintainers. The
26048 @code{maintenance} and @code{flushregs} commands are in this category.
26049 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
26050 commands in this category.
26053 A new command can use a predefined completion function, either by
26054 specifying it via an argument at initialization, or by returning it
26055 from the @code{complete} method. These predefined completion
26056 constants are all defined in the @code{gdb} module:
26059 @findex COMPLETE_NONE
26060 @findex gdb.COMPLETE_NONE
26061 @item gdb.COMPLETE_NONE
26062 This constant means that no completion should be done.
26064 @findex COMPLETE_FILENAME
26065 @findex gdb.COMPLETE_FILENAME
26066 @item gdb.COMPLETE_FILENAME
26067 This constant means that filename completion should be performed.
26069 @findex COMPLETE_LOCATION
26070 @findex gdb.COMPLETE_LOCATION
26071 @item gdb.COMPLETE_LOCATION
26072 This constant means that location completion should be done.
26073 @xref{Specify Location}.
26075 @findex COMPLETE_COMMAND
26076 @findex gdb.COMPLETE_COMMAND
26077 @item gdb.COMPLETE_COMMAND
26078 This constant means that completion should examine @value{GDBN}
26081 @findex COMPLETE_SYMBOL
26082 @findex gdb.COMPLETE_SYMBOL
26083 @item gdb.COMPLETE_SYMBOL
26084 This constant means that completion should be done using symbol names
26087 @findex COMPLETE_EXPRESSION
26088 @findex gdb.COMPLETE_EXPRESSION
26089 @item gdb.COMPLETE_EXPRESSION
26090 This constant means that completion should be done on expressions.
26091 Often this means completing on symbol names, but some language
26092 parsers also have support for completing on field names.
26095 The following code snippet shows how a trivial CLI command can be
26096 implemented in Python:
26099 class HelloWorld (gdb.Command):
26100 """Greet the whole world."""
26102 def __init__ (self):
26103 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
26105 def invoke (self, arg, from_tty):
26106 print "Hello, World!"
26111 The last line instantiates the class, and is necessary to trigger the
26112 registration of the command with @value{GDBN}. Depending on how the
26113 Python code is read into @value{GDBN}, you may need to import the
26114 @code{gdb} module explicitly.
26116 @node Parameters In Python
26117 @subsubsection Parameters In Python
26119 @cindex parameters in python
26120 @cindex python parameters
26121 @tindex gdb.Parameter
26123 You can implement new @value{GDBN} parameters using Python. A new
26124 parameter is implemented as an instance of the @code{gdb.Parameter}
26127 Parameters are exposed to the user via the @code{set} and
26128 @code{show} commands. @xref{Help}.
26130 There are many parameters that already exist and can be set in
26131 @value{GDBN}. Two examples are: @code{set follow fork} and
26132 @code{set charset}. Setting these parameters influences certain
26133 behavior in @value{GDBN}. Similarly, you can define parameters that
26134 can be used to influence behavior in custom Python scripts and commands.
26136 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
26137 The object initializer for @code{Parameter} registers the new
26138 parameter with @value{GDBN}. This initializer is normally invoked
26139 from the subclass' own @code{__init__} method.
26141 @var{name} is the name of the new parameter. If @var{name} consists
26142 of multiple words, then the initial words are looked for as prefix
26143 parameters. An example of this can be illustrated with the
26144 @code{set print} set of parameters. If @var{name} is
26145 @code{print foo}, then @code{print} will be searched as the prefix
26146 parameter. In this case the parameter can subsequently be accessed in
26147 @value{GDBN} as @code{set print foo}.
26149 If @var{name} consists of multiple words, and no prefix parameter group
26150 can be found, an exception is raised.
26152 @var{command-class} should be one of the @samp{COMMAND_} constants
26153 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
26154 categorize the new parameter in the help system.
26156 @var{parameter-class} should be one of the @samp{PARAM_} constants
26157 defined below. This argument tells @value{GDBN} the type of the new
26158 parameter; this information is used for input validation and
26161 If @var{parameter-class} is @code{PARAM_ENUM}, then
26162 @var{enum-sequence} must be a sequence of strings. These strings
26163 represent the possible values for the parameter.
26165 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
26166 of a fourth argument will cause an exception to be thrown.
26168 The help text for the new parameter is taken from the Python
26169 documentation string for the parameter's class, if there is one. If
26170 there is no documentation string, a default value is used.
26173 @defvar Parameter.set_doc
26174 If this attribute exists, and is a string, then its value is used as
26175 the help text for this parameter's @code{set} command. The value is
26176 examined when @code{Parameter.__init__} is invoked; subsequent changes
26180 @defvar Parameter.show_doc
26181 If this attribute exists, and is a string, then its value is used as
26182 the help text for this parameter's @code{show} command. The value is
26183 examined when @code{Parameter.__init__} is invoked; subsequent changes
26187 @defvar Parameter.value
26188 The @code{value} attribute holds the underlying value of the
26189 parameter. It can be read and assigned to just as any other
26190 attribute. @value{GDBN} does validation when assignments are made.
26193 There are two methods that should be implemented in any
26194 @code{Parameter} class. These are:
26196 @defun Parameter.get_set_string (self)
26197 @value{GDBN} will call this method when a @var{parameter}'s value has
26198 been changed via the @code{set} API (for example, @kbd{set foo off}).
26199 The @code{value} attribute has already been populated with the new
26200 value and may be used in output. This method must return a string.
26203 @defun Parameter.get_show_string (self, svalue)
26204 @value{GDBN} will call this method when a @var{parameter}'s
26205 @code{show} API has been invoked (for example, @kbd{show foo}). The
26206 argument @code{svalue} receives the string representation of the
26207 current value. This method must return a string.
26210 When a new parameter is defined, its type must be specified. The
26211 available types are represented by constants defined in the @code{gdb}
26215 @findex PARAM_BOOLEAN
26216 @findex gdb.PARAM_BOOLEAN
26217 @item gdb.PARAM_BOOLEAN
26218 The value is a plain boolean. The Python boolean values, @code{True}
26219 and @code{False} are the only valid values.
26221 @findex PARAM_AUTO_BOOLEAN
26222 @findex gdb.PARAM_AUTO_BOOLEAN
26223 @item gdb.PARAM_AUTO_BOOLEAN
26224 The value has three possible states: true, false, and @samp{auto}. In
26225 Python, true and false are represented using boolean constants, and
26226 @samp{auto} is represented using @code{None}.
26228 @findex PARAM_UINTEGER
26229 @findex gdb.PARAM_UINTEGER
26230 @item gdb.PARAM_UINTEGER
26231 The value is an unsigned integer. The value of 0 should be
26232 interpreted to mean ``unlimited''.
26234 @findex PARAM_INTEGER
26235 @findex gdb.PARAM_INTEGER
26236 @item gdb.PARAM_INTEGER
26237 The value is a signed integer. The value of 0 should be interpreted
26238 to mean ``unlimited''.
26240 @findex PARAM_STRING
26241 @findex gdb.PARAM_STRING
26242 @item gdb.PARAM_STRING
26243 The value is a string. When the user modifies the string, any escape
26244 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
26245 translated into corresponding characters and encoded into the current
26248 @findex PARAM_STRING_NOESCAPE
26249 @findex gdb.PARAM_STRING_NOESCAPE
26250 @item gdb.PARAM_STRING_NOESCAPE
26251 The value is a string. When the user modifies the string, escapes are
26252 passed through untranslated.
26254 @findex PARAM_OPTIONAL_FILENAME
26255 @findex gdb.PARAM_OPTIONAL_FILENAME
26256 @item gdb.PARAM_OPTIONAL_FILENAME
26257 The value is a either a filename (a string), or @code{None}.
26259 @findex PARAM_FILENAME
26260 @findex gdb.PARAM_FILENAME
26261 @item gdb.PARAM_FILENAME
26262 The value is a filename. This is just like
26263 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
26265 @findex PARAM_ZINTEGER
26266 @findex gdb.PARAM_ZINTEGER
26267 @item gdb.PARAM_ZINTEGER
26268 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
26269 is interpreted as itself.
26272 @findex gdb.PARAM_ENUM
26273 @item gdb.PARAM_ENUM
26274 The value is a string, which must be one of a collection string
26275 constants provided when the parameter is created.
26278 @node Functions In Python
26279 @subsubsection Writing new convenience functions
26281 @cindex writing convenience functions
26282 @cindex convenience functions in python
26283 @cindex python convenience functions
26284 @tindex gdb.Function
26286 You can implement new convenience functions (@pxref{Convenience Vars})
26287 in Python. A convenience function is an instance of a subclass of the
26288 class @code{gdb.Function}.
26290 @defun Function.__init__ (name)
26291 The initializer for @code{Function} registers the new function with
26292 @value{GDBN}. The argument @var{name} is the name of the function,
26293 a string. The function will be visible to the user as a convenience
26294 variable of type @code{internal function}, whose name is the same as
26295 the given @var{name}.
26297 The documentation for the new function is taken from the documentation
26298 string for the new class.
26301 @defun Function.invoke (@var{*args})
26302 When a convenience function is evaluated, its arguments are converted
26303 to instances of @code{gdb.Value}, and then the function's
26304 @code{invoke} method is called. Note that @value{GDBN} does not
26305 predetermine the arity of convenience functions. Instead, all
26306 available arguments are passed to @code{invoke}, following the
26307 standard Python calling convention. In particular, a convenience
26308 function can have default values for parameters without ill effect.
26310 The return value of this method is used as its value in the enclosing
26311 expression. If an ordinary Python value is returned, it is converted
26312 to a @code{gdb.Value} following the usual rules.
26315 The following code snippet shows how a trivial convenience function can
26316 be implemented in Python:
26319 class Greet (gdb.Function):
26320 """Return string to greet someone.
26321 Takes a name as argument."""
26323 def __init__ (self):
26324 super (Greet, self).__init__ ("greet")
26326 def invoke (self, name):
26327 return "Hello, %s!" % name.string ()
26332 The last line instantiates the class, and is necessary to trigger the
26333 registration of the function with @value{GDBN}. Depending on how the
26334 Python code is read into @value{GDBN}, you may need to import the
26335 @code{gdb} module explicitly.
26337 Now you can use the function in an expression:
26340 (gdb) print $greet("Bob")
26344 @node Progspaces In Python
26345 @subsubsection Program Spaces In Python
26347 @cindex progspaces in python
26348 @tindex gdb.Progspace
26350 A program space, or @dfn{progspace}, represents a symbolic view
26351 of an address space.
26352 It consists of all of the objfiles of the program.
26353 @xref{Objfiles In Python}.
26354 @xref{Inferiors and Programs, program spaces}, for more details
26355 about program spaces.
26357 The following progspace-related functions are available in the
26360 @findex gdb.current_progspace
26361 @defun gdb.current_progspace ()
26362 This function returns the program space of the currently selected inferior.
26363 @xref{Inferiors and Programs}.
26366 @findex gdb.progspaces
26367 @defun gdb.progspaces ()
26368 Return a sequence of all the progspaces currently known to @value{GDBN}.
26371 Each progspace is represented by an instance of the @code{gdb.Progspace}
26374 @defvar Progspace.filename
26375 The file name of the progspace as a string.
26378 @defvar Progspace.pretty_printers
26379 The @code{pretty_printers} attribute is a list of functions. It is
26380 used to look up pretty-printers. A @code{Value} is passed to each
26381 function in order; if the function returns @code{None}, then the
26382 search continues. Otherwise, the return value should be an object
26383 which is used to format the value. @xref{Pretty Printing API}, for more
26387 @defvar Progspace.type_printers
26388 The @code{type_printers} attribute is a list of type printer objects.
26389 @xref{Type Printing API}, for more information.
26392 @defvar Progspace.frame_filters
26393 The @code{frame_filters} attribute is a dictionary of frame filter
26394 objects. @xref{Frame Filter API}, for more information.
26397 @node Objfiles In Python
26398 @subsubsection Objfiles In Python
26400 @cindex objfiles in python
26401 @tindex gdb.Objfile
26403 @value{GDBN} loads symbols for an inferior from various
26404 symbol-containing files (@pxref{Files}). These include the primary
26405 executable file, any shared libraries used by the inferior, and any
26406 separate debug info files (@pxref{Separate Debug Files}).
26407 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26409 The following objfile-related functions are available in the
26412 @findex gdb.current_objfile
26413 @defun gdb.current_objfile ()
26414 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26415 sets the ``current objfile'' to the corresponding objfile. This
26416 function returns the current objfile. If there is no current objfile,
26417 this function returns @code{None}.
26420 @findex gdb.objfiles
26421 @defun gdb.objfiles ()
26422 Return a sequence of all the objfiles current known to @value{GDBN}.
26423 @xref{Objfiles In Python}.
26426 Each objfile is represented by an instance of the @code{gdb.Objfile}
26429 @defvar Objfile.filename
26430 The file name of the objfile as a string.
26433 @defvar Objfile.pretty_printers
26434 The @code{pretty_printers} attribute is a list of functions. It is
26435 used to look up pretty-printers. A @code{Value} is passed to each
26436 function in order; if the function returns @code{None}, then the
26437 search continues. Otherwise, the return value should be an object
26438 which is used to format the value. @xref{Pretty Printing API}, for more
26442 @defvar Objfile.type_printers
26443 The @code{type_printers} attribute is a list of type printer objects.
26444 @xref{Type Printing API}, for more information.
26447 @defvar Objfile.frame_filters
26448 The @code{frame_filters} attribute is a dictionary of frame filter
26449 objects. @xref{Frame Filter API}, for more information.
26452 A @code{gdb.Objfile} object has the following methods:
26454 @defun Objfile.is_valid ()
26455 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26456 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26457 if the object file it refers to is not loaded in @value{GDBN} any
26458 longer. All other @code{gdb.Objfile} methods will throw an exception
26459 if it is invalid at the time the method is called.
26462 @node Frames In Python
26463 @subsubsection Accessing inferior stack frames from Python.
26465 @cindex frames in python
26466 When the debugged program stops, @value{GDBN} is able to analyze its call
26467 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26468 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26469 while its corresponding frame exists in the inferior's stack. If you try
26470 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26471 exception (@pxref{Exception Handling}).
26473 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26477 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26481 The following frame-related functions are available in the @code{gdb} module:
26483 @findex gdb.selected_frame
26484 @defun gdb.selected_frame ()
26485 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26488 @findex gdb.newest_frame
26489 @defun gdb.newest_frame ()
26490 Return the newest frame object for the selected thread.
26493 @defun gdb.frame_stop_reason_string (reason)
26494 Return a string explaining the reason why @value{GDBN} stopped unwinding
26495 frames, as expressed by the given @var{reason} code (an integer, see the
26496 @code{unwind_stop_reason} method further down in this section).
26499 A @code{gdb.Frame} object has the following methods:
26501 @defun Frame.is_valid ()
26502 Returns true if the @code{gdb.Frame} object is valid, false if not.
26503 A frame object can become invalid if the frame it refers to doesn't
26504 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26505 an exception if it is invalid at the time the method is called.
26508 @defun Frame.name ()
26509 Returns the function name of the frame, or @code{None} if it can't be
26513 @defun Frame.architecture ()
26514 Returns the @code{gdb.Architecture} object corresponding to the frame's
26515 architecture. @xref{Architectures In Python}.
26518 @defun Frame.type ()
26519 Returns the type of the frame. The value can be one of:
26521 @item gdb.NORMAL_FRAME
26522 An ordinary stack frame.
26524 @item gdb.DUMMY_FRAME
26525 A fake stack frame that was created by @value{GDBN} when performing an
26526 inferior function call.
26528 @item gdb.INLINE_FRAME
26529 A frame representing an inlined function. The function was inlined
26530 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26532 @item gdb.TAILCALL_FRAME
26533 A frame representing a tail call. @xref{Tail Call Frames}.
26535 @item gdb.SIGTRAMP_FRAME
26536 A signal trampoline frame. This is the frame created by the OS when
26537 it calls into a signal handler.
26539 @item gdb.ARCH_FRAME
26540 A fake stack frame representing a cross-architecture call.
26542 @item gdb.SENTINEL_FRAME
26543 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26548 @defun Frame.unwind_stop_reason ()
26549 Return an integer representing the reason why it's not possible to find
26550 more frames toward the outermost frame. Use
26551 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26552 function to a string. The value can be one of:
26555 @item gdb.FRAME_UNWIND_NO_REASON
26556 No particular reason (older frames should be available).
26558 @item gdb.FRAME_UNWIND_NULL_ID
26559 The previous frame's analyzer returns an invalid result. This is no
26560 longer used by @value{GDBN}, and is kept only for backward
26563 @item gdb.FRAME_UNWIND_OUTERMOST
26564 This frame is the outermost.
26566 @item gdb.FRAME_UNWIND_UNAVAILABLE
26567 Cannot unwind further, because that would require knowing the
26568 values of registers or memory that have not been collected.
26570 @item gdb.FRAME_UNWIND_INNER_ID
26571 This frame ID looks like it ought to belong to a NEXT frame,
26572 but we got it for a PREV frame. Normally, this is a sign of
26573 unwinder failure. It could also indicate stack corruption.
26575 @item gdb.FRAME_UNWIND_SAME_ID
26576 This frame has the same ID as the previous one. That means
26577 that unwinding further would almost certainly give us another
26578 frame with exactly the same ID, so break the chain. Normally,
26579 this is a sign of unwinder failure. It could also indicate
26582 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26583 The frame unwinder did not find any saved PC, but we needed
26584 one to unwind further.
26586 @item gdb.FRAME_UNWIND_FIRST_ERROR
26587 Any stop reason greater or equal to this value indicates some kind
26588 of error. This special value facilitates writing code that tests
26589 for errors in unwinding in a way that will work correctly even if
26590 the list of the other values is modified in future @value{GDBN}
26591 versions. Using it, you could write:
26593 reason = gdb.selected_frame().unwind_stop_reason ()
26594 reason_str = gdb.frame_stop_reason_string (reason)
26595 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26596 print "An error occured: %s" % reason_str
26603 Returns the frame's resume address.
26606 @defun Frame.block ()
26607 Return the frame's code block. @xref{Blocks In Python}.
26610 @defun Frame.function ()
26611 Return the symbol for the function corresponding to this frame.
26612 @xref{Symbols In Python}.
26615 @defun Frame.older ()
26616 Return the frame that called this frame.
26619 @defun Frame.newer ()
26620 Return the frame called by this frame.
26623 @defun Frame.find_sal ()
26624 Return the frame's symtab and line object.
26625 @xref{Symbol Tables In Python}.
26628 @defun Frame.read_var (variable @r{[}, block@r{]})
26629 Return the value of @var{variable} in this frame. If the optional
26630 argument @var{block} is provided, search for the variable from that
26631 block; otherwise start at the frame's current block (which is
26632 determined by the frame's current program counter). @var{variable}
26633 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26634 @code{gdb.Block} object.
26637 @defun Frame.select ()
26638 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26642 @node Blocks In Python
26643 @subsubsection Accessing blocks from Python.
26645 @cindex blocks in python
26648 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26649 roughly to a scope in the source code. Blocks are organized
26650 hierarchically, and are represented individually in Python as a
26651 @code{gdb.Block}. Blocks rely on debugging information being
26654 A frame has a block. Please see @ref{Frames In Python}, for a more
26655 in-depth discussion of frames.
26657 The outermost block is known as the @dfn{global block}. The global
26658 block typically holds public global variables and functions.
26660 The block nested just inside the global block is the @dfn{static
26661 block}. The static block typically holds file-scoped variables and
26664 @value{GDBN} provides a method to get a block's superblock, but there
26665 is currently no way to examine the sub-blocks of a block, or to
26666 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26669 Here is a short example that should help explain blocks:
26672 /* This is in the global block. */
26675 /* This is in the static block. */
26676 static int file_scope;
26678 /* 'function' is in the global block, and 'argument' is
26679 in a block nested inside of 'function'. */
26680 int function (int argument)
26682 /* 'local' is in a block inside 'function'. It may or may
26683 not be in the same block as 'argument'. */
26687 /* 'inner' is in a block whose superblock is the one holding
26691 /* If this call is expanded by the compiler, you may see
26692 a nested block here whose function is 'inline_function'
26693 and whose superblock is the one holding 'inner'. */
26694 inline_function ();
26699 A @code{gdb.Block} is iterable. The iterator returns the symbols
26700 (@pxref{Symbols In Python}) local to the block. Python programs
26701 should not assume that a specific block object will always contain a
26702 given symbol, since changes in @value{GDBN} features and
26703 infrastructure may cause symbols move across blocks in a symbol
26706 The following block-related functions are available in the @code{gdb}
26709 @findex gdb.block_for_pc
26710 @defun gdb.block_for_pc (pc)
26711 Return the innermost @code{gdb.Block} containing the given @var{pc}
26712 value. If the block cannot be found for the @var{pc} value specified,
26713 the function will return @code{None}.
26716 A @code{gdb.Block} object has the following methods:
26718 @defun Block.is_valid ()
26719 Returns @code{True} if the @code{gdb.Block} object is valid,
26720 @code{False} if not. A block object can become invalid if the block it
26721 refers to doesn't exist anymore in the inferior. All other
26722 @code{gdb.Block} methods will throw an exception if it is invalid at
26723 the time the method is called. The block's validity is also checked
26724 during iteration over symbols of the block.
26727 A @code{gdb.Block} object has the following attributes:
26729 @defvar Block.start
26730 The start address of the block. This attribute is not writable.
26734 The end address of the block. This attribute is not writable.
26737 @defvar Block.function
26738 The name of the block represented as a @code{gdb.Symbol}. If the
26739 block is not named, then this attribute holds @code{None}. This
26740 attribute is not writable.
26742 For ordinary function blocks, the superblock is the static block.
26743 However, you should note that it is possible for a function block to
26744 have a superblock that is not the static block -- for instance this
26745 happens for an inlined function.
26748 @defvar Block.superblock
26749 The block containing this block. If this parent block does not exist,
26750 this attribute holds @code{None}. This attribute is not writable.
26753 @defvar Block.global_block
26754 The global block associated with this block. This attribute is not
26758 @defvar Block.static_block
26759 The static block associated with this block. This attribute is not
26763 @defvar Block.is_global
26764 @code{True} if the @code{gdb.Block} object is a global block,
26765 @code{False} if not. This attribute is not
26769 @defvar Block.is_static
26770 @code{True} if the @code{gdb.Block} object is a static block,
26771 @code{False} if not. This attribute is not writable.
26774 @node Symbols In Python
26775 @subsubsection Python representation of Symbols.
26777 @cindex symbols in python
26780 @value{GDBN} represents every variable, function and type as an
26781 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26782 Similarly, Python represents these symbols in @value{GDBN} with the
26783 @code{gdb.Symbol} object.
26785 The following symbol-related functions are available in the @code{gdb}
26788 @findex gdb.lookup_symbol
26789 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26790 This function searches for a symbol by name. The search scope can be
26791 restricted to the parameters defined in the optional domain and block
26794 @var{name} is the name of the symbol. It must be a string. The
26795 optional @var{block} argument restricts the search to symbols visible
26796 in that @var{block}. The @var{block} argument must be a
26797 @code{gdb.Block} object. If omitted, the block for the current frame
26798 is used. The optional @var{domain} argument restricts
26799 the search to the domain type. The @var{domain} argument must be a
26800 domain constant defined in the @code{gdb} module and described later
26803 The result is a tuple of two elements.
26804 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26806 If the symbol is found, the second element is @code{True} if the symbol
26807 is a field of a method's object (e.g., @code{this} in C@t{++}),
26808 otherwise it is @code{False}.
26809 If the symbol is not found, the second element is @code{False}.
26812 @findex gdb.lookup_global_symbol
26813 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26814 This function searches for a global symbol by name.
26815 The search scope can be restricted to by the domain argument.
26817 @var{name} is the name of the symbol. It must be a string.
26818 The optional @var{domain} argument restricts the search to the domain type.
26819 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26820 module and described later in this chapter.
26822 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26826 A @code{gdb.Symbol} object has the following attributes:
26828 @defvar Symbol.type
26829 The type of the symbol or @code{None} if no type is recorded.
26830 This attribute is represented as a @code{gdb.Type} object.
26831 @xref{Types In Python}. This attribute is not writable.
26834 @defvar Symbol.symtab
26835 The symbol table in which the symbol appears. This attribute is
26836 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26837 Python}. This attribute is not writable.
26840 @defvar Symbol.line
26841 The line number in the source code at which the symbol was defined.
26842 This is an integer.
26845 @defvar Symbol.name
26846 The name of the symbol as a string. This attribute is not writable.
26849 @defvar Symbol.linkage_name
26850 The name of the symbol, as used by the linker (i.e., may be mangled).
26851 This attribute is not writable.
26854 @defvar Symbol.print_name
26855 The name of the symbol in a form suitable for output. This is either
26856 @code{name} or @code{linkage_name}, depending on whether the user
26857 asked @value{GDBN} to display demangled or mangled names.
26860 @defvar Symbol.addr_class
26861 The address class of the symbol. This classifies how to find the value
26862 of a symbol. Each address class is a constant defined in the
26863 @code{gdb} module and described later in this chapter.
26866 @defvar Symbol.needs_frame
26867 This is @code{True} if evaluating this symbol's value requires a frame
26868 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26869 local variables will require a frame, but other symbols will not.
26872 @defvar Symbol.is_argument
26873 @code{True} if the symbol is an argument of a function.
26876 @defvar Symbol.is_constant
26877 @code{True} if the symbol is a constant.
26880 @defvar Symbol.is_function
26881 @code{True} if the symbol is a function or a method.
26884 @defvar Symbol.is_variable
26885 @code{True} if the symbol is a variable.
26888 A @code{gdb.Symbol} object has the following methods:
26890 @defun Symbol.is_valid ()
26891 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26892 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26893 the symbol it refers to does not exist in @value{GDBN} any longer.
26894 All other @code{gdb.Symbol} methods will throw an exception if it is
26895 invalid at the time the method is called.
26898 @defun Symbol.value (@r{[}frame@r{]})
26899 Compute the value of the symbol, as a @code{gdb.Value}. For
26900 functions, this computes the address of the function, cast to the
26901 appropriate type. If the symbol requires a frame in order to compute
26902 its value, then @var{frame} must be given. If @var{frame} is not
26903 given, or if @var{frame} is invalid, then this method will throw an
26907 The available domain categories in @code{gdb.Symbol} are represented
26908 as constants in the @code{gdb} module:
26911 @findex SYMBOL_UNDEF_DOMAIN
26912 @findex gdb.SYMBOL_UNDEF_DOMAIN
26913 @item gdb.SYMBOL_UNDEF_DOMAIN
26914 This is used when a domain has not been discovered or none of the
26915 following domains apply. This usually indicates an error either
26916 in the symbol information or in @value{GDBN}'s handling of symbols.
26917 @findex SYMBOL_VAR_DOMAIN
26918 @findex gdb.SYMBOL_VAR_DOMAIN
26919 @item gdb.SYMBOL_VAR_DOMAIN
26920 This domain contains variables, function names, typedef names and enum
26922 @findex SYMBOL_STRUCT_DOMAIN
26923 @findex gdb.SYMBOL_STRUCT_DOMAIN
26924 @item gdb.SYMBOL_STRUCT_DOMAIN
26925 This domain holds struct, union and enum type names.
26926 @findex SYMBOL_LABEL_DOMAIN
26927 @findex gdb.SYMBOL_LABEL_DOMAIN
26928 @item gdb.SYMBOL_LABEL_DOMAIN
26929 This domain contains names of labels (for gotos).
26930 @findex SYMBOL_VARIABLES_DOMAIN
26931 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26932 @item gdb.SYMBOL_VARIABLES_DOMAIN
26933 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
26934 contains everything minus functions and types.
26935 @findex SYMBOL_FUNCTIONS_DOMAIN
26936 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
26937 @item gdb.SYMBOL_FUNCTION_DOMAIN
26938 This domain contains all functions.
26939 @findex SYMBOL_TYPES_DOMAIN
26940 @findex gdb.SYMBOL_TYPES_DOMAIN
26941 @item gdb.SYMBOL_TYPES_DOMAIN
26942 This domain contains all types.
26945 The available address class categories in @code{gdb.Symbol} are represented
26946 as constants in the @code{gdb} module:
26949 @findex SYMBOL_LOC_UNDEF
26950 @findex gdb.SYMBOL_LOC_UNDEF
26951 @item gdb.SYMBOL_LOC_UNDEF
26952 If this is returned by address class, it indicates an error either in
26953 the symbol information or in @value{GDBN}'s handling of symbols.
26954 @findex SYMBOL_LOC_CONST
26955 @findex gdb.SYMBOL_LOC_CONST
26956 @item gdb.SYMBOL_LOC_CONST
26957 Value is constant int.
26958 @findex SYMBOL_LOC_STATIC
26959 @findex gdb.SYMBOL_LOC_STATIC
26960 @item gdb.SYMBOL_LOC_STATIC
26961 Value is at a fixed address.
26962 @findex SYMBOL_LOC_REGISTER
26963 @findex gdb.SYMBOL_LOC_REGISTER
26964 @item gdb.SYMBOL_LOC_REGISTER
26965 Value is in a register.
26966 @findex SYMBOL_LOC_ARG
26967 @findex gdb.SYMBOL_LOC_ARG
26968 @item gdb.SYMBOL_LOC_ARG
26969 Value is an argument. This value is at the offset stored within the
26970 symbol inside the frame's argument list.
26971 @findex SYMBOL_LOC_REF_ARG
26972 @findex gdb.SYMBOL_LOC_REF_ARG
26973 @item gdb.SYMBOL_LOC_REF_ARG
26974 Value address is stored in the frame's argument list. Just like
26975 @code{LOC_ARG} except that the value's address is stored at the
26976 offset, not the value itself.
26977 @findex SYMBOL_LOC_REGPARM_ADDR
26978 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
26979 @item gdb.SYMBOL_LOC_REGPARM_ADDR
26980 Value is a specified register. Just like @code{LOC_REGISTER} except
26981 the register holds the address of the argument instead of the argument
26983 @findex SYMBOL_LOC_LOCAL
26984 @findex gdb.SYMBOL_LOC_LOCAL
26985 @item gdb.SYMBOL_LOC_LOCAL
26986 Value is a local variable.
26987 @findex SYMBOL_LOC_TYPEDEF
26988 @findex gdb.SYMBOL_LOC_TYPEDEF
26989 @item gdb.SYMBOL_LOC_TYPEDEF
26990 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
26992 @findex SYMBOL_LOC_BLOCK
26993 @findex gdb.SYMBOL_LOC_BLOCK
26994 @item gdb.SYMBOL_LOC_BLOCK
26996 @findex SYMBOL_LOC_CONST_BYTES
26997 @findex gdb.SYMBOL_LOC_CONST_BYTES
26998 @item gdb.SYMBOL_LOC_CONST_BYTES
26999 Value is a byte-sequence.
27000 @findex SYMBOL_LOC_UNRESOLVED
27001 @findex gdb.SYMBOL_LOC_UNRESOLVED
27002 @item gdb.SYMBOL_LOC_UNRESOLVED
27003 Value is at a fixed address, but the address of the variable has to be
27004 determined from the minimal symbol table whenever the variable is
27006 @findex SYMBOL_LOC_OPTIMIZED_OUT
27007 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
27008 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
27009 The value does not actually exist in the program.
27010 @findex SYMBOL_LOC_COMPUTED
27011 @findex gdb.SYMBOL_LOC_COMPUTED
27012 @item gdb.SYMBOL_LOC_COMPUTED
27013 The value's address is a computed location.
27016 @node Symbol Tables In Python
27017 @subsubsection Symbol table representation in Python.
27019 @cindex symbol tables in python
27021 @tindex gdb.Symtab_and_line
27023 Access to symbol table data maintained by @value{GDBN} on the inferior
27024 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
27025 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
27026 from the @code{find_sal} method in @code{gdb.Frame} object.
27027 @xref{Frames In Python}.
27029 For more information on @value{GDBN}'s symbol table management, see
27030 @ref{Symbols, ,Examining the Symbol Table}, for more information.
27032 A @code{gdb.Symtab_and_line} object has the following attributes:
27034 @defvar Symtab_and_line.symtab
27035 The symbol table object (@code{gdb.Symtab}) for this frame.
27036 This attribute is not writable.
27039 @defvar Symtab_and_line.pc
27040 Indicates the start of the address range occupied by code for the
27041 current source line. This attribute is not writable.
27044 @defvar Symtab_and_line.last
27045 Indicates the end of the address range occupied by code for the current
27046 source line. This attribute is not writable.
27049 @defvar Symtab_and_line.line
27050 Indicates the current line number for this object. This
27051 attribute is not writable.
27054 A @code{gdb.Symtab_and_line} object has the following methods:
27056 @defun Symtab_and_line.is_valid ()
27057 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
27058 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
27059 invalid if the Symbol table and line object it refers to does not
27060 exist in @value{GDBN} any longer. All other
27061 @code{gdb.Symtab_and_line} methods will throw an exception if it is
27062 invalid at the time the method is called.
27065 A @code{gdb.Symtab} object has the following attributes:
27067 @defvar Symtab.filename
27068 The symbol table's source filename. This attribute is not writable.
27071 @defvar Symtab.objfile
27072 The symbol table's backing object file. @xref{Objfiles In Python}.
27073 This attribute is not writable.
27076 A @code{gdb.Symtab} object has the following methods:
27078 @defun Symtab.is_valid ()
27079 Returns @code{True} if the @code{gdb.Symtab} object is valid,
27080 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
27081 the symbol table it refers to does not exist in @value{GDBN} any
27082 longer. All other @code{gdb.Symtab} methods will throw an exception
27083 if it is invalid at the time the method is called.
27086 @defun Symtab.fullname ()
27087 Return the symbol table's source absolute file name.
27090 @defun Symtab.global_block ()
27091 Return the global block of the underlying symbol table.
27092 @xref{Blocks In Python}.
27095 @defun Symtab.static_block ()
27096 Return the static block of the underlying symbol table.
27097 @xref{Blocks In Python}.
27100 @defun Symtab.linetable ()
27101 Return the line table associated with the symbol table.
27102 @xref{Line Tables In Python}.
27105 @node Line Tables In Python
27106 @subsubsection Manipulating line tables using Python
27108 @cindex line tables in python
27109 @tindex gdb.LineTable
27111 Python code can request and inspect line table information from a
27112 symbol table that is loaded in @value{GDBN}. A line table is a
27113 mapping of source lines to their executable locations in memory. To
27114 acquire the line table information for a particular symbol table, use
27115 the @code{linetable} function (@pxref{Symbol Tables In Python}).
27117 A @code{gdb.LineTable} is iterable. The iterator returns
27118 @code{LineTableEntry} objects that correspond to the source line and
27119 address for each line table entry. @code{LineTableEntry} objects have
27120 the following attributes:
27122 @defvar LineTableEntry.line
27123 The source line number for this line table entry. This number
27124 corresponds to the actual line of source. This attribute is not
27128 @defvar LineTableEntry.pc
27129 The address that is associated with the line table entry where the
27130 executable code for that source line resides in memory. This
27131 attribute is not writable.
27134 As there can be multiple addresses for a single source line, you may
27135 receive multiple @code{LineTableEntry} objects with matching
27136 @code{line} attributes, but with different @code{pc} attributes. The
27137 iterator is sorted in ascending @code{pc} order. Here is a small
27138 example illustrating iterating over a line table.
27141 symtab = gdb.selected_frame().find_sal().symtab
27142 linetable = symtab.linetable()
27143 for line in linetable:
27144 print "Line: "+str(line.line)+" Address: "+hex(line.pc)
27147 This will have the following output:
27150 Line: 33 Address: 0x4005c8L
27151 Line: 37 Address: 0x4005caL
27152 Line: 39 Address: 0x4005d2L
27153 Line: 40 Address: 0x4005f8L
27154 Line: 42 Address: 0x4005ffL
27155 Line: 44 Address: 0x400608L
27156 Line: 42 Address: 0x40060cL
27157 Line: 45 Address: 0x400615L
27160 In addition to being able to iterate over a @code{LineTable}, it also
27161 has the following direct access methods:
27163 @defun LineTable.line (line)
27164 Return a Python @code{Tuple} of @code{LineTableEntry} objects for any
27165 entries in the line table for the given @var{line}. @var{line} refers
27166 to the source code line. If there are no entries for that source code
27167 @var{line}, the Python @code{None} is returned.
27170 @defun LineTable.has_line (line)
27171 Return a Python @code{Boolean} indicating whether there is an entry in
27172 the line table for this source line. Return @code{True} if an entry
27173 is found, or @code{False} if not.
27176 @defun LineTable.source_lines ()
27177 Return a Python @code{List} of the source line numbers in the symbol
27178 table. Only lines with executable code locations are returned. The
27179 contents of the @code{List} will just be the source line entries
27180 represented as Python @code{Long} values.
27183 @node Breakpoints In Python
27184 @subsubsection Manipulating breakpoints using Python
27186 @cindex breakpoints in python
27187 @tindex gdb.Breakpoint
27189 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
27192 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]})
27193 Create a new breakpoint. @var{spec} is a string naming the location
27194 of the breakpoint, or an expression that defines a watchpoint. The
27195 contents can be any location recognized by the @code{break} command,
27196 or in the case of a watchpoint, by the @code{watch} command. The
27197 optional @var{type} denotes the breakpoint to create from the types
27198 defined later in this chapter. This argument can be either:
27199 @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
27200 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal}
27201 argument allows the breakpoint to become invisible to the user. The
27202 breakpoint will neither be reported when created, nor will it be
27203 listed in the output from @code{info breakpoints} (but will be listed
27204 with the @code{maint info breakpoints} command). The optional
27205 @var{temporary} argument makes the breakpoint a temporary breakpoint.
27206 Temporary breakpoints are deleted after they have been hit. Any
27207 further access to the Python breakpoint after it has been hit will
27208 result in a runtime error (as that breakpoint has now been
27209 automatically deleted). The optional @var{wp_class} argument defines
27210 the class of watchpoint to create, if @var{type} is
27211 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it
27212 is assumed to be a @code{gdb.WP_WRITE} class.
27215 @defun Breakpoint.stop (self)
27216 The @code{gdb.Breakpoint} class can be sub-classed and, in
27217 particular, you may choose to implement the @code{stop} method.
27218 If this method is defined in a sub-class of @code{gdb.Breakpoint},
27219 it will be called when the inferior reaches any location of a
27220 breakpoint which instantiates that sub-class. If the method returns
27221 @code{True}, the inferior will be stopped at the location of the
27222 breakpoint, otherwise the inferior will continue.
27224 If there are multiple breakpoints at the same location with a
27225 @code{stop} method, each one will be called regardless of the
27226 return status of the previous. This ensures that all @code{stop}
27227 methods have a chance to execute at that location. In this scenario
27228 if one of the methods returns @code{True} but the others return
27229 @code{False}, the inferior will still be stopped.
27231 You should not alter the execution state of the inferior (i.e.@:, step,
27232 next, etc.), alter the current frame context (i.e.@:, change the current
27233 active frame), or alter, add or delete any breakpoint. As a general
27234 rule, you should not alter any data within @value{GDBN} or the inferior
27237 Example @code{stop} implementation:
27240 class MyBreakpoint (gdb.Breakpoint):
27242 inf_val = gdb.parse_and_eval("foo")
27249 The available watchpoint types represented by constants are defined in the
27254 @findex gdb.WP_READ
27256 Read only watchpoint.
27259 @findex gdb.WP_WRITE
27261 Write only watchpoint.
27264 @findex gdb.WP_ACCESS
27265 @item gdb.WP_ACCESS
27266 Read/Write watchpoint.
27269 @defun Breakpoint.is_valid ()
27270 Return @code{True} if this @code{Breakpoint} object is valid,
27271 @code{False} otherwise. A @code{Breakpoint} object can become invalid
27272 if the user deletes the breakpoint. In this case, the object still
27273 exists, but the underlying breakpoint does not. In the cases of
27274 watchpoint scope, the watchpoint remains valid even if execution of the
27275 inferior leaves the scope of that watchpoint.
27278 @defun Breakpoint.delete
27279 Permanently deletes the @value{GDBN} breakpoint. This also
27280 invalidates the Python @code{Breakpoint} object. Any further access
27281 to this object's attributes or methods will raise an error.
27284 @defvar Breakpoint.enabled
27285 This attribute is @code{True} if the breakpoint is enabled, and
27286 @code{False} otherwise. This attribute is writable.
27289 @defvar Breakpoint.silent
27290 This attribute is @code{True} if the breakpoint is silent, and
27291 @code{False} otherwise. This attribute is writable.
27293 Note that a breakpoint can also be silent if it has commands and the
27294 first command is @code{silent}. This is not reported by the
27295 @code{silent} attribute.
27298 @defvar Breakpoint.thread
27299 If the breakpoint is thread-specific, this attribute holds the thread
27300 id. If the breakpoint is not thread-specific, this attribute is
27301 @code{None}. This attribute is writable.
27304 @defvar Breakpoint.task
27305 If the breakpoint is Ada task-specific, this attribute holds the Ada task
27306 id. If the breakpoint is not task-specific (or the underlying
27307 language is not Ada), this attribute is @code{None}. This attribute
27311 @defvar Breakpoint.ignore_count
27312 This attribute holds the ignore count for the breakpoint, an integer.
27313 This attribute is writable.
27316 @defvar Breakpoint.number
27317 This attribute holds the breakpoint's number --- the identifier used by
27318 the user to manipulate the breakpoint. This attribute is not writable.
27321 @defvar Breakpoint.type
27322 This attribute holds the breakpoint's type --- the identifier used to
27323 determine the actual breakpoint type or use-case. This attribute is not
27327 @defvar Breakpoint.visible
27328 This attribute tells whether the breakpoint is visible to the user
27329 when set, or when the @samp{info breakpoints} command is run. This
27330 attribute is not writable.
27333 @defvar Breakpoint.temporary
27334 This attribute indicates whether the breakpoint was created as a
27335 temporary breakpoint. Temporary breakpoints are automatically deleted
27336 after that breakpoint has been hit. Access to this attribute, and all
27337 other attributes and functions other than the @code{is_valid}
27338 function, will result in an error after the breakpoint has been hit
27339 (as it has been automatically deleted). This attribute is not
27343 The available types are represented by constants defined in the @code{gdb}
27347 @findex BP_BREAKPOINT
27348 @findex gdb.BP_BREAKPOINT
27349 @item gdb.BP_BREAKPOINT
27350 Normal code breakpoint.
27352 @findex BP_WATCHPOINT
27353 @findex gdb.BP_WATCHPOINT
27354 @item gdb.BP_WATCHPOINT
27355 Watchpoint breakpoint.
27357 @findex BP_HARDWARE_WATCHPOINT
27358 @findex gdb.BP_HARDWARE_WATCHPOINT
27359 @item gdb.BP_HARDWARE_WATCHPOINT
27360 Hardware assisted watchpoint.
27362 @findex BP_READ_WATCHPOINT
27363 @findex gdb.BP_READ_WATCHPOINT
27364 @item gdb.BP_READ_WATCHPOINT
27365 Hardware assisted read watchpoint.
27367 @findex BP_ACCESS_WATCHPOINT
27368 @findex gdb.BP_ACCESS_WATCHPOINT
27369 @item gdb.BP_ACCESS_WATCHPOINT
27370 Hardware assisted access watchpoint.
27373 @defvar Breakpoint.hit_count
27374 This attribute holds the hit count for the breakpoint, an integer.
27375 This attribute is writable, but currently it can only be set to zero.
27378 @defvar Breakpoint.location
27379 This attribute holds the location of the breakpoint, as specified by
27380 the user. It is a string. If the breakpoint does not have a location
27381 (that is, it is a watchpoint) the attribute's value is @code{None}. This
27382 attribute is not writable.
27385 @defvar Breakpoint.expression
27386 This attribute holds a breakpoint expression, as specified by
27387 the user. It is a string. If the breakpoint does not have an
27388 expression (the breakpoint is not a watchpoint) the attribute's value
27389 is @code{None}. This attribute is not writable.
27392 @defvar Breakpoint.condition
27393 This attribute holds the condition of the breakpoint, as specified by
27394 the user. It is a string. If there is no condition, this attribute's
27395 value is @code{None}. This attribute is writable.
27398 @defvar Breakpoint.commands
27399 This attribute holds the commands attached to the breakpoint. If
27400 there are commands, this attribute's value is a string holding all the
27401 commands, separated by newlines. If there are no commands, this
27402 attribute is @code{None}. This attribute is not writable.
27405 @node Finish Breakpoints in Python
27406 @subsubsection Finish Breakpoints
27408 @cindex python finish breakpoints
27409 @tindex gdb.FinishBreakpoint
27411 A finish breakpoint is a temporary breakpoint set at the return address of
27412 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27413 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27414 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27415 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27416 Finish breakpoints are thread specific and must be create with the right
27419 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27420 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27421 object @var{frame}. If @var{frame} is not provided, this defaults to the
27422 newest frame. The optional @var{internal} argument allows the breakpoint to
27423 become invisible to the user. @xref{Breakpoints In Python}, for further
27424 details about this argument.
27427 @defun FinishBreakpoint.out_of_scope (self)
27428 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27429 @code{return} command, @dots{}), a function may not properly terminate, and
27430 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27431 situation, the @code{out_of_scope} callback will be triggered.
27433 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27437 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27439 print "normal finish"
27442 def out_of_scope ():
27443 print "abnormal finish"
27447 @defvar FinishBreakpoint.return_value
27448 When @value{GDBN} is stopped at a finish breakpoint and the frame
27449 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27450 attribute will contain a @code{gdb.Value} object corresponding to the return
27451 value of the function. The value will be @code{None} if the function return
27452 type is @code{void} or if the return value was not computable. This attribute
27456 @node Lazy Strings In Python
27457 @subsubsection Python representation of lazy strings.
27459 @cindex lazy strings in python
27460 @tindex gdb.LazyString
27462 A @dfn{lazy string} is a string whose contents is not retrieved or
27463 encoded until it is needed.
27465 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27466 @code{address} that points to a region of memory, an @code{encoding}
27467 that will be used to encode that region of memory, and a @code{length}
27468 to delimit the region of memory that represents the string. The
27469 difference between a @code{gdb.LazyString} and a string wrapped within
27470 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27471 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27472 retrieved and encoded during printing, while a @code{gdb.Value}
27473 wrapping a string is immediately retrieved and encoded on creation.
27475 A @code{gdb.LazyString} object has the following functions:
27477 @defun LazyString.value ()
27478 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27479 will point to the string in memory, but will lose all the delayed
27480 retrieval, encoding and handling that @value{GDBN} applies to a
27481 @code{gdb.LazyString}.
27484 @defvar LazyString.address
27485 This attribute holds the address of the string. This attribute is not
27489 @defvar LazyString.length
27490 This attribute holds the length of the string in characters. If the
27491 length is -1, then the string will be fetched and encoded up to the
27492 first null of appropriate width. This attribute is not writable.
27495 @defvar LazyString.encoding
27496 This attribute holds the encoding that will be applied to the string
27497 when the string is printed by @value{GDBN}. If the encoding is not
27498 set, or contains an empty string, then @value{GDBN} will select the
27499 most appropriate encoding when the string is printed. This attribute
27503 @defvar LazyString.type
27504 This attribute holds the type that is represented by the lazy string's
27505 type. For a lazy string this will always be a pointer type. To
27506 resolve this to the lazy string's character type, use the type's
27507 @code{target} method. @xref{Types In Python}. This attribute is not
27511 @node Architectures In Python
27512 @subsubsection Python representation of architectures
27513 @cindex Python architectures
27515 @value{GDBN} uses architecture specific parameters and artifacts in a
27516 number of its various computations. An architecture is represented
27517 by an instance of the @code{gdb.Architecture} class.
27519 A @code{gdb.Architecture} class has the following methods:
27521 @defun Architecture.name ()
27522 Return the name (string value) of the architecture.
27525 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27526 Return a list of disassembled instructions starting from the memory
27527 address @var{start_pc}. The optional arguments @var{end_pc} and
27528 @var{count} determine the number of instructions in the returned list.
27529 If both the optional arguments @var{end_pc} and @var{count} are
27530 specified, then a list of at most @var{count} disassembled instructions
27531 whose start address falls in the closed memory address interval from
27532 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27533 specified, but @var{count} is specified, then @var{count} number of
27534 instructions starting from the address @var{start_pc} are returned. If
27535 @var{count} is not specified but @var{end_pc} is specified, then all
27536 instructions whose start address falls in the closed memory address
27537 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27538 @var{end_pc} nor @var{count} are specified, then a single instruction at
27539 @var{start_pc} is returned. For all of these cases, each element of the
27540 returned list is a Python @code{dict} with the following string keys:
27545 The value corresponding to this key is a Python long integer capturing
27546 the memory address of the instruction.
27549 The value corresponding to this key is a string value which represents
27550 the instruction with assembly language mnemonics. The assembly
27551 language flavor used is the same as that specified by the current CLI
27552 variable @code{disassembly-flavor}. @xref{Machine Code}.
27555 The value corresponding to this key is the length (integer value) of the
27556 instruction in bytes.
27561 @node Python Auto-loading
27562 @subsection Python Auto-loading
27563 @cindex Python auto-loading
27565 When a new object file is read (for example, due to the @code{file}
27566 command, or because the inferior has loaded a shared library),
27567 @value{GDBN} will look for Python support scripts in several ways:
27568 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
27569 and @code{.debug_gdb_scripts} section
27570 (@pxref{dotdebug_gdb_scripts section}).
27572 The auto-loading feature is useful for supplying application-specific
27573 debugging commands and scripts.
27575 Auto-loading can be enabled or disabled,
27576 and the list of auto-loaded scripts can be printed.
27579 @anchor{set auto-load python-scripts}
27580 @kindex set auto-load python-scripts
27581 @item set auto-load python-scripts [on|off]
27582 Enable or disable the auto-loading of Python scripts.
27584 @anchor{show auto-load python-scripts}
27585 @kindex show auto-load python-scripts
27586 @item show auto-load python-scripts
27587 Show whether auto-loading of Python scripts is enabled or disabled.
27589 @anchor{info auto-load python-scripts}
27590 @kindex info auto-load python-scripts
27591 @cindex print list of auto-loaded Python scripts
27592 @item info auto-load python-scripts [@var{regexp}]
27593 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27595 Also printed is the list of Python scripts that were mentioned in
27596 the @code{.debug_gdb_scripts} section and were not found
27597 (@pxref{dotdebug_gdb_scripts section}).
27598 This is useful because their names are not printed when @value{GDBN}
27599 tries to load them and fails. There may be many of them, and printing
27600 an error message for each one is problematic.
27602 If @var{regexp} is supplied only Python scripts with matching names are printed.
27607 (gdb) info auto-load python-scripts
27609 Yes py-section-script.py
27610 full name: /tmp/py-section-script.py
27611 No my-foo-pretty-printers.py
27615 When reading an auto-loaded file, @value{GDBN} sets the
27616 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27617 function (@pxref{Objfiles In Python}). This can be useful for
27618 registering objfile-specific pretty-printers and frame-filters.
27621 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
27622 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
27623 * Which flavor to choose?::
27626 @node objfile-gdb.py file
27627 @subsubsection The @file{@var{objfile}-gdb.py} file
27628 @cindex @file{@var{objfile}-gdb.py}
27630 When a new object file is read, @value{GDBN} looks for
27631 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
27632 where @var{objfile} is the object file's real name, formed by ensuring
27633 that the file name is absolute, following all symlinks, and resolving
27634 @code{.} and @code{..} components. If this file exists and is
27635 readable, @value{GDBN} will evaluate it as a Python script.
27637 If this file does not exist, then @value{GDBN} will look for
27638 @var{script-name} file in all of the directories as specified below.
27640 Note that loading of this script file also requires accordingly configured
27641 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27643 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27644 scripts normally according to its @file{.exe} filename. But if no scripts are
27645 found @value{GDBN} also tries script filenames matching the object file without
27646 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27647 is attempted on any platform. This makes the script filenames compatible
27648 between Unix and MS-Windows hosts.
27651 @anchor{set auto-load scripts-directory}
27652 @kindex set auto-load scripts-directory
27653 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27654 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27655 may be delimited by the host platform path separator in use
27656 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27658 Each entry here needs to be covered also by the security setting
27659 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27661 @anchor{with-auto-load-dir}
27662 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27663 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27664 configuration option @option{--with-auto-load-dir}.
27666 Any reference to @file{$debugdir} will get replaced by
27667 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27668 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27669 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27670 @file{$datadir} must be placed as a directory component --- either alone or
27671 delimited by @file{/} or @file{\} directory separators, depending on the host
27674 The list of directories uses path separator (@samp{:} on GNU and Unix
27675 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27676 to the @env{PATH} environment variable.
27678 @anchor{show auto-load scripts-directory}
27679 @kindex show auto-load scripts-directory
27680 @item show auto-load scripts-directory
27681 Show @value{GDBN} auto-loaded scripts location.
27684 @value{GDBN} does not track which files it has already auto-loaded this way.
27685 @value{GDBN} will load the associated script every time the corresponding
27686 @var{objfile} is opened.
27687 So your @file{-gdb.py} file should be careful to avoid errors if it
27688 is evaluated more than once.
27690 @node dotdebug_gdb_scripts section
27691 @subsubsection The @code{.debug_gdb_scripts} section
27692 @cindex @code{.debug_gdb_scripts} section
27694 For systems using file formats like ELF and COFF,
27695 when @value{GDBN} loads a new object file
27696 it will look for a special section named @samp{.debug_gdb_scripts}.
27697 If this section exists, its contents is a list of names of scripts to load.
27699 @value{GDBN} will look for each specified script file first in the
27700 current directory and then along the source search path
27701 (@pxref{Source Path, ,Specifying Source Directories}),
27702 except that @file{$cdir} is not searched, since the compilation
27703 directory is not relevant to scripts.
27705 Entries can be placed in section @code{.debug_gdb_scripts} with,
27706 for example, this GCC macro:
27709 /* Note: The "MS" section flags are to remove duplicates. */
27710 #define DEFINE_GDB_SCRIPT(script_name) \
27712 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27714 .asciz \"" script_name "\"\n\
27720 Then one can reference the macro in a header or source file like this:
27723 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
27726 The script name may include directories if desired.
27728 Note that loading of this script file also requires accordingly configured
27729 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27731 If the macro is put in a header, any application or library
27732 using this header will get a reference to the specified script.
27734 @node Which flavor to choose?
27735 @subsubsection Which flavor to choose?
27737 Given the multiple ways of auto-loading Python scripts, it might not always
27738 be clear which one to choose. This section provides some guidance.
27740 Benefits of the @file{-gdb.py} way:
27744 Can be used with file formats that don't support multiple sections.
27747 Ease of finding scripts for public libraries.
27749 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27750 in the source search path.
27751 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27752 isn't a source directory in which to find the script.
27755 Doesn't require source code additions.
27758 Benefits of the @code{.debug_gdb_scripts} way:
27762 Works with static linking.
27764 Scripts for libraries done the @file{-gdb.py} way require an objfile to
27765 trigger their loading. When an application is statically linked the only
27766 objfile available is the executable, and it is cumbersome to attach all the
27767 scripts from all the input libraries to the executable's @file{-gdb.py} script.
27770 Works with classes that are entirely inlined.
27772 Some classes can be entirely inlined, and thus there may not be an associated
27773 shared library to attach a @file{-gdb.py} script to.
27776 Scripts needn't be copied out of the source tree.
27778 In some circumstances, apps can be built out of large collections of internal
27779 libraries, and the build infrastructure necessary to install the
27780 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
27781 cumbersome. It may be easier to specify the scripts in the
27782 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27783 top of the source tree to the source search path.
27786 @node Python modules
27787 @subsection Python modules
27788 @cindex python modules
27790 @value{GDBN} comes with several modules to assist writing Python code.
27793 * gdb.printing:: Building and registering pretty-printers.
27794 * gdb.types:: Utilities for working with types.
27795 * gdb.prompt:: Utilities for prompt value substitution.
27799 @subsubsection gdb.printing
27800 @cindex gdb.printing
27802 This module provides a collection of utilities for working with
27806 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27807 This class specifies the API that makes @samp{info pretty-printer},
27808 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27809 Pretty-printers should generally inherit from this class.
27811 @item SubPrettyPrinter (@var{name})
27812 For printers that handle multiple types, this class specifies the
27813 corresponding API for the subprinters.
27815 @item RegexpCollectionPrettyPrinter (@var{name})
27816 Utility class for handling multiple printers, all recognized via
27817 regular expressions.
27818 @xref{Writing a Pretty-Printer}, for an example.
27820 @item FlagEnumerationPrinter (@var{name})
27821 A pretty-printer which handles printing of @code{enum} values. Unlike
27822 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27823 work properly when there is some overlap between the enumeration
27824 constants. @var{name} is the name of the printer and also the name of
27825 the @code{enum} type to look up.
27827 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27828 Register @var{printer} with the pretty-printer list of @var{obj}.
27829 If @var{replace} is @code{True} then any existing copy of the printer
27830 is replaced. Otherwise a @code{RuntimeError} exception is raised
27831 if a printer with the same name already exists.
27835 @subsubsection gdb.types
27838 This module provides a collection of utilities for working with
27839 @code{gdb.Type} objects.
27842 @item get_basic_type (@var{type})
27843 Return @var{type} with const and volatile qualifiers stripped,
27844 and with typedefs and C@t{++} references converted to the underlying type.
27849 typedef const int const_int;
27851 const_int& foo_ref (foo);
27852 int main () @{ return 0; @}
27859 (gdb) python import gdb.types
27860 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27861 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27865 @item has_field (@var{type}, @var{field})
27866 Return @code{True} if @var{type}, assumed to be a type with fields
27867 (e.g., a structure or union), has field @var{field}.
27869 @item make_enum_dict (@var{enum_type})
27870 Return a Python @code{dictionary} type produced from @var{enum_type}.
27872 @item deep_items (@var{type})
27873 Returns a Python iterator similar to the standard
27874 @code{gdb.Type.iteritems} method, except that the iterator returned
27875 by @code{deep_items} will recursively traverse anonymous struct or
27876 union fields. For example:
27890 Then in @value{GDBN}:
27892 (@value{GDBP}) python import gdb.types
27893 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27894 (@value{GDBP}) python print struct_a.keys ()
27896 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27897 @{['a', 'b0', 'b1']@}
27900 @item get_type_recognizers ()
27901 Return a list of the enabled type recognizers for the current context.
27902 This is called by @value{GDBN} during the type-printing process
27903 (@pxref{Type Printing API}).
27905 @item apply_type_recognizers (recognizers, type_obj)
27906 Apply the type recognizers, @var{recognizers}, to the type object
27907 @var{type_obj}. If any recognizer returns a string, return that
27908 string. Otherwise, return @code{None}. This is called by
27909 @value{GDBN} during the type-printing process (@pxref{Type Printing
27912 @item register_type_printer (locus, printer)
27913 This is a convenience function to register a type printer.
27914 @var{printer} is the type printer to register. It must implement the
27915 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27916 which case the printer is registered with that objfile; a
27917 @code{gdb.Progspace}, in which case the printer is registered with
27918 that progspace; or @code{None}, in which case the printer is
27919 registered globally.
27922 This is a base class that implements the type printer protocol. Type
27923 printers are encouraged, but not required, to derive from this class.
27924 It defines a constructor:
27926 @defmethod TypePrinter __init__ (self, name)
27927 Initialize the type printer with the given name. The new printer
27928 starts in the enabled state.
27934 @subsubsection gdb.prompt
27937 This module provides a method for prompt value-substitution.
27940 @item substitute_prompt (@var{string})
27941 Return @var{string} with escape sequences substituted by values. Some
27942 escape sequences take arguments. You can specify arguments inside
27943 ``@{@}'' immediately following the escape sequence.
27945 The escape sequences you can pass to this function are:
27949 Substitute a backslash.
27951 Substitute an ESC character.
27953 Substitute the selected frame; an argument names a frame parameter.
27955 Substitute a newline.
27957 Substitute a parameter's value; the argument names the parameter.
27959 Substitute a carriage return.
27961 Substitute the selected thread; an argument names a thread parameter.
27963 Substitute the version of GDB.
27965 Substitute the current working directory.
27967 Begin a sequence of non-printing characters. These sequences are
27968 typically used with the ESC character, and are not counted in the string
27969 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27970 blue-colored ``(gdb)'' prompt where the length is five.
27972 End a sequence of non-printing characters.
27978 substitute_prompt (``frame: \f,
27979 print arguments: \p@{print frame-arguments@}'')
27982 @exdent will return the string:
27985 "frame: main, print arguments: scalars"
27990 @section Creating new spellings of existing commands
27991 @cindex aliases for commands
27993 It is often useful to define alternate spellings of existing commands.
27994 For example, if a new @value{GDBN} command defined in Python has
27995 a long name to type, it is handy to have an abbreviated version of it
27996 that involves less typing.
27998 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27999 of the @samp{step} command even though it is otherwise an ambiguous
28000 abbreviation of other commands like @samp{set} and @samp{show}.
28002 Aliases are also used to provide shortened or more common versions
28003 of multi-word commands. For example, @value{GDBN} provides the
28004 @samp{tty} alias of the @samp{set inferior-tty} command.
28006 You can define a new alias with the @samp{alias} command.
28011 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
28015 @var{ALIAS} specifies the name of the new alias.
28016 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
28019 @var{COMMAND} specifies the name of an existing command
28020 that is being aliased.
28022 The @samp{-a} option specifies that the new alias is an abbreviation
28023 of the command. Abbreviations are not shown in command
28024 lists displayed by the @samp{help} command.
28026 The @samp{--} option specifies the end of options,
28027 and is useful when @var{ALIAS} begins with a dash.
28029 Here is a simple example showing how to make an abbreviation
28030 of a command so that there is less to type.
28031 Suppose you were tired of typing @samp{disas}, the current
28032 shortest unambiguous abbreviation of the @samp{disassemble} command
28033 and you wanted an even shorter version named @samp{di}.
28034 The following will accomplish this.
28037 (gdb) alias -a di = disas
28040 Note that aliases are different from user-defined commands.
28041 With a user-defined command, you also need to write documentation
28042 for it with the @samp{document} command.
28043 An alias automatically picks up the documentation of the existing command.
28045 Here is an example where we make @samp{elms} an abbreviation of
28046 @samp{elements} in the @samp{set print elements} command.
28047 This is to show that you can make an abbreviation of any part
28051 (gdb) alias -a set print elms = set print elements
28052 (gdb) alias -a show print elms = show print elements
28053 (gdb) set p elms 20
28055 Limit on string chars or array elements to print is 200.
28058 Note that if you are defining an alias of a @samp{set} command,
28059 and you want to have an alias for the corresponding @samp{show}
28060 command, then you need to define the latter separately.
28062 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
28063 @var{ALIAS}, just as they are normally.
28066 (gdb) alias -a set pr elms = set p ele
28069 Finally, here is an example showing the creation of a one word
28070 alias for a more complex command.
28071 This creates alias @samp{spe} of the command @samp{set print elements}.
28074 (gdb) alias spe = set print elements
28079 @chapter Command Interpreters
28080 @cindex command interpreters
28082 @value{GDBN} supports multiple command interpreters, and some command
28083 infrastructure to allow users or user interface writers to switch
28084 between interpreters or run commands in other interpreters.
28086 @value{GDBN} currently supports two command interpreters, the console
28087 interpreter (sometimes called the command-line interpreter or @sc{cli})
28088 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28089 describes both of these interfaces in great detail.
28091 By default, @value{GDBN} will start with the console interpreter.
28092 However, the user may choose to start @value{GDBN} with another
28093 interpreter by specifying the @option{-i} or @option{--interpreter}
28094 startup options. Defined interpreters include:
28098 @cindex console interpreter
28099 The traditional console or command-line interpreter. This is the most often
28100 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28101 @value{GDBN} will use this interpreter.
28104 @cindex mi interpreter
28105 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
28106 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28107 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28111 @cindex mi2 interpreter
28112 The current @sc{gdb/mi} interface.
28115 @cindex mi1 interpreter
28116 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
28120 @cindex invoke another interpreter
28121 The interpreter being used by @value{GDBN} may not be dynamically
28122 switched at runtime. Although possible, this could lead to a very
28123 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
28124 enters the command "interpreter-set console" in a console view,
28125 @value{GDBN} would switch to using the console interpreter, rendering
28126 the IDE inoperable!
28128 @kindex interpreter-exec
28129 Although you may only choose a single interpreter at startup, you may execute
28130 commands in any interpreter from the current interpreter using the appropriate
28131 command. If you are running the console interpreter, simply use the
28132 @code{interpreter-exec} command:
28135 interpreter-exec mi "-data-list-register-names"
28138 @sc{gdb/mi} has a similar command, although it is only available in versions of
28139 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28142 @chapter @value{GDBN} Text User Interface
28144 @cindex Text User Interface
28147 * TUI Overview:: TUI overview
28148 * TUI Keys:: TUI key bindings
28149 * TUI Single Key Mode:: TUI single key mode
28150 * TUI Commands:: TUI-specific commands
28151 * TUI Configuration:: TUI configuration variables
28154 The @value{GDBN} Text User Interface (TUI) is a terminal
28155 interface which uses the @code{curses} library to show the source
28156 file, the assembly output, the program registers and @value{GDBN}
28157 commands in separate text windows. The TUI mode is supported only
28158 on platforms where a suitable version of the @code{curses} library
28161 The TUI mode is enabled by default when you invoke @value{GDBN} as
28162 @samp{@value{GDBP} -tui}.
28163 You can also switch in and out of TUI mode while @value{GDBN} runs by
28164 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
28165 @xref{TUI Keys, ,TUI Key Bindings}.
28168 @section TUI Overview
28170 In TUI mode, @value{GDBN} can display several text windows:
28174 This window is the @value{GDBN} command window with the @value{GDBN}
28175 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28176 managed using readline.
28179 The source window shows the source file of the program. The current
28180 line and active breakpoints are displayed in this window.
28183 The assembly window shows the disassembly output of the program.
28186 This window shows the processor registers. Registers are highlighted
28187 when their values change.
28190 The source and assembly windows show the current program position
28191 by highlighting the current line and marking it with a @samp{>} marker.
28192 Breakpoints are indicated with two markers. The first marker
28193 indicates the breakpoint type:
28197 Breakpoint which was hit at least once.
28200 Breakpoint which was never hit.
28203 Hardware breakpoint which was hit at least once.
28206 Hardware breakpoint which was never hit.
28209 The second marker indicates whether the breakpoint is enabled or not:
28213 Breakpoint is enabled.
28216 Breakpoint is disabled.
28219 The source, assembly and register windows are updated when the current
28220 thread changes, when the frame changes, or when the program counter
28223 These windows are not all visible at the same time. The command
28224 window is always visible. The others can be arranged in several
28235 source and assembly,
28238 source and registers, or
28241 assembly and registers.
28244 A status line above the command window shows the following information:
28248 Indicates the current @value{GDBN} target.
28249 (@pxref{Targets, ,Specifying a Debugging Target}).
28252 Gives the current process or thread number.
28253 When no process is being debugged, this field is set to @code{No process}.
28256 Gives the current function name for the selected frame.
28257 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28258 When there is no symbol corresponding to the current program counter,
28259 the string @code{??} is displayed.
28262 Indicates the current line number for the selected frame.
28263 When the current line number is not known, the string @code{??} is displayed.
28266 Indicates the current program counter address.
28270 @section TUI Key Bindings
28271 @cindex TUI key bindings
28273 The TUI installs several key bindings in the readline keymaps
28274 @ifset SYSTEM_READLINE
28275 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28277 @ifclear SYSTEM_READLINE
28278 (@pxref{Command Line Editing}).
28280 The following key bindings are installed for both TUI mode and the
28281 @value{GDBN} standard mode.
28290 Enter or leave the TUI mode. When leaving the TUI mode,
28291 the curses window management stops and @value{GDBN} operates using
28292 its standard mode, writing on the terminal directly. When reentering
28293 the TUI mode, control is given back to the curses windows.
28294 The screen is then refreshed.
28298 Use a TUI layout with only one window. The layout will
28299 either be @samp{source} or @samp{assembly}. When the TUI mode
28300 is not active, it will switch to the TUI mode.
28302 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28306 Use a TUI layout with at least two windows. When the current
28307 layout already has two windows, the next layout with two windows is used.
28308 When a new layout is chosen, one window will always be common to the
28309 previous layout and the new one.
28311 Think of it as the Emacs @kbd{C-x 2} binding.
28315 Change the active window. The TUI associates several key bindings
28316 (like scrolling and arrow keys) with the active window. This command
28317 gives the focus to the next TUI window.
28319 Think of it as the Emacs @kbd{C-x o} binding.
28323 Switch in and out of the TUI SingleKey mode that binds single
28324 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28327 The following key bindings only work in the TUI mode:
28332 Scroll the active window one page up.
28336 Scroll the active window one page down.
28340 Scroll the active window one line up.
28344 Scroll the active window one line down.
28348 Scroll the active window one column left.
28352 Scroll the active window one column right.
28356 Refresh the screen.
28359 Because the arrow keys scroll the active window in the TUI mode, they
28360 are not available for their normal use by readline unless the command
28361 window has the focus. When another window is active, you must use
28362 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28363 and @kbd{C-f} to control the command window.
28365 @node TUI Single Key Mode
28366 @section TUI Single Key Mode
28367 @cindex TUI single key mode
28369 The TUI also provides a @dfn{SingleKey} mode, which binds several
28370 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28371 switch into this mode, where the following key bindings are used:
28374 @kindex c @r{(SingleKey TUI key)}
28378 @kindex d @r{(SingleKey TUI key)}
28382 @kindex f @r{(SingleKey TUI key)}
28386 @kindex n @r{(SingleKey TUI key)}
28390 @kindex q @r{(SingleKey TUI key)}
28392 exit the SingleKey mode.
28394 @kindex r @r{(SingleKey TUI key)}
28398 @kindex s @r{(SingleKey TUI key)}
28402 @kindex u @r{(SingleKey TUI key)}
28406 @kindex v @r{(SingleKey TUI key)}
28410 @kindex w @r{(SingleKey TUI key)}
28415 Other keys temporarily switch to the @value{GDBN} command prompt.
28416 The key that was pressed is inserted in the editing buffer so that
28417 it is possible to type most @value{GDBN} commands without interaction
28418 with the TUI SingleKey mode. Once the command is entered the TUI
28419 SingleKey mode is restored. The only way to permanently leave
28420 this mode is by typing @kbd{q} or @kbd{C-x s}.
28424 @section TUI-specific Commands
28425 @cindex TUI commands
28427 The TUI has specific commands to control the text windows.
28428 These commands are always available, even when @value{GDBN} is not in
28429 the TUI mode. When @value{GDBN} is in the standard mode, most
28430 of these commands will automatically switch to the TUI mode.
28432 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28433 terminal, or @value{GDBN} has been started with the machine interface
28434 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28435 these commands will fail with an error, because it would not be
28436 possible or desirable to enable curses window management.
28441 List and give the size of all displayed windows.
28445 Display the next layout.
28448 Display the previous layout.
28451 Display the source window only.
28454 Display the assembly window only.
28457 Display the source and assembly window.
28460 Display the register window together with the source or assembly window.
28464 Make the next window active for scrolling.
28467 Make the previous window active for scrolling.
28470 Make the source window active for scrolling.
28473 Make the assembly window active for scrolling.
28476 Make the register window active for scrolling.
28479 Make the command window active for scrolling.
28483 Refresh the screen. This is similar to typing @kbd{C-L}.
28485 @item tui reg float
28487 Show the floating point registers in the register window.
28489 @item tui reg general
28490 Show the general registers in the register window.
28493 Show the next register group. The list of register groups as well as
28494 their order is target specific. The predefined register groups are the
28495 following: @code{general}, @code{float}, @code{system}, @code{vector},
28496 @code{all}, @code{save}, @code{restore}.
28498 @item tui reg system
28499 Show the system registers in the register window.
28503 Update the source window and the current execution point.
28505 @item winheight @var{name} +@var{count}
28506 @itemx winheight @var{name} -@var{count}
28508 Change the height of the window @var{name} by @var{count}
28509 lines. Positive counts increase the height, while negative counts
28512 @item tabset @var{nchars}
28514 Set the width of tab stops to be @var{nchars} characters.
28517 @node TUI Configuration
28518 @section TUI Configuration Variables
28519 @cindex TUI configuration variables
28521 Several configuration variables control the appearance of TUI windows.
28524 @item set tui border-kind @var{kind}
28525 @kindex set tui border-kind
28526 Select the border appearance for the source, assembly and register windows.
28527 The possible values are the following:
28530 Use a space character to draw the border.
28533 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28536 Use the Alternate Character Set to draw the border. The border is
28537 drawn using character line graphics if the terminal supports them.
28540 @item set tui border-mode @var{mode}
28541 @kindex set tui border-mode
28542 @itemx set tui active-border-mode @var{mode}
28543 @kindex set tui active-border-mode
28544 Select the display attributes for the borders of the inactive windows
28545 or the active window. The @var{mode} can be one of the following:
28548 Use normal attributes to display the border.
28554 Use reverse video mode.
28557 Use half bright mode.
28559 @item half-standout
28560 Use half bright and standout mode.
28563 Use extra bright or bold mode.
28565 @item bold-standout
28566 Use extra bright or bold and standout mode.
28571 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28574 @cindex @sc{gnu} Emacs
28575 A special interface allows you to use @sc{gnu} Emacs to view (and
28576 edit) the source files for the program you are debugging with
28579 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28580 executable file you want to debug as an argument. This command starts
28581 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28582 created Emacs buffer.
28583 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28585 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28590 All ``terminal'' input and output goes through an Emacs buffer, called
28593 This applies both to @value{GDBN} commands and their output, and to the input
28594 and output done by the program you are debugging.
28596 This is useful because it means that you can copy the text of previous
28597 commands and input them again; you can even use parts of the output
28600 All the facilities of Emacs' Shell mode are available for interacting
28601 with your program. In particular, you can send signals the usual
28602 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28606 @value{GDBN} displays source code through Emacs.
28608 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28609 source file for that frame and puts an arrow (@samp{=>}) at the
28610 left margin of the current line. Emacs uses a separate buffer for
28611 source display, and splits the screen to show both your @value{GDBN} session
28614 Explicit @value{GDBN} @code{list} or search commands still produce output as
28615 usual, but you probably have no reason to use them from Emacs.
28618 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28619 a graphical mode, enabled by default, which provides further buffers
28620 that can control the execution and describe the state of your program.
28621 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28623 If you specify an absolute file name when prompted for the @kbd{M-x
28624 gdb} argument, then Emacs sets your current working directory to where
28625 your program resides. If you only specify the file name, then Emacs
28626 sets your current working directory to the directory associated
28627 with the previous buffer. In this case, @value{GDBN} may find your
28628 program by searching your environment's @code{PATH} variable, but on
28629 some operating systems it might not find the source. So, although the
28630 @value{GDBN} input and output session proceeds normally, the auxiliary
28631 buffer does not display the current source and line of execution.
28633 The initial working directory of @value{GDBN} is printed on the top
28634 line of the GUD buffer and this serves as a default for the commands
28635 that specify files for @value{GDBN} to operate on. @xref{Files,
28636 ,Commands to Specify Files}.
28638 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28639 need to call @value{GDBN} by a different name (for example, if you
28640 keep several configurations around, with different names) you can
28641 customize the Emacs variable @code{gud-gdb-command-name} to run the
28644 In the GUD buffer, you can use these special Emacs commands in
28645 addition to the standard Shell mode commands:
28649 Describe the features of Emacs' GUD Mode.
28652 Execute to another source line, like the @value{GDBN} @code{step} command; also
28653 update the display window to show the current file and location.
28656 Execute to next source line in this function, skipping all function
28657 calls, like the @value{GDBN} @code{next} command. Then update the display window
28658 to show the current file and location.
28661 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28662 display window accordingly.
28665 Execute until exit from the selected stack frame, like the @value{GDBN}
28666 @code{finish} command.
28669 Continue execution of your program, like the @value{GDBN} @code{continue}
28673 Go up the number of frames indicated by the numeric argument
28674 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28675 like the @value{GDBN} @code{up} command.
28678 Go down the number of frames indicated by the numeric argument, like the
28679 @value{GDBN} @code{down} command.
28682 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28683 tells @value{GDBN} to set a breakpoint on the source line point is on.
28685 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28686 separate frame which shows a backtrace when the GUD buffer is current.
28687 Move point to any frame in the stack and type @key{RET} to make it
28688 become the current frame and display the associated source in the
28689 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28690 selected frame become the current one. In graphical mode, the
28691 speedbar displays watch expressions.
28693 If you accidentally delete the source-display buffer, an easy way to get
28694 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28695 request a frame display; when you run under Emacs, this recreates
28696 the source buffer if necessary to show you the context of the current
28699 The source files displayed in Emacs are in ordinary Emacs buffers
28700 which are visiting the source files in the usual way. You can edit
28701 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28702 communicates with Emacs in terms of line numbers. If you add or
28703 delete lines from the text, the line numbers that @value{GDBN} knows cease
28704 to correspond properly with the code.
28706 A more detailed description of Emacs' interaction with @value{GDBN} is
28707 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28711 @chapter The @sc{gdb/mi} Interface
28713 @unnumberedsec Function and Purpose
28715 @cindex @sc{gdb/mi}, its purpose
28716 @sc{gdb/mi} is a line based machine oriented text interface to
28717 @value{GDBN} and is activated by specifying using the
28718 @option{--interpreter} command line option (@pxref{Mode Options}). It
28719 is specifically intended to support the development of systems which
28720 use the debugger as just one small component of a larger system.
28722 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28723 in the form of a reference manual.
28725 Note that @sc{gdb/mi} is still under construction, so some of the
28726 features described below are incomplete and subject to change
28727 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28729 @unnumberedsec Notation and Terminology
28731 @cindex notational conventions, for @sc{gdb/mi}
28732 This chapter uses the following notation:
28736 @code{|} separates two alternatives.
28739 @code{[ @var{something} ]} indicates that @var{something} is optional:
28740 it may or may not be given.
28743 @code{( @var{group} )*} means that @var{group} inside the parentheses
28744 may repeat zero or more times.
28747 @code{( @var{group} )+} means that @var{group} inside the parentheses
28748 may repeat one or more times.
28751 @code{"@var{string}"} means a literal @var{string}.
28755 @heading Dependencies
28759 * GDB/MI General Design::
28760 * GDB/MI Command Syntax::
28761 * GDB/MI Compatibility with CLI::
28762 * GDB/MI Development and Front Ends::
28763 * GDB/MI Output Records::
28764 * GDB/MI Simple Examples::
28765 * GDB/MI Command Description Format::
28766 * GDB/MI Breakpoint Commands::
28767 * GDB/MI Catchpoint Commands::
28768 * GDB/MI Program Context::
28769 * GDB/MI Thread Commands::
28770 * GDB/MI Ada Tasking Commands::
28771 * GDB/MI Program Execution::
28772 * GDB/MI Stack Manipulation::
28773 * GDB/MI Variable Objects::
28774 * GDB/MI Data Manipulation::
28775 * GDB/MI Tracepoint Commands::
28776 * GDB/MI Symbol Query::
28777 * GDB/MI File Commands::
28779 * GDB/MI Kod Commands::
28780 * GDB/MI Memory Overlay Commands::
28781 * GDB/MI Signal Handling Commands::
28783 * GDB/MI Target Manipulation::
28784 * GDB/MI File Transfer Commands::
28785 * GDB/MI Ada Exceptions Commands::
28786 * GDB/MI Miscellaneous Commands::
28789 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28790 @node GDB/MI General Design
28791 @section @sc{gdb/mi} General Design
28792 @cindex GDB/MI General Design
28794 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28795 parts---commands sent to @value{GDBN}, responses to those commands
28796 and notifications. Each command results in exactly one response,
28797 indicating either successful completion of the command, or an error.
28798 For the commands that do not resume the target, the response contains the
28799 requested information. For the commands that resume the target, the
28800 response only indicates whether the target was successfully resumed.
28801 Notifications is the mechanism for reporting changes in the state of the
28802 target, or in @value{GDBN} state, that cannot conveniently be associated with
28803 a command and reported as part of that command response.
28805 The important examples of notifications are:
28809 Exec notifications. These are used to report changes in
28810 target state---when a target is resumed, or stopped. It would not
28811 be feasible to include this information in response of resuming
28812 commands, because one resume commands can result in multiple events in
28813 different threads. Also, quite some time may pass before any event
28814 happens in the target, while a frontend needs to know whether the resuming
28815 command itself was successfully executed.
28818 Console output, and status notifications. Console output
28819 notifications are used to report output of CLI commands, as well as
28820 diagnostics for other commands. Status notifications are used to
28821 report the progress of a long-running operation. Naturally, including
28822 this information in command response would mean no output is produced
28823 until the command is finished, which is undesirable.
28826 General notifications. Commands may have various side effects on
28827 the @value{GDBN} or target state beyond their official purpose. For example,
28828 a command may change the selected thread. Although such changes can
28829 be included in command response, using notification allows for more
28830 orthogonal frontend design.
28834 There's no guarantee that whenever an MI command reports an error,
28835 @value{GDBN} or the target are in any specific state, and especially,
28836 the state is not reverted to the state before the MI command was
28837 processed. Therefore, whenever an MI command results in an error,
28838 we recommend that the frontend refreshes all the information shown in
28839 the user interface.
28843 * Context management::
28844 * Asynchronous and non-stop modes::
28848 @node Context management
28849 @subsection Context management
28851 @subsubsection Threads and Frames
28853 In most cases when @value{GDBN} accesses the target, this access is
28854 done in context of a specific thread and frame (@pxref{Frames}).
28855 Often, even when accessing global data, the target requires that a thread
28856 be specified. The CLI interface maintains the selected thread and frame,
28857 and supplies them to target on each command. This is convenient,
28858 because a command line user would not want to specify that information
28859 explicitly on each command, and because user interacts with
28860 @value{GDBN} via a single terminal, so no confusion is possible as
28861 to what thread and frame are the current ones.
28863 In the case of MI, the concept of selected thread and frame is less
28864 useful. First, a frontend can easily remember this information
28865 itself. Second, a graphical frontend can have more than one window,
28866 each one used for debugging a different thread, and the frontend might
28867 want to access additional threads for internal purposes. This
28868 increases the risk that by relying on implicitly selected thread, the
28869 frontend may be operating on a wrong one. Therefore, each MI command
28870 should explicitly specify which thread and frame to operate on. To
28871 make it possible, each MI command accepts the @samp{--thread} and
28872 @samp{--frame} options, the value to each is @value{GDBN} identifier
28873 for thread and frame to operate on.
28875 Usually, each top-level window in a frontend allows the user to select
28876 a thread and a frame, and remembers the user selection for further
28877 operations. However, in some cases @value{GDBN} may suggest that the
28878 current thread be changed. For example, when stopping on a breakpoint
28879 it is reasonable to switch to the thread where breakpoint is hit. For
28880 another example, if the user issues the CLI @samp{thread} command via
28881 the frontend, it is desirable to change the frontend's selected thread to the
28882 one specified by user. @value{GDBN} communicates the suggestion to
28883 change current thread using the @samp{=thread-selected} notification.
28884 No such notification is available for the selected frame at the moment.
28886 Note that historically, MI shares the selected thread with CLI, so
28887 frontends used the @code{-thread-select} to execute commands in the
28888 right context. However, getting this to work right is cumbersome. The
28889 simplest way is for frontend to emit @code{-thread-select} command
28890 before every command. This doubles the number of commands that need
28891 to be sent. The alternative approach is to suppress @code{-thread-select}
28892 if the selected thread in @value{GDBN} is supposed to be identical to the
28893 thread the frontend wants to operate on. However, getting this
28894 optimization right can be tricky. In particular, if the frontend
28895 sends several commands to @value{GDBN}, and one of the commands changes the
28896 selected thread, then the behaviour of subsequent commands will
28897 change. So, a frontend should either wait for response from such
28898 problematic commands, or explicitly add @code{-thread-select} for
28899 all subsequent commands. No frontend is known to do this exactly
28900 right, so it is suggested to just always pass the @samp{--thread} and
28901 @samp{--frame} options.
28903 @subsubsection Language
28905 The execution of several commands depends on which language is selected.
28906 By default, the current language (@pxref{show language}) is used.
28907 But for commands known to be language-sensitive, it is recommended
28908 to use the @samp{--language} option. This option takes one argument,
28909 which is the name of the language to use while executing the command.
28913 -data-evaluate-expression --language c "sizeof (void*)"
28918 The valid language names are the same names accepted by the
28919 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
28920 @samp{local} or @samp{unknown}.
28922 @node Asynchronous and non-stop modes
28923 @subsection Asynchronous command execution and non-stop mode
28925 On some targets, @value{GDBN} is capable of processing MI commands
28926 even while the target is running. This is called @dfn{asynchronous
28927 command execution} (@pxref{Background Execution}). The frontend may
28928 specify a preferrence for asynchronous execution using the
28929 @code{-gdb-set target-async 1} command, which should be emitted before
28930 either running the executable or attaching to the target. After the
28931 frontend has started the executable or attached to the target, it can
28932 find if asynchronous execution is enabled using the
28933 @code{-list-target-features} command.
28935 Even if @value{GDBN} can accept a command while target is running,
28936 many commands that access the target do not work when the target is
28937 running. Therefore, asynchronous command execution is most useful
28938 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28939 it is possible to examine the state of one thread, while other threads
28942 When a given thread is running, MI commands that try to access the
28943 target in the context of that thread may not work, or may work only on
28944 some targets. In particular, commands that try to operate on thread's
28945 stack will not work, on any target. Commands that read memory, or
28946 modify breakpoints, may work or not work, depending on the target. Note
28947 that even commands that operate on global state, such as @code{print},
28948 @code{set}, and breakpoint commands, still access the target in the
28949 context of a specific thread, so frontend should try to find a
28950 stopped thread and perform the operation on that thread (using the
28951 @samp{--thread} option).
28953 Which commands will work in the context of a running thread is
28954 highly target dependent. However, the two commands
28955 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28956 to find the state of a thread, will always work.
28958 @node Thread groups
28959 @subsection Thread groups
28960 @value{GDBN} may be used to debug several processes at the same time.
28961 On some platfroms, @value{GDBN} may support debugging of several
28962 hardware systems, each one having several cores with several different
28963 processes running on each core. This section describes the MI
28964 mechanism to support such debugging scenarios.
28966 The key observation is that regardless of the structure of the
28967 target, MI can have a global list of threads, because most commands that
28968 accept the @samp{--thread} option do not need to know what process that
28969 thread belongs to. Therefore, it is not necessary to introduce
28970 neither additional @samp{--process} option, nor an notion of the
28971 current process in the MI interface. The only strictly new feature
28972 that is required is the ability to find how the threads are grouped
28975 To allow the user to discover such grouping, and to support arbitrary
28976 hierarchy of machines/cores/processes, MI introduces the concept of a
28977 @dfn{thread group}. Thread group is a collection of threads and other
28978 thread groups. A thread group always has a string identifier, a type,
28979 and may have additional attributes specific to the type. A new
28980 command, @code{-list-thread-groups}, returns the list of top-level
28981 thread groups, which correspond to processes that @value{GDBN} is
28982 debugging at the moment. By passing an identifier of a thread group
28983 to the @code{-list-thread-groups} command, it is possible to obtain
28984 the members of specific thread group.
28986 To allow the user to easily discover processes, and other objects, he
28987 wishes to debug, a concept of @dfn{available thread group} is
28988 introduced. Available thread group is an thread group that
28989 @value{GDBN} is not debugging, but that can be attached to, using the
28990 @code{-target-attach} command. The list of available top-level thread
28991 groups can be obtained using @samp{-list-thread-groups --available}.
28992 In general, the content of a thread group may be only retrieved only
28993 after attaching to that thread group.
28995 Thread groups are related to inferiors (@pxref{Inferiors and
28996 Programs}). Each inferior corresponds to a thread group of a special
28997 type @samp{process}, and some additional operations are permitted on
28998 such thread groups.
29000 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29001 @node GDB/MI Command Syntax
29002 @section @sc{gdb/mi} Command Syntax
29005 * GDB/MI Input Syntax::
29006 * GDB/MI Output Syntax::
29009 @node GDB/MI Input Syntax
29010 @subsection @sc{gdb/mi} Input Syntax
29012 @cindex input syntax for @sc{gdb/mi}
29013 @cindex @sc{gdb/mi}, input syntax
29015 @item @var{command} @expansion{}
29016 @code{@var{cli-command} | @var{mi-command}}
29018 @item @var{cli-command} @expansion{}
29019 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29020 @var{cli-command} is any existing @value{GDBN} CLI command.
29022 @item @var{mi-command} @expansion{}
29023 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29024 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29026 @item @var{token} @expansion{}
29027 "any sequence of digits"
29029 @item @var{option} @expansion{}
29030 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29032 @item @var{parameter} @expansion{}
29033 @code{@var{non-blank-sequence} | @var{c-string}}
29035 @item @var{operation} @expansion{}
29036 @emph{any of the operations described in this chapter}
29038 @item @var{non-blank-sequence} @expansion{}
29039 @emph{anything, provided it doesn't contain special characters such as
29040 "-", @var{nl}, """ and of course " "}
29042 @item @var{c-string} @expansion{}
29043 @code{""" @var{seven-bit-iso-c-string-content} """}
29045 @item @var{nl} @expansion{}
29054 The CLI commands are still handled by the @sc{mi} interpreter; their
29055 output is described below.
29058 The @code{@var{token}}, when present, is passed back when the command
29062 Some @sc{mi} commands accept optional arguments as part of the parameter
29063 list. Each option is identified by a leading @samp{-} (dash) and may be
29064 followed by an optional argument parameter. Options occur first in the
29065 parameter list and can be delimited from normal parameters using
29066 @samp{--} (this is useful when some parameters begin with a dash).
29073 We want easy access to the existing CLI syntax (for debugging).
29076 We want it to be easy to spot a @sc{mi} operation.
29079 @node GDB/MI Output Syntax
29080 @subsection @sc{gdb/mi} Output Syntax
29082 @cindex output syntax of @sc{gdb/mi}
29083 @cindex @sc{gdb/mi}, output syntax
29084 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29085 followed, optionally, by a single result record. This result record
29086 is for the most recent command. The sequence of output records is
29087 terminated by @samp{(gdb)}.
29089 If an input command was prefixed with a @code{@var{token}} then the
29090 corresponding output for that command will also be prefixed by that same
29094 @item @var{output} @expansion{}
29095 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29097 @item @var{result-record} @expansion{}
29098 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29100 @item @var{out-of-band-record} @expansion{}
29101 @code{@var{async-record} | @var{stream-record}}
29103 @item @var{async-record} @expansion{}
29104 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29106 @item @var{exec-async-output} @expansion{}
29107 @code{[ @var{token} ] "*" @var{async-output}}
29109 @item @var{status-async-output} @expansion{}
29110 @code{[ @var{token} ] "+" @var{async-output}}
29112 @item @var{notify-async-output} @expansion{}
29113 @code{[ @var{token} ] "=" @var{async-output}}
29115 @item @var{async-output} @expansion{}
29116 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
29118 @item @var{result-class} @expansion{}
29119 @code{"done" | "running" | "connected" | "error" | "exit"}
29121 @item @var{async-class} @expansion{}
29122 @code{"stopped" | @var{others}} (where @var{others} will be added
29123 depending on the needs---this is still in development).
29125 @item @var{result} @expansion{}
29126 @code{ @var{variable} "=" @var{value}}
29128 @item @var{variable} @expansion{}
29129 @code{ @var{string} }
29131 @item @var{value} @expansion{}
29132 @code{ @var{const} | @var{tuple} | @var{list} }
29134 @item @var{const} @expansion{}
29135 @code{@var{c-string}}
29137 @item @var{tuple} @expansion{}
29138 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29140 @item @var{list} @expansion{}
29141 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29142 @var{result} ( "," @var{result} )* "]" }
29144 @item @var{stream-record} @expansion{}
29145 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29147 @item @var{console-stream-output} @expansion{}
29148 @code{"~" @var{c-string}}
29150 @item @var{target-stream-output} @expansion{}
29151 @code{"@@" @var{c-string}}
29153 @item @var{log-stream-output} @expansion{}
29154 @code{"&" @var{c-string}}
29156 @item @var{nl} @expansion{}
29159 @item @var{token} @expansion{}
29160 @emph{any sequence of digits}.
29168 All output sequences end in a single line containing a period.
29171 The @code{@var{token}} is from the corresponding request. Note that
29172 for all async output, while the token is allowed by the grammar and
29173 may be output by future versions of @value{GDBN} for select async
29174 output messages, it is generally omitted. Frontends should treat
29175 all async output as reporting general changes in the state of the
29176 target and there should be no need to associate async output to any
29180 @cindex status output in @sc{gdb/mi}
29181 @var{status-async-output} contains on-going status information about the
29182 progress of a slow operation. It can be discarded. All status output is
29183 prefixed by @samp{+}.
29186 @cindex async output in @sc{gdb/mi}
29187 @var{exec-async-output} contains asynchronous state change on the target
29188 (stopped, started, disappeared). All async output is prefixed by
29192 @cindex notify output in @sc{gdb/mi}
29193 @var{notify-async-output} contains supplementary information that the
29194 client should handle (e.g., a new breakpoint information). All notify
29195 output is prefixed by @samp{=}.
29198 @cindex console output in @sc{gdb/mi}
29199 @var{console-stream-output} is output that should be displayed as is in the
29200 console. It is the textual response to a CLI command. All the console
29201 output is prefixed by @samp{~}.
29204 @cindex target output in @sc{gdb/mi}
29205 @var{target-stream-output} is the output produced by the target program.
29206 All the target output is prefixed by @samp{@@}.
29209 @cindex log output in @sc{gdb/mi}
29210 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29211 instance messages that should be displayed as part of an error log. All
29212 the log output is prefixed by @samp{&}.
29215 @cindex list output in @sc{gdb/mi}
29216 New @sc{gdb/mi} commands should only output @var{lists} containing
29222 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29223 details about the various output records.
29225 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29226 @node GDB/MI Compatibility with CLI
29227 @section @sc{gdb/mi} Compatibility with CLI
29229 @cindex compatibility, @sc{gdb/mi} and CLI
29230 @cindex @sc{gdb/mi}, compatibility with CLI
29232 For the developers convenience CLI commands can be entered directly,
29233 but there may be some unexpected behaviour. For example, commands
29234 that query the user will behave as if the user replied yes, breakpoint
29235 command lists are not executed and some CLI commands, such as
29236 @code{if}, @code{when} and @code{define}, prompt for further input with
29237 @samp{>}, which is not valid MI output.
29239 This feature may be removed at some stage in the future and it is
29240 recommended that front ends use the @code{-interpreter-exec} command
29241 (@pxref{-interpreter-exec}).
29243 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29244 @node GDB/MI Development and Front Ends
29245 @section @sc{gdb/mi} Development and Front Ends
29246 @cindex @sc{gdb/mi} development
29248 The application which takes the MI output and presents the state of the
29249 program being debugged to the user is called a @dfn{front end}.
29251 Although @sc{gdb/mi} is still incomplete, it is currently being used
29252 by a variety of front ends to @value{GDBN}. This makes it difficult
29253 to introduce new functionality without breaking existing usage. This
29254 section tries to minimize the problems by describing how the protocol
29257 Some changes in MI need not break a carefully designed front end, and
29258 for these the MI version will remain unchanged. The following is a
29259 list of changes that may occur within one level, so front ends should
29260 parse MI output in a way that can handle them:
29264 New MI commands may be added.
29267 New fields may be added to the output of any MI command.
29270 The range of values for fields with specified values, e.g.,
29271 @code{in_scope} (@pxref{-var-update}) may be extended.
29273 @c The format of field's content e.g type prefix, may change so parse it
29274 @c at your own risk. Yes, in general?
29276 @c The order of fields may change? Shouldn't really matter but it might
29277 @c resolve inconsistencies.
29280 If the changes are likely to break front ends, the MI version level
29281 will be increased by one. This will allow the front end to parse the
29282 output according to the MI version. Apart from mi0, new versions of
29283 @value{GDBN} will not support old versions of MI and it will be the
29284 responsibility of the front end to work with the new one.
29286 @c Starting with mi3, add a new command -mi-version that prints the MI
29289 The best way to avoid unexpected changes in MI that might break your front
29290 end is to make your project known to @value{GDBN} developers and
29291 follow development on @email{gdb@@sourceware.org} and
29292 @email{gdb-patches@@sourceware.org}.
29293 @cindex mailing lists
29295 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29296 @node GDB/MI Output Records
29297 @section @sc{gdb/mi} Output Records
29300 * GDB/MI Result Records::
29301 * GDB/MI Stream Records::
29302 * GDB/MI Async Records::
29303 * GDB/MI Breakpoint Information::
29304 * GDB/MI Frame Information::
29305 * GDB/MI Thread Information::
29306 * GDB/MI Ada Exception Information::
29309 @node GDB/MI Result Records
29310 @subsection @sc{gdb/mi} Result Records
29312 @cindex result records in @sc{gdb/mi}
29313 @cindex @sc{gdb/mi}, result records
29314 In addition to a number of out-of-band notifications, the response to a
29315 @sc{gdb/mi} command includes one of the following result indications:
29319 @item "^done" [ "," @var{results} ]
29320 The synchronous operation was successful, @code{@var{results}} are the return
29325 This result record is equivalent to @samp{^done}. Historically, it
29326 was output instead of @samp{^done} if the command has resumed the
29327 target. This behaviour is maintained for backward compatibility, but
29328 all frontends should treat @samp{^done} and @samp{^running}
29329 identically and rely on the @samp{*running} output record to determine
29330 which threads are resumed.
29334 @value{GDBN} has connected to a remote target.
29336 @item "^error" "," @var{c-string}
29338 The operation failed. The @code{@var{c-string}} contains the corresponding
29343 @value{GDBN} has terminated.
29347 @node GDB/MI Stream Records
29348 @subsection @sc{gdb/mi} Stream Records
29350 @cindex @sc{gdb/mi}, stream records
29351 @cindex stream records in @sc{gdb/mi}
29352 @value{GDBN} internally maintains a number of output streams: the console, the
29353 target, and the log. The output intended for each of these streams is
29354 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29356 Each stream record begins with a unique @dfn{prefix character} which
29357 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29358 Syntax}). In addition to the prefix, each stream record contains a
29359 @code{@var{string-output}}. This is either raw text (with an implicit new
29360 line) or a quoted C string (which does not contain an implicit newline).
29363 @item "~" @var{string-output}
29364 The console output stream contains text that should be displayed in the
29365 CLI console window. It contains the textual responses to CLI commands.
29367 @item "@@" @var{string-output}
29368 The target output stream contains any textual output from the running
29369 target. This is only present when GDB's event loop is truly
29370 asynchronous, which is currently only the case for remote targets.
29372 @item "&" @var{string-output}
29373 The log stream contains debugging messages being produced by @value{GDBN}'s
29377 @node GDB/MI Async Records
29378 @subsection @sc{gdb/mi} Async Records
29380 @cindex async records in @sc{gdb/mi}
29381 @cindex @sc{gdb/mi}, async records
29382 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29383 additional changes that have occurred. Those changes can either be a
29384 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29385 target activity (e.g., target stopped).
29387 The following is the list of possible async records:
29391 @item *running,thread-id="@var{thread}"
29392 The target is now running. The @var{thread} field tells which
29393 specific thread is now running, and can be @samp{all} if all threads
29394 are running. The frontend should assume that no interaction with a
29395 running thread is possible after this notification is produced.
29396 The frontend should not assume that this notification is output
29397 only once for any command. @value{GDBN} may emit this notification
29398 several times, either for different threads, because it cannot resume
29399 all threads together, or even for a single thread, if the thread must
29400 be stepped though some code before letting it run freely.
29402 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29403 The target has stopped. The @var{reason} field can have one of the
29407 @item breakpoint-hit
29408 A breakpoint was reached.
29409 @item watchpoint-trigger
29410 A watchpoint was triggered.
29411 @item read-watchpoint-trigger
29412 A read watchpoint was triggered.
29413 @item access-watchpoint-trigger
29414 An access watchpoint was triggered.
29415 @item function-finished
29416 An -exec-finish or similar CLI command was accomplished.
29417 @item location-reached
29418 An -exec-until or similar CLI command was accomplished.
29419 @item watchpoint-scope
29420 A watchpoint has gone out of scope.
29421 @item end-stepping-range
29422 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29423 similar CLI command was accomplished.
29424 @item exited-signalled
29425 The inferior exited because of a signal.
29427 The inferior exited.
29428 @item exited-normally
29429 The inferior exited normally.
29430 @item signal-received
29431 A signal was received by the inferior.
29433 The inferior has stopped due to a library being loaded or unloaded.
29434 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29435 set or when a @code{catch load} or @code{catch unload} catchpoint is
29436 in use (@pxref{Set Catchpoints}).
29438 The inferior has forked. This is reported when @code{catch fork}
29439 (@pxref{Set Catchpoints}) has been used.
29441 The inferior has vforked. This is reported in when @code{catch vfork}
29442 (@pxref{Set Catchpoints}) has been used.
29443 @item syscall-entry
29444 The inferior entered a system call. This is reported when @code{catch
29445 syscall} (@pxref{Set Catchpoints}) has been used.
29446 @item syscall-entry
29447 The inferior returned from a system call. This is reported when
29448 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29450 The inferior called @code{exec}. This is reported when @code{catch exec}
29451 (@pxref{Set Catchpoints}) has been used.
29454 The @var{id} field identifies the thread that directly caused the stop
29455 -- for example by hitting a breakpoint. Depending on whether all-stop
29456 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29457 stop all threads, or only the thread that directly triggered the stop.
29458 If all threads are stopped, the @var{stopped} field will have the
29459 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29460 field will be a list of thread identifiers. Presently, this list will
29461 always include a single thread, but frontend should be prepared to see
29462 several threads in the list. The @var{core} field reports the
29463 processor core on which the stop event has happened. This field may be absent
29464 if such information is not available.
29466 @item =thread-group-added,id="@var{id}"
29467 @itemx =thread-group-removed,id="@var{id}"
29468 A thread group was either added or removed. The @var{id} field
29469 contains the @value{GDBN} identifier of the thread group. When a thread
29470 group is added, it generally might not be associated with a running
29471 process. When a thread group is removed, its id becomes invalid and
29472 cannot be used in any way.
29474 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29475 A thread group became associated with a running program,
29476 either because the program was just started or the thread group
29477 was attached to a program. The @var{id} field contains the
29478 @value{GDBN} identifier of the thread group. The @var{pid} field
29479 contains process identifier, specific to the operating system.
29481 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29482 A thread group is no longer associated with a running program,
29483 either because the program has exited, or because it was detached
29484 from. The @var{id} field contains the @value{GDBN} identifier of the
29485 thread group. @var{code} is the exit code of the inferior; it exists
29486 only when the inferior exited with some code.
29488 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29489 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29490 A thread either was created, or has exited. The @var{id} field
29491 contains the @value{GDBN} identifier of the thread. The @var{gid}
29492 field identifies the thread group this thread belongs to.
29494 @item =thread-selected,id="@var{id}"
29495 Informs that the selected thread was changed as result of the last
29496 command. This notification is not emitted as result of @code{-thread-select}
29497 command but is emitted whenever an MI command that is not documented
29498 to change the selected thread actually changes it. In particular,
29499 invoking, directly or indirectly (via user-defined command), the CLI
29500 @code{thread} command, will generate this notification.
29502 We suggest that in response to this notification, front ends
29503 highlight the selected thread and cause subsequent commands to apply to
29506 @item =library-loaded,...
29507 Reports that a new library file was loaded by the program. This
29508 notification has 4 fields---@var{id}, @var{target-name},
29509 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29510 opaque identifier of the library. For remote debugging case,
29511 @var{target-name} and @var{host-name} fields give the name of the
29512 library file on the target, and on the host respectively. For native
29513 debugging, both those fields have the same value. The
29514 @var{symbols-loaded} field is emitted only for backward compatibility
29515 and should not be relied on to convey any useful information. The
29516 @var{thread-group} field, if present, specifies the id of the thread
29517 group in whose context the library was loaded. If the field is
29518 absent, it means the library was loaded in the context of all present
29521 @item =library-unloaded,...
29522 Reports that a library was unloaded by the program. This notification
29523 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29524 the same meaning as for the @code{=library-loaded} notification.
29525 The @var{thread-group} field, if present, specifies the id of the
29526 thread group in whose context the library was unloaded. If the field is
29527 absent, it means the library was unloaded in the context of all present
29530 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29531 @itemx =traceframe-changed,end
29532 Reports that the trace frame was changed and its new number is
29533 @var{tfnum}. The number of the tracepoint associated with this trace
29534 frame is @var{tpnum}.
29536 @item =tsv-created,name=@var{name},initial=@var{initial}
29537 Reports that the new trace state variable @var{name} is created with
29538 initial value @var{initial}.
29540 @item =tsv-deleted,name=@var{name}
29541 @itemx =tsv-deleted
29542 Reports that the trace state variable @var{name} is deleted or all
29543 trace state variables are deleted.
29545 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29546 Reports that the trace state variable @var{name} is modified with
29547 the initial value @var{initial}. The current value @var{current} of
29548 trace state variable is optional and is reported if the current
29549 value of trace state variable is known.
29551 @item =breakpoint-created,bkpt=@{...@}
29552 @itemx =breakpoint-modified,bkpt=@{...@}
29553 @itemx =breakpoint-deleted,id=@var{number}
29554 Reports that a breakpoint was created, modified, or deleted,
29555 respectively. Only user-visible breakpoints are reported to the MI
29558 The @var{bkpt} argument is of the same form as returned by the various
29559 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29560 @var{number} is the ordinal number of the breakpoint.
29562 Note that if a breakpoint is emitted in the result record of a
29563 command, then it will not also be emitted in an async record.
29565 @item =record-started,thread-group="@var{id}"
29566 @itemx =record-stopped,thread-group="@var{id}"
29567 Execution log recording was either started or stopped on an
29568 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29569 group corresponding to the affected inferior.
29571 @item =cmd-param-changed,param=@var{param},value=@var{value}
29572 Reports that a parameter of the command @code{set @var{param}} is
29573 changed to @var{value}. In the multi-word @code{set} command,
29574 the @var{param} is the whole parameter list to @code{set} command.
29575 For example, In command @code{set check type on}, @var{param}
29576 is @code{check type} and @var{value} is @code{on}.
29578 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29579 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29580 written in an inferior. The @var{id} is the identifier of the
29581 thread group corresponding to the affected inferior. The optional
29582 @code{type="code"} part is reported if the memory written to holds
29586 @node GDB/MI Breakpoint Information
29587 @subsection @sc{gdb/mi} Breakpoint Information
29589 When @value{GDBN} reports information about a breakpoint, a
29590 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29595 The breakpoint number. For a breakpoint that represents one location
29596 of a multi-location breakpoint, this will be a dotted pair, like
29600 The type of the breakpoint. For ordinary breakpoints this will be
29601 @samp{breakpoint}, but many values are possible.
29604 If the type of the breakpoint is @samp{catchpoint}, then this
29605 indicates the exact type of catchpoint.
29608 This is the breakpoint disposition---either @samp{del}, meaning that
29609 the breakpoint will be deleted at the next stop, or @samp{keep},
29610 meaning that the breakpoint will not be deleted.
29613 This indicates whether the breakpoint is enabled, in which case the
29614 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29615 Note that this is not the same as the field @code{enable}.
29618 The address of the breakpoint. This may be a hexidecimal number,
29619 giving the address; or the string @samp{<PENDING>}, for a pending
29620 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29621 multiple locations. This field will not be present if no address can
29622 be determined. For example, a watchpoint does not have an address.
29625 If known, the function in which the breakpoint appears.
29626 If not known, this field is not present.
29629 The name of the source file which contains this function, if known.
29630 If not known, this field is not present.
29633 The full file name of the source file which contains this function, if
29634 known. If not known, this field is not present.
29637 The line number at which this breakpoint appears, if known.
29638 If not known, this field is not present.
29641 If the source file is not known, this field may be provided. If
29642 provided, this holds the address of the breakpoint, possibly followed
29646 If this breakpoint is pending, this field is present and holds the
29647 text used to set the breakpoint, as entered by the user.
29650 Where this breakpoint's condition is evaluated, either @samp{host} or
29654 If this is a thread-specific breakpoint, then this identifies the
29655 thread in which the breakpoint can trigger.
29658 If this breakpoint is restricted to a particular Ada task, then this
29659 field will hold the task identifier.
29662 If the breakpoint is conditional, this is the condition expression.
29665 The ignore count of the breakpoint.
29668 The enable count of the breakpoint.
29670 @item traceframe-usage
29673 @item static-tracepoint-marker-string-id
29674 For a static tracepoint, the name of the static tracepoint marker.
29677 For a masked watchpoint, this is the mask.
29680 A tracepoint's pass count.
29682 @item original-location
29683 The location of the breakpoint as originally specified by the user.
29684 This field is optional.
29687 The number of times the breakpoint has been hit.
29690 This field is only given for tracepoints. This is either @samp{y},
29691 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29695 Some extra data, the exact contents of which are type-dependent.
29699 For example, here is what the output of @code{-break-insert}
29700 (@pxref{GDB/MI Breakpoint Commands}) might be:
29703 -> -break-insert main
29704 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29705 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29706 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29711 @node GDB/MI Frame Information
29712 @subsection @sc{gdb/mi} Frame Information
29714 Response from many MI commands includes an information about stack
29715 frame. This information is a tuple that may have the following
29720 The level of the stack frame. The innermost frame has the level of
29721 zero. This field is always present.
29724 The name of the function corresponding to the frame. This field may
29725 be absent if @value{GDBN} is unable to determine the function name.
29728 The code address for the frame. This field is always present.
29731 The name of the source files that correspond to the frame's code
29732 address. This field may be absent.
29735 The source line corresponding to the frames' code address. This field
29739 The name of the binary file (either executable or shared library) the
29740 corresponds to the frame's code address. This field may be absent.
29744 @node GDB/MI Thread Information
29745 @subsection @sc{gdb/mi} Thread Information
29747 Whenever @value{GDBN} has to report an information about a thread, it
29748 uses a tuple with the following fields:
29752 The numeric id assigned to the thread by @value{GDBN}. This field is
29756 Target-specific string identifying the thread. This field is always present.
29759 Additional information about the thread provided by the target.
29760 It is supposed to be human-readable and not interpreted by the
29761 frontend. This field is optional.
29764 Either @samp{stopped} or @samp{running}, depending on whether the
29765 thread is presently running. This field is always present.
29768 The value of this field is an integer number of the processor core the
29769 thread was last seen on. This field is optional.
29772 @node GDB/MI Ada Exception Information
29773 @subsection @sc{gdb/mi} Ada Exception Information
29775 Whenever a @code{*stopped} record is emitted because the program
29776 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29777 @value{GDBN} provides the name of the exception that was raised via
29778 the @code{exception-name} field.
29780 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29781 @node GDB/MI Simple Examples
29782 @section Simple Examples of @sc{gdb/mi} Interaction
29783 @cindex @sc{gdb/mi}, simple examples
29785 This subsection presents several simple examples of interaction using
29786 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29787 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29788 the output received from @sc{gdb/mi}.
29790 Note the line breaks shown in the examples are here only for
29791 readability, they don't appear in the real output.
29793 @subheading Setting a Breakpoint
29795 Setting a breakpoint generates synchronous output which contains detailed
29796 information of the breakpoint.
29799 -> -break-insert main
29800 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29801 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29802 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29807 @subheading Program Execution
29809 Program execution generates asynchronous records and MI gives the
29810 reason that execution stopped.
29816 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29817 frame=@{addr="0x08048564",func="main",
29818 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29819 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29824 <- *stopped,reason="exited-normally"
29828 @subheading Quitting @value{GDBN}
29830 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29838 Please note that @samp{^exit} is printed immediately, but it might
29839 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29840 performs necessary cleanups, including killing programs being debugged
29841 or disconnecting from debug hardware, so the frontend should wait till
29842 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29843 fails to exit in reasonable time.
29845 @subheading A Bad Command
29847 Here's what happens if you pass a non-existent command:
29851 <- ^error,msg="Undefined MI command: rubbish"
29856 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29857 @node GDB/MI Command Description Format
29858 @section @sc{gdb/mi} Command Description Format
29860 The remaining sections describe blocks of commands. Each block of
29861 commands is laid out in a fashion similar to this section.
29863 @subheading Motivation
29865 The motivation for this collection of commands.
29867 @subheading Introduction
29869 A brief introduction to this collection of commands as a whole.
29871 @subheading Commands
29873 For each command in the block, the following is described:
29875 @subsubheading Synopsis
29878 -command @var{args}@dots{}
29881 @subsubheading Result
29883 @subsubheading @value{GDBN} Command
29885 The corresponding @value{GDBN} CLI command(s), if any.
29887 @subsubheading Example
29889 Example(s) formatted for readability. Some of the described commands have
29890 not been implemented yet and these are labeled N.A.@: (not available).
29893 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29894 @node GDB/MI Breakpoint Commands
29895 @section @sc{gdb/mi} Breakpoint Commands
29897 @cindex breakpoint commands for @sc{gdb/mi}
29898 @cindex @sc{gdb/mi}, breakpoint commands
29899 This section documents @sc{gdb/mi} commands for manipulating
29902 @subheading The @code{-break-after} Command
29903 @findex -break-after
29905 @subsubheading Synopsis
29908 -break-after @var{number} @var{count}
29911 The breakpoint number @var{number} is not in effect until it has been
29912 hit @var{count} times. To see how this is reflected in the output of
29913 the @samp{-break-list} command, see the description of the
29914 @samp{-break-list} command below.
29916 @subsubheading @value{GDBN} Command
29918 The corresponding @value{GDBN} command is @samp{ignore}.
29920 @subsubheading Example
29925 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29926 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29927 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29935 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29936 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29937 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29938 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29939 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29940 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29941 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29942 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29943 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29944 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29949 @subheading The @code{-break-catch} Command
29950 @findex -break-catch
29953 @subheading The @code{-break-commands} Command
29954 @findex -break-commands
29956 @subsubheading Synopsis
29959 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29962 Specifies the CLI commands that should be executed when breakpoint
29963 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29964 are the commands. If no command is specified, any previously-set
29965 commands are cleared. @xref{Break Commands}. Typical use of this
29966 functionality is tracing a program, that is, printing of values of
29967 some variables whenever breakpoint is hit and then continuing.
29969 @subsubheading @value{GDBN} Command
29971 The corresponding @value{GDBN} command is @samp{commands}.
29973 @subsubheading Example
29978 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29979 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29980 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29983 -break-commands 1 "print v" "continue"
29988 @subheading The @code{-break-condition} Command
29989 @findex -break-condition
29991 @subsubheading Synopsis
29994 -break-condition @var{number} @var{expr}
29997 Breakpoint @var{number} will stop the program only if the condition in
29998 @var{expr} is true. The condition becomes part of the
29999 @samp{-break-list} output (see the description of the @samp{-break-list}
30002 @subsubheading @value{GDBN} Command
30004 The corresponding @value{GDBN} command is @samp{condition}.
30006 @subsubheading Example
30010 -break-condition 1 1
30014 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30015 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30016 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30017 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30018 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30019 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30020 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30021 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30022 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30023 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30027 @subheading The @code{-break-delete} Command
30028 @findex -break-delete
30030 @subsubheading Synopsis
30033 -break-delete ( @var{breakpoint} )+
30036 Delete the breakpoint(s) whose number(s) are specified in the argument
30037 list. This is obviously reflected in the breakpoint list.
30039 @subsubheading @value{GDBN} Command
30041 The corresponding @value{GDBN} command is @samp{delete}.
30043 @subsubheading Example
30051 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30052 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30053 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30054 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30055 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30056 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30057 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30062 @subheading The @code{-break-disable} Command
30063 @findex -break-disable
30065 @subsubheading Synopsis
30068 -break-disable ( @var{breakpoint} )+
30071 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30072 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30074 @subsubheading @value{GDBN} Command
30076 The corresponding @value{GDBN} command is @samp{disable}.
30078 @subsubheading Example
30086 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30087 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30088 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30089 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30090 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30091 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30092 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30093 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30094 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30095 line="5",thread-groups=["i1"],times="0"@}]@}
30099 @subheading The @code{-break-enable} Command
30100 @findex -break-enable
30102 @subsubheading Synopsis
30105 -break-enable ( @var{breakpoint} )+
30108 Enable (previously disabled) @var{breakpoint}(s).
30110 @subsubheading @value{GDBN} Command
30112 The corresponding @value{GDBN} command is @samp{enable}.
30114 @subsubheading Example
30122 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30123 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30124 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30125 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30126 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30127 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30128 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30129 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30130 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30131 line="5",thread-groups=["i1"],times="0"@}]@}
30135 @subheading The @code{-break-info} Command
30136 @findex -break-info
30138 @subsubheading Synopsis
30141 -break-info @var{breakpoint}
30145 Get information about a single breakpoint.
30147 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30148 Information}, for details on the format of each breakpoint in the
30151 @subsubheading @value{GDBN} Command
30153 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30155 @subsubheading Example
30158 @subheading The @code{-break-insert} Command
30159 @findex -break-insert
30161 @subsubheading Synopsis
30164 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
30165 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30166 [ -p @var{thread-id} ] [ @var{location} ]
30170 If specified, @var{location}, can be one of:
30177 @item filename:linenum
30178 @item filename:function
30182 The possible optional parameters of this command are:
30186 Insert a temporary breakpoint.
30188 Insert a hardware breakpoint.
30190 If @var{location} cannot be parsed (for example if it
30191 refers to unknown files or functions), create a pending
30192 breakpoint. Without this flag, @value{GDBN} will report
30193 an error, and won't create a breakpoint, if @var{location}
30196 Create a disabled breakpoint.
30198 Create a tracepoint. @xref{Tracepoints}. When this parameter
30199 is used together with @samp{-h}, a fast tracepoint is created.
30200 @item -c @var{condition}
30201 Make the breakpoint conditional on @var{condition}.
30202 @item -i @var{ignore-count}
30203 Initialize the @var{ignore-count}.
30204 @item -p @var{thread-id}
30205 Restrict the breakpoint to the specified @var{thread-id}.
30208 @subsubheading Result
30210 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30211 resulting breakpoint.
30213 Note: this format is open to change.
30214 @c An out-of-band breakpoint instead of part of the result?
30216 @subsubheading @value{GDBN} Command
30218 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30219 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30221 @subsubheading Example
30226 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30227 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30230 -break-insert -t foo
30231 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30232 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30236 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30237 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30238 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30239 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30240 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30241 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30242 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30243 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30244 addr="0x0001072c", func="main",file="recursive2.c",
30245 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30247 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30248 addr="0x00010774",func="foo",file="recursive2.c",
30249 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30252 @c -break-insert -r foo.*
30253 @c ~int foo(int, int);
30254 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30255 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30260 @subheading The @code{-dprintf-insert} Command
30261 @findex -dprintf-insert
30263 @subsubheading Synopsis
30266 -dprintf-insert [ -t ] [ -f ] [ -d ]
30267 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30268 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30273 If specified, @var{location}, can be one of:
30276 @item @var{function}
30279 @c @item @var{linenum}
30280 @item @var{filename}:@var{linenum}
30281 @item @var{filename}:function
30282 @item *@var{address}
30285 The possible optional parameters of this command are:
30289 Insert a temporary breakpoint.
30291 If @var{location} cannot be parsed (for example, if it
30292 refers to unknown files or functions), create a pending
30293 breakpoint. Without this flag, @value{GDBN} will report
30294 an error, and won't create a breakpoint, if @var{location}
30297 Create a disabled breakpoint.
30298 @item -c @var{condition}
30299 Make the breakpoint conditional on @var{condition}.
30300 @item -i @var{ignore-count}
30301 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30302 to @var{ignore-count}.
30303 @item -p @var{thread-id}
30304 Restrict the breakpoint to the specified @var{thread-id}.
30307 @subsubheading Result
30309 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30310 resulting breakpoint.
30312 @c An out-of-band breakpoint instead of part of the result?
30314 @subsubheading @value{GDBN} Command
30316 The corresponding @value{GDBN} command is @samp{dprintf}.
30318 @subsubheading Example
30322 4-dprintf-insert foo "At foo entry\n"
30323 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30324 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30325 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30326 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30327 original-location="foo"@}
30329 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30330 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30331 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30332 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30333 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30334 original-location="mi-dprintf.c:26"@}
30338 @subheading The @code{-break-list} Command
30339 @findex -break-list
30341 @subsubheading Synopsis
30347 Displays the list of inserted breakpoints, showing the following fields:
30351 number of the breakpoint
30353 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30355 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30358 is the breakpoint enabled or no: @samp{y} or @samp{n}
30360 memory location at which the breakpoint is set
30362 logical location of the breakpoint, expressed by function name, file
30364 @item Thread-groups
30365 list of thread groups to which this breakpoint applies
30367 number of times the breakpoint has been hit
30370 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30371 @code{body} field is an empty list.
30373 @subsubheading @value{GDBN} Command
30375 The corresponding @value{GDBN} command is @samp{info break}.
30377 @subsubheading Example
30382 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30383 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30384 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30385 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30386 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30387 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30388 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30389 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30390 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30392 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30393 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30394 line="13",thread-groups=["i1"],times="0"@}]@}
30398 Here's an example of the result when there are no breakpoints:
30403 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30404 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30405 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30406 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30407 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30408 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30409 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30414 @subheading The @code{-break-passcount} Command
30415 @findex -break-passcount
30417 @subsubheading Synopsis
30420 -break-passcount @var{tracepoint-number} @var{passcount}
30423 Set the passcount for tracepoint @var{tracepoint-number} to
30424 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30425 is not a tracepoint, error is emitted. This corresponds to CLI
30426 command @samp{passcount}.
30428 @subheading The @code{-break-watch} Command
30429 @findex -break-watch
30431 @subsubheading Synopsis
30434 -break-watch [ -a | -r ]
30437 Create a watchpoint. With the @samp{-a} option it will create an
30438 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30439 read from or on a write to the memory location. With the @samp{-r}
30440 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30441 trigger only when the memory location is accessed for reading. Without
30442 either of the options, the watchpoint created is a regular watchpoint,
30443 i.e., it will trigger when the memory location is accessed for writing.
30444 @xref{Set Watchpoints, , Setting Watchpoints}.
30446 Note that @samp{-break-list} will report a single list of watchpoints and
30447 breakpoints inserted.
30449 @subsubheading @value{GDBN} Command
30451 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30454 @subsubheading Example
30456 Setting a watchpoint on a variable in the @code{main} function:
30461 ^done,wpt=@{number="2",exp="x"@}
30466 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30467 value=@{old="-268439212",new="55"@},
30468 frame=@{func="main",args=[],file="recursive2.c",
30469 fullname="/home/foo/bar/recursive2.c",line="5"@}
30473 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30474 the program execution twice: first for the variable changing value, then
30475 for the watchpoint going out of scope.
30480 ^done,wpt=@{number="5",exp="C"@}
30485 *stopped,reason="watchpoint-trigger",
30486 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30487 frame=@{func="callee4",args=[],
30488 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30489 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30494 *stopped,reason="watchpoint-scope",wpnum="5",
30495 frame=@{func="callee3",args=[@{name="strarg",
30496 value="0x11940 \"A string argument.\""@}],
30497 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30498 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30502 Listing breakpoints and watchpoints, at different points in the program
30503 execution. Note that once the watchpoint goes out of scope, it is
30509 ^done,wpt=@{number="2",exp="C"@}
30512 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30513 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30514 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30515 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30516 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30517 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30518 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30519 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30520 addr="0x00010734",func="callee4",
30521 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30522 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30524 bkpt=@{number="2",type="watchpoint",disp="keep",
30525 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30530 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30531 value=@{old="-276895068",new="3"@},
30532 frame=@{func="callee4",args=[],
30533 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30534 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30537 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30538 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30539 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30540 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30541 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30542 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30543 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30544 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30545 addr="0x00010734",func="callee4",
30546 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30547 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30549 bkpt=@{number="2",type="watchpoint",disp="keep",
30550 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30554 ^done,reason="watchpoint-scope",wpnum="2",
30555 frame=@{func="callee3",args=[@{name="strarg",
30556 value="0x11940 \"A string argument.\""@}],
30557 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30558 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30561 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30562 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30563 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30564 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30565 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30566 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30567 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30568 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30569 addr="0x00010734",func="callee4",
30570 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30571 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30572 thread-groups=["i1"],times="1"@}]@}
30577 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30578 @node GDB/MI Catchpoint Commands
30579 @section @sc{gdb/mi} Catchpoint Commands
30581 This section documents @sc{gdb/mi} commands for manipulating
30585 * Shared Library GDB/MI Catchpoint Commands::
30586 * Ada Exception GDB/MI Catchpoint Commands::
30589 @node Shared Library GDB/MI Catchpoint Commands
30590 @subsection Shared Library @sc{gdb/mi} Catchpoints
30592 @subheading The @code{-catch-load} Command
30593 @findex -catch-load
30595 @subsubheading Synopsis
30598 -catch-load [ -t ] [ -d ] @var{regexp}
30601 Add a catchpoint for library load events. If the @samp{-t} option is used,
30602 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30603 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30604 in a disabled state. The @samp{regexp} argument is a regular
30605 expression used to match the name of the loaded library.
30608 @subsubheading @value{GDBN} Command
30610 The corresponding @value{GDBN} command is @samp{catch load}.
30612 @subsubheading Example
30615 -catch-load -t foo.so
30616 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30617 what="load of library matching foo.so",catch-type="load",times="0"@}
30622 @subheading The @code{-catch-unload} Command
30623 @findex -catch-unload
30625 @subsubheading Synopsis
30628 -catch-unload [ -t ] [ -d ] @var{regexp}
30631 Add a catchpoint for library unload events. If the @samp{-t} option is
30632 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30633 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30634 created in a disabled state. The @samp{regexp} argument is a regular
30635 expression used to match the name of the unloaded library.
30637 @subsubheading @value{GDBN} Command
30639 The corresponding @value{GDBN} command is @samp{catch unload}.
30641 @subsubheading Example
30644 -catch-unload -d bar.so
30645 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30646 what="load of library matching bar.so",catch-type="unload",times="0"@}
30650 @node Ada Exception GDB/MI Catchpoint Commands
30651 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30653 The following @sc{gdb/mi} commands can be used to create catchpoints
30654 that stop the execution when Ada exceptions are being raised.
30656 @subheading The @code{-catch-assert} Command
30657 @findex -catch-assert
30659 @subsubheading Synopsis
30662 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30665 Add a catchpoint for failed Ada assertions.
30667 The possible optional parameters for this command are:
30670 @item -c @var{condition}
30671 Make the catchpoint conditional on @var{condition}.
30673 Create a disabled catchpoint.
30675 Create a temporary catchpoint.
30678 @subsubheading @value{GDBN} Command
30680 The corresponding @value{GDBN} command is @samp{catch assert}.
30682 @subsubheading Example
30686 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30687 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30688 thread-groups=["i1"],times="0",
30689 original-location="__gnat_debug_raise_assert_failure"@}
30693 @subheading The @code{-catch-exception} Command
30694 @findex -catch-exception
30696 @subsubheading Synopsis
30699 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30703 Add a catchpoint stopping when Ada exceptions are raised.
30704 By default, the command stops the program when any Ada exception
30705 gets raised. But it is also possible, by using some of the
30706 optional parameters described below, to create more selective
30709 The possible optional parameters for this command are:
30712 @item -c @var{condition}
30713 Make the catchpoint conditional on @var{condition}.
30715 Create a disabled catchpoint.
30716 @item -e @var{exception-name}
30717 Only stop when @var{exception-name} is raised. This option cannot
30718 be used combined with @samp{-u}.
30720 Create a temporary catchpoint.
30722 Stop only when an unhandled exception gets raised. This option
30723 cannot be used combined with @samp{-e}.
30726 @subsubheading @value{GDBN} Command
30728 The corresponding @value{GDBN} commands are @samp{catch exception}
30729 and @samp{catch exception unhandled}.
30731 @subsubheading Example
30734 -catch-exception -e Program_Error
30735 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30736 enabled="y",addr="0x0000000000404874",
30737 what="`Program_Error' Ada exception", thread-groups=["i1"],
30738 times="0",original-location="__gnat_debug_raise_exception"@}
30742 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30743 @node GDB/MI Program Context
30744 @section @sc{gdb/mi} Program Context
30746 @subheading The @code{-exec-arguments} Command
30747 @findex -exec-arguments
30750 @subsubheading Synopsis
30753 -exec-arguments @var{args}
30756 Set the inferior program arguments, to be used in the next
30759 @subsubheading @value{GDBN} Command
30761 The corresponding @value{GDBN} command is @samp{set args}.
30763 @subsubheading Example
30767 -exec-arguments -v word
30774 @subheading The @code{-exec-show-arguments} Command
30775 @findex -exec-show-arguments
30777 @subsubheading Synopsis
30780 -exec-show-arguments
30783 Print the arguments of the program.
30785 @subsubheading @value{GDBN} Command
30787 The corresponding @value{GDBN} command is @samp{show args}.
30789 @subsubheading Example
30794 @subheading The @code{-environment-cd} Command
30795 @findex -environment-cd
30797 @subsubheading Synopsis
30800 -environment-cd @var{pathdir}
30803 Set @value{GDBN}'s working directory.
30805 @subsubheading @value{GDBN} Command
30807 The corresponding @value{GDBN} command is @samp{cd}.
30809 @subsubheading Example
30813 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30819 @subheading The @code{-environment-directory} Command
30820 @findex -environment-directory
30822 @subsubheading Synopsis
30825 -environment-directory [ -r ] [ @var{pathdir} ]+
30828 Add directories @var{pathdir} to beginning of search path for source files.
30829 If the @samp{-r} option is used, the search path is reset to the default
30830 search path. If directories @var{pathdir} are supplied in addition to the
30831 @samp{-r} option, the search path is first reset and then addition
30833 Multiple directories may be specified, separated by blanks. Specifying
30834 multiple directories in a single command
30835 results in the directories added to the beginning of the
30836 search path in the same order they were presented in the command.
30837 If blanks are needed as
30838 part of a directory name, double-quotes should be used around
30839 the name. In the command output, the path will show up separated
30840 by the system directory-separator character. The directory-separator
30841 character must not be used
30842 in any directory name.
30843 If no directories are specified, the current search path is displayed.
30845 @subsubheading @value{GDBN} Command
30847 The corresponding @value{GDBN} command is @samp{dir}.
30849 @subsubheading Example
30853 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30854 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30856 -environment-directory ""
30857 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30859 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30860 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30862 -environment-directory -r
30863 ^done,source-path="$cdir:$cwd"
30868 @subheading The @code{-environment-path} Command
30869 @findex -environment-path
30871 @subsubheading Synopsis
30874 -environment-path [ -r ] [ @var{pathdir} ]+
30877 Add directories @var{pathdir} to beginning of search path for object files.
30878 If the @samp{-r} option is used, the search path is reset to the original
30879 search path that existed at gdb start-up. If directories @var{pathdir} are
30880 supplied in addition to the
30881 @samp{-r} option, the search path is first reset and then addition
30883 Multiple directories may be specified, separated by blanks. Specifying
30884 multiple directories in a single command
30885 results in the directories added to the beginning of the
30886 search path in the same order they were presented in the command.
30887 If blanks are needed as
30888 part of a directory name, double-quotes should be used around
30889 the name. In the command output, the path will show up separated
30890 by the system directory-separator character. The directory-separator
30891 character must not be used
30892 in any directory name.
30893 If no directories are specified, the current path is displayed.
30896 @subsubheading @value{GDBN} Command
30898 The corresponding @value{GDBN} command is @samp{path}.
30900 @subsubheading Example
30905 ^done,path="/usr/bin"
30907 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30908 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30910 -environment-path -r /usr/local/bin
30911 ^done,path="/usr/local/bin:/usr/bin"
30916 @subheading The @code{-environment-pwd} Command
30917 @findex -environment-pwd
30919 @subsubheading Synopsis
30925 Show the current working directory.
30927 @subsubheading @value{GDBN} Command
30929 The corresponding @value{GDBN} command is @samp{pwd}.
30931 @subsubheading Example
30936 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30940 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30941 @node GDB/MI Thread Commands
30942 @section @sc{gdb/mi} Thread Commands
30945 @subheading The @code{-thread-info} Command
30946 @findex -thread-info
30948 @subsubheading Synopsis
30951 -thread-info [ @var{thread-id} ]
30954 Reports information about either a specific thread, if
30955 the @var{thread-id} parameter is present, or about all
30956 threads. When printing information about all threads,
30957 also reports the current thread.
30959 @subsubheading @value{GDBN} Command
30961 The @samp{info thread} command prints the same information
30964 @subsubheading Result
30966 The result is a list of threads. The following attributes are
30967 defined for a given thread:
30971 This field exists only for the current thread. It has the value @samp{*}.
30974 The identifier that @value{GDBN} uses to refer to the thread.
30977 The identifier that the target uses to refer to the thread.
30980 Extra information about the thread, in a target-specific format. This
30984 The name of the thread. If the user specified a name using the
30985 @code{thread name} command, then this name is given. Otherwise, if
30986 @value{GDBN} can extract the thread name from the target, then that
30987 name is given. If @value{GDBN} cannot find the thread name, then this
30991 The stack frame currently executing in the thread.
30994 The thread's state. The @samp{state} field may have the following
30999 The thread is stopped. Frame information is available for stopped
31003 The thread is running. There's no frame information for running
31009 If @value{GDBN} can find the CPU core on which this thread is running,
31010 then this field is the core identifier. This field is optional.
31014 @subsubheading Example
31019 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31020 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31021 args=[]@},state="running"@},
31022 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31023 frame=@{level="0",addr="0x0804891f",func="foo",
31024 args=[@{name="i",value="10"@}],
31025 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
31026 state="running"@}],
31027 current-thread-id="1"
31031 @subheading The @code{-thread-list-ids} Command
31032 @findex -thread-list-ids
31034 @subsubheading Synopsis
31040 Produces a list of the currently known @value{GDBN} thread ids. At the
31041 end of the list it also prints the total number of such threads.
31043 This command is retained for historical reasons, the
31044 @code{-thread-info} command should be used instead.
31046 @subsubheading @value{GDBN} Command
31048 Part of @samp{info threads} supplies the same information.
31050 @subsubheading Example
31055 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31056 current-thread-id="1",number-of-threads="3"
31061 @subheading The @code{-thread-select} Command
31062 @findex -thread-select
31064 @subsubheading Synopsis
31067 -thread-select @var{threadnum}
31070 Make @var{threadnum} the current thread. It prints the number of the new
31071 current thread, and the topmost frame for that thread.
31073 This command is deprecated in favor of explicitly using the
31074 @samp{--thread} option to each command.
31076 @subsubheading @value{GDBN} Command
31078 The corresponding @value{GDBN} command is @samp{thread}.
31080 @subsubheading Example
31087 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31088 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31092 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31093 number-of-threads="3"
31096 ^done,new-thread-id="3",
31097 frame=@{level="0",func="vprintf",
31098 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31099 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
31103 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31104 @node GDB/MI Ada Tasking Commands
31105 @section @sc{gdb/mi} Ada Tasking Commands
31107 @subheading The @code{-ada-task-info} Command
31108 @findex -ada-task-info
31110 @subsubheading Synopsis
31113 -ada-task-info [ @var{task-id} ]
31116 Reports information about either a specific Ada task, if the
31117 @var{task-id} parameter is present, or about all Ada tasks.
31119 @subsubheading @value{GDBN} Command
31121 The @samp{info tasks} command prints the same information
31122 about all Ada tasks (@pxref{Ada Tasks}).
31124 @subsubheading Result
31126 The result is a table of Ada tasks. The following columns are
31127 defined for each Ada task:
31131 This field exists only for the current thread. It has the value @samp{*}.
31134 The identifier that @value{GDBN} uses to refer to the Ada task.
31137 The identifier that the target uses to refer to the Ada task.
31140 The identifier of the thread corresponding to the Ada task.
31142 This field should always exist, as Ada tasks are always implemented
31143 on top of a thread. But if @value{GDBN} cannot find this corresponding
31144 thread for any reason, the field is omitted.
31147 This field exists only when the task was created by another task.
31148 In this case, it provides the ID of the parent task.
31151 The base priority of the task.
31154 The current state of the task. For a detailed description of the
31155 possible states, see @ref{Ada Tasks}.
31158 The name of the task.
31162 @subsubheading Example
31166 ^done,tasks=@{nr_rows="3",nr_cols="8",
31167 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31168 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31169 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31170 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31171 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31172 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31173 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31174 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31175 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31176 state="Child Termination Wait",name="main_task"@}]@}
31180 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31181 @node GDB/MI Program Execution
31182 @section @sc{gdb/mi} Program Execution
31184 These are the asynchronous commands which generate the out-of-band
31185 record @samp{*stopped}. Currently @value{GDBN} only really executes
31186 asynchronously with remote targets and this interaction is mimicked in
31189 @subheading The @code{-exec-continue} Command
31190 @findex -exec-continue
31192 @subsubheading Synopsis
31195 -exec-continue [--reverse] [--all|--thread-group N]
31198 Resumes the execution of the inferior program, which will continue
31199 to execute until it reaches a debugger stop event. If the
31200 @samp{--reverse} option is specified, execution resumes in reverse until
31201 it reaches a stop event. Stop events may include
31204 breakpoints or watchpoints
31206 signals or exceptions
31208 the end of the process (or its beginning under @samp{--reverse})
31210 the end or beginning of a replay log if one is being used.
31212 In all-stop mode (@pxref{All-Stop
31213 Mode}), may resume only one thread, or all threads, depending on the
31214 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31215 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31216 ignored in all-stop mode. If the @samp{--thread-group} options is
31217 specified, then all threads in that thread group are resumed.
31219 @subsubheading @value{GDBN} Command
31221 The corresponding @value{GDBN} corresponding is @samp{continue}.
31223 @subsubheading Example
31230 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31231 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31237 @subheading The @code{-exec-finish} Command
31238 @findex -exec-finish
31240 @subsubheading Synopsis
31243 -exec-finish [--reverse]
31246 Resumes the execution of the inferior program until the current
31247 function is exited. Displays the results returned by the function.
31248 If the @samp{--reverse} option is specified, resumes the reverse
31249 execution of the inferior program until the point where current
31250 function was called.
31252 @subsubheading @value{GDBN} Command
31254 The corresponding @value{GDBN} command is @samp{finish}.
31256 @subsubheading Example
31258 Function returning @code{void}.
31265 *stopped,reason="function-finished",frame=@{func="main",args=[],
31266 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
31270 Function returning other than @code{void}. The name of the internal
31271 @value{GDBN} variable storing the result is printed, together with the
31278 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31279 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31280 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31281 gdb-result-var="$1",return-value="0"
31286 @subheading The @code{-exec-interrupt} Command
31287 @findex -exec-interrupt
31289 @subsubheading Synopsis
31292 -exec-interrupt [--all|--thread-group N]
31295 Interrupts the background execution of the target. Note how the token
31296 associated with the stop message is the one for the execution command
31297 that has been interrupted. The token for the interrupt itself only
31298 appears in the @samp{^done} output. If the user is trying to
31299 interrupt a non-running program, an error message will be printed.
31301 Note that when asynchronous execution is enabled, this command is
31302 asynchronous just like other execution commands. That is, first the
31303 @samp{^done} response will be printed, and the target stop will be
31304 reported after that using the @samp{*stopped} notification.
31306 In non-stop mode, only the context thread is interrupted by default.
31307 All threads (in all inferiors) will be interrupted if the
31308 @samp{--all} option is specified. If the @samp{--thread-group}
31309 option is specified, all threads in that group will be interrupted.
31311 @subsubheading @value{GDBN} Command
31313 The corresponding @value{GDBN} command is @samp{interrupt}.
31315 @subsubheading Example
31326 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31327 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31328 fullname="/home/foo/bar/try.c",line="13"@}
31333 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31337 @subheading The @code{-exec-jump} Command
31340 @subsubheading Synopsis
31343 -exec-jump @var{location}
31346 Resumes execution of the inferior program at the location specified by
31347 parameter. @xref{Specify Location}, for a description of the
31348 different forms of @var{location}.
31350 @subsubheading @value{GDBN} Command
31352 The corresponding @value{GDBN} command is @samp{jump}.
31354 @subsubheading Example
31357 -exec-jump foo.c:10
31358 *running,thread-id="all"
31363 @subheading The @code{-exec-next} Command
31366 @subsubheading Synopsis
31369 -exec-next [--reverse]
31372 Resumes execution of the inferior program, stopping when the beginning
31373 of the next source line is reached.
31375 If the @samp{--reverse} option is specified, resumes reverse execution
31376 of the inferior program, stopping at the beginning of the previous
31377 source line. If you issue this command on the first line of a
31378 function, it will take you back to the caller of that function, to the
31379 source line where the function was called.
31382 @subsubheading @value{GDBN} Command
31384 The corresponding @value{GDBN} command is @samp{next}.
31386 @subsubheading Example
31392 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31397 @subheading The @code{-exec-next-instruction} Command
31398 @findex -exec-next-instruction
31400 @subsubheading Synopsis
31403 -exec-next-instruction [--reverse]
31406 Executes one machine instruction. If the instruction is a function
31407 call, continues until the function returns. If the program stops at an
31408 instruction in the middle of a source line, the address will be
31411 If the @samp{--reverse} option is specified, resumes reverse execution
31412 of the inferior program, stopping at the previous instruction. If the
31413 previously executed instruction was a return from another function,
31414 it will continue to execute in reverse until the call to that function
31415 (from the current stack frame) is reached.
31417 @subsubheading @value{GDBN} Command
31419 The corresponding @value{GDBN} command is @samp{nexti}.
31421 @subsubheading Example
31425 -exec-next-instruction
31429 *stopped,reason="end-stepping-range",
31430 addr="0x000100d4",line="5",file="hello.c"
31435 @subheading The @code{-exec-return} Command
31436 @findex -exec-return
31438 @subsubheading Synopsis
31444 Makes current function return immediately. Doesn't execute the inferior.
31445 Displays the new current frame.
31447 @subsubheading @value{GDBN} Command
31449 The corresponding @value{GDBN} command is @samp{return}.
31451 @subsubheading Example
31455 200-break-insert callee4
31456 200^done,bkpt=@{number="1",addr="0x00010734",
31457 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31462 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31463 frame=@{func="callee4",args=[],
31464 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31465 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31471 111^done,frame=@{level="0",func="callee3",
31472 args=[@{name="strarg",
31473 value="0x11940 \"A string argument.\""@}],
31474 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31475 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
31480 @subheading The @code{-exec-run} Command
31483 @subsubheading Synopsis
31486 -exec-run [ --all | --thread-group N ] [ --start ]
31489 Starts execution of the inferior from the beginning. The inferior
31490 executes until either a breakpoint is encountered or the program
31491 exits. In the latter case the output will include an exit code, if
31492 the program has exited exceptionally.
31494 When neither the @samp{--all} nor the @samp{--thread-group} option
31495 is specified, the current inferior is started. If the
31496 @samp{--thread-group} option is specified, it should refer to a thread
31497 group of type @samp{process}, and that thread group will be started.
31498 If the @samp{--all} option is specified, then all inferiors will be started.
31500 Using the @samp{--start} option instructs the debugger to stop
31501 the execution at the start of the inferior's main subprogram,
31502 following the same behavior as the @code{start} command
31503 (@pxref{Starting}).
31505 @subsubheading @value{GDBN} Command
31507 The corresponding @value{GDBN} command is @samp{run}.
31509 @subsubheading Examples
31514 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31519 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31520 frame=@{func="main",args=[],file="recursive2.c",
31521 fullname="/home/foo/bar/recursive2.c",line="4"@}
31526 Program exited normally:
31534 *stopped,reason="exited-normally"
31539 Program exited exceptionally:
31547 *stopped,reason="exited",exit-code="01"
31551 Another way the program can terminate is if it receives a signal such as
31552 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31556 *stopped,reason="exited-signalled",signal-name="SIGINT",
31557 signal-meaning="Interrupt"
31561 @c @subheading -exec-signal
31564 @subheading The @code{-exec-step} Command
31567 @subsubheading Synopsis
31570 -exec-step [--reverse]
31573 Resumes execution of the inferior program, stopping when the beginning
31574 of the next source line is reached, if the next source line is not a
31575 function call. If it is, stop at the first instruction of the called
31576 function. If the @samp{--reverse} option is specified, resumes reverse
31577 execution of the inferior program, stopping at the beginning of the
31578 previously executed source line.
31580 @subsubheading @value{GDBN} Command
31582 The corresponding @value{GDBN} command is @samp{step}.
31584 @subsubheading Example
31586 Stepping into a function:
31592 *stopped,reason="end-stepping-range",
31593 frame=@{func="foo",args=[@{name="a",value="10"@},
31594 @{name="b",value="0"@}],file="recursive2.c",
31595 fullname="/home/foo/bar/recursive2.c",line="11"@}
31605 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31610 @subheading The @code{-exec-step-instruction} Command
31611 @findex -exec-step-instruction
31613 @subsubheading Synopsis
31616 -exec-step-instruction [--reverse]
31619 Resumes the inferior which executes one machine instruction. If the
31620 @samp{--reverse} option is specified, resumes reverse execution of the
31621 inferior program, stopping at the previously executed instruction.
31622 The output, once @value{GDBN} has stopped, will vary depending on
31623 whether we have stopped in the middle of a source line or not. In the
31624 former case, the address at which the program stopped will be printed
31627 @subsubheading @value{GDBN} Command
31629 The corresponding @value{GDBN} command is @samp{stepi}.
31631 @subsubheading Example
31635 -exec-step-instruction
31639 *stopped,reason="end-stepping-range",
31640 frame=@{func="foo",args=[],file="try.c",
31641 fullname="/home/foo/bar/try.c",line="10"@}
31643 -exec-step-instruction
31647 *stopped,reason="end-stepping-range",
31648 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31649 fullname="/home/foo/bar/try.c",line="10"@}
31654 @subheading The @code{-exec-until} Command
31655 @findex -exec-until
31657 @subsubheading Synopsis
31660 -exec-until [ @var{location} ]
31663 Executes the inferior until the @var{location} specified in the
31664 argument is reached. If there is no argument, the inferior executes
31665 until a source line greater than the current one is reached. The
31666 reason for stopping in this case will be @samp{location-reached}.
31668 @subsubheading @value{GDBN} Command
31670 The corresponding @value{GDBN} command is @samp{until}.
31672 @subsubheading Example
31676 -exec-until recursive2.c:6
31680 *stopped,reason="location-reached",frame=@{func="main",args=[],
31681 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31686 @subheading -file-clear
31687 Is this going away????
31690 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31691 @node GDB/MI Stack Manipulation
31692 @section @sc{gdb/mi} Stack Manipulation Commands
31694 @subheading The @code{-enable-frame-filters} Command
31695 @findex -enable-frame-filters
31698 -enable-frame-filters
31701 @value{GDBN} allows Python-based frame filters to affect the output of
31702 the MI commands relating to stack traces. As there is no way to
31703 implement this in a fully backward-compatible way, a front end must
31704 request that this functionality be enabled.
31706 Once enabled, this feature cannot be disabled.
31708 Note that if Python support has not been compiled into @value{GDBN},
31709 this command will still succeed (and do nothing).
31711 @subheading The @code{-stack-info-frame} Command
31712 @findex -stack-info-frame
31714 @subsubheading Synopsis
31720 Get info on the selected frame.
31722 @subsubheading @value{GDBN} Command
31724 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31725 (without arguments).
31727 @subsubheading Example
31732 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31733 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31734 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31738 @subheading The @code{-stack-info-depth} Command
31739 @findex -stack-info-depth
31741 @subsubheading Synopsis
31744 -stack-info-depth [ @var{max-depth} ]
31747 Return the depth of the stack. If the integer argument @var{max-depth}
31748 is specified, do not count beyond @var{max-depth} frames.
31750 @subsubheading @value{GDBN} Command
31752 There's no equivalent @value{GDBN} command.
31754 @subsubheading Example
31756 For a stack with frame levels 0 through 11:
31763 -stack-info-depth 4
31766 -stack-info-depth 12
31769 -stack-info-depth 11
31772 -stack-info-depth 13
31777 @anchor{-stack-list-arguments}
31778 @subheading The @code{-stack-list-arguments} Command
31779 @findex -stack-list-arguments
31781 @subsubheading Synopsis
31784 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31785 [ @var{low-frame} @var{high-frame} ]
31788 Display a list of the arguments for the frames between @var{low-frame}
31789 and @var{high-frame} (inclusive). If @var{low-frame} and
31790 @var{high-frame} are not provided, list the arguments for the whole
31791 call stack. If the two arguments are equal, show the single frame
31792 at the corresponding level. It is an error if @var{low-frame} is
31793 larger than the actual number of frames. On the other hand,
31794 @var{high-frame} may be larger than the actual number of frames, in
31795 which case only existing frames will be returned.
31797 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31798 the variables; if it is 1 or @code{--all-values}, print also their
31799 values; and if it is 2 or @code{--simple-values}, print the name,
31800 type and value for simple data types, and the name and type for arrays,
31801 structures and unions. If the option @code{--no-frame-filters} is
31802 supplied, then Python frame filters will not be executed.
31804 If the @code{--skip-unavailable} option is specified, arguments that
31805 are not available are not listed. Partially available arguments
31806 are still displayed, however.
31808 Use of this command to obtain arguments in a single frame is
31809 deprecated in favor of the @samp{-stack-list-variables} command.
31811 @subsubheading @value{GDBN} Command
31813 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31814 @samp{gdb_get_args} command which partially overlaps with the
31815 functionality of @samp{-stack-list-arguments}.
31817 @subsubheading Example
31824 frame=@{level="0",addr="0x00010734",func="callee4",
31825 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31826 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31827 frame=@{level="1",addr="0x0001076c",func="callee3",
31828 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31829 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31830 frame=@{level="2",addr="0x0001078c",func="callee2",
31831 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31832 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31833 frame=@{level="3",addr="0x000107b4",func="callee1",
31834 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31835 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31836 frame=@{level="4",addr="0x000107e0",func="main",
31837 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31838 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31840 -stack-list-arguments 0
31843 frame=@{level="0",args=[]@},
31844 frame=@{level="1",args=[name="strarg"]@},
31845 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31846 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31847 frame=@{level="4",args=[]@}]
31849 -stack-list-arguments 1
31852 frame=@{level="0",args=[]@},
31854 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31855 frame=@{level="2",args=[
31856 @{name="intarg",value="2"@},
31857 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31858 @{frame=@{level="3",args=[
31859 @{name="intarg",value="2"@},
31860 @{name="strarg",value="0x11940 \"A string argument.\""@},
31861 @{name="fltarg",value="3.5"@}]@},
31862 frame=@{level="4",args=[]@}]
31864 -stack-list-arguments 0 2 2
31865 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31867 -stack-list-arguments 1 2 2
31868 ^done,stack-args=[frame=@{level="2",
31869 args=[@{name="intarg",value="2"@},
31870 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31874 @c @subheading -stack-list-exception-handlers
31877 @anchor{-stack-list-frames}
31878 @subheading The @code{-stack-list-frames} Command
31879 @findex -stack-list-frames
31881 @subsubheading Synopsis
31884 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31887 List the frames currently on the stack. For each frame it displays the
31892 The frame number, 0 being the topmost frame, i.e., the innermost function.
31894 The @code{$pc} value for that frame.
31898 File name of the source file where the function lives.
31899 @item @var{fullname}
31900 The full file name of the source file where the function lives.
31902 Line number corresponding to the @code{$pc}.
31904 The shared library where this function is defined. This is only given
31905 if the frame's function is not known.
31908 If invoked without arguments, this command prints a backtrace for the
31909 whole stack. If given two integer arguments, it shows the frames whose
31910 levels are between the two arguments (inclusive). If the two arguments
31911 are equal, it shows the single frame at the corresponding level. It is
31912 an error if @var{low-frame} is larger than the actual number of
31913 frames. On the other hand, @var{high-frame} may be larger than the
31914 actual number of frames, in which case only existing frames will be
31915 returned. If the option @code{--no-frame-filters} is supplied, then
31916 Python frame filters will not be executed.
31918 @subsubheading @value{GDBN} Command
31920 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31922 @subsubheading Example
31924 Full stack backtrace:
31930 [frame=@{level="0",addr="0x0001076c",func="foo",
31931 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
31932 frame=@{level="1",addr="0x000107a4",func="foo",
31933 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31934 frame=@{level="2",addr="0x000107a4",func="foo",
31935 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31936 frame=@{level="3",addr="0x000107a4",func="foo",
31937 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31938 frame=@{level="4",addr="0x000107a4",func="foo",
31939 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31940 frame=@{level="5",addr="0x000107a4",func="foo",
31941 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31942 frame=@{level="6",addr="0x000107a4",func="foo",
31943 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31944 frame=@{level="7",addr="0x000107a4",func="foo",
31945 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31946 frame=@{level="8",addr="0x000107a4",func="foo",
31947 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31948 frame=@{level="9",addr="0x000107a4",func="foo",
31949 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31950 frame=@{level="10",addr="0x000107a4",func="foo",
31951 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31952 frame=@{level="11",addr="0x00010738",func="main",
31953 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
31957 Show frames between @var{low_frame} and @var{high_frame}:
31961 -stack-list-frames 3 5
31963 [frame=@{level="3",addr="0x000107a4",func="foo",
31964 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31965 frame=@{level="4",addr="0x000107a4",func="foo",
31966 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31967 frame=@{level="5",addr="0x000107a4",func="foo",
31968 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31972 Show a single frame:
31976 -stack-list-frames 3 3
31978 [frame=@{level="3",addr="0x000107a4",func="foo",
31979 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31984 @subheading The @code{-stack-list-locals} Command
31985 @findex -stack-list-locals
31986 @anchor{-stack-list-locals}
31988 @subsubheading Synopsis
31991 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31994 Display the local variable names for the selected frame. If
31995 @var{print-values} is 0 or @code{--no-values}, print only the names of
31996 the variables; if it is 1 or @code{--all-values}, print also their
31997 values; and if it is 2 or @code{--simple-values}, print the name,
31998 type and value for simple data types, and the name and type for arrays,
31999 structures and unions. In this last case, a frontend can immediately
32000 display the value of simple data types and create variable objects for
32001 other data types when the user wishes to explore their values in
32002 more detail. If the option @code{--no-frame-filters} is supplied, then
32003 Python frame filters will not be executed.
32005 If the @code{--skip-unavailable} option is specified, local variables
32006 that are not available are not listed. Partially available local
32007 variables are still displayed, however.
32009 This command is deprecated in favor of the
32010 @samp{-stack-list-variables} command.
32012 @subsubheading @value{GDBN} Command
32014 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32016 @subsubheading Example
32020 -stack-list-locals 0
32021 ^done,locals=[name="A",name="B",name="C"]
32023 -stack-list-locals --all-values
32024 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32025 @{name="C",value="@{1, 2, 3@}"@}]
32026 -stack-list-locals --simple-values
32027 ^done,locals=[@{name="A",type="int",value="1"@},
32028 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32032 @anchor{-stack-list-variables}
32033 @subheading The @code{-stack-list-variables} Command
32034 @findex -stack-list-variables
32036 @subsubheading Synopsis
32039 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32042 Display the names of local variables and function arguments for the selected frame. If
32043 @var{print-values} is 0 or @code{--no-values}, print only the names of
32044 the variables; if it is 1 or @code{--all-values}, print also their
32045 values; and if it is 2 or @code{--simple-values}, print the name,
32046 type and value for simple data types, and the name and type for arrays,
32047 structures and unions. If the option @code{--no-frame-filters} is
32048 supplied, then Python frame filters will not be executed.
32050 If the @code{--skip-unavailable} option is specified, local variables
32051 and arguments that are not available are not listed. Partially
32052 available arguments and local variables are still displayed, however.
32054 @subsubheading Example
32058 -stack-list-variables --thread 1 --frame 0 --all-values
32059 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32064 @subheading The @code{-stack-select-frame} Command
32065 @findex -stack-select-frame
32067 @subsubheading Synopsis
32070 -stack-select-frame @var{framenum}
32073 Change the selected frame. Select a different frame @var{framenum} on
32076 This command in deprecated in favor of passing the @samp{--frame}
32077 option to every command.
32079 @subsubheading @value{GDBN} Command
32081 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32082 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32084 @subsubheading Example
32088 -stack-select-frame 2
32093 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32094 @node GDB/MI Variable Objects
32095 @section @sc{gdb/mi} Variable Objects
32099 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32101 For the implementation of a variable debugger window (locals, watched
32102 expressions, etc.), we are proposing the adaptation of the existing code
32103 used by @code{Insight}.
32105 The two main reasons for that are:
32109 It has been proven in practice (it is already on its second generation).
32112 It will shorten development time (needless to say how important it is
32116 The original interface was designed to be used by Tcl code, so it was
32117 slightly changed so it could be used through @sc{gdb/mi}. This section
32118 describes the @sc{gdb/mi} operations that will be available and gives some
32119 hints about their use.
32121 @emph{Note}: In addition to the set of operations described here, we
32122 expect the @sc{gui} implementation of a variable window to require, at
32123 least, the following operations:
32126 @item @code{-gdb-show} @code{output-radix}
32127 @item @code{-stack-list-arguments}
32128 @item @code{-stack-list-locals}
32129 @item @code{-stack-select-frame}
32134 @subheading Introduction to Variable Objects
32136 @cindex variable objects in @sc{gdb/mi}
32138 Variable objects are "object-oriented" MI interface for examining and
32139 changing values of expressions. Unlike some other MI interfaces that
32140 work with expressions, variable objects are specifically designed for
32141 simple and efficient presentation in the frontend. A variable object
32142 is identified by string name. When a variable object is created, the
32143 frontend specifies the expression for that variable object. The
32144 expression can be a simple variable, or it can be an arbitrary complex
32145 expression, and can even involve CPU registers. After creating a
32146 variable object, the frontend can invoke other variable object
32147 operations---for example to obtain or change the value of a variable
32148 object, or to change display format.
32150 Variable objects have hierarchical tree structure. Any variable object
32151 that corresponds to a composite type, such as structure in C, has
32152 a number of child variable objects, for example corresponding to each
32153 element of a structure. A child variable object can itself have
32154 children, recursively. Recursion ends when we reach
32155 leaf variable objects, which always have built-in types. Child variable
32156 objects are created only by explicit request, so if a frontend
32157 is not interested in the children of a particular variable object, no
32158 child will be created.
32160 For a leaf variable object it is possible to obtain its value as a
32161 string, or set the value from a string. String value can be also
32162 obtained for a non-leaf variable object, but it's generally a string
32163 that only indicates the type of the object, and does not list its
32164 contents. Assignment to a non-leaf variable object is not allowed.
32166 A frontend does not need to read the values of all variable objects each time
32167 the program stops. Instead, MI provides an update command that lists all
32168 variable objects whose values has changed since the last update
32169 operation. This considerably reduces the amount of data that must
32170 be transferred to the frontend. As noted above, children variable
32171 objects are created on demand, and only leaf variable objects have a
32172 real value. As result, gdb will read target memory only for leaf
32173 variables that frontend has created.
32175 The automatic update is not always desirable. For example, a frontend
32176 might want to keep a value of some expression for future reference,
32177 and never update it. For another example, fetching memory is
32178 relatively slow for embedded targets, so a frontend might want
32179 to disable automatic update for the variables that are either not
32180 visible on the screen, or ``closed''. This is possible using so
32181 called ``frozen variable objects''. Such variable objects are never
32182 implicitly updated.
32184 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32185 fixed variable object, the expression is parsed when the variable
32186 object is created, including associating identifiers to specific
32187 variables. The meaning of expression never changes. For a floating
32188 variable object the values of variables whose names appear in the
32189 expressions are re-evaluated every time in the context of the current
32190 frame. Consider this example:
32195 struct work_state state;
32202 If a fixed variable object for the @code{state} variable is created in
32203 this function, and we enter the recursive call, the variable
32204 object will report the value of @code{state} in the top-level
32205 @code{do_work} invocation. On the other hand, a floating variable
32206 object will report the value of @code{state} in the current frame.
32208 If an expression specified when creating a fixed variable object
32209 refers to a local variable, the variable object becomes bound to the
32210 thread and frame in which the variable object is created. When such
32211 variable object is updated, @value{GDBN} makes sure that the
32212 thread/frame combination the variable object is bound to still exists,
32213 and re-evaluates the variable object in context of that thread/frame.
32215 The following is the complete set of @sc{gdb/mi} operations defined to
32216 access this functionality:
32218 @multitable @columnfractions .4 .6
32219 @item @strong{Operation}
32220 @tab @strong{Description}
32222 @item @code{-enable-pretty-printing}
32223 @tab enable Python-based pretty-printing
32224 @item @code{-var-create}
32225 @tab create a variable object
32226 @item @code{-var-delete}
32227 @tab delete the variable object and/or its children
32228 @item @code{-var-set-format}
32229 @tab set the display format of this variable
32230 @item @code{-var-show-format}
32231 @tab show the display format of this variable
32232 @item @code{-var-info-num-children}
32233 @tab tells how many children this object has
32234 @item @code{-var-list-children}
32235 @tab return a list of the object's children
32236 @item @code{-var-info-type}
32237 @tab show the type of this variable object
32238 @item @code{-var-info-expression}
32239 @tab print parent-relative expression that this variable object represents
32240 @item @code{-var-info-path-expression}
32241 @tab print full expression that this variable object represents
32242 @item @code{-var-show-attributes}
32243 @tab is this variable editable? does it exist here?
32244 @item @code{-var-evaluate-expression}
32245 @tab get the value of this variable
32246 @item @code{-var-assign}
32247 @tab set the value of this variable
32248 @item @code{-var-update}
32249 @tab update the variable and its children
32250 @item @code{-var-set-frozen}
32251 @tab set frozeness attribute
32252 @item @code{-var-set-update-range}
32253 @tab set range of children to display on update
32256 In the next subsection we describe each operation in detail and suggest
32257 how it can be used.
32259 @subheading Description And Use of Operations on Variable Objects
32261 @subheading The @code{-enable-pretty-printing} Command
32262 @findex -enable-pretty-printing
32265 -enable-pretty-printing
32268 @value{GDBN} allows Python-based visualizers to affect the output of the
32269 MI variable object commands. However, because there was no way to
32270 implement this in a fully backward-compatible way, a front end must
32271 request that this functionality be enabled.
32273 Once enabled, this feature cannot be disabled.
32275 Note that if Python support has not been compiled into @value{GDBN},
32276 this command will still succeed (and do nothing).
32278 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32279 may work differently in future versions of @value{GDBN}.
32281 @subheading The @code{-var-create} Command
32282 @findex -var-create
32284 @subsubheading Synopsis
32287 -var-create @{@var{name} | "-"@}
32288 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32291 This operation creates a variable object, which allows the monitoring of
32292 a variable, the result of an expression, a memory cell or a CPU
32295 The @var{name} parameter is the string by which the object can be
32296 referenced. It must be unique. If @samp{-} is specified, the varobj
32297 system will generate a string ``varNNNNNN'' automatically. It will be
32298 unique provided that one does not specify @var{name} of that format.
32299 The command fails if a duplicate name is found.
32301 The frame under which the expression should be evaluated can be
32302 specified by @var{frame-addr}. A @samp{*} indicates that the current
32303 frame should be used. A @samp{@@} indicates that a floating variable
32304 object must be created.
32306 @var{expression} is any expression valid on the current language set (must not
32307 begin with a @samp{*}), or one of the following:
32311 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32314 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32317 @samp{$@var{regname}} --- a CPU register name
32320 @cindex dynamic varobj
32321 A varobj's contents may be provided by a Python-based pretty-printer. In this
32322 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32323 have slightly different semantics in some cases. If the
32324 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32325 will never create a dynamic varobj. This ensures backward
32326 compatibility for existing clients.
32328 @subsubheading Result
32330 This operation returns attributes of the newly-created varobj. These
32335 The name of the varobj.
32338 The number of children of the varobj. This number is not necessarily
32339 reliable for a dynamic varobj. Instead, you must examine the
32340 @samp{has_more} attribute.
32343 The varobj's scalar value. For a varobj whose type is some sort of
32344 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32345 will not be interesting.
32348 The varobj's type. This is a string representation of the type, as
32349 would be printed by the @value{GDBN} CLI. If @samp{print object}
32350 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32351 @emph{actual} (derived) type of the object is shown rather than the
32352 @emph{declared} one.
32355 If a variable object is bound to a specific thread, then this is the
32356 thread's identifier.
32359 For a dynamic varobj, this indicates whether there appear to be any
32360 children available. For a non-dynamic varobj, this will be 0.
32363 This attribute will be present and have the value @samp{1} if the
32364 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32365 then this attribute will not be present.
32368 A dynamic varobj can supply a display hint to the front end. The
32369 value comes directly from the Python pretty-printer object's
32370 @code{display_hint} method. @xref{Pretty Printing API}.
32373 Typical output will look like this:
32376 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32377 has_more="@var{has_more}"
32381 @subheading The @code{-var-delete} Command
32382 @findex -var-delete
32384 @subsubheading Synopsis
32387 -var-delete [ -c ] @var{name}
32390 Deletes a previously created variable object and all of its children.
32391 With the @samp{-c} option, just deletes the children.
32393 Returns an error if the object @var{name} is not found.
32396 @subheading The @code{-var-set-format} Command
32397 @findex -var-set-format
32399 @subsubheading Synopsis
32402 -var-set-format @var{name} @var{format-spec}
32405 Sets the output format for the value of the object @var{name} to be
32408 @anchor{-var-set-format}
32409 The syntax for the @var{format-spec} is as follows:
32412 @var{format-spec} @expansion{}
32413 @{binary | decimal | hexadecimal | octal | natural@}
32416 The natural format is the default format choosen automatically
32417 based on the variable type (like decimal for an @code{int}, hex
32418 for pointers, etc.).
32420 For a variable with children, the format is set only on the
32421 variable itself, and the children are not affected.
32423 @subheading The @code{-var-show-format} Command
32424 @findex -var-show-format
32426 @subsubheading Synopsis
32429 -var-show-format @var{name}
32432 Returns the format used to display the value of the object @var{name}.
32435 @var{format} @expansion{}
32440 @subheading The @code{-var-info-num-children} Command
32441 @findex -var-info-num-children
32443 @subsubheading Synopsis
32446 -var-info-num-children @var{name}
32449 Returns the number of children of a variable object @var{name}:
32455 Note that this number is not completely reliable for a dynamic varobj.
32456 It will return the current number of children, but more children may
32460 @subheading The @code{-var-list-children} Command
32461 @findex -var-list-children
32463 @subsubheading Synopsis
32466 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32468 @anchor{-var-list-children}
32470 Return a list of the children of the specified variable object and
32471 create variable objects for them, if they do not already exist. With
32472 a single argument or if @var{print-values} has a value of 0 or
32473 @code{--no-values}, print only the names of the variables; if
32474 @var{print-values} is 1 or @code{--all-values}, also print their
32475 values; and if it is 2 or @code{--simple-values} print the name and
32476 value for simple data types and just the name for arrays, structures
32479 @var{from} and @var{to}, if specified, indicate the range of children
32480 to report. If @var{from} or @var{to} is less than zero, the range is
32481 reset and all children will be reported. Otherwise, children starting
32482 at @var{from} (zero-based) and up to and excluding @var{to} will be
32485 If a child range is requested, it will only affect the current call to
32486 @code{-var-list-children}, but not future calls to @code{-var-update}.
32487 For this, you must instead use @code{-var-set-update-range}. The
32488 intent of this approach is to enable a front end to implement any
32489 update approach it likes; for example, scrolling a view may cause the
32490 front end to request more children with @code{-var-list-children}, and
32491 then the front end could call @code{-var-set-update-range} with a
32492 different range to ensure that future updates are restricted to just
32495 For each child the following results are returned:
32500 Name of the variable object created for this child.
32503 The expression to be shown to the user by the front end to designate this child.
32504 For example this may be the name of a structure member.
32506 For a dynamic varobj, this value cannot be used to form an
32507 expression. There is no way to do this at all with a dynamic varobj.
32509 For C/C@t{++} structures there are several pseudo children returned to
32510 designate access qualifiers. For these pseudo children @var{exp} is
32511 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32512 type and value are not present.
32514 A dynamic varobj will not report the access qualifying
32515 pseudo-children, regardless of the language. This information is not
32516 available at all with a dynamic varobj.
32519 Number of children this child has. For a dynamic varobj, this will be
32523 The type of the child. If @samp{print object}
32524 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32525 @emph{actual} (derived) type of the object is shown rather than the
32526 @emph{declared} one.
32529 If values were requested, this is the value.
32532 If this variable object is associated with a thread, this is the thread id.
32533 Otherwise this result is not present.
32536 If the variable object is frozen, this variable will be present with a value of 1.
32539 A dynamic varobj can supply a display hint to the front end. The
32540 value comes directly from the Python pretty-printer object's
32541 @code{display_hint} method. @xref{Pretty Printing API}.
32544 This attribute will be present and have the value @samp{1} if the
32545 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32546 then this attribute will not be present.
32550 The result may have its own attributes:
32554 A dynamic varobj can supply a display hint to the front end. The
32555 value comes directly from the Python pretty-printer object's
32556 @code{display_hint} method. @xref{Pretty Printing API}.
32559 This is an integer attribute which is nonzero if there are children
32560 remaining after the end of the selected range.
32563 @subsubheading Example
32567 -var-list-children n
32568 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32569 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32571 -var-list-children --all-values n
32572 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32573 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32577 @subheading The @code{-var-info-type} Command
32578 @findex -var-info-type
32580 @subsubheading Synopsis
32583 -var-info-type @var{name}
32586 Returns the type of the specified variable @var{name}. The type is
32587 returned as a string in the same format as it is output by the
32591 type=@var{typename}
32595 @subheading The @code{-var-info-expression} Command
32596 @findex -var-info-expression
32598 @subsubheading Synopsis
32601 -var-info-expression @var{name}
32604 Returns a string that is suitable for presenting this
32605 variable object in user interface. The string is generally
32606 not valid expression in the current language, and cannot be evaluated.
32608 For example, if @code{a} is an array, and variable object
32609 @code{A} was created for @code{a}, then we'll get this output:
32612 (gdb) -var-info-expression A.1
32613 ^done,lang="C",exp="1"
32617 Here, the value of @code{lang} is the language name, which can be
32618 found in @ref{Supported Languages}.
32620 Note that the output of the @code{-var-list-children} command also
32621 includes those expressions, so the @code{-var-info-expression} command
32624 @subheading The @code{-var-info-path-expression} Command
32625 @findex -var-info-path-expression
32627 @subsubheading Synopsis
32630 -var-info-path-expression @var{name}
32633 Returns an expression that can be evaluated in the current
32634 context and will yield the same value that a variable object has.
32635 Compare this with the @code{-var-info-expression} command, which
32636 result can be used only for UI presentation. Typical use of
32637 the @code{-var-info-path-expression} command is creating a
32638 watchpoint from a variable object.
32640 This command is currently not valid for children of a dynamic varobj,
32641 and will give an error when invoked on one.
32643 For example, suppose @code{C} is a C@t{++} class, derived from class
32644 @code{Base}, and that the @code{Base} class has a member called
32645 @code{m_size}. Assume a variable @code{c} is has the type of
32646 @code{C} and a variable object @code{C} was created for variable
32647 @code{c}. Then, we'll get this output:
32649 (gdb) -var-info-path-expression C.Base.public.m_size
32650 ^done,path_expr=((Base)c).m_size)
32653 @subheading The @code{-var-show-attributes} Command
32654 @findex -var-show-attributes
32656 @subsubheading Synopsis
32659 -var-show-attributes @var{name}
32662 List attributes of the specified variable object @var{name}:
32665 status=@var{attr} [ ( ,@var{attr} )* ]
32669 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32671 @subheading The @code{-var-evaluate-expression} Command
32672 @findex -var-evaluate-expression
32674 @subsubheading Synopsis
32677 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32680 Evaluates the expression that is represented by the specified variable
32681 object and returns its value as a string. The format of the string
32682 can be specified with the @samp{-f} option. The possible values of
32683 this option are the same as for @code{-var-set-format}
32684 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32685 the current display format will be used. The current display format
32686 can be changed using the @code{-var-set-format} command.
32692 Note that one must invoke @code{-var-list-children} for a variable
32693 before the value of a child variable can be evaluated.
32695 @subheading The @code{-var-assign} Command
32696 @findex -var-assign
32698 @subsubheading Synopsis
32701 -var-assign @var{name} @var{expression}
32704 Assigns the value of @var{expression} to the variable object specified
32705 by @var{name}. The object must be @samp{editable}. If the variable's
32706 value is altered by the assign, the variable will show up in any
32707 subsequent @code{-var-update} list.
32709 @subsubheading Example
32717 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32721 @subheading The @code{-var-update} Command
32722 @findex -var-update
32724 @subsubheading Synopsis
32727 -var-update [@var{print-values}] @{@var{name} | "*"@}
32730 Reevaluate the expressions corresponding to the variable object
32731 @var{name} and all its direct and indirect children, and return the
32732 list of variable objects whose values have changed; @var{name} must
32733 be a root variable object. Here, ``changed'' means that the result of
32734 @code{-var-evaluate-expression} before and after the
32735 @code{-var-update} is different. If @samp{*} is used as the variable
32736 object names, all existing variable objects are updated, except
32737 for frozen ones (@pxref{-var-set-frozen}). The option
32738 @var{print-values} determines whether both names and values, or just
32739 names are printed. The possible values of this option are the same
32740 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32741 recommended to use the @samp{--all-values} option, to reduce the
32742 number of MI commands needed on each program stop.
32744 With the @samp{*} parameter, if a variable object is bound to a
32745 currently running thread, it will not be updated, without any
32748 If @code{-var-set-update-range} was previously used on a varobj, then
32749 only the selected range of children will be reported.
32751 @code{-var-update} reports all the changed varobjs in a tuple named
32754 Each item in the change list is itself a tuple holding:
32758 The name of the varobj.
32761 If values were requested for this update, then this field will be
32762 present and will hold the value of the varobj.
32765 @anchor{-var-update}
32766 This field is a string which may take one of three values:
32770 The variable object's current value is valid.
32773 The variable object does not currently hold a valid value but it may
32774 hold one in the future if its associated expression comes back into
32778 The variable object no longer holds a valid value.
32779 This can occur when the executable file being debugged has changed,
32780 either through recompilation or by using the @value{GDBN} @code{file}
32781 command. The front end should normally choose to delete these variable
32785 In the future new values may be added to this list so the front should
32786 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32789 This is only present if the varobj is still valid. If the type
32790 changed, then this will be the string @samp{true}; otherwise it will
32793 When a varobj's type changes, its children are also likely to have
32794 become incorrect. Therefore, the varobj's children are automatically
32795 deleted when this attribute is @samp{true}. Also, the varobj's update
32796 range, when set using the @code{-var-set-update-range} command, is
32800 If the varobj's type changed, then this field will be present and will
32803 @item new_num_children
32804 For a dynamic varobj, if the number of children changed, or if the
32805 type changed, this will be the new number of children.
32807 The @samp{numchild} field in other varobj responses is generally not
32808 valid for a dynamic varobj -- it will show the number of children that
32809 @value{GDBN} knows about, but because dynamic varobjs lazily
32810 instantiate their children, this will not reflect the number of
32811 children which may be available.
32813 The @samp{new_num_children} attribute only reports changes to the
32814 number of children known by @value{GDBN}. This is the only way to
32815 detect whether an update has removed children (which necessarily can
32816 only happen at the end of the update range).
32819 The display hint, if any.
32822 This is an integer value, which will be 1 if there are more children
32823 available outside the varobj's update range.
32826 This attribute will be present and have the value @samp{1} if the
32827 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32828 then this attribute will not be present.
32831 If new children were added to a dynamic varobj within the selected
32832 update range (as set by @code{-var-set-update-range}), then they will
32833 be listed in this attribute.
32836 @subsubheading Example
32843 -var-update --all-values var1
32844 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32845 type_changed="false"@}]
32849 @subheading The @code{-var-set-frozen} Command
32850 @findex -var-set-frozen
32851 @anchor{-var-set-frozen}
32853 @subsubheading Synopsis
32856 -var-set-frozen @var{name} @var{flag}
32859 Set the frozenness flag on the variable object @var{name}. The
32860 @var{flag} parameter should be either @samp{1} to make the variable
32861 frozen or @samp{0} to make it unfrozen. If a variable object is
32862 frozen, then neither itself, nor any of its children, are
32863 implicitly updated by @code{-var-update} of
32864 a parent variable or by @code{-var-update *}. Only
32865 @code{-var-update} of the variable itself will update its value and
32866 values of its children. After a variable object is unfrozen, it is
32867 implicitly updated by all subsequent @code{-var-update} operations.
32868 Unfreezing a variable does not update it, only subsequent
32869 @code{-var-update} does.
32871 @subsubheading Example
32875 -var-set-frozen V 1
32880 @subheading The @code{-var-set-update-range} command
32881 @findex -var-set-update-range
32882 @anchor{-var-set-update-range}
32884 @subsubheading Synopsis
32887 -var-set-update-range @var{name} @var{from} @var{to}
32890 Set the range of children to be returned by future invocations of
32891 @code{-var-update}.
32893 @var{from} and @var{to} indicate the range of children to report. If
32894 @var{from} or @var{to} is less than zero, the range is reset and all
32895 children will be reported. Otherwise, children starting at @var{from}
32896 (zero-based) and up to and excluding @var{to} will be reported.
32898 @subsubheading Example
32902 -var-set-update-range V 1 2
32906 @subheading The @code{-var-set-visualizer} command
32907 @findex -var-set-visualizer
32908 @anchor{-var-set-visualizer}
32910 @subsubheading Synopsis
32913 -var-set-visualizer @var{name} @var{visualizer}
32916 Set a visualizer for the variable object @var{name}.
32918 @var{visualizer} is the visualizer to use. The special value
32919 @samp{None} means to disable any visualizer in use.
32921 If not @samp{None}, @var{visualizer} must be a Python expression.
32922 This expression must evaluate to a callable object which accepts a
32923 single argument. @value{GDBN} will call this object with the value of
32924 the varobj @var{name} as an argument (this is done so that the same
32925 Python pretty-printing code can be used for both the CLI and MI).
32926 When called, this object must return an object which conforms to the
32927 pretty-printing interface (@pxref{Pretty Printing API}).
32929 The pre-defined function @code{gdb.default_visualizer} may be used to
32930 select a visualizer by following the built-in process
32931 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32932 a varobj is created, and so ordinarily is not needed.
32934 This feature is only available if Python support is enabled. The MI
32935 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
32936 can be used to check this.
32938 @subsubheading Example
32940 Resetting the visualizer:
32944 -var-set-visualizer V None
32948 Reselecting the default (type-based) visualizer:
32952 -var-set-visualizer V gdb.default_visualizer
32956 Suppose @code{SomeClass} is a visualizer class. A lambda expression
32957 can be used to instantiate this class for a varobj:
32961 -var-set-visualizer V "lambda val: SomeClass()"
32965 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32966 @node GDB/MI Data Manipulation
32967 @section @sc{gdb/mi} Data Manipulation
32969 @cindex data manipulation, in @sc{gdb/mi}
32970 @cindex @sc{gdb/mi}, data manipulation
32971 This section describes the @sc{gdb/mi} commands that manipulate data:
32972 examine memory and registers, evaluate expressions, etc.
32974 @c REMOVED FROM THE INTERFACE.
32975 @c @subheading -data-assign
32976 @c Change the value of a program variable. Plenty of side effects.
32977 @c @subsubheading GDB Command
32979 @c @subsubheading Example
32982 @subheading The @code{-data-disassemble} Command
32983 @findex -data-disassemble
32985 @subsubheading Synopsis
32989 [ -s @var{start-addr} -e @var{end-addr} ]
32990 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
32998 @item @var{start-addr}
32999 is the beginning address (or @code{$pc})
33000 @item @var{end-addr}
33002 @item @var{filename}
33003 is the name of the file to disassemble
33004 @item @var{linenum}
33005 is the line number to disassemble around
33007 is the number of disassembly lines to be produced. If it is -1,
33008 the whole function will be disassembled, in case no @var{end-addr} is
33009 specified. If @var{end-addr} is specified as a non-zero value, and
33010 @var{lines} is lower than the number of disassembly lines between
33011 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33012 displayed; if @var{lines} is higher than the number of lines between
33013 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33016 is either 0 (meaning only disassembly), 1 (meaning mixed source and
33017 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
33018 mixed source and disassembly with raw opcodes).
33021 @subsubheading Result
33023 The result of the @code{-data-disassemble} command will be a list named
33024 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33025 used with the @code{-data-disassemble} command.
33027 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33032 The address at which this instruction was disassembled.
33035 The name of the function this instruction is within.
33038 The decimal offset in bytes from the start of @samp{func-name}.
33041 The text disassembly for this @samp{address}.
33044 This field is only present for mode 2. This contains the raw opcode
33045 bytes for the @samp{inst} field.
33049 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
33050 @samp{src_and_asm_line}, each of which has the following fields:
33054 The line number within @samp{file}.
33057 The file name from the compilation unit. This might be an absolute
33058 file name or a relative file name depending on the compile command
33062 Absolute file name of @samp{file}. It is converted to a canonical form
33063 using the source file search path
33064 (@pxref{Source Path, ,Specifying Source Directories})
33065 and after resolving all the symbolic links.
33067 If the source file is not found this field will contain the path as
33068 present in the debug information.
33070 @item line_asm_insn
33071 This is a list of tuples containing the disassembly for @samp{line} in
33072 @samp{file}. The fields of each tuple are the same as for
33073 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33074 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33079 Note that whatever included in the @samp{inst} field, is not
33080 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33083 @subsubheading @value{GDBN} Command
33085 The corresponding @value{GDBN} command is @samp{disassemble}.
33087 @subsubheading Example
33089 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33093 -data-disassemble -s $pc -e "$pc + 20" -- 0
33096 @{address="0x000107c0",func-name="main",offset="4",
33097 inst="mov 2, %o0"@},
33098 @{address="0x000107c4",func-name="main",offset="8",
33099 inst="sethi %hi(0x11800), %o2"@},
33100 @{address="0x000107c8",func-name="main",offset="12",
33101 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33102 @{address="0x000107cc",func-name="main",offset="16",
33103 inst="sethi %hi(0x11800), %o2"@},
33104 @{address="0x000107d0",func-name="main",offset="20",
33105 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33109 Disassemble the whole @code{main} function. Line 32 is part of
33113 -data-disassemble -f basics.c -l 32 -- 0
33115 @{address="0x000107bc",func-name="main",offset="0",
33116 inst="save %sp, -112, %sp"@},
33117 @{address="0x000107c0",func-name="main",offset="4",
33118 inst="mov 2, %o0"@},
33119 @{address="0x000107c4",func-name="main",offset="8",
33120 inst="sethi %hi(0x11800), %o2"@},
33122 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33123 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33127 Disassemble 3 instructions from the start of @code{main}:
33131 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33133 @{address="0x000107bc",func-name="main",offset="0",
33134 inst="save %sp, -112, %sp"@},
33135 @{address="0x000107c0",func-name="main",offset="4",
33136 inst="mov 2, %o0"@},
33137 @{address="0x000107c4",func-name="main",offset="8",
33138 inst="sethi %hi(0x11800), %o2"@}]
33142 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33146 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33148 src_and_asm_line=@{line="31",
33149 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33150 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33151 line_asm_insn=[@{address="0x000107bc",
33152 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33153 src_and_asm_line=@{line="32",
33154 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33155 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33156 line_asm_insn=[@{address="0x000107c0",
33157 func-name="main",offset="4",inst="mov 2, %o0"@},
33158 @{address="0x000107c4",func-name="main",offset="8",
33159 inst="sethi %hi(0x11800), %o2"@}]@}]
33164 @subheading The @code{-data-evaluate-expression} Command
33165 @findex -data-evaluate-expression
33167 @subsubheading Synopsis
33170 -data-evaluate-expression @var{expr}
33173 Evaluate @var{expr} as an expression. The expression could contain an
33174 inferior function call. The function call will execute synchronously.
33175 If the expression contains spaces, it must be enclosed in double quotes.
33177 @subsubheading @value{GDBN} Command
33179 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33180 @samp{call}. In @code{gdbtk} only, there's a corresponding
33181 @samp{gdb_eval} command.
33183 @subsubheading Example
33185 In the following example, the numbers that precede the commands are the
33186 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33187 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33191 211-data-evaluate-expression A
33194 311-data-evaluate-expression &A
33195 311^done,value="0xefffeb7c"
33197 411-data-evaluate-expression A+3
33200 511-data-evaluate-expression "A + 3"
33206 @subheading The @code{-data-list-changed-registers} Command
33207 @findex -data-list-changed-registers
33209 @subsubheading Synopsis
33212 -data-list-changed-registers
33215 Display a list of the registers that have changed.
33217 @subsubheading @value{GDBN} Command
33219 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33220 has the corresponding command @samp{gdb_changed_register_list}.
33222 @subsubheading Example
33224 On a PPC MBX board:
33232 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33233 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33236 -data-list-changed-registers
33237 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33238 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33239 "24","25","26","27","28","30","31","64","65","66","67","69"]
33244 @subheading The @code{-data-list-register-names} Command
33245 @findex -data-list-register-names
33247 @subsubheading Synopsis
33250 -data-list-register-names [ ( @var{regno} )+ ]
33253 Show a list of register names for the current target. If no arguments
33254 are given, it shows a list of the names of all the registers. If
33255 integer numbers are given as arguments, it will print a list of the
33256 names of the registers corresponding to the arguments. To ensure
33257 consistency between a register name and its number, the output list may
33258 include empty register names.
33260 @subsubheading @value{GDBN} Command
33262 @value{GDBN} does not have a command which corresponds to
33263 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33264 corresponding command @samp{gdb_regnames}.
33266 @subsubheading Example
33268 For the PPC MBX board:
33271 -data-list-register-names
33272 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33273 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33274 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33275 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33276 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33277 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33278 "", "pc","ps","cr","lr","ctr","xer"]
33280 -data-list-register-names 1 2 3
33281 ^done,register-names=["r1","r2","r3"]
33285 @subheading The @code{-data-list-register-values} Command
33286 @findex -data-list-register-values
33288 @subsubheading Synopsis
33291 -data-list-register-values
33292 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33295 Display the registers' contents. @var{fmt} is the format according to
33296 which the registers' contents are to be returned, followed by an optional
33297 list of numbers specifying the registers to display. A missing list of
33298 numbers indicates that the contents of all the registers must be
33299 returned. The @code{--skip-unavailable} option indicates that only
33300 the available registers are to be returned.
33302 Allowed formats for @var{fmt} are:
33319 @subsubheading @value{GDBN} Command
33321 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33322 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33324 @subsubheading Example
33326 For a PPC MBX board (note: line breaks are for readability only, they
33327 don't appear in the actual output):
33331 -data-list-register-values r 64 65
33332 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33333 @{number="65",value="0x00029002"@}]
33335 -data-list-register-values x
33336 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33337 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33338 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33339 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33340 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33341 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33342 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33343 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33344 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33345 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33346 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33347 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33348 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33349 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33350 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33351 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33352 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33353 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33354 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33355 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33356 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33357 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33358 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33359 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33360 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33361 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33362 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33363 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33364 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33365 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33366 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33367 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33368 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33369 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33370 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33371 @{number="69",value="0x20002b03"@}]
33376 @subheading The @code{-data-read-memory} Command
33377 @findex -data-read-memory
33379 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33381 @subsubheading Synopsis
33384 -data-read-memory [ -o @var{byte-offset} ]
33385 @var{address} @var{word-format} @var{word-size}
33386 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33393 @item @var{address}
33394 An expression specifying the address of the first memory word to be
33395 read. Complex expressions containing embedded white space should be
33396 quoted using the C convention.
33398 @item @var{word-format}
33399 The format to be used to print the memory words. The notation is the
33400 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33403 @item @var{word-size}
33404 The size of each memory word in bytes.
33406 @item @var{nr-rows}
33407 The number of rows in the output table.
33409 @item @var{nr-cols}
33410 The number of columns in the output table.
33413 If present, indicates that each row should include an @sc{ascii} dump. The
33414 value of @var{aschar} is used as a padding character when a byte is not a
33415 member of the printable @sc{ascii} character set (printable @sc{ascii}
33416 characters are those whose code is between 32 and 126, inclusively).
33418 @item @var{byte-offset}
33419 An offset to add to the @var{address} before fetching memory.
33422 This command displays memory contents as a table of @var{nr-rows} by
33423 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33424 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33425 (returned as @samp{total-bytes}). Should less than the requested number
33426 of bytes be returned by the target, the missing words are identified
33427 using @samp{N/A}. The number of bytes read from the target is returned
33428 in @samp{nr-bytes} and the starting address used to read memory in
33431 The address of the next/previous row or page is available in
33432 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33435 @subsubheading @value{GDBN} Command
33437 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33438 @samp{gdb_get_mem} memory read command.
33440 @subsubheading Example
33442 Read six bytes of memory starting at @code{bytes+6} but then offset by
33443 @code{-6} bytes. Format as three rows of two columns. One byte per
33444 word. Display each word in hex.
33448 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33449 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33450 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33451 prev-page="0x0000138a",memory=[
33452 @{addr="0x00001390",data=["0x00","0x01"]@},
33453 @{addr="0x00001392",data=["0x02","0x03"]@},
33454 @{addr="0x00001394",data=["0x04","0x05"]@}]
33458 Read two bytes of memory starting at address @code{shorts + 64} and
33459 display as a single word formatted in decimal.
33463 5-data-read-memory shorts+64 d 2 1 1
33464 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33465 next-row="0x00001512",prev-row="0x0000150e",
33466 next-page="0x00001512",prev-page="0x0000150e",memory=[
33467 @{addr="0x00001510",data=["128"]@}]
33471 Read thirty two bytes of memory starting at @code{bytes+16} and format
33472 as eight rows of four columns. Include a string encoding with @samp{x}
33473 used as the non-printable character.
33477 4-data-read-memory bytes+16 x 1 8 4 x
33478 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33479 next-row="0x000013c0",prev-row="0x0000139c",
33480 next-page="0x000013c0",prev-page="0x00001380",memory=[
33481 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33482 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33483 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33484 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33485 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33486 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33487 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33488 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33492 @subheading The @code{-data-read-memory-bytes} Command
33493 @findex -data-read-memory-bytes
33495 @subsubheading Synopsis
33498 -data-read-memory-bytes [ -o @var{byte-offset} ]
33499 @var{address} @var{count}
33506 @item @var{address}
33507 An expression specifying the address of the first memory word to be
33508 read. Complex expressions containing embedded white space should be
33509 quoted using the C convention.
33512 The number of bytes to read. This should be an integer literal.
33514 @item @var{byte-offset}
33515 The offsets in bytes relative to @var{address} at which to start
33516 reading. This should be an integer literal. This option is provided
33517 so that a frontend is not required to first evaluate address and then
33518 perform address arithmetics itself.
33522 This command attempts to read all accessible memory regions in the
33523 specified range. First, all regions marked as unreadable in the memory
33524 map (if one is defined) will be skipped. @xref{Memory Region
33525 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33526 regions. For each one, if reading full region results in an errors,
33527 @value{GDBN} will try to read a subset of the region.
33529 In general, every single byte in the region may be readable or not,
33530 and the only way to read every readable byte is to try a read at
33531 every address, which is not practical. Therefore, @value{GDBN} will
33532 attempt to read all accessible bytes at either beginning or the end
33533 of the region, using a binary division scheme. This heuristic works
33534 well for reading accross a memory map boundary. Note that if a region
33535 has a readable range that is neither at the beginning or the end,
33536 @value{GDBN} will not read it.
33538 The result record (@pxref{GDB/MI Result Records}) that is output of
33539 the command includes a field named @samp{memory} whose content is a
33540 list of tuples. Each tuple represent a successfully read memory block
33541 and has the following fields:
33545 The start address of the memory block, as hexadecimal literal.
33548 The end address of the memory block, as hexadecimal literal.
33551 The offset of the memory block, as hexadecimal literal, relative to
33552 the start address passed to @code{-data-read-memory-bytes}.
33555 The contents of the memory block, in hex.
33561 @subsubheading @value{GDBN} Command
33563 The corresponding @value{GDBN} command is @samp{x}.
33565 @subsubheading Example
33569 -data-read-memory-bytes &a 10
33570 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33572 contents="01000000020000000300"@}]
33577 @subheading The @code{-data-write-memory-bytes} Command
33578 @findex -data-write-memory-bytes
33580 @subsubheading Synopsis
33583 -data-write-memory-bytes @var{address} @var{contents}
33584 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33591 @item @var{address}
33592 An expression specifying the address of the first memory word to be
33593 read. Complex expressions containing embedded white space should be
33594 quoted using the C convention.
33596 @item @var{contents}
33597 The hex-encoded bytes to write.
33600 Optional argument indicating the number of bytes to be written. If @var{count}
33601 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33602 write @var{contents} until it fills @var{count} bytes.
33606 @subsubheading @value{GDBN} Command
33608 There's no corresponding @value{GDBN} command.
33610 @subsubheading Example
33614 -data-write-memory-bytes &a "aabbccdd"
33621 -data-write-memory-bytes &a "aabbccdd" 16e
33626 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33627 @node GDB/MI Tracepoint Commands
33628 @section @sc{gdb/mi} Tracepoint Commands
33630 The commands defined in this section implement MI support for
33631 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33633 @subheading The @code{-trace-find} Command
33634 @findex -trace-find
33636 @subsubheading Synopsis
33639 -trace-find @var{mode} [@var{parameters}@dots{}]
33642 Find a trace frame using criteria defined by @var{mode} and
33643 @var{parameters}. The following table lists permissible
33644 modes and their parameters. For details of operation, see @ref{tfind}.
33649 No parameters are required. Stops examining trace frames.
33652 An integer is required as parameter. Selects tracepoint frame with
33655 @item tracepoint-number
33656 An integer is required as parameter. Finds next
33657 trace frame that corresponds to tracepoint with the specified number.
33660 An address is required as parameter. Finds
33661 next trace frame that corresponds to any tracepoint at the specified
33664 @item pc-inside-range
33665 Two addresses are required as parameters. Finds next trace
33666 frame that corresponds to a tracepoint at an address inside the
33667 specified range. Both bounds are considered to be inside the range.
33669 @item pc-outside-range
33670 Two addresses are required as parameters. Finds
33671 next trace frame that corresponds to a tracepoint at an address outside
33672 the specified range. Both bounds are considered to be inside the range.
33675 Line specification is required as parameter. @xref{Specify Location}.
33676 Finds next trace frame that corresponds to a tracepoint at
33677 the specified location.
33681 If @samp{none} was passed as @var{mode}, the response does not
33682 have fields. Otherwise, the response may have the following fields:
33686 This field has either @samp{0} or @samp{1} as the value, depending
33687 on whether a matching tracepoint was found.
33690 The index of the found traceframe. This field is present iff
33691 the @samp{found} field has value of @samp{1}.
33694 The index of the found tracepoint. This field is present iff
33695 the @samp{found} field has value of @samp{1}.
33698 The information about the frame corresponding to the found trace
33699 frame. This field is present only if a trace frame was found.
33700 @xref{GDB/MI Frame Information}, for description of this field.
33704 @subsubheading @value{GDBN} Command
33706 The corresponding @value{GDBN} command is @samp{tfind}.
33708 @subheading -trace-define-variable
33709 @findex -trace-define-variable
33711 @subsubheading Synopsis
33714 -trace-define-variable @var{name} [ @var{value} ]
33717 Create trace variable @var{name} if it does not exist. If
33718 @var{value} is specified, sets the initial value of the specified
33719 trace variable to that value. Note that the @var{name} should start
33720 with the @samp{$} character.
33722 @subsubheading @value{GDBN} Command
33724 The corresponding @value{GDBN} command is @samp{tvariable}.
33726 @subheading The @code{-trace-frame-collected} Command
33727 @findex -trace-frame-collected
33729 @subsubheading Synopsis
33732 -trace-frame-collected
33733 [--var-print-values @var{var_pval}]
33734 [--comp-print-values @var{comp_pval}]
33735 [--registers-format @var{regformat}]
33736 [--memory-contents]
33739 This command returns the set of collected objects, register names,
33740 trace state variable names, memory ranges and computed expressions
33741 that have been collected at a particular trace frame. The optional
33742 parameters to the command affect the output format in different ways.
33743 See the output description table below for more details.
33745 The reported names can be used in the normal manner to create
33746 varobjs and inspect the objects themselves. The items returned by
33747 this command are categorized so that it is clear which is a variable,
33748 which is a register, which is a trace state variable, which is a
33749 memory range and which is a computed expression.
33751 For instance, if the actions were
33753 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33754 collect *(int*)0xaf02bef0@@40
33758 the object collected in its entirety would be @code{myVar}. The
33759 object @code{myArray} would be partially collected, because only the
33760 element at index @code{myIndex} would be collected. The remaining
33761 objects would be computed expressions.
33763 An example output would be:
33767 -trace-frame-collected
33769 explicit-variables=[@{name="myVar",value="1"@}],
33770 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33771 @{name="myObj.field",value="0"@},
33772 @{name="myPtr->field",value="1"@},
33773 @{name="myCount + 2",value="3"@},
33774 @{name="$tvar1 + 1",value="43970027"@}],
33775 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33776 @{number="1",value="0x0"@},
33777 @{number="2",value="0x4"@},
33779 @{number="125",value="0x0"@}],
33780 tvars=[@{name="$tvar1",current="43970026"@}],
33781 memory=[@{address="0x0000000000602264",length="4"@},
33782 @{address="0x0000000000615bc0",length="4"@}]
33789 @item explicit-variables
33790 The set of objects that have been collected in their entirety (as
33791 opposed to collecting just a few elements of an array or a few struct
33792 members). For each object, its name and value are printed.
33793 The @code{--var-print-values} option affects how or whether the value
33794 field is output. If @var{var_pval} is 0, then print only the names;
33795 if it is 1, print also their values; and if it is 2, print the name,
33796 type and value for simple data types, and the name and type for
33797 arrays, structures and unions.
33799 @item computed-expressions
33800 The set of computed expressions that have been collected at the
33801 current trace frame. The @code{--comp-print-values} option affects
33802 this set like the @code{--var-print-values} option affects the
33803 @code{explicit-variables} set. See above.
33806 The registers that have been collected at the current trace frame.
33807 For each register collected, the name and current value are returned.
33808 The value is formatted according to the @code{--registers-format}
33809 option. See the @command{-data-list-register-values} command for a
33810 list of the allowed formats. The default is @samp{x}.
33813 The trace state variables that have been collected at the current
33814 trace frame. For each trace state variable collected, the name and
33815 current value are returned.
33818 The set of memory ranges that have been collected at the current trace
33819 frame. Its content is a list of tuples. Each tuple represents a
33820 collected memory range and has the following fields:
33824 The start address of the memory range, as hexadecimal literal.
33827 The length of the memory range, as decimal literal.
33830 The contents of the memory block, in hex. This field is only present
33831 if the @code{--memory-contents} option is specified.
33837 @subsubheading @value{GDBN} Command
33839 There is no corresponding @value{GDBN} command.
33841 @subsubheading Example
33843 @subheading -trace-list-variables
33844 @findex -trace-list-variables
33846 @subsubheading Synopsis
33849 -trace-list-variables
33852 Return a table of all defined trace variables. Each element of the
33853 table has the following fields:
33857 The name of the trace variable. This field is always present.
33860 The initial value. This is a 64-bit signed integer. This
33861 field is always present.
33864 The value the trace variable has at the moment. This is a 64-bit
33865 signed integer. This field is absent iff current value is
33866 not defined, for example if the trace was never run, or is
33871 @subsubheading @value{GDBN} Command
33873 The corresponding @value{GDBN} command is @samp{tvariables}.
33875 @subsubheading Example
33879 -trace-list-variables
33880 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33881 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33882 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33883 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33884 body=[variable=@{name="$trace_timestamp",initial="0"@}
33885 variable=@{name="$foo",initial="10",current="15"@}]@}
33889 @subheading -trace-save
33890 @findex -trace-save
33892 @subsubheading Synopsis
33895 -trace-save [-r ] @var{filename}
33898 Saves the collected trace data to @var{filename}. Without the
33899 @samp{-r} option, the data is downloaded from the target and saved
33900 in a local file. With the @samp{-r} option the target is asked
33901 to perform the save.
33903 @subsubheading @value{GDBN} Command
33905 The corresponding @value{GDBN} command is @samp{tsave}.
33908 @subheading -trace-start
33909 @findex -trace-start
33911 @subsubheading Synopsis
33917 Starts a tracing experiments. The result of this command does not
33920 @subsubheading @value{GDBN} Command
33922 The corresponding @value{GDBN} command is @samp{tstart}.
33924 @subheading -trace-status
33925 @findex -trace-status
33927 @subsubheading Synopsis
33933 Obtains the status of a tracing experiment. The result may include
33934 the following fields:
33939 May have a value of either @samp{0}, when no tracing operations are
33940 supported, @samp{1}, when all tracing operations are supported, or
33941 @samp{file} when examining trace file. In the latter case, examining
33942 of trace frame is possible but new tracing experiement cannot be
33943 started. This field is always present.
33946 May have a value of either @samp{0} or @samp{1} depending on whether
33947 tracing experiement is in progress on target. This field is present
33948 if @samp{supported} field is not @samp{0}.
33951 Report the reason why the tracing was stopped last time. This field
33952 may be absent iff tracing was never stopped on target yet. The
33953 value of @samp{request} means the tracing was stopped as result of
33954 the @code{-trace-stop} command. The value of @samp{overflow} means
33955 the tracing buffer is full. The value of @samp{disconnection} means
33956 tracing was automatically stopped when @value{GDBN} has disconnected.
33957 The value of @samp{passcount} means tracing was stopped when a
33958 tracepoint was passed a maximal number of times for that tracepoint.
33959 This field is present if @samp{supported} field is not @samp{0}.
33961 @item stopping-tracepoint
33962 The number of tracepoint whose passcount as exceeded. This field is
33963 present iff the @samp{stop-reason} field has the value of
33967 @itemx frames-created
33968 The @samp{frames} field is a count of the total number of trace frames
33969 in the trace buffer, while @samp{frames-created} is the total created
33970 during the run, including ones that were discarded, such as when a
33971 circular trace buffer filled up. Both fields are optional.
33975 These fields tell the current size of the tracing buffer and the
33976 remaining space. These fields are optional.
33979 The value of the circular trace buffer flag. @code{1} means that the
33980 trace buffer is circular and old trace frames will be discarded if
33981 necessary to make room, @code{0} means that the trace buffer is linear
33985 The value of the disconnected tracing flag. @code{1} means that
33986 tracing will continue after @value{GDBN} disconnects, @code{0} means
33987 that the trace run will stop.
33990 The filename of the trace file being examined. This field is
33991 optional, and only present when examining a trace file.
33995 @subsubheading @value{GDBN} Command
33997 The corresponding @value{GDBN} command is @samp{tstatus}.
33999 @subheading -trace-stop
34000 @findex -trace-stop
34002 @subsubheading Synopsis
34008 Stops a tracing experiment. The result of this command has the same
34009 fields as @code{-trace-status}, except that the @samp{supported} and
34010 @samp{running} fields are not output.
34012 @subsubheading @value{GDBN} Command
34014 The corresponding @value{GDBN} command is @samp{tstop}.
34017 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34018 @node GDB/MI Symbol Query
34019 @section @sc{gdb/mi} Symbol Query Commands
34023 @subheading The @code{-symbol-info-address} Command
34024 @findex -symbol-info-address
34026 @subsubheading Synopsis
34029 -symbol-info-address @var{symbol}
34032 Describe where @var{symbol} is stored.
34034 @subsubheading @value{GDBN} Command
34036 The corresponding @value{GDBN} command is @samp{info address}.
34038 @subsubheading Example
34042 @subheading The @code{-symbol-info-file} Command
34043 @findex -symbol-info-file
34045 @subsubheading Synopsis
34051 Show the file for the symbol.
34053 @subsubheading @value{GDBN} Command
34055 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34056 @samp{gdb_find_file}.
34058 @subsubheading Example
34062 @subheading The @code{-symbol-info-function} Command
34063 @findex -symbol-info-function
34065 @subsubheading Synopsis
34068 -symbol-info-function
34071 Show which function the symbol lives in.
34073 @subsubheading @value{GDBN} Command
34075 @samp{gdb_get_function} in @code{gdbtk}.
34077 @subsubheading Example
34081 @subheading The @code{-symbol-info-line} Command
34082 @findex -symbol-info-line
34084 @subsubheading Synopsis
34090 Show the core addresses of the code for a source line.
34092 @subsubheading @value{GDBN} Command
34094 The corresponding @value{GDBN} command is @samp{info line}.
34095 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34097 @subsubheading Example
34101 @subheading The @code{-symbol-info-symbol} Command
34102 @findex -symbol-info-symbol
34104 @subsubheading Synopsis
34107 -symbol-info-symbol @var{addr}
34110 Describe what symbol is at location @var{addr}.
34112 @subsubheading @value{GDBN} Command
34114 The corresponding @value{GDBN} command is @samp{info symbol}.
34116 @subsubheading Example
34120 @subheading The @code{-symbol-list-functions} Command
34121 @findex -symbol-list-functions
34123 @subsubheading Synopsis
34126 -symbol-list-functions
34129 List the functions in the executable.
34131 @subsubheading @value{GDBN} Command
34133 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34134 @samp{gdb_search} in @code{gdbtk}.
34136 @subsubheading Example
34141 @subheading The @code{-symbol-list-lines} Command
34142 @findex -symbol-list-lines
34144 @subsubheading Synopsis
34147 -symbol-list-lines @var{filename}
34150 Print the list of lines that contain code and their associated program
34151 addresses for the given source filename. The entries are sorted in
34152 ascending PC order.
34154 @subsubheading @value{GDBN} Command
34156 There is no corresponding @value{GDBN} command.
34158 @subsubheading Example
34161 -symbol-list-lines basics.c
34162 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34168 @subheading The @code{-symbol-list-types} Command
34169 @findex -symbol-list-types
34171 @subsubheading Synopsis
34177 List all the type names.
34179 @subsubheading @value{GDBN} Command
34181 The corresponding commands are @samp{info types} in @value{GDBN},
34182 @samp{gdb_search} in @code{gdbtk}.
34184 @subsubheading Example
34188 @subheading The @code{-symbol-list-variables} Command
34189 @findex -symbol-list-variables
34191 @subsubheading Synopsis
34194 -symbol-list-variables
34197 List all the global and static variable names.
34199 @subsubheading @value{GDBN} Command
34201 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34203 @subsubheading Example
34207 @subheading The @code{-symbol-locate} Command
34208 @findex -symbol-locate
34210 @subsubheading Synopsis
34216 @subsubheading @value{GDBN} Command
34218 @samp{gdb_loc} in @code{gdbtk}.
34220 @subsubheading Example
34224 @subheading The @code{-symbol-type} Command
34225 @findex -symbol-type
34227 @subsubheading Synopsis
34230 -symbol-type @var{variable}
34233 Show type of @var{variable}.
34235 @subsubheading @value{GDBN} Command
34237 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
34238 @samp{gdb_obj_variable}.
34240 @subsubheading Example
34245 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34246 @node GDB/MI File Commands
34247 @section @sc{gdb/mi} File Commands
34249 This section describes the GDB/MI commands to specify executable file names
34250 and to read in and obtain symbol table information.
34252 @subheading The @code{-file-exec-and-symbols} Command
34253 @findex -file-exec-and-symbols
34255 @subsubheading Synopsis
34258 -file-exec-and-symbols @var{file}
34261 Specify the executable file to be debugged. This file is the one from
34262 which the symbol table is also read. If no file is specified, the
34263 command clears the executable and symbol information. If breakpoints
34264 are set when using this command with no arguments, @value{GDBN} will produce
34265 error messages. Otherwise, no output is produced, except a completion
34268 @subsubheading @value{GDBN} Command
34270 The corresponding @value{GDBN} command is @samp{file}.
34272 @subsubheading Example
34276 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34282 @subheading The @code{-file-exec-file} Command
34283 @findex -file-exec-file
34285 @subsubheading Synopsis
34288 -file-exec-file @var{file}
34291 Specify the executable file to be debugged. Unlike
34292 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34293 from this file. If used without argument, @value{GDBN} clears the information
34294 about the executable file. No output is produced, except a completion
34297 @subsubheading @value{GDBN} Command
34299 The corresponding @value{GDBN} command is @samp{exec-file}.
34301 @subsubheading Example
34305 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34312 @subheading The @code{-file-list-exec-sections} Command
34313 @findex -file-list-exec-sections
34315 @subsubheading Synopsis
34318 -file-list-exec-sections
34321 List the sections of the current executable file.
34323 @subsubheading @value{GDBN} Command
34325 The @value{GDBN} command @samp{info file} shows, among the rest, the same
34326 information as this command. @code{gdbtk} has a corresponding command
34327 @samp{gdb_load_info}.
34329 @subsubheading Example
34334 @subheading The @code{-file-list-exec-source-file} Command
34335 @findex -file-list-exec-source-file
34337 @subsubheading Synopsis
34340 -file-list-exec-source-file
34343 List the line number, the current source file, and the absolute path
34344 to the current source file for the current executable. The macro
34345 information field has a value of @samp{1} or @samp{0} depending on
34346 whether or not the file includes preprocessor macro information.
34348 @subsubheading @value{GDBN} Command
34350 The @value{GDBN} equivalent is @samp{info source}
34352 @subsubheading Example
34356 123-file-list-exec-source-file
34357 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34362 @subheading The @code{-file-list-exec-source-files} Command
34363 @findex -file-list-exec-source-files
34365 @subsubheading Synopsis
34368 -file-list-exec-source-files
34371 List the source files for the current executable.
34373 It will always output both the filename and fullname (absolute file
34374 name) of a source file.
34376 @subsubheading @value{GDBN} Command
34378 The @value{GDBN} equivalent is @samp{info sources}.
34379 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34381 @subsubheading Example
34384 -file-list-exec-source-files
34386 @{file=foo.c,fullname=/home/foo.c@},
34387 @{file=/home/bar.c,fullname=/home/bar.c@},
34388 @{file=gdb_could_not_find_fullpath.c@}]
34393 @subheading The @code{-file-list-shared-libraries} Command
34394 @findex -file-list-shared-libraries
34396 @subsubheading Synopsis
34399 -file-list-shared-libraries
34402 List the shared libraries in the program.
34404 @subsubheading @value{GDBN} Command
34406 The corresponding @value{GDBN} command is @samp{info shared}.
34408 @subsubheading Example
34412 @subheading The @code{-file-list-symbol-files} Command
34413 @findex -file-list-symbol-files
34415 @subsubheading Synopsis
34418 -file-list-symbol-files
34423 @subsubheading @value{GDBN} Command
34425 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34427 @subsubheading Example
34432 @subheading The @code{-file-symbol-file} Command
34433 @findex -file-symbol-file
34435 @subsubheading Synopsis
34438 -file-symbol-file @var{file}
34441 Read symbol table info from the specified @var{file} argument. When
34442 used without arguments, clears @value{GDBN}'s symbol table info. No output is
34443 produced, except for a completion notification.
34445 @subsubheading @value{GDBN} Command
34447 The corresponding @value{GDBN} command is @samp{symbol-file}.
34449 @subsubheading Example
34453 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34459 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34460 @node GDB/MI Memory Overlay Commands
34461 @section @sc{gdb/mi} Memory Overlay Commands
34463 The memory overlay commands are not implemented.
34465 @c @subheading -overlay-auto
34467 @c @subheading -overlay-list-mapping-state
34469 @c @subheading -overlay-list-overlays
34471 @c @subheading -overlay-map
34473 @c @subheading -overlay-off
34475 @c @subheading -overlay-on
34477 @c @subheading -overlay-unmap
34479 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34480 @node GDB/MI Signal Handling Commands
34481 @section @sc{gdb/mi} Signal Handling Commands
34483 Signal handling commands are not implemented.
34485 @c @subheading -signal-handle
34487 @c @subheading -signal-list-handle-actions
34489 @c @subheading -signal-list-signal-types
34493 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34494 @node GDB/MI Target Manipulation
34495 @section @sc{gdb/mi} Target Manipulation Commands
34498 @subheading The @code{-target-attach} Command
34499 @findex -target-attach
34501 @subsubheading Synopsis
34504 -target-attach @var{pid} | @var{gid} | @var{file}
34507 Attach to a process @var{pid} or a file @var{file} outside of
34508 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34509 group, the id previously returned by
34510 @samp{-list-thread-groups --available} must be used.
34512 @subsubheading @value{GDBN} Command
34514 The corresponding @value{GDBN} command is @samp{attach}.
34516 @subsubheading Example
34520 =thread-created,id="1"
34521 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34527 @subheading The @code{-target-compare-sections} Command
34528 @findex -target-compare-sections
34530 @subsubheading Synopsis
34533 -target-compare-sections [ @var{section} ]
34536 Compare data of section @var{section} on target to the exec file.
34537 Without the argument, all sections are compared.
34539 @subsubheading @value{GDBN} Command
34541 The @value{GDBN} equivalent is @samp{compare-sections}.
34543 @subsubheading Example
34548 @subheading The @code{-target-detach} Command
34549 @findex -target-detach
34551 @subsubheading Synopsis
34554 -target-detach [ @var{pid} | @var{gid} ]
34557 Detach from the remote target which normally resumes its execution.
34558 If either @var{pid} or @var{gid} is specified, detaches from either
34559 the specified process, or specified thread group. There's no output.
34561 @subsubheading @value{GDBN} Command
34563 The corresponding @value{GDBN} command is @samp{detach}.
34565 @subsubheading Example
34575 @subheading The @code{-target-disconnect} Command
34576 @findex -target-disconnect
34578 @subsubheading Synopsis
34584 Disconnect from the remote target. There's no output and the target is
34585 generally not resumed.
34587 @subsubheading @value{GDBN} Command
34589 The corresponding @value{GDBN} command is @samp{disconnect}.
34591 @subsubheading Example
34601 @subheading The @code{-target-download} Command
34602 @findex -target-download
34604 @subsubheading Synopsis
34610 Loads the executable onto the remote target.
34611 It prints out an update message every half second, which includes the fields:
34615 The name of the section.
34617 The size of what has been sent so far for that section.
34619 The size of the section.
34621 The total size of what was sent so far (the current and the previous sections).
34623 The size of the overall executable to download.
34627 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34628 @sc{gdb/mi} Output Syntax}).
34630 In addition, it prints the name and size of the sections, as they are
34631 downloaded. These messages include the following fields:
34635 The name of the section.
34637 The size of the section.
34639 The size of the overall executable to download.
34643 At the end, a summary is printed.
34645 @subsubheading @value{GDBN} Command
34647 The corresponding @value{GDBN} command is @samp{load}.
34649 @subsubheading Example
34651 Note: each status message appears on a single line. Here the messages
34652 have been broken down so that they can fit onto a page.
34657 +download,@{section=".text",section-size="6668",total-size="9880"@}
34658 +download,@{section=".text",section-sent="512",section-size="6668",
34659 total-sent="512",total-size="9880"@}
34660 +download,@{section=".text",section-sent="1024",section-size="6668",
34661 total-sent="1024",total-size="9880"@}
34662 +download,@{section=".text",section-sent="1536",section-size="6668",
34663 total-sent="1536",total-size="9880"@}
34664 +download,@{section=".text",section-sent="2048",section-size="6668",
34665 total-sent="2048",total-size="9880"@}
34666 +download,@{section=".text",section-sent="2560",section-size="6668",
34667 total-sent="2560",total-size="9880"@}
34668 +download,@{section=".text",section-sent="3072",section-size="6668",
34669 total-sent="3072",total-size="9880"@}
34670 +download,@{section=".text",section-sent="3584",section-size="6668",
34671 total-sent="3584",total-size="9880"@}
34672 +download,@{section=".text",section-sent="4096",section-size="6668",
34673 total-sent="4096",total-size="9880"@}
34674 +download,@{section=".text",section-sent="4608",section-size="6668",
34675 total-sent="4608",total-size="9880"@}
34676 +download,@{section=".text",section-sent="5120",section-size="6668",
34677 total-sent="5120",total-size="9880"@}
34678 +download,@{section=".text",section-sent="5632",section-size="6668",
34679 total-sent="5632",total-size="9880"@}
34680 +download,@{section=".text",section-sent="6144",section-size="6668",
34681 total-sent="6144",total-size="9880"@}
34682 +download,@{section=".text",section-sent="6656",section-size="6668",
34683 total-sent="6656",total-size="9880"@}
34684 +download,@{section=".init",section-size="28",total-size="9880"@}
34685 +download,@{section=".fini",section-size="28",total-size="9880"@}
34686 +download,@{section=".data",section-size="3156",total-size="9880"@}
34687 +download,@{section=".data",section-sent="512",section-size="3156",
34688 total-sent="7236",total-size="9880"@}
34689 +download,@{section=".data",section-sent="1024",section-size="3156",
34690 total-sent="7748",total-size="9880"@}
34691 +download,@{section=".data",section-sent="1536",section-size="3156",
34692 total-sent="8260",total-size="9880"@}
34693 +download,@{section=".data",section-sent="2048",section-size="3156",
34694 total-sent="8772",total-size="9880"@}
34695 +download,@{section=".data",section-sent="2560",section-size="3156",
34696 total-sent="9284",total-size="9880"@}
34697 +download,@{section=".data",section-sent="3072",section-size="3156",
34698 total-sent="9796",total-size="9880"@}
34699 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34706 @subheading The @code{-target-exec-status} Command
34707 @findex -target-exec-status
34709 @subsubheading Synopsis
34712 -target-exec-status
34715 Provide information on the state of the target (whether it is running or
34716 not, for instance).
34718 @subsubheading @value{GDBN} Command
34720 There's no equivalent @value{GDBN} command.
34722 @subsubheading Example
34726 @subheading The @code{-target-list-available-targets} Command
34727 @findex -target-list-available-targets
34729 @subsubheading Synopsis
34732 -target-list-available-targets
34735 List the possible targets to connect to.
34737 @subsubheading @value{GDBN} Command
34739 The corresponding @value{GDBN} command is @samp{help target}.
34741 @subsubheading Example
34745 @subheading The @code{-target-list-current-targets} Command
34746 @findex -target-list-current-targets
34748 @subsubheading Synopsis
34751 -target-list-current-targets
34754 Describe the current target.
34756 @subsubheading @value{GDBN} Command
34758 The corresponding information is printed by @samp{info file} (among
34761 @subsubheading Example
34765 @subheading The @code{-target-list-parameters} Command
34766 @findex -target-list-parameters
34768 @subsubheading Synopsis
34771 -target-list-parameters
34777 @subsubheading @value{GDBN} Command
34781 @subsubheading Example
34785 @subheading The @code{-target-select} Command
34786 @findex -target-select
34788 @subsubheading Synopsis
34791 -target-select @var{type} @var{parameters @dots{}}
34794 Connect @value{GDBN} to the remote target. This command takes two args:
34798 The type of target, for instance @samp{remote}, etc.
34799 @item @var{parameters}
34800 Device names, host names and the like. @xref{Target Commands, ,
34801 Commands for Managing Targets}, for more details.
34804 The output is a connection notification, followed by the address at
34805 which the target program is, in the following form:
34808 ^connected,addr="@var{address}",func="@var{function name}",
34809 args=[@var{arg list}]
34812 @subsubheading @value{GDBN} Command
34814 The corresponding @value{GDBN} command is @samp{target}.
34816 @subsubheading Example
34820 -target-select remote /dev/ttya
34821 ^connected,addr="0xfe00a300",func="??",args=[]
34825 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34826 @node GDB/MI File Transfer Commands
34827 @section @sc{gdb/mi} File Transfer Commands
34830 @subheading The @code{-target-file-put} Command
34831 @findex -target-file-put
34833 @subsubheading Synopsis
34836 -target-file-put @var{hostfile} @var{targetfile}
34839 Copy file @var{hostfile} from the host system (the machine running
34840 @value{GDBN}) to @var{targetfile} on the target system.
34842 @subsubheading @value{GDBN} Command
34844 The corresponding @value{GDBN} command is @samp{remote put}.
34846 @subsubheading Example
34850 -target-file-put localfile remotefile
34856 @subheading The @code{-target-file-get} Command
34857 @findex -target-file-get
34859 @subsubheading Synopsis
34862 -target-file-get @var{targetfile} @var{hostfile}
34865 Copy file @var{targetfile} from the target system to @var{hostfile}
34866 on the host system.
34868 @subsubheading @value{GDBN} Command
34870 The corresponding @value{GDBN} command is @samp{remote get}.
34872 @subsubheading Example
34876 -target-file-get remotefile localfile
34882 @subheading The @code{-target-file-delete} Command
34883 @findex -target-file-delete
34885 @subsubheading Synopsis
34888 -target-file-delete @var{targetfile}
34891 Delete @var{targetfile} from the target system.
34893 @subsubheading @value{GDBN} Command
34895 The corresponding @value{GDBN} command is @samp{remote delete}.
34897 @subsubheading Example
34901 -target-file-delete remotefile
34907 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34908 @node GDB/MI Ada Exceptions Commands
34909 @section Ada Exceptions @sc{gdb/mi} Commands
34911 @subheading The @code{-info-ada-exceptions} Command
34912 @findex -info-ada-exceptions
34914 @subsubheading Synopsis
34917 -info-ada-exceptions [ @var{regexp}]
34920 List all Ada exceptions defined within the program being debugged.
34921 With a regular expression @var{regexp}, only those exceptions whose
34922 names match @var{regexp} are listed.
34924 @subsubheading @value{GDBN} Command
34926 The corresponding @value{GDBN} command is @samp{info exceptions}.
34928 @subsubheading Result
34930 The result is a table of Ada exceptions. The following columns are
34931 defined for each exception:
34935 The name of the exception.
34938 The address of the exception.
34942 @subsubheading Example
34945 -info-ada-exceptions aint
34946 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
34947 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
34948 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
34949 body=[@{name="constraint_error",address="0x0000000000613da0"@},
34950 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
34953 @subheading Catching Ada Exceptions
34955 The commands describing how to ask @value{GDBN} to stop when a program
34956 raises an exception are described at @ref{Ada Exception GDB/MI
34957 Catchpoint Commands}.
34960 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34961 @node GDB/MI Miscellaneous Commands
34962 @section Miscellaneous @sc{gdb/mi} Commands
34964 @c @subheading -gdb-complete
34966 @subheading The @code{-gdb-exit} Command
34969 @subsubheading Synopsis
34975 Exit @value{GDBN} immediately.
34977 @subsubheading @value{GDBN} Command
34979 Approximately corresponds to @samp{quit}.
34981 @subsubheading Example
34991 @subheading The @code{-exec-abort} Command
34992 @findex -exec-abort
34994 @subsubheading Synopsis
35000 Kill the inferior running program.
35002 @subsubheading @value{GDBN} Command
35004 The corresponding @value{GDBN} command is @samp{kill}.
35006 @subsubheading Example
35011 @subheading The @code{-gdb-set} Command
35014 @subsubheading Synopsis
35020 Set an internal @value{GDBN} variable.
35021 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
35023 @subsubheading @value{GDBN} Command
35025 The corresponding @value{GDBN} command is @samp{set}.
35027 @subsubheading Example
35037 @subheading The @code{-gdb-show} Command
35040 @subsubheading Synopsis
35046 Show the current value of a @value{GDBN} variable.
35048 @subsubheading @value{GDBN} Command
35050 The corresponding @value{GDBN} command is @samp{show}.
35052 @subsubheading Example
35061 @c @subheading -gdb-source
35064 @subheading The @code{-gdb-version} Command
35065 @findex -gdb-version
35067 @subsubheading Synopsis
35073 Show version information for @value{GDBN}. Used mostly in testing.
35075 @subsubheading @value{GDBN} Command
35077 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
35078 default shows this information when you start an interactive session.
35080 @subsubheading Example
35082 @c This example modifies the actual output from GDB to avoid overfull
35088 ~Copyright 2000 Free Software Foundation, Inc.
35089 ~GDB is free software, covered by the GNU General Public License, and
35090 ~you are welcome to change it and/or distribute copies of it under
35091 ~ certain conditions.
35092 ~Type "show copying" to see the conditions.
35093 ~There is absolutely no warranty for GDB. Type "show warranty" for
35095 ~This GDB was configured as
35096 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
35101 @subheading The @code{-list-features} Command
35102 @findex -list-features
35104 Returns a list of particular features of the MI protocol that
35105 this version of gdb implements. A feature can be a command,
35106 or a new field in an output of some command, or even an
35107 important bugfix. While a frontend can sometimes detect presence
35108 of a feature at runtime, it is easier to perform detection at debugger
35111 The command returns a list of strings, with each string naming an
35112 available feature. Each returned string is just a name, it does not
35113 have any internal structure. The list of possible feature names
35119 (gdb) -list-features
35120 ^done,result=["feature1","feature2"]
35123 The current list of features is:
35126 @item frozen-varobjs
35127 Indicates support for the @code{-var-set-frozen} command, as well
35128 as possible presense of the @code{frozen} field in the output
35129 of @code{-varobj-create}.
35130 @item pending-breakpoints
35131 Indicates support for the @option{-f} option to the @code{-break-insert}
35134 Indicates Python scripting support, Python-based
35135 pretty-printing commands, and possible presence of the
35136 @samp{display_hint} field in the output of @code{-var-list-children}
35138 Indicates support for the @code{-thread-info} command.
35139 @item data-read-memory-bytes
35140 Indicates support for the @code{-data-read-memory-bytes} and the
35141 @code{-data-write-memory-bytes} commands.
35142 @item breakpoint-notifications
35143 Indicates that changes to breakpoints and breakpoints created via the
35144 CLI will be announced via async records.
35145 @item ada-task-info
35146 Indicates support for the @code{-ada-task-info} command.
35147 @item ada-exceptions
35148 Indicates support for the following commands, all of them related to Ada
35149 exceptions: @code{-info-ada-exceptions}, @code{-catch-assert} and
35150 @code{-catch-exception}.
35151 @item language-option
35152 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
35153 option (@pxref{Context management}).
35156 @subheading The @code{-list-target-features} Command
35157 @findex -list-target-features
35159 Returns a list of particular features that are supported by the
35160 target. Those features affect the permitted MI commands, but
35161 unlike the features reported by the @code{-list-features} command, the
35162 features depend on which target GDB is using at the moment. Whenever
35163 a target can change, due to commands such as @code{-target-select},
35164 @code{-target-attach} or @code{-exec-run}, the list of target features
35165 may change, and the frontend should obtain it again.
35169 (gdb) -list-target-features
35170 ^done,result=["async"]
35173 The current list of features is:
35177 Indicates that the target is capable of asynchronous command
35178 execution, which means that @value{GDBN} will accept further commands
35179 while the target is running.
35182 Indicates that the target is capable of reverse execution.
35183 @xref{Reverse Execution}, for more information.
35187 @subheading The @code{-list-thread-groups} Command
35188 @findex -list-thread-groups
35190 @subheading Synopsis
35193 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
35196 Lists thread groups (@pxref{Thread groups}). When a single thread
35197 group is passed as the argument, lists the children of that group.
35198 When several thread group are passed, lists information about those
35199 thread groups. Without any parameters, lists information about all
35200 top-level thread groups.
35202 Normally, thread groups that are being debugged are reported.
35203 With the @samp{--available} option, @value{GDBN} reports thread groups
35204 available on the target.
35206 The output of this command may have either a @samp{threads} result or
35207 a @samp{groups} result. The @samp{thread} result has a list of tuples
35208 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
35209 Information}). The @samp{groups} result has a list of tuples as value,
35210 each tuple describing a thread group. If top-level groups are
35211 requested (that is, no parameter is passed), or when several groups
35212 are passed, the output always has a @samp{groups} result. The format
35213 of the @samp{group} result is described below.
35215 To reduce the number of roundtrips it's possible to list thread groups
35216 together with their children, by passing the @samp{--recurse} option
35217 and the recursion depth. Presently, only recursion depth of 1 is
35218 permitted. If this option is present, then every reported thread group
35219 will also include its children, either as @samp{group} or
35220 @samp{threads} field.
35222 In general, any combination of option and parameters is permitted, with
35223 the following caveats:
35227 When a single thread group is passed, the output will typically
35228 be the @samp{threads} result. Because threads may not contain
35229 anything, the @samp{recurse} option will be ignored.
35232 When the @samp{--available} option is passed, limited information may
35233 be available. In particular, the list of threads of a process might
35234 be inaccessible. Further, specifying specific thread groups might
35235 not give any performance advantage over listing all thread groups.
35236 The frontend should assume that @samp{-list-thread-groups --available}
35237 is always an expensive operation and cache the results.
35241 The @samp{groups} result is a list of tuples, where each tuple may
35242 have the following fields:
35246 Identifier of the thread group. This field is always present.
35247 The identifier is an opaque string; frontends should not try to
35248 convert it to an integer, even though it might look like one.
35251 The type of the thread group. At present, only @samp{process} is a
35255 The target-specific process identifier. This field is only present
35256 for thread groups of type @samp{process} and only if the process exists.
35259 The number of children this thread group has. This field may be
35260 absent for an available thread group.
35263 This field has a list of tuples as value, each tuple describing a
35264 thread. It may be present if the @samp{--recurse} option is
35265 specified, and it's actually possible to obtain the threads.
35268 This field is a list of integers, each identifying a core that one
35269 thread of the group is running on. This field may be absent if
35270 such information is not available.
35273 The name of the executable file that corresponds to this thread group.
35274 The field is only present for thread groups of type @samp{process},
35275 and only if there is a corresponding executable file.
35279 @subheading Example
35283 -list-thread-groups
35284 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
35285 -list-thread-groups 17
35286 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
35287 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
35288 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
35289 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
35290 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
35291 -list-thread-groups --available
35292 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
35293 -list-thread-groups --available --recurse 1
35294 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35295 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35296 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
35297 -list-thread-groups --available --recurse 1 17 18
35298 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35299 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35300 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
35303 @subheading The @code{-info-os} Command
35306 @subsubheading Synopsis
35309 -info-os [ @var{type} ]
35312 If no argument is supplied, the command returns a table of available
35313 operating-system-specific information types. If one of these types is
35314 supplied as an argument @var{type}, then the command returns a table
35315 of data of that type.
35317 The types of information available depend on the target operating
35320 @subsubheading @value{GDBN} Command
35322 The corresponding @value{GDBN} command is @samp{info os}.
35324 @subsubheading Example
35326 When run on a @sc{gnu}/Linux system, the output will look something
35332 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
35333 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35334 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35335 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35336 body=[item=@{col0="processes",col1="Listing of all processes",
35337 col2="Processes"@},
35338 item=@{col0="procgroups",col1="Listing of all process groups",
35339 col2="Process groups"@},
35340 item=@{col0="threads",col1="Listing of all threads",
35342 item=@{col0="files",col1="Listing of all file descriptors",
35343 col2="File descriptors"@},
35344 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
35346 item=@{col0="shm",col1="Listing of all shared-memory regions",
35347 col2="Shared-memory regions"@},
35348 item=@{col0="semaphores",col1="Listing of all semaphores",
35349 col2="Semaphores"@},
35350 item=@{col0="msg",col1="Listing of all message queues",
35351 col2="Message queues"@},
35352 item=@{col0="modules",col1="Listing of all loaded kernel modules",
35353 col2="Kernel modules"@}]@}
35356 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
35357 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
35358 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
35359 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
35360 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
35361 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
35362 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
35363 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35365 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35366 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35370 (Note that the MI output here includes a @code{"Title"} column that
35371 does not appear in command-line @code{info os}; this column is useful
35372 for MI clients that want to enumerate the types of data, such as in a
35373 popup menu, but is needless clutter on the command line, and
35374 @code{info os} omits it.)
35376 @subheading The @code{-add-inferior} Command
35377 @findex -add-inferior
35379 @subheading Synopsis
35385 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35386 inferior is not associated with any executable. Such association may
35387 be established with the @samp{-file-exec-and-symbols} command
35388 (@pxref{GDB/MI File Commands}). The command response has a single
35389 field, @samp{inferior}, whose value is the identifier of the
35390 thread group corresponding to the new inferior.
35392 @subheading Example
35397 ^done,inferior="i3"
35400 @subheading The @code{-interpreter-exec} Command
35401 @findex -interpreter-exec
35403 @subheading Synopsis
35406 -interpreter-exec @var{interpreter} @var{command}
35408 @anchor{-interpreter-exec}
35410 Execute the specified @var{command} in the given @var{interpreter}.
35412 @subheading @value{GDBN} Command
35414 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35416 @subheading Example
35420 -interpreter-exec console "break main"
35421 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35422 &"During symbol reading, bad structure-type format.\n"
35423 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35428 @subheading The @code{-inferior-tty-set} Command
35429 @findex -inferior-tty-set
35431 @subheading Synopsis
35434 -inferior-tty-set /dev/pts/1
35437 Set terminal for future runs of the program being debugged.
35439 @subheading @value{GDBN} Command
35441 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35443 @subheading Example
35447 -inferior-tty-set /dev/pts/1
35452 @subheading The @code{-inferior-tty-show} Command
35453 @findex -inferior-tty-show
35455 @subheading Synopsis
35461 Show terminal for future runs of program being debugged.
35463 @subheading @value{GDBN} Command
35465 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35467 @subheading Example
35471 -inferior-tty-set /dev/pts/1
35475 ^done,inferior_tty_terminal="/dev/pts/1"
35479 @subheading The @code{-enable-timings} Command
35480 @findex -enable-timings
35482 @subheading Synopsis
35485 -enable-timings [yes | no]
35488 Toggle the printing of the wallclock, user and system times for an MI
35489 command as a field in its output. This command is to help frontend
35490 developers optimize the performance of their code. No argument is
35491 equivalent to @samp{yes}.
35493 @subheading @value{GDBN} Command
35497 @subheading Example
35505 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35506 addr="0x080484ed",func="main",file="myprog.c",
35507 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35509 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35517 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35518 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35519 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35520 fullname="/home/nickrob/myprog.c",line="73"@}
35525 @chapter @value{GDBN} Annotations
35527 This chapter describes annotations in @value{GDBN}. Annotations were
35528 designed to interface @value{GDBN} to graphical user interfaces or other
35529 similar programs which want to interact with @value{GDBN} at a
35530 relatively high level.
35532 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35536 This is Edition @value{EDITION}, @value{DATE}.
35540 * Annotations Overview:: What annotations are; the general syntax.
35541 * Server Prefix:: Issuing a command without affecting user state.
35542 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35543 * Errors:: Annotations for error messages.
35544 * Invalidation:: Some annotations describe things now invalid.
35545 * Annotations for Running::
35546 Whether the program is running, how it stopped, etc.
35547 * Source Annotations:: Annotations describing source code.
35550 @node Annotations Overview
35551 @section What is an Annotation?
35552 @cindex annotations
35554 Annotations start with a newline character, two @samp{control-z}
35555 characters, and the name of the annotation. If there is no additional
35556 information associated with this annotation, the name of the annotation
35557 is followed immediately by a newline. If there is additional
35558 information, the name of the annotation is followed by a space, the
35559 additional information, and a newline. The additional information
35560 cannot contain newline characters.
35562 Any output not beginning with a newline and two @samp{control-z}
35563 characters denotes literal output from @value{GDBN}. Currently there is
35564 no need for @value{GDBN} to output a newline followed by two
35565 @samp{control-z} characters, but if there was such a need, the
35566 annotations could be extended with an @samp{escape} annotation which
35567 means those three characters as output.
35569 The annotation @var{level}, which is specified using the
35570 @option{--annotate} command line option (@pxref{Mode Options}), controls
35571 how much information @value{GDBN} prints together with its prompt,
35572 values of expressions, source lines, and other types of output. Level 0
35573 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35574 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35575 for programs that control @value{GDBN}, and level 2 annotations have
35576 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35577 Interface, annotate, GDB's Obsolete Annotations}).
35580 @kindex set annotate
35581 @item set annotate @var{level}
35582 The @value{GDBN} command @code{set annotate} sets the level of
35583 annotations to the specified @var{level}.
35585 @item show annotate
35586 @kindex show annotate
35587 Show the current annotation level.
35590 This chapter describes level 3 annotations.
35592 A simple example of starting up @value{GDBN} with annotations is:
35595 $ @kbd{gdb --annotate=3}
35597 Copyright 2003 Free Software Foundation, Inc.
35598 GDB is free software, covered by the GNU General Public License,
35599 and you are welcome to change it and/or distribute copies of it
35600 under certain conditions.
35601 Type "show copying" to see the conditions.
35602 There is absolutely no warranty for GDB. Type "show warranty"
35604 This GDB was configured as "i386-pc-linux-gnu"
35615 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35616 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35617 denotes a @samp{control-z} character) are annotations; the rest is
35618 output from @value{GDBN}.
35620 @node Server Prefix
35621 @section The Server Prefix
35622 @cindex server prefix
35624 If you prefix a command with @samp{server } then it will not affect
35625 the command history, nor will it affect @value{GDBN}'s notion of which
35626 command to repeat if @key{RET} is pressed on a line by itself. This
35627 means that commands can be run behind a user's back by a front-end in
35628 a transparent manner.
35630 The @code{server } prefix does not affect the recording of values into
35631 the value history; to print a value without recording it into the
35632 value history, use the @code{output} command instead of the
35633 @code{print} command.
35635 Using this prefix also disables confirmation requests
35636 (@pxref{confirmation requests}).
35639 @section Annotation for @value{GDBN} Input
35641 @cindex annotations for prompts
35642 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35643 to know when to send output, when the output from a given command is
35646 Different kinds of input each have a different @dfn{input type}. Each
35647 input type has three annotations: a @code{pre-} annotation, which
35648 denotes the beginning of any prompt which is being output, a plain
35649 annotation, which denotes the end of the prompt, and then a @code{post-}
35650 annotation which denotes the end of any echo which may (or may not) be
35651 associated with the input. For example, the @code{prompt} input type
35652 features the following annotations:
35660 The input types are
35663 @findex pre-prompt annotation
35664 @findex prompt annotation
35665 @findex post-prompt annotation
35667 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35669 @findex pre-commands annotation
35670 @findex commands annotation
35671 @findex post-commands annotation
35673 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35674 command. The annotations are repeated for each command which is input.
35676 @findex pre-overload-choice annotation
35677 @findex overload-choice annotation
35678 @findex post-overload-choice annotation
35679 @item overload-choice
35680 When @value{GDBN} wants the user to select between various overloaded functions.
35682 @findex pre-query annotation
35683 @findex query annotation
35684 @findex post-query annotation
35686 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35688 @findex pre-prompt-for-continue annotation
35689 @findex prompt-for-continue annotation
35690 @findex post-prompt-for-continue annotation
35691 @item prompt-for-continue
35692 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35693 expect this to work well; instead use @code{set height 0} to disable
35694 prompting. This is because the counting of lines is buggy in the
35695 presence of annotations.
35700 @cindex annotations for errors, warnings and interrupts
35702 @findex quit annotation
35707 This annotation occurs right before @value{GDBN} responds to an interrupt.
35709 @findex error annotation
35714 This annotation occurs right before @value{GDBN} responds to an error.
35716 Quit and error annotations indicate that any annotations which @value{GDBN} was
35717 in the middle of may end abruptly. For example, if a
35718 @code{value-history-begin} annotation is followed by a @code{error}, one
35719 cannot expect to receive the matching @code{value-history-end}. One
35720 cannot expect not to receive it either, however; an error annotation
35721 does not necessarily mean that @value{GDBN} is immediately returning all the way
35724 @findex error-begin annotation
35725 A quit or error annotation may be preceded by
35731 Any output between that and the quit or error annotation is the error
35734 Warning messages are not yet annotated.
35735 @c If we want to change that, need to fix warning(), type_error(),
35736 @c range_error(), and possibly other places.
35739 @section Invalidation Notices
35741 @cindex annotations for invalidation messages
35742 The following annotations say that certain pieces of state may have
35746 @findex frames-invalid annotation
35747 @item ^Z^Zframes-invalid
35749 The frames (for example, output from the @code{backtrace} command) may
35752 @findex breakpoints-invalid annotation
35753 @item ^Z^Zbreakpoints-invalid
35755 The breakpoints may have changed. For example, the user just added or
35756 deleted a breakpoint.
35759 @node Annotations for Running
35760 @section Running the Program
35761 @cindex annotations for running programs
35763 @findex starting annotation
35764 @findex stopping annotation
35765 When the program starts executing due to a @value{GDBN} command such as
35766 @code{step} or @code{continue},
35772 is output. When the program stops,
35778 is output. Before the @code{stopped} annotation, a variety of
35779 annotations describe how the program stopped.
35782 @findex exited annotation
35783 @item ^Z^Zexited @var{exit-status}
35784 The program exited, and @var{exit-status} is the exit status (zero for
35785 successful exit, otherwise nonzero).
35787 @findex signalled annotation
35788 @findex signal-name annotation
35789 @findex signal-name-end annotation
35790 @findex signal-string annotation
35791 @findex signal-string-end annotation
35792 @item ^Z^Zsignalled
35793 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35794 annotation continues:
35800 ^Z^Zsignal-name-end
35804 ^Z^Zsignal-string-end
35809 where @var{name} is the name of the signal, such as @code{SIGILL} or
35810 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35811 as @code{Illegal Instruction} or @code{Segmentation fault}.
35812 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35813 user's benefit and have no particular format.
35815 @findex signal annotation
35817 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35818 just saying that the program received the signal, not that it was
35819 terminated with it.
35821 @findex breakpoint annotation
35822 @item ^Z^Zbreakpoint @var{number}
35823 The program hit breakpoint number @var{number}.
35825 @findex watchpoint annotation
35826 @item ^Z^Zwatchpoint @var{number}
35827 The program hit watchpoint number @var{number}.
35830 @node Source Annotations
35831 @section Displaying Source
35832 @cindex annotations for source display
35834 @findex source annotation
35835 The following annotation is used instead of displaying source code:
35838 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
35841 where @var{filename} is an absolute file name indicating which source
35842 file, @var{line} is the line number within that file (where 1 is the
35843 first line in the file), @var{character} is the character position
35844 within the file (where 0 is the first character in the file) (for most
35845 debug formats this will necessarily point to the beginning of a line),
35846 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
35847 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
35848 @var{addr} is the address in the target program associated with the
35849 source which is being displayed. @var{addr} is in the form @samp{0x}
35850 followed by one or more lowercase hex digits (note that this does not
35851 depend on the language).
35853 @node JIT Interface
35854 @chapter JIT Compilation Interface
35855 @cindex just-in-time compilation
35856 @cindex JIT compilation interface
35858 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
35859 interface. A JIT compiler is a program or library that generates native
35860 executable code at runtime and executes it, usually in order to achieve good
35861 performance while maintaining platform independence.
35863 Programs that use JIT compilation are normally difficult to debug because
35864 portions of their code are generated at runtime, instead of being loaded from
35865 object files, which is where @value{GDBN} normally finds the program's symbols
35866 and debug information. In order to debug programs that use JIT compilation,
35867 @value{GDBN} has an interface that allows the program to register in-memory
35868 symbol files with @value{GDBN} at runtime.
35870 If you are using @value{GDBN} to debug a program that uses this interface, then
35871 it should work transparently so long as you have not stripped the binary. If
35872 you are developing a JIT compiler, then the interface is documented in the rest
35873 of this chapter. At this time, the only known client of this interface is the
35876 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
35877 JIT compiler communicates with @value{GDBN} by writing data into a global
35878 variable and calling a fuction at a well-known symbol. When @value{GDBN}
35879 attaches, it reads a linked list of symbol files from the global variable to
35880 find existing code, and puts a breakpoint in the function so that it can find
35881 out about additional code.
35884 * Declarations:: Relevant C struct declarations
35885 * Registering Code:: Steps to register code
35886 * Unregistering Code:: Steps to unregister code
35887 * Custom Debug Info:: Emit debug information in a custom format
35891 @section JIT Declarations
35893 These are the relevant struct declarations that a C program should include to
35894 implement the interface:
35904 struct jit_code_entry
35906 struct jit_code_entry *next_entry;
35907 struct jit_code_entry *prev_entry;
35908 const char *symfile_addr;
35909 uint64_t symfile_size;
35912 struct jit_descriptor
35915 /* This type should be jit_actions_t, but we use uint32_t
35916 to be explicit about the bitwidth. */
35917 uint32_t action_flag;
35918 struct jit_code_entry *relevant_entry;
35919 struct jit_code_entry *first_entry;
35922 /* GDB puts a breakpoint in this function. */
35923 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
35925 /* Make sure to specify the version statically, because the
35926 debugger may check the version before we can set it. */
35927 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
35930 If the JIT is multi-threaded, then it is important that the JIT synchronize any
35931 modifications to this global data properly, which can easily be done by putting
35932 a global mutex around modifications to these structures.
35934 @node Registering Code
35935 @section Registering Code
35937 To register code with @value{GDBN}, the JIT should follow this protocol:
35941 Generate an object file in memory with symbols and other desired debug
35942 information. The file must include the virtual addresses of the sections.
35945 Create a code entry for the file, which gives the start and size of the symbol
35949 Add it to the linked list in the JIT descriptor.
35952 Point the relevant_entry field of the descriptor at the entry.
35955 Set @code{action_flag} to @code{JIT_REGISTER} and call
35956 @code{__jit_debug_register_code}.
35959 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
35960 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
35961 new code. However, the linked list must still be maintained in order to allow
35962 @value{GDBN} to attach to a running process and still find the symbol files.
35964 @node Unregistering Code
35965 @section Unregistering Code
35967 If code is freed, then the JIT should use the following protocol:
35971 Remove the code entry corresponding to the code from the linked list.
35974 Point the @code{relevant_entry} field of the descriptor at the code entry.
35977 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
35978 @code{__jit_debug_register_code}.
35981 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
35982 and the JIT will leak the memory used for the associated symbol files.
35984 @node Custom Debug Info
35985 @section Custom Debug Info
35986 @cindex custom JIT debug info
35987 @cindex JIT debug info reader
35989 Generating debug information in platform-native file formats (like ELF
35990 or COFF) may be an overkill for JIT compilers; especially if all the
35991 debug info is used for is displaying a meaningful backtrace. The
35992 issue can be resolved by having the JIT writers decide on a debug info
35993 format and also provide a reader that parses the debug info generated
35994 by the JIT compiler. This section gives a brief overview on writing
35995 such a parser. More specific details can be found in the source file
35996 @file{gdb/jit-reader.in}, which is also installed as a header at
35997 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35999 The reader is implemented as a shared object (so this functionality is
36000 not available on platforms which don't allow loading shared objects at
36001 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
36002 @code{jit-reader-unload} are provided, to be used to load and unload
36003 the readers from a preconfigured directory. Once loaded, the shared
36004 object is used the parse the debug information emitted by the JIT
36008 * Using JIT Debug Info Readers:: How to use supplied readers correctly
36009 * Writing JIT Debug Info Readers:: Creating a debug-info reader
36012 @node Using JIT Debug Info Readers
36013 @subsection Using JIT Debug Info Readers
36014 @kindex jit-reader-load
36015 @kindex jit-reader-unload
36017 Readers can be loaded and unloaded using the @code{jit-reader-load}
36018 and @code{jit-reader-unload} commands.
36021 @item jit-reader-load @var{reader}
36022 Load the JIT reader named @var{reader}. @var{reader} is a shared
36023 object specified as either an absolute or a relative file name. In
36024 the latter case, @value{GDBN} will try to load the reader from a
36025 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
36026 system (here @var{libdir} is the system library directory, often
36027 @file{/usr/local/lib}).
36029 Only one reader can be active at a time; trying to load a second
36030 reader when one is already loaded will result in @value{GDBN}
36031 reporting an error. A new JIT reader can be loaded by first unloading
36032 the current one using @code{jit-reader-unload} and then invoking
36033 @code{jit-reader-load}.
36035 @item jit-reader-unload
36036 Unload the currently loaded JIT reader.
36040 @node Writing JIT Debug Info Readers
36041 @subsection Writing JIT Debug Info Readers
36042 @cindex writing JIT debug info readers
36044 As mentioned, a reader is essentially a shared object conforming to a
36045 certain ABI. This ABI is described in @file{jit-reader.h}.
36047 @file{jit-reader.h} defines the structures, macros and functions
36048 required to write a reader. It is installed (along with
36049 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36050 the system include directory.
36052 Readers need to be released under a GPL compatible license. A reader
36053 can be declared as released under such a license by placing the macro
36054 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
36056 The entry point for readers is the symbol @code{gdb_init_reader},
36057 which is expected to be a function with the prototype
36059 @findex gdb_init_reader
36061 extern struct gdb_reader_funcs *gdb_init_reader (void);
36064 @cindex @code{struct gdb_reader_funcs}
36066 @code{struct gdb_reader_funcs} contains a set of pointers to callback
36067 functions. These functions are executed to read the debug info
36068 generated by the JIT compiler (@code{read}), to unwind stack frames
36069 (@code{unwind}) and to create canonical frame IDs
36070 (@code{get_Frame_id}). It also has a callback that is called when the
36071 reader is being unloaded (@code{destroy}). The struct looks like this
36074 struct gdb_reader_funcs
36076 /* Must be set to GDB_READER_INTERFACE_VERSION. */
36077 int reader_version;
36079 /* For use by the reader. */
36082 gdb_read_debug_info *read;
36083 gdb_unwind_frame *unwind;
36084 gdb_get_frame_id *get_frame_id;
36085 gdb_destroy_reader *destroy;
36089 @cindex @code{struct gdb_symbol_callbacks}
36090 @cindex @code{struct gdb_unwind_callbacks}
36092 The callbacks are provided with another set of callbacks by
36093 @value{GDBN} to do their job. For @code{read}, these callbacks are
36094 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
36095 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
36096 @code{struct gdb_symbol_callbacks} has callbacks to create new object
36097 files and new symbol tables inside those object files. @code{struct
36098 gdb_unwind_callbacks} has callbacks to read registers off the current
36099 frame and to write out the values of the registers in the previous
36100 frame. Both have a callback (@code{target_read}) to read bytes off the
36101 target's address space.
36103 @node In-Process Agent
36104 @chapter In-Process Agent
36105 @cindex debugging agent
36106 The traditional debugging model is conceptually low-speed, but works fine,
36107 because most bugs can be reproduced in debugging-mode execution. However,
36108 as multi-core or many-core processors are becoming mainstream, and
36109 multi-threaded programs become more and more popular, there should be more
36110 and more bugs that only manifest themselves at normal-mode execution, for
36111 example, thread races, because debugger's interference with the program's
36112 timing may conceal the bugs. On the other hand, in some applications,
36113 it is not feasible for the debugger to interrupt the program's execution
36114 long enough for the developer to learn anything helpful about its behavior.
36115 If the program's correctness depends on its real-time behavior, delays
36116 introduced by a debugger might cause the program to fail, even when the
36117 code itself is correct. It is useful to be able to observe the program's
36118 behavior without interrupting it.
36120 Therefore, traditional debugging model is too intrusive to reproduce
36121 some bugs. In order to reduce the interference with the program, we can
36122 reduce the number of operations performed by debugger. The
36123 @dfn{In-Process Agent}, a shared library, is running within the same
36124 process with inferior, and is able to perform some debugging operations
36125 itself. As a result, debugger is only involved when necessary, and
36126 performance of debugging can be improved accordingly. Note that
36127 interference with program can be reduced but can't be removed completely,
36128 because the in-process agent will still stop or slow down the program.
36130 The in-process agent can interpret and execute Agent Expressions
36131 (@pxref{Agent Expressions}) during performing debugging operations. The
36132 agent expressions can be used for different purposes, such as collecting
36133 data in tracepoints, and condition evaluation in breakpoints.
36135 @anchor{Control Agent}
36136 You can control whether the in-process agent is used as an aid for
36137 debugging with the following commands:
36140 @kindex set agent on
36142 Causes the in-process agent to perform some operations on behalf of the
36143 debugger. Just which operations requested by the user will be done
36144 by the in-process agent depends on the its capabilities. For example,
36145 if you request to evaluate breakpoint conditions in the in-process agent,
36146 and the in-process agent has such capability as well, then breakpoint
36147 conditions will be evaluated in the in-process agent.
36149 @kindex set agent off
36150 @item set agent off
36151 Disables execution of debugging operations by the in-process agent. All
36152 of the operations will be performed by @value{GDBN}.
36156 Display the current setting of execution of debugging operations by
36157 the in-process agent.
36161 * In-Process Agent Protocol::
36164 @node In-Process Agent Protocol
36165 @section In-Process Agent Protocol
36166 @cindex in-process agent protocol
36168 The in-process agent is able to communicate with both @value{GDBN} and
36169 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
36170 used for communications between @value{GDBN} or GDBserver and the IPA.
36171 In general, @value{GDBN} or GDBserver sends commands
36172 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
36173 in-process agent replies back with the return result of the command, or
36174 some other information. The data sent to in-process agent is composed
36175 of primitive data types, such as 4-byte or 8-byte type, and composite
36176 types, which are called objects (@pxref{IPA Protocol Objects}).
36179 * IPA Protocol Objects::
36180 * IPA Protocol Commands::
36183 @node IPA Protocol Objects
36184 @subsection IPA Protocol Objects
36185 @cindex ipa protocol objects
36187 The commands sent to and results received from agent may contain some
36188 complex data types called @dfn{objects}.
36190 The in-process agent is running on the same machine with @value{GDBN}
36191 or GDBserver, so it doesn't have to handle as much differences between
36192 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
36193 However, there are still some differences of two ends in two processes:
36197 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
36198 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
36200 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
36201 GDBserver is compiled with one, and in-process agent is compiled with
36205 Here are the IPA Protocol Objects:
36209 agent expression object. It represents an agent expression
36210 (@pxref{Agent Expressions}).
36211 @anchor{agent expression object}
36213 tracepoint action object. It represents a tracepoint action
36214 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
36215 memory, static trace data and to evaluate expression.
36216 @anchor{tracepoint action object}
36218 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
36219 @anchor{tracepoint object}
36223 The following table describes important attributes of each IPA protocol
36226 @multitable @columnfractions .30 .20 .50
36227 @headitem Name @tab Size @tab Description
36228 @item @emph{agent expression object} @tab @tab
36229 @item length @tab 4 @tab length of bytes code
36230 @item byte code @tab @var{length} @tab contents of byte code
36231 @item @emph{tracepoint action for collecting memory} @tab @tab
36232 @item 'M' @tab 1 @tab type of tracepoint action
36233 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
36234 address of the lowest byte to collect, otherwise @var{addr} is the offset
36235 of @var{basereg} for memory collecting.
36236 @item len @tab 8 @tab length of memory for collecting
36237 @item basereg @tab 4 @tab the register number containing the starting
36238 memory address for collecting.
36239 @item @emph{tracepoint action for collecting registers} @tab @tab
36240 @item 'R' @tab 1 @tab type of tracepoint action
36241 @item @emph{tracepoint action for collecting static trace data} @tab @tab
36242 @item 'L' @tab 1 @tab type of tracepoint action
36243 @item @emph{tracepoint action for expression evaluation} @tab @tab
36244 @item 'X' @tab 1 @tab type of tracepoint action
36245 @item agent expression @tab length of @tab @ref{agent expression object}
36246 @item @emph{tracepoint object} @tab @tab
36247 @item number @tab 4 @tab number of tracepoint
36248 @item address @tab 8 @tab address of tracepoint inserted on
36249 @item type @tab 4 @tab type of tracepoint
36250 @item enabled @tab 1 @tab enable or disable of tracepoint
36251 @item step_count @tab 8 @tab step
36252 @item pass_count @tab 8 @tab pass
36253 @item numactions @tab 4 @tab number of tracepoint actions
36254 @item hit count @tab 8 @tab hit count
36255 @item trace frame usage @tab 8 @tab trace frame usage
36256 @item compiled_cond @tab 8 @tab compiled condition
36257 @item orig_size @tab 8 @tab orig size
36258 @item condition @tab 4 if condition is NULL otherwise length of
36259 @ref{agent expression object}
36260 @tab zero if condition is NULL, otherwise is
36261 @ref{agent expression object}
36262 @item actions @tab variable
36263 @tab numactions number of @ref{tracepoint action object}
36266 @node IPA Protocol Commands
36267 @subsection IPA Protocol Commands
36268 @cindex ipa protocol commands
36270 The spaces in each command are delimiters to ease reading this commands
36271 specification. They don't exist in real commands.
36275 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
36276 Installs a new fast tracepoint described by @var{tracepoint_object}
36277 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
36278 head of @dfn{jumppad}, which is used to jump to data collection routine
36283 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
36284 @var{target_address} is address of tracepoint in the inferior.
36285 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
36286 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
36287 @var{fjump} contains a sequence of instructions jump to jumppad entry.
36288 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
36295 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
36296 is about to kill inferiors.
36304 @item probe_marker_at:@var{address}
36305 Asks in-process agent to probe the marker at @var{address}.
36312 @item unprobe_marker_at:@var{address}
36313 Asks in-process agent to unprobe the marker at @var{address}.
36317 @chapter Reporting Bugs in @value{GDBN}
36318 @cindex bugs in @value{GDBN}
36319 @cindex reporting bugs in @value{GDBN}
36321 Your bug reports play an essential role in making @value{GDBN} reliable.
36323 Reporting a bug may help you by bringing a solution to your problem, or it
36324 may not. But in any case the principal function of a bug report is to help
36325 the entire community by making the next version of @value{GDBN} work better. Bug
36326 reports are your contribution to the maintenance of @value{GDBN}.
36328 In order for a bug report to serve its purpose, you must include the
36329 information that enables us to fix the bug.
36332 * Bug Criteria:: Have you found a bug?
36333 * Bug Reporting:: How to report bugs
36337 @section Have You Found a Bug?
36338 @cindex bug criteria
36340 If you are not sure whether you have found a bug, here are some guidelines:
36343 @cindex fatal signal
36344 @cindex debugger crash
36345 @cindex crash of debugger
36347 If the debugger gets a fatal signal, for any input whatever, that is a
36348 @value{GDBN} bug. Reliable debuggers never crash.
36350 @cindex error on valid input
36352 If @value{GDBN} produces an error message for valid input, that is a
36353 bug. (Note that if you're cross debugging, the problem may also be
36354 somewhere in the connection to the target.)
36356 @cindex invalid input
36358 If @value{GDBN} does not produce an error message for invalid input,
36359 that is a bug. However, you should note that your idea of
36360 ``invalid input'' might be our idea of ``an extension'' or ``support
36361 for traditional practice''.
36364 If you are an experienced user of debugging tools, your suggestions
36365 for improvement of @value{GDBN} are welcome in any case.
36368 @node Bug Reporting
36369 @section How to Report Bugs
36370 @cindex bug reports
36371 @cindex @value{GDBN} bugs, reporting
36373 A number of companies and individuals offer support for @sc{gnu} products.
36374 If you obtained @value{GDBN} from a support organization, we recommend you
36375 contact that organization first.
36377 You can find contact information for many support companies and
36378 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36380 @c should add a web page ref...
36383 @ifset BUGURL_DEFAULT
36384 In any event, we also recommend that you submit bug reports for
36385 @value{GDBN}. The preferred method is to submit them directly using
36386 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36387 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36390 @strong{Do not send bug reports to @samp{info-gdb}, or to
36391 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36392 not want to receive bug reports. Those that do have arranged to receive
36395 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36396 serves as a repeater. The mailing list and the newsgroup carry exactly
36397 the same messages. Often people think of posting bug reports to the
36398 newsgroup instead of mailing them. This appears to work, but it has one
36399 problem which can be crucial: a newsgroup posting often lacks a mail
36400 path back to the sender. Thus, if we need to ask for more information,
36401 we may be unable to reach you. For this reason, it is better to send
36402 bug reports to the mailing list.
36404 @ifclear BUGURL_DEFAULT
36405 In any event, we also recommend that you submit bug reports for
36406 @value{GDBN} to @value{BUGURL}.
36410 The fundamental principle of reporting bugs usefully is this:
36411 @strong{report all the facts}. If you are not sure whether to state a
36412 fact or leave it out, state it!
36414 Often people omit facts because they think they know what causes the
36415 problem and assume that some details do not matter. Thus, you might
36416 assume that the name of the variable you use in an example does not matter.
36417 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36418 stray memory reference which happens to fetch from the location where that
36419 name is stored in memory; perhaps, if the name were different, the contents
36420 of that location would fool the debugger into doing the right thing despite
36421 the bug. Play it safe and give a specific, complete example. That is the
36422 easiest thing for you to do, and the most helpful.
36424 Keep in mind that the purpose of a bug report is to enable us to fix the
36425 bug. It may be that the bug has been reported previously, but neither
36426 you nor we can know that unless your bug report is complete and
36429 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36430 bell?'' Those bug reports are useless, and we urge everyone to
36431 @emph{refuse to respond to them} except to chide the sender to report
36434 To enable us to fix the bug, you should include all these things:
36438 The version of @value{GDBN}. @value{GDBN} announces it if you start
36439 with no arguments; you can also print it at any time using @code{show
36442 Without this, we will not know whether there is any point in looking for
36443 the bug in the current version of @value{GDBN}.
36446 The type of machine you are using, and the operating system name and
36450 The details of the @value{GDBN} build-time configuration.
36451 @value{GDBN} shows these details if you invoke it with the
36452 @option{--configuration} command-line option, or if you type
36453 @code{show configuration} at @value{GDBN}'s prompt.
36456 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36457 ``@value{GCC}--2.8.1''.
36460 What compiler (and its version) was used to compile the program you are
36461 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36462 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36463 to get this information; for other compilers, see the documentation for
36467 The command arguments you gave the compiler to compile your example and
36468 observe the bug. For example, did you use @samp{-O}? To guarantee
36469 you will not omit something important, list them all. A copy of the
36470 Makefile (or the output from make) is sufficient.
36472 If we were to try to guess the arguments, we would probably guess wrong
36473 and then we might not encounter the bug.
36476 A complete input script, and all necessary source files, that will
36480 A description of what behavior you observe that you believe is
36481 incorrect. For example, ``It gets a fatal signal.''
36483 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36484 will certainly notice it. But if the bug is incorrect output, we might
36485 not notice unless it is glaringly wrong. You might as well not give us
36486 a chance to make a mistake.
36488 Even if the problem you experience is a fatal signal, you should still
36489 say so explicitly. Suppose something strange is going on, such as, your
36490 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36491 the C library on your system. (This has happened!) Your copy might
36492 crash and ours would not. If you told us to expect a crash, then when
36493 ours fails to crash, we would know that the bug was not happening for
36494 us. If you had not told us to expect a crash, then we would not be able
36495 to draw any conclusion from our observations.
36498 @cindex recording a session script
36499 To collect all this information, you can use a session recording program
36500 such as @command{script}, which is available on many Unix systems.
36501 Just run your @value{GDBN} session inside @command{script} and then
36502 include the @file{typescript} file with your bug report.
36504 Another way to record a @value{GDBN} session is to run @value{GDBN}
36505 inside Emacs and then save the entire buffer to a file.
36508 If you wish to suggest changes to the @value{GDBN} source, send us context
36509 diffs. If you even discuss something in the @value{GDBN} source, refer to
36510 it by context, not by line number.
36512 The line numbers in our development sources will not match those in your
36513 sources. Your line numbers would convey no useful information to us.
36517 Here are some things that are not necessary:
36521 A description of the envelope of the bug.
36523 Often people who encounter a bug spend a lot of time investigating
36524 which changes to the input file will make the bug go away and which
36525 changes will not affect it.
36527 This is often time consuming and not very useful, because the way we
36528 will find the bug is by running a single example under the debugger
36529 with breakpoints, not by pure deduction from a series of examples.
36530 We recommend that you save your time for something else.
36532 Of course, if you can find a simpler example to report @emph{instead}
36533 of the original one, that is a convenience for us. Errors in the
36534 output will be easier to spot, running under the debugger will take
36535 less time, and so on.
36537 However, simplification is not vital; if you do not want to do this,
36538 report the bug anyway and send us the entire test case you used.
36541 A patch for the bug.
36543 A patch for the bug does help us if it is a good one. But do not omit
36544 the necessary information, such as the test case, on the assumption that
36545 a patch is all we need. We might see problems with your patch and decide
36546 to fix the problem another way, or we might not understand it at all.
36548 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36549 construct an example that will make the program follow a certain path
36550 through the code. If you do not send us the example, we will not be able
36551 to construct one, so we will not be able to verify that the bug is fixed.
36553 And if we cannot understand what bug you are trying to fix, or why your
36554 patch should be an improvement, we will not install it. A test case will
36555 help us to understand.
36558 A guess about what the bug is or what it depends on.
36560 Such guesses are usually wrong. Even we cannot guess right about such
36561 things without first using the debugger to find the facts.
36564 @c The readline documentation is distributed with the readline code
36565 @c and consists of the two following files:
36568 @c Use -I with makeinfo to point to the appropriate directory,
36569 @c environment var TEXINPUTS with TeX.
36570 @ifclear SYSTEM_READLINE
36571 @include rluser.texi
36572 @include hsuser.texi
36576 @appendix In Memoriam
36578 The @value{GDBN} project mourns the loss of the following long-time
36583 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36584 to Free Software in general. Outside of @value{GDBN}, he was known in
36585 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36587 @item Michael Snyder
36588 Michael was one of the Global Maintainers of the @value{GDBN} project,
36589 with contributions recorded as early as 1996, until 2011. In addition
36590 to his day to day participation, he was a large driving force behind
36591 adding Reverse Debugging to @value{GDBN}.
36594 Beyond their technical contributions to the project, they were also
36595 enjoyable members of the Free Software Community. We will miss them.
36597 @node Formatting Documentation
36598 @appendix Formatting Documentation
36600 @cindex @value{GDBN} reference card
36601 @cindex reference card
36602 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36603 for printing with PostScript or Ghostscript, in the @file{gdb}
36604 subdirectory of the main source directory@footnote{In
36605 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36606 release.}. If you can use PostScript or Ghostscript with your printer,
36607 you can print the reference card immediately with @file{refcard.ps}.
36609 The release also includes the source for the reference card. You
36610 can format it, using @TeX{}, by typing:
36616 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36617 mode on US ``letter'' size paper;
36618 that is, on a sheet 11 inches wide by 8.5 inches
36619 high. You will need to specify this form of printing as an option to
36620 your @sc{dvi} output program.
36622 @cindex documentation
36624 All the documentation for @value{GDBN} comes as part of the machine-readable
36625 distribution. The documentation is written in Texinfo format, which is
36626 a documentation system that uses a single source file to produce both
36627 on-line information and a printed manual. You can use one of the Info
36628 formatting commands to create the on-line version of the documentation
36629 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36631 @value{GDBN} includes an already formatted copy of the on-line Info
36632 version of this manual in the @file{gdb} subdirectory. The main Info
36633 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36634 subordinate files matching @samp{gdb.info*} in the same directory. If
36635 necessary, you can print out these files, or read them with any editor;
36636 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36637 Emacs or the standalone @code{info} program, available as part of the
36638 @sc{gnu} Texinfo distribution.
36640 If you want to format these Info files yourself, you need one of the
36641 Info formatting programs, such as @code{texinfo-format-buffer} or
36644 If you have @code{makeinfo} installed, and are in the top level
36645 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36646 version @value{GDBVN}), you can make the Info file by typing:
36653 If you want to typeset and print copies of this manual, you need @TeX{},
36654 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36655 Texinfo definitions file.
36657 @TeX{} is a typesetting program; it does not print files directly, but
36658 produces output files called @sc{dvi} files. To print a typeset
36659 document, you need a program to print @sc{dvi} files. If your system
36660 has @TeX{} installed, chances are it has such a program. The precise
36661 command to use depends on your system; @kbd{lpr -d} is common; another
36662 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36663 require a file name without any extension or a @samp{.dvi} extension.
36665 @TeX{} also requires a macro definitions file called
36666 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36667 written in Texinfo format. On its own, @TeX{} cannot either read or
36668 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36669 and is located in the @file{gdb-@var{version-number}/texinfo}
36672 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36673 typeset and print this manual. First switch to the @file{gdb}
36674 subdirectory of the main source directory (for example, to
36675 @file{gdb-@value{GDBVN}/gdb}) and type:
36681 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36683 @node Installing GDB
36684 @appendix Installing @value{GDBN}
36685 @cindex installation
36688 * Requirements:: Requirements for building @value{GDBN}
36689 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36690 * Separate Objdir:: Compiling @value{GDBN} in another directory
36691 * Config Names:: Specifying names for hosts and targets
36692 * Configure Options:: Summary of options for configure
36693 * System-wide configuration:: Having a system-wide init file
36697 @section Requirements for Building @value{GDBN}
36698 @cindex building @value{GDBN}, requirements for
36700 Building @value{GDBN} requires various tools and packages to be available.
36701 Other packages will be used only if they are found.
36703 @heading Tools/Packages Necessary for Building @value{GDBN}
36705 @item ISO C90 compiler
36706 @value{GDBN} is written in ISO C90. It should be buildable with any
36707 working C90 compiler, e.g.@: GCC.
36711 @heading Tools/Packages Optional for Building @value{GDBN}
36715 @value{GDBN} can use the Expat XML parsing library. This library may be
36716 included with your operating system distribution; if it is not, you
36717 can get the latest version from @url{http://expat.sourceforge.net}.
36718 The @file{configure} script will search for this library in several
36719 standard locations; if it is installed in an unusual path, you can
36720 use the @option{--with-libexpat-prefix} option to specify its location.
36726 Remote protocol memory maps (@pxref{Memory Map Format})
36728 Target descriptions (@pxref{Target Descriptions})
36730 Remote shared library lists (@xref{Library List Format},
36731 or alternatively @pxref{Library List Format for SVR4 Targets})
36733 MS-Windows shared libraries (@pxref{Shared Libraries})
36735 Traceframe info (@pxref{Traceframe Info Format})
36737 Branch trace (@pxref{Branch Trace Format})
36741 @cindex compressed debug sections
36742 @value{GDBN} will use the @samp{zlib} library, if available, to read
36743 compressed debug sections. Some linkers, such as GNU gold, are capable
36744 of producing binaries with compressed debug sections. If @value{GDBN}
36745 is compiled with @samp{zlib}, it will be able to read the debug
36746 information in such binaries.
36748 The @samp{zlib} library is likely included with your operating system
36749 distribution; if it is not, you can get the latest version from
36750 @url{http://zlib.net}.
36753 @value{GDBN}'s features related to character sets (@pxref{Character
36754 Sets}) require a functioning @code{iconv} implementation. If you are
36755 on a GNU system, then this is provided by the GNU C Library. Some
36756 other systems also provide a working @code{iconv}.
36758 If @value{GDBN} is using the @code{iconv} program which is installed
36759 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36760 This is done with @option{--with-iconv-bin} which specifies the
36761 directory that contains the @code{iconv} program.
36763 On systems without @code{iconv}, you can install GNU Libiconv. If you
36764 have previously installed Libiconv, you can use the
36765 @option{--with-libiconv-prefix} option to configure.
36767 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36768 arrange to build Libiconv if a directory named @file{libiconv} appears
36769 in the top-most source directory. If Libiconv is built this way, and
36770 if the operating system does not provide a suitable @code{iconv}
36771 implementation, then the just-built library will automatically be used
36772 by @value{GDBN}. One easy way to set this up is to download GNU
36773 Libiconv, unpack it, and then rename the directory holding the
36774 Libiconv source code to @samp{libiconv}.
36777 @node Running Configure
36778 @section Invoking the @value{GDBN} @file{configure} Script
36779 @cindex configuring @value{GDBN}
36780 @value{GDBN} comes with a @file{configure} script that automates the process
36781 of preparing @value{GDBN} for installation; you can then use @code{make} to
36782 build the @code{gdb} program.
36784 @c irrelevant in info file; it's as current as the code it lives with.
36785 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36786 look at the @file{README} file in the sources; we may have improved the
36787 installation procedures since publishing this manual.}
36790 The @value{GDBN} distribution includes all the source code you need for
36791 @value{GDBN} in a single directory, whose name is usually composed by
36792 appending the version number to @samp{gdb}.
36794 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36795 @file{gdb-@value{GDBVN}} directory. That directory contains:
36798 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36799 script for configuring @value{GDBN} and all its supporting libraries
36801 @item gdb-@value{GDBVN}/gdb
36802 the source specific to @value{GDBN} itself
36804 @item gdb-@value{GDBVN}/bfd
36805 source for the Binary File Descriptor library
36807 @item gdb-@value{GDBVN}/include
36808 @sc{gnu} include files
36810 @item gdb-@value{GDBVN}/libiberty
36811 source for the @samp{-liberty} free software library
36813 @item gdb-@value{GDBVN}/opcodes
36814 source for the library of opcode tables and disassemblers
36816 @item gdb-@value{GDBVN}/readline
36817 source for the @sc{gnu} command-line interface
36819 @item gdb-@value{GDBVN}/glob
36820 source for the @sc{gnu} filename pattern-matching subroutine
36822 @item gdb-@value{GDBVN}/mmalloc
36823 source for the @sc{gnu} memory-mapped malloc package
36826 The simplest way to configure and build @value{GDBN} is to run @file{configure}
36827 from the @file{gdb-@var{version-number}} source directory, which in
36828 this example is the @file{gdb-@value{GDBVN}} directory.
36830 First switch to the @file{gdb-@var{version-number}} source directory
36831 if you are not already in it; then run @file{configure}. Pass the
36832 identifier for the platform on which @value{GDBN} will run as an
36838 cd gdb-@value{GDBVN}
36839 ./configure @var{host}
36844 where @var{host} is an identifier such as @samp{sun4} or
36845 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
36846 (You can often leave off @var{host}; @file{configure} tries to guess the
36847 correct value by examining your system.)
36849 Running @samp{configure @var{host}} and then running @code{make} builds the
36850 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
36851 libraries, then @code{gdb} itself. The configured source files, and the
36852 binaries, are left in the corresponding source directories.
36855 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
36856 system does not recognize this automatically when you run a different
36857 shell, you may need to run @code{sh} on it explicitly:
36860 sh configure @var{host}
36863 If you run @file{configure} from a directory that contains source
36864 directories for multiple libraries or programs, such as the
36865 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
36867 creates configuration files for every directory level underneath (unless
36868 you tell it not to, with the @samp{--norecursion} option).
36870 You should run the @file{configure} script from the top directory in the
36871 source tree, the @file{gdb-@var{version-number}} directory. If you run
36872 @file{configure} from one of the subdirectories, you will configure only
36873 that subdirectory. That is usually not what you want. In particular,
36874 if you run the first @file{configure} from the @file{gdb} subdirectory
36875 of the @file{gdb-@var{version-number}} directory, you will omit the
36876 configuration of @file{bfd}, @file{readline}, and other sibling
36877 directories of the @file{gdb} subdirectory. This leads to build errors
36878 about missing include files such as @file{bfd/bfd.h}.
36880 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
36881 However, you should make sure that the shell on your path (named by
36882 the @samp{SHELL} environment variable) is publicly readable. Remember
36883 that @value{GDBN} uses the shell to start your program---some systems refuse to
36884 let @value{GDBN} debug child processes whose programs are not readable.
36886 @node Separate Objdir
36887 @section Compiling @value{GDBN} in Another Directory
36889 If you want to run @value{GDBN} versions for several host or target machines,
36890 you need a different @code{gdb} compiled for each combination of
36891 host and target. @file{configure} is designed to make this easy by
36892 allowing you to generate each configuration in a separate subdirectory,
36893 rather than in the source directory. If your @code{make} program
36894 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36895 @code{make} in each of these directories builds the @code{gdb}
36896 program specified there.
36898 To build @code{gdb} in a separate directory, run @file{configure}
36899 with the @samp{--srcdir} option to specify where to find the source.
36900 (You also need to specify a path to find @file{configure}
36901 itself from your working directory. If the path to @file{configure}
36902 would be the same as the argument to @samp{--srcdir}, you can leave out
36903 the @samp{--srcdir} option; it is assumed.)
36905 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
36906 separate directory for a Sun 4 like this:
36910 cd gdb-@value{GDBVN}
36913 ../gdb-@value{GDBVN}/configure sun4
36918 When @file{configure} builds a configuration using a remote source
36919 directory, it creates a tree for the binaries with the same structure
36920 (and using the same names) as the tree under the source directory. In
36921 the example, you'd find the Sun 4 library @file{libiberty.a} in the
36922 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
36923 @file{gdb-sun4/gdb}.
36925 Make sure that your path to the @file{configure} script has just one
36926 instance of @file{gdb} in it. If your path to @file{configure} looks
36927 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
36928 one subdirectory of @value{GDBN}, not the whole package. This leads to
36929 build errors about missing include files such as @file{bfd/bfd.h}.
36931 One popular reason to build several @value{GDBN} configurations in separate
36932 directories is to configure @value{GDBN} for cross-compiling (where
36933 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
36934 programs that run on another machine---the @dfn{target}).
36935 You specify a cross-debugging target by
36936 giving the @samp{--target=@var{target}} option to @file{configure}.
36938 When you run @code{make} to build a program or library, you must run
36939 it in a configured directory---whatever directory you were in when you
36940 called @file{configure} (or one of its subdirectories).
36942 The @code{Makefile} that @file{configure} generates in each source
36943 directory also runs recursively. If you type @code{make} in a source
36944 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
36945 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
36946 will build all the required libraries, and then build GDB.
36948 When you have multiple hosts or targets configured in separate
36949 directories, you can run @code{make} on them in parallel (for example,
36950 if they are NFS-mounted on each of the hosts); they will not interfere
36954 @section Specifying Names for Hosts and Targets
36956 The specifications used for hosts and targets in the @file{configure}
36957 script are based on a three-part naming scheme, but some short predefined
36958 aliases are also supported. The full naming scheme encodes three pieces
36959 of information in the following pattern:
36962 @var{architecture}-@var{vendor}-@var{os}
36965 For example, you can use the alias @code{sun4} as a @var{host} argument,
36966 or as the value for @var{target} in a @code{--target=@var{target}}
36967 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36969 The @file{configure} script accompanying @value{GDBN} does not provide
36970 any query facility to list all supported host and target names or
36971 aliases. @file{configure} calls the Bourne shell script
36972 @code{config.sub} to map abbreviations to full names; you can read the
36973 script, if you wish, or you can use it to test your guesses on
36974 abbreviations---for example:
36977 % sh config.sub i386-linux
36979 % sh config.sub alpha-linux
36980 alpha-unknown-linux-gnu
36981 % sh config.sub hp9k700
36983 % sh config.sub sun4
36984 sparc-sun-sunos4.1.1
36985 % sh config.sub sun3
36986 m68k-sun-sunos4.1.1
36987 % sh config.sub i986v
36988 Invalid configuration `i986v': machine `i986v' not recognized
36992 @code{config.sub} is also distributed in the @value{GDBN} source
36993 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36995 @node Configure Options
36996 @section @file{configure} Options
36998 Here is a summary of the @file{configure} options and arguments that
36999 are most often useful for building @value{GDBN}. @file{configure} also has
37000 several other options not listed here. @inforef{What Configure
37001 Does,,configure.info}, for a full explanation of @file{configure}.
37004 configure @r{[}--help@r{]}
37005 @r{[}--prefix=@var{dir}@r{]}
37006 @r{[}--exec-prefix=@var{dir}@r{]}
37007 @r{[}--srcdir=@var{dirname}@r{]}
37008 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
37009 @r{[}--target=@var{target}@r{]}
37014 You may introduce options with a single @samp{-} rather than
37015 @samp{--} if you prefer; but you may abbreviate option names if you use
37020 Display a quick summary of how to invoke @file{configure}.
37022 @item --prefix=@var{dir}
37023 Configure the source to install programs and files under directory
37026 @item --exec-prefix=@var{dir}
37027 Configure the source to install programs under directory
37030 @c avoid splitting the warning from the explanation:
37032 @item --srcdir=@var{dirname}
37033 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
37034 @code{make} that implements the @code{VPATH} feature.}@*
37035 Use this option to make configurations in directories separate from the
37036 @value{GDBN} source directories. Among other things, you can use this to
37037 build (or maintain) several configurations simultaneously, in separate
37038 directories. @file{configure} writes configuration-specific files in
37039 the current directory, but arranges for them to use the source in the
37040 directory @var{dirname}. @file{configure} creates directories under
37041 the working directory in parallel to the source directories below
37044 @item --norecursion
37045 Configure only the directory level where @file{configure} is executed; do not
37046 propagate configuration to subdirectories.
37048 @item --target=@var{target}
37049 Configure @value{GDBN} for cross-debugging programs running on the specified
37050 @var{target}. Without this option, @value{GDBN} is configured to debug
37051 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
37053 There is no convenient way to generate a list of all available targets.
37055 @item @var{host} @dots{}
37056 Configure @value{GDBN} to run on the specified @var{host}.
37058 There is no convenient way to generate a list of all available hosts.
37061 There are many other options available as well, but they are generally
37062 needed for special purposes only.
37064 @node System-wide configuration
37065 @section System-wide configuration and settings
37066 @cindex system-wide init file
37068 @value{GDBN} can be configured to have a system-wide init file;
37069 this file will be read and executed at startup (@pxref{Startup, , What
37070 @value{GDBN} does during startup}).
37072 Here is the corresponding configure option:
37075 @item --with-system-gdbinit=@var{file}
37076 Specify that the default location of the system-wide init file is
37080 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
37081 it may be subject to relocation. Two possible cases:
37085 If the default location of this init file contains @file{$prefix},
37086 it will be subject to relocation. Suppose that the configure options
37087 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
37088 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
37089 init file is looked for as @file{$install/etc/gdbinit} instead of
37090 @file{$prefix/etc/gdbinit}.
37093 By contrast, if the default location does not contain the prefix,
37094 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
37095 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
37096 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
37097 wherever @value{GDBN} is installed.
37100 If the configured location of the system-wide init file (as given by the
37101 @option{--with-system-gdbinit} option at configure time) is in the
37102 data-directory (as specified by @option{--with-gdb-datadir} at configure
37103 time) or in one of its subdirectories, then @value{GDBN} will look for the
37104 system-wide init file in the directory specified by the
37105 @option{--data-directory} command-line option.
37106 Note that the system-wide init file is only read once, during @value{GDBN}
37107 initialization. If the data-directory is changed after @value{GDBN} has
37108 started with the @code{set data-directory} command, the file will not be
37112 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
37115 @node System-wide Configuration Scripts
37116 @subsection Installed System-wide Configuration Scripts
37117 @cindex system-wide configuration scripts
37119 The @file{system-gdbinit} directory, located inside the data-directory
37120 (as specified by @option{--with-gdb-datadir} at configure time) contains
37121 a number of scripts which can be used as system-wide init files. To
37122 automatically source those scripts at startup, @value{GDBN} should be
37123 configured with @option{--with-system-gdbinit}. Otherwise, any user
37124 should be able to source them by hand as needed.
37126 The following scripts are currently available:
37129 @item @file{elinos.py}
37131 @cindex ELinOS system-wide configuration script
37132 This script is useful when debugging a program on an ELinOS target.
37133 It takes advantage of the environment variables defined in a standard
37134 ELinOS environment in order to determine the location of the system
37135 shared libraries, and then sets the @samp{solib-absolute-prefix}
37136 and @samp{solib-search-path} variables appropriately.
37138 @item @file{wrs-linux.py}
37139 @pindex wrs-linux.py
37140 @cindex Wind River Linux system-wide configuration script
37141 This script is useful when debugging a program on a target running
37142 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
37143 the host-side sysroot used by the target system.
37147 @node Maintenance Commands
37148 @appendix Maintenance Commands
37149 @cindex maintenance commands
37150 @cindex internal commands
37152 In addition to commands intended for @value{GDBN} users, @value{GDBN}
37153 includes a number of commands intended for @value{GDBN} developers,
37154 that are not documented elsewhere in this manual. These commands are
37155 provided here for reference. (For commands that turn on debugging
37156 messages, see @ref{Debugging Output}.)
37159 @kindex maint agent
37160 @kindex maint agent-eval
37161 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37162 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37163 Translate the given @var{expression} into remote agent bytecodes.
37164 This command is useful for debugging the Agent Expression mechanism
37165 (@pxref{Agent Expressions}). The @samp{agent} version produces an
37166 expression useful for data collection, such as by tracepoints, while
37167 @samp{maint agent-eval} produces an expression that evaluates directly
37168 to a result. For instance, a collection expression for @code{globa +
37169 globb} will include bytecodes to record four bytes of memory at each
37170 of the addresses of @code{globa} and @code{globb}, while discarding
37171 the result of the addition, while an evaluation expression will do the
37172 addition and return the sum.
37173 If @code{-at} is given, generate remote agent bytecode for @var{location}.
37174 If not, generate remote agent bytecode for current frame PC address.
37176 @kindex maint agent-printf
37177 @item maint agent-printf @var{format},@var{expr},...
37178 Translate the given format string and list of argument expressions
37179 into remote agent bytecodes and display them as a disassembled list.
37180 This command is useful for debugging the agent version of dynamic
37181 printf (@pxref{Dynamic Printf}).
37183 @kindex maint info breakpoints
37184 @item @anchor{maint info breakpoints}maint info breakpoints
37185 Using the same format as @samp{info breakpoints}, display both the
37186 breakpoints you've set explicitly, and those @value{GDBN} is using for
37187 internal purposes. Internal breakpoints are shown with negative
37188 breakpoint numbers. The type column identifies what kind of breakpoint
37193 Normal, explicitly set breakpoint.
37196 Normal, explicitly set watchpoint.
37199 Internal breakpoint, used to handle correctly stepping through
37200 @code{longjmp} calls.
37202 @item longjmp resume
37203 Internal breakpoint at the target of a @code{longjmp}.
37206 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
37209 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
37212 Shared library events.
37216 @kindex maint info bfds
37217 @item maint info bfds
37218 This prints information about each @code{bfd} object that is known to
37219 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
37221 @kindex set displaced-stepping
37222 @kindex show displaced-stepping
37223 @cindex displaced stepping support
37224 @cindex out-of-line single-stepping
37225 @item set displaced-stepping
37226 @itemx show displaced-stepping
37227 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
37228 if the target supports it. Displaced stepping is a way to single-step
37229 over breakpoints without removing them from the inferior, by executing
37230 an out-of-line copy of the instruction that was originally at the
37231 breakpoint location. It is also known as out-of-line single-stepping.
37234 @item set displaced-stepping on
37235 If the target architecture supports it, @value{GDBN} will use
37236 displaced stepping to step over breakpoints.
37238 @item set displaced-stepping off
37239 @value{GDBN} will not use displaced stepping to step over breakpoints,
37240 even if such is supported by the target architecture.
37242 @cindex non-stop mode, and @samp{set displaced-stepping}
37243 @item set displaced-stepping auto
37244 This is the default mode. @value{GDBN} will use displaced stepping
37245 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
37246 architecture supports displaced stepping.
37249 @kindex maint check-psymtabs
37250 @item maint check-psymtabs
37251 Check the consistency of currently expanded psymtabs versus symtabs.
37252 Use this to check, for example, whether a symbol is in one but not the other.
37254 @kindex maint check-symtabs
37255 @item maint check-symtabs
37256 Check the consistency of currently expanded symtabs.
37258 @kindex maint expand-symtabs
37259 @item maint expand-symtabs [@var{regexp}]
37260 Expand symbol tables.
37261 If @var{regexp} is specified, only expand symbol tables for file
37262 names matching @var{regexp}.
37264 @kindex maint cplus first_component
37265 @item maint cplus first_component @var{name}
37266 Print the first C@t{++} class/namespace component of @var{name}.
37268 @kindex maint cplus namespace
37269 @item maint cplus namespace
37270 Print the list of possible C@t{++} namespaces.
37272 @kindex maint demangle
37273 @item maint demangle @var{name}
37274 Demangle a C@t{++} or Objective-C mangled @var{name}.
37276 @kindex maint deprecate
37277 @kindex maint undeprecate
37278 @cindex deprecated commands
37279 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
37280 @itemx maint undeprecate @var{command}
37281 Deprecate or undeprecate the named @var{command}. Deprecated commands
37282 cause @value{GDBN} to issue a warning when you use them. The optional
37283 argument @var{replacement} says which newer command should be used in
37284 favor of the deprecated one; if it is given, @value{GDBN} will mention
37285 the replacement as part of the warning.
37287 @kindex maint dump-me
37288 @item maint dump-me
37289 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
37290 Cause a fatal signal in the debugger and force it to dump its core.
37291 This is supported only on systems which support aborting a program
37292 with the @code{SIGQUIT} signal.
37294 @kindex maint internal-error
37295 @kindex maint internal-warning
37296 @item maint internal-error @r{[}@var{message-text}@r{]}
37297 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
37298 Cause @value{GDBN} to call the internal function @code{internal_error}
37299 or @code{internal_warning} and hence behave as though an internal error
37300 or internal warning has been detected. In addition to reporting the
37301 internal problem, these functions give the user the opportunity to
37302 either quit @value{GDBN} or create a core file of the current
37303 @value{GDBN} session.
37305 These commands take an optional parameter @var{message-text} that is
37306 used as the text of the error or warning message.
37308 Here's an example of using @code{internal-error}:
37311 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
37312 @dots{}/maint.c:121: internal-error: testing, 1, 2
37313 A problem internal to GDB has been detected. Further
37314 debugging may prove unreliable.
37315 Quit this debugging session? (y or n) @kbd{n}
37316 Create a core file? (y or n) @kbd{n}
37320 @cindex @value{GDBN} internal error
37321 @cindex internal errors, control of @value{GDBN} behavior
37323 @kindex maint set internal-error
37324 @kindex maint show internal-error
37325 @kindex maint set internal-warning
37326 @kindex maint show internal-warning
37327 @item maint set internal-error @var{action} [ask|yes|no]
37328 @itemx maint show internal-error @var{action}
37329 @itemx maint set internal-warning @var{action} [ask|yes|no]
37330 @itemx maint show internal-warning @var{action}
37331 When @value{GDBN} reports an internal problem (error or warning) it
37332 gives the user the opportunity to both quit @value{GDBN} and create a
37333 core file of the current @value{GDBN} session. These commands let you
37334 override the default behaviour for each particular @var{action},
37335 described in the table below.
37339 You can specify that @value{GDBN} should always (yes) or never (no)
37340 quit. The default is to ask the user what to do.
37343 You can specify that @value{GDBN} should always (yes) or never (no)
37344 create a core file. The default is to ask the user what to do.
37347 @kindex maint packet
37348 @item maint packet @var{text}
37349 If @value{GDBN} is talking to an inferior via the serial protocol,
37350 then this command sends the string @var{text} to the inferior, and
37351 displays the response packet. @value{GDBN} supplies the initial
37352 @samp{$} character, the terminating @samp{#} character, and the
37355 @kindex maint print architecture
37356 @item maint print architecture @r{[}@var{file}@r{]}
37357 Print the entire architecture configuration. The optional argument
37358 @var{file} names the file where the output goes.
37360 @kindex maint print c-tdesc
37361 @item maint print c-tdesc
37362 Print the current target description (@pxref{Target Descriptions}) as
37363 a C source file. The created source file can be used in @value{GDBN}
37364 when an XML parser is not available to parse the description.
37366 @kindex maint print dummy-frames
37367 @item maint print dummy-frames
37368 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37371 (@value{GDBP}) @kbd{b add}
37373 (@value{GDBP}) @kbd{print add(2,3)}
37374 Breakpoint 2, add (a=2, b=3) at @dots{}
37376 The program being debugged stopped while in a function called from GDB.
37378 (@value{GDBP}) @kbd{maint print dummy-frames}
37379 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
37380 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
37381 call_lo=0x01014000 call_hi=0x01014001
37385 Takes an optional file parameter.
37387 @kindex maint print registers
37388 @kindex maint print raw-registers
37389 @kindex maint print cooked-registers
37390 @kindex maint print register-groups
37391 @kindex maint print remote-registers
37392 @item maint print registers @r{[}@var{file}@r{]}
37393 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37394 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37395 @itemx maint print register-groups @r{[}@var{file}@r{]}
37396 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37397 Print @value{GDBN}'s internal register data structures.
37399 The command @code{maint print raw-registers} includes the contents of
37400 the raw register cache; the command @code{maint print
37401 cooked-registers} includes the (cooked) value of all registers,
37402 including registers which aren't available on the target nor visible
37403 to user; the command @code{maint print register-groups} includes the
37404 groups that each register is a member of; and the command @code{maint
37405 print remote-registers} includes the remote target's register numbers
37406 and offsets in the `G' packets.
37408 These commands take an optional parameter, a file name to which to
37409 write the information.
37411 @kindex maint print reggroups
37412 @item maint print reggroups @r{[}@var{file}@r{]}
37413 Print @value{GDBN}'s internal register group data structures. The
37414 optional argument @var{file} tells to what file to write the
37417 The register groups info looks like this:
37420 (@value{GDBP}) @kbd{maint print reggroups}
37433 This command forces @value{GDBN} to flush its internal register cache.
37435 @kindex maint print objfiles
37436 @cindex info for known object files
37437 @item maint print objfiles @r{[}@var{regexp}@r{]}
37438 Print a dump of all known object files.
37439 If @var{regexp} is specified, only print object files whose names
37440 match @var{regexp}. For each object file, this command prints its name,
37441 address in memory, and all of its psymtabs and symtabs.
37443 @kindex maint print section-scripts
37444 @cindex info for known .debug_gdb_scripts-loaded scripts
37445 @item maint print section-scripts [@var{regexp}]
37446 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37447 If @var{regexp} is specified, only print scripts loaded by object files
37448 matching @var{regexp}.
37449 For each script, this command prints its name as specified in the objfile,
37450 and the full path if known.
37451 @xref{dotdebug_gdb_scripts section}.
37453 @kindex maint print statistics
37454 @cindex bcache statistics
37455 @item maint print statistics
37456 This command prints, for each object file in the program, various data
37457 about that object file followed by the byte cache (@dfn{bcache})
37458 statistics for the object file. The objfile data includes the number
37459 of minimal, partial, full, and stabs symbols, the number of types
37460 defined by the objfile, the number of as yet unexpanded psym tables,
37461 the number of line tables and string tables, and the amount of memory
37462 used by the various tables. The bcache statistics include the counts,
37463 sizes, and counts of duplicates of all and unique objects, max,
37464 average, and median entry size, total memory used and its overhead and
37465 savings, and various measures of the hash table size and chain
37468 @kindex maint print target-stack
37469 @cindex target stack description
37470 @item maint print target-stack
37471 A @dfn{target} is an interface between the debugger and a particular
37472 kind of file or process. Targets can be stacked in @dfn{strata},
37473 so that more than one target can potentially respond to a request.
37474 In particular, memory accesses will walk down the stack of targets
37475 until they find a target that is interested in handling that particular
37478 This command prints a short description of each layer that was pushed on
37479 the @dfn{target stack}, starting from the top layer down to the bottom one.
37481 @kindex maint print type
37482 @cindex type chain of a data type
37483 @item maint print type @var{expr}
37484 Print the type chain for a type specified by @var{expr}. The argument
37485 can be either a type name or a symbol. If it is a symbol, the type of
37486 that symbol is described. The type chain produced by this command is
37487 a recursive definition of the data type as stored in @value{GDBN}'s
37488 data structures, including its flags and contained types.
37490 @kindex maint set dwarf2 always-disassemble
37491 @kindex maint show dwarf2 always-disassemble
37492 @item maint set dwarf2 always-disassemble
37493 @item maint show dwarf2 always-disassemble
37494 Control the behavior of @code{info address} when using DWARF debugging
37497 The default is @code{off}, which means that @value{GDBN} should try to
37498 describe a variable's location in an easily readable format. When
37499 @code{on}, @value{GDBN} will instead display the DWARF location
37500 expression in an assembly-like format. Note that some locations are
37501 too complex for @value{GDBN} to describe simply; in this case you will
37502 always see the disassembly form.
37504 Here is an example of the resulting disassembly:
37507 (gdb) info addr argc
37508 Symbol "argc" is a complex DWARF expression:
37512 For more information on these expressions, see
37513 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37515 @kindex maint set dwarf2 max-cache-age
37516 @kindex maint show dwarf2 max-cache-age
37517 @item maint set dwarf2 max-cache-age
37518 @itemx maint show dwarf2 max-cache-age
37519 Control the DWARF 2 compilation unit cache.
37521 @cindex DWARF 2 compilation units cache
37522 In object files with inter-compilation-unit references, such as those
37523 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
37524 reader needs to frequently refer to previously read compilation units.
37525 This setting controls how long a compilation unit will remain in the
37526 cache if it is not referenced. A higher limit means that cached
37527 compilation units will be stored in memory longer, and more total
37528 memory will be used. Setting it to zero disables caching, which will
37529 slow down @value{GDBN} startup, but reduce memory consumption.
37531 @kindex maint set profile
37532 @kindex maint show profile
37533 @cindex profiling GDB
37534 @item maint set profile
37535 @itemx maint show profile
37536 Control profiling of @value{GDBN}.
37538 Profiling will be disabled until you use the @samp{maint set profile}
37539 command to enable it. When you enable profiling, the system will begin
37540 collecting timing and execution count data; when you disable profiling or
37541 exit @value{GDBN}, the results will be written to a log file. Remember that
37542 if you use profiling, @value{GDBN} will overwrite the profiling log file
37543 (often called @file{gmon.out}). If you have a record of important profiling
37544 data in a @file{gmon.out} file, be sure to move it to a safe location.
37546 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37547 compiled with the @samp{-pg} compiler option.
37549 @kindex maint set show-debug-regs
37550 @kindex maint show show-debug-regs
37551 @cindex hardware debug registers
37552 @item maint set show-debug-regs
37553 @itemx maint show show-debug-regs
37554 Control whether to show variables that mirror the hardware debug
37555 registers. Use @code{on} to enable, @code{off} to disable. If
37556 enabled, the debug registers values are shown when @value{GDBN} inserts or
37557 removes a hardware breakpoint or watchpoint, and when the inferior
37558 triggers a hardware-assisted breakpoint or watchpoint.
37560 @kindex maint set show-all-tib
37561 @kindex maint show show-all-tib
37562 @item maint set show-all-tib
37563 @itemx maint show show-all-tib
37564 Control whether to show all non zero areas within a 1k block starting
37565 at thread local base, when using the @samp{info w32 thread-information-block}
37568 @kindex maint set per-command
37569 @kindex maint show per-command
37570 @item maint set per-command
37571 @itemx maint show per-command
37572 @cindex resources used by commands
37574 @value{GDBN} can display the resources used by each command.
37575 This is useful in debugging performance problems.
37578 @item maint set per-command space [on|off]
37579 @itemx maint show per-command space
37580 Enable or disable the printing of the memory used by GDB for each command.
37581 If enabled, @value{GDBN} will display how much memory each command
37582 took, following the command's own output.
37583 This can also be requested by invoking @value{GDBN} with the
37584 @option{--statistics} command-line switch (@pxref{Mode Options}).
37586 @item maint set per-command time [on|off]
37587 @itemx maint show per-command time
37588 Enable or disable the printing of the execution time of @value{GDBN}
37590 If enabled, @value{GDBN} will display how much time it
37591 took to execute each command, following the command's own output.
37592 Both CPU time and wallclock time are printed.
37593 Printing both is useful when trying to determine whether the cost is
37594 CPU or, e.g., disk/network latency.
37595 Note that the CPU time printed is for @value{GDBN} only, it does not include
37596 the execution time of the inferior because there's no mechanism currently
37597 to compute how much time was spent by @value{GDBN} and how much time was
37598 spent by the program been debugged.
37599 This can also be requested by invoking @value{GDBN} with the
37600 @option{--statistics} command-line switch (@pxref{Mode Options}).
37602 @item maint set per-command symtab [on|off]
37603 @itemx maint show per-command symtab
37604 Enable or disable the printing of basic symbol table statistics
37606 If enabled, @value{GDBN} will display the following information:
37610 number of symbol tables
37612 number of primary symbol tables
37614 number of blocks in the blockvector
37618 @kindex maint space
37619 @cindex memory used by commands
37620 @item maint space @var{value}
37621 An alias for @code{maint set per-command space}.
37622 A non-zero value enables it, zero disables it.
37625 @cindex time of command execution
37626 @item maint time @var{value}
37627 An alias for @code{maint set per-command time}.
37628 A non-zero value enables it, zero disables it.
37630 @kindex maint translate-address
37631 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37632 Find the symbol stored at the location specified by the address
37633 @var{addr} and an optional section name @var{section}. If found,
37634 @value{GDBN} prints the name of the closest symbol and an offset from
37635 the symbol's location to the specified address. This is similar to
37636 the @code{info address} command (@pxref{Symbols}), except that this
37637 command also allows to find symbols in other sections.
37639 If section was not specified, the section in which the symbol was found
37640 is also printed. For dynamically linked executables, the name of
37641 executable or shared library containing the symbol is printed as well.
37645 The following command is useful for non-interactive invocations of
37646 @value{GDBN}, such as in the test suite.
37649 @item set watchdog @var{nsec}
37650 @kindex set watchdog
37651 @cindex watchdog timer
37652 @cindex timeout for commands
37653 Set the maximum number of seconds @value{GDBN} will wait for the
37654 target operation to finish. If this time expires, @value{GDBN}
37655 reports and error and the command is aborted.
37657 @item show watchdog
37658 Show the current setting of the target wait timeout.
37661 @node Remote Protocol
37662 @appendix @value{GDBN} Remote Serial Protocol
37667 * Stop Reply Packets::
37668 * General Query Packets::
37669 * Architecture-Specific Protocol Details::
37670 * Tracepoint Packets::
37671 * Host I/O Packets::
37673 * Notification Packets::
37674 * Remote Non-Stop::
37675 * Packet Acknowledgment::
37677 * File-I/O Remote Protocol Extension::
37678 * Library List Format::
37679 * Library List Format for SVR4 Targets::
37680 * Memory Map Format::
37681 * Thread List Format::
37682 * Traceframe Info Format::
37683 * Branch Trace Format::
37689 There may be occasions when you need to know something about the
37690 protocol---for example, if there is only one serial port to your target
37691 machine, you might want your program to do something special if it
37692 recognizes a packet meant for @value{GDBN}.
37694 In the examples below, @samp{->} and @samp{<-} are used to indicate
37695 transmitted and received data, respectively.
37697 @cindex protocol, @value{GDBN} remote serial
37698 @cindex serial protocol, @value{GDBN} remote
37699 @cindex remote serial protocol
37700 All @value{GDBN} commands and responses (other than acknowledgments
37701 and notifications, see @ref{Notification Packets}) are sent as a
37702 @var{packet}. A @var{packet} is introduced with the character
37703 @samp{$}, the actual @var{packet-data}, and the terminating character
37704 @samp{#} followed by a two-digit @var{checksum}:
37707 @code{$}@var{packet-data}@code{#}@var{checksum}
37711 @cindex checksum, for @value{GDBN} remote
37713 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37714 characters between the leading @samp{$} and the trailing @samp{#} (an
37715 eight bit unsigned checksum).
37717 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37718 specification also included an optional two-digit @var{sequence-id}:
37721 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37724 @cindex sequence-id, for @value{GDBN} remote
37726 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37727 has never output @var{sequence-id}s. Stubs that handle packets added
37728 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37730 When either the host or the target machine receives a packet, the first
37731 response expected is an acknowledgment: either @samp{+} (to indicate
37732 the package was received correctly) or @samp{-} (to request
37736 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37741 The @samp{+}/@samp{-} acknowledgments can be disabled
37742 once a connection is established.
37743 @xref{Packet Acknowledgment}, for details.
37745 The host (@value{GDBN}) sends @var{command}s, and the target (the
37746 debugging stub incorporated in your program) sends a @var{response}. In
37747 the case of step and continue @var{command}s, the response is only sent
37748 when the operation has completed, and the target has again stopped all
37749 threads in all attached processes. This is the default all-stop mode
37750 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37751 execution mode; see @ref{Remote Non-Stop}, for details.
37753 @var{packet-data} consists of a sequence of characters with the
37754 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37757 @cindex remote protocol, field separator
37758 Fields within the packet should be separated using @samp{,} @samp{;} or
37759 @samp{:}. Except where otherwise noted all numbers are represented in
37760 @sc{hex} with leading zeros suppressed.
37762 Implementors should note that prior to @value{GDBN} 5.0, the character
37763 @samp{:} could not appear as the third character in a packet (as it
37764 would potentially conflict with the @var{sequence-id}).
37766 @cindex remote protocol, binary data
37767 @anchor{Binary Data}
37768 Binary data in most packets is encoded either as two hexadecimal
37769 digits per byte of binary data. This allowed the traditional remote
37770 protocol to work over connections which were only seven-bit clean.
37771 Some packets designed more recently assume an eight-bit clean
37772 connection, and use a more efficient encoding to send and receive
37775 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37776 as an escape character. Any escaped byte is transmitted as the escape
37777 character followed by the original character XORed with @code{0x20}.
37778 For example, the byte @code{0x7d} would be transmitted as the two
37779 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37780 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37781 @samp{@}}) must always be escaped. Responses sent by the stub
37782 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37783 is not interpreted as the start of a run-length encoded sequence
37786 Response @var{data} can be run-length encoded to save space.
37787 Run-length encoding replaces runs of identical characters with one
37788 instance of the repeated character, followed by a @samp{*} and a
37789 repeat count. The repeat count is itself sent encoded, to avoid
37790 binary characters in @var{data}: a value of @var{n} is sent as
37791 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37792 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37793 code 32) for a repeat count of 3. (This is because run-length
37794 encoding starts to win for counts 3 or more.) Thus, for example,
37795 @samp{0* } is a run-length encoding of ``0000'': the space character
37796 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37799 The printable characters @samp{#} and @samp{$} or with a numeric value
37800 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37801 seven repeats (@samp{$}) can be expanded using a repeat count of only
37802 five (@samp{"}). For example, @samp{00000000} can be encoded as
37805 The error response returned for some packets includes a two character
37806 error number. That number is not well defined.
37808 @cindex empty response, for unsupported packets
37809 For any @var{command} not supported by the stub, an empty response
37810 (@samp{$#00}) should be returned. That way it is possible to extend the
37811 protocol. A newer @value{GDBN} can tell if a packet is supported based
37814 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37815 commands for register access, and the @samp{m} and @samp{M} commands
37816 for memory access. Stubs that only control single-threaded targets
37817 can implement run control with the @samp{c} (continue), and @samp{s}
37818 (step) commands. Stubs that support multi-threading targets should
37819 support the @samp{vCont} command. All other commands are optional.
37824 The following table provides a complete list of all currently defined
37825 @var{command}s and their corresponding response @var{data}.
37826 @xref{File-I/O Remote Protocol Extension}, for details about the File
37827 I/O extension of the remote protocol.
37829 Each packet's description has a template showing the packet's overall
37830 syntax, followed by an explanation of the packet's meaning. We
37831 include spaces in some of the templates for clarity; these are not
37832 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37833 separate its components. For example, a template like @samp{foo
37834 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37835 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37836 @var{baz}. @value{GDBN} does not transmit a space character between the
37837 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37840 @cindex @var{thread-id}, in remote protocol
37841 @anchor{thread-id syntax}
37842 Several packets and replies include a @var{thread-id} field to identify
37843 a thread. Normally these are positive numbers with a target-specific
37844 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37845 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37848 In addition, the remote protocol supports a multiprocess feature in
37849 which the @var{thread-id} syntax is extended to optionally include both
37850 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37851 The @var{pid} (process) and @var{tid} (thread) components each have the
37852 format described above: a positive number with target-specific
37853 interpretation formatted as a big-endian hex string, literal @samp{-1}
37854 to indicate all processes or threads (respectively), or @samp{0} to
37855 indicate an arbitrary process or thread. Specifying just a process, as
37856 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37857 error to specify all processes but a specific thread, such as
37858 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37859 for those packets and replies explicitly documented to include a process
37860 ID, rather than a @var{thread-id}.
37862 The multiprocess @var{thread-id} syntax extensions are only used if both
37863 @value{GDBN} and the stub report support for the @samp{multiprocess}
37864 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37867 Note that all packet forms beginning with an upper- or lower-case
37868 letter, other than those described here, are reserved for future use.
37870 Here are the packet descriptions.
37875 @cindex @samp{!} packet
37876 @anchor{extended mode}
37877 Enable extended mode. In extended mode, the remote server is made
37878 persistent. The @samp{R} packet is used to restart the program being
37884 The remote target both supports and has enabled extended mode.
37888 @cindex @samp{?} packet
37889 Indicate the reason the target halted. The reply is the same as for
37890 step and continue. This packet has a special interpretation when the
37891 target is in non-stop mode; see @ref{Remote Non-Stop}.
37894 @xref{Stop Reply Packets}, for the reply specifications.
37896 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37897 @cindex @samp{A} packet
37898 Initialized @code{argv[]} array passed into program. @var{arglen}
37899 specifies the number of bytes in the hex encoded byte stream
37900 @var{arg}. See @code{gdbserver} for more details.
37905 The arguments were set.
37911 @cindex @samp{b} packet
37912 (Don't use this packet; its behavior is not well-defined.)
37913 Change the serial line speed to @var{baud}.
37915 JTC: @emph{When does the transport layer state change? When it's
37916 received, or after the ACK is transmitted. In either case, there are
37917 problems if the command or the acknowledgment packet is dropped.}
37919 Stan: @emph{If people really wanted to add something like this, and get
37920 it working for the first time, they ought to modify ser-unix.c to send
37921 some kind of out-of-band message to a specially-setup stub and have the
37922 switch happen "in between" packets, so that from remote protocol's point
37923 of view, nothing actually happened.}
37925 @item B @var{addr},@var{mode}
37926 @cindex @samp{B} packet
37927 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37928 breakpoint at @var{addr}.
37930 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37931 (@pxref{insert breakpoint or watchpoint packet}).
37933 @cindex @samp{bc} packet
37936 Backward continue. Execute the target system in reverse. No parameter.
37937 @xref{Reverse Execution}, for more information.
37940 @xref{Stop Reply Packets}, for the reply specifications.
37942 @cindex @samp{bs} packet
37945 Backward single step. Execute one instruction in reverse. No parameter.
37946 @xref{Reverse Execution}, for more information.
37949 @xref{Stop Reply Packets}, for the reply specifications.
37951 @item c @r{[}@var{addr}@r{]}
37952 @cindex @samp{c} packet
37953 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
37954 resume at current address.
37956 This packet is deprecated for multi-threading support. @xref{vCont
37960 @xref{Stop Reply Packets}, for the reply specifications.
37962 @item C @var{sig}@r{[};@var{addr}@r{]}
37963 @cindex @samp{C} packet
37964 Continue with signal @var{sig} (hex signal number). If
37965 @samp{;@var{addr}} is omitted, resume at same address.
37967 This packet is deprecated for multi-threading support. @xref{vCont
37971 @xref{Stop Reply Packets}, for the reply specifications.
37974 @cindex @samp{d} packet
37977 Don't use this packet; instead, define a general set packet
37978 (@pxref{General Query Packets}).
37982 @cindex @samp{D} packet
37983 The first form of the packet is used to detach @value{GDBN} from the
37984 remote system. It is sent to the remote target
37985 before @value{GDBN} disconnects via the @code{detach} command.
37987 The second form, including a process ID, is used when multiprocess
37988 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37989 detach only a specific process. The @var{pid} is specified as a
37990 big-endian hex string.
38000 @item F @var{RC},@var{EE},@var{CF};@var{XX}
38001 @cindex @samp{F} packet
38002 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
38003 This is part of the File-I/O protocol extension. @xref{File-I/O
38004 Remote Protocol Extension}, for the specification.
38007 @anchor{read registers packet}
38008 @cindex @samp{g} packet
38009 Read general registers.
38013 @item @var{XX@dots{}}
38014 Each byte of register data is described by two hex digits. The bytes
38015 with the register are transmitted in target byte order. The size of
38016 each register and their position within the @samp{g} packet are
38017 determined by the @value{GDBN} internal gdbarch functions
38018 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
38019 specification of several standard @samp{g} packets is specified below.
38021 When reading registers from a trace frame (@pxref{Analyze Collected
38022 Data,,Using the Collected Data}), the stub may also return a string of
38023 literal @samp{x}'s in place of the register data digits, to indicate
38024 that the corresponding register has not been collected, thus its value
38025 is unavailable. For example, for an architecture with 4 registers of
38026 4 bytes each, the following reply indicates to @value{GDBN} that
38027 registers 0 and 2 have not been collected, while registers 1 and 3
38028 have been collected, and both have zero value:
38032 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
38039 @item G @var{XX@dots{}}
38040 @cindex @samp{G} packet
38041 Write general registers. @xref{read registers packet}, for a
38042 description of the @var{XX@dots{}} data.
38052 @item H @var{op} @var{thread-id}
38053 @cindex @samp{H} packet
38054 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
38055 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
38056 it should be @samp{c} for step and continue operations (note that this
38057 is deprecated, supporting the @samp{vCont} command is a better
38058 option), @samp{g} for other operations. The thread designator
38059 @var{thread-id} has the format and interpretation described in
38060 @ref{thread-id syntax}.
38071 @c 'H': How restrictive (or permissive) is the thread model. If a
38072 @c thread is selected and stopped, are other threads allowed
38073 @c to continue to execute? As I mentioned above, I think the
38074 @c semantics of each command when a thread is selected must be
38075 @c described. For example:
38077 @c 'g': If the stub supports threads and a specific thread is
38078 @c selected, returns the register block from that thread;
38079 @c otherwise returns current registers.
38081 @c 'G' If the stub supports threads and a specific thread is
38082 @c selected, sets the registers of the register block of
38083 @c that thread; otherwise sets current registers.
38085 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
38086 @anchor{cycle step packet}
38087 @cindex @samp{i} packet
38088 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
38089 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
38090 step starting at that address.
38093 @cindex @samp{I} packet
38094 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
38098 @cindex @samp{k} packet
38101 FIXME: @emph{There is no description of how to operate when a specific
38102 thread context has been selected (i.e.@: does 'k' kill only that
38105 @item m @var{addr},@var{length}
38106 @cindex @samp{m} packet
38107 Read @var{length} bytes of memory starting at address @var{addr}.
38108 Note that @var{addr} may not be aligned to any particular boundary.
38110 The stub need not use any particular size or alignment when gathering
38111 data from memory for the response; even if @var{addr} is word-aligned
38112 and @var{length} is a multiple of the word size, the stub is free to
38113 use byte accesses, or not. For this reason, this packet may not be
38114 suitable for accessing memory-mapped I/O devices.
38115 @cindex alignment of remote memory accesses
38116 @cindex size of remote memory accesses
38117 @cindex memory, alignment and size of remote accesses
38121 @item @var{XX@dots{}}
38122 Memory contents; each byte is transmitted as a two-digit hexadecimal
38123 number. The reply may contain fewer bytes than requested if the
38124 server was able to read only part of the region of memory.
38129 @item M @var{addr},@var{length}:@var{XX@dots{}}
38130 @cindex @samp{M} packet
38131 Write @var{length} bytes of memory starting at address @var{addr}.
38132 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
38133 hexadecimal number.
38140 for an error (this includes the case where only part of the data was
38145 @cindex @samp{p} packet
38146 Read the value of register @var{n}; @var{n} is in hex.
38147 @xref{read registers packet}, for a description of how the returned
38148 register value is encoded.
38152 @item @var{XX@dots{}}
38153 the register's value
38157 Indicating an unrecognized @var{query}.
38160 @item P @var{n@dots{}}=@var{r@dots{}}
38161 @anchor{write register packet}
38162 @cindex @samp{P} packet
38163 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
38164 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
38165 digits for each byte in the register (target byte order).
38175 @item q @var{name} @var{params}@dots{}
38176 @itemx Q @var{name} @var{params}@dots{}
38177 @cindex @samp{q} packet
38178 @cindex @samp{Q} packet
38179 General query (@samp{q}) and set (@samp{Q}). These packets are
38180 described fully in @ref{General Query Packets}.
38183 @cindex @samp{r} packet
38184 Reset the entire system.
38186 Don't use this packet; use the @samp{R} packet instead.
38189 @cindex @samp{R} packet
38190 Restart the program being debugged. @var{XX}, while needed, is ignored.
38191 This packet is only available in extended mode (@pxref{extended mode}).
38193 The @samp{R} packet has no reply.
38195 @item s @r{[}@var{addr}@r{]}
38196 @cindex @samp{s} packet
38197 Single step. @var{addr} is the address at which to resume. If
38198 @var{addr} is omitted, resume at same address.
38200 This packet is deprecated for multi-threading support. @xref{vCont
38204 @xref{Stop Reply Packets}, for the reply specifications.
38206 @item S @var{sig}@r{[};@var{addr}@r{]}
38207 @anchor{step with signal packet}
38208 @cindex @samp{S} packet
38209 Step with signal. This is analogous to the @samp{C} packet, but
38210 requests a single-step, rather than a normal resumption of execution.
38212 This packet is deprecated for multi-threading support. @xref{vCont
38216 @xref{Stop Reply Packets}, for the reply specifications.
38218 @item t @var{addr}:@var{PP},@var{MM}
38219 @cindex @samp{t} packet
38220 Search backwards starting at address @var{addr} for a match with pattern
38221 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
38222 @var{addr} must be at least 3 digits.
38224 @item T @var{thread-id}
38225 @cindex @samp{T} packet
38226 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
38231 thread is still alive
38237 Packets starting with @samp{v} are identified by a multi-letter name,
38238 up to the first @samp{;} or @samp{?} (or the end of the packet).
38240 @item vAttach;@var{pid}
38241 @cindex @samp{vAttach} packet
38242 Attach to a new process with the specified process ID @var{pid}.
38243 The process ID is a
38244 hexadecimal integer identifying the process. In all-stop mode, all
38245 threads in the attached process are stopped; in non-stop mode, it may be
38246 attached without being stopped if that is supported by the target.
38248 @c In non-stop mode, on a successful vAttach, the stub should set the
38249 @c current thread to a thread of the newly-attached process. After
38250 @c attaching, GDB queries for the attached process's thread ID with qC.
38251 @c Also note that, from a user perspective, whether or not the
38252 @c target is stopped on attach in non-stop mode depends on whether you
38253 @c use the foreground or background version of the attach command, not
38254 @c on what vAttach does; GDB does the right thing with respect to either
38255 @c stopping or restarting threads.
38257 This packet is only available in extended mode (@pxref{extended mode}).
38263 @item @r{Any stop packet}
38264 for success in all-stop mode (@pxref{Stop Reply Packets})
38266 for success in non-stop mode (@pxref{Remote Non-Stop})
38269 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
38270 @cindex @samp{vCont} packet
38271 @anchor{vCont packet}
38272 Resume the inferior, specifying different actions for each thread.
38273 If an action is specified with no @var{thread-id}, then it is applied to any
38274 threads that don't have a specific action specified; if no default action is
38275 specified then other threads should remain stopped in all-stop mode and
38276 in their current state in non-stop mode.
38277 Specifying multiple
38278 default actions is an error; specifying no actions is also an error.
38279 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
38281 Currently supported actions are:
38287 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
38291 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
38294 @item r @var{start},@var{end}
38295 Step once, and then keep stepping as long as the thread stops at
38296 addresses between @var{start} (inclusive) and @var{end} (exclusive).
38297 The remote stub reports a stop reply when either the thread goes out
38298 of the range or is stopped due to an unrelated reason, such as hitting
38299 a breakpoint. @xref{range stepping}.
38301 If the range is empty (@var{start} == @var{end}), then the action
38302 becomes equivalent to the @samp{s} action. In other words,
38303 single-step once, and report the stop (even if the stepped instruction
38304 jumps to @var{start}).
38306 (A stop reply may be sent at any point even if the PC is still within
38307 the stepping range; for example, it is valid to implement this packet
38308 in a degenerate way as a single instruction step operation.)
38312 The optional argument @var{addr} normally associated with the
38313 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
38314 not supported in @samp{vCont}.
38316 The @samp{t} action is only relevant in non-stop mode
38317 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
38318 A stop reply should be generated for any affected thread not already stopped.
38319 When a thread is stopped by means of a @samp{t} action,
38320 the corresponding stop reply should indicate that the thread has stopped with
38321 signal @samp{0}, regardless of whether the target uses some other signal
38322 as an implementation detail.
38324 The stub must support @samp{vCont} if it reports support for
38325 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
38326 this case @samp{vCont} actions can be specified to apply to all threads
38327 in a process by using the @samp{p@var{pid}.-1} form of the
38331 @xref{Stop Reply Packets}, for the reply specifications.
38334 @cindex @samp{vCont?} packet
38335 Request a list of actions supported by the @samp{vCont} packet.
38339 @item vCont@r{[};@var{action}@dots{}@r{]}
38340 The @samp{vCont} packet is supported. Each @var{action} is a supported
38341 command in the @samp{vCont} packet.
38343 The @samp{vCont} packet is not supported.
38346 @item vFile:@var{operation}:@var{parameter}@dots{}
38347 @cindex @samp{vFile} packet
38348 Perform a file operation on the target system. For details,
38349 see @ref{Host I/O Packets}.
38351 @item vFlashErase:@var{addr},@var{length}
38352 @cindex @samp{vFlashErase} packet
38353 Direct the stub to erase @var{length} bytes of flash starting at
38354 @var{addr}. The region may enclose any number of flash blocks, but
38355 its start and end must fall on block boundaries, as indicated by the
38356 flash block size appearing in the memory map (@pxref{Memory Map
38357 Format}). @value{GDBN} groups flash memory programming operations
38358 together, and sends a @samp{vFlashDone} request after each group; the
38359 stub is allowed to delay erase operation until the @samp{vFlashDone}
38360 packet is received.
38370 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38371 @cindex @samp{vFlashWrite} packet
38372 Direct the stub to write data to flash address @var{addr}. The data
38373 is passed in binary form using the same encoding as for the @samp{X}
38374 packet (@pxref{Binary Data}). The memory ranges specified by
38375 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38376 not overlap, and must appear in order of increasing addresses
38377 (although @samp{vFlashErase} packets for higher addresses may already
38378 have been received; the ordering is guaranteed only between
38379 @samp{vFlashWrite} packets). If a packet writes to an address that was
38380 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38381 target-specific method, the results are unpredictable.
38389 for vFlashWrite addressing non-flash memory
38395 @cindex @samp{vFlashDone} packet
38396 Indicate to the stub that flash programming operation is finished.
38397 The stub is permitted to delay or batch the effects of a group of
38398 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38399 @samp{vFlashDone} packet is received. The contents of the affected
38400 regions of flash memory are unpredictable until the @samp{vFlashDone}
38401 request is completed.
38403 @item vKill;@var{pid}
38404 @cindex @samp{vKill} packet
38405 Kill the process with the specified process ID. @var{pid} is a
38406 hexadecimal integer identifying the process. This packet is used in
38407 preference to @samp{k} when multiprocess protocol extensions are
38408 supported; see @ref{multiprocess extensions}.
38418 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38419 @cindex @samp{vRun} packet
38420 Run the program @var{filename}, passing it each @var{argument} on its
38421 command line. The file and arguments are hex-encoded strings. If
38422 @var{filename} is an empty string, the stub may use a default program
38423 (e.g.@: the last program run). The program is created in the stopped
38426 @c FIXME: What about non-stop mode?
38428 This packet is only available in extended mode (@pxref{extended mode}).
38434 @item @r{Any stop packet}
38435 for success (@pxref{Stop Reply Packets})
38439 @cindex @samp{vStopped} packet
38440 @xref{Notification Packets}.
38442 @item X @var{addr},@var{length}:@var{XX@dots{}}
38444 @cindex @samp{X} packet
38445 Write data to memory, where the data is transmitted in binary.
38446 @var{addr} is address, @var{length} is number of bytes,
38447 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38457 @item z @var{type},@var{addr},@var{kind}
38458 @itemx Z @var{type},@var{addr},@var{kind}
38459 @anchor{insert breakpoint or watchpoint packet}
38460 @cindex @samp{z} packet
38461 @cindex @samp{Z} packets
38462 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38463 watchpoint starting at address @var{address} of kind @var{kind}.
38465 Each breakpoint and watchpoint packet @var{type} is documented
38468 @emph{Implementation notes: A remote target shall return an empty string
38469 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38470 remote target shall support either both or neither of a given
38471 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38472 avoid potential problems with duplicate packets, the operations should
38473 be implemented in an idempotent way.}
38475 @item z0,@var{addr},@var{kind}
38476 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38477 @cindex @samp{z0} packet
38478 @cindex @samp{Z0} packet
38479 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
38480 @var{addr} of type @var{kind}.
38482 A memory breakpoint is implemented by replacing the instruction at
38483 @var{addr} with a software breakpoint or trap instruction. The
38484 @var{kind} is target-specific and typically indicates the size of
38485 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
38486 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38487 architectures have additional meanings for @var{kind};
38488 @var{cond_list} is an optional list of conditional expressions in bytecode
38489 form that should be evaluated on the target's side. These are the
38490 conditions that should be taken into consideration when deciding if
38491 the breakpoint trigger should be reported back to @var{GDBN}.
38493 The @var{cond_list} parameter is comprised of a series of expressions,
38494 concatenated without separators. Each expression has the following form:
38498 @item X @var{len},@var{expr}
38499 @var{len} is the length of the bytecode expression and @var{expr} is the
38500 actual conditional expression in bytecode form.
38504 The optional @var{cmd_list} parameter introduces commands that may be
38505 run on the target, rather than being reported back to @value{GDBN}.
38506 The parameter starts with a numeric flag @var{persist}; if the flag is
38507 nonzero, then the breakpoint may remain active and the commands
38508 continue to be run even when @value{GDBN} disconnects from the target.
38509 Following this flag is a series of expressions concatenated with no
38510 separators. Each expression has the following form:
38514 @item X @var{len},@var{expr}
38515 @var{len} is the length of the bytecode expression and @var{expr} is the
38516 actual conditional expression in bytecode form.
38520 see @ref{Architecture-Specific Protocol Details}.
38522 @emph{Implementation note: It is possible for a target to copy or move
38523 code that contains memory breakpoints (e.g., when implementing
38524 overlays). The behavior of this packet, in the presence of such a
38525 target, is not defined.}
38537 @item z1,@var{addr},@var{kind}
38538 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
38539 @cindex @samp{z1} packet
38540 @cindex @samp{Z1} packet
38541 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38542 address @var{addr}.
38544 A hardware breakpoint is implemented using a mechanism that is not
38545 dependant on being able to modify the target's memory. @var{kind}
38546 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
38548 @emph{Implementation note: A hardware breakpoint is not affected by code
38561 @item z2,@var{addr},@var{kind}
38562 @itemx Z2,@var{addr},@var{kind}
38563 @cindex @samp{z2} packet
38564 @cindex @samp{Z2} packet
38565 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38566 @var{kind} is interpreted as the number of bytes to watch.
38578 @item z3,@var{addr},@var{kind}
38579 @itemx Z3,@var{addr},@var{kind}
38580 @cindex @samp{z3} packet
38581 @cindex @samp{Z3} packet
38582 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38583 @var{kind} is interpreted as the number of bytes to watch.
38595 @item z4,@var{addr},@var{kind}
38596 @itemx Z4,@var{addr},@var{kind}
38597 @cindex @samp{z4} packet
38598 @cindex @samp{Z4} packet
38599 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38600 @var{kind} is interpreted as the number of bytes to watch.
38614 @node Stop Reply Packets
38615 @section Stop Reply Packets
38616 @cindex stop reply packets
38618 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38619 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38620 receive any of the below as a reply. Except for @samp{?}
38621 and @samp{vStopped}, that reply is only returned
38622 when the target halts. In the below the exact meaning of @dfn{signal
38623 number} is defined by the header @file{include/gdb/signals.h} in the
38624 @value{GDBN} source code.
38626 As in the description of request packets, we include spaces in the
38627 reply templates for clarity; these are not part of the reply packet's
38628 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38634 The program received signal number @var{AA} (a two-digit hexadecimal
38635 number). This is equivalent to a @samp{T} response with no
38636 @var{n}:@var{r} pairs.
38638 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38639 @cindex @samp{T} packet reply
38640 The program received signal number @var{AA} (a two-digit hexadecimal
38641 number). This is equivalent to an @samp{S} response, except that the
38642 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38643 and other information directly in the stop reply packet, reducing
38644 round-trip latency. Single-step and breakpoint traps are reported
38645 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38649 If @var{n} is a hexadecimal number, it is a register number, and the
38650 corresponding @var{r} gives that register's value. @var{r} is a
38651 series of bytes in target byte order, with each byte given by a
38652 two-digit hex number.
38655 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38656 the stopped thread, as specified in @ref{thread-id syntax}.
38659 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38660 the core on which the stop event was detected.
38663 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38664 specific event that stopped the target. The currently defined stop
38665 reasons are listed below. @var{aa} should be @samp{05}, the trap
38666 signal. At most one stop reason should be present.
38669 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38670 and go on to the next; this allows us to extend the protocol in the
38674 The currently defined stop reasons are:
38680 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38683 @cindex shared library events, remote reply
38685 The packet indicates that the loaded libraries have changed.
38686 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38687 list of loaded libraries. @var{r} is ignored.
38689 @cindex replay log events, remote reply
38691 The packet indicates that the target cannot continue replaying
38692 logged execution events, because it has reached the end (or the
38693 beginning when executing backward) of the log. The value of @var{r}
38694 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38695 for more information.
38699 @itemx W @var{AA} ; process:@var{pid}
38700 The process exited, and @var{AA} is the exit status. This is only
38701 applicable to certain targets.
38703 The second form of the response, including the process ID of the exited
38704 process, can be used only when @value{GDBN} has reported support for
38705 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38706 The @var{pid} is formatted as a big-endian hex string.
38709 @itemx X @var{AA} ; process:@var{pid}
38710 The process terminated with signal @var{AA}.
38712 The second form of the response, including the process ID of the
38713 terminated process, can be used only when @value{GDBN} has reported
38714 support for multiprocess protocol extensions; see @ref{multiprocess
38715 extensions}. The @var{pid} is formatted as a big-endian hex string.
38717 @item O @var{XX}@dots{}
38718 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38719 written as the program's console output. This can happen at any time
38720 while the program is running and the debugger should continue to wait
38721 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38723 @item F @var{call-id},@var{parameter}@dots{}
38724 @var{call-id} is the identifier which says which host system call should
38725 be called. This is just the name of the function. Translation into the
38726 correct system call is only applicable as it's defined in @value{GDBN}.
38727 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38730 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38731 this very system call.
38733 The target replies with this packet when it expects @value{GDBN} to
38734 call a host system call on behalf of the target. @value{GDBN} replies
38735 with an appropriate @samp{F} packet and keeps up waiting for the next
38736 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38737 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38738 Protocol Extension}, for more details.
38742 @node General Query Packets
38743 @section General Query Packets
38744 @cindex remote query requests
38746 Packets starting with @samp{q} are @dfn{general query packets};
38747 packets starting with @samp{Q} are @dfn{general set packets}. General
38748 query and set packets are a semi-unified form for retrieving and
38749 sending information to and from the stub.
38751 The initial letter of a query or set packet is followed by a name
38752 indicating what sort of thing the packet applies to. For example,
38753 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38754 definitions with the stub. These packet names follow some
38759 The name must not contain commas, colons or semicolons.
38761 Most @value{GDBN} query and set packets have a leading upper case
38764 The names of custom vendor packets should use a company prefix, in
38765 lower case, followed by a period. For example, packets designed at
38766 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38767 foos) or @samp{Qacme.bar} (for setting bars).
38770 The name of a query or set packet should be separated from any
38771 parameters by a @samp{:}; the parameters themselves should be
38772 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38773 full packet name, and check for a separator or the end of the packet,
38774 in case two packet names share a common prefix. New packets should not begin
38775 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38776 packets predate these conventions, and have arguments without any terminator
38777 for the packet name; we suspect they are in widespread use in places that
38778 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38779 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38782 Like the descriptions of the other packets, each description here
38783 has a template showing the packet's overall syntax, followed by an
38784 explanation of the packet's meaning. We include spaces in some of the
38785 templates for clarity; these are not part of the packet's syntax. No
38786 @value{GDBN} packet uses spaces to separate its components.
38788 Here are the currently defined query and set packets:
38794 Turn on or off the agent as a helper to perform some debugging operations
38795 delegated from @value{GDBN} (@pxref{Control Agent}).
38797 @item QAllow:@var{op}:@var{val}@dots{}
38798 @cindex @samp{QAllow} packet
38799 Specify which operations @value{GDBN} expects to request of the
38800 target, as a semicolon-separated list of operation name and value
38801 pairs. Possible values for @var{op} include @samp{WriteReg},
38802 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38803 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38804 indicating that @value{GDBN} will not request the operation, or 1,
38805 indicating that it may. (The target can then use this to set up its
38806 own internals optimally, for instance if the debugger never expects to
38807 insert breakpoints, it may not need to install its own trap handler.)
38810 @cindex current thread, remote request
38811 @cindex @samp{qC} packet
38812 Return the current thread ID.
38816 @item QC @var{thread-id}
38817 Where @var{thread-id} is a thread ID as documented in
38818 @ref{thread-id syntax}.
38819 @item @r{(anything else)}
38820 Any other reply implies the old thread ID.
38823 @item qCRC:@var{addr},@var{length}
38824 @cindex CRC of memory block, remote request
38825 @cindex @samp{qCRC} packet
38826 Compute the CRC checksum of a block of memory using CRC-32 defined in
38827 IEEE 802.3. The CRC is computed byte at a time, taking the most
38828 significant bit of each byte first. The initial pattern code
38829 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38831 @emph{Note:} This is the same CRC used in validating separate debug
38832 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38833 Files}). However the algorithm is slightly different. When validating
38834 separate debug files, the CRC is computed taking the @emph{least}
38835 significant bit of each byte first, and the final result is inverted to
38836 detect trailing zeros.
38841 An error (such as memory fault)
38842 @item C @var{crc32}
38843 The specified memory region's checksum is @var{crc32}.
38846 @item QDisableRandomization:@var{value}
38847 @cindex disable address space randomization, remote request
38848 @cindex @samp{QDisableRandomization} packet
38849 Some target operating systems will randomize the virtual address space
38850 of the inferior process as a security feature, but provide a feature
38851 to disable such randomization, e.g.@: to allow for a more deterministic
38852 debugging experience. On such systems, this packet with a @var{value}
38853 of 1 directs the target to disable address space randomization for
38854 processes subsequently started via @samp{vRun} packets, while a packet
38855 with a @var{value} of 0 tells the target to enable address space
38858 This packet is only available in extended mode (@pxref{extended mode}).
38863 The request succeeded.
38866 An error occurred. @var{nn} are hex digits.
38869 An empty reply indicates that @samp{QDisableRandomization} is not supported
38873 This packet is not probed by default; the remote stub must request it,
38874 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38875 This should only be done on targets that actually support disabling
38876 address space randomization.
38879 @itemx qsThreadInfo
38880 @cindex list active threads, remote request
38881 @cindex @samp{qfThreadInfo} packet
38882 @cindex @samp{qsThreadInfo} packet
38883 Obtain a list of all active thread IDs from the target (OS). Since there
38884 may be too many active threads to fit into one reply packet, this query
38885 works iteratively: it may require more than one query/reply sequence to
38886 obtain the entire list of threads. The first query of the sequence will
38887 be the @samp{qfThreadInfo} query; subsequent queries in the
38888 sequence will be the @samp{qsThreadInfo} query.
38890 NOTE: This packet replaces the @samp{qL} query (see below).
38894 @item m @var{thread-id}
38896 @item m @var{thread-id},@var{thread-id}@dots{}
38897 a comma-separated list of thread IDs
38899 (lower case letter @samp{L}) denotes end of list.
38902 In response to each query, the target will reply with a list of one or
38903 more thread IDs, separated by commas.
38904 @value{GDBN} will respond to each reply with a request for more thread
38905 ids (using the @samp{qs} form of the query), until the target responds
38906 with @samp{l} (lower-case ell, for @dfn{last}).
38907 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38910 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38911 @cindex get thread-local storage address, remote request
38912 @cindex @samp{qGetTLSAddr} packet
38913 Fetch the address associated with thread local storage specified
38914 by @var{thread-id}, @var{offset}, and @var{lm}.
38916 @var{thread-id} is the thread ID associated with the
38917 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38919 @var{offset} is the (big endian, hex encoded) offset associated with the
38920 thread local variable. (This offset is obtained from the debug
38921 information associated with the variable.)
38923 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38924 load module associated with the thread local storage. For example,
38925 a @sc{gnu}/Linux system will pass the link map address of the shared
38926 object associated with the thread local storage under consideration.
38927 Other operating environments may choose to represent the load module
38928 differently, so the precise meaning of this parameter will vary.
38932 @item @var{XX}@dots{}
38933 Hex encoded (big endian) bytes representing the address of the thread
38934 local storage requested.
38937 An error occurred. @var{nn} are hex digits.
38940 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38943 @item qGetTIBAddr:@var{thread-id}
38944 @cindex get thread information block address
38945 @cindex @samp{qGetTIBAddr} packet
38946 Fetch address of the Windows OS specific Thread Information Block.
38948 @var{thread-id} is the thread ID associated with the thread.
38952 @item @var{XX}@dots{}
38953 Hex encoded (big endian) bytes representing the linear address of the
38954 thread information block.
38957 An error occured. This means that either the thread was not found, or the
38958 address could not be retrieved.
38961 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38964 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38965 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38966 digit) is one to indicate the first query and zero to indicate a
38967 subsequent query; @var{threadcount} (two hex digits) is the maximum
38968 number of threads the response packet can contain; and @var{nextthread}
38969 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38970 returned in the response as @var{argthread}.
38972 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38976 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38977 Where: @var{count} (two hex digits) is the number of threads being
38978 returned; @var{done} (one hex digit) is zero to indicate more threads
38979 and one indicates no further threads; @var{argthreadid} (eight hex
38980 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38981 is a sequence of thread IDs from the target. @var{threadid} (eight hex
38982 digits). See @code{remote.c:parse_threadlist_response()}.
38986 @cindex section offsets, remote request
38987 @cindex @samp{qOffsets} packet
38988 Get section offsets that the target used when relocating the downloaded
38993 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38994 Relocate the @code{Text} section by @var{xxx} from its original address.
38995 Relocate the @code{Data} section by @var{yyy} from its original address.
38996 If the object file format provides segment information (e.g.@: @sc{elf}
38997 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38998 segments by the supplied offsets.
39000 @emph{Note: while a @code{Bss} offset may be included in the response,
39001 @value{GDBN} ignores this and instead applies the @code{Data} offset
39002 to the @code{Bss} section.}
39004 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
39005 Relocate the first segment of the object file, which conventionally
39006 contains program code, to a starting address of @var{xxx}. If
39007 @samp{DataSeg} is specified, relocate the second segment, which
39008 conventionally contains modifiable data, to a starting address of
39009 @var{yyy}. @value{GDBN} will report an error if the object file
39010 does not contain segment information, or does not contain at least
39011 as many segments as mentioned in the reply. Extra segments are
39012 kept at fixed offsets relative to the last relocated segment.
39015 @item qP @var{mode} @var{thread-id}
39016 @cindex thread information, remote request
39017 @cindex @samp{qP} packet
39018 Returns information on @var{thread-id}. Where: @var{mode} is a hex
39019 encoded 32 bit mode; @var{thread-id} is a thread ID
39020 (@pxref{thread-id syntax}).
39022 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
39025 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
39029 @cindex non-stop mode, remote request
39030 @cindex @samp{QNonStop} packet
39032 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
39033 @xref{Remote Non-Stop}, for more information.
39038 The request succeeded.
39041 An error occurred. @var{nn} are hex digits.
39044 An empty reply indicates that @samp{QNonStop} is not supported by
39048 This packet is not probed by default; the remote stub must request it,
39049 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39050 Use of this packet is controlled by the @code{set non-stop} command;
39051 @pxref{Non-Stop Mode}.
39053 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39054 @cindex pass signals to inferior, remote request
39055 @cindex @samp{QPassSignals} packet
39056 @anchor{QPassSignals}
39057 Each listed @var{signal} should be passed directly to the inferior process.
39058 Signals are numbered identically to continue packets and stop replies
39059 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39060 strictly greater than the previous item. These signals do not need to stop
39061 the inferior, or be reported to @value{GDBN}. All other signals should be
39062 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
39063 combine; any earlier @samp{QPassSignals} list is completely replaced by the
39064 new list. This packet improves performance when using @samp{handle
39065 @var{signal} nostop noprint pass}.
39070 The request succeeded.
39073 An error occurred. @var{nn} are hex digits.
39076 An empty reply indicates that @samp{QPassSignals} is not supported by
39080 Use of this packet is controlled by the @code{set remote pass-signals}
39081 command (@pxref{Remote Configuration, set remote pass-signals}).
39082 This packet is not probed by default; the remote stub must request it,
39083 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39085 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39086 @cindex signals the inferior may see, remote request
39087 @cindex @samp{QProgramSignals} packet
39088 @anchor{QProgramSignals}
39089 Each listed @var{signal} may be delivered to the inferior process.
39090 Others should be silently discarded.
39092 In some cases, the remote stub may need to decide whether to deliver a
39093 signal to the program or not without @value{GDBN} involvement. One
39094 example of that is while detaching --- the program's threads may have
39095 stopped for signals that haven't yet had a chance of being reported to
39096 @value{GDBN}, and so the remote stub can use the signal list specified
39097 by this packet to know whether to deliver or ignore those pending
39100 This does not influence whether to deliver a signal as requested by a
39101 resumption packet (@pxref{vCont packet}).
39103 Signals are numbered identically to continue packets and stop replies
39104 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39105 strictly greater than the previous item. Multiple
39106 @samp{QProgramSignals} packets do not combine; any earlier
39107 @samp{QProgramSignals} list is completely replaced by the new list.
39112 The request succeeded.
39115 An error occurred. @var{nn} are hex digits.
39118 An empty reply indicates that @samp{QProgramSignals} is not supported
39122 Use of this packet is controlled by the @code{set remote program-signals}
39123 command (@pxref{Remote Configuration, set remote program-signals}).
39124 This packet is not probed by default; the remote stub must request it,
39125 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39127 @item qRcmd,@var{command}
39128 @cindex execute remote command, remote request
39129 @cindex @samp{qRcmd} packet
39130 @var{command} (hex encoded) is passed to the local interpreter for
39131 execution. Invalid commands should be reported using the output
39132 string. Before the final result packet, the target may also respond
39133 with a number of intermediate @samp{O@var{output}} console output
39134 packets. @emph{Implementors should note that providing access to a
39135 stubs's interpreter may have security implications}.
39140 A command response with no output.
39142 A command response with the hex encoded output string @var{OUTPUT}.
39144 Indicate a badly formed request.
39146 An empty reply indicates that @samp{qRcmd} is not recognized.
39149 (Note that the @code{qRcmd} packet's name is separated from the
39150 command by a @samp{,}, not a @samp{:}, contrary to the naming
39151 conventions above. Please don't use this packet as a model for new
39154 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39155 @cindex searching memory, in remote debugging
39157 @cindex @samp{qSearch:memory} packet
39159 @cindex @samp{qSearch memory} packet
39160 @anchor{qSearch memory}
39161 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39162 @var{address} and @var{length} are encoded in hex.
39163 @var{search-pattern} is a sequence of bytes, hex encoded.
39168 The pattern was not found.
39170 The pattern was found at @var{address}.
39172 A badly formed request or an error was encountered while searching memory.
39174 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39177 @item QStartNoAckMode
39178 @cindex @samp{QStartNoAckMode} packet
39179 @anchor{QStartNoAckMode}
39180 Request that the remote stub disable the normal @samp{+}/@samp{-}
39181 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39186 The stub has switched to no-acknowledgment mode.
39187 @value{GDBN} acknowledges this reponse,
39188 but neither the stub nor @value{GDBN} shall send or expect further
39189 @samp{+}/@samp{-} acknowledgments in the current connection.
39191 An empty reply indicates that the stub does not support no-acknowledgment mode.
39194 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39195 @cindex supported packets, remote query
39196 @cindex features of the remote protocol
39197 @cindex @samp{qSupported} packet
39198 @anchor{qSupported}
39199 Tell the remote stub about features supported by @value{GDBN}, and
39200 query the stub for features it supports. This packet allows
39201 @value{GDBN} and the remote stub to take advantage of each others'
39202 features. @samp{qSupported} also consolidates multiple feature probes
39203 at startup, to improve @value{GDBN} performance---a single larger
39204 packet performs better than multiple smaller probe packets on
39205 high-latency links. Some features may enable behavior which must not
39206 be on by default, e.g.@: because it would confuse older clients or
39207 stubs. Other features may describe packets which could be
39208 automatically probed for, but are not. These features must be
39209 reported before @value{GDBN} will use them. This ``default
39210 unsupported'' behavior is not appropriate for all packets, but it
39211 helps to keep the initial connection time under control with new
39212 versions of @value{GDBN} which support increasing numbers of packets.
39216 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39217 The stub supports or does not support each returned @var{stubfeature},
39218 depending on the form of each @var{stubfeature} (see below for the
39221 An empty reply indicates that @samp{qSupported} is not recognized,
39222 or that no features needed to be reported to @value{GDBN}.
39225 The allowed forms for each feature (either a @var{gdbfeature} in the
39226 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39230 @item @var{name}=@var{value}
39231 The remote protocol feature @var{name} is supported, and associated
39232 with the specified @var{value}. The format of @var{value} depends
39233 on the feature, but it must not include a semicolon.
39235 The remote protocol feature @var{name} is supported, and does not
39236 need an associated value.
39238 The remote protocol feature @var{name} is not supported.
39240 The remote protocol feature @var{name} may be supported, and
39241 @value{GDBN} should auto-detect support in some other way when it is
39242 needed. This form will not be used for @var{gdbfeature} notifications,
39243 but may be used for @var{stubfeature} responses.
39246 Whenever the stub receives a @samp{qSupported} request, the
39247 supplied set of @value{GDBN} features should override any previous
39248 request. This allows @value{GDBN} to put the stub in a known
39249 state, even if the stub had previously been communicating with
39250 a different version of @value{GDBN}.
39252 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39257 This feature indicates whether @value{GDBN} supports multiprocess
39258 extensions to the remote protocol. @value{GDBN} does not use such
39259 extensions unless the stub also reports that it supports them by
39260 including @samp{multiprocess+} in its @samp{qSupported} reply.
39261 @xref{multiprocess extensions}, for details.
39264 This feature indicates that @value{GDBN} supports the XML target
39265 description. If the stub sees @samp{xmlRegisters=} with target
39266 specific strings separated by a comma, it will report register
39270 This feature indicates whether @value{GDBN} supports the
39271 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39272 instruction reply packet}).
39275 Stubs should ignore any unknown values for
39276 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39277 packet supports receiving packets of unlimited length (earlier
39278 versions of @value{GDBN} may reject overly long responses). Additional values
39279 for @var{gdbfeature} may be defined in the future to let the stub take
39280 advantage of new features in @value{GDBN}, e.g.@: incompatible
39281 improvements in the remote protocol---the @samp{multiprocess} feature is
39282 an example of such a feature. The stub's reply should be independent
39283 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39284 describes all the features it supports, and then the stub replies with
39285 all the features it supports.
39287 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39288 responses, as long as each response uses one of the standard forms.
39290 Some features are flags. A stub which supports a flag feature
39291 should respond with a @samp{+} form response. Other features
39292 require values, and the stub should respond with an @samp{=}
39295 Each feature has a default value, which @value{GDBN} will use if
39296 @samp{qSupported} is not available or if the feature is not mentioned
39297 in the @samp{qSupported} response. The default values are fixed; a
39298 stub is free to omit any feature responses that match the defaults.
39300 Not all features can be probed, but for those which can, the probing
39301 mechanism is useful: in some cases, a stub's internal
39302 architecture may not allow the protocol layer to know some information
39303 about the underlying target in advance. This is especially common in
39304 stubs which may be configured for multiple targets.
39306 These are the currently defined stub features and their properties:
39308 @multitable @columnfractions 0.35 0.2 0.12 0.2
39309 @c NOTE: The first row should be @headitem, but we do not yet require
39310 @c a new enough version of Texinfo (4.7) to use @headitem.
39312 @tab Value Required
39316 @item @samp{PacketSize}
39321 @item @samp{qXfer:auxv:read}
39326 @item @samp{qXfer:btrace:read}
39331 @item @samp{qXfer:features:read}
39336 @item @samp{qXfer:libraries:read}
39341 @item @samp{qXfer:libraries-svr4:read}
39346 @item @samp{augmented-libraries-svr4-read}
39351 @item @samp{qXfer:memory-map:read}
39356 @item @samp{qXfer:sdata:read}
39361 @item @samp{qXfer:spu:read}
39366 @item @samp{qXfer:spu:write}
39371 @item @samp{qXfer:siginfo:read}
39376 @item @samp{qXfer:siginfo:write}
39381 @item @samp{qXfer:threads:read}
39386 @item @samp{qXfer:traceframe-info:read}
39391 @item @samp{qXfer:uib:read}
39396 @item @samp{qXfer:fdpic:read}
39401 @item @samp{Qbtrace:off}
39406 @item @samp{Qbtrace:bts}
39411 @item @samp{QNonStop}
39416 @item @samp{QPassSignals}
39421 @item @samp{QStartNoAckMode}
39426 @item @samp{multiprocess}
39431 @item @samp{ConditionalBreakpoints}
39436 @item @samp{ConditionalTracepoints}
39441 @item @samp{ReverseContinue}
39446 @item @samp{ReverseStep}
39451 @item @samp{TracepointSource}
39456 @item @samp{QAgent}
39461 @item @samp{QAllow}
39466 @item @samp{QDisableRandomization}
39471 @item @samp{EnableDisableTracepoints}
39476 @item @samp{QTBuffer:size}
39481 @item @samp{tracenz}
39486 @item @samp{BreakpointCommands}
39493 These are the currently defined stub features, in more detail:
39496 @cindex packet size, remote protocol
39497 @item PacketSize=@var{bytes}
39498 The remote stub can accept packets up to at least @var{bytes} in
39499 length. @value{GDBN} will send packets up to this size for bulk
39500 transfers, and will never send larger packets. This is a limit on the
39501 data characters in the packet, including the frame and checksum.
39502 There is no trailing NUL byte in a remote protocol packet; if the stub
39503 stores packets in a NUL-terminated format, it should allow an extra
39504 byte in its buffer for the NUL. If this stub feature is not supported,
39505 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39507 @item qXfer:auxv:read
39508 The remote stub understands the @samp{qXfer:auxv:read} packet
39509 (@pxref{qXfer auxiliary vector read}).
39511 @item qXfer:btrace:read
39512 The remote stub understands the @samp{qXfer:btrace:read}
39513 packet (@pxref{qXfer btrace read}).
39515 @item qXfer:features:read
39516 The remote stub understands the @samp{qXfer:features:read} packet
39517 (@pxref{qXfer target description read}).
39519 @item qXfer:libraries:read
39520 The remote stub understands the @samp{qXfer:libraries:read} packet
39521 (@pxref{qXfer library list read}).
39523 @item qXfer:libraries-svr4:read
39524 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39525 (@pxref{qXfer svr4 library list read}).
39527 @item augmented-libraries-svr4-read
39528 The remote stub understands the augmented form of the
39529 @samp{qXfer:libraries-svr4:read} packet
39530 (@pxref{qXfer svr4 library list read}).
39532 @item qXfer:memory-map:read
39533 The remote stub understands the @samp{qXfer:memory-map:read} packet
39534 (@pxref{qXfer memory map read}).
39536 @item qXfer:sdata:read
39537 The remote stub understands the @samp{qXfer:sdata:read} packet
39538 (@pxref{qXfer sdata read}).
39540 @item qXfer:spu:read
39541 The remote stub understands the @samp{qXfer:spu:read} packet
39542 (@pxref{qXfer spu read}).
39544 @item qXfer:spu:write
39545 The remote stub understands the @samp{qXfer:spu:write} packet
39546 (@pxref{qXfer spu write}).
39548 @item qXfer:siginfo:read
39549 The remote stub understands the @samp{qXfer:siginfo:read} packet
39550 (@pxref{qXfer siginfo read}).
39552 @item qXfer:siginfo:write
39553 The remote stub understands the @samp{qXfer:siginfo:write} packet
39554 (@pxref{qXfer siginfo write}).
39556 @item qXfer:threads:read
39557 The remote stub understands the @samp{qXfer:threads:read} packet
39558 (@pxref{qXfer threads read}).
39560 @item qXfer:traceframe-info:read
39561 The remote stub understands the @samp{qXfer:traceframe-info:read}
39562 packet (@pxref{qXfer traceframe info read}).
39564 @item qXfer:uib:read
39565 The remote stub understands the @samp{qXfer:uib:read}
39566 packet (@pxref{qXfer unwind info block}).
39568 @item qXfer:fdpic:read
39569 The remote stub understands the @samp{qXfer:fdpic:read}
39570 packet (@pxref{qXfer fdpic loadmap read}).
39573 The remote stub understands the @samp{QNonStop} packet
39574 (@pxref{QNonStop}).
39577 The remote stub understands the @samp{QPassSignals} packet
39578 (@pxref{QPassSignals}).
39580 @item QStartNoAckMode
39581 The remote stub understands the @samp{QStartNoAckMode} packet and
39582 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39585 @anchor{multiprocess extensions}
39586 @cindex multiprocess extensions, in remote protocol
39587 The remote stub understands the multiprocess extensions to the remote
39588 protocol syntax. The multiprocess extensions affect the syntax of
39589 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39590 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39591 replies. Note that reporting this feature indicates support for the
39592 syntactic extensions only, not that the stub necessarily supports
39593 debugging of more than one process at a time. The stub must not use
39594 multiprocess extensions in packet replies unless @value{GDBN} has also
39595 indicated it supports them in its @samp{qSupported} request.
39597 @item qXfer:osdata:read
39598 The remote stub understands the @samp{qXfer:osdata:read} packet
39599 ((@pxref{qXfer osdata read}).
39601 @item ConditionalBreakpoints
39602 The target accepts and implements evaluation of conditional expressions
39603 defined for breakpoints. The target will only report breakpoint triggers
39604 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39606 @item ConditionalTracepoints
39607 The remote stub accepts and implements conditional expressions defined
39608 for tracepoints (@pxref{Tracepoint Conditions}).
39610 @item ReverseContinue
39611 The remote stub accepts and implements the reverse continue packet
39615 The remote stub accepts and implements the reverse step packet
39618 @item TracepointSource
39619 The remote stub understands the @samp{QTDPsrc} packet that supplies
39620 the source form of tracepoint definitions.
39623 The remote stub understands the @samp{QAgent} packet.
39626 The remote stub understands the @samp{QAllow} packet.
39628 @item QDisableRandomization
39629 The remote stub understands the @samp{QDisableRandomization} packet.
39631 @item StaticTracepoint
39632 @cindex static tracepoints, in remote protocol
39633 The remote stub supports static tracepoints.
39635 @item InstallInTrace
39636 @anchor{install tracepoint in tracing}
39637 The remote stub supports installing tracepoint in tracing.
39639 @item EnableDisableTracepoints
39640 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39641 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39642 to be enabled and disabled while a trace experiment is running.
39644 @item QTBuffer:size
39645 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39646 packet that allows to change the size of the trace buffer.
39649 @cindex string tracing, in remote protocol
39650 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39651 See @ref{Bytecode Descriptions} for details about the bytecode.
39653 @item BreakpointCommands
39654 @cindex breakpoint commands, in remote protocol
39655 The remote stub supports running a breakpoint's command list itself,
39656 rather than reporting the hit to @value{GDBN}.
39659 The remote stub understands the @samp{Qbtrace:off} packet.
39662 The remote stub understands the @samp{Qbtrace:bts} packet.
39667 @cindex symbol lookup, remote request
39668 @cindex @samp{qSymbol} packet
39669 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39670 requests. Accept requests from the target for the values of symbols.
39675 The target does not need to look up any (more) symbols.
39676 @item qSymbol:@var{sym_name}
39677 The target requests the value of symbol @var{sym_name} (hex encoded).
39678 @value{GDBN} may provide the value by using the
39679 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39683 @item qSymbol:@var{sym_value}:@var{sym_name}
39684 Set the value of @var{sym_name} to @var{sym_value}.
39686 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39687 target has previously requested.
39689 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39690 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39696 The target does not need to look up any (more) symbols.
39697 @item qSymbol:@var{sym_name}
39698 The target requests the value of a new symbol @var{sym_name} (hex
39699 encoded). @value{GDBN} will continue to supply the values of symbols
39700 (if available), until the target ceases to request them.
39705 @itemx QTDisconnected
39712 @itemx qTMinFTPILen
39714 @xref{Tracepoint Packets}.
39716 @item qThreadExtraInfo,@var{thread-id}
39717 @cindex thread attributes info, remote request
39718 @cindex @samp{qThreadExtraInfo} packet
39719 Obtain a printable string description of a thread's attributes from
39720 the target OS. @var{thread-id} is a thread ID;
39721 see @ref{thread-id syntax}. This
39722 string may contain anything that the target OS thinks is interesting
39723 for @value{GDBN} to tell the user about the thread. The string is
39724 displayed in @value{GDBN}'s @code{info threads} display. Some
39725 examples of possible thread extra info strings are @samp{Runnable}, or
39726 @samp{Blocked on Mutex}.
39730 @item @var{XX}@dots{}
39731 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39732 comprising the printable string containing the extra information about
39733 the thread's attributes.
39736 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39737 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39738 conventions above. Please don't use this packet as a model for new
39757 @xref{Tracepoint Packets}.
39759 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39760 @cindex read special object, remote request
39761 @cindex @samp{qXfer} packet
39762 @anchor{qXfer read}
39763 Read uninterpreted bytes from the target's special data area
39764 identified by the keyword @var{object}. Request @var{length} bytes
39765 starting at @var{offset} bytes into the data. The content and
39766 encoding of @var{annex} is specific to @var{object}; it can supply
39767 additional details about what data to access.
39769 Here are the specific requests of this form defined so far. All
39770 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39771 formats, listed below.
39774 @item qXfer:auxv:read::@var{offset},@var{length}
39775 @anchor{qXfer auxiliary vector read}
39776 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39777 auxiliary vector}. Note @var{annex} must be empty.
39779 This packet is not probed by default; the remote stub must request it,
39780 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39782 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39783 @anchor{qXfer btrace read}
39785 Return a description of the current branch trace.
39786 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39787 packet may have one of the following values:
39791 Returns all available branch trace.
39794 Returns all available branch trace if the branch trace changed since
39795 the last read request.
39798 This packet is not probed by default; the remote stub must request it
39799 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39801 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39802 @anchor{qXfer target description read}
39803 Access the @dfn{target description}. @xref{Target Descriptions}. The
39804 annex specifies which XML document to access. The main description is
39805 always loaded from the @samp{target.xml} annex.
39807 This packet is not probed by default; the remote stub must request it,
39808 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39810 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39811 @anchor{qXfer library list read}
39812 Access the target's list of loaded libraries. @xref{Library List Format}.
39813 The annex part of the generic @samp{qXfer} packet must be empty
39814 (@pxref{qXfer read}).
39816 Targets which maintain a list of libraries in the program's memory do
39817 not need to implement this packet; it is designed for platforms where
39818 the operating system manages the list of loaded libraries.
39820 This packet is not probed by default; the remote stub must request it,
39821 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39823 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39824 @anchor{qXfer svr4 library list read}
39825 Access the target's list of loaded libraries when the target is an SVR4
39826 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39827 of the generic @samp{qXfer} packet must be empty unless the remote
39828 stub indicated it supports the augmented form of this packet
39829 by supplying an appropriate @samp{qSupported} response
39830 (@pxref{qXfer read}, @ref{qSupported}).
39832 This packet is optional for better performance on SVR4 targets.
39833 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39835 This packet is not probed by default; the remote stub must request it,
39836 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39838 If the remote stub indicates it supports the augmented form of this
39839 packet then the annex part of the generic @samp{qXfer} packet may
39840 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39841 arguments. The currently supported arguments are:
39844 @item start=@var{address}
39845 A hexadecimal number specifying the address of the @samp{struct
39846 link_map} to start reading the library list from. If unset or zero
39847 then the first @samp{struct link_map} in the library list will be
39848 chosen as the starting point.
39850 @item prev=@var{address}
39851 A hexadecimal number specifying the address of the @samp{struct
39852 link_map} immediately preceding the @samp{struct link_map}
39853 specified by the @samp{start} argument. If unset or zero then
39854 the remote stub will expect that no @samp{struct link_map}
39855 exists prior to the starting point.
39859 Arguments that are not understood by the remote stub will be silently
39862 @item qXfer:memory-map:read::@var{offset},@var{length}
39863 @anchor{qXfer memory map read}
39864 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39865 annex part of the generic @samp{qXfer} packet must be empty
39866 (@pxref{qXfer read}).
39868 This packet is not probed by default; the remote stub must request it,
39869 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39871 @item qXfer:sdata:read::@var{offset},@var{length}
39872 @anchor{qXfer sdata read}
39874 Read contents of the extra collected static tracepoint marker
39875 information. The annex part of the generic @samp{qXfer} packet must
39876 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39879 This packet is not probed by default; the remote stub must request it,
39880 by supplying an appropriate @samp{qSupported} response
39881 (@pxref{qSupported}).
39883 @item qXfer:siginfo:read::@var{offset},@var{length}
39884 @anchor{qXfer siginfo read}
39885 Read contents of the extra signal information on the target
39886 system. The annex part of the generic @samp{qXfer} packet must be
39887 empty (@pxref{qXfer read}).
39889 This packet is not probed by default; the remote stub must request it,
39890 by supplying an appropriate @samp{qSupported} response
39891 (@pxref{qSupported}).
39893 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39894 @anchor{qXfer spu read}
39895 Read contents of an @code{spufs} file on the target system. The
39896 annex specifies which file to read; it must be of the form
39897 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39898 in the target process, and @var{name} identifes the @code{spufs} file
39899 in that context to be accessed.
39901 This packet is not probed by default; the remote stub must request it,
39902 by supplying an appropriate @samp{qSupported} response
39903 (@pxref{qSupported}).
39905 @item qXfer:threads:read::@var{offset},@var{length}
39906 @anchor{qXfer threads read}
39907 Access the list of threads on target. @xref{Thread List Format}. The
39908 annex part of the generic @samp{qXfer} packet must be empty
39909 (@pxref{qXfer read}).
39911 This packet is not probed by default; the remote stub must request it,
39912 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39914 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39915 @anchor{qXfer traceframe info read}
39917 Return a description of the current traceframe's contents.
39918 @xref{Traceframe Info Format}. The annex part of the generic
39919 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39921 This packet is not probed by default; the remote stub must request it,
39922 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39924 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39925 @anchor{qXfer unwind info block}
39927 Return the unwind information block for @var{pc}. This packet is used
39928 on OpenVMS/ia64 to ask the kernel unwind information.
39930 This packet is not probed by default.
39932 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39933 @anchor{qXfer fdpic loadmap read}
39934 Read contents of @code{loadmap}s on the target system. The
39935 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39936 executable @code{loadmap} or interpreter @code{loadmap} to read.
39938 This packet is not probed by default; the remote stub must request it,
39939 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39941 @item qXfer:osdata:read::@var{offset},@var{length}
39942 @anchor{qXfer osdata read}
39943 Access the target's @dfn{operating system information}.
39944 @xref{Operating System Information}.
39951 Data @var{data} (@pxref{Binary Data}) has been read from the
39952 target. There may be more data at a higher address (although
39953 it is permitted to return @samp{m} even for the last valid
39954 block of data, as long as at least one byte of data was read).
39955 @var{data} may have fewer bytes than the @var{length} in the
39959 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39960 There is no more data to be read. @var{data} may have fewer bytes
39961 than the @var{length} in the request.
39964 The @var{offset} in the request is at the end of the data.
39965 There is no more data to be read.
39968 The request was malformed, or @var{annex} was invalid.
39971 The offset was invalid, or there was an error encountered reading the data.
39972 @var{nn} is a hex-encoded @code{errno} value.
39975 An empty reply indicates the @var{object} string was not recognized by
39976 the stub, or that the object does not support reading.
39979 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39980 @cindex write data into object, remote request
39981 @anchor{qXfer write}
39982 Write uninterpreted bytes into the target's special data area
39983 identified by the keyword @var{object}, starting at @var{offset} bytes
39984 into the data. @var{data}@dots{} is the binary-encoded data
39985 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
39986 is specific to @var{object}; it can supply additional details about what data
39989 Here are the specific requests of this form defined so far. All
39990 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39991 formats, listed below.
39994 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39995 @anchor{qXfer siginfo write}
39996 Write @var{data} to the extra signal information on the target system.
39997 The annex part of the generic @samp{qXfer} packet must be
39998 empty (@pxref{qXfer write}).
40000 This packet is not probed by default; the remote stub must request it,
40001 by supplying an appropriate @samp{qSupported} response
40002 (@pxref{qSupported}).
40004 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
40005 @anchor{qXfer spu write}
40006 Write @var{data} to an @code{spufs} file on the target system. The
40007 annex specifies which file to write; it must be of the form
40008 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40009 in the target process, and @var{name} identifes the @code{spufs} file
40010 in that context to be accessed.
40012 This packet is not probed by default; the remote stub must request it,
40013 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40019 @var{nn} (hex encoded) is the number of bytes written.
40020 This may be fewer bytes than supplied in the request.
40023 The request was malformed, or @var{annex} was invalid.
40026 The offset was invalid, or there was an error encountered writing the data.
40027 @var{nn} is a hex-encoded @code{errno} value.
40030 An empty reply indicates the @var{object} string was not
40031 recognized by the stub, or that the object does not support writing.
40034 @item qXfer:@var{object}:@var{operation}:@dots{}
40035 Requests of this form may be added in the future. When a stub does
40036 not recognize the @var{object} keyword, or its support for
40037 @var{object} does not recognize the @var{operation} keyword, the stub
40038 must respond with an empty packet.
40040 @item qAttached:@var{pid}
40041 @cindex query attached, remote request
40042 @cindex @samp{qAttached} packet
40043 Return an indication of whether the remote server attached to an
40044 existing process or created a new process. When the multiprocess
40045 protocol extensions are supported (@pxref{multiprocess extensions}),
40046 @var{pid} is an integer in hexadecimal format identifying the target
40047 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40048 the query packet will be simplified as @samp{qAttached}.
40050 This query is used, for example, to know whether the remote process
40051 should be detached or killed when a @value{GDBN} session is ended with
40052 the @code{quit} command.
40057 The remote server attached to an existing process.
40059 The remote server created a new process.
40061 A badly formed request or an error was encountered.
40065 Enable branch tracing for the current thread using bts tracing.
40070 Branch tracing has been enabled.
40072 A badly formed request or an error was encountered.
40076 Disable branch tracing for the current thread.
40081 Branch tracing has been disabled.
40083 A badly formed request or an error was encountered.
40088 @node Architecture-Specific Protocol Details
40089 @section Architecture-Specific Protocol Details
40091 This section describes how the remote protocol is applied to specific
40092 target architectures. Also see @ref{Standard Target Features}, for
40093 details of XML target descriptions for each architecture.
40096 * ARM-Specific Protocol Details::
40097 * MIPS-Specific Protocol Details::
40100 @node ARM-Specific Protocol Details
40101 @subsection @acronym{ARM}-specific Protocol Details
40104 * ARM Breakpoint Kinds::
40107 @node ARM Breakpoint Kinds
40108 @subsubsection @acronym{ARM} Breakpoint Kinds
40109 @cindex breakpoint kinds, @acronym{ARM}
40111 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40116 16-bit Thumb mode breakpoint.
40119 32-bit Thumb mode (Thumb-2) breakpoint.
40122 32-bit @acronym{ARM} mode breakpoint.
40126 @node MIPS-Specific Protocol Details
40127 @subsection @acronym{MIPS}-specific Protocol Details
40130 * MIPS Register packet Format::
40131 * MIPS Breakpoint Kinds::
40134 @node MIPS Register packet Format
40135 @subsubsection @acronym{MIPS} Register Packet Format
40136 @cindex register packet format, @acronym{MIPS}
40138 The following @code{g}/@code{G} packets have previously been defined.
40139 In the below, some thirty-two bit registers are transferred as
40140 sixty-four bits. Those registers should be zero/sign extended (which?)
40141 to fill the space allocated. Register bytes are transferred in target
40142 byte order. The two nibbles within a register byte are transferred
40143 most-significant -- least-significant.
40148 All registers are transferred as thirty-two bit quantities in the order:
40149 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40150 registers; fsr; fir; fp.
40153 All registers are transferred as sixty-four bit quantities (including
40154 thirty-two bit registers such as @code{sr}). The ordering is the same
40159 @node MIPS Breakpoint Kinds
40160 @subsubsection @acronym{MIPS} Breakpoint Kinds
40161 @cindex breakpoint kinds, @acronym{MIPS}
40163 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40168 16-bit @acronym{MIPS16} mode breakpoint.
40171 16-bit @acronym{microMIPS} mode breakpoint.
40174 32-bit standard @acronym{MIPS} mode breakpoint.
40177 32-bit @acronym{microMIPS} mode breakpoint.
40181 @node Tracepoint Packets
40182 @section Tracepoint Packets
40183 @cindex tracepoint packets
40184 @cindex packets, tracepoint
40186 Here we describe the packets @value{GDBN} uses to implement
40187 tracepoints (@pxref{Tracepoints}).
40191 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40192 @cindex @samp{QTDP} packet
40193 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40194 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40195 the tracepoint is disabled. @var{step} is the tracepoint's step
40196 count, and @var{pass} is its pass count. If an @samp{F} is present,
40197 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40198 the number of bytes that the target should copy elsewhere to make room
40199 for the tracepoint. If an @samp{X} is present, it introduces a
40200 tracepoint condition, which consists of a hexadecimal length, followed
40201 by a comma and hex-encoded bytes, in a manner similar to action
40202 encodings as described below. If the trailing @samp{-} is present,
40203 further @samp{QTDP} packets will follow to specify this tracepoint's
40209 The packet was understood and carried out.
40211 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40213 The packet was not recognized.
40216 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40217 Define actions to be taken when a tracepoint is hit. @var{n} and
40218 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40219 this tracepoint. This packet may only be sent immediately after
40220 another @samp{QTDP} packet that ended with a @samp{-}. If the
40221 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40222 specifying more actions for this tracepoint.
40224 In the series of action packets for a given tracepoint, at most one
40225 can have an @samp{S} before its first @var{action}. If such a packet
40226 is sent, it and the following packets define ``while-stepping''
40227 actions. Any prior packets define ordinary actions --- that is, those
40228 taken when the tracepoint is first hit. If no action packet has an
40229 @samp{S}, then all the packets in the series specify ordinary
40230 tracepoint actions.
40232 The @samp{@var{action}@dots{}} portion of the packet is a series of
40233 actions, concatenated without separators. Each action has one of the
40239 Collect the registers whose bits are set in @var{mask}. @var{mask} is
40240 a hexadecimal number whose @var{i}'th bit is set if register number
40241 @var{i} should be collected. (The least significant bit is numbered
40242 zero.) Note that @var{mask} may be any number of digits long; it may
40243 not fit in a 32-bit word.
40245 @item M @var{basereg},@var{offset},@var{len}
40246 Collect @var{len} bytes of memory starting at the address in register
40247 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40248 @samp{-1}, then the range has a fixed address: @var{offset} is the
40249 address of the lowest byte to collect. The @var{basereg},
40250 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40251 values (the @samp{-1} value for @var{basereg} is a special case).
40253 @item X @var{len},@var{expr}
40254 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40255 it directs. @var{expr} is an agent expression, as described in
40256 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40257 two-digit hex number in the packet; @var{len} is the number of bytes
40258 in the expression (and thus one-half the number of hex digits in the
40263 Any number of actions may be packed together in a single @samp{QTDP}
40264 packet, as long as the packet does not exceed the maximum packet
40265 length (400 bytes, for many stubs). There may be only one @samp{R}
40266 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40267 actions. Any registers referred to by @samp{M} and @samp{X} actions
40268 must be collected by a preceding @samp{R} action. (The
40269 ``while-stepping'' actions are treated as if they were attached to a
40270 separate tracepoint, as far as these restrictions are concerned.)
40275 The packet was understood and carried out.
40277 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40279 The packet was not recognized.
40282 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40283 @cindex @samp{QTDPsrc} packet
40284 Specify a source string of tracepoint @var{n} at address @var{addr}.
40285 This is useful to get accurate reproduction of the tracepoints
40286 originally downloaded at the beginning of the trace run. @var{type}
40287 is the name of the tracepoint part, such as @samp{cond} for the
40288 tracepoint's conditional expression (see below for a list of types), while
40289 @var{bytes} is the string, encoded in hexadecimal.
40291 @var{start} is the offset of the @var{bytes} within the overall source
40292 string, while @var{slen} is the total length of the source string.
40293 This is intended for handling source strings that are longer than will
40294 fit in a single packet.
40295 @c Add detailed example when this info is moved into a dedicated
40296 @c tracepoint descriptions section.
40298 The available string types are @samp{at} for the location,
40299 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40300 @value{GDBN} sends a separate packet for each command in the action
40301 list, in the same order in which the commands are stored in the list.
40303 The target does not need to do anything with source strings except
40304 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40307 Although this packet is optional, and @value{GDBN} will only send it
40308 if the target replies with @samp{TracepointSource} @xref{General
40309 Query Packets}, it makes both disconnected tracing and trace files
40310 much easier to use. Otherwise the user must be careful that the
40311 tracepoints in effect while looking at trace frames are identical to
40312 the ones in effect during the trace run; even a small discrepancy
40313 could cause @samp{tdump} not to work, or a particular trace frame not
40316 @item QTDV:@var{n}:@var{value}
40317 @cindex define trace state variable, remote request
40318 @cindex @samp{QTDV} packet
40319 Create a new trace state variable, number @var{n}, with an initial
40320 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40321 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40322 the option of not using this packet for initial values of zero; the
40323 target should simply create the trace state variables as they are
40324 mentioned in expressions.
40326 @item QTFrame:@var{n}
40327 @cindex @samp{QTFrame} packet
40328 Select the @var{n}'th tracepoint frame from the buffer, and use the
40329 register and memory contents recorded there to answer subsequent
40330 request packets from @value{GDBN}.
40332 A successful reply from the stub indicates that the stub has found the
40333 requested frame. The response is a series of parts, concatenated
40334 without separators, describing the frame we selected. Each part has
40335 one of the following forms:
40339 The selected frame is number @var{n} in the trace frame buffer;
40340 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40341 was no frame matching the criteria in the request packet.
40344 The selected trace frame records a hit of tracepoint number @var{t};
40345 @var{t} is a hexadecimal number.
40349 @item QTFrame:pc:@var{addr}
40350 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40351 currently selected frame whose PC is @var{addr};
40352 @var{addr} is a hexadecimal number.
40354 @item QTFrame:tdp:@var{t}
40355 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40356 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40357 is a hexadecimal number.
40359 @item QTFrame:range:@var{start}:@var{end}
40360 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40361 currently selected frame whose PC is between @var{start} (inclusive)
40362 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40365 @item QTFrame:outside:@var{start}:@var{end}
40366 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40367 frame @emph{outside} the given range of addresses (exclusive).
40370 @cindex @samp{qTMinFTPILen} packet
40371 This packet requests the minimum length of instruction at which a fast
40372 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40373 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40374 it depends on the target system being able to create trampolines in
40375 the first 64K of memory, which might or might not be possible for that
40376 system. So the reply to this packet will be 4 if it is able to
40383 The minimum instruction length is currently unknown.
40385 The minimum instruction length is @var{length}, where @var{length} is greater
40386 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
40387 that a fast tracepoint may be placed on any instruction regardless of size.
40389 An error has occurred.
40391 An empty reply indicates that the request is not supported by the stub.
40395 @cindex @samp{QTStart} packet
40396 Begin the tracepoint experiment. Begin collecting data from
40397 tracepoint hits in the trace frame buffer. This packet supports the
40398 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40399 instruction reply packet}).
40402 @cindex @samp{QTStop} packet
40403 End the tracepoint experiment. Stop collecting trace frames.
40405 @item QTEnable:@var{n}:@var{addr}
40407 @cindex @samp{QTEnable} packet
40408 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40409 experiment. If the tracepoint was previously disabled, then collection
40410 of data from it will resume.
40412 @item QTDisable:@var{n}:@var{addr}
40414 @cindex @samp{QTDisable} packet
40415 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40416 experiment. No more data will be collected from the tracepoint unless
40417 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40420 @cindex @samp{QTinit} packet
40421 Clear the table of tracepoints, and empty the trace frame buffer.
40423 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40424 @cindex @samp{QTro} packet
40425 Establish the given ranges of memory as ``transparent''. The stub
40426 will answer requests for these ranges from memory's current contents,
40427 if they were not collected as part of the tracepoint hit.
40429 @value{GDBN} uses this to mark read-only regions of memory, like those
40430 containing program code. Since these areas never change, they should
40431 still have the same contents they did when the tracepoint was hit, so
40432 there's no reason for the stub to refuse to provide their contents.
40434 @item QTDisconnected:@var{value}
40435 @cindex @samp{QTDisconnected} packet
40436 Set the choice to what to do with the tracing run when @value{GDBN}
40437 disconnects from the target. A @var{value} of 1 directs the target to
40438 continue the tracing run, while 0 tells the target to stop tracing if
40439 @value{GDBN} is no longer in the picture.
40442 @cindex @samp{qTStatus} packet
40443 Ask the stub if there is a trace experiment running right now.
40445 The reply has the form:
40449 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40450 @var{running} is a single digit @code{1} if the trace is presently
40451 running, or @code{0} if not. It is followed by semicolon-separated
40452 optional fields that an agent may use to report additional status.
40456 If the trace is not running, the agent may report any of several
40457 explanations as one of the optional fields:
40462 No trace has been run yet.
40464 @item tstop[:@var{text}]:0
40465 The trace was stopped by a user-originated stop command. The optional
40466 @var{text} field is a user-supplied string supplied as part of the
40467 stop command (for instance, an explanation of why the trace was
40468 stopped manually). It is hex-encoded.
40471 The trace stopped because the trace buffer filled up.
40473 @item tdisconnected:0
40474 The trace stopped because @value{GDBN} disconnected from the target.
40476 @item tpasscount:@var{tpnum}
40477 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40479 @item terror:@var{text}:@var{tpnum}
40480 The trace stopped because tracepoint @var{tpnum} had an error. The
40481 string @var{text} is available to describe the nature of the error
40482 (for instance, a divide by zero in the condition expression).
40483 @var{text} is hex encoded.
40486 The trace stopped for some other reason.
40490 Additional optional fields supply statistical and other information.
40491 Although not required, they are extremely useful for users monitoring
40492 the progress of a trace run. If a trace has stopped, and these
40493 numbers are reported, they must reflect the state of the just-stopped
40498 @item tframes:@var{n}
40499 The number of trace frames in the buffer.
40501 @item tcreated:@var{n}
40502 The total number of trace frames created during the run. This may
40503 be larger than the trace frame count, if the buffer is circular.
40505 @item tsize:@var{n}
40506 The total size of the trace buffer, in bytes.
40508 @item tfree:@var{n}
40509 The number of bytes still unused in the buffer.
40511 @item circular:@var{n}
40512 The value of the circular trace buffer flag. @code{1} means that the
40513 trace buffer is circular and old trace frames will be discarded if
40514 necessary to make room, @code{0} means that the trace buffer is linear
40517 @item disconn:@var{n}
40518 The value of the disconnected tracing flag. @code{1} means that
40519 tracing will continue after @value{GDBN} disconnects, @code{0} means
40520 that the trace run will stop.
40524 @item qTP:@var{tp}:@var{addr}
40525 @cindex tracepoint status, remote request
40526 @cindex @samp{qTP} packet
40527 Ask the stub for the current state of tracepoint number @var{tp} at
40528 address @var{addr}.
40532 @item V@var{hits}:@var{usage}
40533 The tracepoint has been hit @var{hits} times so far during the trace
40534 run, and accounts for @var{usage} in the trace buffer. Note that
40535 @code{while-stepping} steps are not counted as separate hits, but the
40536 steps' space consumption is added into the usage number.
40540 @item qTV:@var{var}
40541 @cindex trace state variable value, remote request
40542 @cindex @samp{qTV} packet
40543 Ask the stub for the value of the trace state variable number @var{var}.
40548 The value of the variable is @var{value}. This will be the current
40549 value of the variable if the user is examining a running target, or a
40550 saved value if the variable was collected in the trace frame that the
40551 user is looking at. Note that multiple requests may result in
40552 different reply values, such as when requesting values while the
40553 program is running.
40556 The value of the variable is unknown. This would occur, for example,
40557 if the user is examining a trace frame in which the requested variable
40562 @cindex @samp{qTfP} packet
40564 @cindex @samp{qTsP} packet
40565 These packets request data about tracepoints that are being used by
40566 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40567 of data, and multiple @code{qTsP} to get additional pieces. Replies
40568 to these packets generally take the form of the @code{QTDP} packets
40569 that define tracepoints. (FIXME add detailed syntax)
40572 @cindex @samp{qTfV} packet
40574 @cindex @samp{qTsV} packet
40575 These packets request data about trace state variables that are on the
40576 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40577 and multiple @code{qTsV} to get additional variables. Replies to
40578 these packets follow the syntax of the @code{QTDV} packets that define
40579 trace state variables.
40585 @cindex @samp{qTfSTM} packet
40586 @cindex @samp{qTsSTM} packet
40587 These packets request data about static tracepoint markers that exist
40588 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40589 first piece of data, and multiple @code{qTsSTM} to get additional
40590 pieces. Replies to these packets take the following form:
40594 @item m @var{address}:@var{id}:@var{extra}
40596 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40597 a comma-separated list of markers
40599 (lower case letter @samp{L}) denotes end of list.
40601 An error occurred. @var{nn} are hex digits.
40603 An empty reply indicates that the request is not supported by the
40607 @var{address} is encoded in hex.
40608 @var{id} and @var{extra} are strings encoded in hex.
40610 In response to each query, the target will reply with a list of one or
40611 more markers, separated by commas. @value{GDBN} will respond to each
40612 reply with a request for more markers (using the @samp{qs} form of the
40613 query), until the target responds with @samp{l} (lower-case ell, for
40616 @item qTSTMat:@var{address}
40618 @cindex @samp{qTSTMat} packet
40619 This packets requests data about static tracepoint markers in the
40620 target program at @var{address}. Replies to this packet follow the
40621 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40622 tracepoint markers.
40624 @item QTSave:@var{filename}
40625 @cindex @samp{QTSave} packet
40626 This packet directs the target to save trace data to the file name
40627 @var{filename} in the target's filesystem. @var{filename} is encoded
40628 as a hex string; the interpretation of the file name (relative vs
40629 absolute, wild cards, etc) is up to the target.
40631 @item qTBuffer:@var{offset},@var{len}
40632 @cindex @samp{qTBuffer} packet
40633 Return up to @var{len} bytes of the current contents of trace buffer,
40634 starting at @var{offset}. The trace buffer is treated as if it were
40635 a contiguous collection of traceframes, as per the trace file format.
40636 The reply consists as many hex-encoded bytes as the target can deliver
40637 in a packet; it is not an error to return fewer than were asked for.
40638 A reply consisting of just @code{l} indicates that no bytes are
40641 @item QTBuffer:circular:@var{value}
40642 This packet directs the target to use a circular trace buffer if
40643 @var{value} is 1, or a linear buffer if the value is 0.
40645 @item QTBuffer:size:@var{size}
40646 @anchor{QTBuffer-size}
40647 @cindex @samp{QTBuffer size} packet
40648 This packet directs the target to make the trace buffer be of size
40649 @var{size} if possible. A value of @code{-1} tells the target to
40650 use whatever size it prefers.
40652 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40653 @cindex @samp{QTNotes} packet
40654 This packet adds optional textual notes to the trace run. Allowable
40655 types include @code{user}, @code{notes}, and @code{tstop}, the
40656 @var{text} fields are arbitrary strings, hex-encoded.
40660 @subsection Relocate instruction reply packet
40661 When installing fast tracepoints in memory, the target may need to
40662 relocate the instruction currently at the tracepoint address to a
40663 different address in memory. For most instructions, a simple copy is
40664 enough, but, for example, call instructions that implicitly push the
40665 return address on the stack, and relative branches or other
40666 PC-relative instructions require offset adjustment, so that the effect
40667 of executing the instruction at a different address is the same as if
40668 it had executed in the original location.
40670 In response to several of the tracepoint packets, the target may also
40671 respond with a number of intermediate @samp{qRelocInsn} request
40672 packets before the final result packet, to have @value{GDBN} handle
40673 this relocation operation. If a packet supports this mechanism, its
40674 documentation will explicitly say so. See for example the above
40675 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40676 format of the request is:
40679 @item qRelocInsn:@var{from};@var{to}
40681 This requests @value{GDBN} to copy instruction at address @var{from}
40682 to address @var{to}, possibly adjusted so that executing the
40683 instruction at @var{to} has the same effect as executing it at
40684 @var{from}. @value{GDBN} writes the adjusted instruction to target
40685 memory starting at @var{to}.
40690 @item qRelocInsn:@var{adjusted_size}
40691 Informs the stub the relocation is complete. @var{adjusted_size} is
40692 the length in bytes of resulting relocated instruction sequence.
40694 A badly formed request was detected, or an error was encountered while
40695 relocating the instruction.
40698 @node Host I/O Packets
40699 @section Host I/O Packets
40700 @cindex Host I/O, remote protocol
40701 @cindex file transfer, remote protocol
40703 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40704 operations on the far side of a remote link. For example, Host I/O is
40705 used to upload and download files to a remote target with its own
40706 filesystem. Host I/O uses the same constant values and data structure
40707 layout as the target-initiated File-I/O protocol. However, the
40708 Host I/O packets are structured differently. The target-initiated
40709 protocol relies on target memory to store parameters and buffers.
40710 Host I/O requests are initiated by @value{GDBN}, and the
40711 target's memory is not involved. @xref{File-I/O Remote Protocol
40712 Extension}, for more details on the target-initiated protocol.
40714 The Host I/O request packets all encode a single operation along with
40715 its arguments. They have this format:
40719 @item vFile:@var{operation}: @var{parameter}@dots{}
40720 @var{operation} is the name of the particular request; the target
40721 should compare the entire packet name up to the second colon when checking
40722 for a supported operation. The format of @var{parameter} depends on
40723 the operation. Numbers are always passed in hexadecimal. Negative
40724 numbers have an explicit minus sign (i.e.@: two's complement is not
40725 used). Strings (e.g.@: filenames) are encoded as a series of
40726 hexadecimal bytes. The last argument to a system call may be a
40727 buffer of escaped binary data (@pxref{Binary Data}).
40731 The valid responses to Host I/O packets are:
40735 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40736 @var{result} is the integer value returned by this operation, usually
40737 non-negative for success and -1 for errors. If an error has occured,
40738 @var{errno} will be included in the result. @var{errno} will have a
40739 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40740 operations which return data, @var{attachment} supplies the data as a
40741 binary buffer. Binary buffers in response packets are escaped in the
40742 normal way (@pxref{Binary Data}). See the individual packet
40743 documentation for the interpretation of @var{result} and
40747 An empty response indicates that this operation is not recognized.
40751 These are the supported Host I/O operations:
40754 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40755 Open a file at @var{pathname} and return a file descriptor for it, or
40756 return -1 if an error occurs. @var{pathname} is a string,
40757 @var{flags} is an integer indicating a mask of open flags
40758 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40759 of mode bits to use if the file is created (@pxref{mode_t Values}).
40760 @xref{open}, for details of the open flags and mode values.
40762 @item vFile:close: @var{fd}
40763 Close the open file corresponding to @var{fd} and return 0, or
40764 -1 if an error occurs.
40766 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40767 Read data from the open file corresponding to @var{fd}. Up to
40768 @var{count} bytes will be read from the file, starting at @var{offset}
40769 relative to the start of the file. The target may read fewer bytes;
40770 common reasons include packet size limits and an end-of-file
40771 condition. The number of bytes read is returned. Zero should only be
40772 returned for a successful read at the end of the file, or if
40773 @var{count} was zero.
40775 The data read should be returned as a binary attachment on success.
40776 If zero bytes were read, the response should include an empty binary
40777 attachment (i.e.@: a trailing semicolon). The return value is the
40778 number of target bytes read; the binary attachment may be longer if
40779 some characters were escaped.
40781 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40782 Write @var{data} (a binary buffer) to the open file corresponding
40783 to @var{fd}. Start the write at @var{offset} from the start of the
40784 file. Unlike many @code{write} system calls, there is no
40785 separate @var{count} argument; the length of @var{data} in the
40786 packet is used. @samp{vFile:write} returns the number of bytes written,
40787 which may be shorter than the length of @var{data}, or -1 if an
40790 @item vFile:unlink: @var{pathname}
40791 Delete the file at @var{pathname} on the target. Return 0,
40792 or -1 if an error occurs. @var{pathname} is a string.
40794 @item vFile:readlink: @var{filename}
40795 Read value of symbolic link @var{filename} on the target. Return
40796 the number of bytes read, or -1 if an error occurs.
40798 The data read should be returned as a binary attachment on success.
40799 If zero bytes were read, the response should include an empty binary
40800 attachment (i.e.@: a trailing semicolon). The return value is the
40801 number of target bytes read; the binary attachment may be longer if
40802 some characters were escaped.
40807 @section Interrupts
40808 @cindex interrupts (remote protocol)
40810 When a program on the remote target is running, @value{GDBN} may
40811 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
40812 a @code{BREAK} followed by @code{g},
40813 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40815 The precise meaning of @code{BREAK} is defined by the transport
40816 mechanism and may, in fact, be undefined. @value{GDBN} does not
40817 currently define a @code{BREAK} mechanism for any of the network
40818 interfaces except for TCP, in which case @value{GDBN} sends the
40819 @code{telnet} BREAK sequence.
40821 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40822 transport mechanisms. It is represented by sending the single byte
40823 @code{0x03} without any of the usual packet overhead described in
40824 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40825 transmitted as part of a packet, it is considered to be packet data
40826 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40827 (@pxref{X packet}), used for binary downloads, may include an unescaped
40828 @code{0x03} as part of its packet.
40830 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40831 When Linux kernel receives this sequence from serial port,
40832 it stops execution and connects to gdb.
40834 Stubs are not required to recognize these interrupt mechanisms and the
40835 precise meaning associated with receipt of the interrupt is
40836 implementation defined. If the target supports debugging of multiple
40837 threads and/or processes, it should attempt to interrupt all
40838 currently-executing threads and processes.
40839 If the stub is successful at interrupting the
40840 running program, it should send one of the stop
40841 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40842 of successfully stopping the program in all-stop mode, and a stop reply
40843 for each stopped thread in non-stop mode.
40844 Interrupts received while the
40845 program is stopped are discarded.
40847 @node Notification Packets
40848 @section Notification Packets
40849 @cindex notification packets
40850 @cindex packets, notification
40852 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40853 packets that require no acknowledgment. Both the GDB and the stub
40854 may send notifications (although the only notifications defined at
40855 present are sent by the stub). Notifications carry information
40856 without incurring the round-trip latency of an acknowledgment, and so
40857 are useful for low-impact communications where occasional packet loss
40860 A notification packet has the form @samp{% @var{data} #
40861 @var{checksum}}, where @var{data} is the content of the notification,
40862 and @var{checksum} is a checksum of @var{data}, computed and formatted
40863 as for ordinary @value{GDBN} packets. A notification's @var{data}
40864 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40865 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40866 to acknowledge the notification's receipt or to report its corruption.
40868 Every notification's @var{data} begins with a name, which contains no
40869 colon characters, followed by a colon character.
40871 Recipients should silently ignore corrupted notifications and
40872 notifications they do not understand. Recipients should restart
40873 timeout periods on receipt of a well-formed notification, whether or
40874 not they understand it.
40876 Senders should only send the notifications described here when this
40877 protocol description specifies that they are permitted. In the
40878 future, we may extend the protocol to permit existing notifications in
40879 new contexts; this rule helps older senders avoid confusing newer
40882 (Older versions of @value{GDBN} ignore bytes received until they see
40883 the @samp{$} byte that begins an ordinary packet, so new stubs may
40884 transmit notifications without fear of confusing older clients. There
40885 are no notifications defined for @value{GDBN} to send at the moment, but we
40886 assume that most older stubs would ignore them, as well.)
40888 Each notification is comprised of three parts:
40890 @item @var{name}:@var{event}
40891 The notification packet is sent by the side that initiates the
40892 exchange (currently, only the stub does that), with @var{event}
40893 carrying the specific information about the notification.
40894 @var{name} is the name of the notification.
40896 The acknowledge sent by the other side, usually @value{GDBN}, to
40897 acknowledge the exchange and request the event.
40900 The purpose of an asynchronous notification mechanism is to report to
40901 @value{GDBN} that something interesting happened in the remote stub.
40903 The remote stub may send notification @var{name}:@var{event}
40904 at any time, but @value{GDBN} acknowledges the notification when
40905 appropriate. The notification event is pending before @value{GDBN}
40906 acknowledges. Only one notification at a time may be pending; if
40907 additional events occur before @value{GDBN} has acknowledged the
40908 previous notification, they must be queued by the stub for later
40909 synchronous transmission in response to @var{ack} packets from
40910 @value{GDBN}. Because the notification mechanism is unreliable,
40911 the stub is permitted to resend a notification if it believes
40912 @value{GDBN} may not have received it.
40914 Specifically, notifications may appear when @value{GDBN} is not
40915 otherwise reading input from the stub, or when @value{GDBN} is
40916 expecting to read a normal synchronous response or a
40917 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40918 Notification packets are distinct from any other communication from
40919 the stub so there is no ambiguity.
40921 After receiving a notification, @value{GDBN} shall acknowledge it by
40922 sending a @var{ack} packet as a regular, synchronous request to the
40923 stub. Such acknowledgment is not required to happen immediately, as
40924 @value{GDBN} is permitted to send other, unrelated packets to the
40925 stub first, which the stub should process normally.
40927 Upon receiving a @var{ack} packet, if the stub has other queued
40928 events to report to @value{GDBN}, it shall respond by sending a
40929 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40930 packet to solicit further responses; again, it is permitted to send
40931 other, unrelated packets as well which the stub should process
40934 If the stub receives a @var{ack} packet and there are no additional
40935 @var{event} to report, the stub shall return an @samp{OK} response.
40936 At this point, @value{GDBN} has finished processing a notification
40937 and the stub has completed sending any queued events. @value{GDBN}
40938 won't accept any new notifications until the final @samp{OK} is
40939 received . If further notification events occur, the stub shall send
40940 a new notification, @value{GDBN} shall accept the notification, and
40941 the process shall be repeated.
40943 The process of asynchronous notification can be illustrated by the
40946 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40949 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40951 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40956 The following notifications are defined:
40957 @multitable @columnfractions 0.12 0.12 0.38 0.38
40966 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40967 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40968 for information on how these notifications are acknowledged by
40970 @tab Report an asynchronous stop event in non-stop mode.
40974 @node Remote Non-Stop
40975 @section Remote Protocol Support for Non-Stop Mode
40977 @value{GDBN}'s remote protocol supports non-stop debugging of
40978 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40979 supports non-stop mode, it should report that to @value{GDBN} by including
40980 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40982 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40983 establishing a new connection with the stub. Entering non-stop mode
40984 does not alter the state of any currently-running threads, but targets
40985 must stop all threads in any already-attached processes when entering
40986 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40987 probe the target state after a mode change.
40989 In non-stop mode, when an attached process encounters an event that
40990 would otherwise be reported with a stop reply, it uses the
40991 asynchronous notification mechanism (@pxref{Notification Packets}) to
40992 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40993 in all processes are stopped when a stop reply is sent, in non-stop
40994 mode only the thread reporting the stop event is stopped. That is,
40995 when reporting a @samp{S} or @samp{T} response to indicate completion
40996 of a step operation, hitting a breakpoint, or a fault, only the
40997 affected thread is stopped; any other still-running threads continue
40998 to run. When reporting a @samp{W} or @samp{X} response, all running
40999 threads belonging to other attached processes continue to run.
41001 In non-stop mode, the target shall respond to the @samp{?} packet as
41002 follows. First, any incomplete stop reply notification/@samp{vStopped}
41003 sequence in progress is abandoned. The target must begin a new
41004 sequence reporting stop events for all stopped threads, whether or not
41005 it has previously reported those events to @value{GDBN}. The first
41006 stop reply is sent as a synchronous reply to the @samp{?} packet, and
41007 subsequent stop replies are sent as responses to @samp{vStopped} packets
41008 using the mechanism described above. The target must not send
41009 asynchronous stop reply notifications until the sequence is complete.
41010 If all threads are running when the target receives the @samp{?} packet,
41011 or if the target is not attached to any process, it shall respond
41014 @node Packet Acknowledgment
41015 @section Packet Acknowledgment
41017 @cindex acknowledgment, for @value{GDBN} remote
41018 @cindex packet acknowledgment, for @value{GDBN} remote
41019 By default, when either the host or the target machine receives a packet,
41020 the first response expected is an acknowledgment: either @samp{+} (to indicate
41021 the package was received correctly) or @samp{-} (to request retransmission).
41022 This mechanism allows the @value{GDBN} remote protocol to operate over
41023 unreliable transport mechanisms, such as a serial line.
41025 In cases where the transport mechanism is itself reliable (such as a pipe or
41026 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
41027 It may be desirable to disable them in that case to reduce communication
41028 overhead, or for other reasons. This can be accomplished by means of the
41029 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41031 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41032 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41033 and response format still includes the normal checksum, as described in
41034 @ref{Overview}, but the checksum may be ignored by the receiver.
41036 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41037 no-acknowledgment mode, it should report that to @value{GDBN}
41038 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41039 @pxref{qSupported}.
41040 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41041 disabled via the @code{set remote noack-packet off} command
41042 (@pxref{Remote Configuration}),
41043 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41044 Only then may the stub actually turn off packet acknowledgments.
41045 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41046 response, which can be safely ignored by the stub.
41048 Note that @code{set remote noack-packet} command only affects negotiation
41049 between @value{GDBN} and the stub when subsequent connections are made;
41050 it does not affect the protocol acknowledgment state for any current
41052 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41053 new connection is established,
41054 there is also no protocol request to re-enable the acknowledgments
41055 for the current connection, once disabled.
41060 Example sequence of a target being re-started. Notice how the restart
41061 does not get any direct output:
41066 @emph{target restarts}
41069 <- @code{T001:1234123412341234}
41073 Example sequence of a target being stepped by a single instruction:
41076 -> @code{G1445@dots{}}
41081 <- @code{T001:1234123412341234}
41085 <- @code{1455@dots{}}
41089 @node File-I/O Remote Protocol Extension
41090 @section File-I/O Remote Protocol Extension
41091 @cindex File-I/O remote protocol extension
41094 * File-I/O Overview::
41095 * Protocol Basics::
41096 * The F Request Packet::
41097 * The F Reply Packet::
41098 * The Ctrl-C Message::
41100 * List of Supported Calls::
41101 * Protocol-specific Representation of Datatypes::
41103 * File-I/O Examples::
41106 @node File-I/O Overview
41107 @subsection File-I/O Overview
41108 @cindex file-i/o overview
41110 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41111 target to use the host's file system and console I/O to perform various
41112 system calls. System calls on the target system are translated into a
41113 remote protocol packet to the host system, which then performs the needed
41114 actions and returns a response packet to the target system.
41115 This simulates file system operations even on targets that lack file systems.
41117 The protocol is defined to be independent of both the host and target systems.
41118 It uses its own internal representation of datatypes and values. Both
41119 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41120 translating the system-dependent value representations into the internal
41121 protocol representations when data is transmitted.
41123 The communication is synchronous. A system call is possible only when
41124 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41125 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41126 the target is stopped to allow deterministic access to the target's
41127 memory. Therefore File-I/O is not interruptible by target signals. On
41128 the other hand, it is possible to interrupt File-I/O by a user interrupt
41129 (@samp{Ctrl-C}) within @value{GDBN}.
41131 The target's request to perform a host system call does not finish
41132 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41133 after finishing the system call, the target returns to continuing the
41134 previous activity (continue, step). No additional continue or step
41135 request from @value{GDBN} is required.
41138 (@value{GDBP}) continue
41139 <- target requests 'system call X'
41140 target is stopped, @value{GDBN} executes system call
41141 -> @value{GDBN} returns result
41142 ... target continues, @value{GDBN} returns to wait for the target
41143 <- target hits breakpoint and sends a Txx packet
41146 The protocol only supports I/O on the console and to regular files on
41147 the host file system. Character or block special devices, pipes,
41148 named pipes, sockets or any other communication method on the host
41149 system are not supported by this protocol.
41151 File I/O is not supported in non-stop mode.
41153 @node Protocol Basics
41154 @subsection Protocol Basics
41155 @cindex protocol basics, file-i/o
41157 The File-I/O protocol uses the @code{F} packet as the request as well
41158 as reply packet. Since a File-I/O system call can only occur when
41159 @value{GDBN} is waiting for a response from the continuing or stepping target,
41160 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41161 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41162 This @code{F} packet contains all information needed to allow @value{GDBN}
41163 to call the appropriate host system call:
41167 A unique identifier for the requested system call.
41170 All parameters to the system call. Pointers are given as addresses
41171 in the target memory address space. Pointers to strings are given as
41172 pointer/length pair. Numerical values are given as they are.
41173 Numerical control flags are given in a protocol-specific representation.
41177 At this point, @value{GDBN} has to perform the following actions.
41181 If the parameters include pointer values to data needed as input to a
41182 system call, @value{GDBN} requests this data from the target with a
41183 standard @code{m} packet request. This additional communication has to be
41184 expected by the target implementation and is handled as any other @code{m}
41188 @value{GDBN} translates all value from protocol representation to host
41189 representation as needed. Datatypes are coerced into the host types.
41192 @value{GDBN} calls the system call.
41195 It then coerces datatypes back to protocol representation.
41198 If the system call is expected to return data in buffer space specified
41199 by pointer parameters to the call, the data is transmitted to the
41200 target using a @code{M} or @code{X} packet. This packet has to be expected
41201 by the target implementation and is handled as any other @code{M} or @code{X}
41206 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41207 necessary information for the target to continue. This at least contains
41214 @code{errno}, if has been changed by the system call.
41221 After having done the needed type and value coercion, the target continues
41222 the latest continue or step action.
41224 @node The F Request Packet
41225 @subsection The @code{F} Request Packet
41226 @cindex file-i/o request packet
41227 @cindex @code{F} request packet
41229 The @code{F} request packet has the following format:
41232 @item F@var{call-id},@var{parameter@dots{}}
41234 @var{call-id} is the identifier to indicate the host system call to be called.
41235 This is just the name of the function.
41237 @var{parameter@dots{}} are the parameters to the system call.
41238 Parameters are hexadecimal integer values, either the actual values in case
41239 of scalar datatypes, pointers to target buffer space in case of compound
41240 datatypes and unspecified memory areas, or pointer/length pairs in case
41241 of string parameters. These are appended to the @var{call-id} as a
41242 comma-delimited list. All values are transmitted in ASCII
41243 string representation, pointer/length pairs separated by a slash.
41249 @node The F Reply Packet
41250 @subsection The @code{F} Reply Packet
41251 @cindex file-i/o reply packet
41252 @cindex @code{F} reply packet
41254 The @code{F} reply packet has the following format:
41258 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41260 @var{retcode} is the return code of the system call as hexadecimal value.
41262 @var{errno} is the @code{errno} set by the call, in protocol-specific
41264 This parameter can be omitted if the call was successful.
41266 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41267 case, @var{errno} must be sent as well, even if the call was successful.
41268 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41275 or, if the call was interrupted before the host call has been performed:
41282 assuming 4 is the protocol-specific representation of @code{EINTR}.
41287 @node The Ctrl-C Message
41288 @subsection The @samp{Ctrl-C} Message
41289 @cindex ctrl-c message, in file-i/o protocol
41291 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41292 reply packet (@pxref{The F Reply Packet}),
41293 the target should behave as if it had
41294 gotten a break message. The meaning for the target is ``system call
41295 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41296 (as with a break message) and return to @value{GDBN} with a @code{T02}
41299 It's important for the target to know in which
41300 state the system call was interrupted. There are two possible cases:
41304 The system call hasn't been performed on the host yet.
41307 The system call on the host has been finished.
41311 These two states can be distinguished by the target by the value of the
41312 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41313 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41314 on POSIX systems. In any other case, the target may presume that the
41315 system call has been finished --- successfully or not --- and should behave
41316 as if the break message arrived right after the system call.
41318 @value{GDBN} must behave reliably. If the system call has not been called
41319 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41320 @code{errno} in the packet. If the system call on the host has been finished
41321 before the user requests a break, the full action must be finished by
41322 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41323 The @code{F} packet may only be sent when either nothing has happened
41324 or the full action has been completed.
41327 @subsection Console I/O
41328 @cindex console i/o as part of file-i/o
41330 By default and if not explicitly closed by the target system, the file
41331 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41332 on the @value{GDBN} console is handled as any other file output operation
41333 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41334 by @value{GDBN} so that after the target read request from file descriptor
41335 0 all following typing is buffered until either one of the following
41340 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41342 system call is treated as finished.
41345 The user presses @key{RET}. This is treated as end of input with a trailing
41349 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41350 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41354 If the user has typed more characters than fit in the buffer given to
41355 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41356 either another @code{read(0, @dots{})} is requested by the target, or debugging
41357 is stopped at the user's request.
41360 @node List of Supported Calls
41361 @subsection List of Supported Calls
41362 @cindex list of supported file-i/o calls
41379 @unnumberedsubsubsec open
41380 @cindex open, file-i/o system call
41385 int open(const char *pathname, int flags);
41386 int open(const char *pathname, int flags, mode_t mode);
41390 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41393 @var{flags} is the bitwise @code{OR} of the following values:
41397 If the file does not exist it will be created. The host
41398 rules apply as far as file ownership and time stamps
41402 When used with @code{O_CREAT}, if the file already exists it is
41403 an error and open() fails.
41406 If the file already exists and the open mode allows
41407 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41408 truncated to zero length.
41411 The file is opened in append mode.
41414 The file is opened for reading only.
41417 The file is opened for writing only.
41420 The file is opened for reading and writing.
41424 Other bits are silently ignored.
41428 @var{mode} is the bitwise @code{OR} of the following values:
41432 User has read permission.
41435 User has write permission.
41438 Group has read permission.
41441 Group has write permission.
41444 Others have read permission.
41447 Others have write permission.
41451 Other bits are silently ignored.
41454 @item Return value:
41455 @code{open} returns the new file descriptor or -1 if an error
41462 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41465 @var{pathname} refers to a directory.
41468 The requested access is not allowed.
41471 @var{pathname} was too long.
41474 A directory component in @var{pathname} does not exist.
41477 @var{pathname} refers to a device, pipe, named pipe or socket.
41480 @var{pathname} refers to a file on a read-only filesystem and
41481 write access was requested.
41484 @var{pathname} is an invalid pointer value.
41487 No space on device to create the file.
41490 The process already has the maximum number of files open.
41493 The limit on the total number of files open on the system
41497 The call was interrupted by the user.
41503 @unnumberedsubsubsec close
41504 @cindex close, file-i/o system call
41513 @samp{Fclose,@var{fd}}
41515 @item Return value:
41516 @code{close} returns zero on success, or -1 if an error occurred.
41522 @var{fd} isn't a valid open file descriptor.
41525 The call was interrupted by the user.
41531 @unnumberedsubsubsec read
41532 @cindex read, file-i/o system call
41537 int read(int fd, void *buf, unsigned int count);
41541 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41543 @item Return value:
41544 On success, the number of bytes read is returned.
41545 Zero indicates end of file. If count is zero, read
41546 returns zero as well. On error, -1 is returned.
41552 @var{fd} is not a valid file descriptor or is not open for
41556 @var{bufptr} is an invalid pointer value.
41559 The call was interrupted by the user.
41565 @unnumberedsubsubsec write
41566 @cindex write, file-i/o system call
41571 int write(int fd, const void *buf, unsigned int count);
41575 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41577 @item Return value:
41578 On success, the number of bytes written are returned.
41579 Zero indicates nothing was written. On error, -1
41586 @var{fd} is not a valid file descriptor or is not open for
41590 @var{bufptr} is an invalid pointer value.
41593 An attempt was made to write a file that exceeds the
41594 host-specific maximum file size allowed.
41597 No space on device to write the data.
41600 The call was interrupted by the user.
41606 @unnumberedsubsubsec lseek
41607 @cindex lseek, file-i/o system call
41612 long lseek (int fd, long offset, int flag);
41616 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41618 @var{flag} is one of:
41622 The offset is set to @var{offset} bytes.
41625 The offset is set to its current location plus @var{offset}
41629 The offset is set to the size of the file plus @var{offset}
41633 @item Return value:
41634 On success, the resulting unsigned offset in bytes from
41635 the beginning of the file is returned. Otherwise, a
41636 value of -1 is returned.
41642 @var{fd} is not a valid open file descriptor.
41645 @var{fd} is associated with the @value{GDBN} console.
41648 @var{flag} is not a proper value.
41651 The call was interrupted by the user.
41657 @unnumberedsubsubsec rename
41658 @cindex rename, file-i/o system call
41663 int rename(const char *oldpath, const char *newpath);
41667 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41669 @item Return value:
41670 On success, zero is returned. On error, -1 is returned.
41676 @var{newpath} is an existing directory, but @var{oldpath} is not a
41680 @var{newpath} is a non-empty directory.
41683 @var{oldpath} or @var{newpath} is a directory that is in use by some
41687 An attempt was made to make a directory a subdirectory
41691 A component used as a directory in @var{oldpath} or new
41692 path is not a directory. Or @var{oldpath} is a directory
41693 and @var{newpath} exists but is not a directory.
41696 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41699 No access to the file or the path of the file.
41703 @var{oldpath} or @var{newpath} was too long.
41706 A directory component in @var{oldpath} or @var{newpath} does not exist.
41709 The file is on a read-only filesystem.
41712 The device containing the file has no room for the new
41716 The call was interrupted by the user.
41722 @unnumberedsubsubsec unlink
41723 @cindex unlink, file-i/o system call
41728 int unlink(const char *pathname);
41732 @samp{Funlink,@var{pathnameptr}/@var{len}}
41734 @item Return value:
41735 On success, zero is returned. On error, -1 is returned.
41741 No access to the file or the path of the file.
41744 The system does not allow unlinking of directories.
41747 The file @var{pathname} cannot be unlinked because it's
41748 being used by another process.
41751 @var{pathnameptr} is an invalid pointer value.
41754 @var{pathname} was too long.
41757 A directory component in @var{pathname} does not exist.
41760 A component of the path is not a directory.
41763 The file is on a read-only filesystem.
41766 The call was interrupted by the user.
41772 @unnumberedsubsubsec stat/fstat
41773 @cindex fstat, file-i/o system call
41774 @cindex stat, file-i/o system call
41779 int stat(const char *pathname, struct stat *buf);
41780 int fstat(int fd, struct stat *buf);
41784 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41785 @samp{Ffstat,@var{fd},@var{bufptr}}
41787 @item Return value:
41788 On success, zero is returned. On error, -1 is returned.
41794 @var{fd} is not a valid open file.
41797 A directory component in @var{pathname} does not exist or the
41798 path is an empty string.
41801 A component of the path is not a directory.
41804 @var{pathnameptr} is an invalid pointer value.
41807 No access to the file or the path of the file.
41810 @var{pathname} was too long.
41813 The call was interrupted by the user.
41819 @unnumberedsubsubsec gettimeofday
41820 @cindex gettimeofday, file-i/o system call
41825 int gettimeofday(struct timeval *tv, void *tz);
41829 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41831 @item Return value:
41832 On success, 0 is returned, -1 otherwise.
41838 @var{tz} is a non-NULL pointer.
41841 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41847 @unnumberedsubsubsec isatty
41848 @cindex isatty, file-i/o system call
41853 int isatty(int fd);
41857 @samp{Fisatty,@var{fd}}
41859 @item Return value:
41860 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41866 The call was interrupted by the user.
41871 Note that the @code{isatty} call is treated as a special case: it returns
41872 1 to the target if the file descriptor is attached
41873 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41874 would require implementing @code{ioctl} and would be more complex than
41879 @unnumberedsubsubsec system
41880 @cindex system, file-i/o system call
41885 int system(const char *command);
41889 @samp{Fsystem,@var{commandptr}/@var{len}}
41891 @item Return value:
41892 If @var{len} is zero, the return value indicates whether a shell is
41893 available. A zero return value indicates a shell is not available.
41894 For non-zero @var{len}, the value returned is -1 on error and the
41895 return status of the command otherwise. Only the exit status of the
41896 command is returned, which is extracted from the host's @code{system}
41897 return value by calling @code{WEXITSTATUS(retval)}. In case
41898 @file{/bin/sh} could not be executed, 127 is returned.
41904 The call was interrupted by the user.
41909 @value{GDBN} takes over the full task of calling the necessary host calls
41910 to perform the @code{system} call. The return value of @code{system} on
41911 the host is simplified before it's returned
41912 to the target. Any termination signal information from the child process
41913 is discarded, and the return value consists
41914 entirely of the exit status of the called command.
41916 Due to security concerns, the @code{system} call is by default refused
41917 by @value{GDBN}. The user has to allow this call explicitly with the
41918 @code{set remote system-call-allowed 1} command.
41921 @item set remote system-call-allowed
41922 @kindex set remote system-call-allowed
41923 Control whether to allow the @code{system} calls in the File I/O
41924 protocol for the remote target. The default is zero (disabled).
41926 @item show remote system-call-allowed
41927 @kindex show remote system-call-allowed
41928 Show whether the @code{system} calls are allowed in the File I/O
41932 @node Protocol-specific Representation of Datatypes
41933 @subsection Protocol-specific Representation of Datatypes
41934 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41937 * Integral Datatypes::
41939 * Memory Transfer::
41944 @node Integral Datatypes
41945 @unnumberedsubsubsec Integral Datatypes
41946 @cindex integral datatypes, in file-i/o protocol
41948 The integral datatypes used in the system calls are @code{int},
41949 @code{unsigned int}, @code{long}, @code{unsigned long},
41950 @code{mode_t}, and @code{time_t}.
41952 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41953 implemented as 32 bit values in this protocol.
41955 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41957 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41958 in @file{limits.h}) to allow range checking on host and target.
41960 @code{time_t} datatypes are defined as seconds since the Epoch.
41962 All integral datatypes transferred as part of a memory read or write of a
41963 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41966 @node Pointer Values
41967 @unnumberedsubsubsec Pointer Values
41968 @cindex pointer values, in file-i/o protocol
41970 Pointers to target data are transmitted as they are. An exception
41971 is made for pointers to buffers for which the length isn't
41972 transmitted as part of the function call, namely strings. Strings
41973 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41980 which is a pointer to data of length 18 bytes at position 0x1aaf.
41981 The length is defined as the full string length in bytes, including
41982 the trailing null byte. For example, the string @code{"hello world"}
41983 at address 0x123456 is transmitted as
41989 @node Memory Transfer
41990 @unnumberedsubsubsec Memory Transfer
41991 @cindex memory transfer, in file-i/o protocol
41993 Structured data which is transferred using a memory read or write (for
41994 example, a @code{struct stat}) is expected to be in a protocol-specific format
41995 with all scalar multibyte datatypes being big endian. Translation to
41996 this representation needs to be done both by the target before the @code{F}
41997 packet is sent, and by @value{GDBN} before
41998 it transfers memory to the target. Transferred pointers to structured
41999 data should point to the already-coerced data at any time.
42003 @unnumberedsubsubsec struct stat
42004 @cindex struct stat, in file-i/o protocol
42006 The buffer of type @code{struct stat} used by the target and @value{GDBN}
42007 is defined as follows:
42011 unsigned int st_dev; /* device */
42012 unsigned int st_ino; /* inode */
42013 mode_t st_mode; /* protection */
42014 unsigned int st_nlink; /* number of hard links */
42015 unsigned int st_uid; /* user ID of owner */
42016 unsigned int st_gid; /* group ID of owner */
42017 unsigned int st_rdev; /* device type (if inode device) */
42018 unsigned long st_size; /* total size, in bytes */
42019 unsigned long st_blksize; /* blocksize for filesystem I/O */
42020 unsigned long st_blocks; /* number of blocks allocated */
42021 time_t st_atime; /* time of last access */
42022 time_t st_mtime; /* time of last modification */
42023 time_t st_ctime; /* time of last change */
42027 The integral datatypes conform to the definitions given in the
42028 appropriate section (see @ref{Integral Datatypes}, for details) so this
42029 structure is of size 64 bytes.
42031 The values of several fields have a restricted meaning and/or
42037 A value of 0 represents a file, 1 the console.
42040 No valid meaning for the target. Transmitted unchanged.
42043 Valid mode bits are described in @ref{Constants}. Any other
42044 bits have currently no meaning for the target.
42049 No valid meaning for the target. Transmitted unchanged.
42054 These values have a host and file system dependent
42055 accuracy. Especially on Windows hosts, the file system may not
42056 support exact timing values.
42059 The target gets a @code{struct stat} of the above representation and is
42060 responsible for coercing it to the target representation before
42063 Note that due to size differences between the host, target, and protocol
42064 representations of @code{struct stat} members, these members could eventually
42065 get truncated on the target.
42067 @node struct timeval
42068 @unnumberedsubsubsec struct timeval
42069 @cindex struct timeval, in file-i/o protocol
42071 The buffer of type @code{struct timeval} used by the File-I/O protocol
42072 is defined as follows:
42076 time_t tv_sec; /* second */
42077 long tv_usec; /* microsecond */
42081 The integral datatypes conform to the definitions given in the
42082 appropriate section (see @ref{Integral Datatypes}, for details) so this
42083 structure is of size 8 bytes.
42086 @subsection Constants
42087 @cindex constants, in file-i/o protocol
42089 The following values are used for the constants inside of the
42090 protocol. @value{GDBN} and target are responsible for translating these
42091 values before and after the call as needed.
42102 @unnumberedsubsubsec Open Flags
42103 @cindex open flags, in file-i/o protocol
42105 All values are given in hexadecimal representation.
42117 @node mode_t Values
42118 @unnumberedsubsubsec mode_t Values
42119 @cindex mode_t values, in file-i/o protocol
42121 All values are given in octal representation.
42138 @unnumberedsubsubsec Errno Values
42139 @cindex errno values, in file-i/o protocol
42141 All values are given in decimal representation.
42166 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42167 any error value not in the list of supported error numbers.
42170 @unnumberedsubsubsec Lseek Flags
42171 @cindex lseek flags, in file-i/o protocol
42180 @unnumberedsubsubsec Limits
42181 @cindex limits, in file-i/o protocol
42183 All values are given in decimal representation.
42186 INT_MIN -2147483648
42188 UINT_MAX 4294967295
42189 LONG_MIN -9223372036854775808
42190 LONG_MAX 9223372036854775807
42191 ULONG_MAX 18446744073709551615
42194 @node File-I/O Examples
42195 @subsection File-I/O Examples
42196 @cindex file-i/o examples
42198 Example sequence of a write call, file descriptor 3, buffer is at target
42199 address 0x1234, 6 bytes should be written:
42202 <- @code{Fwrite,3,1234,6}
42203 @emph{request memory read from target}
42206 @emph{return "6 bytes written"}
42210 Example sequence of a read call, file descriptor 3, buffer is at target
42211 address 0x1234, 6 bytes should be read:
42214 <- @code{Fread,3,1234,6}
42215 @emph{request memory write to target}
42216 -> @code{X1234,6:XXXXXX}
42217 @emph{return "6 bytes read"}
42221 Example sequence of a read call, call fails on the host due to invalid
42222 file descriptor (@code{EBADF}):
42225 <- @code{Fread,3,1234,6}
42229 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42233 <- @code{Fread,3,1234,6}
42238 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42242 <- @code{Fread,3,1234,6}
42243 -> @code{X1234,6:XXXXXX}
42247 @node Library List Format
42248 @section Library List Format
42249 @cindex library list format, remote protocol
42251 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42252 same process as your application to manage libraries. In this case,
42253 @value{GDBN} can use the loader's symbol table and normal memory
42254 operations to maintain a list of shared libraries. On other
42255 platforms, the operating system manages loaded libraries.
42256 @value{GDBN} can not retrieve the list of currently loaded libraries
42257 through memory operations, so it uses the @samp{qXfer:libraries:read}
42258 packet (@pxref{qXfer library list read}) instead. The remote stub
42259 queries the target's operating system and reports which libraries
42262 The @samp{qXfer:libraries:read} packet returns an XML document which
42263 lists loaded libraries and their offsets. Each library has an
42264 associated name and one or more segment or section base addresses,
42265 which report where the library was loaded in memory.
42267 For the common case of libraries that are fully linked binaries, the
42268 library should have a list of segments. If the target supports
42269 dynamic linking of a relocatable object file, its library XML element
42270 should instead include a list of allocated sections. The segment or
42271 section bases are start addresses, not relocation offsets; they do not
42272 depend on the library's link-time base addresses.
42274 @value{GDBN} must be linked with the Expat library to support XML
42275 library lists. @xref{Expat}.
42277 A simple memory map, with one loaded library relocated by a single
42278 offset, looks like this:
42282 <library name="/lib/libc.so.6">
42283 <segment address="0x10000000"/>
42288 Another simple memory map, with one loaded library with three
42289 allocated sections (.text, .data, .bss), looks like this:
42293 <library name="sharedlib.o">
42294 <section address="0x10000000"/>
42295 <section address="0x20000000"/>
42296 <section address="0x30000000"/>
42301 The format of a library list is described by this DTD:
42304 <!-- library-list: Root element with versioning -->
42305 <!ELEMENT library-list (library)*>
42306 <!ATTLIST library-list version CDATA #FIXED "1.0">
42307 <!ELEMENT library (segment*, section*)>
42308 <!ATTLIST library name CDATA #REQUIRED>
42309 <!ELEMENT segment EMPTY>
42310 <!ATTLIST segment address CDATA #REQUIRED>
42311 <!ELEMENT section EMPTY>
42312 <!ATTLIST section address CDATA #REQUIRED>
42315 In addition, segments and section descriptors cannot be mixed within a
42316 single library element, and you must supply at least one segment or
42317 section for each library.
42319 @node Library List Format for SVR4 Targets
42320 @section Library List Format for SVR4 Targets
42321 @cindex library list format, remote protocol
42323 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42324 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42325 shared libraries. Still a special library list provided by this packet is
42326 more efficient for the @value{GDBN} remote protocol.
42328 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42329 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42330 target, the following parameters are reported:
42334 @code{name}, the absolute file name from the @code{l_name} field of
42335 @code{struct link_map}.
42337 @code{lm} with address of @code{struct link_map} used for TLS
42338 (Thread Local Storage) access.
42340 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42341 @code{struct link_map}. For prelinked libraries this is not an absolute
42342 memory address. It is a displacement of absolute memory address against
42343 address the file was prelinked to during the library load.
42345 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42348 Additionally the single @code{main-lm} attribute specifies address of
42349 @code{struct link_map} used for the main executable. This parameter is used
42350 for TLS access and its presence is optional.
42352 @value{GDBN} must be linked with the Expat library to support XML
42353 SVR4 library lists. @xref{Expat}.
42355 A simple memory map, with two loaded libraries (which do not use prelink),
42359 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42360 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42362 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42364 </library-list-svr>
42367 The format of an SVR4 library list is described by this DTD:
42370 <!-- library-list-svr4: Root element with versioning -->
42371 <!ELEMENT library-list-svr4 (library)*>
42372 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42373 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42374 <!ELEMENT library EMPTY>
42375 <!ATTLIST library name CDATA #REQUIRED>
42376 <!ATTLIST library lm CDATA #REQUIRED>
42377 <!ATTLIST library l_addr CDATA #REQUIRED>
42378 <!ATTLIST library l_ld CDATA #REQUIRED>
42381 @node Memory Map Format
42382 @section Memory Map Format
42383 @cindex memory map format
42385 To be able to write into flash memory, @value{GDBN} needs to obtain a
42386 memory map from the target. This section describes the format of the
42389 The memory map is obtained using the @samp{qXfer:memory-map:read}
42390 (@pxref{qXfer memory map read}) packet and is an XML document that
42391 lists memory regions.
42393 @value{GDBN} must be linked with the Expat library to support XML
42394 memory maps. @xref{Expat}.
42396 The top-level structure of the document is shown below:
42399 <?xml version="1.0"?>
42400 <!DOCTYPE memory-map
42401 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42402 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42408 Each region can be either:
42413 A region of RAM starting at @var{addr} and extending for @var{length}
42417 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42422 A region of read-only memory:
42425 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42430 A region of flash memory, with erasure blocks @var{blocksize}
42434 <memory type="flash" start="@var{addr}" length="@var{length}">
42435 <property name="blocksize">@var{blocksize}</property>
42441 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42442 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42443 packets to write to addresses in such ranges.
42445 The formal DTD for memory map format is given below:
42448 <!-- ................................................... -->
42449 <!-- Memory Map XML DTD ................................ -->
42450 <!-- File: memory-map.dtd .............................. -->
42451 <!-- .................................... .............. -->
42452 <!-- memory-map.dtd -->
42453 <!-- memory-map: Root element with versioning -->
42454 <!ELEMENT memory-map (memory | property)>
42455 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42456 <!ELEMENT memory (property)>
42457 <!-- memory: Specifies a memory region,
42458 and its type, or device. -->
42459 <!ATTLIST memory type CDATA #REQUIRED
42460 start CDATA #REQUIRED
42461 length CDATA #REQUIRED
42462 device CDATA #IMPLIED>
42463 <!-- property: Generic attribute tag -->
42464 <!ELEMENT property (#PCDATA | property)*>
42465 <!ATTLIST property name CDATA #REQUIRED>
42468 @node Thread List Format
42469 @section Thread List Format
42470 @cindex thread list format
42472 To efficiently update the list of threads and their attributes,
42473 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42474 (@pxref{qXfer threads read}) and obtains the XML document with
42475 the following structure:
42478 <?xml version="1.0"?>
42480 <thread id="id" core="0">
42481 ... description ...
42486 Each @samp{thread} element must have the @samp{id} attribute that
42487 identifies the thread (@pxref{thread-id syntax}). The
42488 @samp{core} attribute, if present, specifies which processor core
42489 the thread was last executing on. The content of the of @samp{thread}
42490 element is interpreted as human-readable auxilliary information.
42492 @node Traceframe Info Format
42493 @section Traceframe Info Format
42494 @cindex traceframe info format
42496 To be able to know which objects in the inferior can be examined when
42497 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42498 memory ranges, registers and trace state variables that have been
42499 collected in a traceframe.
42501 This list is obtained using the @samp{qXfer:traceframe-info:read}
42502 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42504 @value{GDBN} must be linked with the Expat library to support XML
42505 traceframe info discovery. @xref{Expat}.
42507 The top-level structure of the document is shown below:
42510 <?xml version="1.0"?>
42511 <!DOCTYPE traceframe-info
42512 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42513 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42519 Each traceframe block can be either:
42524 A region of collected memory starting at @var{addr} and extending for
42525 @var{length} bytes from there:
42528 <memory start="@var{addr}" length="@var{length}"/>
42532 A block indicating trace state variable numbered @var{number} has been
42536 <tvar id="@var{number}"/>
42541 The formal DTD for the traceframe info format is given below:
42544 <!ELEMENT traceframe-info (memory | tvar)* >
42545 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42547 <!ELEMENT memory EMPTY>
42548 <!ATTLIST memory start CDATA #REQUIRED
42549 length CDATA #REQUIRED>
42551 <!ATTLIST tvar id CDATA #REQUIRED>
42554 @node Branch Trace Format
42555 @section Branch Trace Format
42556 @cindex branch trace format
42558 In order to display the branch trace of an inferior thread,
42559 @value{GDBN} needs to obtain the list of branches. This list is
42560 represented as list of sequential code blocks that are connected via
42561 branches. The code in each block has been executed sequentially.
42563 This list is obtained using the @samp{qXfer:btrace:read}
42564 (@pxref{qXfer btrace read}) packet and is an XML document.
42566 @value{GDBN} must be linked with the Expat library to support XML
42567 traceframe info discovery. @xref{Expat}.
42569 The top-level structure of the document is shown below:
42572 <?xml version="1.0"?>
42574 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42575 "http://sourceware.org/gdb/gdb-btrace.dtd">
42584 A block of sequentially executed instructions starting at @var{begin}
42585 and ending at @var{end}:
42588 <block begin="@var{begin}" end="@var{end}"/>
42593 The formal DTD for the branch trace format is given below:
42596 <!ELEMENT btrace (block)* >
42597 <!ATTLIST btrace version CDATA #FIXED "1.0">
42599 <!ELEMENT block EMPTY>
42600 <!ATTLIST block begin CDATA #REQUIRED
42601 end CDATA #REQUIRED>
42604 @include agentexpr.texi
42606 @node Target Descriptions
42607 @appendix Target Descriptions
42608 @cindex target descriptions
42610 One of the challenges of using @value{GDBN} to debug embedded systems
42611 is that there are so many minor variants of each processor
42612 architecture in use. It is common practice for vendors to start with
42613 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42614 and then make changes to adapt it to a particular market niche. Some
42615 architectures have hundreds of variants, available from dozens of
42616 vendors. This leads to a number of problems:
42620 With so many different customized processors, it is difficult for
42621 the @value{GDBN} maintainers to keep up with the changes.
42623 Since individual variants may have short lifetimes or limited
42624 audiences, it may not be worthwhile to carry information about every
42625 variant in the @value{GDBN} source tree.
42627 When @value{GDBN} does support the architecture of the embedded system
42628 at hand, the task of finding the correct architecture name to give the
42629 @command{set architecture} command can be error-prone.
42632 To address these problems, the @value{GDBN} remote protocol allows a
42633 target system to not only identify itself to @value{GDBN}, but to
42634 actually describe its own features. This lets @value{GDBN} support
42635 processor variants it has never seen before --- to the extent that the
42636 descriptions are accurate, and that @value{GDBN} understands them.
42638 @value{GDBN} must be linked with the Expat library to support XML
42639 target descriptions. @xref{Expat}.
42642 * Retrieving Descriptions:: How descriptions are fetched from a target.
42643 * Target Description Format:: The contents of a target description.
42644 * Predefined Target Types:: Standard types available for target
42646 * Standard Target Features:: Features @value{GDBN} knows about.
42649 @node Retrieving Descriptions
42650 @section Retrieving Descriptions
42652 Target descriptions can be read from the target automatically, or
42653 specified by the user manually. The default behavior is to read the
42654 description from the target. @value{GDBN} retrieves it via the remote
42655 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42656 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42657 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42658 XML document, of the form described in @ref{Target Description
42661 Alternatively, you can specify a file to read for the target description.
42662 If a file is set, the target will not be queried. The commands to
42663 specify a file are:
42666 @cindex set tdesc filename
42667 @item set tdesc filename @var{path}
42668 Read the target description from @var{path}.
42670 @cindex unset tdesc filename
42671 @item unset tdesc filename
42672 Do not read the XML target description from a file. @value{GDBN}
42673 will use the description supplied by the current target.
42675 @cindex show tdesc filename
42676 @item show tdesc filename
42677 Show the filename to read for a target description, if any.
42681 @node Target Description Format
42682 @section Target Description Format
42683 @cindex target descriptions, XML format
42685 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42686 document which complies with the Document Type Definition provided in
42687 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42688 means you can use generally available tools like @command{xmllint} to
42689 check that your feature descriptions are well-formed and valid.
42690 However, to help people unfamiliar with XML write descriptions for
42691 their targets, we also describe the grammar here.
42693 Target descriptions can identify the architecture of the remote target
42694 and (for some architectures) provide information about custom register
42695 sets. They can also identify the OS ABI of the remote target.
42696 @value{GDBN} can use this information to autoconfigure for your
42697 target, or to warn you if you connect to an unsupported target.
42699 Here is a simple target description:
42702 <target version="1.0">
42703 <architecture>i386:x86-64</architecture>
42708 This minimal description only says that the target uses
42709 the x86-64 architecture.
42711 A target description has the following overall form, with [ ] marking
42712 optional elements and @dots{} marking repeatable elements. The elements
42713 are explained further below.
42716 <?xml version="1.0"?>
42717 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42718 <target version="1.0">
42719 @r{[}@var{architecture}@r{]}
42720 @r{[}@var{osabi}@r{]}
42721 @r{[}@var{compatible}@r{]}
42722 @r{[}@var{feature}@dots{}@r{]}
42727 The description is generally insensitive to whitespace and line
42728 breaks, under the usual common-sense rules. The XML version
42729 declaration and document type declaration can generally be omitted
42730 (@value{GDBN} does not require them), but specifying them may be
42731 useful for XML validation tools. The @samp{version} attribute for
42732 @samp{<target>} may also be omitted, but we recommend
42733 including it; if future versions of @value{GDBN} use an incompatible
42734 revision of @file{gdb-target.dtd}, they will detect and report
42735 the version mismatch.
42737 @subsection Inclusion
42738 @cindex target descriptions, inclusion
42741 @cindex <xi:include>
42744 It can sometimes be valuable to split a target description up into
42745 several different annexes, either for organizational purposes, or to
42746 share files between different possible target descriptions. You can
42747 divide a description into multiple files by replacing any element of
42748 the target description with an inclusion directive of the form:
42751 <xi:include href="@var{document}"/>
42755 When @value{GDBN} encounters an element of this form, it will retrieve
42756 the named XML @var{document}, and replace the inclusion directive with
42757 the contents of that document. If the current description was read
42758 using @samp{qXfer}, then so will be the included document;
42759 @var{document} will be interpreted as the name of an annex. If the
42760 current description was read from a file, @value{GDBN} will look for
42761 @var{document} as a file in the same directory where it found the
42762 original description.
42764 @subsection Architecture
42765 @cindex <architecture>
42767 An @samp{<architecture>} element has this form:
42770 <architecture>@var{arch}</architecture>
42773 @var{arch} is one of the architectures from the set accepted by
42774 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42777 @cindex @code{<osabi>}
42779 This optional field was introduced in @value{GDBN} version 7.0.
42780 Previous versions of @value{GDBN} ignore it.
42782 An @samp{<osabi>} element has this form:
42785 <osabi>@var{abi-name}</osabi>
42788 @var{abi-name} is an OS ABI name from the same selection accepted by
42789 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42791 @subsection Compatible Architecture
42792 @cindex @code{<compatible>}
42794 This optional field was introduced in @value{GDBN} version 7.0.
42795 Previous versions of @value{GDBN} ignore it.
42797 A @samp{<compatible>} element has this form:
42800 <compatible>@var{arch}</compatible>
42803 @var{arch} is one of the architectures from the set accepted by
42804 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42806 A @samp{<compatible>} element is used to specify that the target
42807 is able to run binaries in some other than the main target architecture
42808 given by the @samp{<architecture>} element. For example, on the
42809 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42810 or @code{powerpc:common64}, but the system is able to run binaries
42811 in the @code{spu} architecture as well. The way to describe this
42812 capability with @samp{<compatible>} is as follows:
42815 <architecture>powerpc:common</architecture>
42816 <compatible>spu</compatible>
42819 @subsection Features
42822 Each @samp{<feature>} describes some logical portion of the target
42823 system. Features are currently used to describe available CPU
42824 registers and the types of their contents. A @samp{<feature>} element
42828 <feature name="@var{name}">
42829 @r{[}@var{type}@dots{}@r{]}
42835 Each feature's name should be unique within the description. The name
42836 of a feature does not matter unless @value{GDBN} has some special
42837 knowledge of the contents of that feature; if it does, the feature
42838 should have its standard name. @xref{Standard Target Features}.
42842 Any register's value is a collection of bits which @value{GDBN} must
42843 interpret. The default interpretation is a two's complement integer,
42844 but other types can be requested by name in the register description.
42845 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42846 Target Types}), and the description can define additional composite types.
42848 Each type element must have an @samp{id} attribute, which gives
42849 a unique (within the containing @samp{<feature>}) name to the type.
42850 Types must be defined before they are used.
42853 Some targets offer vector registers, which can be treated as arrays
42854 of scalar elements. These types are written as @samp{<vector>} elements,
42855 specifying the array element type, @var{type}, and the number of elements,
42859 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42863 If a register's value is usefully viewed in multiple ways, define it
42864 with a union type containing the useful representations. The
42865 @samp{<union>} element contains one or more @samp{<field>} elements,
42866 each of which has a @var{name} and a @var{type}:
42869 <union id="@var{id}">
42870 <field name="@var{name}" type="@var{type}"/>
42876 If a register's value is composed from several separate values, define
42877 it with a structure type. There are two forms of the @samp{<struct>}
42878 element; a @samp{<struct>} element must either contain only bitfields
42879 or contain no bitfields. If the structure contains only bitfields,
42880 its total size in bytes must be specified, each bitfield must have an
42881 explicit start and end, and bitfields are automatically assigned an
42882 integer type. The field's @var{start} should be less than or
42883 equal to its @var{end}, and zero represents the least significant bit.
42886 <struct id="@var{id}" size="@var{size}">
42887 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42892 If the structure contains no bitfields, then each field has an
42893 explicit type, and no implicit padding is added.
42896 <struct id="@var{id}">
42897 <field name="@var{name}" type="@var{type}"/>
42903 If a register's value is a series of single-bit flags, define it with
42904 a flags type. The @samp{<flags>} element has an explicit @var{size}
42905 and contains one or more @samp{<field>} elements. Each field has a
42906 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
42910 <flags id="@var{id}" size="@var{size}">
42911 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42916 @subsection Registers
42919 Each register is represented as an element with this form:
42922 <reg name="@var{name}"
42923 bitsize="@var{size}"
42924 @r{[}regnum="@var{num}"@r{]}
42925 @r{[}save-restore="@var{save-restore}"@r{]}
42926 @r{[}type="@var{type}"@r{]}
42927 @r{[}group="@var{group}"@r{]}/>
42931 The components are as follows:
42936 The register's name; it must be unique within the target description.
42939 The register's size, in bits.
42942 The register's number. If omitted, a register's number is one greater
42943 than that of the previous register (either in the current feature or in
42944 a preceding feature); the first register in the target description
42945 defaults to zero. This register number is used to read or write
42946 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42947 packets, and registers appear in the @code{g} and @code{G} packets
42948 in order of increasing register number.
42951 Whether the register should be preserved across inferior function
42952 calls; this must be either @code{yes} or @code{no}. The default is
42953 @code{yes}, which is appropriate for most registers except for
42954 some system control registers; this is not related to the target's
42958 The type of the register. @var{type} may be a predefined type, a type
42959 defined in the current feature, or one of the special types @code{int}
42960 and @code{float}. @code{int} is an integer type of the correct size
42961 for @var{bitsize}, and @code{float} is a floating point type (in the
42962 architecture's normal floating point format) of the correct size for
42963 @var{bitsize}. The default is @code{int}.
42966 The register group to which this register belongs. @var{group} must
42967 be either @code{general}, @code{float}, or @code{vector}. If no
42968 @var{group} is specified, @value{GDBN} will not display the register
42969 in @code{info registers}.
42973 @node Predefined Target Types
42974 @section Predefined Target Types
42975 @cindex target descriptions, predefined types
42977 Type definitions in the self-description can build up composite types
42978 from basic building blocks, but can not define fundamental types. Instead,
42979 standard identifiers are provided by @value{GDBN} for the fundamental
42980 types. The currently supported types are:
42989 Signed integer types holding the specified number of bits.
42996 Unsigned integer types holding the specified number of bits.
43000 Pointers to unspecified code and data. The program counter and
43001 any dedicated return address register may be marked as code
43002 pointers; printing a code pointer converts it into a symbolic
43003 address. The stack pointer and any dedicated address registers
43004 may be marked as data pointers.
43007 Single precision IEEE floating point.
43010 Double precision IEEE floating point.
43013 The 12-byte extended precision format used by ARM FPA registers.
43016 The 10-byte extended precision format used by x87 registers.
43019 32bit @sc{eflags} register used by x86.
43022 32bit @sc{mxcsr} register used by x86.
43026 @node Standard Target Features
43027 @section Standard Target Features
43028 @cindex target descriptions, standard features
43030 A target description must contain either no registers or all the
43031 target's registers. If the description contains no registers, then
43032 @value{GDBN} will assume a default register layout, selected based on
43033 the architecture. If the description contains any registers, the
43034 default layout will not be used; the standard registers must be
43035 described in the target description, in such a way that @value{GDBN}
43036 can recognize them.
43038 This is accomplished by giving specific names to feature elements
43039 which contain standard registers. @value{GDBN} will look for features
43040 with those names and verify that they contain the expected registers;
43041 if any known feature is missing required registers, or if any required
43042 feature is missing, @value{GDBN} will reject the target
43043 description. You can add additional registers to any of the
43044 standard features --- @value{GDBN} will display them just as if
43045 they were added to an unrecognized feature.
43047 This section lists the known features and their expected contents.
43048 Sample XML documents for these features are included in the
43049 @value{GDBN} source tree, in the directory @file{gdb/features}.
43051 Names recognized by @value{GDBN} should include the name of the
43052 company or organization which selected the name, and the overall
43053 architecture to which the feature applies; so e.g.@: the feature
43054 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43056 The names of registers are not case sensitive for the purpose
43057 of recognizing standard features, but @value{GDBN} will only display
43058 registers using the capitalization used in the description.
43061 * AArch64 Features::
43066 * Nios II Features::
43067 * PowerPC Features::
43068 * S/390 and System z Features::
43073 @node AArch64 Features
43074 @subsection AArch64 Features
43075 @cindex target descriptions, AArch64 features
43077 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43078 targets. It should contain registers @samp{x0} through @samp{x30},
43079 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43081 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43082 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43086 @subsection ARM Features
43087 @cindex target descriptions, ARM features
43089 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43091 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43092 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43094 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43095 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43096 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43099 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43100 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43102 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43103 it should contain at least registers @samp{wR0} through @samp{wR15} and
43104 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43105 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43107 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43108 should contain at least registers @samp{d0} through @samp{d15}. If
43109 they are present, @samp{d16} through @samp{d31} should also be included.
43110 @value{GDBN} will synthesize the single-precision registers from
43111 halves of the double-precision registers.
43113 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43114 need to contain registers; it instructs @value{GDBN} to display the
43115 VFP double-precision registers as vectors and to synthesize the
43116 quad-precision registers from pairs of double-precision registers.
43117 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43118 be present and include 32 double-precision registers.
43120 @node i386 Features
43121 @subsection i386 Features
43122 @cindex target descriptions, i386 features
43124 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43125 targets. It should describe the following registers:
43129 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43131 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43133 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43134 @samp{fs}, @samp{gs}
43136 @samp{st0} through @samp{st7}
43138 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43139 @samp{foseg}, @samp{fooff} and @samp{fop}
43142 The register sets may be different, depending on the target.
43144 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43145 describe registers:
43149 @samp{xmm0} through @samp{xmm7} for i386
43151 @samp{xmm0} through @samp{xmm15} for amd64
43156 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43157 @samp{org.gnu.gdb.i386.sse} feature. It should
43158 describe the upper 128 bits of @sc{ymm} registers:
43162 @samp{ymm0h} through @samp{ymm7h} for i386
43164 @samp{ymm0h} through @samp{ymm15h} for amd64
43167 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43168 describe a single register, @samp{orig_eax}.
43170 @node MIPS Features
43171 @subsection @acronym{MIPS} Features
43172 @cindex target descriptions, @acronym{MIPS} features
43174 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43175 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43176 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43179 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43180 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43181 registers. They may be 32-bit or 64-bit depending on the target.
43183 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43184 it may be optional in a future version of @value{GDBN}. It should
43185 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43186 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43188 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43189 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43190 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43191 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43193 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43194 contain a single register, @samp{restart}, which is used by the
43195 Linux kernel to control restartable syscalls.
43197 @node M68K Features
43198 @subsection M68K Features
43199 @cindex target descriptions, M68K features
43202 @item @samp{org.gnu.gdb.m68k.core}
43203 @itemx @samp{org.gnu.gdb.coldfire.core}
43204 @itemx @samp{org.gnu.gdb.fido.core}
43205 One of those features must be always present.
43206 The feature that is present determines which flavor of m68k is
43207 used. The feature that is present should contain registers
43208 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43209 @samp{sp}, @samp{ps} and @samp{pc}.
43211 @item @samp{org.gnu.gdb.coldfire.fp}
43212 This feature is optional. If present, it should contain registers
43213 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43217 @node Nios II Features
43218 @subsection Nios II Features
43219 @cindex target descriptions, Nios II features
43221 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43222 targets. It should contain the 32 core registers (@samp{zero},
43223 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43224 @samp{pc}, and the 16 control registers (@samp{status} through
43227 @node PowerPC Features
43228 @subsection PowerPC Features
43229 @cindex target descriptions, PowerPC features
43231 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43232 targets. It should contain registers @samp{r0} through @samp{r31},
43233 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43234 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43236 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43237 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43239 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43240 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43243 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43244 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
43245 will combine these registers with the floating point registers
43246 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
43247 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
43248 through @samp{vs63}, the set of vector registers for POWER7.
43250 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43251 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43252 @samp{spefscr}. SPE targets should provide 32-bit registers in
43253 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43254 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43255 these to present registers @samp{ev0} through @samp{ev31} to the
43258 @node S/390 and System z Features
43259 @subsection S/390 and System z Features
43260 @cindex target descriptions, S/390 features
43261 @cindex target descriptions, System z features
43263 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43264 System z targets. It should contain the PSW and the 16 general
43265 registers. In particular, System z targets should provide the 64-bit
43266 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43267 S/390 targets should provide the 32-bit versions of these registers.
43268 A System z target that runs in 31-bit addressing mode should provide
43269 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43270 register's upper halves @samp{r0h} through @samp{r15h}, and their
43271 lower halves @samp{r0l} through @samp{r15l}.
43273 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43274 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43277 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43278 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43280 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43281 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43282 targets and 32-bit otherwise. In addition, the feature may contain
43283 the @samp{last_break} register, whose width depends on the addressing
43284 mode, as well as the @samp{system_call} register, which is always
43287 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43288 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43289 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43291 @node TIC6x Features
43292 @subsection TMS320C6x Features
43293 @cindex target descriptions, TIC6x features
43294 @cindex target descriptions, TMS320C6x features
43295 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43296 targets. It should contain registers @samp{A0} through @samp{A15},
43297 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43299 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43300 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43301 through @samp{B31}.
43303 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43304 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43306 @node Operating System Information
43307 @appendix Operating System Information
43308 @cindex operating system information
43314 Users of @value{GDBN} often wish to obtain information about the state of
43315 the operating system running on the target---for example the list of
43316 processes, or the list of open files. This section describes the
43317 mechanism that makes it possible. This mechanism is similar to the
43318 target features mechanism (@pxref{Target Descriptions}), but focuses
43319 on a different aspect of target.
43321 Operating system information is retrived from the target via the
43322 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43323 read}). The object name in the request should be @samp{osdata}, and
43324 the @var{annex} identifies the data to be fetched.
43327 @appendixsection Process list
43328 @cindex operating system information, process list
43330 When requesting the process list, the @var{annex} field in the
43331 @samp{qXfer} request should be @samp{processes}. The returned data is
43332 an XML document. The formal syntax of this document is defined in
43333 @file{gdb/features/osdata.dtd}.
43335 An example document is:
43338 <?xml version="1.0"?>
43339 <!DOCTYPE target SYSTEM "osdata.dtd">
43340 <osdata type="processes">
43342 <column name="pid">1</column>
43343 <column name="user">root</column>
43344 <column name="command">/sbin/init</column>
43345 <column name="cores">1,2,3</column>
43350 Each item should include a column whose name is @samp{pid}. The value
43351 of that column should identify the process on the target. The
43352 @samp{user} and @samp{command} columns are optional, and will be
43353 displayed by @value{GDBN}. The @samp{cores} column, if present,
43354 should contain a comma-separated list of cores that this process
43355 is running on. Target may provide additional columns,
43356 which @value{GDBN} currently ignores.
43358 @node Trace File Format
43359 @appendix Trace File Format
43360 @cindex trace file format
43362 The trace file comes in three parts: a header, a textual description
43363 section, and a trace frame section with binary data.
43365 The header has the form @code{\x7fTRACE0\n}. The first byte is
43366 @code{0x7f} so as to indicate that the file contains binary data,
43367 while the @code{0} is a version number that may have different values
43370 The description section consists of multiple lines of @sc{ascii} text
43371 separated by newline characters (@code{0xa}). The lines may include a
43372 variety of optional descriptive or context-setting information, such
43373 as tracepoint definitions or register set size. @value{GDBN} will
43374 ignore any line that it does not recognize. An empty line marks the end
43377 @c FIXME add some specific types of data
43379 The trace frame section consists of a number of consecutive frames.
43380 Each frame begins with a two-byte tracepoint number, followed by a
43381 four-byte size giving the amount of data in the frame. The data in
43382 the frame consists of a number of blocks, each introduced by a
43383 character indicating its type (at least register, memory, and trace
43384 state variable). The data in this section is raw binary, not a
43385 hexadecimal or other encoding; its endianness matches the target's
43388 @c FIXME bi-arch may require endianness/arch info in description section
43391 @item R @var{bytes}
43392 Register block. The number and ordering of bytes matches that of a
43393 @code{g} packet in the remote protocol. Note that these are the
43394 actual bytes, in target order and @value{GDBN} register order, not a
43395 hexadecimal encoding.
43397 @item M @var{address} @var{length} @var{bytes}...
43398 Memory block. This is a contiguous block of memory, at the 8-byte
43399 address @var{address}, with a 2-byte length @var{length}, followed by
43400 @var{length} bytes.
43402 @item V @var{number} @var{value}
43403 Trace state variable block. This records the 8-byte signed value
43404 @var{value} of trace state variable numbered @var{number}.
43408 Future enhancements of the trace file format may include additional types
43411 @node Index Section Format
43412 @appendix @code{.gdb_index} section format
43413 @cindex .gdb_index section format
43414 @cindex index section format
43416 This section documents the index section that is created by @code{save
43417 gdb-index} (@pxref{Index Files}). The index section is
43418 DWARF-specific; some knowledge of DWARF is assumed in this
43421 The mapped index file format is designed to be directly
43422 @code{mmap}able on any architecture. In most cases, a datum is
43423 represented using a little-endian 32-bit integer value, called an
43424 @code{offset_type}. Big endian machines must byte-swap the values
43425 before using them. Exceptions to this rule are noted. The data is
43426 laid out such that alignment is always respected.
43428 A mapped index consists of several areas, laid out in order.
43432 The file header. This is a sequence of values, of @code{offset_type}
43433 unless otherwise noted:
43437 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43438 Version 4 uses a different hashing function from versions 5 and 6.
43439 Version 6 includes symbols for inlined functions, whereas versions 4
43440 and 5 do not. Version 7 adds attributes to the CU indices in the
43441 symbol table. Version 8 specifies that symbols from DWARF type units
43442 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43443 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43445 @value{GDBN} will only read version 4, 5, or 6 indices
43446 by specifying @code{set use-deprecated-index-sections on}.
43447 GDB has a workaround for potentially broken version 7 indices so it is
43448 currently not flagged as deprecated.
43451 The offset, from the start of the file, of the CU list.
43454 The offset, from the start of the file, of the types CU list. Note
43455 that this area can be empty, in which case this offset will be equal
43456 to the next offset.
43459 The offset, from the start of the file, of the address area.
43462 The offset, from the start of the file, of the symbol table.
43465 The offset, from the start of the file, of the constant pool.
43469 The CU list. This is a sequence of pairs of 64-bit little-endian
43470 values, sorted by the CU offset. The first element in each pair is
43471 the offset of a CU in the @code{.debug_info} section. The second
43472 element in each pair is the length of that CU. References to a CU
43473 elsewhere in the map are done using a CU index, which is just the
43474 0-based index into this table. Note that if there are type CUs, then
43475 conceptually CUs and type CUs form a single list for the purposes of
43479 The types CU list. This is a sequence of triplets of 64-bit
43480 little-endian values. In a triplet, the first value is the CU offset,
43481 the second value is the type offset in the CU, and the third value is
43482 the type signature. The types CU list is not sorted.
43485 The address area. The address area consists of a sequence of address
43486 entries. Each address entry has three elements:
43490 The low address. This is a 64-bit little-endian value.
43493 The high address. This is a 64-bit little-endian value. Like
43494 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43497 The CU index. This is an @code{offset_type} value.
43501 The symbol table. This is an open-addressed hash table. The size of
43502 the hash table is always a power of 2.
43504 Each slot in the hash table consists of a pair of @code{offset_type}
43505 values. The first value is the offset of the symbol's name in the
43506 constant pool. The second value is the offset of the CU vector in the
43509 If both values are 0, then this slot in the hash table is empty. This
43510 is ok because while 0 is a valid constant pool index, it cannot be a
43511 valid index for both a string and a CU vector.
43513 The hash value for a table entry is computed by applying an
43514 iterative hash function to the symbol's name. Starting with an
43515 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43516 the string is incorporated into the hash using the formula depending on the
43521 The formula is @code{r = r * 67 + c - 113}.
43523 @item Versions 5 to 7
43524 The formula is @code{r = r * 67 + tolower (c) - 113}.
43527 The terminating @samp{\0} is not incorporated into the hash.
43529 The step size used in the hash table is computed via
43530 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43531 value, and @samp{size} is the size of the hash table. The step size
43532 is used to find the next candidate slot when handling a hash
43535 The names of C@t{++} symbols in the hash table are canonicalized. We
43536 don't currently have a simple description of the canonicalization
43537 algorithm; if you intend to create new index sections, you must read
43541 The constant pool. This is simply a bunch of bytes. It is organized
43542 so that alignment is correct: CU vectors are stored first, followed by
43545 A CU vector in the constant pool is a sequence of @code{offset_type}
43546 values. The first value is the number of CU indices in the vector.
43547 Each subsequent value is the index and symbol attributes of a CU in
43548 the CU list. This element in the hash table is used to indicate which
43549 CUs define the symbol and how the symbol is used.
43550 See below for the format of each CU index+attributes entry.
43552 A string in the constant pool is zero-terminated.
43555 Attributes were added to CU index values in @code{.gdb_index} version 7.
43556 If a symbol has multiple uses within a CU then there is one
43557 CU index+attributes value for each use.
43559 The format of each CU index+attributes entry is as follows
43565 This is the index of the CU in the CU list.
43567 These bits are reserved for future purposes and must be zero.
43569 The kind of the symbol in the CU.
43573 This value is reserved and should not be used.
43574 By reserving zero the full @code{offset_type} value is backwards compatible
43575 with previous versions of the index.
43577 The symbol is a type.
43579 The symbol is a variable or an enum value.
43581 The symbol is a function.
43583 Any other kind of symbol.
43585 These values are reserved.
43589 This bit is zero if the value is global and one if it is static.
43591 The determination of whether a symbol is global or static is complicated.
43592 The authorative reference is the file @file{dwarf2read.c} in
43593 @value{GDBN} sources.
43597 This pseudo-code describes the computation of a symbol's kind and
43598 global/static attributes in the index.
43601 is_external = get_attribute (die, DW_AT_external);
43602 language = get_attribute (cu_die, DW_AT_language);
43605 case DW_TAG_typedef:
43606 case DW_TAG_base_type:
43607 case DW_TAG_subrange_type:
43611 case DW_TAG_enumerator:
43613 is_static = (language != CPLUS && language != JAVA);
43615 case DW_TAG_subprogram:
43617 is_static = ! (is_external || language == ADA);
43619 case DW_TAG_constant:
43621 is_static = ! is_external;
43623 case DW_TAG_variable:
43625 is_static = ! is_external;
43627 case DW_TAG_namespace:
43631 case DW_TAG_class_type:
43632 case DW_TAG_interface_type:
43633 case DW_TAG_structure_type:
43634 case DW_TAG_union_type:
43635 case DW_TAG_enumeration_type:
43637 is_static = (language != CPLUS && language != JAVA);
43645 @appendix Manual pages
43649 * gdb man:: The GNU Debugger man page
43650 * gdbserver man:: Remote Server for the GNU Debugger man page
43651 * gcore man:: Generate a core file of a running program
43652 * gdbinit man:: gdbinit scripts
43658 @c man title gdb The GNU Debugger
43660 @c man begin SYNOPSIS gdb
43661 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43662 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43663 [@option{-b}@w{ }@var{bps}]
43664 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43665 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43666 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43667 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43668 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43671 @c man begin DESCRIPTION gdb
43672 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43673 going on ``inside'' another program while it executes -- or what another
43674 program was doing at the moment it crashed.
43676 @value{GDBN} can do four main kinds of things (plus other things in support of
43677 these) to help you catch bugs in the act:
43681 Start your program, specifying anything that might affect its behavior.
43684 Make your program stop on specified conditions.
43687 Examine what has happened, when your program has stopped.
43690 Change things in your program, so you can experiment with correcting the
43691 effects of one bug and go on to learn about another.
43694 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43697 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43698 commands from the terminal until you tell it to exit with the @value{GDBN}
43699 command @code{quit}. You can get online help from @value{GDBN} itself
43700 by using the command @code{help}.
43702 You can run @code{gdb} with no arguments or options; but the most
43703 usual way to start @value{GDBN} is with one argument or two, specifying an
43704 executable program as the argument:
43710 You can also start with both an executable program and a core file specified:
43716 You can, instead, specify a process ID as a second argument, if you want
43717 to debug a running process:
43725 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43726 named @file{1234}; @value{GDBN} does check for a core file first).
43727 With option @option{-p} you can omit the @var{program} filename.
43729 Here are some of the most frequently needed @value{GDBN} commands:
43731 @c pod2man highlights the right hand side of the @item lines.
43733 @item break [@var{file}:]@var{functiop}
43734 Set a breakpoint at @var{function} (in @var{file}).
43736 @item run [@var{arglist}]
43737 Start your program (with @var{arglist}, if specified).
43740 Backtrace: display the program stack.
43742 @item print @var{expr}
43743 Display the value of an expression.
43746 Continue running your program (after stopping, e.g. at a breakpoint).
43749 Execute next program line (after stopping); step @emph{over} any
43750 function calls in the line.
43752 @item edit [@var{file}:]@var{function}
43753 look at the program line where it is presently stopped.
43755 @item list [@var{file}:]@var{function}
43756 type the text of the program in the vicinity of where it is presently stopped.
43759 Execute next program line (after stopping); step @emph{into} any
43760 function calls in the line.
43762 @item help [@var{name}]
43763 Show information about @value{GDBN} command @var{name}, or general information
43764 about using @value{GDBN}.
43767 Exit from @value{GDBN}.
43771 For full details on @value{GDBN},
43772 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43773 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43774 as the @code{gdb} entry in the @code{info} program.
43778 @c man begin OPTIONS gdb
43779 Any arguments other than options specify an executable
43780 file and core file (or process ID); that is, the first argument
43781 encountered with no
43782 associated option flag is equivalent to a @option{-se} option, and the second,
43783 if any, is equivalent to a @option{-c} option if it's the name of a file.
43785 both long and short forms; both are shown here. The long forms are also
43786 recognized if you truncate them, so long as enough of the option is
43787 present to be unambiguous. (If you prefer, you can flag option
43788 arguments with @option{+} rather than @option{-}, though we illustrate the
43789 more usual convention.)
43791 All the options and command line arguments you give are processed
43792 in sequential order. The order makes a difference when the @option{-x}
43798 List all options, with brief explanations.
43800 @item -symbols=@var{file}
43801 @itemx -s @var{file}
43802 Read symbol table from file @var{file}.
43805 Enable writing into executable and core files.
43807 @item -exec=@var{file}
43808 @itemx -e @var{file}
43809 Use file @var{file} as the executable file to execute when
43810 appropriate, and for examining pure data in conjunction with a core
43813 @item -se=@var{file}
43814 Read symbol table from file @var{file} and use it as the executable
43817 @item -core=@var{file}
43818 @itemx -c @var{file}
43819 Use file @var{file} as a core dump to examine.
43821 @item -command=@var{file}
43822 @itemx -x @var{file}
43823 Execute @value{GDBN} commands from file @var{file}.
43825 @item -ex @var{command}
43826 Execute given @value{GDBN} @var{command}.
43828 @item -directory=@var{directory}
43829 @itemx -d @var{directory}
43830 Add @var{directory} to the path to search for source files.
43833 Do not execute commands from @file{~/.gdbinit}.
43837 Do not execute commands from any @file{.gdbinit} initialization files.
43841 ``Quiet''. Do not print the introductory and copyright messages. These
43842 messages are also suppressed in batch mode.
43845 Run in batch mode. Exit with status @code{0} after processing all the command
43846 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43847 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43848 commands in the command files.
43850 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43851 download and run a program on another computer; in order to make this
43852 more useful, the message
43855 Program exited normally.
43859 (which is ordinarily issued whenever a program running under @value{GDBN} control
43860 terminates) is not issued when running in batch mode.
43862 @item -cd=@var{directory}
43863 Run @value{GDBN} using @var{directory} as its working directory,
43864 instead of the current directory.
43868 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43869 @value{GDBN} to output the full file name and line number in a standard,
43870 recognizable fashion each time a stack frame is displayed (which
43871 includes each time the program stops). This recognizable format looks
43872 like two @samp{\032} characters, followed by the file name, line number
43873 and character position separated by colons, and a newline. The
43874 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43875 characters as a signal to display the source code for the frame.
43878 Set the line speed (baud rate or bits per second) of any serial
43879 interface used by @value{GDBN} for remote debugging.
43881 @item -tty=@var{device}
43882 Run using @var{device} for your program's standard input and output.
43886 @c man begin SEEALSO gdb
43888 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43889 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43890 documentation are properly installed at your site, the command
43897 should give you access to the complete manual.
43899 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43900 Richard M. Stallman and Roland H. Pesch, July 1991.
43904 @node gdbserver man
43905 @heading gdbserver man
43907 @c man title gdbserver Remote Server for the GNU Debugger
43909 @c man begin SYNOPSIS gdbserver
43910 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43912 gdbserver --attach @var{comm} @var{pid}
43914 gdbserver --multi @var{comm}
43918 @c man begin DESCRIPTION gdbserver
43919 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43920 than the one which is running the program being debugged.
43923 @subheading Usage (server (target) side)
43926 Usage (server (target) side):
43929 First, you need to have a copy of the program you want to debug put onto
43930 the target system. The program can be stripped to save space if needed, as
43931 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43932 the @value{GDBN} running on the host system.
43934 To use the server, you log on to the target system, and run the @command{gdbserver}
43935 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43936 your program, and (c) its arguments. The general syntax is:
43939 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43942 For example, using a serial port, you might say:
43946 @c @file would wrap it as F</dev/com1>.
43947 target> gdbserver /dev/com1 emacs foo.txt
43950 target> gdbserver @file{/dev/com1} emacs foo.txt
43954 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43955 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43956 waits patiently for the host @value{GDBN} to communicate with it.
43958 To use a TCP connection, you could say:
43961 target> gdbserver host:2345 emacs foo.txt
43964 This says pretty much the same thing as the last example, except that we are
43965 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43966 that we are expecting to see a TCP connection from @code{host} to local TCP port
43967 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43968 want for the port number as long as it does not conflict with any existing TCP
43969 ports on the target system. This same port number must be used in the host
43970 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43971 you chose a port number that conflicts with another service, @command{gdbserver} will
43972 print an error message and exit.
43974 @command{gdbserver} can also attach to running programs.
43975 This is accomplished via the @option{--attach} argument. The syntax is:
43978 target> gdbserver --attach @var{comm} @var{pid}
43981 @var{pid} is the process ID of a currently running process. It isn't
43982 necessary to point @command{gdbserver} at a binary for the running process.
43984 To start @code{gdbserver} without supplying an initial command to run
43985 or process ID to attach, use the @option{--multi} command line option.
43986 In such case you should connect using @kbd{target extended-remote} to start
43987 the program you want to debug.
43990 target> gdbserver --multi @var{comm}
43994 @subheading Usage (host side)
44000 You need an unstripped copy of the target program on your host system, since
44001 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
44002 would, with the target program as the first argument. (You may need to use the
44003 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44004 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44005 new command you need to know about is @code{target remote}
44006 (or @code{target extended-remote}). Its argument is either
44007 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44008 descriptor. For example:
44012 @c @file would wrap it as F</dev/ttyb>.
44013 (gdb) target remote /dev/ttyb
44016 (gdb) target remote @file{/dev/ttyb}
44021 communicates with the server via serial line @file{/dev/ttyb}, and:
44024 (gdb) target remote the-target:2345
44028 communicates via a TCP connection to port 2345 on host `the-target', where
44029 you previously started up @command{gdbserver} with the same port number. Note that for
44030 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44031 command, otherwise you may get an error that looks something like
44032 `Connection refused'.
44034 @command{gdbserver} can also debug multiple inferiors at once,
44037 the @value{GDBN} manual in node @code{Inferiors and Programs}
44038 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44041 @ref{Inferiors and Programs}.
44043 In such case use the @code{extended-remote} @value{GDBN} command variant:
44046 (gdb) target extended-remote the-target:2345
44049 The @command{gdbserver} option @option{--multi} may or may not be used in such
44053 @c man begin OPTIONS gdbserver
44054 There are three different modes for invoking @command{gdbserver}:
44059 Debug a specific program specified by its program name:
44062 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44065 The @var{comm} parameter specifies how should the server communicate
44066 with @value{GDBN}; it is either a device name (to use a serial line),
44067 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44068 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44069 debug in @var{prog}. Any remaining arguments will be passed to the
44070 program verbatim. When the program exits, @value{GDBN} will close the
44071 connection, and @code{gdbserver} will exit.
44074 Debug a specific program by specifying the process ID of a running
44078 gdbserver --attach @var{comm} @var{pid}
44081 The @var{comm} parameter is as described above. Supply the process ID
44082 of a running program in @var{pid}; @value{GDBN} will do everything
44083 else. Like with the previous mode, when the process @var{pid} exits,
44084 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44087 Multi-process mode -- debug more than one program/process:
44090 gdbserver --multi @var{comm}
44093 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44094 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44095 close the connection when a process being debugged exits, so you can
44096 debug several processes in the same session.
44099 In each of the modes you may specify these options:
44104 List all options, with brief explanations.
44107 This option causes @command{gdbserver} to print its version number and exit.
44110 @command{gdbserver} will attach to a running program. The syntax is:
44113 target> gdbserver --attach @var{comm} @var{pid}
44116 @var{pid} is the process ID of a currently running process. It isn't
44117 necessary to point @command{gdbserver} at a binary for the running process.
44120 To start @code{gdbserver} without supplying an initial command to run
44121 or process ID to attach, use this command line option.
44122 Then you can connect using @kbd{target extended-remote} and start
44123 the program you want to debug. The syntax is:
44126 target> gdbserver --multi @var{comm}
44130 Instruct @code{gdbserver} to display extra status information about the debugging
44132 This option is intended for @code{gdbserver} development and for bug reports to
44135 @item --remote-debug
44136 Instruct @code{gdbserver} to display remote protocol debug output.
44137 This option is intended for @code{gdbserver} development and for bug reports to
44141 Specify a wrapper to launch programs
44142 for debugging. The option should be followed by the name of the
44143 wrapper, then any command-line arguments to pass to the wrapper, then
44144 @kbd{--} indicating the end of the wrapper arguments.
44147 By default, @command{gdbserver} keeps the listening TCP port open, so that
44148 additional connections are possible. However, if you start @code{gdbserver}
44149 with the @option{--once} option, it will stop listening for any further
44150 connection attempts after connecting to the first @value{GDBN} session.
44152 @c --disable-packet is not documented for users.
44154 @c --disable-randomization and --no-disable-randomization are superseded by
44155 @c QDisableRandomization.
44160 @c man begin SEEALSO gdbserver
44162 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44163 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44164 documentation are properly installed at your site, the command
44170 should give you access to the complete manual.
44172 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44173 Richard M. Stallman and Roland H. Pesch, July 1991.
44180 @c man title gcore Generate a core file of a running program
44183 @c man begin SYNOPSIS gcore
44184 gcore [-o @var{filename}] @var{pid}
44188 @c man begin DESCRIPTION gcore
44189 Generate a core dump of a running program with process ID @var{pid}.
44190 Produced file is equivalent to a kernel produced core file as if the process
44191 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
44192 limit). Unlike after a crash, after @command{gcore} the program remains
44193 running without any change.
44196 @c man begin OPTIONS gcore
44198 @item -o @var{filename}
44199 The optional argument
44200 @var{filename} specifies the file name where to put the core dump.
44201 If not specified, the file name defaults to @file{core.@var{pid}},
44202 where @var{pid} is the running program process ID.
44206 @c man begin SEEALSO gcore
44208 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44209 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44210 documentation are properly installed at your site, the command
44217 should give you access to the complete manual.
44219 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44220 Richard M. Stallman and Roland H. Pesch, July 1991.
44227 @c man title gdbinit GDB initialization scripts
44230 @c man begin SYNOPSIS gdbinit
44231 @ifset SYSTEM_GDBINIT
44232 @value{SYSTEM_GDBINIT}
44241 @c man begin DESCRIPTION gdbinit
44242 These files contain @value{GDBN} commands to automatically execute during
44243 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44246 the @value{GDBN} manual in node @code{Sequences}
44247 -- shell command @code{info -f gdb -n Sequences}.
44253 Please read more in
44255 the @value{GDBN} manual in node @code{Startup}
44256 -- shell command @code{info -f gdb -n Startup}.
44263 @ifset SYSTEM_GDBINIT
44264 @item @value{SYSTEM_GDBINIT}
44266 @ifclear SYSTEM_GDBINIT
44267 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44269 System-wide initialization file. It is executed unless user specified
44270 @value{GDBN} option @code{-nx} or @code{-n}.
44273 the @value{GDBN} manual in node @code{System-wide configuration}
44274 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44277 @ref{System-wide configuration}.
44281 User initialization file. It is executed unless user specified
44282 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44285 Initialization file for current directory. It may need to be enabled with
44286 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44289 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44290 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44293 @ref{Init File in the Current Directory}.
44298 @c man begin SEEALSO gdbinit
44300 gdb(1), @code{info -f gdb -n Startup}
44302 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44303 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44304 documentation are properly installed at your site, the command
44310 should give you access to the complete manual.
44312 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44313 Richard M. Stallman and Roland H. Pesch, July 1991.
44319 @node GNU Free Documentation License
44320 @appendix GNU Free Documentation License
44323 @node Concept Index
44324 @unnumbered Concept Index
44328 @node Command and Variable Index
44329 @unnumbered Command, Variable, and Function Index
44334 % I think something like @@colophon should be in texinfo. In the
44336 \long\def\colophon{\hbox to0pt{}\vfill
44337 \centerline{The body of this manual is set in}
44338 \centerline{\fontname\tenrm,}
44339 \centerline{with headings in {\bf\fontname\tenbf}}
44340 \centerline{and examples in {\tt\fontname\tentt}.}
44341 \centerline{{\it\fontname\tenit\/},}
44342 \centerline{{\bf\fontname\tenbf}, and}
44343 \centerline{{\sl\fontname\tensl\/}}
44344 \centerline{are used for emphasis.}\vfill}
44346 % Blame: doc@@cygnus.com, 1991.