1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2013 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
51 @c man begin COPYRIGHT
52 Copyright @copyright{} 1988-2013 Free Software Foundation, Inc.
54 Permission is granted to copy, distribute and/or modify this document
55 under the terms of the GNU Free Documentation License, Version 1.3 or
56 any later version published by the Free Software Foundation; with the
57 Invariant Sections being ``Free Software'' and ``Free Software Needs
58 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
59 and with the Back-Cover Texts as in (a) below.
61 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
62 this GNU Manual. Buying copies from GNU Press supports the FSF in
63 developing GNU and promoting software freedom.''
68 This file documents the @sc{gnu} debugger @value{GDBN}.
70 This is the @value{EDITION} Edition, of @cite{Debugging with
71 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
72 @ifset VERSION_PACKAGE
73 @value{VERSION_PACKAGE}
75 Version @value{GDBVN}.
81 @title Debugging with @value{GDBN}
82 @subtitle The @sc{gnu} Source-Level Debugger
84 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
85 @ifset VERSION_PACKAGE
87 @subtitle @value{VERSION_PACKAGE}
89 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
93 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
94 \hfill {\it Debugging with @value{GDBN}}\par
95 \hfill \TeX{}info \texinfoversion\par
99 @vskip 0pt plus 1filll
100 Published by the Free Software Foundation @*
101 51 Franklin Street, Fifth Floor,
102 Boston, MA 02110-1301, USA@*
103 ISBN 978-0-9831592-3-0 @*
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2013 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Process Record and Replay:: Recording inferior's execution and replaying it
138 * Stack:: Examining the stack
139 * Source:: Examining source files
140 * Data:: Examining data
141 * Optimized Code:: Debugging optimized code
142 * Macros:: Preprocessor Macros
143 * Tracepoints:: Debugging remote targets non-intrusively
144 * Overlays:: Debugging programs that use overlays
146 * Languages:: Using @value{GDBN} with different languages
148 * Symbols:: Examining the symbol table
149 * Altering:: Altering execution
150 * GDB Files:: @value{GDBN} files
151 * Targets:: Specifying a debugging target
152 * Remote Debugging:: Debugging remote programs
153 * Configurations:: Configuration-specific information
154 * Controlling GDB:: Controlling @value{GDBN}
155 * Extending GDB:: Extending @value{GDBN}
156 * Interpreters:: Command Interpreters
157 * TUI:: @value{GDBN} Text User Interface
158 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
159 * GDB/MI:: @value{GDBN}'s Machine Interface.
160 * Annotations:: @value{GDBN}'s annotation interface.
161 * JIT Interface:: Using the JIT debugging interface.
162 * In-Process Agent:: In-Process Agent
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 @ifset SYSTEM_READLINE
167 * Command Line Editing: (rluserman). Command Line Editing
168 * Using History Interactively: (history). Using History Interactively
170 @ifclear SYSTEM_READLINE
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
174 * In Memoriam:: In Memoriam
175 * Formatting Documentation:: How to format and print @value{GDBN} documentation
176 * Installing GDB:: Installing GDB
177 * Maintenance Commands:: Maintenance Commands
178 * Remote Protocol:: GDB Remote Serial Protocol
179 * Agent Expressions:: The GDB Agent Expression Mechanism
180 * Target Descriptions:: How targets can describe themselves to
182 * Operating System Information:: Getting additional information from
184 * Trace File Format:: GDB trace file format
185 * Index Section Format:: .gdb_index section format
186 * Man Pages:: Manual pages
187 * Copying:: GNU General Public License says
188 how you can copy and share GDB
189 * GNU Free Documentation License:: The license for this documentation
190 * Concept Index:: Index of @value{GDBN} concepts
191 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
192 functions, and Python data types
200 @unnumbered Summary of @value{GDBN}
202 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
203 going on ``inside'' another program while it executes---or what another
204 program was doing at the moment it crashed.
206 @value{GDBN} can do four main kinds of things (plus other things in support of
207 these) to help you catch bugs in the act:
211 Start your program, specifying anything that might affect its behavior.
214 Make your program stop on specified conditions.
217 Examine what has happened, when your program has stopped.
220 Change things in your program, so you can experiment with correcting the
221 effects of one bug and go on to learn about another.
224 You can use @value{GDBN} to debug programs written in C and C@t{++}.
225 For more information, see @ref{Supported Languages,,Supported Languages}.
226 For more information, see @ref{C,,C and C++}.
228 Support for D is partial. For information on D, see
232 Support for Modula-2 is partial. For information on Modula-2, see
233 @ref{Modula-2,,Modula-2}.
235 Support for OpenCL C is partial. For information on OpenCL C, see
236 @ref{OpenCL C,,OpenCL C}.
239 Debugging Pascal programs which use sets, subranges, file variables, or
240 nested functions does not currently work. @value{GDBN} does not support
241 entering expressions, printing values, or similar features using Pascal
245 @value{GDBN} can be used to debug programs written in Fortran, although
246 it may be necessary to refer to some variables with a trailing
249 @value{GDBN} can be used to debug programs written in Objective-C,
250 using either the Apple/NeXT or the GNU Objective-C runtime.
253 * Free Software:: Freely redistributable software
254 * Free Documentation:: Free Software Needs Free Documentation
255 * Contributors:: Contributors to GDB
259 @unnumberedsec Free Software
261 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
262 General Public License
263 (GPL). The GPL gives you the freedom to copy or adapt a licensed
264 program---but every person getting a copy also gets with it the
265 freedom to modify that copy (which means that they must get access to
266 the source code), and the freedom to distribute further copies.
267 Typical software companies use copyrights to limit your freedoms; the
268 Free Software Foundation uses the GPL to preserve these freedoms.
270 Fundamentally, the General Public License is a license which says that
271 you have these freedoms and that you cannot take these freedoms away
274 @node Free Documentation
275 @unnumberedsec Free Software Needs Free Documentation
277 The biggest deficiency in the free software community today is not in
278 the software---it is the lack of good free documentation that we can
279 include with the free software. Many of our most important
280 programs do not come with free reference manuals and free introductory
281 texts. Documentation is an essential part of any software package;
282 when an important free software package does not come with a free
283 manual and a free tutorial, that is a major gap. We have many such
286 Consider Perl, for instance. The tutorial manuals that people
287 normally use are non-free. How did this come about? Because the
288 authors of those manuals published them with restrictive terms---no
289 copying, no modification, source files not available---which exclude
290 them from the free software world.
292 That wasn't the first time this sort of thing happened, and it was far
293 from the last. Many times we have heard a GNU user eagerly describe a
294 manual that he is writing, his intended contribution to the community,
295 only to learn that he had ruined everything by signing a publication
296 contract to make it non-free.
298 Free documentation, like free software, is a matter of freedom, not
299 price. The problem with the non-free manual is not that publishers
300 charge a price for printed copies---that in itself is fine. (The Free
301 Software Foundation sells printed copies of manuals, too.) The
302 problem is the restrictions on the use of the manual. Free manuals
303 are available in source code form, and give you permission to copy and
304 modify. Non-free manuals do not allow this.
306 The criteria of freedom for a free manual are roughly the same as for
307 free software. Redistribution (including the normal kinds of
308 commercial redistribution) must be permitted, so that the manual can
309 accompany every copy of the program, both on-line and on paper.
311 Permission for modification of the technical content is crucial too.
312 When people modify the software, adding or changing features, if they
313 are conscientious they will change the manual too---so they can
314 provide accurate and clear documentation for the modified program. A
315 manual that leaves you no choice but to write a new manual to document
316 a changed version of the program is not really available to our
319 Some kinds of limits on the way modification is handled are
320 acceptable. For example, requirements to preserve the original
321 author's copyright notice, the distribution terms, or the list of
322 authors, are ok. It is also no problem to require modified versions
323 to include notice that they were modified. Even entire sections that
324 may not be deleted or changed are acceptable, as long as they deal
325 with nontechnical topics (like this one). These kinds of restrictions
326 are acceptable because they don't obstruct the community's normal use
329 However, it must be possible to modify all the @emph{technical}
330 content of the manual, and then distribute the result in all the usual
331 media, through all the usual channels. Otherwise, the restrictions
332 obstruct the use of the manual, it is not free, and we need another
333 manual to replace it.
335 Please spread the word about this issue. Our community continues to
336 lose manuals to proprietary publishing. If we spread the word that
337 free software needs free reference manuals and free tutorials, perhaps
338 the next person who wants to contribute by writing documentation will
339 realize, before it is too late, that only free manuals contribute to
340 the free software community.
342 If you are writing documentation, please insist on publishing it under
343 the GNU Free Documentation License or another free documentation
344 license. Remember that this decision requires your approval---you
345 don't have to let the publisher decide. Some commercial publishers
346 will use a free license if you insist, but they will not propose the
347 option; it is up to you to raise the issue and say firmly that this is
348 what you want. If the publisher you are dealing with refuses, please
349 try other publishers. If you're not sure whether a proposed license
350 is free, write to @email{licensing@@gnu.org}.
352 You can encourage commercial publishers to sell more free, copylefted
353 manuals and tutorials by buying them, and particularly by buying
354 copies from the publishers that paid for their writing or for major
355 improvements. Meanwhile, try to avoid buying non-free documentation
356 at all. Check the distribution terms of a manual before you buy it,
357 and insist that whoever seeks your business must respect your freedom.
358 Check the history of the book, and try to reward the publishers that
359 have paid or pay the authors to work on it.
361 The Free Software Foundation maintains a list of free documentation
362 published by other publishers, at
363 @url{http://www.fsf.org/doc/other-free-books.html}.
366 @unnumberedsec Contributors to @value{GDBN}
368 Richard Stallman was the original author of @value{GDBN}, and of many
369 other @sc{gnu} programs. Many others have contributed to its
370 development. This section attempts to credit major contributors. One
371 of the virtues of free software is that everyone is free to contribute
372 to it; with regret, we cannot actually acknowledge everyone here. The
373 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
374 blow-by-blow account.
376 Changes much prior to version 2.0 are lost in the mists of time.
379 @emph{Plea:} Additions to this section are particularly welcome. If you
380 or your friends (or enemies, to be evenhanded) have been unfairly
381 omitted from this list, we would like to add your names!
384 So that they may not regard their many labors as thankless, we
385 particularly thank those who shepherded @value{GDBN} through major
387 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
388 Jim Blandy (release 4.18);
389 Jason Molenda (release 4.17);
390 Stan Shebs (release 4.14);
391 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
392 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
393 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
394 Jim Kingdon (releases 3.5, 3.4, and 3.3);
395 and Randy Smith (releases 3.2, 3.1, and 3.0).
397 Richard Stallman, assisted at various times by Peter TerMaat, Chris
398 Hanson, and Richard Mlynarik, handled releases through 2.8.
400 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
401 in @value{GDBN}, with significant additional contributions from Per
402 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
403 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
404 much general update work leading to release 3.0).
406 @value{GDBN} uses the BFD subroutine library to examine multiple
407 object-file formats; BFD was a joint project of David V.
408 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
410 David Johnson wrote the original COFF support; Pace Willison did
411 the original support for encapsulated COFF.
413 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
415 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
416 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
418 Jean-Daniel Fekete contributed Sun 386i support.
419 Chris Hanson improved the HP9000 support.
420 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
421 David Johnson contributed Encore Umax support.
422 Jyrki Kuoppala contributed Altos 3068 support.
423 Jeff Law contributed HP PA and SOM support.
424 Keith Packard contributed NS32K support.
425 Doug Rabson contributed Acorn Risc Machine support.
426 Bob Rusk contributed Harris Nighthawk CX-UX support.
427 Chris Smith contributed Convex support (and Fortran debugging).
428 Jonathan Stone contributed Pyramid support.
429 Michael Tiemann contributed SPARC support.
430 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
431 Pace Willison contributed Intel 386 support.
432 Jay Vosburgh contributed Symmetry support.
433 Marko Mlinar contributed OpenRISC 1000 support.
435 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
437 Rich Schaefer and Peter Schauer helped with support of SunOS shared
440 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
441 about several machine instruction sets.
443 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
444 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
445 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
446 and RDI targets, respectively.
448 Brian Fox is the author of the readline libraries providing
449 command-line editing and command history.
451 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
452 Modula-2 support, and contributed the Languages chapter of this manual.
454 Fred Fish wrote most of the support for Unix System Vr4.
455 He also enhanced the command-completion support to cover C@t{++} overloaded
458 Hitachi America (now Renesas America), Ltd. sponsored the support for
459 H8/300, H8/500, and Super-H processors.
461 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
463 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
466 Toshiba sponsored the support for the TX39 Mips processor.
468 Matsushita sponsored the support for the MN10200 and MN10300 processors.
470 Fujitsu sponsored the support for SPARClite and FR30 processors.
472 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
475 Michael Snyder added support for tracepoints.
477 Stu Grossman wrote gdbserver.
479 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
480 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
482 The following people at the Hewlett-Packard Company contributed
483 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
484 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
485 compiler, and the Text User Interface (nee Terminal User Interface):
486 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
487 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
488 provided HP-specific information in this manual.
490 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
491 Robert Hoehne made significant contributions to the DJGPP port.
493 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
494 development since 1991. Cygnus engineers who have worked on @value{GDBN}
495 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
496 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
497 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
498 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
499 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
500 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
501 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
502 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
503 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
504 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
505 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
506 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
507 Zuhn have made contributions both large and small.
509 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
510 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
512 Jim Blandy added support for preprocessor macros, while working for Red
515 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
516 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
517 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
518 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
519 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
520 with the migration of old architectures to this new framework.
522 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
523 unwinder framework, this consisting of a fresh new design featuring
524 frame IDs, independent frame sniffers, and the sentinel frame. Mark
525 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
526 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
527 trad unwinders. The architecture-specific changes, each involving a
528 complete rewrite of the architecture's frame code, were carried out by
529 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
530 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
531 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
532 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
535 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
536 Tensilica, Inc.@: contributed support for Xtensa processors. Others
537 who have worked on the Xtensa port of @value{GDBN} in the past include
538 Steve Tjiang, John Newlin, and Scott Foehner.
540 Michael Eager and staff of Xilinx, Inc., contributed support for the
541 Xilinx MicroBlaze architecture.
544 @chapter A Sample @value{GDBN} Session
546 You can use this manual at your leisure to read all about @value{GDBN}.
547 However, a handful of commands are enough to get started using the
548 debugger. This chapter illustrates those commands.
551 In this sample session, we emphasize user input like this: @b{input},
552 to make it easier to pick out from the surrounding output.
555 @c FIXME: this example may not be appropriate for some configs, where
556 @c FIXME...primary interest is in remote use.
558 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
559 processor) exhibits the following bug: sometimes, when we change its
560 quote strings from the default, the commands used to capture one macro
561 definition within another stop working. In the following short @code{m4}
562 session, we define a macro @code{foo} which expands to @code{0000}; we
563 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
564 same thing. However, when we change the open quote string to
565 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
566 procedure fails to define a new synonym @code{baz}:
575 @b{define(bar,defn(`foo'))}
579 @b{changequote(<QUOTE>,<UNQUOTE>)}
581 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
584 m4: End of input: 0: fatal error: EOF in string
588 Let us use @value{GDBN} to try to see what is going on.
591 $ @b{@value{GDBP} m4}
592 @c FIXME: this falsifies the exact text played out, to permit smallbook
593 @c FIXME... format to come out better.
594 @value{GDBN} is free software and you are welcome to distribute copies
595 of it under certain conditions; type "show copying" to see
597 There is absolutely no warranty for @value{GDBN}; type "show warranty"
600 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
605 @value{GDBN} reads only enough symbol data to know where to find the
606 rest when needed; as a result, the first prompt comes up very quickly.
607 We now tell @value{GDBN} to use a narrower display width than usual, so
608 that examples fit in this manual.
611 (@value{GDBP}) @b{set width 70}
615 We need to see how the @code{m4} built-in @code{changequote} works.
616 Having looked at the source, we know the relevant subroutine is
617 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
618 @code{break} command.
621 (@value{GDBP}) @b{break m4_changequote}
622 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
626 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
627 control; as long as control does not reach the @code{m4_changequote}
628 subroutine, the program runs as usual:
631 (@value{GDBP}) @b{run}
632 Starting program: /work/Editorial/gdb/gnu/m4/m4
640 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
641 suspends execution of @code{m4}, displaying information about the
642 context where it stops.
645 @b{changequote(<QUOTE>,<UNQUOTE>)}
647 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
649 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
653 Now we use the command @code{n} (@code{next}) to advance execution to
654 the next line of the current function.
658 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
663 @code{set_quotes} looks like a promising subroutine. We can go into it
664 by using the command @code{s} (@code{step}) instead of @code{next}.
665 @code{step} goes to the next line to be executed in @emph{any}
666 subroutine, so it steps into @code{set_quotes}.
670 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
672 530 if (lquote != def_lquote)
676 The display that shows the subroutine where @code{m4} is now
677 suspended (and its arguments) is called a stack frame display. It
678 shows a summary of the stack. We can use the @code{backtrace}
679 command (which can also be spelled @code{bt}), to see where we are
680 in the stack as a whole: the @code{backtrace} command displays a
681 stack frame for each active subroutine.
684 (@value{GDBP}) @b{bt}
685 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
687 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
689 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
690 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
692 #4 0x79dc in expand_input () at macro.c:40
693 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
697 We step through a few more lines to see what happens. The first two
698 times, we can use @samp{s}; the next two times we use @code{n} to avoid
699 falling into the @code{xstrdup} subroutine.
703 0x3b5c 532 if (rquote != def_rquote)
705 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
706 def_lquote : xstrdup(lq);
708 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
711 538 len_lquote = strlen(rquote);
715 The last line displayed looks a little odd; we can examine the variables
716 @code{lquote} and @code{rquote} to see if they are in fact the new left
717 and right quotes we specified. We use the command @code{p}
718 (@code{print}) to see their values.
721 (@value{GDBP}) @b{p lquote}
722 $1 = 0x35d40 "<QUOTE>"
723 (@value{GDBP}) @b{p rquote}
724 $2 = 0x35d50 "<UNQUOTE>"
728 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
729 To look at some context, we can display ten lines of source
730 surrounding the current line with the @code{l} (@code{list}) command.
736 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
738 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
741 538 len_lquote = strlen(rquote);
742 539 len_rquote = strlen(lquote);
749 Let us step past the two lines that set @code{len_lquote} and
750 @code{len_rquote}, and then examine the values of those variables.
754 539 len_rquote = strlen(lquote);
757 (@value{GDBP}) @b{p len_lquote}
759 (@value{GDBP}) @b{p len_rquote}
764 That certainly looks wrong, assuming @code{len_lquote} and
765 @code{len_rquote} are meant to be the lengths of @code{lquote} and
766 @code{rquote} respectively. We can set them to better values using
767 the @code{p} command, since it can print the value of
768 any expression---and that expression can include subroutine calls and
772 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
774 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
779 Is that enough to fix the problem of using the new quotes with the
780 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
781 executing with the @code{c} (@code{continue}) command, and then try the
782 example that caused trouble initially:
788 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
795 Success! The new quotes now work just as well as the default ones. The
796 problem seems to have been just the two typos defining the wrong
797 lengths. We allow @code{m4} exit by giving it an EOF as input:
801 Program exited normally.
805 The message @samp{Program exited normally.} is from @value{GDBN}; it
806 indicates @code{m4} has finished executing. We can end our @value{GDBN}
807 session with the @value{GDBN} @code{quit} command.
810 (@value{GDBP}) @b{quit}
814 @chapter Getting In and Out of @value{GDBN}
816 This chapter discusses how to start @value{GDBN}, and how to get out of it.
820 type @samp{@value{GDBP}} to start @value{GDBN}.
822 type @kbd{quit} or @kbd{Ctrl-d} to exit.
826 * Invoking GDB:: How to start @value{GDBN}
827 * Quitting GDB:: How to quit @value{GDBN}
828 * Shell Commands:: How to use shell commands inside @value{GDBN}
829 * Logging Output:: How to log @value{GDBN}'s output to a file
833 @section Invoking @value{GDBN}
835 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
836 @value{GDBN} reads commands from the terminal until you tell it to exit.
838 You can also run @code{@value{GDBP}} with a variety of arguments and options,
839 to specify more of your debugging environment at the outset.
841 The command-line options described here are designed
842 to cover a variety of situations; in some environments, some of these
843 options may effectively be unavailable.
845 The most usual way to start @value{GDBN} is with one argument,
846 specifying an executable program:
849 @value{GDBP} @var{program}
853 You can also start with both an executable program and a core file
857 @value{GDBP} @var{program} @var{core}
860 You can, instead, specify a process ID as a second argument, if you want
861 to debug a running process:
864 @value{GDBP} @var{program} 1234
868 would attach @value{GDBN} to process @code{1234} (unless you also have a file
869 named @file{1234}; @value{GDBN} does check for a core file first).
871 Taking advantage of the second command-line argument requires a fairly
872 complete operating system; when you use @value{GDBN} as a remote
873 debugger attached to a bare board, there may not be any notion of
874 ``process'', and there is often no way to get a core dump. @value{GDBN}
875 will warn you if it is unable to attach or to read core dumps.
877 You can optionally have @code{@value{GDBP}} pass any arguments after the
878 executable file to the inferior using @code{--args}. This option stops
881 @value{GDBP} --args gcc -O2 -c foo.c
883 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
884 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
886 You can run @code{@value{GDBP}} without printing the front material, which describes
887 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
894 You can further control how @value{GDBN} starts up by using command-line
895 options. @value{GDBN} itself can remind you of the options available.
905 to display all available options and briefly describe their use
906 (@samp{@value{GDBP} -h} is a shorter equivalent).
908 All options and command line arguments you give are processed
909 in sequential order. The order makes a difference when the
910 @samp{-x} option is used.
914 * File Options:: Choosing files
915 * Mode Options:: Choosing modes
916 * Startup:: What @value{GDBN} does during startup
920 @subsection Choosing Files
922 When @value{GDBN} starts, it reads any arguments other than options as
923 specifying an executable file and core file (or process ID). This is
924 the same as if the arguments were specified by the @samp{-se} and
925 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
926 first argument that does not have an associated option flag as
927 equivalent to the @samp{-se} option followed by that argument; and the
928 second argument that does not have an associated option flag, if any, as
929 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
930 If the second argument begins with a decimal digit, @value{GDBN} will
931 first attempt to attach to it as a process, and if that fails, attempt
932 to open it as a corefile. If you have a corefile whose name begins with
933 a digit, you can prevent @value{GDBN} from treating it as a pid by
934 prefixing it with @file{./}, e.g.@: @file{./12345}.
936 If @value{GDBN} has not been configured to included core file support,
937 such as for most embedded targets, then it will complain about a second
938 argument and ignore it.
940 Many options have both long and short forms; both are shown in the
941 following list. @value{GDBN} also recognizes the long forms if you truncate
942 them, so long as enough of the option is present to be unambiguous.
943 (If you prefer, you can flag option arguments with @samp{--} rather
944 than @samp{-}, though we illustrate the more usual convention.)
946 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
947 @c way, both those who look for -foo and --foo in the index, will find
951 @item -symbols @var{file}
953 @cindex @code{--symbols}
955 Read symbol table from file @var{file}.
957 @item -exec @var{file}
959 @cindex @code{--exec}
961 Use file @var{file} as the executable file to execute when appropriate,
962 and for examining pure data in conjunction with a core dump.
966 Read symbol table from file @var{file} and use it as the executable
969 @item -core @var{file}
971 @cindex @code{--core}
973 Use file @var{file} as a core dump to examine.
975 @item -pid @var{number}
976 @itemx -p @var{number}
979 Connect to process ID @var{number}, as with the @code{attach} command.
981 @item -command @var{file}
983 @cindex @code{--command}
985 Execute commands from file @var{file}. The contents of this file is
986 evaluated exactly as the @code{source} command would.
987 @xref{Command Files,, Command files}.
989 @item -eval-command @var{command}
990 @itemx -ex @var{command}
991 @cindex @code{--eval-command}
993 Execute a single @value{GDBN} command.
995 This option may be used multiple times to call multiple commands. It may
996 also be interleaved with @samp{-command} as required.
999 @value{GDBP} -ex 'target sim' -ex 'load' \
1000 -x setbreakpoints -ex 'run' a.out
1003 @item -init-command @var{file}
1004 @itemx -ix @var{file}
1005 @cindex @code{--init-command}
1007 Execute commands from file @var{file} before loading the inferior (but
1008 after loading gdbinit files).
1011 @item -init-eval-command @var{command}
1012 @itemx -iex @var{command}
1013 @cindex @code{--init-eval-command}
1015 Execute a single @value{GDBN} command before loading the inferior (but
1016 after loading gdbinit files).
1019 @item -directory @var{directory}
1020 @itemx -d @var{directory}
1021 @cindex @code{--directory}
1023 Add @var{directory} to the path to search for source and script files.
1027 @cindex @code{--readnow}
1029 Read each symbol file's entire symbol table immediately, rather than
1030 the default, which is to read it incrementally as it is needed.
1031 This makes startup slower, but makes future operations faster.
1036 @subsection Choosing Modes
1038 You can run @value{GDBN} in various alternative modes---for example, in
1039 batch mode or quiet mode.
1047 Do not execute commands found in any initialization file.
1048 There are three init files, loaded in the following order:
1051 @item @file{system.gdbinit}
1052 This is the system-wide init file.
1053 Its location is specified with the @code{--with-system-gdbinit}
1054 configure option (@pxref{System-wide configuration}).
1055 It is loaded first when @value{GDBN} starts, before command line options
1056 have been processed.
1057 @item @file{~/.gdbinit}
1058 This is the init file in your home directory.
1059 It is loaded next, after @file{system.gdbinit}, and before
1060 command options have been processed.
1061 @item @file{./.gdbinit}
1062 This is the init file in the current directory.
1063 It is loaded last, after command line options other than @code{-x} and
1064 @code{-ex} have been processed. Command line options @code{-x} and
1065 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1068 For further documentation on startup processing, @xref{Startup}.
1069 For documentation on how to write command files,
1070 @xref{Command Files,,Command Files}.
1075 Do not execute commands found in @file{~/.gdbinit}, the init file
1076 in your home directory.
1082 @cindex @code{--quiet}
1083 @cindex @code{--silent}
1085 ``Quiet''. Do not print the introductory and copyright messages. These
1086 messages are also suppressed in batch mode.
1089 @cindex @code{--batch}
1090 Run in batch mode. Exit with status @code{0} after processing all the
1091 command files specified with @samp{-x} (and all commands from
1092 initialization files, if not inhibited with @samp{-n}). Exit with
1093 nonzero status if an error occurs in executing the @value{GDBN} commands
1094 in the command files. Batch mode also disables pagination, sets unlimited
1095 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1096 off} were in effect (@pxref{Messages/Warnings}).
1098 Batch mode may be useful for running @value{GDBN} as a filter, for
1099 example to download and run a program on another computer; in order to
1100 make this more useful, the message
1103 Program exited normally.
1107 (which is ordinarily issued whenever a program running under
1108 @value{GDBN} control terminates) is not issued when running in batch
1112 @cindex @code{--batch-silent}
1113 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1114 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1115 unaffected). This is much quieter than @samp{-silent} and would be useless
1116 for an interactive session.
1118 This is particularly useful when using targets that give @samp{Loading section}
1119 messages, for example.
1121 Note that targets that give their output via @value{GDBN}, as opposed to
1122 writing directly to @code{stdout}, will also be made silent.
1124 @item -return-child-result
1125 @cindex @code{--return-child-result}
1126 The return code from @value{GDBN} will be the return code from the child
1127 process (the process being debugged), with the following exceptions:
1131 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1132 internal error. In this case the exit code is the same as it would have been
1133 without @samp{-return-child-result}.
1135 The user quits with an explicit value. E.g., @samp{quit 1}.
1137 The child process never runs, or is not allowed to terminate, in which case
1138 the exit code will be -1.
1141 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1142 when @value{GDBN} is being used as a remote program loader or simulator
1147 @cindex @code{--nowindows}
1149 ``No windows''. If @value{GDBN} comes with a graphical user interface
1150 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1151 interface. If no GUI is available, this option has no effect.
1155 @cindex @code{--windows}
1157 If @value{GDBN} includes a GUI, then this option requires it to be
1160 @item -cd @var{directory}
1162 Run @value{GDBN} using @var{directory} as its working directory,
1163 instead of the current directory.
1165 @item -data-directory @var{directory}
1166 @cindex @code{--data-directory}
1167 Run @value{GDBN} using @var{directory} as its data directory.
1168 The data directory is where @value{GDBN} searches for its
1169 auxiliary files. @xref{Data Files}.
1173 @cindex @code{--fullname}
1175 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1176 subprocess. It tells @value{GDBN} to output the full file name and line
1177 number in a standard, recognizable fashion each time a stack frame is
1178 displayed (which includes each time your program stops). This
1179 recognizable format looks like two @samp{\032} characters, followed by
1180 the file name, line number and character position separated by colons,
1181 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1182 @samp{\032} characters as a signal to display the source code for the
1185 @item -annotate @var{level}
1186 @cindex @code{--annotate}
1187 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1188 effect is identical to using @samp{set annotate @var{level}}
1189 (@pxref{Annotations}). The annotation @var{level} controls how much
1190 information @value{GDBN} prints together with its prompt, values of
1191 expressions, source lines, and other types of output. Level 0 is the
1192 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1193 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1194 that control @value{GDBN}, and level 2 has been deprecated.
1196 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1200 @cindex @code{--args}
1201 Change interpretation of command line so that arguments following the
1202 executable file are passed as command line arguments to the inferior.
1203 This option stops option processing.
1205 @item -baud @var{bps}
1207 @cindex @code{--baud}
1209 Set the line speed (baud rate or bits per second) of any serial
1210 interface used by @value{GDBN} for remote debugging.
1212 @item -l @var{timeout}
1214 Set the timeout (in seconds) of any communication used by @value{GDBN}
1215 for remote debugging.
1217 @item -tty @var{device}
1218 @itemx -t @var{device}
1219 @cindex @code{--tty}
1221 Run using @var{device} for your program's standard input and output.
1222 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1224 @c resolve the situation of these eventually
1226 @cindex @code{--tui}
1227 Activate the @dfn{Text User Interface} when starting. The Text User
1228 Interface manages several text windows on the terminal, showing
1229 source, assembly, registers and @value{GDBN} command outputs
1230 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1231 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1232 Using @value{GDBN} under @sc{gnu} Emacs}).
1235 @c @cindex @code{--xdb}
1236 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1237 @c For information, see the file @file{xdb_trans.html}, which is usually
1238 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1241 @item -interpreter @var{interp}
1242 @cindex @code{--interpreter}
1243 Use the interpreter @var{interp} for interface with the controlling
1244 program or device. This option is meant to be set by programs which
1245 communicate with @value{GDBN} using it as a back end.
1246 @xref{Interpreters, , Command Interpreters}.
1248 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1249 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1250 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1251 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1252 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1253 @sc{gdb/mi} interfaces are no longer supported.
1256 @cindex @code{--write}
1257 Open the executable and core files for both reading and writing. This
1258 is equivalent to the @samp{set write on} command inside @value{GDBN}
1262 @cindex @code{--statistics}
1263 This option causes @value{GDBN} to print statistics about time and
1264 memory usage after it completes each command and returns to the prompt.
1267 @cindex @code{--version}
1268 This option causes @value{GDBN} to print its version number and
1269 no-warranty blurb, and exit.
1271 @item -configuration
1272 @cindex @code{--configuration}
1273 This option causes @value{GDBN} to print details about its build-time
1274 configuration parameters, and then exit. These details can be
1275 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1280 @subsection What @value{GDBN} Does During Startup
1281 @cindex @value{GDBN} startup
1283 Here's the description of what @value{GDBN} does during session startup:
1287 Sets up the command interpreter as specified by the command line
1288 (@pxref{Mode Options, interpreter}).
1292 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1293 used when building @value{GDBN}; @pxref{System-wide configuration,
1294 ,System-wide configuration and settings}) and executes all the commands in
1297 @anchor{Home Directory Init File}
1299 Reads the init file (if any) in your home directory@footnote{On
1300 DOS/Windows systems, the home directory is the one pointed to by the
1301 @code{HOME} environment variable.} and executes all the commands in
1304 @anchor{Option -init-eval-command}
1306 Executes commands and command files specified by the @samp{-iex} and
1307 @samp{-ix} options in their specified order. Usually you should use the
1308 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1309 settings before @value{GDBN} init files get executed and before inferior
1313 Processes command line options and operands.
1315 @anchor{Init File in the Current Directory during Startup}
1317 Reads and executes the commands from init file (if any) in the current
1318 working directory as long as @samp{set auto-load local-gdbinit} is set to
1319 @samp{on} (@pxref{Init File in the Current Directory}).
1320 This is only done if the current directory is
1321 different from your home directory. Thus, you can have more than one
1322 init file, one generic in your home directory, and another, specific
1323 to the program you are debugging, in the directory where you invoke
1327 If the command line specified a program to debug, or a process to
1328 attach to, or a core file, @value{GDBN} loads any auto-loaded
1329 scripts provided for the program or for its loaded shared libraries.
1330 @xref{Auto-loading}.
1332 If you wish to disable the auto-loading during startup,
1333 you must do something like the following:
1336 $ gdb -iex "set auto-load python-scripts off" myprogram
1339 Option @samp{-ex} does not work because the auto-loading is then turned
1343 Executes commands and command files specified by the @samp{-ex} and
1344 @samp{-x} options in their specified order. @xref{Command Files}, for
1345 more details about @value{GDBN} command files.
1348 Reads the command history recorded in the @dfn{history file}.
1349 @xref{Command History}, for more details about the command history and the
1350 files where @value{GDBN} records it.
1353 Init files use the same syntax as @dfn{command files} (@pxref{Command
1354 Files}) and are processed by @value{GDBN} in the same way. The init
1355 file in your home directory can set options (such as @samp{set
1356 complaints}) that affect subsequent processing of command line options
1357 and operands. Init files are not executed if you use the @samp{-nx}
1358 option (@pxref{Mode Options, ,Choosing Modes}).
1360 To display the list of init files loaded by gdb at startup, you
1361 can use @kbd{gdb --help}.
1363 @cindex init file name
1364 @cindex @file{.gdbinit}
1365 @cindex @file{gdb.ini}
1366 The @value{GDBN} init files are normally called @file{.gdbinit}.
1367 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1368 the limitations of file names imposed by DOS filesystems. The Windows
1369 port of @value{GDBN} uses the standard name, but if it finds a
1370 @file{gdb.ini} file in your home directory, it warns you about that
1371 and suggests to rename the file to the standard name.
1375 @section Quitting @value{GDBN}
1376 @cindex exiting @value{GDBN}
1377 @cindex leaving @value{GDBN}
1380 @kindex quit @r{[}@var{expression}@r{]}
1381 @kindex q @r{(@code{quit})}
1382 @item quit @r{[}@var{expression}@r{]}
1384 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1385 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1386 do not supply @var{expression}, @value{GDBN} will terminate normally;
1387 otherwise it will terminate using the result of @var{expression} as the
1392 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1393 terminates the action of any @value{GDBN} command that is in progress and
1394 returns to @value{GDBN} command level. It is safe to type the interrupt
1395 character at any time because @value{GDBN} does not allow it to take effect
1396 until a time when it is safe.
1398 If you have been using @value{GDBN} to control an attached process or
1399 device, you can release it with the @code{detach} command
1400 (@pxref{Attach, ,Debugging an Already-running Process}).
1402 @node Shell Commands
1403 @section Shell Commands
1405 If you need to execute occasional shell commands during your
1406 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1407 just use the @code{shell} command.
1412 @cindex shell escape
1413 @item shell @var{command-string}
1414 @itemx !@var{command-string}
1415 Invoke a standard shell to execute @var{command-string}.
1416 Note that no space is needed between @code{!} and @var{command-string}.
1417 If it exists, the environment variable @code{SHELL} determines which
1418 shell to run. Otherwise @value{GDBN} uses the default shell
1419 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1422 The utility @code{make} is often needed in development environments.
1423 You do not have to use the @code{shell} command for this purpose in
1428 @cindex calling make
1429 @item make @var{make-args}
1430 Execute the @code{make} program with the specified
1431 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1434 @node Logging Output
1435 @section Logging Output
1436 @cindex logging @value{GDBN} output
1437 @cindex save @value{GDBN} output to a file
1439 You may want to save the output of @value{GDBN} commands to a file.
1440 There are several commands to control @value{GDBN}'s logging.
1444 @item set logging on
1446 @item set logging off
1448 @cindex logging file name
1449 @item set logging file @var{file}
1450 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1451 @item set logging overwrite [on|off]
1452 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1453 you want @code{set logging on} to overwrite the logfile instead.
1454 @item set logging redirect [on|off]
1455 By default, @value{GDBN} output will go to both the terminal and the logfile.
1456 Set @code{redirect} if you want output to go only to the log file.
1457 @kindex show logging
1459 Show the current values of the logging settings.
1463 @chapter @value{GDBN} Commands
1465 You can abbreviate a @value{GDBN} command to the first few letters of the command
1466 name, if that abbreviation is unambiguous; and you can repeat certain
1467 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1468 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1469 show you the alternatives available, if there is more than one possibility).
1472 * Command Syntax:: How to give commands to @value{GDBN}
1473 * Completion:: Command completion
1474 * Help:: How to ask @value{GDBN} for help
1477 @node Command Syntax
1478 @section Command Syntax
1480 A @value{GDBN} command is a single line of input. There is no limit on
1481 how long it can be. It starts with a command name, which is followed by
1482 arguments whose meaning depends on the command name. For example, the
1483 command @code{step} accepts an argument which is the number of times to
1484 step, as in @samp{step 5}. You can also use the @code{step} command
1485 with no arguments. Some commands do not allow any arguments.
1487 @cindex abbreviation
1488 @value{GDBN} command names may always be truncated if that abbreviation is
1489 unambiguous. Other possible command abbreviations are listed in the
1490 documentation for individual commands. In some cases, even ambiguous
1491 abbreviations are allowed; for example, @code{s} is specially defined as
1492 equivalent to @code{step} even though there are other commands whose
1493 names start with @code{s}. You can test abbreviations by using them as
1494 arguments to the @code{help} command.
1496 @cindex repeating commands
1497 @kindex RET @r{(repeat last command)}
1498 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1499 repeat the previous command. Certain commands (for example, @code{run})
1500 will not repeat this way; these are commands whose unintentional
1501 repetition might cause trouble and which you are unlikely to want to
1502 repeat. User-defined commands can disable this feature; see
1503 @ref{Define, dont-repeat}.
1505 The @code{list} and @code{x} commands, when you repeat them with
1506 @key{RET}, construct new arguments rather than repeating
1507 exactly as typed. This permits easy scanning of source or memory.
1509 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1510 output, in a way similar to the common utility @code{more}
1511 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1512 @key{RET} too many in this situation, @value{GDBN} disables command
1513 repetition after any command that generates this sort of display.
1515 @kindex # @r{(a comment)}
1517 Any text from a @kbd{#} to the end of the line is a comment; it does
1518 nothing. This is useful mainly in command files (@pxref{Command
1519 Files,,Command Files}).
1521 @cindex repeating command sequences
1522 @kindex Ctrl-o @r{(operate-and-get-next)}
1523 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1524 commands. This command accepts the current line, like @key{RET}, and
1525 then fetches the next line relative to the current line from the history
1529 @section Command Completion
1532 @cindex word completion
1533 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1534 only one possibility; it can also show you what the valid possibilities
1535 are for the next word in a command, at any time. This works for @value{GDBN}
1536 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1538 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1539 of a word. If there is only one possibility, @value{GDBN} fills in the
1540 word, and waits for you to finish the command (or press @key{RET} to
1541 enter it). For example, if you type
1543 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1544 @c complete accuracy in these examples; space introduced for clarity.
1545 @c If texinfo enhancements make it unnecessary, it would be nice to
1546 @c replace " @key" by "@key" in the following...
1548 (@value{GDBP}) info bre @key{TAB}
1552 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1553 the only @code{info} subcommand beginning with @samp{bre}:
1556 (@value{GDBP}) info breakpoints
1560 You can either press @key{RET} at this point, to run the @code{info
1561 breakpoints} command, or backspace and enter something else, if
1562 @samp{breakpoints} does not look like the command you expected. (If you
1563 were sure you wanted @code{info breakpoints} in the first place, you
1564 might as well just type @key{RET} immediately after @samp{info bre},
1565 to exploit command abbreviations rather than command completion).
1567 If there is more than one possibility for the next word when you press
1568 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1569 characters and try again, or just press @key{TAB} a second time;
1570 @value{GDBN} displays all the possible completions for that word. For
1571 example, you might want to set a breakpoint on a subroutine whose name
1572 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1573 just sounds the bell. Typing @key{TAB} again displays all the
1574 function names in your program that begin with those characters, for
1578 (@value{GDBP}) b make_ @key{TAB}
1579 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1580 make_a_section_from_file make_environ
1581 make_abs_section make_function_type
1582 make_blockvector make_pointer_type
1583 make_cleanup make_reference_type
1584 make_command make_symbol_completion_list
1585 (@value{GDBP}) b make_
1589 After displaying the available possibilities, @value{GDBN} copies your
1590 partial input (@samp{b make_} in the example) so you can finish the
1593 If you just want to see the list of alternatives in the first place, you
1594 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1595 means @kbd{@key{META} ?}. You can type this either by holding down a
1596 key designated as the @key{META} shift on your keyboard (if there is
1597 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1599 @cindex quotes in commands
1600 @cindex completion of quoted strings
1601 Sometimes the string you need, while logically a ``word'', may contain
1602 parentheses or other characters that @value{GDBN} normally excludes from
1603 its notion of a word. To permit word completion to work in this
1604 situation, you may enclose words in @code{'} (single quote marks) in
1605 @value{GDBN} commands.
1607 The most likely situation where you might need this is in typing the
1608 name of a C@t{++} function. This is because C@t{++} allows function
1609 overloading (multiple definitions of the same function, distinguished
1610 by argument type). For example, when you want to set a breakpoint you
1611 may need to distinguish whether you mean the version of @code{name}
1612 that takes an @code{int} parameter, @code{name(int)}, or the version
1613 that takes a @code{float} parameter, @code{name(float)}. To use the
1614 word-completion facilities in this situation, type a single quote
1615 @code{'} at the beginning of the function name. This alerts
1616 @value{GDBN} that it may need to consider more information than usual
1617 when you press @key{TAB} or @kbd{M-?} to request word completion:
1620 (@value{GDBP}) b 'bubble( @kbd{M-?}
1621 bubble(double,double) bubble(int,int)
1622 (@value{GDBP}) b 'bubble(
1625 In some cases, @value{GDBN} can tell that completing a name requires using
1626 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1627 completing as much as it can) if you do not type the quote in the first
1631 (@value{GDBP}) b bub @key{TAB}
1632 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1633 (@value{GDBP}) b 'bubble(
1637 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1638 you have not yet started typing the argument list when you ask for
1639 completion on an overloaded symbol.
1641 For more information about overloaded functions, see @ref{C Plus Plus
1642 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1643 overload-resolution off} to disable overload resolution;
1644 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1646 @cindex completion of structure field names
1647 @cindex structure field name completion
1648 @cindex completion of union field names
1649 @cindex union field name completion
1650 When completing in an expression which looks up a field in a
1651 structure, @value{GDBN} also tries@footnote{The completer can be
1652 confused by certain kinds of invalid expressions. Also, it only
1653 examines the static type of the expression, not the dynamic type.} to
1654 limit completions to the field names available in the type of the
1658 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1659 magic to_fputs to_rewind
1660 to_data to_isatty to_write
1661 to_delete to_put to_write_async_safe
1666 This is because the @code{gdb_stdout} is a variable of the type
1667 @code{struct ui_file} that is defined in @value{GDBN} sources as
1674 ui_file_flush_ftype *to_flush;
1675 ui_file_write_ftype *to_write;
1676 ui_file_write_async_safe_ftype *to_write_async_safe;
1677 ui_file_fputs_ftype *to_fputs;
1678 ui_file_read_ftype *to_read;
1679 ui_file_delete_ftype *to_delete;
1680 ui_file_isatty_ftype *to_isatty;
1681 ui_file_rewind_ftype *to_rewind;
1682 ui_file_put_ftype *to_put;
1689 @section Getting Help
1690 @cindex online documentation
1693 You can always ask @value{GDBN} itself for information on its commands,
1694 using the command @code{help}.
1697 @kindex h @r{(@code{help})}
1700 You can use @code{help} (abbreviated @code{h}) with no arguments to
1701 display a short list of named classes of commands:
1705 List of classes of commands:
1707 aliases -- Aliases of other commands
1708 breakpoints -- Making program stop at certain points
1709 data -- Examining data
1710 files -- Specifying and examining files
1711 internals -- Maintenance commands
1712 obscure -- Obscure features
1713 running -- Running the program
1714 stack -- Examining the stack
1715 status -- Status inquiries
1716 support -- Support facilities
1717 tracepoints -- Tracing of program execution without
1718 stopping the program
1719 user-defined -- User-defined commands
1721 Type "help" followed by a class name for a list of
1722 commands in that class.
1723 Type "help" followed by command name for full
1725 Command name abbreviations are allowed if unambiguous.
1728 @c the above line break eliminates huge line overfull...
1730 @item help @var{class}
1731 Using one of the general help classes as an argument, you can get a
1732 list of the individual commands in that class. For example, here is the
1733 help display for the class @code{status}:
1736 (@value{GDBP}) help status
1741 @c Line break in "show" line falsifies real output, but needed
1742 @c to fit in smallbook page size.
1743 info -- Generic command for showing things
1744 about the program being debugged
1745 show -- Generic command for showing things
1748 Type "help" followed by command name for full
1750 Command name abbreviations are allowed if unambiguous.
1754 @item help @var{command}
1755 With a command name as @code{help} argument, @value{GDBN} displays a
1756 short paragraph on how to use that command.
1759 @item apropos @var{args}
1760 The @code{apropos} command searches through all of the @value{GDBN}
1761 commands, and their documentation, for the regular expression specified in
1762 @var{args}. It prints out all matches found. For example:
1773 alias -- Define a new command that is an alias of an existing command
1774 aliases -- Aliases of other commands
1775 d -- Delete some breakpoints or auto-display expressions
1776 del -- Delete some breakpoints or auto-display expressions
1777 delete -- Delete some breakpoints or auto-display expressions
1782 @item complete @var{args}
1783 The @code{complete @var{args}} command lists all the possible completions
1784 for the beginning of a command. Use @var{args} to specify the beginning of the
1785 command you want completed. For example:
1791 @noindent results in:
1802 @noindent This is intended for use by @sc{gnu} Emacs.
1805 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1806 and @code{show} to inquire about the state of your program, or the state
1807 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1808 manual introduces each of them in the appropriate context. The listings
1809 under @code{info} and under @code{show} in the Command, Variable, and
1810 Function Index point to all the sub-commands. @xref{Command and Variable
1816 @kindex i @r{(@code{info})}
1818 This command (abbreviated @code{i}) is for describing the state of your
1819 program. For example, you can show the arguments passed to a function
1820 with @code{info args}, list the registers currently in use with @code{info
1821 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1822 You can get a complete list of the @code{info} sub-commands with
1823 @w{@code{help info}}.
1827 You can assign the result of an expression to an environment variable with
1828 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1829 @code{set prompt $}.
1833 In contrast to @code{info}, @code{show} is for describing the state of
1834 @value{GDBN} itself.
1835 You can change most of the things you can @code{show}, by using the
1836 related command @code{set}; for example, you can control what number
1837 system is used for displays with @code{set radix}, or simply inquire
1838 which is currently in use with @code{show radix}.
1841 To display all the settable parameters and their current
1842 values, you can use @code{show} with no arguments; you may also use
1843 @code{info set}. Both commands produce the same display.
1844 @c FIXME: "info set" violates the rule that "info" is for state of
1845 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1846 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1850 Here are several miscellaneous @code{show} subcommands, all of which are
1851 exceptional in lacking corresponding @code{set} commands:
1854 @kindex show version
1855 @cindex @value{GDBN} version number
1857 Show what version of @value{GDBN} is running. You should include this
1858 information in @value{GDBN} bug-reports. If multiple versions of
1859 @value{GDBN} are in use at your site, you may need to determine which
1860 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1861 commands are introduced, and old ones may wither away. Also, many
1862 system vendors ship variant versions of @value{GDBN}, and there are
1863 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1864 The version number is the same as the one announced when you start
1867 @kindex show copying
1868 @kindex info copying
1869 @cindex display @value{GDBN} copyright
1872 Display information about permission for copying @value{GDBN}.
1874 @kindex show warranty
1875 @kindex info warranty
1877 @itemx info warranty
1878 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1879 if your version of @value{GDBN} comes with one.
1881 @kindex show configuration
1882 @item show configuration
1883 Display detailed information about the way @value{GDBN} was configured
1884 when it was built. This displays the optional arguments passed to the
1885 @file{configure} script and also configuration parameters detected
1886 automatically by @command{configure}. When reporting a @value{GDBN}
1887 bug (@pxref{GDB Bugs}), it is important to include this information in
1893 @chapter Running Programs Under @value{GDBN}
1895 When you run a program under @value{GDBN}, you must first generate
1896 debugging information when you compile it.
1898 You may start @value{GDBN} with its arguments, if any, in an environment
1899 of your choice. If you are doing native debugging, you may redirect
1900 your program's input and output, debug an already running process, or
1901 kill a child process.
1904 * Compilation:: Compiling for debugging
1905 * Starting:: Starting your program
1906 * Arguments:: Your program's arguments
1907 * Environment:: Your program's environment
1909 * Working Directory:: Your program's working directory
1910 * Input/Output:: Your program's input and output
1911 * Attach:: Debugging an already-running process
1912 * Kill Process:: Killing the child process
1914 * Inferiors and Programs:: Debugging multiple inferiors and programs
1915 * Threads:: Debugging programs with multiple threads
1916 * Forks:: Debugging forks
1917 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1921 @section Compiling for Debugging
1923 In order to debug a program effectively, you need to generate
1924 debugging information when you compile it. This debugging information
1925 is stored in the object file; it describes the data type of each
1926 variable or function and the correspondence between source line numbers
1927 and addresses in the executable code.
1929 To request debugging information, specify the @samp{-g} option when you run
1932 Programs that are to be shipped to your customers are compiled with
1933 optimizations, using the @samp{-O} compiler option. However, some
1934 compilers are unable to handle the @samp{-g} and @samp{-O} options
1935 together. Using those compilers, you cannot generate optimized
1936 executables containing debugging information.
1938 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1939 without @samp{-O}, making it possible to debug optimized code. We
1940 recommend that you @emph{always} use @samp{-g} whenever you compile a
1941 program. You may think your program is correct, but there is no sense
1942 in pushing your luck. For more information, see @ref{Optimized Code}.
1944 Older versions of the @sc{gnu} C compiler permitted a variant option
1945 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1946 format; if your @sc{gnu} C compiler has this option, do not use it.
1948 @value{GDBN} knows about preprocessor macros and can show you their
1949 expansion (@pxref{Macros}). Most compilers do not include information
1950 about preprocessor macros in the debugging information if you specify
1951 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1952 the @sc{gnu} C compiler, provides macro information if you are using
1953 the DWARF debugging format, and specify the option @option{-g3}.
1955 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1956 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1957 information on @value{NGCC} options affecting debug information.
1959 You will have the best debugging experience if you use the latest
1960 version of the DWARF debugging format that your compiler supports.
1961 DWARF is currently the most expressive and best supported debugging
1962 format in @value{GDBN}.
1966 @section Starting your Program
1972 @kindex r @r{(@code{run})}
1975 Use the @code{run} command to start your program under @value{GDBN}.
1976 You must first specify the program name (except on VxWorks) with an
1977 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1978 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1979 (@pxref{Files, ,Commands to Specify Files}).
1983 If you are running your program in an execution environment that
1984 supports processes, @code{run} creates an inferior process and makes
1985 that process run your program. In some environments without processes,
1986 @code{run} jumps to the start of your program. Other targets,
1987 like @samp{remote}, are always running. If you get an error
1988 message like this one:
1991 The "remote" target does not support "run".
1992 Try "help target" or "continue".
1996 then use @code{continue} to run your program. You may need @code{load}
1997 first (@pxref{load}).
1999 The execution of a program is affected by certain information it
2000 receives from its superior. @value{GDBN} provides ways to specify this
2001 information, which you must do @emph{before} starting your program. (You
2002 can change it after starting your program, but such changes only affect
2003 your program the next time you start it.) This information may be
2004 divided into four categories:
2007 @item The @emph{arguments.}
2008 Specify the arguments to give your program as the arguments of the
2009 @code{run} command. If a shell is available on your target, the shell
2010 is used to pass the arguments, so that you may use normal conventions
2011 (such as wildcard expansion or variable substitution) in describing
2013 In Unix systems, you can control which shell is used with the
2014 @code{SHELL} environment variable.
2015 @xref{Arguments, ,Your Program's Arguments}.
2017 @item The @emph{environment.}
2018 Your program normally inherits its environment from @value{GDBN}, but you can
2019 use the @value{GDBN} commands @code{set environment} and @code{unset
2020 environment} to change parts of the environment that affect
2021 your program. @xref{Environment, ,Your Program's Environment}.
2023 @item The @emph{working directory.}
2024 Your program inherits its working directory from @value{GDBN}. You can set
2025 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2026 @xref{Working Directory, ,Your Program's Working Directory}.
2028 @item The @emph{standard input and output.}
2029 Your program normally uses the same device for standard input and
2030 standard output as @value{GDBN} is using. You can redirect input and output
2031 in the @code{run} command line, or you can use the @code{tty} command to
2032 set a different device for your program.
2033 @xref{Input/Output, ,Your Program's Input and Output}.
2036 @emph{Warning:} While input and output redirection work, you cannot use
2037 pipes to pass the output of the program you are debugging to another
2038 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2042 When you issue the @code{run} command, your program begins to execute
2043 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2044 of how to arrange for your program to stop. Once your program has
2045 stopped, you may call functions in your program, using the @code{print}
2046 or @code{call} commands. @xref{Data, ,Examining Data}.
2048 If the modification time of your symbol file has changed since the last
2049 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2050 table, and reads it again. When it does this, @value{GDBN} tries to retain
2051 your current breakpoints.
2056 @cindex run to main procedure
2057 The name of the main procedure can vary from language to language.
2058 With C or C@t{++}, the main procedure name is always @code{main}, but
2059 other languages such as Ada do not require a specific name for their
2060 main procedure. The debugger provides a convenient way to start the
2061 execution of the program and to stop at the beginning of the main
2062 procedure, depending on the language used.
2064 The @samp{start} command does the equivalent of setting a temporary
2065 breakpoint at the beginning of the main procedure and then invoking
2066 the @samp{run} command.
2068 @cindex elaboration phase
2069 Some programs contain an @dfn{elaboration} phase where some startup code is
2070 executed before the main procedure is called. This depends on the
2071 languages used to write your program. In C@t{++}, for instance,
2072 constructors for static and global objects are executed before
2073 @code{main} is called. It is therefore possible that the debugger stops
2074 before reaching the main procedure. However, the temporary breakpoint
2075 will remain to halt execution.
2077 Specify the arguments to give to your program as arguments to the
2078 @samp{start} command. These arguments will be given verbatim to the
2079 underlying @samp{run} command. Note that the same arguments will be
2080 reused if no argument is provided during subsequent calls to
2081 @samp{start} or @samp{run}.
2083 It is sometimes necessary to debug the program during elaboration. In
2084 these cases, using the @code{start} command would stop the execution of
2085 your program too late, as the program would have already completed the
2086 elaboration phase. Under these circumstances, insert breakpoints in your
2087 elaboration code before running your program.
2089 @kindex set exec-wrapper
2090 @item set exec-wrapper @var{wrapper}
2091 @itemx show exec-wrapper
2092 @itemx unset exec-wrapper
2093 When @samp{exec-wrapper} is set, the specified wrapper is used to
2094 launch programs for debugging. @value{GDBN} starts your program
2095 with a shell command of the form @kbd{exec @var{wrapper}
2096 @var{program}}. Quoting is added to @var{program} and its
2097 arguments, but not to @var{wrapper}, so you should add quotes if
2098 appropriate for your shell. The wrapper runs until it executes
2099 your program, and then @value{GDBN} takes control.
2101 You can use any program that eventually calls @code{execve} with
2102 its arguments as a wrapper. Several standard Unix utilities do
2103 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2104 with @code{exec "$@@"} will also work.
2106 For example, you can use @code{env} to pass an environment variable to
2107 the debugged program, without setting the variable in your shell's
2111 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2115 This command is available when debugging locally on most targets, excluding
2116 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2118 @kindex set disable-randomization
2119 @item set disable-randomization
2120 @itemx set disable-randomization on
2121 This option (enabled by default in @value{GDBN}) will turn off the native
2122 randomization of the virtual address space of the started program. This option
2123 is useful for multiple debugging sessions to make the execution better
2124 reproducible and memory addresses reusable across debugging sessions.
2126 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2127 On @sc{gnu}/Linux you can get the same behavior using
2130 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2133 @item set disable-randomization off
2134 Leave the behavior of the started executable unchanged. Some bugs rear their
2135 ugly heads only when the program is loaded at certain addresses. If your bug
2136 disappears when you run the program under @value{GDBN}, that might be because
2137 @value{GDBN} by default disables the address randomization on platforms, such
2138 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2139 disable-randomization off} to try to reproduce such elusive bugs.
2141 On targets where it is available, virtual address space randomization
2142 protects the programs against certain kinds of security attacks. In these
2143 cases the attacker needs to know the exact location of a concrete executable
2144 code. Randomizing its location makes it impossible to inject jumps misusing
2145 a code at its expected addresses.
2147 Prelinking shared libraries provides a startup performance advantage but it
2148 makes addresses in these libraries predictable for privileged processes by
2149 having just unprivileged access at the target system. Reading the shared
2150 library binary gives enough information for assembling the malicious code
2151 misusing it. Still even a prelinked shared library can get loaded at a new
2152 random address just requiring the regular relocation process during the
2153 startup. Shared libraries not already prelinked are always loaded at
2154 a randomly chosen address.
2156 Position independent executables (PIE) contain position independent code
2157 similar to the shared libraries and therefore such executables get loaded at
2158 a randomly chosen address upon startup. PIE executables always load even
2159 already prelinked shared libraries at a random address. You can build such
2160 executable using @command{gcc -fPIE -pie}.
2162 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2163 (as long as the randomization is enabled).
2165 @item show disable-randomization
2166 Show the current setting of the explicit disable of the native randomization of
2167 the virtual address space of the started program.
2172 @section Your Program's Arguments
2174 @cindex arguments (to your program)
2175 The arguments to your program can be specified by the arguments of the
2177 They are passed to a shell, which expands wildcard characters and
2178 performs redirection of I/O, and thence to your program. Your
2179 @code{SHELL} environment variable (if it exists) specifies what shell
2180 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2181 the default shell (@file{/bin/sh} on Unix).
2183 On non-Unix systems, the program is usually invoked directly by
2184 @value{GDBN}, which emulates I/O redirection via the appropriate system
2185 calls, and the wildcard characters are expanded by the startup code of
2186 the program, not by the shell.
2188 @code{run} with no arguments uses the same arguments used by the previous
2189 @code{run}, or those set by the @code{set args} command.
2194 Specify the arguments to be used the next time your program is run. If
2195 @code{set args} has no arguments, @code{run} executes your program
2196 with no arguments. Once you have run your program with arguments,
2197 using @code{set args} before the next @code{run} is the only way to run
2198 it again without arguments.
2202 Show the arguments to give your program when it is started.
2206 @section Your Program's Environment
2208 @cindex environment (of your program)
2209 The @dfn{environment} consists of a set of environment variables and
2210 their values. Environment variables conventionally record such things as
2211 your user name, your home directory, your terminal type, and your search
2212 path for programs to run. Usually you set up environment variables with
2213 the shell and they are inherited by all the other programs you run. When
2214 debugging, it can be useful to try running your program with a modified
2215 environment without having to start @value{GDBN} over again.
2219 @item path @var{directory}
2220 Add @var{directory} to the front of the @code{PATH} environment variable
2221 (the search path for executables) that will be passed to your program.
2222 The value of @code{PATH} used by @value{GDBN} does not change.
2223 You may specify several directory names, separated by whitespace or by a
2224 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2225 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2226 is moved to the front, so it is searched sooner.
2228 You can use the string @samp{$cwd} to refer to whatever is the current
2229 working directory at the time @value{GDBN} searches the path. If you
2230 use @samp{.} instead, it refers to the directory where you executed the
2231 @code{path} command. @value{GDBN} replaces @samp{.} in the
2232 @var{directory} argument (with the current path) before adding
2233 @var{directory} to the search path.
2234 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2235 @c document that, since repeating it would be a no-op.
2239 Display the list of search paths for executables (the @code{PATH}
2240 environment variable).
2242 @kindex show environment
2243 @item show environment @r{[}@var{varname}@r{]}
2244 Print the value of environment variable @var{varname} to be given to
2245 your program when it starts. If you do not supply @var{varname},
2246 print the names and values of all environment variables to be given to
2247 your program. You can abbreviate @code{environment} as @code{env}.
2249 @kindex set environment
2250 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2251 Set environment variable @var{varname} to @var{value}. The value
2252 changes for your program only, not for @value{GDBN} itself. @var{value} may
2253 be any string; the values of environment variables are just strings, and
2254 any interpretation is supplied by your program itself. The @var{value}
2255 parameter is optional; if it is eliminated, the variable is set to a
2257 @c "any string" here does not include leading, trailing
2258 @c blanks. Gnu asks: does anyone care?
2260 For example, this command:
2267 tells the debugged program, when subsequently run, that its user is named
2268 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2269 are not actually required.)
2271 @kindex unset environment
2272 @item unset environment @var{varname}
2273 Remove variable @var{varname} from the environment to be passed to your
2274 program. This is different from @samp{set env @var{varname} =};
2275 @code{unset environment} removes the variable from the environment,
2276 rather than assigning it an empty value.
2279 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2281 by your @code{SHELL} environment variable if it exists (or
2282 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2283 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2284 @file{.bashrc} for BASH---any variables you set in that file affect
2285 your program. You may wish to move setting of environment variables to
2286 files that are only run when you sign on, such as @file{.login} or
2289 @node Working Directory
2290 @section Your Program's Working Directory
2292 @cindex working directory (of your program)
2293 Each time you start your program with @code{run}, it inherits its
2294 working directory from the current working directory of @value{GDBN}.
2295 The @value{GDBN} working directory is initially whatever it inherited
2296 from its parent process (typically the shell), but you can specify a new
2297 working directory in @value{GDBN} with the @code{cd} command.
2299 The @value{GDBN} working directory also serves as a default for the commands
2300 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2305 @cindex change working directory
2306 @item cd @r{[}@var{directory}@r{]}
2307 Set the @value{GDBN} working directory to @var{directory}. If not
2308 given, @var{directory} uses @file{'~'}.
2312 Print the @value{GDBN} working directory.
2315 It is generally impossible to find the current working directory of
2316 the process being debugged (since a program can change its directory
2317 during its run). If you work on a system where @value{GDBN} is
2318 configured with the @file{/proc} support, you can use the @code{info
2319 proc} command (@pxref{SVR4 Process Information}) to find out the
2320 current working directory of the debuggee.
2323 @section Your Program's Input and Output
2328 By default, the program you run under @value{GDBN} does input and output to
2329 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2330 to its own terminal modes to interact with you, but it records the terminal
2331 modes your program was using and switches back to them when you continue
2332 running your program.
2335 @kindex info terminal
2337 Displays information recorded by @value{GDBN} about the terminal modes your
2341 You can redirect your program's input and/or output using shell
2342 redirection with the @code{run} command. For example,
2349 starts your program, diverting its output to the file @file{outfile}.
2352 @cindex controlling terminal
2353 Another way to specify where your program should do input and output is
2354 with the @code{tty} command. This command accepts a file name as
2355 argument, and causes this file to be the default for future @code{run}
2356 commands. It also resets the controlling terminal for the child
2357 process, for future @code{run} commands. For example,
2364 directs that processes started with subsequent @code{run} commands
2365 default to do input and output on the terminal @file{/dev/ttyb} and have
2366 that as their controlling terminal.
2368 An explicit redirection in @code{run} overrides the @code{tty} command's
2369 effect on the input/output device, but not its effect on the controlling
2372 When you use the @code{tty} command or redirect input in the @code{run}
2373 command, only the input @emph{for your program} is affected. The input
2374 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2375 for @code{set inferior-tty}.
2377 @cindex inferior tty
2378 @cindex set inferior controlling terminal
2379 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2380 display the name of the terminal that will be used for future runs of your
2384 @item set inferior-tty /dev/ttyb
2385 @kindex set inferior-tty
2386 Set the tty for the program being debugged to /dev/ttyb.
2388 @item show inferior-tty
2389 @kindex show inferior-tty
2390 Show the current tty for the program being debugged.
2394 @section Debugging an Already-running Process
2399 @item attach @var{process-id}
2400 This command attaches to a running process---one that was started
2401 outside @value{GDBN}. (@code{info files} shows your active
2402 targets.) The command takes as argument a process ID. The usual way to
2403 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2404 or with the @samp{jobs -l} shell command.
2406 @code{attach} does not repeat if you press @key{RET} a second time after
2407 executing the command.
2410 To use @code{attach}, your program must be running in an environment
2411 which supports processes; for example, @code{attach} does not work for
2412 programs on bare-board targets that lack an operating system. You must
2413 also have permission to send the process a signal.
2415 When you use @code{attach}, the debugger finds the program running in
2416 the process first by looking in the current working directory, then (if
2417 the program is not found) by using the source file search path
2418 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2419 the @code{file} command to load the program. @xref{Files, ,Commands to
2422 The first thing @value{GDBN} does after arranging to debug the specified
2423 process is to stop it. You can examine and modify an attached process
2424 with all the @value{GDBN} commands that are ordinarily available when
2425 you start processes with @code{run}. You can insert breakpoints; you
2426 can step and continue; you can modify storage. If you would rather the
2427 process continue running, you may use the @code{continue} command after
2428 attaching @value{GDBN} to the process.
2433 When you have finished debugging the attached process, you can use the
2434 @code{detach} command to release it from @value{GDBN} control. Detaching
2435 the process continues its execution. After the @code{detach} command,
2436 that process and @value{GDBN} become completely independent once more, and you
2437 are ready to @code{attach} another process or start one with @code{run}.
2438 @code{detach} does not repeat if you press @key{RET} again after
2439 executing the command.
2442 If you exit @value{GDBN} while you have an attached process, you detach
2443 that process. If you use the @code{run} command, you kill that process.
2444 By default, @value{GDBN} asks for confirmation if you try to do either of these
2445 things; you can control whether or not you need to confirm by using the
2446 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2450 @section Killing the Child Process
2455 Kill the child process in which your program is running under @value{GDBN}.
2458 This command is useful if you wish to debug a core dump instead of a
2459 running process. @value{GDBN} ignores any core dump file while your program
2462 On some operating systems, a program cannot be executed outside @value{GDBN}
2463 while you have breakpoints set on it inside @value{GDBN}. You can use the
2464 @code{kill} command in this situation to permit running your program
2465 outside the debugger.
2467 The @code{kill} command is also useful if you wish to recompile and
2468 relink your program, since on many systems it is impossible to modify an
2469 executable file while it is running in a process. In this case, when you
2470 next type @code{run}, @value{GDBN} notices that the file has changed, and
2471 reads the symbol table again (while trying to preserve your current
2472 breakpoint settings).
2474 @node Inferiors and Programs
2475 @section Debugging Multiple Inferiors and Programs
2477 @value{GDBN} lets you run and debug multiple programs in a single
2478 session. In addition, @value{GDBN} on some systems may let you run
2479 several programs simultaneously (otherwise you have to exit from one
2480 before starting another). In the most general case, you can have
2481 multiple threads of execution in each of multiple processes, launched
2482 from multiple executables.
2485 @value{GDBN} represents the state of each program execution with an
2486 object called an @dfn{inferior}. An inferior typically corresponds to
2487 a process, but is more general and applies also to targets that do not
2488 have processes. Inferiors may be created before a process runs, and
2489 may be retained after a process exits. Inferiors have unique
2490 identifiers that are different from process ids. Usually each
2491 inferior will also have its own distinct address space, although some
2492 embedded targets may have several inferiors running in different parts
2493 of a single address space. Each inferior may in turn have multiple
2494 threads running in it.
2496 To find out what inferiors exist at any moment, use @w{@code{info
2500 @kindex info inferiors
2501 @item info inferiors
2502 Print a list of all inferiors currently being managed by @value{GDBN}.
2504 @value{GDBN} displays for each inferior (in this order):
2508 the inferior number assigned by @value{GDBN}
2511 the target system's inferior identifier
2514 the name of the executable the inferior is running.
2519 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2520 indicates the current inferior.
2524 @c end table here to get a little more width for example
2527 (@value{GDBP}) info inferiors
2528 Num Description Executable
2529 2 process 2307 hello
2530 * 1 process 3401 goodbye
2533 To switch focus between inferiors, use the @code{inferior} command:
2536 @kindex inferior @var{infno}
2537 @item inferior @var{infno}
2538 Make inferior number @var{infno} the current inferior. The argument
2539 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2540 in the first field of the @samp{info inferiors} display.
2544 You can get multiple executables into a debugging session via the
2545 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2546 systems @value{GDBN} can add inferiors to the debug session
2547 automatically by following calls to @code{fork} and @code{exec}. To
2548 remove inferiors from the debugging session use the
2549 @w{@code{remove-inferiors}} command.
2552 @kindex add-inferior
2553 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2554 Adds @var{n} inferiors to be run using @var{executable} as the
2555 executable. @var{n} defaults to 1. If no executable is specified,
2556 the inferiors begins empty, with no program. You can still assign or
2557 change the program assigned to the inferior at any time by using the
2558 @code{file} command with the executable name as its argument.
2560 @kindex clone-inferior
2561 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2562 Adds @var{n} inferiors ready to execute the same program as inferior
2563 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2564 number of the current inferior. This is a convenient command when you
2565 want to run another instance of the inferior you are debugging.
2568 (@value{GDBP}) info inferiors
2569 Num Description Executable
2570 * 1 process 29964 helloworld
2571 (@value{GDBP}) clone-inferior
2574 (@value{GDBP}) info inferiors
2575 Num Description Executable
2577 * 1 process 29964 helloworld
2580 You can now simply switch focus to inferior 2 and run it.
2582 @kindex remove-inferiors
2583 @item remove-inferiors @var{infno}@dots{}
2584 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2585 possible to remove an inferior that is running with this command. For
2586 those, use the @code{kill} or @code{detach} command first.
2590 To quit debugging one of the running inferiors that is not the current
2591 inferior, you can either detach from it by using the @w{@code{detach
2592 inferior}} command (allowing it to run independently), or kill it
2593 using the @w{@code{kill inferiors}} command:
2596 @kindex detach inferiors @var{infno}@dots{}
2597 @item detach inferior @var{infno}@dots{}
2598 Detach from the inferior or inferiors identified by @value{GDBN}
2599 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2600 still stays on the list of inferiors shown by @code{info inferiors},
2601 but its Description will show @samp{<null>}.
2603 @kindex kill inferiors @var{infno}@dots{}
2604 @item kill inferiors @var{infno}@dots{}
2605 Kill the inferior or inferiors identified by @value{GDBN} inferior
2606 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2607 stays on the list of inferiors shown by @code{info inferiors}, but its
2608 Description will show @samp{<null>}.
2611 After the successful completion of a command such as @code{detach},
2612 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2613 a normal process exit, the inferior is still valid and listed with
2614 @code{info inferiors}, ready to be restarted.
2617 To be notified when inferiors are started or exit under @value{GDBN}'s
2618 control use @w{@code{set print inferior-events}}:
2621 @kindex set print inferior-events
2622 @cindex print messages on inferior start and exit
2623 @item set print inferior-events
2624 @itemx set print inferior-events on
2625 @itemx set print inferior-events off
2626 The @code{set print inferior-events} command allows you to enable or
2627 disable printing of messages when @value{GDBN} notices that new
2628 inferiors have started or that inferiors have exited or have been
2629 detached. By default, these messages will not be printed.
2631 @kindex show print inferior-events
2632 @item show print inferior-events
2633 Show whether messages will be printed when @value{GDBN} detects that
2634 inferiors have started, exited or have been detached.
2637 Many commands will work the same with multiple programs as with a
2638 single program: e.g., @code{print myglobal} will simply display the
2639 value of @code{myglobal} in the current inferior.
2642 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2643 get more info about the relationship of inferiors, programs, address
2644 spaces in a debug session. You can do that with the @w{@code{maint
2645 info program-spaces}} command.
2648 @kindex maint info program-spaces
2649 @item maint info program-spaces
2650 Print a list of all program spaces currently being managed by
2653 @value{GDBN} displays for each program space (in this order):
2657 the program space number assigned by @value{GDBN}
2660 the name of the executable loaded into the program space, with e.g.,
2661 the @code{file} command.
2666 An asterisk @samp{*} preceding the @value{GDBN} program space number
2667 indicates the current program space.
2669 In addition, below each program space line, @value{GDBN} prints extra
2670 information that isn't suitable to display in tabular form. For
2671 example, the list of inferiors bound to the program space.
2674 (@value{GDBP}) maint info program-spaces
2677 Bound inferiors: ID 1 (process 21561)
2681 Here we can see that no inferior is running the program @code{hello},
2682 while @code{process 21561} is running the program @code{goodbye}. On
2683 some targets, it is possible that multiple inferiors are bound to the
2684 same program space. The most common example is that of debugging both
2685 the parent and child processes of a @code{vfork} call. For example,
2688 (@value{GDBP}) maint info program-spaces
2691 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2694 Here, both inferior 2 and inferior 1 are running in the same program
2695 space as a result of inferior 1 having executed a @code{vfork} call.
2699 @section Debugging Programs with Multiple Threads
2701 @cindex threads of execution
2702 @cindex multiple threads
2703 @cindex switching threads
2704 In some operating systems, such as HP-UX and Solaris, a single program
2705 may have more than one @dfn{thread} of execution. The precise semantics
2706 of threads differ from one operating system to another, but in general
2707 the threads of a single program are akin to multiple processes---except
2708 that they share one address space (that is, they can all examine and
2709 modify the same variables). On the other hand, each thread has its own
2710 registers and execution stack, and perhaps private memory.
2712 @value{GDBN} provides these facilities for debugging multi-thread
2716 @item automatic notification of new threads
2717 @item @samp{thread @var{threadno}}, a command to switch among threads
2718 @item @samp{info threads}, a command to inquire about existing threads
2719 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2720 a command to apply a command to a list of threads
2721 @item thread-specific breakpoints
2722 @item @samp{set print thread-events}, which controls printing of
2723 messages on thread start and exit.
2724 @item @samp{set libthread-db-search-path @var{path}}, which lets
2725 the user specify which @code{libthread_db} to use if the default choice
2726 isn't compatible with the program.
2730 @emph{Warning:} These facilities are not yet available on every
2731 @value{GDBN} configuration where the operating system supports threads.
2732 If your @value{GDBN} does not support threads, these commands have no
2733 effect. For example, a system without thread support shows no output
2734 from @samp{info threads}, and always rejects the @code{thread} command,
2738 (@value{GDBP}) info threads
2739 (@value{GDBP}) thread 1
2740 Thread ID 1 not known. Use the "info threads" command to
2741 see the IDs of currently known threads.
2743 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2744 @c doesn't support threads"?
2747 @cindex focus of debugging
2748 @cindex current thread
2749 The @value{GDBN} thread debugging facility allows you to observe all
2750 threads while your program runs---but whenever @value{GDBN} takes
2751 control, one thread in particular is always the focus of debugging.
2752 This thread is called the @dfn{current thread}. Debugging commands show
2753 program information from the perspective of the current thread.
2755 @cindex @code{New} @var{systag} message
2756 @cindex thread identifier (system)
2757 @c FIXME-implementors!! It would be more helpful if the [New...] message
2758 @c included GDB's numeric thread handle, so you could just go to that
2759 @c thread without first checking `info threads'.
2760 Whenever @value{GDBN} detects a new thread in your program, it displays
2761 the target system's identification for the thread with a message in the
2762 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2763 whose form varies depending on the particular system. For example, on
2764 @sc{gnu}/Linux, you might see
2767 [New Thread 0x41e02940 (LWP 25582)]
2771 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2772 the @var{systag} is simply something like @samp{process 368}, with no
2775 @c FIXME!! (1) Does the [New...] message appear even for the very first
2776 @c thread of a program, or does it only appear for the
2777 @c second---i.e.@: when it becomes obvious we have a multithread
2779 @c (2) *Is* there necessarily a first thread always? Or do some
2780 @c multithread systems permit starting a program with multiple
2781 @c threads ab initio?
2783 @cindex thread number
2784 @cindex thread identifier (GDB)
2785 For debugging purposes, @value{GDBN} associates its own thread
2786 number---always a single integer---with each thread in your program.
2789 @kindex info threads
2790 @item info threads @r{[}@var{id}@dots{}@r{]}
2791 Display a summary of all threads currently in your program. Optional
2792 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2793 means to print information only about the specified thread or threads.
2794 @value{GDBN} displays for each thread (in this order):
2798 the thread number assigned by @value{GDBN}
2801 the target system's thread identifier (@var{systag})
2804 the thread's name, if one is known. A thread can either be named by
2805 the user (see @code{thread name}, below), or, in some cases, by the
2809 the current stack frame summary for that thread
2813 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2814 indicates the current thread.
2818 @c end table here to get a little more width for example
2821 (@value{GDBP}) info threads
2823 3 process 35 thread 27 0x34e5 in sigpause ()
2824 2 process 35 thread 23 0x34e5 in sigpause ()
2825 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2829 On Solaris, you can display more information about user threads with a
2830 Solaris-specific command:
2833 @item maint info sol-threads
2834 @kindex maint info sol-threads
2835 @cindex thread info (Solaris)
2836 Display info on Solaris user threads.
2840 @kindex thread @var{threadno}
2841 @item thread @var{threadno}
2842 Make thread number @var{threadno} the current thread. The command
2843 argument @var{threadno} is the internal @value{GDBN} thread number, as
2844 shown in the first field of the @samp{info threads} display.
2845 @value{GDBN} responds by displaying the system identifier of the thread
2846 you selected, and its current stack frame summary:
2849 (@value{GDBP}) thread 2
2850 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2851 #0 some_function (ignore=0x0) at example.c:8
2852 8 printf ("hello\n");
2856 As with the @samp{[New @dots{}]} message, the form of the text after
2857 @samp{Switching to} depends on your system's conventions for identifying
2860 @vindex $_thread@r{, convenience variable}
2861 The debugger convenience variable @samp{$_thread} contains the number
2862 of the current thread. You may find this useful in writing breakpoint
2863 conditional expressions, command scripts, and so forth. See
2864 @xref{Convenience Vars,, Convenience Variables}, for general
2865 information on convenience variables.
2867 @kindex thread apply
2868 @cindex apply command to several threads
2869 @item thread apply [@var{threadno} | all] @var{command}
2870 The @code{thread apply} command allows you to apply the named
2871 @var{command} to one or more threads. Specify the numbers of the
2872 threads that you want affected with the command argument
2873 @var{threadno}. It can be a single thread number, one of the numbers
2874 shown in the first field of the @samp{info threads} display; or it
2875 could be a range of thread numbers, as in @code{2-4}. To apply a
2876 command to all threads, type @kbd{thread apply all @var{command}}.
2879 @cindex name a thread
2880 @item thread name [@var{name}]
2881 This command assigns a name to the current thread. If no argument is
2882 given, any existing user-specified name is removed. The thread name
2883 appears in the @samp{info threads} display.
2885 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2886 determine the name of the thread as given by the OS. On these
2887 systems, a name specified with @samp{thread name} will override the
2888 system-give name, and removing the user-specified name will cause
2889 @value{GDBN} to once again display the system-specified name.
2892 @cindex search for a thread
2893 @item thread find [@var{regexp}]
2894 Search for and display thread ids whose name or @var{systag}
2895 matches the supplied regular expression.
2897 As well as being the complement to the @samp{thread name} command,
2898 this command also allows you to identify a thread by its target
2899 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2903 (@value{GDBN}) thread find 26688
2904 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2905 (@value{GDBN}) info thread 4
2907 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2910 @kindex set print thread-events
2911 @cindex print messages on thread start and exit
2912 @item set print thread-events
2913 @itemx set print thread-events on
2914 @itemx set print thread-events off
2915 The @code{set print thread-events} command allows you to enable or
2916 disable printing of messages when @value{GDBN} notices that new threads have
2917 started or that threads have exited. By default, these messages will
2918 be printed if detection of these events is supported by the target.
2919 Note that these messages cannot be disabled on all targets.
2921 @kindex show print thread-events
2922 @item show print thread-events
2923 Show whether messages will be printed when @value{GDBN} detects that threads
2924 have started and exited.
2927 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2928 more information about how @value{GDBN} behaves when you stop and start
2929 programs with multiple threads.
2931 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2932 watchpoints in programs with multiple threads.
2934 @anchor{set libthread-db-search-path}
2936 @kindex set libthread-db-search-path
2937 @cindex search path for @code{libthread_db}
2938 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2939 If this variable is set, @var{path} is a colon-separated list of
2940 directories @value{GDBN} will use to search for @code{libthread_db}.
2941 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2942 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2943 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2946 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2947 @code{libthread_db} library to obtain information about threads in the
2948 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2949 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2950 specific thread debugging library loading is enabled
2951 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2953 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2954 refers to the default system directories that are
2955 normally searched for loading shared libraries. The @samp{$sdir} entry
2956 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2957 (@pxref{libthread_db.so.1 file}).
2959 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2960 refers to the directory from which @code{libpthread}
2961 was loaded in the inferior process.
2963 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2964 @value{GDBN} attempts to initialize it with the current inferior process.
2965 If this initialization fails (which could happen because of a version
2966 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2967 will unload @code{libthread_db}, and continue with the next directory.
2968 If none of @code{libthread_db} libraries initialize successfully,
2969 @value{GDBN} will issue a warning and thread debugging will be disabled.
2971 Setting @code{libthread-db-search-path} is currently implemented
2972 only on some platforms.
2974 @kindex show libthread-db-search-path
2975 @item show libthread-db-search-path
2976 Display current libthread_db search path.
2978 @kindex set debug libthread-db
2979 @kindex show debug libthread-db
2980 @cindex debugging @code{libthread_db}
2981 @item set debug libthread-db
2982 @itemx show debug libthread-db
2983 Turns on or off display of @code{libthread_db}-related events.
2984 Use @code{1} to enable, @code{0} to disable.
2988 @section Debugging Forks
2990 @cindex fork, debugging programs which call
2991 @cindex multiple processes
2992 @cindex processes, multiple
2993 On most systems, @value{GDBN} has no special support for debugging
2994 programs which create additional processes using the @code{fork}
2995 function. When a program forks, @value{GDBN} will continue to debug the
2996 parent process and the child process will run unimpeded. If you have
2997 set a breakpoint in any code which the child then executes, the child
2998 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2999 will cause it to terminate.
3001 However, if you want to debug the child process there is a workaround
3002 which isn't too painful. Put a call to @code{sleep} in the code which
3003 the child process executes after the fork. It may be useful to sleep
3004 only if a certain environment variable is set, or a certain file exists,
3005 so that the delay need not occur when you don't want to run @value{GDBN}
3006 on the child. While the child is sleeping, use the @code{ps} program to
3007 get its process ID. Then tell @value{GDBN} (a new invocation of
3008 @value{GDBN} if you are also debugging the parent process) to attach to
3009 the child process (@pxref{Attach}). From that point on you can debug
3010 the child process just like any other process which you attached to.
3012 On some systems, @value{GDBN} provides support for debugging programs that
3013 create additional processes using the @code{fork} or @code{vfork} functions.
3014 Currently, the only platforms with this feature are HP-UX (11.x and later
3015 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3017 By default, when a program forks, @value{GDBN} will continue to debug
3018 the parent process and the child process will run unimpeded.
3020 If you want to follow the child process instead of the parent process,
3021 use the command @w{@code{set follow-fork-mode}}.
3024 @kindex set follow-fork-mode
3025 @item set follow-fork-mode @var{mode}
3026 Set the debugger response to a program call of @code{fork} or
3027 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3028 process. The @var{mode} argument can be:
3032 The original process is debugged after a fork. The child process runs
3033 unimpeded. This is the default.
3036 The new process is debugged after a fork. The parent process runs
3041 @kindex show follow-fork-mode
3042 @item show follow-fork-mode
3043 Display the current debugger response to a @code{fork} or @code{vfork} call.
3046 @cindex debugging multiple processes
3047 On Linux, if you want to debug both the parent and child processes, use the
3048 command @w{@code{set detach-on-fork}}.
3051 @kindex set detach-on-fork
3052 @item set detach-on-fork @var{mode}
3053 Tells gdb whether to detach one of the processes after a fork, or
3054 retain debugger control over them both.
3058 The child process (or parent process, depending on the value of
3059 @code{follow-fork-mode}) will be detached and allowed to run
3060 independently. This is the default.
3063 Both processes will be held under the control of @value{GDBN}.
3064 One process (child or parent, depending on the value of
3065 @code{follow-fork-mode}) is debugged as usual, while the other
3070 @kindex show detach-on-fork
3071 @item show detach-on-fork
3072 Show whether detach-on-fork mode is on/off.
3075 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3076 will retain control of all forked processes (including nested forks).
3077 You can list the forked processes under the control of @value{GDBN} by
3078 using the @w{@code{info inferiors}} command, and switch from one fork
3079 to another by using the @code{inferior} command (@pxref{Inferiors and
3080 Programs, ,Debugging Multiple Inferiors and Programs}).
3082 To quit debugging one of the forked processes, you can either detach
3083 from it by using the @w{@code{detach inferiors}} command (allowing it
3084 to run independently), or kill it using the @w{@code{kill inferiors}}
3085 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3088 If you ask to debug a child process and a @code{vfork} is followed by an
3089 @code{exec}, @value{GDBN} executes the new target up to the first
3090 breakpoint in the new target. If you have a breakpoint set on
3091 @code{main} in your original program, the breakpoint will also be set on
3092 the child process's @code{main}.
3094 On some systems, when a child process is spawned by @code{vfork}, you
3095 cannot debug the child or parent until an @code{exec} call completes.
3097 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3098 call executes, the new target restarts. To restart the parent
3099 process, use the @code{file} command with the parent executable name
3100 as its argument. By default, after an @code{exec} call executes,
3101 @value{GDBN} discards the symbols of the previous executable image.
3102 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3106 @kindex set follow-exec-mode
3107 @item set follow-exec-mode @var{mode}
3109 Set debugger response to a program call of @code{exec}. An
3110 @code{exec} call replaces the program image of a process.
3112 @code{follow-exec-mode} can be:
3116 @value{GDBN} creates a new inferior and rebinds the process to this
3117 new inferior. The program the process was running before the
3118 @code{exec} call can be restarted afterwards by restarting the
3124 (@value{GDBP}) info inferiors
3126 Id Description Executable
3129 process 12020 is executing new program: prog2
3130 Program exited normally.
3131 (@value{GDBP}) info inferiors
3132 Id Description Executable
3138 @value{GDBN} keeps the process bound to the same inferior. The new
3139 executable image replaces the previous executable loaded in the
3140 inferior. Restarting the inferior after the @code{exec} call, with
3141 e.g., the @code{run} command, restarts the executable the process was
3142 running after the @code{exec} call. This is the default mode.
3147 (@value{GDBP}) info inferiors
3148 Id Description Executable
3151 process 12020 is executing new program: prog2
3152 Program exited normally.
3153 (@value{GDBP}) info inferiors
3154 Id Description Executable
3161 You can use the @code{catch} command to make @value{GDBN} stop whenever
3162 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3163 Catchpoints, ,Setting Catchpoints}.
3165 @node Checkpoint/Restart
3166 @section Setting a @emph{Bookmark} to Return to Later
3171 @cindex snapshot of a process
3172 @cindex rewind program state
3174 On certain operating systems@footnote{Currently, only
3175 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3176 program's state, called a @dfn{checkpoint}, and come back to it
3179 Returning to a checkpoint effectively undoes everything that has
3180 happened in the program since the @code{checkpoint} was saved. This
3181 includes changes in memory, registers, and even (within some limits)
3182 system state. Effectively, it is like going back in time to the
3183 moment when the checkpoint was saved.
3185 Thus, if you're stepping thru a program and you think you're
3186 getting close to the point where things go wrong, you can save
3187 a checkpoint. Then, if you accidentally go too far and miss
3188 the critical statement, instead of having to restart your program
3189 from the beginning, you can just go back to the checkpoint and
3190 start again from there.
3192 This can be especially useful if it takes a lot of time or
3193 steps to reach the point where you think the bug occurs.
3195 To use the @code{checkpoint}/@code{restart} method of debugging:
3200 Save a snapshot of the debugged program's current execution state.
3201 The @code{checkpoint} command takes no arguments, but each checkpoint
3202 is assigned a small integer id, similar to a breakpoint id.
3204 @kindex info checkpoints
3205 @item info checkpoints
3206 List the checkpoints that have been saved in the current debugging
3207 session. For each checkpoint, the following information will be
3214 @item Source line, or label
3217 @kindex restart @var{checkpoint-id}
3218 @item restart @var{checkpoint-id}
3219 Restore the program state that was saved as checkpoint number
3220 @var{checkpoint-id}. All program variables, registers, stack frames
3221 etc.@: will be returned to the values that they had when the checkpoint
3222 was saved. In essence, gdb will ``wind back the clock'' to the point
3223 in time when the checkpoint was saved.
3225 Note that breakpoints, @value{GDBN} variables, command history etc.
3226 are not affected by restoring a checkpoint. In general, a checkpoint
3227 only restores things that reside in the program being debugged, not in
3230 @kindex delete checkpoint @var{checkpoint-id}
3231 @item delete checkpoint @var{checkpoint-id}
3232 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3236 Returning to a previously saved checkpoint will restore the user state
3237 of the program being debugged, plus a significant subset of the system
3238 (OS) state, including file pointers. It won't ``un-write'' data from
3239 a file, but it will rewind the file pointer to the previous location,
3240 so that the previously written data can be overwritten. For files
3241 opened in read mode, the pointer will also be restored so that the
3242 previously read data can be read again.
3244 Of course, characters that have been sent to a printer (or other
3245 external device) cannot be ``snatched back'', and characters received
3246 from eg.@: a serial device can be removed from internal program buffers,
3247 but they cannot be ``pushed back'' into the serial pipeline, ready to
3248 be received again. Similarly, the actual contents of files that have
3249 been changed cannot be restored (at this time).
3251 However, within those constraints, you actually can ``rewind'' your
3252 program to a previously saved point in time, and begin debugging it
3253 again --- and you can change the course of events so as to debug a
3254 different execution path this time.
3256 @cindex checkpoints and process id
3257 Finally, there is one bit of internal program state that will be
3258 different when you return to a checkpoint --- the program's process
3259 id. Each checkpoint will have a unique process id (or @var{pid}),
3260 and each will be different from the program's original @var{pid}.
3261 If your program has saved a local copy of its process id, this could
3262 potentially pose a problem.
3264 @subsection A Non-obvious Benefit of Using Checkpoints
3266 On some systems such as @sc{gnu}/Linux, address space randomization
3267 is performed on new processes for security reasons. This makes it
3268 difficult or impossible to set a breakpoint, or watchpoint, on an
3269 absolute address if you have to restart the program, since the
3270 absolute location of a symbol will change from one execution to the
3273 A checkpoint, however, is an @emph{identical} copy of a process.
3274 Therefore if you create a checkpoint at (eg.@:) the start of main,
3275 and simply return to that checkpoint instead of restarting the
3276 process, you can avoid the effects of address randomization and
3277 your symbols will all stay in the same place.
3280 @chapter Stopping and Continuing
3282 The principal purposes of using a debugger are so that you can stop your
3283 program before it terminates; or so that, if your program runs into
3284 trouble, you can investigate and find out why.
3286 Inside @value{GDBN}, your program may stop for any of several reasons,
3287 such as a signal, a breakpoint, or reaching a new line after a
3288 @value{GDBN} command such as @code{step}. You may then examine and
3289 change variables, set new breakpoints or remove old ones, and then
3290 continue execution. Usually, the messages shown by @value{GDBN} provide
3291 ample explanation of the status of your program---but you can also
3292 explicitly request this information at any time.
3295 @kindex info program
3297 Display information about the status of your program: whether it is
3298 running or not, what process it is, and why it stopped.
3302 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3303 * Continuing and Stepping:: Resuming execution
3304 * Skipping Over Functions and Files::
3305 Skipping over functions and files
3307 * Thread Stops:: Stopping and starting multi-thread programs
3311 @section Breakpoints, Watchpoints, and Catchpoints
3314 A @dfn{breakpoint} makes your program stop whenever a certain point in
3315 the program is reached. For each breakpoint, you can add conditions to
3316 control in finer detail whether your program stops. You can set
3317 breakpoints with the @code{break} command and its variants (@pxref{Set
3318 Breaks, ,Setting Breakpoints}), to specify the place where your program
3319 should stop by line number, function name or exact address in the
3322 On some systems, you can set breakpoints in shared libraries before
3323 the executable is run. There is a minor limitation on HP-UX systems:
3324 you must wait until the executable is run in order to set breakpoints
3325 in shared library routines that are not called directly by the program
3326 (for example, routines that are arguments in a @code{pthread_create}
3330 @cindex data breakpoints
3331 @cindex memory tracing
3332 @cindex breakpoint on memory address
3333 @cindex breakpoint on variable modification
3334 A @dfn{watchpoint} is a special breakpoint that stops your program
3335 when the value of an expression changes. The expression may be a value
3336 of a variable, or it could involve values of one or more variables
3337 combined by operators, such as @samp{a + b}. This is sometimes called
3338 @dfn{data breakpoints}. You must use a different command to set
3339 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3340 from that, you can manage a watchpoint like any other breakpoint: you
3341 enable, disable, and delete both breakpoints and watchpoints using the
3344 You can arrange to have values from your program displayed automatically
3345 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3349 @cindex breakpoint on events
3350 A @dfn{catchpoint} is another special breakpoint that stops your program
3351 when a certain kind of event occurs, such as the throwing of a C@t{++}
3352 exception or the loading of a library. As with watchpoints, you use a
3353 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3354 Catchpoints}), but aside from that, you can manage a catchpoint like any
3355 other breakpoint. (To stop when your program receives a signal, use the
3356 @code{handle} command; see @ref{Signals, ,Signals}.)
3358 @cindex breakpoint numbers
3359 @cindex numbers for breakpoints
3360 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3361 catchpoint when you create it; these numbers are successive integers
3362 starting with one. In many of the commands for controlling various
3363 features of breakpoints you use the breakpoint number to say which
3364 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3365 @dfn{disabled}; if disabled, it has no effect on your program until you
3368 @cindex breakpoint ranges
3369 @cindex ranges of breakpoints
3370 Some @value{GDBN} commands accept a range of breakpoints on which to
3371 operate. A breakpoint range is either a single breakpoint number, like
3372 @samp{5}, or two such numbers, in increasing order, separated by a
3373 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3374 all breakpoints in that range are operated on.
3377 * Set Breaks:: Setting breakpoints
3378 * Set Watchpoints:: Setting watchpoints
3379 * Set Catchpoints:: Setting catchpoints
3380 * Delete Breaks:: Deleting breakpoints
3381 * Disabling:: Disabling breakpoints
3382 * Conditions:: Break conditions
3383 * Break Commands:: Breakpoint command lists
3384 * Dynamic Printf:: Dynamic printf
3385 * Save Breakpoints:: How to save breakpoints in a file
3386 * Static Probe Points:: Listing static probe points
3387 * Error in Breakpoints:: ``Cannot insert breakpoints''
3388 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3392 @subsection Setting Breakpoints
3394 @c FIXME LMB what does GDB do if no code on line of breakpt?
3395 @c consider in particular declaration with/without initialization.
3397 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3400 @kindex b @r{(@code{break})}
3401 @vindex $bpnum@r{, convenience variable}
3402 @cindex latest breakpoint
3403 Breakpoints are set with the @code{break} command (abbreviated
3404 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3405 number of the breakpoint you've set most recently; see @ref{Convenience
3406 Vars,, Convenience Variables}, for a discussion of what you can do with
3407 convenience variables.
3410 @item break @var{location}
3411 Set a breakpoint at the given @var{location}, which can specify a
3412 function name, a line number, or an address of an instruction.
3413 (@xref{Specify Location}, for a list of all the possible ways to
3414 specify a @var{location}.) The breakpoint will stop your program just
3415 before it executes any of the code in the specified @var{location}.
3417 When using source languages that permit overloading of symbols, such as
3418 C@t{++}, a function name may refer to more than one possible place to break.
3419 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3422 It is also possible to insert a breakpoint that will stop the program
3423 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3424 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3427 When called without any arguments, @code{break} sets a breakpoint at
3428 the next instruction to be executed in the selected stack frame
3429 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3430 innermost, this makes your program stop as soon as control
3431 returns to that frame. This is similar to the effect of a
3432 @code{finish} command in the frame inside the selected frame---except
3433 that @code{finish} does not leave an active breakpoint. If you use
3434 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3435 the next time it reaches the current location; this may be useful
3438 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3439 least one instruction has been executed. If it did not do this, you
3440 would be unable to proceed past a breakpoint without first disabling the
3441 breakpoint. This rule applies whether or not the breakpoint already
3442 existed when your program stopped.
3444 @item break @dots{} if @var{cond}
3445 Set a breakpoint with condition @var{cond}; evaluate the expression
3446 @var{cond} each time the breakpoint is reached, and stop only if the
3447 value is nonzero---that is, if @var{cond} evaluates as true.
3448 @samp{@dots{}} stands for one of the possible arguments described
3449 above (or no argument) specifying where to break. @xref{Conditions,
3450 ,Break Conditions}, for more information on breakpoint conditions.
3453 @item tbreak @var{args}
3454 Set a breakpoint enabled only for one stop. @var{args} are the
3455 same as for the @code{break} command, and the breakpoint is set in the same
3456 way, but the breakpoint is automatically deleted after the first time your
3457 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3460 @cindex hardware breakpoints
3461 @item hbreak @var{args}
3462 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3463 @code{break} command and the breakpoint is set in the same way, but the
3464 breakpoint requires hardware support and some target hardware may not
3465 have this support. The main purpose of this is EPROM/ROM code
3466 debugging, so you can set a breakpoint at an instruction without
3467 changing the instruction. This can be used with the new trap-generation
3468 provided by SPARClite DSU and most x86-based targets. These targets
3469 will generate traps when a program accesses some data or instruction
3470 address that is assigned to the debug registers. However the hardware
3471 breakpoint registers can take a limited number of breakpoints. For
3472 example, on the DSU, only two data breakpoints can be set at a time, and
3473 @value{GDBN} will reject this command if more than two are used. Delete
3474 or disable unused hardware breakpoints before setting new ones
3475 (@pxref{Disabling, ,Disabling Breakpoints}).
3476 @xref{Conditions, ,Break Conditions}.
3477 For remote targets, you can restrict the number of hardware
3478 breakpoints @value{GDBN} will use, see @ref{set remote
3479 hardware-breakpoint-limit}.
3482 @item thbreak @var{args}
3483 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3484 are the same as for the @code{hbreak} command and the breakpoint is set in
3485 the same way. However, like the @code{tbreak} command,
3486 the breakpoint is automatically deleted after the
3487 first time your program stops there. Also, like the @code{hbreak}
3488 command, the breakpoint requires hardware support and some target hardware
3489 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3490 See also @ref{Conditions, ,Break Conditions}.
3493 @cindex regular expression
3494 @cindex breakpoints at functions matching a regexp
3495 @cindex set breakpoints in many functions
3496 @item rbreak @var{regex}
3497 Set breakpoints on all functions matching the regular expression
3498 @var{regex}. This command sets an unconditional breakpoint on all
3499 matches, printing a list of all breakpoints it set. Once these
3500 breakpoints are set, they are treated just like the breakpoints set with
3501 the @code{break} command. You can delete them, disable them, or make
3502 them conditional the same way as any other breakpoint.
3504 The syntax of the regular expression is the standard one used with tools
3505 like @file{grep}. Note that this is different from the syntax used by
3506 shells, so for instance @code{foo*} matches all functions that include
3507 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3508 @code{.*} leading and trailing the regular expression you supply, so to
3509 match only functions that begin with @code{foo}, use @code{^foo}.
3511 @cindex non-member C@t{++} functions, set breakpoint in
3512 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3513 breakpoints on overloaded functions that are not members of any special
3516 @cindex set breakpoints on all functions
3517 The @code{rbreak} command can be used to set breakpoints in
3518 @strong{all} the functions in a program, like this:
3521 (@value{GDBP}) rbreak .
3524 @item rbreak @var{file}:@var{regex}
3525 If @code{rbreak} is called with a filename qualification, it limits
3526 the search for functions matching the given regular expression to the
3527 specified @var{file}. This can be used, for example, to set breakpoints on
3528 every function in a given file:
3531 (@value{GDBP}) rbreak file.c:.
3534 The colon separating the filename qualifier from the regex may
3535 optionally be surrounded by spaces.
3537 @kindex info breakpoints
3538 @cindex @code{$_} and @code{info breakpoints}
3539 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3540 @itemx info break @r{[}@var{n}@dots{}@r{]}
3541 Print a table of all breakpoints, watchpoints, and catchpoints set and
3542 not deleted. Optional argument @var{n} means print information only
3543 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3544 For each breakpoint, following columns are printed:
3547 @item Breakpoint Numbers
3549 Breakpoint, watchpoint, or catchpoint.
3551 Whether the breakpoint is marked to be disabled or deleted when hit.
3552 @item Enabled or Disabled
3553 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3554 that are not enabled.
3556 Where the breakpoint is in your program, as a memory address. For a
3557 pending breakpoint whose address is not yet known, this field will
3558 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3559 library that has the symbol or line referred by breakpoint is loaded.
3560 See below for details. A breakpoint with several locations will
3561 have @samp{<MULTIPLE>} in this field---see below for details.
3563 Where the breakpoint is in the source for your program, as a file and
3564 line number. For a pending breakpoint, the original string passed to
3565 the breakpoint command will be listed as it cannot be resolved until
3566 the appropriate shared library is loaded in the future.
3570 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3571 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3572 @value{GDBN} on the host's side. If it is ``target'', then the condition
3573 is evaluated by the target. The @code{info break} command shows
3574 the condition on the line following the affected breakpoint, together with
3575 its condition evaluation mode in between parentheses.
3577 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3578 allowed to have a condition specified for it. The condition is not parsed for
3579 validity until a shared library is loaded that allows the pending
3580 breakpoint to resolve to a valid location.
3583 @code{info break} with a breakpoint
3584 number @var{n} as argument lists only that breakpoint. The
3585 convenience variable @code{$_} and the default examining-address for
3586 the @code{x} command are set to the address of the last breakpoint
3587 listed (@pxref{Memory, ,Examining Memory}).
3590 @code{info break} displays a count of the number of times the breakpoint
3591 has been hit. This is especially useful in conjunction with the
3592 @code{ignore} command. You can ignore a large number of breakpoint
3593 hits, look at the breakpoint info to see how many times the breakpoint
3594 was hit, and then run again, ignoring one less than that number. This
3595 will get you quickly to the last hit of that breakpoint.
3598 For a breakpoints with an enable count (xref) greater than 1,
3599 @code{info break} also displays that count.
3603 @value{GDBN} allows you to set any number of breakpoints at the same place in
3604 your program. There is nothing silly or meaningless about this. When
3605 the breakpoints are conditional, this is even useful
3606 (@pxref{Conditions, ,Break Conditions}).
3608 @cindex multiple locations, breakpoints
3609 @cindex breakpoints, multiple locations
3610 It is possible that a breakpoint corresponds to several locations
3611 in your program. Examples of this situation are:
3615 Multiple functions in the program may have the same name.
3618 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3619 instances of the function body, used in different cases.
3622 For a C@t{++} template function, a given line in the function can
3623 correspond to any number of instantiations.
3626 For an inlined function, a given source line can correspond to
3627 several places where that function is inlined.
3630 In all those cases, @value{GDBN} will insert a breakpoint at all
3631 the relevant locations.
3633 A breakpoint with multiple locations is displayed in the breakpoint
3634 table using several rows---one header row, followed by one row for
3635 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3636 address column. The rows for individual locations contain the actual
3637 addresses for locations, and show the functions to which those
3638 locations belong. The number column for a location is of the form
3639 @var{breakpoint-number}.@var{location-number}.
3644 Num Type Disp Enb Address What
3645 1 breakpoint keep y <MULTIPLE>
3647 breakpoint already hit 1 time
3648 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3649 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3652 Each location can be individually enabled or disabled by passing
3653 @var{breakpoint-number}.@var{location-number} as argument to the
3654 @code{enable} and @code{disable} commands. Note that you cannot
3655 delete the individual locations from the list, you can only delete the
3656 entire list of locations that belong to their parent breakpoint (with
3657 the @kbd{delete @var{num}} command, where @var{num} is the number of
3658 the parent breakpoint, 1 in the above example). Disabling or enabling
3659 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3660 that belong to that breakpoint.
3662 @cindex pending breakpoints
3663 It's quite common to have a breakpoint inside a shared library.
3664 Shared libraries can be loaded and unloaded explicitly,
3665 and possibly repeatedly, as the program is executed. To support
3666 this use case, @value{GDBN} updates breakpoint locations whenever
3667 any shared library is loaded or unloaded. Typically, you would
3668 set a breakpoint in a shared library at the beginning of your
3669 debugging session, when the library is not loaded, and when the
3670 symbols from the library are not available. When you try to set
3671 breakpoint, @value{GDBN} will ask you if you want to set
3672 a so called @dfn{pending breakpoint}---breakpoint whose address
3673 is not yet resolved.
3675 After the program is run, whenever a new shared library is loaded,
3676 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3677 shared library contains the symbol or line referred to by some
3678 pending breakpoint, that breakpoint is resolved and becomes an
3679 ordinary breakpoint. When a library is unloaded, all breakpoints
3680 that refer to its symbols or source lines become pending again.
3682 This logic works for breakpoints with multiple locations, too. For
3683 example, if you have a breakpoint in a C@t{++} template function, and
3684 a newly loaded shared library has an instantiation of that template,
3685 a new location is added to the list of locations for the breakpoint.
3687 Except for having unresolved address, pending breakpoints do not
3688 differ from regular breakpoints. You can set conditions or commands,
3689 enable and disable them and perform other breakpoint operations.
3691 @value{GDBN} provides some additional commands for controlling what
3692 happens when the @samp{break} command cannot resolve breakpoint
3693 address specification to an address:
3695 @kindex set breakpoint pending
3696 @kindex show breakpoint pending
3698 @item set breakpoint pending auto
3699 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3700 location, it queries you whether a pending breakpoint should be created.
3702 @item set breakpoint pending on
3703 This indicates that an unrecognized breakpoint location should automatically
3704 result in a pending breakpoint being created.
3706 @item set breakpoint pending off
3707 This indicates that pending breakpoints are not to be created. Any
3708 unrecognized breakpoint location results in an error. This setting does
3709 not affect any pending breakpoints previously created.
3711 @item show breakpoint pending
3712 Show the current behavior setting for creating pending breakpoints.
3715 The settings above only affect the @code{break} command and its
3716 variants. Once breakpoint is set, it will be automatically updated
3717 as shared libraries are loaded and unloaded.
3719 @cindex automatic hardware breakpoints
3720 For some targets, @value{GDBN} can automatically decide if hardware or
3721 software breakpoints should be used, depending on whether the
3722 breakpoint address is read-only or read-write. This applies to
3723 breakpoints set with the @code{break} command as well as to internal
3724 breakpoints set by commands like @code{next} and @code{finish}. For
3725 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3728 You can control this automatic behaviour with the following commands::
3730 @kindex set breakpoint auto-hw
3731 @kindex show breakpoint auto-hw
3733 @item set breakpoint auto-hw on
3734 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3735 will try to use the target memory map to decide if software or hardware
3736 breakpoint must be used.
3738 @item set breakpoint auto-hw off
3739 This indicates @value{GDBN} should not automatically select breakpoint
3740 type. If the target provides a memory map, @value{GDBN} will warn when
3741 trying to set software breakpoint at a read-only address.
3744 @value{GDBN} normally implements breakpoints by replacing the program code
3745 at the breakpoint address with a special instruction, which, when
3746 executed, given control to the debugger. By default, the program
3747 code is so modified only when the program is resumed. As soon as
3748 the program stops, @value{GDBN} restores the original instructions. This
3749 behaviour guards against leaving breakpoints inserted in the
3750 target should gdb abrubptly disconnect. However, with slow remote
3751 targets, inserting and removing breakpoint can reduce the performance.
3752 This behavior can be controlled with the following commands::
3754 @kindex set breakpoint always-inserted
3755 @kindex show breakpoint always-inserted
3757 @item set breakpoint always-inserted off
3758 All breakpoints, including newly added by the user, are inserted in
3759 the target only when the target is resumed. All breakpoints are
3760 removed from the target when it stops.
3762 @item set breakpoint always-inserted on
3763 Causes all breakpoints to be inserted in the target at all times. If
3764 the user adds a new breakpoint, or changes an existing breakpoint, the
3765 breakpoints in the target are updated immediately. A breakpoint is
3766 removed from the target only when breakpoint itself is removed.
3768 @cindex non-stop mode, and @code{breakpoint always-inserted}
3769 @item set breakpoint always-inserted auto
3770 This is the default mode. If @value{GDBN} is controlling the inferior
3771 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3772 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3773 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3774 @code{breakpoint always-inserted} mode is off.
3777 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3778 when a breakpoint breaks. If the condition is true, then the process being
3779 debugged stops, otherwise the process is resumed.
3781 If the target supports evaluating conditions on its end, @value{GDBN} may
3782 download the breakpoint, together with its conditions, to it.
3784 This feature can be controlled via the following commands:
3786 @kindex set breakpoint condition-evaluation
3787 @kindex show breakpoint condition-evaluation
3789 @item set breakpoint condition-evaluation host
3790 This option commands @value{GDBN} to evaluate the breakpoint
3791 conditions on the host's side. Unconditional breakpoints are sent to
3792 the target which in turn receives the triggers and reports them back to GDB
3793 for condition evaluation. This is the standard evaluation mode.
3795 @item set breakpoint condition-evaluation target
3796 This option commands @value{GDBN} to download breakpoint conditions
3797 to the target at the moment of their insertion. The target
3798 is responsible for evaluating the conditional expression and reporting
3799 breakpoint stop events back to @value{GDBN} whenever the condition
3800 is true. Due to limitations of target-side evaluation, some conditions
3801 cannot be evaluated there, e.g., conditions that depend on local data
3802 that is only known to the host. Examples include
3803 conditional expressions involving convenience variables, complex types
3804 that cannot be handled by the agent expression parser and expressions
3805 that are too long to be sent over to the target, specially when the
3806 target is a remote system. In these cases, the conditions will be
3807 evaluated by @value{GDBN}.
3809 @item set breakpoint condition-evaluation auto
3810 This is the default mode. If the target supports evaluating breakpoint
3811 conditions on its end, @value{GDBN} will download breakpoint conditions to
3812 the target (limitations mentioned previously apply). If the target does
3813 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3814 to evaluating all these conditions on the host's side.
3818 @cindex negative breakpoint numbers
3819 @cindex internal @value{GDBN} breakpoints
3820 @value{GDBN} itself sometimes sets breakpoints in your program for
3821 special purposes, such as proper handling of @code{longjmp} (in C
3822 programs). These internal breakpoints are assigned negative numbers,
3823 starting with @code{-1}; @samp{info breakpoints} does not display them.
3824 You can see these breakpoints with the @value{GDBN} maintenance command
3825 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3828 @node Set Watchpoints
3829 @subsection Setting Watchpoints
3831 @cindex setting watchpoints
3832 You can use a watchpoint to stop execution whenever the value of an
3833 expression changes, without having to predict a particular place where
3834 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3835 The expression may be as simple as the value of a single variable, or
3836 as complex as many variables combined by operators. Examples include:
3840 A reference to the value of a single variable.
3843 An address cast to an appropriate data type. For example,
3844 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3845 address (assuming an @code{int} occupies 4 bytes).
3848 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3849 expression can use any operators valid in the program's native
3850 language (@pxref{Languages}).
3853 You can set a watchpoint on an expression even if the expression can
3854 not be evaluated yet. For instance, you can set a watchpoint on
3855 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3856 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3857 the expression produces a valid value. If the expression becomes
3858 valid in some other way than changing a variable (e.g.@: if the memory
3859 pointed to by @samp{*global_ptr} becomes readable as the result of a
3860 @code{malloc} call), @value{GDBN} may not stop until the next time
3861 the expression changes.
3863 @cindex software watchpoints
3864 @cindex hardware watchpoints
3865 Depending on your system, watchpoints may be implemented in software or
3866 hardware. @value{GDBN} does software watchpointing by single-stepping your
3867 program and testing the variable's value each time, which is hundreds of
3868 times slower than normal execution. (But this may still be worth it, to
3869 catch errors where you have no clue what part of your program is the
3872 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3873 x86-based targets, @value{GDBN} includes support for hardware
3874 watchpoints, which do not slow down the running of your program.
3878 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3879 Set a watchpoint for an expression. @value{GDBN} will break when the
3880 expression @var{expr} is written into by the program and its value
3881 changes. The simplest (and the most popular) use of this command is
3882 to watch the value of a single variable:
3885 (@value{GDBP}) watch foo
3888 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3889 argument, @value{GDBN} breaks only when the thread identified by
3890 @var{threadnum} changes the value of @var{expr}. If any other threads
3891 change the value of @var{expr}, @value{GDBN} will not break. Note
3892 that watchpoints restricted to a single thread in this way only work
3893 with Hardware Watchpoints.
3895 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3896 (see below). The @code{-location} argument tells @value{GDBN} to
3897 instead watch the memory referred to by @var{expr}. In this case,
3898 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3899 and watch the memory at that address. The type of the result is used
3900 to determine the size of the watched memory. If the expression's
3901 result does not have an address, then @value{GDBN} will print an
3904 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3905 of masked watchpoints, if the current architecture supports this
3906 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3907 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3908 to an address to watch. The mask specifies that some bits of an address
3909 (the bits which are reset in the mask) should be ignored when matching
3910 the address accessed by the inferior against the watchpoint address.
3911 Thus, a masked watchpoint watches many addresses simultaneously---those
3912 addresses whose unmasked bits are identical to the unmasked bits in the
3913 watchpoint address. The @code{mask} argument implies @code{-location}.
3917 (@value{GDBP}) watch foo mask 0xffff00ff
3918 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3922 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3923 Set a watchpoint that will break when the value of @var{expr} is read
3927 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3928 Set a watchpoint that will break when @var{expr} is either read from
3929 or written into by the program.
3931 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3932 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3933 This command prints a list of watchpoints, using the same format as
3934 @code{info break} (@pxref{Set Breaks}).
3937 If you watch for a change in a numerically entered address you need to
3938 dereference it, as the address itself is just a constant number which will
3939 never change. @value{GDBN} refuses to create a watchpoint that watches
3940 a never-changing value:
3943 (@value{GDBP}) watch 0x600850
3944 Cannot watch constant value 0x600850.
3945 (@value{GDBP}) watch *(int *) 0x600850
3946 Watchpoint 1: *(int *) 6293584
3949 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3950 watchpoints execute very quickly, and the debugger reports a change in
3951 value at the exact instruction where the change occurs. If @value{GDBN}
3952 cannot set a hardware watchpoint, it sets a software watchpoint, which
3953 executes more slowly and reports the change in value at the next
3954 @emph{statement}, not the instruction, after the change occurs.
3956 @cindex use only software watchpoints
3957 You can force @value{GDBN} to use only software watchpoints with the
3958 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3959 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3960 the underlying system supports them. (Note that hardware-assisted
3961 watchpoints that were set @emph{before} setting
3962 @code{can-use-hw-watchpoints} to zero will still use the hardware
3963 mechanism of watching expression values.)
3966 @item set can-use-hw-watchpoints
3967 @kindex set can-use-hw-watchpoints
3968 Set whether or not to use hardware watchpoints.
3970 @item show can-use-hw-watchpoints
3971 @kindex show can-use-hw-watchpoints
3972 Show the current mode of using hardware watchpoints.
3975 For remote targets, you can restrict the number of hardware
3976 watchpoints @value{GDBN} will use, see @ref{set remote
3977 hardware-breakpoint-limit}.
3979 When you issue the @code{watch} command, @value{GDBN} reports
3982 Hardware watchpoint @var{num}: @var{expr}
3986 if it was able to set a hardware watchpoint.
3988 Currently, the @code{awatch} and @code{rwatch} commands can only set
3989 hardware watchpoints, because accesses to data that don't change the
3990 value of the watched expression cannot be detected without examining
3991 every instruction as it is being executed, and @value{GDBN} does not do
3992 that currently. If @value{GDBN} finds that it is unable to set a
3993 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3994 will print a message like this:
3997 Expression cannot be implemented with read/access watchpoint.
4000 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4001 data type of the watched expression is wider than what a hardware
4002 watchpoint on the target machine can handle. For example, some systems
4003 can only watch regions that are up to 4 bytes wide; on such systems you
4004 cannot set hardware watchpoints for an expression that yields a
4005 double-precision floating-point number (which is typically 8 bytes
4006 wide). As a work-around, it might be possible to break the large region
4007 into a series of smaller ones and watch them with separate watchpoints.
4009 If you set too many hardware watchpoints, @value{GDBN} might be unable
4010 to insert all of them when you resume the execution of your program.
4011 Since the precise number of active watchpoints is unknown until such
4012 time as the program is about to be resumed, @value{GDBN} might not be
4013 able to warn you about this when you set the watchpoints, and the
4014 warning will be printed only when the program is resumed:
4017 Hardware watchpoint @var{num}: Could not insert watchpoint
4021 If this happens, delete or disable some of the watchpoints.
4023 Watching complex expressions that reference many variables can also
4024 exhaust the resources available for hardware-assisted watchpoints.
4025 That's because @value{GDBN} needs to watch every variable in the
4026 expression with separately allocated resources.
4028 If you call a function interactively using @code{print} or @code{call},
4029 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4030 kind of breakpoint or the call completes.
4032 @value{GDBN} automatically deletes watchpoints that watch local
4033 (automatic) variables, or expressions that involve such variables, when
4034 they go out of scope, that is, when the execution leaves the block in
4035 which these variables were defined. In particular, when the program
4036 being debugged terminates, @emph{all} local variables go out of scope,
4037 and so only watchpoints that watch global variables remain set. If you
4038 rerun the program, you will need to set all such watchpoints again. One
4039 way of doing that would be to set a code breakpoint at the entry to the
4040 @code{main} function and when it breaks, set all the watchpoints.
4042 @cindex watchpoints and threads
4043 @cindex threads and watchpoints
4044 In multi-threaded programs, watchpoints will detect changes to the
4045 watched expression from every thread.
4048 @emph{Warning:} In multi-threaded programs, software watchpoints
4049 have only limited usefulness. If @value{GDBN} creates a software
4050 watchpoint, it can only watch the value of an expression @emph{in a
4051 single thread}. If you are confident that the expression can only
4052 change due to the current thread's activity (and if you are also
4053 confident that no other thread can become current), then you can use
4054 software watchpoints as usual. However, @value{GDBN} may not notice
4055 when a non-current thread's activity changes the expression. (Hardware
4056 watchpoints, in contrast, watch an expression in all threads.)
4059 @xref{set remote hardware-watchpoint-limit}.
4061 @node Set Catchpoints
4062 @subsection Setting Catchpoints
4063 @cindex catchpoints, setting
4064 @cindex exception handlers
4065 @cindex event handling
4067 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4068 kinds of program events, such as C@t{++} exceptions or the loading of a
4069 shared library. Use the @code{catch} command to set a catchpoint.
4073 @item catch @var{event}
4074 Stop when @var{event} occurs. @var{event} can be any of the following:
4077 @cindex stop on C@t{++} exceptions
4078 The throwing of a C@t{++} exception.
4081 The catching of a C@t{++} exception.
4084 @cindex Ada exception catching
4085 @cindex catch Ada exceptions
4086 An Ada exception being raised. If an exception name is specified
4087 at the end of the command (eg @code{catch exception Program_Error}),
4088 the debugger will stop only when this specific exception is raised.
4089 Otherwise, the debugger stops execution when any Ada exception is raised.
4091 When inserting an exception catchpoint on a user-defined exception whose
4092 name is identical to one of the exceptions defined by the language, the
4093 fully qualified name must be used as the exception name. Otherwise,
4094 @value{GDBN} will assume that it should stop on the pre-defined exception
4095 rather than the user-defined one. For instance, assuming an exception
4096 called @code{Constraint_Error} is defined in package @code{Pck}, then
4097 the command to use to catch such exceptions is @kbd{catch exception
4098 Pck.Constraint_Error}.
4100 @item exception unhandled
4101 An exception that was raised but is not handled by the program.
4104 A failed Ada assertion.
4107 @cindex break on fork/exec
4108 A call to @code{exec}. This is currently only available for HP-UX
4112 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4113 @cindex break on a system call.
4114 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4115 syscall is a mechanism for application programs to request a service
4116 from the operating system (OS) or one of the OS system services.
4117 @value{GDBN} can catch some or all of the syscalls issued by the
4118 debuggee, and show the related information for each syscall. If no
4119 argument is specified, calls to and returns from all system calls
4122 @var{name} can be any system call name that is valid for the
4123 underlying OS. Just what syscalls are valid depends on the OS. On
4124 GNU and Unix systems, you can find the full list of valid syscall
4125 names on @file{/usr/include/asm/unistd.h}.
4127 @c For MS-Windows, the syscall names and the corresponding numbers
4128 @c can be found, e.g., on this URL:
4129 @c http://www.metasploit.com/users/opcode/syscalls.html
4130 @c but we don't support Windows syscalls yet.
4132 Normally, @value{GDBN} knows in advance which syscalls are valid for
4133 each OS, so you can use the @value{GDBN} command-line completion
4134 facilities (@pxref{Completion,, command completion}) to list the
4137 You may also specify the system call numerically. A syscall's
4138 number is the value passed to the OS's syscall dispatcher to
4139 identify the requested service. When you specify the syscall by its
4140 name, @value{GDBN} uses its database of syscalls to convert the name
4141 into the corresponding numeric code, but using the number directly
4142 may be useful if @value{GDBN}'s database does not have the complete
4143 list of syscalls on your system (e.g., because @value{GDBN} lags
4144 behind the OS upgrades).
4146 The example below illustrates how this command works if you don't provide
4150 (@value{GDBP}) catch syscall
4151 Catchpoint 1 (syscall)
4153 Starting program: /tmp/catch-syscall
4155 Catchpoint 1 (call to syscall 'close'), \
4156 0xffffe424 in __kernel_vsyscall ()
4160 Catchpoint 1 (returned from syscall 'close'), \
4161 0xffffe424 in __kernel_vsyscall ()
4165 Here is an example of catching a system call by name:
4168 (@value{GDBP}) catch syscall chroot
4169 Catchpoint 1 (syscall 'chroot' [61])
4171 Starting program: /tmp/catch-syscall
4173 Catchpoint 1 (call to syscall 'chroot'), \
4174 0xffffe424 in __kernel_vsyscall ()
4178 Catchpoint 1 (returned from syscall 'chroot'), \
4179 0xffffe424 in __kernel_vsyscall ()
4183 An example of specifying a system call numerically. In the case
4184 below, the syscall number has a corresponding entry in the XML
4185 file, so @value{GDBN} finds its name and prints it:
4188 (@value{GDBP}) catch syscall 252
4189 Catchpoint 1 (syscall(s) 'exit_group')
4191 Starting program: /tmp/catch-syscall
4193 Catchpoint 1 (call to syscall 'exit_group'), \
4194 0xffffe424 in __kernel_vsyscall ()
4198 Program exited normally.
4202 However, there can be situations when there is no corresponding name
4203 in XML file for that syscall number. In this case, @value{GDBN} prints
4204 a warning message saying that it was not able to find the syscall name,
4205 but the catchpoint will be set anyway. See the example below:
4208 (@value{GDBP}) catch syscall 764
4209 warning: The number '764' does not represent a known syscall.
4210 Catchpoint 2 (syscall 764)
4214 If you configure @value{GDBN} using the @samp{--without-expat} option,
4215 it will not be able to display syscall names. Also, if your
4216 architecture does not have an XML file describing its system calls,
4217 you will not be able to see the syscall names. It is important to
4218 notice that these two features are used for accessing the syscall
4219 name database. In either case, you will see a warning like this:
4222 (@value{GDBP}) catch syscall
4223 warning: Could not open "syscalls/i386-linux.xml"
4224 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4225 GDB will not be able to display syscall names.
4226 Catchpoint 1 (syscall)
4230 Of course, the file name will change depending on your architecture and system.
4232 Still using the example above, you can also try to catch a syscall by its
4233 number. In this case, you would see something like:
4236 (@value{GDBP}) catch syscall 252
4237 Catchpoint 1 (syscall(s) 252)
4240 Again, in this case @value{GDBN} would not be able to display syscall's names.
4243 A call to @code{fork}. This is currently only available for HP-UX
4247 A call to @code{vfork}. This is currently only available for HP-UX
4250 @item load @r{[}regexp@r{]}
4251 @itemx unload @r{[}regexp@r{]}
4252 The loading or unloading of a shared library. If @var{regexp} is
4253 given, then the catchpoint will stop only if the regular expression
4254 matches one of the affected libraries.
4256 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4257 The delivery of a signal.
4259 With no arguments, this catchpoint will catch any signal that is not
4260 used internally by @value{GDBN}, specifically, all signals except
4261 @samp{SIGTRAP} and @samp{SIGINT}.
4263 With the argument @samp{all}, all signals, including those used by
4264 @value{GDBN}, will be caught. This argument cannot be used with other
4267 Otherwise, the arguments are a list of signal names as given to
4268 @code{handle} (@pxref{Signals}). Only signals specified in this list
4271 One reason that @code{catch signal} can be more useful than
4272 @code{handle} is that you can attach commands and conditions to the
4275 When a signal is caught by a catchpoint, the signal's @code{stop} and
4276 @code{print} settings, as specified by @code{handle}, are ignored.
4277 However, whether the signal is still delivered to the inferior depends
4278 on the @code{pass} setting; this can be changed in the catchpoint's
4283 @item tcatch @var{event}
4284 Set a catchpoint that is enabled only for one stop. The catchpoint is
4285 automatically deleted after the first time the event is caught.
4289 Use the @code{info break} command to list the current catchpoints.
4291 There are currently some limitations to C@t{++} exception handling
4292 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4296 If you call a function interactively, @value{GDBN} normally returns
4297 control to you when the function has finished executing. If the call
4298 raises an exception, however, the call may bypass the mechanism that
4299 returns control to you and cause your program either to abort or to
4300 simply continue running until it hits a breakpoint, catches a signal
4301 that @value{GDBN} is listening for, or exits. This is the case even if
4302 you set a catchpoint for the exception; catchpoints on exceptions are
4303 disabled within interactive calls.
4306 You cannot raise an exception interactively.
4309 You cannot install an exception handler interactively.
4314 @subsection Deleting Breakpoints
4316 @cindex clearing breakpoints, watchpoints, catchpoints
4317 @cindex deleting breakpoints, watchpoints, catchpoints
4318 It is often necessary to eliminate a breakpoint, watchpoint, or
4319 catchpoint once it has done its job and you no longer want your program
4320 to stop there. This is called @dfn{deleting} the breakpoint. A
4321 breakpoint that has been deleted no longer exists; it is forgotten.
4323 With the @code{clear} command you can delete breakpoints according to
4324 where they are in your program. With the @code{delete} command you can
4325 delete individual breakpoints, watchpoints, or catchpoints by specifying
4326 their breakpoint numbers.
4328 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4329 automatically ignores breakpoints on the first instruction to be executed
4330 when you continue execution without changing the execution address.
4335 Delete any breakpoints at the next instruction to be executed in the
4336 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4337 the innermost frame is selected, this is a good way to delete a
4338 breakpoint where your program just stopped.
4340 @item clear @var{location}
4341 Delete any breakpoints set at the specified @var{location}.
4342 @xref{Specify Location}, for the various forms of @var{location}; the
4343 most useful ones are listed below:
4346 @item clear @var{function}
4347 @itemx clear @var{filename}:@var{function}
4348 Delete any breakpoints set at entry to the named @var{function}.
4350 @item clear @var{linenum}
4351 @itemx clear @var{filename}:@var{linenum}
4352 Delete any breakpoints set at or within the code of the specified
4353 @var{linenum} of the specified @var{filename}.
4356 @cindex delete breakpoints
4358 @kindex d @r{(@code{delete})}
4359 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4360 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4361 ranges specified as arguments. If no argument is specified, delete all
4362 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4363 confirm off}). You can abbreviate this command as @code{d}.
4367 @subsection Disabling Breakpoints
4369 @cindex enable/disable a breakpoint
4370 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4371 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4372 it had been deleted, but remembers the information on the breakpoint so
4373 that you can @dfn{enable} it again later.
4375 You disable and enable breakpoints, watchpoints, and catchpoints with
4376 the @code{enable} and @code{disable} commands, optionally specifying
4377 one or more breakpoint numbers as arguments. Use @code{info break} to
4378 print a list of all breakpoints, watchpoints, and catchpoints if you
4379 do not know which numbers to use.
4381 Disabling and enabling a breakpoint that has multiple locations
4382 affects all of its locations.
4384 A breakpoint, watchpoint, or catchpoint can have any of several
4385 different states of enablement:
4389 Enabled. The breakpoint stops your program. A breakpoint set
4390 with the @code{break} command starts out in this state.
4392 Disabled. The breakpoint has no effect on your program.
4394 Enabled once. The breakpoint stops your program, but then becomes
4397 Enabled for a count. The breakpoint stops your program for the next
4398 N times, then becomes disabled.
4400 Enabled for deletion. The breakpoint stops your program, but
4401 immediately after it does so it is deleted permanently. A breakpoint
4402 set with the @code{tbreak} command starts out in this state.
4405 You can use the following commands to enable or disable breakpoints,
4406 watchpoints, and catchpoints:
4410 @kindex dis @r{(@code{disable})}
4411 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4412 Disable the specified breakpoints---or all breakpoints, if none are
4413 listed. A disabled breakpoint has no effect but is not forgotten. All
4414 options such as ignore-counts, conditions and commands are remembered in
4415 case the breakpoint is enabled again later. You may abbreviate
4416 @code{disable} as @code{dis}.
4419 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4420 Enable the specified breakpoints (or all defined breakpoints). They
4421 become effective once again in stopping your program.
4423 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4424 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4425 of these breakpoints immediately after stopping your program.
4427 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4428 Enable the specified breakpoints temporarily. @value{GDBN} records
4429 @var{count} with each of the specified breakpoints, and decrements a
4430 breakpoint's count when it is hit. When any count reaches 0,
4431 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4432 count (@pxref{Conditions, ,Break Conditions}), that will be
4433 decremented to 0 before @var{count} is affected.
4435 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4436 Enable the specified breakpoints to work once, then die. @value{GDBN}
4437 deletes any of these breakpoints as soon as your program stops there.
4438 Breakpoints set by the @code{tbreak} command start out in this state.
4441 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4442 @c confusing: tbreak is also initially enabled.
4443 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4444 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4445 subsequently, they become disabled or enabled only when you use one of
4446 the commands above. (The command @code{until} can set and delete a
4447 breakpoint of its own, but it does not change the state of your other
4448 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4452 @subsection Break Conditions
4453 @cindex conditional breakpoints
4454 @cindex breakpoint conditions
4456 @c FIXME what is scope of break condition expr? Context where wanted?
4457 @c in particular for a watchpoint?
4458 The simplest sort of breakpoint breaks every time your program reaches a
4459 specified place. You can also specify a @dfn{condition} for a
4460 breakpoint. A condition is just a Boolean expression in your
4461 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4462 a condition evaluates the expression each time your program reaches it,
4463 and your program stops only if the condition is @emph{true}.
4465 This is the converse of using assertions for program validation; in that
4466 situation, you want to stop when the assertion is violated---that is,
4467 when the condition is false. In C, if you want to test an assertion expressed
4468 by the condition @var{assert}, you should set the condition
4469 @samp{! @var{assert}} on the appropriate breakpoint.
4471 Conditions are also accepted for watchpoints; you may not need them,
4472 since a watchpoint is inspecting the value of an expression anyhow---but
4473 it might be simpler, say, to just set a watchpoint on a variable name,
4474 and specify a condition that tests whether the new value is an interesting
4477 Break conditions can have side effects, and may even call functions in
4478 your program. This can be useful, for example, to activate functions
4479 that log program progress, or to use your own print functions to
4480 format special data structures. The effects are completely predictable
4481 unless there is another enabled breakpoint at the same address. (In
4482 that case, @value{GDBN} might see the other breakpoint first and stop your
4483 program without checking the condition of this one.) Note that
4484 breakpoint commands are usually more convenient and flexible than break
4486 purpose of performing side effects when a breakpoint is reached
4487 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4489 Breakpoint conditions can also be evaluated on the target's side if
4490 the target supports it. Instead of evaluating the conditions locally,
4491 @value{GDBN} encodes the expression into an agent expression
4492 (@pxref{Agent Expressions}) suitable for execution on the target,
4493 independently of @value{GDBN}. Global variables become raw memory
4494 locations, locals become stack accesses, and so forth.
4496 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4497 when its condition evaluates to true. This mechanism may provide faster
4498 response times depending on the performance characteristics of the target
4499 since it does not need to keep @value{GDBN} informed about
4500 every breakpoint trigger, even those with false conditions.
4502 Break conditions can be specified when a breakpoint is set, by using
4503 @samp{if} in the arguments to the @code{break} command. @xref{Set
4504 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4505 with the @code{condition} command.
4507 You can also use the @code{if} keyword with the @code{watch} command.
4508 The @code{catch} command does not recognize the @code{if} keyword;
4509 @code{condition} is the only way to impose a further condition on a
4514 @item condition @var{bnum} @var{expression}
4515 Specify @var{expression} as the break condition for breakpoint,
4516 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4517 breakpoint @var{bnum} stops your program only if the value of
4518 @var{expression} is true (nonzero, in C). When you use
4519 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4520 syntactic correctness, and to determine whether symbols in it have
4521 referents in the context of your breakpoint. If @var{expression} uses
4522 symbols not referenced in the context of the breakpoint, @value{GDBN}
4523 prints an error message:
4526 No symbol "foo" in current context.
4531 not actually evaluate @var{expression} at the time the @code{condition}
4532 command (or a command that sets a breakpoint with a condition, like
4533 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4535 @item condition @var{bnum}
4536 Remove the condition from breakpoint number @var{bnum}. It becomes
4537 an ordinary unconditional breakpoint.
4540 @cindex ignore count (of breakpoint)
4541 A special case of a breakpoint condition is to stop only when the
4542 breakpoint has been reached a certain number of times. This is so
4543 useful that there is a special way to do it, using the @dfn{ignore
4544 count} of the breakpoint. Every breakpoint has an ignore count, which
4545 is an integer. Most of the time, the ignore count is zero, and
4546 therefore has no effect. But if your program reaches a breakpoint whose
4547 ignore count is positive, then instead of stopping, it just decrements
4548 the ignore count by one and continues. As a result, if the ignore count
4549 value is @var{n}, the breakpoint does not stop the next @var{n} times
4550 your program reaches it.
4554 @item ignore @var{bnum} @var{count}
4555 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4556 The next @var{count} times the breakpoint is reached, your program's
4557 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4560 To make the breakpoint stop the next time it is reached, specify
4563 When you use @code{continue} to resume execution of your program from a
4564 breakpoint, you can specify an ignore count directly as an argument to
4565 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4566 Stepping,,Continuing and Stepping}.
4568 If a breakpoint has a positive ignore count and a condition, the
4569 condition is not checked. Once the ignore count reaches zero,
4570 @value{GDBN} resumes checking the condition.
4572 You could achieve the effect of the ignore count with a condition such
4573 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4574 is decremented each time. @xref{Convenience Vars, ,Convenience
4578 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4581 @node Break Commands
4582 @subsection Breakpoint Command Lists
4584 @cindex breakpoint commands
4585 You can give any breakpoint (or watchpoint or catchpoint) a series of
4586 commands to execute when your program stops due to that breakpoint. For
4587 example, you might want to print the values of certain expressions, or
4588 enable other breakpoints.
4592 @kindex end@r{ (breakpoint commands)}
4593 @item commands @r{[}@var{range}@dots{}@r{]}
4594 @itemx @dots{} @var{command-list} @dots{}
4596 Specify a list of commands for the given breakpoints. The commands
4597 themselves appear on the following lines. Type a line containing just
4598 @code{end} to terminate the commands.
4600 To remove all commands from a breakpoint, type @code{commands} and
4601 follow it immediately with @code{end}; that is, give no commands.
4603 With no argument, @code{commands} refers to the last breakpoint,
4604 watchpoint, or catchpoint set (not to the breakpoint most recently
4605 encountered). If the most recent breakpoints were set with a single
4606 command, then the @code{commands} will apply to all the breakpoints
4607 set by that command. This applies to breakpoints set by
4608 @code{rbreak}, and also applies when a single @code{break} command
4609 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4613 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4614 disabled within a @var{command-list}.
4616 You can use breakpoint commands to start your program up again. Simply
4617 use the @code{continue} command, or @code{step}, or any other command
4618 that resumes execution.
4620 Any other commands in the command list, after a command that resumes
4621 execution, are ignored. This is because any time you resume execution
4622 (even with a simple @code{next} or @code{step}), you may encounter
4623 another breakpoint---which could have its own command list, leading to
4624 ambiguities about which list to execute.
4627 If the first command you specify in a command list is @code{silent}, the
4628 usual message about stopping at a breakpoint is not printed. This may
4629 be desirable for breakpoints that are to print a specific message and
4630 then continue. If none of the remaining commands print anything, you
4631 see no sign that the breakpoint was reached. @code{silent} is
4632 meaningful only at the beginning of a breakpoint command list.
4634 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4635 print precisely controlled output, and are often useful in silent
4636 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4638 For example, here is how you could use breakpoint commands to print the
4639 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4645 printf "x is %d\n",x
4650 One application for breakpoint commands is to compensate for one bug so
4651 you can test for another. Put a breakpoint just after the erroneous line
4652 of code, give it a condition to detect the case in which something
4653 erroneous has been done, and give it commands to assign correct values
4654 to any variables that need them. End with the @code{continue} command
4655 so that your program does not stop, and start with the @code{silent}
4656 command so that no output is produced. Here is an example:
4667 @node Dynamic Printf
4668 @subsection Dynamic Printf
4670 @cindex dynamic printf
4672 The dynamic printf command @code{dprintf} combines a breakpoint with
4673 formatted printing of your program's data to give you the effect of
4674 inserting @code{printf} calls into your program on-the-fly, without
4675 having to recompile it.
4677 In its most basic form, the output goes to the GDB console. However,
4678 you can set the variable @code{dprintf-style} for alternate handling.
4679 For instance, you can ask to format the output by calling your
4680 program's @code{printf} function. This has the advantage that the
4681 characters go to the program's output device, so they can recorded in
4682 redirects to files and so forth.
4684 If you are doing remote debugging with a stub or agent, you can also
4685 ask to have the printf handled by the remote agent. In addition to
4686 ensuring that the output goes to the remote program's device along
4687 with any other output the program might produce, you can also ask that
4688 the dprintf remain active even after disconnecting from the remote
4689 target. Using the stub/agent is also more efficient, as it can do
4690 everything without needing to communicate with @value{GDBN}.
4694 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4695 Whenever execution reaches @var{location}, print the values of one or
4696 more @var{expressions} under the control of the string @var{template}.
4697 To print several values, separate them with commas.
4699 @item set dprintf-style @var{style}
4700 Set the dprintf output to be handled in one of several different
4701 styles enumerated below. A change of style affects all existing
4702 dynamic printfs immediately. (If you need individual control over the
4703 print commands, simply define normal breakpoints with
4704 explicitly-supplied command lists.)
4707 @kindex dprintf-style gdb
4708 Handle the output using the @value{GDBN} @code{printf} command.
4711 @kindex dprintf-style call
4712 Handle the output by calling a function in your program (normally
4716 @kindex dprintf-style agent
4717 Have the remote debugging agent (such as @code{gdbserver}) handle
4718 the output itself. This style is only available for agents that
4719 support running commands on the target.
4721 @item set dprintf-function @var{function}
4722 Set the function to call if the dprintf style is @code{call}. By
4723 default its value is @code{printf}. You may set it to any expression.
4724 that @value{GDBN} can evaluate to a function, as per the @code{call}
4727 @item set dprintf-channel @var{channel}
4728 Set a ``channel'' for dprintf. If set to a non-empty value,
4729 @value{GDBN} will evaluate it as an expression and pass the result as
4730 a first argument to the @code{dprintf-function}, in the manner of
4731 @code{fprintf} and similar functions. Otherwise, the dprintf format
4732 string will be the first argument, in the manner of @code{printf}.
4734 As an example, if you wanted @code{dprintf} output to go to a logfile
4735 that is a standard I/O stream assigned to the variable @code{mylog},
4736 you could do the following:
4739 (gdb) set dprintf-style call
4740 (gdb) set dprintf-function fprintf
4741 (gdb) set dprintf-channel mylog
4742 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4743 Dprintf 1 at 0x123456: file main.c, line 25.
4745 1 dprintf keep y 0x00123456 in main at main.c:25
4746 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4751 Note that the @code{info break} displays the dynamic printf commands
4752 as normal breakpoint commands; you can thus easily see the effect of
4753 the variable settings.
4755 @item set disconnected-dprintf on
4756 @itemx set disconnected-dprintf off
4757 @kindex set disconnected-dprintf
4758 Choose whether @code{dprintf} commands should continue to run if
4759 @value{GDBN} has disconnected from the target. This only applies
4760 if the @code{dprintf-style} is @code{agent}.
4762 @item show disconnected-dprintf off
4763 @kindex show disconnected-dprintf
4764 Show the current choice for disconnected @code{dprintf}.
4768 @value{GDBN} does not check the validity of function and channel,
4769 relying on you to supply values that are meaningful for the contexts
4770 in which they are being used. For instance, the function and channel
4771 may be the values of local variables, but if that is the case, then
4772 all enabled dynamic prints must be at locations within the scope of
4773 those locals. If evaluation fails, @value{GDBN} will report an error.
4775 @node Save Breakpoints
4776 @subsection How to save breakpoints to a file
4778 To save breakpoint definitions to a file use the @w{@code{save
4779 breakpoints}} command.
4782 @kindex save breakpoints
4783 @cindex save breakpoints to a file for future sessions
4784 @item save breakpoints [@var{filename}]
4785 This command saves all current breakpoint definitions together with
4786 their commands and ignore counts, into a file @file{@var{filename}}
4787 suitable for use in a later debugging session. This includes all
4788 types of breakpoints (breakpoints, watchpoints, catchpoints,
4789 tracepoints). To read the saved breakpoint definitions, use the
4790 @code{source} command (@pxref{Command Files}). Note that watchpoints
4791 with expressions involving local variables may fail to be recreated
4792 because it may not be possible to access the context where the
4793 watchpoint is valid anymore. Because the saved breakpoint definitions
4794 are simply a sequence of @value{GDBN} commands that recreate the
4795 breakpoints, you can edit the file in your favorite editing program,
4796 and remove the breakpoint definitions you're not interested in, or
4797 that can no longer be recreated.
4800 @node Static Probe Points
4801 @subsection Static Probe Points
4803 @cindex static probe point, SystemTap
4804 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4805 for Statically Defined Tracing, and the probes are designed to have a tiny
4806 runtime code and data footprint, and no dynamic relocations. They are
4807 usable from assembly, C and C@t{++} languages. See
4808 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4809 for a good reference on how the @acronym{SDT} probes are implemented.
4811 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4812 @acronym{SDT} probes are supported on ELF-compatible systems. See
4813 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4814 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4815 in your applications.
4817 @cindex semaphores on static probe points
4818 Some probes have an associated semaphore variable; for instance, this
4819 happens automatically if you defined your probe using a DTrace-style
4820 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4821 automatically enable it when you specify a breakpoint using the
4822 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4823 location by some other method (e.g., @code{break file:line}), then
4824 @value{GDBN} will not automatically set the semaphore.
4826 You can examine the available static static probes using @code{info
4827 probes}, with optional arguments:
4831 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4832 If given, @var{provider} is a regular expression used to match against provider
4833 names when selecting which probes to list. If omitted, probes by all
4834 probes from all providers are listed.
4836 If given, @var{name} is a regular expression to match against probe names
4837 when selecting which probes to list. If omitted, probe names are not
4838 considered when deciding whether to display them.
4840 If given, @var{objfile} is a regular expression used to select which
4841 object files (executable or shared libraries) to examine. If not
4842 given, all object files are considered.
4844 @item info probes all
4845 List the available static probes, from all types.
4848 @vindex $_probe_arg@r{, convenience variable}
4849 A probe may specify up to twelve arguments. These are available at the
4850 point at which the probe is defined---that is, when the current PC is
4851 at the probe's location. The arguments are available using the
4852 convenience variables (@pxref{Convenience Vars})
4853 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4854 an integer of the appropriate size; types are not preserved. The
4855 convenience variable @code{$_probe_argc} holds the number of arguments
4856 at the current probe point.
4858 These variables are always available, but attempts to access them at
4859 any location other than a probe point will cause @value{GDBN} to give
4863 @c @ifclear BARETARGET
4864 @node Error in Breakpoints
4865 @subsection ``Cannot insert breakpoints''
4867 If you request too many active hardware-assisted breakpoints and
4868 watchpoints, you will see this error message:
4870 @c FIXME: the precise wording of this message may change; the relevant
4871 @c source change is not committed yet (Sep 3, 1999).
4873 Stopped; cannot insert breakpoints.
4874 You may have requested too many hardware breakpoints and watchpoints.
4878 This message is printed when you attempt to resume the program, since
4879 only then @value{GDBN} knows exactly how many hardware breakpoints and
4880 watchpoints it needs to insert.
4882 When this message is printed, you need to disable or remove some of the
4883 hardware-assisted breakpoints and watchpoints, and then continue.
4885 @node Breakpoint-related Warnings
4886 @subsection ``Breakpoint address adjusted...''
4887 @cindex breakpoint address adjusted
4889 Some processor architectures place constraints on the addresses at
4890 which breakpoints may be placed. For architectures thus constrained,
4891 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4892 with the constraints dictated by the architecture.
4894 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4895 a VLIW architecture in which a number of RISC-like instructions may be
4896 bundled together for parallel execution. The FR-V architecture
4897 constrains the location of a breakpoint instruction within such a
4898 bundle to the instruction with the lowest address. @value{GDBN}
4899 honors this constraint by adjusting a breakpoint's address to the
4900 first in the bundle.
4902 It is not uncommon for optimized code to have bundles which contain
4903 instructions from different source statements, thus it may happen that
4904 a breakpoint's address will be adjusted from one source statement to
4905 another. Since this adjustment may significantly alter @value{GDBN}'s
4906 breakpoint related behavior from what the user expects, a warning is
4907 printed when the breakpoint is first set and also when the breakpoint
4910 A warning like the one below is printed when setting a breakpoint
4911 that's been subject to address adjustment:
4914 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4917 Such warnings are printed both for user settable and @value{GDBN}'s
4918 internal breakpoints. If you see one of these warnings, you should
4919 verify that a breakpoint set at the adjusted address will have the
4920 desired affect. If not, the breakpoint in question may be removed and
4921 other breakpoints may be set which will have the desired behavior.
4922 E.g., it may be sufficient to place the breakpoint at a later
4923 instruction. A conditional breakpoint may also be useful in some
4924 cases to prevent the breakpoint from triggering too often.
4926 @value{GDBN} will also issue a warning when stopping at one of these
4927 adjusted breakpoints:
4930 warning: Breakpoint 1 address previously adjusted from 0x00010414
4934 When this warning is encountered, it may be too late to take remedial
4935 action except in cases where the breakpoint is hit earlier or more
4936 frequently than expected.
4938 @node Continuing and Stepping
4939 @section Continuing and Stepping
4943 @cindex resuming execution
4944 @dfn{Continuing} means resuming program execution until your program
4945 completes normally. In contrast, @dfn{stepping} means executing just
4946 one more ``step'' of your program, where ``step'' may mean either one
4947 line of source code, or one machine instruction (depending on what
4948 particular command you use). Either when continuing or when stepping,
4949 your program may stop even sooner, due to a breakpoint or a signal. (If
4950 it stops due to a signal, you may want to use @code{handle}, or use
4951 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4955 @kindex c @r{(@code{continue})}
4956 @kindex fg @r{(resume foreground execution)}
4957 @item continue @r{[}@var{ignore-count}@r{]}
4958 @itemx c @r{[}@var{ignore-count}@r{]}
4959 @itemx fg @r{[}@var{ignore-count}@r{]}
4960 Resume program execution, at the address where your program last stopped;
4961 any breakpoints set at that address are bypassed. The optional argument
4962 @var{ignore-count} allows you to specify a further number of times to
4963 ignore a breakpoint at this location; its effect is like that of
4964 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4966 The argument @var{ignore-count} is meaningful only when your program
4967 stopped due to a breakpoint. At other times, the argument to
4968 @code{continue} is ignored.
4970 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4971 debugged program is deemed to be the foreground program) are provided
4972 purely for convenience, and have exactly the same behavior as
4976 To resume execution at a different place, you can use @code{return}
4977 (@pxref{Returning, ,Returning from a Function}) to go back to the
4978 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4979 Different Address}) to go to an arbitrary location in your program.
4981 A typical technique for using stepping is to set a breakpoint
4982 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4983 beginning of the function or the section of your program where a problem
4984 is believed to lie, run your program until it stops at that breakpoint,
4985 and then step through the suspect area, examining the variables that are
4986 interesting, until you see the problem happen.
4990 @kindex s @r{(@code{step})}
4992 Continue running your program until control reaches a different source
4993 line, then stop it and return control to @value{GDBN}. This command is
4994 abbreviated @code{s}.
4997 @c "without debugging information" is imprecise; actually "without line
4998 @c numbers in the debugging information". (gcc -g1 has debugging info but
4999 @c not line numbers). But it seems complex to try to make that
5000 @c distinction here.
5001 @emph{Warning:} If you use the @code{step} command while control is
5002 within a function that was compiled without debugging information,
5003 execution proceeds until control reaches a function that does have
5004 debugging information. Likewise, it will not step into a function which
5005 is compiled without debugging information. To step through functions
5006 without debugging information, use the @code{stepi} command, described
5010 The @code{step} command only stops at the first instruction of a source
5011 line. This prevents the multiple stops that could otherwise occur in
5012 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5013 to stop if a function that has debugging information is called within
5014 the line. In other words, @code{step} @emph{steps inside} any functions
5015 called within the line.
5017 Also, the @code{step} command only enters a function if there is line
5018 number information for the function. Otherwise it acts like the
5019 @code{next} command. This avoids problems when using @code{cc -gl}
5020 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5021 was any debugging information about the routine.
5023 @item step @var{count}
5024 Continue running as in @code{step}, but do so @var{count} times. If a
5025 breakpoint is reached, or a signal not related to stepping occurs before
5026 @var{count} steps, stepping stops right away.
5029 @kindex n @r{(@code{next})}
5030 @item next @r{[}@var{count}@r{]}
5031 Continue to the next source line in the current (innermost) stack frame.
5032 This is similar to @code{step}, but function calls that appear within
5033 the line of code are executed without stopping. Execution stops when
5034 control reaches a different line of code at the original stack level
5035 that was executing when you gave the @code{next} command. This command
5036 is abbreviated @code{n}.
5038 An argument @var{count} is a repeat count, as for @code{step}.
5041 @c FIX ME!! Do we delete this, or is there a way it fits in with
5042 @c the following paragraph? --- Vctoria
5044 @c @code{next} within a function that lacks debugging information acts like
5045 @c @code{step}, but any function calls appearing within the code of the
5046 @c function are executed without stopping.
5048 The @code{next} command only stops at the first instruction of a
5049 source line. This prevents multiple stops that could otherwise occur in
5050 @code{switch} statements, @code{for} loops, etc.
5052 @kindex set step-mode
5054 @cindex functions without line info, and stepping
5055 @cindex stepping into functions with no line info
5056 @itemx set step-mode on
5057 The @code{set step-mode on} command causes the @code{step} command to
5058 stop at the first instruction of a function which contains no debug line
5059 information rather than stepping over it.
5061 This is useful in cases where you may be interested in inspecting the
5062 machine instructions of a function which has no symbolic info and do not
5063 want @value{GDBN} to automatically skip over this function.
5065 @item set step-mode off
5066 Causes the @code{step} command to step over any functions which contains no
5067 debug information. This is the default.
5069 @item show step-mode
5070 Show whether @value{GDBN} will stop in or step over functions without
5071 source line debug information.
5074 @kindex fin @r{(@code{finish})}
5076 Continue running until just after function in the selected stack frame
5077 returns. Print the returned value (if any). This command can be
5078 abbreviated as @code{fin}.
5080 Contrast this with the @code{return} command (@pxref{Returning,
5081 ,Returning from a Function}).
5084 @kindex u @r{(@code{until})}
5085 @cindex run until specified location
5088 Continue running until a source line past the current line, in the
5089 current stack frame, is reached. This command is used to avoid single
5090 stepping through a loop more than once. It is like the @code{next}
5091 command, except that when @code{until} encounters a jump, it
5092 automatically continues execution until the program counter is greater
5093 than the address of the jump.
5095 This means that when you reach the end of a loop after single stepping
5096 though it, @code{until} makes your program continue execution until it
5097 exits the loop. In contrast, a @code{next} command at the end of a loop
5098 simply steps back to the beginning of the loop, which forces you to step
5099 through the next iteration.
5101 @code{until} always stops your program if it attempts to exit the current
5104 @code{until} may produce somewhat counterintuitive results if the order
5105 of machine code does not match the order of the source lines. For
5106 example, in the following excerpt from a debugging session, the @code{f}
5107 (@code{frame}) command shows that execution is stopped at line
5108 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5112 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5114 (@value{GDBP}) until
5115 195 for ( ; argc > 0; NEXTARG) @{
5118 This happened because, for execution efficiency, the compiler had
5119 generated code for the loop closure test at the end, rather than the
5120 start, of the loop---even though the test in a C @code{for}-loop is
5121 written before the body of the loop. The @code{until} command appeared
5122 to step back to the beginning of the loop when it advanced to this
5123 expression; however, it has not really gone to an earlier
5124 statement---not in terms of the actual machine code.
5126 @code{until} with no argument works by means of single
5127 instruction stepping, and hence is slower than @code{until} with an
5130 @item until @var{location}
5131 @itemx u @var{location}
5132 Continue running your program until either the specified location is
5133 reached, or the current stack frame returns. @var{location} is any of
5134 the forms described in @ref{Specify Location}.
5135 This form of the command uses temporary breakpoints, and
5136 hence is quicker than @code{until} without an argument. The specified
5137 location is actually reached only if it is in the current frame. This
5138 implies that @code{until} can be used to skip over recursive function
5139 invocations. For instance in the code below, if the current location is
5140 line @code{96}, issuing @code{until 99} will execute the program up to
5141 line @code{99} in the same invocation of factorial, i.e., after the inner
5142 invocations have returned.
5145 94 int factorial (int value)
5147 96 if (value > 1) @{
5148 97 value *= factorial (value - 1);
5155 @kindex advance @var{location}
5156 @item advance @var{location}
5157 Continue running the program up to the given @var{location}. An argument is
5158 required, which should be of one of the forms described in
5159 @ref{Specify Location}.
5160 Execution will also stop upon exit from the current stack
5161 frame. This command is similar to @code{until}, but @code{advance} will
5162 not skip over recursive function calls, and the target location doesn't
5163 have to be in the same frame as the current one.
5167 @kindex si @r{(@code{stepi})}
5169 @itemx stepi @var{arg}
5171 Execute one machine instruction, then stop and return to the debugger.
5173 It is often useful to do @samp{display/i $pc} when stepping by machine
5174 instructions. This makes @value{GDBN} automatically display the next
5175 instruction to be executed, each time your program stops. @xref{Auto
5176 Display,, Automatic Display}.
5178 An argument is a repeat count, as in @code{step}.
5182 @kindex ni @r{(@code{nexti})}
5184 @itemx nexti @var{arg}
5186 Execute one machine instruction, but if it is a function call,
5187 proceed until the function returns.
5189 An argument is a repeat count, as in @code{next}.
5192 @node Skipping Over Functions and Files
5193 @section Skipping Over Functions and Files
5194 @cindex skipping over functions and files
5196 The program you are debugging may contain some functions which are
5197 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5198 skip a function or all functions in a file when stepping.
5200 For example, consider the following C function:
5211 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5212 are not interested in stepping through @code{boring}. If you run @code{step}
5213 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5214 step over both @code{foo} and @code{boring}!
5216 One solution is to @code{step} into @code{boring} and use the @code{finish}
5217 command to immediately exit it. But this can become tedious if @code{boring}
5218 is called from many places.
5220 A more flexible solution is to execute @kbd{skip boring}. This instructs
5221 @value{GDBN} never to step into @code{boring}. Now when you execute
5222 @code{step} at line 103, you'll step over @code{boring} and directly into
5225 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5226 example, @code{skip file boring.c}.
5229 @kindex skip function
5230 @item skip @r{[}@var{linespec}@r{]}
5231 @itemx skip function @r{[}@var{linespec}@r{]}
5232 After running this command, the function named by @var{linespec} or the
5233 function containing the line named by @var{linespec} will be skipped over when
5234 stepping. @xref{Specify Location}.
5236 If you do not specify @var{linespec}, the function you're currently debugging
5239 (If you have a function called @code{file} that you want to skip, use
5240 @kbd{skip function file}.)
5243 @item skip file @r{[}@var{filename}@r{]}
5244 After running this command, any function whose source lives in @var{filename}
5245 will be skipped over when stepping.
5247 If you do not specify @var{filename}, functions whose source lives in the file
5248 you're currently debugging will be skipped.
5251 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5252 These are the commands for managing your list of skips:
5256 @item info skip @r{[}@var{range}@r{]}
5257 Print details about the specified skip(s). If @var{range} is not specified,
5258 print a table with details about all functions and files marked for skipping.
5259 @code{info skip} prints the following information about each skip:
5263 A number identifying this skip.
5265 The type of this skip, either @samp{function} or @samp{file}.
5266 @item Enabled or Disabled
5267 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5269 For function skips, this column indicates the address in memory of the function
5270 being skipped. If you've set a function skip on a function which has not yet
5271 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5272 which has the function is loaded, @code{info skip} will show the function's
5275 For file skips, this field contains the filename being skipped. For functions
5276 skips, this field contains the function name and its line number in the file
5277 where it is defined.
5281 @item skip delete @r{[}@var{range}@r{]}
5282 Delete the specified skip(s). If @var{range} is not specified, delete all
5286 @item skip enable @r{[}@var{range}@r{]}
5287 Enable the specified skip(s). If @var{range} is not specified, enable all
5290 @kindex skip disable
5291 @item skip disable @r{[}@var{range}@r{]}
5292 Disable the specified skip(s). If @var{range} is not specified, disable all
5301 A signal is an asynchronous event that can happen in a program. The
5302 operating system defines the possible kinds of signals, and gives each
5303 kind a name and a number. For example, in Unix @code{SIGINT} is the
5304 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5305 @code{SIGSEGV} is the signal a program gets from referencing a place in
5306 memory far away from all the areas in use; @code{SIGALRM} occurs when
5307 the alarm clock timer goes off (which happens only if your program has
5308 requested an alarm).
5310 @cindex fatal signals
5311 Some signals, including @code{SIGALRM}, are a normal part of the
5312 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5313 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5314 program has not specified in advance some other way to handle the signal.
5315 @code{SIGINT} does not indicate an error in your program, but it is normally
5316 fatal so it can carry out the purpose of the interrupt: to kill the program.
5318 @value{GDBN} has the ability to detect any occurrence of a signal in your
5319 program. You can tell @value{GDBN} in advance what to do for each kind of
5322 @cindex handling signals
5323 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5324 @code{SIGALRM} be silently passed to your program
5325 (so as not to interfere with their role in the program's functioning)
5326 but to stop your program immediately whenever an error signal happens.
5327 You can change these settings with the @code{handle} command.
5330 @kindex info signals
5334 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5335 handle each one. You can use this to see the signal numbers of all
5336 the defined types of signals.
5338 @item info signals @var{sig}
5339 Similar, but print information only about the specified signal number.
5341 @code{info handle} is an alias for @code{info signals}.
5343 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5344 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5345 for details about this command.
5348 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5349 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5350 can be the number of a signal or its name (with or without the
5351 @samp{SIG} at the beginning); a list of signal numbers of the form
5352 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5353 known signals. Optional arguments @var{keywords}, described below,
5354 say what change to make.
5358 The keywords allowed by the @code{handle} command can be abbreviated.
5359 Their full names are:
5363 @value{GDBN} should not stop your program when this signal happens. It may
5364 still print a message telling you that the signal has come in.
5367 @value{GDBN} should stop your program when this signal happens. This implies
5368 the @code{print} keyword as well.
5371 @value{GDBN} should print a message when this signal happens.
5374 @value{GDBN} should not mention the occurrence of the signal at all. This
5375 implies the @code{nostop} keyword as well.
5379 @value{GDBN} should allow your program to see this signal; your program
5380 can handle the signal, or else it may terminate if the signal is fatal
5381 and not handled. @code{pass} and @code{noignore} are synonyms.
5385 @value{GDBN} should not allow your program to see this signal.
5386 @code{nopass} and @code{ignore} are synonyms.
5390 When a signal stops your program, the signal is not visible to the
5392 continue. Your program sees the signal then, if @code{pass} is in
5393 effect for the signal in question @emph{at that time}. In other words,
5394 after @value{GDBN} reports a signal, you can use the @code{handle}
5395 command with @code{pass} or @code{nopass} to control whether your
5396 program sees that signal when you continue.
5398 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5399 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5400 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5403 You can also use the @code{signal} command to prevent your program from
5404 seeing a signal, or cause it to see a signal it normally would not see,
5405 or to give it any signal at any time. For example, if your program stopped
5406 due to some sort of memory reference error, you might store correct
5407 values into the erroneous variables and continue, hoping to see more
5408 execution; but your program would probably terminate immediately as
5409 a result of the fatal signal once it saw the signal. To prevent this,
5410 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5413 @cindex extra signal information
5414 @anchor{extra signal information}
5416 On some targets, @value{GDBN} can inspect extra signal information
5417 associated with the intercepted signal, before it is actually
5418 delivered to the program being debugged. This information is exported
5419 by the convenience variable @code{$_siginfo}, and consists of data
5420 that is passed by the kernel to the signal handler at the time of the
5421 receipt of a signal. The data type of the information itself is
5422 target dependent. You can see the data type using the @code{ptype
5423 $_siginfo} command. On Unix systems, it typically corresponds to the
5424 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5427 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5428 referenced address that raised a segmentation fault.
5432 (@value{GDBP}) continue
5433 Program received signal SIGSEGV, Segmentation fault.
5434 0x0000000000400766 in main ()
5436 (@value{GDBP}) ptype $_siginfo
5443 struct @{...@} _kill;
5444 struct @{...@} _timer;
5446 struct @{...@} _sigchld;
5447 struct @{...@} _sigfault;
5448 struct @{...@} _sigpoll;
5451 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5455 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5456 $1 = (void *) 0x7ffff7ff7000
5460 Depending on target support, @code{$_siginfo} may also be writable.
5463 @section Stopping and Starting Multi-thread Programs
5465 @cindex stopped threads
5466 @cindex threads, stopped
5468 @cindex continuing threads
5469 @cindex threads, continuing
5471 @value{GDBN} supports debugging programs with multiple threads
5472 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5473 are two modes of controlling execution of your program within the
5474 debugger. In the default mode, referred to as @dfn{all-stop mode},
5475 when any thread in your program stops (for example, at a breakpoint
5476 or while being stepped), all other threads in the program are also stopped by
5477 @value{GDBN}. On some targets, @value{GDBN} also supports
5478 @dfn{non-stop mode}, in which other threads can continue to run freely while
5479 you examine the stopped thread in the debugger.
5482 * All-Stop Mode:: All threads stop when GDB takes control
5483 * Non-Stop Mode:: Other threads continue to execute
5484 * Background Execution:: Running your program asynchronously
5485 * Thread-Specific Breakpoints:: Controlling breakpoints
5486 * Interrupted System Calls:: GDB may interfere with system calls
5487 * Observer Mode:: GDB does not alter program behavior
5491 @subsection All-Stop Mode
5493 @cindex all-stop mode
5495 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5496 @emph{all} threads of execution stop, not just the current thread. This
5497 allows you to examine the overall state of the program, including
5498 switching between threads, without worrying that things may change
5501 Conversely, whenever you restart the program, @emph{all} threads start
5502 executing. @emph{This is true even when single-stepping} with commands
5503 like @code{step} or @code{next}.
5505 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5506 Since thread scheduling is up to your debugging target's operating
5507 system (not controlled by @value{GDBN}), other threads may
5508 execute more than one statement while the current thread completes a
5509 single step. Moreover, in general other threads stop in the middle of a
5510 statement, rather than at a clean statement boundary, when the program
5513 You might even find your program stopped in another thread after
5514 continuing or even single-stepping. This happens whenever some other
5515 thread runs into a breakpoint, a signal, or an exception before the
5516 first thread completes whatever you requested.
5518 @cindex automatic thread selection
5519 @cindex switching threads automatically
5520 @cindex threads, automatic switching
5521 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5522 signal, it automatically selects the thread where that breakpoint or
5523 signal happened. @value{GDBN} alerts you to the context switch with a
5524 message such as @samp{[Switching to Thread @var{n}]} to identify the
5527 On some OSes, you can modify @value{GDBN}'s default behavior by
5528 locking the OS scheduler to allow only a single thread to run.
5531 @item set scheduler-locking @var{mode}
5532 @cindex scheduler locking mode
5533 @cindex lock scheduler
5534 Set the scheduler locking mode. If it is @code{off}, then there is no
5535 locking and any thread may run at any time. If @code{on}, then only the
5536 current thread may run when the inferior is resumed. The @code{step}
5537 mode optimizes for single-stepping; it prevents other threads
5538 from preempting the current thread while you are stepping, so that
5539 the focus of debugging does not change unexpectedly.
5540 Other threads only rarely (or never) get a chance to run
5541 when you step. They are more likely to run when you @samp{next} over a
5542 function call, and they are completely free to run when you use commands
5543 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5544 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5545 the current thread away from the thread that you are debugging.
5547 @item show scheduler-locking
5548 Display the current scheduler locking mode.
5551 @cindex resume threads of multiple processes simultaneously
5552 By default, when you issue one of the execution commands such as
5553 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5554 threads of the current inferior to run. For example, if @value{GDBN}
5555 is attached to two inferiors, each with two threads, the
5556 @code{continue} command resumes only the two threads of the current
5557 inferior. This is useful, for example, when you debug a program that
5558 forks and you want to hold the parent stopped (so that, for instance,
5559 it doesn't run to exit), while you debug the child. In other
5560 situations, you may not be interested in inspecting the current state
5561 of any of the processes @value{GDBN} is attached to, and you may want
5562 to resume them all until some breakpoint is hit. In the latter case,
5563 you can instruct @value{GDBN} to allow all threads of all the
5564 inferiors to run with the @w{@code{set schedule-multiple}} command.
5567 @kindex set schedule-multiple
5568 @item set schedule-multiple
5569 Set the mode for allowing threads of multiple processes to be resumed
5570 when an execution command is issued. When @code{on}, all threads of
5571 all processes are allowed to run. When @code{off}, only the threads
5572 of the current process are resumed. The default is @code{off}. The
5573 @code{scheduler-locking} mode takes precedence when set to @code{on},
5574 or while you are stepping and set to @code{step}.
5576 @item show schedule-multiple
5577 Display the current mode for resuming the execution of threads of
5582 @subsection Non-Stop Mode
5584 @cindex non-stop mode
5586 @c This section is really only a place-holder, and needs to be expanded
5587 @c with more details.
5589 For some multi-threaded targets, @value{GDBN} supports an optional
5590 mode of operation in which you can examine stopped program threads in
5591 the debugger while other threads continue to execute freely. This
5592 minimizes intrusion when debugging live systems, such as programs
5593 where some threads have real-time constraints or must continue to
5594 respond to external events. This is referred to as @dfn{non-stop} mode.
5596 In non-stop mode, when a thread stops to report a debugging event,
5597 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5598 threads as well, in contrast to the all-stop mode behavior. Additionally,
5599 execution commands such as @code{continue} and @code{step} apply by default
5600 only to the current thread in non-stop mode, rather than all threads as
5601 in all-stop mode. This allows you to control threads explicitly in
5602 ways that are not possible in all-stop mode --- for example, stepping
5603 one thread while allowing others to run freely, stepping
5604 one thread while holding all others stopped, or stepping several threads
5605 independently and simultaneously.
5607 To enter non-stop mode, use this sequence of commands before you run
5608 or attach to your program:
5611 # Enable the async interface.
5614 # If using the CLI, pagination breaks non-stop.
5617 # Finally, turn it on!
5621 You can use these commands to manipulate the non-stop mode setting:
5624 @kindex set non-stop
5625 @item set non-stop on
5626 Enable selection of non-stop mode.
5627 @item set non-stop off
5628 Disable selection of non-stop mode.
5629 @kindex show non-stop
5631 Show the current non-stop enablement setting.
5634 Note these commands only reflect whether non-stop mode is enabled,
5635 not whether the currently-executing program is being run in non-stop mode.
5636 In particular, the @code{set non-stop} preference is only consulted when
5637 @value{GDBN} starts or connects to the target program, and it is generally
5638 not possible to switch modes once debugging has started. Furthermore,
5639 since not all targets support non-stop mode, even when you have enabled
5640 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5643 In non-stop mode, all execution commands apply only to the current thread
5644 by default. That is, @code{continue} only continues one thread.
5645 To continue all threads, issue @code{continue -a} or @code{c -a}.
5647 You can use @value{GDBN}'s background execution commands
5648 (@pxref{Background Execution}) to run some threads in the background
5649 while you continue to examine or step others from @value{GDBN}.
5650 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5651 always executed asynchronously in non-stop mode.
5653 Suspending execution is done with the @code{interrupt} command when
5654 running in the background, or @kbd{Ctrl-c} during foreground execution.
5655 In all-stop mode, this stops the whole process;
5656 but in non-stop mode the interrupt applies only to the current thread.
5657 To stop the whole program, use @code{interrupt -a}.
5659 Other execution commands do not currently support the @code{-a} option.
5661 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5662 that thread current, as it does in all-stop mode. This is because the
5663 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5664 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5665 changed to a different thread just as you entered a command to operate on the
5666 previously current thread.
5668 @node Background Execution
5669 @subsection Background Execution
5671 @cindex foreground execution
5672 @cindex background execution
5673 @cindex asynchronous execution
5674 @cindex execution, foreground, background and asynchronous
5676 @value{GDBN}'s execution commands have two variants: the normal
5677 foreground (synchronous) behavior, and a background
5678 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5679 the program to report that some thread has stopped before prompting for
5680 another command. In background execution, @value{GDBN} immediately gives
5681 a command prompt so that you can issue other commands while your program runs.
5683 You need to explicitly enable asynchronous mode before you can use
5684 background execution commands. You can use these commands to
5685 manipulate the asynchronous mode setting:
5688 @kindex set target-async
5689 @item set target-async on
5690 Enable asynchronous mode.
5691 @item set target-async off
5692 Disable asynchronous mode.
5693 @kindex show target-async
5694 @item show target-async
5695 Show the current target-async setting.
5698 If the target doesn't support async mode, @value{GDBN} issues an error
5699 message if you attempt to use the background execution commands.
5701 To specify background execution, add a @code{&} to the command. For example,
5702 the background form of the @code{continue} command is @code{continue&}, or
5703 just @code{c&}. The execution commands that accept background execution
5709 @xref{Starting, , Starting your Program}.
5713 @xref{Attach, , Debugging an Already-running Process}.
5717 @xref{Continuing and Stepping, step}.
5721 @xref{Continuing and Stepping, stepi}.
5725 @xref{Continuing and Stepping, next}.
5729 @xref{Continuing and Stepping, nexti}.
5733 @xref{Continuing and Stepping, continue}.
5737 @xref{Continuing and Stepping, finish}.
5741 @xref{Continuing and Stepping, until}.
5745 Background execution is especially useful in conjunction with non-stop
5746 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5747 However, you can also use these commands in the normal all-stop mode with
5748 the restriction that you cannot issue another execution command until the
5749 previous one finishes. Examples of commands that are valid in all-stop
5750 mode while the program is running include @code{help} and @code{info break}.
5752 You can interrupt your program while it is running in the background by
5753 using the @code{interrupt} command.
5760 Suspend execution of the running program. In all-stop mode,
5761 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5762 only the current thread. To stop the whole program in non-stop mode,
5763 use @code{interrupt -a}.
5766 @node Thread-Specific Breakpoints
5767 @subsection Thread-Specific Breakpoints
5769 When your program has multiple threads (@pxref{Threads,, Debugging
5770 Programs with Multiple Threads}), you can choose whether to set
5771 breakpoints on all threads, or on a particular thread.
5774 @cindex breakpoints and threads
5775 @cindex thread breakpoints
5776 @kindex break @dots{} thread @var{threadno}
5777 @item break @var{linespec} thread @var{threadno}
5778 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5779 @var{linespec} specifies source lines; there are several ways of
5780 writing them (@pxref{Specify Location}), but the effect is always to
5781 specify some source line.
5783 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5784 to specify that you only want @value{GDBN} to stop the program when a
5785 particular thread reaches this breakpoint. @var{threadno} is one of the
5786 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5787 column of the @samp{info threads} display.
5789 If you do not specify @samp{thread @var{threadno}} when you set a
5790 breakpoint, the breakpoint applies to @emph{all} threads of your
5793 You can use the @code{thread} qualifier on conditional breakpoints as
5794 well; in this case, place @samp{thread @var{threadno}} before or
5795 after the breakpoint condition, like this:
5798 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5803 @node Interrupted System Calls
5804 @subsection Interrupted System Calls
5806 @cindex thread breakpoints and system calls
5807 @cindex system calls and thread breakpoints
5808 @cindex premature return from system calls
5809 There is an unfortunate side effect when using @value{GDBN} to debug
5810 multi-threaded programs. If one thread stops for a
5811 breakpoint, or for some other reason, and another thread is blocked in a
5812 system call, then the system call may return prematurely. This is a
5813 consequence of the interaction between multiple threads and the signals
5814 that @value{GDBN} uses to implement breakpoints and other events that
5817 To handle this problem, your program should check the return value of
5818 each system call and react appropriately. This is good programming
5821 For example, do not write code like this:
5827 The call to @code{sleep} will return early if a different thread stops
5828 at a breakpoint or for some other reason.
5830 Instead, write this:
5835 unslept = sleep (unslept);
5838 A system call is allowed to return early, so the system is still
5839 conforming to its specification. But @value{GDBN} does cause your
5840 multi-threaded program to behave differently than it would without
5843 Also, @value{GDBN} uses internal breakpoints in the thread library to
5844 monitor certain events such as thread creation and thread destruction.
5845 When such an event happens, a system call in another thread may return
5846 prematurely, even though your program does not appear to stop.
5849 @subsection Observer Mode
5851 If you want to build on non-stop mode and observe program behavior
5852 without any chance of disruption by @value{GDBN}, you can set
5853 variables to disable all of the debugger's attempts to modify state,
5854 whether by writing memory, inserting breakpoints, etc. These operate
5855 at a low level, intercepting operations from all commands.
5857 When all of these are set to @code{off}, then @value{GDBN} is said to
5858 be @dfn{observer mode}. As a convenience, the variable
5859 @code{observer} can be set to disable these, plus enable non-stop
5862 Note that @value{GDBN} will not prevent you from making nonsensical
5863 combinations of these settings. For instance, if you have enabled
5864 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5865 then breakpoints that work by writing trap instructions into the code
5866 stream will still not be able to be placed.
5871 @item set observer on
5872 @itemx set observer off
5873 When set to @code{on}, this disables all the permission variables
5874 below (except for @code{insert-fast-tracepoints}), plus enables
5875 non-stop debugging. Setting this to @code{off} switches back to
5876 normal debugging, though remaining in non-stop mode.
5879 Show whether observer mode is on or off.
5881 @kindex may-write-registers
5882 @item set may-write-registers on
5883 @itemx set may-write-registers off
5884 This controls whether @value{GDBN} will attempt to alter the values of
5885 registers, such as with assignment expressions in @code{print}, or the
5886 @code{jump} command. It defaults to @code{on}.
5888 @item show may-write-registers
5889 Show the current permission to write registers.
5891 @kindex may-write-memory
5892 @item set may-write-memory on
5893 @itemx set may-write-memory off
5894 This controls whether @value{GDBN} will attempt to alter the contents
5895 of memory, such as with assignment expressions in @code{print}. It
5896 defaults to @code{on}.
5898 @item show may-write-memory
5899 Show the current permission to write memory.
5901 @kindex may-insert-breakpoints
5902 @item set may-insert-breakpoints on
5903 @itemx set may-insert-breakpoints off
5904 This controls whether @value{GDBN} will attempt to insert breakpoints.
5905 This affects all breakpoints, including internal breakpoints defined
5906 by @value{GDBN}. It defaults to @code{on}.
5908 @item show may-insert-breakpoints
5909 Show the current permission to insert breakpoints.
5911 @kindex may-insert-tracepoints
5912 @item set may-insert-tracepoints on
5913 @itemx set may-insert-tracepoints off
5914 This controls whether @value{GDBN} will attempt to insert (regular)
5915 tracepoints at the beginning of a tracing experiment. It affects only
5916 non-fast tracepoints, fast tracepoints being under the control of
5917 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5919 @item show may-insert-tracepoints
5920 Show the current permission to insert tracepoints.
5922 @kindex may-insert-fast-tracepoints
5923 @item set may-insert-fast-tracepoints on
5924 @itemx set may-insert-fast-tracepoints off
5925 This controls whether @value{GDBN} will attempt to insert fast
5926 tracepoints at the beginning of a tracing experiment. It affects only
5927 fast tracepoints, regular (non-fast) tracepoints being under the
5928 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5930 @item show may-insert-fast-tracepoints
5931 Show the current permission to insert fast tracepoints.
5933 @kindex may-interrupt
5934 @item set may-interrupt on
5935 @itemx set may-interrupt off
5936 This controls whether @value{GDBN} will attempt to interrupt or stop
5937 program execution. When this variable is @code{off}, the
5938 @code{interrupt} command will have no effect, nor will
5939 @kbd{Ctrl-c}. It defaults to @code{on}.
5941 @item show may-interrupt
5942 Show the current permission to interrupt or stop the program.
5946 @node Reverse Execution
5947 @chapter Running programs backward
5948 @cindex reverse execution
5949 @cindex running programs backward
5951 When you are debugging a program, it is not unusual to realize that
5952 you have gone too far, and some event of interest has already happened.
5953 If the target environment supports it, @value{GDBN} can allow you to
5954 ``rewind'' the program by running it backward.
5956 A target environment that supports reverse execution should be able
5957 to ``undo'' the changes in machine state that have taken place as the
5958 program was executing normally. Variables, registers etc.@: should
5959 revert to their previous values. Obviously this requires a great
5960 deal of sophistication on the part of the target environment; not
5961 all target environments can support reverse execution.
5963 When a program is executed in reverse, the instructions that
5964 have most recently been executed are ``un-executed'', in reverse
5965 order. The program counter runs backward, following the previous
5966 thread of execution in reverse. As each instruction is ``un-executed'',
5967 the values of memory and/or registers that were changed by that
5968 instruction are reverted to their previous states. After executing
5969 a piece of source code in reverse, all side effects of that code
5970 should be ``undone'', and all variables should be returned to their
5971 prior values@footnote{
5972 Note that some side effects are easier to undo than others. For instance,
5973 memory and registers are relatively easy, but device I/O is hard. Some
5974 targets may be able undo things like device I/O, and some may not.
5976 The contract between @value{GDBN} and the reverse executing target
5977 requires only that the target do something reasonable when
5978 @value{GDBN} tells it to execute backwards, and then report the
5979 results back to @value{GDBN}. Whatever the target reports back to
5980 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5981 assumes that the memory and registers that the target reports are in a
5982 consistant state, but @value{GDBN} accepts whatever it is given.
5985 If you are debugging in a target environment that supports
5986 reverse execution, @value{GDBN} provides the following commands.
5989 @kindex reverse-continue
5990 @kindex rc @r{(@code{reverse-continue})}
5991 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5992 @itemx rc @r{[}@var{ignore-count}@r{]}
5993 Beginning at the point where your program last stopped, start executing
5994 in reverse. Reverse execution will stop for breakpoints and synchronous
5995 exceptions (signals), just like normal execution. Behavior of
5996 asynchronous signals depends on the target environment.
5998 @kindex reverse-step
5999 @kindex rs @r{(@code{step})}
6000 @item reverse-step @r{[}@var{count}@r{]}
6001 Run the program backward until control reaches the start of a
6002 different source line; then stop it, and return control to @value{GDBN}.
6004 Like the @code{step} command, @code{reverse-step} will only stop
6005 at the beginning of a source line. It ``un-executes'' the previously
6006 executed source line. If the previous source line included calls to
6007 debuggable functions, @code{reverse-step} will step (backward) into
6008 the called function, stopping at the beginning of the @emph{last}
6009 statement in the called function (typically a return statement).
6011 Also, as with the @code{step} command, if non-debuggable functions are
6012 called, @code{reverse-step} will run thru them backward without stopping.
6014 @kindex reverse-stepi
6015 @kindex rsi @r{(@code{reverse-stepi})}
6016 @item reverse-stepi @r{[}@var{count}@r{]}
6017 Reverse-execute one machine instruction. Note that the instruction
6018 to be reverse-executed is @emph{not} the one pointed to by the program
6019 counter, but the instruction executed prior to that one. For instance,
6020 if the last instruction was a jump, @code{reverse-stepi} will take you
6021 back from the destination of the jump to the jump instruction itself.
6023 @kindex reverse-next
6024 @kindex rn @r{(@code{reverse-next})}
6025 @item reverse-next @r{[}@var{count}@r{]}
6026 Run backward to the beginning of the previous line executed in
6027 the current (innermost) stack frame. If the line contains function
6028 calls, they will be ``un-executed'' without stopping. Starting from
6029 the first line of a function, @code{reverse-next} will take you back
6030 to the caller of that function, @emph{before} the function was called,
6031 just as the normal @code{next} command would take you from the last
6032 line of a function back to its return to its caller
6033 @footnote{Unless the code is too heavily optimized.}.
6035 @kindex reverse-nexti
6036 @kindex rni @r{(@code{reverse-nexti})}
6037 @item reverse-nexti @r{[}@var{count}@r{]}
6038 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6039 in reverse, except that called functions are ``un-executed'' atomically.
6040 That is, if the previously executed instruction was a return from
6041 another function, @code{reverse-nexti} will continue to execute
6042 in reverse until the call to that function (from the current stack
6045 @kindex reverse-finish
6046 @item reverse-finish
6047 Just as the @code{finish} command takes you to the point where the
6048 current function returns, @code{reverse-finish} takes you to the point
6049 where it was called. Instead of ending up at the end of the current
6050 function invocation, you end up at the beginning.
6052 @kindex set exec-direction
6053 @item set exec-direction
6054 Set the direction of target execution.
6055 @item set exec-direction reverse
6056 @cindex execute forward or backward in time
6057 @value{GDBN} will perform all execution commands in reverse, until the
6058 exec-direction mode is changed to ``forward''. Affected commands include
6059 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6060 command cannot be used in reverse mode.
6061 @item set exec-direction forward
6062 @value{GDBN} will perform all execution commands in the normal fashion.
6063 This is the default.
6067 @node Process Record and Replay
6068 @chapter Recording Inferior's Execution and Replaying It
6069 @cindex process record and replay
6070 @cindex recording inferior's execution and replaying it
6072 On some platforms, @value{GDBN} provides a special @dfn{process record
6073 and replay} target that can record a log of the process execution, and
6074 replay it later with both forward and reverse execution commands.
6077 When this target is in use, if the execution log includes the record
6078 for the next instruction, @value{GDBN} will debug in @dfn{replay
6079 mode}. In the replay mode, the inferior does not really execute code
6080 instructions. Instead, all the events that normally happen during
6081 code execution are taken from the execution log. While code is not
6082 really executed in replay mode, the values of registers (including the
6083 program counter register) and the memory of the inferior are still
6084 changed as they normally would. Their contents are taken from the
6088 If the record for the next instruction is not in the execution log,
6089 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6090 inferior executes normally, and @value{GDBN} records the execution log
6093 The process record and replay target supports reverse execution
6094 (@pxref{Reverse Execution}), even if the platform on which the
6095 inferior runs does not. However, the reverse execution is limited in
6096 this case by the range of the instructions recorded in the execution
6097 log. In other words, reverse execution on platforms that don't
6098 support it directly can only be done in the replay mode.
6100 When debugging in the reverse direction, @value{GDBN} will work in
6101 replay mode as long as the execution log includes the record for the
6102 previous instruction; otherwise, it will work in record mode, if the
6103 platform supports reverse execution, or stop if not.
6105 For architecture environments that support process record and replay,
6106 @value{GDBN} provides the following commands:
6109 @kindex target record
6110 @kindex target record-full
6111 @kindex target record-btrace
6114 @kindex record btrace
6118 @item record @var{method}
6119 This command starts the process record and replay target. The
6120 recording method can be specified as parameter. Without a parameter
6121 the command uses the @code{full} recording method. The following
6122 recording methods are available:
6126 Full record/replay recording using @value{GDBN}'s software record and
6127 replay implementation. This method allows replaying and reverse
6131 Hardware-supported instruction recording. This method does not allow
6132 replaying and reverse execution.
6134 This recording method may not be available on all processors.
6137 The process record and replay target can only debug a process that is
6138 already running. Therefore, you need first to start the process with
6139 the @kbd{run} or @kbd{start} commands, and then start the recording
6140 with the @kbd{record @var{method}} command.
6142 Both @code{record @var{method}} and @code{rec @var{method}} are
6143 aliases of @code{target record-@var{method}}.
6145 @cindex displaced stepping, and process record and replay
6146 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6147 will be automatically disabled when process record and replay target
6148 is started. That's because the process record and replay target
6149 doesn't support displaced stepping.
6151 @cindex non-stop mode, and process record and replay
6152 @cindex asynchronous execution, and process record and replay
6153 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6154 the asynchronous execution mode (@pxref{Background Execution}), not
6155 all recording methods are available. The @code{full} recording method
6156 does not support these two modes.
6161 Stop the process record and replay target. When process record and
6162 replay target stops, the entire execution log will be deleted and the
6163 inferior will either be terminated, or will remain in its final state.
6165 When you stop the process record and replay target in record mode (at
6166 the end of the execution log), the inferior will be stopped at the
6167 next instruction that would have been recorded. In other words, if
6168 you record for a while and then stop recording, the inferior process
6169 will be left in the same state as if the recording never happened.
6171 On the other hand, if the process record and replay target is stopped
6172 while in replay mode (that is, not at the end of the execution log,
6173 but at some earlier point), the inferior process will become ``live''
6174 at that earlier state, and it will then be possible to continue the
6175 usual ``live'' debugging of the process from that state.
6177 When the inferior process exits, or @value{GDBN} detaches from it,
6178 process record and replay target will automatically stop itself.
6181 @item record save @var{filename}
6182 Save the execution log to a file @file{@var{filename}}.
6183 Default filename is @file{gdb_record.@var{process_id}}, where
6184 @var{process_id} is the process ID of the inferior.
6186 This command may not be available for all recording methods.
6188 @kindex record restore
6189 @item record restore @var{filename}
6190 Restore the execution log from a file @file{@var{filename}}.
6191 File must have been created with @code{record save}.
6193 @kindex set record full
6194 @item set record full insn-number-max @var{limit}
6195 @itemx set record full insn-number-max unlimited
6196 Set the limit of instructions to be recorded for the @code{full}
6197 recording method. Default value is 200000.
6199 If @var{limit} is a positive number, then @value{GDBN} will start
6200 deleting instructions from the log once the number of the record
6201 instructions becomes greater than @var{limit}. For every new recorded
6202 instruction, @value{GDBN} will delete the earliest recorded
6203 instruction to keep the number of recorded instructions at the limit.
6204 (Since deleting recorded instructions loses information, @value{GDBN}
6205 lets you control what happens when the limit is reached, by means of
6206 the @code{stop-at-limit} option, described below.)
6208 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6209 delete recorded instructions from the execution log. The number of
6210 recorded instructions is limited only by the available memory.
6212 @kindex show record full
6213 @item show record full insn-number-max
6214 Show the limit of instructions to be recorded with the @code{full}
6217 @item set record full stop-at-limit
6218 Control the behavior of the @code{full} recording method when the
6219 number of recorded instructions reaches the limit. If ON (the
6220 default), @value{GDBN} will stop when the limit is reached for the
6221 first time and ask you whether you want to stop the inferior or
6222 continue running it and recording the execution log. If you decide
6223 to continue recording, each new recorded instruction will cause the
6224 oldest one to be deleted.
6226 If this option is OFF, @value{GDBN} will automatically delete the
6227 oldest record to make room for each new one, without asking.
6229 @item show record full stop-at-limit
6230 Show the current setting of @code{stop-at-limit}.
6232 @item set record full memory-query
6233 Control the behavior when @value{GDBN} is unable to record memory
6234 changes caused by an instruction for the @code{full} recording method.
6235 If ON, @value{GDBN} will query whether to stop the inferior in that
6238 If this option is OFF (the default), @value{GDBN} will automatically
6239 ignore the effect of such instructions on memory. Later, when
6240 @value{GDBN} replays this execution log, it will mark the log of this
6241 instruction as not accessible, and it will not affect the replay
6244 @item show record full memory-query
6245 Show the current setting of @code{memory-query}.
6249 Show various statistics about the recording depending on the recording
6254 For the @code{full} recording method, it shows the state of process
6255 record and its in-memory execution log buffer, including:
6259 Whether in record mode or replay mode.
6261 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6263 Highest recorded instruction number.
6265 Current instruction about to be replayed (if in replay mode).
6267 Number of instructions contained in the execution log.
6269 Maximum number of instructions that may be contained in the execution log.
6273 For the @code{btrace} recording method, it shows the number of
6274 instructions that have been recorded and the number of blocks of
6275 sequential control-flow that is formed by the recorded instructions.
6278 @kindex record delete
6281 When record target runs in replay mode (``in the past''), delete the
6282 subsequent execution log and begin to record a new execution log starting
6283 from the current address. This means you will abandon the previously
6284 recorded ``future'' and begin recording a new ``future''.
6286 @kindex record instruction-history
6287 @kindex rec instruction-history
6288 @item record instruction-history
6289 Disassembles instructions from the recorded execution log. By
6290 default, ten instructions are disassembled. This can be changed using
6291 the @code{set record instruction-history-size} command. Instructions
6292 are printed in execution order. There are several ways to specify
6293 what part of the execution log to disassemble:
6296 @item record instruction-history @var{insn}
6297 Disassembles ten instructions starting from instruction number
6300 @item record instruction-history @var{insn}, +/-@var{n}
6301 Disassembles @var{n} instructions around instruction number
6302 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6303 @var{n} instructions after instruction number @var{insn}. If
6304 @var{n} is preceded with @code{-}, disassembles @var{n}
6305 instructions before instruction number @var{insn}.
6307 @item record instruction-history
6308 Disassembles ten more instructions after the last disassembly.
6310 @item record instruction-history -
6311 Disassembles ten more instructions before the last disassembly.
6313 @item record instruction-history @var{begin} @var{end}
6314 Disassembles instructions beginning with instruction number
6315 @var{begin} until instruction number @var{end}. The instruction
6316 number @var{end} is not included.
6319 This command may not be available for all recording methods.
6322 @item set record instruction-history-size @var{size}
6323 @itemx set record instruction-history-size unlimited
6324 Define how many instructions to disassemble in the @code{record
6325 instruction-history} command. The default value is 10.
6326 A @var{size} of @code{unlimited} means unlimited instructions.
6329 @item show record instruction-history-size
6330 Show how many instructions to disassemble in the @code{record
6331 instruction-history} command.
6333 @kindex record function-call-history
6334 @kindex rec function-call-history
6335 @item record function-call-history
6336 Prints the execution history at function granularity. It prints one
6337 line for each sequence of instructions that belong to the same
6338 function giving the name of that function, the source lines
6339 for this instruction sequence (if the @code{/l} modifier is
6340 specified), and the instructions numbers that form the sequence (if
6341 the @code{/i} modifier is specified).
6344 (@value{GDBP}) @b{list 1, 10}
6355 (@value{GDBP}) @b{record function-call-history /l}
6361 By default, ten lines are printed. This can be changed using the
6362 @code{set record function-call-history-size} command. Functions are
6363 printed in execution order. There are several ways to specify what
6367 @item record function-call-history @var{func}
6368 Prints ten functions starting from function number @var{func}.
6370 @item record function-call-history @var{func}, +/-@var{n}
6371 Prints @var{n} functions around function number @var{func}. If
6372 @var{n} is preceded with @code{+}, prints @var{n} functions after
6373 function number @var{func}. If @var{n} is preceded with @code{-},
6374 prints @var{n} functions before function number @var{func}.
6376 @item record function-call-history
6377 Prints ten more functions after the last ten-line print.
6379 @item record function-call-history -
6380 Prints ten more functions before the last ten-line print.
6382 @item record function-call-history @var{begin} @var{end}
6383 Prints functions beginning with function number @var{begin} until
6384 function number @var{end}. The function number @var{end} is not
6388 This command may not be available for all recording methods.
6390 @item set record function-call-history-size @var{size}
6391 @itemx set record function-call-history-size unlimited
6392 Define how many lines to print in the
6393 @code{record function-call-history} command. The default value is 10.
6394 A size of @code{unlimited} means unlimited lines.
6396 @item show record function-call-history-size
6397 Show how many lines to print in the
6398 @code{record function-call-history} command.
6403 @chapter Examining the Stack
6405 When your program has stopped, the first thing you need to know is where it
6406 stopped and how it got there.
6409 Each time your program performs a function call, information about the call
6411 That information includes the location of the call in your program,
6412 the arguments of the call,
6413 and the local variables of the function being called.
6414 The information is saved in a block of data called a @dfn{stack frame}.
6415 The stack frames are allocated in a region of memory called the @dfn{call
6418 When your program stops, the @value{GDBN} commands for examining the
6419 stack allow you to see all of this information.
6421 @cindex selected frame
6422 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6423 @value{GDBN} commands refer implicitly to the selected frame. In
6424 particular, whenever you ask @value{GDBN} for the value of a variable in
6425 your program, the value is found in the selected frame. There are
6426 special @value{GDBN} commands to select whichever frame you are
6427 interested in. @xref{Selection, ,Selecting a Frame}.
6429 When your program stops, @value{GDBN} automatically selects the
6430 currently executing frame and describes it briefly, similar to the
6431 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6434 * Frames:: Stack frames
6435 * Backtrace:: Backtraces
6436 * Selection:: Selecting a frame
6437 * Frame Info:: Information on a frame
6442 @section Stack Frames
6444 @cindex frame, definition
6446 The call stack is divided up into contiguous pieces called @dfn{stack
6447 frames}, or @dfn{frames} for short; each frame is the data associated
6448 with one call to one function. The frame contains the arguments given
6449 to the function, the function's local variables, and the address at
6450 which the function is executing.
6452 @cindex initial frame
6453 @cindex outermost frame
6454 @cindex innermost frame
6455 When your program is started, the stack has only one frame, that of the
6456 function @code{main}. This is called the @dfn{initial} frame or the
6457 @dfn{outermost} frame. Each time a function is called, a new frame is
6458 made. Each time a function returns, the frame for that function invocation
6459 is eliminated. If a function is recursive, there can be many frames for
6460 the same function. The frame for the function in which execution is
6461 actually occurring is called the @dfn{innermost} frame. This is the most
6462 recently created of all the stack frames that still exist.
6464 @cindex frame pointer
6465 Inside your program, stack frames are identified by their addresses. A
6466 stack frame consists of many bytes, each of which has its own address; each
6467 kind of computer has a convention for choosing one byte whose
6468 address serves as the address of the frame. Usually this address is kept
6469 in a register called the @dfn{frame pointer register}
6470 (@pxref{Registers, $fp}) while execution is going on in that frame.
6472 @cindex frame number
6473 @value{GDBN} assigns numbers to all existing stack frames, starting with
6474 zero for the innermost frame, one for the frame that called it,
6475 and so on upward. These numbers do not really exist in your program;
6476 they are assigned by @value{GDBN} to give you a way of designating stack
6477 frames in @value{GDBN} commands.
6479 @c The -fomit-frame-pointer below perennially causes hbox overflow
6480 @c underflow problems.
6481 @cindex frameless execution
6482 Some compilers provide a way to compile functions so that they operate
6483 without stack frames. (For example, the @value{NGCC} option
6485 @samp{-fomit-frame-pointer}
6487 generates functions without a frame.)
6488 This is occasionally done with heavily used library functions to save
6489 the frame setup time. @value{GDBN} has limited facilities for dealing
6490 with these function invocations. If the innermost function invocation
6491 has no stack frame, @value{GDBN} nevertheless regards it as though
6492 it had a separate frame, which is numbered zero as usual, allowing
6493 correct tracing of the function call chain. However, @value{GDBN} has
6494 no provision for frameless functions elsewhere in the stack.
6497 @kindex frame@r{, command}
6498 @cindex current stack frame
6499 @item frame @var{args}
6500 The @code{frame} command allows you to move from one stack frame to another,
6501 and to print the stack frame you select. @var{args} may be either the
6502 address of the frame or the stack frame number. Without an argument,
6503 @code{frame} prints the current stack frame.
6505 @kindex select-frame
6506 @cindex selecting frame silently
6508 The @code{select-frame} command allows you to move from one stack frame
6509 to another without printing the frame. This is the silent version of
6517 @cindex call stack traces
6518 A backtrace is a summary of how your program got where it is. It shows one
6519 line per frame, for many frames, starting with the currently executing
6520 frame (frame zero), followed by its caller (frame one), and on up the
6525 @kindex bt @r{(@code{backtrace})}
6528 Print a backtrace of the entire stack: one line per frame for all
6529 frames in the stack.
6531 You can stop the backtrace at any time by typing the system interrupt
6532 character, normally @kbd{Ctrl-c}.
6534 @item backtrace @var{n}
6536 Similar, but print only the innermost @var{n} frames.
6538 @item backtrace -@var{n}
6540 Similar, but print only the outermost @var{n} frames.
6542 @item backtrace full
6544 @itemx bt full @var{n}
6545 @itemx bt full -@var{n}
6546 Print the values of the local variables also. @var{n} specifies the
6547 number of frames to print, as described above.
6552 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6553 are additional aliases for @code{backtrace}.
6555 @cindex multiple threads, backtrace
6556 In a multi-threaded program, @value{GDBN} by default shows the
6557 backtrace only for the current thread. To display the backtrace for
6558 several or all of the threads, use the command @code{thread apply}
6559 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6560 apply all backtrace}, @value{GDBN} will display the backtrace for all
6561 the threads; this is handy when you debug a core dump of a
6562 multi-threaded program.
6564 Each line in the backtrace shows the frame number and the function name.
6565 The program counter value is also shown---unless you use @code{set
6566 print address off}. The backtrace also shows the source file name and
6567 line number, as well as the arguments to the function. The program
6568 counter value is omitted if it is at the beginning of the code for that
6571 Here is an example of a backtrace. It was made with the command
6572 @samp{bt 3}, so it shows the innermost three frames.
6576 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6578 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6579 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6581 (More stack frames follow...)
6586 The display for frame zero does not begin with a program counter
6587 value, indicating that your program has stopped at the beginning of the
6588 code for line @code{993} of @code{builtin.c}.
6591 The value of parameter @code{data} in frame 1 has been replaced by
6592 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6593 only if it is a scalar (integer, pointer, enumeration, etc). See command
6594 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6595 on how to configure the way function parameter values are printed.
6597 @cindex optimized out, in backtrace
6598 @cindex function call arguments, optimized out
6599 If your program was compiled with optimizations, some compilers will
6600 optimize away arguments passed to functions if those arguments are
6601 never used after the call. Such optimizations generate code that
6602 passes arguments through registers, but doesn't store those arguments
6603 in the stack frame. @value{GDBN} has no way of displaying such
6604 arguments in stack frames other than the innermost one. Here's what
6605 such a backtrace might look like:
6609 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6611 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6612 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6614 (More stack frames follow...)
6619 The values of arguments that were not saved in their stack frames are
6620 shown as @samp{<optimized out>}.
6622 If you need to display the values of such optimized-out arguments,
6623 either deduce that from other variables whose values depend on the one
6624 you are interested in, or recompile without optimizations.
6626 @cindex backtrace beyond @code{main} function
6627 @cindex program entry point
6628 @cindex startup code, and backtrace
6629 Most programs have a standard user entry point---a place where system
6630 libraries and startup code transition into user code. For C this is
6631 @code{main}@footnote{
6632 Note that embedded programs (the so-called ``free-standing''
6633 environment) are not required to have a @code{main} function as the
6634 entry point. They could even have multiple entry points.}.
6635 When @value{GDBN} finds the entry function in a backtrace
6636 it will terminate the backtrace, to avoid tracing into highly
6637 system-specific (and generally uninteresting) code.
6639 If you need to examine the startup code, or limit the number of levels
6640 in a backtrace, you can change this behavior:
6643 @item set backtrace past-main
6644 @itemx set backtrace past-main on
6645 @kindex set backtrace
6646 Backtraces will continue past the user entry point.
6648 @item set backtrace past-main off
6649 Backtraces will stop when they encounter the user entry point. This is the
6652 @item show backtrace past-main
6653 @kindex show backtrace
6654 Display the current user entry point backtrace policy.
6656 @item set backtrace past-entry
6657 @itemx set backtrace past-entry on
6658 Backtraces will continue past the internal entry point of an application.
6659 This entry point is encoded by the linker when the application is built,
6660 and is likely before the user entry point @code{main} (or equivalent) is called.
6662 @item set backtrace past-entry off
6663 Backtraces will stop when they encounter the internal entry point of an
6664 application. This is the default.
6666 @item show backtrace past-entry
6667 Display the current internal entry point backtrace policy.
6669 @item set backtrace limit @var{n}
6670 @itemx set backtrace limit 0
6671 @itemx set backtrace limit unlimited
6672 @cindex backtrace limit
6673 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6674 or zero means unlimited levels.
6676 @item show backtrace limit
6677 Display the current limit on backtrace levels.
6680 You can control how file names are displayed.
6683 @item set filename-display
6684 @itemx set filename-display relative
6685 @cindex filename-display
6686 Display file names relative to the compilation directory. This is the default.
6688 @item set filename-display basename
6689 Display only basename of a filename.
6691 @item set filename-display absolute
6692 Display an absolute filename.
6694 @item show filename-display
6695 Show the current way to display filenames.
6699 @section Selecting a Frame
6701 Most commands for examining the stack and other data in your program work on
6702 whichever stack frame is selected at the moment. Here are the commands for
6703 selecting a stack frame; all of them finish by printing a brief description
6704 of the stack frame just selected.
6707 @kindex frame@r{, selecting}
6708 @kindex f @r{(@code{frame})}
6711 Select frame number @var{n}. Recall that frame zero is the innermost
6712 (currently executing) frame, frame one is the frame that called the
6713 innermost one, and so on. The highest-numbered frame is the one for
6716 @item frame @var{addr}
6718 Select the frame at address @var{addr}. This is useful mainly if the
6719 chaining of stack frames has been damaged by a bug, making it
6720 impossible for @value{GDBN} to assign numbers properly to all frames. In
6721 addition, this can be useful when your program has multiple stacks and
6722 switches between them.
6724 On the SPARC architecture, @code{frame} needs two addresses to
6725 select an arbitrary frame: a frame pointer and a stack pointer.
6727 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6728 pointer and a program counter.
6730 On the 29k architecture, it needs three addresses: a register stack
6731 pointer, a program counter, and a memory stack pointer.
6735 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6736 advances toward the outermost frame, to higher frame numbers, to frames
6737 that have existed longer. @var{n} defaults to one.
6740 @kindex do @r{(@code{down})}
6742 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6743 advances toward the innermost frame, to lower frame numbers, to frames
6744 that were created more recently. @var{n} defaults to one. You may
6745 abbreviate @code{down} as @code{do}.
6748 All of these commands end by printing two lines of output describing the
6749 frame. The first line shows the frame number, the function name, the
6750 arguments, and the source file and line number of execution in that
6751 frame. The second line shows the text of that source line.
6759 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6761 10 read_input_file (argv[i]);
6765 After such a printout, the @code{list} command with no arguments
6766 prints ten lines centered on the point of execution in the frame.
6767 You can also edit the program at the point of execution with your favorite
6768 editing program by typing @code{edit}.
6769 @xref{List, ,Printing Source Lines},
6773 @kindex down-silently
6775 @item up-silently @var{n}
6776 @itemx down-silently @var{n}
6777 These two commands are variants of @code{up} and @code{down},
6778 respectively; they differ in that they do their work silently, without
6779 causing display of the new frame. They are intended primarily for use
6780 in @value{GDBN} command scripts, where the output might be unnecessary and
6785 @section Information About a Frame
6787 There are several other commands to print information about the selected
6793 When used without any argument, this command does not change which
6794 frame is selected, but prints a brief description of the currently
6795 selected stack frame. It can be abbreviated @code{f}. With an
6796 argument, this command is used to select a stack frame.
6797 @xref{Selection, ,Selecting a Frame}.
6800 @kindex info f @r{(@code{info frame})}
6803 This command prints a verbose description of the selected stack frame,
6808 the address of the frame
6810 the address of the next frame down (called by this frame)
6812 the address of the next frame up (caller of this frame)
6814 the language in which the source code corresponding to this frame is written
6816 the address of the frame's arguments
6818 the address of the frame's local variables
6820 the program counter saved in it (the address of execution in the caller frame)
6822 which registers were saved in the frame
6825 @noindent The verbose description is useful when
6826 something has gone wrong that has made the stack format fail to fit
6827 the usual conventions.
6829 @item info frame @var{addr}
6830 @itemx info f @var{addr}
6831 Print a verbose description of the frame at address @var{addr}, without
6832 selecting that frame. The selected frame remains unchanged by this
6833 command. This requires the same kind of address (more than one for some
6834 architectures) that you specify in the @code{frame} command.
6835 @xref{Selection, ,Selecting a Frame}.
6839 Print the arguments of the selected frame, each on a separate line.
6843 Print the local variables of the selected frame, each on a separate
6844 line. These are all variables (declared either static or automatic)
6845 accessible at the point of execution of the selected frame.
6851 @chapter Examining Source Files
6853 @value{GDBN} can print parts of your program's source, since the debugging
6854 information recorded in the program tells @value{GDBN} what source files were
6855 used to build it. When your program stops, @value{GDBN} spontaneously prints
6856 the line where it stopped. Likewise, when you select a stack frame
6857 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6858 execution in that frame has stopped. You can print other portions of
6859 source files by explicit command.
6861 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6862 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6863 @value{GDBN} under @sc{gnu} Emacs}.
6866 * List:: Printing source lines
6867 * Specify Location:: How to specify code locations
6868 * Edit:: Editing source files
6869 * Search:: Searching source files
6870 * Source Path:: Specifying source directories
6871 * Machine Code:: Source and machine code
6875 @section Printing Source Lines
6878 @kindex l @r{(@code{list})}
6879 To print lines from a source file, use the @code{list} command
6880 (abbreviated @code{l}). By default, ten lines are printed.
6881 There are several ways to specify what part of the file you want to
6882 print; see @ref{Specify Location}, for the full list.
6884 Here are the forms of the @code{list} command most commonly used:
6887 @item list @var{linenum}
6888 Print lines centered around line number @var{linenum} in the
6889 current source file.
6891 @item list @var{function}
6892 Print lines centered around the beginning of function
6896 Print more lines. If the last lines printed were printed with a
6897 @code{list} command, this prints lines following the last lines
6898 printed; however, if the last line printed was a solitary line printed
6899 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6900 Stack}), this prints lines centered around that line.
6903 Print lines just before the lines last printed.
6906 @cindex @code{list}, how many lines to display
6907 By default, @value{GDBN} prints ten source lines with any of these forms of
6908 the @code{list} command. You can change this using @code{set listsize}:
6911 @kindex set listsize
6912 @item set listsize @var{count}
6913 @itemx set listsize unlimited
6914 Make the @code{list} command display @var{count} source lines (unless
6915 the @code{list} argument explicitly specifies some other number).
6916 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
6918 @kindex show listsize
6920 Display the number of lines that @code{list} prints.
6923 Repeating a @code{list} command with @key{RET} discards the argument,
6924 so it is equivalent to typing just @code{list}. This is more useful
6925 than listing the same lines again. An exception is made for an
6926 argument of @samp{-}; that argument is preserved in repetition so that
6927 each repetition moves up in the source file.
6929 In general, the @code{list} command expects you to supply zero, one or two
6930 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6931 of writing them (@pxref{Specify Location}), but the effect is always
6932 to specify some source line.
6934 Here is a complete description of the possible arguments for @code{list}:
6937 @item list @var{linespec}
6938 Print lines centered around the line specified by @var{linespec}.
6940 @item list @var{first},@var{last}
6941 Print lines from @var{first} to @var{last}. Both arguments are
6942 linespecs. When a @code{list} command has two linespecs, and the
6943 source file of the second linespec is omitted, this refers to
6944 the same source file as the first linespec.
6946 @item list ,@var{last}
6947 Print lines ending with @var{last}.
6949 @item list @var{first},
6950 Print lines starting with @var{first}.
6953 Print lines just after the lines last printed.
6956 Print lines just before the lines last printed.
6959 As described in the preceding table.
6962 @node Specify Location
6963 @section Specifying a Location
6964 @cindex specifying location
6967 Several @value{GDBN} commands accept arguments that specify a location
6968 of your program's code. Since @value{GDBN} is a source-level
6969 debugger, a location usually specifies some line in the source code;
6970 for that reason, locations are also known as @dfn{linespecs}.
6972 Here are all the different ways of specifying a code location that
6973 @value{GDBN} understands:
6977 Specifies the line number @var{linenum} of the current source file.
6980 @itemx +@var{offset}
6981 Specifies the line @var{offset} lines before or after the @dfn{current
6982 line}. For the @code{list} command, the current line is the last one
6983 printed; for the breakpoint commands, this is the line at which
6984 execution stopped in the currently selected @dfn{stack frame}
6985 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6986 used as the second of the two linespecs in a @code{list} command,
6987 this specifies the line @var{offset} lines up or down from the first
6990 @item @var{filename}:@var{linenum}
6991 Specifies the line @var{linenum} in the source file @var{filename}.
6992 If @var{filename} is a relative file name, then it will match any
6993 source file name with the same trailing components. For example, if
6994 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6995 name of @file{/build/trunk/gcc/expr.c}, but not
6996 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6998 @item @var{function}
6999 Specifies the line that begins the body of the function @var{function}.
7000 For example, in C, this is the line with the open brace.
7002 @item @var{function}:@var{label}
7003 Specifies the line where @var{label} appears in @var{function}.
7005 @item @var{filename}:@var{function}
7006 Specifies the line that begins the body of the function @var{function}
7007 in the file @var{filename}. You only need the file name with a
7008 function name to avoid ambiguity when there are identically named
7009 functions in different source files.
7012 Specifies the line at which the label named @var{label} appears.
7013 @value{GDBN} searches for the label in the function corresponding to
7014 the currently selected stack frame. If there is no current selected
7015 stack frame (for instance, if the inferior is not running), then
7016 @value{GDBN} will not search for a label.
7018 @item *@var{address}
7019 Specifies the program address @var{address}. For line-oriented
7020 commands, such as @code{list} and @code{edit}, this specifies a source
7021 line that contains @var{address}. For @code{break} and other
7022 breakpoint oriented commands, this can be used to set breakpoints in
7023 parts of your program which do not have debugging information or
7026 Here @var{address} may be any expression valid in the current working
7027 language (@pxref{Languages, working language}) that specifies a code
7028 address. In addition, as a convenience, @value{GDBN} extends the
7029 semantics of expressions used in locations to cover the situations
7030 that frequently happen during debugging. Here are the various forms
7034 @item @var{expression}
7035 Any expression valid in the current working language.
7037 @item @var{funcaddr}
7038 An address of a function or procedure derived from its name. In C,
7039 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7040 simply the function's name @var{function} (and actually a special case
7041 of a valid expression). In Pascal and Modula-2, this is
7042 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7043 (although the Pascal form also works).
7045 This form specifies the address of the function's first instruction,
7046 before the stack frame and arguments have been set up.
7048 @item '@var{filename}'::@var{funcaddr}
7049 Like @var{funcaddr} above, but also specifies the name of the source
7050 file explicitly. This is useful if the name of the function does not
7051 specify the function unambiguously, e.g., if there are several
7052 functions with identical names in different source files.
7055 @cindex breakpoint at static probe point
7056 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7057 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7058 applications to embed static probes. @xref{Static Probe Points}, for more
7059 information on finding and using static probes. This form of linespec
7060 specifies the location of such a static probe.
7062 If @var{objfile} is given, only probes coming from that shared library
7063 or executable matching @var{objfile} as a regular expression are considered.
7064 If @var{provider} is given, then only probes from that provider are considered.
7065 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7066 each one of those probes.
7072 @section Editing Source Files
7073 @cindex editing source files
7076 @kindex e @r{(@code{edit})}
7077 To edit the lines in a source file, use the @code{edit} command.
7078 The editing program of your choice
7079 is invoked with the current line set to
7080 the active line in the program.
7081 Alternatively, there are several ways to specify what part of the file you
7082 want to print if you want to see other parts of the program:
7085 @item edit @var{location}
7086 Edit the source file specified by @code{location}. Editing starts at
7087 that @var{location}, e.g., at the specified source line of the
7088 specified file. @xref{Specify Location}, for all the possible forms
7089 of the @var{location} argument; here are the forms of the @code{edit}
7090 command most commonly used:
7093 @item edit @var{number}
7094 Edit the current source file with @var{number} as the active line number.
7096 @item edit @var{function}
7097 Edit the file containing @var{function} at the beginning of its definition.
7102 @subsection Choosing your Editor
7103 You can customize @value{GDBN} to use any editor you want
7105 The only restriction is that your editor (say @code{ex}), recognizes the
7106 following command-line syntax:
7108 ex +@var{number} file
7110 The optional numeric value +@var{number} specifies the number of the line in
7111 the file where to start editing.}.
7112 By default, it is @file{@value{EDITOR}}, but you can change this
7113 by setting the environment variable @code{EDITOR} before using
7114 @value{GDBN}. For example, to configure @value{GDBN} to use the
7115 @code{vi} editor, you could use these commands with the @code{sh} shell:
7121 or in the @code{csh} shell,
7123 setenv EDITOR /usr/bin/vi
7128 @section Searching Source Files
7129 @cindex searching source files
7131 There are two commands for searching through the current source file for a
7136 @kindex forward-search
7137 @kindex fo @r{(@code{forward-search})}
7138 @item forward-search @var{regexp}
7139 @itemx search @var{regexp}
7140 The command @samp{forward-search @var{regexp}} checks each line,
7141 starting with the one following the last line listed, for a match for
7142 @var{regexp}. It lists the line that is found. You can use the
7143 synonym @samp{search @var{regexp}} or abbreviate the command name as
7146 @kindex reverse-search
7147 @item reverse-search @var{regexp}
7148 The command @samp{reverse-search @var{regexp}} checks each line, starting
7149 with the one before the last line listed and going backward, for a match
7150 for @var{regexp}. It lists the line that is found. You can abbreviate
7151 this command as @code{rev}.
7155 @section Specifying Source Directories
7158 @cindex directories for source files
7159 Executable programs sometimes do not record the directories of the source
7160 files from which they were compiled, just the names. Even when they do,
7161 the directories could be moved between the compilation and your debugging
7162 session. @value{GDBN} has a list of directories to search for source files;
7163 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7164 it tries all the directories in the list, in the order they are present
7165 in the list, until it finds a file with the desired name.
7167 For example, suppose an executable references the file
7168 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7169 @file{/mnt/cross}. The file is first looked up literally; if this
7170 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7171 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7172 message is printed. @value{GDBN} does not look up the parts of the
7173 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7174 Likewise, the subdirectories of the source path are not searched: if
7175 the source path is @file{/mnt/cross}, and the binary refers to
7176 @file{foo.c}, @value{GDBN} would not find it under
7177 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7179 Plain file names, relative file names with leading directories, file
7180 names containing dots, etc.@: are all treated as described above; for
7181 instance, if the source path is @file{/mnt/cross}, and the source file
7182 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7183 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7184 that---@file{/mnt/cross/foo.c}.
7186 Note that the executable search path is @emph{not} used to locate the
7189 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7190 any information it has cached about where source files are found and where
7191 each line is in the file.
7195 When you start @value{GDBN}, its source path includes only @samp{cdir}
7196 and @samp{cwd}, in that order.
7197 To add other directories, use the @code{directory} command.
7199 The search path is used to find both program source files and @value{GDBN}
7200 script files (read using the @samp{-command} option and @samp{source} command).
7202 In addition to the source path, @value{GDBN} provides a set of commands
7203 that manage a list of source path substitution rules. A @dfn{substitution
7204 rule} specifies how to rewrite source directories stored in the program's
7205 debug information in case the sources were moved to a different
7206 directory between compilation and debugging. A rule is made of
7207 two strings, the first specifying what needs to be rewritten in
7208 the path, and the second specifying how it should be rewritten.
7209 In @ref{set substitute-path}, we name these two parts @var{from} and
7210 @var{to} respectively. @value{GDBN} does a simple string replacement
7211 of @var{from} with @var{to} at the start of the directory part of the
7212 source file name, and uses that result instead of the original file
7213 name to look up the sources.
7215 Using the previous example, suppose the @file{foo-1.0} tree has been
7216 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7217 @value{GDBN} to replace @file{/usr/src} in all source path names with
7218 @file{/mnt/cross}. The first lookup will then be
7219 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7220 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7221 substitution rule, use the @code{set substitute-path} command
7222 (@pxref{set substitute-path}).
7224 To avoid unexpected substitution results, a rule is applied only if the
7225 @var{from} part of the directory name ends at a directory separator.
7226 For instance, a rule substituting @file{/usr/source} into
7227 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7228 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7229 is applied only at the beginning of the directory name, this rule will
7230 not be applied to @file{/root/usr/source/baz.c} either.
7232 In many cases, you can achieve the same result using the @code{directory}
7233 command. However, @code{set substitute-path} can be more efficient in
7234 the case where the sources are organized in a complex tree with multiple
7235 subdirectories. With the @code{directory} command, you need to add each
7236 subdirectory of your project. If you moved the entire tree while
7237 preserving its internal organization, then @code{set substitute-path}
7238 allows you to direct the debugger to all the sources with one single
7241 @code{set substitute-path} is also more than just a shortcut command.
7242 The source path is only used if the file at the original location no
7243 longer exists. On the other hand, @code{set substitute-path} modifies
7244 the debugger behavior to look at the rewritten location instead. So, if
7245 for any reason a source file that is not relevant to your executable is
7246 located at the original location, a substitution rule is the only
7247 method available to point @value{GDBN} at the new location.
7249 @cindex @samp{--with-relocated-sources}
7250 @cindex default source path substitution
7251 You can configure a default source path substitution rule by
7252 configuring @value{GDBN} with the
7253 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7254 should be the name of a directory under @value{GDBN}'s configured
7255 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7256 directory names in debug information under @var{dir} will be adjusted
7257 automatically if the installed @value{GDBN} is moved to a new
7258 location. This is useful if @value{GDBN}, libraries or executables
7259 with debug information and corresponding source code are being moved
7263 @item directory @var{dirname} @dots{}
7264 @item dir @var{dirname} @dots{}
7265 Add directory @var{dirname} to the front of the source path. Several
7266 directory names may be given to this command, separated by @samp{:}
7267 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7268 part of absolute file names) or
7269 whitespace. You may specify a directory that is already in the source
7270 path; this moves it forward, so @value{GDBN} searches it sooner.
7274 @vindex $cdir@r{, convenience variable}
7275 @vindex $cwd@r{, convenience variable}
7276 @cindex compilation directory
7277 @cindex current directory
7278 @cindex working directory
7279 @cindex directory, current
7280 @cindex directory, compilation
7281 You can use the string @samp{$cdir} to refer to the compilation
7282 directory (if one is recorded), and @samp{$cwd} to refer to the current
7283 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7284 tracks the current working directory as it changes during your @value{GDBN}
7285 session, while the latter is immediately expanded to the current
7286 directory at the time you add an entry to the source path.
7289 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7291 @c RET-repeat for @code{directory} is explicitly disabled, but since
7292 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7294 @item set directories @var{path-list}
7295 @kindex set directories
7296 Set the source path to @var{path-list}.
7297 @samp{$cdir:$cwd} are added if missing.
7299 @item show directories
7300 @kindex show directories
7301 Print the source path: show which directories it contains.
7303 @anchor{set substitute-path}
7304 @item set substitute-path @var{from} @var{to}
7305 @kindex set substitute-path
7306 Define a source path substitution rule, and add it at the end of the
7307 current list of existing substitution rules. If a rule with the same
7308 @var{from} was already defined, then the old rule is also deleted.
7310 For example, if the file @file{/foo/bar/baz.c} was moved to
7311 @file{/mnt/cross/baz.c}, then the command
7314 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7318 will tell @value{GDBN} to replace @samp{/usr/src} with
7319 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7320 @file{baz.c} even though it was moved.
7322 In the case when more than one substitution rule have been defined,
7323 the rules are evaluated one by one in the order where they have been
7324 defined. The first one matching, if any, is selected to perform
7327 For instance, if we had entered the following commands:
7330 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7331 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7335 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7336 @file{/mnt/include/defs.h} by using the first rule. However, it would
7337 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7338 @file{/mnt/src/lib/foo.c}.
7341 @item unset substitute-path [path]
7342 @kindex unset substitute-path
7343 If a path is specified, search the current list of substitution rules
7344 for a rule that would rewrite that path. Delete that rule if found.
7345 A warning is emitted by the debugger if no rule could be found.
7347 If no path is specified, then all substitution rules are deleted.
7349 @item show substitute-path [path]
7350 @kindex show substitute-path
7351 If a path is specified, then print the source path substitution rule
7352 which would rewrite that path, if any.
7354 If no path is specified, then print all existing source path substitution
7359 If your source path is cluttered with directories that are no longer of
7360 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7361 versions of source. You can correct the situation as follows:
7365 Use @code{directory} with no argument to reset the source path to its default value.
7368 Use @code{directory} with suitable arguments to reinstall the
7369 directories you want in the source path. You can add all the
7370 directories in one command.
7374 @section Source and Machine Code
7375 @cindex source line and its code address
7377 You can use the command @code{info line} to map source lines to program
7378 addresses (and vice versa), and the command @code{disassemble} to display
7379 a range of addresses as machine instructions. You can use the command
7380 @code{set disassemble-next-line} to set whether to disassemble next
7381 source line when execution stops. When run under @sc{gnu} Emacs
7382 mode, the @code{info line} command causes the arrow to point to the
7383 line specified. Also, @code{info line} prints addresses in symbolic form as
7388 @item info line @var{linespec}
7389 Print the starting and ending addresses of the compiled code for
7390 source line @var{linespec}. You can specify source lines in any of
7391 the ways documented in @ref{Specify Location}.
7394 For example, we can use @code{info line} to discover the location of
7395 the object code for the first line of function
7396 @code{m4_changequote}:
7398 @c FIXME: I think this example should also show the addresses in
7399 @c symbolic form, as they usually would be displayed.
7401 (@value{GDBP}) info line m4_changequote
7402 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7406 @cindex code address and its source line
7407 We can also inquire (using @code{*@var{addr}} as the form for
7408 @var{linespec}) what source line covers a particular address:
7410 (@value{GDBP}) info line *0x63ff
7411 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7414 @cindex @code{$_} and @code{info line}
7415 @cindex @code{x} command, default address
7416 @kindex x@r{(examine), and} info line
7417 After @code{info line}, the default address for the @code{x} command
7418 is changed to the starting address of the line, so that @samp{x/i} is
7419 sufficient to begin examining the machine code (@pxref{Memory,
7420 ,Examining Memory}). Also, this address is saved as the value of the
7421 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7426 @cindex assembly instructions
7427 @cindex instructions, assembly
7428 @cindex machine instructions
7429 @cindex listing machine instructions
7431 @itemx disassemble /m
7432 @itemx disassemble /r
7433 This specialized command dumps a range of memory as machine
7434 instructions. It can also print mixed source+disassembly by specifying
7435 the @code{/m} modifier and print the raw instructions in hex as well as
7436 in symbolic form by specifying the @code{/r}.
7437 The default memory range is the function surrounding the
7438 program counter of the selected frame. A single argument to this
7439 command is a program counter value; @value{GDBN} dumps the function
7440 surrounding this value. When two arguments are given, they should
7441 be separated by a comma, possibly surrounded by whitespace. The
7442 arguments specify a range of addresses to dump, in one of two forms:
7445 @item @var{start},@var{end}
7446 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7447 @item @var{start},+@var{length}
7448 the addresses from @var{start} (inclusive) to
7449 @code{@var{start}+@var{length}} (exclusive).
7453 When 2 arguments are specified, the name of the function is also
7454 printed (since there could be several functions in the given range).
7456 The argument(s) can be any expression yielding a numeric value, such as
7457 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7459 If the range of memory being disassembled contains current program counter,
7460 the instruction at that location is shown with a @code{=>} marker.
7463 The following example shows the disassembly of a range of addresses of
7464 HP PA-RISC 2.0 code:
7467 (@value{GDBP}) disas 0x32c4, 0x32e4
7468 Dump of assembler code from 0x32c4 to 0x32e4:
7469 0x32c4 <main+204>: addil 0,dp
7470 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7471 0x32cc <main+212>: ldil 0x3000,r31
7472 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7473 0x32d4 <main+220>: ldo 0(r31),rp
7474 0x32d8 <main+224>: addil -0x800,dp
7475 0x32dc <main+228>: ldo 0x588(r1),r26
7476 0x32e0 <main+232>: ldil 0x3000,r31
7477 End of assembler dump.
7480 Here is an example showing mixed source+assembly for Intel x86, when the
7481 program is stopped just after function prologue:
7484 (@value{GDBP}) disas /m main
7485 Dump of assembler code for function main:
7487 0x08048330 <+0>: push %ebp
7488 0x08048331 <+1>: mov %esp,%ebp
7489 0x08048333 <+3>: sub $0x8,%esp
7490 0x08048336 <+6>: and $0xfffffff0,%esp
7491 0x08048339 <+9>: sub $0x10,%esp
7493 6 printf ("Hello.\n");
7494 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7495 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7499 0x08048348 <+24>: mov $0x0,%eax
7500 0x0804834d <+29>: leave
7501 0x0804834e <+30>: ret
7503 End of assembler dump.
7506 Here is another example showing raw instructions in hex for AMD x86-64,
7509 (gdb) disas /r 0x400281,+10
7510 Dump of assembler code from 0x400281 to 0x40028b:
7511 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7512 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7513 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7514 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7515 End of assembler dump.
7518 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7519 So, for example, if you want to disassemble function @code{bar}
7520 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7521 and not @samp{disassemble foo.c:bar}.
7523 Some architectures have more than one commonly-used set of instruction
7524 mnemonics or other syntax.
7526 For programs that were dynamically linked and use shared libraries,
7527 instructions that call functions or branch to locations in the shared
7528 libraries might show a seemingly bogus location---it's actually a
7529 location of the relocation table. On some architectures, @value{GDBN}
7530 might be able to resolve these to actual function names.
7533 @kindex set disassembly-flavor
7534 @cindex Intel disassembly flavor
7535 @cindex AT&T disassembly flavor
7536 @item set disassembly-flavor @var{instruction-set}
7537 Select the instruction set to use when disassembling the
7538 program via the @code{disassemble} or @code{x/i} commands.
7540 Currently this command is only defined for the Intel x86 family. You
7541 can set @var{instruction-set} to either @code{intel} or @code{att}.
7542 The default is @code{att}, the AT&T flavor used by default by Unix
7543 assemblers for x86-based targets.
7545 @kindex show disassembly-flavor
7546 @item show disassembly-flavor
7547 Show the current setting of the disassembly flavor.
7551 @kindex set disassemble-next-line
7552 @kindex show disassemble-next-line
7553 @item set disassemble-next-line
7554 @itemx show disassemble-next-line
7555 Control whether or not @value{GDBN} will disassemble the next source
7556 line or instruction when execution stops. If ON, @value{GDBN} will
7557 display disassembly of the next source line when execution of the
7558 program being debugged stops. This is @emph{in addition} to
7559 displaying the source line itself, which @value{GDBN} always does if
7560 possible. If the next source line cannot be displayed for some reason
7561 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7562 info in the debug info), @value{GDBN} will display disassembly of the
7563 next @emph{instruction} instead of showing the next source line. If
7564 AUTO, @value{GDBN} will display disassembly of next instruction only
7565 if the source line cannot be displayed. This setting causes
7566 @value{GDBN} to display some feedback when you step through a function
7567 with no line info or whose source file is unavailable. The default is
7568 OFF, which means never display the disassembly of the next line or
7574 @chapter Examining Data
7576 @cindex printing data
7577 @cindex examining data
7580 The usual way to examine data in your program is with the @code{print}
7581 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7582 evaluates and prints the value of an expression of the language your
7583 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7584 Different Languages}). It may also print the expression using a
7585 Python-based pretty-printer (@pxref{Pretty Printing}).
7588 @item print @var{expr}
7589 @itemx print /@var{f} @var{expr}
7590 @var{expr} is an expression (in the source language). By default the
7591 value of @var{expr} is printed in a format appropriate to its data type;
7592 you can choose a different format by specifying @samp{/@var{f}}, where
7593 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7597 @itemx print /@var{f}
7598 @cindex reprint the last value
7599 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7600 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7601 conveniently inspect the same value in an alternative format.
7604 A more low-level way of examining data is with the @code{x} command.
7605 It examines data in memory at a specified address and prints it in a
7606 specified format. @xref{Memory, ,Examining Memory}.
7608 If you are interested in information about types, or about how the
7609 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7610 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7613 @cindex exploring hierarchical data structures
7615 Another way of examining values of expressions and type information is
7616 through the Python extension command @code{explore} (available only if
7617 the @value{GDBN} build is configured with @code{--with-python}). It
7618 offers an interactive way to start at the highest level (or, the most
7619 abstract level) of the data type of an expression (or, the data type
7620 itself) and explore all the way down to leaf scalar values/fields
7621 embedded in the higher level data types.
7624 @item explore @var{arg}
7625 @var{arg} is either an expression (in the source language), or a type
7626 visible in the current context of the program being debugged.
7629 The working of the @code{explore} command can be illustrated with an
7630 example. If a data type @code{struct ComplexStruct} is defined in your
7640 struct ComplexStruct
7642 struct SimpleStruct *ss_p;
7648 followed by variable declarations as
7651 struct SimpleStruct ss = @{ 10, 1.11 @};
7652 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7656 then, the value of the variable @code{cs} can be explored using the
7657 @code{explore} command as follows.
7661 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7662 the following fields:
7664 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7665 arr = <Enter 1 to explore this field of type `int [10]'>
7667 Enter the field number of choice:
7671 Since the fields of @code{cs} are not scalar values, you are being
7672 prompted to chose the field you want to explore. Let's say you choose
7673 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7674 pointer, you will be asked if it is pointing to a single value. From
7675 the declaration of @code{cs} above, it is indeed pointing to a single
7676 value, hence you enter @code{y}. If you enter @code{n}, then you will
7677 be asked if it were pointing to an array of values, in which case this
7678 field will be explored as if it were an array.
7681 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7682 Continue exploring it as a pointer to a single value [y/n]: y
7683 The value of `*(cs.ss_p)' is a struct/class of type `struct
7684 SimpleStruct' with the following fields:
7686 i = 10 .. (Value of type `int')
7687 d = 1.1100000000000001 .. (Value of type `double')
7689 Press enter to return to parent value:
7693 If the field @code{arr} of @code{cs} was chosen for exploration by
7694 entering @code{1} earlier, then since it is as array, you will be
7695 prompted to enter the index of the element in the array that you want
7699 `cs.arr' is an array of `int'.
7700 Enter the index of the element you want to explore in `cs.arr': 5
7702 `(cs.arr)[5]' is a scalar value of type `int'.
7706 Press enter to return to parent value:
7709 In general, at any stage of exploration, you can go deeper towards the
7710 leaf values by responding to the prompts appropriately, or hit the
7711 return key to return to the enclosing data structure (the @i{higher}
7712 level data structure).
7714 Similar to exploring values, you can use the @code{explore} command to
7715 explore types. Instead of specifying a value (which is typically a
7716 variable name or an expression valid in the current context of the
7717 program being debugged), you specify a type name. If you consider the
7718 same example as above, your can explore the type
7719 @code{struct ComplexStruct} by passing the argument
7720 @code{struct ComplexStruct} to the @code{explore} command.
7723 (gdb) explore struct ComplexStruct
7727 By responding to the prompts appropriately in the subsequent interactive
7728 session, you can explore the type @code{struct ComplexStruct} in a
7729 manner similar to how the value @code{cs} was explored in the above
7732 The @code{explore} command also has two sub-commands,
7733 @code{explore value} and @code{explore type}. The former sub-command is
7734 a way to explicitly specify that value exploration of the argument is
7735 being invoked, while the latter is a way to explicitly specify that type
7736 exploration of the argument is being invoked.
7739 @item explore value @var{expr}
7740 @cindex explore value
7741 This sub-command of @code{explore} explores the value of the
7742 expression @var{expr} (if @var{expr} is an expression valid in the
7743 current context of the program being debugged). The behavior of this
7744 command is identical to that of the behavior of the @code{explore}
7745 command being passed the argument @var{expr}.
7747 @item explore type @var{arg}
7748 @cindex explore type
7749 This sub-command of @code{explore} explores the type of @var{arg} (if
7750 @var{arg} is a type visible in the current context of program being
7751 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7752 is an expression valid in the current context of the program being
7753 debugged). If @var{arg} is a type, then the behavior of this command is
7754 identical to that of the @code{explore} command being passed the
7755 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7756 this command will be identical to that of the @code{explore} command
7757 being passed the type of @var{arg} as the argument.
7761 * Expressions:: Expressions
7762 * Ambiguous Expressions:: Ambiguous Expressions
7763 * Variables:: Program variables
7764 * Arrays:: Artificial arrays
7765 * Output Formats:: Output formats
7766 * Memory:: Examining memory
7767 * Auto Display:: Automatic display
7768 * Print Settings:: Print settings
7769 * Pretty Printing:: Python pretty printing
7770 * Value History:: Value history
7771 * Convenience Vars:: Convenience variables
7772 * Convenience Funs:: Convenience functions
7773 * Registers:: Registers
7774 * Floating Point Hardware:: Floating point hardware
7775 * Vector Unit:: Vector Unit
7776 * OS Information:: Auxiliary data provided by operating system
7777 * Memory Region Attributes:: Memory region attributes
7778 * Dump/Restore Files:: Copy between memory and a file
7779 * Core File Generation:: Cause a program dump its core
7780 * Character Sets:: Debugging programs that use a different
7781 character set than GDB does
7782 * Caching Remote Data:: Data caching for remote targets
7783 * Searching Memory:: Searching memory for a sequence of bytes
7787 @section Expressions
7790 @code{print} and many other @value{GDBN} commands accept an expression and
7791 compute its value. Any kind of constant, variable or operator defined
7792 by the programming language you are using is valid in an expression in
7793 @value{GDBN}. This includes conditional expressions, function calls,
7794 casts, and string constants. It also includes preprocessor macros, if
7795 you compiled your program to include this information; see
7798 @cindex arrays in expressions
7799 @value{GDBN} supports array constants in expressions input by
7800 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7801 you can use the command @code{print @{1, 2, 3@}} to create an array
7802 of three integers. If you pass an array to a function or assign it
7803 to a program variable, @value{GDBN} copies the array to memory that
7804 is @code{malloc}ed in the target program.
7806 Because C is so widespread, most of the expressions shown in examples in
7807 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7808 Languages}, for information on how to use expressions in other
7811 In this section, we discuss operators that you can use in @value{GDBN}
7812 expressions regardless of your programming language.
7814 @cindex casts, in expressions
7815 Casts are supported in all languages, not just in C, because it is so
7816 useful to cast a number into a pointer in order to examine a structure
7817 at that address in memory.
7818 @c FIXME: casts supported---Mod2 true?
7820 @value{GDBN} supports these operators, in addition to those common
7821 to programming languages:
7825 @samp{@@} is a binary operator for treating parts of memory as arrays.
7826 @xref{Arrays, ,Artificial Arrays}, for more information.
7829 @samp{::} allows you to specify a variable in terms of the file or
7830 function where it is defined. @xref{Variables, ,Program Variables}.
7832 @cindex @{@var{type}@}
7833 @cindex type casting memory
7834 @cindex memory, viewing as typed object
7835 @cindex casts, to view memory
7836 @item @{@var{type}@} @var{addr}
7837 Refers to an object of type @var{type} stored at address @var{addr} in
7838 memory. @var{addr} may be any expression whose value is an integer or
7839 pointer (but parentheses are required around binary operators, just as in
7840 a cast). This construct is allowed regardless of what kind of data is
7841 normally supposed to reside at @var{addr}.
7844 @node Ambiguous Expressions
7845 @section Ambiguous Expressions
7846 @cindex ambiguous expressions
7848 Expressions can sometimes contain some ambiguous elements. For instance,
7849 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7850 a single function name to be defined several times, for application in
7851 different contexts. This is called @dfn{overloading}. Another example
7852 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7853 templates and is typically instantiated several times, resulting in
7854 the same function name being defined in different contexts.
7856 In some cases and depending on the language, it is possible to adjust
7857 the expression to remove the ambiguity. For instance in C@t{++}, you
7858 can specify the signature of the function you want to break on, as in
7859 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7860 qualified name of your function often makes the expression unambiguous
7863 When an ambiguity that needs to be resolved is detected, the debugger
7864 has the capability to display a menu of numbered choices for each
7865 possibility, and then waits for the selection with the prompt @samp{>}.
7866 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7867 aborts the current command. If the command in which the expression was
7868 used allows more than one choice to be selected, the next option in the
7869 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7872 For example, the following session excerpt shows an attempt to set a
7873 breakpoint at the overloaded symbol @code{String::after}.
7874 We choose three particular definitions of that function name:
7876 @c FIXME! This is likely to change to show arg type lists, at least
7879 (@value{GDBP}) b String::after
7882 [2] file:String.cc; line number:867
7883 [3] file:String.cc; line number:860
7884 [4] file:String.cc; line number:875
7885 [5] file:String.cc; line number:853
7886 [6] file:String.cc; line number:846
7887 [7] file:String.cc; line number:735
7889 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7890 Breakpoint 2 at 0xb344: file String.cc, line 875.
7891 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7892 Multiple breakpoints were set.
7893 Use the "delete" command to delete unwanted
7900 @kindex set multiple-symbols
7901 @item set multiple-symbols @var{mode}
7902 @cindex multiple-symbols menu
7904 This option allows you to adjust the debugger behavior when an expression
7907 By default, @var{mode} is set to @code{all}. If the command with which
7908 the expression is used allows more than one choice, then @value{GDBN}
7909 automatically selects all possible choices. For instance, inserting
7910 a breakpoint on a function using an ambiguous name results in a breakpoint
7911 inserted on each possible match. However, if a unique choice must be made,
7912 then @value{GDBN} uses the menu to help you disambiguate the expression.
7913 For instance, printing the address of an overloaded function will result
7914 in the use of the menu.
7916 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7917 when an ambiguity is detected.
7919 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7920 an error due to the ambiguity and the command is aborted.
7922 @kindex show multiple-symbols
7923 @item show multiple-symbols
7924 Show the current value of the @code{multiple-symbols} setting.
7928 @section Program Variables
7930 The most common kind of expression to use is the name of a variable
7933 Variables in expressions are understood in the selected stack frame
7934 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7938 global (or file-static)
7945 visible according to the scope rules of the
7946 programming language from the point of execution in that frame
7949 @noindent This means that in the function
7964 you can examine and use the variable @code{a} whenever your program is
7965 executing within the function @code{foo}, but you can only use or
7966 examine the variable @code{b} while your program is executing inside
7967 the block where @code{b} is declared.
7969 @cindex variable name conflict
7970 There is an exception: you can refer to a variable or function whose
7971 scope is a single source file even if the current execution point is not
7972 in this file. But it is possible to have more than one such variable or
7973 function with the same name (in different source files). If that
7974 happens, referring to that name has unpredictable effects. If you wish,
7975 you can specify a static variable in a particular function or file by
7976 using the colon-colon (@code{::}) notation:
7978 @cindex colon-colon, context for variables/functions
7980 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7981 @cindex @code{::}, context for variables/functions
7984 @var{file}::@var{variable}
7985 @var{function}::@var{variable}
7989 Here @var{file} or @var{function} is the name of the context for the
7990 static @var{variable}. In the case of file names, you can use quotes to
7991 make sure @value{GDBN} parses the file name as a single word---for example,
7992 to print a global value of @code{x} defined in @file{f2.c}:
7995 (@value{GDBP}) p 'f2.c'::x
7998 The @code{::} notation is normally used for referring to
7999 static variables, since you typically disambiguate uses of local variables
8000 in functions by selecting the appropriate frame and using the
8001 simple name of the variable. However, you may also use this notation
8002 to refer to local variables in frames enclosing the selected frame:
8011 process (a); /* Stop here */
8022 For example, if there is a breakpoint at the commented line,
8023 here is what you might see
8024 when the program stops after executing the call @code{bar(0)}:
8029 (@value{GDBP}) p bar::a
8032 #2 0x080483d0 in foo (a=5) at foobar.c:12
8035 (@value{GDBP}) p bar::a
8039 @cindex C@t{++} scope resolution
8040 These uses of @samp{::} are very rarely in conflict with the very similar
8041 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8042 scope resolution operator in @value{GDBN} expressions.
8043 @c FIXME: Um, so what happens in one of those rare cases where it's in
8046 @cindex wrong values
8047 @cindex variable values, wrong
8048 @cindex function entry/exit, wrong values of variables
8049 @cindex optimized code, wrong values of variables
8051 @emph{Warning:} Occasionally, a local variable may appear to have the
8052 wrong value at certain points in a function---just after entry to a new
8053 scope, and just before exit.
8055 You may see this problem when you are stepping by machine instructions.
8056 This is because, on most machines, it takes more than one instruction to
8057 set up a stack frame (including local variable definitions); if you are
8058 stepping by machine instructions, variables may appear to have the wrong
8059 values until the stack frame is completely built. On exit, it usually
8060 also takes more than one machine instruction to destroy a stack frame;
8061 after you begin stepping through that group of instructions, local
8062 variable definitions may be gone.
8064 This may also happen when the compiler does significant optimizations.
8065 To be sure of always seeing accurate values, turn off all optimization
8068 @cindex ``No symbol "foo" in current context''
8069 Another possible effect of compiler optimizations is to optimize
8070 unused variables out of existence, or assign variables to registers (as
8071 opposed to memory addresses). Depending on the support for such cases
8072 offered by the debug info format used by the compiler, @value{GDBN}
8073 might not be able to display values for such local variables. If that
8074 happens, @value{GDBN} will print a message like this:
8077 No symbol "foo" in current context.
8080 To solve such problems, either recompile without optimizations, or use a
8081 different debug info format, if the compiler supports several such
8082 formats. @xref{Compilation}, for more information on choosing compiler
8083 options. @xref{C, ,C and C@t{++}}, for more information about debug
8084 info formats that are best suited to C@t{++} programs.
8086 If you ask to print an object whose contents are unknown to
8087 @value{GDBN}, e.g., because its data type is not completely specified
8088 by the debug information, @value{GDBN} will say @samp{<incomplete
8089 type>}. @xref{Symbols, incomplete type}, for more about this.
8091 If you append @kbd{@@entry} string to a function parameter name you get its
8092 value at the time the function got called. If the value is not available an
8093 error message is printed. Entry values are available only with some compilers.
8094 Entry values are normally also printed at the function parameter list according
8095 to @ref{set print entry-values}.
8098 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8104 (gdb) print i@@entry
8108 Strings are identified as arrays of @code{char} values without specified
8109 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8110 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8111 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8112 defines literal string type @code{"char"} as @code{char} without a sign.
8117 signed char var1[] = "A";
8120 You get during debugging
8125 $2 = @{65 'A', 0 '\0'@}
8129 @section Artificial Arrays
8131 @cindex artificial array
8133 @kindex @@@r{, referencing memory as an array}
8134 It is often useful to print out several successive objects of the
8135 same type in memory; a section of an array, or an array of
8136 dynamically determined size for which only a pointer exists in the
8139 You can do this by referring to a contiguous span of memory as an
8140 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8141 operand of @samp{@@} should be the first element of the desired array
8142 and be an individual object. The right operand should be the desired length
8143 of the array. The result is an array value whose elements are all of
8144 the type of the left argument. The first element is actually the left
8145 argument; the second element comes from bytes of memory immediately
8146 following those that hold the first element, and so on. Here is an
8147 example. If a program says
8150 int *array = (int *) malloc (len * sizeof (int));
8154 you can print the contents of @code{array} with
8160 The left operand of @samp{@@} must reside in memory. Array values made
8161 with @samp{@@} in this way behave just like other arrays in terms of
8162 subscripting, and are coerced to pointers when used in expressions.
8163 Artificial arrays most often appear in expressions via the value history
8164 (@pxref{Value History, ,Value History}), after printing one out.
8166 Another way to create an artificial array is to use a cast.
8167 This re-interprets a value as if it were an array.
8168 The value need not be in memory:
8170 (@value{GDBP}) p/x (short[2])0x12345678
8171 $1 = @{0x1234, 0x5678@}
8174 As a convenience, if you leave the array length out (as in
8175 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8176 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8178 (@value{GDBP}) p/x (short[])0x12345678
8179 $2 = @{0x1234, 0x5678@}
8182 Sometimes the artificial array mechanism is not quite enough; in
8183 moderately complex data structures, the elements of interest may not
8184 actually be adjacent---for example, if you are interested in the values
8185 of pointers in an array. One useful work-around in this situation is
8186 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8187 Variables}) as a counter in an expression that prints the first
8188 interesting value, and then repeat that expression via @key{RET}. For
8189 instance, suppose you have an array @code{dtab} of pointers to
8190 structures, and you are interested in the values of a field @code{fv}
8191 in each structure. Here is an example of what you might type:
8201 @node Output Formats
8202 @section Output Formats
8204 @cindex formatted output
8205 @cindex output formats
8206 By default, @value{GDBN} prints a value according to its data type. Sometimes
8207 this is not what you want. For example, you might want to print a number
8208 in hex, or a pointer in decimal. Or you might want to view data in memory
8209 at a certain address as a character string or as an instruction. To do
8210 these things, specify an @dfn{output format} when you print a value.
8212 The simplest use of output formats is to say how to print a value
8213 already computed. This is done by starting the arguments of the
8214 @code{print} command with a slash and a format letter. The format
8215 letters supported are:
8219 Regard the bits of the value as an integer, and print the integer in
8223 Print as integer in signed decimal.
8226 Print as integer in unsigned decimal.
8229 Print as integer in octal.
8232 Print as integer in binary. The letter @samp{t} stands for ``two''.
8233 @footnote{@samp{b} cannot be used because these format letters are also
8234 used with the @code{x} command, where @samp{b} stands for ``byte'';
8235 see @ref{Memory,,Examining Memory}.}
8238 @cindex unknown address, locating
8239 @cindex locate address
8240 Print as an address, both absolute in hexadecimal and as an offset from
8241 the nearest preceding symbol. You can use this format used to discover
8242 where (in what function) an unknown address is located:
8245 (@value{GDBP}) p/a 0x54320
8246 $3 = 0x54320 <_initialize_vx+396>
8250 The command @code{info symbol 0x54320} yields similar results.
8251 @xref{Symbols, info symbol}.
8254 Regard as an integer and print it as a character constant. This
8255 prints both the numerical value and its character representation. The
8256 character representation is replaced with the octal escape @samp{\nnn}
8257 for characters outside the 7-bit @sc{ascii} range.
8259 Without this format, @value{GDBN} displays @code{char},
8260 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8261 constants. Single-byte members of vectors are displayed as integer
8265 Regard the bits of the value as a floating point number and print
8266 using typical floating point syntax.
8269 @cindex printing strings
8270 @cindex printing byte arrays
8271 Regard as a string, if possible. With this format, pointers to single-byte
8272 data are displayed as null-terminated strings and arrays of single-byte data
8273 are displayed as fixed-length strings. Other values are displayed in their
8276 Without this format, @value{GDBN} displays pointers to and arrays of
8277 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8278 strings. Single-byte members of a vector are displayed as an integer
8282 @cindex raw printing
8283 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8284 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8285 Printing}). This typically results in a higher-level display of the
8286 value's contents. The @samp{r} format bypasses any Python
8287 pretty-printer which might exist.
8290 For example, to print the program counter in hex (@pxref{Registers}), type
8297 Note that no space is required before the slash; this is because command
8298 names in @value{GDBN} cannot contain a slash.
8300 To reprint the last value in the value history with a different format,
8301 you can use the @code{print} command with just a format and no
8302 expression. For example, @samp{p/x} reprints the last value in hex.
8305 @section Examining Memory
8307 You can use the command @code{x} (for ``examine'') to examine memory in
8308 any of several formats, independently of your program's data types.
8310 @cindex examining memory
8312 @kindex x @r{(examine memory)}
8313 @item x/@var{nfu} @var{addr}
8316 Use the @code{x} command to examine memory.
8319 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8320 much memory to display and how to format it; @var{addr} is an
8321 expression giving the address where you want to start displaying memory.
8322 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8323 Several commands set convenient defaults for @var{addr}.
8326 @item @var{n}, the repeat count
8327 The repeat count is a decimal integer; the default is 1. It specifies
8328 how much memory (counting by units @var{u}) to display.
8329 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8332 @item @var{f}, the display format
8333 The display format is one of the formats used by @code{print}
8334 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8335 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8336 The default is @samp{x} (hexadecimal) initially. The default changes
8337 each time you use either @code{x} or @code{print}.
8339 @item @var{u}, the unit size
8340 The unit size is any of
8346 Halfwords (two bytes).
8348 Words (four bytes). This is the initial default.
8350 Giant words (eight bytes).
8353 Each time you specify a unit size with @code{x}, that size becomes the
8354 default unit the next time you use @code{x}. For the @samp{i} format,
8355 the unit size is ignored and is normally not written. For the @samp{s} format,
8356 the unit size defaults to @samp{b}, unless it is explicitly given.
8357 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8358 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8359 Note that the results depend on the programming language of the
8360 current compilation unit. If the language is C, the @samp{s}
8361 modifier will use the UTF-16 encoding while @samp{w} will use
8362 UTF-32. The encoding is set by the programming language and cannot
8365 @item @var{addr}, starting display address
8366 @var{addr} is the address where you want @value{GDBN} to begin displaying
8367 memory. The expression need not have a pointer value (though it may);
8368 it is always interpreted as an integer address of a byte of memory.
8369 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8370 @var{addr} is usually just after the last address examined---but several
8371 other commands also set the default address: @code{info breakpoints} (to
8372 the address of the last breakpoint listed), @code{info line} (to the
8373 starting address of a line), and @code{print} (if you use it to display
8374 a value from memory).
8377 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8378 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8379 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8380 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8381 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8383 Since the letters indicating unit sizes are all distinct from the
8384 letters specifying output formats, you do not have to remember whether
8385 unit size or format comes first; either order works. The output
8386 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8387 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8389 Even though the unit size @var{u} is ignored for the formats @samp{s}
8390 and @samp{i}, you might still want to use a count @var{n}; for example,
8391 @samp{3i} specifies that you want to see three machine instructions,
8392 including any operands. For convenience, especially when used with
8393 the @code{display} command, the @samp{i} format also prints branch delay
8394 slot instructions, if any, beyond the count specified, which immediately
8395 follow the last instruction that is within the count. The command
8396 @code{disassemble} gives an alternative way of inspecting machine
8397 instructions; see @ref{Machine Code,,Source and Machine Code}.
8399 All the defaults for the arguments to @code{x} are designed to make it
8400 easy to continue scanning memory with minimal specifications each time
8401 you use @code{x}. For example, after you have inspected three machine
8402 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8403 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8404 the repeat count @var{n} is used again; the other arguments default as
8405 for successive uses of @code{x}.
8407 When examining machine instructions, the instruction at current program
8408 counter is shown with a @code{=>} marker. For example:
8411 (@value{GDBP}) x/5i $pc-6
8412 0x804837f <main+11>: mov %esp,%ebp
8413 0x8048381 <main+13>: push %ecx
8414 0x8048382 <main+14>: sub $0x4,%esp
8415 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8416 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8419 @cindex @code{$_}, @code{$__}, and value history
8420 The addresses and contents printed by the @code{x} command are not saved
8421 in the value history because there is often too much of them and they
8422 would get in the way. Instead, @value{GDBN} makes these values available for
8423 subsequent use in expressions as values of the convenience variables
8424 @code{$_} and @code{$__}. After an @code{x} command, the last address
8425 examined is available for use in expressions in the convenience variable
8426 @code{$_}. The contents of that address, as examined, are available in
8427 the convenience variable @code{$__}.
8429 If the @code{x} command has a repeat count, the address and contents saved
8430 are from the last memory unit printed; this is not the same as the last
8431 address printed if several units were printed on the last line of output.
8433 @cindex remote memory comparison
8434 @cindex verify remote memory image
8435 When you are debugging a program running on a remote target machine
8436 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8437 remote machine's memory against the executable file you downloaded to
8438 the target. The @code{compare-sections} command is provided for such
8442 @kindex compare-sections
8443 @item compare-sections @r{[}@var{section-name}@r{]}
8444 Compare the data of a loadable section @var{section-name} in the
8445 executable file of the program being debugged with the same section in
8446 the remote machine's memory, and report any mismatches. With no
8447 arguments, compares all loadable sections. This command's
8448 availability depends on the target's support for the @code{"qCRC"}
8453 @section Automatic Display
8454 @cindex automatic display
8455 @cindex display of expressions
8457 If you find that you want to print the value of an expression frequently
8458 (to see how it changes), you might want to add it to the @dfn{automatic
8459 display list} so that @value{GDBN} prints its value each time your program stops.
8460 Each expression added to the list is given a number to identify it;
8461 to remove an expression from the list, you specify that number.
8462 The automatic display looks like this:
8466 3: bar[5] = (struct hack *) 0x3804
8470 This display shows item numbers, expressions and their current values. As with
8471 displays you request manually using @code{x} or @code{print}, you can
8472 specify the output format you prefer; in fact, @code{display} decides
8473 whether to use @code{print} or @code{x} depending your format
8474 specification---it uses @code{x} if you specify either the @samp{i}
8475 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8479 @item display @var{expr}
8480 Add the expression @var{expr} to the list of expressions to display
8481 each time your program stops. @xref{Expressions, ,Expressions}.
8483 @code{display} does not repeat if you press @key{RET} again after using it.
8485 @item display/@var{fmt} @var{expr}
8486 For @var{fmt} specifying only a display format and not a size or
8487 count, add the expression @var{expr} to the auto-display list but
8488 arrange to display it each time in the specified format @var{fmt}.
8489 @xref{Output Formats,,Output Formats}.
8491 @item display/@var{fmt} @var{addr}
8492 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8493 number of units, add the expression @var{addr} as a memory address to
8494 be examined each time your program stops. Examining means in effect
8495 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8498 For example, @samp{display/i $pc} can be helpful, to see the machine
8499 instruction about to be executed each time execution stops (@samp{$pc}
8500 is a common name for the program counter; @pxref{Registers, ,Registers}).
8503 @kindex delete display
8505 @item undisplay @var{dnums}@dots{}
8506 @itemx delete display @var{dnums}@dots{}
8507 Remove items from the list of expressions to display. Specify the
8508 numbers of the displays that you want affected with the command
8509 argument @var{dnums}. It can be a single display number, one of the
8510 numbers shown in the first field of the @samp{info display} display;
8511 or it could be a range of display numbers, as in @code{2-4}.
8513 @code{undisplay} does not repeat if you press @key{RET} after using it.
8514 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8516 @kindex disable display
8517 @item disable display @var{dnums}@dots{}
8518 Disable the display of item numbers @var{dnums}. A disabled display
8519 item is not printed automatically, but is not forgotten. It may be
8520 enabled again later. Specify the numbers of the displays that you
8521 want affected with the command argument @var{dnums}. It can be a
8522 single display number, one of the numbers shown in the first field of
8523 the @samp{info display} display; or it could be a range of display
8524 numbers, as in @code{2-4}.
8526 @kindex enable display
8527 @item enable display @var{dnums}@dots{}
8528 Enable display of item numbers @var{dnums}. It becomes effective once
8529 again in auto display of its expression, until you specify otherwise.
8530 Specify the numbers of the displays that you want affected with the
8531 command argument @var{dnums}. It can be a single display number, one
8532 of the numbers shown in the first field of the @samp{info display}
8533 display; or it could be a range of display numbers, as in @code{2-4}.
8536 Display the current values of the expressions on the list, just as is
8537 done when your program stops.
8539 @kindex info display
8541 Print the list of expressions previously set up to display
8542 automatically, each one with its item number, but without showing the
8543 values. This includes disabled expressions, which are marked as such.
8544 It also includes expressions which would not be displayed right now
8545 because they refer to automatic variables not currently available.
8548 @cindex display disabled out of scope
8549 If a display expression refers to local variables, then it does not make
8550 sense outside the lexical context for which it was set up. Such an
8551 expression is disabled when execution enters a context where one of its
8552 variables is not defined. For example, if you give the command
8553 @code{display last_char} while inside a function with an argument
8554 @code{last_char}, @value{GDBN} displays this argument while your program
8555 continues to stop inside that function. When it stops elsewhere---where
8556 there is no variable @code{last_char}---the display is disabled
8557 automatically. The next time your program stops where @code{last_char}
8558 is meaningful, you can enable the display expression once again.
8560 @node Print Settings
8561 @section Print Settings
8563 @cindex format options
8564 @cindex print settings
8565 @value{GDBN} provides the following ways to control how arrays, structures,
8566 and symbols are printed.
8569 These settings are useful for debugging programs in any language:
8573 @item set print address
8574 @itemx set print address on
8575 @cindex print/don't print memory addresses
8576 @value{GDBN} prints memory addresses showing the location of stack
8577 traces, structure values, pointer values, breakpoints, and so forth,
8578 even when it also displays the contents of those addresses. The default
8579 is @code{on}. For example, this is what a stack frame display looks like with
8580 @code{set print address on}:
8585 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8587 530 if (lquote != def_lquote)
8591 @item set print address off
8592 Do not print addresses when displaying their contents. For example,
8593 this is the same stack frame displayed with @code{set print address off}:
8597 (@value{GDBP}) set print addr off
8599 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8600 530 if (lquote != def_lquote)
8604 You can use @samp{set print address off} to eliminate all machine
8605 dependent displays from the @value{GDBN} interface. For example, with
8606 @code{print address off}, you should get the same text for backtraces on
8607 all machines---whether or not they involve pointer arguments.
8610 @item show print address
8611 Show whether or not addresses are to be printed.
8614 When @value{GDBN} prints a symbolic address, it normally prints the
8615 closest earlier symbol plus an offset. If that symbol does not uniquely
8616 identify the address (for example, it is a name whose scope is a single
8617 source file), you may need to clarify. One way to do this is with
8618 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8619 you can set @value{GDBN} to print the source file and line number when
8620 it prints a symbolic address:
8623 @item set print symbol-filename on
8624 @cindex source file and line of a symbol
8625 @cindex symbol, source file and line
8626 Tell @value{GDBN} to print the source file name and line number of a
8627 symbol in the symbolic form of an address.
8629 @item set print symbol-filename off
8630 Do not print source file name and line number of a symbol. This is the
8633 @item show print symbol-filename
8634 Show whether or not @value{GDBN} will print the source file name and
8635 line number of a symbol in the symbolic form of an address.
8638 Another situation where it is helpful to show symbol filenames and line
8639 numbers is when disassembling code; @value{GDBN} shows you the line
8640 number and source file that corresponds to each instruction.
8642 Also, you may wish to see the symbolic form only if the address being
8643 printed is reasonably close to the closest earlier symbol:
8646 @item set print max-symbolic-offset @var{max-offset}
8647 @itemx set print max-symbolic-offset unlimited
8648 @cindex maximum value for offset of closest symbol
8649 Tell @value{GDBN} to only display the symbolic form of an address if the
8650 offset between the closest earlier symbol and the address is less than
8651 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8652 to always print the symbolic form of an address if any symbol precedes
8653 it. Zero is equivalent to @code{unlimited}.
8655 @item show print max-symbolic-offset
8656 Ask how large the maximum offset is that @value{GDBN} prints in a
8660 @cindex wild pointer, interpreting
8661 @cindex pointer, finding referent
8662 If you have a pointer and you are not sure where it points, try
8663 @samp{set print symbol-filename on}. Then you can determine the name
8664 and source file location of the variable where it points, using
8665 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8666 For example, here @value{GDBN} shows that a variable @code{ptt} points
8667 at another variable @code{t}, defined in @file{hi2.c}:
8670 (@value{GDBP}) set print symbol-filename on
8671 (@value{GDBP}) p/a ptt
8672 $4 = 0xe008 <t in hi2.c>
8676 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8677 does not show the symbol name and filename of the referent, even with
8678 the appropriate @code{set print} options turned on.
8681 You can also enable @samp{/a}-like formatting all the time using
8682 @samp{set print symbol on}:
8685 @item set print symbol on
8686 Tell @value{GDBN} to print the symbol corresponding to an address, if
8689 @item set print symbol off
8690 Tell @value{GDBN} not to print the symbol corresponding to an
8691 address. In this mode, @value{GDBN} will still print the symbol
8692 corresponding to pointers to functions. This is the default.
8694 @item show print symbol
8695 Show whether @value{GDBN} will display the symbol corresponding to an
8699 Other settings control how different kinds of objects are printed:
8702 @item set print array
8703 @itemx set print array on
8704 @cindex pretty print arrays
8705 Pretty print arrays. This format is more convenient to read,
8706 but uses more space. The default is off.
8708 @item set print array off
8709 Return to compressed format for arrays.
8711 @item show print array
8712 Show whether compressed or pretty format is selected for displaying
8715 @cindex print array indexes
8716 @item set print array-indexes
8717 @itemx set print array-indexes on
8718 Print the index of each element when displaying arrays. May be more
8719 convenient to locate a given element in the array or quickly find the
8720 index of a given element in that printed array. The default is off.
8722 @item set print array-indexes off
8723 Stop printing element indexes when displaying arrays.
8725 @item show print array-indexes
8726 Show whether the index of each element is printed when displaying
8729 @item set print elements @var{number-of-elements}
8730 @itemx set print elements unlimited
8731 @cindex number of array elements to print
8732 @cindex limit on number of printed array elements
8733 Set a limit on how many elements of an array @value{GDBN} will print.
8734 If @value{GDBN} is printing a large array, it stops printing after it has
8735 printed the number of elements set by the @code{set print elements} command.
8736 This limit also applies to the display of strings.
8737 When @value{GDBN} starts, this limit is set to 200.
8738 Setting @var{number-of-elements} to @code{unlimited} or zero means
8739 that the number of elements to print is unlimited.
8741 @item show print elements
8742 Display the number of elements of a large array that @value{GDBN} will print.
8743 If the number is 0, then the printing is unlimited.
8745 @item set print frame-arguments @var{value}
8746 @kindex set print frame-arguments
8747 @cindex printing frame argument values
8748 @cindex print all frame argument values
8749 @cindex print frame argument values for scalars only
8750 @cindex do not print frame argument values
8751 This command allows to control how the values of arguments are printed
8752 when the debugger prints a frame (@pxref{Frames}). The possible
8757 The values of all arguments are printed.
8760 Print the value of an argument only if it is a scalar. The value of more
8761 complex arguments such as arrays, structures, unions, etc, is replaced
8762 by @code{@dots{}}. This is the default. Here is an example where
8763 only scalar arguments are shown:
8766 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8771 None of the argument values are printed. Instead, the value of each argument
8772 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8775 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8780 By default, only scalar arguments are printed. This command can be used
8781 to configure the debugger to print the value of all arguments, regardless
8782 of their type. However, it is often advantageous to not print the value
8783 of more complex parameters. For instance, it reduces the amount of
8784 information printed in each frame, making the backtrace more readable.
8785 Also, it improves performance when displaying Ada frames, because
8786 the computation of large arguments can sometimes be CPU-intensive,
8787 especially in large applications. Setting @code{print frame-arguments}
8788 to @code{scalars} (the default) or @code{none} avoids this computation,
8789 thus speeding up the display of each Ada frame.
8791 @item show print frame-arguments
8792 Show how the value of arguments should be displayed when printing a frame.
8794 @anchor{set print entry-values}
8795 @item set print entry-values @var{value}
8796 @kindex set print entry-values
8797 Set printing of frame argument values at function entry. In some cases
8798 @value{GDBN} can determine the value of function argument which was passed by
8799 the function caller, even if the value was modified inside the called function
8800 and therefore is different. With optimized code, the current value could be
8801 unavailable, but the entry value may still be known.
8803 The default value is @code{default} (see below for its description). Older
8804 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8805 this feature will behave in the @code{default} setting the same way as with the
8808 This functionality is currently supported only by DWARF 2 debugging format and
8809 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8810 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8813 The @var{value} parameter can be one of the following:
8817 Print only actual parameter values, never print values from function entry
8821 #0 different (val=6)
8822 #0 lost (val=<optimized out>)
8824 #0 invalid (val=<optimized out>)
8828 Print only parameter values from function entry point. The actual parameter
8829 values are never printed.
8831 #0 equal (val@@entry=5)
8832 #0 different (val@@entry=5)
8833 #0 lost (val@@entry=5)
8834 #0 born (val@@entry=<optimized out>)
8835 #0 invalid (val@@entry=<optimized out>)
8839 Print only parameter values from function entry point. If value from function
8840 entry point is not known while the actual value is known, print the actual
8841 value for such parameter.
8843 #0 equal (val@@entry=5)
8844 #0 different (val@@entry=5)
8845 #0 lost (val@@entry=5)
8847 #0 invalid (val@@entry=<optimized out>)
8851 Print actual parameter values. If actual parameter value is not known while
8852 value from function entry point is known, print the entry point value for such
8856 #0 different (val=6)
8857 #0 lost (val@@entry=5)
8859 #0 invalid (val=<optimized out>)
8863 Always print both the actual parameter value and its value from function entry
8864 point, even if values of one or both are not available due to compiler
8867 #0 equal (val=5, val@@entry=5)
8868 #0 different (val=6, val@@entry=5)
8869 #0 lost (val=<optimized out>, val@@entry=5)
8870 #0 born (val=10, val@@entry=<optimized out>)
8871 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8875 Print the actual parameter value if it is known and also its value from
8876 function entry point if it is known. If neither is known, print for the actual
8877 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8878 values are known and identical, print the shortened
8879 @code{param=param@@entry=VALUE} notation.
8881 #0 equal (val=val@@entry=5)
8882 #0 different (val=6, val@@entry=5)
8883 #0 lost (val@@entry=5)
8885 #0 invalid (val=<optimized out>)
8889 Always print the actual parameter value. Print also its value from function
8890 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8891 if both values are known and identical, print the shortened
8892 @code{param=param@@entry=VALUE} notation.
8894 #0 equal (val=val@@entry=5)
8895 #0 different (val=6, val@@entry=5)
8896 #0 lost (val=<optimized out>, val@@entry=5)
8898 #0 invalid (val=<optimized out>)
8902 For analysis messages on possible failures of frame argument values at function
8903 entry resolution see @ref{set debug entry-values}.
8905 @item show print entry-values
8906 Show the method being used for printing of frame argument values at function
8909 @item set print repeats @var{number-of-repeats}
8910 @itemx set print repeats unlimited
8911 @cindex repeated array elements
8912 Set the threshold for suppressing display of repeated array
8913 elements. When the number of consecutive identical elements of an
8914 array exceeds the threshold, @value{GDBN} prints the string
8915 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8916 identical repetitions, instead of displaying the identical elements
8917 themselves. Setting the threshold to @code{unlimited} or zero will
8918 cause all elements to be individually printed. The default threshold
8921 @item show print repeats
8922 Display the current threshold for printing repeated identical
8925 @item set print null-stop
8926 @cindex @sc{null} elements in arrays
8927 Cause @value{GDBN} to stop printing the characters of an array when the first
8928 @sc{null} is encountered. This is useful when large arrays actually
8929 contain only short strings.
8932 @item show print null-stop
8933 Show whether @value{GDBN} stops printing an array on the first
8934 @sc{null} character.
8936 @item set print pretty on
8937 @cindex print structures in indented form
8938 @cindex indentation in structure display
8939 Cause @value{GDBN} to print structures in an indented format with one member
8940 per line, like this:
8955 @item set print pretty off
8956 Cause @value{GDBN} to print structures in a compact format, like this:
8960 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8961 meat = 0x54 "Pork"@}
8966 This is the default format.
8968 @item show print pretty
8969 Show which format @value{GDBN} is using to print structures.
8971 @item set print sevenbit-strings on
8972 @cindex eight-bit characters in strings
8973 @cindex octal escapes in strings
8974 Print using only seven-bit characters; if this option is set,
8975 @value{GDBN} displays any eight-bit characters (in strings or
8976 character values) using the notation @code{\}@var{nnn}. This setting is
8977 best if you are working in English (@sc{ascii}) and you use the
8978 high-order bit of characters as a marker or ``meta'' bit.
8980 @item set print sevenbit-strings off
8981 Print full eight-bit characters. This allows the use of more
8982 international character sets, and is the default.
8984 @item show print sevenbit-strings
8985 Show whether or not @value{GDBN} is printing only seven-bit characters.
8987 @item set print union on
8988 @cindex unions in structures, printing
8989 Tell @value{GDBN} to print unions which are contained in structures
8990 and other unions. This is the default setting.
8992 @item set print union off
8993 Tell @value{GDBN} not to print unions which are contained in
8994 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8997 @item show print union
8998 Ask @value{GDBN} whether or not it will print unions which are contained in
8999 structures and other unions.
9001 For example, given the declarations
9004 typedef enum @{Tree, Bug@} Species;
9005 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9006 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9017 struct thing foo = @{Tree, @{Acorn@}@};
9021 with @code{set print union on} in effect @samp{p foo} would print
9024 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9028 and with @code{set print union off} in effect it would print
9031 $1 = @{it = Tree, form = @{...@}@}
9035 @code{set print union} affects programs written in C-like languages
9041 These settings are of interest when debugging C@t{++} programs:
9044 @cindex demangling C@t{++} names
9045 @item set print demangle
9046 @itemx set print demangle on
9047 Print C@t{++} names in their source form rather than in the encoded
9048 (``mangled'') form passed to the assembler and linker for type-safe
9049 linkage. The default is on.
9051 @item show print demangle
9052 Show whether C@t{++} names are printed in mangled or demangled form.
9054 @item set print asm-demangle
9055 @itemx set print asm-demangle on
9056 Print C@t{++} names in their source form rather than their mangled form, even
9057 in assembler code printouts such as instruction disassemblies.
9060 @item show print asm-demangle
9061 Show whether C@t{++} names in assembly listings are printed in mangled
9064 @cindex C@t{++} symbol decoding style
9065 @cindex symbol decoding style, C@t{++}
9066 @kindex set demangle-style
9067 @item set demangle-style @var{style}
9068 Choose among several encoding schemes used by different compilers to
9069 represent C@t{++} names. The choices for @var{style} are currently:
9073 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9074 This is the default.
9077 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9080 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9083 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9086 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9087 @strong{Warning:} this setting alone is not sufficient to allow
9088 debugging @code{cfront}-generated executables. @value{GDBN} would
9089 require further enhancement to permit that.
9092 If you omit @var{style}, you will see a list of possible formats.
9094 @item show demangle-style
9095 Display the encoding style currently in use for decoding C@t{++} symbols.
9097 @item set print object
9098 @itemx set print object on
9099 @cindex derived type of an object, printing
9100 @cindex display derived types
9101 When displaying a pointer to an object, identify the @emph{actual}
9102 (derived) type of the object rather than the @emph{declared} type, using
9103 the virtual function table. Note that the virtual function table is
9104 required---this feature can only work for objects that have run-time
9105 type identification; a single virtual method in the object's declared
9106 type is sufficient. Note that this setting is also taken into account when
9107 working with variable objects via MI (@pxref{GDB/MI}).
9109 @item set print object off
9110 Display only the declared type of objects, without reference to the
9111 virtual function table. This is the default setting.
9113 @item show print object
9114 Show whether actual, or declared, object types are displayed.
9116 @item set print static-members
9117 @itemx set print static-members on
9118 @cindex static members of C@t{++} objects
9119 Print static members when displaying a C@t{++} object. The default is on.
9121 @item set print static-members off
9122 Do not print static members when displaying a C@t{++} object.
9124 @item show print static-members
9125 Show whether C@t{++} static members are printed or not.
9127 @item set print pascal_static-members
9128 @itemx set print pascal_static-members on
9129 @cindex static members of Pascal objects
9130 @cindex Pascal objects, static members display
9131 Print static members when displaying a Pascal object. The default is on.
9133 @item set print pascal_static-members off
9134 Do not print static members when displaying a Pascal object.
9136 @item show print pascal_static-members
9137 Show whether Pascal static members are printed or not.
9139 @c These don't work with HP ANSI C++ yet.
9140 @item set print vtbl
9141 @itemx set print vtbl on
9142 @cindex pretty print C@t{++} virtual function tables
9143 @cindex virtual functions (C@t{++}) display
9144 @cindex VTBL display
9145 Pretty print C@t{++} virtual function tables. The default is off.
9146 (The @code{vtbl} commands do not work on programs compiled with the HP
9147 ANSI C@t{++} compiler (@code{aCC}).)
9149 @item set print vtbl off
9150 Do not pretty print C@t{++} virtual function tables.
9152 @item show print vtbl
9153 Show whether C@t{++} virtual function tables are pretty printed, or not.
9156 @node Pretty Printing
9157 @section Pretty Printing
9159 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9160 Python code. It greatly simplifies the display of complex objects. This
9161 mechanism works for both MI and the CLI.
9164 * Pretty-Printer Introduction:: Introduction to pretty-printers
9165 * Pretty-Printer Example:: An example pretty-printer
9166 * Pretty-Printer Commands:: Pretty-printer commands
9169 @node Pretty-Printer Introduction
9170 @subsection Pretty-Printer Introduction
9172 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9173 registered for the value. If there is then @value{GDBN} invokes the
9174 pretty-printer to print the value. Otherwise the value is printed normally.
9176 Pretty-printers are normally named. This makes them easy to manage.
9177 The @samp{info pretty-printer} command will list all the installed
9178 pretty-printers with their names.
9179 If a pretty-printer can handle multiple data types, then its
9180 @dfn{subprinters} are the printers for the individual data types.
9181 Each such subprinter has its own name.
9182 The format of the name is @var{printer-name};@var{subprinter-name}.
9184 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9185 Typically they are automatically loaded and registered when the corresponding
9186 debug information is loaded, thus making them available without having to
9187 do anything special.
9189 There are three places where a pretty-printer can be registered.
9193 Pretty-printers registered globally are available when debugging
9197 Pretty-printers registered with a program space are available only
9198 when debugging that program.
9199 @xref{Progspaces In Python}, for more details on program spaces in Python.
9202 Pretty-printers registered with an objfile are loaded and unloaded
9203 with the corresponding objfile (e.g., shared library).
9204 @xref{Objfiles In Python}, for more details on objfiles in Python.
9207 @xref{Selecting Pretty-Printers}, for further information on how
9208 pretty-printers are selected,
9210 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9213 @node Pretty-Printer Example
9214 @subsection Pretty-Printer Example
9216 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9219 (@value{GDBP}) print s
9221 static npos = 4294967295,
9223 <std::allocator<char>> = @{
9224 <__gnu_cxx::new_allocator<char>> = @{
9225 <No data fields>@}, <No data fields>
9227 members of std::basic_string<char, std::char_traits<char>,
9228 std::allocator<char> >::_Alloc_hider:
9229 _M_p = 0x804a014 "abcd"
9234 With a pretty-printer for @code{std::string} only the contents are printed:
9237 (@value{GDBP}) print s
9241 @node Pretty-Printer Commands
9242 @subsection Pretty-Printer Commands
9243 @cindex pretty-printer commands
9246 @kindex info pretty-printer
9247 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9248 Print the list of installed pretty-printers.
9249 This includes disabled pretty-printers, which are marked as such.
9251 @var{object-regexp} is a regular expression matching the objects
9252 whose pretty-printers to list.
9253 Objects can be @code{global}, the program space's file
9254 (@pxref{Progspaces In Python}),
9255 and the object files within that program space (@pxref{Objfiles In Python}).
9256 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9257 looks up a printer from these three objects.
9259 @var{name-regexp} is a regular expression matching the name of the printers
9262 @kindex disable pretty-printer
9263 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9264 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9265 A disabled pretty-printer is not forgotten, it may be enabled again later.
9267 @kindex enable pretty-printer
9268 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9269 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9274 Suppose we have three pretty-printers installed: one from library1.so
9275 named @code{foo} that prints objects of type @code{foo}, and
9276 another from library2.so named @code{bar} that prints two types of objects,
9277 @code{bar1} and @code{bar2}.
9280 (gdb) info pretty-printer
9287 (gdb) info pretty-printer library2
9292 (gdb) disable pretty-printer library1
9294 2 of 3 printers enabled
9295 (gdb) info pretty-printer
9302 (gdb) disable pretty-printer library2 bar:bar1
9304 1 of 3 printers enabled
9305 (gdb) info pretty-printer library2
9312 (gdb) disable pretty-printer library2 bar
9314 0 of 3 printers enabled
9315 (gdb) info pretty-printer library2
9324 Note that for @code{bar} the entire printer can be disabled,
9325 as can each individual subprinter.
9328 @section Value History
9330 @cindex value history
9331 @cindex history of values printed by @value{GDBN}
9332 Values printed by the @code{print} command are saved in the @value{GDBN}
9333 @dfn{value history}. This allows you to refer to them in other expressions.
9334 Values are kept until the symbol table is re-read or discarded
9335 (for example with the @code{file} or @code{symbol-file} commands).
9336 When the symbol table changes, the value history is discarded,
9337 since the values may contain pointers back to the types defined in the
9342 @cindex history number
9343 The values printed are given @dfn{history numbers} by which you can
9344 refer to them. These are successive integers starting with one.
9345 @code{print} shows you the history number assigned to a value by
9346 printing @samp{$@var{num} = } before the value; here @var{num} is the
9349 To refer to any previous value, use @samp{$} followed by the value's
9350 history number. The way @code{print} labels its output is designed to
9351 remind you of this. Just @code{$} refers to the most recent value in
9352 the history, and @code{$$} refers to the value before that.
9353 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9354 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9355 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9357 For example, suppose you have just printed a pointer to a structure and
9358 want to see the contents of the structure. It suffices to type
9364 If you have a chain of structures where the component @code{next} points
9365 to the next one, you can print the contents of the next one with this:
9372 You can print successive links in the chain by repeating this
9373 command---which you can do by just typing @key{RET}.
9375 Note that the history records values, not expressions. If the value of
9376 @code{x} is 4 and you type these commands:
9384 then the value recorded in the value history by the @code{print} command
9385 remains 4 even though the value of @code{x} has changed.
9390 Print the last ten values in the value history, with their item numbers.
9391 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9392 values} does not change the history.
9394 @item show values @var{n}
9395 Print ten history values centered on history item number @var{n}.
9398 Print ten history values just after the values last printed. If no more
9399 values are available, @code{show values +} produces no display.
9402 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9403 same effect as @samp{show values +}.
9405 @node Convenience Vars
9406 @section Convenience Variables
9408 @cindex convenience variables
9409 @cindex user-defined variables
9410 @value{GDBN} provides @dfn{convenience variables} that you can use within
9411 @value{GDBN} to hold on to a value and refer to it later. These variables
9412 exist entirely within @value{GDBN}; they are not part of your program, and
9413 setting a convenience variable has no direct effect on further execution
9414 of your program. That is why you can use them freely.
9416 Convenience variables are prefixed with @samp{$}. Any name preceded by
9417 @samp{$} can be used for a convenience variable, unless it is one of
9418 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9419 (Value history references, in contrast, are @emph{numbers} preceded
9420 by @samp{$}. @xref{Value History, ,Value History}.)
9422 You can save a value in a convenience variable with an assignment
9423 expression, just as you would set a variable in your program.
9427 set $foo = *object_ptr
9431 would save in @code{$foo} the value contained in the object pointed to by
9434 Using a convenience variable for the first time creates it, but its
9435 value is @code{void} until you assign a new value. You can alter the
9436 value with another assignment at any time.
9438 Convenience variables have no fixed types. You can assign a convenience
9439 variable any type of value, including structures and arrays, even if
9440 that variable already has a value of a different type. The convenience
9441 variable, when used as an expression, has the type of its current value.
9444 @kindex show convenience
9445 @cindex show all user variables and functions
9446 @item show convenience
9447 Print a list of convenience variables used so far, and their values,
9448 as well as a list of the convenience functions.
9449 Abbreviated @code{show conv}.
9451 @kindex init-if-undefined
9452 @cindex convenience variables, initializing
9453 @item init-if-undefined $@var{variable} = @var{expression}
9454 Set a convenience variable if it has not already been set. This is useful
9455 for user-defined commands that keep some state. It is similar, in concept,
9456 to using local static variables with initializers in C (except that
9457 convenience variables are global). It can also be used to allow users to
9458 override default values used in a command script.
9460 If the variable is already defined then the expression is not evaluated so
9461 any side-effects do not occur.
9464 One of the ways to use a convenience variable is as a counter to be
9465 incremented or a pointer to be advanced. For example, to print
9466 a field from successive elements of an array of structures:
9470 print bar[$i++]->contents
9474 Repeat that command by typing @key{RET}.
9476 Some convenience variables are created automatically by @value{GDBN} and given
9477 values likely to be useful.
9480 @vindex $_@r{, convenience variable}
9482 The variable @code{$_} is automatically set by the @code{x} command to
9483 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9484 commands which provide a default address for @code{x} to examine also
9485 set @code{$_} to that address; these commands include @code{info line}
9486 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9487 except when set by the @code{x} command, in which case it is a pointer
9488 to the type of @code{$__}.
9490 @vindex $__@r{, convenience variable}
9492 The variable @code{$__} is automatically set by the @code{x} command
9493 to the value found in the last address examined. Its type is chosen
9494 to match the format in which the data was printed.
9497 @vindex $_exitcode@r{, convenience variable}
9498 The variable @code{$_exitcode} is automatically set to the exit code when
9499 the program being debugged terminates.
9502 @itemx $_probe_arg0@dots{}$_probe_arg11
9503 Arguments to a static probe. @xref{Static Probe Points}.
9506 @vindex $_sdata@r{, inspect, convenience variable}
9507 The variable @code{$_sdata} contains extra collected static tracepoint
9508 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9509 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9510 if extra static tracepoint data has not been collected.
9513 @vindex $_siginfo@r{, convenience variable}
9514 The variable @code{$_siginfo} contains extra signal information
9515 (@pxref{extra signal information}). Note that @code{$_siginfo}
9516 could be empty, if the application has not yet received any signals.
9517 For example, it will be empty before you execute the @code{run} command.
9520 @vindex $_tlb@r{, convenience variable}
9521 The variable @code{$_tlb} is automatically set when debugging
9522 applications running on MS-Windows in native mode or connected to
9523 gdbserver that supports the @code{qGetTIBAddr} request.
9524 @xref{General Query Packets}.
9525 This variable contains the address of the thread information block.
9529 On HP-UX systems, if you refer to a function or variable name that
9530 begins with a dollar sign, @value{GDBN} searches for a user or system
9531 name first, before it searches for a convenience variable.
9533 @node Convenience Funs
9534 @section Convenience Functions
9536 @cindex convenience functions
9537 @value{GDBN} also supplies some @dfn{convenience functions}. These
9538 have a syntax similar to convenience variables. A convenience
9539 function can be used in an expression just like an ordinary function;
9540 however, a convenience function is implemented internally to
9543 These functions require @value{GDBN} to be configured with
9544 @code{Python} support.
9548 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9549 @findex $_memeq@r{, convenience function}
9550 Returns one if the @var{length} bytes at the addresses given by
9551 @var{buf1} and @var{buf2} are equal.
9552 Otherwise it returns zero.
9554 @item $_regex(@var{str}, @var{regex})
9555 @findex $_regex@r{, convenience function}
9556 Returns one if the string @var{str} matches the regular expression
9557 @var{regex}. Otherwise it returns zero.
9558 The syntax of the regular expression is that specified by @code{Python}'s
9559 regular expression support.
9561 @item $_streq(@var{str1}, @var{str2})
9562 @findex $_streq@r{, convenience function}
9563 Returns one if the strings @var{str1} and @var{str2} are equal.
9564 Otherwise it returns zero.
9566 @item $_strlen(@var{str})
9567 @findex $_strlen@r{, convenience function}
9568 Returns the length of string @var{str}.
9572 @value{GDBN} provides the ability to list and get help on
9573 convenience functions.
9577 @kindex help function
9578 @cindex show all convenience functions
9579 Print a list of all convenience functions.
9586 You can refer to machine register contents, in expressions, as variables
9587 with names starting with @samp{$}. The names of registers are different
9588 for each machine; use @code{info registers} to see the names used on
9592 @kindex info registers
9593 @item info registers
9594 Print the names and values of all registers except floating-point
9595 and vector registers (in the selected stack frame).
9597 @kindex info all-registers
9598 @cindex floating point registers
9599 @item info all-registers
9600 Print the names and values of all registers, including floating-point
9601 and vector registers (in the selected stack frame).
9603 @item info registers @var{regname} @dots{}
9604 Print the @dfn{relativized} value of each specified register @var{regname}.
9605 As discussed in detail below, register values are normally relative to
9606 the selected stack frame. @var{regname} may be any register name valid on
9607 the machine you are using, with or without the initial @samp{$}.
9610 @cindex stack pointer register
9611 @cindex program counter register
9612 @cindex process status register
9613 @cindex frame pointer register
9614 @cindex standard registers
9615 @value{GDBN} has four ``standard'' register names that are available (in
9616 expressions) on most machines---whenever they do not conflict with an
9617 architecture's canonical mnemonics for registers. The register names
9618 @code{$pc} and @code{$sp} are used for the program counter register and
9619 the stack pointer. @code{$fp} is used for a register that contains a
9620 pointer to the current stack frame, and @code{$ps} is used for a
9621 register that contains the processor status. For example,
9622 you could print the program counter in hex with
9629 or print the instruction to be executed next with
9636 or add four to the stack pointer@footnote{This is a way of removing
9637 one word from the stack, on machines where stacks grow downward in
9638 memory (most machines, nowadays). This assumes that the innermost
9639 stack frame is selected; setting @code{$sp} is not allowed when other
9640 stack frames are selected. To pop entire frames off the stack,
9641 regardless of machine architecture, use @code{return};
9642 see @ref{Returning, ,Returning from a Function}.} with
9648 Whenever possible, these four standard register names are available on
9649 your machine even though the machine has different canonical mnemonics,
9650 so long as there is no conflict. The @code{info registers} command
9651 shows the canonical names. For example, on the SPARC, @code{info
9652 registers} displays the processor status register as @code{$psr} but you
9653 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9654 is an alias for the @sc{eflags} register.
9656 @value{GDBN} always considers the contents of an ordinary register as an
9657 integer when the register is examined in this way. Some machines have
9658 special registers which can hold nothing but floating point; these
9659 registers are considered to have floating point values. There is no way
9660 to refer to the contents of an ordinary register as floating point value
9661 (although you can @emph{print} it as a floating point value with
9662 @samp{print/f $@var{regname}}).
9664 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9665 means that the data format in which the register contents are saved by
9666 the operating system is not the same one that your program normally
9667 sees. For example, the registers of the 68881 floating point
9668 coprocessor are always saved in ``extended'' (raw) format, but all C
9669 programs expect to work with ``double'' (virtual) format. In such
9670 cases, @value{GDBN} normally works with the virtual format only (the format
9671 that makes sense for your program), but the @code{info registers} command
9672 prints the data in both formats.
9674 @cindex SSE registers (x86)
9675 @cindex MMX registers (x86)
9676 Some machines have special registers whose contents can be interpreted
9677 in several different ways. For example, modern x86-based machines
9678 have SSE and MMX registers that can hold several values packed
9679 together in several different formats. @value{GDBN} refers to such
9680 registers in @code{struct} notation:
9683 (@value{GDBP}) print $xmm1
9685 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9686 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9687 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9688 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9689 v4_int32 = @{0, 20657912, 11, 13@},
9690 v2_int64 = @{88725056443645952, 55834574859@},
9691 uint128 = 0x0000000d0000000b013b36f800000000
9696 To set values of such registers, you need to tell @value{GDBN} which
9697 view of the register you wish to change, as if you were assigning
9698 value to a @code{struct} member:
9701 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9704 Normally, register values are relative to the selected stack frame
9705 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9706 value that the register would contain if all stack frames farther in
9707 were exited and their saved registers restored. In order to see the
9708 true contents of hardware registers, you must select the innermost
9709 frame (with @samp{frame 0}).
9711 However, @value{GDBN} must deduce where registers are saved, from the machine
9712 code generated by your compiler. If some registers are not saved, or if
9713 @value{GDBN} is unable to locate the saved registers, the selected stack
9714 frame makes no difference.
9716 @node Floating Point Hardware
9717 @section Floating Point Hardware
9718 @cindex floating point
9720 Depending on the configuration, @value{GDBN} may be able to give
9721 you more information about the status of the floating point hardware.
9726 Display hardware-dependent information about the floating
9727 point unit. The exact contents and layout vary depending on the
9728 floating point chip. Currently, @samp{info float} is supported on
9729 the ARM and x86 machines.
9733 @section Vector Unit
9736 Depending on the configuration, @value{GDBN} may be able to give you
9737 more information about the status of the vector unit.
9742 Display information about the vector unit. The exact contents and
9743 layout vary depending on the hardware.
9746 @node OS Information
9747 @section Operating System Auxiliary Information
9748 @cindex OS information
9750 @value{GDBN} provides interfaces to useful OS facilities that can help
9751 you debug your program.
9753 @cindex auxiliary vector
9754 @cindex vector, auxiliary
9755 Some operating systems supply an @dfn{auxiliary vector} to programs at
9756 startup. This is akin to the arguments and environment that you
9757 specify for a program, but contains a system-dependent variety of
9758 binary values that tell system libraries important details about the
9759 hardware, operating system, and process. Each value's purpose is
9760 identified by an integer tag; the meanings are well-known but system-specific.
9761 Depending on the configuration and operating system facilities,
9762 @value{GDBN} may be able to show you this information. For remote
9763 targets, this functionality may further depend on the remote stub's
9764 support of the @samp{qXfer:auxv:read} packet, see
9765 @ref{qXfer auxiliary vector read}.
9770 Display the auxiliary vector of the inferior, which can be either a
9771 live process or a core dump file. @value{GDBN} prints each tag value
9772 numerically, and also shows names and text descriptions for recognized
9773 tags. Some values in the vector are numbers, some bit masks, and some
9774 pointers to strings or other data. @value{GDBN} displays each value in the
9775 most appropriate form for a recognized tag, and in hexadecimal for
9776 an unrecognized tag.
9779 On some targets, @value{GDBN} can access operating system-specific
9780 information and show it to you. The types of information available
9781 will differ depending on the type of operating system running on the
9782 target. The mechanism used to fetch the data is described in
9783 @ref{Operating System Information}. For remote targets, this
9784 functionality depends on the remote stub's support of the
9785 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9789 @item info os @var{infotype}
9791 Display OS information of the requested type.
9793 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9795 @anchor{linux info os infotypes}
9797 @kindex info os processes
9799 Display the list of processes on the target. For each process,
9800 @value{GDBN} prints the process identifier, the name of the user, the
9801 command corresponding to the process, and the list of processor cores
9802 that the process is currently running on. (To understand what these
9803 properties mean, for this and the following info types, please consult
9804 the general @sc{gnu}/Linux documentation.)
9806 @kindex info os procgroups
9808 Display the list of process groups on the target. For each process,
9809 @value{GDBN} prints the identifier of the process group that it belongs
9810 to, the command corresponding to the process group leader, the process
9811 identifier, and the command line of the process. The list is sorted
9812 first by the process group identifier, then by the process identifier,
9813 so that processes belonging to the same process group are grouped together
9814 and the process group leader is listed first.
9816 @kindex info os threads
9818 Display the list of threads running on the target. For each thread,
9819 @value{GDBN} prints the identifier of the process that the thread
9820 belongs to, the command of the process, the thread identifier, and the
9821 processor core that it is currently running on. The main thread of a
9822 process is not listed.
9824 @kindex info os files
9826 Display the list of open file descriptors on the target. For each
9827 file descriptor, @value{GDBN} prints the identifier of the process
9828 owning the descriptor, the command of the owning process, the value
9829 of the descriptor, and the target of the descriptor.
9831 @kindex info os sockets
9833 Display the list of Internet-domain sockets on the target. For each
9834 socket, @value{GDBN} prints the address and port of the local and
9835 remote endpoints, the current state of the connection, the creator of
9836 the socket, the IP address family of the socket, and the type of the
9841 Display the list of all System V shared-memory regions on the target.
9842 For each shared-memory region, @value{GDBN} prints the region key,
9843 the shared-memory identifier, the access permissions, the size of the
9844 region, the process that created the region, the process that last
9845 attached to or detached from the region, the current number of live
9846 attaches to the region, and the times at which the region was last
9847 attached to, detach from, and changed.
9849 @kindex info os semaphores
9851 Display the list of all System V semaphore sets on the target. For each
9852 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9853 set identifier, the access permissions, the number of semaphores in the
9854 set, the user and group of the owner and creator of the semaphore set,
9855 and the times at which the semaphore set was operated upon and changed.
9859 Display the list of all System V message queues on the target. For each
9860 message queue, @value{GDBN} prints the message queue key, the message
9861 queue identifier, the access permissions, the current number of bytes
9862 on the queue, the current number of messages on the queue, the processes
9863 that last sent and received a message on the queue, the user and group
9864 of the owner and creator of the message queue, the times at which a
9865 message was last sent and received on the queue, and the time at which
9866 the message queue was last changed.
9868 @kindex info os modules
9870 Display the list of all loaded kernel modules on the target. For each
9871 module, @value{GDBN} prints the module name, the size of the module in
9872 bytes, the number of times the module is used, the dependencies of the
9873 module, the status of the module, and the address of the loaded module
9878 If @var{infotype} is omitted, then list the possible values for
9879 @var{infotype} and the kind of OS information available for each
9880 @var{infotype}. If the target does not return a list of possible
9881 types, this command will report an error.
9884 @node Memory Region Attributes
9885 @section Memory Region Attributes
9886 @cindex memory region attributes
9888 @dfn{Memory region attributes} allow you to describe special handling
9889 required by regions of your target's memory. @value{GDBN} uses
9890 attributes to determine whether to allow certain types of memory
9891 accesses; whether to use specific width accesses; and whether to cache
9892 target memory. By default the description of memory regions is
9893 fetched from the target (if the current target supports this), but the
9894 user can override the fetched regions.
9896 Defined memory regions can be individually enabled and disabled. When a
9897 memory region is disabled, @value{GDBN} uses the default attributes when
9898 accessing memory in that region. Similarly, if no memory regions have
9899 been defined, @value{GDBN} uses the default attributes when accessing
9902 When a memory region is defined, it is given a number to identify it;
9903 to enable, disable, or remove a memory region, you specify that number.
9907 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9908 Define a memory region bounded by @var{lower} and @var{upper} with
9909 attributes @var{attributes}@dots{}, and add it to the list of regions
9910 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9911 case: it is treated as the target's maximum memory address.
9912 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9915 Discard any user changes to the memory regions and use target-supplied
9916 regions, if available, or no regions if the target does not support.
9919 @item delete mem @var{nums}@dots{}
9920 Remove memory regions @var{nums}@dots{} from the list of regions
9921 monitored by @value{GDBN}.
9924 @item disable mem @var{nums}@dots{}
9925 Disable monitoring of memory regions @var{nums}@dots{}.
9926 A disabled memory region is not forgotten.
9927 It may be enabled again later.
9930 @item enable mem @var{nums}@dots{}
9931 Enable monitoring of memory regions @var{nums}@dots{}.
9935 Print a table of all defined memory regions, with the following columns
9939 @item Memory Region Number
9940 @item Enabled or Disabled.
9941 Enabled memory regions are marked with @samp{y}.
9942 Disabled memory regions are marked with @samp{n}.
9945 The address defining the inclusive lower bound of the memory region.
9948 The address defining the exclusive upper bound of the memory region.
9951 The list of attributes set for this memory region.
9956 @subsection Attributes
9958 @subsubsection Memory Access Mode
9959 The access mode attributes set whether @value{GDBN} may make read or
9960 write accesses to a memory region.
9962 While these attributes prevent @value{GDBN} from performing invalid
9963 memory accesses, they do nothing to prevent the target system, I/O DMA,
9964 etc.@: from accessing memory.
9968 Memory is read only.
9970 Memory is write only.
9972 Memory is read/write. This is the default.
9975 @subsubsection Memory Access Size
9976 The access size attribute tells @value{GDBN} to use specific sized
9977 accesses in the memory region. Often memory mapped device registers
9978 require specific sized accesses. If no access size attribute is
9979 specified, @value{GDBN} may use accesses of any size.
9983 Use 8 bit memory accesses.
9985 Use 16 bit memory accesses.
9987 Use 32 bit memory accesses.
9989 Use 64 bit memory accesses.
9992 @c @subsubsection Hardware/Software Breakpoints
9993 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9994 @c will use hardware or software breakpoints for the internal breakpoints
9995 @c used by the step, next, finish, until, etc. commands.
9999 @c Always use hardware breakpoints
10000 @c @item swbreak (default)
10003 @subsubsection Data Cache
10004 The data cache attributes set whether @value{GDBN} will cache target
10005 memory. While this generally improves performance by reducing debug
10006 protocol overhead, it can lead to incorrect results because @value{GDBN}
10007 does not know about volatile variables or memory mapped device
10012 Enable @value{GDBN} to cache target memory.
10014 Disable @value{GDBN} from caching target memory. This is the default.
10017 @subsection Memory Access Checking
10018 @value{GDBN} can be instructed to refuse accesses to memory that is
10019 not explicitly described. This can be useful if accessing such
10020 regions has undesired effects for a specific target, or to provide
10021 better error checking. The following commands control this behaviour.
10024 @kindex set mem inaccessible-by-default
10025 @item set mem inaccessible-by-default [on|off]
10026 If @code{on} is specified, make @value{GDBN} treat memory not
10027 explicitly described by the memory ranges as non-existent and refuse accesses
10028 to such memory. The checks are only performed if there's at least one
10029 memory range defined. If @code{off} is specified, make @value{GDBN}
10030 treat the memory not explicitly described by the memory ranges as RAM.
10031 The default value is @code{on}.
10032 @kindex show mem inaccessible-by-default
10033 @item show mem inaccessible-by-default
10034 Show the current handling of accesses to unknown memory.
10038 @c @subsubsection Memory Write Verification
10039 @c The memory write verification attributes set whether @value{GDBN}
10040 @c will re-reads data after each write to verify the write was successful.
10044 @c @item noverify (default)
10047 @node Dump/Restore Files
10048 @section Copy Between Memory and a File
10049 @cindex dump/restore files
10050 @cindex append data to a file
10051 @cindex dump data to a file
10052 @cindex restore data from a file
10054 You can use the commands @code{dump}, @code{append}, and
10055 @code{restore} to copy data between target memory and a file. The
10056 @code{dump} and @code{append} commands write data to a file, and the
10057 @code{restore} command reads data from a file back into the inferior's
10058 memory. Files may be in binary, Motorola S-record, Intel hex, or
10059 Tektronix Hex format; however, @value{GDBN} can only append to binary
10065 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10066 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10067 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10068 or the value of @var{expr}, to @var{filename} in the given format.
10070 The @var{format} parameter may be any one of:
10077 Motorola S-record format.
10079 Tektronix Hex format.
10082 @value{GDBN} uses the same definitions of these formats as the
10083 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10084 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10088 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10089 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10090 Append the contents of memory from @var{start_addr} to @var{end_addr},
10091 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10092 (@value{GDBN} can only append data to files in raw binary form.)
10095 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10096 Restore the contents of file @var{filename} into memory. The
10097 @code{restore} command can automatically recognize any known @sc{bfd}
10098 file format, except for raw binary. To restore a raw binary file you
10099 must specify the optional keyword @code{binary} after the filename.
10101 If @var{bias} is non-zero, its value will be added to the addresses
10102 contained in the file. Binary files always start at address zero, so
10103 they will be restored at address @var{bias}. Other bfd files have
10104 a built-in location; they will be restored at offset @var{bias}
10105 from that location.
10107 If @var{start} and/or @var{end} are non-zero, then only data between
10108 file offset @var{start} and file offset @var{end} will be restored.
10109 These offsets are relative to the addresses in the file, before
10110 the @var{bias} argument is applied.
10114 @node Core File Generation
10115 @section How to Produce a Core File from Your Program
10116 @cindex dump core from inferior
10118 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10119 image of a running process and its process status (register values
10120 etc.). Its primary use is post-mortem debugging of a program that
10121 crashed while it ran outside a debugger. A program that crashes
10122 automatically produces a core file, unless this feature is disabled by
10123 the user. @xref{Files}, for information on invoking @value{GDBN} in
10124 the post-mortem debugging mode.
10126 Occasionally, you may wish to produce a core file of the program you
10127 are debugging in order to preserve a snapshot of its state.
10128 @value{GDBN} has a special command for that.
10132 @kindex generate-core-file
10133 @item generate-core-file [@var{file}]
10134 @itemx gcore [@var{file}]
10135 Produce a core dump of the inferior process. The optional argument
10136 @var{file} specifies the file name where to put the core dump. If not
10137 specified, the file name defaults to @file{core.@var{pid}}, where
10138 @var{pid} is the inferior process ID.
10140 Note that this command is implemented only for some systems (as of
10141 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10144 @node Character Sets
10145 @section Character Sets
10146 @cindex character sets
10148 @cindex translating between character sets
10149 @cindex host character set
10150 @cindex target character set
10152 If the program you are debugging uses a different character set to
10153 represent characters and strings than the one @value{GDBN} uses itself,
10154 @value{GDBN} can automatically translate between the character sets for
10155 you. The character set @value{GDBN} uses we call the @dfn{host
10156 character set}; the one the inferior program uses we call the
10157 @dfn{target character set}.
10159 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10160 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10161 remote protocol (@pxref{Remote Debugging}) to debug a program
10162 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10163 then the host character set is Latin-1, and the target character set is
10164 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10165 target-charset EBCDIC-US}, then @value{GDBN} translates between
10166 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10167 character and string literals in expressions.
10169 @value{GDBN} has no way to automatically recognize which character set
10170 the inferior program uses; you must tell it, using the @code{set
10171 target-charset} command, described below.
10173 Here are the commands for controlling @value{GDBN}'s character set
10177 @item set target-charset @var{charset}
10178 @kindex set target-charset
10179 Set the current target character set to @var{charset}. To display the
10180 list of supported target character sets, type
10181 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10183 @item set host-charset @var{charset}
10184 @kindex set host-charset
10185 Set the current host character set to @var{charset}.
10187 By default, @value{GDBN} uses a host character set appropriate to the
10188 system it is running on; you can override that default using the
10189 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10190 automatically determine the appropriate host character set. In this
10191 case, @value{GDBN} uses @samp{UTF-8}.
10193 @value{GDBN} can only use certain character sets as its host character
10194 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10195 @value{GDBN} will list the host character sets it supports.
10197 @item set charset @var{charset}
10198 @kindex set charset
10199 Set the current host and target character sets to @var{charset}. As
10200 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10201 @value{GDBN} will list the names of the character sets that can be used
10202 for both host and target.
10205 @kindex show charset
10206 Show the names of the current host and target character sets.
10208 @item show host-charset
10209 @kindex show host-charset
10210 Show the name of the current host character set.
10212 @item show target-charset
10213 @kindex show target-charset
10214 Show the name of the current target character set.
10216 @item set target-wide-charset @var{charset}
10217 @kindex set target-wide-charset
10218 Set the current target's wide character set to @var{charset}. This is
10219 the character set used by the target's @code{wchar_t} type. To
10220 display the list of supported wide character sets, type
10221 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10223 @item show target-wide-charset
10224 @kindex show target-wide-charset
10225 Show the name of the current target's wide character set.
10228 Here is an example of @value{GDBN}'s character set support in action.
10229 Assume that the following source code has been placed in the file
10230 @file{charset-test.c}:
10236 = @{72, 101, 108, 108, 111, 44, 32, 119,
10237 111, 114, 108, 100, 33, 10, 0@};
10238 char ibm1047_hello[]
10239 = @{200, 133, 147, 147, 150, 107, 64, 166,
10240 150, 153, 147, 132, 90, 37, 0@};
10244 printf ("Hello, world!\n");
10248 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10249 containing the string @samp{Hello, world!} followed by a newline,
10250 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10252 We compile the program, and invoke the debugger on it:
10255 $ gcc -g charset-test.c -o charset-test
10256 $ gdb -nw charset-test
10257 GNU gdb 2001-12-19-cvs
10258 Copyright 2001 Free Software Foundation, Inc.
10263 We can use the @code{show charset} command to see what character sets
10264 @value{GDBN} is currently using to interpret and display characters and
10268 (@value{GDBP}) show charset
10269 The current host and target character set is `ISO-8859-1'.
10273 For the sake of printing this manual, let's use @sc{ascii} as our
10274 initial character set:
10276 (@value{GDBP}) set charset ASCII
10277 (@value{GDBP}) show charset
10278 The current host and target character set is `ASCII'.
10282 Let's assume that @sc{ascii} is indeed the correct character set for our
10283 host system --- in other words, let's assume that if @value{GDBN} prints
10284 characters using the @sc{ascii} character set, our terminal will display
10285 them properly. Since our current target character set is also
10286 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10289 (@value{GDBP}) print ascii_hello
10290 $1 = 0x401698 "Hello, world!\n"
10291 (@value{GDBP}) print ascii_hello[0]
10296 @value{GDBN} uses the target character set for character and string
10297 literals you use in expressions:
10300 (@value{GDBP}) print '+'
10305 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10308 @value{GDBN} relies on the user to tell it which character set the
10309 target program uses. If we print @code{ibm1047_hello} while our target
10310 character set is still @sc{ascii}, we get jibberish:
10313 (@value{GDBP}) print ibm1047_hello
10314 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10315 (@value{GDBP}) print ibm1047_hello[0]
10320 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10321 @value{GDBN} tells us the character sets it supports:
10324 (@value{GDBP}) set target-charset
10325 ASCII EBCDIC-US IBM1047 ISO-8859-1
10326 (@value{GDBP}) set target-charset
10329 We can select @sc{ibm1047} as our target character set, and examine the
10330 program's strings again. Now the @sc{ascii} string is wrong, but
10331 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10332 target character set, @sc{ibm1047}, to the host character set,
10333 @sc{ascii}, and they display correctly:
10336 (@value{GDBP}) set target-charset IBM1047
10337 (@value{GDBP}) show charset
10338 The current host character set is `ASCII'.
10339 The current target character set is `IBM1047'.
10340 (@value{GDBP}) print ascii_hello
10341 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10342 (@value{GDBP}) print ascii_hello[0]
10344 (@value{GDBP}) print ibm1047_hello
10345 $8 = 0x4016a8 "Hello, world!\n"
10346 (@value{GDBP}) print ibm1047_hello[0]
10351 As above, @value{GDBN} uses the target character set for character and
10352 string literals you use in expressions:
10355 (@value{GDBP}) print '+'
10360 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10363 @node Caching Remote Data
10364 @section Caching Data of Remote Targets
10365 @cindex caching data of remote targets
10367 @value{GDBN} caches data exchanged between the debugger and a
10368 remote target (@pxref{Remote Debugging}). Such caching generally improves
10369 performance, because it reduces the overhead of the remote protocol by
10370 bundling memory reads and writes into large chunks. Unfortunately, simply
10371 caching everything would lead to incorrect results, since @value{GDBN}
10372 does not necessarily know anything about volatile values, memory-mapped I/O
10373 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10374 memory can be changed @emph{while} a gdb command is executing.
10375 Therefore, by default, @value{GDBN} only caches data
10376 known to be on the stack@footnote{In non-stop mode, it is moderately
10377 rare for a running thread to modify the stack of a stopped thread
10378 in a way that would interfere with a backtrace, and caching of
10379 stack reads provides a significant speed up of remote backtraces.}.
10380 Other regions of memory can be explicitly marked as
10381 cacheable; see @pxref{Memory Region Attributes}.
10384 @kindex set remotecache
10385 @item set remotecache on
10386 @itemx set remotecache off
10387 This option no longer does anything; it exists for compatibility
10390 @kindex show remotecache
10391 @item show remotecache
10392 Show the current state of the obsolete remotecache flag.
10394 @kindex set stack-cache
10395 @item set stack-cache on
10396 @itemx set stack-cache off
10397 Enable or disable caching of stack accesses. When @code{ON}, use
10398 caching. By default, this option is @code{ON}.
10400 @kindex show stack-cache
10401 @item show stack-cache
10402 Show the current state of data caching for memory accesses.
10404 @kindex info dcache
10405 @item info dcache @r{[}line@r{]}
10406 Print the information about the data cache performance. The
10407 information displayed includes the dcache width and depth, and for
10408 each cache line, its number, address, and how many times it was
10409 referenced. This command is useful for debugging the data cache
10412 If a line number is specified, the contents of that line will be
10415 @item set dcache size @var{size}
10416 @cindex dcache size
10417 @kindex set dcache size
10418 Set maximum number of entries in dcache (dcache depth above).
10420 @item set dcache line-size @var{line-size}
10421 @cindex dcache line-size
10422 @kindex set dcache line-size
10423 Set number of bytes each dcache entry caches (dcache width above).
10424 Must be a power of 2.
10426 @item show dcache size
10427 @kindex show dcache size
10428 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10430 @item show dcache line-size
10431 @kindex show dcache line-size
10432 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10436 @node Searching Memory
10437 @section Search Memory
10438 @cindex searching memory
10440 Memory can be searched for a particular sequence of bytes with the
10441 @code{find} command.
10445 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10446 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10447 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10448 etc. The search begins at address @var{start_addr} and continues for either
10449 @var{len} bytes or through to @var{end_addr} inclusive.
10452 @var{s} and @var{n} are optional parameters.
10453 They may be specified in either order, apart or together.
10456 @item @var{s}, search query size
10457 The size of each search query value.
10463 halfwords (two bytes)
10467 giant words (eight bytes)
10470 All values are interpreted in the current language.
10471 This means, for example, that if the current source language is C/C@t{++}
10472 then searching for the string ``hello'' includes the trailing '\0'.
10474 If the value size is not specified, it is taken from the
10475 value's type in the current language.
10476 This is useful when one wants to specify the search
10477 pattern as a mixture of types.
10478 Note that this means, for example, that in the case of C-like languages
10479 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10480 which is typically four bytes.
10482 @item @var{n}, maximum number of finds
10483 The maximum number of matches to print. The default is to print all finds.
10486 You can use strings as search values. Quote them with double-quotes
10488 The string value is copied into the search pattern byte by byte,
10489 regardless of the endianness of the target and the size specification.
10491 The address of each match found is printed as well as a count of the
10492 number of matches found.
10494 The address of the last value found is stored in convenience variable
10496 A count of the number of matches is stored in @samp{$numfound}.
10498 For example, if stopped at the @code{printf} in this function:
10504 static char hello[] = "hello-hello";
10505 static struct @{ char c; short s; int i; @}
10506 __attribute__ ((packed)) mixed
10507 = @{ 'c', 0x1234, 0x87654321 @};
10508 printf ("%s\n", hello);
10513 you get during debugging:
10516 (gdb) find &hello[0], +sizeof(hello), "hello"
10517 0x804956d <hello.1620+6>
10519 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10520 0x8049567 <hello.1620>
10521 0x804956d <hello.1620+6>
10523 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10524 0x8049567 <hello.1620>
10526 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10527 0x8049560 <mixed.1625>
10529 (gdb) print $numfound
10532 $2 = (void *) 0x8049560
10535 @node Optimized Code
10536 @chapter Debugging Optimized Code
10537 @cindex optimized code, debugging
10538 @cindex debugging optimized code
10540 Almost all compilers support optimization. With optimization
10541 disabled, the compiler generates assembly code that corresponds
10542 directly to your source code, in a simplistic way. As the compiler
10543 applies more powerful optimizations, the generated assembly code
10544 diverges from your original source code. With help from debugging
10545 information generated by the compiler, @value{GDBN} can map from
10546 the running program back to constructs from your original source.
10548 @value{GDBN} is more accurate with optimization disabled. If you
10549 can recompile without optimization, it is easier to follow the
10550 progress of your program during debugging. But, there are many cases
10551 where you may need to debug an optimized version.
10553 When you debug a program compiled with @samp{-g -O}, remember that the
10554 optimizer has rearranged your code; the debugger shows you what is
10555 really there. Do not be too surprised when the execution path does not
10556 exactly match your source file! An extreme example: if you define a
10557 variable, but never use it, @value{GDBN} never sees that
10558 variable---because the compiler optimizes it out of existence.
10560 Some things do not work as well with @samp{-g -O} as with just
10561 @samp{-g}, particularly on machines with instruction scheduling. If in
10562 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10563 please report it to us as a bug (including a test case!).
10564 @xref{Variables}, for more information about debugging optimized code.
10567 * Inline Functions:: How @value{GDBN} presents inlining
10568 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10571 @node Inline Functions
10572 @section Inline Functions
10573 @cindex inline functions, debugging
10575 @dfn{Inlining} is an optimization that inserts a copy of the function
10576 body directly at each call site, instead of jumping to a shared
10577 routine. @value{GDBN} displays inlined functions just like
10578 non-inlined functions. They appear in backtraces. You can view their
10579 arguments and local variables, step into them with @code{step}, skip
10580 them with @code{next}, and escape from them with @code{finish}.
10581 You can check whether a function was inlined by using the
10582 @code{info frame} command.
10584 For @value{GDBN} to support inlined functions, the compiler must
10585 record information about inlining in the debug information ---
10586 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10587 other compilers do also. @value{GDBN} only supports inlined functions
10588 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10589 do not emit two required attributes (@samp{DW_AT_call_file} and
10590 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10591 function calls with earlier versions of @value{NGCC}. It instead
10592 displays the arguments and local variables of inlined functions as
10593 local variables in the caller.
10595 The body of an inlined function is directly included at its call site;
10596 unlike a non-inlined function, there are no instructions devoted to
10597 the call. @value{GDBN} still pretends that the call site and the
10598 start of the inlined function are different instructions. Stepping to
10599 the call site shows the call site, and then stepping again shows
10600 the first line of the inlined function, even though no additional
10601 instructions are executed.
10603 This makes source-level debugging much clearer; you can see both the
10604 context of the call and then the effect of the call. Only stepping by
10605 a single instruction using @code{stepi} or @code{nexti} does not do
10606 this; single instruction steps always show the inlined body.
10608 There are some ways that @value{GDBN} does not pretend that inlined
10609 function calls are the same as normal calls:
10613 Setting breakpoints at the call site of an inlined function may not
10614 work, because the call site does not contain any code. @value{GDBN}
10615 may incorrectly move the breakpoint to the next line of the enclosing
10616 function, after the call. This limitation will be removed in a future
10617 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10618 or inside the inlined function instead.
10621 @value{GDBN} cannot locate the return value of inlined calls after
10622 using the @code{finish} command. This is a limitation of compiler-generated
10623 debugging information; after @code{finish}, you can step to the next line
10624 and print a variable where your program stored the return value.
10628 @node Tail Call Frames
10629 @section Tail Call Frames
10630 @cindex tail call frames, debugging
10632 Function @code{B} can call function @code{C} in its very last statement. In
10633 unoptimized compilation the call of @code{C} is immediately followed by return
10634 instruction at the end of @code{B} code. Optimizing compiler may replace the
10635 call and return in function @code{B} into one jump to function @code{C}
10636 instead. Such use of a jump instruction is called @dfn{tail call}.
10638 During execution of function @code{C}, there will be no indication in the
10639 function call stack frames that it was tail-called from @code{B}. If function
10640 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10641 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10642 some cases @value{GDBN} can determine that @code{C} was tail-called from
10643 @code{B}, and it will then create fictitious call frame for that, with the
10644 return address set up as if @code{B} called @code{C} normally.
10646 This functionality is currently supported only by DWARF 2 debugging format and
10647 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10648 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10651 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10652 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10656 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10658 Stack level 1, frame at 0x7fffffffda30:
10659 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10660 tail call frame, caller of frame at 0x7fffffffda30
10661 source language c++.
10662 Arglist at unknown address.
10663 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10666 The detection of all the possible code path executions can find them ambiguous.
10667 There is no execution history stored (possible @ref{Reverse Execution} is never
10668 used for this purpose) and the last known caller could have reached the known
10669 callee by multiple different jump sequences. In such case @value{GDBN} still
10670 tries to show at least all the unambiguous top tail callers and all the
10671 unambiguous bottom tail calees, if any.
10674 @anchor{set debug entry-values}
10675 @item set debug entry-values
10676 @kindex set debug entry-values
10677 When set to on, enables printing of analysis messages for both frame argument
10678 values at function entry and tail calls. It will show all the possible valid
10679 tail calls code paths it has considered. It will also print the intersection
10680 of them with the final unambiguous (possibly partial or even empty) code path
10683 @item show debug entry-values
10684 @kindex show debug entry-values
10685 Show the current state of analysis messages printing for both frame argument
10686 values at function entry and tail calls.
10689 The analysis messages for tail calls can for example show why the virtual tail
10690 call frame for function @code{c} has not been recognized (due to the indirect
10691 reference by variable @code{x}):
10694 static void __attribute__((noinline, noclone)) c (void);
10695 void (*x) (void) = c;
10696 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10697 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10698 int main (void) @{ x (); return 0; @}
10700 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10701 DW_TAG_GNU_call_site 0x40039a in main
10703 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10706 #1 0x000000000040039a in main () at t.c:5
10709 Another possibility is an ambiguous virtual tail call frames resolution:
10713 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10714 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10715 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10716 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10717 static void __attribute__((noinline, noclone)) b (void)
10718 @{ if (i) c (); else e (); @}
10719 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10720 int main (void) @{ a (); return 0; @}
10722 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10723 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10724 tailcall: reduced: 0x4004d2(a) |
10727 #1 0x00000000004004d2 in a () at t.c:8
10728 #2 0x0000000000400395 in main () at t.c:9
10731 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10732 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10734 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10735 @ifset HAVE_MAKEINFO_CLICK
10736 @set ARROW @click{}
10737 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10738 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10740 @ifclear HAVE_MAKEINFO_CLICK
10742 @set CALLSEQ1B @value{CALLSEQ1A}
10743 @set CALLSEQ2B @value{CALLSEQ2A}
10746 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10747 The code can have possible execution paths @value{CALLSEQ1B} or
10748 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10750 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10751 has found. It then finds another possible calling sequcen - that one is
10752 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10753 printed as the @code{reduced:} calling sequence. That one could have many
10754 futher @code{compare:} and @code{reduced:} statements as long as there remain
10755 any non-ambiguous sequence entries.
10757 For the frame of function @code{b} in both cases there are different possible
10758 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10759 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10760 therefore this one is displayed to the user while the ambiguous frames are
10763 There can be also reasons why printing of frame argument values at function
10768 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10769 static void __attribute__((noinline, noclone)) a (int i);
10770 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10771 static void __attribute__((noinline, noclone)) a (int i)
10772 @{ if (i) b (i - 1); else c (0); @}
10773 int main (void) @{ a (5); return 0; @}
10776 #0 c (i=i@@entry=0) at t.c:2
10777 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10778 function "a" at 0x400420 can call itself via tail calls
10779 i=<optimized out>) at t.c:6
10780 #2 0x000000000040036e in main () at t.c:7
10783 @value{GDBN} cannot find out from the inferior state if and how many times did
10784 function @code{a} call itself (via function @code{b}) as these calls would be
10785 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10786 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10787 prints @code{<optimized out>} instead.
10790 @chapter C Preprocessor Macros
10792 Some languages, such as C and C@t{++}, provide a way to define and invoke
10793 ``preprocessor macros'' which expand into strings of tokens.
10794 @value{GDBN} can evaluate expressions containing macro invocations, show
10795 the result of macro expansion, and show a macro's definition, including
10796 where it was defined.
10798 You may need to compile your program specially to provide @value{GDBN}
10799 with information about preprocessor macros. Most compilers do not
10800 include macros in their debugging information, even when you compile
10801 with the @option{-g} flag. @xref{Compilation}.
10803 A program may define a macro at one point, remove that definition later,
10804 and then provide a different definition after that. Thus, at different
10805 points in the program, a macro may have different definitions, or have
10806 no definition at all. If there is a current stack frame, @value{GDBN}
10807 uses the macros in scope at that frame's source code line. Otherwise,
10808 @value{GDBN} uses the macros in scope at the current listing location;
10811 Whenever @value{GDBN} evaluates an expression, it always expands any
10812 macro invocations present in the expression. @value{GDBN} also provides
10813 the following commands for working with macros explicitly.
10817 @kindex macro expand
10818 @cindex macro expansion, showing the results of preprocessor
10819 @cindex preprocessor macro expansion, showing the results of
10820 @cindex expanding preprocessor macros
10821 @item macro expand @var{expression}
10822 @itemx macro exp @var{expression}
10823 Show the results of expanding all preprocessor macro invocations in
10824 @var{expression}. Since @value{GDBN} simply expands macros, but does
10825 not parse the result, @var{expression} need not be a valid expression;
10826 it can be any string of tokens.
10829 @item macro expand-once @var{expression}
10830 @itemx macro exp1 @var{expression}
10831 @cindex expand macro once
10832 @i{(This command is not yet implemented.)} Show the results of
10833 expanding those preprocessor macro invocations that appear explicitly in
10834 @var{expression}. Macro invocations appearing in that expansion are
10835 left unchanged. This command allows you to see the effect of a
10836 particular macro more clearly, without being confused by further
10837 expansions. Since @value{GDBN} simply expands macros, but does not
10838 parse the result, @var{expression} need not be a valid expression; it
10839 can be any string of tokens.
10842 @cindex macro definition, showing
10843 @cindex definition of a macro, showing
10844 @cindex macros, from debug info
10845 @item info macro [-a|-all] [--] @var{macro}
10846 Show the current definition or all definitions of the named @var{macro},
10847 and describe the source location or compiler command-line where that
10848 definition was established. The optional double dash is to signify the end of
10849 argument processing and the beginning of @var{macro} for non C-like macros where
10850 the macro may begin with a hyphen.
10852 @kindex info macros
10853 @item info macros @var{linespec}
10854 Show all macro definitions that are in effect at the location specified
10855 by @var{linespec}, and describe the source location or compiler
10856 command-line where those definitions were established.
10858 @kindex macro define
10859 @cindex user-defined macros
10860 @cindex defining macros interactively
10861 @cindex macros, user-defined
10862 @item macro define @var{macro} @var{replacement-list}
10863 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10864 Introduce a definition for a preprocessor macro named @var{macro},
10865 invocations of which are replaced by the tokens given in
10866 @var{replacement-list}. The first form of this command defines an
10867 ``object-like'' macro, which takes no arguments; the second form
10868 defines a ``function-like'' macro, which takes the arguments given in
10871 A definition introduced by this command is in scope in every
10872 expression evaluated in @value{GDBN}, until it is removed with the
10873 @code{macro undef} command, described below. The definition overrides
10874 all definitions for @var{macro} present in the program being debugged,
10875 as well as any previous user-supplied definition.
10877 @kindex macro undef
10878 @item macro undef @var{macro}
10879 Remove any user-supplied definition for the macro named @var{macro}.
10880 This command only affects definitions provided with the @code{macro
10881 define} command, described above; it cannot remove definitions present
10882 in the program being debugged.
10886 List all the macros defined using the @code{macro define} command.
10889 @cindex macros, example of debugging with
10890 Here is a transcript showing the above commands in action. First, we
10891 show our source files:
10896 #include "sample.h"
10899 #define ADD(x) (M + x)
10904 printf ("Hello, world!\n");
10906 printf ("We're so creative.\n");
10908 printf ("Goodbye, world!\n");
10915 Now, we compile the program using the @sc{gnu} C compiler,
10916 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10917 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10918 and @option{-gdwarf-4}; we recommend always choosing the most recent
10919 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10920 includes information about preprocessor macros in the debugging
10924 $ gcc -gdwarf-2 -g3 sample.c -o sample
10928 Now, we start @value{GDBN} on our sample program:
10932 GNU gdb 2002-05-06-cvs
10933 Copyright 2002 Free Software Foundation, Inc.
10934 GDB is free software, @dots{}
10938 We can expand macros and examine their definitions, even when the
10939 program is not running. @value{GDBN} uses the current listing position
10940 to decide which macro definitions are in scope:
10943 (@value{GDBP}) list main
10946 5 #define ADD(x) (M + x)
10951 10 printf ("Hello, world!\n");
10953 12 printf ("We're so creative.\n");
10954 (@value{GDBP}) info macro ADD
10955 Defined at /home/jimb/gdb/macros/play/sample.c:5
10956 #define ADD(x) (M + x)
10957 (@value{GDBP}) info macro Q
10958 Defined at /home/jimb/gdb/macros/play/sample.h:1
10959 included at /home/jimb/gdb/macros/play/sample.c:2
10961 (@value{GDBP}) macro expand ADD(1)
10962 expands to: (42 + 1)
10963 (@value{GDBP}) macro expand-once ADD(1)
10964 expands to: once (M + 1)
10968 In the example above, note that @code{macro expand-once} expands only
10969 the macro invocation explicit in the original text --- the invocation of
10970 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10971 which was introduced by @code{ADD}.
10973 Once the program is running, @value{GDBN} uses the macro definitions in
10974 force at the source line of the current stack frame:
10977 (@value{GDBP}) break main
10978 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10980 Starting program: /home/jimb/gdb/macros/play/sample
10982 Breakpoint 1, main () at sample.c:10
10983 10 printf ("Hello, world!\n");
10987 At line 10, the definition of the macro @code{N} at line 9 is in force:
10990 (@value{GDBP}) info macro N
10991 Defined at /home/jimb/gdb/macros/play/sample.c:9
10993 (@value{GDBP}) macro expand N Q M
10994 expands to: 28 < 42
10995 (@value{GDBP}) print N Q M
11000 As we step over directives that remove @code{N}'s definition, and then
11001 give it a new definition, @value{GDBN} finds the definition (or lack
11002 thereof) in force at each point:
11005 (@value{GDBP}) next
11007 12 printf ("We're so creative.\n");
11008 (@value{GDBP}) info macro N
11009 The symbol `N' has no definition as a C/C++ preprocessor macro
11010 at /home/jimb/gdb/macros/play/sample.c:12
11011 (@value{GDBP}) next
11013 14 printf ("Goodbye, world!\n");
11014 (@value{GDBP}) info macro N
11015 Defined at /home/jimb/gdb/macros/play/sample.c:13
11017 (@value{GDBP}) macro expand N Q M
11018 expands to: 1729 < 42
11019 (@value{GDBP}) print N Q M
11024 In addition to source files, macros can be defined on the compilation command
11025 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11026 such a way, @value{GDBN} displays the location of their definition as line zero
11027 of the source file submitted to the compiler.
11030 (@value{GDBP}) info macro __STDC__
11031 Defined at /home/jimb/gdb/macros/play/sample.c:0
11038 @chapter Tracepoints
11039 @c This chapter is based on the documentation written by Michael
11040 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11042 @cindex tracepoints
11043 In some applications, it is not feasible for the debugger to interrupt
11044 the program's execution long enough for the developer to learn
11045 anything helpful about its behavior. If the program's correctness
11046 depends on its real-time behavior, delays introduced by a debugger
11047 might cause the program to change its behavior drastically, or perhaps
11048 fail, even when the code itself is correct. It is useful to be able
11049 to observe the program's behavior without interrupting it.
11051 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11052 specify locations in the program, called @dfn{tracepoints}, and
11053 arbitrary expressions to evaluate when those tracepoints are reached.
11054 Later, using the @code{tfind} command, you can examine the values
11055 those expressions had when the program hit the tracepoints. The
11056 expressions may also denote objects in memory---structures or arrays,
11057 for example---whose values @value{GDBN} should record; while visiting
11058 a particular tracepoint, you may inspect those objects as if they were
11059 in memory at that moment. However, because @value{GDBN} records these
11060 values without interacting with you, it can do so quickly and
11061 unobtrusively, hopefully not disturbing the program's behavior.
11063 The tracepoint facility is currently available only for remote
11064 targets. @xref{Targets}. In addition, your remote target must know
11065 how to collect trace data. This functionality is implemented in the
11066 remote stub; however, none of the stubs distributed with @value{GDBN}
11067 support tracepoints as of this writing. The format of the remote
11068 packets used to implement tracepoints are described in @ref{Tracepoint
11071 It is also possible to get trace data from a file, in a manner reminiscent
11072 of corefiles; you specify the filename, and use @code{tfind} to search
11073 through the file. @xref{Trace Files}, for more details.
11075 This chapter describes the tracepoint commands and features.
11078 * Set Tracepoints::
11079 * Analyze Collected Data::
11080 * Tracepoint Variables::
11084 @node Set Tracepoints
11085 @section Commands to Set Tracepoints
11087 Before running such a @dfn{trace experiment}, an arbitrary number of
11088 tracepoints can be set. A tracepoint is actually a special type of
11089 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11090 standard breakpoint commands. For instance, as with breakpoints,
11091 tracepoint numbers are successive integers starting from one, and many
11092 of the commands associated with tracepoints take the tracepoint number
11093 as their argument, to identify which tracepoint to work on.
11095 For each tracepoint, you can specify, in advance, some arbitrary set
11096 of data that you want the target to collect in the trace buffer when
11097 it hits that tracepoint. The collected data can include registers,
11098 local variables, or global data. Later, you can use @value{GDBN}
11099 commands to examine the values these data had at the time the
11100 tracepoint was hit.
11102 Tracepoints do not support every breakpoint feature. Ignore counts on
11103 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11104 commands when they are hit. Tracepoints may not be thread-specific
11107 @cindex fast tracepoints
11108 Some targets may support @dfn{fast tracepoints}, which are inserted in
11109 a different way (such as with a jump instead of a trap), that is
11110 faster but possibly restricted in where they may be installed.
11112 @cindex static tracepoints
11113 @cindex markers, static tracepoints
11114 @cindex probing markers, static tracepoints
11115 Regular and fast tracepoints are dynamic tracing facilities, meaning
11116 that they can be used to insert tracepoints at (almost) any location
11117 in the target. Some targets may also support controlling @dfn{static
11118 tracepoints} from @value{GDBN}. With static tracing, a set of
11119 instrumentation points, also known as @dfn{markers}, are embedded in
11120 the target program, and can be activated or deactivated by name or
11121 address. These are usually placed at locations which facilitate
11122 investigating what the target is actually doing. @value{GDBN}'s
11123 support for static tracing includes being able to list instrumentation
11124 points, and attach them with @value{GDBN} defined high level
11125 tracepoints that expose the whole range of convenience of
11126 @value{GDBN}'s tracepoints support. Namely, support for collecting
11127 registers values and values of global or local (to the instrumentation
11128 point) variables; tracepoint conditions and trace state variables.
11129 The act of installing a @value{GDBN} static tracepoint on an
11130 instrumentation point, or marker, is referred to as @dfn{probing} a
11131 static tracepoint marker.
11133 @code{gdbserver} supports tracepoints on some target systems.
11134 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11136 This section describes commands to set tracepoints and associated
11137 conditions and actions.
11140 * Create and Delete Tracepoints::
11141 * Enable and Disable Tracepoints::
11142 * Tracepoint Passcounts::
11143 * Tracepoint Conditions::
11144 * Trace State Variables::
11145 * Tracepoint Actions::
11146 * Listing Tracepoints::
11147 * Listing Static Tracepoint Markers::
11148 * Starting and Stopping Trace Experiments::
11149 * Tracepoint Restrictions::
11152 @node Create and Delete Tracepoints
11153 @subsection Create and Delete Tracepoints
11156 @cindex set tracepoint
11158 @item trace @var{location}
11159 The @code{trace} command is very similar to the @code{break} command.
11160 Its argument @var{location} can be a source line, a function name, or
11161 an address in the target program. @xref{Specify Location}. The
11162 @code{trace} command defines a tracepoint, which is a point in the
11163 target program where the debugger will briefly stop, collect some
11164 data, and then allow the program to continue. Setting a tracepoint or
11165 changing its actions takes effect immediately if the remote stub
11166 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11168 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11169 these changes don't take effect until the next @code{tstart}
11170 command, and once a trace experiment is running, further changes will
11171 not have any effect until the next trace experiment starts. In addition,
11172 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11173 address is not yet resolved. (This is similar to pending breakpoints.)
11174 Pending tracepoints are not downloaded to the target and not installed
11175 until they are resolved. The resolution of pending tracepoints requires
11176 @value{GDBN} support---when debugging with the remote target, and
11177 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11178 tracing}), pending tracepoints can not be resolved (and downloaded to
11179 the remote stub) while @value{GDBN} is disconnected.
11181 Here are some examples of using the @code{trace} command:
11184 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11186 (@value{GDBP}) @b{trace +2} // 2 lines forward
11188 (@value{GDBP}) @b{trace my_function} // first source line of function
11190 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11192 (@value{GDBP}) @b{trace *0x2117c4} // an address
11196 You can abbreviate @code{trace} as @code{tr}.
11198 @item trace @var{location} if @var{cond}
11199 Set a tracepoint with condition @var{cond}; evaluate the expression
11200 @var{cond} each time the tracepoint is reached, and collect data only
11201 if the value is nonzero---that is, if @var{cond} evaluates as true.
11202 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11203 information on tracepoint conditions.
11205 @item ftrace @var{location} [ if @var{cond} ]
11206 @cindex set fast tracepoint
11207 @cindex fast tracepoints, setting
11209 The @code{ftrace} command sets a fast tracepoint. For targets that
11210 support them, fast tracepoints will use a more efficient but possibly
11211 less general technique to trigger data collection, such as a jump
11212 instruction instead of a trap, or some sort of hardware support. It
11213 may not be possible to create a fast tracepoint at the desired
11214 location, in which case the command will exit with an explanatory
11217 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11220 On 32-bit x86-architecture systems, fast tracepoints normally need to
11221 be placed at an instruction that is 5 bytes or longer, but can be
11222 placed at 4-byte instructions if the low 64K of memory of the target
11223 program is available to install trampolines. Some Unix-type systems,
11224 such as @sc{gnu}/Linux, exclude low addresses from the program's
11225 address space; but for instance with the Linux kernel it is possible
11226 to let @value{GDBN} use this area by doing a @command{sysctl} command
11227 to set the @code{mmap_min_addr} kernel parameter, as in
11230 sudo sysctl -w vm.mmap_min_addr=32768
11234 which sets the low address to 32K, which leaves plenty of room for
11235 trampolines. The minimum address should be set to a page boundary.
11237 @item strace @var{location} [ if @var{cond} ]
11238 @cindex set static tracepoint
11239 @cindex static tracepoints, setting
11240 @cindex probe static tracepoint marker
11242 The @code{strace} command sets a static tracepoint. For targets that
11243 support it, setting a static tracepoint probes a static
11244 instrumentation point, or marker, found at @var{location}. It may not
11245 be possible to set a static tracepoint at the desired location, in
11246 which case the command will exit with an explanatory message.
11248 @value{GDBN} handles arguments to @code{strace} exactly as for
11249 @code{trace}, with the addition that the user can also specify
11250 @code{-m @var{marker}} as @var{location}. This probes the marker
11251 identified by the @var{marker} string identifier. This identifier
11252 depends on the static tracepoint backend library your program is
11253 using. You can find all the marker identifiers in the @samp{ID} field
11254 of the @code{info static-tracepoint-markers} command output.
11255 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11256 Markers}. For example, in the following small program using the UST
11262 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11267 the marker id is composed of joining the first two arguments to the
11268 @code{trace_mark} call with a slash, which translates to:
11271 (@value{GDBP}) info static-tracepoint-markers
11272 Cnt Enb ID Address What
11273 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11279 so you may probe the marker above with:
11282 (@value{GDBP}) strace -m ust/bar33
11285 Static tracepoints accept an extra collect action --- @code{collect
11286 $_sdata}. This collects arbitrary user data passed in the probe point
11287 call to the tracing library. In the UST example above, you'll see
11288 that the third argument to @code{trace_mark} is a printf-like format
11289 string. The user data is then the result of running that formating
11290 string against the following arguments. Note that @code{info
11291 static-tracepoint-markers} command output lists that format string in
11292 the @samp{Data:} field.
11294 You can inspect this data when analyzing the trace buffer, by printing
11295 the $_sdata variable like any other variable available to
11296 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11299 @cindex last tracepoint number
11300 @cindex recent tracepoint number
11301 @cindex tracepoint number
11302 The convenience variable @code{$tpnum} records the tracepoint number
11303 of the most recently set tracepoint.
11305 @kindex delete tracepoint
11306 @cindex tracepoint deletion
11307 @item delete tracepoint @r{[}@var{num}@r{]}
11308 Permanently delete one or more tracepoints. With no argument, the
11309 default is to delete all tracepoints. Note that the regular
11310 @code{delete} command can remove tracepoints also.
11315 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11317 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11321 You can abbreviate this command as @code{del tr}.
11324 @node Enable and Disable Tracepoints
11325 @subsection Enable and Disable Tracepoints
11327 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11330 @kindex disable tracepoint
11331 @item disable tracepoint @r{[}@var{num}@r{]}
11332 Disable tracepoint @var{num}, or all tracepoints if no argument
11333 @var{num} is given. A disabled tracepoint will have no effect during
11334 a trace experiment, but it is not forgotten. You can re-enable
11335 a disabled tracepoint using the @code{enable tracepoint} command.
11336 If the command is issued during a trace experiment and the debug target
11337 has support for disabling tracepoints during a trace experiment, then the
11338 change will be effective immediately. Otherwise, it will be applied to the
11339 next trace experiment.
11341 @kindex enable tracepoint
11342 @item enable tracepoint @r{[}@var{num}@r{]}
11343 Enable tracepoint @var{num}, or all tracepoints. If this command is
11344 issued during a trace experiment and the debug target supports enabling
11345 tracepoints during a trace experiment, then the enabled tracepoints will
11346 become effective immediately. Otherwise, they will become effective the
11347 next time a trace experiment is run.
11350 @node Tracepoint Passcounts
11351 @subsection Tracepoint Passcounts
11355 @cindex tracepoint pass count
11356 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11357 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11358 automatically stop a trace experiment. If a tracepoint's passcount is
11359 @var{n}, then the trace experiment will be automatically stopped on
11360 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11361 @var{num} is not specified, the @code{passcount} command sets the
11362 passcount of the most recently defined tracepoint. If no passcount is
11363 given, the trace experiment will run until stopped explicitly by the
11369 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11370 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11372 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11373 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11374 (@value{GDBP}) @b{trace foo}
11375 (@value{GDBP}) @b{pass 3}
11376 (@value{GDBP}) @b{trace bar}
11377 (@value{GDBP}) @b{pass 2}
11378 (@value{GDBP}) @b{trace baz}
11379 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11380 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11381 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11382 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11386 @node Tracepoint Conditions
11387 @subsection Tracepoint Conditions
11388 @cindex conditional tracepoints
11389 @cindex tracepoint conditions
11391 The simplest sort of tracepoint collects data every time your program
11392 reaches a specified place. You can also specify a @dfn{condition} for
11393 a tracepoint. A condition is just a Boolean expression in your
11394 programming language (@pxref{Expressions, ,Expressions}). A
11395 tracepoint with a condition evaluates the expression each time your
11396 program reaches it, and data collection happens only if the condition
11399 Tracepoint conditions can be specified when a tracepoint is set, by
11400 using @samp{if} in the arguments to the @code{trace} command.
11401 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11402 also be set or changed at any time with the @code{condition} command,
11403 just as with breakpoints.
11405 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11406 the conditional expression itself. Instead, @value{GDBN} encodes the
11407 expression into an agent expression (@pxref{Agent Expressions})
11408 suitable for execution on the target, independently of @value{GDBN}.
11409 Global variables become raw memory locations, locals become stack
11410 accesses, and so forth.
11412 For instance, suppose you have a function that is usually called
11413 frequently, but should not be called after an error has occurred. You
11414 could use the following tracepoint command to collect data about calls
11415 of that function that happen while the error code is propagating
11416 through the program; an unconditional tracepoint could end up
11417 collecting thousands of useless trace frames that you would have to
11421 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11424 @node Trace State Variables
11425 @subsection Trace State Variables
11426 @cindex trace state variables
11428 A @dfn{trace state variable} is a special type of variable that is
11429 created and managed by target-side code. The syntax is the same as
11430 that for GDB's convenience variables (a string prefixed with ``$''),
11431 but they are stored on the target. They must be created explicitly,
11432 using a @code{tvariable} command. They are always 64-bit signed
11435 Trace state variables are remembered by @value{GDBN}, and downloaded
11436 to the target along with tracepoint information when the trace
11437 experiment starts. There are no intrinsic limits on the number of
11438 trace state variables, beyond memory limitations of the target.
11440 @cindex convenience variables, and trace state variables
11441 Although trace state variables are managed by the target, you can use
11442 them in print commands and expressions as if they were convenience
11443 variables; @value{GDBN} will get the current value from the target
11444 while the trace experiment is running. Trace state variables share
11445 the same namespace as other ``$'' variables, which means that you
11446 cannot have trace state variables with names like @code{$23} or
11447 @code{$pc}, nor can you have a trace state variable and a convenience
11448 variable with the same name.
11452 @item tvariable $@var{name} [ = @var{expression} ]
11454 The @code{tvariable} command creates a new trace state variable named
11455 @code{$@var{name}}, and optionally gives it an initial value of
11456 @var{expression}. @var{expression} is evaluated when this command is
11457 entered; the result will be converted to an integer if possible,
11458 otherwise @value{GDBN} will report an error. A subsequent
11459 @code{tvariable} command specifying the same name does not create a
11460 variable, but instead assigns the supplied initial value to the
11461 existing variable of that name, overwriting any previous initial
11462 value. The default initial value is 0.
11464 @item info tvariables
11465 @kindex info tvariables
11466 List all the trace state variables along with their initial values.
11467 Their current values may also be displayed, if the trace experiment is
11470 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11471 @kindex delete tvariable
11472 Delete the given trace state variables, or all of them if no arguments
11477 @node Tracepoint Actions
11478 @subsection Tracepoint Action Lists
11482 @cindex tracepoint actions
11483 @item actions @r{[}@var{num}@r{]}
11484 This command will prompt for a list of actions to be taken when the
11485 tracepoint is hit. If the tracepoint number @var{num} is not
11486 specified, this command sets the actions for the one that was most
11487 recently defined (so that you can define a tracepoint and then say
11488 @code{actions} without bothering about its number). You specify the
11489 actions themselves on the following lines, one action at a time, and
11490 terminate the actions list with a line containing just @code{end}. So
11491 far, the only defined actions are @code{collect}, @code{teval}, and
11492 @code{while-stepping}.
11494 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11495 Commands, ,Breakpoint Command Lists}), except that only the defined
11496 actions are allowed; any other @value{GDBN} command is rejected.
11498 @cindex remove actions from a tracepoint
11499 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11500 and follow it immediately with @samp{end}.
11503 (@value{GDBP}) @b{collect @var{data}} // collect some data
11505 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11507 (@value{GDBP}) @b{end} // signals the end of actions.
11510 In the following example, the action list begins with @code{collect}
11511 commands indicating the things to be collected when the tracepoint is
11512 hit. Then, in order to single-step and collect additional data
11513 following the tracepoint, a @code{while-stepping} command is used,
11514 followed by the list of things to be collected after each step in a
11515 sequence of single steps. The @code{while-stepping} command is
11516 terminated by its own separate @code{end} command. Lastly, the action
11517 list is terminated by an @code{end} command.
11520 (@value{GDBP}) @b{trace foo}
11521 (@value{GDBP}) @b{actions}
11522 Enter actions for tracepoint 1, one per line:
11525 > while-stepping 12
11526 > collect $pc, arr[i]
11531 @kindex collect @r{(tracepoints)}
11532 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11533 Collect values of the given expressions when the tracepoint is hit.
11534 This command accepts a comma-separated list of any valid expressions.
11535 In addition to global, static, or local variables, the following
11536 special arguments are supported:
11540 Collect all registers.
11543 Collect all function arguments.
11546 Collect all local variables.
11549 Collect the return address. This is helpful if you want to see more
11553 Collects the number of arguments from the static probe at which the
11554 tracepoint is located.
11555 @xref{Static Probe Points}.
11557 @item $_probe_arg@var{n}
11558 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11559 from the static probe at which the tracepoint is located.
11560 @xref{Static Probe Points}.
11563 @vindex $_sdata@r{, collect}
11564 Collect static tracepoint marker specific data. Only available for
11565 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11566 Lists}. On the UST static tracepoints library backend, an
11567 instrumentation point resembles a @code{printf} function call. The
11568 tracing library is able to collect user specified data formatted to a
11569 character string using the format provided by the programmer that
11570 instrumented the program. Other backends have similar mechanisms.
11571 Here's an example of a UST marker call:
11574 const char master_name[] = "$your_name";
11575 trace_mark(channel1, marker1, "hello %s", master_name)
11578 In this case, collecting @code{$_sdata} collects the string
11579 @samp{hello $yourname}. When analyzing the trace buffer, you can
11580 inspect @samp{$_sdata} like any other variable available to
11584 You can give several consecutive @code{collect} commands, each one
11585 with a single argument, or one @code{collect} command with several
11586 arguments separated by commas; the effect is the same.
11588 The optional @var{mods} changes the usual handling of the arguments.
11589 @code{s} requests that pointers to chars be handled as strings, in
11590 particular collecting the contents of the memory being pointed at, up
11591 to the first zero. The upper bound is by default the value of the
11592 @code{print elements} variable; if @code{s} is followed by a decimal
11593 number, that is the upper bound instead. So for instance
11594 @samp{collect/s25 mystr} collects as many as 25 characters at
11597 The command @code{info scope} (@pxref{Symbols, info scope}) is
11598 particularly useful for figuring out what data to collect.
11600 @kindex teval @r{(tracepoints)}
11601 @item teval @var{expr1}, @var{expr2}, @dots{}
11602 Evaluate the given expressions when the tracepoint is hit. This
11603 command accepts a comma-separated list of expressions. The results
11604 are discarded, so this is mainly useful for assigning values to trace
11605 state variables (@pxref{Trace State Variables}) without adding those
11606 values to the trace buffer, as would be the case if the @code{collect}
11609 @kindex while-stepping @r{(tracepoints)}
11610 @item while-stepping @var{n}
11611 Perform @var{n} single-step instruction traces after the tracepoint,
11612 collecting new data after each step. The @code{while-stepping}
11613 command is followed by the list of what to collect while stepping
11614 (followed by its own @code{end} command):
11617 > while-stepping 12
11618 > collect $regs, myglobal
11624 Note that @code{$pc} is not automatically collected by
11625 @code{while-stepping}; you need to explicitly collect that register if
11626 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11629 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11630 @kindex set default-collect
11631 @cindex default collection action
11632 This variable is a list of expressions to collect at each tracepoint
11633 hit. It is effectively an additional @code{collect} action prepended
11634 to every tracepoint action list. The expressions are parsed
11635 individually for each tracepoint, so for instance a variable named
11636 @code{xyz} may be interpreted as a global for one tracepoint, and a
11637 local for another, as appropriate to the tracepoint's location.
11639 @item show default-collect
11640 @kindex show default-collect
11641 Show the list of expressions that are collected by default at each
11646 @node Listing Tracepoints
11647 @subsection Listing Tracepoints
11650 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11651 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11652 @cindex information about tracepoints
11653 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11654 Display information about the tracepoint @var{num}. If you don't
11655 specify a tracepoint number, displays information about all the
11656 tracepoints defined so far. The format is similar to that used for
11657 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11658 command, simply restricting itself to tracepoints.
11660 A tracepoint's listing may include additional information specific to
11665 its passcount as given by the @code{passcount @var{n}} command
11668 the state about installed on target of each location
11672 (@value{GDBP}) @b{info trace}
11673 Num Type Disp Enb Address What
11674 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11676 collect globfoo, $regs
11681 2 tracepoint keep y <MULTIPLE>
11683 2.1 y 0x0804859c in func4 at change-loc.h:35
11684 installed on target
11685 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11686 installed on target
11687 2.3 y <PENDING> set_tracepoint
11688 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11689 not installed on target
11694 This command can be abbreviated @code{info tp}.
11697 @node Listing Static Tracepoint Markers
11698 @subsection Listing Static Tracepoint Markers
11701 @kindex info static-tracepoint-markers
11702 @cindex information about static tracepoint markers
11703 @item info static-tracepoint-markers
11704 Display information about all static tracepoint markers defined in the
11707 For each marker, the following columns are printed:
11711 An incrementing counter, output to help readability. This is not a
11714 The marker ID, as reported by the target.
11715 @item Enabled or Disabled
11716 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11717 that are not enabled.
11719 Where the marker is in your program, as a memory address.
11721 Where the marker is in the source for your program, as a file and line
11722 number. If the debug information included in the program does not
11723 allow @value{GDBN} to locate the source of the marker, this column
11724 will be left blank.
11728 In addition, the following information may be printed for each marker:
11732 User data passed to the tracing library by the marker call. In the
11733 UST backend, this is the format string passed as argument to the
11735 @item Static tracepoints probing the marker
11736 The list of static tracepoints attached to the marker.
11740 (@value{GDBP}) info static-tracepoint-markers
11741 Cnt ID Enb Address What
11742 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11743 Data: number1 %d number2 %d
11744 Probed by static tracepoints: #2
11745 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11751 @node Starting and Stopping Trace Experiments
11752 @subsection Starting and Stopping Trace Experiments
11755 @kindex tstart [ @var{notes} ]
11756 @cindex start a new trace experiment
11757 @cindex collected data discarded
11759 This command starts the trace experiment, and begins collecting data.
11760 It has the side effect of discarding all the data collected in the
11761 trace buffer during the previous trace experiment. If any arguments
11762 are supplied, they are taken as a note and stored with the trace
11763 experiment's state. The notes may be arbitrary text, and are
11764 especially useful with disconnected tracing in a multi-user context;
11765 the notes can explain what the trace is doing, supply user contact
11766 information, and so forth.
11768 @kindex tstop [ @var{notes} ]
11769 @cindex stop a running trace experiment
11771 This command stops the trace experiment. If any arguments are
11772 supplied, they are recorded with the experiment as a note. This is
11773 useful if you are stopping a trace started by someone else, for
11774 instance if the trace is interfering with the system's behavior and
11775 needs to be stopped quickly.
11777 @strong{Note}: a trace experiment and data collection may stop
11778 automatically if any tracepoint's passcount is reached
11779 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11782 @cindex status of trace data collection
11783 @cindex trace experiment, status of
11785 This command displays the status of the current trace data
11789 Here is an example of the commands we described so far:
11792 (@value{GDBP}) @b{trace gdb_c_test}
11793 (@value{GDBP}) @b{actions}
11794 Enter actions for tracepoint #1, one per line.
11795 > collect $regs,$locals,$args
11796 > while-stepping 11
11800 (@value{GDBP}) @b{tstart}
11801 [time passes @dots{}]
11802 (@value{GDBP}) @b{tstop}
11805 @anchor{disconnected tracing}
11806 @cindex disconnected tracing
11807 You can choose to continue running the trace experiment even if
11808 @value{GDBN} disconnects from the target, voluntarily or
11809 involuntarily. For commands such as @code{detach}, the debugger will
11810 ask what you want to do with the trace. But for unexpected
11811 terminations (@value{GDBN} crash, network outage), it would be
11812 unfortunate to lose hard-won trace data, so the variable
11813 @code{disconnected-tracing} lets you decide whether the trace should
11814 continue running without @value{GDBN}.
11817 @item set disconnected-tracing on
11818 @itemx set disconnected-tracing off
11819 @kindex set disconnected-tracing
11820 Choose whether a tracing run should continue to run if @value{GDBN}
11821 has disconnected from the target. Note that @code{detach} or
11822 @code{quit} will ask you directly what to do about a running trace no
11823 matter what this variable's setting, so the variable is mainly useful
11824 for handling unexpected situations, such as loss of the network.
11826 @item show disconnected-tracing
11827 @kindex show disconnected-tracing
11828 Show the current choice for disconnected tracing.
11832 When you reconnect to the target, the trace experiment may or may not
11833 still be running; it might have filled the trace buffer in the
11834 meantime, or stopped for one of the other reasons. If it is running,
11835 it will continue after reconnection.
11837 Upon reconnection, the target will upload information about the
11838 tracepoints in effect. @value{GDBN} will then compare that
11839 information to the set of tracepoints currently defined, and attempt
11840 to match them up, allowing for the possibility that the numbers may
11841 have changed due to creation and deletion in the meantime. If one of
11842 the target's tracepoints does not match any in @value{GDBN}, the
11843 debugger will create a new tracepoint, so that you have a number with
11844 which to specify that tracepoint. This matching-up process is
11845 necessarily heuristic, and it may result in useless tracepoints being
11846 created; you may simply delete them if they are of no use.
11848 @cindex circular trace buffer
11849 If your target agent supports a @dfn{circular trace buffer}, then you
11850 can run a trace experiment indefinitely without filling the trace
11851 buffer; when space runs out, the agent deletes already-collected trace
11852 frames, oldest first, until there is enough room to continue
11853 collecting. This is especially useful if your tracepoints are being
11854 hit too often, and your trace gets terminated prematurely because the
11855 buffer is full. To ask for a circular trace buffer, simply set
11856 @samp{circular-trace-buffer} to on. You can set this at any time,
11857 including during tracing; if the agent can do it, it will change
11858 buffer handling on the fly, otherwise it will not take effect until
11862 @item set circular-trace-buffer on
11863 @itemx set circular-trace-buffer off
11864 @kindex set circular-trace-buffer
11865 Choose whether a tracing run should use a linear or circular buffer
11866 for trace data. A linear buffer will not lose any trace data, but may
11867 fill up prematurely, while a circular buffer will discard old trace
11868 data, but it will have always room for the latest tracepoint hits.
11870 @item show circular-trace-buffer
11871 @kindex show circular-trace-buffer
11872 Show the current choice for the trace buffer. Note that this may not
11873 match the agent's current buffer handling, nor is it guaranteed to
11874 match the setting that might have been in effect during a past run,
11875 for instance if you are looking at frames from a trace file.
11880 @item set trace-buffer-size @var{n}
11881 @itemx set trace-buffer-size unlimited
11882 @kindex set trace-buffer-size
11883 Request that the target use a trace buffer of @var{n} bytes. Not all
11884 targets will honor the request; they may have a compiled-in size for
11885 the trace buffer, or some other limitation. Set to a value of
11886 @code{unlimited} or @code{-1} to let the target use whatever size it
11887 likes. This is also the default.
11889 @item show trace-buffer-size
11890 @kindex show trace-buffer-size
11891 Show the current requested size for the trace buffer. Note that this
11892 will only match the actual size if the target supports size-setting,
11893 and was able to handle the requested size. For instance, if the
11894 target can only change buffer size between runs, this variable will
11895 not reflect the change until the next run starts. Use @code{tstatus}
11896 to get a report of the actual buffer size.
11900 @item set trace-user @var{text}
11901 @kindex set trace-user
11903 @item show trace-user
11904 @kindex show trace-user
11906 @item set trace-notes @var{text}
11907 @kindex set trace-notes
11908 Set the trace run's notes.
11910 @item show trace-notes
11911 @kindex show trace-notes
11912 Show the trace run's notes.
11914 @item set trace-stop-notes @var{text}
11915 @kindex set trace-stop-notes
11916 Set the trace run's stop notes. The handling of the note is as for
11917 @code{tstop} arguments; the set command is convenient way to fix a
11918 stop note that is mistaken or incomplete.
11920 @item show trace-stop-notes
11921 @kindex show trace-stop-notes
11922 Show the trace run's stop notes.
11926 @node Tracepoint Restrictions
11927 @subsection Tracepoint Restrictions
11929 @cindex tracepoint restrictions
11930 There are a number of restrictions on the use of tracepoints. As
11931 described above, tracepoint data gathering occurs on the target
11932 without interaction from @value{GDBN}. Thus the full capabilities of
11933 the debugger are not available during data gathering, and then at data
11934 examination time, you will be limited by only having what was
11935 collected. The following items describe some common problems, but it
11936 is not exhaustive, and you may run into additional difficulties not
11942 Tracepoint expressions are intended to gather objects (lvalues). Thus
11943 the full flexibility of GDB's expression evaluator is not available.
11944 You cannot call functions, cast objects to aggregate types, access
11945 convenience variables or modify values (except by assignment to trace
11946 state variables). Some language features may implicitly call
11947 functions (for instance Objective-C fields with accessors), and therefore
11948 cannot be collected either.
11951 Collection of local variables, either individually or in bulk with
11952 @code{$locals} or @code{$args}, during @code{while-stepping} may
11953 behave erratically. The stepping action may enter a new scope (for
11954 instance by stepping into a function), or the location of the variable
11955 may change (for instance it is loaded into a register). The
11956 tracepoint data recorded uses the location information for the
11957 variables that is correct for the tracepoint location. When the
11958 tracepoint is created, it is not possible, in general, to determine
11959 where the steps of a @code{while-stepping} sequence will advance the
11960 program---particularly if a conditional branch is stepped.
11963 Collection of an incompletely-initialized or partially-destroyed object
11964 may result in something that @value{GDBN} cannot display, or displays
11965 in a misleading way.
11968 When @value{GDBN} displays a pointer to character it automatically
11969 dereferences the pointer to also display characters of the string
11970 being pointed to. However, collecting the pointer during tracing does
11971 not automatically collect the string. You need to explicitly
11972 dereference the pointer and provide size information if you want to
11973 collect not only the pointer, but the memory pointed to. For example,
11974 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11978 It is not possible to collect a complete stack backtrace at a
11979 tracepoint. Instead, you may collect the registers and a few hundred
11980 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11981 (adjust to use the name of the actual stack pointer register on your
11982 target architecture, and the amount of stack you wish to capture).
11983 Then the @code{backtrace} command will show a partial backtrace when
11984 using a trace frame. The number of stack frames that can be examined
11985 depends on the sizes of the frames in the collected stack. Note that
11986 if you ask for a block so large that it goes past the bottom of the
11987 stack, the target agent may report an error trying to read from an
11991 If you do not collect registers at a tracepoint, @value{GDBN} can
11992 infer that the value of @code{$pc} must be the same as the address of
11993 the tracepoint and use that when you are looking at a trace frame
11994 for that tracepoint. However, this cannot work if the tracepoint has
11995 multiple locations (for instance if it was set in a function that was
11996 inlined), or if it has a @code{while-stepping} loop. In those cases
11997 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12002 @node Analyze Collected Data
12003 @section Using the Collected Data
12005 After the tracepoint experiment ends, you use @value{GDBN} commands
12006 for examining the trace data. The basic idea is that each tracepoint
12007 collects a trace @dfn{snapshot} every time it is hit and another
12008 snapshot every time it single-steps. All these snapshots are
12009 consecutively numbered from zero and go into a buffer, and you can
12010 examine them later. The way you examine them is to @dfn{focus} on a
12011 specific trace snapshot. When the remote stub is focused on a trace
12012 snapshot, it will respond to all @value{GDBN} requests for memory and
12013 registers by reading from the buffer which belongs to that snapshot,
12014 rather than from @emph{real} memory or registers of the program being
12015 debugged. This means that @strong{all} @value{GDBN} commands
12016 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12017 behave as if we were currently debugging the program state as it was
12018 when the tracepoint occurred. Any requests for data that are not in
12019 the buffer will fail.
12022 * tfind:: How to select a trace snapshot
12023 * tdump:: How to display all data for a snapshot
12024 * save tracepoints:: How to save tracepoints for a future run
12028 @subsection @code{tfind @var{n}}
12031 @cindex select trace snapshot
12032 @cindex find trace snapshot
12033 The basic command for selecting a trace snapshot from the buffer is
12034 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12035 counting from zero. If no argument @var{n} is given, the next
12036 snapshot is selected.
12038 Here are the various forms of using the @code{tfind} command.
12042 Find the first snapshot in the buffer. This is a synonym for
12043 @code{tfind 0} (since 0 is the number of the first snapshot).
12046 Stop debugging trace snapshots, resume @emph{live} debugging.
12049 Same as @samp{tfind none}.
12052 No argument means find the next trace snapshot.
12055 Find the previous trace snapshot before the current one. This permits
12056 retracing earlier steps.
12058 @item tfind tracepoint @var{num}
12059 Find the next snapshot associated with tracepoint @var{num}. Search
12060 proceeds forward from the last examined trace snapshot. If no
12061 argument @var{num} is given, it means find the next snapshot collected
12062 for the same tracepoint as the current snapshot.
12064 @item tfind pc @var{addr}
12065 Find the next snapshot associated with the value @var{addr} of the
12066 program counter. Search proceeds forward from the last examined trace
12067 snapshot. If no argument @var{addr} is given, it means find the next
12068 snapshot with the same value of PC as the current snapshot.
12070 @item tfind outside @var{addr1}, @var{addr2}
12071 Find the next snapshot whose PC is outside the given range of
12072 addresses (exclusive).
12074 @item tfind range @var{addr1}, @var{addr2}
12075 Find the next snapshot whose PC is between @var{addr1} and
12076 @var{addr2} (inclusive).
12078 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12079 Find the next snapshot associated with the source line @var{n}. If
12080 the optional argument @var{file} is given, refer to line @var{n} in
12081 that source file. Search proceeds forward from the last examined
12082 trace snapshot. If no argument @var{n} is given, it means find the
12083 next line other than the one currently being examined; thus saying
12084 @code{tfind line} repeatedly can appear to have the same effect as
12085 stepping from line to line in a @emph{live} debugging session.
12088 The default arguments for the @code{tfind} commands are specifically
12089 designed to make it easy to scan through the trace buffer. For
12090 instance, @code{tfind} with no argument selects the next trace
12091 snapshot, and @code{tfind -} with no argument selects the previous
12092 trace snapshot. So, by giving one @code{tfind} command, and then
12093 simply hitting @key{RET} repeatedly you can examine all the trace
12094 snapshots in order. Or, by saying @code{tfind -} and then hitting
12095 @key{RET} repeatedly you can examine the snapshots in reverse order.
12096 The @code{tfind line} command with no argument selects the snapshot
12097 for the next source line executed. The @code{tfind pc} command with
12098 no argument selects the next snapshot with the same program counter
12099 (PC) as the current frame. The @code{tfind tracepoint} command with
12100 no argument selects the next trace snapshot collected by the same
12101 tracepoint as the current one.
12103 In addition to letting you scan through the trace buffer manually,
12104 these commands make it easy to construct @value{GDBN} scripts that
12105 scan through the trace buffer and print out whatever collected data
12106 you are interested in. Thus, if we want to examine the PC, FP, and SP
12107 registers from each trace frame in the buffer, we can say this:
12110 (@value{GDBP}) @b{tfind start}
12111 (@value{GDBP}) @b{while ($trace_frame != -1)}
12112 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12113 $trace_frame, $pc, $sp, $fp
12117 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12118 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12119 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12120 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12121 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12122 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12123 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12124 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12125 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12126 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12127 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12130 Or, if we want to examine the variable @code{X} at each source line in
12134 (@value{GDBP}) @b{tfind start}
12135 (@value{GDBP}) @b{while ($trace_frame != -1)}
12136 > printf "Frame %d, X == %d\n", $trace_frame, X
12146 @subsection @code{tdump}
12148 @cindex dump all data collected at tracepoint
12149 @cindex tracepoint data, display
12151 This command takes no arguments. It prints all the data collected at
12152 the current trace snapshot.
12155 (@value{GDBP}) @b{trace 444}
12156 (@value{GDBP}) @b{actions}
12157 Enter actions for tracepoint #2, one per line:
12158 > collect $regs, $locals, $args, gdb_long_test
12161 (@value{GDBP}) @b{tstart}
12163 (@value{GDBP}) @b{tfind line 444}
12164 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12166 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12168 (@value{GDBP}) @b{tdump}
12169 Data collected at tracepoint 2, trace frame 1:
12170 d0 0xc4aa0085 -995491707
12174 d4 0x71aea3d 119204413
12177 d7 0x380035 3670069
12178 a0 0x19e24a 1696330
12179 a1 0x3000668 50333288
12181 a3 0x322000 3284992
12182 a4 0x3000698 50333336
12183 a5 0x1ad3cc 1758156
12184 fp 0x30bf3c 0x30bf3c
12185 sp 0x30bf34 0x30bf34
12187 pc 0x20b2c8 0x20b2c8
12191 p = 0x20e5b4 "gdb-test"
12198 gdb_long_test = 17 '\021'
12203 @code{tdump} works by scanning the tracepoint's current collection
12204 actions and printing the value of each expression listed. So
12205 @code{tdump} can fail, if after a run, you change the tracepoint's
12206 actions to mention variables that were not collected during the run.
12208 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12209 uses the collected value of @code{$pc} to distinguish between trace
12210 frames that were collected at the tracepoint hit, and frames that were
12211 collected while stepping. This allows it to correctly choose whether
12212 to display the basic list of collections, or the collections from the
12213 body of the while-stepping loop. However, if @code{$pc} was not collected,
12214 then @code{tdump} will always attempt to dump using the basic collection
12215 list, and may fail if a while-stepping frame does not include all the
12216 same data that is collected at the tracepoint hit.
12217 @c This is getting pretty arcane, example would be good.
12219 @node save tracepoints
12220 @subsection @code{save tracepoints @var{filename}}
12221 @kindex save tracepoints
12222 @kindex save-tracepoints
12223 @cindex save tracepoints for future sessions
12225 This command saves all current tracepoint definitions together with
12226 their actions and passcounts, into a file @file{@var{filename}}
12227 suitable for use in a later debugging session. To read the saved
12228 tracepoint definitions, use the @code{source} command (@pxref{Command
12229 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12230 alias for @w{@code{save tracepoints}}
12232 @node Tracepoint Variables
12233 @section Convenience Variables for Tracepoints
12234 @cindex tracepoint variables
12235 @cindex convenience variables for tracepoints
12238 @vindex $trace_frame
12239 @item (int) $trace_frame
12240 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12241 snapshot is selected.
12243 @vindex $tracepoint
12244 @item (int) $tracepoint
12245 The tracepoint for the current trace snapshot.
12247 @vindex $trace_line
12248 @item (int) $trace_line
12249 The line number for the current trace snapshot.
12251 @vindex $trace_file
12252 @item (char []) $trace_file
12253 The source file for the current trace snapshot.
12255 @vindex $trace_func
12256 @item (char []) $trace_func
12257 The name of the function containing @code{$tracepoint}.
12260 Note: @code{$trace_file} is not suitable for use in @code{printf},
12261 use @code{output} instead.
12263 Here's a simple example of using these convenience variables for
12264 stepping through all the trace snapshots and printing some of their
12265 data. Note that these are not the same as trace state variables,
12266 which are managed by the target.
12269 (@value{GDBP}) @b{tfind start}
12271 (@value{GDBP}) @b{while $trace_frame != -1}
12272 > output $trace_file
12273 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12279 @section Using Trace Files
12280 @cindex trace files
12282 In some situations, the target running a trace experiment may no
12283 longer be available; perhaps it crashed, or the hardware was needed
12284 for a different activity. To handle these cases, you can arrange to
12285 dump the trace data into a file, and later use that file as a source
12286 of trace data, via the @code{target tfile} command.
12291 @item tsave [ -r ] @var{filename}
12292 @itemx tsave [-ctf] @var{dirname}
12293 Save the trace data to @var{filename}. By default, this command
12294 assumes that @var{filename} refers to the host filesystem, so if
12295 necessary @value{GDBN} will copy raw trace data up from the target and
12296 then save it. If the target supports it, you can also supply the
12297 optional argument @code{-r} (``remote'') to direct the target to save
12298 the data directly into @var{filename} in its own filesystem, which may be
12299 more efficient if the trace buffer is very large. (Note, however, that
12300 @code{target tfile} can only read from files accessible to the host.)
12301 By default, this command will save trace frame in tfile format.
12302 You can supply the optional argument @code{-ctf} to save date in CTF
12303 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12304 that can be shared by multiple debugging and tracing tools. Please go to
12305 @indicateurl{http://www.efficios.com/ctf} to get more information.
12307 @kindex target tfile
12311 @item target tfile @var{filename}
12312 @itemx target ctf @var{dirname}
12313 Use the file named @var{filename} or directory named @var{dirname} as
12314 a source of trace data. Commands that examine data work as they do with
12315 a live target, but it is not possible to run any new trace experiments.
12316 @code{tstatus} will report the state of the trace run at the moment
12317 the data was saved, as well as the current trace frame you are examining.
12318 @var{filename} or @var{dirname} must be on a filesystem accessible to
12322 (@value{GDBP}) target ctf ctf.ctf
12323 (@value{GDBP}) tfind
12324 Found trace frame 0, tracepoint 2
12325 39 ++a; /* set tracepoint 1 here */
12326 (@value{GDBP}) tdump
12327 Data collected at tracepoint 2, trace frame 0:
12331 c = @{"123", "456", "789", "123", "456", "789"@}
12332 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12340 @chapter Debugging Programs That Use Overlays
12343 If your program is too large to fit completely in your target system's
12344 memory, you can sometimes use @dfn{overlays} to work around this
12345 problem. @value{GDBN} provides some support for debugging programs that
12349 * How Overlays Work:: A general explanation of overlays.
12350 * Overlay Commands:: Managing overlays in @value{GDBN}.
12351 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12352 mapped by asking the inferior.
12353 * Overlay Sample Program:: A sample program using overlays.
12356 @node How Overlays Work
12357 @section How Overlays Work
12358 @cindex mapped overlays
12359 @cindex unmapped overlays
12360 @cindex load address, overlay's
12361 @cindex mapped address
12362 @cindex overlay area
12364 Suppose you have a computer whose instruction address space is only 64
12365 kilobytes long, but which has much more memory which can be accessed by
12366 other means: special instructions, segment registers, or memory
12367 management hardware, for example. Suppose further that you want to
12368 adapt a program which is larger than 64 kilobytes to run on this system.
12370 One solution is to identify modules of your program which are relatively
12371 independent, and need not call each other directly; call these modules
12372 @dfn{overlays}. Separate the overlays from the main program, and place
12373 their machine code in the larger memory. Place your main program in
12374 instruction memory, but leave at least enough space there to hold the
12375 largest overlay as well.
12377 Now, to call a function located in an overlay, you must first copy that
12378 overlay's machine code from the large memory into the space set aside
12379 for it in the instruction memory, and then jump to its entry point
12382 @c NB: In the below the mapped area's size is greater or equal to the
12383 @c size of all overlays. This is intentional to remind the developer
12384 @c that overlays don't necessarily need to be the same size.
12388 Data Instruction Larger
12389 Address Space Address Space Address Space
12390 +-----------+ +-----------+ +-----------+
12392 +-----------+ +-----------+ +-----------+<-- overlay 1
12393 | program | | main | .----| overlay 1 | load address
12394 | variables | | program | | +-----------+
12395 | and heap | | | | | |
12396 +-----------+ | | | +-----------+<-- overlay 2
12397 | | +-----------+ | | | load address
12398 +-----------+ | | | .-| overlay 2 |
12400 mapped --->+-----------+ | | +-----------+
12401 address | | | | | |
12402 | overlay | <-' | | |
12403 | area | <---' +-----------+<-- overlay 3
12404 | | <---. | | load address
12405 +-----------+ `--| overlay 3 |
12412 @anchor{A code overlay}A code overlay
12416 The diagram (@pxref{A code overlay}) shows a system with separate data
12417 and instruction address spaces. To map an overlay, the program copies
12418 its code from the larger address space to the instruction address space.
12419 Since the overlays shown here all use the same mapped address, only one
12420 may be mapped at a time. For a system with a single address space for
12421 data and instructions, the diagram would be similar, except that the
12422 program variables and heap would share an address space with the main
12423 program and the overlay area.
12425 An overlay loaded into instruction memory and ready for use is called a
12426 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12427 instruction memory. An overlay not present (or only partially present)
12428 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12429 is its address in the larger memory. The mapped address is also called
12430 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12431 called the @dfn{load memory address}, or @dfn{LMA}.
12433 Unfortunately, overlays are not a completely transparent way to adapt a
12434 program to limited instruction memory. They introduce a new set of
12435 global constraints you must keep in mind as you design your program:
12440 Before calling or returning to a function in an overlay, your program
12441 must make sure that overlay is actually mapped. Otherwise, the call or
12442 return will transfer control to the right address, but in the wrong
12443 overlay, and your program will probably crash.
12446 If the process of mapping an overlay is expensive on your system, you
12447 will need to choose your overlays carefully to minimize their effect on
12448 your program's performance.
12451 The executable file you load onto your system must contain each
12452 overlay's instructions, appearing at the overlay's load address, not its
12453 mapped address. However, each overlay's instructions must be relocated
12454 and its symbols defined as if the overlay were at its mapped address.
12455 You can use GNU linker scripts to specify different load and relocation
12456 addresses for pieces of your program; see @ref{Overlay Description,,,
12457 ld.info, Using ld: the GNU linker}.
12460 The procedure for loading executable files onto your system must be able
12461 to load their contents into the larger address space as well as the
12462 instruction and data spaces.
12466 The overlay system described above is rather simple, and could be
12467 improved in many ways:
12472 If your system has suitable bank switch registers or memory management
12473 hardware, you could use those facilities to make an overlay's load area
12474 contents simply appear at their mapped address in instruction space.
12475 This would probably be faster than copying the overlay to its mapped
12476 area in the usual way.
12479 If your overlays are small enough, you could set aside more than one
12480 overlay area, and have more than one overlay mapped at a time.
12483 You can use overlays to manage data, as well as instructions. In
12484 general, data overlays are even less transparent to your design than
12485 code overlays: whereas code overlays only require care when you call or
12486 return to functions, data overlays require care every time you access
12487 the data. Also, if you change the contents of a data overlay, you
12488 must copy its contents back out to its load address before you can copy a
12489 different data overlay into the same mapped area.
12494 @node Overlay Commands
12495 @section Overlay Commands
12497 To use @value{GDBN}'s overlay support, each overlay in your program must
12498 correspond to a separate section of the executable file. The section's
12499 virtual memory address and load memory address must be the overlay's
12500 mapped and load addresses. Identifying overlays with sections allows
12501 @value{GDBN} to determine the appropriate address of a function or
12502 variable, depending on whether the overlay is mapped or not.
12504 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12505 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12510 Disable @value{GDBN}'s overlay support. When overlay support is
12511 disabled, @value{GDBN} assumes that all functions and variables are
12512 always present at their mapped addresses. By default, @value{GDBN}'s
12513 overlay support is disabled.
12515 @item overlay manual
12516 @cindex manual overlay debugging
12517 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12518 relies on you to tell it which overlays are mapped, and which are not,
12519 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12520 commands described below.
12522 @item overlay map-overlay @var{overlay}
12523 @itemx overlay map @var{overlay}
12524 @cindex map an overlay
12525 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12526 be the name of the object file section containing the overlay. When an
12527 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12528 functions and variables at their mapped addresses. @value{GDBN} assumes
12529 that any other overlays whose mapped ranges overlap that of
12530 @var{overlay} are now unmapped.
12532 @item overlay unmap-overlay @var{overlay}
12533 @itemx overlay unmap @var{overlay}
12534 @cindex unmap an overlay
12535 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12536 must be the name of the object file section containing the overlay.
12537 When an overlay is unmapped, @value{GDBN} assumes it can find the
12538 overlay's functions and variables at their load addresses.
12541 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12542 consults a data structure the overlay manager maintains in the inferior
12543 to see which overlays are mapped. For details, see @ref{Automatic
12544 Overlay Debugging}.
12546 @item overlay load-target
12547 @itemx overlay load
12548 @cindex reloading the overlay table
12549 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12550 re-reads the table @value{GDBN} automatically each time the inferior
12551 stops, so this command should only be necessary if you have changed the
12552 overlay mapping yourself using @value{GDBN}. This command is only
12553 useful when using automatic overlay debugging.
12555 @item overlay list-overlays
12556 @itemx overlay list
12557 @cindex listing mapped overlays
12558 Display a list of the overlays currently mapped, along with their mapped
12559 addresses, load addresses, and sizes.
12563 Normally, when @value{GDBN} prints a code address, it includes the name
12564 of the function the address falls in:
12567 (@value{GDBP}) print main
12568 $3 = @{int ()@} 0x11a0 <main>
12571 When overlay debugging is enabled, @value{GDBN} recognizes code in
12572 unmapped overlays, and prints the names of unmapped functions with
12573 asterisks around them. For example, if @code{foo} is a function in an
12574 unmapped overlay, @value{GDBN} prints it this way:
12577 (@value{GDBP}) overlay list
12578 No sections are mapped.
12579 (@value{GDBP}) print foo
12580 $5 = @{int (int)@} 0x100000 <*foo*>
12583 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12587 (@value{GDBP}) overlay list
12588 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12589 mapped at 0x1016 - 0x104a
12590 (@value{GDBP}) print foo
12591 $6 = @{int (int)@} 0x1016 <foo>
12594 When overlay debugging is enabled, @value{GDBN} can find the correct
12595 address for functions and variables in an overlay, whether or not the
12596 overlay is mapped. This allows most @value{GDBN} commands, like
12597 @code{break} and @code{disassemble}, to work normally, even on unmapped
12598 code. However, @value{GDBN}'s breakpoint support has some limitations:
12602 @cindex breakpoints in overlays
12603 @cindex overlays, setting breakpoints in
12604 You can set breakpoints in functions in unmapped overlays, as long as
12605 @value{GDBN} can write to the overlay at its load address.
12607 @value{GDBN} can not set hardware or simulator-based breakpoints in
12608 unmapped overlays. However, if you set a breakpoint at the end of your
12609 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12610 you are using manual overlay management), @value{GDBN} will re-set its
12611 breakpoints properly.
12615 @node Automatic Overlay Debugging
12616 @section Automatic Overlay Debugging
12617 @cindex automatic overlay debugging
12619 @value{GDBN} can automatically track which overlays are mapped and which
12620 are not, given some simple co-operation from the overlay manager in the
12621 inferior. If you enable automatic overlay debugging with the
12622 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12623 looks in the inferior's memory for certain variables describing the
12624 current state of the overlays.
12626 Here are the variables your overlay manager must define to support
12627 @value{GDBN}'s automatic overlay debugging:
12631 @item @code{_ovly_table}:
12632 This variable must be an array of the following structures:
12637 /* The overlay's mapped address. */
12640 /* The size of the overlay, in bytes. */
12641 unsigned long size;
12643 /* The overlay's load address. */
12646 /* Non-zero if the overlay is currently mapped;
12648 unsigned long mapped;
12652 @item @code{_novlys}:
12653 This variable must be a four-byte signed integer, holding the total
12654 number of elements in @code{_ovly_table}.
12658 To decide whether a particular overlay is mapped or not, @value{GDBN}
12659 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12660 @code{lma} members equal the VMA and LMA of the overlay's section in the
12661 executable file. When @value{GDBN} finds a matching entry, it consults
12662 the entry's @code{mapped} member to determine whether the overlay is
12665 In addition, your overlay manager may define a function called
12666 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12667 will silently set a breakpoint there. If the overlay manager then
12668 calls this function whenever it has changed the overlay table, this
12669 will enable @value{GDBN} to accurately keep track of which overlays
12670 are in program memory, and update any breakpoints that may be set
12671 in overlays. This will allow breakpoints to work even if the
12672 overlays are kept in ROM or other non-writable memory while they
12673 are not being executed.
12675 @node Overlay Sample Program
12676 @section Overlay Sample Program
12677 @cindex overlay example program
12679 When linking a program which uses overlays, you must place the overlays
12680 at their load addresses, while relocating them to run at their mapped
12681 addresses. To do this, you must write a linker script (@pxref{Overlay
12682 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12683 since linker scripts are specific to a particular host system, target
12684 architecture, and target memory layout, this manual cannot provide
12685 portable sample code demonstrating @value{GDBN}'s overlay support.
12687 However, the @value{GDBN} source distribution does contain an overlaid
12688 program, with linker scripts for a few systems, as part of its test
12689 suite. The program consists of the following files from
12690 @file{gdb/testsuite/gdb.base}:
12694 The main program file.
12696 A simple overlay manager, used by @file{overlays.c}.
12701 Overlay modules, loaded and used by @file{overlays.c}.
12704 Linker scripts for linking the test program on the @code{d10v-elf}
12705 and @code{m32r-elf} targets.
12708 You can build the test program using the @code{d10v-elf} GCC
12709 cross-compiler like this:
12712 $ d10v-elf-gcc -g -c overlays.c
12713 $ d10v-elf-gcc -g -c ovlymgr.c
12714 $ d10v-elf-gcc -g -c foo.c
12715 $ d10v-elf-gcc -g -c bar.c
12716 $ d10v-elf-gcc -g -c baz.c
12717 $ d10v-elf-gcc -g -c grbx.c
12718 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12719 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12722 The build process is identical for any other architecture, except that
12723 you must substitute the appropriate compiler and linker script for the
12724 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12728 @chapter Using @value{GDBN} with Different Languages
12731 Although programming languages generally have common aspects, they are
12732 rarely expressed in the same manner. For instance, in ANSI C,
12733 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12734 Modula-2, it is accomplished by @code{p^}. Values can also be
12735 represented (and displayed) differently. Hex numbers in C appear as
12736 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12738 @cindex working language
12739 Language-specific information is built into @value{GDBN} for some languages,
12740 allowing you to express operations like the above in your program's
12741 native language, and allowing @value{GDBN} to output values in a manner
12742 consistent with the syntax of your program's native language. The
12743 language you use to build expressions is called the @dfn{working
12747 * Setting:: Switching between source languages
12748 * Show:: Displaying the language
12749 * Checks:: Type and range checks
12750 * Supported Languages:: Supported languages
12751 * Unsupported Languages:: Unsupported languages
12755 @section Switching Between Source Languages
12757 There are two ways to control the working language---either have @value{GDBN}
12758 set it automatically, or select it manually yourself. You can use the
12759 @code{set language} command for either purpose. On startup, @value{GDBN}
12760 defaults to setting the language automatically. The working language is
12761 used to determine how expressions you type are interpreted, how values
12764 In addition to the working language, every source file that
12765 @value{GDBN} knows about has its own working language. For some object
12766 file formats, the compiler might indicate which language a particular
12767 source file is in. However, most of the time @value{GDBN} infers the
12768 language from the name of the file. The language of a source file
12769 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12770 show each frame appropriately for its own language. There is no way to
12771 set the language of a source file from within @value{GDBN}, but you can
12772 set the language associated with a filename extension. @xref{Show, ,
12773 Displaying the Language}.
12775 This is most commonly a problem when you use a program, such
12776 as @code{cfront} or @code{f2c}, that generates C but is written in
12777 another language. In that case, make the
12778 program use @code{#line} directives in its C output; that way
12779 @value{GDBN} will know the correct language of the source code of the original
12780 program, and will display that source code, not the generated C code.
12783 * Filenames:: Filename extensions and languages.
12784 * Manually:: Setting the working language manually
12785 * Automatically:: Having @value{GDBN} infer the source language
12789 @subsection List of Filename Extensions and Languages
12791 If a source file name ends in one of the following extensions, then
12792 @value{GDBN} infers that its language is the one indicated.
12810 C@t{++} source file
12816 Objective-C source file
12820 Fortran source file
12823 Modula-2 source file
12827 Assembler source file. This actually behaves almost like C, but
12828 @value{GDBN} does not skip over function prologues when stepping.
12831 In addition, you may set the language associated with a filename
12832 extension. @xref{Show, , Displaying the Language}.
12835 @subsection Setting the Working Language
12837 If you allow @value{GDBN} to set the language automatically,
12838 expressions are interpreted the same way in your debugging session and
12841 @kindex set language
12842 If you wish, you may set the language manually. To do this, issue the
12843 command @samp{set language @var{lang}}, where @var{lang} is the name of
12844 a language, such as
12845 @code{c} or @code{modula-2}.
12846 For a list of the supported languages, type @samp{set language}.
12848 Setting the language manually prevents @value{GDBN} from updating the working
12849 language automatically. This can lead to confusion if you try
12850 to debug a program when the working language is not the same as the
12851 source language, when an expression is acceptable to both
12852 languages---but means different things. For instance, if the current
12853 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12861 might not have the effect you intended. In C, this means to add
12862 @code{b} and @code{c} and place the result in @code{a}. The result
12863 printed would be the value of @code{a}. In Modula-2, this means to compare
12864 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12866 @node Automatically
12867 @subsection Having @value{GDBN} Infer the Source Language
12869 To have @value{GDBN} set the working language automatically, use
12870 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12871 then infers the working language. That is, when your program stops in a
12872 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12873 working language to the language recorded for the function in that
12874 frame. If the language for a frame is unknown (that is, if the function
12875 or block corresponding to the frame was defined in a source file that
12876 does not have a recognized extension), the current working language is
12877 not changed, and @value{GDBN} issues a warning.
12879 This may not seem necessary for most programs, which are written
12880 entirely in one source language. However, program modules and libraries
12881 written in one source language can be used by a main program written in
12882 a different source language. Using @samp{set language auto} in this
12883 case frees you from having to set the working language manually.
12886 @section Displaying the Language
12888 The following commands help you find out which language is the
12889 working language, and also what language source files were written in.
12892 @item show language
12893 @kindex show language
12894 Display the current working language. This is the
12895 language you can use with commands such as @code{print} to
12896 build and compute expressions that may involve variables in your program.
12899 @kindex info frame@r{, show the source language}
12900 Display the source language for this frame. This language becomes the
12901 working language if you use an identifier from this frame.
12902 @xref{Frame Info, ,Information about a Frame}, to identify the other
12903 information listed here.
12906 @kindex info source@r{, show the source language}
12907 Display the source language of this source file.
12908 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12909 information listed here.
12912 In unusual circumstances, you may have source files with extensions
12913 not in the standard list. You can then set the extension associated
12914 with a language explicitly:
12917 @item set extension-language @var{ext} @var{language}
12918 @kindex set extension-language
12919 Tell @value{GDBN} that source files with extension @var{ext} are to be
12920 assumed as written in the source language @var{language}.
12922 @item info extensions
12923 @kindex info extensions
12924 List all the filename extensions and the associated languages.
12928 @section Type and Range Checking
12930 Some languages are designed to guard you against making seemingly common
12931 errors through a series of compile- and run-time checks. These include
12932 checking the type of arguments to functions and operators and making
12933 sure mathematical overflows are caught at run time. Checks such as
12934 these help to ensure a program's correctness once it has been compiled
12935 by eliminating type mismatches and providing active checks for range
12936 errors when your program is running.
12938 By default @value{GDBN} checks for these errors according to the
12939 rules of the current source language. Although @value{GDBN} does not check
12940 the statements in your program, it can check expressions entered directly
12941 into @value{GDBN} for evaluation via the @code{print} command, for example.
12944 * Type Checking:: An overview of type checking
12945 * Range Checking:: An overview of range checking
12948 @cindex type checking
12949 @cindex checks, type
12950 @node Type Checking
12951 @subsection An Overview of Type Checking
12953 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12954 arguments to operators and functions have to be of the correct type,
12955 otherwise an error occurs. These checks prevent type mismatch
12956 errors from ever causing any run-time problems. For example,
12959 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12961 (@value{GDBP}) print obj.my_method (0)
12964 (@value{GDBP}) print obj.my_method (0x1234)
12965 Cannot resolve method klass::my_method to any overloaded instance
12968 The second example fails because in C@t{++} the integer constant
12969 @samp{0x1234} is not type-compatible with the pointer parameter type.
12971 For the expressions you use in @value{GDBN} commands, you can tell
12972 @value{GDBN} to not enforce strict type checking or
12973 to treat any mismatches as errors and abandon the expression;
12974 When type checking is disabled, @value{GDBN} successfully evaluates
12975 expressions like the second example above.
12977 Even if type checking is off, there may be other reasons
12978 related to type that prevent @value{GDBN} from evaluating an expression.
12979 For instance, @value{GDBN} does not know how to add an @code{int} and
12980 a @code{struct foo}. These particular type errors have nothing to do
12981 with the language in use and usually arise from expressions which make
12982 little sense to evaluate anyway.
12984 @value{GDBN} provides some additional commands for controlling type checking:
12986 @kindex set check type
12987 @kindex show check type
12989 @item set check type on
12990 @itemx set check type off
12991 Set strict type checking on or off. If any type mismatches occur in
12992 evaluating an expression while type checking is on, @value{GDBN} prints a
12993 message and aborts evaluation of the expression.
12995 @item show check type
12996 Show the current setting of type checking and whether @value{GDBN}
12997 is enforcing strict type checking rules.
13000 @cindex range checking
13001 @cindex checks, range
13002 @node Range Checking
13003 @subsection An Overview of Range Checking
13005 In some languages (such as Modula-2), it is an error to exceed the
13006 bounds of a type; this is enforced with run-time checks. Such range
13007 checking is meant to ensure program correctness by making sure
13008 computations do not overflow, or indices on an array element access do
13009 not exceed the bounds of the array.
13011 For expressions you use in @value{GDBN} commands, you can tell
13012 @value{GDBN} to treat range errors in one of three ways: ignore them,
13013 always treat them as errors and abandon the expression, or issue
13014 warnings but evaluate the expression anyway.
13016 A range error can result from numerical overflow, from exceeding an
13017 array index bound, or when you type a constant that is not a member
13018 of any type. Some languages, however, do not treat overflows as an
13019 error. In many implementations of C, mathematical overflow causes the
13020 result to ``wrap around'' to lower values---for example, if @var{m} is
13021 the largest integer value, and @var{s} is the smallest, then
13024 @var{m} + 1 @result{} @var{s}
13027 This, too, is specific to individual languages, and in some cases
13028 specific to individual compilers or machines. @xref{Supported Languages, ,
13029 Supported Languages}, for further details on specific languages.
13031 @value{GDBN} provides some additional commands for controlling the range checker:
13033 @kindex set check range
13034 @kindex show check range
13036 @item set check range auto
13037 Set range checking on or off based on the current working language.
13038 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13041 @item set check range on
13042 @itemx set check range off
13043 Set range checking on or off, overriding the default setting for the
13044 current working language. A warning is issued if the setting does not
13045 match the language default. If a range error occurs and range checking is on,
13046 then a message is printed and evaluation of the expression is aborted.
13048 @item set check range warn
13049 Output messages when the @value{GDBN} range checker detects a range error,
13050 but attempt to evaluate the expression anyway. Evaluating the
13051 expression may still be impossible for other reasons, such as accessing
13052 memory that the process does not own (a typical example from many Unix
13056 Show the current setting of the range checker, and whether or not it is
13057 being set automatically by @value{GDBN}.
13060 @node Supported Languages
13061 @section Supported Languages
13063 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13064 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13065 @c This is false ...
13066 Some @value{GDBN} features may be used in expressions regardless of the
13067 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13068 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13069 ,Expressions}) can be used with the constructs of any supported
13072 The following sections detail to what degree each source language is
13073 supported by @value{GDBN}. These sections are not meant to be language
13074 tutorials or references, but serve only as a reference guide to what the
13075 @value{GDBN} expression parser accepts, and what input and output
13076 formats should look like for different languages. There are many good
13077 books written on each of these languages; please look to these for a
13078 language reference or tutorial.
13081 * C:: C and C@t{++}
13084 * Objective-C:: Objective-C
13085 * OpenCL C:: OpenCL C
13086 * Fortran:: Fortran
13088 * Modula-2:: Modula-2
13093 @subsection C and C@t{++}
13095 @cindex C and C@t{++}
13096 @cindex expressions in C or C@t{++}
13098 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13099 to both languages. Whenever this is the case, we discuss those languages
13103 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13104 @cindex @sc{gnu} C@t{++}
13105 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13106 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13107 effectively, you must compile your C@t{++} programs with a supported
13108 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13109 compiler (@code{aCC}).
13112 * C Operators:: C and C@t{++} operators
13113 * C Constants:: C and C@t{++} constants
13114 * C Plus Plus Expressions:: C@t{++} expressions
13115 * C Defaults:: Default settings for C and C@t{++}
13116 * C Checks:: C and C@t{++} type and range checks
13117 * Debugging C:: @value{GDBN} and C
13118 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13119 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13123 @subsubsection C and C@t{++} Operators
13125 @cindex C and C@t{++} operators
13127 Operators must be defined on values of specific types. For instance,
13128 @code{+} is defined on numbers, but not on structures. Operators are
13129 often defined on groups of types.
13131 For the purposes of C and C@t{++}, the following definitions hold:
13136 @emph{Integral types} include @code{int} with any of its storage-class
13137 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13140 @emph{Floating-point types} include @code{float}, @code{double}, and
13141 @code{long double} (if supported by the target platform).
13144 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13147 @emph{Scalar types} include all of the above.
13152 The following operators are supported. They are listed here
13153 in order of increasing precedence:
13157 The comma or sequencing operator. Expressions in a comma-separated list
13158 are evaluated from left to right, with the result of the entire
13159 expression being the last expression evaluated.
13162 Assignment. The value of an assignment expression is the value
13163 assigned. Defined on scalar types.
13166 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13167 and translated to @w{@code{@var{a} = @var{a op b}}}.
13168 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13169 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13170 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13173 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13174 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13178 Logical @sc{or}. Defined on integral types.
13181 Logical @sc{and}. Defined on integral types.
13184 Bitwise @sc{or}. Defined on integral types.
13187 Bitwise exclusive-@sc{or}. Defined on integral types.
13190 Bitwise @sc{and}. Defined on integral types.
13193 Equality and inequality. Defined on scalar types. The value of these
13194 expressions is 0 for false and non-zero for true.
13196 @item <@r{, }>@r{, }<=@r{, }>=
13197 Less than, greater than, less than or equal, greater than or equal.
13198 Defined on scalar types. The value of these expressions is 0 for false
13199 and non-zero for true.
13202 left shift, and right shift. Defined on integral types.
13205 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13208 Addition and subtraction. Defined on integral types, floating-point types and
13211 @item *@r{, }/@r{, }%
13212 Multiplication, division, and modulus. Multiplication and division are
13213 defined on integral and floating-point types. Modulus is defined on
13217 Increment and decrement. When appearing before a variable, the
13218 operation is performed before the variable is used in an expression;
13219 when appearing after it, the variable's value is used before the
13220 operation takes place.
13223 Pointer dereferencing. Defined on pointer types. Same precedence as
13227 Address operator. Defined on variables. Same precedence as @code{++}.
13229 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13230 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13231 to examine the address
13232 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13236 Negative. Defined on integral and floating-point types. Same
13237 precedence as @code{++}.
13240 Logical negation. Defined on integral types. Same precedence as
13244 Bitwise complement operator. Defined on integral types. Same precedence as
13249 Structure member, and pointer-to-structure member. For convenience,
13250 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13251 pointer based on the stored type information.
13252 Defined on @code{struct} and @code{union} data.
13255 Dereferences of pointers to members.
13258 Array indexing. @code{@var{a}[@var{i}]} is defined as
13259 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13262 Function parameter list. Same precedence as @code{->}.
13265 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13266 and @code{class} types.
13269 Doubled colons also represent the @value{GDBN} scope operator
13270 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13274 If an operator is redefined in the user code, @value{GDBN} usually
13275 attempts to invoke the redefined version instead of using the operator's
13276 predefined meaning.
13279 @subsubsection C and C@t{++} Constants
13281 @cindex C and C@t{++} constants
13283 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13288 Integer constants are a sequence of digits. Octal constants are
13289 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13290 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13291 @samp{l}, specifying that the constant should be treated as a
13295 Floating point constants are a sequence of digits, followed by a decimal
13296 point, followed by a sequence of digits, and optionally followed by an
13297 exponent. An exponent is of the form:
13298 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13299 sequence of digits. The @samp{+} is optional for positive exponents.
13300 A floating-point constant may also end with a letter @samp{f} or
13301 @samp{F}, specifying that the constant should be treated as being of
13302 the @code{float} (as opposed to the default @code{double}) type; or with
13303 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13307 Enumerated constants consist of enumerated identifiers, or their
13308 integral equivalents.
13311 Character constants are a single character surrounded by single quotes
13312 (@code{'}), or a number---the ordinal value of the corresponding character
13313 (usually its @sc{ascii} value). Within quotes, the single character may
13314 be represented by a letter or by @dfn{escape sequences}, which are of
13315 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13316 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13317 @samp{@var{x}} is a predefined special character---for example,
13318 @samp{\n} for newline.
13320 Wide character constants can be written by prefixing a character
13321 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13322 form of @samp{x}. The target wide character set is used when
13323 computing the value of this constant (@pxref{Character Sets}).
13326 String constants are a sequence of character constants surrounded by
13327 double quotes (@code{"}). Any valid character constant (as described
13328 above) may appear. Double quotes within the string must be preceded by
13329 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13332 Wide string constants can be written by prefixing a string constant
13333 with @samp{L}, as in C. The target wide character set is used when
13334 computing the value of this constant (@pxref{Character Sets}).
13337 Pointer constants are an integral value. You can also write pointers
13338 to constants using the C operator @samp{&}.
13341 Array constants are comma-separated lists surrounded by braces @samp{@{}
13342 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13343 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13344 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13347 @node C Plus Plus Expressions
13348 @subsubsection C@t{++} Expressions
13350 @cindex expressions in C@t{++}
13351 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13353 @cindex debugging C@t{++} programs
13354 @cindex C@t{++} compilers
13355 @cindex debug formats and C@t{++}
13356 @cindex @value{NGCC} and C@t{++}
13358 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13359 the proper compiler and the proper debug format. Currently,
13360 @value{GDBN} works best when debugging C@t{++} code that is compiled
13361 with the most recent version of @value{NGCC} possible. The DWARF
13362 debugging format is preferred; @value{NGCC} defaults to this on most
13363 popular platforms. Other compilers and/or debug formats are likely to
13364 work badly or not at all when using @value{GDBN} to debug C@t{++}
13365 code. @xref{Compilation}.
13370 @cindex member functions
13372 Member function calls are allowed; you can use expressions like
13375 count = aml->GetOriginal(x, y)
13378 @vindex this@r{, inside C@t{++} member functions}
13379 @cindex namespace in C@t{++}
13381 While a member function is active (in the selected stack frame), your
13382 expressions have the same namespace available as the member function;
13383 that is, @value{GDBN} allows implicit references to the class instance
13384 pointer @code{this} following the same rules as C@t{++}. @code{using}
13385 declarations in the current scope are also respected by @value{GDBN}.
13387 @cindex call overloaded functions
13388 @cindex overloaded functions, calling
13389 @cindex type conversions in C@t{++}
13391 You can call overloaded functions; @value{GDBN} resolves the function
13392 call to the right definition, with some restrictions. @value{GDBN} does not
13393 perform overload resolution involving user-defined type conversions,
13394 calls to constructors, or instantiations of templates that do not exist
13395 in the program. It also cannot handle ellipsis argument lists or
13398 It does perform integral conversions and promotions, floating-point
13399 promotions, arithmetic conversions, pointer conversions, conversions of
13400 class objects to base classes, and standard conversions such as those of
13401 functions or arrays to pointers; it requires an exact match on the
13402 number of function arguments.
13404 Overload resolution is always performed, unless you have specified
13405 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13406 ,@value{GDBN} Features for C@t{++}}.
13408 You must specify @code{set overload-resolution off} in order to use an
13409 explicit function signature to call an overloaded function, as in
13411 p 'foo(char,int)'('x', 13)
13414 The @value{GDBN} command-completion facility can simplify this;
13415 see @ref{Completion, ,Command Completion}.
13417 @cindex reference declarations
13419 @value{GDBN} understands variables declared as C@t{++} references; you can use
13420 them in expressions just as you do in C@t{++} source---they are automatically
13423 In the parameter list shown when @value{GDBN} displays a frame, the values of
13424 reference variables are not displayed (unlike other variables); this
13425 avoids clutter, since references are often used for large structures.
13426 The @emph{address} of a reference variable is always shown, unless
13427 you have specified @samp{set print address off}.
13430 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13431 expressions can use it just as expressions in your program do. Since
13432 one scope may be defined in another, you can use @code{::} repeatedly if
13433 necessary, for example in an expression like
13434 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13435 resolving name scope by reference to source files, in both C and C@t{++}
13436 debugging (@pxref{Variables, ,Program Variables}).
13439 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13444 @subsubsection C and C@t{++} Defaults
13446 @cindex C and C@t{++} defaults
13448 If you allow @value{GDBN} to set range checking automatically, it
13449 defaults to @code{off} whenever the working language changes to
13450 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13451 selects the working language.
13453 If you allow @value{GDBN} to set the language automatically, it
13454 recognizes source files whose names end with @file{.c}, @file{.C}, or
13455 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13456 these files, it sets the working language to C or C@t{++}.
13457 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13458 for further details.
13461 @subsubsection C and C@t{++} Type and Range Checks
13463 @cindex C and C@t{++} checks
13465 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13466 checking is used. However, if you turn type checking off, @value{GDBN}
13467 will allow certain non-standard conversions, such as promoting integer
13468 constants to pointers.
13470 Range checking, if turned on, is done on mathematical operations. Array
13471 indices are not checked, since they are often used to index a pointer
13472 that is not itself an array.
13475 @subsubsection @value{GDBN} and C
13477 The @code{set print union} and @code{show print union} commands apply to
13478 the @code{union} type. When set to @samp{on}, any @code{union} that is
13479 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13480 appears as @samp{@{...@}}.
13482 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13483 with pointers and a memory allocation function. @xref{Expressions,
13486 @node Debugging C Plus Plus
13487 @subsubsection @value{GDBN} Features for C@t{++}
13489 @cindex commands for C@t{++}
13491 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13492 designed specifically for use with C@t{++}. Here is a summary:
13495 @cindex break in overloaded functions
13496 @item @r{breakpoint menus}
13497 When you want a breakpoint in a function whose name is overloaded,
13498 @value{GDBN} has the capability to display a menu of possible breakpoint
13499 locations to help you specify which function definition you want.
13500 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13502 @cindex overloading in C@t{++}
13503 @item rbreak @var{regex}
13504 Setting breakpoints using regular expressions is helpful for setting
13505 breakpoints on overloaded functions that are not members of any special
13507 @xref{Set Breaks, ,Setting Breakpoints}.
13509 @cindex C@t{++} exception handling
13512 Debug C@t{++} exception handling using these commands. @xref{Set
13513 Catchpoints, , Setting Catchpoints}.
13515 @cindex inheritance
13516 @item ptype @var{typename}
13517 Print inheritance relationships as well as other information for type
13519 @xref{Symbols, ,Examining the Symbol Table}.
13521 @item info vtbl @var{expression}.
13522 The @code{info vtbl} command can be used to display the virtual
13523 method tables of the object computed by @var{expression}. This shows
13524 one entry per virtual table; there may be multiple virtual tables when
13525 multiple inheritance is in use.
13527 @cindex C@t{++} symbol display
13528 @item set print demangle
13529 @itemx show print demangle
13530 @itemx set print asm-demangle
13531 @itemx show print asm-demangle
13532 Control whether C@t{++} symbols display in their source form, both when
13533 displaying code as C@t{++} source and when displaying disassemblies.
13534 @xref{Print Settings, ,Print Settings}.
13536 @item set print object
13537 @itemx show print object
13538 Choose whether to print derived (actual) or declared types of objects.
13539 @xref{Print Settings, ,Print Settings}.
13541 @item set print vtbl
13542 @itemx show print vtbl
13543 Control the format for printing virtual function tables.
13544 @xref{Print Settings, ,Print Settings}.
13545 (The @code{vtbl} commands do not work on programs compiled with the HP
13546 ANSI C@t{++} compiler (@code{aCC}).)
13548 @kindex set overload-resolution
13549 @cindex overloaded functions, overload resolution
13550 @item set overload-resolution on
13551 Enable overload resolution for C@t{++} expression evaluation. The default
13552 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13553 and searches for a function whose signature matches the argument types,
13554 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13555 Expressions, ,C@t{++} Expressions}, for details).
13556 If it cannot find a match, it emits a message.
13558 @item set overload-resolution off
13559 Disable overload resolution for C@t{++} expression evaluation. For
13560 overloaded functions that are not class member functions, @value{GDBN}
13561 chooses the first function of the specified name that it finds in the
13562 symbol table, whether or not its arguments are of the correct type. For
13563 overloaded functions that are class member functions, @value{GDBN}
13564 searches for a function whose signature @emph{exactly} matches the
13567 @kindex show overload-resolution
13568 @item show overload-resolution
13569 Show the current setting of overload resolution.
13571 @item @r{Overloaded symbol names}
13572 You can specify a particular definition of an overloaded symbol, using
13573 the same notation that is used to declare such symbols in C@t{++}: type
13574 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13575 also use the @value{GDBN} command-line word completion facilities to list the
13576 available choices, or to finish the type list for you.
13577 @xref{Completion,, Command Completion}, for details on how to do this.
13580 @node Decimal Floating Point
13581 @subsubsection Decimal Floating Point format
13582 @cindex decimal floating point format
13584 @value{GDBN} can examine, set and perform computations with numbers in
13585 decimal floating point format, which in the C language correspond to the
13586 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13587 specified by the extension to support decimal floating-point arithmetic.
13589 There are two encodings in use, depending on the architecture: BID (Binary
13590 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13591 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13594 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13595 to manipulate decimal floating point numbers, it is not possible to convert
13596 (using a cast, for example) integers wider than 32-bit to decimal float.
13598 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13599 point computations, error checking in decimal float operations ignores
13600 underflow, overflow and divide by zero exceptions.
13602 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13603 to inspect @code{_Decimal128} values stored in floating point registers.
13604 See @ref{PowerPC,,PowerPC} for more details.
13610 @value{GDBN} can be used to debug programs written in D and compiled with
13611 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13612 specific feature --- dynamic arrays.
13617 @cindex Go (programming language)
13618 @value{GDBN} can be used to debug programs written in Go and compiled with
13619 @file{gccgo} or @file{6g} compilers.
13621 Here is a summary of the Go-specific features and restrictions:
13624 @cindex current Go package
13625 @item The current Go package
13626 The name of the current package does not need to be specified when
13627 specifying global variables and functions.
13629 For example, given the program:
13633 var myglob = "Shall we?"
13639 When stopped inside @code{main} either of these work:
13643 (gdb) p main.myglob
13646 @cindex builtin Go types
13647 @item Builtin Go types
13648 The @code{string} type is recognized by @value{GDBN} and is printed
13651 @cindex builtin Go functions
13652 @item Builtin Go functions
13653 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13654 function and handles it internally.
13656 @cindex restrictions on Go expressions
13657 @item Restrictions on Go expressions
13658 All Go operators are supported except @code{&^}.
13659 The Go @code{_} ``blank identifier'' is not supported.
13660 Automatic dereferencing of pointers is not supported.
13664 @subsection Objective-C
13666 @cindex Objective-C
13667 This section provides information about some commands and command
13668 options that are useful for debugging Objective-C code. See also
13669 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13670 few more commands specific to Objective-C support.
13673 * Method Names in Commands::
13674 * The Print Command with Objective-C::
13677 @node Method Names in Commands
13678 @subsubsection Method Names in Commands
13680 The following commands have been extended to accept Objective-C method
13681 names as line specifications:
13683 @kindex clear@r{, and Objective-C}
13684 @kindex break@r{, and Objective-C}
13685 @kindex info line@r{, and Objective-C}
13686 @kindex jump@r{, and Objective-C}
13687 @kindex list@r{, and Objective-C}
13691 @item @code{info line}
13696 A fully qualified Objective-C method name is specified as
13699 -[@var{Class} @var{methodName}]
13702 where the minus sign is used to indicate an instance method and a
13703 plus sign (not shown) is used to indicate a class method. The class
13704 name @var{Class} and method name @var{methodName} are enclosed in
13705 brackets, similar to the way messages are specified in Objective-C
13706 source code. For example, to set a breakpoint at the @code{create}
13707 instance method of class @code{Fruit} in the program currently being
13711 break -[Fruit create]
13714 To list ten program lines around the @code{initialize} class method,
13718 list +[NSText initialize]
13721 In the current version of @value{GDBN}, the plus or minus sign is
13722 required. In future versions of @value{GDBN}, the plus or minus
13723 sign will be optional, but you can use it to narrow the search. It
13724 is also possible to specify just a method name:
13730 You must specify the complete method name, including any colons. If
13731 your program's source files contain more than one @code{create} method,
13732 you'll be presented with a numbered list of classes that implement that
13733 method. Indicate your choice by number, or type @samp{0} to exit if
13736 As another example, to clear a breakpoint established at the
13737 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13740 clear -[NSWindow makeKeyAndOrderFront:]
13743 @node The Print Command with Objective-C
13744 @subsubsection The Print Command With Objective-C
13745 @cindex Objective-C, print objects
13746 @kindex print-object
13747 @kindex po @r{(@code{print-object})}
13749 The print command has also been extended to accept methods. For example:
13752 print -[@var{object} hash]
13755 @cindex print an Objective-C object description
13756 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13758 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13759 and print the result. Also, an additional command has been added,
13760 @code{print-object} or @code{po} for short, which is meant to print
13761 the description of an object. However, this command may only work
13762 with certain Objective-C libraries that have a particular hook
13763 function, @code{_NSPrintForDebugger}, defined.
13766 @subsection OpenCL C
13769 This section provides information about @value{GDBN}s OpenCL C support.
13772 * OpenCL C Datatypes::
13773 * OpenCL C Expressions::
13774 * OpenCL C Operators::
13777 @node OpenCL C Datatypes
13778 @subsubsection OpenCL C Datatypes
13780 @cindex OpenCL C Datatypes
13781 @value{GDBN} supports the builtin scalar and vector datatypes specified
13782 by OpenCL 1.1. In addition the half- and double-precision floating point
13783 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13784 extensions are also known to @value{GDBN}.
13786 @node OpenCL C Expressions
13787 @subsubsection OpenCL C Expressions
13789 @cindex OpenCL C Expressions
13790 @value{GDBN} supports accesses to vector components including the access as
13791 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13792 supported by @value{GDBN} can be used as well.
13794 @node OpenCL C Operators
13795 @subsubsection OpenCL C Operators
13797 @cindex OpenCL C Operators
13798 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13802 @subsection Fortran
13803 @cindex Fortran-specific support in @value{GDBN}
13805 @value{GDBN} can be used to debug programs written in Fortran, but it
13806 currently supports only the features of Fortran 77 language.
13808 @cindex trailing underscore, in Fortran symbols
13809 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13810 among them) append an underscore to the names of variables and
13811 functions. When you debug programs compiled by those compilers, you
13812 will need to refer to variables and functions with a trailing
13816 * Fortran Operators:: Fortran operators and expressions
13817 * Fortran Defaults:: Default settings for Fortran
13818 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13821 @node Fortran Operators
13822 @subsubsection Fortran Operators and Expressions
13824 @cindex Fortran operators and expressions
13826 Operators must be defined on values of specific types. For instance,
13827 @code{+} is defined on numbers, but not on characters or other non-
13828 arithmetic types. Operators are often defined on groups of types.
13832 The exponentiation operator. It raises the first operand to the power
13836 The range operator. Normally used in the form of array(low:high) to
13837 represent a section of array.
13840 The access component operator. Normally used to access elements in derived
13841 types. Also suitable for unions. As unions aren't part of regular Fortran,
13842 this can only happen when accessing a register that uses a gdbarch-defined
13846 @node Fortran Defaults
13847 @subsubsection Fortran Defaults
13849 @cindex Fortran Defaults
13851 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13852 default uses case-insensitive matches for Fortran symbols. You can
13853 change that with the @samp{set case-insensitive} command, see
13854 @ref{Symbols}, for the details.
13856 @node Special Fortran Commands
13857 @subsubsection Special Fortran Commands
13859 @cindex Special Fortran commands
13861 @value{GDBN} has some commands to support Fortran-specific features,
13862 such as displaying common blocks.
13865 @cindex @code{COMMON} blocks, Fortran
13866 @kindex info common
13867 @item info common @r{[}@var{common-name}@r{]}
13868 This command prints the values contained in the Fortran @code{COMMON}
13869 block whose name is @var{common-name}. With no argument, the names of
13870 all @code{COMMON} blocks visible at the current program location are
13877 @cindex Pascal support in @value{GDBN}, limitations
13878 Debugging Pascal programs which use sets, subranges, file variables, or
13879 nested functions does not currently work. @value{GDBN} does not support
13880 entering expressions, printing values, or similar features using Pascal
13883 The Pascal-specific command @code{set print pascal_static-members}
13884 controls whether static members of Pascal objects are displayed.
13885 @xref{Print Settings, pascal_static-members}.
13888 @subsection Modula-2
13890 @cindex Modula-2, @value{GDBN} support
13892 The extensions made to @value{GDBN} to support Modula-2 only support
13893 output from the @sc{gnu} Modula-2 compiler (which is currently being
13894 developed). Other Modula-2 compilers are not currently supported, and
13895 attempting to debug executables produced by them is most likely
13896 to give an error as @value{GDBN} reads in the executable's symbol
13899 @cindex expressions in Modula-2
13901 * M2 Operators:: Built-in operators
13902 * Built-In Func/Proc:: Built-in functions and procedures
13903 * M2 Constants:: Modula-2 constants
13904 * M2 Types:: Modula-2 types
13905 * M2 Defaults:: Default settings for Modula-2
13906 * Deviations:: Deviations from standard Modula-2
13907 * M2 Checks:: Modula-2 type and range checks
13908 * M2 Scope:: The scope operators @code{::} and @code{.}
13909 * GDB/M2:: @value{GDBN} and Modula-2
13913 @subsubsection Operators
13914 @cindex Modula-2 operators
13916 Operators must be defined on values of specific types. For instance,
13917 @code{+} is defined on numbers, but not on structures. Operators are
13918 often defined on groups of types. For the purposes of Modula-2, the
13919 following definitions hold:
13924 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13928 @emph{Character types} consist of @code{CHAR} and its subranges.
13931 @emph{Floating-point types} consist of @code{REAL}.
13934 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13938 @emph{Scalar types} consist of all of the above.
13941 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13944 @emph{Boolean types} consist of @code{BOOLEAN}.
13948 The following operators are supported, and appear in order of
13949 increasing precedence:
13953 Function argument or array index separator.
13956 Assignment. The value of @var{var} @code{:=} @var{value} is
13960 Less than, greater than on integral, floating-point, or enumerated
13964 Less than or equal to, greater than or equal to
13965 on integral, floating-point and enumerated types, or set inclusion on
13966 set types. Same precedence as @code{<}.
13968 @item =@r{, }<>@r{, }#
13969 Equality and two ways of expressing inequality, valid on scalar types.
13970 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13971 available for inequality, since @code{#} conflicts with the script
13975 Set membership. Defined on set types and the types of their members.
13976 Same precedence as @code{<}.
13979 Boolean disjunction. Defined on boolean types.
13982 Boolean conjunction. Defined on boolean types.
13985 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13988 Addition and subtraction on integral and floating-point types, or union
13989 and difference on set types.
13992 Multiplication on integral and floating-point types, or set intersection
13996 Division on floating-point types, or symmetric set difference on set
13997 types. Same precedence as @code{*}.
14000 Integer division and remainder. Defined on integral types. Same
14001 precedence as @code{*}.
14004 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14007 Pointer dereferencing. Defined on pointer types.
14010 Boolean negation. Defined on boolean types. Same precedence as
14014 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14015 precedence as @code{^}.
14018 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14021 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14025 @value{GDBN} and Modula-2 scope operators.
14029 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14030 treats the use of the operator @code{IN}, or the use of operators
14031 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14032 @code{<=}, and @code{>=} on sets as an error.
14036 @node Built-In Func/Proc
14037 @subsubsection Built-in Functions and Procedures
14038 @cindex Modula-2 built-ins
14040 Modula-2 also makes available several built-in procedures and functions.
14041 In describing these, the following metavariables are used:
14046 represents an @code{ARRAY} variable.
14049 represents a @code{CHAR} constant or variable.
14052 represents a variable or constant of integral type.
14055 represents an identifier that belongs to a set. Generally used in the
14056 same function with the metavariable @var{s}. The type of @var{s} should
14057 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14060 represents a variable or constant of integral or floating-point type.
14063 represents a variable or constant of floating-point type.
14069 represents a variable.
14072 represents a variable or constant of one of many types. See the
14073 explanation of the function for details.
14076 All Modula-2 built-in procedures also return a result, described below.
14080 Returns the absolute value of @var{n}.
14083 If @var{c} is a lower case letter, it returns its upper case
14084 equivalent, otherwise it returns its argument.
14087 Returns the character whose ordinal value is @var{i}.
14090 Decrements the value in the variable @var{v} by one. Returns the new value.
14092 @item DEC(@var{v},@var{i})
14093 Decrements the value in the variable @var{v} by @var{i}. Returns the
14096 @item EXCL(@var{m},@var{s})
14097 Removes the element @var{m} from the set @var{s}. Returns the new
14100 @item FLOAT(@var{i})
14101 Returns the floating point equivalent of the integer @var{i}.
14103 @item HIGH(@var{a})
14104 Returns the index of the last member of @var{a}.
14107 Increments the value in the variable @var{v} by one. Returns the new value.
14109 @item INC(@var{v},@var{i})
14110 Increments the value in the variable @var{v} by @var{i}. Returns the
14113 @item INCL(@var{m},@var{s})
14114 Adds the element @var{m} to the set @var{s} if it is not already
14115 there. Returns the new set.
14118 Returns the maximum value of the type @var{t}.
14121 Returns the minimum value of the type @var{t}.
14124 Returns boolean TRUE if @var{i} is an odd number.
14127 Returns the ordinal value of its argument. For example, the ordinal
14128 value of a character is its @sc{ascii} value (on machines supporting the
14129 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14130 integral, character and enumerated types.
14132 @item SIZE(@var{x})
14133 Returns the size of its argument. @var{x} can be a variable or a type.
14135 @item TRUNC(@var{r})
14136 Returns the integral part of @var{r}.
14138 @item TSIZE(@var{x})
14139 Returns the size of its argument. @var{x} can be a variable or a type.
14141 @item VAL(@var{t},@var{i})
14142 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14146 @emph{Warning:} Sets and their operations are not yet supported, so
14147 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14151 @cindex Modula-2 constants
14153 @subsubsection Constants
14155 @value{GDBN} allows you to express the constants of Modula-2 in the following
14161 Integer constants are simply a sequence of digits. When used in an
14162 expression, a constant is interpreted to be type-compatible with the
14163 rest of the expression. Hexadecimal integers are specified by a
14164 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14167 Floating point constants appear as a sequence of digits, followed by a
14168 decimal point and another sequence of digits. An optional exponent can
14169 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14170 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14171 digits of the floating point constant must be valid decimal (base 10)
14175 Character constants consist of a single character enclosed by a pair of
14176 like quotes, either single (@code{'}) or double (@code{"}). They may
14177 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14178 followed by a @samp{C}.
14181 String constants consist of a sequence of characters enclosed by a
14182 pair of like quotes, either single (@code{'}) or double (@code{"}).
14183 Escape sequences in the style of C are also allowed. @xref{C
14184 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14188 Enumerated constants consist of an enumerated identifier.
14191 Boolean constants consist of the identifiers @code{TRUE} and
14195 Pointer constants consist of integral values only.
14198 Set constants are not yet supported.
14202 @subsubsection Modula-2 Types
14203 @cindex Modula-2 types
14205 Currently @value{GDBN} can print the following data types in Modula-2
14206 syntax: array types, record types, set types, pointer types, procedure
14207 types, enumerated types, subrange types and base types. You can also
14208 print the contents of variables declared using these type.
14209 This section gives a number of simple source code examples together with
14210 sample @value{GDBN} sessions.
14212 The first example contains the following section of code:
14221 and you can request @value{GDBN} to interrogate the type and value of
14222 @code{r} and @code{s}.
14225 (@value{GDBP}) print s
14227 (@value{GDBP}) ptype s
14229 (@value{GDBP}) print r
14231 (@value{GDBP}) ptype r
14236 Likewise if your source code declares @code{s} as:
14240 s: SET ['A'..'Z'] ;
14244 then you may query the type of @code{s} by:
14247 (@value{GDBP}) ptype s
14248 type = SET ['A'..'Z']
14252 Note that at present you cannot interactively manipulate set
14253 expressions using the debugger.
14255 The following example shows how you might declare an array in Modula-2
14256 and how you can interact with @value{GDBN} to print its type and contents:
14260 s: ARRAY [-10..10] OF CHAR ;
14264 (@value{GDBP}) ptype s
14265 ARRAY [-10..10] OF CHAR
14268 Note that the array handling is not yet complete and although the type
14269 is printed correctly, expression handling still assumes that all
14270 arrays have a lower bound of zero and not @code{-10} as in the example
14273 Here are some more type related Modula-2 examples:
14277 colour = (blue, red, yellow, green) ;
14278 t = [blue..yellow] ;
14286 The @value{GDBN} interaction shows how you can query the data type
14287 and value of a variable.
14290 (@value{GDBP}) print s
14292 (@value{GDBP}) ptype t
14293 type = [blue..yellow]
14297 In this example a Modula-2 array is declared and its contents
14298 displayed. Observe that the contents are written in the same way as
14299 their @code{C} counterparts.
14303 s: ARRAY [1..5] OF CARDINAL ;
14309 (@value{GDBP}) print s
14310 $1 = @{1, 0, 0, 0, 0@}
14311 (@value{GDBP}) ptype s
14312 type = ARRAY [1..5] OF CARDINAL
14315 The Modula-2 language interface to @value{GDBN} also understands
14316 pointer types as shown in this example:
14320 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14327 and you can request that @value{GDBN} describes the type of @code{s}.
14330 (@value{GDBP}) ptype s
14331 type = POINTER TO ARRAY [1..5] OF CARDINAL
14334 @value{GDBN} handles compound types as we can see in this example.
14335 Here we combine array types, record types, pointer types and subrange
14346 myarray = ARRAY myrange OF CARDINAL ;
14347 myrange = [-2..2] ;
14349 s: POINTER TO ARRAY myrange OF foo ;
14353 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14357 (@value{GDBP}) ptype s
14358 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14361 f3 : ARRAY [-2..2] OF CARDINAL;
14366 @subsubsection Modula-2 Defaults
14367 @cindex Modula-2 defaults
14369 If type and range checking are set automatically by @value{GDBN}, they
14370 both default to @code{on} whenever the working language changes to
14371 Modula-2. This happens regardless of whether you or @value{GDBN}
14372 selected the working language.
14374 If you allow @value{GDBN} to set the language automatically, then entering
14375 code compiled from a file whose name ends with @file{.mod} sets the
14376 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14377 Infer the Source Language}, for further details.
14380 @subsubsection Deviations from Standard Modula-2
14381 @cindex Modula-2, deviations from
14383 A few changes have been made to make Modula-2 programs easier to debug.
14384 This is done primarily via loosening its type strictness:
14388 Unlike in standard Modula-2, pointer constants can be formed by
14389 integers. This allows you to modify pointer variables during
14390 debugging. (In standard Modula-2, the actual address contained in a
14391 pointer variable is hidden from you; it can only be modified
14392 through direct assignment to another pointer variable or expression that
14393 returned a pointer.)
14396 C escape sequences can be used in strings and characters to represent
14397 non-printable characters. @value{GDBN} prints out strings with these
14398 escape sequences embedded. Single non-printable characters are
14399 printed using the @samp{CHR(@var{nnn})} format.
14402 The assignment operator (@code{:=}) returns the value of its right-hand
14406 All built-in procedures both modify @emph{and} return their argument.
14410 @subsubsection Modula-2 Type and Range Checks
14411 @cindex Modula-2 checks
14414 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14417 @c FIXME remove warning when type/range checks added
14419 @value{GDBN} considers two Modula-2 variables type equivalent if:
14423 They are of types that have been declared equivalent via a @code{TYPE
14424 @var{t1} = @var{t2}} statement
14427 They have been declared on the same line. (Note: This is true of the
14428 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14431 As long as type checking is enabled, any attempt to combine variables
14432 whose types are not equivalent is an error.
14434 Range checking is done on all mathematical operations, assignment, array
14435 index bounds, and all built-in functions and procedures.
14438 @subsubsection The Scope Operators @code{::} and @code{.}
14440 @cindex @code{.}, Modula-2 scope operator
14441 @cindex colon, doubled as scope operator
14443 @vindex colon-colon@r{, in Modula-2}
14444 @c Info cannot handle :: but TeX can.
14447 @vindex ::@r{, in Modula-2}
14450 There are a few subtle differences between the Modula-2 scope operator
14451 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14456 @var{module} . @var{id}
14457 @var{scope} :: @var{id}
14461 where @var{scope} is the name of a module or a procedure,
14462 @var{module} the name of a module, and @var{id} is any declared
14463 identifier within your program, except another module.
14465 Using the @code{::} operator makes @value{GDBN} search the scope
14466 specified by @var{scope} for the identifier @var{id}. If it is not
14467 found in the specified scope, then @value{GDBN} searches all scopes
14468 enclosing the one specified by @var{scope}.
14470 Using the @code{.} operator makes @value{GDBN} search the current scope for
14471 the identifier specified by @var{id} that was imported from the
14472 definition module specified by @var{module}. With this operator, it is
14473 an error if the identifier @var{id} was not imported from definition
14474 module @var{module}, or if @var{id} is not an identifier in
14478 @subsubsection @value{GDBN} and Modula-2
14480 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14481 Five subcommands of @code{set print} and @code{show print} apply
14482 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14483 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14484 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14485 analogue in Modula-2.
14487 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14488 with any language, is not useful with Modula-2. Its
14489 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14490 created in Modula-2 as they can in C or C@t{++}. However, because an
14491 address can be specified by an integral constant, the construct
14492 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14494 @cindex @code{#} in Modula-2
14495 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14496 interpreted as the beginning of a comment. Use @code{<>} instead.
14502 The extensions made to @value{GDBN} for Ada only support
14503 output from the @sc{gnu} Ada (GNAT) compiler.
14504 Other Ada compilers are not currently supported, and
14505 attempting to debug executables produced by them is most likely
14509 @cindex expressions in Ada
14511 * Ada Mode Intro:: General remarks on the Ada syntax
14512 and semantics supported by Ada mode
14514 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14515 * Additions to Ada:: Extensions of the Ada expression syntax.
14516 * Stopping Before Main Program:: Debugging the program during elaboration.
14517 * Ada Tasks:: Listing and setting breakpoints in tasks.
14518 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14519 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14521 * Ada Glitches:: Known peculiarities of Ada mode.
14524 @node Ada Mode Intro
14525 @subsubsection Introduction
14526 @cindex Ada mode, general
14528 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14529 syntax, with some extensions.
14530 The philosophy behind the design of this subset is
14534 That @value{GDBN} should provide basic literals and access to operations for
14535 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14536 leaving more sophisticated computations to subprograms written into the
14537 program (which therefore may be called from @value{GDBN}).
14540 That type safety and strict adherence to Ada language restrictions
14541 are not particularly important to the @value{GDBN} user.
14544 That brevity is important to the @value{GDBN} user.
14547 Thus, for brevity, the debugger acts as if all names declared in
14548 user-written packages are directly visible, even if they are not visible
14549 according to Ada rules, thus making it unnecessary to fully qualify most
14550 names with their packages, regardless of context. Where this causes
14551 ambiguity, @value{GDBN} asks the user's intent.
14553 The debugger will start in Ada mode if it detects an Ada main program.
14554 As for other languages, it will enter Ada mode when stopped in a program that
14555 was translated from an Ada source file.
14557 While in Ada mode, you may use `@t{--}' for comments. This is useful
14558 mostly for documenting command files. The standard @value{GDBN} comment
14559 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14560 middle (to allow based literals).
14562 The debugger supports limited overloading. Given a subprogram call in which
14563 the function symbol has multiple definitions, it will use the number of
14564 actual parameters and some information about their types to attempt to narrow
14565 the set of definitions. It also makes very limited use of context, preferring
14566 procedures to functions in the context of the @code{call} command, and
14567 functions to procedures elsewhere.
14569 @node Omissions from Ada
14570 @subsubsection Omissions from Ada
14571 @cindex Ada, omissions from
14573 Here are the notable omissions from the subset:
14577 Only a subset of the attributes are supported:
14581 @t{'First}, @t{'Last}, and @t{'Length}
14582 on array objects (not on types and subtypes).
14585 @t{'Min} and @t{'Max}.
14588 @t{'Pos} and @t{'Val}.
14594 @t{'Range} on array objects (not subtypes), but only as the right
14595 operand of the membership (@code{in}) operator.
14598 @t{'Access}, @t{'Unchecked_Access}, and
14599 @t{'Unrestricted_Access} (a GNAT extension).
14607 @code{Characters.Latin_1} are not available and
14608 concatenation is not implemented. Thus, escape characters in strings are
14609 not currently available.
14612 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14613 equality of representations. They will generally work correctly
14614 for strings and arrays whose elements have integer or enumeration types.
14615 They may not work correctly for arrays whose element
14616 types have user-defined equality, for arrays of real values
14617 (in particular, IEEE-conformant floating point, because of negative
14618 zeroes and NaNs), and for arrays whose elements contain unused bits with
14619 indeterminate values.
14622 The other component-by-component array operations (@code{and}, @code{or},
14623 @code{xor}, @code{not}, and relational tests other than equality)
14624 are not implemented.
14627 @cindex array aggregates (Ada)
14628 @cindex record aggregates (Ada)
14629 @cindex aggregates (Ada)
14630 There is limited support for array and record aggregates. They are
14631 permitted only on the right sides of assignments, as in these examples:
14634 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14635 (@value{GDBP}) set An_Array := (1, others => 0)
14636 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14637 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14638 (@value{GDBP}) set A_Record := (1, "Peter", True);
14639 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14643 discriminant's value by assigning an aggregate has an
14644 undefined effect if that discriminant is used within the record.
14645 However, you can first modify discriminants by directly assigning to
14646 them (which normally would not be allowed in Ada), and then performing an
14647 aggregate assignment. For example, given a variable @code{A_Rec}
14648 declared to have a type such as:
14651 type Rec (Len : Small_Integer := 0) is record
14653 Vals : IntArray (1 .. Len);
14657 you can assign a value with a different size of @code{Vals} with two
14661 (@value{GDBP}) set A_Rec.Len := 4
14662 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14665 As this example also illustrates, @value{GDBN} is very loose about the usual
14666 rules concerning aggregates. You may leave out some of the
14667 components of an array or record aggregate (such as the @code{Len}
14668 component in the assignment to @code{A_Rec} above); they will retain their
14669 original values upon assignment. You may freely use dynamic values as
14670 indices in component associations. You may even use overlapping or
14671 redundant component associations, although which component values are
14672 assigned in such cases is not defined.
14675 Calls to dispatching subprograms are not implemented.
14678 The overloading algorithm is much more limited (i.e., less selective)
14679 than that of real Ada. It makes only limited use of the context in
14680 which a subexpression appears to resolve its meaning, and it is much
14681 looser in its rules for allowing type matches. As a result, some
14682 function calls will be ambiguous, and the user will be asked to choose
14683 the proper resolution.
14686 The @code{new} operator is not implemented.
14689 Entry calls are not implemented.
14692 Aside from printing, arithmetic operations on the native VAX floating-point
14693 formats are not supported.
14696 It is not possible to slice a packed array.
14699 The names @code{True} and @code{False}, when not part of a qualified name,
14700 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14702 Should your program
14703 redefine these names in a package or procedure (at best a dubious practice),
14704 you will have to use fully qualified names to access their new definitions.
14707 @node Additions to Ada
14708 @subsubsection Additions to Ada
14709 @cindex Ada, deviations from
14711 As it does for other languages, @value{GDBN} makes certain generic
14712 extensions to Ada (@pxref{Expressions}):
14716 If the expression @var{E} is a variable residing in memory (typically
14717 a local variable or array element) and @var{N} is a positive integer,
14718 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14719 @var{N}-1 adjacent variables following it in memory as an array. In
14720 Ada, this operator is generally not necessary, since its prime use is
14721 in displaying parts of an array, and slicing will usually do this in
14722 Ada. However, there are occasional uses when debugging programs in
14723 which certain debugging information has been optimized away.
14726 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14727 appears in function or file @var{B}.'' When @var{B} is a file name,
14728 you must typically surround it in single quotes.
14731 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14732 @var{type} that appears at address @var{addr}.''
14735 A name starting with @samp{$} is a convenience variable
14736 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14739 In addition, @value{GDBN} provides a few other shortcuts and outright
14740 additions specific to Ada:
14744 The assignment statement is allowed as an expression, returning
14745 its right-hand operand as its value. Thus, you may enter
14748 (@value{GDBP}) set x := y + 3
14749 (@value{GDBP}) print A(tmp := y + 1)
14753 The semicolon is allowed as an ``operator,'' returning as its value
14754 the value of its right-hand operand.
14755 This allows, for example,
14756 complex conditional breaks:
14759 (@value{GDBP}) break f
14760 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14764 Rather than use catenation and symbolic character names to introduce special
14765 characters into strings, one may instead use a special bracket notation,
14766 which is also used to print strings. A sequence of characters of the form
14767 @samp{["@var{XX}"]} within a string or character literal denotes the
14768 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14769 sequence of characters @samp{["""]} also denotes a single quotation mark
14770 in strings. For example,
14772 "One line.["0a"]Next line.["0a"]"
14775 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14779 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14780 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14784 (@value{GDBP}) print 'max(x, y)
14788 When printing arrays, @value{GDBN} uses positional notation when the
14789 array has a lower bound of 1, and uses a modified named notation otherwise.
14790 For example, a one-dimensional array of three integers with a lower bound
14791 of 3 might print as
14798 That is, in contrast to valid Ada, only the first component has a @code{=>}
14802 You may abbreviate attributes in expressions with any unique,
14803 multi-character subsequence of
14804 their names (an exact match gets preference).
14805 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14806 in place of @t{a'length}.
14809 @cindex quoting Ada internal identifiers
14810 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14811 to lower case. The GNAT compiler uses upper-case characters for
14812 some of its internal identifiers, which are normally of no interest to users.
14813 For the rare occasions when you actually have to look at them,
14814 enclose them in angle brackets to avoid the lower-case mapping.
14817 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14821 Printing an object of class-wide type or dereferencing an
14822 access-to-class-wide value will display all the components of the object's
14823 specific type (as indicated by its run-time tag). Likewise, component
14824 selection on such a value will operate on the specific type of the
14829 @node Stopping Before Main Program
14830 @subsubsection Stopping at the Very Beginning
14832 @cindex breakpointing Ada elaboration code
14833 It is sometimes necessary to debug the program during elaboration, and
14834 before reaching the main procedure.
14835 As defined in the Ada Reference
14836 Manual, the elaboration code is invoked from a procedure called
14837 @code{adainit}. To run your program up to the beginning of
14838 elaboration, simply use the following two commands:
14839 @code{tbreak adainit} and @code{run}.
14842 @subsubsection Extensions for Ada Tasks
14843 @cindex Ada, tasking
14845 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14846 @value{GDBN} provides the following task-related commands:
14851 This command shows a list of current Ada tasks, as in the following example:
14858 (@value{GDBP}) info tasks
14859 ID TID P-ID Pri State Name
14860 1 8088000 0 15 Child Activation Wait main_task
14861 2 80a4000 1 15 Accept Statement b
14862 3 809a800 1 15 Child Activation Wait a
14863 * 4 80ae800 3 15 Runnable c
14868 In this listing, the asterisk before the last task indicates it to be the
14869 task currently being inspected.
14873 Represents @value{GDBN}'s internal task number.
14879 The parent's task ID (@value{GDBN}'s internal task number).
14882 The base priority of the task.
14885 Current state of the task.
14889 The task has been created but has not been activated. It cannot be
14893 The task is not blocked for any reason known to Ada. (It may be waiting
14894 for a mutex, though.) It is conceptually "executing" in normal mode.
14897 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14898 that were waiting on terminate alternatives have been awakened and have
14899 terminated themselves.
14901 @item Child Activation Wait
14902 The task is waiting for created tasks to complete activation.
14904 @item Accept Statement
14905 The task is waiting on an accept or selective wait statement.
14907 @item Waiting on entry call
14908 The task is waiting on an entry call.
14910 @item Async Select Wait
14911 The task is waiting to start the abortable part of an asynchronous
14915 The task is waiting on a select statement with only a delay
14918 @item Child Termination Wait
14919 The task is sleeping having completed a master within itself, and is
14920 waiting for the tasks dependent on that master to become terminated or
14921 waiting on a terminate Phase.
14923 @item Wait Child in Term Alt
14924 The task is sleeping waiting for tasks on terminate alternatives to
14925 finish terminating.
14927 @item Accepting RV with @var{taskno}
14928 The task is accepting a rendez-vous with the task @var{taskno}.
14932 Name of the task in the program.
14936 @kindex info task @var{taskno}
14937 @item info task @var{taskno}
14938 This command shows detailled informations on the specified task, as in
14939 the following example:
14944 (@value{GDBP}) info tasks
14945 ID TID P-ID Pri State Name
14946 1 8077880 0 15 Child Activation Wait main_task
14947 * 2 807c468 1 15 Runnable task_1
14948 (@value{GDBP}) info task 2
14949 Ada Task: 0x807c468
14952 Parent: 1 (main_task)
14958 @kindex task@r{ (Ada)}
14959 @cindex current Ada task ID
14960 This command prints the ID of the current task.
14966 (@value{GDBP}) info tasks
14967 ID TID P-ID Pri State Name
14968 1 8077870 0 15 Child Activation Wait main_task
14969 * 2 807c458 1 15 Runnable t
14970 (@value{GDBP}) task
14971 [Current task is 2]
14974 @item task @var{taskno}
14975 @cindex Ada task switching
14976 This command is like the @code{thread @var{threadno}}
14977 command (@pxref{Threads}). It switches the context of debugging
14978 from the current task to the given task.
14984 (@value{GDBP}) info tasks
14985 ID TID P-ID Pri State Name
14986 1 8077870 0 15 Child Activation Wait main_task
14987 * 2 807c458 1 15 Runnable t
14988 (@value{GDBP}) task 1
14989 [Switching to task 1]
14990 #0 0x8067726 in pthread_cond_wait ()
14992 #0 0x8067726 in pthread_cond_wait ()
14993 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14994 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14995 #3 0x806153e in system.tasking.stages.activate_tasks ()
14996 #4 0x804aacc in un () at un.adb:5
14999 @item break @var{linespec} task @var{taskno}
15000 @itemx break @var{linespec} task @var{taskno} if @dots{}
15001 @cindex breakpoints and tasks, in Ada
15002 @cindex task breakpoints, in Ada
15003 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15004 These commands are like the @code{break @dots{} thread @dots{}}
15005 command (@pxref{Thread Stops}).
15006 @var{linespec} specifies source lines, as described
15007 in @ref{Specify Location}.
15009 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15010 to specify that you only want @value{GDBN} to stop the program when a
15011 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15012 numeric task identifiers assigned by @value{GDBN}, shown in the first
15013 column of the @samp{info tasks} display.
15015 If you do not specify @samp{task @var{taskno}} when you set a
15016 breakpoint, the breakpoint applies to @emph{all} tasks of your
15019 You can use the @code{task} qualifier on conditional breakpoints as
15020 well; in this case, place @samp{task @var{taskno}} before the
15021 breakpoint condition (before the @code{if}).
15029 (@value{GDBP}) info tasks
15030 ID TID P-ID Pri State Name
15031 1 140022020 0 15 Child Activation Wait main_task
15032 2 140045060 1 15 Accept/Select Wait t2
15033 3 140044840 1 15 Runnable t1
15034 * 4 140056040 1 15 Runnable t3
15035 (@value{GDBP}) b 15 task 2
15036 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15037 (@value{GDBP}) cont
15042 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15044 (@value{GDBP}) info tasks
15045 ID TID P-ID Pri State Name
15046 1 140022020 0 15 Child Activation Wait main_task
15047 * 2 140045060 1 15 Runnable t2
15048 3 140044840 1 15 Runnable t1
15049 4 140056040 1 15 Delay Sleep t3
15053 @node Ada Tasks and Core Files
15054 @subsubsection Tasking Support when Debugging Core Files
15055 @cindex Ada tasking and core file debugging
15057 When inspecting a core file, as opposed to debugging a live program,
15058 tasking support may be limited or even unavailable, depending on
15059 the platform being used.
15060 For instance, on x86-linux, the list of tasks is available, but task
15061 switching is not supported. On Tru64, however, task switching will work
15064 On certain platforms, including Tru64, the debugger needs to perform some
15065 memory writes in order to provide Ada tasking support. When inspecting
15066 a core file, this means that the core file must be opened with read-write
15067 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15068 Under these circumstances, you should make a backup copy of the core
15069 file before inspecting it with @value{GDBN}.
15071 @node Ravenscar Profile
15072 @subsubsection Tasking Support when using the Ravenscar Profile
15073 @cindex Ravenscar Profile
15075 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15076 specifically designed for systems with safety-critical real-time
15080 @kindex set ravenscar task-switching on
15081 @cindex task switching with program using Ravenscar Profile
15082 @item set ravenscar task-switching on
15083 Allows task switching when debugging a program that uses the Ravenscar
15084 Profile. This is the default.
15086 @kindex set ravenscar task-switching off
15087 @item set ravenscar task-switching off
15088 Turn off task switching when debugging a program that uses the Ravenscar
15089 Profile. This is mostly intended to disable the code that adds support
15090 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15091 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15092 To be effective, this command should be run before the program is started.
15094 @kindex show ravenscar task-switching
15095 @item show ravenscar task-switching
15096 Show whether it is possible to switch from task to task in a program
15097 using the Ravenscar Profile.
15102 @subsubsection Known Peculiarities of Ada Mode
15103 @cindex Ada, problems
15105 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15106 we know of several problems with and limitations of Ada mode in
15108 some of which will be fixed with planned future releases of the debugger
15109 and the GNU Ada compiler.
15113 Static constants that the compiler chooses not to materialize as objects in
15114 storage are invisible to the debugger.
15117 Named parameter associations in function argument lists are ignored (the
15118 argument lists are treated as positional).
15121 Many useful library packages are currently invisible to the debugger.
15124 Fixed-point arithmetic, conversions, input, and output is carried out using
15125 floating-point arithmetic, and may give results that only approximate those on
15129 The GNAT compiler never generates the prefix @code{Standard} for any of
15130 the standard symbols defined by the Ada language. @value{GDBN} knows about
15131 this: it will strip the prefix from names when you use it, and will never
15132 look for a name you have so qualified among local symbols, nor match against
15133 symbols in other packages or subprograms. If you have
15134 defined entities anywhere in your program other than parameters and
15135 local variables whose simple names match names in @code{Standard},
15136 GNAT's lack of qualification here can cause confusion. When this happens,
15137 you can usually resolve the confusion
15138 by qualifying the problematic names with package
15139 @code{Standard} explicitly.
15142 Older versions of the compiler sometimes generate erroneous debugging
15143 information, resulting in the debugger incorrectly printing the value
15144 of affected entities. In some cases, the debugger is able to work
15145 around an issue automatically. In other cases, the debugger is able
15146 to work around the issue, but the work-around has to be specifically
15149 @kindex set ada trust-PAD-over-XVS
15150 @kindex show ada trust-PAD-over-XVS
15153 @item set ada trust-PAD-over-XVS on
15154 Configure GDB to strictly follow the GNAT encoding when computing the
15155 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15156 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15157 a complete description of the encoding used by the GNAT compiler).
15158 This is the default.
15160 @item set ada trust-PAD-over-XVS off
15161 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15162 sometimes prints the wrong value for certain entities, changing @code{ada
15163 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15164 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15165 @code{off}, but this incurs a slight performance penalty, so it is
15166 recommended to leave this setting to @code{on} unless necessary.
15170 @node Unsupported Languages
15171 @section Unsupported Languages
15173 @cindex unsupported languages
15174 @cindex minimal language
15175 In addition to the other fully-supported programming languages,
15176 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15177 It does not represent a real programming language, but provides a set
15178 of capabilities close to what the C or assembly languages provide.
15179 This should allow most simple operations to be performed while debugging
15180 an application that uses a language currently not supported by @value{GDBN}.
15182 If the language is set to @code{auto}, @value{GDBN} will automatically
15183 select this language if the current frame corresponds to an unsupported
15187 @chapter Examining the Symbol Table
15189 The commands described in this chapter allow you to inquire about the
15190 symbols (names of variables, functions and types) defined in your
15191 program. This information is inherent in the text of your program and
15192 does not change as your program executes. @value{GDBN} finds it in your
15193 program's symbol table, in the file indicated when you started @value{GDBN}
15194 (@pxref{File Options, ,Choosing Files}), or by one of the
15195 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15197 @cindex symbol names
15198 @cindex names of symbols
15199 @cindex quoting names
15200 Occasionally, you may need to refer to symbols that contain unusual
15201 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15202 most frequent case is in referring to static variables in other
15203 source files (@pxref{Variables,,Program Variables}). File names
15204 are recorded in object files as debugging symbols, but @value{GDBN} would
15205 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15206 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15207 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15214 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15217 @cindex case-insensitive symbol names
15218 @cindex case sensitivity in symbol names
15219 @kindex set case-sensitive
15220 @item set case-sensitive on
15221 @itemx set case-sensitive off
15222 @itemx set case-sensitive auto
15223 Normally, when @value{GDBN} looks up symbols, it matches their names
15224 with case sensitivity determined by the current source language.
15225 Occasionally, you may wish to control that. The command @code{set
15226 case-sensitive} lets you do that by specifying @code{on} for
15227 case-sensitive matches or @code{off} for case-insensitive ones. If
15228 you specify @code{auto}, case sensitivity is reset to the default
15229 suitable for the source language. The default is case-sensitive
15230 matches for all languages except for Fortran, for which the default is
15231 case-insensitive matches.
15233 @kindex show case-sensitive
15234 @item show case-sensitive
15235 This command shows the current setting of case sensitivity for symbols
15238 @kindex set print type methods
15239 @item set print type methods
15240 @itemx set print type methods on
15241 @itemx set print type methods off
15242 Normally, when @value{GDBN} prints a class, it displays any methods
15243 declared in that class. You can control this behavior either by
15244 passing the appropriate flag to @code{ptype}, or using @command{set
15245 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15246 display the methods; this is the default. Specifying @code{off} will
15247 cause @value{GDBN} to omit the methods.
15249 @kindex show print type methods
15250 @item show print type methods
15251 This command shows the current setting of method display when printing
15254 @kindex set print type typedefs
15255 @item set print type typedefs
15256 @itemx set print type typedefs on
15257 @itemx set print type typedefs off
15259 Normally, when @value{GDBN} prints a class, it displays any typedefs
15260 defined in that class. You can control this behavior either by
15261 passing the appropriate flag to @code{ptype}, or using @command{set
15262 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15263 display the typedef definitions; this is the default. Specifying
15264 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15265 Note that this controls whether the typedef definition itself is
15266 printed, not whether typedef names are substituted when printing other
15269 @kindex show print type typedefs
15270 @item show print type typedefs
15271 This command shows the current setting of typedef display when
15274 @kindex info address
15275 @cindex address of a symbol
15276 @item info address @var{symbol}
15277 Describe where the data for @var{symbol} is stored. For a register
15278 variable, this says which register it is kept in. For a non-register
15279 local variable, this prints the stack-frame offset at which the variable
15282 Note the contrast with @samp{print &@var{symbol}}, which does not work
15283 at all for a register variable, and for a stack local variable prints
15284 the exact address of the current instantiation of the variable.
15286 @kindex info symbol
15287 @cindex symbol from address
15288 @cindex closest symbol and offset for an address
15289 @item info symbol @var{addr}
15290 Print the name of a symbol which is stored at the address @var{addr}.
15291 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15292 nearest symbol and an offset from it:
15295 (@value{GDBP}) info symbol 0x54320
15296 _initialize_vx + 396 in section .text
15300 This is the opposite of the @code{info address} command. You can use
15301 it to find out the name of a variable or a function given its address.
15303 For dynamically linked executables, the name of executable or shared
15304 library containing the symbol is also printed:
15307 (@value{GDBP}) info symbol 0x400225
15308 _start + 5 in section .text of /tmp/a.out
15309 (@value{GDBP}) info symbol 0x2aaaac2811cf
15310 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15314 @item whatis[/@var{flags}] [@var{arg}]
15315 Print the data type of @var{arg}, which can be either an expression
15316 or a name of a data type. With no argument, print the data type of
15317 @code{$}, the last value in the value history.
15319 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15320 is not actually evaluated, and any side-effecting operations (such as
15321 assignments or function calls) inside it do not take place.
15323 If @var{arg} is a variable or an expression, @code{whatis} prints its
15324 literal type as it is used in the source code. If the type was
15325 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15326 the data type underlying the @code{typedef}. If the type of the
15327 variable or the expression is a compound data type, such as
15328 @code{struct} or @code{class}, @code{whatis} never prints their
15329 fields or methods. It just prints the @code{struct}/@code{class}
15330 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15331 such a compound data type, use @code{ptype}.
15333 If @var{arg} is a type name that was defined using @code{typedef},
15334 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15335 Unrolling means that @code{whatis} will show the underlying type used
15336 in the @code{typedef} declaration of @var{arg}. However, if that
15337 underlying type is also a @code{typedef}, @code{whatis} will not
15340 For C code, the type names may also have the form @samp{class
15341 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15342 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15344 @var{flags} can be used to modify how the type is displayed.
15345 Available flags are:
15349 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15350 parameters and typedefs defined in a class when printing the class'
15351 members. The @code{/r} flag disables this.
15354 Do not print methods defined in the class.
15357 Print methods defined in the class. This is the default, but the flag
15358 exists in case you change the default with @command{set print type methods}.
15361 Do not print typedefs defined in the class. Note that this controls
15362 whether the typedef definition itself is printed, not whether typedef
15363 names are substituted when printing other types.
15366 Print typedefs defined in the class. This is the default, but the flag
15367 exists in case you change the default with @command{set print type typedefs}.
15371 @item ptype[/@var{flags}] [@var{arg}]
15372 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15373 detailed description of the type, instead of just the name of the type.
15374 @xref{Expressions, ,Expressions}.
15376 Contrary to @code{whatis}, @code{ptype} always unrolls any
15377 @code{typedef}s in its argument declaration, whether the argument is
15378 a variable, expression, or a data type. This means that @code{ptype}
15379 of a variable or an expression will not print literally its type as
15380 present in the source code---use @code{whatis} for that. @code{typedef}s at
15381 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15382 fields, methods and inner @code{class typedef}s of @code{struct}s,
15383 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15385 For example, for this variable declaration:
15388 typedef double real_t;
15389 struct complex @{ real_t real; double imag; @};
15390 typedef struct complex complex_t;
15392 real_t *real_pointer_var;
15396 the two commands give this output:
15400 (@value{GDBP}) whatis var
15402 (@value{GDBP}) ptype var
15403 type = struct complex @{
15407 (@value{GDBP}) whatis complex_t
15408 type = struct complex
15409 (@value{GDBP}) whatis struct complex
15410 type = struct complex
15411 (@value{GDBP}) ptype struct complex
15412 type = struct complex @{
15416 (@value{GDBP}) whatis real_pointer_var
15418 (@value{GDBP}) ptype real_pointer_var
15424 As with @code{whatis}, using @code{ptype} without an argument refers to
15425 the type of @code{$}, the last value in the value history.
15427 @cindex incomplete type
15428 Sometimes, programs use opaque data types or incomplete specifications
15429 of complex data structure. If the debug information included in the
15430 program does not allow @value{GDBN} to display a full declaration of
15431 the data type, it will say @samp{<incomplete type>}. For example,
15432 given these declarations:
15436 struct foo *fooptr;
15440 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15443 (@value{GDBP}) ptype foo
15444 $1 = <incomplete type>
15448 ``Incomplete type'' is C terminology for data types that are not
15449 completely specified.
15452 @item info types @var{regexp}
15454 Print a brief description of all types whose names match the regular
15455 expression @var{regexp} (or all types in your program, if you supply
15456 no argument). Each complete typename is matched as though it were a
15457 complete line; thus, @samp{i type value} gives information on all
15458 types in your program whose names include the string @code{value}, but
15459 @samp{i type ^value$} gives information only on types whose complete
15460 name is @code{value}.
15462 This command differs from @code{ptype} in two ways: first, like
15463 @code{whatis}, it does not print a detailed description; second, it
15464 lists all source files where a type is defined.
15466 @kindex info type-printers
15467 @item info type-printers
15468 Versions of @value{GDBN} that ship with Python scripting enabled may
15469 have ``type printers'' available. When using @command{ptype} or
15470 @command{whatis}, these printers are consulted when the name of a type
15471 is needed. @xref{Type Printing API}, for more information on writing
15474 @code{info type-printers} displays all the available type printers.
15476 @kindex enable type-printer
15477 @kindex disable type-printer
15478 @item enable type-printer @var{name}@dots{}
15479 @item disable type-printer @var{name}@dots{}
15480 These commands can be used to enable or disable type printers.
15483 @cindex local variables
15484 @item info scope @var{location}
15485 List all the variables local to a particular scope. This command
15486 accepts a @var{location} argument---a function name, a source line, or
15487 an address preceded by a @samp{*}, and prints all the variables local
15488 to the scope defined by that location. (@xref{Specify Location}, for
15489 details about supported forms of @var{location}.) For example:
15492 (@value{GDBP}) @b{info scope command_line_handler}
15493 Scope for command_line_handler:
15494 Symbol rl is an argument at stack/frame offset 8, length 4.
15495 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15496 Symbol linelength is in static storage at address 0x150a1c, length 4.
15497 Symbol p is a local variable in register $esi, length 4.
15498 Symbol p1 is a local variable in register $ebx, length 4.
15499 Symbol nline is a local variable in register $edx, length 4.
15500 Symbol repeat is a local variable at frame offset -8, length 4.
15504 This command is especially useful for determining what data to collect
15505 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15508 @kindex info source
15510 Show information about the current source file---that is, the source file for
15511 the function containing the current point of execution:
15514 the name of the source file, and the directory containing it,
15516 the directory it was compiled in,
15518 its length, in lines,
15520 which programming language it is written in,
15522 whether the executable includes debugging information for that file, and
15523 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15525 whether the debugging information includes information about
15526 preprocessor macros.
15530 @kindex info sources
15532 Print the names of all source files in your program for which there is
15533 debugging information, organized into two lists: files whose symbols
15534 have already been read, and files whose symbols will be read when needed.
15536 @kindex info functions
15537 @item info functions
15538 Print the names and data types of all defined functions.
15540 @item info functions @var{regexp}
15541 Print the names and data types of all defined functions
15542 whose names contain a match for regular expression @var{regexp}.
15543 Thus, @samp{info fun step} finds all functions whose names
15544 include @code{step}; @samp{info fun ^step} finds those whose names
15545 start with @code{step}. If a function name contains characters
15546 that conflict with the regular expression language (e.g.@:
15547 @samp{operator*()}), they may be quoted with a backslash.
15549 @kindex info variables
15550 @item info variables
15551 Print the names and data types of all variables that are defined
15552 outside of functions (i.e.@: excluding local variables).
15554 @item info variables @var{regexp}
15555 Print the names and data types of all variables (except for local
15556 variables) whose names contain a match for regular expression
15559 @kindex info classes
15560 @cindex Objective-C, classes and selectors
15562 @itemx info classes @var{regexp}
15563 Display all Objective-C classes in your program, or
15564 (with the @var{regexp} argument) all those matching a particular regular
15567 @kindex info selectors
15568 @item info selectors
15569 @itemx info selectors @var{regexp}
15570 Display all Objective-C selectors in your program, or
15571 (with the @var{regexp} argument) all those matching a particular regular
15575 This was never implemented.
15576 @kindex info methods
15578 @itemx info methods @var{regexp}
15579 The @code{info methods} command permits the user to examine all defined
15580 methods within C@t{++} program, or (with the @var{regexp} argument) a
15581 specific set of methods found in the various C@t{++} classes. Many
15582 C@t{++} classes provide a large number of methods. Thus, the output
15583 from the @code{ptype} command can be overwhelming and hard to use. The
15584 @code{info-methods} command filters the methods, printing only those
15585 which match the regular-expression @var{regexp}.
15588 @cindex opaque data types
15589 @kindex set opaque-type-resolution
15590 @item set opaque-type-resolution on
15591 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15592 declared as a pointer to a @code{struct}, @code{class}, or
15593 @code{union}---for example, @code{struct MyType *}---that is used in one
15594 source file although the full declaration of @code{struct MyType} is in
15595 another source file. The default is on.
15597 A change in the setting of this subcommand will not take effect until
15598 the next time symbols for a file are loaded.
15600 @item set opaque-type-resolution off
15601 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15602 is printed as follows:
15604 @{<no data fields>@}
15607 @kindex show opaque-type-resolution
15608 @item show opaque-type-resolution
15609 Show whether opaque types are resolved or not.
15611 @kindex maint print symbols
15612 @cindex symbol dump
15613 @kindex maint print psymbols
15614 @cindex partial symbol dump
15615 @item maint print symbols @var{filename}
15616 @itemx maint print psymbols @var{filename}
15617 @itemx maint print msymbols @var{filename}
15618 Write a dump of debugging symbol data into the file @var{filename}.
15619 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15620 symbols with debugging data are included. If you use @samp{maint print
15621 symbols}, @value{GDBN} includes all the symbols for which it has already
15622 collected full details: that is, @var{filename} reflects symbols for
15623 only those files whose symbols @value{GDBN} has read. You can use the
15624 command @code{info sources} to find out which files these are. If you
15625 use @samp{maint print psymbols} instead, the dump shows information about
15626 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15627 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15628 @samp{maint print msymbols} dumps just the minimal symbol information
15629 required for each object file from which @value{GDBN} has read some symbols.
15630 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15631 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15633 @kindex maint info symtabs
15634 @kindex maint info psymtabs
15635 @cindex listing @value{GDBN}'s internal symbol tables
15636 @cindex symbol tables, listing @value{GDBN}'s internal
15637 @cindex full symbol tables, listing @value{GDBN}'s internal
15638 @cindex partial symbol tables, listing @value{GDBN}'s internal
15639 @item maint info symtabs @r{[} @var{regexp} @r{]}
15640 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15642 List the @code{struct symtab} or @code{struct partial_symtab}
15643 structures whose names match @var{regexp}. If @var{regexp} is not
15644 given, list them all. The output includes expressions which you can
15645 copy into a @value{GDBN} debugging this one to examine a particular
15646 structure in more detail. For example:
15649 (@value{GDBP}) maint info psymtabs dwarf2read
15650 @{ objfile /home/gnu/build/gdb/gdb
15651 ((struct objfile *) 0x82e69d0)
15652 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15653 ((struct partial_symtab *) 0x8474b10)
15656 text addresses 0x814d3c8 -- 0x8158074
15657 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15658 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15659 dependencies (none)
15662 (@value{GDBP}) maint info symtabs
15666 We see that there is one partial symbol table whose filename contains
15667 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15668 and we see that @value{GDBN} has not read in any symtabs yet at all.
15669 If we set a breakpoint on a function, that will cause @value{GDBN} to
15670 read the symtab for the compilation unit containing that function:
15673 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15674 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15676 (@value{GDBP}) maint info symtabs
15677 @{ objfile /home/gnu/build/gdb/gdb
15678 ((struct objfile *) 0x82e69d0)
15679 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15680 ((struct symtab *) 0x86c1f38)
15683 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15684 linetable ((struct linetable *) 0x8370fa0)
15685 debugformat DWARF 2
15694 @chapter Altering Execution
15696 Once you think you have found an error in your program, you might want to
15697 find out for certain whether correcting the apparent error would lead to
15698 correct results in the rest of the run. You can find the answer by
15699 experiment, using the @value{GDBN} features for altering execution of the
15702 For example, you can store new values into variables or memory
15703 locations, give your program a signal, restart it at a different
15704 address, or even return prematurely from a function.
15707 * Assignment:: Assignment to variables
15708 * Jumping:: Continuing at a different address
15709 * Signaling:: Giving your program a signal
15710 * Returning:: Returning from a function
15711 * Calling:: Calling your program's functions
15712 * Patching:: Patching your program
15716 @section Assignment to Variables
15719 @cindex setting variables
15720 To alter the value of a variable, evaluate an assignment expression.
15721 @xref{Expressions, ,Expressions}. For example,
15728 stores the value 4 into the variable @code{x}, and then prints the
15729 value of the assignment expression (which is 4).
15730 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15731 information on operators in supported languages.
15733 @kindex set variable
15734 @cindex variables, setting
15735 If you are not interested in seeing the value of the assignment, use the
15736 @code{set} command instead of the @code{print} command. @code{set} is
15737 really the same as @code{print} except that the expression's value is
15738 not printed and is not put in the value history (@pxref{Value History,
15739 ,Value History}). The expression is evaluated only for its effects.
15741 If the beginning of the argument string of the @code{set} command
15742 appears identical to a @code{set} subcommand, use the @code{set
15743 variable} command instead of just @code{set}. This command is identical
15744 to @code{set} except for its lack of subcommands. For example, if your
15745 program has a variable @code{width}, you get an error if you try to set
15746 a new value with just @samp{set width=13}, because @value{GDBN} has the
15747 command @code{set width}:
15750 (@value{GDBP}) whatis width
15752 (@value{GDBP}) p width
15754 (@value{GDBP}) set width=47
15755 Invalid syntax in expression.
15759 The invalid expression, of course, is @samp{=47}. In
15760 order to actually set the program's variable @code{width}, use
15763 (@value{GDBP}) set var width=47
15766 Because the @code{set} command has many subcommands that can conflict
15767 with the names of program variables, it is a good idea to use the
15768 @code{set variable} command instead of just @code{set}. For example, if
15769 your program has a variable @code{g}, you run into problems if you try
15770 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15771 the command @code{set gnutarget}, abbreviated @code{set g}:
15775 (@value{GDBP}) whatis g
15779 (@value{GDBP}) set g=4
15783 The program being debugged has been started already.
15784 Start it from the beginning? (y or n) y
15785 Starting program: /home/smith/cc_progs/a.out
15786 "/home/smith/cc_progs/a.out": can't open to read symbols:
15787 Invalid bfd target.
15788 (@value{GDBP}) show g
15789 The current BFD target is "=4".
15794 The program variable @code{g} did not change, and you silently set the
15795 @code{gnutarget} to an invalid value. In order to set the variable
15799 (@value{GDBP}) set var g=4
15802 @value{GDBN} allows more implicit conversions in assignments than C; you can
15803 freely store an integer value into a pointer variable or vice versa,
15804 and you can convert any structure to any other structure that is the
15805 same length or shorter.
15806 @comment FIXME: how do structs align/pad in these conversions?
15807 @comment /doc@cygnus.com 18dec1990
15809 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15810 construct to generate a value of specified type at a specified address
15811 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15812 to memory location @code{0x83040} as an integer (which implies a certain size
15813 and representation in memory), and
15816 set @{int@}0x83040 = 4
15820 stores the value 4 into that memory location.
15823 @section Continuing at a Different Address
15825 Ordinarily, when you continue your program, you do so at the place where
15826 it stopped, with the @code{continue} command. You can instead continue at
15827 an address of your own choosing, with the following commands:
15831 @kindex j @r{(@code{jump})}
15832 @item jump @var{linespec}
15833 @itemx j @var{linespec}
15834 @itemx jump @var{location}
15835 @itemx j @var{location}
15836 Resume execution at line @var{linespec} or at address given by
15837 @var{location}. Execution stops again immediately if there is a
15838 breakpoint there. @xref{Specify Location}, for a description of the
15839 different forms of @var{linespec} and @var{location}. It is common
15840 practice to use the @code{tbreak} command in conjunction with
15841 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15843 The @code{jump} command does not change the current stack frame, or
15844 the stack pointer, or the contents of any memory location or any
15845 register other than the program counter. If line @var{linespec} is in
15846 a different function from the one currently executing, the results may
15847 be bizarre if the two functions expect different patterns of arguments or
15848 of local variables. For this reason, the @code{jump} command requests
15849 confirmation if the specified line is not in the function currently
15850 executing. However, even bizarre results are predictable if you are
15851 well acquainted with the machine-language code of your program.
15854 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15855 On many systems, you can get much the same effect as the @code{jump}
15856 command by storing a new value into the register @code{$pc}. The
15857 difference is that this does not start your program running; it only
15858 changes the address of where it @emph{will} run when you continue. For
15866 makes the next @code{continue} command or stepping command execute at
15867 address @code{0x485}, rather than at the address where your program stopped.
15868 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15870 The most common occasion to use the @code{jump} command is to back
15871 up---perhaps with more breakpoints set---over a portion of a program
15872 that has already executed, in order to examine its execution in more
15877 @section Giving your Program a Signal
15878 @cindex deliver a signal to a program
15882 @item signal @var{signal}
15883 Resume execution where your program stopped, but immediately give it the
15884 signal @var{signal}. @var{signal} can be the name or the number of a
15885 signal. For example, on many systems @code{signal 2} and @code{signal
15886 SIGINT} are both ways of sending an interrupt signal.
15888 Alternatively, if @var{signal} is zero, continue execution without
15889 giving a signal. This is useful when your program stopped on account of
15890 a signal and would ordinarily see the signal when resumed with the
15891 @code{continue} command; @samp{signal 0} causes it to resume without a
15894 @code{signal} does not repeat when you press @key{RET} a second time
15895 after executing the command.
15899 Invoking the @code{signal} command is not the same as invoking the
15900 @code{kill} utility from the shell. Sending a signal with @code{kill}
15901 causes @value{GDBN} to decide what to do with the signal depending on
15902 the signal handling tables (@pxref{Signals}). The @code{signal} command
15903 passes the signal directly to your program.
15907 @section Returning from a Function
15910 @cindex returning from a function
15913 @itemx return @var{expression}
15914 You can cancel execution of a function call with the @code{return}
15915 command. If you give an
15916 @var{expression} argument, its value is used as the function's return
15920 When you use @code{return}, @value{GDBN} discards the selected stack frame
15921 (and all frames within it). You can think of this as making the
15922 discarded frame return prematurely. If you wish to specify a value to
15923 be returned, give that value as the argument to @code{return}.
15925 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15926 Frame}), and any other frames inside of it, leaving its caller as the
15927 innermost remaining frame. That frame becomes selected. The
15928 specified value is stored in the registers used for returning values
15931 The @code{return} command does not resume execution; it leaves the
15932 program stopped in the state that would exist if the function had just
15933 returned. In contrast, the @code{finish} command (@pxref{Continuing
15934 and Stepping, ,Continuing and Stepping}) resumes execution until the
15935 selected stack frame returns naturally.
15937 @value{GDBN} needs to know how the @var{expression} argument should be set for
15938 the inferior. The concrete registers assignment depends on the OS ABI and the
15939 type being returned by the selected stack frame. For example it is common for
15940 OS ABI to return floating point values in FPU registers while integer values in
15941 CPU registers. Still some ABIs return even floating point values in CPU
15942 registers. Larger integer widths (such as @code{long long int}) also have
15943 specific placement rules. @value{GDBN} already knows the OS ABI from its
15944 current target so it needs to find out also the type being returned to make the
15945 assignment into the right register(s).
15947 Normally, the selected stack frame has debug info. @value{GDBN} will always
15948 use the debug info instead of the implicit type of @var{expression} when the
15949 debug info is available. For example, if you type @kbd{return -1}, and the
15950 function in the current stack frame is declared to return a @code{long long
15951 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15952 into a @code{long long int}:
15955 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15957 (@value{GDBP}) return -1
15958 Make func return now? (y or n) y
15959 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15960 43 printf ("result=%lld\n", func ());
15964 However, if the selected stack frame does not have a debug info, e.g., if the
15965 function was compiled without debug info, @value{GDBN} has to find out the type
15966 to return from user. Specifying a different type by mistake may set the value
15967 in different inferior registers than the caller code expects. For example,
15968 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15969 of a @code{long long int} result for a debug info less function (on 32-bit
15970 architectures). Therefore the user is required to specify the return type by
15971 an appropriate cast explicitly:
15974 Breakpoint 2, 0x0040050b in func ()
15975 (@value{GDBP}) return -1
15976 Return value type not available for selected stack frame.
15977 Please use an explicit cast of the value to return.
15978 (@value{GDBP}) return (long long int) -1
15979 Make selected stack frame return now? (y or n) y
15980 #0 0x00400526 in main ()
15985 @section Calling Program Functions
15988 @cindex calling functions
15989 @cindex inferior functions, calling
15990 @item print @var{expr}
15991 Evaluate the expression @var{expr} and display the resulting value.
15992 @var{expr} may include calls to functions in the program being
15996 @item call @var{expr}
15997 Evaluate the expression @var{expr} without displaying @code{void}
16000 You can use this variant of the @code{print} command if you want to
16001 execute a function from your program that does not return anything
16002 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16003 with @code{void} returned values that @value{GDBN} will otherwise
16004 print. If the result is not void, it is printed and saved in the
16008 It is possible for the function you call via the @code{print} or
16009 @code{call} command to generate a signal (e.g., if there's a bug in
16010 the function, or if you passed it incorrect arguments). What happens
16011 in that case is controlled by the @code{set unwindonsignal} command.
16013 Similarly, with a C@t{++} program it is possible for the function you
16014 call via the @code{print} or @code{call} command to generate an
16015 exception that is not handled due to the constraints of the dummy
16016 frame. In this case, any exception that is raised in the frame, but has
16017 an out-of-frame exception handler will not be found. GDB builds a
16018 dummy-frame for the inferior function call, and the unwinder cannot
16019 seek for exception handlers outside of this dummy-frame. What happens
16020 in that case is controlled by the
16021 @code{set unwind-on-terminating-exception} command.
16024 @item set unwindonsignal
16025 @kindex set unwindonsignal
16026 @cindex unwind stack in called functions
16027 @cindex call dummy stack unwinding
16028 Set unwinding of the stack if a signal is received while in a function
16029 that @value{GDBN} called in the program being debugged. If set to on,
16030 @value{GDBN} unwinds the stack it created for the call and restores
16031 the context to what it was before the call. If set to off (the
16032 default), @value{GDBN} stops in the frame where the signal was
16035 @item show unwindonsignal
16036 @kindex show unwindonsignal
16037 Show the current setting of stack unwinding in the functions called by
16040 @item set unwind-on-terminating-exception
16041 @kindex set unwind-on-terminating-exception
16042 @cindex unwind stack in called functions with unhandled exceptions
16043 @cindex call dummy stack unwinding on unhandled exception.
16044 Set unwinding of the stack if a C@t{++} exception is raised, but left
16045 unhandled while in a function that @value{GDBN} called in the program being
16046 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16047 it created for the call and restores the context to what it was before
16048 the call. If set to off, @value{GDBN} the exception is delivered to
16049 the default C@t{++} exception handler and the inferior terminated.
16051 @item show unwind-on-terminating-exception
16052 @kindex show unwind-on-terminating-exception
16053 Show the current setting of stack unwinding in the functions called by
16058 @cindex weak alias functions
16059 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16060 for another function. In such case, @value{GDBN} might not pick up
16061 the type information, including the types of the function arguments,
16062 which causes @value{GDBN} to call the inferior function incorrectly.
16063 As a result, the called function will function erroneously and may
16064 even crash. A solution to that is to use the name of the aliased
16068 @section Patching Programs
16070 @cindex patching binaries
16071 @cindex writing into executables
16072 @cindex writing into corefiles
16074 By default, @value{GDBN} opens the file containing your program's
16075 executable code (or the corefile) read-only. This prevents accidental
16076 alterations to machine code; but it also prevents you from intentionally
16077 patching your program's binary.
16079 If you'd like to be able to patch the binary, you can specify that
16080 explicitly with the @code{set write} command. For example, you might
16081 want to turn on internal debugging flags, or even to make emergency
16087 @itemx set write off
16088 If you specify @samp{set write on}, @value{GDBN} opens executable and
16089 core files for both reading and writing; if you specify @kbd{set write
16090 off} (the default), @value{GDBN} opens them read-only.
16092 If you have already loaded a file, you must load it again (using the
16093 @code{exec-file} or @code{core-file} command) after changing @code{set
16094 write}, for your new setting to take effect.
16098 Display whether executable files and core files are opened for writing
16099 as well as reading.
16103 @chapter @value{GDBN} Files
16105 @value{GDBN} needs to know the file name of the program to be debugged,
16106 both in order to read its symbol table and in order to start your
16107 program. To debug a core dump of a previous run, you must also tell
16108 @value{GDBN} the name of the core dump file.
16111 * Files:: Commands to specify files
16112 * Separate Debug Files:: Debugging information in separate files
16113 * MiniDebugInfo:: Debugging information in a special section
16114 * Index Files:: Index files speed up GDB
16115 * Symbol Errors:: Errors reading symbol files
16116 * Data Files:: GDB data files
16120 @section Commands to Specify Files
16122 @cindex symbol table
16123 @cindex core dump file
16125 You may want to specify executable and core dump file names. The usual
16126 way to do this is at start-up time, using the arguments to
16127 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16128 Out of @value{GDBN}}).
16130 Occasionally it is necessary to change to a different file during a
16131 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16132 specify a file you want to use. Or you are debugging a remote target
16133 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16134 Program}). In these situations the @value{GDBN} commands to specify
16135 new files are useful.
16138 @cindex executable file
16140 @item file @var{filename}
16141 Use @var{filename} as the program to be debugged. It is read for its
16142 symbols and for the contents of pure memory. It is also the program
16143 executed when you use the @code{run} command. If you do not specify a
16144 directory and the file is not found in the @value{GDBN} working directory,
16145 @value{GDBN} uses the environment variable @code{PATH} as a list of
16146 directories to search, just as the shell does when looking for a program
16147 to run. You can change the value of this variable, for both @value{GDBN}
16148 and your program, using the @code{path} command.
16150 @cindex unlinked object files
16151 @cindex patching object files
16152 You can load unlinked object @file{.o} files into @value{GDBN} using
16153 the @code{file} command. You will not be able to ``run'' an object
16154 file, but you can disassemble functions and inspect variables. Also,
16155 if the underlying BFD functionality supports it, you could use
16156 @kbd{gdb -write} to patch object files using this technique. Note
16157 that @value{GDBN} can neither interpret nor modify relocations in this
16158 case, so branches and some initialized variables will appear to go to
16159 the wrong place. But this feature is still handy from time to time.
16162 @code{file} with no argument makes @value{GDBN} discard any information it
16163 has on both executable file and the symbol table.
16166 @item exec-file @r{[} @var{filename} @r{]}
16167 Specify that the program to be run (but not the symbol table) is found
16168 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16169 if necessary to locate your program. Omitting @var{filename} means to
16170 discard information on the executable file.
16172 @kindex symbol-file
16173 @item symbol-file @r{[} @var{filename} @r{]}
16174 Read symbol table information from file @var{filename}. @code{PATH} is
16175 searched when necessary. Use the @code{file} command to get both symbol
16176 table and program to run from the same file.
16178 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16179 program's symbol table.
16181 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16182 some breakpoints and auto-display expressions. This is because they may
16183 contain pointers to the internal data recording symbols and data types,
16184 which are part of the old symbol table data being discarded inside
16187 @code{symbol-file} does not repeat if you press @key{RET} again after
16190 When @value{GDBN} is configured for a particular environment, it
16191 understands debugging information in whatever format is the standard
16192 generated for that environment; you may use either a @sc{gnu} compiler, or
16193 other compilers that adhere to the local conventions.
16194 Best results are usually obtained from @sc{gnu} compilers; for example,
16195 using @code{@value{NGCC}} you can generate debugging information for
16198 For most kinds of object files, with the exception of old SVR3 systems
16199 using COFF, the @code{symbol-file} command does not normally read the
16200 symbol table in full right away. Instead, it scans the symbol table
16201 quickly to find which source files and which symbols are present. The
16202 details are read later, one source file at a time, as they are needed.
16204 The purpose of this two-stage reading strategy is to make @value{GDBN}
16205 start up faster. For the most part, it is invisible except for
16206 occasional pauses while the symbol table details for a particular source
16207 file are being read. (The @code{set verbose} command can turn these
16208 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16209 Warnings and Messages}.)
16211 We have not implemented the two-stage strategy for COFF yet. When the
16212 symbol table is stored in COFF format, @code{symbol-file} reads the
16213 symbol table data in full right away. Note that ``stabs-in-COFF''
16214 still does the two-stage strategy, since the debug info is actually
16218 @cindex reading symbols immediately
16219 @cindex symbols, reading immediately
16220 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16221 @itemx file @r{[} -readnow @r{]} @var{filename}
16222 You can override the @value{GDBN} two-stage strategy for reading symbol
16223 tables by using the @samp{-readnow} option with any of the commands that
16224 load symbol table information, if you want to be sure @value{GDBN} has the
16225 entire symbol table available.
16227 @c FIXME: for now no mention of directories, since this seems to be in
16228 @c flux. 13mar1992 status is that in theory GDB would look either in
16229 @c current dir or in same dir as myprog; but issues like competing
16230 @c GDB's, or clutter in system dirs, mean that in practice right now
16231 @c only current dir is used. FFish says maybe a special GDB hierarchy
16232 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16236 @item core-file @r{[}@var{filename}@r{]}
16238 Specify the whereabouts of a core dump file to be used as the ``contents
16239 of memory''. Traditionally, core files contain only some parts of the
16240 address space of the process that generated them; @value{GDBN} can access the
16241 executable file itself for other parts.
16243 @code{core-file} with no argument specifies that no core file is
16246 Note that the core file is ignored when your program is actually running
16247 under @value{GDBN}. So, if you have been running your program and you
16248 wish to debug a core file instead, you must kill the subprocess in which
16249 the program is running. To do this, use the @code{kill} command
16250 (@pxref{Kill Process, ,Killing the Child Process}).
16252 @kindex add-symbol-file
16253 @cindex dynamic linking
16254 @item add-symbol-file @var{filename} @var{address}
16255 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16256 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16257 The @code{add-symbol-file} command reads additional symbol table
16258 information from the file @var{filename}. You would use this command
16259 when @var{filename} has been dynamically loaded (by some other means)
16260 into the program that is running. @var{address} should be the memory
16261 address at which the file has been loaded; @value{GDBN} cannot figure
16262 this out for itself. You can additionally specify an arbitrary number
16263 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16264 section name and base address for that section. You can specify any
16265 @var{address} as an expression.
16267 The symbol table of the file @var{filename} is added to the symbol table
16268 originally read with the @code{symbol-file} command. You can use the
16269 @code{add-symbol-file} command any number of times; the new symbol data
16270 thus read keeps adding to the old. To discard all old symbol data
16271 instead, use the @code{symbol-file} command without any arguments.
16273 @cindex relocatable object files, reading symbols from
16274 @cindex object files, relocatable, reading symbols from
16275 @cindex reading symbols from relocatable object files
16276 @cindex symbols, reading from relocatable object files
16277 @cindex @file{.o} files, reading symbols from
16278 Although @var{filename} is typically a shared library file, an
16279 executable file, or some other object file which has been fully
16280 relocated for loading into a process, you can also load symbolic
16281 information from relocatable @file{.o} files, as long as:
16285 the file's symbolic information refers only to linker symbols defined in
16286 that file, not to symbols defined by other object files,
16288 every section the file's symbolic information refers to has actually
16289 been loaded into the inferior, as it appears in the file, and
16291 you can determine the address at which every section was loaded, and
16292 provide these to the @code{add-symbol-file} command.
16296 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16297 relocatable files into an already running program; such systems
16298 typically make the requirements above easy to meet. However, it's
16299 important to recognize that many native systems use complex link
16300 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16301 assembly, for example) that make the requirements difficult to meet. In
16302 general, one cannot assume that using @code{add-symbol-file} to read a
16303 relocatable object file's symbolic information will have the same effect
16304 as linking the relocatable object file into the program in the normal
16307 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16309 @kindex add-symbol-file-from-memory
16310 @cindex @code{syscall DSO}
16311 @cindex load symbols from memory
16312 @item add-symbol-file-from-memory @var{address}
16313 Load symbols from the given @var{address} in a dynamically loaded
16314 object file whose image is mapped directly into the inferior's memory.
16315 For example, the Linux kernel maps a @code{syscall DSO} into each
16316 process's address space; this DSO provides kernel-specific code for
16317 some system calls. The argument can be any expression whose
16318 evaluation yields the address of the file's shared object file header.
16319 For this command to work, you must have used @code{symbol-file} or
16320 @code{exec-file} commands in advance.
16322 @kindex add-shared-symbol-files
16324 @item add-shared-symbol-files @var{library-file}
16325 @itemx assf @var{library-file}
16326 The @code{add-shared-symbol-files} command can currently be used only
16327 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16328 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16329 @value{GDBN} automatically looks for shared libraries, however if
16330 @value{GDBN} does not find yours, you can invoke
16331 @code{add-shared-symbol-files}. It takes one argument: the shared
16332 library's file name. @code{assf} is a shorthand alias for
16333 @code{add-shared-symbol-files}.
16336 @item section @var{section} @var{addr}
16337 The @code{section} command changes the base address of the named
16338 @var{section} of the exec file to @var{addr}. This can be used if the
16339 exec file does not contain section addresses, (such as in the
16340 @code{a.out} format), or when the addresses specified in the file
16341 itself are wrong. Each section must be changed separately. The
16342 @code{info files} command, described below, lists all the sections and
16346 @kindex info target
16349 @code{info files} and @code{info target} are synonymous; both print the
16350 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16351 including the names of the executable and core dump files currently in
16352 use by @value{GDBN}, and the files from which symbols were loaded. The
16353 command @code{help target} lists all possible targets rather than
16356 @kindex maint info sections
16357 @item maint info sections
16358 Another command that can give you extra information about program sections
16359 is @code{maint info sections}. In addition to the section information
16360 displayed by @code{info files}, this command displays the flags and file
16361 offset of each section in the executable and core dump files. In addition,
16362 @code{maint info sections} provides the following command options (which
16363 may be arbitrarily combined):
16367 Display sections for all loaded object files, including shared libraries.
16368 @item @var{sections}
16369 Display info only for named @var{sections}.
16370 @item @var{section-flags}
16371 Display info only for sections for which @var{section-flags} are true.
16372 The section flags that @value{GDBN} currently knows about are:
16375 Section will have space allocated in the process when loaded.
16376 Set for all sections except those containing debug information.
16378 Section will be loaded from the file into the child process memory.
16379 Set for pre-initialized code and data, clear for @code{.bss} sections.
16381 Section needs to be relocated before loading.
16383 Section cannot be modified by the child process.
16385 Section contains executable code only.
16387 Section contains data only (no executable code).
16389 Section will reside in ROM.
16391 Section contains data for constructor/destructor lists.
16393 Section is not empty.
16395 An instruction to the linker to not output the section.
16396 @item COFF_SHARED_LIBRARY
16397 A notification to the linker that the section contains
16398 COFF shared library information.
16400 Section contains common symbols.
16403 @kindex set trust-readonly-sections
16404 @cindex read-only sections
16405 @item set trust-readonly-sections on
16406 Tell @value{GDBN} that readonly sections in your object file
16407 really are read-only (i.e.@: that their contents will not change).
16408 In that case, @value{GDBN} can fetch values from these sections
16409 out of the object file, rather than from the target program.
16410 For some targets (notably embedded ones), this can be a significant
16411 enhancement to debugging performance.
16413 The default is off.
16415 @item set trust-readonly-sections off
16416 Tell @value{GDBN} not to trust readonly sections. This means that
16417 the contents of the section might change while the program is running,
16418 and must therefore be fetched from the target when needed.
16420 @item show trust-readonly-sections
16421 Show the current setting of trusting readonly sections.
16424 All file-specifying commands allow both absolute and relative file names
16425 as arguments. @value{GDBN} always converts the file name to an absolute file
16426 name and remembers it that way.
16428 @cindex shared libraries
16429 @anchor{Shared Libraries}
16430 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16431 and IBM RS/6000 AIX shared libraries.
16433 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16434 shared libraries. @xref{Expat}.
16436 @value{GDBN} automatically loads symbol definitions from shared libraries
16437 when you use the @code{run} command, or when you examine a core file.
16438 (Before you issue the @code{run} command, @value{GDBN} does not understand
16439 references to a function in a shared library, however---unless you are
16440 debugging a core file).
16442 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16443 automatically loads the symbols at the time of the @code{shl_load} call.
16445 @c FIXME: some @value{GDBN} release may permit some refs to undef
16446 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16447 @c FIXME...lib; check this from time to time when updating manual
16449 There are times, however, when you may wish to not automatically load
16450 symbol definitions from shared libraries, such as when they are
16451 particularly large or there are many of them.
16453 To control the automatic loading of shared library symbols, use the
16457 @kindex set auto-solib-add
16458 @item set auto-solib-add @var{mode}
16459 If @var{mode} is @code{on}, symbols from all shared object libraries
16460 will be loaded automatically when the inferior begins execution, you
16461 attach to an independently started inferior, or when the dynamic linker
16462 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16463 is @code{off}, symbols must be loaded manually, using the
16464 @code{sharedlibrary} command. The default value is @code{on}.
16466 @cindex memory used for symbol tables
16467 If your program uses lots of shared libraries with debug info that
16468 takes large amounts of memory, you can decrease the @value{GDBN}
16469 memory footprint by preventing it from automatically loading the
16470 symbols from shared libraries. To that end, type @kbd{set
16471 auto-solib-add off} before running the inferior, then load each
16472 library whose debug symbols you do need with @kbd{sharedlibrary
16473 @var{regexp}}, where @var{regexp} is a regular expression that matches
16474 the libraries whose symbols you want to be loaded.
16476 @kindex show auto-solib-add
16477 @item show auto-solib-add
16478 Display the current autoloading mode.
16481 @cindex load shared library
16482 To explicitly load shared library symbols, use the @code{sharedlibrary}
16486 @kindex info sharedlibrary
16488 @item info share @var{regex}
16489 @itemx info sharedlibrary @var{regex}
16490 Print the names of the shared libraries which are currently loaded
16491 that match @var{regex}. If @var{regex} is omitted then print
16492 all shared libraries that are loaded.
16494 @kindex sharedlibrary
16496 @item sharedlibrary @var{regex}
16497 @itemx share @var{regex}
16498 Load shared object library symbols for files matching a
16499 Unix regular expression.
16500 As with files loaded automatically, it only loads shared libraries
16501 required by your program for a core file or after typing @code{run}. If
16502 @var{regex} is omitted all shared libraries required by your program are
16505 @item nosharedlibrary
16506 @kindex nosharedlibrary
16507 @cindex unload symbols from shared libraries
16508 Unload all shared object library symbols. This discards all symbols
16509 that have been loaded from all shared libraries. Symbols from shared
16510 libraries that were loaded by explicit user requests are not
16514 Sometimes you may wish that @value{GDBN} stops and gives you control
16515 when any of shared library events happen. The best way to do this is
16516 to use @code{catch load} and @code{catch unload} (@pxref{Set
16519 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16520 command for this. This command exists for historical reasons. It is
16521 less useful than setting a catchpoint, because it does not allow for
16522 conditions or commands as a catchpoint does.
16525 @item set stop-on-solib-events
16526 @kindex set stop-on-solib-events
16527 This command controls whether @value{GDBN} should give you control
16528 when the dynamic linker notifies it about some shared library event.
16529 The most common event of interest is loading or unloading of a new
16532 @item show stop-on-solib-events
16533 @kindex show stop-on-solib-events
16534 Show whether @value{GDBN} stops and gives you control when shared
16535 library events happen.
16538 Shared libraries are also supported in many cross or remote debugging
16539 configurations. @value{GDBN} needs to have access to the target's libraries;
16540 this can be accomplished either by providing copies of the libraries
16541 on the host system, or by asking @value{GDBN} to automatically retrieve the
16542 libraries from the target. If copies of the target libraries are
16543 provided, they need to be the same as the target libraries, although the
16544 copies on the target can be stripped as long as the copies on the host are
16547 @cindex where to look for shared libraries
16548 For remote debugging, you need to tell @value{GDBN} where the target
16549 libraries are, so that it can load the correct copies---otherwise, it
16550 may try to load the host's libraries. @value{GDBN} has two variables
16551 to specify the search directories for target libraries.
16554 @cindex prefix for shared library file names
16555 @cindex system root, alternate
16556 @kindex set solib-absolute-prefix
16557 @kindex set sysroot
16558 @item set sysroot @var{path}
16559 Use @var{path} as the system root for the program being debugged. Any
16560 absolute shared library paths will be prefixed with @var{path}; many
16561 runtime loaders store the absolute paths to the shared library in the
16562 target program's memory. If you use @code{set sysroot} to find shared
16563 libraries, they need to be laid out in the same way that they are on
16564 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16567 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16568 retrieve the target libraries from the remote system. This is only
16569 supported when using a remote target that supports the @code{remote get}
16570 command (@pxref{File Transfer,,Sending files to a remote system}).
16571 The part of @var{path} following the initial @file{remote:}
16572 (if present) is used as system root prefix on the remote file system.
16573 @footnote{If you want to specify a local system root using a directory
16574 that happens to be named @file{remote:}, you need to use some equivalent
16575 variant of the name like @file{./remote:}.}
16577 For targets with an MS-DOS based filesystem, such as MS-Windows and
16578 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16579 absolute file name with @var{path}. But first, on Unix hosts,
16580 @value{GDBN} converts all backslash directory separators into forward
16581 slashes, because the backslash is not a directory separator on Unix:
16584 c:\foo\bar.dll @result{} c:/foo/bar.dll
16587 Then, @value{GDBN} attempts prefixing the target file name with
16588 @var{path}, and looks for the resulting file name in the host file
16592 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16595 If that does not find the shared library, @value{GDBN} tries removing
16596 the @samp{:} character from the drive spec, both for convenience, and,
16597 for the case of the host file system not supporting file names with
16601 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16604 This makes it possible to have a system root that mirrors a target
16605 with more than one drive. E.g., you may want to setup your local
16606 copies of the target system shared libraries like so (note @samp{c} vs
16610 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16611 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16612 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16616 and point the system root at @file{/path/to/sysroot}, so that
16617 @value{GDBN} can find the correct copies of both
16618 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16620 If that still does not find the shared library, @value{GDBN} tries
16621 removing the whole drive spec from the target file name:
16624 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16627 This last lookup makes it possible to not care about the drive name,
16628 if you don't want or need to.
16630 The @code{set solib-absolute-prefix} command is an alias for @code{set
16633 @cindex default system root
16634 @cindex @samp{--with-sysroot}
16635 You can set the default system root by using the configure-time
16636 @samp{--with-sysroot} option. If the system root is inside
16637 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16638 @samp{--exec-prefix}), then the default system root will be updated
16639 automatically if the installed @value{GDBN} is moved to a new
16642 @kindex show sysroot
16644 Display the current shared library prefix.
16646 @kindex set solib-search-path
16647 @item set solib-search-path @var{path}
16648 If this variable is set, @var{path} is a colon-separated list of
16649 directories to search for shared libraries. @samp{solib-search-path}
16650 is used after @samp{sysroot} fails to locate the library, or if the
16651 path to the library is relative instead of absolute. If you want to
16652 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16653 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16654 finding your host's libraries. @samp{sysroot} is preferred; setting
16655 it to a nonexistent directory may interfere with automatic loading
16656 of shared library symbols.
16658 @kindex show solib-search-path
16659 @item show solib-search-path
16660 Display the current shared library search path.
16662 @cindex DOS file-name semantics of file names.
16663 @kindex set target-file-system-kind (unix|dos-based|auto)
16664 @kindex show target-file-system-kind
16665 @item set target-file-system-kind @var{kind}
16666 Set assumed file system kind for target reported file names.
16668 Shared library file names as reported by the target system may not
16669 make sense as is on the system @value{GDBN} is running on. For
16670 example, when remote debugging a target that has MS-DOS based file
16671 system semantics, from a Unix host, the target may be reporting to
16672 @value{GDBN} a list of loaded shared libraries with file names such as
16673 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16674 drive letters, so the @samp{c:\} prefix is not normally understood as
16675 indicating an absolute file name, and neither is the backslash
16676 normally considered a directory separator character. In that case,
16677 the native file system would interpret this whole absolute file name
16678 as a relative file name with no directory components. This would make
16679 it impossible to point @value{GDBN} at a copy of the remote target's
16680 shared libraries on the host using @code{set sysroot}, and impractical
16681 with @code{set solib-search-path}. Setting
16682 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16683 to interpret such file names similarly to how the target would, and to
16684 map them to file names valid on @value{GDBN}'s native file system
16685 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16686 to one of the supported file system kinds. In that case, @value{GDBN}
16687 tries to determine the appropriate file system variant based on the
16688 current target's operating system (@pxref{ABI, ,Configuring the
16689 Current ABI}). The supported file system settings are:
16693 Instruct @value{GDBN} to assume the target file system is of Unix
16694 kind. Only file names starting the forward slash (@samp{/}) character
16695 are considered absolute, and the directory separator character is also
16699 Instruct @value{GDBN} to assume the target file system is DOS based.
16700 File names starting with either a forward slash, or a drive letter
16701 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16702 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16703 considered directory separators.
16706 Instruct @value{GDBN} to use the file system kind associated with the
16707 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16708 This is the default.
16712 @cindex file name canonicalization
16713 @cindex base name differences
16714 When processing file names provided by the user, @value{GDBN}
16715 frequently needs to compare them to the file names recorded in the
16716 program's debug info. Normally, @value{GDBN} compares just the
16717 @dfn{base names} of the files as strings, which is reasonably fast
16718 even for very large programs. (The base name of a file is the last
16719 portion of its name, after stripping all the leading directories.)
16720 This shortcut in comparison is based upon the assumption that files
16721 cannot have more than one base name. This is usually true, but
16722 references to files that use symlinks or similar filesystem
16723 facilities violate that assumption. If your program records files
16724 using such facilities, or if you provide file names to @value{GDBN}
16725 using symlinks etc., you can set @code{basenames-may-differ} to
16726 @code{true} to instruct @value{GDBN} to completely canonicalize each
16727 pair of file names it needs to compare. This will make file-name
16728 comparisons accurate, but at a price of a significant slowdown.
16731 @item set basenames-may-differ
16732 @kindex set basenames-may-differ
16733 Set whether a source file may have multiple base names.
16735 @item show basenames-may-differ
16736 @kindex show basenames-may-differ
16737 Show whether a source file may have multiple base names.
16740 @node Separate Debug Files
16741 @section Debugging Information in Separate Files
16742 @cindex separate debugging information files
16743 @cindex debugging information in separate files
16744 @cindex @file{.debug} subdirectories
16745 @cindex debugging information directory, global
16746 @cindex global debugging information directories
16747 @cindex build ID, and separate debugging files
16748 @cindex @file{.build-id} directory
16750 @value{GDBN} allows you to put a program's debugging information in a
16751 file separate from the executable itself, in a way that allows
16752 @value{GDBN} to find and load the debugging information automatically.
16753 Since debugging information can be very large---sometimes larger
16754 than the executable code itself---some systems distribute debugging
16755 information for their executables in separate files, which users can
16756 install only when they need to debug a problem.
16758 @value{GDBN} supports two ways of specifying the separate debug info
16763 The executable contains a @dfn{debug link} that specifies the name of
16764 the separate debug info file. The separate debug file's name is
16765 usually @file{@var{executable}.debug}, where @var{executable} is the
16766 name of the corresponding executable file without leading directories
16767 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16768 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16769 checksum for the debug file, which @value{GDBN} uses to validate that
16770 the executable and the debug file came from the same build.
16773 The executable contains a @dfn{build ID}, a unique bit string that is
16774 also present in the corresponding debug info file. (This is supported
16775 only on some operating systems, notably those which use the ELF format
16776 for binary files and the @sc{gnu} Binutils.) For more details about
16777 this feature, see the description of the @option{--build-id}
16778 command-line option in @ref{Options, , Command Line Options, ld.info,
16779 The GNU Linker}. The debug info file's name is not specified
16780 explicitly by the build ID, but can be computed from the build ID, see
16784 Depending on the way the debug info file is specified, @value{GDBN}
16785 uses two different methods of looking for the debug file:
16789 For the ``debug link'' method, @value{GDBN} looks up the named file in
16790 the directory of the executable file, then in a subdirectory of that
16791 directory named @file{.debug}, and finally under each one of the global debug
16792 directories, in a subdirectory whose name is identical to the leading
16793 directories of the executable's absolute file name.
16796 For the ``build ID'' method, @value{GDBN} looks in the
16797 @file{.build-id} subdirectory of each one of the global debug directories for
16798 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16799 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16800 are the rest of the bit string. (Real build ID strings are 32 or more
16801 hex characters, not 10.)
16804 So, for example, suppose you ask @value{GDBN} to debug
16805 @file{/usr/bin/ls}, which has a debug link that specifies the
16806 file @file{ls.debug}, and a build ID whose value in hex is
16807 @code{abcdef1234}. If the list of the global debug directories includes
16808 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16809 debug information files, in the indicated order:
16813 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16815 @file{/usr/bin/ls.debug}
16817 @file{/usr/bin/.debug/ls.debug}
16819 @file{/usr/lib/debug/usr/bin/ls.debug}.
16822 @anchor{debug-file-directory}
16823 Global debugging info directories default to what is set by @value{GDBN}
16824 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16825 you can also set the global debugging info directories, and view the list
16826 @value{GDBN} is currently using.
16830 @kindex set debug-file-directory
16831 @item set debug-file-directory @var{directories}
16832 Set the directories which @value{GDBN} searches for separate debugging
16833 information files to @var{directory}. Multiple path components can be set
16834 concatenating them by a path separator.
16836 @kindex show debug-file-directory
16837 @item show debug-file-directory
16838 Show the directories @value{GDBN} searches for separate debugging
16843 @cindex @code{.gnu_debuglink} sections
16844 @cindex debug link sections
16845 A debug link is a special section of the executable file named
16846 @code{.gnu_debuglink}. The section must contain:
16850 A filename, with any leading directory components removed, followed by
16853 zero to three bytes of padding, as needed to reach the next four-byte
16854 boundary within the section, and
16856 a four-byte CRC checksum, stored in the same endianness used for the
16857 executable file itself. The checksum is computed on the debugging
16858 information file's full contents by the function given below, passing
16859 zero as the @var{crc} argument.
16862 Any executable file format can carry a debug link, as long as it can
16863 contain a section named @code{.gnu_debuglink} with the contents
16866 @cindex @code{.note.gnu.build-id} sections
16867 @cindex build ID sections
16868 The build ID is a special section in the executable file (and in other
16869 ELF binary files that @value{GDBN} may consider). This section is
16870 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16871 It contains unique identification for the built files---the ID remains
16872 the same across multiple builds of the same build tree. The default
16873 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16874 content for the build ID string. The same section with an identical
16875 value is present in the original built binary with symbols, in its
16876 stripped variant, and in the separate debugging information file.
16878 The debugging information file itself should be an ordinary
16879 executable, containing a full set of linker symbols, sections, and
16880 debugging information. The sections of the debugging information file
16881 should have the same names, addresses, and sizes as the original file,
16882 but they need not contain any data---much like a @code{.bss} section
16883 in an ordinary executable.
16885 The @sc{gnu} binary utilities (Binutils) package includes the
16886 @samp{objcopy} utility that can produce
16887 the separated executable / debugging information file pairs using the
16888 following commands:
16891 @kbd{objcopy --only-keep-debug foo foo.debug}
16896 These commands remove the debugging
16897 information from the executable file @file{foo} and place it in the file
16898 @file{foo.debug}. You can use the first, second or both methods to link the
16903 The debug link method needs the following additional command to also leave
16904 behind a debug link in @file{foo}:
16907 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16910 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16911 a version of the @code{strip} command such that the command @kbd{strip foo -f
16912 foo.debug} has the same functionality as the two @code{objcopy} commands and
16913 the @code{ln -s} command above, together.
16916 Build ID gets embedded into the main executable using @code{ld --build-id} or
16917 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16918 compatibility fixes for debug files separation are present in @sc{gnu} binary
16919 utilities (Binutils) package since version 2.18.
16924 @cindex CRC algorithm definition
16925 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16926 IEEE 802.3 using the polynomial:
16928 @c TexInfo requires naked braces for multi-digit exponents for Tex
16929 @c output, but this causes HTML output to barf. HTML has to be set using
16930 @c raw commands. So we end up having to specify this equation in 2
16935 <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>
16936 + <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
16942 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16943 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16947 The function is computed byte at a time, taking the least
16948 significant bit of each byte first. The initial pattern
16949 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16950 the final result is inverted to ensure trailing zeros also affect the
16953 @emph{Note:} This is the same CRC polynomial as used in handling the
16954 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16955 , @value{GDBN} Remote Serial Protocol}). However in the
16956 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16957 significant bit first, and the result is not inverted, so trailing
16958 zeros have no effect on the CRC value.
16960 To complete the description, we show below the code of the function
16961 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16962 initially supplied @code{crc} argument means that an initial call to
16963 this function passing in zero will start computing the CRC using
16966 @kindex gnu_debuglink_crc32
16969 gnu_debuglink_crc32 (unsigned long crc,
16970 unsigned char *buf, size_t len)
16972 static const unsigned long crc32_table[256] =
16974 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16975 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16976 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16977 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16978 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16979 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16980 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16981 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16982 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16983 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16984 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16985 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16986 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16987 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16988 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16989 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16990 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16991 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16992 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16993 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16994 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16995 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16996 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16997 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16998 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16999 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17000 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17001 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17002 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17003 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17004 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17005 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17006 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17007 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17008 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17009 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17010 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17011 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17012 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17013 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17014 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17015 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17016 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17017 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17018 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17019 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17020 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17021 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17022 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17023 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17024 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17027 unsigned char *end;
17029 crc = ~crc & 0xffffffff;
17030 for (end = buf + len; buf < end; ++buf)
17031 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17032 return ~crc & 0xffffffff;
17037 This computation does not apply to the ``build ID'' method.
17039 @node MiniDebugInfo
17040 @section Debugging information in a special section
17041 @cindex separate debug sections
17042 @cindex @samp{.gnu_debugdata} section
17044 Some systems ship pre-built executables and libraries that have a
17045 special @samp{.gnu_debugdata} section. This feature is called
17046 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17047 is used to supply extra symbols for backtraces.
17049 The intent of this section is to provide extra minimal debugging
17050 information for use in simple backtraces. It is not intended to be a
17051 replacement for full separate debugging information (@pxref{Separate
17052 Debug Files}). The example below shows the intended use; however,
17053 @value{GDBN} does not currently put restrictions on what sort of
17054 debugging information might be included in the section.
17056 @value{GDBN} has support for this extension. If the section exists,
17057 then it is used provided that no other source of debugging information
17058 can be found, and that @value{GDBN} was configured with LZMA support.
17060 This section can be easily created using @command{objcopy} and other
17061 standard utilities:
17064 # Extract the dynamic symbols from the main binary, there is no need
17065 # to also have these in the normal symbol table
17066 nm -D @var{binary} --format=posix --defined-only \
17067 | awk '@{ print $1 @}' | sort > dynsyms
17069 # Extract all the text (i.e. function) symbols from the debuginfo .
17070 nm @var{binary} --format=posix --defined-only \
17071 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
17074 # Keep all the function symbols not already in the dynamic symbol
17076 comm -13 dynsyms funcsyms > keep_symbols
17078 # Copy the full debuginfo, keeping only a minimal set of symbols and
17079 # removing some unnecessary sections.
17080 objcopy -S --remove-section .gdb_index --remove-section .comment \
17081 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
17083 # Inject the compressed data into the .gnu_debugdata section of the
17086 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17090 @section Index Files Speed Up @value{GDBN}
17091 @cindex index files
17092 @cindex @samp{.gdb_index} section
17094 When @value{GDBN} finds a symbol file, it scans the symbols in the
17095 file in order to construct an internal symbol table. This lets most
17096 @value{GDBN} operations work quickly---at the cost of a delay early
17097 on. For large programs, this delay can be quite lengthy, so
17098 @value{GDBN} provides a way to build an index, which speeds up
17101 The index is stored as a section in the symbol file. @value{GDBN} can
17102 write the index to a file, then you can put it into the symbol file
17103 using @command{objcopy}.
17105 To create an index file, use the @code{save gdb-index} command:
17108 @item save gdb-index @var{directory}
17109 @kindex save gdb-index
17110 Create an index file for each symbol file currently known by
17111 @value{GDBN}. Each file is named after its corresponding symbol file,
17112 with @samp{.gdb-index} appended, and is written into the given
17116 Once you have created an index file you can merge it into your symbol
17117 file, here named @file{symfile}, using @command{objcopy}:
17120 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17121 --set-section-flags .gdb_index=readonly symfile symfile
17124 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17125 sections that have been deprecated. Usually they are deprecated because
17126 they are missing a new feature or have performance issues.
17127 To tell @value{GDBN} to use a deprecated index section anyway
17128 specify @code{set use-deprecated-index-sections on}.
17129 The default is @code{off}.
17130 This can speed up startup, but may result in some functionality being lost.
17131 @xref{Index Section Format}.
17133 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17134 must be done before gdb reads the file. The following will not work:
17137 $ gdb -ex "set use-deprecated-index-sections on" <program>
17140 Instead you must do, for example,
17143 $ gdb -iex "set use-deprecated-index-sections on" <program>
17146 There are currently some limitation on indices. They only work when
17147 for DWARF debugging information, not stabs. And, they do not
17148 currently work for programs using Ada.
17150 @node Symbol Errors
17151 @section Errors Reading Symbol Files
17153 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17154 such as symbol types it does not recognize, or known bugs in compiler
17155 output. By default, @value{GDBN} does not notify you of such problems, since
17156 they are relatively common and primarily of interest to people
17157 debugging compilers. If you are interested in seeing information
17158 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17159 only one message about each such type of problem, no matter how many
17160 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17161 to see how many times the problems occur, with the @code{set
17162 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17165 The messages currently printed, and their meanings, include:
17168 @item inner block not inside outer block in @var{symbol}
17170 The symbol information shows where symbol scopes begin and end
17171 (such as at the start of a function or a block of statements). This
17172 error indicates that an inner scope block is not fully contained
17173 in its outer scope blocks.
17175 @value{GDBN} circumvents the problem by treating the inner block as if it had
17176 the same scope as the outer block. In the error message, @var{symbol}
17177 may be shown as ``@code{(don't know)}'' if the outer block is not a
17180 @item block at @var{address} out of order
17182 The symbol information for symbol scope blocks should occur in
17183 order of increasing addresses. This error indicates that it does not
17186 @value{GDBN} does not circumvent this problem, and has trouble
17187 locating symbols in the source file whose symbols it is reading. (You
17188 can often determine what source file is affected by specifying
17189 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17192 @item bad block start address patched
17194 The symbol information for a symbol scope block has a start address
17195 smaller than the address of the preceding source line. This is known
17196 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17198 @value{GDBN} circumvents the problem by treating the symbol scope block as
17199 starting on the previous source line.
17201 @item bad string table offset in symbol @var{n}
17204 Symbol number @var{n} contains a pointer into the string table which is
17205 larger than the size of the string table.
17207 @value{GDBN} circumvents the problem by considering the symbol to have the
17208 name @code{foo}, which may cause other problems if many symbols end up
17211 @item unknown symbol type @code{0x@var{nn}}
17213 The symbol information contains new data types that @value{GDBN} does
17214 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17215 uncomprehended information, in hexadecimal.
17217 @value{GDBN} circumvents the error by ignoring this symbol information.
17218 This usually allows you to debug your program, though certain symbols
17219 are not accessible. If you encounter such a problem and feel like
17220 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17221 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17222 and examine @code{*bufp} to see the symbol.
17224 @item stub type has NULL name
17226 @value{GDBN} could not find the full definition for a struct or class.
17228 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17229 The symbol information for a C@t{++} member function is missing some
17230 information that recent versions of the compiler should have output for
17233 @item info mismatch between compiler and debugger
17235 @value{GDBN} could not parse a type specification output by the compiler.
17240 @section GDB Data Files
17242 @cindex prefix for data files
17243 @value{GDBN} will sometimes read an auxiliary data file. These files
17244 are kept in a directory known as the @dfn{data directory}.
17246 You can set the data directory's name, and view the name @value{GDBN}
17247 is currently using.
17250 @kindex set data-directory
17251 @item set data-directory @var{directory}
17252 Set the directory which @value{GDBN} searches for auxiliary data files
17253 to @var{directory}.
17255 @kindex show data-directory
17256 @item show data-directory
17257 Show the directory @value{GDBN} searches for auxiliary data files.
17260 @cindex default data directory
17261 @cindex @samp{--with-gdb-datadir}
17262 You can set the default data directory by using the configure-time
17263 @samp{--with-gdb-datadir} option. If the data directory is inside
17264 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17265 @samp{--exec-prefix}), then the default data directory will be updated
17266 automatically if the installed @value{GDBN} is moved to a new
17269 The data directory may also be specified with the
17270 @code{--data-directory} command line option.
17271 @xref{Mode Options}.
17274 @chapter Specifying a Debugging Target
17276 @cindex debugging target
17277 A @dfn{target} is the execution environment occupied by your program.
17279 Often, @value{GDBN} runs in the same host environment as your program;
17280 in that case, the debugging target is specified as a side effect when
17281 you use the @code{file} or @code{core} commands. When you need more
17282 flexibility---for example, running @value{GDBN} on a physically separate
17283 host, or controlling a standalone system over a serial port or a
17284 realtime system over a TCP/IP connection---you can use the @code{target}
17285 command to specify one of the target types configured for @value{GDBN}
17286 (@pxref{Target Commands, ,Commands for Managing Targets}).
17288 @cindex target architecture
17289 It is possible to build @value{GDBN} for several different @dfn{target
17290 architectures}. When @value{GDBN} is built like that, you can choose
17291 one of the available architectures with the @kbd{set architecture}
17295 @kindex set architecture
17296 @kindex show architecture
17297 @item set architecture @var{arch}
17298 This command sets the current target architecture to @var{arch}. The
17299 value of @var{arch} can be @code{"auto"}, in addition to one of the
17300 supported architectures.
17302 @item show architecture
17303 Show the current target architecture.
17305 @item set processor
17307 @kindex set processor
17308 @kindex show processor
17309 These are alias commands for, respectively, @code{set architecture}
17310 and @code{show architecture}.
17314 * Active Targets:: Active targets
17315 * Target Commands:: Commands for managing targets
17316 * Byte Order:: Choosing target byte order
17319 @node Active Targets
17320 @section Active Targets
17322 @cindex stacking targets
17323 @cindex active targets
17324 @cindex multiple targets
17326 There are multiple classes of targets such as: processes, executable files or
17327 recording sessions. Core files belong to the process class, making core file
17328 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17329 on multiple active targets, one in each class. This allows you to (for
17330 example) start a process and inspect its activity, while still having access to
17331 the executable file after the process finishes. Or if you start process
17332 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17333 presented a virtual layer of the recording target, while the process target
17334 remains stopped at the chronologically last point of the process execution.
17336 Use the @code{core-file} and @code{exec-file} commands to select a new core
17337 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17338 specify as a target a process that is already running, use the @code{attach}
17339 command (@pxref{Attach, ,Debugging an Already-running Process}).
17341 @node Target Commands
17342 @section Commands for Managing Targets
17345 @item target @var{type} @var{parameters}
17346 Connects the @value{GDBN} host environment to a target machine or
17347 process. A target is typically a protocol for talking to debugging
17348 facilities. You use the argument @var{type} to specify the type or
17349 protocol of the target machine.
17351 Further @var{parameters} are interpreted by the target protocol, but
17352 typically include things like device names or host names to connect
17353 with, process numbers, and baud rates.
17355 The @code{target} command does not repeat if you press @key{RET} again
17356 after executing the command.
17358 @kindex help target
17360 Displays the names of all targets available. To display targets
17361 currently selected, use either @code{info target} or @code{info files}
17362 (@pxref{Files, ,Commands to Specify Files}).
17364 @item help target @var{name}
17365 Describe a particular target, including any parameters necessary to
17368 @kindex set gnutarget
17369 @item set gnutarget @var{args}
17370 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17371 knows whether it is reading an @dfn{executable},
17372 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17373 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17374 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17377 @emph{Warning:} To specify a file format with @code{set gnutarget},
17378 you must know the actual BFD name.
17382 @xref{Files, , Commands to Specify Files}.
17384 @kindex show gnutarget
17385 @item show gnutarget
17386 Use the @code{show gnutarget} command to display what file format
17387 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17388 @value{GDBN} will determine the file format for each file automatically,
17389 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17392 @cindex common targets
17393 Here are some common targets (available, or not, depending on the GDB
17398 @item target exec @var{program}
17399 @cindex executable file target
17400 An executable file. @samp{target exec @var{program}} is the same as
17401 @samp{exec-file @var{program}}.
17403 @item target core @var{filename}
17404 @cindex core dump file target
17405 A core dump file. @samp{target core @var{filename}} is the same as
17406 @samp{core-file @var{filename}}.
17408 @item target remote @var{medium}
17409 @cindex remote target
17410 A remote system connected to @value{GDBN} via a serial line or network
17411 connection. This command tells @value{GDBN} to use its own remote
17412 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17414 For example, if you have a board connected to @file{/dev/ttya} on the
17415 machine running @value{GDBN}, you could say:
17418 target remote /dev/ttya
17421 @code{target remote} supports the @code{load} command. This is only
17422 useful if you have some other way of getting the stub to the target
17423 system, and you can put it somewhere in memory where it won't get
17424 clobbered by the download.
17426 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17427 @cindex built-in simulator target
17428 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17436 works; however, you cannot assume that a specific memory map, device
17437 drivers, or even basic I/O is available, although some simulators do
17438 provide these. For info about any processor-specific simulator details,
17439 see the appropriate section in @ref{Embedded Processors, ,Embedded
17444 Some configurations may include these targets as well:
17448 @item target nrom @var{dev}
17449 @cindex NetROM ROM emulator target
17450 NetROM ROM emulator. This target only supports downloading.
17454 Different targets are available on different configurations of @value{GDBN};
17455 your configuration may have more or fewer targets.
17457 Many remote targets require you to download the executable's code once
17458 you've successfully established a connection. You may wish to control
17459 various aspects of this process.
17464 @kindex set hash@r{, for remote monitors}
17465 @cindex hash mark while downloading
17466 This command controls whether a hash mark @samp{#} is displayed while
17467 downloading a file to the remote monitor. If on, a hash mark is
17468 displayed after each S-record is successfully downloaded to the
17472 @kindex show hash@r{, for remote monitors}
17473 Show the current status of displaying the hash mark.
17475 @item set debug monitor
17476 @kindex set debug monitor
17477 @cindex display remote monitor communications
17478 Enable or disable display of communications messages between
17479 @value{GDBN} and the remote monitor.
17481 @item show debug monitor
17482 @kindex show debug monitor
17483 Show the current status of displaying communications between
17484 @value{GDBN} and the remote monitor.
17489 @kindex load @var{filename}
17490 @item load @var{filename}
17492 Depending on what remote debugging facilities are configured into
17493 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17494 is meant to make @var{filename} (an executable) available for debugging
17495 on the remote system---by downloading, or dynamic linking, for example.
17496 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17497 the @code{add-symbol-file} command.
17499 If your @value{GDBN} does not have a @code{load} command, attempting to
17500 execute it gets the error message ``@code{You can't do that when your
17501 target is @dots{}}''
17503 The file is loaded at whatever address is specified in the executable.
17504 For some object file formats, you can specify the load address when you
17505 link the program; for other formats, like a.out, the object file format
17506 specifies a fixed address.
17507 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17509 Depending on the remote side capabilities, @value{GDBN} may be able to
17510 load programs into flash memory.
17512 @code{load} does not repeat if you press @key{RET} again after using it.
17516 @section Choosing Target Byte Order
17518 @cindex choosing target byte order
17519 @cindex target byte order
17521 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17522 offer the ability to run either big-endian or little-endian byte
17523 orders. Usually the executable or symbol will include a bit to
17524 designate the endian-ness, and you will not need to worry about
17525 which to use. However, you may still find it useful to adjust
17526 @value{GDBN}'s idea of processor endian-ness manually.
17530 @item set endian big
17531 Instruct @value{GDBN} to assume the target is big-endian.
17533 @item set endian little
17534 Instruct @value{GDBN} to assume the target is little-endian.
17536 @item set endian auto
17537 Instruct @value{GDBN} to use the byte order associated with the
17541 Display @value{GDBN}'s current idea of the target byte order.
17545 Note that these commands merely adjust interpretation of symbolic
17546 data on the host, and that they have absolutely no effect on the
17550 @node Remote Debugging
17551 @chapter Debugging Remote Programs
17552 @cindex remote debugging
17554 If you are trying to debug a program running on a machine that cannot run
17555 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17556 For example, you might use remote debugging on an operating system kernel,
17557 or on a small system which does not have a general purpose operating system
17558 powerful enough to run a full-featured debugger.
17560 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17561 to make this work with particular debugging targets. In addition,
17562 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17563 but not specific to any particular target system) which you can use if you
17564 write the remote stubs---the code that runs on the remote system to
17565 communicate with @value{GDBN}.
17567 Other remote targets may be available in your
17568 configuration of @value{GDBN}; use @code{help target} to list them.
17571 * Connecting:: Connecting to a remote target
17572 * File Transfer:: Sending files to a remote system
17573 * Server:: Using the gdbserver program
17574 * Remote Configuration:: Remote configuration
17575 * Remote Stub:: Implementing a remote stub
17579 @section Connecting to a Remote Target
17581 On the @value{GDBN} host machine, you will need an unstripped copy of
17582 your program, since @value{GDBN} needs symbol and debugging information.
17583 Start up @value{GDBN} as usual, using the name of the local copy of your
17584 program as the first argument.
17586 @cindex @code{target remote}
17587 @value{GDBN} can communicate with the target over a serial line, or
17588 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17589 each case, @value{GDBN} uses the same protocol for debugging your
17590 program; only the medium carrying the debugging packets varies. The
17591 @code{target remote} command establishes a connection to the target.
17592 Its arguments indicate which medium to use:
17596 @item target remote @var{serial-device}
17597 @cindex serial line, @code{target remote}
17598 Use @var{serial-device} to communicate with the target. For example,
17599 to use a serial line connected to the device named @file{/dev/ttyb}:
17602 target remote /dev/ttyb
17605 If you're using a serial line, you may want to give @value{GDBN} the
17606 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17607 (@pxref{Remote Configuration, set remotebaud}) before the
17608 @code{target} command.
17610 @item target remote @code{@var{host}:@var{port}}
17611 @itemx target remote @code{tcp:@var{host}:@var{port}}
17612 @cindex @acronym{TCP} port, @code{target remote}
17613 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17614 The @var{host} may be either a host name or a numeric @acronym{IP}
17615 address; @var{port} must be a decimal number. The @var{host} could be
17616 the target machine itself, if it is directly connected to the net, or
17617 it might be a terminal server which in turn has a serial line to the
17620 For example, to connect to port 2828 on a terminal server named
17624 target remote manyfarms:2828
17627 If your remote target is actually running on the same machine as your
17628 debugger session (e.g.@: a simulator for your target running on the
17629 same host), you can omit the hostname. For example, to connect to
17630 port 1234 on your local machine:
17633 target remote :1234
17637 Note that the colon is still required here.
17639 @item target remote @code{udp:@var{host}:@var{port}}
17640 @cindex @acronym{UDP} port, @code{target remote}
17641 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17642 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17645 target remote udp:manyfarms:2828
17648 When using a @acronym{UDP} connection for remote debugging, you should
17649 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17650 can silently drop packets on busy or unreliable networks, which will
17651 cause havoc with your debugging session.
17653 @item target remote | @var{command}
17654 @cindex pipe, @code{target remote} to
17655 Run @var{command} in the background and communicate with it using a
17656 pipe. The @var{command} is a shell command, to be parsed and expanded
17657 by the system's command shell, @code{/bin/sh}; it should expect remote
17658 protocol packets on its standard input, and send replies on its
17659 standard output. You could use this to run a stand-alone simulator
17660 that speaks the remote debugging protocol, to make net connections
17661 using programs like @code{ssh}, or for other similar tricks.
17663 If @var{command} closes its standard output (perhaps by exiting),
17664 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17665 program has already exited, this will have no effect.)
17669 Once the connection has been established, you can use all the usual
17670 commands to examine and change data. The remote program is already
17671 running; you can use @kbd{step} and @kbd{continue}, and you do not
17672 need to use @kbd{run}.
17674 @cindex interrupting remote programs
17675 @cindex remote programs, interrupting
17676 Whenever @value{GDBN} is waiting for the remote program, if you type the
17677 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17678 program. This may or may not succeed, depending in part on the hardware
17679 and the serial drivers the remote system uses. If you type the
17680 interrupt character once again, @value{GDBN} displays this prompt:
17683 Interrupted while waiting for the program.
17684 Give up (and stop debugging it)? (y or n)
17687 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17688 (If you decide you want to try again later, you can use @samp{target
17689 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17690 goes back to waiting.
17693 @kindex detach (remote)
17695 When you have finished debugging the remote program, you can use the
17696 @code{detach} command to release it from @value{GDBN} control.
17697 Detaching from the target normally resumes its execution, but the results
17698 will depend on your particular remote stub. After the @code{detach}
17699 command, @value{GDBN} is free to connect to another target.
17703 The @code{disconnect} command behaves like @code{detach}, except that
17704 the target is generally not resumed. It will wait for @value{GDBN}
17705 (this instance or another one) to connect and continue debugging. After
17706 the @code{disconnect} command, @value{GDBN} is again free to connect to
17709 @cindex send command to remote monitor
17710 @cindex extend @value{GDBN} for remote targets
17711 @cindex add new commands for external monitor
17713 @item monitor @var{cmd}
17714 This command allows you to send arbitrary commands directly to the
17715 remote monitor. Since @value{GDBN} doesn't care about the commands it
17716 sends like this, this command is the way to extend @value{GDBN}---you
17717 can add new commands that only the external monitor will understand
17721 @node File Transfer
17722 @section Sending files to a remote system
17723 @cindex remote target, file transfer
17724 @cindex file transfer
17725 @cindex sending files to remote systems
17727 Some remote targets offer the ability to transfer files over the same
17728 connection used to communicate with @value{GDBN}. This is convenient
17729 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17730 running @code{gdbserver} over a network interface. For other targets,
17731 e.g.@: embedded devices with only a single serial port, this may be
17732 the only way to upload or download files.
17734 Not all remote targets support these commands.
17738 @item remote put @var{hostfile} @var{targetfile}
17739 Copy file @var{hostfile} from the host system (the machine running
17740 @value{GDBN}) to @var{targetfile} on the target system.
17743 @item remote get @var{targetfile} @var{hostfile}
17744 Copy file @var{targetfile} from the target system to @var{hostfile}
17745 on the host system.
17747 @kindex remote delete
17748 @item remote delete @var{targetfile}
17749 Delete @var{targetfile} from the target system.
17754 @section Using the @code{gdbserver} Program
17757 @cindex remote connection without stubs
17758 @code{gdbserver} is a control program for Unix-like systems, which
17759 allows you to connect your program with a remote @value{GDBN} via
17760 @code{target remote}---but without linking in the usual debugging stub.
17762 @code{gdbserver} is not a complete replacement for the debugging stubs,
17763 because it requires essentially the same operating-system facilities
17764 that @value{GDBN} itself does. In fact, a system that can run
17765 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17766 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17767 because it is a much smaller program than @value{GDBN} itself. It is
17768 also easier to port than all of @value{GDBN}, so you may be able to get
17769 started more quickly on a new system by using @code{gdbserver}.
17770 Finally, if you develop code for real-time systems, you may find that
17771 the tradeoffs involved in real-time operation make it more convenient to
17772 do as much development work as possible on another system, for example
17773 by cross-compiling. You can use @code{gdbserver} to make a similar
17774 choice for debugging.
17776 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17777 or a TCP connection, using the standard @value{GDBN} remote serial
17781 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17782 Do not run @code{gdbserver} connected to any public network; a
17783 @value{GDBN} connection to @code{gdbserver} provides access to the
17784 target system with the same privileges as the user running
17788 @subsection Running @code{gdbserver}
17789 @cindex arguments, to @code{gdbserver}
17790 @cindex @code{gdbserver}, command-line arguments
17792 Run @code{gdbserver} on the target system. You need a copy of the
17793 program you want to debug, including any libraries it requires.
17794 @code{gdbserver} does not need your program's symbol table, so you can
17795 strip the program if necessary to save space. @value{GDBN} on the host
17796 system does all the symbol handling.
17798 To use the server, you must tell it how to communicate with @value{GDBN};
17799 the name of your program; and the arguments for your program. The usual
17803 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17806 @var{comm} is either a device name (to use a serial line), or a TCP
17807 hostname and portnumber, or @code{-} or @code{stdio} to use
17808 stdin/stdout of @code{gdbserver}.
17809 For example, to debug Emacs with the argument
17810 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17814 target> gdbserver /dev/com1 emacs foo.txt
17817 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17820 To use a TCP connection instead of a serial line:
17823 target> gdbserver host:2345 emacs foo.txt
17826 The only difference from the previous example is the first argument,
17827 specifying that you are communicating with the host @value{GDBN} via
17828 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17829 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17830 (Currently, the @samp{host} part is ignored.) You can choose any number
17831 you want for the port number as long as it does not conflict with any
17832 TCP ports already in use on the target system (for example, @code{23} is
17833 reserved for @code{telnet}).@footnote{If you choose a port number that
17834 conflicts with another service, @code{gdbserver} prints an error message
17835 and exits.} You must use the same port number with the host @value{GDBN}
17836 @code{target remote} command.
17838 The @code{stdio} connection is useful when starting @code{gdbserver}
17842 (gdb) target remote | ssh -T hostname gdbserver - hello
17845 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17846 and we don't want escape-character handling. Ssh does this by default when
17847 a command is provided, the flag is provided to make it explicit.
17848 You could elide it if you want to.
17850 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17851 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17852 display through a pipe connected to gdbserver.
17853 Both @code{stdout} and @code{stderr} use the same pipe.
17855 @subsubsection Attaching to a Running Program
17856 @cindex attach to a program, @code{gdbserver}
17857 @cindex @option{--attach}, @code{gdbserver} option
17859 On some targets, @code{gdbserver} can also attach to running programs.
17860 This is accomplished via the @code{--attach} argument. The syntax is:
17863 target> gdbserver --attach @var{comm} @var{pid}
17866 @var{pid} is the process ID of a currently running process. It isn't necessary
17867 to point @code{gdbserver} at a binary for the running process.
17870 You can debug processes by name instead of process ID if your target has the
17871 @code{pidof} utility:
17874 target> gdbserver --attach @var{comm} `pidof @var{program}`
17877 In case more than one copy of @var{program} is running, or @var{program}
17878 has multiple threads, most versions of @code{pidof} support the
17879 @code{-s} option to only return the first process ID.
17881 @subsubsection Multi-Process Mode for @code{gdbserver}
17882 @cindex @code{gdbserver}, multiple processes
17883 @cindex multiple processes with @code{gdbserver}
17885 When you connect to @code{gdbserver} using @code{target remote},
17886 @code{gdbserver} debugs the specified program only once. When the
17887 program exits, or you detach from it, @value{GDBN} closes the connection
17888 and @code{gdbserver} exits.
17890 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17891 enters multi-process mode. When the debugged program exits, or you
17892 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17893 though no program is running. The @code{run} and @code{attach}
17894 commands instruct @code{gdbserver} to run or attach to a new program.
17895 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17896 remote exec-file}) to select the program to run. Command line
17897 arguments are supported, except for wildcard expansion and I/O
17898 redirection (@pxref{Arguments}).
17900 @cindex @option{--multi}, @code{gdbserver} option
17901 To start @code{gdbserver} without supplying an initial command to run
17902 or process ID to attach, use the @option{--multi} command line option.
17903 Then you can connect using @kbd{target extended-remote} and start
17904 the program you want to debug.
17906 In multi-process mode @code{gdbserver} does not automatically exit unless you
17907 use the option @option{--once}. You can terminate it by using
17908 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17909 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17910 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17911 @option{--multi} option to @code{gdbserver} has no influence on that.
17913 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17915 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17917 @code{gdbserver} normally terminates after all of its debugged processes have
17918 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17919 extended-remote}, @code{gdbserver} stays running even with no processes left.
17920 @value{GDBN} normally terminates the spawned debugged process on its exit,
17921 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17922 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17923 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17924 stays running even in the @kbd{target remote} mode.
17926 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17927 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17928 completeness, at most one @value{GDBN} can be connected at a time.
17930 @cindex @option{--once}, @code{gdbserver} option
17931 By default, @code{gdbserver} keeps the listening TCP port open, so that
17932 additional connections are possible. However, if you start @code{gdbserver}
17933 with the @option{--once} option, it will stop listening for any further
17934 connection attempts after connecting to the first @value{GDBN} session. This
17935 means no further connections to @code{gdbserver} will be possible after the
17936 first one. It also means @code{gdbserver} will terminate after the first
17937 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17938 connections and even in the @kbd{target extended-remote} mode. The
17939 @option{--once} option allows reusing the same port number for connecting to
17940 multiple instances of @code{gdbserver} running on the same host, since each
17941 instance closes its port after the first connection.
17943 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17945 @cindex @option{--debug}, @code{gdbserver} option
17946 The @option{--debug} option tells @code{gdbserver} to display extra
17947 status information about the debugging process.
17948 @cindex @option{--remote-debug}, @code{gdbserver} option
17949 The @option{--remote-debug} option tells @code{gdbserver} to display
17950 remote protocol debug output. These options are intended for
17951 @code{gdbserver} development and for bug reports to the developers.
17953 @cindex @option{--wrapper}, @code{gdbserver} option
17954 The @option{--wrapper} option specifies a wrapper to launch programs
17955 for debugging. The option should be followed by the name of the
17956 wrapper, then any command-line arguments to pass to the wrapper, then
17957 @kbd{--} indicating the end of the wrapper arguments.
17959 @code{gdbserver} runs the specified wrapper program with a combined
17960 command line including the wrapper arguments, then the name of the
17961 program to debug, then any arguments to the program. The wrapper
17962 runs until it executes your program, and then @value{GDBN} gains control.
17964 You can use any program that eventually calls @code{execve} with
17965 its arguments as a wrapper. Several standard Unix utilities do
17966 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17967 with @code{exec "$@@"} will also work.
17969 For example, you can use @code{env} to pass an environment variable to
17970 the debugged program, without setting the variable in @code{gdbserver}'s
17974 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17977 @subsection Connecting to @code{gdbserver}
17979 Run @value{GDBN} on the host system.
17981 First make sure you have the necessary symbol files. Load symbols for
17982 your application using the @code{file} command before you connect. Use
17983 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17984 was compiled with the correct sysroot using @code{--with-sysroot}).
17986 The symbol file and target libraries must exactly match the executable
17987 and libraries on the target, with one exception: the files on the host
17988 system should not be stripped, even if the files on the target system
17989 are. Mismatched or missing files will lead to confusing results
17990 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17991 files may also prevent @code{gdbserver} from debugging multi-threaded
17994 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17995 For TCP connections, you must start up @code{gdbserver} prior to using
17996 the @code{target remote} command. Otherwise you may get an error whose
17997 text depends on the host system, but which usually looks something like
17998 @samp{Connection refused}. Don't use the @code{load}
17999 command in @value{GDBN} when using @code{gdbserver}, since the program is
18000 already on the target.
18002 @subsection Monitor Commands for @code{gdbserver}
18003 @cindex monitor commands, for @code{gdbserver}
18004 @anchor{Monitor Commands for gdbserver}
18006 During a @value{GDBN} session using @code{gdbserver}, you can use the
18007 @code{monitor} command to send special requests to @code{gdbserver}.
18008 Here are the available commands.
18012 List the available monitor commands.
18014 @item monitor set debug 0
18015 @itemx monitor set debug 1
18016 Disable or enable general debugging messages.
18018 @item monitor set remote-debug 0
18019 @itemx monitor set remote-debug 1
18020 Disable or enable specific debugging messages associated with the remote
18021 protocol (@pxref{Remote Protocol}).
18023 @item monitor set libthread-db-search-path [PATH]
18024 @cindex gdbserver, search path for @code{libthread_db}
18025 When this command is issued, @var{path} is a colon-separated list of
18026 directories to search for @code{libthread_db} (@pxref{Threads,,set
18027 libthread-db-search-path}). If you omit @var{path},
18028 @samp{libthread-db-search-path} will be reset to its default value.
18030 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18031 not supported in @code{gdbserver}.
18034 Tell gdbserver to exit immediately. This command should be followed by
18035 @code{disconnect} to close the debugging session. @code{gdbserver} will
18036 detach from any attached processes and kill any processes it created.
18037 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18038 of a multi-process mode debug session.
18042 @subsection Tracepoints support in @code{gdbserver}
18043 @cindex tracepoints support in @code{gdbserver}
18045 On some targets, @code{gdbserver} supports tracepoints, fast
18046 tracepoints and static tracepoints.
18048 For fast or static tracepoints to work, a special library called the
18049 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18050 This library is built and distributed as an integral part of
18051 @code{gdbserver}. In addition, support for static tracepoints
18052 requires building the in-process agent library with static tracepoints
18053 support. At present, the UST (LTTng Userspace Tracer,
18054 @url{http://lttng.org/ust}) tracing engine is supported. This support
18055 is automatically available if UST development headers are found in the
18056 standard include path when @code{gdbserver} is built, or if
18057 @code{gdbserver} was explicitly configured using @option{--with-ust}
18058 to point at such headers. You can explicitly disable the support
18059 using @option{--with-ust=no}.
18061 There are several ways to load the in-process agent in your program:
18064 @item Specifying it as dependency at link time
18066 You can link your program dynamically with the in-process agent
18067 library. On most systems, this is accomplished by adding
18068 @code{-linproctrace} to the link command.
18070 @item Using the system's preloading mechanisms
18072 You can force loading the in-process agent at startup time by using
18073 your system's support for preloading shared libraries. Many Unixes
18074 support the concept of preloading user defined libraries. In most
18075 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18076 in the environment. See also the description of @code{gdbserver}'s
18077 @option{--wrapper} command line option.
18079 @item Using @value{GDBN} to force loading the agent at run time
18081 On some systems, you can force the inferior to load a shared library,
18082 by calling a dynamic loader function in the inferior that takes care
18083 of dynamically looking up and loading a shared library. On most Unix
18084 systems, the function is @code{dlopen}. You'll use the @code{call}
18085 command for that. For example:
18088 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18091 Note that on most Unix systems, for the @code{dlopen} function to be
18092 available, the program needs to be linked with @code{-ldl}.
18095 On systems that have a userspace dynamic loader, like most Unix
18096 systems, when you connect to @code{gdbserver} using @code{target
18097 remote}, you'll find that the program is stopped at the dynamic
18098 loader's entry point, and no shared library has been loaded in the
18099 program's address space yet, including the in-process agent. In that
18100 case, before being able to use any of the fast or static tracepoints
18101 features, you need to let the loader run and load the shared
18102 libraries. The simplest way to do that is to run the program to the
18103 main procedure. E.g., if debugging a C or C@t{++} program, start
18104 @code{gdbserver} like so:
18107 $ gdbserver :9999 myprogram
18110 Start GDB and connect to @code{gdbserver} like so, and run to main:
18114 (@value{GDBP}) target remote myhost:9999
18115 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18116 (@value{GDBP}) b main
18117 (@value{GDBP}) continue
18120 The in-process tracing agent library should now be loaded into the
18121 process; you can confirm it with the @code{info sharedlibrary}
18122 command, which will list @file{libinproctrace.so} as loaded in the
18123 process. You are now ready to install fast tracepoints, list static
18124 tracepoint markers, probe static tracepoints markers, and start
18127 @node Remote Configuration
18128 @section Remote Configuration
18131 @kindex show remote
18132 This section documents the configuration options available when
18133 debugging remote programs. For the options related to the File I/O
18134 extensions of the remote protocol, see @ref{system,
18135 system-call-allowed}.
18138 @item set remoteaddresssize @var{bits}
18139 @cindex address size for remote targets
18140 @cindex bits in remote address
18141 Set the maximum size of address in a memory packet to the specified
18142 number of bits. @value{GDBN} will mask off the address bits above
18143 that number, when it passes addresses to the remote target. The
18144 default value is the number of bits in the target's address.
18146 @item show remoteaddresssize
18147 Show the current value of remote address size in bits.
18149 @item set remotebaud @var{n}
18150 @cindex baud rate for remote targets
18151 Set the baud rate for the remote serial I/O to @var{n} baud. The
18152 value is used to set the speed of the serial port used for debugging
18155 @item show remotebaud
18156 Show the current speed of the remote connection.
18158 @item set remotebreak
18159 @cindex interrupt remote programs
18160 @cindex BREAK signal instead of Ctrl-C
18161 @anchor{set remotebreak}
18162 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18163 when you type @kbd{Ctrl-c} to interrupt the program running
18164 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18165 character instead. The default is off, since most remote systems
18166 expect to see @samp{Ctrl-C} as the interrupt signal.
18168 @item show remotebreak
18169 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18170 interrupt the remote program.
18172 @item set remoteflow on
18173 @itemx set remoteflow off
18174 @kindex set remoteflow
18175 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18176 on the serial port used to communicate to the remote target.
18178 @item show remoteflow
18179 @kindex show remoteflow
18180 Show the current setting of hardware flow control.
18182 @item set remotelogbase @var{base}
18183 Set the base (a.k.a.@: radix) of logging serial protocol
18184 communications to @var{base}. Supported values of @var{base} are:
18185 @code{ascii}, @code{octal}, and @code{hex}. The default is
18188 @item show remotelogbase
18189 Show the current setting of the radix for logging remote serial
18192 @item set remotelogfile @var{file}
18193 @cindex record serial communications on file
18194 Record remote serial communications on the named @var{file}. The
18195 default is not to record at all.
18197 @item show remotelogfile.
18198 Show the current setting of the file name on which to record the
18199 serial communications.
18201 @item set remotetimeout @var{num}
18202 @cindex timeout for serial communications
18203 @cindex remote timeout
18204 Set the timeout limit to wait for the remote target to respond to
18205 @var{num} seconds. The default is 2 seconds.
18207 @item show remotetimeout
18208 Show the current number of seconds to wait for the remote target
18211 @cindex limit hardware breakpoints and watchpoints
18212 @cindex remote target, limit break- and watchpoints
18213 @anchor{set remote hardware-watchpoint-limit}
18214 @anchor{set remote hardware-breakpoint-limit}
18215 @item set remote hardware-watchpoint-limit @var{limit}
18216 @itemx set remote hardware-breakpoint-limit @var{limit}
18217 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18218 watchpoints. A limit of -1, the default, is treated as unlimited.
18220 @cindex limit hardware watchpoints length
18221 @cindex remote target, limit watchpoints length
18222 @anchor{set remote hardware-watchpoint-length-limit}
18223 @item set remote hardware-watchpoint-length-limit @var{limit}
18224 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18225 a remote hardware watchpoint. A limit of -1, the default, is treated
18228 @item show remote hardware-watchpoint-length-limit
18229 Show the current limit (in bytes) of the maximum length of
18230 a remote hardware watchpoint.
18232 @item set remote exec-file @var{filename}
18233 @itemx show remote exec-file
18234 @anchor{set remote exec-file}
18235 @cindex executable file, for remote target
18236 Select the file used for @code{run} with @code{target
18237 extended-remote}. This should be set to a filename valid on the
18238 target system. If it is not set, the target will use a default
18239 filename (e.g.@: the last program run).
18241 @item set remote interrupt-sequence
18242 @cindex interrupt remote programs
18243 @cindex select Ctrl-C, BREAK or BREAK-g
18244 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18245 @samp{BREAK-g} as the
18246 sequence to the remote target in order to interrupt the execution.
18247 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18248 is high level of serial line for some certain time.
18249 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18250 It is @code{BREAK} signal followed by character @code{g}.
18252 @item show interrupt-sequence
18253 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18254 is sent by @value{GDBN} to interrupt the remote program.
18255 @code{BREAK-g} is BREAK signal followed by @code{g} and
18256 also known as Magic SysRq g.
18258 @item set remote interrupt-on-connect
18259 @cindex send interrupt-sequence on start
18260 Specify whether interrupt-sequence is sent to remote target when
18261 @value{GDBN} connects to it. This is mostly needed when you debug
18262 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18263 which is known as Magic SysRq g in order to connect @value{GDBN}.
18265 @item show interrupt-on-connect
18266 Show whether interrupt-sequence is sent
18267 to remote target when @value{GDBN} connects to it.
18271 @item set tcp auto-retry on
18272 @cindex auto-retry, for remote TCP target
18273 Enable auto-retry for remote TCP connections. This is useful if the remote
18274 debugging agent is launched in parallel with @value{GDBN}; there is a race
18275 condition because the agent may not become ready to accept the connection
18276 before @value{GDBN} attempts to connect. When auto-retry is
18277 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18278 to establish the connection using the timeout specified by
18279 @code{set tcp connect-timeout}.
18281 @item set tcp auto-retry off
18282 Do not auto-retry failed TCP connections.
18284 @item show tcp auto-retry
18285 Show the current auto-retry setting.
18287 @item set tcp connect-timeout @var{seconds}
18288 @itemx set tcp connect-timeout unlimited
18289 @cindex connection timeout, for remote TCP target
18290 @cindex timeout, for remote target connection
18291 Set the timeout for establishing a TCP connection to the remote target to
18292 @var{seconds}. The timeout affects both polling to retry failed connections
18293 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18294 that are merely slow to complete, and represents an approximate cumulative
18295 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18296 @value{GDBN} will keep attempting to establish a connection forever,
18297 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18299 @item show tcp connect-timeout
18300 Show the current connection timeout setting.
18303 @cindex remote packets, enabling and disabling
18304 The @value{GDBN} remote protocol autodetects the packets supported by
18305 your debugging stub. If you need to override the autodetection, you
18306 can use these commands to enable or disable individual packets. Each
18307 packet can be set to @samp{on} (the remote target supports this
18308 packet), @samp{off} (the remote target does not support this packet),
18309 or @samp{auto} (detect remote target support for this packet). They
18310 all default to @samp{auto}. For more information about each packet,
18311 see @ref{Remote Protocol}.
18313 During normal use, you should not have to use any of these commands.
18314 If you do, that may be a bug in your remote debugging stub, or a bug
18315 in @value{GDBN}. You may want to report the problem to the
18316 @value{GDBN} developers.
18318 For each packet @var{name}, the command to enable or disable the
18319 packet is @code{set remote @var{name}-packet}. The available settings
18322 @multitable @columnfractions 0.28 0.32 0.25
18325 @tab Related Features
18327 @item @code{fetch-register}
18329 @tab @code{info registers}
18331 @item @code{set-register}
18335 @item @code{binary-download}
18337 @tab @code{load}, @code{set}
18339 @item @code{read-aux-vector}
18340 @tab @code{qXfer:auxv:read}
18341 @tab @code{info auxv}
18343 @item @code{symbol-lookup}
18344 @tab @code{qSymbol}
18345 @tab Detecting multiple threads
18347 @item @code{attach}
18348 @tab @code{vAttach}
18351 @item @code{verbose-resume}
18353 @tab Stepping or resuming multiple threads
18359 @item @code{software-breakpoint}
18363 @item @code{hardware-breakpoint}
18367 @item @code{write-watchpoint}
18371 @item @code{read-watchpoint}
18375 @item @code{access-watchpoint}
18379 @item @code{target-features}
18380 @tab @code{qXfer:features:read}
18381 @tab @code{set architecture}
18383 @item @code{library-info}
18384 @tab @code{qXfer:libraries:read}
18385 @tab @code{info sharedlibrary}
18387 @item @code{memory-map}
18388 @tab @code{qXfer:memory-map:read}
18389 @tab @code{info mem}
18391 @item @code{read-sdata-object}
18392 @tab @code{qXfer:sdata:read}
18393 @tab @code{print $_sdata}
18395 @item @code{read-spu-object}
18396 @tab @code{qXfer:spu:read}
18397 @tab @code{info spu}
18399 @item @code{write-spu-object}
18400 @tab @code{qXfer:spu:write}
18401 @tab @code{info spu}
18403 @item @code{read-siginfo-object}
18404 @tab @code{qXfer:siginfo:read}
18405 @tab @code{print $_siginfo}
18407 @item @code{write-siginfo-object}
18408 @tab @code{qXfer:siginfo:write}
18409 @tab @code{set $_siginfo}
18411 @item @code{threads}
18412 @tab @code{qXfer:threads:read}
18413 @tab @code{info threads}
18415 @item @code{get-thread-local-@*storage-address}
18416 @tab @code{qGetTLSAddr}
18417 @tab Displaying @code{__thread} variables
18419 @item @code{get-thread-information-block-address}
18420 @tab @code{qGetTIBAddr}
18421 @tab Display MS-Windows Thread Information Block.
18423 @item @code{search-memory}
18424 @tab @code{qSearch:memory}
18427 @item @code{supported-packets}
18428 @tab @code{qSupported}
18429 @tab Remote communications parameters
18431 @item @code{pass-signals}
18432 @tab @code{QPassSignals}
18433 @tab @code{handle @var{signal}}
18435 @item @code{program-signals}
18436 @tab @code{QProgramSignals}
18437 @tab @code{handle @var{signal}}
18439 @item @code{hostio-close-packet}
18440 @tab @code{vFile:close}
18441 @tab @code{remote get}, @code{remote put}
18443 @item @code{hostio-open-packet}
18444 @tab @code{vFile:open}
18445 @tab @code{remote get}, @code{remote put}
18447 @item @code{hostio-pread-packet}
18448 @tab @code{vFile:pread}
18449 @tab @code{remote get}, @code{remote put}
18451 @item @code{hostio-pwrite-packet}
18452 @tab @code{vFile:pwrite}
18453 @tab @code{remote get}, @code{remote put}
18455 @item @code{hostio-unlink-packet}
18456 @tab @code{vFile:unlink}
18457 @tab @code{remote delete}
18459 @item @code{hostio-readlink-packet}
18460 @tab @code{vFile:readlink}
18463 @item @code{noack-packet}
18464 @tab @code{QStartNoAckMode}
18465 @tab Packet acknowledgment
18467 @item @code{osdata}
18468 @tab @code{qXfer:osdata:read}
18469 @tab @code{info os}
18471 @item @code{query-attached}
18472 @tab @code{qAttached}
18473 @tab Querying remote process attach state.
18475 @item @code{trace-buffer-size}
18476 @tab @code{QTBuffer:size}
18477 @tab @code{set trace-buffer-size}
18479 @item @code{trace-status}
18480 @tab @code{qTStatus}
18481 @tab @code{tstatus}
18483 @item @code{traceframe-info}
18484 @tab @code{qXfer:traceframe-info:read}
18485 @tab Traceframe info
18487 @item @code{install-in-trace}
18488 @tab @code{InstallInTrace}
18489 @tab Install tracepoint in tracing
18491 @item @code{disable-randomization}
18492 @tab @code{QDisableRandomization}
18493 @tab @code{set disable-randomization}
18495 @item @code{conditional-breakpoints-packet}
18496 @tab @code{Z0 and Z1}
18497 @tab @code{Support for target-side breakpoint condition evaluation}
18501 @section Implementing a Remote Stub
18503 @cindex debugging stub, example
18504 @cindex remote stub, example
18505 @cindex stub example, remote debugging
18506 The stub files provided with @value{GDBN} implement the target side of the
18507 communication protocol, and the @value{GDBN} side is implemented in the
18508 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18509 these subroutines to communicate, and ignore the details. (If you're
18510 implementing your own stub file, you can still ignore the details: start
18511 with one of the existing stub files. @file{sparc-stub.c} is the best
18512 organized, and therefore the easiest to read.)
18514 @cindex remote serial debugging, overview
18515 To debug a program running on another machine (the debugging
18516 @dfn{target} machine), you must first arrange for all the usual
18517 prerequisites for the program to run by itself. For example, for a C
18522 A startup routine to set up the C runtime environment; these usually
18523 have a name like @file{crt0}. The startup routine may be supplied by
18524 your hardware supplier, or you may have to write your own.
18527 A C subroutine library to support your program's
18528 subroutine calls, notably managing input and output.
18531 A way of getting your program to the other machine---for example, a
18532 download program. These are often supplied by the hardware
18533 manufacturer, but you may have to write your own from hardware
18537 The next step is to arrange for your program to use a serial port to
18538 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18539 machine). In general terms, the scheme looks like this:
18543 @value{GDBN} already understands how to use this protocol; when everything
18544 else is set up, you can simply use the @samp{target remote} command
18545 (@pxref{Targets,,Specifying a Debugging Target}).
18547 @item On the target,
18548 you must link with your program a few special-purpose subroutines that
18549 implement the @value{GDBN} remote serial protocol. The file containing these
18550 subroutines is called a @dfn{debugging stub}.
18552 On certain remote targets, you can use an auxiliary program
18553 @code{gdbserver} instead of linking a stub into your program.
18554 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18557 The debugging stub is specific to the architecture of the remote
18558 machine; for example, use @file{sparc-stub.c} to debug programs on
18561 @cindex remote serial stub list
18562 These working remote stubs are distributed with @value{GDBN}:
18567 @cindex @file{i386-stub.c}
18570 For Intel 386 and compatible architectures.
18573 @cindex @file{m68k-stub.c}
18574 @cindex Motorola 680x0
18576 For Motorola 680x0 architectures.
18579 @cindex @file{sh-stub.c}
18582 For Renesas SH architectures.
18585 @cindex @file{sparc-stub.c}
18587 For @sc{sparc} architectures.
18589 @item sparcl-stub.c
18590 @cindex @file{sparcl-stub.c}
18593 For Fujitsu @sc{sparclite} architectures.
18597 The @file{README} file in the @value{GDBN} distribution may list other
18598 recently added stubs.
18601 * Stub Contents:: What the stub can do for you
18602 * Bootstrapping:: What you must do for the stub
18603 * Debug Session:: Putting it all together
18606 @node Stub Contents
18607 @subsection What the Stub Can Do for You
18609 @cindex remote serial stub
18610 The debugging stub for your architecture supplies these three
18614 @item set_debug_traps
18615 @findex set_debug_traps
18616 @cindex remote serial stub, initialization
18617 This routine arranges for @code{handle_exception} to run when your
18618 program stops. You must call this subroutine explicitly in your
18619 program's startup code.
18621 @item handle_exception
18622 @findex handle_exception
18623 @cindex remote serial stub, main routine
18624 This is the central workhorse, but your program never calls it
18625 explicitly---the setup code arranges for @code{handle_exception} to
18626 run when a trap is triggered.
18628 @code{handle_exception} takes control when your program stops during
18629 execution (for example, on a breakpoint), and mediates communications
18630 with @value{GDBN} on the host machine. This is where the communications
18631 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18632 representative on the target machine. It begins by sending summary
18633 information on the state of your program, then continues to execute,
18634 retrieving and transmitting any information @value{GDBN} needs, until you
18635 execute a @value{GDBN} command that makes your program resume; at that point,
18636 @code{handle_exception} returns control to your own code on the target
18640 @cindex @code{breakpoint} subroutine, remote
18641 Use this auxiliary subroutine to make your program contain a
18642 breakpoint. Depending on the particular situation, this may be the only
18643 way for @value{GDBN} to get control. For instance, if your target
18644 machine has some sort of interrupt button, you won't need to call this;
18645 pressing the interrupt button transfers control to
18646 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18647 simply receiving characters on the serial port may also trigger a trap;
18648 again, in that situation, you don't need to call @code{breakpoint} from
18649 your own program---simply running @samp{target remote} from the host
18650 @value{GDBN} session gets control.
18652 Call @code{breakpoint} if none of these is true, or if you simply want
18653 to make certain your program stops at a predetermined point for the
18654 start of your debugging session.
18657 @node Bootstrapping
18658 @subsection What You Must Do for the Stub
18660 @cindex remote stub, support routines
18661 The debugging stubs that come with @value{GDBN} are set up for a particular
18662 chip architecture, but they have no information about the rest of your
18663 debugging target machine.
18665 First of all you need to tell the stub how to communicate with the
18669 @item int getDebugChar()
18670 @findex getDebugChar
18671 Write this subroutine to read a single character from the serial port.
18672 It may be identical to @code{getchar} for your target system; a
18673 different name is used to allow you to distinguish the two if you wish.
18675 @item void putDebugChar(int)
18676 @findex putDebugChar
18677 Write this subroutine to write a single character to the serial port.
18678 It may be identical to @code{putchar} for your target system; a
18679 different name is used to allow you to distinguish the two if you wish.
18682 @cindex control C, and remote debugging
18683 @cindex interrupting remote targets
18684 If you want @value{GDBN} to be able to stop your program while it is
18685 running, you need to use an interrupt-driven serial driver, and arrange
18686 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18687 character). That is the character which @value{GDBN} uses to tell the
18688 remote system to stop.
18690 Getting the debugging target to return the proper status to @value{GDBN}
18691 probably requires changes to the standard stub; one quick and dirty way
18692 is to just execute a breakpoint instruction (the ``dirty'' part is that
18693 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18695 Other routines you need to supply are:
18698 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18699 @findex exceptionHandler
18700 Write this function to install @var{exception_address} in the exception
18701 handling tables. You need to do this because the stub does not have any
18702 way of knowing what the exception handling tables on your target system
18703 are like (for example, the processor's table might be in @sc{rom},
18704 containing entries which point to a table in @sc{ram}).
18705 @var{exception_number} is the exception number which should be changed;
18706 its meaning is architecture-dependent (for example, different numbers
18707 might represent divide by zero, misaligned access, etc). When this
18708 exception occurs, control should be transferred directly to
18709 @var{exception_address}, and the processor state (stack, registers,
18710 and so on) should be just as it is when a processor exception occurs. So if
18711 you want to use a jump instruction to reach @var{exception_address}, it
18712 should be a simple jump, not a jump to subroutine.
18714 For the 386, @var{exception_address} should be installed as an interrupt
18715 gate so that interrupts are masked while the handler runs. The gate
18716 should be at privilege level 0 (the most privileged level). The
18717 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18718 help from @code{exceptionHandler}.
18720 @item void flush_i_cache()
18721 @findex flush_i_cache
18722 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18723 instruction cache, if any, on your target machine. If there is no
18724 instruction cache, this subroutine may be a no-op.
18726 On target machines that have instruction caches, @value{GDBN} requires this
18727 function to make certain that the state of your program is stable.
18731 You must also make sure this library routine is available:
18734 @item void *memset(void *, int, int)
18736 This is the standard library function @code{memset} that sets an area of
18737 memory to a known value. If you have one of the free versions of
18738 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18739 either obtain it from your hardware manufacturer, or write your own.
18742 If you do not use the GNU C compiler, you may need other standard
18743 library subroutines as well; this varies from one stub to another,
18744 but in general the stubs are likely to use any of the common library
18745 subroutines which @code{@value{NGCC}} generates as inline code.
18748 @node Debug Session
18749 @subsection Putting it All Together
18751 @cindex remote serial debugging summary
18752 In summary, when your program is ready to debug, you must follow these
18757 Make sure you have defined the supporting low-level routines
18758 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18760 @code{getDebugChar}, @code{putDebugChar},
18761 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18765 Insert these lines in your program's startup code, before the main
18766 procedure is called:
18773 On some machines, when a breakpoint trap is raised, the hardware
18774 automatically makes the PC point to the instruction after the
18775 breakpoint. If your machine doesn't do that, you may need to adjust
18776 @code{handle_exception} to arrange for it to return to the instruction
18777 after the breakpoint on this first invocation, so that your program
18778 doesn't keep hitting the initial breakpoint instead of making
18782 For the 680x0 stub only, you need to provide a variable called
18783 @code{exceptionHook}. Normally you just use:
18786 void (*exceptionHook)() = 0;
18790 but if before calling @code{set_debug_traps}, you set it to point to a
18791 function in your program, that function is called when
18792 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18793 error). The function indicated by @code{exceptionHook} is called with
18794 one parameter: an @code{int} which is the exception number.
18797 Compile and link together: your program, the @value{GDBN} debugging stub for
18798 your target architecture, and the supporting subroutines.
18801 Make sure you have a serial connection between your target machine and
18802 the @value{GDBN} host, and identify the serial port on the host.
18805 @c The "remote" target now provides a `load' command, so we should
18806 @c document that. FIXME.
18807 Download your program to your target machine (or get it there by
18808 whatever means the manufacturer provides), and start it.
18811 Start @value{GDBN} on the host, and connect to the target
18812 (@pxref{Connecting,,Connecting to a Remote Target}).
18816 @node Configurations
18817 @chapter Configuration-Specific Information
18819 While nearly all @value{GDBN} commands are available for all native and
18820 cross versions of the debugger, there are some exceptions. This chapter
18821 describes things that are only available in certain configurations.
18823 There are three major categories of configurations: native
18824 configurations, where the host and target are the same, embedded
18825 operating system configurations, which are usually the same for several
18826 different processor architectures, and bare embedded processors, which
18827 are quite different from each other.
18832 * Embedded Processors::
18839 This section describes details specific to particular native
18844 * BSD libkvm Interface:: Debugging BSD kernel memory images
18845 * SVR4 Process Information:: SVR4 process information
18846 * DJGPP Native:: Features specific to the DJGPP port
18847 * Cygwin Native:: Features specific to the Cygwin port
18848 * Hurd Native:: Features specific to @sc{gnu} Hurd
18849 * Darwin:: Features specific to Darwin
18855 On HP-UX systems, if you refer to a function or variable name that
18856 begins with a dollar sign, @value{GDBN} searches for a user or system
18857 name first, before it searches for a convenience variable.
18860 @node BSD libkvm Interface
18861 @subsection BSD libkvm Interface
18864 @cindex kernel memory image
18865 @cindex kernel crash dump
18867 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18868 interface that provides a uniform interface for accessing kernel virtual
18869 memory images, including live systems and crash dumps. @value{GDBN}
18870 uses this interface to allow you to debug live kernels and kernel crash
18871 dumps on many native BSD configurations. This is implemented as a
18872 special @code{kvm} debugging target. For debugging a live system, load
18873 the currently running kernel into @value{GDBN} and connect to the
18877 (@value{GDBP}) @b{target kvm}
18880 For debugging crash dumps, provide the file name of the crash dump as an
18884 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18887 Once connected to the @code{kvm} target, the following commands are
18893 Set current context from the @dfn{Process Control Block} (PCB) address.
18896 Set current context from proc address. This command isn't available on
18897 modern FreeBSD systems.
18900 @node SVR4 Process Information
18901 @subsection SVR4 Process Information
18903 @cindex examine process image
18904 @cindex process info via @file{/proc}
18906 Many versions of SVR4 and compatible systems provide a facility called
18907 @samp{/proc} that can be used to examine the image of a running
18908 process using file-system subroutines.
18910 If @value{GDBN} is configured for an operating system with this
18911 facility, the command @code{info proc} is available to report
18912 information about the process running your program, or about any
18913 process running on your system. This includes, as of this writing,
18914 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18915 not HP-UX, for example.
18917 This command may also work on core files that were created on a system
18918 that has the @samp{/proc} facility.
18924 @itemx info proc @var{process-id}
18925 Summarize available information about any running process. If a
18926 process ID is specified by @var{process-id}, display information about
18927 that process; otherwise display information about the program being
18928 debugged. The summary includes the debugged process ID, the command
18929 line used to invoke it, its current working directory, and its
18930 executable file's absolute file name.
18932 On some systems, @var{process-id} can be of the form
18933 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18934 within a process. If the optional @var{pid} part is missing, it means
18935 a thread from the process being debugged (the leading @samp{/} still
18936 needs to be present, or else @value{GDBN} will interpret the number as
18937 a process ID rather than a thread ID).
18939 @item info proc cmdline
18940 @cindex info proc cmdline
18941 Show the original command line of the process. This command is
18942 specific to @sc{gnu}/Linux.
18944 @item info proc cwd
18945 @cindex info proc cwd
18946 Show the current working directory of the process. This command is
18947 specific to @sc{gnu}/Linux.
18949 @item info proc exe
18950 @cindex info proc exe
18951 Show the name of executable of the process. This command is specific
18954 @item info proc mappings
18955 @cindex memory address space mappings
18956 Report the memory address space ranges accessible in the program, with
18957 information on whether the process has read, write, or execute access
18958 rights to each range. On @sc{gnu}/Linux systems, each memory range
18959 includes the object file which is mapped to that range, instead of the
18960 memory access rights to that range.
18962 @item info proc stat
18963 @itemx info proc status
18964 @cindex process detailed status information
18965 These subcommands are specific to @sc{gnu}/Linux systems. They show
18966 the process-related information, including the user ID and group ID;
18967 how many threads are there in the process; its virtual memory usage;
18968 the signals that are pending, blocked, and ignored; its TTY; its
18969 consumption of system and user time; its stack size; its @samp{nice}
18970 value; etc. For more information, see the @samp{proc} man page
18971 (type @kbd{man 5 proc} from your shell prompt).
18973 @item info proc all
18974 Show all the information about the process described under all of the
18975 above @code{info proc} subcommands.
18978 @comment These sub-options of 'info proc' were not included when
18979 @comment procfs.c was re-written. Keep their descriptions around
18980 @comment against the day when someone finds the time to put them back in.
18981 @kindex info proc times
18982 @item info proc times
18983 Starting time, user CPU time, and system CPU time for your program and
18986 @kindex info proc id
18988 Report on the process IDs related to your program: its own process ID,
18989 the ID of its parent, the process group ID, and the session ID.
18992 @item set procfs-trace
18993 @kindex set procfs-trace
18994 @cindex @code{procfs} API calls
18995 This command enables and disables tracing of @code{procfs} API calls.
18997 @item show procfs-trace
18998 @kindex show procfs-trace
18999 Show the current state of @code{procfs} API call tracing.
19001 @item set procfs-file @var{file}
19002 @kindex set procfs-file
19003 Tell @value{GDBN} to write @code{procfs} API trace to the named
19004 @var{file}. @value{GDBN} appends the trace info to the previous
19005 contents of the file. The default is to display the trace on the
19008 @item show procfs-file
19009 @kindex show procfs-file
19010 Show the file to which @code{procfs} API trace is written.
19012 @item proc-trace-entry
19013 @itemx proc-trace-exit
19014 @itemx proc-untrace-entry
19015 @itemx proc-untrace-exit
19016 @kindex proc-trace-entry
19017 @kindex proc-trace-exit
19018 @kindex proc-untrace-entry
19019 @kindex proc-untrace-exit
19020 These commands enable and disable tracing of entries into and exits
19021 from the @code{syscall} interface.
19024 @kindex info pidlist
19025 @cindex process list, QNX Neutrino
19026 For QNX Neutrino only, this command displays the list of all the
19027 processes and all the threads within each process.
19030 @kindex info meminfo
19031 @cindex mapinfo list, QNX Neutrino
19032 For QNX Neutrino only, this command displays the list of all mapinfos.
19036 @subsection Features for Debugging @sc{djgpp} Programs
19037 @cindex @sc{djgpp} debugging
19038 @cindex native @sc{djgpp} debugging
19039 @cindex MS-DOS-specific commands
19042 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19043 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19044 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19045 top of real-mode DOS systems and their emulations.
19047 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19048 defines a few commands specific to the @sc{djgpp} port. This
19049 subsection describes those commands.
19054 This is a prefix of @sc{djgpp}-specific commands which print
19055 information about the target system and important OS structures.
19058 @cindex MS-DOS system info
19059 @cindex free memory information (MS-DOS)
19060 @item info dos sysinfo
19061 This command displays assorted information about the underlying
19062 platform: the CPU type and features, the OS version and flavor, the
19063 DPMI version, and the available conventional and DPMI memory.
19068 @cindex segment descriptor tables
19069 @cindex descriptor tables display
19071 @itemx info dos ldt
19072 @itemx info dos idt
19073 These 3 commands display entries from, respectively, Global, Local,
19074 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19075 tables are data structures which store a descriptor for each segment
19076 that is currently in use. The segment's selector is an index into a
19077 descriptor table; the table entry for that index holds the
19078 descriptor's base address and limit, and its attributes and access
19081 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19082 segment (used for both data and the stack), and a DOS segment (which
19083 allows access to DOS/BIOS data structures and absolute addresses in
19084 conventional memory). However, the DPMI host will usually define
19085 additional segments in order to support the DPMI environment.
19087 @cindex garbled pointers
19088 These commands allow to display entries from the descriptor tables.
19089 Without an argument, all entries from the specified table are
19090 displayed. An argument, which should be an integer expression, means
19091 display a single entry whose index is given by the argument. For
19092 example, here's a convenient way to display information about the
19093 debugged program's data segment:
19096 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19097 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19101 This comes in handy when you want to see whether a pointer is outside
19102 the data segment's limit (i.e.@: @dfn{garbled}).
19104 @cindex page tables display (MS-DOS)
19106 @itemx info dos pte
19107 These two commands display entries from, respectively, the Page
19108 Directory and the Page Tables. Page Directories and Page Tables are
19109 data structures which control how virtual memory addresses are mapped
19110 into physical addresses. A Page Table includes an entry for every
19111 page of memory that is mapped into the program's address space; there
19112 may be several Page Tables, each one holding up to 4096 entries. A
19113 Page Directory has up to 4096 entries, one each for every Page Table
19114 that is currently in use.
19116 Without an argument, @kbd{info dos pde} displays the entire Page
19117 Directory, and @kbd{info dos pte} displays all the entries in all of
19118 the Page Tables. An argument, an integer expression, given to the
19119 @kbd{info dos pde} command means display only that entry from the Page
19120 Directory table. An argument given to the @kbd{info dos pte} command
19121 means display entries from a single Page Table, the one pointed to by
19122 the specified entry in the Page Directory.
19124 @cindex direct memory access (DMA) on MS-DOS
19125 These commands are useful when your program uses @dfn{DMA} (Direct
19126 Memory Access), which needs physical addresses to program the DMA
19129 These commands are supported only with some DPMI servers.
19131 @cindex physical address from linear address
19132 @item info dos address-pte @var{addr}
19133 This command displays the Page Table entry for a specified linear
19134 address. The argument @var{addr} is a linear address which should
19135 already have the appropriate segment's base address added to it,
19136 because this command accepts addresses which may belong to @emph{any}
19137 segment. For example, here's how to display the Page Table entry for
19138 the page where a variable @code{i} is stored:
19141 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19142 @exdent @code{Page Table entry for address 0x11a00d30:}
19143 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19147 This says that @code{i} is stored at offset @code{0xd30} from the page
19148 whose physical base address is @code{0x02698000}, and shows all the
19149 attributes of that page.
19151 Note that you must cast the addresses of variables to a @code{char *},
19152 since otherwise the value of @code{__djgpp_base_address}, the base
19153 address of all variables and functions in a @sc{djgpp} program, will
19154 be added using the rules of C pointer arithmetics: if @code{i} is
19155 declared an @code{int}, @value{GDBN} will add 4 times the value of
19156 @code{__djgpp_base_address} to the address of @code{i}.
19158 Here's another example, it displays the Page Table entry for the
19162 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19163 @exdent @code{Page Table entry for address 0x29110:}
19164 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19168 (The @code{+ 3} offset is because the transfer buffer's address is the
19169 3rd member of the @code{_go32_info_block} structure.) The output
19170 clearly shows that this DPMI server maps the addresses in conventional
19171 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19172 linear (@code{0x29110}) addresses are identical.
19174 This command is supported only with some DPMI servers.
19177 @cindex DOS serial data link, remote debugging
19178 In addition to native debugging, the DJGPP port supports remote
19179 debugging via a serial data link. The following commands are specific
19180 to remote serial debugging in the DJGPP port of @value{GDBN}.
19183 @kindex set com1base
19184 @kindex set com1irq
19185 @kindex set com2base
19186 @kindex set com2irq
19187 @kindex set com3base
19188 @kindex set com3irq
19189 @kindex set com4base
19190 @kindex set com4irq
19191 @item set com1base @var{addr}
19192 This command sets the base I/O port address of the @file{COM1} serial
19195 @item set com1irq @var{irq}
19196 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19197 for the @file{COM1} serial port.
19199 There are similar commands @samp{set com2base}, @samp{set com3irq},
19200 etc.@: for setting the port address and the @code{IRQ} lines for the
19203 @kindex show com1base
19204 @kindex show com1irq
19205 @kindex show com2base
19206 @kindex show com2irq
19207 @kindex show com3base
19208 @kindex show com3irq
19209 @kindex show com4base
19210 @kindex show com4irq
19211 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19212 display the current settings of the base address and the @code{IRQ}
19213 lines used by the COM ports.
19216 @kindex info serial
19217 @cindex DOS serial port status
19218 This command prints the status of the 4 DOS serial ports. For each
19219 port, it prints whether it's active or not, its I/O base address and
19220 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19221 counts of various errors encountered so far.
19225 @node Cygwin Native
19226 @subsection Features for Debugging MS Windows PE Executables
19227 @cindex MS Windows debugging
19228 @cindex native Cygwin debugging
19229 @cindex Cygwin-specific commands
19231 @value{GDBN} supports native debugging of MS Windows programs, including
19232 DLLs with and without symbolic debugging information.
19234 @cindex Ctrl-BREAK, MS-Windows
19235 @cindex interrupt debuggee on MS-Windows
19236 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19237 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19238 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19239 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19240 sequence, which can be used to interrupt the debuggee even if it
19243 There are various additional Cygwin-specific commands, described in
19244 this section. Working with DLLs that have no debugging symbols is
19245 described in @ref{Non-debug DLL Symbols}.
19250 This is a prefix of MS Windows-specific commands which print
19251 information about the target system and important OS structures.
19253 @item info w32 selector
19254 This command displays information returned by
19255 the Win32 API @code{GetThreadSelectorEntry} function.
19256 It takes an optional argument that is evaluated to
19257 a long value to give the information about this given selector.
19258 Without argument, this command displays information
19259 about the six segment registers.
19261 @item info w32 thread-information-block
19262 This command displays thread specific information stored in the
19263 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19264 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19268 This is a Cygwin-specific alias of @code{info shared}.
19270 @kindex dll-symbols
19272 This command loads symbols from a dll similarly to
19273 add-sym command but without the need to specify a base address.
19275 @kindex set cygwin-exceptions
19276 @cindex debugging the Cygwin DLL
19277 @cindex Cygwin DLL, debugging
19278 @item set cygwin-exceptions @var{mode}
19279 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19280 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19281 @value{GDBN} will delay recognition of exceptions, and may ignore some
19282 exceptions which seem to be caused by internal Cygwin DLL
19283 ``bookkeeping''. This option is meant primarily for debugging the
19284 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19285 @value{GDBN} users with false @code{SIGSEGV} signals.
19287 @kindex show cygwin-exceptions
19288 @item show cygwin-exceptions
19289 Displays whether @value{GDBN} will break on exceptions that happen
19290 inside the Cygwin DLL itself.
19292 @kindex set new-console
19293 @item set new-console @var{mode}
19294 If @var{mode} is @code{on} the debuggee will
19295 be started in a new console on next start.
19296 If @var{mode} is @code{off}, the debuggee will
19297 be started in the same console as the debugger.
19299 @kindex show new-console
19300 @item show new-console
19301 Displays whether a new console is used
19302 when the debuggee is started.
19304 @kindex set new-group
19305 @item set new-group @var{mode}
19306 This boolean value controls whether the debuggee should
19307 start a new group or stay in the same group as the debugger.
19308 This affects the way the Windows OS handles
19311 @kindex show new-group
19312 @item show new-group
19313 Displays current value of new-group boolean.
19315 @kindex set debugevents
19316 @item set debugevents
19317 This boolean value adds debug output concerning kernel events related
19318 to the debuggee seen by the debugger. This includes events that
19319 signal thread and process creation and exit, DLL loading and
19320 unloading, console interrupts, and debugging messages produced by the
19321 Windows @code{OutputDebugString} API call.
19323 @kindex set debugexec
19324 @item set debugexec
19325 This boolean value adds debug output concerning execute events
19326 (such as resume thread) seen by the debugger.
19328 @kindex set debugexceptions
19329 @item set debugexceptions
19330 This boolean value adds debug output concerning exceptions in the
19331 debuggee seen by the debugger.
19333 @kindex set debugmemory
19334 @item set debugmemory
19335 This boolean value adds debug output concerning debuggee memory reads
19336 and writes by the debugger.
19340 This boolean values specifies whether the debuggee is called
19341 via a shell or directly (default value is on).
19345 Displays if the debuggee will be started with a shell.
19350 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19353 @node Non-debug DLL Symbols
19354 @subsubsection Support for DLLs without Debugging Symbols
19355 @cindex DLLs with no debugging symbols
19356 @cindex Minimal symbols and DLLs
19358 Very often on windows, some of the DLLs that your program relies on do
19359 not include symbolic debugging information (for example,
19360 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19361 symbols in a DLL, it relies on the minimal amount of symbolic
19362 information contained in the DLL's export table. This section
19363 describes working with such symbols, known internally to @value{GDBN} as
19364 ``minimal symbols''.
19366 Note that before the debugged program has started execution, no DLLs
19367 will have been loaded. The easiest way around this problem is simply to
19368 start the program --- either by setting a breakpoint or letting the
19369 program run once to completion. It is also possible to force
19370 @value{GDBN} to load a particular DLL before starting the executable ---
19371 see the shared library information in @ref{Files}, or the
19372 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19373 explicitly loading symbols from a DLL with no debugging information will
19374 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19375 which may adversely affect symbol lookup performance.
19377 @subsubsection DLL Name Prefixes
19379 In keeping with the naming conventions used by the Microsoft debugging
19380 tools, DLL export symbols are made available with a prefix based on the
19381 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19382 also entered into the symbol table, so @code{CreateFileA} is often
19383 sufficient. In some cases there will be name clashes within a program
19384 (particularly if the executable itself includes full debugging symbols)
19385 necessitating the use of the fully qualified name when referring to the
19386 contents of the DLL. Use single-quotes around the name to avoid the
19387 exclamation mark (``!'') being interpreted as a language operator.
19389 Note that the internal name of the DLL may be all upper-case, even
19390 though the file name of the DLL is lower-case, or vice-versa. Since
19391 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19392 some confusion. If in doubt, try the @code{info functions} and
19393 @code{info variables} commands or even @code{maint print msymbols}
19394 (@pxref{Symbols}). Here's an example:
19397 (@value{GDBP}) info function CreateFileA
19398 All functions matching regular expression "CreateFileA":
19400 Non-debugging symbols:
19401 0x77e885f4 CreateFileA
19402 0x77e885f4 KERNEL32!CreateFileA
19406 (@value{GDBP}) info function !
19407 All functions matching regular expression "!":
19409 Non-debugging symbols:
19410 0x6100114c cygwin1!__assert
19411 0x61004034 cygwin1!_dll_crt0@@0
19412 0x61004240 cygwin1!dll_crt0(per_process *)
19416 @subsubsection Working with Minimal Symbols
19418 Symbols extracted from a DLL's export table do not contain very much
19419 type information. All that @value{GDBN} can do is guess whether a symbol
19420 refers to a function or variable depending on the linker section that
19421 contains the symbol. Also note that the actual contents of the memory
19422 contained in a DLL are not available unless the program is running. This
19423 means that you cannot examine the contents of a variable or disassemble
19424 a function within a DLL without a running program.
19426 Variables are generally treated as pointers and dereferenced
19427 automatically. For this reason, it is often necessary to prefix a
19428 variable name with the address-of operator (``&'') and provide explicit
19429 type information in the command. Here's an example of the type of
19433 (@value{GDBP}) print 'cygwin1!__argv'
19438 (@value{GDBP}) x 'cygwin1!__argv'
19439 0x10021610: "\230y\""
19442 And two possible solutions:
19445 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19446 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19450 (@value{GDBP}) x/2x &'cygwin1!__argv'
19451 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19452 (@value{GDBP}) x/x 0x10021608
19453 0x10021608: 0x0022fd98
19454 (@value{GDBP}) x/s 0x0022fd98
19455 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19458 Setting a break point within a DLL is possible even before the program
19459 starts execution. However, under these circumstances, @value{GDBN} can't
19460 examine the initial instructions of the function in order to skip the
19461 function's frame set-up code. You can work around this by using ``*&''
19462 to set the breakpoint at a raw memory address:
19465 (@value{GDBP}) break *&'python22!PyOS_Readline'
19466 Breakpoint 1 at 0x1e04eff0
19469 The author of these extensions is not entirely convinced that setting a
19470 break point within a shared DLL like @file{kernel32.dll} is completely
19474 @subsection Commands Specific to @sc{gnu} Hurd Systems
19475 @cindex @sc{gnu} Hurd debugging
19477 This subsection describes @value{GDBN} commands specific to the
19478 @sc{gnu} Hurd native debugging.
19483 @kindex set signals@r{, Hurd command}
19484 @kindex set sigs@r{, Hurd command}
19485 This command toggles the state of inferior signal interception by
19486 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19487 affected by this command. @code{sigs} is a shorthand alias for
19492 @kindex show signals@r{, Hurd command}
19493 @kindex show sigs@r{, Hurd command}
19494 Show the current state of intercepting inferior's signals.
19496 @item set signal-thread
19497 @itemx set sigthread
19498 @kindex set signal-thread
19499 @kindex set sigthread
19500 This command tells @value{GDBN} which thread is the @code{libc} signal
19501 thread. That thread is run when a signal is delivered to a running
19502 process. @code{set sigthread} is the shorthand alias of @code{set
19505 @item show signal-thread
19506 @itemx show sigthread
19507 @kindex show signal-thread
19508 @kindex show sigthread
19509 These two commands show which thread will run when the inferior is
19510 delivered a signal.
19513 @kindex set stopped@r{, Hurd command}
19514 This commands tells @value{GDBN} that the inferior process is stopped,
19515 as with the @code{SIGSTOP} signal. The stopped process can be
19516 continued by delivering a signal to it.
19519 @kindex show stopped@r{, Hurd command}
19520 This command shows whether @value{GDBN} thinks the debuggee is
19523 @item set exceptions
19524 @kindex set exceptions@r{, Hurd command}
19525 Use this command to turn off trapping of exceptions in the inferior.
19526 When exception trapping is off, neither breakpoints nor
19527 single-stepping will work. To restore the default, set exception
19530 @item show exceptions
19531 @kindex show exceptions@r{, Hurd command}
19532 Show the current state of trapping exceptions in the inferior.
19534 @item set task pause
19535 @kindex set task@r{, Hurd commands}
19536 @cindex task attributes (@sc{gnu} Hurd)
19537 @cindex pause current task (@sc{gnu} Hurd)
19538 This command toggles task suspension when @value{GDBN} has control.
19539 Setting it to on takes effect immediately, and the task is suspended
19540 whenever @value{GDBN} gets control. Setting it to off will take
19541 effect the next time the inferior is continued. If this option is set
19542 to off, you can use @code{set thread default pause on} or @code{set
19543 thread pause on} (see below) to pause individual threads.
19545 @item show task pause
19546 @kindex show task@r{, Hurd commands}
19547 Show the current state of task suspension.
19549 @item set task detach-suspend-count
19550 @cindex task suspend count
19551 @cindex detach from task, @sc{gnu} Hurd
19552 This command sets the suspend count the task will be left with when
19553 @value{GDBN} detaches from it.
19555 @item show task detach-suspend-count
19556 Show the suspend count the task will be left with when detaching.
19558 @item set task exception-port
19559 @itemx set task excp
19560 @cindex task exception port, @sc{gnu} Hurd
19561 This command sets the task exception port to which @value{GDBN} will
19562 forward exceptions. The argument should be the value of the @dfn{send
19563 rights} of the task. @code{set task excp} is a shorthand alias.
19565 @item set noninvasive
19566 @cindex noninvasive task options
19567 This command switches @value{GDBN} to a mode that is the least
19568 invasive as far as interfering with the inferior is concerned. This
19569 is the same as using @code{set task pause}, @code{set exceptions}, and
19570 @code{set signals} to values opposite to the defaults.
19572 @item info send-rights
19573 @itemx info receive-rights
19574 @itemx info port-rights
19575 @itemx info port-sets
19576 @itemx info dead-names
19579 @cindex send rights, @sc{gnu} Hurd
19580 @cindex receive rights, @sc{gnu} Hurd
19581 @cindex port rights, @sc{gnu} Hurd
19582 @cindex port sets, @sc{gnu} Hurd
19583 @cindex dead names, @sc{gnu} Hurd
19584 These commands display information about, respectively, send rights,
19585 receive rights, port rights, port sets, and dead names of a task.
19586 There are also shorthand aliases: @code{info ports} for @code{info
19587 port-rights} and @code{info psets} for @code{info port-sets}.
19589 @item set thread pause
19590 @kindex set thread@r{, Hurd command}
19591 @cindex thread properties, @sc{gnu} Hurd
19592 @cindex pause current thread (@sc{gnu} Hurd)
19593 This command toggles current thread suspension when @value{GDBN} has
19594 control. Setting it to on takes effect immediately, and the current
19595 thread is suspended whenever @value{GDBN} gets control. Setting it to
19596 off will take effect the next time the inferior is continued.
19597 Normally, this command has no effect, since when @value{GDBN} has
19598 control, the whole task is suspended. However, if you used @code{set
19599 task pause off} (see above), this command comes in handy to suspend
19600 only the current thread.
19602 @item show thread pause
19603 @kindex show thread@r{, Hurd command}
19604 This command shows the state of current thread suspension.
19606 @item set thread run
19607 This command sets whether the current thread is allowed to run.
19609 @item show thread run
19610 Show whether the current thread is allowed to run.
19612 @item set thread detach-suspend-count
19613 @cindex thread suspend count, @sc{gnu} Hurd
19614 @cindex detach from thread, @sc{gnu} Hurd
19615 This command sets the suspend count @value{GDBN} will leave on a
19616 thread when detaching. This number is relative to the suspend count
19617 found by @value{GDBN} when it notices the thread; use @code{set thread
19618 takeover-suspend-count} to force it to an absolute value.
19620 @item show thread detach-suspend-count
19621 Show the suspend count @value{GDBN} will leave on the thread when
19624 @item set thread exception-port
19625 @itemx set thread excp
19626 Set the thread exception port to which to forward exceptions. This
19627 overrides the port set by @code{set task exception-port} (see above).
19628 @code{set thread excp} is the shorthand alias.
19630 @item set thread takeover-suspend-count
19631 Normally, @value{GDBN}'s thread suspend counts are relative to the
19632 value @value{GDBN} finds when it notices each thread. This command
19633 changes the suspend counts to be absolute instead.
19635 @item set thread default
19636 @itemx show thread default
19637 @cindex thread default settings, @sc{gnu} Hurd
19638 Each of the above @code{set thread} commands has a @code{set thread
19639 default} counterpart (e.g., @code{set thread default pause}, @code{set
19640 thread default exception-port}, etc.). The @code{thread default}
19641 variety of commands sets the default thread properties for all
19642 threads; you can then change the properties of individual threads with
19643 the non-default commands.
19650 @value{GDBN} provides the following commands specific to the Darwin target:
19653 @item set debug darwin @var{num}
19654 @kindex set debug darwin
19655 When set to a non zero value, enables debugging messages specific to
19656 the Darwin support. Higher values produce more verbose output.
19658 @item show debug darwin
19659 @kindex show debug darwin
19660 Show the current state of Darwin messages.
19662 @item set debug mach-o @var{num}
19663 @kindex set debug mach-o
19664 When set to a non zero value, enables debugging messages while
19665 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19666 file format used on Darwin for object and executable files.) Higher
19667 values produce more verbose output. This is a command to diagnose
19668 problems internal to @value{GDBN} and should not be needed in normal
19671 @item show debug mach-o
19672 @kindex show debug mach-o
19673 Show the current state of Mach-O file messages.
19675 @item set mach-exceptions on
19676 @itemx set mach-exceptions off
19677 @kindex set mach-exceptions
19678 On Darwin, faults are first reported as a Mach exception and are then
19679 mapped to a Posix signal. Use this command to turn on trapping of
19680 Mach exceptions in the inferior. This might be sometimes useful to
19681 better understand the cause of a fault. The default is off.
19683 @item show mach-exceptions
19684 @kindex show mach-exceptions
19685 Show the current state of exceptions trapping.
19690 @section Embedded Operating Systems
19692 This section describes configurations involving the debugging of
19693 embedded operating systems that are available for several different
19697 * VxWorks:: Using @value{GDBN} with VxWorks
19700 @value{GDBN} includes the ability to debug programs running on
19701 various real-time operating systems.
19704 @subsection Using @value{GDBN} with VxWorks
19710 @kindex target vxworks
19711 @item target vxworks @var{machinename}
19712 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19713 is the target system's machine name or IP address.
19717 On VxWorks, @code{load} links @var{filename} dynamically on the
19718 current target system as well as adding its symbols in @value{GDBN}.
19720 @value{GDBN} enables developers to spawn and debug tasks running on networked
19721 VxWorks targets from a Unix host. Already-running tasks spawned from
19722 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19723 both the Unix host and on the VxWorks target. The program
19724 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19725 installed with the name @code{vxgdb}, to distinguish it from a
19726 @value{GDBN} for debugging programs on the host itself.)
19729 @item VxWorks-timeout @var{args}
19730 @kindex vxworks-timeout
19731 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19732 This option is set by the user, and @var{args} represents the number of
19733 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19734 your VxWorks target is a slow software simulator or is on the far side
19735 of a thin network line.
19738 The following information on connecting to VxWorks was current when
19739 this manual was produced; newer releases of VxWorks may use revised
19742 @findex INCLUDE_RDB
19743 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19744 to include the remote debugging interface routines in the VxWorks
19745 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19746 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19747 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19748 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19749 information on configuring and remaking VxWorks, see the manufacturer's
19751 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19753 Once you have included @file{rdb.a} in your VxWorks system image and set
19754 your Unix execution search path to find @value{GDBN}, you are ready to
19755 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19756 @code{vxgdb}, depending on your installation).
19758 @value{GDBN} comes up showing the prompt:
19765 * VxWorks Connection:: Connecting to VxWorks
19766 * VxWorks Download:: VxWorks download
19767 * VxWorks Attach:: Running tasks
19770 @node VxWorks Connection
19771 @subsubsection Connecting to VxWorks
19773 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19774 network. To connect to a target whose host name is ``@code{tt}'', type:
19777 (vxgdb) target vxworks tt
19781 @value{GDBN} displays messages like these:
19784 Attaching remote machine across net...
19789 @value{GDBN} then attempts to read the symbol tables of any object modules
19790 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19791 these files by searching the directories listed in the command search
19792 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19793 to find an object file, it displays a message such as:
19796 prog.o: No such file or directory.
19799 When this happens, add the appropriate directory to the search path with
19800 the @value{GDBN} command @code{path}, and execute the @code{target}
19803 @node VxWorks Download
19804 @subsubsection VxWorks Download
19806 @cindex download to VxWorks
19807 If you have connected to the VxWorks target and you want to debug an
19808 object that has not yet been loaded, you can use the @value{GDBN}
19809 @code{load} command to download a file from Unix to VxWorks
19810 incrementally. The object file given as an argument to the @code{load}
19811 command is actually opened twice: first by the VxWorks target in order
19812 to download the code, then by @value{GDBN} in order to read the symbol
19813 table. This can lead to problems if the current working directories on
19814 the two systems differ. If both systems have NFS mounted the same
19815 filesystems, you can avoid these problems by using absolute paths.
19816 Otherwise, it is simplest to set the working directory on both systems
19817 to the directory in which the object file resides, and then to reference
19818 the file by its name, without any path. For instance, a program
19819 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19820 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19821 program, type this on VxWorks:
19824 -> cd "@var{vxpath}/vw/demo/rdb"
19828 Then, in @value{GDBN}, type:
19831 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19832 (vxgdb) load prog.o
19835 @value{GDBN} displays a response similar to this:
19838 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19841 You can also use the @code{load} command to reload an object module
19842 after editing and recompiling the corresponding source file. Note that
19843 this makes @value{GDBN} delete all currently-defined breakpoints,
19844 auto-displays, and convenience variables, and to clear the value
19845 history. (This is necessary in order to preserve the integrity of
19846 debugger's data structures that reference the target system's symbol
19849 @node VxWorks Attach
19850 @subsubsection Running Tasks
19852 @cindex running VxWorks tasks
19853 You can also attach to an existing task using the @code{attach} command as
19857 (vxgdb) attach @var{task}
19861 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19862 or suspended when you attach to it. Running tasks are suspended at
19863 the time of attachment.
19865 @node Embedded Processors
19866 @section Embedded Processors
19868 This section goes into details specific to particular embedded
19871 @cindex send command to simulator
19872 Whenever a specific embedded processor has a simulator, @value{GDBN}
19873 allows to send an arbitrary command to the simulator.
19876 @item sim @var{command}
19877 @kindex sim@r{, a command}
19878 Send an arbitrary @var{command} string to the simulator. Consult the
19879 documentation for the specific simulator in use for information about
19880 acceptable commands.
19886 * M32R/D:: Renesas M32R/D
19887 * M68K:: Motorola M68K
19888 * MicroBlaze:: Xilinx MicroBlaze
19889 * MIPS Embedded:: MIPS Embedded
19890 * PowerPC Embedded:: PowerPC Embedded
19891 * PA:: HP PA Embedded
19892 * Sparclet:: Tsqware Sparclet
19893 * Sparclite:: Fujitsu Sparclite
19894 * Z8000:: Zilog Z8000
19897 * Super-H:: Renesas Super-H
19906 @item target rdi @var{dev}
19907 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19908 use this target to communicate with both boards running the Angel
19909 monitor, or with the EmbeddedICE JTAG debug device.
19912 @item target rdp @var{dev}
19917 @value{GDBN} provides the following ARM-specific commands:
19920 @item set arm disassembler
19922 This commands selects from a list of disassembly styles. The
19923 @code{"std"} style is the standard style.
19925 @item show arm disassembler
19927 Show the current disassembly style.
19929 @item set arm apcs32
19930 @cindex ARM 32-bit mode
19931 This command toggles ARM operation mode between 32-bit and 26-bit.
19933 @item show arm apcs32
19934 Display the current usage of the ARM 32-bit mode.
19936 @item set arm fpu @var{fputype}
19937 This command sets the ARM floating-point unit (FPU) type. The
19938 argument @var{fputype} can be one of these:
19942 Determine the FPU type by querying the OS ABI.
19944 Software FPU, with mixed-endian doubles on little-endian ARM
19947 GCC-compiled FPA co-processor.
19949 Software FPU with pure-endian doubles.
19955 Show the current type of the FPU.
19958 This command forces @value{GDBN} to use the specified ABI.
19961 Show the currently used ABI.
19963 @item set arm fallback-mode (arm|thumb|auto)
19964 @value{GDBN} uses the symbol table, when available, to determine
19965 whether instructions are ARM or Thumb. This command controls
19966 @value{GDBN}'s default behavior when the symbol table is not
19967 available. The default is @samp{auto}, which causes @value{GDBN} to
19968 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19971 @item show arm fallback-mode
19972 Show the current fallback instruction mode.
19974 @item set arm force-mode (arm|thumb|auto)
19975 This command overrides use of the symbol table to determine whether
19976 instructions are ARM or Thumb. The default is @samp{auto}, which
19977 causes @value{GDBN} to use the symbol table and then the setting
19978 of @samp{set arm fallback-mode}.
19980 @item show arm force-mode
19981 Show the current forced instruction mode.
19983 @item set debug arm
19984 Toggle whether to display ARM-specific debugging messages from the ARM
19985 target support subsystem.
19987 @item show debug arm
19988 Show whether ARM-specific debugging messages are enabled.
19991 The following commands are available when an ARM target is debugged
19992 using the RDI interface:
19995 @item rdilogfile @r{[}@var{file}@r{]}
19997 @cindex ADP (Angel Debugger Protocol) logging
19998 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19999 With an argument, sets the log file to the specified @var{file}. With
20000 no argument, show the current log file name. The default log file is
20003 @item rdilogenable @r{[}@var{arg}@r{]}
20004 @kindex rdilogenable
20005 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20006 enables logging, with an argument 0 or @code{"no"} disables it. With
20007 no arguments displays the current setting. When logging is enabled,
20008 ADP packets exchanged between @value{GDBN} and the RDI target device
20009 are logged to a file.
20011 @item set rdiromatzero
20012 @kindex set rdiromatzero
20013 @cindex ROM at zero address, RDI
20014 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20015 vector catching is disabled, so that zero address can be used. If off
20016 (the default), vector catching is enabled. For this command to take
20017 effect, it needs to be invoked prior to the @code{target rdi} command.
20019 @item show rdiromatzero
20020 @kindex show rdiromatzero
20021 Show the current setting of ROM at zero address.
20023 @item set rdiheartbeat
20024 @kindex set rdiheartbeat
20025 @cindex RDI heartbeat
20026 Enable or disable RDI heartbeat packets. It is not recommended to
20027 turn on this option, since it confuses ARM and EPI JTAG interface, as
20028 well as the Angel monitor.
20030 @item show rdiheartbeat
20031 @kindex show rdiheartbeat
20032 Show the setting of RDI heartbeat packets.
20036 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20037 The @value{GDBN} ARM simulator accepts the following optional arguments.
20040 @item --swi-support=@var{type}
20041 Tell the simulator which SWI interfaces to support.
20042 @var{type} may be a comma separated list of the following values.
20043 The default value is @code{all}.
20056 @subsection Renesas M32R/D and M32R/SDI
20059 @kindex target m32r
20060 @item target m32r @var{dev}
20061 Renesas M32R/D ROM monitor.
20063 @kindex target m32rsdi
20064 @item target m32rsdi @var{dev}
20065 Renesas M32R SDI server, connected via parallel port to the board.
20068 The following @value{GDBN} commands are specific to the M32R monitor:
20071 @item set download-path @var{path}
20072 @kindex set download-path
20073 @cindex find downloadable @sc{srec} files (M32R)
20074 Set the default path for finding downloadable @sc{srec} files.
20076 @item show download-path
20077 @kindex show download-path
20078 Show the default path for downloadable @sc{srec} files.
20080 @item set board-address @var{addr}
20081 @kindex set board-address
20082 @cindex M32-EVA target board address
20083 Set the IP address for the M32R-EVA target board.
20085 @item show board-address
20086 @kindex show board-address
20087 Show the current IP address of the target board.
20089 @item set server-address @var{addr}
20090 @kindex set server-address
20091 @cindex download server address (M32R)
20092 Set the IP address for the download server, which is the @value{GDBN}'s
20095 @item show server-address
20096 @kindex show server-address
20097 Display the IP address of the download server.
20099 @item upload @r{[}@var{file}@r{]}
20100 @kindex upload@r{, M32R}
20101 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20102 upload capability. If no @var{file} argument is given, the current
20103 executable file is uploaded.
20105 @item tload @r{[}@var{file}@r{]}
20106 @kindex tload@r{, M32R}
20107 Test the @code{upload} command.
20110 The following commands are available for M32R/SDI:
20115 @cindex reset SDI connection, M32R
20116 This command resets the SDI connection.
20120 This command shows the SDI connection status.
20123 @kindex debug_chaos
20124 @cindex M32R/Chaos debugging
20125 Instructs the remote that M32R/Chaos debugging is to be used.
20127 @item use_debug_dma
20128 @kindex use_debug_dma
20129 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20132 @kindex use_mon_code
20133 Instructs the remote to use the MON_CODE method of accessing memory.
20136 @kindex use_ib_break
20137 Instructs the remote to set breakpoints by IB break.
20139 @item use_dbt_break
20140 @kindex use_dbt_break
20141 Instructs the remote to set breakpoints by DBT.
20147 The Motorola m68k configuration includes ColdFire support, and a
20148 target command for the following ROM monitor.
20152 @kindex target dbug
20153 @item target dbug @var{dev}
20154 dBUG ROM monitor for Motorola ColdFire.
20159 @subsection MicroBlaze
20160 @cindex Xilinx MicroBlaze
20161 @cindex XMD, Xilinx Microprocessor Debugger
20163 The MicroBlaze is a soft-core processor supported on various Xilinx
20164 FPGAs, such as Spartan or Virtex series. Boards with these processors
20165 usually have JTAG ports which connect to a host system running the Xilinx
20166 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20167 This host system is used to download the configuration bitstream to
20168 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20169 communicates with the target board using the JTAG interface and
20170 presents a @code{gdbserver} interface to the board. By default
20171 @code{xmd} uses port @code{1234}. (While it is possible to change
20172 this default port, it requires the use of undocumented @code{xmd}
20173 commands. Contact Xilinx support if you need to do this.)
20175 Use these GDB commands to connect to the MicroBlaze target processor.
20178 @item target remote :1234
20179 Use this command to connect to the target if you are running @value{GDBN}
20180 on the same system as @code{xmd}.
20182 @item target remote @var{xmd-host}:1234
20183 Use this command to connect to the target if it is connected to @code{xmd}
20184 running on a different system named @var{xmd-host}.
20187 Use this command to download a program to the MicroBlaze target.
20189 @item set debug microblaze @var{n}
20190 Enable MicroBlaze-specific debugging messages if non-zero.
20192 @item show debug microblaze @var{n}
20193 Show MicroBlaze-specific debugging level.
20196 @node MIPS Embedded
20197 @subsection @acronym{MIPS} Embedded
20199 @cindex @acronym{MIPS} boards
20200 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20201 @acronym{MIPS} board attached to a serial line. This is available when
20202 you configure @value{GDBN} with @samp{--target=mips-elf}.
20205 Use these @value{GDBN} commands to specify the connection to your target board:
20208 @item target mips @var{port}
20209 @kindex target mips @var{port}
20210 To run a program on the board, start up @code{@value{GDBP}} with the
20211 name of your program as the argument. To connect to the board, use the
20212 command @samp{target mips @var{port}}, where @var{port} is the name of
20213 the serial port connected to the board. If the program has not already
20214 been downloaded to the board, you may use the @code{load} command to
20215 download it. You can then use all the usual @value{GDBN} commands.
20217 For example, this sequence connects to the target board through a serial
20218 port, and loads and runs a program called @var{prog} through the
20222 host$ @value{GDBP} @var{prog}
20223 @value{GDBN} is free software and @dots{}
20224 (@value{GDBP}) target mips /dev/ttyb
20225 (@value{GDBP}) load @var{prog}
20229 @item target mips @var{hostname}:@var{portnumber}
20230 On some @value{GDBN} host configurations, you can specify a TCP
20231 connection (for instance, to a serial line managed by a terminal
20232 concentrator) instead of a serial port, using the syntax
20233 @samp{@var{hostname}:@var{portnumber}}.
20235 @item target pmon @var{port}
20236 @kindex target pmon @var{port}
20239 @item target ddb @var{port}
20240 @kindex target ddb @var{port}
20241 NEC's DDB variant of PMON for Vr4300.
20243 @item target lsi @var{port}
20244 @kindex target lsi @var{port}
20245 LSI variant of PMON.
20247 @kindex target r3900
20248 @item target r3900 @var{dev}
20249 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20251 @kindex target array
20252 @item target array @var{dev}
20253 Array Tech LSI33K RAID controller board.
20259 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20262 @item set mipsfpu double
20263 @itemx set mipsfpu single
20264 @itemx set mipsfpu none
20265 @itemx set mipsfpu auto
20266 @itemx show mipsfpu
20267 @kindex set mipsfpu
20268 @kindex show mipsfpu
20269 @cindex @acronym{MIPS} remote floating point
20270 @cindex floating point, @acronym{MIPS} remote
20271 If your target board does not support the @acronym{MIPS} floating point
20272 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20273 need this, you may wish to put the command in your @value{GDBN} init
20274 file). This tells @value{GDBN} how to find the return value of
20275 functions which return floating point values. It also allows
20276 @value{GDBN} to avoid saving the floating point registers when calling
20277 functions on the board. If you are using a floating point coprocessor
20278 with only single precision floating point support, as on the @sc{r4650}
20279 processor, use the command @samp{set mipsfpu single}. The default
20280 double precision floating point coprocessor may be selected using
20281 @samp{set mipsfpu double}.
20283 In previous versions the only choices were double precision or no
20284 floating point, so @samp{set mipsfpu on} will select double precision
20285 and @samp{set mipsfpu off} will select no floating point.
20287 As usual, you can inquire about the @code{mipsfpu} variable with
20288 @samp{show mipsfpu}.
20290 @item set timeout @var{seconds}
20291 @itemx set retransmit-timeout @var{seconds}
20292 @itemx show timeout
20293 @itemx show retransmit-timeout
20294 @cindex @code{timeout}, @acronym{MIPS} protocol
20295 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20296 @kindex set timeout
20297 @kindex show timeout
20298 @kindex set retransmit-timeout
20299 @kindex show retransmit-timeout
20300 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20301 remote protocol, with the @code{set timeout @var{seconds}} command. The
20302 default is 5 seconds. Similarly, you can control the timeout used while
20303 waiting for an acknowledgment of a packet with the @code{set
20304 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20305 You can inspect both values with @code{show timeout} and @code{show
20306 retransmit-timeout}. (These commands are @emph{only} available when
20307 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20309 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20310 is waiting for your program to stop. In that case, @value{GDBN} waits
20311 forever because it has no way of knowing how long the program is going
20312 to run before stopping.
20314 @item set syn-garbage-limit @var{num}
20315 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20316 @cindex synchronize with remote @acronym{MIPS} target
20317 Limit the maximum number of characters @value{GDBN} should ignore when
20318 it tries to synchronize with the remote target. The default is 10
20319 characters. Setting the limit to -1 means there's no limit.
20321 @item show syn-garbage-limit
20322 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20323 Show the current limit on the number of characters to ignore when
20324 trying to synchronize with the remote system.
20326 @item set monitor-prompt @var{prompt}
20327 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20328 @cindex remote monitor prompt
20329 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20330 remote monitor. The default depends on the target:
20340 @item show monitor-prompt
20341 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20342 Show the current strings @value{GDBN} expects as the prompt from the
20345 @item set monitor-warnings
20346 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20347 Enable or disable monitor warnings about hardware breakpoints. This
20348 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20349 display warning messages whose codes are returned by the @code{lsi}
20350 PMON monitor for breakpoint commands.
20352 @item show monitor-warnings
20353 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20354 Show the current setting of printing monitor warnings.
20356 @item pmon @var{command}
20357 @kindex pmon@r{, @acronym{MIPS} remote}
20358 @cindex send PMON command
20359 This command allows sending an arbitrary @var{command} string to the
20360 monitor. The monitor must be in debug mode for this to work.
20363 @node PowerPC Embedded
20364 @subsection PowerPC Embedded
20366 @cindex DVC register
20367 @value{GDBN} supports using the DVC (Data Value Compare) register to
20368 implement in hardware simple hardware watchpoint conditions of the form:
20371 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20372 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20375 The DVC register will be automatically used when @value{GDBN} detects
20376 such pattern in a condition expression, and the created watchpoint uses one
20377 debug register (either the @code{exact-watchpoints} option is on and the
20378 variable is scalar, or the variable has a length of one byte). This feature
20379 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20382 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20383 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20384 in which case watchpoints using only one debug register are created when
20385 watching variables of scalar types.
20387 You can create an artificial array to watch an arbitrary memory
20388 region using one of the following commands (@pxref{Expressions}):
20391 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20392 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20395 PowerPC embedded processors support masked watchpoints. See the discussion
20396 about the @code{mask} argument in @ref{Set Watchpoints}.
20398 @cindex ranged breakpoint
20399 PowerPC embedded processors support hardware accelerated
20400 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20401 the inferior whenever it executes an instruction at any address within
20402 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20403 use the @code{break-range} command.
20405 @value{GDBN} provides the following PowerPC-specific commands:
20408 @kindex break-range
20409 @item break-range @var{start-location}, @var{end-location}
20410 Set a breakpoint for an address range.
20411 @var{start-location} and @var{end-location} can specify a function name,
20412 a line number, an offset of lines from the current line or from the start
20413 location, or an address of an instruction (see @ref{Specify Location},
20414 for a list of all the possible ways to specify a @var{location}.)
20415 The breakpoint will stop execution of the inferior whenever it
20416 executes an instruction at any address within the specified range,
20417 (including @var{start-location} and @var{end-location}.)
20419 @kindex set powerpc
20420 @item set powerpc soft-float
20421 @itemx show powerpc soft-float
20422 Force @value{GDBN} to use (or not use) a software floating point calling
20423 convention. By default, @value{GDBN} selects the calling convention based
20424 on the selected architecture and the provided executable file.
20426 @item set powerpc vector-abi
20427 @itemx show powerpc vector-abi
20428 Force @value{GDBN} to use the specified calling convention for vector
20429 arguments and return values. The valid options are @samp{auto};
20430 @samp{generic}, to avoid vector registers even if they are present;
20431 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20432 registers. By default, @value{GDBN} selects the calling convention
20433 based on the selected architecture and the provided executable file.
20435 @item set powerpc exact-watchpoints
20436 @itemx show powerpc exact-watchpoints
20437 Allow @value{GDBN} to use only one debug register when watching a variable
20438 of scalar type, thus assuming that the variable is accessed through the
20439 address of its first byte.
20441 @kindex target dink32
20442 @item target dink32 @var{dev}
20443 DINK32 ROM monitor.
20445 @kindex target ppcbug
20446 @item target ppcbug @var{dev}
20447 @kindex target ppcbug1
20448 @item target ppcbug1 @var{dev}
20449 PPCBUG ROM monitor for PowerPC.
20452 @item target sds @var{dev}
20453 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20456 @cindex SDS protocol
20457 The following commands specific to the SDS protocol are supported
20461 @item set sdstimeout @var{nsec}
20462 @kindex set sdstimeout
20463 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20464 default is 2 seconds.
20466 @item show sdstimeout
20467 @kindex show sdstimeout
20468 Show the current value of the SDS timeout.
20470 @item sds @var{command}
20471 @kindex sds@r{, a command}
20472 Send the specified @var{command} string to the SDS monitor.
20477 @subsection HP PA Embedded
20481 @kindex target op50n
20482 @item target op50n @var{dev}
20483 OP50N monitor, running on an OKI HPPA board.
20485 @kindex target w89k
20486 @item target w89k @var{dev}
20487 W89K monitor, running on a Winbond HPPA board.
20492 @subsection Tsqware Sparclet
20496 @value{GDBN} enables developers to debug tasks running on
20497 Sparclet targets from a Unix host.
20498 @value{GDBN} uses code that runs on
20499 both the Unix host and on the Sparclet target. The program
20500 @code{@value{GDBP}} is installed and executed on the Unix host.
20503 @item remotetimeout @var{args}
20504 @kindex remotetimeout
20505 @value{GDBN} supports the option @code{remotetimeout}.
20506 This option is set by the user, and @var{args} represents the number of
20507 seconds @value{GDBN} waits for responses.
20510 @cindex compiling, on Sparclet
20511 When compiling for debugging, include the options @samp{-g} to get debug
20512 information and @samp{-Ttext} to relocate the program to where you wish to
20513 load it on the target. You may also want to add the options @samp{-n} or
20514 @samp{-N} in order to reduce the size of the sections. Example:
20517 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20520 You can use @code{objdump} to verify that the addresses are what you intended:
20523 sparclet-aout-objdump --headers --syms prog
20526 @cindex running, on Sparclet
20528 your Unix execution search path to find @value{GDBN}, you are ready to
20529 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20530 (or @code{sparclet-aout-gdb}, depending on your installation).
20532 @value{GDBN} comes up showing the prompt:
20539 * Sparclet File:: Setting the file to debug
20540 * Sparclet Connection:: Connecting to Sparclet
20541 * Sparclet Download:: Sparclet download
20542 * Sparclet Execution:: Running and debugging
20545 @node Sparclet File
20546 @subsubsection Setting File to Debug
20548 The @value{GDBN} command @code{file} lets you choose with program to debug.
20551 (gdbslet) file prog
20555 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20556 @value{GDBN} locates
20557 the file by searching the directories listed in the command search
20559 If the file was compiled with debug information (option @samp{-g}), source
20560 files will be searched as well.
20561 @value{GDBN} locates
20562 the source files by searching the directories listed in the directory search
20563 path (@pxref{Environment, ,Your Program's Environment}).
20565 to find a file, it displays a message such as:
20568 prog: No such file or directory.
20571 When this happens, add the appropriate directories to the search paths with
20572 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20573 @code{target} command again.
20575 @node Sparclet Connection
20576 @subsubsection Connecting to Sparclet
20578 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20579 To connect to a target on serial port ``@code{ttya}'', type:
20582 (gdbslet) target sparclet /dev/ttya
20583 Remote target sparclet connected to /dev/ttya
20584 main () at ../prog.c:3
20588 @value{GDBN} displays messages like these:
20594 @node Sparclet Download
20595 @subsubsection Sparclet Download
20597 @cindex download to Sparclet
20598 Once connected to the Sparclet target,
20599 you can use the @value{GDBN}
20600 @code{load} command to download the file from the host to the target.
20601 The file name and load offset should be given as arguments to the @code{load}
20603 Since the file format is aout, the program must be loaded to the starting
20604 address. You can use @code{objdump} to find out what this value is. The load
20605 offset is an offset which is added to the VMA (virtual memory address)
20606 of each of the file's sections.
20607 For instance, if the program
20608 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20609 and bss at 0x12010170, in @value{GDBN}, type:
20612 (gdbslet) load prog 0x12010000
20613 Loading section .text, size 0xdb0 vma 0x12010000
20616 If the code is loaded at a different address then what the program was linked
20617 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20618 to tell @value{GDBN} where to map the symbol table.
20620 @node Sparclet Execution
20621 @subsubsection Running and Debugging
20623 @cindex running and debugging Sparclet programs
20624 You can now begin debugging the task using @value{GDBN}'s execution control
20625 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20626 manual for the list of commands.
20630 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20632 Starting program: prog
20633 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20634 3 char *symarg = 0;
20636 4 char *execarg = "hello!";
20641 @subsection Fujitsu Sparclite
20645 @kindex target sparclite
20646 @item target sparclite @var{dev}
20647 Fujitsu sparclite boards, used only for the purpose of loading.
20648 You must use an additional command to debug the program.
20649 For example: target remote @var{dev} using @value{GDBN} standard
20655 @subsection Zilog Z8000
20658 @cindex simulator, Z8000
20659 @cindex Zilog Z8000 simulator
20661 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20664 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20665 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20666 segmented variant). The simulator recognizes which architecture is
20667 appropriate by inspecting the object code.
20670 @item target sim @var{args}
20672 @kindex target sim@r{, with Z8000}
20673 Debug programs on a simulated CPU. If the simulator supports setup
20674 options, specify them via @var{args}.
20678 After specifying this target, you can debug programs for the simulated
20679 CPU in the same style as programs for your host computer; use the
20680 @code{file} command to load a new program image, the @code{run} command
20681 to run your program, and so on.
20683 As well as making available all the usual machine registers
20684 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20685 additional items of information as specially named registers:
20690 Counts clock-ticks in the simulator.
20693 Counts instructions run in the simulator.
20696 Execution time in 60ths of a second.
20700 You can refer to these values in @value{GDBN} expressions with the usual
20701 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20702 conditional breakpoint that suspends only after at least 5000
20703 simulated clock ticks.
20706 @subsection Atmel AVR
20709 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20710 following AVR-specific commands:
20713 @item info io_registers
20714 @kindex info io_registers@r{, AVR}
20715 @cindex I/O registers (Atmel AVR)
20716 This command displays information about the AVR I/O registers. For
20717 each register, @value{GDBN} prints its number and value.
20724 When configured for debugging CRIS, @value{GDBN} provides the
20725 following CRIS-specific commands:
20728 @item set cris-version @var{ver}
20729 @cindex CRIS version
20730 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20731 The CRIS version affects register names and sizes. This command is useful in
20732 case autodetection of the CRIS version fails.
20734 @item show cris-version
20735 Show the current CRIS version.
20737 @item set cris-dwarf2-cfi
20738 @cindex DWARF-2 CFI and CRIS
20739 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20740 Change to @samp{off} when using @code{gcc-cris} whose version is below
20743 @item show cris-dwarf2-cfi
20744 Show the current state of using DWARF-2 CFI.
20746 @item set cris-mode @var{mode}
20748 Set the current CRIS mode to @var{mode}. It should only be changed when
20749 debugging in guru mode, in which case it should be set to
20750 @samp{guru} (the default is @samp{normal}).
20752 @item show cris-mode
20753 Show the current CRIS mode.
20757 @subsection Renesas Super-H
20760 For the Renesas Super-H processor, @value{GDBN} provides these
20764 @item set sh calling-convention @var{convention}
20765 @kindex set sh calling-convention
20766 Set the calling-convention used when calling functions from @value{GDBN}.
20767 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20768 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20769 convention. If the DWARF-2 information of the called function specifies
20770 that the function follows the Renesas calling convention, the function
20771 is called using the Renesas calling convention. If the calling convention
20772 is set to @samp{renesas}, the Renesas calling convention is always used,
20773 regardless of the DWARF-2 information. This can be used to override the
20774 default of @samp{gcc} if debug information is missing, or the compiler
20775 does not emit the DWARF-2 calling convention entry for a function.
20777 @item show sh calling-convention
20778 @kindex show sh calling-convention
20779 Show the current calling convention setting.
20784 @node Architectures
20785 @section Architectures
20787 This section describes characteristics of architectures that affect
20788 all uses of @value{GDBN} with the architecture, both native and cross.
20795 * HPPA:: HP PA architecture
20796 * SPU:: Cell Broadband Engine SPU architecture
20801 @subsection AArch64
20802 @cindex AArch64 support
20804 When @value{GDBN} is debugging the AArch64 architecture, it provides the
20805 following special commands:
20808 @item set debug aarch64
20809 @kindex set debug aarch64
20810 This command determines whether AArch64 architecture-specific debugging
20811 messages are to be displayed.
20813 @item show debug aarch64
20814 Show whether AArch64 debugging messages are displayed.
20819 @subsection x86 Architecture-specific Issues
20822 @item set struct-convention @var{mode}
20823 @kindex set struct-convention
20824 @cindex struct return convention
20825 @cindex struct/union returned in registers
20826 Set the convention used by the inferior to return @code{struct}s and
20827 @code{union}s from functions to @var{mode}. Possible values of
20828 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20829 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20830 are returned on the stack, while @code{"reg"} means that a
20831 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20832 be returned in a register.
20834 @item show struct-convention
20835 @kindex show struct-convention
20836 Show the current setting of the convention to return @code{struct}s
20843 See the following section.
20846 @subsection @acronym{MIPS}
20848 @cindex stack on Alpha
20849 @cindex stack on @acronym{MIPS}
20850 @cindex Alpha stack
20851 @cindex @acronym{MIPS} stack
20852 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20853 sometimes requires @value{GDBN} to search backward in the object code to
20854 find the beginning of a function.
20856 @cindex response time, @acronym{MIPS} debugging
20857 To improve response time (especially for embedded applications, where
20858 @value{GDBN} may be restricted to a slow serial line for this search)
20859 you may want to limit the size of this search, using one of these
20863 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20864 @item set heuristic-fence-post @var{limit}
20865 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20866 search for the beginning of a function. A value of @var{0} (the
20867 default) means there is no limit. However, except for @var{0}, the
20868 larger the limit the more bytes @code{heuristic-fence-post} must search
20869 and therefore the longer it takes to run. You should only need to use
20870 this command when debugging a stripped executable.
20872 @item show heuristic-fence-post
20873 Display the current limit.
20877 These commands are available @emph{only} when @value{GDBN} is configured
20878 for debugging programs on Alpha or @acronym{MIPS} processors.
20880 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20884 @item set mips abi @var{arg}
20885 @kindex set mips abi
20886 @cindex set ABI for @acronym{MIPS}
20887 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20888 values of @var{arg} are:
20892 The default ABI associated with the current binary (this is the
20902 @item show mips abi
20903 @kindex show mips abi
20904 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20906 @item set mips compression @var{arg}
20907 @kindex set mips compression
20908 @cindex code compression, @acronym{MIPS}
20909 Tell @value{GDBN} which @acronym{MIPS} compressed
20910 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20911 inferior. @value{GDBN} uses this for code disassembly and other
20912 internal interpretation purposes. This setting is only referred to
20913 when no executable has been associated with the debugging session or
20914 the executable does not provide information about the encoding it uses.
20915 Otherwise this setting is automatically updated from information
20916 provided by the executable.
20918 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20919 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20920 executables containing @acronym{MIPS16} code frequently are not
20921 identified as such.
20923 This setting is ``sticky''; that is, it retains its value across
20924 debugging sessions until reset either explicitly with this command or
20925 implicitly from an executable.
20927 The compiler and/or assembler typically add symbol table annotations to
20928 identify functions compiled for the @acronym{MIPS16} or
20929 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20930 are present, @value{GDBN} uses them in preference to the global
20931 compressed @acronym{ISA} encoding setting.
20933 @item show mips compression
20934 @kindex show mips compression
20935 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20936 @value{GDBN} to debug the inferior.
20939 @itemx show mipsfpu
20940 @xref{MIPS Embedded, set mipsfpu}.
20942 @item set mips mask-address @var{arg}
20943 @kindex set mips mask-address
20944 @cindex @acronym{MIPS} addresses, masking
20945 This command determines whether the most-significant 32 bits of 64-bit
20946 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20947 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20948 setting, which lets @value{GDBN} determine the correct value.
20950 @item show mips mask-address
20951 @kindex show mips mask-address
20952 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20955 @item set remote-mips64-transfers-32bit-regs
20956 @kindex set remote-mips64-transfers-32bit-regs
20957 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20958 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20959 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20960 and 64 bits for other registers, set this option to @samp{on}.
20962 @item show remote-mips64-transfers-32bit-regs
20963 @kindex show remote-mips64-transfers-32bit-regs
20964 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
20966 @item set debug mips
20967 @kindex set debug mips
20968 This command turns on and off debugging messages for the @acronym{MIPS}-specific
20969 target code in @value{GDBN}.
20971 @item show debug mips
20972 @kindex show debug mips
20973 Show the current setting of @acronym{MIPS} debugging messages.
20979 @cindex HPPA support
20981 When @value{GDBN} is debugging the HP PA architecture, it provides the
20982 following special commands:
20985 @item set debug hppa
20986 @kindex set debug hppa
20987 This command determines whether HPPA architecture-specific debugging
20988 messages are to be displayed.
20990 @item show debug hppa
20991 Show whether HPPA debugging messages are displayed.
20993 @item maint print unwind @var{address}
20994 @kindex maint print unwind@r{, HPPA}
20995 This command displays the contents of the unwind table entry at the
20996 given @var{address}.
21002 @subsection Cell Broadband Engine SPU architecture
21003 @cindex Cell Broadband Engine
21006 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21007 it provides the following special commands:
21010 @item info spu event
21012 Display SPU event facility status. Shows current event mask
21013 and pending event status.
21015 @item info spu signal
21016 Display SPU signal notification facility status. Shows pending
21017 signal-control word and signal notification mode of both signal
21018 notification channels.
21020 @item info spu mailbox
21021 Display SPU mailbox facility status. Shows all pending entries,
21022 in order of processing, in each of the SPU Write Outbound,
21023 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21026 Display MFC DMA status. Shows all pending commands in the MFC
21027 DMA queue. For each entry, opcode, tag, class IDs, effective
21028 and local store addresses and transfer size are shown.
21030 @item info spu proxydma
21031 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21032 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21033 and local store addresses and transfer size are shown.
21037 When @value{GDBN} is debugging a combined PowerPC/SPU application
21038 on the Cell Broadband Engine, it provides in addition the following
21042 @item set spu stop-on-load @var{arg}
21044 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21045 will give control to the user when a new SPE thread enters its @code{main}
21046 function. The default is @code{off}.
21048 @item show spu stop-on-load
21050 Show whether to stop for new SPE threads.
21052 @item set spu auto-flush-cache @var{arg}
21053 Set whether to automatically flush the software-managed cache. When set to
21054 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21055 cache to be flushed whenever SPE execution stops. This provides a consistent
21056 view of PowerPC memory that is accessed via the cache. If an application
21057 does not use the software-managed cache, this option has no effect.
21059 @item show spu auto-flush-cache
21060 Show whether to automatically flush the software-managed cache.
21065 @subsection PowerPC
21066 @cindex PowerPC architecture
21068 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21069 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21070 numbers stored in the floating point registers. These values must be stored
21071 in two consecutive registers, always starting at an even register like
21072 @code{f0} or @code{f2}.
21074 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21075 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21076 @code{f2} and @code{f3} for @code{$dl1} and so on.
21078 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21079 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21082 @node Controlling GDB
21083 @chapter Controlling @value{GDBN}
21085 You can alter the way @value{GDBN} interacts with you by using the
21086 @code{set} command. For commands controlling how @value{GDBN} displays
21087 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21092 * Editing:: Command editing
21093 * Command History:: Command history
21094 * Screen Size:: Screen size
21095 * Numbers:: Numbers
21096 * ABI:: Configuring the current ABI
21097 * Auto-loading:: Automatically loading associated files
21098 * Messages/Warnings:: Optional warnings and messages
21099 * Debugging Output:: Optional messages about internal happenings
21100 * Other Misc Settings:: Other Miscellaneous Settings
21108 @value{GDBN} indicates its readiness to read a command by printing a string
21109 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21110 can change the prompt string with the @code{set prompt} command. For
21111 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21112 the prompt in one of the @value{GDBN} sessions so that you can always tell
21113 which one you are talking to.
21115 @emph{Note:} @code{set prompt} does not add a space for you after the
21116 prompt you set. This allows you to set a prompt which ends in a space
21117 or a prompt that does not.
21121 @item set prompt @var{newprompt}
21122 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21124 @kindex show prompt
21126 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21129 Versions of @value{GDBN} that ship with Python scripting enabled have
21130 prompt extensions. The commands for interacting with these extensions
21134 @kindex set extended-prompt
21135 @item set extended-prompt @var{prompt}
21136 Set an extended prompt that allows for substitutions.
21137 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21138 substitution. Any escape sequences specified as part of the prompt
21139 string are replaced with the corresponding strings each time the prompt
21145 set extended-prompt Current working directory: \w (gdb)
21148 Note that when an extended-prompt is set, it takes control of the
21149 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21151 @kindex show extended-prompt
21152 @item show extended-prompt
21153 Prints the extended prompt. Any escape sequences specified as part of
21154 the prompt string with @code{set extended-prompt}, are replaced with the
21155 corresponding strings each time the prompt is displayed.
21159 @section Command Editing
21161 @cindex command line editing
21163 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21164 @sc{gnu} library provides consistent behavior for programs which provide a
21165 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21166 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21167 substitution, and a storage and recall of command history across
21168 debugging sessions.
21170 You may control the behavior of command line editing in @value{GDBN} with the
21171 command @code{set}.
21174 @kindex set editing
21177 @itemx set editing on
21178 Enable command line editing (enabled by default).
21180 @item set editing off
21181 Disable command line editing.
21183 @kindex show editing
21185 Show whether command line editing is enabled.
21188 @ifset SYSTEM_READLINE
21189 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21191 @ifclear SYSTEM_READLINE
21192 @xref{Command Line Editing},
21194 for more details about the Readline
21195 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21196 encouraged to read that chapter.
21198 @node Command History
21199 @section Command History
21200 @cindex command history
21202 @value{GDBN} can keep track of the commands you type during your
21203 debugging sessions, so that you can be certain of precisely what
21204 happened. Use these commands to manage the @value{GDBN} command
21207 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21208 package, to provide the history facility.
21209 @ifset SYSTEM_READLINE
21210 @xref{Using History Interactively, , , history, GNU History Library},
21212 @ifclear SYSTEM_READLINE
21213 @xref{Using History Interactively},
21215 for the detailed description of the History library.
21217 To issue a command to @value{GDBN} without affecting certain aspects of
21218 the state which is seen by users, prefix it with @samp{server }
21219 (@pxref{Server Prefix}). This
21220 means that this command will not affect the command history, nor will it
21221 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21222 pressed on a line by itself.
21224 @cindex @code{server}, command prefix
21225 The server prefix does not affect the recording of values into the value
21226 history; to print a value without recording it into the value history,
21227 use the @code{output} command instead of the @code{print} command.
21229 Here is the description of @value{GDBN} commands related to command
21233 @cindex history substitution
21234 @cindex history file
21235 @kindex set history filename
21236 @cindex @env{GDBHISTFILE}, environment variable
21237 @item set history filename @var{fname}
21238 Set the name of the @value{GDBN} command history file to @var{fname}.
21239 This is the file where @value{GDBN} reads an initial command history
21240 list, and where it writes the command history from this session when it
21241 exits. You can access this list through history expansion or through
21242 the history command editing characters listed below. This file defaults
21243 to the value of the environment variable @code{GDBHISTFILE}, or to
21244 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21247 @cindex save command history
21248 @kindex set history save
21249 @item set history save
21250 @itemx set history save on
21251 Record command history in a file, whose name may be specified with the
21252 @code{set history filename} command. By default, this option is disabled.
21254 @item set history save off
21255 Stop recording command history in a file.
21257 @cindex history size
21258 @kindex set history size
21259 @cindex @env{HISTSIZE}, environment variable
21260 @item set history size @var{size}
21261 @itemx set history size unlimited
21262 Set the number of commands which @value{GDBN} keeps in its history list.
21263 This defaults to the value of the environment variable
21264 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21265 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21266 history list is unlimited.
21269 History expansion assigns special meaning to the character @kbd{!}.
21270 @ifset SYSTEM_READLINE
21271 @xref{Event Designators, , , history, GNU History Library},
21273 @ifclear SYSTEM_READLINE
21274 @xref{Event Designators},
21278 @cindex history expansion, turn on/off
21279 Since @kbd{!} is also the logical not operator in C, history expansion
21280 is off by default. If you decide to enable history expansion with the
21281 @code{set history expansion on} command, you may sometimes need to
21282 follow @kbd{!} (when it is used as logical not, in an expression) with
21283 a space or a tab to prevent it from being expanded. The readline
21284 history facilities do not attempt substitution on the strings
21285 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21287 The commands to control history expansion are:
21290 @item set history expansion on
21291 @itemx set history expansion
21292 @kindex set history expansion
21293 Enable history expansion. History expansion is off by default.
21295 @item set history expansion off
21296 Disable history expansion.
21299 @kindex show history
21301 @itemx show history filename
21302 @itemx show history save
21303 @itemx show history size
21304 @itemx show history expansion
21305 These commands display the state of the @value{GDBN} history parameters.
21306 @code{show history} by itself displays all four states.
21311 @kindex show commands
21312 @cindex show last commands
21313 @cindex display command history
21314 @item show commands
21315 Display the last ten commands in the command history.
21317 @item show commands @var{n}
21318 Print ten commands centered on command number @var{n}.
21320 @item show commands +
21321 Print ten commands just after the commands last printed.
21325 @section Screen Size
21326 @cindex size of screen
21327 @cindex pauses in output
21329 Certain commands to @value{GDBN} may produce large amounts of
21330 information output to the screen. To help you read all of it,
21331 @value{GDBN} pauses and asks you for input at the end of each page of
21332 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21333 to discard the remaining output. Also, the screen width setting
21334 determines when to wrap lines of output. Depending on what is being
21335 printed, @value{GDBN} tries to break the line at a readable place,
21336 rather than simply letting it overflow onto the following line.
21338 Normally @value{GDBN} knows the size of the screen from the terminal
21339 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21340 together with the value of the @code{TERM} environment variable and the
21341 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21342 you can override it with the @code{set height} and @code{set
21349 @kindex show height
21350 @item set height @var{lpp}
21351 @itemx set height unlimited
21353 @itemx set width @var{cpl}
21354 @itemx set width unlimited
21356 These @code{set} commands specify a screen height of @var{lpp} lines and
21357 a screen width of @var{cpl} characters. The associated @code{show}
21358 commands display the current settings.
21360 If you specify a height of either @code{unlimited} or zero lines,
21361 @value{GDBN} does not pause during output no matter how long the
21362 output is. This is useful if output is to a file or to an editor
21365 Likewise, you can specify @samp{set width unlimited} or @samp{set
21366 width 0} to prevent @value{GDBN} from wrapping its output.
21368 @item set pagination on
21369 @itemx set pagination off
21370 @kindex set pagination
21371 Turn the output pagination on or off; the default is on. Turning
21372 pagination off is the alternative to @code{set height unlimited}. Note that
21373 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21374 Options, -batch}) also automatically disables pagination.
21376 @item show pagination
21377 @kindex show pagination
21378 Show the current pagination mode.
21383 @cindex number representation
21384 @cindex entering numbers
21386 You can always enter numbers in octal, decimal, or hexadecimal in
21387 @value{GDBN} by the usual conventions: octal numbers begin with
21388 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21389 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21390 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21391 10; likewise, the default display for numbers---when no particular
21392 format is specified---is base 10. You can change the default base for
21393 both input and output with the commands described below.
21396 @kindex set input-radix
21397 @item set input-radix @var{base}
21398 Set the default base for numeric input. Supported choices
21399 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21400 specified either unambiguously or using the current input radix; for
21404 set input-radix 012
21405 set input-radix 10.
21406 set input-radix 0xa
21410 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21411 leaves the input radix unchanged, no matter what it was, since
21412 @samp{10}, being without any leading or trailing signs of its base, is
21413 interpreted in the current radix. Thus, if the current radix is 16,
21414 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21417 @kindex set output-radix
21418 @item set output-radix @var{base}
21419 Set the default base for numeric display. Supported choices
21420 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21421 specified either unambiguously or using the current input radix.
21423 @kindex show input-radix
21424 @item show input-radix
21425 Display the current default base for numeric input.
21427 @kindex show output-radix
21428 @item show output-radix
21429 Display the current default base for numeric display.
21431 @item set radix @r{[}@var{base}@r{]}
21435 These commands set and show the default base for both input and output
21436 of numbers. @code{set radix} sets the radix of input and output to
21437 the same base; without an argument, it resets the radix back to its
21438 default value of 10.
21443 @section Configuring the Current ABI
21445 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21446 application automatically. However, sometimes you need to override its
21447 conclusions. Use these commands to manage @value{GDBN}'s view of the
21453 @cindex Newlib OS ABI and its influence on the longjmp handling
21455 One @value{GDBN} configuration can debug binaries for multiple operating
21456 system targets, either via remote debugging or native emulation.
21457 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21458 but you can override its conclusion using the @code{set osabi} command.
21459 One example where this is useful is in debugging of binaries which use
21460 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21461 not have the same identifying marks that the standard C library for your
21464 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21465 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21466 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21467 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21471 Show the OS ABI currently in use.
21474 With no argument, show the list of registered available OS ABI's.
21476 @item set osabi @var{abi}
21477 Set the current OS ABI to @var{abi}.
21480 @cindex float promotion
21482 Generally, the way that an argument of type @code{float} is passed to a
21483 function depends on whether the function is prototyped. For a prototyped
21484 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21485 according to the architecture's convention for @code{float}. For unprototyped
21486 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21487 @code{double} and then passed.
21489 Unfortunately, some forms of debug information do not reliably indicate whether
21490 a function is prototyped. If @value{GDBN} calls a function that is not marked
21491 as prototyped, it consults @kbd{set coerce-float-to-double}.
21494 @kindex set coerce-float-to-double
21495 @item set coerce-float-to-double
21496 @itemx set coerce-float-to-double on
21497 Arguments of type @code{float} will be promoted to @code{double} when passed
21498 to an unprototyped function. This is the default setting.
21500 @item set coerce-float-to-double off
21501 Arguments of type @code{float} will be passed directly to unprototyped
21504 @kindex show coerce-float-to-double
21505 @item show coerce-float-to-double
21506 Show the current setting of promoting @code{float} to @code{double}.
21510 @kindex show cp-abi
21511 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21512 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21513 used to build your application. @value{GDBN} only fully supports
21514 programs with a single C@t{++} ABI; if your program contains code using
21515 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21516 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21517 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21518 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21519 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21520 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21525 Show the C@t{++} ABI currently in use.
21528 With no argument, show the list of supported C@t{++} ABI's.
21530 @item set cp-abi @var{abi}
21531 @itemx set cp-abi auto
21532 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21536 @section Automatically loading associated files
21537 @cindex auto-loading
21539 @value{GDBN} sometimes reads files with commands and settings automatically,
21540 without being explicitly told so by the user. We call this feature
21541 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21542 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21543 results or introduce security risks (e.g., if the file comes from untrusted
21546 Note that loading of these associated files (including the local @file{.gdbinit}
21547 file) requires accordingly configured @code{auto-load safe-path}
21548 (@pxref{Auto-loading safe path}).
21550 For these reasons, @value{GDBN} includes commands and options to let you
21551 control when to auto-load files and which files should be auto-loaded.
21554 @anchor{set auto-load off}
21555 @kindex set auto-load off
21556 @item set auto-load off
21557 Globally disable loading of all auto-loaded files.
21558 You may want to use this command with the @samp{-iex} option
21559 (@pxref{Option -init-eval-command}) such as:
21561 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21564 Be aware that system init file (@pxref{System-wide configuration})
21565 and init files from your home directory (@pxref{Home Directory Init File})
21566 still get read (as they come from generally trusted directories).
21567 To prevent @value{GDBN} from auto-loading even those init files, use the
21568 @option{-nx} option (@pxref{Mode Options}), in addition to
21569 @code{set auto-load no}.
21571 @anchor{show auto-load}
21572 @kindex show auto-load
21573 @item show auto-load
21574 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21578 (gdb) show auto-load
21579 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21580 libthread-db: Auto-loading of inferior specific libthread_db is on.
21581 local-gdbinit: Auto-loading of .gdbinit script from current directory
21583 python-scripts: Auto-loading of Python scripts is on.
21584 safe-path: List of directories from which it is safe to auto-load files
21585 is $debugdir:$datadir/auto-load.
21586 scripts-directory: List of directories from which to load auto-loaded scripts
21587 is $debugdir:$datadir/auto-load.
21590 @anchor{info auto-load}
21591 @kindex info auto-load
21592 @item info auto-load
21593 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21597 (gdb) info auto-load
21600 Yes /home/user/gdb/gdb-gdb.gdb
21601 libthread-db: No auto-loaded libthread-db.
21602 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21606 Yes /home/user/gdb/gdb-gdb.py
21610 These are various kinds of files @value{GDBN} can automatically load:
21614 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21616 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21618 @xref{dotdebug_gdb_scripts section},
21619 controlled by @ref{set auto-load python-scripts}.
21621 @xref{Init File in the Current Directory},
21622 controlled by @ref{set auto-load local-gdbinit}.
21624 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21627 These are @value{GDBN} control commands for the auto-loading:
21629 @multitable @columnfractions .5 .5
21630 @item @xref{set auto-load off}.
21631 @tab Disable auto-loading globally.
21632 @item @xref{show auto-load}.
21633 @tab Show setting of all kinds of files.
21634 @item @xref{info auto-load}.
21635 @tab Show state of all kinds of files.
21636 @item @xref{set auto-load gdb-scripts}.
21637 @tab Control for @value{GDBN} command scripts.
21638 @item @xref{show auto-load gdb-scripts}.
21639 @tab Show setting of @value{GDBN} command scripts.
21640 @item @xref{info auto-load gdb-scripts}.
21641 @tab Show state of @value{GDBN} command scripts.
21642 @item @xref{set auto-load python-scripts}.
21643 @tab Control for @value{GDBN} Python scripts.
21644 @item @xref{show auto-load python-scripts}.
21645 @tab Show setting of @value{GDBN} Python scripts.
21646 @item @xref{info auto-load python-scripts}.
21647 @tab Show state of @value{GDBN} Python scripts.
21648 @item @xref{set auto-load scripts-directory}.
21649 @tab Control for @value{GDBN} auto-loaded scripts location.
21650 @item @xref{show auto-load scripts-directory}.
21651 @tab Show @value{GDBN} auto-loaded scripts location.
21652 @item @xref{set auto-load local-gdbinit}.
21653 @tab Control for init file in the current directory.
21654 @item @xref{show auto-load local-gdbinit}.
21655 @tab Show setting of init file in the current directory.
21656 @item @xref{info auto-load local-gdbinit}.
21657 @tab Show state of init file in the current directory.
21658 @item @xref{set auto-load libthread-db}.
21659 @tab Control for thread debugging library.
21660 @item @xref{show auto-load libthread-db}.
21661 @tab Show setting of thread debugging library.
21662 @item @xref{info auto-load libthread-db}.
21663 @tab Show state of thread debugging library.
21664 @item @xref{set auto-load safe-path}.
21665 @tab Control directories trusted for automatic loading.
21666 @item @xref{show auto-load safe-path}.
21667 @tab Show directories trusted for automatic loading.
21668 @item @xref{add-auto-load-safe-path}.
21669 @tab Add directory trusted for automatic loading.
21673 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21674 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21675 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21676 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21677 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21678 @xref{Python Auto-loading}.
21681 @node Init File in the Current Directory
21682 @subsection Automatically loading init file in the current directory
21683 @cindex auto-loading init file in the current directory
21685 By default, @value{GDBN} reads and executes the canned sequences of commands
21686 from init file (if any) in the current working directory,
21687 see @ref{Init File in the Current Directory during Startup}.
21689 Note that loading of this local @file{.gdbinit} file also requires accordingly
21690 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21693 @anchor{set auto-load local-gdbinit}
21694 @kindex set auto-load local-gdbinit
21695 @item set auto-load local-gdbinit [on|off]
21696 Enable or disable the auto-loading of canned sequences of commands
21697 (@pxref{Sequences}) found in init file in the current directory.
21699 @anchor{show auto-load local-gdbinit}
21700 @kindex show auto-load local-gdbinit
21701 @item show auto-load local-gdbinit
21702 Show whether auto-loading of canned sequences of commands from init file in the
21703 current directory is enabled or disabled.
21705 @anchor{info auto-load local-gdbinit}
21706 @kindex info auto-load local-gdbinit
21707 @item info auto-load local-gdbinit
21708 Print whether canned sequences of commands from init file in the
21709 current directory have been auto-loaded.
21712 @node libthread_db.so.1 file
21713 @subsection Automatically loading thread debugging library
21714 @cindex auto-loading libthread_db.so.1
21716 This feature is currently present only on @sc{gnu}/Linux native hosts.
21718 @value{GDBN} reads in some cases thread debugging library from places specific
21719 to the inferior (@pxref{set libthread-db-search-path}).
21721 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21722 without checking this @samp{set auto-load libthread-db} switch as system
21723 libraries have to be trusted in general. In all other cases of
21724 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21725 auto-load libthread-db} is enabled before trying to open such thread debugging
21728 Note that loading of this debugging library also requires accordingly configured
21729 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21732 @anchor{set auto-load libthread-db}
21733 @kindex set auto-load libthread-db
21734 @item set auto-load libthread-db [on|off]
21735 Enable or disable the auto-loading of inferior specific thread debugging library.
21737 @anchor{show auto-load libthread-db}
21738 @kindex show auto-load libthread-db
21739 @item show auto-load libthread-db
21740 Show whether auto-loading of inferior specific thread debugging library is
21741 enabled or disabled.
21743 @anchor{info auto-load libthread-db}
21744 @kindex info auto-load libthread-db
21745 @item info auto-load libthread-db
21746 Print the list of all loaded inferior specific thread debugging libraries and
21747 for each such library print list of inferior @var{pid}s using it.
21750 @node objfile-gdb.gdb file
21751 @subsection The @file{@var{objfile}-gdb.gdb} file
21752 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21754 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21755 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21756 auto-load gdb-scripts} is set to @samp{on}.
21758 Note that loading of this script file also requires accordingly configured
21759 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21761 For more background refer to the similar Python scripts auto-loading
21762 description (@pxref{objfile-gdb.py file}).
21765 @anchor{set auto-load gdb-scripts}
21766 @kindex set auto-load gdb-scripts
21767 @item set auto-load gdb-scripts [on|off]
21768 Enable or disable the auto-loading of canned sequences of commands scripts.
21770 @anchor{show auto-load gdb-scripts}
21771 @kindex show auto-load gdb-scripts
21772 @item show auto-load gdb-scripts
21773 Show whether auto-loading of canned sequences of commands scripts is enabled or
21776 @anchor{info auto-load gdb-scripts}
21777 @kindex info auto-load gdb-scripts
21778 @cindex print list of auto-loaded canned sequences of commands scripts
21779 @item info auto-load gdb-scripts [@var{regexp}]
21780 Print the list of all canned sequences of commands scripts that @value{GDBN}
21784 If @var{regexp} is supplied only canned sequences of commands scripts with
21785 matching names are printed.
21787 @node Auto-loading safe path
21788 @subsection Security restriction for auto-loading
21789 @cindex auto-loading safe-path
21791 As the files of inferior can come from untrusted source (such as submitted by
21792 an application user) @value{GDBN} does not always load any files automatically.
21793 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21794 directories trusted for loading files not explicitly requested by user.
21795 Each directory can also be a shell wildcard pattern.
21797 If the path is not set properly you will see a warning and the file will not
21802 Reading symbols from /home/user/gdb/gdb...done.
21803 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21804 declined by your `auto-load safe-path' set
21805 to "$debugdir:$datadir/auto-load".
21806 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21807 declined by your `auto-load safe-path' set
21808 to "$debugdir:$datadir/auto-load".
21812 To instruct @value{GDBN} to go ahead and use the init files anyway,
21813 invoke @value{GDBN} like this:
21816 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
21819 The list of trusted directories is controlled by the following commands:
21822 @anchor{set auto-load safe-path}
21823 @kindex set auto-load safe-path
21824 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21825 Set the list of directories (and their subdirectories) trusted for automatic
21826 loading and execution of scripts. You can also enter a specific trusted file.
21827 Each directory can also be a shell wildcard pattern; wildcards do not match
21828 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21829 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21830 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21831 its default value as specified during @value{GDBN} compilation.
21833 The list of directories uses path separator (@samp{:} on GNU and Unix
21834 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21835 to the @env{PATH} environment variable.
21837 @anchor{show auto-load safe-path}
21838 @kindex show auto-load safe-path
21839 @item show auto-load safe-path
21840 Show the list of directories trusted for automatic loading and execution of
21843 @anchor{add-auto-load-safe-path}
21844 @kindex add-auto-load-safe-path
21845 @item add-auto-load-safe-path
21846 Add an entry (or list of entries) the list of directories trusted for automatic
21847 loading and execution of scripts. Multiple entries may be delimited by the
21848 host platform path separator in use.
21851 This variable defaults to what @code{--with-auto-load-dir} has been configured
21852 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21853 substitution applies the same as for @ref{set auto-load scripts-directory}.
21854 The default @code{set auto-load safe-path} value can be also overriden by
21855 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21857 Setting this variable to @file{/} disables this security protection,
21858 corresponding @value{GDBN} configuration option is
21859 @option{--without-auto-load-safe-path}.
21860 This variable is supposed to be set to the system directories writable by the
21861 system superuser only. Users can add their source directories in init files in
21862 their home directories (@pxref{Home Directory Init File}). See also deprecated
21863 init file in the current directory
21864 (@pxref{Init File in the Current Directory during Startup}).
21866 To force @value{GDBN} to load the files it declined to load in the previous
21867 example, you could use one of the following ways:
21870 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21871 Specify this trusted directory (or a file) as additional component of the list.
21872 You have to specify also any existing directories displayed by
21873 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21875 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21876 Specify this directory as in the previous case but just for a single
21877 @value{GDBN} session.
21879 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21880 Disable auto-loading safety for a single @value{GDBN} session.
21881 This assumes all the files you debug during this @value{GDBN} session will come
21882 from trusted sources.
21884 @item @kbd{./configure --without-auto-load-safe-path}
21885 During compilation of @value{GDBN} you may disable any auto-loading safety.
21886 This assumes all the files you will ever debug with this @value{GDBN} come from
21890 On the other hand you can also explicitly forbid automatic files loading which
21891 also suppresses any such warning messages:
21894 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21895 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21897 @item @file{~/.gdbinit}: @samp{set auto-load no}
21898 Disable auto-loading globally for the user
21899 (@pxref{Home Directory Init File}). While it is improbable, you could also
21900 use system init file instead (@pxref{System-wide configuration}).
21903 This setting applies to the file names as entered by user. If no entry matches
21904 @value{GDBN} tries as a last resort to also resolve all the file names into
21905 their canonical form (typically resolving symbolic links) and compare the
21906 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21907 own before starting the comparison so a canonical form of directories is
21908 recommended to be entered.
21910 @node Auto-loading verbose mode
21911 @subsection Displaying files tried for auto-load
21912 @cindex auto-loading verbose mode
21914 For better visibility of all the file locations where you can place scripts to
21915 be auto-loaded with inferior --- or to protect yourself against accidental
21916 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21917 all the files attempted to be loaded. Both existing and non-existing files may
21920 For example the list of directories from which it is safe to auto-load files
21921 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21922 may not be too obvious while setting it up.
21925 (gdb) set debug auto-load on
21926 (gdb) file ~/src/t/true
21927 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21928 for objfile "/tmp/true".
21929 auto-load: Updating directories of "/usr:/opt".
21930 auto-load: Using directory "/usr".
21931 auto-load: Using directory "/opt".
21932 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21933 by your `auto-load safe-path' set to "/usr:/opt".
21937 @anchor{set debug auto-load}
21938 @kindex set debug auto-load
21939 @item set debug auto-load [on|off]
21940 Set whether to print the filenames attempted to be auto-loaded.
21942 @anchor{show debug auto-load}
21943 @kindex show debug auto-load
21944 @item show debug auto-load
21945 Show whether printing of the filenames attempted to be auto-loaded is turned
21949 @node Messages/Warnings
21950 @section Optional Warnings and Messages
21952 @cindex verbose operation
21953 @cindex optional warnings
21954 By default, @value{GDBN} is silent about its inner workings. If you are
21955 running on a slow machine, you may want to use the @code{set verbose}
21956 command. This makes @value{GDBN} tell you when it does a lengthy
21957 internal operation, so you will not think it has crashed.
21959 Currently, the messages controlled by @code{set verbose} are those
21960 which announce that the symbol table for a source file is being read;
21961 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21964 @kindex set verbose
21965 @item set verbose on
21966 Enables @value{GDBN} output of certain informational messages.
21968 @item set verbose off
21969 Disables @value{GDBN} output of certain informational messages.
21971 @kindex show verbose
21973 Displays whether @code{set verbose} is on or off.
21976 By default, if @value{GDBN} encounters bugs in the symbol table of an
21977 object file, it is silent; but if you are debugging a compiler, you may
21978 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21983 @kindex set complaints
21984 @item set complaints @var{limit}
21985 Permits @value{GDBN} to output @var{limit} complaints about each type of
21986 unusual symbols before becoming silent about the problem. Set
21987 @var{limit} to zero to suppress all complaints; set it to a large number
21988 to prevent complaints from being suppressed.
21990 @kindex show complaints
21991 @item show complaints
21992 Displays how many symbol complaints @value{GDBN} is permitted to produce.
21996 @anchor{confirmation requests}
21997 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
21998 lot of stupid questions to confirm certain commands. For example, if
21999 you try to run a program which is already running:
22003 The program being debugged has been started already.
22004 Start it from the beginning? (y or n)
22007 If you are willing to unflinchingly face the consequences of your own
22008 commands, you can disable this ``feature'':
22012 @kindex set confirm
22014 @cindex confirmation
22015 @cindex stupid questions
22016 @item set confirm off
22017 Disables confirmation requests. Note that running @value{GDBN} with
22018 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22019 automatically disables confirmation requests.
22021 @item set confirm on
22022 Enables confirmation requests (the default).
22024 @kindex show confirm
22026 Displays state of confirmation requests.
22030 @cindex command tracing
22031 If you need to debug user-defined commands or sourced files you may find it
22032 useful to enable @dfn{command tracing}. In this mode each command will be
22033 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22034 quantity denoting the call depth of each command.
22037 @kindex set trace-commands
22038 @cindex command scripts, debugging
22039 @item set trace-commands on
22040 Enable command tracing.
22041 @item set trace-commands off
22042 Disable command tracing.
22043 @item show trace-commands
22044 Display the current state of command tracing.
22047 @node Debugging Output
22048 @section Optional Messages about Internal Happenings
22049 @cindex optional debugging messages
22051 @value{GDBN} has commands that enable optional debugging messages from
22052 various @value{GDBN} subsystems; normally these commands are of
22053 interest to @value{GDBN} maintainers, or when reporting a bug. This
22054 section documents those commands.
22057 @kindex set exec-done-display
22058 @item set exec-done-display
22059 Turns on or off the notification of asynchronous commands'
22060 completion. When on, @value{GDBN} will print a message when an
22061 asynchronous command finishes its execution. The default is off.
22062 @kindex show exec-done-display
22063 @item show exec-done-display
22064 Displays the current setting of asynchronous command completion
22067 @cindex ARM AArch64
22068 @item set debug aarch64
22069 Turns on or off display of debugging messages related to ARM AArch64.
22070 The default is off.
22072 @item show debug aarch64
22073 Displays the current state of displaying debugging messages related to
22075 @cindex gdbarch debugging info
22076 @cindex architecture debugging info
22077 @item set debug arch
22078 Turns on or off display of gdbarch debugging info. The default is off
22079 @item show debug arch
22080 Displays the current state of displaying gdbarch debugging info.
22081 @item set debug aix-thread
22082 @cindex AIX threads
22083 Display debugging messages about inner workings of the AIX thread
22085 @item show debug aix-thread
22086 Show the current state of AIX thread debugging info display.
22087 @item set debug check-physname
22089 Check the results of the ``physname'' computation. When reading DWARF
22090 debugging information for C@t{++}, @value{GDBN} attempts to compute
22091 each entity's name. @value{GDBN} can do this computation in two
22092 different ways, depending on exactly what information is present.
22093 When enabled, this setting causes @value{GDBN} to compute the names
22094 both ways and display any discrepancies.
22095 @item show debug check-physname
22096 Show the current state of ``physname'' checking.
22097 @item set debug coff-pe-read
22098 @cindex COFF/PE exported symbols
22099 Control display of debugging messages related to reading of COFF/PE
22100 exported symbols. The default is off.
22101 @item show debug coff-pe-read
22102 Displays the current state of displaying debugging messages related to
22103 reading of COFF/PE exported symbols.
22104 @item set debug dwarf2-die
22105 @cindex DWARF2 DIEs
22106 Dump DWARF2 DIEs after they are read in.
22107 The value is the number of nesting levels to print.
22108 A value of zero turns off the display.
22109 @item show debug dwarf2-die
22110 Show the current state of DWARF2 DIE debugging.
22111 @item set debug dwarf2-read
22112 @cindex DWARF2 Reading
22113 Turns on or off display of debugging messages related to reading
22114 DWARF debug info. The default is off.
22115 @item show debug dwarf2-read
22116 Show the current state of DWARF2 reader debugging.
22117 @item set debug displaced
22118 @cindex displaced stepping debugging info
22119 Turns on or off display of @value{GDBN} debugging info for the
22120 displaced stepping support. The default is off.
22121 @item show debug displaced
22122 Displays the current state of displaying @value{GDBN} debugging info
22123 related to displaced stepping.
22124 @item set debug event
22125 @cindex event debugging info
22126 Turns on or off display of @value{GDBN} event debugging info. The
22128 @item show debug event
22129 Displays the current state of displaying @value{GDBN} event debugging
22131 @item set debug expression
22132 @cindex expression debugging info
22133 Turns on or off display of debugging info about @value{GDBN}
22134 expression parsing. The default is off.
22135 @item show debug expression
22136 Displays the current state of displaying debugging info about
22137 @value{GDBN} expression parsing.
22138 @item set debug frame
22139 @cindex frame debugging info
22140 Turns on or off display of @value{GDBN} frame debugging info. The
22142 @item show debug frame
22143 Displays the current state of displaying @value{GDBN} frame debugging
22145 @item set debug gnu-nat
22146 @cindex @sc{gnu}/Hurd debug messages
22147 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22148 @item show debug gnu-nat
22149 Show the current state of @sc{gnu}/Hurd debugging messages.
22150 @item set debug infrun
22151 @cindex inferior debugging info
22152 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22153 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22154 for implementing operations such as single-stepping the inferior.
22155 @item show debug infrun
22156 Displays the current state of @value{GDBN} inferior debugging.
22157 @item set debug jit
22158 @cindex just-in-time compilation, debugging messages
22159 Turns on or off debugging messages from JIT debug support.
22160 @item show debug jit
22161 Displays the current state of @value{GDBN} JIT debugging.
22162 @item set debug lin-lwp
22163 @cindex @sc{gnu}/Linux LWP debug messages
22164 @cindex Linux lightweight processes
22165 Turns on or off debugging messages from the Linux LWP debug support.
22166 @item show debug lin-lwp
22167 Show the current state of Linux LWP debugging messages.
22168 @item set debug mach-o
22169 @cindex Mach-O symbols processing
22170 Control display of debugging messages related to Mach-O symbols
22171 processing. The default is off.
22172 @item show debug mach-o
22173 Displays the current state of displaying debugging messages related to
22174 reading of COFF/PE exported symbols.
22175 @item set debug notification
22176 @cindex remote async notification debugging info
22177 Turns on or off debugging messages about remote async notification.
22178 The default is off.
22179 @item show debug notification
22180 Displays the current state of remote async notification debugging messages.
22181 @item set debug observer
22182 @cindex observer debugging info
22183 Turns on or off display of @value{GDBN} observer debugging. This
22184 includes info such as the notification of observable events.
22185 @item show debug observer
22186 Displays the current state of observer debugging.
22187 @item set debug overload
22188 @cindex C@t{++} overload debugging info
22189 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22190 info. This includes info such as ranking of functions, etc. The default
22192 @item show debug overload
22193 Displays the current state of displaying @value{GDBN} C@t{++} overload
22195 @cindex expression parser, debugging info
22196 @cindex debug expression parser
22197 @item set debug parser
22198 Turns on or off the display of expression parser debugging output.
22199 Internally, this sets the @code{yydebug} variable in the expression
22200 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22201 details. The default is off.
22202 @item show debug parser
22203 Show the current state of expression parser debugging.
22204 @cindex packets, reporting on stdout
22205 @cindex serial connections, debugging
22206 @cindex debug remote protocol
22207 @cindex remote protocol debugging
22208 @cindex display remote packets
22209 @item set debug remote
22210 Turns on or off display of reports on all packets sent back and forth across
22211 the serial line to the remote machine. The info is printed on the
22212 @value{GDBN} standard output stream. The default is off.
22213 @item show debug remote
22214 Displays the state of display of remote packets.
22215 @item set debug serial
22216 Turns on or off display of @value{GDBN} serial debugging info. The
22218 @item show debug serial
22219 Displays the current state of displaying @value{GDBN} serial debugging
22221 @item set debug solib-frv
22222 @cindex FR-V shared-library debugging
22223 Turns on or off debugging messages for FR-V shared-library code.
22224 @item show debug solib-frv
22225 Display the current state of FR-V shared-library code debugging
22227 @item set debug symtab-create
22228 @cindex symbol table creation
22229 Turns on or off display of debugging messages related to symbol table creation.
22230 The default is off.
22231 @item show debug symtab-create
22232 Show the current state of symbol table creation debugging.
22233 @item set debug target
22234 @cindex target debugging info
22235 Turns on or off display of @value{GDBN} target debugging info. This info
22236 includes what is going on at the target level of GDB, as it happens. The
22237 default is 0. Set it to 1 to track events, and to 2 to also track the
22238 value of large memory transfers. Changes to this flag do not take effect
22239 until the next time you connect to a target or use the @code{run} command.
22240 @item show debug target
22241 Displays the current state of displaying @value{GDBN} target debugging
22243 @item set debug timestamp
22244 @cindex timestampping debugging info
22245 Turns on or off display of timestamps with @value{GDBN} debugging info.
22246 When enabled, seconds and microseconds are displayed before each debugging
22248 @item show debug timestamp
22249 Displays the current state of displaying timestamps with @value{GDBN}
22251 @item set debugvarobj
22252 @cindex variable object debugging info
22253 Turns on or off display of @value{GDBN} variable object debugging
22254 info. The default is off.
22255 @item show debugvarobj
22256 Displays the current state of displaying @value{GDBN} variable object
22258 @item set debug xml
22259 @cindex XML parser debugging
22260 Turns on or off debugging messages for built-in XML parsers.
22261 @item show debug xml
22262 Displays the current state of XML debugging messages.
22265 @node Other Misc Settings
22266 @section Other Miscellaneous Settings
22267 @cindex miscellaneous settings
22270 @kindex set interactive-mode
22271 @item set interactive-mode
22272 If @code{on}, forces @value{GDBN} to assume that GDB was started
22273 in a terminal. In practice, this means that @value{GDBN} should wait
22274 for the user to answer queries generated by commands entered at
22275 the command prompt. If @code{off}, forces @value{GDBN} to operate
22276 in the opposite mode, and it uses the default answers to all queries.
22277 If @code{auto} (the default), @value{GDBN} tries to determine whether
22278 its standard input is a terminal, and works in interactive-mode if it
22279 is, non-interactively otherwise.
22281 In the vast majority of cases, the debugger should be able to guess
22282 correctly which mode should be used. But this setting can be useful
22283 in certain specific cases, such as running a MinGW @value{GDBN}
22284 inside a cygwin window.
22286 @kindex show interactive-mode
22287 @item show interactive-mode
22288 Displays whether the debugger is operating in interactive mode or not.
22291 @node Extending GDB
22292 @chapter Extending @value{GDBN}
22293 @cindex extending GDB
22295 @value{GDBN} provides three mechanisms for extension. The first is based
22296 on composition of @value{GDBN} commands, the second is based on the
22297 Python scripting language, and the third is for defining new aliases of
22300 To facilitate the use of the first two extensions, @value{GDBN} is capable
22301 of evaluating the contents of a file. When doing so, @value{GDBN}
22302 can recognize which scripting language is being used by looking at
22303 the filename extension. Files with an unrecognized filename extension
22304 are always treated as a @value{GDBN} Command Files.
22305 @xref{Command Files,, Command files}.
22307 You can control how @value{GDBN} evaluates these files with the following
22311 @kindex set script-extension
22312 @kindex show script-extension
22313 @item set script-extension off
22314 All scripts are always evaluated as @value{GDBN} Command Files.
22316 @item set script-extension soft
22317 The debugger determines the scripting language based on filename
22318 extension. If this scripting language is supported, @value{GDBN}
22319 evaluates the script using that language. Otherwise, it evaluates
22320 the file as a @value{GDBN} Command File.
22322 @item set script-extension strict
22323 The debugger determines the scripting language based on filename
22324 extension, and evaluates the script using that language. If the
22325 language is not supported, then the evaluation fails.
22327 @item show script-extension
22328 Display the current value of the @code{script-extension} option.
22333 * Sequences:: Canned Sequences of Commands
22334 * Python:: Scripting @value{GDBN} using Python
22335 * Aliases:: Creating new spellings of existing commands
22339 @section Canned Sequences of Commands
22341 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22342 Command Lists}), @value{GDBN} provides two ways to store sequences of
22343 commands for execution as a unit: user-defined commands and command
22347 * Define:: How to define your own commands
22348 * Hooks:: Hooks for user-defined commands
22349 * Command Files:: How to write scripts of commands to be stored in a file
22350 * Output:: Commands for controlled output
22354 @subsection User-defined Commands
22356 @cindex user-defined command
22357 @cindex arguments, to user-defined commands
22358 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22359 which you assign a new name as a command. This is done with the
22360 @code{define} command. User commands may accept up to 10 arguments
22361 separated by whitespace. Arguments are accessed within the user command
22362 via @code{$arg0@dots{}$arg9}. A trivial example:
22366 print $arg0 + $arg1 + $arg2
22371 To execute the command use:
22378 This defines the command @code{adder}, which prints the sum of
22379 its three arguments. Note the arguments are text substitutions, so they may
22380 reference variables, use complex expressions, or even perform inferior
22383 @cindex argument count in user-defined commands
22384 @cindex how many arguments (user-defined commands)
22385 In addition, @code{$argc} may be used to find out how many arguments have
22386 been passed. This expands to a number in the range 0@dots{}10.
22391 print $arg0 + $arg1
22394 print $arg0 + $arg1 + $arg2
22402 @item define @var{commandname}
22403 Define a command named @var{commandname}. If there is already a command
22404 by that name, you are asked to confirm that you want to redefine it.
22405 @var{commandname} may be a bare command name consisting of letters,
22406 numbers, dashes, and underscores. It may also start with any predefined
22407 prefix command. For example, @samp{define target my-target} creates
22408 a user-defined @samp{target my-target} command.
22410 The definition of the command is made up of other @value{GDBN} command lines,
22411 which are given following the @code{define} command. The end of these
22412 commands is marked by a line containing @code{end}.
22415 @kindex end@r{ (user-defined commands)}
22416 @item document @var{commandname}
22417 Document the user-defined command @var{commandname}, so that it can be
22418 accessed by @code{help}. The command @var{commandname} must already be
22419 defined. This command reads lines of documentation just as @code{define}
22420 reads the lines of the command definition, ending with @code{end}.
22421 After the @code{document} command is finished, @code{help} on command
22422 @var{commandname} displays the documentation you have written.
22424 You may use the @code{document} command again to change the
22425 documentation of a command. Redefining the command with @code{define}
22426 does not change the documentation.
22428 @kindex dont-repeat
22429 @cindex don't repeat command
22431 Used inside a user-defined command, this tells @value{GDBN} that this
22432 command should not be repeated when the user hits @key{RET}
22433 (@pxref{Command Syntax, repeat last command}).
22435 @kindex help user-defined
22436 @item help user-defined
22437 List all user-defined commands and all python commands defined in class
22438 COMAND_USER. The first line of the documentation or docstring is
22443 @itemx show user @var{commandname}
22444 Display the @value{GDBN} commands used to define @var{commandname} (but
22445 not its documentation). If no @var{commandname} is given, display the
22446 definitions for all user-defined commands.
22447 This does not work for user-defined python commands.
22449 @cindex infinite recursion in user-defined commands
22450 @kindex show max-user-call-depth
22451 @kindex set max-user-call-depth
22452 @item show max-user-call-depth
22453 @itemx set max-user-call-depth
22454 The value of @code{max-user-call-depth} controls how many recursion
22455 levels are allowed in user-defined commands before @value{GDBN} suspects an
22456 infinite recursion and aborts the command.
22457 This does not apply to user-defined python commands.
22460 In addition to the above commands, user-defined commands frequently
22461 use control flow commands, described in @ref{Command Files}.
22463 When user-defined commands are executed, the
22464 commands of the definition are not printed. An error in any command
22465 stops execution of the user-defined command.
22467 If used interactively, commands that would ask for confirmation proceed
22468 without asking when used inside a user-defined command. Many @value{GDBN}
22469 commands that normally print messages to say what they are doing omit the
22470 messages when used in a user-defined command.
22473 @subsection User-defined Command Hooks
22474 @cindex command hooks
22475 @cindex hooks, for commands
22476 @cindex hooks, pre-command
22479 You may define @dfn{hooks}, which are a special kind of user-defined
22480 command. Whenever you run the command @samp{foo}, if the user-defined
22481 command @samp{hook-foo} exists, it is executed (with no arguments)
22482 before that command.
22484 @cindex hooks, post-command
22486 A hook may also be defined which is run after the command you executed.
22487 Whenever you run the command @samp{foo}, if the user-defined command
22488 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22489 that command. Post-execution hooks may exist simultaneously with
22490 pre-execution hooks, for the same command.
22492 It is valid for a hook to call the command which it hooks. If this
22493 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22495 @c It would be nice if hookpost could be passed a parameter indicating
22496 @c if the command it hooks executed properly or not. FIXME!
22498 @kindex stop@r{, a pseudo-command}
22499 In addition, a pseudo-command, @samp{stop} exists. Defining
22500 (@samp{hook-stop}) makes the associated commands execute every time
22501 execution stops in your program: before breakpoint commands are run,
22502 displays are printed, or the stack frame is printed.
22504 For example, to ignore @code{SIGALRM} signals while
22505 single-stepping, but treat them normally during normal execution,
22510 handle SIGALRM nopass
22514 handle SIGALRM pass
22517 define hook-continue
22518 handle SIGALRM pass
22522 As a further example, to hook at the beginning and end of the @code{echo}
22523 command, and to add extra text to the beginning and end of the message,
22531 define hookpost-echo
22535 (@value{GDBP}) echo Hello World
22536 <<<---Hello World--->>>
22541 You can define a hook for any single-word command in @value{GDBN}, but
22542 not for command aliases; you should define a hook for the basic command
22543 name, e.g.@: @code{backtrace} rather than @code{bt}.
22544 @c FIXME! So how does Joe User discover whether a command is an alias
22546 You can hook a multi-word command by adding @code{hook-} or
22547 @code{hookpost-} to the last word of the command, e.g.@:
22548 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22550 If an error occurs during the execution of your hook, execution of
22551 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22552 (before the command that you actually typed had a chance to run).
22554 If you try to define a hook which does not match any known command, you
22555 get a warning from the @code{define} command.
22557 @node Command Files
22558 @subsection Command Files
22560 @cindex command files
22561 @cindex scripting commands
22562 A command file for @value{GDBN} is a text file made of lines that are
22563 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22564 also be included. An empty line in a command file does nothing; it
22565 does not mean to repeat the last command, as it would from the
22568 You can request the execution of a command file with the @code{source}
22569 command. Note that the @code{source} command is also used to evaluate
22570 scripts that are not Command Files. The exact behavior can be configured
22571 using the @code{script-extension} setting.
22572 @xref{Extending GDB,, Extending GDB}.
22576 @cindex execute commands from a file
22577 @item source [-s] [-v] @var{filename}
22578 Execute the command file @var{filename}.
22581 The lines in a command file are generally executed sequentially,
22582 unless the order of execution is changed by one of the
22583 @emph{flow-control commands} described below. The commands are not
22584 printed as they are executed. An error in any command terminates
22585 execution of the command file and control is returned to the console.
22587 @value{GDBN} first searches for @var{filename} in the current directory.
22588 If the file is not found there, and @var{filename} does not specify a
22589 directory, then @value{GDBN} also looks for the file on the source search path
22590 (specified with the @samp{directory} command);
22591 except that @file{$cdir} is not searched because the compilation directory
22592 is not relevant to scripts.
22594 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22595 on the search path even if @var{filename} specifies a directory.
22596 The search is done by appending @var{filename} to each element of the
22597 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22598 and the search path contains @file{/home/user} then @value{GDBN} will
22599 look for the script @file{/home/user/mylib/myscript}.
22600 The search is also done if @var{filename} is an absolute path.
22601 For example, if @var{filename} is @file{/tmp/myscript} and
22602 the search path contains @file{/home/user} then @value{GDBN} will
22603 look for the script @file{/home/user/tmp/myscript}.
22604 For DOS-like systems, if @var{filename} contains a drive specification,
22605 it is stripped before concatenation. For example, if @var{filename} is
22606 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22607 will look for the script @file{c:/tmp/myscript}.
22609 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22610 each command as it is executed. The option must be given before
22611 @var{filename}, and is interpreted as part of the filename anywhere else.
22613 Commands that would ask for confirmation if used interactively proceed
22614 without asking when used in a command file. Many @value{GDBN} commands that
22615 normally print messages to say what they are doing omit the messages
22616 when called from command files.
22618 @value{GDBN} also accepts command input from standard input. In this
22619 mode, normal output goes to standard output and error output goes to
22620 standard error. Errors in a command file supplied on standard input do
22621 not terminate execution of the command file---execution continues with
22625 gdb < cmds > log 2>&1
22628 (The syntax above will vary depending on the shell used.) This example
22629 will execute commands from the file @file{cmds}. All output and errors
22630 would be directed to @file{log}.
22632 Since commands stored on command files tend to be more general than
22633 commands typed interactively, they frequently need to deal with
22634 complicated situations, such as different or unexpected values of
22635 variables and symbols, changes in how the program being debugged is
22636 built, etc. @value{GDBN} provides a set of flow-control commands to
22637 deal with these complexities. Using these commands, you can write
22638 complex scripts that loop over data structures, execute commands
22639 conditionally, etc.
22646 This command allows to include in your script conditionally executed
22647 commands. The @code{if} command takes a single argument, which is an
22648 expression to evaluate. It is followed by a series of commands that
22649 are executed only if the expression is true (its value is nonzero).
22650 There can then optionally be an @code{else} line, followed by a series
22651 of commands that are only executed if the expression was false. The
22652 end of the list is marked by a line containing @code{end}.
22656 This command allows to write loops. Its syntax is similar to
22657 @code{if}: the command takes a single argument, which is an expression
22658 to evaluate, and must be followed by the commands to execute, one per
22659 line, terminated by an @code{end}. These commands are called the
22660 @dfn{body} of the loop. The commands in the body of @code{while} are
22661 executed repeatedly as long as the expression evaluates to true.
22665 This command exits the @code{while} loop in whose body it is included.
22666 Execution of the script continues after that @code{while}s @code{end}
22669 @kindex loop_continue
22670 @item loop_continue
22671 This command skips the execution of the rest of the body of commands
22672 in the @code{while} loop in whose body it is included. Execution
22673 branches to the beginning of the @code{while} loop, where it evaluates
22674 the controlling expression.
22676 @kindex end@r{ (if/else/while commands)}
22678 Terminate the block of commands that are the body of @code{if},
22679 @code{else}, or @code{while} flow-control commands.
22684 @subsection Commands for Controlled Output
22686 During the execution of a command file or a user-defined command, normal
22687 @value{GDBN} output is suppressed; the only output that appears is what is
22688 explicitly printed by the commands in the definition. This section
22689 describes three commands useful for generating exactly the output you
22694 @item echo @var{text}
22695 @c I do not consider backslash-space a standard C escape sequence
22696 @c because it is not in ANSI.
22697 Print @var{text}. Nonprinting characters can be included in
22698 @var{text} using C escape sequences, such as @samp{\n} to print a
22699 newline. @strong{No newline is printed unless you specify one.}
22700 In addition to the standard C escape sequences, a backslash followed
22701 by a space stands for a space. This is useful for displaying a
22702 string with spaces at the beginning or the end, since leading and
22703 trailing spaces are otherwise trimmed from all arguments.
22704 To print @samp{@w{ }and foo =@w{ }}, use the command
22705 @samp{echo \@w{ }and foo = \@w{ }}.
22707 A backslash at the end of @var{text} can be used, as in C, to continue
22708 the command onto subsequent lines. For example,
22711 echo This is some text\n\
22712 which is continued\n\
22713 onto several lines.\n
22716 produces the same output as
22719 echo This is some text\n
22720 echo which is continued\n
22721 echo onto several lines.\n
22725 @item output @var{expression}
22726 Print the value of @var{expression} and nothing but that value: no
22727 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22728 value history either. @xref{Expressions, ,Expressions}, for more information
22731 @item output/@var{fmt} @var{expression}
22732 Print the value of @var{expression} in format @var{fmt}. You can use
22733 the same formats as for @code{print}. @xref{Output Formats,,Output
22734 Formats}, for more information.
22737 @item printf @var{template}, @var{expressions}@dots{}
22738 Print the values of one or more @var{expressions} under the control of
22739 the string @var{template}. To print several values, make
22740 @var{expressions} be a comma-separated list of individual expressions,
22741 which may be either numbers or pointers. Their values are printed as
22742 specified by @var{template}, exactly as a C program would do by
22743 executing the code below:
22746 printf (@var{template}, @var{expressions}@dots{});
22749 As in @code{C} @code{printf}, ordinary characters in @var{template}
22750 are printed verbatim, while @dfn{conversion specification} introduced
22751 by the @samp{%} character cause subsequent @var{expressions} to be
22752 evaluated, their values converted and formatted according to type and
22753 style information encoded in the conversion specifications, and then
22756 For example, you can print two values in hex like this:
22759 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22762 @code{printf} supports all the standard @code{C} conversion
22763 specifications, including the flags and modifiers between the @samp{%}
22764 character and the conversion letter, with the following exceptions:
22768 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22771 The modifier @samp{*} is not supported for specifying precision or
22775 The @samp{'} flag (for separation of digits into groups according to
22776 @code{LC_NUMERIC'}) is not supported.
22779 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22783 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22786 The conversion letters @samp{a} and @samp{A} are not supported.
22790 Note that the @samp{ll} type modifier is supported only if the
22791 underlying @code{C} implementation used to build @value{GDBN} supports
22792 the @code{long long int} type, and the @samp{L} type modifier is
22793 supported only if @code{long double} type is available.
22795 As in @code{C}, @code{printf} supports simple backslash-escape
22796 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22797 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22798 single character. Octal and hexadecimal escape sequences are not
22801 Additionally, @code{printf} supports conversion specifications for DFP
22802 (@dfn{Decimal Floating Point}) types using the following length modifiers
22803 together with a floating point specifier.
22808 @samp{H} for printing @code{Decimal32} types.
22811 @samp{D} for printing @code{Decimal64} types.
22814 @samp{DD} for printing @code{Decimal128} types.
22817 If the underlying @code{C} implementation used to build @value{GDBN} has
22818 support for the three length modifiers for DFP types, other modifiers
22819 such as width and precision will also be available for @value{GDBN} to use.
22821 In case there is no such @code{C} support, no additional modifiers will be
22822 available and the value will be printed in the standard way.
22824 Here's an example of printing DFP types using the above conversion letters:
22826 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22830 @item eval @var{template}, @var{expressions}@dots{}
22831 Convert the values of one or more @var{expressions} under the control of
22832 the string @var{template} to a command line, and call it.
22837 @section Scripting @value{GDBN} using Python
22838 @cindex python scripting
22839 @cindex scripting with python
22841 You can script @value{GDBN} using the @uref{http://www.python.org/,
22842 Python programming language}. This feature is available only if
22843 @value{GDBN} was configured using @option{--with-python}.
22845 @cindex python directory
22846 Python scripts used by @value{GDBN} should be installed in
22847 @file{@var{data-directory}/python}, where @var{data-directory} is
22848 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22849 This directory, known as the @dfn{python directory},
22850 is automatically added to the Python Search Path in order to allow
22851 the Python interpreter to locate all scripts installed at this location.
22853 Additionally, @value{GDBN} commands and convenience functions which
22854 are written in Python and are located in the
22855 @file{@var{data-directory}/python/gdb/command} or
22856 @file{@var{data-directory}/python/gdb/function} directories are
22857 automatically imported when @value{GDBN} starts.
22860 * Python Commands:: Accessing Python from @value{GDBN}.
22861 * Python API:: Accessing @value{GDBN} from Python.
22862 * Python Auto-loading:: Automatically loading Python code.
22863 * Python modules:: Python modules provided by @value{GDBN}.
22866 @node Python Commands
22867 @subsection Python Commands
22868 @cindex python commands
22869 @cindex commands to access python
22871 @value{GDBN} provides two commands for accessing the Python interpreter,
22872 and one related setting:
22875 @kindex python-interactive
22877 @item python-interactive @r{[}@var{command}@r{]}
22878 @itemx pi @r{[}@var{command}@r{]}
22879 Without an argument, the @code{python-interactive} command can be used
22880 to start an interactive Python prompt. To return to @value{GDBN},
22881 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22883 Alternatively, a single-line Python command can be given as an
22884 argument and evaluated. If the command is an expression, the result
22885 will be printed; otherwise, nothing will be printed. For example:
22888 (@value{GDBP}) python-interactive 2 + 3
22894 @item python @r{[}@var{command}@r{]}
22895 @itemx py @r{[}@var{command}@r{]}
22896 The @code{python} command can be used to evaluate Python code.
22898 If given an argument, the @code{python} command will evaluate the
22899 argument as a Python command. For example:
22902 (@value{GDBP}) python print 23
22906 If you do not provide an argument to @code{python}, it will act as a
22907 multi-line command, like @code{define}. In this case, the Python
22908 script is made up of subsequent command lines, given after the
22909 @code{python} command. This command list is terminated using a line
22910 containing @code{end}. For example:
22913 (@value{GDBP}) python
22915 End with a line saying just "end".
22921 @kindex set python print-stack
22922 @item set python print-stack
22923 By default, @value{GDBN} will print only the message component of a
22924 Python exception when an error occurs in a Python script. This can be
22925 controlled using @code{set python print-stack}: if @code{full}, then
22926 full Python stack printing is enabled; if @code{none}, then Python stack
22927 and message printing is disabled; if @code{message}, the default, only
22928 the message component of the error is printed.
22931 It is also possible to execute a Python script from the @value{GDBN}
22935 @item source @file{script-name}
22936 The script name must end with @samp{.py} and @value{GDBN} must be configured
22937 to recognize the script language based on filename extension using
22938 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22940 @item python execfile ("script-name")
22941 This method is based on the @code{execfile} Python built-in function,
22942 and thus is always available.
22946 @subsection Python API
22948 @cindex programming in python
22950 @cindex python stdout
22951 @cindex python pagination
22952 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22953 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22954 A Python program which outputs to one of these streams may have its
22955 output interrupted by the user (@pxref{Screen Size}). In this
22956 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22959 * Basic Python:: Basic Python Functions.
22960 * Exception Handling:: How Python exceptions are translated.
22961 * Values From Inferior:: Python representation of values.
22962 * Types In Python:: Python representation of types.
22963 * Pretty Printing API:: Pretty-printing values.
22964 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22965 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22966 * Type Printing API:: Pretty-printing types.
22967 * Inferiors In Python:: Python representation of inferiors (processes)
22968 * Events In Python:: Listening for events from @value{GDBN}.
22969 * Threads In Python:: Accessing inferior threads from Python.
22970 * Commands In Python:: Implementing new commands in Python.
22971 * Parameters In Python:: Adding new @value{GDBN} parameters.
22972 * Functions In Python:: Writing new convenience functions.
22973 * Progspaces In Python:: Program spaces.
22974 * Objfiles In Python:: Object files.
22975 * Frames In Python:: Accessing inferior stack frames from Python.
22976 * Blocks In Python:: Accessing frame blocks from Python.
22977 * Symbols In Python:: Python representation of symbols.
22978 * Symbol Tables In Python:: Python representation of symbol tables.
22979 * Breakpoints In Python:: Manipulating breakpoints using Python.
22980 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22982 * Lazy Strings In Python:: Python representation of lazy strings.
22983 * Architectures In Python:: Python representation of architectures.
22987 @subsubsection Basic Python
22989 @cindex python functions
22990 @cindex python module
22992 @value{GDBN} introduces a new Python module, named @code{gdb}. All
22993 methods and classes added by @value{GDBN} are placed in this module.
22994 @value{GDBN} automatically @code{import}s the @code{gdb} module for
22995 use in all scripts evaluated by the @code{python} command.
22997 @findex gdb.PYTHONDIR
22998 @defvar gdb.PYTHONDIR
22999 A string containing the python directory (@pxref{Python}).
23002 @findex gdb.execute
23003 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23004 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23005 If a GDB exception happens while @var{command} runs, it is
23006 translated as described in @ref{Exception Handling,,Exception Handling}.
23008 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23009 command as having originated from the user invoking it interactively.
23010 It must be a boolean value. If omitted, it defaults to @code{False}.
23012 By default, any output produced by @var{command} is sent to
23013 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23014 @code{True}, then output will be collected by @code{gdb.execute} and
23015 returned as a string. The default is @code{False}, in which case the
23016 return value is @code{None}. If @var{to_string} is @code{True}, the
23017 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23018 and height, and its pagination will be disabled; @pxref{Screen Size}.
23021 @findex gdb.breakpoints
23022 @defun gdb.breakpoints ()
23023 Return a sequence holding all of @value{GDBN}'s breakpoints.
23024 @xref{Breakpoints In Python}, for more information.
23027 @findex gdb.parameter
23028 @defun gdb.parameter (parameter)
23029 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23030 string naming the parameter to look up; @var{parameter} may contain
23031 spaces if the parameter has a multi-part name. For example,
23032 @samp{print object} is a valid parameter name.
23034 If the named parameter does not exist, this function throws a
23035 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23036 parameter's value is converted to a Python value of the appropriate
23037 type, and returned.
23040 @findex gdb.history
23041 @defun gdb.history (number)
23042 Return a value from @value{GDBN}'s value history (@pxref{Value
23043 History}). @var{number} indicates which history element to return.
23044 If @var{number} is negative, then @value{GDBN} will take its absolute value
23045 and count backward from the last element (i.e., the most recent element) to
23046 find the value to return. If @var{number} is zero, then @value{GDBN} will
23047 return the most recent element. If the element specified by @var{number}
23048 doesn't exist in the value history, a @code{gdb.error} exception will be
23051 If no exception is raised, the return value is always an instance of
23052 @code{gdb.Value} (@pxref{Values From Inferior}).
23055 @findex gdb.parse_and_eval
23056 @defun gdb.parse_and_eval (expression)
23057 Parse @var{expression} as an expression in the current language,
23058 evaluate it, and return the result as a @code{gdb.Value}.
23059 @var{expression} must be a string.
23061 This function can be useful when implementing a new command
23062 (@pxref{Commands In Python}), as it provides a way to parse the
23063 command's argument as an expression. It is also useful simply to
23064 compute values, for example, it is the only way to get the value of a
23065 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23068 @findex gdb.find_pc_line
23069 @defun gdb.find_pc_line (pc)
23070 Return the @code{gdb.Symtab_and_line} object corresponding to the
23071 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23072 value of @var{pc} is passed as an argument, then the @code{symtab} and
23073 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23074 will be @code{None} and 0 respectively.
23077 @findex gdb.post_event
23078 @defun gdb.post_event (event)
23079 Put @var{event}, a callable object taking no arguments, into
23080 @value{GDBN}'s internal event queue. This callable will be invoked at
23081 some later point, during @value{GDBN}'s event processing. Events
23082 posted using @code{post_event} will be run in the order in which they
23083 were posted; however, there is no way to know when they will be
23084 processed relative to other events inside @value{GDBN}.
23086 @value{GDBN} is not thread-safe. If your Python program uses multiple
23087 threads, you must be careful to only call @value{GDBN}-specific
23088 functions in the main @value{GDBN} thread. @code{post_event} ensures
23092 (@value{GDBP}) python
23096 > def __init__(self, message):
23097 > self.message = message;
23098 > def __call__(self):
23099 > gdb.write(self.message)
23101 >class MyThread1 (threading.Thread):
23103 > gdb.post_event(Writer("Hello "))
23105 >class MyThread2 (threading.Thread):
23107 > gdb.post_event(Writer("World\n"))
23109 >MyThread1().start()
23110 >MyThread2().start()
23112 (@value{GDBP}) Hello World
23117 @defun gdb.write (string @r{[}, stream{]})
23118 Print a string to @value{GDBN}'s paginated output stream. The
23119 optional @var{stream} determines the stream to print to. The default
23120 stream is @value{GDBN}'s standard output stream. Possible stream
23127 @value{GDBN}'s standard output stream.
23132 @value{GDBN}'s standard error stream.
23137 @value{GDBN}'s log stream (@pxref{Logging Output}).
23140 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23141 call this function and will automatically direct the output to the
23146 @defun gdb.flush ()
23147 Flush the buffer of a @value{GDBN} paginated stream so that the
23148 contents are displayed immediately. @value{GDBN} will flush the
23149 contents of a stream automatically when it encounters a newline in the
23150 buffer. The optional @var{stream} determines the stream to flush. The
23151 default stream is @value{GDBN}'s standard output stream. Possible
23158 @value{GDBN}'s standard output stream.
23163 @value{GDBN}'s standard error stream.
23168 @value{GDBN}'s log stream (@pxref{Logging Output}).
23172 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23173 call this function for the relevant stream.
23176 @findex gdb.target_charset
23177 @defun gdb.target_charset ()
23178 Return the name of the current target character set (@pxref{Character
23179 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23180 that @samp{auto} is never returned.
23183 @findex gdb.target_wide_charset
23184 @defun gdb.target_wide_charset ()
23185 Return the name of the current target wide character set
23186 (@pxref{Character Sets}). This differs from
23187 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23191 @findex gdb.solib_name
23192 @defun gdb.solib_name (address)
23193 Return the name of the shared library holding the given @var{address}
23194 as a string, or @code{None}.
23197 @findex gdb.decode_line
23198 @defun gdb.decode_line @r{[}expression@r{]}
23199 Return locations of the line specified by @var{expression}, or of the
23200 current line if no argument was given. This function returns a Python
23201 tuple containing two elements. The first element contains a string
23202 holding any unparsed section of @var{expression} (or @code{None} if
23203 the expression has been fully parsed). The second element contains
23204 either @code{None} or another tuple that contains all the locations
23205 that match the expression represented as @code{gdb.Symtab_and_line}
23206 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23207 provided, it is decoded the way that @value{GDBN}'s inbuilt
23208 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23211 @defun gdb.prompt_hook (current_prompt)
23212 @anchor{prompt_hook}
23214 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23215 assigned to this operation before a prompt is displayed by
23218 The parameter @code{current_prompt} contains the current @value{GDBN}
23219 prompt. This method must return a Python string, or @code{None}. If
23220 a string is returned, the @value{GDBN} prompt will be set to that
23221 string. If @code{None} is returned, @value{GDBN} will continue to use
23222 the current prompt.
23224 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23225 such as those used by readline for command input, and annotation
23226 related prompts are prohibited from being changed.
23229 @node Exception Handling
23230 @subsubsection Exception Handling
23231 @cindex python exceptions
23232 @cindex exceptions, python
23234 When executing the @code{python} command, Python exceptions
23235 uncaught within the Python code are translated to calls to
23236 @value{GDBN} error-reporting mechanism. If the command that called
23237 @code{python} does not handle the error, @value{GDBN} will
23238 terminate it and print an error message containing the Python
23239 exception name, the associated value, and the Python call stack
23240 backtrace at the point where the exception was raised. Example:
23243 (@value{GDBP}) python print foo
23244 Traceback (most recent call last):
23245 File "<string>", line 1, in <module>
23246 NameError: name 'foo' is not defined
23249 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23250 Python code are converted to Python exceptions. The type of the
23251 Python exception depends on the error.
23255 This is the base class for most exceptions generated by @value{GDBN}.
23256 It is derived from @code{RuntimeError}, for compatibility with earlier
23257 versions of @value{GDBN}.
23259 If an error occurring in @value{GDBN} does not fit into some more
23260 specific category, then the generated exception will have this type.
23262 @item gdb.MemoryError
23263 This is a subclass of @code{gdb.error} which is thrown when an
23264 operation tried to access invalid memory in the inferior.
23266 @item KeyboardInterrupt
23267 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23268 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23271 In all cases, your exception handler will see the @value{GDBN} error
23272 message as its value and the Python call stack backtrace at the Python
23273 statement closest to where the @value{GDBN} error occured as the
23276 @findex gdb.GdbError
23277 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23278 it is useful to be able to throw an exception that doesn't cause a
23279 traceback to be printed. For example, the user may have invoked the
23280 command incorrectly. Use the @code{gdb.GdbError} exception
23281 to handle this case. Example:
23285 >class HelloWorld (gdb.Command):
23286 > """Greet the whole world."""
23287 > def __init__ (self):
23288 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23289 > def invoke (self, args, from_tty):
23290 > argv = gdb.string_to_argv (args)
23291 > if len (argv) != 0:
23292 > raise gdb.GdbError ("hello-world takes no arguments")
23293 > print "Hello, World!"
23296 (gdb) hello-world 42
23297 hello-world takes no arguments
23300 @node Values From Inferior
23301 @subsubsection Values From Inferior
23302 @cindex values from inferior, with Python
23303 @cindex python, working with values from inferior
23305 @cindex @code{gdb.Value}
23306 @value{GDBN} provides values it obtains from the inferior program in
23307 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23308 for its internal bookkeeping of the inferior's values, and for
23309 fetching values when necessary.
23311 Inferior values that are simple scalars can be used directly in
23312 Python expressions that are valid for the value's data type. Here's
23313 an example for an integer or floating-point value @code{some_val}:
23320 As result of this, @code{bar} will also be a @code{gdb.Value} object
23321 whose values are of the same type as those of @code{some_val}.
23323 Inferior values that are structures or instances of some class can
23324 be accessed using the Python @dfn{dictionary syntax}. For example, if
23325 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23326 can access its @code{foo} element with:
23329 bar = some_val['foo']
23332 Again, @code{bar} will also be a @code{gdb.Value} object.
23334 A @code{gdb.Value} that represents a function can be executed via
23335 inferior function call. Any arguments provided to the call must match
23336 the function's prototype, and must be provided in the order specified
23339 For example, @code{some_val} is a @code{gdb.Value} instance
23340 representing a function that takes two integers as arguments. To
23341 execute this function, call it like so:
23344 result = some_val (10,20)
23347 Any values returned from a function call will be stored as a
23350 The following attributes are provided:
23352 @defvar Value.address
23353 If this object is addressable, this read-only attribute holds a
23354 @code{gdb.Value} object representing the address. Otherwise,
23355 this attribute holds @code{None}.
23358 @cindex optimized out value in Python
23359 @defvar Value.is_optimized_out
23360 This read-only boolean attribute is true if the compiler optimized out
23361 this value, thus it is not available for fetching from the inferior.
23365 The type of this @code{gdb.Value}. The value of this attribute is a
23366 @code{gdb.Type} object (@pxref{Types In Python}).
23369 @defvar Value.dynamic_type
23370 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23371 type information (@acronym{RTTI}) to determine the dynamic type of the
23372 value. If this value is of class type, it will return the class in
23373 which the value is embedded, if any. If this value is of pointer or
23374 reference to a class type, it will compute the dynamic type of the
23375 referenced object, and return a pointer or reference to that type,
23376 respectively. In all other cases, it will return the value's static
23379 Note that this feature will only work when debugging a C@t{++} program
23380 that includes @acronym{RTTI} for the object in question. Otherwise,
23381 it will just return the static type of the value as in @kbd{ptype foo}
23382 (@pxref{Symbols, ptype}).
23385 @defvar Value.is_lazy
23386 The value of this read-only boolean attribute is @code{True} if this
23387 @code{gdb.Value} has not yet been fetched from the inferior.
23388 @value{GDBN} does not fetch values until necessary, for efficiency.
23392 myval = gdb.parse_and_eval ('somevar')
23395 The value of @code{somevar} is not fetched at this time. It will be
23396 fetched when the value is needed, or when the @code{fetch_lazy}
23400 The following methods are provided:
23402 @defun Value.__init__ (@var{val})
23403 Many Python values can be converted directly to a @code{gdb.Value} via
23404 this object initializer. Specifically:
23407 @item Python boolean
23408 A Python boolean is converted to the boolean type from the current
23411 @item Python integer
23412 A Python integer is converted to the C @code{long} type for the
23413 current architecture.
23416 A Python long is converted to the C @code{long long} type for the
23417 current architecture.
23420 A Python float is converted to the C @code{double} type for the
23421 current architecture.
23423 @item Python string
23424 A Python string is converted to a target string, using the current
23427 @item @code{gdb.Value}
23428 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23430 @item @code{gdb.LazyString}
23431 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23432 Python}), then the lazy string's @code{value} method is called, and
23433 its result is used.
23437 @defun Value.cast (type)
23438 Return a new instance of @code{gdb.Value} that is the result of
23439 casting this instance to the type described by @var{type}, which must
23440 be a @code{gdb.Type} object. If the cast cannot be performed for some
23441 reason, this method throws an exception.
23444 @defun Value.dereference ()
23445 For pointer data types, this method returns a new @code{gdb.Value} object
23446 whose contents is the object pointed to by the pointer. For example, if
23447 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23454 then you can use the corresponding @code{gdb.Value} to access what
23455 @code{foo} points to like this:
23458 bar = foo.dereference ()
23461 The result @code{bar} will be a @code{gdb.Value} object holding the
23462 value pointed to by @code{foo}.
23464 A similar function @code{Value.referenced_value} exists which also
23465 returns @code{gdb.Value} objects corresonding to the values pointed to
23466 by pointer values (and additionally, values referenced by reference
23467 values). However, the behavior of @code{Value.dereference}
23468 differs from @code{Value.referenced_value} by the fact that the
23469 behavior of @code{Value.dereference} is identical to applying the C
23470 unary operator @code{*} on a given value. For example, consider a
23471 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23475 typedef int *intptr;
23479 intptr &ptrref = ptr;
23482 Though @code{ptrref} is a reference value, one can apply the method
23483 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23484 to it and obtain a @code{gdb.Value} which is identical to that
23485 corresponding to @code{val}. However, if you apply the method
23486 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23487 object identical to that corresponding to @code{ptr}.
23490 py_ptrref = gdb.parse_and_eval ("ptrref")
23491 py_val = py_ptrref.dereference ()
23492 py_ptr = py_ptrref.referenced_value ()
23495 The @code{gdb.Value} object @code{py_val} is identical to that
23496 corresponding to @code{val}, and @code{py_ptr} is identical to that
23497 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23498 be applied whenever the C unary operator @code{*} can be applied
23499 to the corresponding C value. For those cases where applying both
23500 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23501 the results obtained need not be identical (as we have seen in the above
23502 example). The results are however identical when applied on
23503 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23504 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23507 @defun Value.referenced_value ()
23508 For pointer or reference data types, this method returns a new
23509 @code{gdb.Value} object corresponding to the value referenced by the
23510 pointer/reference value. For pointer data types,
23511 @code{Value.dereference} and @code{Value.referenced_value} produce
23512 identical results. The difference between these methods is that
23513 @code{Value.dereference} cannot get the values referenced by reference
23514 values. For example, consider a reference to an @code{int}, declared
23515 in your C@t{++} program as
23523 then applying @code{Value.dereference} to the @code{gdb.Value} object
23524 corresponding to @code{ref} will result in an error, while applying
23525 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23526 identical to that corresponding to @code{val}.
23529 py_ref = gdb.parse_and_eval ("ref")
23530 er_ref = py_ref.dereference () # Results in error
23531 py_val = py_ref.referenced_value () # Returns the referenced value
23534 The @code{gdb.Value} object @code{py_val} is identical to that
23535 corresponding to @code{val}.
23538 @defun Value.dynamic_cast (type)
23539 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23540 operator were used. Consult a C@t{++} reference for details.
23543 @defun Value.reinterpret_cast (type)
23544 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23545 operator were used. Consult a C@t{++} reference for details.
23548 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23549 If this @code{gdb.Value} represents a string, then this method
23550 converts the contents to a Python string. Otherwise, this method will
23551 throw an exception.
23553 Strings are recognized in a language-specific way; whether a given
23554 @code{gdb.Value} represents a string is determined by the current
23557 For C-like languages, a value is a string if it is a pointer to or an
23558 array of characters or ints. The string is assumed to be terminated
23559 by a zero of the appropriate width. However if the optional length
23560 argument is given, the string will be converted to that given length,
23561 ignoring any embedded zeros that the string may contain.
23563 If the optional @var{encoding} argument is given, it must be a string
23564 naming the encoding of the string in the @code{gdb.Value}, such as
23565 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23566 the same encodings as the corresponding argument to Python's
23567 @code{string.decode} method, and the Python codec machinery will be used
23568 to convert the string. If @var{encoding} is not given, or if
23569 @var{encoding} is the empty string, then either the @code{target-charset}
23570 (@pxref{Character Sets}) will be used, or a language-specific encoding
23571 will be used, if the current language is able to supply one.
23573 The optional @var{errors} argument is the same as the corresponding
23574 argument to Python's @code{string.decode} method.
23576 If the optional @var{length} argument is given, the string will be
23577 fetched and converted to the given length.
23580 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23581 If this @code{gdb.Value} represents a string, then this method
23582 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23583 In Python}). Otherwise, this method will throw an exception.
23585 If the optional @var{encoding} argument is given, it must be a string
23586 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23587 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23588 @var{encoding} argument is an encoding that @value{GDBN} does
23589 recognize, @value{GDBN} will raise an error.
23591 When a lazy string is printed, the @value{GDBN} encoding machinery is
23592 used to convert the string during printing. If the optional
23593 @var{encoding} argument is not provided, or is an empty string,
23594 @value{GDBN} will automatically select the encoding most suitable for
23595 the string type. For further information on encoding in @value{GDBN}
23596 please see @ref{Character Sets}.
23598 If the optional @var{length} argument is given, the string will be
23599 fetched and encoded to the length of characters specified. If
23600 the @var{length} argument is not provided, the string will be fetched
23601 and encoded until a null of appropriate width is found.
23604 @defun Value.fetch_lazy ()
23605 If the @code{gdb.Value} object is currently a lazy value
23606 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23607 fetched from the inferior. Any errors that occur in the process
23608 will produce a Python exception.
23610 If the @code{gdb.Value} object is not a lazy value, this method
23613 This method does not return a value.
23617 @node Types In Python
23618 @subsubsection Types In Python
23619 @cindex types in Python
23620 @cindex Python, working with types
23623 @value{GDBN} represents types from the inferior using the class
23626 The following type-related functions are available in the @code{gdb}
23629 @findex gdb.lookup_type
23630 @defun gdb.lookup_type (name @r{[}, block@r{]})
23631 This function looks up a type by name. @var{name} is the name of the
23632 type to look up. It must be a string.
23634 If @var{block} is given, then @var{name} is looked up in that scope.
23635 Otherwise, it is searched for globally.
23637 Ordinarily, this function will return an instance of @code{gdb.Type}.
23638 If the named type cannot be found, it will throw an exception.
23641 If the type is a structure or class type, or an enum type, the fields
23642 of that type can be accessed using the Python @dfn{dictionary syntax}.
23643 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23644 a structure type, you can access its @code{foo} field with:
23647 bar = some_type['foo']
23650 @code{bar} will be a @code{gdb.Field} object; see below under the
23651 description of the @code{Type.fields} method for a description of the
23652 @code{gdb.Field} class.
23654 An instance of @code{Type} has the following attributes:
23657 The type code for this type. The type code will be one of the
23658 @code{TYPE_CODE_} constants defined below.
23661 @defvar Type.sizeof
23662 The size of this type, in target @code{char} units. Usually, a
23663 target's @code{char} type will be an 8-bit byte. However, on some
23664 unusual platforms, this type may have a different size.
23668 The tag name for this type. The tag name is the name after
23669 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23670 languages have this concept. If this type has no tag name, then
23671 @code{None} is returned.
23674 The following methods are provided:
23676 @defun Type.fields ()
23677 For structure and union types, this method returns the fields. Range
23678 types have two fields, the minimum and maximum values. Enum types
23679 have one field per enum constant. Function and method types have one
23680 field per parameter. The base types of C@t{++} classes are also
23681 represented as fields. If the type has no fields, or does not fit
23682 into one of these categories, an empty sequence will be returned.
23684 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23687 This attribute is not available for @code{static} fields (as in
23688 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23689 position of the field. For @code{enum} fields, the value is the
23690 enumeration member's integer representation.
23693 The name of the field, or @code{None} for anonymous fields.
23696 This is @code{True} if the field is artificial, usually meaning that
23697 it was provided by the compiler and not the user. This attribute is
23698 always provided, and is @code{False} if the field is not artificial.
23700 @item is_base_class
23701 This is @code{True} if the field represents a base class of a C@t{++}
23702 structure. This attribute is always provided, and is @code{False}
23703 if the field is not a base class of the type that is the argument of
23704 @code{fields}, or if that type was not a C@t{++} class.
23707 If the field is packed, or is a bitfield, then this will have a
23708 non-zero value, which is the size of the field in bits. Otherwise,
23709 this will be zero; in this case the field's size is given by its type.
23712 The type of the field. This is usually an instance of @code{Type},
23713 but it can be @code{None} in some situations.
23717 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23718 Return a new @code{gdb.Type} object which represents an array of this
23719 type. If one argument is given, it is the inclusive upper bound of
23720 the array; in this case the lower bound is zero. If two arguments are
23721 given, the first argument is the lower bound of the array, and the
23722 second argument is the upper bound of the array. An array's length
23723 must not be negative, but the bounds can be.
23726 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23727 Return a new @code{gdb.Type} object which represents a vector of this
23728 type. If one argument is given, it is the inclusive upper bound of
23729 the vector; in this case the lower bound is zero. If two arguments are
23730 given, the first argument is the lower bound of the vector, and the
23731 second argument is the upper bound of the vector. A vector's length
23732 must not be negative, but the bounds can be.
23734 The difference between an @code{array} and a @code{vector} is that
23735 arrays behave like in C: when used in expressions they decay to a pointer
23736 to the first element whereas vectors are treated as first class values.
23739 @defun Type.const ()
23740 Return a new @code{gdb.Type} object which represents a
23741 @code{const}-qualified variant of this type.
23744 @defun Type.volatile ()
23745 Return a new @code{gdb.Type} object which represents a
23746 @code{volatile}-qualified variant of this type.
23749 @defun Type.unqualified ()
23750 Return a new @code{gdb.Type} object which represents an unqualified
23751 variant of this type. That is, the result is neither @code{const} nor
23755 @defun Type.range ()
23756 Return a Python @code{Tuple} object that contains two elements: the
23757 low bound of the argument type and the high bound of that type. If
23758 the type does not have a range, @value{GDBN} will raise a
23759 @code{gdb.error} exception (@pxref{Exception Handling}).
23762 @defun Type.reference ()
23763 Return a new @code{gdb.Type} object which represents a reference to this
23767 @defun Type.pointer ()
23768 Return a new @code{gdb.Type} object which represents a pointer to this
23772 @defun Type.strip_typedefs ()
23773 Return a new @code{gdb.Type} that represents the real type,
23774 after removing all layers of typedefs.
23777 @defun Type.target ()
23778 Return a new @code{gdb.Type} object which represents the target type
23781 For a pointer type, the target type is the type of the pointed-to
23782 object. For an array type (meaning C-like arrays), the target type is
23783 the type of the elements of the array. For a function or method type,
23784 the target type is the type of the return value. For a complex type,
23785 the target type is the type of the elements. For a typedef, the
23786 target type is the aliased type.
23788 If the type does not have a target, this method will throw an
23792 @defun Type.template_argument (n @r{[}, block@r{]})
23793 If this @code{gdb.Type} is an instantiation of a template, this will
23794 return a new @code{gdb.Type} which represents the type of the
23795 @var{n}th template argument.
23797 If this @code{gdb.Type} is not a template type, this will throw an
23798 exception. Ordinarily, only C@t{++} code will have template types.
23800 If @var{block} is given, then @var{name} is looked up in that scope.
23801 Otherwise, it is searched for globally.
23805 Each type has a code, which indicates what category this type falls
23806 into. The available type categories are represented by constants
23807 defined in the @code{gdb} module:
23810 @findex TYPE_CODE_PTR
23811 @findex gdb.TYPE_CODE_PTR
23812 @item gdb.TYPE_CODE_PTR
23813 The type is a pointer.
23815 @findex TYPE_CODE_ARRAY
23816 @findex gdb.TYPE_CODE_ARRAY
23817 @item gdb.TYPE_CODE_ARRAY
23818 The type is an array.
23820 @findex TYPE_CODE_STRUCT
23821 @findex gdb.TYPE_CODE_STRUCT
23822 @item gdb.TYPE_CODE_STRUCT
23823 The type is a structure.
23825 @findex TYPE_CODE_UNION
23826 @findex gdb.TYPE_CODE_UNION
23827 @item gdb.TYPE_CODE_UNION
23828 The type is a union.
23830 @findex TYPE_CODE_ENUM
23831 @findex gdb.TYPE_CODE_ENUM
23832 @item gdb.TYPE_CODE_ENUM
23833 The type is an enum.
23835 @findex TYPE_CODE_FLAGS
23836 @findex gdb.TYPE_CODE_FLAGS
23837 @item gdb.TYPE_CODE_FLAGS
23838 A bit flags type, used for things such as status registers.
23840 @findex TYPE_CODE_FUNC
23841 @findex gdb.TYPE_CODE_FUNC
23842 @item gdb.TYPE_CODE_FUNC
23843 The type is a function.
23845 @findex TYPE_CODE_INT
23846 @findex gdb.TYPE_CODE_INT
23847 @item gdb.TYPE_CODE_INT
23848 The type is an integer type.
23850 @findex TYPE_CODE_FLT
23851 @findex gdb.TYPE_CODE_FLT
23852 @item gdb.TYPE_CODE_FLT
23853 A floating point type.
23855 @findex TYPE_CODE_VOID
23856 @findex gdb.TYPE_CODE_VOID
23857 @item gdb.TYPE_CODE_VOID
23858 The special type @code{void}.
23860 @findex TYPE_CODE_SET
23861 @findex gdb.TYPE_CODE_SET
23862 @item gdb.TYPE_CODE_SET
23865 @findex TYPE_CODE_RANGE
23866 @findex gdb.TYPE_CODE_RANGE
23867 @item gdb.TYPE_CODE_RANGE
23868 A range type, that is, an integer type with bounds.
23870 @findex TYPE_CODE_STRING
23871 @findex gdb.TYPE_CODE_STRING
23872 @item gdb.TYPE_CODE_STRING
23873 A string type. Note that this is only used for certain languages with
23874 language-defined string types; C strings are not represented this way.
23876 @findex TYPE_CODE_BITSTRING
23877 @findex gdb.TYPE_CODE_BITSTRING
23878 @item gdb.TYPE_CODE_BITSTRING
23879 A string of bits. It is deprecated.
23881 @findex TYPE_CODE_ERROR
23882 @findex gdb.TYPE_CODE_ERROR
23883 @item gdb.TYPE_CODE_ERROR
23884 An unknown or erroneous type.
23886 @findex TYPE_CODE_METHOD
23887 @findex gdb.TYPE_CODE_METHOD
23888 @item gdb.TYPE_CODE_METHOD
23889 A method type, as found in C@t{++} or Java.
23891 @findex TYPE_CODE_METHODPTR
23892 @findex gdb.TYPE_CODE_METHODPTR
23893 @item gdb.TYPE_CODE_METHODPTR
23894 A pointer-to-member-function.
23896 @findex TYPE_CODE_MEMBERPTR
23897 @findex gdb.TYPE_CODE_MEMBERPTR
23898 @item gdb.TYPE_CODE_MEMBERPTR
23899 A pointer-to-member.
23901 @findex TYPE_CODE_REF
23902 @findex gdb.TYPE_CODE_REF
23903 @item gdb.TYPE_CODE_REF
23906 @findex TYPE_CODE_CHAR
23907 @findex gdb.TYPE_CODE_CHAR
23908 @item gdb.TYPE_CODE_CHAR
23911 @findex TYPE_CODE_BOOL
23912 @findex gdb.TYPE_CODE_BOOL
23913 @item gdb.TYPE_CODE_BOOL
23916 @findex TYPE_CODE_COMPLEX
23917 @findex gdb.TYPE_CODE_COMPLEX
23918 @item gdb.TYPE_CODE_COMPLEX
23919 A complex float type.
23921 @findex TYPE_CODE_TYPEDEF
23922 @findex gdb.TYPE_CODE_TYPEDEF
23923 @item gdb.TYPE_CODE_TYPEDEF
23924 A typedef to some other type.
23926 @findex TYPE_CODE_NAMESPACE
23927 @findex gdb.TYPE_CODE_NAMESPACE
23928 @item gdb.TYPE_CODE_NAMESPACE
23929 A C@t{++} namespace.
23931 @findex TYPE_CODE_DECFLOAT
23932 @findex gdb.TYPE_CODE_DECFLOAT
23933 @item gdb.TYPE_CODE_DECFLOAT
23934 A decimal floating point type.
23936 @findex TYPE_CODE_INTERNAL_FUNCTION
23937 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23938 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23939 A function internal to @value{GDBN}. This is the type used to represent
23940 convenience functions.
23943 Further support for types is provided in the @code{gdb.types}
23944 Python module (@pxref{gdb.types}).
23946 @node Pretty Printing API
23947 @subsubsection Pretty Printing API
23949 An example output is provided (@pxref{Pretty Printing}).
23951 A pretty-printer is just an object that holds a value and implements a
23952 specific interface, defined here.
23954 @defun pretty_printer.children (self)
23955 @value{GDBN} will call this method on a pretty-printer to compute the
23956 children of the pretty-printer's value.
23958 This method must return an object conforming to the Python iterator
23959 protocol. Each item returned by the iterator must be a tuple holding
23960 two elements. The first element is the ``name'' of the child; the
23961 second element is the child's value. The value can be any Python
23962 object which is convertible to a @value{GDBN} value.
23964 This method is optional. If it does not exist, @value{GDBN} will act
23965 as though the value has no children.
23968 @defun pretty_printer.display_hint (self)
23969 The CLI may call this method and use its result to change the
23970 formatting of a value. The result will also be supplied to an MI
23971 consumer as a @samp{displayhint} attribute of the variable being
23974 This method is optional. If it does exist, this method must return a
23977 Some display hints are predefined by @value{GDBN}:
23981 Indicate that the object being printed is ``array-like''. The CLI
23982 uses this to respect parameters such as @code{set print elements} and
23983 @code{set print array}.
23986 Indicate that the object being printed is ``map-like'', and that the
23987 children of this value can be assumed to alternate between keys and
23991 Indicate that the object being printed is ``string-like''. If the
23992 printer's @code{to_string} method returns a Python string of some
23993 kind, then @value{GDBN} will call its internal language-specific
23994 string-printing function to format the string. For the CLI this means
23995 adding quotation marks, possibly escaping some characters, respecting
23996 @code{set print elements}, and the like.
24000 @defun pretty_printer.to_string (self)
24001 @value{GDBN} will call this method to display the string
24002 representation of the value passed to the object's constructor.
24004 When printing from the CLI, if the @code{to_string} method exists,
24005 then @value{GDBN} will prepend its result to the values returned by
24006 @code{children}. Exactly how this formatting is done is dependent on
24007 the display hint, and may change as more hints are added. Also,
24008 depending on the print settings (@pxref{Print Settings}), the CLI may
24009 print just the result of @code{to_string} in a stack trace, omitting
24010 the result of @code{children}.
24012 If this method returns a string, it is printed verbatim.
24014 Otherwise, if this method returns an instance of @code{gdb.Value},
24015 then @value{GDBN} prints this value. This may result in a call to
24016 another pretty-printer.
24018 If instead the method returns a Python value which is convertible to a
24019 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24020 the resulting value. Again, this may result in a call to another
24021 pretty-printer. Python scalars (integers, floats, and booleans) and
24022 strings are convertible to @code{gdb.Value}; other types are not.
24024 Finally, if this method returns @code{None} then no further operations
24025 are peformed in this method and nothing is printed.
24027 If the result is not one of these types, an exception is raised.
24030 @value{GDBN} provides a function which can be used to look up the
24031 default pretty-printer for a @code{gdb.Value}:
24033 @findex gdb.default_visualizer
24034 @defun gdb.default_visualizer (value)
24035 This function takes a @code{gdb.Value} object as an argument. If a
24036 pretty-printer for this value exists, then it is returned. If no such
24037 printer exists, then this returns @code{None}.
24040 @node Selecting Pretty-Printers
24041 @subsubsection Selecting Pretty-Printers
24043 The Python list @code{gdb.pretty_printers} contains an array of
24044 functions or callable objects that have been registered via addition
24045 as a pretty-printer. Printers in this list are called @code{global}
24046 printers, they're available when debugging all inferiors.
24047 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24048 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24051 Each function on these lists is passed a single @code{gdb.Value}
24052 argument and should return a pretty-printer object conforming to the
24053 interface definition above (@pxref{Pretty Printing API}). If a function
24054 cannot create a pretty-printer for the value, it should return
24057 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24058 @code{gdb.Objfile} in the current program space and iteratively calls
24059 each enabled lookup routine in the list for that @code{gdb.Objfile}
24060 until it receives a pretty-printer object.
24061 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24062 searches the pretty-printer list of the current program space,
24063 calling each enabled function until an object is returned.
24064 After these lists have been exhausted, it tries the global
24065 @code{gdb.pretty_printers} list, again calling each enabled function until an
24066 object is returned.
24068 The order in which the objfiles are searched is not specified. For a
24069 given list, functions are always invoked from the head of the list,
24070 and iterated over sequentially until the end of the list, or a printer
24071 object is returned.
24073 For various reasons a pretty-printer may not work.
24074 For example, the underlying data structure may have changed and
24075 the pretty-printer is out of date.
24077 The consequences of a broken pretty-printer are severe enough that
24078 @value{GDBN} provides support for enabling and disabling individual
24079 printers. For example, if @code{print frame-arguments} is on,
24080 a backtrace can become highly illegible if any argument is printed
24081 with a broken printer.
24083 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24084 attribute to the registered function or callable object. If this attribute
24085 is present and its value is @code{False}, the printer is disabled, otherwise
24086 the printer is enabled.
24088 @node Writing a Pretty-Printer
24089 @subsubsection Writing a Pretty-Printer
24090 @cindex writing a pretty-printer
24092 A pretty-printer consists of two parts: a lookup function to detect
24093 if the type is supported, and the printer itself.
24095 Here is an example showing how a @code{std::string} printer might be
24096 written. @xref{Pretty Printing API}, for details on the API this class
24100 class StdStringPrinter(object):
24101 "Print a std::string"
24103 def __init__(self, val):
24106 def to_string(self):
24107 return self.val['_M_dataplus']['_M_p']
24109 def display_hint(self):
24113 And here is an example showing how a lookup function for the printer
24114 example above might be written.
24117 def str_lookup_function(val):
24118 lookup_tag = val.type.tag
24119 if lookup_tag == None:
24121 regex = re.compile("^std::basic_string<char,.*>$")
24122 if regex.match(lookup_tag):
24123 return StdStringPrinter(val)
24127 The example lookup function extracts the value's type, and attempts to
24128 match it to a type that it can pretty-print. If it is a type the
24129 printer can pretty-print, it will return a printer object. If not, it
24130 returns @code{None}.
24132 We recommend that you put your core pretty-printers into a Python
24133 package. If your pretty-printers are for use with a library, we
24134 further recommend embedding a version number into the package name.
24135 This practice will enable @value{GDBN} to load multiple versions of
24136 your pretty-printers at the same time, because they will have
24139 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24140 can be evaluated multiple times without changing its meaning. An
24141 ideal auto-load file will consist solely of @code{import}s of your
24142 printer modules, followed by a call to a register pretty-printers with
24143 the current objfile.
24145 Taken as a whole, this approach will scale nicely to multiple
24146 inferiors, each potentially using a different library version.
24147 Embedding a version number in the Python package name will ensure that
24148 @value{GDBN} is able to load both sets of printers simultaneously.
24149 Then, because the search for pretty-printers is done by objfile, and
24150 because your auto-loaded code took care to register your library's
24151 printers with a specific objfile, @value{GDBN} will find the correct
24152 printers for the specific version of the library used by each
24155 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24156 this code might appear in @code{gdb.libstdcxx.v6}:
24159 def register_printers(objfile):
24160 objfile.pretty_printers.append(str_lookup_function)
24164 And then the corresponding contents of the auto-load file would be:
24167 import gdb.libstdcxx.v6
24168 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24171 The previous example illustrates a basic pretty-printer.
24172 There are a few things that can be improved on.
24173 The printer doesn't have a name, making it hard to identify in a
24174 list of installed printers. The lookup function has a name, but
24175 lookup functions can have arbitrary, even identical, names.
24177 Second, the printer only handles one type, whereas a library typically has
24178 several types. One could install a lookup function for each desired type
24179 in the library, but one could also have a single lookup function recognize
24180 several types. The latter is the conventional way this is handled.
24181 If a pretty-printer can handle multiple data types, then its
24182 @dfn{subprinters} are the printers for the individual data types.
24184 The @code{gdb.printing} module provides a formal way of solving these
24185 problems (@pxref{gdb.printing}).
24186 Here is another example that handles multiple types.
24188 These are the types we are going to pretty-print:
24191 struct foo @{ int a, b; @};
24192 struct bar @{ struct foo x, y; @};
24195 Here are the printers:
24199 """Print a foo object."""
24201 def __init__(self, val):
24204 def to_string(self):
24205 return ("a=<" + str(self.val["a"]) +
24206 "> b=<" + str(self.val["b"]) + ">")
24209 """Print a bar object."""
24211 def __init__(self, val):
24214 def to_string(self):
24215 return ("x=<" + str(self.val["x"]) +
24216 "> y=<" + str(self.val["y"]) + ">")
24219 This example doesn't need a lookup function, that is handled by the
24220 @code{gdb.printing} module. Instead a function is provided to build up
24221 the object that handles the lookup.
24224 import gdb.printing
24226 def build_pretty_printer():
24227 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24229 pp.add_printer('foo', '^foo$', fooPrinter)
24230 pp.add_printer('bar', '^bar$', barPrinter)
24234 And here is the autoload support:
24237 import gdb.printing
24239 gdb.printing.register_pretty_printer(
24240 gdb.current_objfile(),
24241 my_library.build_pretty_printer())
24244 Finally, when this printer is loaded into @value{GDBN}, here is the
24245 corresponding output of @samp{info pretty-printer}:
24248 (gdb) info pretty-printer
24255 @node Type Printing API
24256 @subsubsection Type Printing API
24257 @cindex type printing API for Python
24259 @value{GDBN} provides a way for Python code to customize type display.
24260 This is mainly useful for substituting canonical typedef names for
24263 @cindex type printer
24264 A @dfn{type printer} is just a Python object conforming to a certain
24265 protocol. A simple base class implementing the protocol is provided;
24266 see @ref{gdb.types}. A type printer must supply at least:
24268 @defivar type_printer enabled
24269 A boolean which is True if the printer is enabled, and False
24270 otherwise. This is manipulated by the @code{enable type-printer}
24271 and @code{disable type-printer} commands.
24274 @defivar type_printer name
24275 The name of the type printer. This must be a string. This is used by
24276 the @code{enable type-printer} and @code{disable type-printer}
24280 @defmethod type_printer instantiate (self)
24281 This is called by @value{GDBN} at the start of type-printing. It is
24282 only called if the type printer is enabled. This method must return a
24283 new object that supplies a @code{recognize} method, as described below.
24287 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24288 will compute a list of type recognizers. This is done by iterating
24289 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24290 followed by the per-progspace type printers (@pxref{Progspaces In
24291 Python}), and finally the global type printers.
24293 @value{GDBN} will call the @code{instantiate} method of each enabled
24294 type printer. If this method returns @code{None}, then the result is
24295 ignored; otherwise, it is appended to the list of recognizers.
24297 Then, when @value{GDBN} is going to display a type name, it iterates
24298 over the list of recognizers. For each one, it calls the recognition
24299 function, stopping if the function returns a non-@code{None} value.
24300 The recognition function is defined as:
24302 @defmethod type_recognizer recognize (self, type)
24303 If @var{type} is not recognized, return @code{None}. Otherwise,
24304 return a string which is to be printed as the name of @var{type}.
24305 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24309 @value{GDBN} uses this two-pass approach so that type printers can
24310 efficiently cache information without holding on to it too long. For
24311 example, it can be convenient to look up type information in a type
24312 printer and hold it for a recognizer's lifetime; if a single pass were
24313 done then type printers would have to make use of the event system in
24314 order to avoid holding information that could become stale as the
24317 @node Inferiors In Python
24318 @subsubsection Inferiors In Python
24319 @cindex inferiors in Python
24321 @findex gdb.Inferior
24322 Programs which are being run under @value{GDBN} are called inferiors
24323 (@pxref{Inferiors and Programs}). Python scripts can access
24324 information about and manipulate inferiors controlled by @value{GDBN}
24325 via objects of the @code{gdb.Inferior} class.
24327 The following inferior-related functions are available in the @code{gdb}
24330 @defun gdb.inferiors ()
24331 Return a tuple containing all inferior objects.
24334 @defun gdb.selected_inferior ()
24335 Return an object representing the current inferior.
24338 A @code{gdb.Inferior} object has the following attributes:
24340 @defvar Inferior.num
24341 ID of inferior, as assigned by GDB.
24344 @defvar Inferior.pid
24345 Process ID of the inferior, as assigned by the underlying operating
24349 @defvar Inferior.was_attached
24350 Boolean signaling whether the inferior was created using `attach', or
24351 started by @value{GDBN} itself.
24354 A @code{gdb.Inferior} object has the following methods:
24356 @defun Inferior.is_valid ()
24357 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24358 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24359 if the inferior no longer exists within @value{GDBN}. All other
24360 @code{gdb.Inferior} methods will throw an exception if it is invalid
24361 at the time the method is called.
24364 @defun Inferior.threads ()
24365 This method returns a tuple holding all the threads which are valid
24366 when it is called. If there are no valid threads, the method will
24367 return an empty tuple.
24370 @findex Inferior.read_memory
24371 @defun Inferior.read_memory (address, length)
24372 Read @var{length} bytes of memory from the inferior, starting at
24373 @var{address}. Returns a buffer object, which behaves much like an array
24374 or a string. It can be modified and given to the
24375 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24376 value is a @code{memoryview} object.
24379 @findex Inferior.write_memory
24380 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24381 Write the contents of @var{buffer} to the inferior, starting at
24382 @var{address}. The @var{buffer} parameter must be a Python object
24383 which supports the buffer protocol, i.e., a string, an array or the
24384 object returned from @code{Inferior.read_memory}. If given, @var{length}
24385 determines the number of bytes from @var{buffer} to be written.
24388 @findex gdb.search_memory
24389 @defun Inferior.search_memory (address, length, pattern)
24390 Search a region of the inferior memory starting at @var{address} with
24391 the given @var{length} using the search pattern supplied in
24392 @var{pattern}. The @var{pattern} parameter must be a Python object
24393 which supports the buffer protocol, i.e., a string, an array or the
24394 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24395 containing the address where the pattern was found, or @code{None} if
24396 the pattern could not be found.
24399 @node Events In Python
24400 @subsubsection Events In Python
24401 @cindex inferior events in Python
24403 @value{GDBN} provides a general event facility so that Python code can be
24404 notified of various state changes, particularly changes that occur in
24407 An @dfn{event} is just an object that describes some state change. The
24408 type of the object and its attributes will vary depending on the details
24409 of the change. All the existing events are described below.
24411 In order to be notified of an event, you must register an event handler
24412 with an @dfn{event registry}. An event registry is an object in the
24413 @code{gdb.events} module which dispatches particular events. A registry
24414 provides methods to register and unregister event handlers:
24416 @defun EventRegistry.connect (object)
24417 Add the given callable @var{object} to the registry. This object will be
24418 called when an event corresponding to this registry occurs.
24421 @defun EventRegistry.disconnect (object)
24422 Remove the given @var{object} from the registry. Once removed, the object
24423 will no longer receive notifications of events.
24426 Here is an example:
24429 def exit_handler (event):
24430 print "event type: exit"
24431 print "exit code: %d" % (event.exit_code)
24433 gdb.events.exited.connect (exit_handler)
24436 In the above example we connect our handler @code{exit_handler} to the
24437 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24438 called when the inferior exits. The argument @dfn{event} in this example is
24439 of type @code{gdb.ExitedEvent}. As you can see in the example the
24440 @code{ExitedEvent} object has an attribute which indicates the exit code of
24443 The following is a listing of the event registries that are available and
24444 details of the events they emit:
24449 Emits @code{gdb.ThreadEvent}.
24451 Some events can be thread specific when @value{GDBN} is running in non-stop
24452 mode. When represented in Python, these events all extend
24453 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24454 events which are emitted by this or other modules might extend this event.
24455 Examples of these events are @code{gdb.BreakpointEvent} and
24456 @code{gdb.ContinueEvent}.
24458 @defvar ThreadEvent.inferior_thread
24459 In non-stop mode this attribute will be set to the specific thread which was
24460 involved in the emitted event. Otherwise, it will be set to @code{None}.
24463 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24465 This event indicates that the inferior has been continued after a stop. For
24466 inherited attribute refer to @code{gdb.ThreadEvent} above.
24468 @item events.exited
24469 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24470 @code{events.ExitedEvent} has two attributes:
24471 @defvar ExitedEvent.exit_code
24472 An integer representing the exit code, if available, which the inferior
24473 has returned. (The exit code could be unavailable if, for example,
24474 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24475 the attribute does not exist.
24477 @defvar ExitedEvent inferior
24478 A reference to the inferior which triggered the @code{exited} event.
24482 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24484 Indicates that the inferior has stopped. All events emitted by this registry
24485 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24486 will indicate the stopped thread when @value{GDBN} is running in non-stop
24487 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24489 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24491 This event indicates that the inferior or one of its threads has received as
24492 signal. @code{gdb.SignalEvent} has the following attributes:
24494 @defvar SignalEvent.stop_signal
24495 A string representing the signal received by the inferior. A list of possible
24496 signal values can be obtained by running the command @code{info signals} in
24497 the @value{GDBN} command prompt.
24500 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24502 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24503 been hit, and has the following attributes:
24505 @defvar BreakpointEvent.breakpoints
24506 A sequence containing references to all the breakpoints (type
24507 @code{gdb.Breakpoint}) that were hit.
24508 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24510 @defvar BreakpointEvent.breakpoint
24511 A reference to the first breakpoint that was hit.
24512 This function is maintained for backward compatibility and is now deprecated
24513 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24516 @item events.new_objfile
24517 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24518 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24520 @defvar NewObjFileEvent.new_objfile
24521 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24522 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24527 @node Threads In Python
24528 @subsubsection Threads In Python
24529 @cindex threads in python
24531 @findex gdb.InferiorThread
24532 Python scripts can access information about, and manipulate inferior threads
24533 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24535 The following thread-related functions are available in the @code{gdb}
24538 @findex gdb.selected_thread
24539 @defun gdb.selected_thread ()
24540 This function returns the thread object for the selected thread. If there
24541 is no selected thread, this will return @code{None}.
24544 A @code{gdb.InferiorThread} object has the following attributes:
24546 @defvar InferiorThread.name
24547 The name of the thread. If the user specified a name using
24548 @code{thread name}, then this returns that name. Otherwise, if an
24549 OS-supplied name is available, then it is returned. Otherwise, this
24550 returns @code{None}.
24552 This attribute can be assigned to. The new value must be a string
24553 object, which sets the new name, or @code{None}, which removes any
24554 user-specified thread name.
24557 @defvar InferiorThread.num
24558 ID of the thread, as assigned by GDB.
24561 @defvar InferiorThread.ptid
24562 ID of the thread, as assigned by the operating system. This attribute is a
24563 tuple containing three integers. The first is the Process ID (PID); the second
24564 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24565 Either the LWPID or TID may be 0, which indicates that the operating system
24566 does not use that identifier.
24569 A @code{gdb.InferiorThread} object has the following methods:
24571 @defun InferiorThread.is_valid ()
24572 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24573 @code{False} if not. A @code{gdb.InferiorThread} object will become
24574 invalid if the thread exits, or the inferior that the thread belongs
24575 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24576 exception if it is invalid at the time the method is called.
24579 @defun InferiorThread.switch ()
24580 This changes @value{GDBN}'s currently selected thread to the one represented
24584 @defun InferiorThread.is_stopped ()
24585 Return a Boolean indicating whether the thread is stopped.
24588 @defun InferiorThread.is_running ()
24589 Return a Boolean indicating whether the thread is running.
24592 @defun InferiorThread.is_exited ()
24593 Return a Boolean indicating whether the thread is exited.
24596 @node Commands In Python
24597 @subsubsection Commands In Python
24599 @cindex commands in python
24600 @cindex python commands
24601 You can implement new @value{GDBN} CLI commands in Python. A CLI
24602 command is implemented using an instance of the @code{gdb.Command}
24603 class, most commonly using a subclass.
24605 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24606 The object initializer for @code{Command} registers the new command
24607 with @value{GDBN}. This initializer is normally invoked from the
24608 subclass' own @code{__init__} method.
24610 @var{name} is the name of the command. If @var{name} consists of
24611 multiple words, then the initial words are looked for as prefix
24612 commands. In this case, if one of the prefix commands does not exist,
24613 an exception is raised.
24615 There is no support for multi-line commands.
24617 @var{command_class} should be one of the @samp{COMMAND_} constants
24618 defined below. This argument tells @value{GDBN} how to categorize the
24619 new command in the help system.
24621 @var{completer_class} is an optional argument. If given, it should be
24622 one of the @samp{COMPLETE_} constants defined below. This argument
24623 tells @value{GDBN} how to perform completion for this command. If not
24624 given, @value{GDBN} will attempt to complete using the object's
24625 @code{complete} method (see below); if no such method is found, an
24626 error will occur when completion is attempted.
24628 @var{prefix} is an optional argument. If @code{True}, then the new
24629 command is a prefix command; sub-commands of this command may be
24632 The help text for the new command is taken from the Python
24633 documentation string for the command's class, if there is one. If no
24634 documentation string is provided, the default value ``This command is
24635 not documented.'' is used.
24638 @cindex don't repeat Python command
24639 @defun Command.dont_repeat ()
24640 By default, a @value{GDBN} command is repeated when the user enters a
24641 blank line at the command prompt. A command can suppress this
24642 behavior by invoking the @code{dont_repeat} method. This is similar
24643 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24646 @defun Command.invoke (argument, from_tty)
24647 This method is called by @value{GDBN} when this command is invoked.
24649 @var{argument} is a string. It is the argument to the command, after
24650 leading and trailing whitespace has been stripped.
24652 @var{from_tty} is a boolean argument. When true, this means that the
24653 command was entered by the user at the terminal; when false it means
24654 that the command came from elsewhere.
24656 If this method throws an exception, it is turned into a @value{GDBN}
24657 @code{error} call. Otherwise, the return value is ignored.
24659 @findex gdb.string_to_argv
24660 To break @var{argument} up into an argv-like string use
24661 @code{gdb.string_to_argv}. This function behaves identically to
24662 @value{GDBN}'s internal argument lexer @code{buildargv}.
24663 It is recommended to use this for consistency.
24664 Arguments are separated by spaces and may be quoted.
24668 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24669 ['1', '2 "3', '4 "5', "6 '7"]
24674 @cindex completion of Python commands
24675 @defun Command.complete (text, word)
24676 This method is called by @value{GDBN} when the user attempts
24677 completion on this command. All forms of completion are handled by
24678 this method, that is, the @key{TAB} and @key{M-?} key bindings
24679 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24682 The arguments @var{text} and @var{word} are both strings. @var{text}
24683 holds the complete command line up to the cursor's location.
24684 @var{word} holds the last word of the command line; this is computed
24685 using a word-breaking heuristic.
24687 The @code{complete} method can return several values:
24690 If the return value is a sequence, the contents of the sequence are
24691 used as the completions. It is up to @code{complete} to ensure that the
24692 contents actually do complete the word. A zero-length sequence is
24693 allowed, it means that there were no completions available. Only
24694 string elements of the sequence are used; other elements in the
24695 sequence are ignored.
24698 If the return value is one of the @samp{COMPLETE_} constants defined
24699 below, then the corresponding @value{GDBN}-internal completion
24700 function is invoked, and its result is used.
24703 All other results are treated as though there were no available
24708 When a new command is registered, it must be declared as a member of
24709 some general class of commands. This is used to classify top-level
24710 commands in the on-line help system; note that prefix commands are not
24711 listed under their own category but rather that of their top-level
24712 command. The available classifications are represented by constants
24713 defined in the @code{gdb} module:
24716 @findex COMMAND_NONE
24717 @findex gdb.COMMAND_NONE
24718 @item gdb.COMMAND_NONE
24719 The command does not belong to any particular class. A command in
24720 this category will not be displayed in any of the help categories.
24722 @findex COMMAND_RUNNING
24723 @findex gdb.COMMAND_RUNNING
24724 @item gdb.COMMAND_RUNNING
24725 The command is related to running the inferior. For example,
24726 @code{start}, @code{step}, and @code{continue} are in this category.
24727 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24728 commands in this category.
24730 @findex COMMAND_DATA
24731 @findex gdb.COMMAND_DATA
24732 @item gdb.COMMAND_DATA
24733 The command is related to data or variables. For example,
24734 @code{call}, @code{find}, and @code{print} are in this category. Type
24735 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24738 @findex COMMAND_STACK
24739 @findex gdb.COMMAND_STACK
24740 @item gdb.COMMAND_STACK
24741 The command has to do with manipulation of the stack. For example,
24742 @code{backtrace}, @code{frame}, and @code{return} are in this
24743 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24744 list of commands in this category.
24746 @findex COMMAND_FILES
24747 @findex gdb.COMMAND_FILES
24748 @item gdb.COMMAND_FILES
24749 This class is used for file-related commands. For example,
24750 @code{file}, @code{list} and @code{section} are in this category.
24751 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24752 commands in this category.
24754 @findex COMMAND_SUPPORT
24755 @findex gdb.COMMAND_SUPPORT
24756 @item gdb.COMMAND_SUPPORT
24757 This should be used for ``support facilities'', generally meaning
24758 things that are useful to the user when interacting with @value{GDBN},
24759 but not related to the state of the inferior. For example,
24760 @code{help}, @code{make}, and @code{shell} are in this category. Type
24761 @kbd{help support} at the @value{GDBN} prompt to see a list of
24762 commands in this category.
24764 @findex COMMAND_STATUS
24765 @findex gdb.COMMAND_STATUS
24766 @item gdb.COMMAND_STATUS
24767 The command is an @samp{info}-related command, that is, related to the
24768 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24769 and @code{show} are in this category. Type @kbd{help status} at the
24770 @value{GDBN} prompt to see a list of commands in this category.
24772 @findex COMMAND_BREAKPOINTS
24773 @findex gdb.COMMAND_BREAKPOINTS
24774 @item gdb.COMMAND_BREAKPOINTS
24775 The command has to do with breakpoints. For example, @code{break},
24776 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24777 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24780 @findex COMMAND_TRACEPOINTS
24781 @findex gdb.COMMAND_TRACEPOINTS
24782 @item gdb.COMMAND_TRACEPOINTS
24783 The command has to do with tracepoints. For example, @code{trace},
24784 @code{actions}, and @code{tfind} are in this category. Type
24785 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24786 commands in this category.
24788 @findex COMMAND_USER
24789 @findex gdb.COMMAND_USER
24790 @item gdb.COMMAND_USER
24791 The command is a general purpose command for the user, and typically
24792 does not fit in one of the other categories.
24793 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24794 a list of commands in this category, as well as the list of gdb macros
24795 (@pxref{Sequences}).
24797 @findex COMMAND_OBSCURE
24798 @findex gdb.COMMAND_OBSCURE
24799 @item gdb.COMMAND_OBSCURE
24800 The command is only used in unusual circumstances, or is not of
24801 general interest to users. For example, @code{checkpoint},
24802 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24803 obscure} at the @value{GDBN} prompt to see a list of commands in this
24806 @findex COMMAND_MAINTENANCE
24807 @findex gdb.COMMAND_MAINTENANCE
24808 @item gdb.COMMAND_MAINTENANCE
24809 The command is only useful to @value{GDBN} maintainers. The
24810 @code{maintenance} and @code{flushregs} commands are in this category.
24811 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24812 commands in this category.
24815 A new command can use a predefined completion function, either by
24816 specifying it via an argument at initialization, or by returning it
24817 from the @code{complete} method. These predefined completion
24818 constants are all defined in the @code{gdb} module:
24821 @findex COMPLETE_NONE
24822 @findex gdb.COMPLETE_NONE
24823 @item gdb.COMPLETE_NONE
24824 This constant means that no completion should be done.
24826 @findex COMPLETE_FILENAME
24827 @findex gdb.COMPLETE_FILENAME
24828 @item gdb.COMPLETE_FILENAME
24829 This constant means that filename completion should be performed.
24831 @findex COMPLETE_LOCATION
24832 @findex gdb.COMPLETE_LOCATION
24833 @item gdb.COMPLETE_LOCATION
24834 This constant means that location completion should be done.
24835 @xref{Specify Location}.
24837 @findex COMPLETE_COMMAND
24838 @findex gdb.COMPLETE_COMMAND
24839 @item gdb.COMPLETE_COMMAND
24840 This constant means that completion should examine @value{GDBN}
24843 @findex COMPLETE_SYMBOL
24844 @findex gdb.COMPLETE_SYMBOL
24845 @item gdb.COMPLETE_SYMBOL
24846 This constant means that completion should be done using symbol names
24850 The following code snippet shows how a trivial CLI command can be
24851 implemented in Python:
24854 class HelloWorld (gdb.Command):
24855 """Greet the whole world."""
24857 def __init__ (self):
24858 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24860 def invoke (self, arg, from_tty):
24861 print "Hello, World!"
24866 The last line instantiates the class, and is necessary to trigger the
24867 registration of the command with @value{GDBN}. Depending on how the
24868 Python code is read into @value{GDBN}, you may need to import the
24869 @code{gdb} module explicitly.
24871 @node Parameters In Python
24872 @subsubsection Parameters In Python
24874 @cindex parameters in python
24875 @cindex python parameters
24876 @tindex gdb.Parameter
24878 You can implement new @value{GDBN} parameters using Python. A new
24879 parameter is implemented as an instance of the @code{gdb.Parameter}
24882 Parameters are exposed to the user via the @code{set} and
24883 @code{show} commands. @xref{Help}.
24885 There are many parameters that already exist and can be set in
24886 @value{GDBN}. Two examples are: @code{set follow fork} and
24887 @code{set charset}. Setting these parameters influences certain
24888 behavior in @value{GDBN}. Similarly, you can define parameters that
24889 can be used to influence behavior in custom Python scripts and commands.
24891 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24892 The object initializer for @code{Parameter} registers the new
24893 parameter with @value{GDBN}. This initializer is normally invoked
24894 from the subclass' own @code{__init__} method.
24896 @var{name} is the name of the new parameter. If @var{name} consists
24897 of multiple words, then the initial words are looked for as prefix
24898 parameters. An example of this can be illustrated with the
24899 @code{set print} set of parameters. If @var{name} is
24900 @code{print foo}, then @code{print} will be searched as the prefix
24901 parameter. In this case the parameter can subsequently be accessed in
24902 @value{GDBN} as @code{set print foo}.
24904 If @var{name} consists of multiple words, and no prefix parameter group
24905 can be found, an exception is raised.
24907 @var{command-class} should be one of the @samp{COMMAND_} constants
24908 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24909 categorize the new parameter in the help system.
24911 @var{parameter-class} should be one of the @samp{PARAM_} constants
24912 defined below. This argument tells @value{GDBN} the type of the new
24913 parameter; this information is used for input validation and
24916 If @var{parameter-class} is @code{PARAM_ENUM}, then
24917 @var{enum-sequence} must be a sequence of strings. These strings
24918 represent the possible values for the parameter.
24920 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24921 of a fourth argument will cause an exception to be thrown.
24923 The help text for the new parameter is taken from the Python
24924 documentation string for the parameter's class, if there is one. If
24925 there is no documentation string, a default value is used.
24928 @defvar Parameter.set_doc
24929 If this attribute exists, and is a string, then its value is used as
24930 the help text for this parameter's @code{set} command. The value is
24931 examined when @code{Parameter.__init__} is invoked; subsequent changes
24935 @defvar Parameter.show_doc
24936 If this attribute exists, and is a string, then its value is used as
24937 the help text for this parameter's @code{show} command. The value is
24938 examined when @code{Parameter.__init__} is invoked; subsequent changes
24942 @defvar Parameter.value
24943 The @code{value} attribute holds the underlying value of the
24944 parameter. It can be read and assigned to just as any other
24945 attribute. @value{GDBN} does validation when assignments are made.
24948 There are two methods that should be implemented in any
24949 @code{Parameter} class. These are:
24951 @defun Parameter.get_set_string (self)
24952 @value{GDBN} will call this method when a @var{parameter}'s value has
24953 been changed via the @code{set} API (for example, @kbd{set foo off}).
24954 The @code{value} attribute has already been populated with the new
24955 value and may be used in output. This method must return a string.
24958 @defun Parameter.get_show_string (self, svalue)
24959 @value{GDBN} will call this method when a @var{parameter}'s
24960 @code{show} API has been invoked (for example, @kbd{show foo}). The
24961 argument @code{svalue} receives the string representation of the
24962 current value. This method must return a string.
24965 When a new parameter is defined, its type must be specified. The
24966 available types are represented by constants defined in the @code{gdb}
24970 @findex PARAM_BOOLEAN
24971 @findex gdb.PARAM_BOOLEAN
24972 @item gdb.PARAM_BOOLEAN
24973 The value is a plain boolean. The Python boolean values, @code{True}
24974 and @code{False} are the only valid values.
24976 @findex PARAM_AUTO_BOOLEAN
24977 @findex gdb.PARAM_AUTO_BOOLEAN
24978 @item gdb.PARAM_AUTO_BOOLEAN
24979 The value has three possible states: true, false, and @samp{auto}. In
24980 Python, true and false are represented using boolean constants, and
24981 @samp{auto} is represented using @code{None}.
24983 @findex PARAM_UINTEGER
24984 @findex gdb.PARAM_UINTEGER
24985 @item gdb.PARAM_UINTEGER
24986 The value is an unsigned integer. The value of 0 should be
24987 interpreted to mean ``unlimited''.
24989 @findex PARAM_INTEGER
24990 @findex gdb.PARAM_INTEGER
24991 @item gdb.PARAM_INTEGER
24992 The value is a signed integer. The value of 0 should be interpreted
24993 to mean ``unlimited''.
24995 @findex PARAM_STRING
24996 @findex gdb.PARAM_STRING
24997 @item gdb.PARAM_STRING
24998 The value is a string. When the user modifies the string, any escape
24999 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
25000 translated into corresponding characters and encoded into the current
25003 @findex PARAM_STRING_NOESCAPE
25004 @findex gdb.PARAM_STRING_NOESCAPE
25005 @item gdb.PARAM_STRING_NOESCAPE
25006 The value is a string. When the user modifies the string, escapes are
25007 passed through untranslated.
25009 @findex PARAM_OPTIONAL_FILENAME
25010 @findex gdb.PARAM_OPTIONAL_FILENAME
25011 @item gdb.PARAM_OPTIONAL_FILENAME
25012 The value is a either a filename (a string), or @code{None}.
25014 @findex PARAM_FILENAME
25015 @findex gdb.PARAM_FILENAME
25016 @item gdb.PARAM_FILENAME
25017 The value is a filename. This is just like
25018 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
25020 @findex PARAM_ZINTEGER
25021 @findex gdb.PARAM_ZINTEGER
25022 @item gdb.PARAM_ZINTEGER
25023 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
25024 is interpreted as itself.
25027 @findex gdb.PARAM_ENUM
25028 @item gdb.PARAM_ENUM
25029 The value is a string, which must be one of a collection string
25030 constants provided when the parameter is created.
25033 @node Functions In Python
25034 @subsubsection Writing new convenience functions
25036 @cindex writing convenience functions
25037 @cindex convenience functions in python
25038 @cindex python convenience functions
25039 @tindex gdb.Function
25041 You can implement new convenience functions (@pxref{Convenience Vars})
25042 in Python. A convenience function is an instance of a subclass of the
25043 class @code{gdb.Function}.
25045 @defun Function.__init__ (name)
25046 The initializer for @code{Function} registers the new function with
25047 @value{GDBN}. The argument @var{name} is the name of the function,
25048 a string. The function will be visible to the user as a convenience
25049 variable of type @code{internal function}, whose name is the same as
25050 the given @var{name}.
25052 The documentation for the new function is taken from the documentation
25053 string for the new class.
25056 @defun Function.invoke (@var{*args})
25057 When a convenience function is evaluated, its arguments are converted
25058 to instances of @code{gdb.Value}, and then the function's
25059 @code{invoke} method is called. Note that @value{GDBN} does not
25060 predetermine the arity of convenience functions. Instead, all
25061 available arguments are passed to @code{invoke}, following the
25062 standard Python calling convention. In particular, a convenience
25063 function can have default values for parameters without ill effect.
25065 The return value of this method is used as its value in the enclosing
25066 expression. If an ordinary Python value is returned, it is converted
25067 to a @code{gdb.Value} following the usual rules.
25070 The following code snippet shows how a trivial convenience function can
25071 be implemented in Python:
25074 class Greet (gdb.Function):
25075 """Return string to greet someone.
25076 Takes a name as argument."""
25078 def __init__ (self):
25079 super (Greet, self).__init__ ("greet")
25081 def invoke (self, name):
25082 return "Hello, %s!" % name.string ()
25087 The last line instantiates the class, and is necessary to trigger the
25088 registration of the function with @value{GDBN}. Depending on how the
25089 Python code is read into @value{GDBN}, you may need to import the
25090 @code{gdb} module explicitly.
25092 Now you can use the function in an expression:
25095 (gdb) print $greet("Bob")
25099 @node Progspaces In Python
25100 @subsubsection Program Spaces In Python
25102 @cindex progspaces in python
25103 @tindex gdb.Progspace
25105 A program space, or @dfn{progspace}, represents a symbolic view
25106 of an address space.
25107 It consists of all of the objfiles of the program.
25108 @xref{Objfiles In Python}.
25109 @xref{Inferiors and Programs, program spaces}, for more details
25110 about program spaces.
25112 The following progspace-related functions are available in the
25115 @findex gdb.current_progspace
25116 @defun gdb.current_progspace ()
25117 This function returns the program space of the currently selected inferior.
25118 @xref{Inferiors and Programs}.
25121 @findex gdb.progspaces
25122 @defun gdb.progspaces ()
25123 Return a sequence of all the progspaces currently known to @value{GDBN}.
25126 Each progspace is represented by an instance of the @code{gdb.Progspace}
25129 @defvar Progspace.filename
25130 The file name of the progspace as a string.
25133 @defvar Progspace.pretty_printers
25134 The @code{pretty_printers} attribute is a list of functions. It is
25135 used to look up pretty-printers. A @code{Value} is passed to each
25136 function in order; if the function returns @code{None}, then the
25137 search continues. Otherwise, the return value should be an object
25138 which is used to format the value. @xref{Pretty Printing API}, for more
25142 @defvar Progspace.type_printers
25143 The @code{type_printers} attribute is a list of type printer objects.
25144 @xref{Type Printing API}, for more information.
25147 @node Objfiles In Python
25148 @subsubsection Objfiles In Python
25150 @cindex objfiles in python
25151 @tindex gdb.Objfile
25153 @value{GDBN} loads symbols for an inferior from various
25154 symbol-containing files (@pxref{Files}). These include the primary
25155 executable file, any shared libraries used by the inferior, and any
25156 separate debug info files (@pxref{Separate Debug Files}).
25157 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
25159 The following objfile-related functions are available in the
25162 @findex gdb.current_objfile
25163 @defun gdb.current_objfile ()
25164 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
25165 sets the ``current objfile'' to the corresponding objfile. This
25166 function returns the current objfile. If there is no current objfile,
25167 this function returns @code{None}.
25170 @findex gdb.objfiles
25171 @defun gdb.objfiles ()
25172 Return a sequence of all the objfiles current known to @value{GDBN}.
25173 @xref{Objfiles In Python}.
25176 Each objfile is represented by an instance of the @code{gdb.Objfile}
25179 @defvar Objfile.filename
25180 The file name of the objfile as a string.
25183 @defvar Objfile.pretty_printers
25184 The @code{pretty_printers} attribute is a list of functions. It is
25185 used to look up pretty-printers. A @code{Value} is passed to each
25186 function in order; if the function returns @code{None}, then the
25187 search continues. Otherwise, the return value should be an object
25188 which is used to format the value. @xref{Pretty Printing API}, for more
25192 @defvar Objfile.type_printers
25193 The @code{type_printers} attribute is a list of type printer objects.
25194 @xref{Type Printing API}, for more information.
25197 A @code{gdb.Objfile} object has the following methods:
25199 @defun Objfile.is_valid ()
25200 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25201 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25202 if the object file it refers to is not loaded in @value{GDBN} any
25203 longer. All other @code{gdb.Objfile} methods will throw an exception
25204 if it is invalid at the time the method is called.
25207 @node Frames In Python
25208 @subsubsection Accessing inferior stack frames from Python.
25210 @cindex frames in python
25211 When the debugged program stops, @value{GDBN} is able to analyze its call
25212 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25213 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25214 while its corresponding frame exists in the inferior's stack. If you try
25215 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25216 exception (@pxref{Exception Handling}).
25218 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25222 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25226 The following frame-related functions are available in the @code{gdb} module:
25228 @findex gdb.selected_frame
25229 @defun gdb.selected_frame ()
25230 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25233 @findex gdb.newest_frame
25234 @defun gdb.newest_frame ()
25235 Return the newest frame object for the selected thread.
25238 @defun gdb.frame_stop_reason_string (reason)
25239 Return a string explaining the reason why @value{GDBN} stopped unwinding
25240 frames, as expressed by the given @var{reason} code (an integer, see the
25241 @code{unwind_stop_reason} method further down in this section).
25244 A @code{gdb.Frame} object has the following methods:
25246 @defun Frame.is_valid ()
25247 Returns true if the @code{gdb.Frame} object is valid, false if not.
25248 A frame object can become invalid if the frame it refers to doesn't
25249 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25250 an exception if it is invalid at the time the method is called.
25253 @defun Frame.name ()
25254 Returns the function name of the frame, or @code{None} if it can't be
25258 @defun Frame.architecture ()
25259 Returns the @code{gdb.Architecture} object corresponding to the frame's
25260 architecture. @xref{Architectures In Python}.
25263 @defun Frame.type ()
25264 Returns the type of the frame. The value can be one of:
25266 @item gdb.NORMAL_FRAME
25267 An ordinary stack frame.
25269 @item gdb.DUMMY_FRAME
25270 A fake stack frame that was created by @value{GDBN} when performing an
25271 inferior function call.
25273 @item gdb.INLINE_FRAME
25274 A frame representing an inlined function. The function was inlined
25275 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25277 @item gdb.TAILCALL_FRAME
25278 A frame representing a tail call. @xref{Tail Call Frames}.
25280 @item gdb.SIGTRAMP_FRAME
25281 A signal trampoline frame. This is the frame created by the OS when
25282 it calls into a signal handler.
25284 @item gdb.ARCH_FRAME
25285 A fake stack frame representing a cross-architecture call.
25287 @item gdb.SENTINEL_FRAME
25288 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25293 @defun Frame.unwind_stop_reason ()
25294 Return an integer representing the reason why it's not possible to find
25295 more frames toward the outermost frame. Use
25296 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25297 function to a string. The value can be one of:
25300 @item gdb.FRAME_UNWIND_NO_REASON
25301 No particular reason (older frames should be available).
25303 @item gdb.FRAME_UNWIND_NULL_ID
25304 The previous frame's analyzer returns an invalid result.
25306 @item gdb.FRAME_UNWIND_OUTERMOST
25307 This frame is the outermost.
25309 @item gdb.FRAME_UNWIND_UNAVAILABLE
25310 Cannot unwind further, because that would require knowing the
25311 values of registers or memory that have not been collected.
25313 @item gdb.FRAME_UNWIND_INNER_ID
25314 This frame ID looks like it ought to belong to a NEXT frame,
25315 but we got it for a PREV frame. Normally, this is a sign of
25316 unwinder failure. It could also indicate stack corruption.
25318 @item gdb.FRAME_UNWIND_SAME_ID
25319 This frame has the same ID as the previous one. That means
25320 that unwinding further would almost certainly give us another
25321 frame with exactly the same ID, so break the chain. Normally,
25322 this is a sign of unwinder failure. It could also indicate
25325 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25326 The frame unwinder did not find any saved PC, but we needed
25327 one to unwind further.
25329 @item gdb.FRAME_UNWIND_FIRST_ERROR
25330 Any stop reason greater or equal to this value indicates some kind
25331 of error. This special value facilitates writing code that tests
25332 for errors in unwinding in a way that will work correctly even if
25333 the list of the other values is modified in future @value{GDBN}
25334 versions. Using it, you could write:
25336 reason = gdb.selected_frame().unwind_stop_reason ()
25337 reason_str = gdb.frame_stop_reason_string (reason)
25338 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25339 print "An error occured: %s" % reason_str
25346 Returns the frame's resume address.
25349 @defun Frame.block ()
25350 Return the frame's code block. @xref{Blocks In Python}.
25353 @defun Frame.function ()
25354 Return the symbol for the function corresponding to this frame.
25355 @xref{Symbols In Python}.
25358 @defun Frame.older ()
25359 Return the frame that called this frame.
25362 @defun Frame.newer ()
25363 Return the frame called by this frame.
25366 @defun Frame.find_sal ()
25367 Return the frame's symtab and line object.
25368 @xref{Symbol Tables In Python}.
25371 @defun Frame.read_var (variable @r{[}, block@r{]})
25372 Return the value of @var{variable} in this frame. If the optional
25373 argument @var{block} is provided, search for the variable from that
25374 block; otherwise start at the frame's current block (which is
25375 determined by the frame's current program counter). @var{variable}
25376 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25377 @code{gdb.Block} object.
25380 @defun Frame.select ()
25381 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25385 @node Blocks In Python
25386 @subsubsection Accessing frame blocks from Python.
25388 @cindex blocks in python
25391 Within each frame, @value{GDBN} maintains information on each block
25392 stored in that frame. These blocks are organized hierarchically, and
25393 are represented individually in Python as a @code{gdb.Block}.
25394 Please see @ref{Frames In Python}, for a more in-depth discussion on
25395 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25396 detailed technical information on @value{GDBN}'s book-keeping of the
25399 A @code{gdb.Block} is iterable. The iterator returns the symbols
25400 (@pxref{Symbols In Python}) local to the block. Python programs
25401 should not assume that a specific block object will always contain a
25402 given symbol, since changes in @value{GDBN} features and
25403 infrastructure may cause symbols move across blocks in a symbol
25406 The following block-related functions are available in the @code{gdb}
25409 @findex gdb.block_for_pc
25410 @defun gdb.block_for_pc (pc)
25411 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25412 block cannot be found for the @var{pc} value specified, the function
25413 will return @code{None}.
25416 A @code{gdb.Block} object has the following methods:
25418 @defun Block.is_valid ()
25419 Returns @code{True} if the @code{gdb.Block} object is valid,
25420 @code{False} if not. A block object can become invalid if the block it
25421 refers to doesn't exist anymore in the inferior. All other
25422 @code{gdb.Block} methods will throw an exception if it is invalid at
25423 the time the method is called. The block's validity is also checked
25424 during iteration over symbols of the block.
25427 A @code{gdb.Block} object has the following attributes:
25429 @defvar Block.start
25430 The start address of the block. This attribute is not writable.
25434 The end address of the block. This attribute is not writable.
25437 @defvar Block.function
25438 The name of the block represented as a @code{gdb.Symbol}. If the
25439 block is not named, then this attribute holds @code{None}. This
25440 attribute is not writable.
25443 @defvar Block.superblock
25444 The block containing this block. If this parent block does not exist,
25445 this attribute holds @code{None}. This attribute is not writable.
25448 @defvar Block.global_block
25449 The global block associated with this block. This attribute is not
25453 @defvar Block.static_block
25454 The static block associated with this block. This attribute is not
25458 @defvar Block.is_global
25459 @code{True} if the @code{gdb.Block} object is a global block,
25460 @code{False} if not. This attribute is not
25464 @defvar Block.is_static
25465 @code{True} if the @code{gdb.Block} object is a static block,
25466 @code{False} if not. This attribute is not writable.
25469 @node Symbols In Python
25470 @subsubsection Python representation of Symbols.
25472 @cindex symbols in python
25475 @value{GDBN} represents every variable, function and type as an
25476 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25477 Similarly, Python represents these symbols in @value{GDBN} with the
25478 @code{gdb.Symbol} object.
25480 The following symbol-related functions are available in the @code{gdb}
25483 @findex gdb.lookup_symbol
25484 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25485 This function searches for a symbol by name. The search scope can be
25486 restricted to the parameters defined in the optional domain and block
25489 @var{name} is the name of the symbol. It must be a string. The
25490 optional @var{block} argument restricts the search to symbols visible
25491 in that @var{block}. The @var{block} argument must be a
25492 @code{gdb.Block} object. If omitted, the block for the current frame
25493 is used. The optional @var{domain} argument restricts
25494 the search to the domain type. The @var{domain} argument must be a
25495 domain constant defined in the @code{gdb} module and described later
25498 The result is a tuple of two elements.
25499 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25501 If the symbol is found, the second element is @code{True} if the symbol
25502 is a field of a method's object (e.g., @code{this} in C@t{++}),
25503 otherwise it is @code{False}.
25504 If the symbol is not found, the second element is @code{False}.
25507 @findex gdb.lookup_global_symbol
25508 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25509 This function searches for a global symbol by name.
25510 The search scope can be restricted to by the domain argument.
25512 @var{name} is the name of the symbol. It must be a string.
25513 The optional @var{domain} argument restricts the search to the domain type.
25514 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25515 module and described later in this chapter.
25517 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25521 A @code{gdb.Symbol} object has the following attributes:
25523 @defvar Symbol.type
25524 The type of the symbol or @code{None} if no type is recorded.
25525 This attribute is represented as a @code{gdb.Type} object.
25526 @xref{Types In Python}. This attribute is not writable.
25529 @defvar Symbol.symtab
25530 The symbol table in which the symbol appears. This attribute is
25531 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25532 Python}. This attribute is not writable.
25535 @defvar Symbol.line
25536 The line number in the source code at which the symbol was defined.
25537 This is an integer.
25540 @defvar Symbol.name
25541 The name of the symbol as a string. This attribute is not writable.
25544 @defvar Symbol.linkage_name
25545 The name of the symbol, as used by the linker (i.e., may be mangled).
25546 This attribute is not writable.
25549 @defvar Symbol.print_name
25550 The name of the symbol in a form suitable for output. This is either
25551 @code{name} or @code{linkage_name}, depending on whether the user
25552 asked @value{GDBN} to display demangled or mangled names.
25555 @defvar Symbol.addr_class
25556 The address class of the symbol. This classifies how to find the value
25557 of a symbol. Each address class is a constant defined in the
25558 @code{gdb} module and described later in this chapter.
25561 @defvar Symbol.needs_frame
25562 This is @code{True} if evaluating this symbol's value requires a frame
25563 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25564 local variables will require a frame, but other symbols will not.
25567 @defvar Symbol.is_argument
25568 @code{True} if the symbol is an argument of a function.
25571 @defvar Symbol.is_constant
25572 @code{True} if the symbol is a constant.
25575 @defvar Symbol.is_function
25576 @code{True} if the symbol is a function or a method.
25579 @defvar Symbol.is_variable
25580 @code{True} if the symbol is a variable.
25583 A @code{gdb.Symbol} object has the following methods:
25585 @defun Symbol.is_valid ()
25586 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25587 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25588 the symbol it refers to does not exist in @value{GDBN} any longer.
25589 All other @code{gdb.Symbol} methods will throw an exception if it is
25590 invalid at the time the method is called.
25593 @defun Symbol.value (@r{[}frame@r{]})
25594 Compute the value of the symbol, as a @code{gdb.Value}. For
25595 functions, this computes the address of the function, cast to the
25596 appropriate type. If the symbol requires a frame in order to compute
25597 its value, then @var{frame} must be given. If @var{frame} is not
25598 given, or if @var{frame} is invalid, then this method will throw an
25602 The available domain categories in @code{gdb.Symbol} are represented
25603 as constants in the @code{gdb} module:
25606 @findex SYMBOL_UNDEF_DOMAIN
25607 @findex gdb.SYMBOL_UNDEF_DOMAIN
25608 @item gdb.SYMBOL_UNDEF_DOMAIN
25609 This is used when a domain has not been discovered or none of the
25610 following domains apply. This usually indicates an error either
25611 in the symbol information or in @value{GDBN}'s handling of symbols.
25612 @findex SYMBOL_VAR_DOMAIN
25613 @findex gdb.SYMBOL_VAR_DOMAIN
25614 @item gdb.SYMBOL_VAR_DOMAIN
25615 This domain contains variables, function names, typedef names and enum
25617 @findex SYMBOL_STRUCT_DOMAIN
25618 @findex gdb.SYMBOL_STRUCT_DOMAIN
25619 @item gdb.SYMBOL_STRUCT_DOMAIN
25620 This domain holds struct, union and enum type names.
25621 @findex SYMBOL_LABEL_DOMAIN
25622 @findex gdb.SYMBOL_LABEL_DOMAIN
25623 @item gdb.SYMBOL_LABEL_DOMAIN
25624 This domain contains names of labels (for gotos).
25625 @findex SYMBOL_VARIABLES_DOMAIN
25626 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25627 @item gdb.SYMBOL_VARIABLES_DOMAIN
25628 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25629 contains everything minus functions and types.
25630 @findex SYMBOL_FUNCTIONS_DOMAIN
25631 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25632 @item gdb.SYMBOL_FUNCTION_DOMAIN
25633 This domain contains all functions.
25634 @findex SYMBOL_TYPES_DOMAIN
25635 @findex gdb.SYMBOL_TYPES_DOMAIN
25636 @item gdb.SYMBOL_TYPES_DOMAIN
25637 This domain contains all types.
25640 The available address class categories in @code{gdb.Symbol} are represented
25641 as constants in the @code{gdb} module:
25644 @findex SYMBOL_LOC_UNDEF
25645 @findex gdb.SYMBOL_LOC_UNDEF
25646 @item gdb.SYMBOL_LOC_UNDEF
25647 If this is returned by address class, it indicates an error either in
25648 the symbol information or in @value{GDBN}'s handling of symbols.
25649 @findex SYMBOL_LOC_CONST
25650 @findex gdb.SYMBOL_LOC_CONST
25651 @item gdb.SYMBOL_LOC_CONST
25652 Value is constant int.
25653 @findex SYMBOL_LOC_STATIC
25654 @findex gdb.SYMBOL_LOC_STATIC
25655 @item gdb.SYMBOL_LOC_STATIC
25656 Value is at a fixed address.
25657 @findex SYMBOL_LOC_REGISTER
25658 @findex gdb.SYMBOL_LOC_REGISTER
25659 @item gdb.SYMBOL_LOC_REGISTER
25660 Value is in a register.
25661 @findex SYMBOL_LOC_ARG
25662 @findex gdb.SYMBOL_LOC_ARG
25663 @item gdb.SYMBOL_LOC_ARG
25664 Value is an argument. This value is at the offset stored within the
25665 symbol inside the frame's argument list.
25666 @findex SYMBOL_LOC_REF_ARG
25667 @findex gdb.SYMBOL_LOC_REF_ARG
25668 @item gdb.SYMBOL_LOC_REF_ARG
25669 Value address is stored in the frame's argument list. Just like
25670 @code{LOC_ARG} except that the value's address is stored at the
25671 offset, not the value itself.
25672 @findex SYMBOL_LOC_REGPARM_ADDR
25673 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25674 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25675 Value is a specified register. Just like @code{LOC_REGISTER} except
25676 the register holds the address of the argument instead of the argument
25678 @findex SYMBOL_LOC_LOCAL
25679 @findex gdb.SYMBOL_LOC_LOCAL
25680 @item gdb.SYMBOL_LOC_LOCAL
25681 Value is a local variable.
25682 @findex SYMBOL_LOC_TYPEDEF
25683 @findex gdb.SYMBOL_LOC_TYPEDEF
25684 @item gdb.SYMBOL_LOC_TYPEDEF
25685 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25687 @findex SYMBOL_LOC_BLOCK
25688 @findex gdb.SYMBOL_LOC_BLOCK
25689 @item gdb.SYMBOL_LOC_BLOCK
25691 @findex SYMBOL_LOC_CONST_BYTES
25692 @findex gdb.SYMBOL_LOC_CONST_BYTES
25693 @item gdb.SYMBOL_LOC_CONST_BYTES
25694 Value is a byte-sequence.
25695 @findex SYMBOL_LOC_UNRESOLVED
25696 @findex gdb.SYMBOL_LOC_UNRESOLVED
25697 @item gdb.SYMBOL_LOC_UNRESOLVED
25698 Value is at a fixed address, but the address of the variable has to be
25699 determined from the minimal symbol table whenever the variable is
25701 @findex SYMBOL_LOC_OPTIMIZED_OUT
25702 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25703 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25704 The value does not actually exist in the program.
25705 @findex SYMBOL_LOC_COMPUTED
25706 @findex gdb.SYMBOL_LOC_COMPUTED
25707 @item gdb.SYMBOL_LOC_COMPUTED
25708 The value's address is a computed location.
25711 @node Symbol Tables In Python
25712 @subsubsection Symbol table representation in Python.
25714 @cindex symbol tables in python
25716 @tindex gdb.Symtab_and_line
25718 Access to symbol table data maintained by @value{GDBN} on the inferior
25719 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25720 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25721 from the @code{find_sal} method in @code{gdb.Frame} object.
25722 @xref{Frames In Python}.
25724 For more information on @value{GDBN}'s symbol table management, see
25725 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25727 A @code{gdb.Symtab_and_line} object has the following attributes:
25729 @defvar Symtab_and_line.symtab
25730 The symbol table object (@code{gdb.Symtab}) for this frame.
25731 This attribute is not writable.
25734 @defvar Symtab_and_line.pc
25735 Indicates the start of the address range occupied by code for the
25736 current source line. This attribute is not writable.
25739 @defvar Symtab_and_line.last
25740 Indicates the end of the address range occupied by code for the current
25741 source line. This attribute is not writable.
25744 @defvar Symtab_and_line.line
25745 Indicates the current line number for this object. This
25746 attribute is not writable.
25749 A @code{gdb.Symtab_and_line} object has the following methods:
25751 @defun Symtab_and_line.is_valid ()
25752 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25753 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25754 invalid if the Symbol table and line object it refers to does not
25755 exist in @value{GDBN} any longer. All other
25756 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25757 invalid at the time the method is called.
25760 A @code{gdb.Symtab} object has the following attributes:
25762 @defvar Symtab.filename
25763 The symbol table's source filename. This attribute is not writable.
25766 @defvar Symtab.objfile
25767 The symbol table's backing object file. @xref{Objfiles In Python}.
25768 This attribute is not writable.
25771 A @code{gdb.Symtab} object has the following methods:
25773 @defun Symtab.is_valid ()
25774 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25775 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25776 the symbol table it refers to does not exist in @value{GDBN} any
25777 longer. All other @code{gdb.Symtab} methods will throw an exception
25778 if it is invalid at the time the method is called.
25781 @defun Symtab.fullname ()
25782 Return the symbol table's source absolute file name.
25785 @defun Symtab.global_block ()
25786 Return the global block of the underlying symbol table.
25787 @xref{Blocks In Python}.
25790 @defun Symtab.static_block ()
25791 Return the static block of the underlying symbol table.
25792 @xref{Blocks In Python}.
25795 @node Breakpoints In Python
25796 @subsubsection Manipulating breakpoints using Python
25798 @cindex breakpoints in python
25799 @tindex gdb.Breakpoint
25801 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25804 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25805 Create a new breakpoint. @var{spec} is a string naming the
25806 location of the breakpoint, or an expression that defines a
25807 watchpoint. The contents can be any location recognized by the
25808 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25809 command. The optional @var{type} denotes the breakpoint to create
25810 from the types defined later in this chapter. This argument can be
25811 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25812 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25813 allows the breakpoint to become invisible to the user. The breakpoint
25814 will neither be reported when created, nor will it be listed in the
25815 output from @code{info breakpoints} (but will be listed with the
25816 @code{maint info breakpoints} command). The optional @var{wp_class}
25817 argument defines the class of watchpoint to create, if @var{type} is
25818 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25819 assumed to be a @code{gdb.WP_WRITE} class.
25822 @defun Breakpoint.stop (self)
25823 The @code{gdb.Breakpoint} class can be sub-classed and, in
25824 particular, you may choose to implement the @code{stop} method.
25825 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25826 it will be called when the inferior reaches any location of a
25827 breakpoint which instantiates that sub-class. If the method returns
25828 @code{True}, the inferior will be stopped at the location of the
25829 breakpoint, otherwise the inferior will continue.
25831 If there are multiple breakpoints at the same location with a
25832 @code{stop} method, each one will be called regardless of the
25833 return status of the previous. This ensures that all @code{stop}
25834 methods have a chance to execute at that location. In this scenario
25835 if one of the methods returns @code{True} but the others return
25836 @code{False}, the inferior will still be stopped.
25838 You should not alter the execution state of the inferior (i.e.@:, step,
25839 next, etc.), alter the current frame context (i.e.@:, change the current
25840 active frame), or alter, add or delete any breakpoint. As a general
25841 rule, you should not alter any data within @value{GDBN} or the inferior
25844 Example @code{stop} implementation:
25847 class MyBreakpoint (gdb.Breakpoint):
25849 inf_val = gdb.parse_and_eval("foo")
25856 The available watchpoint types represented by constants are defined in the
25861 @findex gdb.WP_READ
25863 Read only watchpoint.
25866 @findex gdb.WP_WRITE
25868 Write only watchpoint.
25871 @findex gdb.WP_ACCESS
25872 @item gdb.WP_ACCESS
25873 Read/Write watchpoint.
25876 @defun Breakpoint.is_valid ()
25877 Return @code{True} if this @code{Breakpoint} object is valid,
25878 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25879 if the user deletes the breakpoint. In this case, the object still
25880 exists, but the underlying breakpoint does not. In the cases of
25881 watchpoint scope, the watchpoint remains valid even if execution of the
25882 inferior leaves the scope of that watchpoint.
25885 @defun Breakpoint.delete
25886 Permanently deletes the @value{GDBN} breakpoint. This also
25887 invalidates the Python @code{Breakpoint} object. Any further access
25888 to this object's attributes or methods will raise an error.
25891 @defvar Breakpoint.enabled
25892 This attribute is @code{True} if the breakpoint is enabled, and
25893 @code{False} otherwise. This attribute is writable.
25896 @defvar Breakpoint.silent
25897 This attribute is @code{True} if the breakpoint is silent, and
25898 @code{False} otherwise. This attribute is writable.
25900 Note that a breakpoint can also be silent if it has commands and the
25901 first command is @code{silent}. This is not reported by the
25902 @code{silent} attribute.
25905 @defvar Breakpoint.thread
25906 If the breakpoint is thread-specific, this attribute holds the thread
25907 id. If the breakpoint is not thread-specific, this attribute is
25908 @code{None}. This attribute is writable.
25911 @defvar Breakpoint.task
25912 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25913 id. If the breakpoint is not task-specific (or the underlying
25914 language is not Ada), this attribute is @code{None}. This attribute
25918 @defvar Breakpoint.ignore_count
25919 This attribute holds the ignore count for the breakpoint, an integer.
25920 This attribute is writable.
25923 @defvar Breakpoint.number
25924 This attribute holds the breakpoint's number --- the identifier used by
25925 the user to manipulate the breakpoint. This attribute is not writable.
25928 @defvar Breakpoint.type
25929 This attribute holds the breakpoint's type --- the identifier used to
25930 determine the actual breakpoint type or use-case. This attribute is not
25934 @defvar Breakpoint.visible
25935 This attribute tells whether the breakpoint is visible to the user
25936 when set, or when the @samp{info breakpoints} command is run. This
25937 attribute is not writable.
25940 The available types are represented by constants defined in the @code{gdb}
25944 @findex BP_BREAKPOINT
25945 @findex gdb.BP_BREAKPOINT
25946 @item gdb.BP_BREAKPOINT
25947 Normal code breakpoint.
25949 @findex BP_WATCHPOINT
25950 @findex gdb.BP_WATCHPOINT
25951 @item gdb.BP_WATCHPOINT
25952 Watchpoint breakpoint.
25954 @findex BP_HARDWARE_WATCHPOINT
25955 @findex gdb.BP_HARDWARE_WATCHPOINT
25956 @item gdb.BP_HARDWARE_WATCHPOINT
25957 Hardware assisted watchpoint.
25959 @findex BP_READ_WATCHPOINT
25960 @findex gdb.BP_READ_WATCHPOINT
25961 @item gdb.BP_READ_WATCHPOINT
25962 Hardware assisted read watchpoint.
25964 @findex BP_ACCESS_WATCHPOINT
25965 @findex gdb.BP_ACCESS_WATCHPOINT
25966 @item gdb.BP_ACCESS_WATCHPOINT
25967 Hardware assisted access watchpoint.
25970 @defvar Breakpoint.hit_count
25971 This attribute holds the hit count for the breakpoint, an integer.
25972 This attribute is writable, but currently it can only be set to zero.
25975 @defvar Breakpoint.location
25976 This attribute holds the location of the breakpoint, as specified by
25977 the user. It is a string. If the breakpoint does not have a location
25978 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25979 attribute is not writable.
25982 @defvar Breakpoint.expression
25983 This attribute holds a breakpoint expression, as specified by
25984 the user. It is a string. If the breakpoint does not have an
25985 expression (the breakpoint is not a watchpoint) the attribute's value
25986 is @code{None}. This attribute is not writable.
25989 @defvar Breakpoint.condition
25990 This attribute holds the condition of the breakpoint, as specified by
25991 the user. It is a string. If there is no condition, this attribute's
25992 value is @code{None}. This attribute is writable.
25995 @defvar Breakpoint.commands
25996 This attribute holds the commands attached to the breakpoint. If
25997 there are commands, this attribute's value is a string holding all the
25998 commands, separated by newlines. If there are no commands, this
25999 attribute is @code{None}. This attribute is not writable.
26002 @node Finish Breakpoints in Python
26003 @subsubsection Finish Breakpoints
26005 @cindex python finish breakpoints
26006 @tindex gdb.FinishBreakpoint
26008 A finish breakpoint is a temporary breakpoint set at the return address of
26009 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
26010 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
26011 and deleted when the execution will run out of the breakpoint scope (i.e.@:
26012 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
26013 Finish breakpoints are thread specific and must be create with the right
26016 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
26017 Create a finish breakpoint at the return address of the @code{gdb.Frame}
26018 object @var{frame}. If @var{frame} is not provided, this defaults to the
26019 newest frame. The optional @var{internal} argument allows the breakpoint to
26020 become invisible to the user. @xref{Breakpoints In Python}, for further
26021 details about this argument.
26024 @defun FinishBreakpoint.out_of_scope (self)
26025 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
26026 @code{return} command, @dots{}), a function may not properly terminate, and
26027 thus never hit the finish breakpoint. When @value{GDBN} notices such a
26028 situation, the @code{out_of_scope} callback will be triggered.
26030 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
26034 class MyFinishBreakpoint (gdb.FinishBreakpoint)
26036 print "normal finish"
26039 def out_of_scope ():
26040 print "abnormal finish"
26044 @defvar FinishBreakpoint.return_value
26045 When @value{GDBN} is stopped at a finish breakpoint and the frame
26046 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
26047 attribute will contain a @code{gdb.Value} object corresponding to the return
26048 value of the function. The value will be @code{None} if the function return
26049 type is @code{void} or if the return value was not computable. This attribute
26053 @node Lazy Strings In Python
26054 @subsubsection Python representation of lazy strings.
26056 @cindex lazy strings in python
26057 @tindex gdb.LazyString
26059 A @dfn{lazy string} is a string whose contents is not retrieved or
26060 encoded until it is needed.
26062 A @code{gdb.LazyString} is represented in @value{GDBN} as an
26063 @code{address} that points to a region of memory, an @code{encoding}
26064 that will be used to encode that region of memory, and a @code{length}
26065 to delimit the region of memory that represents the string. The
26066 difference between a @code{gdb.LazyString} and a string wrapped within
26067 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
26068 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
26069 retrieved and encoded during printing, while a @code{gdb.Value}
26070 wrapping a string is immediately retrieved and encoded on creation.
26072 A @code{gdb.LazyString} object has the following functions:
26074 @defun LazyString.value ()
26075 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
26076 will point to the string in memory, but will lose all the delayed
26077 retrieval, encoding and handling that @value{GDBN} applies to a
26078 @code{gdb.LazyString}.
26081 @defvar LazyString.address
26082 This attribute holds the address of the string. This attribute is not
26086 @defvar LazyString.length
26087 This attribute holds the length of the string in characters. If the
26088 length is -1, then the string will be fetched and encoded up to the
26089 first null of appropriate width. This attribute is not writable.
26092 @defvar LazyString.encoding
26093 This attribute holds the encoding that will be applied to the string
26094 when the string is printed by @value{GDBN}. If the encoding is not
26095 set, or contains an empty string, then @value{GDBN} will select the
26096 most appropriate encoding when the string is printed. This attribute
26100 @defvar LazyString.type
26101 This attribute holds the type that is represented by the lazy string's
26102 type. For a lazy string this will always be a pointer type. To
26103 resolve this to the lazy string's character type, use the type's
26104 @code{target} method. @xref{Types In Python}. This attribute is not
26108 @node Architectures In Python
26109 @subsubsection Python representation of architectures
26110 @cindex Python architectures
26112 @value{GDBN} uses architecture specific parameters and artifacts in a
26113 number of its various computations. An architecture is represented
26114 by an instance of the @code{gdb.Architecture} class.
26116 A @code{gdb.Architecture} class has the following methods:
26118 @defun Architecture.name ()
26119 Return the name (string value) of the architecture.
26122 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
26123 Return a list of disassembled instructions starting from the memory
26124 address @var{start_pc}. The optional arguments @var{end_pc} and
26125 @var{count} determine the number of instructions in the returned list.
26126 If both the optional arguments @var{end_pc} and @var{count} are
26127 specified, then a list of at most @var{count} disassembled instructions
26128 whose start address falls in the closed memory address interval from
26129 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
26130 specified, but @var{count} is specified, then @var{count} number of
26131 instructions starting from the address @var{start_pc} are returned. If
26132 @var{count} is not specified but @var{end_pc} is specified, then all
26133 instructions whose start address falls in the closed memory address
26134 interval from @var{start_pc} to @var{end_pc} are returned. If neither
26135 @var{end_pc} nor @var{count} are specified, then a single instruction at
26136 @var{start_pc} is returned. For all of these cases, each element of the
26137 returned list is a Python @code{dict} with the following string keys:
26142 The value corresponding to this key is a Python long integer capturing
26143 the memory address of the instruction.
26146 The value corresponding to this key is a string value which represents
26147 the instruction with assembly language mnemonics. The assembly
26148 language flavor used is the same as that specified by the current CLI
26149 variable @code{disassembly-flavor}. @xref{Machine Code}.
26152 The value corresponding to this key is the length (integer value) of the
26153 instruction in bytes.
26158 @node Python Auto-loading
26159 @subsection Python Auto-loading
26160 @cindex Python auto-loading
26162 When a new object file is read (for example, due to the @code{file}
26163 command, or because the inferior has loaded a shared library),
26164 @value{GDBN} will look for Python support scripts in several ways:
26165 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
26166 and @code{.debug_gdb_scripts} section
26167 (@pxref{dotdebug_gdb_scripts section}).
26169 The auto-loading feature is useful for supplying application-specific
26170 debugging commands and scripts.
26172 Auto-loading can be enabled or disabled,
26173 and the list of auto-loaded scripts can be printed.
26176 @anchor{set auto-load python-scripts}
26177 @kindex set auto-load python-scripts
26178 @item set auto-load python-scripts [on|off]
26179 Enable or disable the auto-loading of Python scripts.
26181 @anchor{show auto-load python-scripts}
26182 @kindex show auto-load python-scripts
26183 @item show auto-load python-scripts
26184 Show whether auto-loading of Python scripts is enabled or disabled.
26186 @anchor{info auto-load python-scripts}
26187 @kindex info auto-load python-scripts
26188 @cindex print list of auto-loaded Python scripts
26189 @item info auto-load python-scripts [@var{regexp}]
26190 Print the list of all Python scripts that @value{GDBN} auto-loaded.
26192 Also printed is the list of Python scripts that were mentioned in
26193 the @code{.debug_gdb_scripts} section and were not found
26194 (@pxref{dotdebug_gdb_scripts section}).
26195 This is useful because their names are not printed when @value{GDBN}
26196 tries to load them and fails. There may be many of them, and printing
26197 an error message for each one is problematic.
26199 If @var{regexp} is supplied only Python scripts with matching names are printed.
26204 (gdb) info auto-load python-scripts
26206 Yes py-section-script.py
26207 full name: /tmp/py-section-script.py
26208 No my-foo-pretty-printers.py
26212 When reading an auto-loaded file, @value{GDBN} sets the
26213 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
26214 function (@pxref{Objfiles In Python}). This can be useful for
26215 registering objfile-specific pretty-printers.
26218 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26219 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26220 * Which flavor to choose?::
26223 @node objfile-gdb.py file
26224 @subsubsection The @file{@var{objfile}-gdb.py} file
26225 @cindex @file{@var{objfile}-gdb.py}
26227 When a new object file is read, @value{GDBN} looks for
26228 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26229 where @var{objfile} is the object file's real name, formed by ensuring
26230 that the file name is absolute, following all symlinks, and resolving
26231 @code{.} and @code{..} components. If this file exists and is
26232 readable, @value{GDBN} will evaluate it as a Python script.
26234 If this file does not exist, then @value{GDBN} will look for
26235 @var{script-name} file in all of the directories as specified below.
26237 Note that loading of this script file also requires accordingly configured
26238 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26240 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26241 scripts normally according to its @file{.exe} filename. But if no scripts are
26242 found @value{GDBN} also tries script filenames matching the object file without
26243 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26244 is attempted on any platform. This makes the script filenames compatible
26245 between Unix and MS-Windows hosts.
26248 @anchor{set auto-load scripts-directory}
26249 @kindex set auto-load scripts-directory
26250 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26251 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26252 may be delimited by the host platform path separator in use
26253 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26255 Each entry here needs to be covered also by the security setting
26256 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26258 @anchor{with-auto-load-dir}
26259 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26260 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26261 configuration option @option{--with-auto-load-dir}.
26263 Any reference to @file{$debugdir} will get replaced by
26264 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26265 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26266 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26267 @file{$datadir} must be placed as a directory component --- either alone or
26268 delimited by @file{/} or @file{\} directory separators, depending on the host
26271 The list of directories uses path separator (@samp{:} on GNU and Unix
26272 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26273 to the @env{PATH} environment variable.
26275 @anchor{show auto-load scripts-directory}
26276 @kindex show auto-load scripts-directory
26277 @item show auto-load scripts-directory
26278 Show @value{GDBN} auto-loaded scripts location.
26281 @value{GDBN} does not track which files it has already auto-loaded this way.
26282 @value{GDBN} will load the associated script every time the corresponding
26283 @var{objfile} is opened.
26284 So your @file{-gdb.py} file should be careful to avoid errors if it
26285 is evaluated more than once.
26287 @node dotdebug_gdb_scripts section
26288 @subsubsection The @code{.debug_gdb_scripts} section
26289 @cindex @code{.debug_gdb_scripts} section
26291 For systems using file formats like ELF and COFF,
26292 when @value{GDBN} loads a new object file
26293 it will look for a special section named @samp{.debug_gdb_scripts}.
26294 If this section exists, its contents is a list of names of scripts to load.
26296 @value{GDBN} will look for each specified script file first in the
26297 current directory and then along the source search path
26298 (@pxref{Source Path, ,Specifying Source Directories}),
26299 except that @file{$cdir} is not searched, since the compilation
26300 directory is not relevant to scripts.
26302 Entries can be placed in section @code{.debug_gdb_scripts} with,
26303 for example, this GCC macro:
26306 /* Note: The "MS" section flags are to remove duplicates. */
26307 #define DEFINE_GDB_SCRIPT(script_name) \
26309 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26311 .asciz \"" script_name "\"\n\
26317 Then one can reference the macro in a header or source file like this:
26320 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26323 The script name may include directories if desired.
26325 Note that loading of this script file also requires accordingly configured
26326 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26328 If the macro is put in a header, any application or library
26329 using this header will get a reference to the specified script.
26331 @node Which flavor to choose?
26332 @subsubsection Which flavor to choose?
26334 Given the multiple ways of auto-loading Python scripts, it might not always
26335 be clear which one to choose. This section provides some guidance.
26337 Benefits of the @file{-gdb.py} way:
26341 Can be used with file formats that don't support multiple sections.
26344 Ease of finding scripts for public libraries.
26346 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26347 in the source search path.
26348 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26349 isn't a source directory in which to find the script.
26352 Doesn't require source code additions.
26355 Benefits of the @code{.debug_gdb_scripts} way:
26359 Works with static linking.
26361 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26362 trigger their loading. When an application is statically linked the only
26363 objfile available is the executable, and it is cumbersome to attach all the
26364 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26367 Works with classes that are entirely inlined.
26369 Some classes can be entirely inlined, and thus there may not be an associated
26370 shared library to attach a @file{-gdb.py} script to.
26373 Scripts needn't be copied out of the source tree.
26375 In some circumstances, apps can be built out of large collections of internal
26376 libraries, and the build infrastructure necessary to install the
26377 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26378 cumbersome. It may be easier to specify the scripts in the
26379 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26380 top of the source tree to the source search path.
26383 @node Python modules
26384 @subsection Python modules
26385 @cindex python modules
26387 @value{GDBN} comes with several modules to assist writing Python code.
26390 * gdb.printing:: Building and registering pretty-printers.
26391 * gdb.types:: Utilities for working with types.
26392 * gdb.prompt:: Utilities for prompt value substitution.
26396 @subsubsection gdb.printing
26397 @cindex gdb.printing
26399 This module provides a collection of utilities for working with
26403 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26404 This class specifies the API that makes @samp{info pretty-printer},
26405 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26406 Pretty-printers should generally inherit from this class.
26408 @item SubPrettyPrinter (@var{name})
26409 For printers that handle multiple types, this class specifies the
26410 corresponding API for the subprinters.
26412 @item RegexpCollectionPrettyPrinter (@var{name})
26413 Utility class for handling multiple printers, all recognized via
26414 regular expressions.
26415 @xref{Writing a Pretty-Printer}, for an example.
26417 @item FlagEnumerationPrinter (@var{name})
26418 A pretty-printer which handles printing of @code{enum} values. Unlike
26419 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26420 work properly when there is some overlap between the enumeration
26421 constants. @var{name} is the name of the printer and also the name of
26422 the @code{enum} type to look up.
26424 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26425 Register @var{printer} with the pretty-printer list of @var{obj}.
26426 If @var{replace} is @code{True} then any existing copy of the printer
26427 is replaced. Otherwise a @code{RuntimeError} exception is raised
26428 if a printer with the same name already exists.
26432 @subsubsection gdb.types
26435 This module provides a collection of utilities for working with
26436 @code{gdb.Type} objects.
26439 @item get_basic_type (@var{type})
26440 Return @var{type} with const and volatile qualifiers stripped,
26441 and with typedefs and C@t{++} references converted to the underlying type.
26446 typedef const int const_int;
26448 const_int& foo_ref (foo);
26449 int main () @{ return 0; @}
26456 (gdb) python import gdb.types
26457 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26458 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26462 @item has_field (@var{type}, @var{field})
26463 Return @code{True} if @var{type}, assumed to be a type with fields
26464 (e.g., a structure or union), has field @var{field}.
26466 @item make_enum_dict (@var{enum_type})
26467 Return a Python @code{dictionary} type produced from @var{enum_type}.
26469 @item deep_items (@var{type})
26470 Returns a Python iterator similar to the standard
26471 @code{gdb.Type.iteritems} method, except that the iterator returned
26472 by @code{deep_items} will recursively traverse anonymous struct or
26473 union fields. For example:
26487 Then in @value{GDBN}:
26489 (@value{GDBP}) python import gdb.types
26490 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26491 (@value{GDBP}) python print struct_a.keys ()
26493 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26494 @{['a', 'b0', 'b1']@}
26497 @item get_type_recognizers ()
26498 Return a list of the enabled type recognizers for the current context.
26499 This is called by @value{GDBN} during the type-printing process
26500 (@pxref{Type Printing API}).
26502 @item apply_type_recognizers (recognizers, type_obj)
26503 Apply the type recognizers, @var{recognizers}, to the type object
26504 @var{type_obj}. If any recognizer returns a string, return that
26505 string. Otherwise, return @code{None}. This is called by
26506 @value{GDBN} during the type-printing process (@pxref{Type Printing
26509 @item register_type_printer (locus, printer)
26510 This is a convenience function to register a type printer.
26511 @var{printer} is the type printer to register. It must implement the
26512 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26513 which case the printer is registered with that objfile; a
26514 @code{gdb.Progspace}, in which case the printer is registered with
26515 that progspace; or @code{None}, in which case the printer is
26516 registered globally.
26519 This is a base class that implements the type printer protocol. Type
26520 printers are encouraged, but not required, to derive from this class.
26521 It defines a constructor:
26523 @defmethod TypePrinter __init__ (self, name)
26524 Initialize the type printer with the given name. The new printer
26525 starts in the enabled state.
26531 @subsubsection gdb.prompt
26534 This module provides a method for prompt value-substitution.
26537 @item substitute_prompt (@var{string})
26538 Return @var{string} with escape sequences substituted by values. Some
26539 escape sequences take arguments. You can specify arguments inside
26540 ``@{@}'' immediately following the escape sequence.
26542 The escape sequences you can pass to this function are:
26546 Substitute a backslash.
26548 Substitute an ESC character.
26550 Substitute the selected frame; an argument names a frame parameter.
26552 Substitute a newline.
26554 Substitute a parameter's value; the argument names the parameter.
26556 Substitute a carriage return.
26558 Substitute the selected thread; an argument names a thread parameter.
26560 Substitute the version of GDB.
26562 Substitute the current working directory.
26564 Begin a sequence of non-printing characters. These sequences are
26565 typically used with the ESC character, and are not counted in the string
26566 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26567 blue-colored ``(gdb)'' prompt where the length is five.
26569 End a sequence of non-printing characters.
26575 substitute_prompt (``frame: \f,
26576 print arguments: \p@{print frame-arguments@}'')
26579 @exdent will return the string:
26582 "frame: main, print arguments: scalars"
26587 @section Creating new spellings of existing commands
26588 @cindex aliases for commands
26590 It is often useful to define alternate spellings of existing commands.
26591 For example, if a new @value{GDBN} command defined in Python has
26592 a long name to type, it is handy to have an abbreviated version of it
26593 that involves less typing.
26595 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26596 of the @samp{step} command even though it is otherwise an ambiguous
26597 abbreviation of other commands like @samp{set} and @samp{show}.
26599 Aliases are also used to provide shortened or more common versions
26600 of multi-word commands. For example, @value{GDBN} provides the
26601 @samp{tty} alias of the @samp{set inferior-tty} command.
26603 You can define a new alias with the @samp{alias} command.
26608 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26612 @var{ALIAS} specifies the name of the new alias.
26613 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26616 @var{COMMAND} specifies the name of an existing command
26617 that is being aliased.
26619 The @samp{-a} option specifies that the new alias is an abbreviation
26620 of the command. Abbreviations are not shown in command
26621 lists displayed by the @samp{help} command.
26623 The @samp{--} option specifies the end of options,
26624 and is useful when @var{ALIAS} begins with a dash.
26626 Here is a simple example showing how to make an abbreviation
26627 of a command so that there is less to type.
26628 Suppose you were tired of typing @samp{disas}, the current
26629 shortest unambiguous abbreviation of the @samp{disassemble} command
26630 and you wanted an even shorter version named @samp{di}.
26631 The following will accomplish this.
26634 (gdb) alias -a di = disas
26637 Note that aliases are different from user-defined commands.
26638 With a user-defined command, you also need to write documentation
26639 for it with the @samp{document} command.
26640 An alias automatically picks up the documentation of the existing command.
26642 Here is an example where we make @samp{elms} an abbreviation of
26643 @samp{elements} in the @samp{set print elements} command.
26644 This is to show that you can make an abbreviation of any part
26648 (gdb) alias -a set print elms = set print elements
26649 (gdb) alias -a show print elms = show print elements
26650 (gdb) set p elms 20
26652 Limit on string chars or array elements to print is 200.
26655 Note that if you are defining an alias of a @samp{set} command,
26656 and you want to have an alias for the corresponding @samp{show}
26657 command, then you need to define the latter separately.
26659 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26660 @var{ALIAS}, just as they are normally.
26663 (gdb) alias -a set pr elms = set p ele
26666 Finally, here is an example showing the creation of a one word
26667 alias for a more complex command.
26668 This creates alias @samp{spe} of the command @samp{set print elements}.
26671 (gdb) alias spe = set print elements
26676 @chapter Command Interpreters
26677 @cindex command interpreters
26679 @value{GDBN} supports multiple command interpreters, and some command
26680 infrastructure to allow users or user interface writers to switch
26681 between interpreters or run commands in other interpreters.
26683 @value{GDBN} currently supports two command interpreters, the console
26684 interpreter (sometimes called the command-line interpreter or @sc{cli})
26685 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26686 describes both of these interfaces in great detail.
26688 By default, @value{GDBN} will start with the console interpreter.
26689 However, the user may choose to start @value{GDBN} with another
26690 interpreter by specifying the @option{-i} or @option{--interpreter}
26691 startup options. Defined interpreters include:
26695 @cindex console interpreter
26696 The traditional console or command-line interpreter. This is the most often
26697 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26698 @value{GDBN} will use this interpreter.
26701 @cindex mi interpreter
26702 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26703 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26704 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26708 @cindex mi2 interpreter
26709 The current @sc{gdb/mi} interface.
26712 @cindex mi1 interpreter
26713 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26717 @cindex invoke another interpreter
26718 The interpreter being used by @value{GDBN} may not be dynamically
26719 switched at runtime. Although possible, this could lead to a very
26720 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26721 enters the command "interpreter-set console" in a console view,
26722 @value{GDBN} would switch to using the console interpreter, rendering
26723 the IDE inoperable!
26725 @kindex interpreter-exec
26726 Although you may only choose a single interpreter at startup, you may execute
26727 commands in any interpreter from the current interpreter using the appropriate
26728 command. If you are running the console interpreter, simply use the
26729 @code{interpreter-exec} command:
26732 interpreter-exec mi "-data-list-register-names"
26735 @sc{gdb/mi} has a similar command, although it is only available in versions of
26736 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26739 @chapter @value{GDBN} Text User Interface
26741 @cindex Text User Interface
26744 * TUI Overview:: TUI overview
26745 * TUI Keys:: TUI key bindings
26746 * TUI Single Key Mode:: TUI single key mode
26747 * TUI Commands:: TUI-specific commands
26748 * TUI Configuration:: TUI configuration variables
26751 The @value{GDBN} Text User Interface (TUI) is a terminal
26752 interface which uses the @code{curses} library to show the source
26753 file, the assembly output, the program registers and @value{GDBN}
26754 commands in separate text windows. The TUI mode is supported only
26755 on platforms where a suitable version of the @code{curses} library
26758 The TUI mode is enabled by default when you invoke @value{GDBN} as
26759 @samp{@value{GDBP} -tui}.
26760 You can also switch in and out of TUI mode while @value{GDBN} runs by
26761 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26762 @xref{TUI Keys, ,TUI Key Bindings}.
26765 @section TUI Overview
26767 In TUI mode, @value{GDBN} can display several text windows:
26771 This window is the @value{GDBN} command window with the @value{GDBN}
26772 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26773 managed using readline.
26776 The source window shows the source file of the program. The current
26777 line and active breakpoints are displayed in this window.
26780 The assembly window shows the disassembly output of the program.
26783 This window shows the processor registers. Registers are highlighted
26784 when their values change.
26787 The source and assembly windows show the current program position
26788 by highlighting the current line and marking it with a @samp{>} marker.
26789 Breakpoints are indicated with two markers. The first marker
26790 indicates the breakpoint type:
26794 Breakpoint which was hit at least once.
26797 Breakpoint which was never hit.
26800 Hardware breakpoint which was hit at least once.
26803 Hardware breakpoint which was never hit.
26806 The second marker indicates whether the breakpoint is enabled or not:
26810 Breakpoint is enabled.
26813 Breakpoint is disabled.
26816 The source, assembly and register windows are updated when the current
26817 thread changes, when the frame changes, or when the program counter
26820 These windows are not all visible at the same time. The command
26821 window is always visible. The others can be arranged in several
26832 source and assembly,
26835 source and registers, or
26838 assembly and registers.
26841 A status line above the command window shows the following information:
26845 Indicates the current @value{GDBN} target.
26846 (@pxref{Targets, ,Specifying a Debugging Target}).
26849 Gives the current process or thread number.
26850 When no process is being debugged, this field is set to @code{No process}.
26853 Gives the current function name for the selected frame.
26854 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26855 When there is no symbol corresponding to the current program counter,
26856 the string @code{??} is displayed.
26859 Indicates the current line number for the selected frame.
26860 When the current line number is not known, the string @code{??} is displayed.
26863 Indicates the current program counter address.
26867 @section TUI Key Bindings
26868 @cindex TUI key bindings
26870 The TUI installs several key bindings in the readline keymaps
26871 @ifset SYSTEM_READLINE
26872 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26874 @ifclear SYSTEM_READLINE
26875 (@pxref{Command Line Editing}).
26877 The following key bindings are installed for both TUI mode and the
26878 @value{GDBN} standard mode.
26887 Enter or leave the TUI mode. When leaving the TUI mode,
26888 the curses window management stops and @value{GDBN} operates using
26889 its standard mode, writing on the terminal directly. When reentering
26890 the TUI mode, control is given back to the curses windows.
26891 The screen is then refreshed.
26895 Use a TUI layout with only one window. The layout will
26896 either be @samp{source} or @samp{assembly}. When the TUI mode
26897 is not active, it will switch to the TUI mode.
26899 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26903 Use a TUI layout with at least two windows. When the current
26904 layout already has two windows, the next layout with two windows is used.
26905 When a new layout is chosen, one window will always be common to the
26906 previous layout and the new one.
26908 Think of it as the Emacs @kbd{C-x 2} binding.
26912 Change the active window. The TUI associates several key bindings
26913 (like scrolling and arrow keys) with the active window. This command
26914 gives the focus to the next TUI window.
26916 Think of it as the Emacs @kbd{C-x o} binding.
26920 Switch in and out of the TUI SingleKey mode that binds single
26921 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26924 The following key bindings only work in the TUI mode:
26929 Scroll the active window one page up.
26933 Scroll the active window one page down.
26937 Scroll the active window one line up.
26941 Scroll the active window one line down.
26945 Scroll the active window one column left.
26949 Scroll the active window one column right.
26953 Refresh the screen.
26956 Because the arrow keys scroll the active window in the TUI mode, they
26957 are not available for their normal use by readline unless the command
26958 window has the focus. When another window is active, you must use
26959 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26960 and @kbd{C-f} to control the command window.
26962 @node TUI Single Key Mode
26963 @section TUI Single Key Mode
26964 @cindex TUI single key mode
26966 The TUI also provides a @dfn{SingleKey} mode, which binds several
26967 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26968 switch into this mode, where the following key bindings are used:
26971 @kindex c @r{(SingleKey TUI key)}
26975 @kindex d @r{(SingleKey TUI key)}
26979 @kindex f @r{(SingleKey TUI key)}
26983 @kindex n @r{(SingleKey TUI key)}
26987 @kindex q @r{(SingleKey TUI key)}
26989 exit the SingleKey mode.
26991 @kindex r @r{(SingleKey TUI key)}
26995 @kindex s @r{(SingleKey TUI key)}
26999 @kindex u @r{(SingleKey TUI key)}
27003 @kindex v @r{(SingleKey TUI key)}
27007 @kindex w @r{(SingleKey TUI key)}
27012 Other keys temporarily switch to the @value{GDBN} command prompt.
27013 The key that was pressed is inserted in the editing buffer so that
27014 it is possible to type most @value{GDBN} commands without interaction
27015 with the TUI SingleKey mode. Once the command is entered the TUI
27016 SingleKey mode is restored. The only way to permanently leave
27017 this mode is by typing @kbd{q} or @kbd{C-x s}.
27021 @section TUI-specific Commands
27022 @cindex TUI commands
27024 The TUI has specific commands to control the text windows.
27025 These commands are always available, even when @value{GDBN} is not in
27026 the TUI mode. When @value{GDBN} is in the standard mode, most
27027 of these commands will automatically switch to the TUI mode.
27029 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27030 terminal, or @value{GDBN} has been started with the machine interface
27031 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27032 these commands will fail with an error, because it would not be
27033 possible or desirable to enable curses window management.
27038 List and give the size of all displayed windows.
27042 Display the next layout.
27045 Display the previous layout.
27048 Display the source window only.
27051 Display the assembly window only.
27054 Display the source and assembly window.
27057 Display the register window together with the source or assembly window.
27061 Make the next window active for scrolling.
27064 Make the previous window active for scrolling.
27067 Make the source window active for scrolling.
27070 Make the assembly window active for scrolling.
27073 Make the register window active for scrolling.
27076 Make the command window active for scrolling.
27080 Refresh the screen. This is similar to typing @kbd{C-L}.
27082 @item tui reg float
27084 Show the floating point registers in the register window.
27086 @item tui reg general
27087 Show the general registers in the register window.
27090 Show the next register group. The list of register groups as well as
27091 their order is target specific. The predefined register groups are the
27092 following: @code{general}, @code{float}, @code{system}, @code{vector},
27093 @code{all}, @code{save}, @code{restore}.
27095 @item tui reg system
27096 Show the system registers in the register window.
27100 Update the source window and the current execution point.
27102 @item winheight @var{name} +@var{count}
27103 @itemx winheight @var{name} -@var{count}
27105 Change the height of the window @var{name} by @var{count}
27106 lines. Positive counts increase the height, while negative counts
27109 @item tabset @var{nchars}
27111 Set the width of tab stops to be @var{nchars} characters.
27114 @node TUI Configuration
27115 @section TUI Configuration Variables
27116 @cindex TUI configuration variables
27118 Several configuration variables control the appearance of TUI windows.
27121 @item set tui border-kind @var{kind}
27122 @kindex set tui border-kind
27123 Select the border appearance for the source, assembly and register windows.
27124 The possible values are the following:
27127 Use a space character to draw the border.
27130 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27133 Use the Alternate Character Set to draw the border. The border is
27134 drawn using character line graphics if the terminal supports them.
27137 @item set tui border-mode @var{mode}
27138 @kindex set tui border-mode
27139 @itemx set tui active-border-mode @var{mode}
27140 @kindex set tui active-border-mode
27141 Select the display attributes for the borders of the inactive windows
27142 or the active window. The @var{mode} can be one of the following:
27145 Use normal attributes to display the border.
27151 Use reverse video mode.
27154 Use half bright mode.
27156 @item half-standout
27157 Use half bright and standout mode.
27160 Use extra bright or bold mode.
27162 @item bold-standout
27163 Use extra bright or bold and standout mode.
27168 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27171 @cindex @sc{gnu} Emacs
27172 A special interface allows you to use @sc{gnu} Emacs to view (and
27173 edit) the source files for the program you are debugging with
27176 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27177 executable file you want to debug as an argument. This command starts
27178 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27179 created Emacs buffer.
27180 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27182 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27187 All ``terminal'' input and output goes through an Emacs buffer, called
27190 This applies both to @value{GDBN} commands and their output, and to the input
27191 and output done by the program you are debugging.
27193 This is useful because it means that you can copy the text of previous
27194 commands and input them again; you can even use parts of the output
27197 All the facilities of Emacs' Shell mode are available for interacting
27198 with your program. In particular, you can send signals the usual
27199 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27203 @value{GDBN} displays source code through Emacs.
27205 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27206 source file for that frame and puts an arrow (@samp{=>}) at the
27207 left margin of the current line. Emacs uses a separate buffer for
27208 source display, and splits the screen to show both your @value{GDBN} session
27211 Explicit @value{GDBN} @code{list} or search commands still produce output as
27212 usual, but you probably have no reason to use them from Emacs.
27215 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27216 a graphical mode, enabled by default, which provides further buffers
27217 that can control the execution and describe the state of your program.
27218 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27220 If you specify an absolute file name when prompted for the @kbd{M-x
27221 gdb} argument, then Emacs sets your current working directory to where
27222 your program resides. If you only specify the file name, then Emacs
27223 sets your current working directory to the directory associated
27224 with the previous buffer. In this case, @value{GDBN} may find your
27225 program by searching your environment's @code{PATH} variable, but on
27226 some operating systems it might not find the source. So, although the
27227 @value{GDBN} input and output session proceeds normally, the auxiliary
27228 buffer does not display the current source and line of execution.
27230 The initial working directory of @value{GDBN} is printed on the top
27231 line of the GUD buffer and this serves as a default for the commands
27232 that specify files for @value{GDBN} to operate on. @xref{Files,
27233 ,Commands to Specify Files}.
27235 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27236 need to call @value{GDBN} by a different name (for example, if you
27237 keep several configurations around, with different names) you can
27238 customize the Emacs variable @code{gud-gdb-command-name} to run the
27241 In the GUD buffer, you can use these special Emacs commands in
27242 addition to the standard Shell mode commands:
27246 Describe the features of Emacs' GUD Mode.
27249 Execute to another source line, like the @value{GDBN} @code{step} command; also
27250 update the display window to show the current file and location.
27253 Execute to next source line in this function, skipping all function
27254 calls, like the @value{GDBN} @code{next} command. Then update the display window
27255 to show the current file and location.
27258 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27259 display window accordingly.
27262 Execute until exit from the selected stack frame, like the @value{GDBN}
27263 @code{finish} command.
27266 Continue execution of your program, like the @value{GDBN} @code{continue}
27270 Go up the number of frames indicated by the numeric argument
27271 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27272 like the @value{GDBN} @code{up} command.
27275 Go down the number of frames indicated by the numeric argument, like the
27276 @value{GDBN} @code{down} command.
27279 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27280 tells @value{GDBN} to set a breakpoint on the source line point is on.
27282 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27283 separate frame which shows a backtrace when the GUD buffer is current.
27284 Move point to any frame in the stack and type @key{RET} to make it
27285 become the current frame and display the associated source in the
27286 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27287 selected frame become the current one. In graphical mode, the
27288 speedbar displays watch expressions.
27290 If you accidentally delete the source-display buffer, an easy way to get
27291 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27292 request a frame display; when you run under Emacs, this recreates
27293 the source buffer if necessary to show you the context of the current
27296 The source files displayed in Emacs are in ordinary Emacs buffers
27297 which are visiting the source files in the usual way. You can edit
27298 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27299 communicates with Emacs in terms of line numbers. If you add or
27300 delete lines from the text, the line numbers that @value{GDBN} knows cease
27301 to correspond properly with the code.
27303 A more detailed description of Emacs' interaction with @value{GDBN} is
27304 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27308 @chapter The @sc{gdb/mi} Interface
27310 @unnumberedsec Function and Purpose
27312 @cindex @sc{gdb/mi}, its purpose
27313 @sc{gdb/mi} is a line based machine oriented text interface to
27314 @value{GDBN} and is activated by specifying using the
27315 @option{--interpreter} command line option (@pxref{Mode Options}). It
27316 is specifically intended to support the development of systems which
27317 use the debugger as just one small component of a larger system.
27319 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27320 in the form of a reference manual.
27322 Note that @sc{gdb/mi} is still under construction, so some of the
27323 features described below are incomplete and subject to change
27324 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27326 @unnumberedsec Notation and Terminology
27328 @cindex notational conventions, for @sc{gdb/mi}
27329 This chapter uses the following notation:
27333 @code{|} separates two alternatives.
27336 @code{[ @var{something} ]} indicates that @var{something} is optional:
27337 it may or may not be given.
27340 @code{( @var{group} )*} means that @var{group} inside the parentheses
27341 may repeat zero or more times.
27344 @code{( @var{group} )+} means that @var{group} inside the parentheses
27345 may repeat one or more times.
27348 @code{"@var{string}"} means a literal @var{string}.
27352 @heading Dependencies
27356 * GDB/MI General Design::
27357 * GDB/MI Command Syntax::
27358 * GDB/MI Compatibility with CLI::
27359 * GDB/MI Development and Front Ends::
27360 * GDB/MI Output Records::
27361 * GDB/MI Simple Examples::
27362 * GDB/MI Command Description Format::
27363 * GDB/MI Breakpoint Commands::
27364 * GDB/MI Catchpoint Commands::
27365 * GDB/MI Program Context::
27366 * GDB/MI Thread Commands::
27367 * GDB/MI Ada Tasking Commands::
27368 * GDB/MI Program Execution::
27369 * GDB/MI Stack Manipulation::
27370 * GDB/MI Variable Objects::
27371 * GDB/MI Data Manipulation::
27372 * GDB/MI Tracepoint Commands::
27373 * GDB/MI Symbol Query::
27374 * GDB/MI File Commands::
27376 * GDB/MI Kod Commands::
27377 * GDB/MI Memory Overlay Commands::
27378 * GDB/MI Signal Handling Commands::
27380 * GDB/MI Target Manipulation::
27381 * GDB/MI File Transfer Commands::
27382 * GDB/MI Miscellaneous Commands::
27385 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27386 @node GDB/MI General Design
27387 @section @sc{gdb/mi} General Design
27388 @cindex GDB/MI General Design
27390 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27391 parts---commands sent to @value{GDBN}, responses to those commands
27392 and notifications. Each command results in exactly one response,
27393 indicating either successful completion of the command, or an error.
27394 For the commands that do not resume the target, the response contains the
27395 requested information. For the commands that resume the target, the
27396 response only indicates whether the target was successfully resumed.
27397 Notifications is the mechanism for reporting changes in the state of the
27398 target, or in @value{GDBN} state, that cannot conveniently be associated with
27399 a command and reported as part of that command response.
27401 The important examples of notifications are:
27405 Exec notifications. These are used to report changes in
27406 target state---when a target is resumed, or stopped. It would not
27407 be feasible to include this information in response of resuming
27408 commands, because one resume commands can result in multiple events in
27409 different threads. Also, quite some time may pass before any event
27410 happens in the target, while a frontend needs to know whether the resuming
27411 command itself was successfully executed.
27414 Console output, and status notifications. Console output
27415 notifications are used to report output of CLI commands, as well as
27416 diagnostics for other commands. Status notifications are used to
27417 report the progress of a long-running operation. Naturally, including
27418 this information in command response would mean no output is produced
27419 until the command is finished, which is undesirable.
27422 General notifications. Commands may have various side effects on
27423 the @value{GDBN} or target state beyond their official purpose. For example,
27424 a command may change the selected thread. Although such changes can
27425 be included in command response, using notification allows for more
27426 orthogonal frontend design.
27430 There's no guarantee that whenever an MI command reports an error,
27431 @value{GDBN} or the target are in any specific state, and especially,
27432 the state is not reverted to the state before the MI command was
27433 processed. Therefore, whenever an MI command results in an error,
27434 we recommend that the frontend refreshes all the information shown in
27435 the user interface.
27439 * Context management::
27440 * Asynchronous and non-stop modes::
27444 @node Context management
27445 @subsection Context management
27447 In most cases when @value{GDBN} accesses the target, this access is
27448 done in context of a specific thread and frame (@pxref{Frames}).
27449 Often, even when accessing global data, the target requires that a thread
27450 be specified. The CLI interface maintains the selected thread and frame,
27451 and supplies them to target on each command. This is convenient,
27452 because a command line user would not want to specify that information
27453 explicitly on each command, and because user interacts with
27454 @value{GDBN} via a single terminal, so no confusion is possible as
27455 to what thread and frame are the current ones.
27457 In the case of MI, the concept of selected thread and frame is less
27458 useful. First, a frontend can easily remember this information
27459 itself. Second, a graphical frontend can have more than one window,
27460 each one used for debugging a different thread, and the frontend might
27461 want to access additional threads for internal purposes. This
27462 increases the risk that by relying on implicitly selected thread, the
27463 frontend may be operating on a wrong one. Therefore, each MI command
27464 should explicitly specify which thread and frame to operate on. To
27465 make it possible, each MI command accepts the @samp{--thread} and
27466 @samp{--frame} options, the value to each is @value{GDBN} identifier
27467 for thread and frame to operate on.
27469 Usually, each top-level window in a frontend allows the user to select
27470 a thread and a frame, and remembers the user selection for further
27471 operations. However, in some cases @value{GDBN} may suggest that the
27472 current thread be changed. For example, when stopping on a breakpoint
27473 it is reasonable to switch to the thread where breakpoint is hit. For
27474 another example, if the user issues the CLI @samp{thread} command via
27475 the frontend, it is desirable to change the frontend's selected thread to the
27476 one specified by user. @value{GDBN} communicates the suggestion to
27477 change current thread using the @samp{=thread-selected} notification.
27478 No such notification is available for the selected frame at the moment.
27480 Note that historically, MI shares the selected thread with CLI, so
27481 frontends used the @code{-thread-select} to execute commands in the
27482 right context. However, getting this to work right is cumbersome. The
27483 simplest way is for frontend to emit @code{-thread-select} command
27484 before every command. This doubles the number of commands that need
27485 to be sent. The alternative approach is to suppress @code{-thread-select}
27486 if the selected thread in @value{GDBN} is supposed to be identical to the
27487 thread the frontend wants to operate on. However, getting this
27488 optimization right can be tricky. In particular, if the frontend
27489 sends several commands to @value{GDBN}, and one of the commands changes the
27490 selected thread, then the behaviour of subsequent commands will
27491 change. So, a frontend should either wait for response from such
27492 problematic commands, or explicitly add @code{-thread-select} for
27493 all subsequent commands. No frontend is known to do this exactly
27494 right, so it is suggested to just always pass the @samp{--thread} and
27495 @samp{--frame} options.
27497 @node Asynchronous and non-stop modes
27498 @subsection Asynchronous command execution and non-stop mode
27500 On some targets, @value{GDBN} is capable of processing MI commands
27501 even while the target is running. This is called @dfn{asynchronous
27502 command execution} (@pxref{Background Execution}). The frontend may
27503 specify a preferrence for asynchronous execution using the
27504 @code{-gdb-set target-async 1} command, which should be emitted before
27505 either running the executable or attaching to the target. After the
27506 frontend has started the executable or attached to the target, it can
27507 find if asynchronous execution is enabled using the
27508 @code{-list-target-features} command.
27510 Even if @value{GDBN} can accept a command while target is running,
27511 many commands that access the target do not work when the target is
27512 running. Therefore, asynchronous command execution is most useful
27513 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27514 it is possible to examine the state of one thread, while other threads
27517 When a given thread is running, MI commands that try to access the
27518 target in the context of that thread may not work, or may work only on
27519 some targets. In particular, commands that try to operate on thread's
27520 stack will not work, on any target. Commands that read memory, or
27521 modify breakpoints, may work or not work, depending on the target. Note
27522 that even commands that operate on global state, such as @code{print},
27523 @code{set}, and breakpoint commands, still access the target in the
27524 context of a specific thread, so frontend should try to find a
27525 stopped thread and perform the operation on that thread (using the
27526 @samp{--thread} option).
27528 Which commands will work in the context of a running thread is
27529 highly target dependent. However, the two commands
27530 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27531 to find the state of a thread, will always work.
27533 @node Thread groups
27534 @subsection Thread groups
27535 @value{GDBN} may be used to debug several processes at the same time.
27536 On some platfroms, @value{GDBN} may support debugging of several
27537 hardware systems, each one having several cores with several different
27538 processes running on each core. This section describes the MI
27539 mechanism to support such debugging scenarios.
27541 The key observation is that regardless of the structure of the
27542 target, MI can have a global list of threads, because most commands that
27543 accept the @samp{--thread} option do not need to know what process that
27544 thread belongs to. Therefore, it is not necessary to introduce
27545 neither additional @samp{--process} option, nor an notion of the
27546 current process in the MI interface. The only strictly new feature
27547 that is required is the ability to find how the threads are grouped
27550 To allow the user to discover such grouping, and to support arbitrary
27551 hierarchy of machines/cores/processes, MI introduces the concept of a
27552 @dfn{thread group}. Thread group is a collection of threads and other
27553 thread groups. A thread group always has a string identifier, a type,
27554 and may have additional attributes specific to the type. A new
27555 command, @code{-list-thread-groups}, returns the list of top-level
27556 thread groups, which correspond to processes that @value{GDBN} is
27557 debugging at the moment. By passing an identifier of a thread group
27558 to the @code{-list-thread-groups} command, it is possible to obtain
27559 the members of specific thread group.
27561 To allow the user to easily discover processes, and other objects, he
27562 wishes to debug, a concept of @dfn{available thread group} is
27563 introduced. Available thread group is an thread group that
27564 @value{GDBN} is not debugging, but that can be attached to, using the
27565 @code{-target-attach} command. The list of available top-level thread
27566 groups can be obtained using @samp{-list-thread-groups --available}.
27567 In general, the content of a thread group may be only retrieved only
27568 after attaching to that thread group.
27570 Thread groups are related to inferiors (@pxref{Inferiors and
27571 Programs}). Each inferior corresponds to a thread group of a special
27572 type @samp{process}, and some additional operations are permitted on
27573 such thread groups.
27575 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27576 @node GDB/MI Command Syntax
27577 @section @sc{gdb/mi} Command Syntax
27580 * GDB/MI Input Syntax::
27581 * GDB/MI Output Syntax::
27584 @node GDB/MI Input Syntax
27585 @subsection @sc{gdb/mi} Input Syntax
27587 @cindex input syntax for @sc{gdb/mi}
27588 @cindex @sc{gdb/mi}, input syntax
27590 @item @var{command} @expansion{}
27591 @code{@var{cli-command} | @var{mi-command}}
27593 @item @var{cli-command} @expansion{}
27594 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27595 @var{cli-command} is any existing @value{GDBN} CLI command.
27597 @item @var{mi-command} @expansion{}
27598 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27599 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27601 @item @var{token} @expansion{}
27602 "any sequence of digits"
27604 @item @var{option} @expansion{}
27605 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27607 @item @var{parameter} @expansion{}
27608 @code{@var{non-blank-sequence} | @var{c-string}}
27610 @item @var{operation} @expansion{}
27611 @emph{any of the operations described in this chapter}
27613 @item @var{non-blank-sequence} @expansion{}
27614 @emph{anything, provided it doesn't contain special characters such as
27615 "-", @var{nl}, """ and of course " "}
27617 @item @var{c-string} @expansion{}
27618 @code{""" @var{seven-bit-iso-c-string-content} """}
27620 @item @var{nl} @expansion{}
27629 The CLI commands are still handled by the @sc{mi} interpreter; their
27630 output is described below.
27633 The @code{@var{token}}, when present, is passed back when the command
27637 Some @sc{mi} commands accept optional arguments as part of the parameter
27638 list. Each option is identified by a leading @samp{-} (dash) and may be
27639 followed by an optional argument parameter. Options occur first in the
27640 parameter list and can be delimited from normal parameters using
27641 @samp{--} (this is useful when some parameters begin with a dash).
27648 We want easy access to the existing CLI syntax (for debugging).
27651 We want it to be easy to spot a @sc{mi} operation.
27654 @node GDB/MI Output Syntax
27655 @subsection @sc{gdb/mi} Output Syntax
27657 @cindex output syntax of @sc{gdb/mi}
27658 @cindex @sc{gdb/mi}, output syntax
27659 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27660 followed, optionally, by a single result record. This result record
27661 is for the most recent command. The sequence of output records is
27662 terminated by @samp{(gdb)}.
27664 If an input command was prefixed with a @code{@var{token}} then the
27665 corresponding output for that command will also be prefixed by that same
27669 @item @var{output} @expansion{}
27670 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27672 @item @var{result-record} @expansion{}
27673 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27675 @item @var{out-of-band-record} @expansion{}
27676 @code{@var{async-record} | @var{stream-record}}
27678 @item @var{async-record} @expansion{}
27679 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27681 @item @var{exec-async-output} @expansion{}
27682 @code{[ @var{token} ] "*" @var{async-output}}
27684 @item @var{status-async-output} @expansion{}
27685 @code{[ @var{token} ] "+" @var{async-output}}
27687 @item @var{notify-async-output} @expansion{}
27688 @code{[ @var{token} ] "=" @var{async-output}}
27690 @item @var{async-output} @expansion{}
27691 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27693 @item @var{result-class} @expansion{}
27694 @code{"done" | "running" | "connected" | "error" | "exit"}
27696 @item @var{async-class} @expansion{}
27697 @code{"stopped" | @var{others}} (where @var{others} will be added
27698 depending on the needs---this is still in development).
27700 @item @var{result} @expansion{}
27701 @code{ @var{variable} "=" @var{value}}
27703 @item @var{variable} @expansion{}
27704 @code{ @var{string} }
27706 @item @var{value} @expansion{}
27707 @code{ @var{const} | @var{tuple} | @var{list} }
27709 @item @var{const} @expansion{}
27710 @code{@var{c-string}}
27712 @item @var{tuple} @expansion{}
27713 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27715 @item @var{list} @expansion{}
27716 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27717 @var{result} ( "," @var{result} )* "]" }
27719 @item @var{stream-record} @expansion{}
27720 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27722 @item @var{console-stream-output} @expansion{}
27723 @code{"~" @var{c-string}}
27725 @item @var{target-stream-output} @expansion{}
27726 @code{"@@" @var{c-string}}
27728 @item @var{log-stream-output} @expansion{}
27729 @code{"&" @var{c-string}}
27731 @item @var{nl} @expansion{}
27734 @item @var{token} @expansion{}
27735 @emph{any sequence of digits}.
27743 All output sequences end in a single line containing a period.
27746 The @code{@var{token}} is from the corresponding request. Note that
27747 for all async output, while the token is allowed by the grammar and
27748 may be output by future versions of @value{GDBN} for select async
27749 output messages, it is generally omitted. Frontends should treat
27750 all async output as reporting general changes in the state of the
27751 target and there should be no need to associate async output to any
27755 @cindex status output in @sc{gdb/mi}
27756 @var{status-async-output} contains on-going status information about the
27757 progress of a slow operation. It can be discarded. All status output is
27758 prefixed by @samp{+}.
27761 @cindex async output in @sc{gdb/mi}
27762 @var{exec-async-output} contains asynchronous state change on the target
27763 (stopped, started, disappeared). All async output is prefixed by
27767 @cindex notify output in @sc{gdb/mi}
27768 @var{notify-async-output} contains supplementary information that the
27769 client should handle (e.g., a new breakpoint information). All notify
27770 output is prefixed by @samp{=}.
27773 @cindex console output in @sc{gdb/mi}
27774 @var{console-stream-output} is output that should be displayed as is in the
27775 console. It is the textual response to a CLI command. All the console
27776 output is prefixed by @samp{~}.
27779 @cindex target output in @sc{gdb/mi}
27780 @var{target-stream-output} is the output produced by the target program.
27781 All the target output is prefixed by @samp{@@}.
27784 @cindex log output in @sc{gdb/mi}
27785 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27786 instance messages that should be displayed as part of an error log. All
27787 the log output is prefixed by @samp{&}.
27790 @cindex list output in @sc{gdb/mi}
27791 New @sc{gdb/mi} commands should only output @var{lists} containing
27797 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27798 details about the various output records.
27800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27801 @node GDB/MI Compatibility with CLI
27802 @section @sc{gdb/mi} Compatibility with CLI
27804 @cindex compatibility, @sc{gdb/mi} and CLI
27805 @cindex @sc{gdb/mi}, compatibility with CLI
27807 For the developers convenience CLI commands can be entered directly,
27808 but there may be some unexpected behaviour. For example, commands
27809 that query the user will behave as if the user replied yes, breakpoint
27810 command lists are not executed and some CLI commands, such as
27811 @code{if}, @code{when} and @code{define}, prompt for further input with
27812 @samp{>}, which is not valid MI output.
27814 This feature may be removed at some stage in the future and it is
27815 recommended that front ends use the @code{-interpreter-exec} command
27816 (@pxref{-interpreter-exec}).
27818 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27819 @node GDB/MI Development and Front Ends
27820 @section @sc{gdb/mi} Development and Front Ends
27821 @cindex @sc{gdb/mi} development
27823 The application which takes the MI output and presents the state of the
27824 program being debugged to the user is called a @dfn{front end}.
27826 Although @sc{gdb/mi} is still incomplete, it is currently being used
27827 by a variety of front ends to @value{GDBN}. This makes it difficult
27828 to introduce new functionality without breaking existing usage. This
27829 section tries to minimize the problems by describing how the protocol
27832 Some changes in MI need not break a carefully designed front end, and
27833 for these the MI version will remain unchanged. The following is a
27834 list of changes that may occur within one level, so front ends should
27835 parse MI output in a way that can handle them:
27839 New MI commands may be added.
27842 New fields may be added to the output of any MI command.
27845 The range of values for fields with specified values, e.g.,
27846 @code{in_scope} (@pxref{-var-update}) may be extended.
27848 @c The format of field's content e.g type prefix, may change so parse it
27849 @c at your own risk. Yes, in general?
27851 @c The order of fields may change? Shouldn't really matter but it might
27852 @c resolve inconsistencies.
27855 If the changes are likely to break front ends, the MI version level
27856 will be increased by one. This will allow the front end to parse the
27857 output according to the MI version. Apart from mi0, new versions of
27858 @value{GDBN} will not support old versions of MI and it will be the
27859 responsibility of the front end to work with the new one.
27861 @c Starting with mi3, add a new command -mi-version that prints the MI
27864 The best way to avoid unexpected changes in MI that might break your front
27865 end is to make your project known to @value{GDBN} developers and
27866 follow development on @email{gdb@@sourceware.org} and
27867 @email{gdb-patches@@sourceware.org}.
27868 @cindex mailing lists
27870 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27871 @node GDB/MI Output Records
27872 @section @sc{gdb/mi} Output Records
27875 * GDB/MI Result Records::
27876 * GDB/MI Stream Records::
27877 * GDB/MI Async Records::
27878 * GDB/MI Breakpoint Information::
27879 * GDB/MI Frame Information::
27880 * GDB/MI Thread Information::
27881 * GDB/MI Ada Exception Information::
27884 @node GDB/MI Result Records
27885 @subsection @sc{gdb/mi} Result Records
27887 @cindex result records in @sc{gdb/mi}
27888 @cindex @sc{gdb/mi}, result records
27889 In addition to a number of out-of-band notifications, the response to a
27890 @sc{gdb/mi} command includes one of the following result indications:
27894 @item "^done" [ "," @var{results} ]
27895 The synchronous operation was successful, @code{@var{results}} are the return
27900 This result record is equivalent to @samp{^done}. Historically, it
27901 was output instead of @samp{^done} if the command has resumed the
27902 target. This behaviour is maintained for backward compatibility, but
27903 all frontends should treat @samp{^done} and @samp{^running}
27904 identically and rely on the @samp{*running} output record to determine
27905 which threads are resumed.
27909 @value{GDBN} has connected to a remote target.
27911 @item "^error" "," @var{c-string}
27913 The operation failed. The @code{@var{c-string}} contains the corresponding
27918 @value{GDBN} has terminated.
27922 @node GDB/MI Stream Records
27923 @subsection @sc{gdb/mi} Stream Records
27925 @cindex @sc{gdb/mi}, stream records
27926 @cindex stream records in @sc{gdb/mi}
27927 @value{GDBN} internally maintains a number of output streams: the console, the
27928 target, and the log. The output intended for each of these streams is
27929 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27931 Each stream record begins with a unique @dfn{prefix character} which
27932 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27933 Syntax}). In addition to the prefix, each stream record contains a
27934 @code{@var{string-output}}. This is either raw text (with an implicit new
27935 line) or a quoted C string (which does not contain an implicit newline).
27938 @item "~" @var{string-output}
27939 The console output stream contains text that should be displayed in the
27940 CLI console window. It contains the textual responses to CLI commands.
27942 @item "@@" @var{string-output}
27943 The target output stream contains any textual output from the running
27944 target. This is only present when GDB's event loop is truly
27945 asynchronous, which is currently only the case for remote targets.
27947 @item "&" @var{string-output}
27948 The log stream contains debugging messages being produced by @value{GDBN}'s
27952 @node GDB/MI Async Records
27953 @subsection @sc{gdb/mi} Async Records
27955 @cindex async records in @sc{gdb/mi}
27956 @cindex @sc{gdb/mi}, async records
27957 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27958 additional changes that have occurred. Those changes can either be a
27959 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27960 target activity (e.g., target stopped).
27962 The following is the list of possible async records:
27966 @item *running,thread-id="@var{thread}"
27967 The target is now running. The @var{thread} field tells which
27968 specific thread is now running, and can be @samp{all} if all threads
27969 are running. The frontend should assume that no interaction with a
27970 running thread is possible after this notification is produced.
27971 The frontend should not assume that this notification is output
27972 only once for any command. @value{GDBN} may emit this notification
27973 several times, either for different threads, because it cannot resume
27974 all threads together, or even for a single thread, if the thread must
27975 be stepped though some code before letting it run freely.
27977 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27978 The target has stopped. The @var{reason} field can have one of the
27982 @item breakpoint-hit
27983 A breakpoint was reached.
27984 @item watchpoint-trigger
27985 A watchpoint was triggered.
27986 @item read-watchpoint-trigger
27987 A read watchpoint was triggered.
27988 @item access-watchpoint-trigger
27989 An access watchpoint was triggered.
27990 @item function-finished
27991 An -exec-finish or similar CLI command was accomplished.
27992 @item location-reached
27993 An -exec-until or similar CLI command was accomplished.
27994 @item watchpoint-scope
27995 A watchpoint has gone out of scope.
27996 @item end-stepping-range
27997 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27998 similar CLI command was accomplished.
27999 @item exited-signalled
28000 The inferior exited because of a signal.
28002 The inferior exited.
28003 @item exited-normally
28004 The inferior exited normally.
28005 @item signal-received
28006 A signal was received by the inferior.
28008 The inferior has stopped due to a library being loaded or unloaded.
28009 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28010 set or when a @code{catch load} or @code{catch unload} catchpoint is
28011 in use (@pxref{Set Catchpoints}).
28013 The inferior has forked. This is reported when @code{catch fork}
28014 (@pxref{Set Catchpoints}) has been used.
28016 The inferior has vforked. This is reported in when @code{catch vfork}
28017 (@pxref{Set Catchpoints}) has been used.
28018 @item syscall-entry
28019 The inferior entered a system call. This is reported when @code{catch
28020 syscall} (@pxref{Set Catchpoints}) has been used.
28021 @item syscall-entry
28022 The inferior returned from a system call. This is reported when
28023 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28025 The inferior called @code{exec}. This is reported when @code{catch exec}
28026 (@pxref{Set Catchpoints}) has been used.
28029 The @var{id} field identifies the thread that directly caused the stop
28030 -- for example by hitting a breakpoint. Depending on whether all-stop
28031 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28032 stop all threads, or only the thread that directly triggered the stop.
28033 If all threads are stopped, the @var{stopped} field will have the
28034 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28035 field will be a list of thread identifiers. Presently, this list will
28036 always include a single thread, but frontend should be prepared to see
28037 several threads in the list. The @var{core} field reports the
28038 processor core on which the stop event has happened. This field may be absent
28039 if such information is not available.
28041 @item =thread-group-added,id="@var{id}"
28042 @itemx =thread-group-removed,id="@var{id}"
28043 A thread group was either added or removed. The @var{id} field
28044 contains the @value{GDBN} identifier of the thread group. When a thread
28045 group is added, it generally might not be associated with a running
28046 process. When a thread group is removed, its id becomes invalid and
28047 cannot be used in any way.
28049 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28050 A thread group became associated with a running program,
28051 either because the program was just started or the thread group
28052 was attached to a program. The @var{id} field contains the
28053 @value{GDBN} identifier of the thread group. The @var{pid} field
28054 contains process identifier, specific to the operating system.
28056 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28057 A thread group is no longer associated with a running program,
28058 either because the program has exited, or because it was detached
28059 from. The @var{id} field contains the @value{GDBN} identifier of the
28060 thread group. @var{code} is the exit code of the inferior; it exists
28061 only when the inferior exited with some code.
28063 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28064 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28065 A thread either was created, or has exited. The @var{id} field
28066 contains the @value{GDBN} identifier of the thread. The @var{gid}
28067 field identifies the thread group this thread belongs to.
28069 @item =thread-selected,id="@var{id}"
28070 Informs that the selected thread was changed as result of the last
28071 command. This notification is not emitted as result of @code{-thread-select}
28072 command but is emitted whenever an MI command that is not documented
28073 to change the selected thread actually changes it. In particular,
28074 invoking, directly or indirectly (via user-defined command), the CLI
28075 @code{thread} command, will generate this notification.
28077 We suggest that in response to this notification, front ends
28078 highlight the selected thread and cause subsequent commands to apply to
28081 @item =library-loaded,...
28082 Reports that a new library file was loaded by the program. This
28083 notification has 4 fields---@var{id}, @var{target-name},
28084 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
28085 opaque identifier of the library. For remote debugging case,
28086 @var{target-name} and @var{host-name} fields give the name of the
28087 library file on the target, and on the host respectively. For native
28088 debugging, both those fields have the same value. The
28089 @var{symbols-loaded} field is emitted only for backward compatibility
28090 and should not be relied on to convey any useful information. The
28091 @var{thread-group} field, if present, specifies the id of the thread
28092 group in whose context the library was loaded. If the field is
28093 absent, it means the library was loaded in the context of all present
28096 @item =library-unloaded,...
28097 Reports that a library was unloaded by the program. This notification
28098 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28099 the same meaning as for the @code{=library-loaded} notification.
28100 The @var{thread-group} field, if present, specifies the id of the
28101 thread group in whose context the library was unloaded. If the field is
28102 absent, it means the library was unloaded in the context of all present
28105 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28106 @itemx =traceframe-changed,end
28107 Reports that the trace frame was changed and its new number is
28108 @var{tfnum}. The number of the tracepoint associated with this trace
28109 frame is @var{tpnum}.
28111 @item =tsv-created,name=@var{name},initial=@var{initial}
28112 Reports that the new trace state variable @var{name} is created with
28113 initial value @var{initial}.
28115 @item =tsv-deleted,name=@var{name}
28116 @itemx =tsv-deleted
28117 Reports that the trace state variable @var{name} is deleted or all
28118 trace state variables are deleted.
28120 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28121 Reports that the trace state variable @var{name} is modified with
28122 the initial value @var{initial}. The current value @var{current} of
28123 trace state variable is optional and is reported if the current
28124 value of trace state variable is known.
28126 @item =breakpoint-created,bkpt=@{...@}
28127 @itemx =breakpoint-modified,bkpt=@{...@}
28128 @itemx =breakpoint-deleted,id=@var{number}
28129 Reports that a breakpoint was created, modified, or deleted,
28130 respectively. Only user-visible breakpoints are reported to the MI
28133 The @var{bkpt} argument is of the same form as returned by the various
28134 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28135 @var{number} is the ordinal number of the breakpoint.
28137 Note that if a breakpoint is emitted in the result record of a
28138 command, then it will not also be emitted in an async record.
28140 @item =record-started,thread-group="@var{id}"
28141 @itemx =record-stopped,thread-group="@var{id}"
28142 Execution log recording was either started or stopped on an
28143 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28144 group corresponding to the affected inferior.
28146 @item =cmd-param-changed,param=@var{param},value=@var{value}
28147 Reports that a parameter of the command @code{set @var{param}} is
28148 changed to @var{value}. In the multi-word @code{set} command,
28149 the @var{param} is the whole parameter list to @code{set} command.
28150 For example, In command @code{set check type on}, @var{param}
28151 is @code{check type} and @var{value} is @code{on}.
28153 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28154 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28155 written in an inferior. The @var{id} is the identifier of the
28156 thread group corresponding to the affected inferior. The optional
28157 @code{type="code"} part is reported if the memory written to holds
28161 @node GDB/MI Breakpoint Information
28162 @subsection @sc{gdb/mi} Breakpoint Information
28164 When @value{GDBN} reports information about a breakpoint, a
28165 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28170 The breakpoint number. For a breakpoint that represents one location
28171 of a multi-location breakpoint, this will be a dotted pair, like
28175 The type of the breakpoint. For ordinary breakpoints this will be
28176 @samp{breakpoint}, but many values are possible.
28179 If the type of the breakpoint is @samp{catchpoint}, then this
28180 indicates the exact type of catchpoint.
28183 This is the breakpoint disposition---either @samp{del}, meaning that
28184 the breakpoint will be deleted at the next stop, or @samp{keep},
28185 meaning that the breakpoint will not be deleted.
28188 This indicates whether the breakpoint is enabled, in which case the
28189 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28190 Note that this is not the same as the field @code{enable}.
28193 The address of the breakpoint. This may be a hexidecimal number,
28194 giving the address; or the string @samp{<PENDING>}, for a pending
28195 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28196 multiple locations. This field will not be present if no address can
28197 be determined. For example, a watchpoint does not have an address.
28200 If known, the function in which the breakpoint appears.
28201 If not known, this field is not present.
28204 The name of the source file which contains this function, if known.
28205 If not known, this field is not present.
28208 The full file name of the source file which contains this function, if
28209 known. If not known, this field is not present.
28212 The line number at which this breakpoint appears, if known.
28213 If not known, this field is not present.
28216 If the source file is not known, this field may be provided. If
28217 provided, this holds the address of the breakpoint, possibly followed
28221 If this breakpoint is pending, this field is present and holds the
28222 text used to set the breakpoint, as entered by the user.
28225 Where this breakpoint's condition is evaluated, either @samp{host} or
28229 If this is a thread-specific breakpoint, then this identifies the
28230 thread in which the breakpoint can trigger.
28233 If this breakpoint is restricted to a particular Ada task, then this
28234 field will hold the task identifier.
28237 If the breakpoint is conditional, this is the condition expression.
28240 The ignore count of the breakpoint.
28243 The enable count of the breakpoint.
28245 @item traceframe-usage
28248 @item static-tracepoint-marker-string-id
28249 For a static tracepoint, the name of the static tracepoint marker.
28252 For a masked watchpoint, this is the mask.
28255 A tracepoint's pass count.
28257 @item original-location
28258 The location of the breakpoint as originally specified by the user.
28259 This field is optional.
28262 The number of times the breakpoint has been hit.
28265 This field is only given for tracepoints. This is either @samp{y},
28266 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28270 Some extra data, the exact contents of which are type-dependent.
28274 For example, here is what the output of @code{-break-insert}
28275 (@pxref{GDB/MI Breakpoint Commands}) might be:
28278 -> -break-insert main
28279 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28280 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28281 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28286 @node GDB/MI Frame Information
28287 @subsection @sc{gdb/mi} Frame Information
28289 Response from many MI commands includes an information about stack
28290 frame. This information is a tuple that may have the following
28295 The level of the stack frame. The innermost frame has the level of
28296 zero. This field is always present.
28299 The name of the function corresponding to the frame. This field may
28300 be absent if @value{GDBN} is unable to determine the function name.
28303 The code address for the frame. This field is always present.
28306 The name of the source files that correspond to the frame's code
28307 address. This field may be absent.
28310 The source line corresponding to the frames' code address. This field
28314 The name of the binary file (either executable or shared library) the
28315 corresponds to the frame's code address. This field may be absent.
28319 @node GDB/MI Thread Information
28320 @subsection @sc{gdb/mi} Thread Information
28322 Whenever @value{GDBN} has to report an information about a thread, it
28323 uses a tuple with the following fields:
28327 The numeric id assigned to the thread by @value{GDBN}. This field is
28331 Target-specific string identifying the thread. This field is always present.
28334 Additional information about the thread provided by the target.
28335 It is supposed to be human-readable and not interpreted by the
28336 frontend. This field is optional.
28339 Either @samp{stopped} or @samp{running}, depending on whether the
28340 thread is presently running. This field is always present.
28343 The value of this field is an integer number of the processor core the
28344 thread was last seen on. This field is optional.
28347 @node GDB/MI Ada Exception Information
28348 @subsection @sc{gdb/mi} Ada Exception Information
28350 Whenever a @code{*stopped} record is emitted because the program
28351 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28352 @value{GDBN} provides the name of the exception that was raised via
28353 the @code{exception-name} field.
28355 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28356 @node GDB/MI Simple Examples
28357 @section Simple Examples of @sc{gdb/mi} Interaction
28358 @cindex @sc{gdb/mi}, simple examples
28360 This subsection presents several simple examples of interaction using
28361 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28362 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28363 the output received from @sc{gdb/mi}.
28365 Note the line breaks shown in the examples are here only for
28366 readability, they don't appear in the real output.
28368 @subheading Setting a Breakpoint
28370 Setting a breakpoint generates synchronous output which contains detailed
28371 information of the breakpoint.
28374 -> -break-insert main
28375 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28376 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28377 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28382 @subheading Program Execution
28384 Program execution generates asynchronous records and MI gives the
28385 reason that execution stopped.
28391 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28392 frame=@{addr="0x08048564",func="main",
28393 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28394 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28399 <- *stopped,reason="exited-normally"
28403 @subheading Quitting @value{GDBN}
28405 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28413 Please note that @samp{^exit} is printed immediately, but it might
28414 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28415 performs necessary cleanups, including killing programs being debugged
28416 or disconnecting from debug hardware, so the frontend should wait till
28417 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28418 fails to exit in reasonable time.
28420 @subheading A Bad Command
28422 Here's what happens if you pass a non-existent command:
28426 <- ^error,msg="Undefined MI command: rubbish"
28431 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28432 @node GDB/MI Command Description Format
28433 @section @sc{gdb/mi} Command Description Format
28435 The remaining sections describe blocks of commands. Each block of
28436 commands is laid out in a fashion similar to this section.
28438 @subheading Motivation
28440 The motivation for this collection of commands.
28442 @subheading Introduction
28444 A brief introduction to this collection of commands as a whole.
28446 @subheading Commands
28448 For each command in the block, the following is described:
28450 @subsubheading Synopsis
28453 -command @var{args}@dots{}
28456 @subsubheading Result
28458 @subsubheading @value{GDBN} Command
28460 The corresponding @value{GDBN} CLI command(s), if any.
28462 @subsubheading Example
28464 Example(s) formatted for readability. Some of the described commands have
28465 not been implemented yet and these are labeled N.A.@: (not available).
28468 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28469 @node GDB/MI Breakpoint Commands
28470 @section @sc{gdb/mi} Breakpoint Commands
28472 @cindex breakpoint commands for @sc{gdb/mi}
28473 @cindex @sc{gdb/mi}, breakpoint commands
28474 This section documents @sc{gdb/mi} commands for manipulating
28477 @subheading The @code{-break-after} Command
28478 @findex -break-after
28480 @subsubheading Synopsis
28483 -break-after @var{number} @var{count}
28486 The breakpoint number @var{number} is not in effect until it has been
28487 hit @var{count} times. To see how this is reflected in the output of
28488 the @samp{-break-list} command, see the description of the
28489 @samp{-break-list} command below.
28491 @subsubheading @value{GDBN} Command
28493 The corresponding @value{GDBN} command is @samp{ignore}.
28495 @subsubheading Example
28500 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28501 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28502 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28510 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28511 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28512 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28513 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28514 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28515 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28516 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28517 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28518 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28519 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28524 @subheading The @code{-break-catch} Command
28525 @findex -break-catch
28528 @subheading The @code{-break-commands} Command
28529 @findex -break-commands
28531 @subsubheading Synopsis
28534 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28537 Specifies the CLI commands that should be executed when breakpoint
28538 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28539 are the commands. If no command is specified, any previously-set
28540 commands are cleared. @xref{Break Commands}. Typical use of this
28541 functionality is tracing a program, that is, printing of values of
28542 some variables whenever breakpoint is hit and then continuing.
28544 @subsubheading @value{GDBN} Command
28546 The corresponding @value{GDBN} command is @samp{commands}.
28548 @subsubheading Example
28553 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28554 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28555 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28558 -break-commands 1 "print v" "continue"
28563 @subheading The @code{-break-condition} Command
28564 @findex -break-condition
28566 @subsubheading Synopsis
28569 -break-condition @var{number} @var{expr}
28572 Breakpoint @var{number} will stop the program only if the condition in
28573 @var{expr} is true. The condition becomes part of the
28574 @samp{-break-list} output (see the description of the @samp{-break-list}
28577 @subsubheading @value{GDBN} Command
28579 The corresponding @value{GDBN} command is @samp{condition}.
28581 @subsubheading Example
28585 -break-condition 1 1
28589 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28590 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28591 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28592 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28593 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28594 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28595 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28596 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28597 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28598 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28602 @subheading The @code{-break-delete} Command
28603 @findex -break-delete
28605 @subsubheading Synopsis
28608 -break-delete ( @var{breakpoint} )+
28611 Delete the breakpoint(s) whose number(s) are specified in the argument
28612 list. This is obviously reflected in the breakpoint list.
28614 @subsubheading @value{GDBN} Command
28616 The corresponding @value{GDBN} command is @samp{delete}.
28618 @subsubheading Example
28626 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28627 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28628 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28629 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28630 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28631 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28632 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28637 @subheading The @code{-break-disable} Command
28638 @findex -break-disable
28640 @subsubheading Synopsis
28643 -break-disable ( @var{breakpoint} )+
28646 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28647 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28649 @subsubheading @value{GDBN} Command
28651 The corresponding @value{GDBN} command is @samp{disable}.
28653 @subsubheading Example
28661 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28662 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28663 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28664 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28665 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28666 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28667 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28668 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28669 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28670 line="5",thread-groups=["i1"],times="0"@}]@}
28674 @subheading The @code{-break-enable} Command
28675 @findex -break-enable
28677 @subsubheading Synopsis
28680 -break-enable ( @var{breakpoint} )+
28683 Enable (previously disabled) @var{breakpoint}(s).
28685 @subsubheading @value{GDBN} Command
28687 The corresponding @value{GDBN} command is @samp{enable}.
28689 @subsubheading Example
28697 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28698 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28699 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28700 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28701 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28702 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28703 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28704 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28705 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28706 line="5",thread-groups=["i1"],times="0"@}]@}
28710 @subheading The @code{-break-info} Command
28711 @findex -break-info
28713 @subsubheading Synopsis
28716 -break-info @var{breakpoint}
28720 Get information about a single breakpoint.
28722 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28723 Information}, for details on the format of each breakpoint in the
28726 @subsubheading @value{GDBN} Command
28728 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28730 @subsubheading Example
28733 @subheading The @code{-break-insert} Command
28734 @findex -break-insert
28736 @subsubheading Synopsis
28739 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28740 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28741 [ -p @var{thread-id} ] [ @var{location} ]
28745 If specified, @var{location}, can be one of:
28752 @item filename:linenum
28753 @item filename:function
28757 The possible optional parameters of this command are:
28761 Insert a temporary breakpoint.
28763 Insert a hardware breakpoint.
28765 If @var{location} cannot be parsed (for example if it
28766 refers to unknown files or functions), create a pending
28767 breakpoint. Without this flag, @value{GDBN} will report
28768 an error, and won't create a breakpoint, if @var{location}
28771 Create a disabled breakpoint.
28773 Create a tracepoint. @xref{Tracepoints}. When this parameter
28774 is used together with @samp{-h}, a fast tracepoint is created.
28775 @item -c @var{condition}
28776 Make the breakpoint conditional on @var{condition}.
28777 @item -i @var{ignore-count}
28778 Initialize the @var{ignore-count}.
28779 @item -p @var{thread-id}
28780 Restrict the breakpoint to the specified @var{thread-id}.
28783 @subsubheading Result
28785 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28786 resulting breakpoint.
28788 Note: this format is open to change.
28789 @c An out-of-band breakpoint instead of part of the result?
28791 @subsubheading @value{GDBN} Command
28793 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28794 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28796 @subsubheading Example
28801 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28802 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28805 -break-insert -t foo
28806 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28807 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28811 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28812 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28813 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28814 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28815 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28816 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28817 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28818 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28819 addr="0x0001072c", func="main",file="recursive2.c",
28820 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28822 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28823 addr="0x00010774",func="foo",file="recursive2.c",
28824 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28827 @c -break-insert -r foo.*
28828 @c ~int foo(int, int);
28829 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28830 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28835 @subheading The @code{-break-list} Command
28836 @findex -break-list
28838 @subsubheading Synopsis
28844 Displays the list of inserted breakpoints, showing the following fields:
28848 number of the breakpoint
28850 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28852 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28855 is the breakpoint enabled or no: @samp{y} or @samp{n}
28857 memory location at which the breakpoint is set
28859 logical location of the breakpoint, expressed by function name, file
28861 @item Thread-groups
28862 list of thread groups to which this breakpoint applies
28864 number of times the breakpoint has been hit
28867 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28868 @code{body} field is an empty list.
28870 @subsubheading @value{GDBN} Command
28872 The corresponding @value{GDBN} command is @samp{info break}.
28874 @subsubheading Example
28879 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28880 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28881 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28882 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28883 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28884 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28885 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28886 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28887 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28889 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28890 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28891 line="13",thread-groups=["i1"],times="0"@}]@}
28895 Here's an example of the result when there are no breakpoints:
28900 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28901 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28902 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28903 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28904 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28905 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28906 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28911 @subheading The @code{-break-passcount} Command
28912 @findex -break-passcount
28914 @subsubheading Synopsis
28917 -break-passcount @var{tracepoint-number} @var{passcount}
28920 Set the passcount for tracepoint @var{tracepoint-number} to
28921 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28922 is not a tracepoint, error is emitted. This corresponds to CLI
28923 command @samp{passcount}.
28925 @subheading The @code{-break-watch} Command
28926 @findex -break-watch
28928 @subsubheading Synopsis
28931 -break-watch [ -a | -r ]
28934 Create a watchpoint. With the @samp{-a} option it will create an
28935 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28936 read from or on a write to the memory location. With the @samp{-r}
28937 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28938 trigger only when the memory location is accessed for reading. Without
28939 either of the options, the watchpoint created is a regular watchpoint,
28940 i.e., it will trigger when the memory location is accessed for writing.
28941 @xref{Set Watchpoints, , Setting Watchpoints}.
28943 Note that @samp{-break-list} will report a single list of watchpoints and
28944 breakpoints inserted.
28946 @subsubheading @value{GDBN} Command
28948 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28951 @subsubheading Example
28953 Setting a watchpoint on a variable in the @code{main} function:
28958 ^done,wpt=@{number="2",exp="x"@}
28963 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28964 value=@{old="-268439212",new="55"@},
28965 frame=@{func="main",args=[],file="recursive2.c",
28966 fullname="/home/foo/bar/recursive2.c",line="5"@}
28970 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28971 the program execution twice: first for the variable changing value, then
28972 for the watchpoint going out of scope.
28977 ^done,wpt=@{number="5",exp="C"@}
28982 *stopped,reason="watchpoint-trigger",
28983 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28984 frame=@{func="callee4",args=[],
28985 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28986 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28991 *stopped,reason="watchpoint-scope",wpnum="5",
28992 frame=@{func="callee3",args=[@{name="strarg",
28993 value="0x11940 \"A string argument.\""@}],
28994 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28995 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28999 Listing breakpoints and watchpoints, at different points in the program
29000 execution. Note that once the watchpoint goes out of scope, it is
29006 ^done,wpt=@{number="2",exp="C"@}
29009 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29010 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29011 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29012 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29013 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29014 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29015 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29016 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29017 addr="0x00010734",func="callee4",
29018 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29019 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29021 bkpt=@{number="2",type="watchpoint",disp="keep",
29022 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29027 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29028 value=@{old="-276895068",new="3"@},
29029 frame=@{func="callee4",args=[],
29030 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29031 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29034 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29035 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29036 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29037 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29038 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29039 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29040 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29041 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29042 addr="0x00010734",func="callee4",
29043 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29044 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29046 bkpt=@{number="2",type="watchpoint",disp="keep",
29047 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29051 ^done,reason="watchpoint-scope",wpnum="2",
29052 frame=@{func="callee3",args=[@{name="strarg",
29053 value="0x11940 \"A string argument.\""@}],
29054 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29055 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29058 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29059 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29060 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29061 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29062 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29063 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29064 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29065 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29066 addr="0x00010734",func="callee4",
29067 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29068 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29069 thread-groups=["i1"],times="1"@}]@}
29074 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29075 @node GDB/MI Catchpoint Commands
29076 @section @sc{gdb/mi} Catchpoint Commands
29078 This section documents @sc{gdb/mi} commands for manipulating
29081 @subheading The @code{-catch-load} Command
29082 @findex -catch-load
29084 @subsubheading Synopsis
29087 -catch-load [ -t ] [ -d ] @var{regexp}
29090 Add a catchpoint for library load events. If the @samp{-t} option is used,
29091 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29092 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29093 in a disabled state. The @samp{regexp} argument is a regular
29094 expression used to match the name of the loaded library.
29097 @subsubheading @value{GDBN} Command
29099 The corresponding @value{GDBN} command is @samp{catch load}.
29101 @subsubheading Example
29104 -catch-load -t foo.so
29105 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29106 what="load of library matching foo.so",catch-type="load",times="0"@}
29111 @subheading The @code{-catch-unload} Command
29112 @findex -catch-unload
29114 @subsubheading Synopsis
29117 -catch-unload [ -t ] [ -d ] @var{regexp}
29120 Add a catchpoint for library unload events. If the @samp{-t} option is
29121 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29122 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29123 created in a disabled state. The @samp{regexp} argument is a regular
29124 expression used to match the name of the unloaded library.
29126 @subsubheading @value{GDBN} Command
29128 The corresponding @value{GDBN} command is @samp{catch unload}.
29130 @subsubheading Example
29133 -catch-unload -d bar.so
29134 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29135 what="load of library matching bar.so",catch-type="unload",times="0"@}
29140 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29141 @node GDB/MI Program Context
29142 @section @sc{gdb/mi} Program Context
29144 @subheading The @code{-exec-arguments} Command
29145 @findex -exec-arguments
29148 @subsubheading Synopsis
29151 -exec-arguments @var{args}
29154 Set the inferior program arguments, to be used in the next
29157 @subsubheading @value{GDBN} Command
29159 The corresponding @value{GDBN} command is @samp{set args}.
29161 @subsubheading Example
29165 -exec-arguments -v word
29172 @subheading The @code{-exec-show-arguments} Command
29173 @findex -exec-show-arguments
29175 @subsubheading Synopsis
29178 -exec-show-arguments
29181 Print the arguments of the program.
29183 @subsubheading @value{GDBN} Command
29185 The corresponding @value{GDBN} command is @samp{show args}.
29187 @subsubheading Example
29192 @subheading The @code{-environment-cd} Command
29193 @findex -environment-cd
29195 @subsubheading Synopsis
29198 -environment-cd @var{pathdir}
29201 Set @value{GDBN}'s working directory.
29203 @subsubheading @value{GDBN} Command
29205 The corresponding @value{GDBN} command is @samp{cd}.
29207 @subsubheading Example
29211 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29217 @subheading The @code{-environment-directory} Command
29218 @findex -environment-directory
29220 @subsubheading Synopsis
29223 -environment-directory [ -r ] [ @var{pathdir} ]+
29226 Add directories @var{pathdir} to beginning of search path for source files.
29227 If the @samp{-r} option is used, the search path is reset to the default
29228 search path. If directories @var{pathdir} are supplied in addition to the
29229 @samp{-r} option, the search path is first reset and then addition
29231 Multiple directories may be specified, separated by blanks. Specifying
29232 multiple directories in a single command
29233 results in the directories added to the beginning of the
29234 search path in the same order they were presented in the command.
29235 If blanks are needed as
29236 part of a directory name, double-quotes should be used around
29237 the name. In the command output, the path will show up separated
29238 by the system directory-separator character. The directory-separator
29239 character must not be used
29240 in any directory name.
29241 If no directories are specified, the current search path is displayed.
29243 @subsubheading @value{GDBN} Command
29245 The corresponding @value{GDBN} command is @samp{dir}.
29247 @subsubheading Example
29251 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29252 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29254 -environment-directory ""
29255 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29257 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29258 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29260 -environment-directory -r
29261 ^done,source-path="$cdir:$cwd"
29266 @subheading The @code{-environment-path} Command
29267 @findex -environment-path
29269 @subsubheading Synopsis
29272 -environment-path [ -r ] [ @var{pathdir} ]+
29275 Add directories @var{pathdir} to beginning of search path for object files.
29276 If the @samp{-r} option is used, the search path is reset to the original
29277 search path that existed at gdb start-up. If directories @var{pathdir} are
29278 supplied in addition to the
29279 @samp{-r} option, the search path is first reset and then addition
29281 Multiple directories may be specified, separated by blanks. Specifying
29282 multiple directories in a single command
29283 results in the directories added to the beginning of the
29284 search path in the same order they were presented in the command.
29285 If blanks are needed as
29286 part of a directory name, double-quotes should be used around
29287 the name. In the command output, the path will show up separated
29288 by the system directory-separator character. The directory-separator
29289 character must not be used
29290 in any directory name.
29291 If no directories are specified, the current path is displayed.
29294 @subsubheading @value{GDBN} Command
29296 The corresponding @value{GDBN} command is @samp{path}.
29298 @subsubheading Example
29303 ^done,path="/usr/bin"
29305 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29306 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29308 -environment-path -r /usr/local/bin
29309 ^done,path="/usr/local/bin:/usr/bin"
29314 @subheading The @code{-environment-pwd} Command
29315 @findex -environment-pwd
29317 @subsubheading Synopsis
29323 Show the current working directory.
29325 @subsubheading @value{GDBN} Command
29327 The corresponding @value{GDBN} command is @samp{pwd}.
29329 @subsubheading Example
29334 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29338 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29339 @node GDB/MI Thread Commands
29340 @section @sc{gdb/mi} Thread Commands
29343 @subheading The @code{-thread-info} Command
29344 @findex -thread-info
29346 @subsubheading Synopsis
29349 -thread-info [ @var{thread-id} ]
29352 Reports information about either a specific thread, if
29353 the @var{thread-id} parameter is present, or about all
29354 threads. When printing information about all threads,
29355 also reports the current thread.
29357 @subsubheading @value{GDBN} Command
29359 The @samp{info thread} command prints the same information
29362 @subsubheading Result
29364 The result is a list of threads. The following attributes are
29365 defined for a given thread:
29369 This field exists only for the current thread. It has the value @samp{*}.
29372 The identifier that @value{GDBN} uses to refer to the thread.
29375 The identifier that the target uses to refer to the thread.
29378 Extra information about the thread, in a target-specific format. This
29382 The name of the thread. If the user specified a name using the
29383 @code{thread name} command, then this name is given. Otherwise, if
29384 @value{GDBN} can extract the thread name from the target, then that
29385 name is given. If @value{GDBN} cannot find the thread name, then this
29389 The stack frame currently executing in the thread.
29392 The thread's state. The @samp{state} field may have the following
29397 The thread is stopped. Frame information is available for stopped
29401 The thread is running. There's no frame information for running
29407 If @value{GDBN} can find the CPU core on which this thread is running,
29408 then this field is the core identifier. This field is optional.
29412 @subsubheading Example
29417 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29418 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29419 args=[]@},state="running"@},
29420 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29421 frame=@{level="0",addr="0x0804891f",func="foo",
29422 args=[@{name="i",value="10"@}],
29423 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29424 state="running"@}],
29425 current-thread-id="1"
29429 @subheading The @code{-thread-list-ids} Command
29430 @findex -thread-list-ids
29432 @subsubheading Synopsis
29438 Produces a list of the currently known @value{GDBN} thread ids. At the
29439 end of the list it also prints the total number of such threads.
29441 This command is retained for historical reasons, the
29442 @code{-thread-info} command should be used instead.
29444 @subsubheading @value{GDBN} Command
29446 Part of @samp{info threads} supplies the same information.
29448 @subsubheading Example
29453 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29454 current-thread-id="1",number-of-threads="3"
29459 @subheading The @code{-thread-select} Command
29460 @findex -thread-select
29462 @subsubheading Synopsis
29465 -thread-select @var{threadnum}
29468 Make @var{threadnum} the current thread. It prints the number of the new
29469 current thread, and the topmost frame for that thread.
29471 This command is deprecated in favor of explicitly using the
29472 @samp{--thread} option to each command.
29474 @subsubheading @value{GDBN} Command
29476 The corresponding @value{GDBN} command is @samp{thread}.
29478 @subsubheading Example
29485 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29486 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29490 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29491 number-of-threads="3"
29494 ^done,new-thread-id="3",
29495 frame=@{level="0",func="vprintf",
29496 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29497 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29501 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29502 @node GDB/MI Ada Tasking Commands
29503 @section @sc{gdb/mi} Ada Tasking Commands
29505 @subheading The @code{-ada-task-info} Command
29506 @findex -ada-task-info
29508 @subsubheading Synopsis
29511 -ada-task-info [ @var{task-id} ]
29514 Reports information about either a specific Ada task, if the
29515 @var{task-id} parameter is present, or about all Ada tasks.
29517 @subsubheading @value{GDBN} Command
29519 The @samp{info tasks} command prints the same information
29520 about all Ada tasks (@pxref{Ada Tasks}).
29522 @subsubheading Result
29524 The result is a table of Ada tasks. The following columns are
29525 defined for each Ada task:
29529 This field exists only for the current thread. It has the value @samp{*}.
29532 The identifier that @value{GDBN} uses to refer to the Ada task.
29535 The identifier that the target uses to refer to the Ada task.
29538 The identifier of the thread corresponding to the Ada task.
29540 This field should always exist, as Ada tasks are always implemented
29541 on top of a thread. But if @value{GDBN} cannot find this corresponding
29542 thread for any reason, the field is omitted.
29545 This field exists only when the task was created by another task.
29546 In this case, it provides the ID of the parent task.
29549 The base priority of the task.
29552 The current state of the task. For a detailed description of the
29553 possible states, see @ref{Ada Tasks}.
29556 The name of the task.
29560 @subsubheading Example
29564 ^done,tasks=@{nr_rows="3",nr_cols="8",
29565 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29566 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29567 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29568 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29569 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29570 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29571 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29572 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29573 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29574 state="Child Termination Wait",name="main_task"@}]@}
29578 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29579 @node GDB/MI Program Execution
29580 @section @sc{gdb/mi} Program Execution
29582 These are the asynchronous commands which generate the out-of-band
29583 record @samp{*stopped}. Currently @value{GDBN} only really executes
29584 asynchronously with remote targets and this interaction is mimicked in
29587 @subheading The @code{-exec-continue} Command
29588 @findex -exec-continue
29590 @subsubheading Synopsis
29593 -exec-continue [--reverse] [--all|--thread-group N]
29596 Resumes the execution of the inferior program, which will continue
29597 to execute until it reaches a debugger stop event. If the
29598 @samp{--reverse} option is specified, execution resumes in reverse until
29599 it reaches a stop event. Stop events may include
29602 breakpoints or watchpoints
29604 signals or exceptions
29606 the end of the process (or its beginning under @samp{--reverse})
29608 the end or beginning of a replay log if one is being used.
29610 In all-stop mode (@pxref{All-Stop
29611 Mode}), may resume only one thread, or all threads, depending on the
29612 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29613 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29614 ignored in all-stop mode. If the @samp{--thread-group} options is
29615 specified, then all threads in that thread group are resumed.
29617 @subsubheading @value{GDBN} Command
29619 The corresponding @value{GDBN} corresponding is @samp{continue}.
29621 @subsubheading Example
29628 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29629 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29635 @subheading The @code{-exec-finish} Command
29636 @findex -exec-finish
29638 @subsubheading Synopsis
29641 -exec-finish [--reverse]
29644 Resumes the execution of the inferior program until the current
29645 function is exited. Displays the results returned by the function.
29646 If the @samp{--reverse} option is specified, resumes the reverse
29647 execution of the inferior program until the point where current
29648 function was called.
29650 @subsubheading @value{GDBN} Command
29652 The corresponding @value{GDBN} command is @samp{finish}.
29654 @subsubheading Example
29656 Function returning @code{void}.
29663 *stopped,reason="function-finished",frame=@{func="main",args=[],
29664 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29668 Function returning other than @code{void}. The name of the internal
29669 @value{GDBN} variable storing the result is printed, together with the
29676 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29677 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29678 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29679 gdb-result-var="$1",return-value="0"
29684 @subheading The @code{-exec-interrupt} Command
29685 @findex -exec-interrupt
29687 @subsubheading Synopsis
29690 -exec-interrupt [--all|--thread-group N]
29693 Interrupts the background execution of the target. Note how the token
29694 associated with the stop message is the one for the execution command
29695 that has been interrupted. The token for the interrupt itself only
29696 appears in the @samp{^done} output. If the user is trying to
29697 interrupt a non-running program, an error message will be printed.
29699 Note that when asynchronous execution is enabled, this command is
29700 asynchronous just like other execution commands. That is, first the
29701 @samp{^done} response will be printed, and the target stop will be
29702 reported after that using the @samp{*stopped} notification.
29704 In non-stop mode, only the context thread is interrupted by default.
29705 All threads (in all inferiors) will be interrupted if the
29706 @samp{--all} option is specified. If the @samp{--thread-group}
29707 option is specified, all threads in that group will be interrupted.
29709 @subsubheading @value{GDBN} Command
29711 The corresponding @value{GDBN} command is @samp{interrupt}.
29713 @subsubheading Example
29724 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29725 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29726 fullname="/home/foo/bar/try.c",line="13"@}
29731 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29735 @subheading The @code{-exec-jump} Command
29738 @subsubheading Synopsis
29741 -exec-jump @var{location}
29744 Resumes execution of the inferior program at the location specified by
29745 parameter. @xref{Specify Location}, for a description of the
29746 different forms of @var{location}.
29748 @subsubheading @value{GDBN} Command
29750 The corresponding @value{GDBN} command is @samp{jump}.
29752 @subsubheading Example
29755 -exec-jump foo.c:10
29756 *running,thread-id="all"
29761 @subheading The @code{-exec-next} Command
29764 @subsubheading Synopsis
29767 -exec-next [--reverse]
29770 Resumes execution of the inferior program, stopping when the beginning
29771 of the next source line is reached.
29773 If the @samp{--reverse} option is specified, resumes reverse execution
29774 of the inferior program, stopping at the beginning of the previous
29775 source line. If you issue this command on the first line of a
29776 function, it will take you back to the caller of that function, to the
29777 source line where the function was called.
29780 @subsubheading @value{GDBN} Command
29782 The corresponding @value{GDBN} command is @samp{next}.
29784 @subsubheading Example
29790 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29795 @subheading The @code{-exec-next-instruction} Command
29796 @findex -exec-next-instruction
29798 @subsubheading Synopsis
29801 -exec-next-instruction [--reverse]
29804 Executes one machine instruction. If the instruction is a function
29805 call, continues until the function returns. If the program stops at an
29806 instruction in the middle of a source line, the address will be
29809 If the @samp{--reverse} option is specified, resumes reverse execution
29810 of the inferior program, stopping at the previous instruction. If the
29811 previously executed instruction was a return from another function,
29812 it will continue to execute in reverse until the call to that function
29813 (from the current stack frame) is reached.
29815 @subsubheading @value{GDBN} Command
29817 The corresponding @value{GDBN} command is @samp{nexti}.
29819 @subsubheading Example
29823 -exec-next-instruction
29827 *stopped,reason="end-stepping-range",
29828 addr="0x000100d4",line="5",file="hello.c"
29833 @subheading The @code{-exec-return} Command
29834 @findex -exec-return
29836 @subsubheading Synopsis
29842 Makes current function return immediately. Doesn't execute the inferior.
29843 Displays the new current frame.
29845 @subsubheading @value{GDBN} Command
29847 The corresponding @value{GDBN} command is @samp{return}.
29849 @subsubheading Example
29853 200-break-insert callee4
29854 200^done,bkpt=@{number="1",addr="0x00010734",
29855 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29860 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29861 frame=@{func="callee4",args=[],
29862 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29863 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29869 111^done,frame=@{level="0",func="callee3",
29870 args=[@{name="strarg",
29871 value="0x11940 \"A string argument.\""@}],
29872 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29873 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29878 @subheading The @code{-exec-run} Command
29881 @subsubheading Synopsis
29884 -exec-run [--all | --thread-group N]
29887 Starts execution of the inferior from the beginning. The inferior
29888 executes until either a breakpoint is encountered or the program
29889 exits. In the latter case the output will include an exit code, if
29890 the program has exited exceptionally.
29892 When no option is specified, the current inferior is started. If the
29893 @samp{--thread-group} option is specified, it should refer to a thread
29894 group of type @samp{process}, and that thread group will be started.
29895 If the @samp{--all} option is specified, then all inferiors will be started.
29897 @subsubheading @value{GDBN} Command
29899 The corresponding @value{GDBN} command is @samp{run}.
29901 @subsubheading Examples
29906 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29911 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29912 frame=@{func="main",args=[],file="recursive2.c",
29913 fullname="/home/foo/bar/recursive2.c",line="4"@}
29918 Program exited normally:
29926 *stopped,reason="exited-normally"
29931 Program exited exceptionally:
29939 *stopped,reason="exited",exit-code="01"
29943 Another way the program can terminate is if it receives a signal such as
29944 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29948 *stopped,reason="exited-signalled",signal-name="SIGINT",
29949 signal-meaning="Interrupt"
29953 @c @subheading -exec-signal
29956 @subheading The @code{-exec-step} Command
29959 @subsubheading Synopsis
29962 -exec-step [--reverse]
29965 Resumes execution of the inferior program, stopping when the beginning
29966 of the next source line is reached, if the next source line is not a
29967 function call. If it is, stop at the first instruction of the called
29968 function. If the @samp{--reverse} option is specified, resumes reverse
29969 execution of the inferior program, stopping at the beginning of the
29970 previously executed source line.
29972 @subsubheading @value{GDBN} Command
29974 The corresponding @value{GDBN} command is @samp{step}.
29976 @subsubheading Example
29978 Stepping into a function:
29984 *stopped,reason="end-stepping-range",
29985 frame=@{func="foo",args=[@{name="a",value="10"@},
29986 @{name="b",value="0"@}],file="recursive2.c",
29987 fullname="/home/foo/bar/recursive2.c",line="11"@}
29997 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30002 @subheading The @code{-exec-step-instruction} Command
30003 @findex -exec-step-instruction
30005 @subsubheading Synopsis
30008 -exec-step-instruction [--reverse]
30011 Resumes the inferior which executes one machine instruction. If the
30012 @samp{--reverse} option is specified, resumes reverse execution of the
30013 inferior program, stopping at the previously executed instruction.
30014 The output, once @value{GDBN} has stopped, will vary depending on
30015 whether we have stopped in the middle of a source line or not. In the
30016 former case, the address at which the program stopped will be printed
30019 @subsubheading @value{GDBN} Command
30021 The corresponding @value{GDBN} command is @samp{stepi}.
30023 @subsubheading Example
30027 -exec-step-instruction
30031 *stopped,reason="end-stepping-range",
30032 frame=@{func="foo",args=[],file="try.c",
30033 fullname="/home/foo/bar/try.c",line="10"@}
30035 -exec-step-instruction
30039 *stopped,reason="end-stepping-range",
30040 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30041 fullname="/home/foo/bar/try.c",line="10"@}
30046 @subheading The @code{-exec-until} Command
30047 @findex -exec-until
30049 @subsubheading Synopsis
30052 -exec-until [ @var{location} ]
30055 Executes the inferior until the @var{location} specified in the
30056 argument is reached. If there is no argument, the inferior executes
30057 until a source line greater than the current one is reached. The
30058 reason for stopping in this case will be @samp{location-reached}.
30060 @subsubheading @value{GDBN} Command
30062 The corresponding @value{GDBN} command is @samp{until}.
30064 @subsubheading Example
30068 -exec-until recursive2.c:6
30072 *stopped,reason="location-reached",frame=@{func="main",args=[],
30073 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
30078 @subheading -file-clear
30079 Is this going away????
30082 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30083 @node GDB/MI Stack Manipulation
30084 @section @sc{gdb/mi} Stack Manipulation Commands
30087 @subheading The @code{-stack-info-frame} Command
30088 @findex -stack-info-frame
30090 @subsubheading Synopsis
30096 Get info on the selected frame.
30098 @subsubheading @value{GDBN} Command
30100 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30101 (without arguments).
30103 @subsubheading Example
30108 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30109 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30110 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
30114 @subheading The @code{-stack-info-depth} Command
30115 @findex -stack-info-depth
30117 @subsubheading Synopsis
30120 -stack-info-depth [ @var{max-depth} ]
30123 Return the depth of the stack. If the integer argument @var{max-depth}
30124 is specified, do not count beyond @var{max-depth} frames.
30126 @subsubheading @value{GDBN} Command
30128 There's no equivalent @value{GDBN} command.
30130 @subsubheading Example
30132 For a stack with frame levels 0 through 11:
30139 -stack-info-depth 4
30142 -stack-info-depth 12
30145 -stack-info-depth 11
30148 -stack-info-depth 13
30153 @subheading The @code{-stack-list-arguments} Command
30154 @findex -stack-list-arguments
30156 @subsubheading Synopsis
30159 -stack-list-arguments @var{print-values}
30160 [ @var{low-frame} @var{high-frame} ]
30163 Display a list of the arguments for the frames between @var{low-frame}
30164 and @var{high-frame} (inclusive). If @var{low-frame} and
30165 @var{high-frame} are not provided, list the arguments for the whole
30166 call stack. If the two arguments are equal, show the single frame
30167 at the corresponding level. It is an error if @var{low-frame} is
30168 larger than the actual number of frames. On the other hand,
30169 @var{high-frame} may be larger than the actual number of frames, in
30170 which case only existing frames will be returned.
30172 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30173 the variables; if it is 1 or @code{--all-values}, print also their
30174 values; and if it is 2 or @code{--simple-values}, print the name,
30175 type and value for simple data types, and the name and type for arrays,
30176 structures and unions.
30178 Use of this command to obtain arguments in a single frame is
30179 deprecated in favor of the @samp{-stack-list-variables} command.
30181 @subsubheading @value{GDBN} Command
30183 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30184 @samp{gdb_get_args} command which partially overlaps with the
30185 functionality of @samp{-stack-list-arguments}.
30187 @subsubheading Example
30194 frame=@{level="0",addr="0x00010734",func="callee4",
30195 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30196 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
30197 frame=@{level="1",addr="0x0001076c",func="callee3",
30198 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30199 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
30200 frame=@{level="2",addr="0x0001078c",func="callee2",
30201 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30202 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30203 frame=@{level="3",addr="0x000107b4",func="callee1",
30204 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30205 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30206 frame=@{level="4",addr="0x000107e0",func="main",
30207 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30208 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30210 -stack-list-arguments 0
30213 frame=@{level="0",args=[]@},
30214 frame=@{level="1",args=[name="strarg"]@},
30215 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30216 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30217 frame=@{level="4",args=[]@}]
30219 -stack-list-arguments 1
30222 frame=@{level="0",args=[]@},
30224 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30225 frame=@{level="2",args=[
30226 @{name="intarg",value="2"@},
30227 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30228 @{frame=@{level="3",args=[
30229 @{name="intarg",value="2"@},
30230 @{name="strarg",value="0x11940 \"A string argument.\""@},
30231 @{name="fltarg",value="3.5"@}]@},
30232 frame=@{level="4",args=[]@}]
30234 -stack-list-arguments 0 2 2
30235 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30237 -stack-list-arguments 1 2 2
30238 ^done,stack-args=[frame=@{level="2",
30239 args=[@{name="intarg",value="2"@},
30240 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30244 @c @subheading -stack-list-exception-handlers
30247 @subheading The @code{-stack-list-frames} Command
30248 @findex -stack-list-frames
30250 @subsubheading Synopsis
30253 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
30256 List the frames currently on the stack. For each frame it displays the
30261 The frame number, 0 being the topmost frame, i.e., the innermost function.
30263 The @code{$pc} value for that frame.
30267 File name of the source file where the function lives.
30268 @item @var{fullname}
30269 The full file name of the source file where the function lives.
30271 Line number corresponding to the @code{$pc}.
30273 The shared library where this function is defined. This is only given
30274 if the frame's function is not known.
30277 If invoked without arguments, this command prints a backtrace for the
30278 whole stack. If given two integer arguments, it shows the frames whose
30279 levels are between the two arguments (inclusive). If the two arguments
30280 are equal, it shows the single frame at the corresponding level. It is
30281 an error if @var{low-frame} is larger than the actual number of
30282 frames. On the other hand, @var{high-frame} may be larger than the
30283 actual number of frames, in which case only existing frames will be returned.
30285 @subsubheading @value{GDBN} Command
30287 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30289 @subsubheading Example
30291 Full stack backtrace:
30297 [frame=@{level="0",addr="0x0001076c",func="foo",
30298 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30299 frame=@{level="1",addr="0x000107a4",func="foo",
30300 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30301 frame=@{level="2",addr="0x000107a4",func="foo",
30302 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30303 frame=@{level="3",addr="0x000107a4",func="foo",
30304 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30305 frame=@{level="4",addr="0x000107a4",func="foo",
30306 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30307 frame=@{level="5",addr="0x000107a4",func="foo",
30308 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30309 frame=@{level="6",addr="0x000107a4",func="foo",
30310 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30311 frame=@{level="7",addr="0x000107a4",func="foo",
30312 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30313 frame=@{level="8",addr="0x000107a4",func="foo",
30314 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30315 frame=@{level="9",addr="0x000107a4",func="foo",
30316 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30317 frame=@{level="10",addr="0x000107a4",func="foo",
30318 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30319 frame=@{level="11",addr="0x00010738",func="main",
30320 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30324 Show frames between @var{low_frame} and @var{high_frame}:
30328 -stack-list-frames 3 5
30330 [frame=@{level="3",addr="0x000107a4",func="foo",
30331 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30332 frame=@{level="4",addr="0x000107a4",func="foo",
30333 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30334 frame=@{level="5",addr="0x000107a4",func="foo",
30335 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30339 Show a single frame:
30343 -stack-list-frames 3 3
30345 [frame=@{level="3",addr="0x000107a4",func="foo",
30346 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30351 @subheading The @code{-stack-list-locals} Command
30352 @findex -stack-list-locals
30354 @subsubheading Synopsis
30357 -stack-list-locals @var{print-values}
30360 Display the local variable names for the selected frame. If
30361 @var{print-values} is 0 or @code{--no-values}, print only the names of
30362 the variables; if it is 1 or @code{--all-values}, print also their
30363 values; and if it is 2 or @code{--simple-values}, print the name,
30364 type and value for simple data types, and the name and type for arrays,
30365 structures and unions. In this last case, a frontend can immediately
30366 display the value of simple data types and create variable objects for
30367 other data types when the user wishes to explore their values in
30370 This command is deprecated in favor of the
30371 @samp{-stack-list-variables} command.
30373 @subsubheading @value{GDBN} Command
30375 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30377 @subsubheading Example
30381 -stack-list-locals 0
30382 ^done,locals=[name="A",name="B",name="C"]
30384 -stack-list-locals --all-values
30385 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30386 @{name="C",value="@{1, 2, 3@}"@}]
30387 -stack-list-locals --simple-values
30388 ^done,locals=[@{name="A",type="int",value="1"@},
30389 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30393 @subheading The @code{-stack-list-variables} Command
30394 @findex -stack-list-variables
30396 @subsubheading Synopsis
30399 -stack-list-variables @var{print-values}
30402 Display the names of local variables and function arguments for the selected frame. If
30403 @var{print-values} is 0 or @code{--no-values}, print only the names of
30404 the variables; if it is 1 or @code{--all-values}, print also their
30405 values; and if it is 2 or @code{--simple-values}, print the name,
30406 type and value for simple data types, and the name and type for arrays,
30407 structures and unions.
30409 @subsubheading Example
30413 -stack-list-variables --thread 1 --frame 0 --all-values
30414 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30419 @subheading The @code{-stack-select-frame} Command
30420 @findex -stack-select-frame
30422 @subsubheading Synopsis
30425 -stack-select-frame @var{framenum}
30428 Change the selected frame. Select a different frame @var{framenum} on
30431 This command in deprecated in favor of passing the @samp{--frame}
30432 option to every command.
30434 @subsubheading @value{GDBN} Command
30436 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30437 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30439 @subsubheading Example
30443 -stack-select-frame 2
30448 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30449 @node GDB/MI Variable Objects
30450 @section @sc{gdb/mi} Variable Objects
30454 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30456 For the implementation of a variable debugger window (locals, watched
30457 expressions, etc.), we are proposing the adaptation of the existing code
30458 used by @code{Insight}.
30460 The two main reasons for that are:
30464 It has been proven in practice (it is already on its second generation).
30467 It will shorten development time (needless to say how important it is
30471 The original interface was designed to be used by Tcl code, so it was
30472 slightly changed so it could be used through @sc{gdb/mi}. This section
30473 describes the @sc{gdb/mi} operations that will be available and gives some
30474 hints about their use.
30476 @emph{Note}: In addition to the set of operations described here, we
30477 expect the @sc{gui} implementation of a variable window to require, at
30478 least, the following operations:
30481 @item @code{-gdb-show} @code{output-radix}
30482 @item @code{-stack-list-arguments}
30483 @item @code{-stack-list-locals}
30484 @item @code{-stack-select-frame}
30489 @subheading Introduction to Variable Objects
30491 @cindex variable objects in @sc{gdb/mi}
30493 Variable objects are "object-oriented" MI interface for examining and
30494 changing values of expressions. Unlike some other MI interfaces that
30495 work with expressions, variable objects are specifically designed for
30496 simple and efficient presentation in the frontend. A variable object
30497 is identified by string name. When a variable object is created, the
30498 frontend specifies the expression for that variable object. The
30499 expression can be a simple variable, or it can be an arbitrary complex
30500 expression, and can even involve CPU registers. After creating a
30501 variable object, the frontend can invoke other variable object
30502 operations---for example to obtain or change the value of a variable
30503 object, or to change display format.
30505 Variable objects have hierarchical tree structure. Any variable object
30506 that corresponds to a composite type, such as structure in C, has
30507 a number of child variable objects, for example corresponding to each
30508 element of a structure. A child variable object can itself have
30509 children, recursively. Recursion ends when we reach
30510 leaf variable objects, which always have built-in types. Child variable
30511 objects are created only by explicit request, so if a frontend
30512 is not interested in the children of a particular variable object, no
30513 child will be created.
30515 For a leaf variable object it is possible to obtain its value as a
30516 string, or set the value from a string. String value can be also
30517 obtained for a non-leaf variable object, but it's generally a string
30518 that only indicates the type of the object, and does not list its
30519 contents. Assignment to a non-leaf variable object is not allowed.
30521 A frontend does not need to read the values of all variable objects each time
30522 the program stops. Instead, MI provides an update command that lists all
30523 variable objects whose values has changed since the last update
30524 operation. This considerably reduces the amount of data that must
30525 be transferred to the frontend. As noted above, children variable
30526 objects are created on demand, and only leaf variable objects have a
30527 real value. As result, gdb will read target memory only for leaf
30528 variables that frontend has created.
30530 The automatic update is not always desirable. For example, a frontend
30531 might want to keep a value of some expression for future reference,
30532 and never update it. For another example, fetching memory is
30533 relatively slow for embedded targets, so a frontend might want
30534 to disable automatic update for the variables that are either not
30535 visible on the screen, or ``closed''. This is possible using so
30536 called ``frozen variable objects''. Such variable objects are never
30537 implicitly updated.
30539 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30540 fixed variable object, the expression is parsed when the variable
30541 object is created, including associating identifiers to specific
30542 variables. The meaning of expression never changes. For a floating
30543 variable object the values of variables whose names appear in the
30544 expressions are re-evaluated every time in the context of the current
30545 frame. Consider this example:
30550 struct work_state state;
30557 If a fixed variable object for the @code{state} variable is created in
30558 this function, and we enter the recursive call, the variable
30559 object will report the value of @code{state} in the top-level
30560 @code{do_work} invocation. On the other hand, a floating variable
30561 object will report the value of @code{state} in the current frame.
30563 If an expression specified when creating a fixed variable object
30564 refers to a local variable, the variable object becomes bound to the
30565 thread and frame in which the variable object is created. When such
30566 variable object is updated, @value{GDBN} makes sure that the
30567 thread/frame combination the variable object is bound to still exists,
30568 and re-evaluates the variable object in context of that thread/frame.
30570 The following is the complete set of @sc{gdb/mi} operations defined to
30571 access this functionality:
30573 @multitable @columnfractions .4 .6
30574 @item @strong{Operation}
30575 @tab @strong{Description}
30577 @item @code{-enable-pretty-printing}
30578 @tab enable Python-based pretty-printing
30579 @item @code{-var-create}
30580 @tab create a variable object
30581 @item @code{-var-delete}
30582 @tab delete the variable object and/or its children
30583 @item @code{-var-set-format}
30584 @tab set the display format of this variable
30585 @item @code{-var-show-format}
30586 @tab show the display format of this variable
30587 @item @code{-var-info-num-children}
30588 @tab tells how many children this object has
30589 @item @code{-var-list-children}
30590 @tab return a list of the object's children
30591 @item @code{-var-info-type}
30592 @tab show the type of this variable object
30593 @item @code{-var-info-expression}
30594 @tab print parent-relative expression that this variable object represents
30595 @item @code{-var-info-path-expression}
30596 @tab print full expression that this variable object represents
30597 @item @code{-var-show-attributes}
30598 @tab is this variable editable? does it exist here?
30599 @item @code{-var-evaluate-expression}
30600 @tab get the value of this variable
30601 @item @code{-var-assign}
30602 @tab set the value of this variable
30603 @item @code{-var-update}
30604 @tab update the variable and its children
30605 @item @code{-var-set-frozen}
30606 @tab set frozeness attribute
30607 @item @code{-var-set-update-range}
30608 @tab set range of children to display on update
30611 In the next subsection we describe each operation in detail and suggest
30612 how it can be used.
30614 @subheading Description And Use of Operations on Variable Objects
30616 @subheading The @code{-enable-pretty-printing} Command
30617 @findex -enable-pretty-printing
30620 -enable-pretty-printing
30623 @value{GDBN} allows Python-based visualizers to affect the output of the
30624 MI variable object commands. However, because there was no way to
30625 implement this in a fully backward-compatible way, a front end must
30626 request that this functionality be enabled.
30628 Once enabled, this feature cannot be disabled.
30630 Note that if Python support has not been compiled into @value{GDBN},
30631 this command will still succeed (and do nothing).
30633 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30634 may work differently in future versions of @value{GDBN}.
30636 @subheading The @code{-var-create} Command
30637 @findex -var-create
30639 @subsubheading Synopsis
30642 -var-create @{@var{name} | "-"@}
30643 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30646 This operation creates a variable object, which allows the monitoring of
30647 a variable, the result of an expression, a memory cell or a CPU
30650 The @var{name} parameter is the string by which the object can be
30651 referenced. It must be unique. If @samp{-} is specified, the varobj
30652 system will generate a string ``varNNNNNN'' automatically. It will be
30653 unique provided that one does not specify @var{name} of that format.
30654 The command fails if a duplicate name is found.
30656 The frame under which the expression should be evaluated can be
30657 specified by @var{frame-addr}. A @samp{*} indicates that the current
30658 frame should be used. A @samp{@@} indicates that a floating variable
30659 object must be created.
30661 @var{expression} is any expression valid on the current language set (must not
30662 begin with a @samp{*}), or one of the following:
30666 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30669 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30672 @samp{$@var{regname}} --- a CPU register name
30675 @cindex dynamic varobj
30676 A varobj's contents may be provided by a Python-based pretty-printer. In this
30677 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30678 have slightly different semantics in some cases. If the
30679 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30680 will never create a dynamic varobj. This ensures backward
30681 compatibility for existing clients.
30683 @subsubheading Result
30685 This operation returns attributes of the newly-created varobj. These
30690 The name of the varobj.
30693 The number of children of the varobj. This number is not necessarily
30694 reliable for a dynamic varobj. Instead, you must examine the
30695 @samp{has_more} attribute.
30698 The varobj's scalar value. For a varobj whose type is some sort of
30699 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30700 will not be interesting.
30703 The varobj's type. This is a string representation of the type, as
30704 would be printed by the @value{GDBN} CLI. If @samp{print object}
30705 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30706 @emph{actual} (derived) type of the object is shown rather than the
30707 @emph{declared} one.
30710 If a variable object is bound to a specific thread, then this is the
30711 thread's identifier.
30714 For a dynamic varobj, this indicates whether there appear to be any
30715 children available. For a non-dynamic varobj, this will be 0.
30718 This attribute will be present and have the value @samp{1} if the
30719 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30720 then this attribute will not be present.
30723 A dynamic varobj can supply a display hint to the front end. The
30724 value comes directly from the Python pretty-printer object's
30725 @code{display_hint} method. @xref{Pretty Printing API}.
30728 Typical output will look like this:
30731 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30732 has_more="@var{has_more}"
30736 @subheading The @code{-var-delete} Command
30737 @findex -var-delete
30739 @subsubheading Synopsis
30742 -var-delete [ -c ] @var{name}
30745 Deletes a previously created variable object and all of its children.
30746 With the @samp{-c} option, just deletes the children.
30748 Returns an error if the object @var{name} is not found.
30751 @subheading The @code{-var-set-format} Command
30752 @findex -var-set-format
30754 @subsubheading Synopsis
30757 -var-set-format @var{name} @var{format-spec}
30760 Sets the output format for the value of the object @var{name} to be
30763 @anchor{-var-set-format}
30764 The syntax for the @var{format-spec} is as follows:
30767 @var{format-spec} @expansion{}
30768 @{binary | decimal | hexadecimal | octal | natural@}
30771 The natural format is the default format choosen automatically
30772 based on the variable type (like decimal for an @code{int}, hex
30773 for pointers, etc.).
30775 For a variable with children, the format is set only on the
30776 variable itself, and the children are not affected.
30778 @subheading The @code{-var-show-format} Command
30779 @findex -var-show-format
30781 @subsubheading Synopsis
30784 -var-show-format @var{name}
30787 Returns the format used to display the value of the object @var{name}.
30790 @var{format} @expansion{}
30795 @subheading The @code{-var-info-num-children} Command
30796 @findex -var-info-num-children
30798 @subsubheading Synopsis
30801 -var-info-num-children @var{name}
30804 Returns the number of children of a variable object @var{name}:
30810 Note that this number is not completely reliable for a dynamic varobj.
30811 It will return the current number of children, but more children may
30815 @subheading The @code{-var-list-children} Command
30816 @findex -var-list-children
30818 @subsubheading Synopsis
30821 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30823 @anchor{-var-list-children}
30825 Return a list of the children of the specified variable object and
30826 create variable objects for them, if they do not already exist. With
30827 a single argument or if @var{print-values} has a value of 0 or
30828 @code{--no-values}, print only the names of the variables; if
30829 @var{print-values} is 1 or @code{--all-values}, also print their
30830 values; and if it is 2 or @code{--simple-values} print the name and
30831 value for simple data types and just the name for arrays, structures
30834 @var{from} and @var{to}, if specified, indicate the range of children
30835 to report. If @var{from} or @var{to} is less than zero, the range is
30836 reset and all children will be reported. Otherwise, children starting
30837 at @var{from} (zero-based) and up to and excluding @var{to} will be
30840 If a child range is requested, it will only affect the current call to
30841 @code{-var-list-children}, but not future calls to @code{-var-update}.
30842 For this, you must instead use @code{-var-set-update-range}. The
30843 intent of this approach is to enable a front end to implement any
30844 update approach it likes; for example, scrolling a view may cause the
30845 front end to request more children with @code{-var-list-children}, and
30846 then the front end could call @code{-var-set-update-range} with a
30847 different range to ensure that future updates are restricted to just
30850 For each child the following results are returned:
30855 Name of the variable object created for this child.
30858 The expression to be shown to the user by the front end to designate this child.
30859 For example this may be the name of a structure member.
30861 For a dynamic varobj, this value cannot be used to form an
30862 expression. There is no way to do this at all with a dynamic varobj.
30864 For C/C@t{++} structures there are several pseudo children returned to
30865 designate access qualifiers. For these pseudo children @var{exp} is
30866 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30867 type and value are not present.
30869 A dynamic varobj will not report the access qualifying
30870 pseudo-children, regardless of the language. This information is not
30871 available at all with a dynamic varobj.
30874 Number of children this child has. For a dynamic varobj, this will be
30878 The type of the child. If @samp{print object}
30879 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30880 @emph{actual} (derived) type of the object is shown rather than the
30881 @emph{declared} one.
30884 If values were requested, this is the value.
30887 If this variable object is associated with a thread, this is the thread id.
30888 Otherwise this result is not present.
30891 If the variable object is frozen, this variable will be present with a value of 1.
30894 The result may have its own attributes:
30898 A dynamic varobj can supply a display hint to the front end. The
30899 value comes directly from the Python pretty-printer object's
30900 @code{display_hint} method. @xref{Pretty Printing API}.
30903 This is an integer attribute which is nonzero if there are children
30904 remaining after the end of the selected range.
30907 @subsubheading Example
30911 -var-list-children n
30912 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30913 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30915 -var-list-children --all-values n
30916 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30917 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30921 @subheading The @code{-var-info-type} Command
30922 @findex -var-info-type
30924 @subsubheading Synopsis
30927 -var-info-type @var{name}
30930 Returns the type of the specified variable @var{name}. The type is
30931 returned as a string in the same format as it is output by the
30935 type=@var{typename}
30939 @subheading The @code{-var-info-expression} Command
30940 @findex -var-info-expression
30942 @subsubheading Synopsis
30945 -var-info-expression @var{name}
30948 Returns a string that is suitable for presenting this
30949 variable object in user interface. The string is generally
30950 not valid expression in the current language, and cannot be evaluated.
30952 For example, if @code{a} is an array, and variable object
30953 @code{A} was created for @code{a}, then we'll get this output:
30956 (gdb) -var-info-expression A.1
30957 ^done,lang="C",exp="1"
30961 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30963 Note that the output of the @code{-var-list-children} command also
30964 includes those expressions, so the @code{-var-info-expression} command
30967 @subheading The @code{-var-info-path-expression} Command
30968 @findex -var-info-path-expression
30970 @subsubheading Synopsis
30973 -var-info-path-expression @var{name}
30976 Returns an expression that can be evaluated in the current
30977 context and will yield the same value that a variable object has.
30978 Compare this with the @code{-var-info-expression} command, which
30979 result can be used only for UI presentation. Typical use of
30980 the @code{-var-info-path-expression} command is creating a
30981 watchpoint from a variable object.
30983 This command is currently not valid for children of a dynamic varobj,
30984 and will give an error when invoked on one.
30986 For example, suppose @code{C} is a C@t{++} class, derived from class
30987 @code{Base}, and that the @code{Base} class has a member called
30988 @code{m_size}. Assume a variable @code{c} is has the type of
30989 @code{C} and a variable object @code{C} was created for variable
30990 @code{c}. Then, we'll get this output:
30992 (gdb) -var-info-path-expression C.Base.public.m_size
30993 ^done,path_expr=((Base)c).m_size)
30996 @subheading The @code{-var-show-attributes} Command
30997 @findex -var-show-attributes
30999 @subsubheading Synopsis
31002 -var-show-attributes @var{name}
31005 List attributes of the specified variable object @var{name}:
31008 status=@var{attr} [ ( ,@var{attr} )* ]
31012 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31014 @subheading The @code{-var-evaluate-expression} Command
31015 @findex -var-evaluate-expression
31017 @subsubheading Synopsis
31020 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31023 Evaluates the expression that is represented by the specified variable
31024 object and returns its value as a string. The format of the string
31025 can be specified with the @samp{-f} option. The possible values of
31026 this option are the same as for @code{-var-set-format}
31027 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31028 the current display format will be used. The current display format
31029 can be changed using the @code{-var-set-format} command.
31035 Note that one must invoke @code{-var-list-children} for a variable
31036 before the value of a child variable can be evaluated.
31038 @subheading The @code{-var-assign} Command
31039 @findex -var-assign
31041 @subsubheading Synopsis
31044 -var-assign @var{name} @var{expression}
31047 Assigns the value of @var{expression} to the variable object specified
31048 by @var{name}. The object must be @samp{editable}. If the variable's
31049 value is altered by the assign, the variable will show up in any
31050 subsequent @code{-var-update} list.
31052 @subsubheading Example
31060 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31064 @subheading The @code{-var-update} Command
31065 @findex -var-update
31067 @subsubheading Synopsis
31070 -var-update [@var{print-values}] @{@var{name} | "*"@}
31073 Reevaluate the expressions corresponding to the variable object
31074 @var{name} and all its direct and indirect children, and return the
31075 list of variable objects whose values have changed; @var{name} must
31076 be a root variable object. Here, ``changed'' means that the result of
31077 @code{-var-evaluate-expression} before and after the
31078 @code{-var-update} is different. If @samp{*} is used as the variable
31079 object names, all existing variable objects are updated, except
31080 for frozen ones (@pxref{-var-set-frozen}). The option
31081 @var{print-values} determines whether both names and values, or just
31082 names are printed. The possible values of this option are the same
31083 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31084 recommended to use the @samp{--all-values} option, to reduce the
31085 number of MI commands needed on each program stop.
31087 With the @samp{*} parameter, if a variable object is bound to a
31088 currently running thread, it will not be updated, without any
31091 If @code{-var-set-update-range} was previously used on a varobj, then
31092 only the selected range of children will be reported.
31094 @code{-var-update} reports all the changed varobjs in a tuple named
31097 Each item in the change list is itself a tuple holding:
31101 The name of the varobj.
31104 If values were requested for this update, then this field will be
31105 present and will hold the value of the varobj.
31108 @anchor{-var-update}
31109 This field is a string which may take one of three values:
31113 The variable object's current value is valid.
31116 The variable object does not currently hold a valid value but it may
31117 hold one in the future if its associated expression comes back into
31121 The variable object no longer holds a valid value.
31122 This can occur when the executable file being debugged has changed,
31123 either through recompilation or by using the @value{GDBN} @code{file}
31124 command. The front end should normally choose to delete these variable
31128 In the future new values may be added to this list so the front should
31129 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31132 This is only present if the varobj is still valid. If the type
31133 changed, then this will be the string @samp{true}; otherwise it will
31136 When a varobj's type changes, its children are also likely to have
31137 become incorrect. Therefore, the varobj's children are automatically
31138 deleted when this attribute is @samp{true}. Also, the varobj's update
31139 range, when set using the @code{-var-set-update-range} command, is
31143 If the varobj's type changed, then this field will be present and will
31146 @item new_num_children
31147 For a dynamic varobj, if the number of children changed, or if the
31148 type changed, this will be the new number of children.
31150 The @samp{numchild} field in other varobj responses is generally not
31151 valid for a dynamic varobj -- it will show the number of children that
31152 @value{GDBN} knows about, but because dynamic varobjs lazily
31153 instantiate their children, this will not reflect the number of
31154 children which may be available.
31156 The @samp{new_num_children} attribute only reports changes to the
31157 number of children known by @value{GDBN}. This is the only way to
31158 detect whether an update has removed children (which necessarily can
31159 only happen at the end of the update range).
31162 The display hint, if any.
31165 This is an integer value, which will be 1 if there are more children
31166 available outside the varobj's update range.
31169 This attribute will be present and have the value @samp{1} if the
31170 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31171 then this attribute will not be present.
31174 If new children were added to a dynamic varobj within the selected
31175 update range (as set by @code{-var-set-update-range}), then they will
31176 be listed in this attribute.
31179 @subsubheading Example
31186 -var-update --all-values var1
31187 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31188 type_changed="false"@}]
31192 @subheading The @code{-var-set-frozen} Command
31193 @findex -var-set-frozen
31194 @anchor{-var-set-frozen}
31196 @subsubheading Synopsis
31199 -var-set-frozen @var{name} @var{flag}
31202 Set the frozenness flag on the variable object @var{name}. The
31203 @var{flag} parameter should be either @samp{1} to make the variable
31204 frozen or @samp{0} to make it unfrozen. If a variable object is
31205 frozen, then neither itself, nor any of its children, are
31206 implicitly updated by @code{-var-update} of
31207 a parent variable or by @code{-var-update *}. Only
31208 @code{-var-update} of the variable itself will update its value and
31209 values of its children. After a variable object is unfrozen, it is
31210 implicitly updated by all subsequent @code{-var-update} operations.
31211 Unfreezing a variable does not update it, only subsequent
31212 @code{-var-update} does.
31214 @subsubheading Example
31218 -var-set-frozen V 1
31223 @subheading The @code{-var-set-update-range} command
31224 @findex -var-set-update-range
31225 @anchor{-var-set-update-range}
31227 @subsubheading Synopsis
31230 -var-set-update-range @var{name} @var{from} @var{to}
31233 Set the range of children to be returned by future invocations of
31234 @code{-var-update}.
31236 @var{from} and @var{to} indicate the range of children to report. If
31237 @var{from} or @var{to} is less than zero, the range is reset and all
31238 children will be reported. Otherwise, children starting at @var{from}
31239 (zero-based) and up to and excluding @var{to} will be reported.
31241 @subsubheading Example
31245 -var-set-update-range V 1 2
31249 @subheading The @code{-var-set-visualizer} command
31250 @findex -var-set-visualizer
31251 @anchor{-var-set-visualizer}
31253 @subsubheading Synopsis
31256 -var-set-visualizer @var{name} @var{visualizer}
31259 Set a visualizer for the variable object @var{name}.
31261 @var{visualizer} is the visualizer to use. The special value
31262 @samp{None} means to disable any visualizer in use.
31264 If not @samp{None}, @var{visualizer} must be a Python expression.
31265 This expression must evaluate to a callable object which accepts a
31266 single argument. @value{GDBN} will call this object with the value of
31267 the varobj @var{name} as an argument (this is done so that the same
31268 Python pretty-printing code can be used for both the CLI and MI).
31269 When called, this object must return an object which conforms to the
31270 pretty-printing interface (@pxref{Pretty Printing API}).
31272 The pre-defined function @code{gdb.default_visualizer} may be used to
31273 select a visualizer by following the built-in process
31274 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31275 a varobj is created, and so ordinarily is not needed.
31277 This feature is only available if Python support is enabled. The MI
31278 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
31279 can be used to check this.
31281 @subsubheading Example
31283 Resetting the visualizer:
31287 -var-set-visualizer V None
31291 Reselecting the default (type-based) visualizer:
31295 -var-set-visualizer V gdb.default_visualizer
31299 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31300 can be used to instantiate this class for a varobj:
31304 -var-set-visualizer V "lambda val: SomeClass()"
31308 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31309 @node GDB/MI Data Manipulation
31310 @section @sc{gdb/mi} Data Manipulation
31312 @cindex data manipulation, in @sc{gdb/mi}
31313 @cindex @sc{gdb/mi}, data manipulation
31314 This section describes the @sc{gdb/mi} commands that manipulate data:
31315 examine memory and registers, evaluate expressions, etc.
31317 @c REMOVED FROM THE INTERFACE.
31318 @c @subheading -data-assign
31319 @c Change the value of a program variable. Plenty of side effects.
31320 @c @subsubheading GDB Command
31322 @c @subsubheading Example
31325 @subheading The @code{-data-disassemble} Command
31326 @findex -data-disassemble
31328 @subsubheading Synopsis
31332 [ -s @var{start-addr} -e @var{end-addr} ]
31333 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31341 @item @var{start-addr}
31342 is the beginning address (or @code{$pc})
31343 @item @var{end-addr}
31345 @item @var{filename}
31346 is the name of the file to disassemble
31347 @item @var{linenum}
31348 is the line number to disassemble around
31350 is the number of disassembly lines to be produced. If it is -1,
31351 the whole function will be disassembled, in case no @var{end-addr} is
31352 specified. If @var{end-addr} is specified as a non-zero value, and
31353 @var{lines} is lower than the number of disassembly lines between
31354 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31355 displayed; if @var{lines} is higher than the number of lines between
31356 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31359 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31360 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31361 mixed source and disassembly with raw opcodes).
31364 @subsubheading Result
31366 The result of the @code{-data-disassemble} command will be a list named
31367 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31368 used with the @code{-data-disassemble} command.
31370 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31375 The address at which this instruction was disassembled.
31378 The name of the function this instruction is within.
31381 The decimal offset in bytes from the start of @samp{func-name}.
31384 The text disassembly for this @samp{address}.
31387 This field is only present for mode 2. This contains the raw opcode
31388 bytes for the @samp{inst} field.
31392 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31393 @samp{src_and_asm_line}, each of which has the following fields:
31397 The line number within @samp{file}.
31400 The file name from the compilation unit. This might be an absolute
31401 file name or a relative file name depending on the compile command
31405 Absolute file name of @samp{file}. It is converted to a canonical form
31406 using the source file search path
31407 (@pxref{Source Path, ,Specifying Source Directories})
31408 and after resolving all the symbolic links.
31410 If the source file is not found this field will contain the path as
31411 present in the debug information.
31413 @item line_asm_insn
31414 This is a list of tuples containing the disassembly for @samp{line} in
31415 @samp{file}. The fields of each tuple are the same as for
31416 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31417 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31422 Note that whatever included in the @samp{inst} field, is not
31423 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31426 @subsubheading @value{GDBN} Command
31428 The corresponding @value{GDBN} command is @samp{disassemble}.
31430 @subsubheading Example
31432 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31436 -data-disassemble -s $pc -e "$pc + 20" -- 0
31439 @{address="0x000107c0",func-name="main",offset="4",
31440 inst="mov 2, %o0"@},
31441 @{address="0x000107c4",func-name="main",offset="8",
31442 inst="sethi %hi(0x11800), %o2"@},
31443 @{address="0x000107c8",func-name="main",offset="12",
31444 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31445 @{address="0x000107cc",func-name="main",offset="16",
31446 inst="sethi %hi(0x11800), %o2"@},
31447 @{address="0x000107d0",func-name="main",offset="20",
31448 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31452 Disassemble the whole @code{main} function. Line 32 is part of
31456 -data-disassemble -f basics.c -l 32 -- 0
31458 @{address="0x000107bc",func-name="main",offset="0",
31459 inst="save %sp, -112, %sp"@},
31460 @{address="0x000107c0",func-name="main",offset="4",
31461 inst="mov 2, %o0"@},
31462 @{address="0x000107c4",func-name="main",offset="8",
31463 inst="sethi %hi(0x11800), %o2"@},
31465 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31466 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31470 Disassemble 3 instructions from the start of @code{main}:
31474 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31476 @{address="0x000107bc",func-name="main",offset="0",
31477 inst="save %sp, -112, %sp"@},
31478 @{address="0x000107c0",func-name="main",offset="4",
31479 inst="mov 2, %o0"@},
31480 @{address="0x000107c4",func-name="main",offset="8",
31481 inst="sethi %hi(0x11800), %o2"@}]
31485 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31489 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31491 src_and_asm_line=@{line="31",
31492 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31493 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31494 line_asm_insn=[@{address="0x000107bc",
31495 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31496 src_and_asm_line=@{line="32",
31497 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31498 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31499 line_asm_insn=[@{address="0x000107c0",
31500 func-name="main",offset="4",inst="mov 2, %o0"@},
31501 @{address="0x000107c4",func-name="main",offset="8",
31502 inst="sethi %hi(0x11800), %o2"@}]@}]
31507 @subheading The @code{-data-evaluate-expression} Command
31508 @findex -data-evaluate-expression
31510 @subsubheading Synopsis
31513 -data-evaluate-expression @var{expr}
31516 Evaluate @var{expr} as an expression. The expression could contain an
31517 inferior function call. The function call will execute synchronously.
31518 If the expression contains spaces, it must be enclosed in double quotes.
31520 @subsubheading @value{GDBN} Command
31522 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31523 @samp{call}. In @code{gdbtk} only, there's a corresponding
31524 @samp{gdb_eval} command.
31526 @subsubheading Example
31528 In the following example, the numbers that precede the commands are the
31529 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31530 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31534 211-data-evaluate-expression A
31537 311-data-evaluate-expression &A
31538 311^done,value="0xefffeb7c"
31540 411-data-evaluate-expression A+3
31543 511-data-evaluate-expression "A + 3"
31549 @subheading The @code{-data-list-changed-registers} Command
31550 @findex -data-list-changed-registers
31552 @subsubheading Synopsis
31555 -data-list-changed-registers
31558 Display a list of the registers that have changed.
31560 @subsubheading @value{GDBN} Command
31562 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31563 has the corresponding command @samp{gdb_changed_register_list}.
31565 @subsubheading Example
31567 On a PPC MBX board:
31575 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31576 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31579 -data-list-changed-registers
31580 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31581 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31582 "24","25","26","27","28","30","31","64","65","66","67","69"]
31587 @subheading The @code{-data-list-register-names} Command
31588 @findex -data-list-register-names
31590 @subsubheading Synopsis
31593 -data-list-register-names [ ( @var{regno} )+ ]
31596 Show a list of register names for the current target. If no arguments
31597 are given, it shows a list of the names of all the registers. If
31598 integer numbers are given as arguments, it will print a list of the
31599 names of the registers corresponding to the arguments. To ensure
31600 consistency between a register name and its number, the output list may
31601 include empty register names.
31603 @subsubheading @value{GDBN} Command
31605 @value{GDBN} does not have a command which corresponds to
31606 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31607 corresponding command @samp{gdb_regnames}.
31609 @subsubheading Example
31611 For the PPC MBX board:
31614 -data-list-register-names
31615 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31616 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31617 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31618 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31619 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31620 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31621 "", "pc","ps","cr","lr","ctr","xer"]
31623 -data-list-register-names 1 2 3
31624 ^done,register-names=["r1","r2","r3"]
31628 @subheading The @code{-data-list-register-values} Command
31629 @findex -data-list-register-values
31631 @subsubheading Synopsis
31634 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31637 Display the registers' contents. @var{fmt} is the format according to
31638 which the registers' contents are to be returned, followed by an optional
31639 list of numbers specifying the registers to display. A missing list of
31640 numbers indicates that the contents of all the registers must be returned.
31642 Allowed formats for @var{fmt} are:
31659 @subsubheading @value{GDBN} Command
31661 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31662 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31664 @subsubheading Example
31666 For a PPC MBX board (note: line breaks are for readability only, they
31667 don't appear in the actual output):
31671 -data-list-register-values r 64 65
31672 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31673 @{number="65",value="0x00029002"@}]
31675 -data-list-register-values x
31676 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31677 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31678 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31679 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31680 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31681 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31682 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31683 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31684 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31685 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31686 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31687 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31688 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31689 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31690 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31691 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31692 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31693 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31694 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31695 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31696 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31697 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31698 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31699 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31700 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31701 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31702 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31703 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31704 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31705 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31706 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31707 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31708 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31709 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31710 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31711 @{number="69",value="0x20002b03"@}]
31716 @subheading The @code{-data-read-memory} Command
31717 @findex -data-read-memory
31719 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31721 @subsubheading Synopsis
31724 -data-read-memory [ -o @var{byte-offset} ]
31725 @var{address} @var{word-format} @var{word-size}
31726 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31733 @item @var{address}
31734 An expression specifying the address of the first memory word to be
31735 read. Complex expressions containing embedded white space should be
31736 quoted using the C convention.
31738 @item @var{word-format}
31739 The format to be used to print the memory words. The notation is the
31740 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31743 @item @var{word-size}
31744 The size of each memory word in bytes.
31746 @item @var{nr-rows}
31747 The number of rows in the output table.
31749 @item @var{nr-cols}
31750 The number of columns in the output table.
31753 If present, indicates that each row should include an @sc{ascii} dump. The
31754 value of @var{aschar} is used as a padding character when a byte is not a
31755 member of the printable @sc{ascii} character set (printable @sc{ascii}
31756 characters are those whose code is between 32 and 126, inclusively).
31758 @item @var{byte-offset}
31759 An offset to add to the @var{address} before fetching memory.
31762 This command displays memory contents as a table of @var{nr-rows} by
31763 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31764 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31765 (returned as @samp{total-bytes}). Should less than the requested number
31766 of bytes be returned by the target, the missing words are identified
31767 using @samp{N/A}. The number of bytes read from the target is returned
31768 in @samp{nr-bytes} and the starting address used to read memory in
31771 The address of the next/previous row or page is available in
31772 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31775 @subsubheading @value{GDBN} Command
31777 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31778 @samp{gdb_get_mem} memory read command.
31780 @subsubheading Example
31782 Read six bytes of memory starting at @code{bytes+6} but then offset by
31783 @code{-6} bytes. Format as three rows of two columns. One byte per
31784 word. Display each word in hex.
31788 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31789 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31790 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31791 prev-page="0x0000138a",memory=[
31792 @{addr="0x00001390",data=["0x00","0x01"]@},
31793 @{addr="0x00001392",data=["0x02","0x03"]@},
31794 @{addr="0x00001394",data=["0x04","0x05"]@}]
31798 Read two bytes of memory starting at address @code{shorts + 64} and
31799 display as a single word formatted in decimal.
31803 5-data-read-memory shorts+64 d 2 1 1
31804 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31805 next-row="0x00001512",prev-row="0x0000150e",
31806 next-page="0x00001512",prev-page="0x0000150e",memory=[
31807 @{addr="0x00001510",data=["128"]@}]
31811 Read thirty two bytes of memory starting at @code{bytes+16} and format
31812 as eight rows of four columns. Include a string encoding with @samp{x}
31813 used as the non-printable character.
31817 4-data-read-memory bytes+16 x 1 8 4 x
31818 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31819 next-row="0x000013c0",prev-row="0x0000139c",
31820 next-page="0x000013c0",prev-page="0x00001380",memory=[
31821 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31822 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31823 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31824 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31825 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31826 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31827 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31828 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31832 @subheading The @code{-data-read-memory-bytes} Command
31833 @findex -data-read-memory-bytes
31835 @subsubheading Synopsis
31838 -data-read-memory-bytes [ -o @var{byte-offset} ]
31839 @var{address} @var{count}
31846 @item @var{address}
31847 An expression specifying the address of the first memory word to be
31848 read. Complex expressions containing embedded white space should be
31849 quoted using the C convention.
31852 The number of bytes to read. This should be an integer literal.
31854 @item @var{byte-offset}
31855 The offsets in bytes relative to @var{address} at which to start
31856 reading. This should be an integer literal. This option is provided
31857 so that a frontend is not required to first evaluate address and then
31858 perform address arithmetics itself.
31862 This command attempts to read all accessible memory regions in the
31863 specified range. First, all regions marked as unreadable in the memory
31864 map (if one is defined) will be skipped. @xref{Memory Region
31865 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31866 regions. For each one, if reading full region results in an errors,
31867 @value{GDBN} will try to read a subset of the region.
31869 In general, every single byte in the region may be readable or not,
31870 and the only way to read every readable byte is to try a read at
31871 every address, which is not practical. Therefore, @value{GDBN} will
31872 attempt to read all accessible bytes at either beginning or the end
31873 of the region, using a binary division scheme. This heuristic works
31874 well for reading accross a memory map boundary. Note that if a region
31875 has a readable range that is neither at the beginning or the end,
31876 @value{GDBN} will not read it.
31878 The result record (@pxref{GDB/MI Result Records}) that is output of
31879 the command includes a field named @samp{memory} whose content is a
31880 list of tuples. Each tuple represent a successfully read memory block
31881 and has the following fields:
31885 The start address of the memory block, as hexadecimal literal.
31888 The end address of the memory block, as hexadecimal literal.
31891 The offset of the memory block, as hexadecimal literal, relative to
31892 the start address passed to @code{-data-read-memory-bytes}.
31895 The contents of the memory block, in hex.
31901 @subsubheading @value{GDBN} Command
31903 The corresponding @value{GDBN} command is @samp{x}.
31905 @subsubheading Example
31909 -data-read-memory-bytes &a 10
31910 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31912 contents="01000000020000000300"@}]
31917 @subheading The @code{-data-write-memory-bytes} Command
31918 @findex -data-write-memory-bytes
31920 @subsubheading Synopsis
31923 -data-write-memory-bytes @var{address} @var{contents}
31924 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31931 @item @var{address}
31932 An expression specifying the address of the first memory word to be
31933 read. Complex expressions containing embedded white space should be
31934 quoted using the C convention.
31936 @item @var{contents}
31937 The hex-encoded bytes to write.
31940 Optional argument indicating the number of bytes to be written. If @var{count}
31941 is greater than @var{contents}' length, @value{GDBN} will repeatedly
31942 write @var{contents} until it fills @var{count} bytes.
31946 @subsubheading @value{GDBN} Command
31948 There's no corresponding @value{GDBN} command.
31950 @subsubheading Example
31954 -data-write-memory-bytes &a "aabbccdd"
31961 -data-write-memory-bytes &a "aabbccdd" 16e
31966 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31967 @node GDB/MI Tracepoint Commands
31968 @section @sc{gdb/mi} Tracepoint Commands
31970 The commands defined in this section implement MI support for
31971 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31973 @subheading The @code{-trace-find} Command
31974 @findex -trace-find
31976 @subsubheading Synopsis
31979 -trace-find @var{mode} [@var{parameters}@dots{}]
31982 Find a trace frame using criteria defined by @var{mode} and
31983 @var{parameters}. The following table lists permissible
31984 modes and their parameters. For details of operation, see @ref{tfind}.
31989 No parameters are required. Stops examining trace frames.
31992 An integer is required as parameter. Selects tracepoint frame with
31995 @item tracepoint-number
31996 An integer is required as parameter. Finds next
31997 trace frame that corresponds to tracepoint with the specified number.
32000 An address is required as parameter. Finds
32001 next trace frame that corresponds to any tracepoint at the specified
32004 @item pc-inside-range
32005 Two addresses are required as parameters. Finds next trace
32006 frame that corresponds to a tracepoint at an address inside the
32007 specified range. Both bounds are considered to be inside the range.
32009 @item pc-outside-range
32010 Two addresses are required as parameters. Finds
32011 next trace frame that corresponds to a tracepoint at an address outside
32012 the specified range. Both bounds are considered to be inside the range.
32015 Line specification is required as parameter. @xref{Specify Location}.
32016 Finds next trace frame that corresponds to a tracepoint at
32017 the specified location.
32021 If @samp{none} was passed as @var{mode}, the response does not
32022 have fields. Otherwise, the response may have the following fields:
32026 This field has either @samp{0} or @samp{1} as the value, depending
32027 on whether a matching tracepoint was found.
32030 The index of the found traceframe. This field is present iff
32031 the @samp{found} field has value of @samp{1}.
32034 The index of the found tracepoint. This field is present iff
32035 the @samp{found} field has value of @samp{1}.
32038 The information about the frame corresponding to the found trace
32039 frame. This field is present only if a trace frame was found.
32040 @xref{GDB/MI Frame Information}, for description of this field.
32044 @subsubheading @value{GDBN} Command
32046 The corresponding @value{GDBN} command is @samp{tfind}.
32048 @subheading -trace-define-variable
32049 @findex -trace-define-variable
32051 @subsubheading Synopsis
32054 -trace-define-variable @var{name} [ @var{value} ]
32057 Create trace variable @var{name} if it does not exist. If
32058 @var{value} is specified, sets the initial value of the specified
32059 trace variable to that value. Note that the @var{name} should start
32060 with the @samp{$} character.
32062 @subsubheading @value{GDBN} Command
32064 The corresponding @value{GDBN} command is @samp{tvariable}.
32066 @subheading -trace-list-variables
32067 @findex -trace-list-variables
32069 @subsubheading Synopsis
32072 -trace-list-variables
32075 Return a table of all defined trace variables. Each element of the
32076 table has the following fields:
32080 The name of the trace variable. This field is always present.
32083 The initial value. This is a 64-bit signed integer. This
32084 field is always present.
32087 The value the trace variable has at the moment. This is a 64-bit
32088 signed integer. This field is absent iff current value is
32089 not defined, for example if the trace was never run, or is
32094 @subsubheading @value{GDBN} Command
32096 The corresponding @value{GDBN} command is @samp{tvariables}.
32098 @subsubheading Example
32102 -trace-list-variables
32103 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32104 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32105 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32106 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32107 body=[variable=@{name="$trace_timestamp",initial="0"@}
32108 variable=@{name="$foo",initial="10",current="15"@}]@}
32112 @subheading -trace-save
32113 @findex -trace-save
32115 @subsubheading Synopsis
32118 -trace-save [-r ] @var{filename}
32121 Saves the collected trace data to @var{filename}. Without the
32122 @samp{-r} option, the data is downloaded from the target and saved
32123 in a local file. With the @samp{-r} option the target is asked
32124 to perform the save.
32126 @subsubheading @value{GDBN} Command
32128 The corresponding @value{GDBN} command is @samp{tsave}.
32131 @subheading -trace-start
32132 @findex -trace-start
32134 @subsubheading Synopsis
32140 Starts a tracing experiments. The result of this command does not
32143 @subsubheading @value{GDBN} Command
32145 The corresponding @value{GDBN} command is @samp{tstart}.
32147 @subheading -trace-status
32148 @findex -trace-status
32150 @subsubheading Synopsis
32156 Obtains the status of a tracing experiment. The result may include
32157 the following fields:
32162 May have a value of either @samp{0}, when no tracing operations are
32163 supported, @samp{1}, when all tracing operations are supported, or
32164 @samp{file} when examining trace file. In the latter case, examining
32165 of trace frame is possible but new tracing experiement cannot be
32166 started. This field is always present.
32169 May have a value of either @samp{0} or @samp{1} depending on whether
32170 tracing experiement is in progress on target. This field is present
32171 if @samp{supported} field is not @samp{0}.
32174 Report the reason why the tracing was stopped last time. This field
32175 may be absent iff tracing was never stopped on target yet. The
32176 value of @samp{request} means the tracing was stopped as result of
32177 the @code{-trace-stop} command. The value of @samp{overflow} means
32178 the tracing buffer is full. The value of @samp{disconnection} means
32179 tracing was automatically stopped when @value{GDBN} has disconnected.
32180 The value of @samp{passcount} means tracing was stopped when a
32181 tracepoint was passed a maximal number of times for that tracepoint.
32182 This field is present if @samp{supported} field is not @samp{0}.
32184 @item stopping-tracepoint
32185 The number of tracepoint whose passcount as exceeded. This field is
32186 present iff the @samp{stop-reason} field has the value of
32190 @itemx frames-created
32191 The @samp{frames} field is a count of the total number of trace frames
32192 in the trace buffer, while @samp{frames-created} is the total created
32193 during the run, including ones that were discarded, such as when a
32194 circular trace buffer filled up. Both fields are optional.
32198 These fields tell the current size of the tracing buffer and the
32199 remaining space. These fields are optional.
32202 The value of the circular trace buffer flag. @code{1} means that the
32203 trace buffer is circular and old trace frames will be discarded if
32204 necessary to make room, @code{0} means that the trace buffer is linear
32208 The value of the disconnected tracing flag. @code{1} means that
32209 tracing will continue after @value{GDBN} disconnects, @code{0} means
32210 that the trace run will stop.
32213 The filename of the trace file being examined. This field is
32214 optional, and only present when examining a trace file.
32218 @subsubheading @value{GDBN} Command
32220 The corresponding @value{GDBN} command is @samp{tstatus}.
32222 @subheading -trace-stop
32223 @findex -trace-stop
32225 @subsubheading Synopsis
32231 Stops a tracing experiment. The result of this command has the same
32232 fields as @code{-trace-status}, except that the @samp{supported} and
32233 @samp{running} fields are not output.
32235 @subsubheading @value{GDBN} Command
32237 The corresponding @value{GDBN} command is @samp{tstop}.
32240 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32241 @node GDB/MI Symbol Query
32242 @section @sc{gdb/mi} Symbol Query Commands
32246 @subheading The @code{-symbol-info-address} Command
32247 @findex -symbol-info-address
32249 @subsubheading Synopsis
32252 -symbol-info-address @var{symbol}
32255 Describe where @var{symbol} is stored.
32257 @subsubheading @value{GDBN} Command
32259 The corresponding @value{GDBN} command is @samp{info address}.
32261 @subsubheading Example
32265 @subheading The @code{-symbol-info-file} Command
32266 @findex -symbol-info-file
32268 @subsubheading Synopsis
32274 Show the file for the symbol.
32276 @subsubheading @value{GDBN} Command
32278 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32279 @samp{gdb_find_file}.
32281 @subsubheading Example
32285 @subheading The @code{-symbol-info-function} Command
32286 @findex -symbol-info-function
32288 @subsubheading Synopsis
32291 -symbol-info-function
32294 Show which function the symbol lives in.
32296 @subsubheading @value{GDBN} Command
32298 @samp{gdb_get_function} in @code{gdbtk}.
32300 @subsubheading Example
32304 @subheading The @code{-symbol-info-line} Command
32305 @findex -symbol-info-line
32307 @subsubheading Synopsis
32313 Show the core addresses of the code for a source line.
32315 @subsubheading @value{GDBN} Command
32317 The corresponding @value{GDBN} command is @samp{info line}.
32318 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32320 @subsubheading Example
32324 @subheading The @code{-symbol-info-symbol} Command
32325 @findex -symbol-info-symbol
32327 @subsubheading Synopsis
32330 -symbol-info-symbol @var{addr}
32333 Describe what symbol is at location @var{addr}.
32335 @subsubheading @value{GDBN} Command
32337 The corresponding @value{GDBN} command is @samp{info symbol}.
32339 @subsubheading Example
32343 @subheading The @code{-symbol-list-functions} Command
32344 @findex -symbol-list-functions
32346 @subsubheading Synopsis
32349 -symbol-list-functions
32352 List the functions in the executable.
32354 @subsubheading @value{GDBN} Command
32356 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32357 @samp{gdb_search} in @code{gdbtk}.
32359 @subsubheading Example
32364 @subheading The @code{-symbol-list-lines} Command
32365 @findex -symbol-list-lines
32367 @subsubheading Synopsis
32370 -symbol-list-lines @var{filename}
32373 Print the list of lines that contain code and their associated program
32374 addresses for the given source filename. The entries are sorted in
32375 ascending PC order.
32377 @subsubheading @value{GDBN} Command
32379 There is no corresponding @value{GDBN} command.
32381 @subsubheading Example
32384 -symbol-list-lines basics.c
32385 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32391 @subheading The @code{-symbol-list-types} Command
32392 @findex -symbol-list-types
32394 @subsubheading Synopsis
32400 List all the type names.
32402 @subsubheading @value{GDBN} Command
32404 The corresponding commands are @samp{info types} in @value{GDBN},
32405 @samp{gdb_search} in @code{gdbtk}.
32407 @subsubheading Example
32411 @subheading The @code{-symbol-list-variables} Command
32412 @findex -symbol-list-variables
32414 @subsubheading Synopsis
32417 -symbol-list-variables
32420 List all the global and static variable names.
32422 @subsubheading @value{GDBN} Command
32424 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32426 @subsubheading Example
32430 @subheading The @code{-symbol-locate} Command
32431 @findex -symbol-locate
32433 @subsubheading Synopsis
32439 @subsubheading @value{GDBN} Command
32441 @samp{gdb_loc} in @code{gdbtk}.
32443 @subsubheading Example
32447 @subheading The @code{-symbol-type} Command
32448 @findex -symbol-type
32450 @subsubheading Synopsis
32453 -symbol-type @var{variable}
32456 Show type of @var{variable}.
32458 @subsubheading @value{GDBN} Command
32460 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32461 @samp{gdb_obj_variable}.
32463 @subsubheading Example
32468 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32469 @node GDB/MI File Commands
32470 @section @sc{gdb/mi} File Commands
32472 This section describes the GDB/MI commands to specify executable file names
32473 and to read in and obtain symbol table information.
32475 @subheading The @code{-file-exec-and-symbols} Command
32476 @findex -file-exec-and-symbols
32478 @subsubheading Synopsis
32481 -file-exec-and-symbols @var{file}
32484 Specify the executable file to be debugged. This file is the one from
32485 which the symbol table is also read. If no file is specified, the
32486 command clears the executable and symbol information. If breakpoints
32487 are set when using this command with no arguments, @value{GDBN} will produce
32488 error messages. Otherwise, no output is produced, except a completion
32491 @subsubheading @value{GDBN} Command
32493 The corresponding @value{GDBN} command is @samp{file}.
32495 @subsubheading Example
32499 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32505 @subheading The @code{-file-exec-file} Command
32506 @findex -file-exec-file
32508 @subsubheading Synopsis
32511 -file-exec-file @var{file}
32514 Specify the executable file to be debugged. Unlike
32515 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32516 from this file. If used without argument, @value{GDBN} clears the information
32517 about the executable file. No output is produced, except a completion
32520 @subsubheading @value{GDBN} Command
32522 The corresponding @value{GDBN} command is @samp{exec-file}.
32524 @subsubheading Example
32528 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32535 @subheading The @code{-file-list-exec-sections} Command
32536 @findex -file-list-exec-sections
32538 @subsubheading Synopsis
32541 -file-list-exec-sections
32544 List the sections of the current executable file.
32546 @subsubheading @value{GDBN} Command
32548 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32549 information as this command. @code{gdbtk} has a corresponding command
32550 @samp{gdb_load_info}.
32552 @subsubheading Example
32557 @subheading The @code{-file-list-exec-source-file} Command
32558 @findex -file-list-exec-source-file
32560 @subsubheading Synopsis
32563 -file-list-exec-source-file
32566 List the line number, the current source file, and the absolute path
32567 to the current source file for the current executable. The macro
32568 information field has a value of @samp{1} or @samp{0} depending on
32569 whether or not the file includes preprocessor macro information.
32571 @subsubheading @value{GDBN} Command
32573 The @value{GDBN} equivalent is @samp{info source}
32575 @subsubheading Example
32579 123-file-list-exec-source-file
32580 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32585 @subheading The @code{-file-list-exec-source-files} Command
32586 @findex -file-list-exec-source-files
32588 @subsubheading Synopsis
32591 -file-list-exec-source-files
32594 List the source files for the current executable.
32596 It will always output both the filename and fullname (absolute file
32597 name) of a source file.
32599 @subsubheading @value{GDBN} Command
32601 The @value{GDBN} equivalent is @samp{info sources}.
32602 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32604 @subsubheading Example
32607 -file-list-exec-source-files
32609 @{file=foo.c,fullname=/home/foo.c@},
32610 @{file=/home/bar.c,fullname=/home/bar.c@},
32611 @{file=gdb_could_not_find_fullpath.c@}]
32616 @subheading The @code{-file-list-shared-libraries} Command
32617 @findex -file-list-shared-libraries
32619 @subsubheading Synopsis
32622 -file-list-shared-libraries
32625 List the shared libraries in the program.
32627 @subsubheading @value{GDBN} Command
32629 The corresponding @value{GDBN} command is @samp{info shared}.
32631 @subsubheading Example
32635 @subheading The @code{-file-list-symbol-files} Command
32636 @findex -file-list-symbol-files
32638 @subsubheading Synopsis
32641 -file-list-symbol-files
32646 @subsubheading @value{GDBN} Command
32648 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32650 @subsubheading Example
32655 @subheading The @code{-file-symbol-file} Command
32656 @findex -file-symbol-file
32658 @subsubheading Synopsis
32661 -file-symbol-file @var{file}
32664 Read symbol table info from the specified @var{file} argument. When
32665 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32666 produced, except for a completion notification.
32668 @subsubheading @value{GDBN} Command
32670 The corresponding @value{GDBN} command is @samp{symbol-file}.
32672 @subsubheading Example
32676 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32682 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32683 @node GDB/MI Memory Overlay Commands
32684 @section @sc{gdb/mi} Memory Overlay Commands
32686 The memory overlay commands are not implemented.
32688 @c @subheading -overlay-auto
32690 @c @subheading -overlay-list-mapping-state
32692 @c @subheading -overlay-list-overlays
32694 @c @subheading -overlay-map
32696 @c @subheading -overlay-off
32698 @c @subheading -overlay-on
32700 @c @subheading -overlay-unmap
32702 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32703 @node GDB/MI Signal Handling Commands
32704 @section @sc{gdb/mi} Signal Handling Commands
32706 Signal handling commands are not implemented.
32708 @c @subheading -signal-handle
32710 @c @subheading -signal-list-handle-actions
32712 @c @subheading -signal-list-signal-types
32716 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32717 @node GDB/MI Target Manipulation
32718 @section @sc{gdb/mi} Target Manipulation Commands
32721 @subheading The @code{-target-attach} Command
32722 @findex -target-attach
32724 @subsubheading Synopsis
32727 -target-attach @var{pid} | @var{gid} | @var{file}
32730 Attach to a process @var{pid} or a file @var{file} outside of
32731 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32732 group, the id previously returned by
32733 @samp{-list-thread-groups --available} must be used.
32735 @subsubheading @value{GDBN} Command
32737 The corresponding @value{GDBN} command is @samp{attach}.
32739 @subsubheading Example
32743 =thread-created,id="1"
32744 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32750 @subheading The @code{-target-compare-sections} Command
32751 @findex -target-compare-sections
32753 @subsubheading Synopsis
32756 -target-compare-sections [ @var{section} ]
32759 Compare data of section @var{section} on target to the exec file.
32760 Without the argument, all sections are compared.
32762 @subsubheading @value{GDBN} Command
32764 The @value{GDBN} equivalent is @samp{compare-sections}.
32766 @subsubheading Example
32771 @subheading The @code{-target-detach} Command
32772 @findex -target-detach
32774 @subsubheading Synopsis
32777 -target-detach [ @var{pid} | @var{gid} ]
32780 Detach from the remote target which normally resumes its execution.
32781 If either @var{pid} or @var{gid} is specified, detaches from either
32782 the specified process, or specified thread group. There's no output.
32784 @subsubheading @value{GDBN} Command
32786 The corresponding @value{GDBN} command is @samp{detach}.
32788 @subsubheading Example
32798 @subheading The @code{-target-disconnect} Command
32799 @findex -target-disconnect
32801 @subsubheading Synopsis
32807 Disconnect from the remote target. There's no output and the target is
32808 generally not resumed.
32810 @subsubheading @value{GDBN} Command
32812 The corresponding @value{GDBN} command is @samp{disconnect}.
32814 @subsubheading Example
32824 @subheading The @code{-target-download} Command
32825 @findex -target-download
32827 @subsubheading Synopsis
32833 Loads the executable onto the remote target.
32834 It prints out an update message every half second, which includes the fields:
32838 The name of the section.
32840 The size of what has been sent so far for that section.
32842 The size of the section.
32844 The total size of what was sent so far (the current and the previous sections).
32846 The size of the overall executable to download.
32850 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32851 @sc{gdb/mi} Output Syntax}).
32853 In addition, it prints the name and size of the sections, as they are
32854 downloaded. These messages include the following fields:
32858 The name of the section.
32860 The size of the section.
32862 The size of the overall executable to download.
32866 At the end, a summary is printed.
32868 @subsubheading @value{GDBN} Command
32870 The corresponding @value{GDBN} command is @samp{load}.
32872 @subsubheading Example
32874 Note: each status message appears on a single line. Here the messages
32875 have been broken down so that they can fit onto a page.
32880 +download,@{section=".text",section-size="6668",total-size="9880"@}
32881 +download,@{section=".text",section-sent="512",section-size="6668",
32882 total-sent="512",total-size="9880"@}
32883 +download,@{section=".text",section-sent="1024",section-size="6668",
32884 total-sent="1024",total-size="9880"@}
32885 +download,@{section=".text",section-sent="1536",section-size="6668",
32886 total-sent="1536",total-size="9880"@}
32887 +download,@{section=".text",section-sent="2048",section-size="6668",
32888 total-sent="2048",total-size="9880"@}
32889 +download,@{section=".text",section-sent="2560",section-size="6668",
32890 total-sent="2560",total-size="9880"@}
32891 +download,@{section=".text",section-sent="3072",section-size="6668",
32892 total-sent="3072",total-size="9880"@}
32893 +download,@{section=".text",section-sent="3584",section-size="6668",
32894 total-sent="3584",total-size="9880"@}
32895 +download,@{section=".text",section-sent="4096",section-size="6668",
32896 total-sent="4096",total-size="9880"@}
32897 +download,@{section=".text",section-sent="4608",section-size="6668",
32898 total-sent="4608",total-size="9880"@}
32899 +download,@{section=".text",section-sent="5120",section-size="6668",
32900 total-sent="5120",total-size="9880"@}
32901 +download,@{section=".text",section-sent="5632",section-size="6668",
32902 total-sent="5632",total-size="9880"@}
32903 +download,@{section=".text",section-sent="6144",section-size="6668",
32904 total-sent="6144",total-size="9880"@}
32905 +download,@{section=".text",section-sent="6656",section-size="6668",
32906 total-sent="6656",total-size="9880"@}
32907 +download,@{section=".init",section-size="28",total-size="9880"@}
32908 +download,@{section=".fini",section-size="28",total-size="9880"@}
32909 +download,@{section=".data",section-size="3156",total-size="9880"@}
32910 +download,@{section=".data",section-sent="512",section-size="3156",
32911 total-sent="7236",total-size="9880"@}
32912 +download,@{section=".data",section-sent="1024",section-size="3156",
32913 total-sent="7748",total-size="9880"@}
32914 +download,@{section=".data",section-sent="1536",section-size="3156",
32915 total-sent="8260",total-size="9880"@}
32916 +download,@{section=".data",section-sent="2048",section-size="3156",
32917 total-sent="8772",total-size="9880"@}
32918 +download,@{section=".data",section-sent="2560",section-size="3156",
32919 total-sent="9284",total-size="9880"@}
32920 +download,@{section=".data",section-sent="3072",section-size="3156",
32921 total-sent="9796",total-size="9880"@}
32922 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32929 @subheading The @code{-target-exec-status} Command
32930 @findex -target-exec-status
32932 @subsubheading Synopsis
32935 -target-exec-status
32938 Provide information on the state of the target (whether it is running or
32939 not, for instance).
32941 @subsubheading @value{GDBN} Command
32943 There's no equivalent @value{GDBN} command.
32945 @subsubheading Example
32949 @subheading The @code{-target-list-available-targets} Command
32950 @findex -target-list-available-targets
32952 @subsubheading Synopsis
32955 -target-list-available-targets
32958 List the possible targets to connect to.
32960 @subsubheading @value{GDBN} Command
32962 The corresponding @value{GDBN} command is @samp{help target}.
32964 @subsubheading Example
32968 @subheading The @code{-target-list-current-targets} Command
32969 @findex -target-list-current-targets
32971 @subsubheading Synopsis
32974 -target-list-current-targets
32977 Describe the current target.
32979 @subsubheading @value{GDBN} Command
32981 The corresponding information is printed by @samp{info file} (among
32984 @subsubheading Example
32988 @subheading The @code{-target-list-parameters} Command
32989 @findex -target-list-parameters
32991 @subsubheading Synopsis
32994 -target-list-parameters
33000 @subsubheading @value{GDBN} Command
33004 @subsubheading Example
33008 @subheading The @code{-target-select} Command
33009 @findex -target-select
33011 @subsubheading Synopsis
33014 -target-select @var{type} @var{parameters @dots{}}
33017 Connect @value{GDBN} to the remote target. This command takes two args:
33021 The type of target, for instance @samp{remote}, etc.
33022 @item @var{parameters}
33023 Device names, host names and the like. @xref{Target Commands, ,
33024 Commands for Managing Targets}, for more details.
33027 The output is a connection notification, followed by the address at
33028 which the target program is, in the following form:
33031 ^connected,addr="@var{address}",func="@var{function name}",
33032 args=[@var{arg list}]
33035 @subsubheading @value{GDBN} Command
33037 The corresponding @value{GDBN} command is @samp{target}.
33039 @subsubheading Example
33043 -target-select remote /dev/ttya
33044 ^connected,addr="0xfe00a300",func="??",args=[]
33048 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33049 @node GDB/MI File Transfer Commands
33050 @section @sc{gdb/mi} File Transfer Commands
33053 @subheading The @code{-target-file-put} Command
33054 @findex -target-file-put
33056 @subsubheading Synopsis
33059 -target-file-put @var{hostfile} @var{targetfile}
33062 Copy file @var{hostfile} from the host system (the machine running
33063 @value{GDBN}) to @var{targetfile} on the target system.
33065 @subsubheading @value{GDBN} Command
33067 The corresponding @value{GDBN} command is @samp{remote put}.
33069 @subsubheading Example
33073 -target-file-put localfile remotefile
33079 @subheading The @code{-target-file-get} Command
33080 @findex -target-file-get
33082 @subsubheading Synopsis
33085 -target-file-get @var{targetfile} @var{hostfile}
33088 Copy file @var{targetfile} from the target system to @var{hostfile}
33089 on the host system.
33091 @subsubheading @value{GDBN} Command
33093 The corresponding @value{GDBN} command is @samp{remote get}.
33095 @subsubheading Example
33099 -target-file-get remotefile localfile
33105 @subheading The @code{-target-file-delete} Command
33106 @findex -target-file-delete
33108 @subsubheading Synopsis
33111 -target-file-delete @var{targetfile}
33114 Delete @var{targetfile} from the target system.
33116 @subsubheading @value{GDBN} Command
33118 The corresponding @value{GDBN} command is @samp{remote delete}.
33120 @subsubheading Example
33124 -target-file-delete remotefile
33130 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33131 @node GDB/MI Miscellaneous Commands
33132 @section Miscellaneous @sc{gdb/mi} Commands
33134 @c @subheading -gdb-complete
33136 @subheading The @code{-gdb-exit} Command
33139 @subsubheading Synopsis
33145 Exit @value{GDBN} immediately.
33147 @subsubheading @value{GDBN} Command
33149 Approximately corresponds to @samp{quit}.
33151 @subsubheading Example
33161 @subheading The @code{-exec-abort} Command
33162 @findex -exec-abort
33164 @subsubheading Synopsis
33170 Kill the inferior running program.
33172 @subsubheading @value{GDBN} Command
33174 The corresponding @value{GDBN} command is @samp{kill}.
33176 @subsubheading Example
33181 @subheading The @code{-gdb-set} Command
33184 @subsubheading Synopsis
33190 Set an internal @value{GDBN} variable.
33191 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33193 @subsubheading @value{GDBN} Command
33195 The corresponding @value{GDBN} command is @samp{set}.
33197 @subsubheading Example
33207 @subheading The @code{-gdb-show} Command
33210 @subsubheading Synopsis
33216 Show the current value of a @value{GDBN} variable.
33218 @subsubheading @value{GDBN} Command
33220 The corresponding @value{GDBN} command is @samp{show}.
33222 @subsubheading Example
33231 @c @subheading -gdb-source
33234 @subheading The @code{-gdb-version} Command
33235 @findex -gdb-version
33237 @subsubheading Synopsis
33243 Show version information for @value{GDBN}. Used mostly in testing.
33245 @subsubheading @value{GDBN} Command
33247 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33248 default shows this information when you start an interactive session.
33250 @subsubheading Example
33252 @c This example modifies the actual output from GDB to avoid overfull
33258 ~Copyright 2000 Free Software Foundation, Inc.
33259 ~GDB is free software, covered by the GNU General Public License, and
33260 ~you are welcome to change it and/or distribute copies of it under
33261 ~ certain conditions.
33262 ~Type "show copying" to see the conditions.
33263 ~There is absolutely no warranty for GDB. Type "show warranty" for
33265 ~This GDB was configured as
33266 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33271 @subheading The @code{-list-features} Command
33272 @findex -list-features
33274 Returns a list of particular features of the MI protocol that
33275 this version of gdb implements. A feature can be a command,
33276 or a new field in an output of some command, or even an
33277 important bugfix. While a frontend can sometimes detect presence
33278 of a feature at runtime, it is easier to perform detection at debugger
33281 The command returns a list of strings, with each string naming an
33282 available feature. Each returned string is just a name, it does not
33283 have any internal structure. The list of possible feature names
33289 (gdb) -list-features
33290 ^done,result=["feature1","feature2"]
33293 The current list of features is:
33296 @item frozen-varobjs
33297 Indicates support for the @code{-var-set-frozen} command, as well
33298 as possible presense of the @code{frozen} field in the output
33299 of @code{-varobj-create}.
33300 @item pending-breakpoints
33301 Indicates support for the @option{-f} option to the @code{-break-insert}
33304 Indicates Python scripting support, Python-based
33305 pretty-printing commands, and possible presence of the
33306 @samp{display_hint} field in the output of @code{-var-list-children}
33308 Indicates support for the @code{-thread-info} command.
33309 @item data-read-memory-bytes
33310 Indicates support for the @code{-data-read-memory-bytes} and the
33311 @code{-data-write-memory-bytes} commands.
33312 @item breakpoint-notifications
33313 Indicates that changes to breakpoints and breakpoints created via the
33314 CLI will be announced via async records.
33315 @item ada-task-info
33316 Indicates support for the @code{-ada-task-info} command.
33319 @subheading The @code{-list-target-features} Command
33320 @findex -list-target-features
33322 Returns a list of particular features that are supported by the
33323 target. Those features affect the permitted MI commands, but
33324 unlike the features reported by the @code{-list-features} command, the
33325 features depend on which target GDB is using at the moment. Whenever
33326 a target can change, due to commands such as @code{-target-select},
33327 @code{-target-attach} or @code{-exec-run}, the list of target features
33328 may change, and the frontend should obtain it again.
33332 (gdb) -list-features
33333 ^done,result=["async"]
33336 The current list of features is:
33340 Indicates that the target is capable of asynchronous command
33341 execution, which means that @value{GDBN} will accept further commands
33342 while the target is running.
33345 Indicates that the target is capable of reverse execution.
33346 @xref{Reverse Execution}, for more information.
33350 @subheading The @code{-list-thread-groups} Command
33351 @findex -list-thread-groups
33353 @subheading Synopsis
33356 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33359 Lists thread groups (@pxref{Thread groups}). When a single thread
33360 group is passed as the argument, lists the children of that group.
33361 When several thread group are passed, lists information about those
33362 thread groups. Without any parameters, lists information about all
33363 top-level thread groups.
33365 Normally, thread groups that are being debugged are reported.
33366 With the @samp{--available} option, @value{GDBN} reports thread groups
33367 available on the target.
33369 The output of this command may have either a @samp{threads} result or
33370 a @samp{groups} result. The @samp{thread} result has a list of tuples
33371 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33372 Information}). The @samp{groups} result has a list of tuples as value,
33373 each tuple describing a thread group. If top-level groups are
33374 requested (that is, no parameter is passed), or when several groups
33375 are passed, the output always has a @samp{groups} result. The format
33376 of the @samp{group} result is described below.
33378 To reduce the number of roundtrips it's possible to list thread groups
33379 together with their children, by passing the @samp{--recurse} option
33380 and the recursion depth. Presently, only recursion depth of 1 is
33381 permitted. If this option is present, then every reported thread group
33382 will also include its children, either as @samp{group} or
33383 @samp{threads} field.
33385 In general, any combination of option and parameters is permitted, with
33386 the following caveats:
33390 When a single thread group is passed, the output will typically
33391 be the @samp{threads} result. Because threads may not contain
33392 anything, the @samp{recurse} option will be ignored.
33395 When the @samp{--available} option is passed, limited information may
33396 be available. In particular, the list of threads of a process might
33397 be inaccessible. Further, specifying specific thread groups might
33398 not give any performance advantage over listing all thread groups.
33399 The frontend should assume that @samp{-list-thread-groups --available}
33400 is always an expensive operation and cache the results.
33404 The @samp{groups} result is a list of tuples, where each tuple may
33405 have the following fields:
33409 Identifier of the thread group. This field is always present.
33410 The identifier is an opaque string; frontends should not try to
33411 convert it to an integer, even though it might look like one.
33414 The type of the thread group. At present, only @samp{process} is a
33418 The target-specific process identifier. This field is only present
33419 for thread groups of type @samp{process} and only if the process exists.
33422 The number of children this thread group has. This field may be
33423 absent for an available thread group.
33426 This field has a list of tuples as value, each tuple describing a
33427 thread. It may be present if the @samp{--recurse} option is
33428 specified, and it's actually possible to obtain the threads.
33431 This field is a list of integers, each identifying a core that one
33432 thread of the group is running on. This field may be absent if
33433 such information is not available.
33436 The name of the executable file that corresponds to this thread group.
33437 The field is only present for thread groups of type @samp{process},
33438 and only if there is a corresponding executable file.
33442 @subheading Example
33446 -list-thread-groups
33447 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33448 -list-thread-groups 17
33449 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33450 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33451 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33452 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33453 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33454 -list-thread-groups --available
33455 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33456 -list-thread-groups --available --recurse 1
33457 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33458 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33459 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33460 -list-thread-groups --available --recurse 1 17 18
33461 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33462 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33463 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33466 @subheading The @code{-info-os} Command
33469 @subsubheading Synopsis
33472 -info-os [ @var{type} ]
33475 If no argument is supplied, the command returns a table of available
33476 operating-system-specific information types. If one of these types is
33477 supplied as an argument @var{type}, then the command returns a table
33478 of data of that type.
33480 The types of information available depend on the target operating
33483 @subsubheading @value{GDBN} Command
33485 The corresponding @value{GDBN} command is @samp{info os}.
33487 @subsubheading Example
33489 When run on a @sc{gnu}/Linux system, the output will look something
33495 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33496 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33497 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33498 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33499 body=[item=@{col0="processes",col1="Listing of all processes",
33500 col2="Processes"@},
33501 item=@{col0="procgroups",col1="Listing of all process groups",
33502 col2="Process groups"@},
33503 item=@{col0="threads",col1="Listing of all threads",
33505 item=@{col0="files",col1="Listing of all file descriptors",
33506 col2="File descriptors"@},
33507 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33509 item=@{col0="shm",col1="Listing of all shared-memory regions",
33510 col2="Shared-memory regions"@},
33511 item=@{col0="semaphores",col1="Listing of all semaphores",
33512 col2="Semaphores"@},
33513 item=@{col0="msg",col1="Listing of all message queues",
33514 col2="Message queues"@},
33515 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33516 col2="Kernel modules"@}]@}
33519 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33520 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33521 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33522 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33523 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33524 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33525 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33526 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33528 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33529 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33533 (Note that the MI output here includes a @code{"Title"} column that
33534 does not appear in command-line @code{info os}; this column is useful
33535 for MI clients that want to enumerate the types of data, such as in a
33536 popup menu, but is needless clutter on the command line, and
33537 @code{info os} omits it.)
33539 @subheading The @code{-add-inferior} Command
33540 @findex -add-inferior
33542 @subheading Synopsis
33548 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33549 inferior is not associated with any executable. Such association may
33550 be established with the @samp{-file-exec-and-symbols} command
33551 (@pxref{GDB/MI File Commands}). The command response has a single
33552 field, @samp{thread-group}, whose value is the identifier of the
33553 thread group corresponding to the new inferior.
33555 @subheading Example
33560 ^done,thread-group="i3"
33563 @subheading The @code{-interpreter-exec} Command
33564 @findex -interpreter-exec
33566 @subheading Synopsis
33569 -interpreter-exec @var{interpreter} @var{command}
33571 @anchor{-interpreter-exec}
33573 Execute the specified @var{command} in the given @var{interpreter}.
33575 @subheading @value{GDBN} Command
33577 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33579 @subheading Example
33583 -interpreter-exec console "break main"
33584 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33585 &"During symbol reading, bad structure-type format.\n"
33586 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33591 @subheading The @code{-inferior-tty-set} Command
33592 @findex -inferior-tty-set
33594 @subheading Synopsis
33597 -inferior-tty-set /dev/pts/1
33600 Set terminal for future runs of the program being debugged.
33602 @subheading @value{GDBN} Command
33604 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33606 @subheading Example
33610 -inferior-tty-set /dev/pts/1
33615 @subheading The @code{-inferior-tty-show} Command
33616 @findex -inferior-tty-show
33618 @subheading Synopsis
33624 Show terminal for future runs of program being debugged.
33626 @subheading @value{GDBN} Command
33628 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33630 @subheading Example
33634 -inferior-tty-set /dev/pts/1
33638 ^done,inferior_tty_terminal="/dev/pts/1"
33642 @subheading The @code{-enable-timings} Command
33643 @findex -enable-timings
33645 @subheading Synopsis
33648 -enable-timings [yes | no]
33651 Toggle the printing of the wallclock, user and system times for an MI
33652 command as a field in its output. This command is to help frontend
33653 developers optimize the performance of their code. No argument is
33654 equivalent to @samp{yes}.
33656 @subheading @value{GDBN} Command
33660 @subheading Example
33668 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33669 addr="0x080484ed",func="main",file="myprog.c",
33670 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33672 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33680 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33681 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33682 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33683 fullname="/home/nickrob/myprog.c",line="73"@}
33688 @chapter @value{GDBN} Annotations
33690 This chapter describes annotations in @value{GDBN}. Annotations were
33691 designed to interface @value{GDBN} to graphical user interfaces or other
33692 similar programs which want to interact with @value{GDBN} at a
33693 relatively high level.
33695 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33699 This is Edition @value{EDITION}, @value{DATE}.
33703 * Annotations Overview:: What annotations are; the general syntax.
33704 * Server Prefix:: Issuing a command without affecting user state.
33705 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33706 * Errors:: Annotations for error messages.
33707 * Invalidation:: Some annotations describe things now invalid.
33708 * Annotations for Running::
33709 Whether the program is running, how it stopped, etc.
33710 * Source Annotations:: Annotations describing source code.
33713 @node Annotations Overview
33714 @section What is an Annotation?
33715 @cindex annotations
33717 Annotations start with a newline character, two @samp{control-z}
33718 characters, and the name of the annotation. If there is no additional
33719 information associated with this annotation, the name of the annotation
33720 is followed immediately by a newline. If there is additional
33721 information, the name of the annotation is followed by a space, the
33722 additional information, and a newline. The additional information
33723 cannot contain newline characters.
33725 Any output not beginning with a newline and two @samp{control-z}
33726 characters denotes literal output from @value{GDBN}. Currently there is
33727 no need for @value{GDBN} to output a newline followed by two
33728 @samp{control-z} characters, but if there was such a need, the
33729 annotations could be extended with an @samp{escape} annotation which
33730 means those three characters as output.
33732 The annotation @var{level}, which is specified using the
33733 @option{--annotate} command line option (@pxref{Mode Options}), controls
33734 how much information @value{GDBN} prints together with its prompt,
33735 values of expressions, source lines, and other types of output. Level 0
33736 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33737 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33738 for programs that control @value{GDBN}, and level 2 annotations have
33739 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33740 Interface, annotate, GDB's Obsolete Annotations}).
33743 @kindex set annotate
33744 @item set annotate @var{level}
33745 The @value{GDBN} command @code{set annotate} sets the level of
33746 annotations to the specified @var{level}.
33748 @item show annotate
33749 @kindex show annotate
33750 Show the current annotation level.
33753 This chapter describes level 3 annotations.
33755 A simple example of starting up @value{GDBN} with annotations is:
33758 $ @kbd{gdb --annotate=3}
33760 Copyright 2003 Free Software Foundation, Inc.
33761 GDB is free software, covered by the GNU General Public License,
33762 and you are welcome to change it and/or distribute copies of it
33763 under certain conditions.
33764 Type "show copying" to see the conditions.
33765 There is absolutely no warranty for GDB. Type "show warranty"
33767 This GDB was configured as "i386-pc-linux-gnu"
33778 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33779 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33780 denotes a @samp{control-z} character) are annotations; the rest is
33781 output from @value{GDBN}.
33783 @node Server Prefix
33784 @section The Server Prefix
33785 @cindex server prefix
33787 If you prefix a command with @samp{server } then it will not affect
33788 the command history, nor will it affect @value{GDBN}'s notion of which
33789 command to repeat if @key{RET} is pressed on a line by itself. This
33790 means that commands can be run behind a user's back by a front-end in
33791 a transparent manner.
33793 The @code{server } prefix does not affect the recording of values into
33794 the value history; to print a value without recording it into the
33795 value history, use the @code{output} command instead of the
33796 @code{print} command.
33798 Using this prefix also disables confirmation requests
33799 (@pxref{confirmation requests}).
33802 @section Annotation for @value{GDBN} Input
33804 @cindex annotations for prompts
33805 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33806 to know when to send output, when the output from a given command is
33809 Different kinds of input each have a different @dfn{input type}. Each
33810 input type has three annotations: a @code{pre-} annotation, which
33811 denotes the beginning of any prompt which is being output, a plain
33812 annotation, which denotes the end of the prompt, and then a @code{post-}
33813 annotation which denotes the end of any echo which may (or may not) be
33814 associated with the input. For example, the @code{prompt} input type
33815 features the following annotations:
33823 The input types are
33826 @findex pre-prompt annotation
33827 @findex prompt annotation
33828 @findex post-prompt annotation
33830 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33832 @findex pre-commands annotation
33833 @findex commands annotation
33834 @findex post-commands annotation
33836 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33837 command. The annotations are repeated for each command which is input.
33839 @findex pre-overload-choice annotation
33840 @findex overload-choice annotation
33841 @findex post-overload-choice annotation
33842 @item overload-choice
33843 When @value{GDBN} wants the user to select between various overloaded functions.
33845 @findex pre-query annotation
33846 @findex query annotation
33847 @findex post-query annotation
33849 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33851 @findex pre-prompt-for-continue annotation
33852 @findex prompt-for-continue annotation
33853 @findex post-prompt-for-continue annotation
33854 @item prompt-for-continue
33855 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33856 expect this to work well; instead use @code{set height 0} to disable
33857 prompting. This is because the counting of lines is buggy in the
33858 presence of annotations.
33863 @cindex annotations for errors, warnings and interrupts
33865 @findex quit annotation
33870 This annotation occurs right before @value{GDBN} responds to an interrupt.
33872 @findex error annotation
33877 This annotation occurs right before @value{GDBN} responds to an error.
33879 Quit and error annotations indicate that any annotations which @value{GDBN} was
33880 in the middle of may end abruptly. For example, if a
33881 @code{value-history-begin} annotation is followed by a @code{error}, one
33882 cannot expect to receive the matching @code{value-history-end}. One
33883 cannot expect not to receive it either, however; an error annotation
33884 does not necessarily mean that @value{GDBN} is immediately returning all the way
33887 @findex error-begin annotation
33888 A quit or error annotation may be preceded by
33894 Any output between that and the quit or error annotation is the error
33897 Warning messages are not yet annotated.
33898 @c If we want to change that, need to fix warning(), type_error(),
33899 @c range_error(), and possibly other places.
33902 @section Invalidation Notices
33904 @cindex annotations for invalidation messages
33905 The following annotations say that certain pieces of state may have
33909 @findex frames-invalid annotation
33910 @item ^Z^Zframes-invalid
33912 The frames (for example, output from the @code{backtrace} command) may
33915 @findex breakpoints-invalid annotation
33916 @item ^Z^Zbreakpoints-invalid
33918 The breakpoints may have changed. For example, the user just added or
33919 deleted a breakpoint.
33922 @node Annotations for Running
33923 @section Running the Program
33924 @cindex annotations for running programs
33926 @findex starting annotation
33927 @findex stopping annotation
33928 When the program starts executing due to a @value{GDBN} command such as
33929 @code{step} or @code{continue},
33935 is output. When the program stops,
33941 is output. Before the @code{stopped} annotation, a variety of
33942 annotations describe how the program stopped.
33945 @findex exited annotation
33946 @item ^Z^Zexited @var{exit-status}
33947 The program exited, and @var{exit-status} is the exit status (zero for
33948 successful exit, otherwise nonzero).
33950 @findex signalled annotation
33951 @findex signal-name annotation
33952 @findex signal-name-end annotation
33953 @findex signal-string annotation
33954 @findex signal-string-end annotation
33955 @item ^Z^Zsignalled
33956 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33957 annotation continues:
33963 ^Z^Zsignal-name-end
33967 ^Z^Zsignal-string-end
33972 where @var{name} is the name of the signal, such as @code{SIGILL} or
33973 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33974 as @code{Illegal Instruction} or @code{Segmentation fault}.
33975 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33976 user's benefit and have no particular format.
33978 @findex signal annotation
33980 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33981 just saying that the program received the signal, not that it was
33982 terminated with it.
33984 @findex breakpoint annotation
33985 @item ^Z^Zbreakpoint @var{number}
33986 The program hit breakpoint number @var{number}.
33988 @findex watchpoint annotation
33989 @item ^Z^Zwatchpoint @var{number}
33990 The program hit watchpoint number @var{number}.
33993 @node Source Annotations
33994 @section Displaying Source
33995 @cindex annotations for source display
33997 @findex source annotation
33998 The following annotation is used instead of displaying source code:
34001 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34004 where @var{filename} is an absolute file name indicating which source
34005 file, @var{line} is the line number within that file (where 1 is the
34006 first line in the file), @var{character} is the character position
34007 within the file (where 0 is the first character in the file) (for most
34008 debug formats this will necessarily point to the beginning of a line),
34009 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34010 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34011 @var{addr} is the address in the target program associated with the
34012 source which is being displayed. @var{addr} is in the form @samp{0x}
34013 followed by one or more lowercase hex digits (note that this does not
34014 depend on the language).
34016 @node JIT Interface
34017 @chapter JIT Compilation Interface
34018 @cindex just-in-time compilation
34019 @cindex JIT compilation interface
34021 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34022 interface. A JIT compiler is a program or library that generates native
34023 executable code at runtime and executes it, usually in order to achieve good
34024 performance while maintaining platform independence.
34026 Programs that use JIT compilation are normally difficult to debug because
34027 portions of their code are generated at runtime, instead of being loaded from
34028 object files, which is where @value{GDBN} normally finds the program's symbols
34029 and debug information. In order to debug programs that use JIT compilation,
34030 @value{GDBN} has an interface that allows the program to register in-memory
34031 symbol files with @value{GDBN} at runtime.
34033 If you are using @value{GDBN} to debug a program that uses this interface, then
34034 it should work transparently so long as you have not stripped the binary. If
34035 you are developing a JIT compiler, then the interface is documented in the rest
34036 of this chapter. At this time, the only known client of this interface is the
34039 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34040 JIT compiler communicates with @value{GDBN} by writing data into a global
34041 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34042 attaches, it reads a linked list of symbol files from the global variable to
34043 find existing code, and puts a breakpoint in the function so that it can find
34044 out about additional code.
34047 * Declarations:: Relevant C struct declarations
34048 * Registering Code:: Steps to register code
34049 * Unregistering Code:: Steps to unregister code
34050 * Custom Debug Info:: Emit debug information in a custom format
34054 @section JIT Declarations
34056 These are the relevant struct declarations that a C program should include to
34057 implement the interface:
34067 struct jit_code_entry
34069 struct jit_code_entry *next_entry;
34070 struct jit_code_entry *prev_entry;
34071 const char *symfile_addr;
34072 uint64_t symfile_size;
34075 struct jit_descriptor
34078 /* This type should be jit_actions_t, but we use uint32_t
34079 to be explicit about the bitwidth. */
34080 uint32_t action_flag;
34081 struct jit_code_entry *relevant_entry;
34082 struct jit_code_entry *first_entry;
34085 /* GDB puts a breakpoint in this function. */
34086 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34088 /* Make sure to specify the version statically, because the
34089 debugger may check the version before we can set it. */
34090 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34093 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34094 modifications to this global data properly, which can easily be done by putting
34095 a global mutex around modifications to these structures.
34097 @node Registering Code
34098 @section Registering Code
34100 To register code with @value{GDBN}, the JIT should follow this protocol:
34104 Generate an object file in memory with symbols and other desired debug
34105 information. The file must include the virtual addresses of the sections.
34108 Create a code entry for the file, which gives the start and size of the symbol
34112 Add it to the linked list in the JIT descriptor.
34115 Point the relevant_entry field of the descriptor at the entry.
34118 Set @code{action_flag} to @code{JIT_REGISTER} and call
34119 @code{__jit_debug_register_code}.
34122 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34123 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34124 new code. However, the linked list must still be maintained in order to allow
34125 @value{GDBN} to attach to a running process and still find the symbol files.
34127 @node Unregistering Code
34128 @section Unregistering Code
34130 If code is freed, then the JIT should use the following protocol:
34134 Remove the code entry corresponding to the code from the linked list.
34137 Point the @code{relevant_entry} field of the descriptor at the code entry.
34140 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34141 @code{__jit_debug_register_code}.
34144 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34145 and the JIT will leak the memory used for the associated symbol files.
34147 @node Custom Debug Info
34148 @section Custom Debug Info
34149 @cindex custom JIT debug info
34150 @cindex JIT debug info reader
34152 Generating debug information in platform-native file formats (like ELF
34153 or COFF) may be an overkill for JIT compilers; especially if all the
34154 debug info is used for is displaying a meaningful backtrace. The
34155 issue can be resolved by having the JIT writers decide on a debug info
34156 format and also provide a reader that parses the debug info generated
34157 by the JIT compiler. This section gives a brief overview on writing
34158 such a parser. More specific details can be found in the source file
34159 @file{gdb/jit-reader.in}, which is also installed as a header at
34160 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34162 The reader is implemented as a shared object (so this functionality is
34163 not available on platforms which don't allow loading shared objects at
34164 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34165 @code{jit-reader-unload} are provided, to be used to load and unload
34166 the readers from a preconfigured directory. Once loaded, the shared
34167 object is used the parse the debug information emitted by the JIT
34171 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34172 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34175 @node Using JIT Debug Info Readers
34176 @subsection Using JIT Debug Info Readers
34177 @kindex jit-reader-load
34178 @kindex jit-reader-unload
34180 Readers can be loaded and unloaded using the @code{jit-reader-load}
34181 and @code{jit-reader-unload} commands.
34184 @item jit-reader-load @var{reader}
34185 Load the JIT reader named @var{reader}. @var{reader} is a shared
34186 object specified as either an absolute or a relative file name. In
34187 the latter case, @value{GDBN} will try to load the reader from a
34188 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34189 system (here @var{libdir} is the system library directory, often
34190 @file{/usr/local/lib}).
34192 Only one reader can be active at a time; trying to load a second
34193 reader when one is already loaded will result in @value{GDBN}
34194 reporting an error. A new JIT reader can be loaded by first unloading
34195 the current one using @code{jit-reader-unload} and then invoking
34196 @code{jit-reader-load}.
34198 @item jit-reader-unload
34199 Unload the currently loaded JIT reader.
34203 @node Writing JIT Debug Info Readers
34204 @subsection Writing JIT Debug Info Readers
34205 @cindex writing JIT debug info readers
34207 As mentioned, a reader is essentially a shared object conforming to a
34208 certain ABI. This ABI is described in @file{jit-reader.h}.
34210 @file{jit-reader.h} defines the structures, macros and functions
34211 required to write a reader. It is installed (along with
34212 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34213 the system include directory.
34215 Readers need to be released under a GPL compatible license. A reader
34216 can be declared as released under such a license by placing the macro
34217 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34219 The entry point for readers is the symbol @code{gdb_init_reader},
34220 which is expected to be a function with the prototype
34222 @findex gdb_init_reader
34224 extern struct gdb_reader_funcs *gdb_init_reader (void);
34227 @cindex @code{struct gdb_reader_funcs}
34229 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34230 functions. These functions are executed to read the debug info
34231 generated by the JIT compiler (@code{read}), to unwind stack frames
34232 (@code{unwind}) and to create canonical frame IDs
34233 (@code{get_Frame_id}). It also has a callback that is called when the
34234 reader is being unloaded (@code{destroy}). The struct looks like this
34237 struct gdb_reader_funcs
34239 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34240 int reader_version;
34242 /* For use by the reader. */
34245 gdb_read_debug_info *read;
34246 gdb_unwind_frame *unwind;
34247 gdb_get_frame_id *get_frame_id;
34248 gdb_destroy_reader *destroy;
34252 @cindex @code{struct gdb_symbol_callbacks}
34253 @cindex @code{struct gdb_unwind_callbacks}
34255 The callbacks are provided with another set of callbacks by
34256 @value{GDBN} to do their job. For @code{read}, these callbacks are
34257 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34258 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34259 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34260 files and new symbol tables inside those object files. @code{struct
34261 gdb_unwind_callbacks} has callbacks to read registers off the current
34262 frame and to write out the values of the registers in the previous
34263 frame. Both have a callback (@code{target_read}) to read bytes off the
34264 target's address space.
34266 @node In-Process Agent
34267 @chapter In-Process Agent
34268 @cindex debugging agent
34269 The traditional debugging model is conceptually low-speed, but works fine,
34270 because most bugs can be reproduced in debugging-mode execution. However,
34271 as multi-core or many-core processors are becoming mainstream, and
34272 multi-threaded programs become more and more popular, there should be more
34273 and more bugs that only manifest themselves at normal-mode execution, for
34274 example, thread races, because debugger's interference with the program's
34275 timing may conceal the bugs. On the other hand, in some applications,
34276 it is not feasible for the debugger to interrupt the program's execution
34277 long enough for the developer to learn anything helpful about its behavior.
34278 If the program's correctness depends on its real-time behavior, delays
34279 introduced by a debugger might cause the program to fail, even when the
34280 code itself is correct. It is useful to be able to observe the program's
34281 behavior without interrupting it.
34283 Therefore, traditional debugging model is too intrusive to reproduce
34284 some bugs. In order to reduce the interference with the program, we can
34285 reduce the number of operations performed by debugger. The
34286 @dfn{In-Process Agent}, a shared library, is running within the same
34287 process with inferior, and is able to perform some debugging operations
34288 itself. As a result, debugger is only involved when necessary, and
34289 performance of debugging can be improved accordingly. Note that
34290 interference with program can be reduced but can't be removed completely,
34291 because the in-process agent will still stop or slow down the program.
34293 The in-process agent can interpret and execute Agent Expressions
34294 (@pxref{Agent Expressions}) during performing debugging operations. The
34295 agent expressions can be used for different purposes, such as collecting
34296 data in tracepoints, and condition evaluation in breakpoints.
34298 @anchor{Control Agent}
34299 You can control whether the in-process agent is used as an aid for
34300 debugging with the following commands:
34303 @kindex set agent on
34305 Causes the in-process agent to perform some operations on behalf of the
34306 debugger. Just which operations requested by the user will be done
34307 by the in-process agent depends on the its capabilities. For example,
34308 if you request to evaluate breakpoint conditions in the in-process agent,
34309 and the in-process agent has such capability as well, then breakpoint
34310 conditions will be evaluated in the in-process agent.
34312 @kindex set agent off
34313 @item set agent off
34314 Disables execution of debugging operations by the in-process agent. All
34315 of the operations will be performed by @value{GDBN}.
34319 Display the current setting of execution of debugging operations by
34320 the in-process agent.
34324 * In-Process Agent Protocol::
34327 @node In-Process Agent Protocol
34328 @section In-Process Agent Protocol
34329 @cindex in-process agent protocol
34331 The in-process agent is able to communicate with both @value{GDBN} and
34332 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34333 used for communications between @value{GDBN} or GDBserver and the IPA.
34334 In general, @value{GDBN} or GDBserver sends commands
34335 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34336 in-process agent replies back with the return result of the command, or
34337 some other information. The data sent to in-process agent is composed
34338 of primitive data types, such as 4-byte or 8-byte type, and composite
34339 types, which are called objects (@pxref{IPA Protocol Objects}).
34342 * IPA Protocol Objects::
34343 * IPA Protocol Commands::
34346 @node IPA Protocol Objects
34347 @subsection IPA Protocol Objects
34348 @cindex ipa protocol objects
34350 The commands sent to and results received from agent may contain some
34351 complex data types called @dfn{objects}.
34353 The in-process agent is running on the same machine with @value{GDBN}
34354 or GDBserver, so it doesn't have to handle as much differences between
34355 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34356 However, there are still some differences of two ends in two processes:
34360 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34361 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34363 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34364 GDBserver is compiled with one, and in-process agent is compiled with
34368 Here are the IPA Protocol Objects:
34372 agent expression object. It represents an agent expression
34373 (@pxref{Agent Expressions}).
34374 @anchor{agent expression object}
34376 tracepoint action object. It represents a tracepoint action
34377 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34378 memory, static trace data and to evaluate expression.
34379 @anchor{tracepoint action object}
34381 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34382 @anchor{tracepoint object}
34386 The following table describes important attributes of each IPA protocol
34389 @multitable @columnfractions .30 .20 .50
34390 @headitem Name @tab Size @tab Description
34391 @item @emph{agent expression object} @tab @tab
34392 @item length @tab 4 @tab length of bytes code
34393 @item byte code @tab @var{length} @tab contents of byte code
34394 @item @emph{tracepoint action for collecting memory} @tab @tab
34395 @item 'M' @tab 1 @tab type of tracepoint action
34396 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34397 address of the lowest byte to collect, otherwise @var{addr} is the offset
34398 of @var{basereg} for memory collecting.
34399 @item len @tab 8 @tab length of memory for collecting
34400 @item basereg @tab 4 @tab the register number containing the starting
34401 memory address for collecting.
34402 @item @emph{tracepoint action for collecting registers} @tab @tab
34403 @item 'R' @tab 1 @tab type of tracepoint action
34404 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34405 @item 'L' @tab 1 @tab type of tracepoint action
34406 @item @emph{tracepoint action for expression evaluation} @tab @tab
34407 @item 'X' @tab 1 @tab type of tracepoint action
34408 @item agent expression @tab length of @tab @ref{agent expression object}
34409 @item @emph{tracepoint object} @tab @tab
34410 @item number @tab 4 @tab number of tracepoint
34411 @item address @tab 8 @tab address of tracepoint inserted on
34412 @item type @tab 4 @tab type of tracepoint
34413 @item enabled @tab 1 @tab enable or disable of tracepoint
34414 @item step_count @tab 8 @tab step
34415 @item pass_count @tab 8 @tab pass
34416 @item numactions @tab 4 @tab number of tracepoint actions
34417 @item hit count @tab 8 @tab hit count
34418 @item trace frame usage @tab 8 @tab trace frame usage
34419 @item compiled_cond @tab 8 @tab compiled condition
34420 @item orig_size @tab 8 @tab orig size
34421 @item condition @tab 4 if condition is NULL otherwise length of
34422 @ref{agent expression object}
34423 @tab zero if condition is NULL, otherwise is
34424 @ref{agent expression object}
34425 @item actions @tab variable
34426 @tab numactions number of @ref{tracepoint action object}
34429 @node IPA Protocol Commands
34430 @subsection IPA Protocol Commands
34431 @cindex ipa protocol commands
34433 The spaces in each command are delimiters to ease reading this commands
34434 specification. They don't exist in real commands.
34438 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34439 Installs a new fast tracepoint described by @var{tracepoint_object}
34440 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34441 head of @dfn{jumppad}, which is used to jump to data collection routine
34446 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34447 @var{target_address} is address of tracepoint in the inferior.
34448 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34449 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34450 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34451 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34458 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34459 is about to kill inferiors.
34467 @item probe_marker_at:@var{address}
34468 Asks in-process agent to probe the marker at @var{address}.
34475 @item unprobe_marker_at:@var{address}
34476 Asks in-process agent to unprobe the marker at @var{address}.
34480 @chapter Reporting Bugs in @value{GDBN}
34481 @cindex bugs in @value{GDBN}
34482 @cindex reporting bugs in @value{GDBN}
34484 Your bug reports play an essential role in making @value{GDBN} reliable.
34486 Reporting a bug may help you by bringing a solution to your problem, or it
34487 may not. But in any case the principal function of a bug report is to help
34488 the entire community by making the next version of @value{GDBN} work better. Bug
34489 reports are your contribution to the maintenance of @value{GDBN}.
34491 In order for a bug report to serve its purpose, you must include the
34492 information that enables us to fix the bug.
34495 * Bug Criteria:: Have you found a bug?
34496 * Bug Reporting:: How to report bugs
34500 @section Have You Found a Bug?
34501 @cindex bug criteria
34503 If you are not sure whether you have found a bug, here are some guidelines:
34506 @cindex fatal signal
34507 @cindex debugger crash
34508 @cindex crash of debugger
34510 If the debugger gets a fatal signal, for any input whatever, that is a
34511 @value{GDBN} bug. Reliable debuggers never crash.
34513 @cindex error on valid input
34515 If @value{GDBN} produces an error message for valid input, that is a
34516 bug. (Note that if you're cross debugging, the problem may also be
34517 somewhere in the connection to the target.)
34519 @cindex invalid input
34521 If @value{GDBN} does not produce an error message for invalid input,
34522 that is a bug. However, you should note that your idea of
34523 ``invalid input'' might be our idea of ``an extension'' or ``support
34524 for traditional practice''.
34527 If you are an experienced user of debugging tools, your suggestions
34528 for improvement of @value{GDBN} are welcome in any case.
34531 @node Bug Reporting
34532 @section How to Report Bugs
34533 @cindex bug reports
34534 @cindex @value{GDBN} bugs, reporting
34536 A number of companies and individuals offer support for @sc{gnu} products.
34537 If you obtained @value{GDBN} from a support organization, we recommend you
34538 contact that organization first.
34540 You can find contact information for many support companies and
34541 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34543 @c should add a web page ref...
34546 @ifset BUGURL_DEFAULT
34547 In any event, we also recommend that you submit bug reports for
34548 @value{GDBN}. The preferred method is to submit them directly using
34549 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34550 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34553 @strong{Do not send bug reports to @samp{info-gdb}, or to
34554 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34555 not want to receive bug reports. Those that do have arranged to receive
34558 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34559 serves as a repeater. The mailing list and the newsgroup carry exactly
34560 the same messages. Often people think of posting bug reports to the
34561 newsgroup instead of mailing them. This appears to work, but it has one
34562 problem which can be crucial: a newsgroup posting often lacks a mail
34563 path back to the sender. Thus, if we need to ask for more information,
34564 we may be unable to reach you. For this reason, it is better to send
34565 bug reports to the mailing list.
34567 @ifclear BUGURL_DEFAULT
34568 In any event, we also recommend that you submit bug reports for
34569 @value{GDBN} to @value{BUGURL}.
34573 The fundamental principle of reporting bugs usefully is this:
34574 @strong{report all the facts}. If you are not sure whether to state a
34575 fact or leave it out, state it!
34577 Often people omit facts because they think they know what causes the
34578 problem and assume that some details do not matter. Thus, you might
34579 assume that the name of the variable you use in an example does not matter.
34580 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34581 stray memory reference which happens to fetch from the location where that
34582 name is stored in memory; perhaps, if the name were different, the contents
34583 of that location would fool the debugger into doing the right thing despite
34584 the bug. Play it safe and give a specific, complete example. That is the
34585 easiest thing for you to do, and the most helpful.
34587 Keep in mind that the purpose of a bug report is to enable us to fix the
34588 bug. It may be that the bug has been reported previously, but neither
34589 you nor we can know that unless your bug report is complete and
34592 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34593 bell?'' Those bug reports are useless, and we urge everyone to
34594 @emph{refuse to respond to them} except to chide the sender to report
34597 To enable us to fix the bug, you should include all these things:
34601 The version of @value{GDBN}. @value{GDBN} announces it if you start
34602 with no arguments; you can also print it at any time using @code{show
34605 Without this, we will not know whether there is any point in looking for
34606 the bug in the current version of @value{GDBN}.
34609 The type of machine you are using, and the operating system name and
34613 The details of the @value{GDBN} build-time configuration.
34614 @value{GDBN} shows these details if you invoke it with the
34615 @option{--configuration} command-line option, or if you type
34616 @code{show configuration} at @value{GDBN}'s prompt.
34619 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34620 ``@value{GCC}--2.8.1''.
34623 What compiler (and its version) was used to compile the program you are
34624 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34625 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34626 to get this information; for other compilers, see the documentation for
34630 The command arguments you gave the compiler to compile your example and
34631 observe the bug. For example, did you use @samp{-O}? To guarantee
34632 you will not omit something important, list them all. A copy of the
34633 Makefile (or the output from make) is sufficient.
34635 If we were to try to guess the arguments, we would probably guess wrong
34636 and then we might not encounter the bug.
34639 A complete input script, and all necessary source files, that will
34643 A description of what behavior you observe that you believe is
34644 incorrect. For example, ``It gets a fatal signal.''
34646 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34647 will certainly notice it. But if the bug is incorrect output, we might
34648 not notice unless it is glaringly wrong. You might as well not give us
34649 a chance to make a mistake.
34651 Even if the problem you experience is a fatal signal, you should still
34652 say so explicitly. Suppose something strange is going on, such as, your
34653 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34654 the C library on your system. (This has happened!) Your copy might
34655 crash and ours would not. If you told us to expect a crash, then when
34656 ours fails to crash, we would know that the bug was not happening for
34657 us. If you had not told us to expect a crash, then we would not be able
34658 to draw any conclusion from our observations.
34661 @cindex recording a session script
34662 To collect all this information, you can use a session recording program
34663 such as @command{script}, which is available on many Unix systems.
34664 Just run your @value{GDBN} session inside @command{script} and then
34665 include the @file{typescript} file with your bug report.
34667 Another way to record a @value{GDBN} session is to run @value{GDBN}
34668 inside Emacs and then save the entire buffer to a file.
34671 If you wish to suggest changes to the @value{GDBN} source, send us context
34672 diffs. If you even discuss something in the @value{GDBN} source, refer to
34673 it by context, not by line number.
34675 The line numbers in our development sources will not match those in your
34676 sources. Your line numbers would convey no useful information to us.
34680 Here are some things that are not necessary:
34684 A description of the envelope of the bug.
34686 Often people who encounter a bug spend a lot of time investigating
34687 which changes to the input file will make the bug go away and which
34688 changes will not affect it.
34690 This is often time consuming and not very useful, because the way we
34691 will find the bug is by running a single example under the debugger
34692 with breakpoints, not by pure deduction from a series of examples.
34693 We recommend that you save your time for something else.
34695 Of course, if you can find a simpler example to report @emph{instead}
34696 of the original one, that is a convenience for us. Errors in the
34697 output will be easier to spot, running under the debugger will take
34698 less time, and so on.
34700 However, simplification is not vital; if you do not want to do this,
34701 report the bug anyway and send us the entire test case you used.
34704 A patch for the bug.
34706 A patch for the bug does help us if it is a good one. But do not omit
34707 the necessary information, such as the test case, on the assumption that
34708 a patch is all we need. We might see problems with your patch and decide
34709 to fix the problem another way, or we might not understand it at all.
34711 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34712 construct an example that will make the program follow a certain path
34713 through the code. If you do not send us the example, we will not be able
34714 to construct one, so we will not be able to verify that the bug is fixed.
34716 And if we cannot understand what bug you are trying to fix, or why your
34717 patch should be an improvement, we will not install it. A test case will
34718 help us to understand.
34721 A guess about what the bug is or what it depends on.
34723 Such guesses are usually wrong. Even we cannot guess right about such
34724 things without first using the debugger to find the facts.
34727 @c The readline documentation is distributed with the readline code
34728 @c and consists of the two following files:
34731 @c Use -I with makeinfo to point to the appropriate directory,
34732 @c environment var TEXINPUTS with TeX.
34733 @ifclear SYSTEM_READLINE
34734 @include rluser.texi
34735 @include hsuser.texi
34739 @appendix In Memoriam
34741 The @value{GDBN} project mourns the loss of the following long-time
34746 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34747 to Free Software in general. Outside of @value{GDBN}, he was known in
34748 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34750 @item Michael Snyder
34751 Michael was one of the Global Maintainers of the @value{GDBN} project,
34752 with contributions recorded as early as 1996, until 2011. In addition
34753 to his day to day participation, he was a large driving force behind
34754 adding Reverse Debugging to @value{GDBN}.
34757 Beyond their technical contributions to the project, they were also
34758 enjoyable members of the Free Software Community. We will miss them.
34760 @node Formatting Documentation
34761 @appendix Formatting Documentation
34763 @cindex @value{GDBN} reference card
34764 @cindex reference card
34765 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34766 for printing with PostScript or Ghostscript, in the @file{gdb}
34767 subdirectory of the main source directory@footnote{In
34768 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34769 release.}. If you can use PostScript or Ghostscript with your printer,
34770 you can print the reference card immediately with @file{refcard.ps}.
34772 The release also includes the source for the reference card. You
34773 can format it, using @TeX{}, by typing:
34779 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34780 mode on US ``letter'' size paper;
34781 that is, on a sheet 11 inches wide by 8.5 inches
34782 high. You will need to specify this form of printing as an option to
34783 your @sc{dvi} output program.
34785 @cindex documentation
34787 All the documentation for @value{GDBN} comes as part of the machine-readable
34788 distribution. The documentation is written in Texinfo format, which is
34789 a documentation system that uses a single source file to produce both
34790 on-line information and a printed manual. You can use one of the Info
34791 formatting commands to create the on-line version of the documentation
34792 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34794 @value{GDBN} includes an already formatted copy of the on-line Info
34795 version of this manual in the @file{gdb} subdirectory. The main Info
34796 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34797 subordinate files matching @samp{gdb.info*} in the same directory. If
34798 necessary, you can print out these files, or read them with any editor;
34799 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34800 Emacs or the standalone @code{info} program, available as part of the
34801 @sc{gnu} Texinfo distribution.
34803 If you want to format these Info files yourself, you need one of the
34804 Info formatting programs, such as @code{texinfo-format-buffer} or
34807 If you have @code{makeinfo} installed, and are in the top level
34808 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34809 version @value{GDBVN}), you can make the Info file by typing:
34816 If you want to typeset and print copies of this manual, you need @TeX{},
34817 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34818 Texinfo definitions file.
34820 @TeX{} is a typesetting program; it does not print files directly, but
34821 produces output files called @sc{dvi} files. To print a typeset
34822 document, you need a program to print @sc{dvi} files. If your system
34823 has @TeX{} installed, chances are it has such a program. The precise
34824 command to use depends on your system; @kbd{lpr -d} is common; another
34825 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34826 require a file name without any extension or a @samp{.dvi} extension.
34828 @TeX{} also requires a macro definitions file called
34829 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34830 written in Texinfo format. On its own, @TeX{} cannot either read or
34831 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34832 and is located in the @file{gdb-@var{version-number}/texinfo}
34835 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34836 typeset and print this manual. First switch to the @file{gdb}
34837 subdirectory of the main source directory (for example, to
34838 @file{gdb-@value{GDBVN}/gdb}) and type:
34844 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34846 @node Installing GDB
34847 @appendix Installing @value{GDBN}
34848 @cindex installation
34851 * Requirements:: Requirements for building @value{GDBN}
34852 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34853 * Separate Objdir:: Compiling @value{GDBN} in another directory
34854 * Config Names:: Specifying names for hosts and targets
34855 * Configure Options:: Summary of options for configure
34856 * System-wide configuration:: Having a system-wide init file
34860 @section Requirements for Building @value{GDBN}
34861 @cindex building @value{GDBN}, requirements for
34863 Building @value{GDBN} requires various tools and packages to be available.
34864 Other packages will be used only if they are found.
34866 @heading Tools/Packages Necessary for Building @value{GDBN}
34868 @item ISO C90 compiler
34869 @value{GDBN} is written in ISO C90. It should be buildable with any
34870 working C90 compiler, e.g.@: GCC.
34874 @heading Tools/Packages Optional for Building @value{GDBN}
34878 @value{GDBN} can use the Expat XML parsing library. This library may be
34879 included with your operating system distribution; if it is not, you
34880 can get the latest version from @url{http://expat.sourceforge.net}.
34881 The @file{configure} script will search for this library in several
34882 standard locations; if it is installed in an unusual path, you can
34883 use the @option{--with-libexpat-prefix} option to specify its location.
34889 Remote protocol memory maps (@pxref{Memory Map Format})
34891 Target descriptions (@pxref{Target Descriptions})
34893 Remote shared library lists (@xref{Library List Format},
34894 or alternatively @pxref{Library List Format for SVR4 Targets})
34896 MS-Windows shared libraries (@pxref{Shared Libraries})
34898 Traceframe info (@pxref{Traceframe Info Format})
34900 Branch trace (@pxref{Branch Trace Format})
34904 @cindex compressed debug sections
34905 @value{GDBN} will use the @samp{zlib} library, if available, to read
34906 compressed debug sections. Some linkers, such as GNU gold, are capable
34907 of producing binaries with compressed debug sections. If @value{GDBN}
34908 is compiled with @samp{zlib}, it will be able to read the debug
34909 information in such binaries.
34911 The @samp{zlib} library is likely included with your operating system
34912 distribution; if it is not, you can get the latest version from
34913 @url{http://zlib.net}.
34916 @value{GDBN}'s features related to character sets (@pxref{Character
34917 Sets}) require a functioning @code{iconv} implementation. If you are
34918 on a GNU system, then this is provided by the GNU C Library. Some
34919 other systems also provide a working @code{iconv}.
34921 If @value{GDBN} is using the @code{iconv} program which is installed
34922 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34923 This is done with @option{--with-iconv-bin} which specifies the
34924 directory that contains the @code{iconv} program.
34926 On systems without @code{iconv}, you can install GNU Libiconv. If you
34927 have previously installed Libiconv, you can use the
34928 @option{--with-libiconv-prefix} option to configure.
34930 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34931 arrange to build Libiconv if a directory named @file{libiconv} appears
34932 in the top-most source directory. If Libiconv is built this way, and
34933 if the operating system does not provide a suitable @code{iconv}
34934 implementation, then the just-built library will automatically be used
34935 by @value{GDBN}. One easy way to set this up is to download GNU
34936 Libiconv, unpack it, and then rename the directory holding the
34937 Libiconv source code to @samp{libiconv}.
34940 @node Running Configure
34941 @section Invoking the @value{GDBN} @file{configure} Script
34942 @cindex configuring @value{GDBN}
34943 @value{GDBN} comes with a @file{configure} script that automates the process
34944 of preparing @value{GDBN} for installation; you can then use @code{make} to
34945 build the @code{gdb} program.
34947 @c irrelevant in info file; it's as current as the code it lives with.
34948 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34949 look at the @file{README} file in the sources; we may have improved the
34950 installation procedures since publishing this manual.}
34953 The @value{GDBN} distribution includes all the source code you need for
34954 @value{GDBN} in a single directory, whose name is usually composed by
34955 appending the version number to @samp{gdb}.
34957 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34958 @file{gdb-@value{GDBVN}} directory. That directory contains:
34961 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34962 script for configuring @value{GDBN} and all its supporting libraries
34964 @item gdb-@value{GDBVN}/gdb
34965 the source specific to @value{GDBN} itself
34967 @item gdb-@value{GDBVN}/bfd
34968 source for the Binary File Descriptor library
34970 @item gdb-@value{GDBVN}/include
34971 @sc{gnu} include files
34973 @item gdb-@value{GDBVN}/libiberty
34974 source for the @samp{-liberty} free software library
34976 @item gdb-@value{GDBVN}/opcodes
34977 source for the library of opcode tables and disassemblers
34979 @item gdb-@value{GDBVN}/readline
34980 source for the @sc{gnu} command-line interface
34982 @item gdb-@value{GDBVN}/glob
34983 source for the @sc{gnu} filename pattern-matching subroutine
34985 @item gdb-@value{GDBVN}/mmalloc
34986 source for the @sc{gnu} memory-mapped malloc package
34989 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34990 from the @file{gdb-@var{version-number}} source directory, which in
34991 this example is the @file{gdb-@value{GDBVN}} directory.
34993 First switch to the @file{gdb-@var{version-number}} source directory
34994 if you are not already in it; then run @file{configure}. Pass the
34995 identifier for the platform on which @value{GDBN} will run as an
35001 cd gdb-@value{GDBVN}
35002 ./configure @var{host}
35007 where @var{host} is an identifier such as @samp{sun4} or
35008 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
35009 (You can often leave off @var{host}; @file{configure} tries to guess the
35010 correct value by examining your system.)
35012 Running @samp{configure @var{host}} and then running @code{make} builds the
35013 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
35014 libraries, then @code{gdb} itself. The configured source files, and the
35015 binaries, are left in the corresponding source directories.
35018 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35019 system does not recognize this automatically when you run a different
35020 shell, you may need to run @code{sh} on it explicitly:
35023 sh configure @var{host}
35026 If you run @file{configure} from a directory that contains source
35027 directories for multiple libraries or programs, such as the
35028 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
35030 creates configuration files for every directory level underneath (unless
35031 you tell it not to, with the @samp{--norecursion} option).
35033 You should run the @file{configure} script from the top directory in the
35034 source tree, the @file{gdb-@var{version-number}} directory. If you run
35035 @file{configure} from one of the subdirectories, you will configure only
35036 that subdirectory. That is usually not what you want. In particular,
35037 if you run the first @file{configure} from the @file{gdb} subdirectory
35038 of the @file{gdb-@var{version-number}} directory, you will omit the
35039 configuration of @file{bfd}, @file{readline}, and other sibling
35040 directories of the @file{gdb} subdirectory. This leads to build errors
35041 about missing include files such as @file{bfd/bfd.h}.
35043 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
35044 However, you should make sure that the shell on your path (named by
35045 the @samp{SHELL} environment variable) is publicly readable. Remember
35046 that @value{GDBN} uses the shell to start your program---some systems refuse to
35047 let @value{GDBN} debug child processes whose programs are not readable.
35049 @node Separate Objdir
35050 @section Compiling @value{GDBN} in Another Directory
35052 If you want to run @value{GDBN} versions for several host or target machines,
35053 you need a different @code{gdb} compiled for each combination of
35054 host and target. @file{configure} is designed to make this easy by
35055 allowing you to generate each configuration in a separate subdirectory,
35056 rather than in the source directory. If your @code{make} program
35057 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35058 @code{make} in each of these directories builds the @code{gdb}
35059 program specified there.
35061 To build @code{gdb} in a separate directory, run @file{configure}
35062 with the @samp{--srcdir} option to specify where to find the source.
35063 (You also need to specify a path to find @file{configure}
35064 itself from your working directory. If the path to @file{configure}
35065 would be the same as the argument to @samp{--srcdir}, you can leave out
35066 the @samp{--srcdir} option; it is assumed.)
35068 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35069 separate directory for a Sun 4 like this:
35073 cd gdb-@value{GDBVN}
35076 ../gdb-@value{GDBVN}/configure sun4
35081 When @file{configure} builds a configuration using a remote source
35082 directory, it creates a tree for the binaries with the same structure
35083 (and using the same names) as the tree under the source directory. In
35084 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35085 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35086 @file{gdb-sun4/gdb}.
35088 Make sure that your path to the @file{configure} script has just one
35089 instance of @file{gdb} in it. If your path to @file{configure} looks
35090 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35091 one subdirectory of @value{GDBN}, not the whole package. This leads to
35092 build errors about missing include files such as @file{bfd/bfd.h}.
35094 One popular reason to build several @value{GDBN} configurations in separate
35095 directories is to configure @value{GDBN} for cross-compiling (where
35096 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35097 programs that run on another machine---the @dfn{target}).
35098 You specify a cross-debugging target by
35099 giving the @samp{--target=@var{target}} option to @file{configure}.
35101 When you run @code{make} to build a program or library, you must run
35102 it in a configured directory---whatever directory you were in when you
35103 called @file{configure} (or one of its subdirectories).
35105 The @code{Makefile} that @file{configure} generates in each source
35106 directory also runs recursively. If you type @code{make} in a source
35107 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35108 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35109 will build all the required libraries, and then build GDB.
35111 When you have multiple hosts or targets configured in separate
35112 directories, you can run @code{make} on them in parallel (for example,
35113 if they are NFS-mounted on each of the hosts); they will not interfere
35117 @section Specifying Names for Hosts and Targets
35119 The specifications used for hosts and targets in the @file{configure}
35120 script are based on a three-part naming scheme, but some short predefined
35121 aliases are also supported. The full naming scheme encodes three pieces
35122 of information in the following pattern:
35125 @var{architecture}-@var{vendor}-@var{os}
35128 For example, you can use the alias @code{sun4} as a @var{host} argument,
35129 or as the value for @var{target} in a @code{--target=@var{target}}
35130 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35132 The @file{configure} script accompanying @value{GDBN} does not provide
35133 any query facility to list all supported host and target names or
35134 aliases. @file{configure} calls the Bourne shell script
35135 @code{config.sub} to map abbreviations to full names; you can read the
35136 script, if you wish, or you can use it to test your guesses on
35137 abbreviations---for example:
35140 % sh config.sub i386-linux
35142 % sh config.sub alpha-linux
35143 alpha-unknown-linux-gnu
35144 % sh config.sub hp9k700
35146 % sh config.sub sun4
35147 sparc-sun-sunos4.1.1
35148 % sh config.sub sun3
35149 m68k-sun-sunos4.1.1
35150 % sh config.sub i986v
35151 Invalid configuration `i986v': machine `i986v' not recognized
35155 @code{config.sub} is also distributed in the @value{GDBN} source
35156 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35158 @node Configure Options
35159 @section @file{configure} Options
35161 Here is a summary of the @file{configure} options and arguments that
35162 are most often useful for building @value{GDBN}. @file{configure} also has
35163 several other options not listed here. @inforef{What Configure
35164 Does,,configure.info}, for a full explanation of @file{configure}.
35167 configure @r{[}--help@r{]}
35168 @r{[}--prefix=@var{dir}@r{]}
35169 @r{[}--exec-prefix=@var{dir}@r{]}
35170 @r{[}--srcdir=@var{dirname}@r{]}
35171 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35172 @r{[}--target=@var{target}@r{]}
35177 You may introduce options with a single @samp{-} rather than
35178 @samp{--} if you prefer; but you may abbreviate option names if you use
35183 Display a quick summary of how to invoke @file{configure}.
35185 @item --prefix=@var{dir}
35186 Configure the source to install programs and files under directory
35189 @item --exec-prefix=@var{dir}
35190 Configure the source to install programs under directory
35193 @c avoid splitting the warning from the explanation:
35195 @item --srcdir=@var{dirname}
35196 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35197 @code{make} that implements the @code{VPATH} feature.}@*
35198 Use this option to make configurations in directories separate from the
35199 @value{GDBN} source directories. Among other things, you can use this to
35200 build (or maintain) several configurations simultaneously, in separate
35201 directories. @file{configure} writes configuration-specific files in
35202 the current directory, but arranges for them to use the source in the
35203 directory @var{dirname}. @file{configure} creates directories under
35204 the working directory in parallel to the source directories below
35207 @item --norecursion
35208 Configure only the directory level where @file{configure} is executed; do not
35209 propagate configuration to subdirectories.
35211 @item --target=@var{target}
35212 Configure @value{GDBN} for cross-debugging programs running on the specified
35213 @var{target}. Without this option, @value{GDBN} is configured to debug
35214 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35216 There is no convenient way to generate a list of all available targets.
35218 @item @var{host} @dots{}
35219 Configure @value{GDBN} to run on the specified @var{host}.
35221 There is no convenient way to generate a list of all available hosts.
35224 There are many other options available as well, but they are generally
35225 needed for special purposes only.
35227 @node System-wide configuration
35228 @section System-wide configuration and settings
35229 @cindex system-wide init file
35231 @value{GDBN} can be configured to have a system-wide init file;
35232 this file will be read and executed at startup (@pxref{Startup, , What
35233 @value{GDBN} does during startup}).
35235 Here is the corresponding configure option:
35238 @item --with-system-gdbinit=@var{file}
35239 Specify that the default location of the system-wide init file is
35243 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35244 it may be subject to relocation. Two possible cases:
35248 If the default location of this init file contains @file{$prefix},
35249 it will be subject to relocation. Suppose that the configure options
35250 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35251 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35252 init file is looked for as @file{$install/etc/gdbinit} instead of
35253 @file{$prefix/etc/gdbinit}.
35256 By contrast, if the default location does not contain the prefix,
35257 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35258 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35259 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35260 wherever @value{GDBN} is installed.
35263 If the configured location of the system-wide init file (as given by the
35264 @option{--with-system-gdbinit} option at configure time) is in the
35265 data-directory (as specified by @option{--with-gdb-datadir} at configure
35266 time) or in one of its subdirectories, then @value{GDBN} will look for the
35267 system-wide init file in the directory specified by the
35268 @option{--data-directory} command-line option.
35269 Note that the system-wide init file is only read once, during @value{GDBN}
35270 initialization. If the data-directory is changed after @value{GDBN} has
35271 started with the @code{set data-directory} command, the file will not be
35274 @node Maintenance Commands
35275 @appendix Maintenance Commands
35276 @cindex maintenance commands
35277 @cindex internal commands
35279 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35280 includes a number of commands intended for @value{GDBN} developers,
35281 that are not documented elsewhere in this manual. These commands are
35282 provided here for reference. (For commands that turn on debugging
35283 messages, see @ref{Debugging Output}.)
35286 @kindex maint agent
35287 @kindex maint agent-eval
35288 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35289 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35290 Translate the given @var{expression} into remote agent bytecodes.
35291 This command is useful for debugging the Agent Expression mechanism
35292 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35293 expression useful for data collection, such as by tracepoints, while
35294 @samp{maint agent-eval} produces an expression that evaluates directly
35295 to a result. For instance, a collection expression for @code{globa +
35296 globb} will include bytecodes to record four bytes of memory at each
35297 of the addresses of @code{globa} and @code{globb}, while discarding
35298 the result of the addition, while an evaluation expression will do the
35299 addition and return the sum.
35300 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35301 If not, generate remote agent bytecode for current frame PC address.
35303 @kindex maint agent-printf
35304 @item maint agent-printf @var{format},@var{expr},...
35305 Translate the given format string and list of argument expressions
35306 into remote agent bytecodes and display them as a disassembled list.
35307 This command is useful for debugging the agent version of dynamic
35308 printf (@pxref{Dynamic Printf}).
35310 @kindex maint info breakpoints
35311 @item @anchor{maint info breakpoints}maint info breakpoints
35312 Using the same format as @samp{info breakpoints}, display both the
35313 breakpoints you've set explicitly, and those @value{GDBN} is using for
35314 internal purposes. Internal breakpoints are shown with negative
35315 breakpoint numbers. The type column identifies what kind of breakpoint
35320 Normal, explicitly set breakpoint.
35323 Normal, explicitly set watchpoint.
35326 Internal breakpoint, used to handle correctly stepping through
35327 @code{longjmp} calls.
35329 @item longjmp resume
35330 Internal breakpoint at the target of a @code{longjmp}.
35333 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35336 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35339 Shared library events.
35343 @kindex maint info bfds
35344 @item maint info bfds
35345 This prints information about each @code{bfd} object that is known to
35346 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
35348 @kindex set displaced-stepping
35349 @kindex show displaced-stepping
35350 @cindex displaced stepping support
35351 @cindex out-of-line single-stepping
35352 @item set displaced-stepping
35353 @itemx show displaced-stepping
35354 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35355 if the target supports it. Displaced stepping is a way to single-step
35356 over breakpoints without removing them from the inferior, by executing
35357 an out-of-line copy of the instruction that was originally at the
35358 breakpoint location. It is also known as out-of-line single-stepping.
35361 @item set displaced-stepping on
35362 If the target architecture supports it, @value{GDBN} will use
35363 displaced stepping to step over breakpoints.
35365 @item set displaced-stepping off
35366 @value{GDBN} will not use displaced stepping to step over breakpoints,
35367 even if such is supported by the target architecture.
35369 @cindex non-stop mode, and @samp{set displaced-stepping}
35370 @item set displaced-stepping auto
35371 This is the default mode. @value{GDBN} will use displaced stepping
35372 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35373 architecture supports displaced stepping.
35376 @kindex maint check-symtabs
35377 @item maint check-symtabs
35378 Check the consistency of psymtabs and symtabs.
35380 @kindex maint cplus first_component
35381 @item maint cplus first_component @var{name}
35382 Print the first C@t{++} class/namespace component of @var{name}.
35384 @kindex maint cplus namespace
35385 @item maint cplus namespace
35386 Print the list of possible C@t{++} namespaces.
35388 @kindex maint demangle
35389 @item maint demangle @var{name}
35390 Demangle a C@t{++} or Objective-C mangled @var{name}.
35392 @kindex maint deprecate
35393 @kindex maint undeprecate
35394 @cindex deprecated commands
35395 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35396 @itemx maint undeprecate @var{command}
35397 Deprecate or undeprecate the named @var{command}. Deprecated commands
35398 cause @value{GDBN} to issue a warning when you use them. The optional
35399 argument @var{replacement} says which newer command should be used in
35400 favor of the deprecated one; if it is given, @value{GDBN} will mention
35401 the replacement as part of the warning.
35403 @kindex maint dump-me
35404 @item maint dump-me
35405 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35406 Cause a fatal signal in the debugger and force it to dump its core.
35407 This is supported only on systems which support aborting a program
35408 with the @code{SIGQUIT} signal.
35410 @kindex maint internal-error
35411 @kindex maint internal-warning
35412 @item maint internal-error @r{[}@var{message-text}@r{]}
35413 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35414 Cause @value{GDBN} to call the internal function @code{internal_error}
35415 or @code{internal_warning} and hence behave as though an internal error
35416 or internal warning has been detected. In addition to reporting the
35417 internal problem, these functions give the user the opportunity to
35418 either quit @value{GDBN} or create a core file of the current
35419 @value{GDBN} session.
35421 These commands take an optional parameter @var{message-text} that is
35422 used as the text of the error or warning message.
35424 Here's an example of using @code{internal-error}:
35427 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35428 @dots{}/maint.c:121: internal-error: testing, 1, 2
35429 A problem internal to GDB has been detected. Further
35430 debugging may prove unreliable.
35431 Quit this debugging session? (y or n) @kbd{n}
35432 Create a core file? (y or n) @kbd{n}
35436 @cindex @value{GDBN} internal error
35437 @cindex internal errors, control of @value{GDBN} behavior
35439 @kindex maint set internal-error
35440 @kindex maint show internal-error
35441 @kindex maint set internal-warning
35442 @kindex maint show internal-warning
35443 @item maint set internal-error @var{action} [ask|yes|no]
35444 @itemx maint show internal-error @var{action}
35445 @itemx maint set internal-warning @var{action} [ask|yes|no]
35446 @itemx maint show internal-warning @var{action}
35447 When @value{GDBN} reports an internal problem (error or warning) it
35448 gives the user the opportunity to both quit @value{GDBN} and create a
35449 core file of the current @value{GDBN} session. These commands let you
35450 override the default behaviour for each particular @var{action},
35451 described in the table below.
35455 You can specify that @value{GDBN} should always (yes) or never (no)
35456 quit. The default is to ask the user what to do.
35459 You can specify that @value{GDBN} should always (yes) or never (no)
35460 create a core file. The default is to ask the user what to do.
35463 @kindex maint packet
35464 @item maint packet @var{text}
35465 If @value{GDBN} is talking to an inferior via the serial protocol,
35466 then this command sends the string @var{text} to the inferior, and
35467 displays the response packet. @value{GDBN} supplies the initial
35468 @samp{$} character, the terminating @samp{#} character, and the
35471 @kindex maint print architecture
35472 @item maint print architecture @r{[}@var{file}@r{]}
35473 Print the entire architecture configuration. The optional argument
35474 @var{file} names the file where the output goes.
35476 @kindex maint print c-tdesc
35477 @item maint print c-tdesc
35478 Print the current target description (@pxref{Target Descriptions}) as
35479 a C source file. The created source file can be used in @value{GDBN}
35480 when an XML parser is not available to parse the description.
35482 @kindex maint print dummy-frames
35483 @item maint print dummy-frames
35484 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35487 (@value{GDBP}) @kbd{b add}
35489 (@value{GDBP}) @kbd{print add(2,3)}
35490 Breakpoint 2, add (a=2, b=3) at @dots{}
35492 The program being debugged stopped while in a function called from GDB.
35494 (@value{GDBP}) @kbd{maint print dummy-frames}
35495 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35496 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35497 call_lo=0x01014000 call_hi=0x01014001
35501 Takes an optional file parameter.
35503 @kindex maint print registers
35504 @kindex maint print raw-registers
35505 @kindex maint print cooked-registers
35506 @kindex maint print register-groups
35507 @kindex maint print remote-registers
35508 @item maint print registers @r{[}@var{file}@r{]}
35509 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35510 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35511 @itemx maint print register-groups @r{[}@var{file}@r{]}
35512 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35513 Print @value{GDBN}'s internal register data structures.
35515 The command @code{maint print raw-registers} includes the contents of
35516 the raw register cache; the command @code{maint print
35517 cooked-registers} includes the (cooked) value of all registers,
35518 including registers which aren't available on the target nor visible
35519 to user; the command @code{maint print register-groups} includes the
35520 groups that each register is a member of; and the command @code{maint
35521 print remote-registers} includes the remote target's register numbers
35522 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35523 @value{GDBN} Internals}.
35525 These commands take an optional parameter, a file name to which to
35526 write the information.
35528 @kindex maint print reggroups
35529 @item maint print reggroups @r{[}@var{file}@r{]}
35530 Print @value{GDBN}'s internal register group data structures. The
35531 optional argument @var{file} tells to what file to write the
35534 The register groups info looks like this:
35537 (@value{GDBP}) @kbd{maint print reggroups}
35550 This command forces @value{GDBN} to flush its internal register cache.
35552 @kindex maint print objfiles
35553 @cindex info for known object files
35554 @item maint print objfiles
35555 Print a dump of all known object files. For each object file, this
35556 command prints its name, address in memory, and all of its psymtabs
35559 @kindex maint print section-scripts
35560 @cindex info for known .debug_gdb_scripts-loaded scripts
35561 @item maint print section-scripts [@var{regexp}]
35562 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35563 If @var{regexp} is specified, only print scripts loaded by object files
35564 matching @var{regexp}.
35565 For each script, this command prints its name as specified in the objfile,
35566 and the full path if known.
35567 @xref{dotdebug_gdb_scripts section}.
35569 @kindex maint print statistics
35570 @cindex bcache statistics
35571 @item maint print statistics
35572 This command prints, for each object file in the program, various data
35573 about that object file followed by the byte cache (@dfn{bcache})
35574 statistics for the object file. The objfile data includes the number
35575 of minimal, partial, full, and stabs symbols, the number of types
35576 defined by the objfile, the number of as yet unexpanded psym tables,
35577 the number of line tables and string tables, and the amount of memory
35578 used by the various tables. The bcache statistics include the counts,
35579 sizes, and counts of duplicates of all and unique objects, max,
35580 average, and median entry size, total memory used and its overhead and
35581 savings, and various measures of the hash table size and chain
35584 @kindex maint print target-stack
35585 @cindex target stack description
35586 @item maint print target-stack
35587 A @dfn{target} is an interface between the debugger and a particular
35588 kind of file or process. Targets can be stacked in @dfn{strata},
35589 so that more than one target can potentially respond to a request.
35590 In particular, memory accesses will walk down the stack of targets
35591 until they find a target that is interested in handling that particular
35594 This command prints a short description of each layer that was pushed on
35595 the @dfn{target stack}, starting from the top layer down to the bottom one.
35597 @kindex maint print type
35598 @cindex type chain of a data type
35599 @item maint print type @var{expr}
35600 Print the type chain for a type specified by @var{expr}. The argument
35601 can be either a type name or a symbol. If it is a symbol, the type of
35602 that symbol is described. The type chain produced by this command is
35603 a recursive definition of the data type as stored in @value{GDBN}'s
35604 data structures, including its flags and contained types.
35606 @kindex maint set dwarf2 always-disassemble
35607 @kindex maint show dwarf2 always-disassemble
35608 @item maint set dwarf2 always-disassemble
35609 @item maint show dwarf2 always-disassemble
35610 Control the behavior of @code{info address} when using DWARF debugging
35613 The default is @code{off}, which means that @value{GDBN} should try to
35614 describe a variable's location in an easily readable format. When
35615 @code{on}, @value{GDBN} will instead display the DWARF location
35616 expression in an assembly-like format. Note that some locations are
35617 too complex for @value{GDBN} to describe simply; in this case you will
35618 always see the disassembly form.
35620 Here is an example of the resulting disassembly:
35623 (gdb) info addr argc
35624 Symbol "argc" is a complex DWARF expression:
35628 For more information on these expressions, see
35629 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35631 @kindex maint set dwarf2 max-cache-age
35632 @kindex maint show dwarf2 max-cache-age
35633 @item maint set dwarf2 max-cache-age
35634 @itemx maint show dwarf2 max-cache-age
35635 Control the DWARF 2 compilation unit cache.
35637 @cindex DWARF 2 compilation units cache
35638 In object files with inter-compilation-unit references, such as those
35639 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35640 reader needs to frequently refer to previously read compilation units.
35641 This setting controls how long a compilation unit will remain in the
35642 cache if it is not referenced. A higher limit means that cached
35643 compilation units will be stored in memory longer, and more total
35644 memory will be used. Setting it to zero disables caching, which will
35645 slow down @value{GDBN} startup, but reduce memory consumption.
35647 @kindex maint set profile
35648 @kindex maint show profile
35649 @cindex profiling GDB
35650 @item maint set profile
35651 @itemx maint show profile
35652 Control profiling of @value{GDBN}.
35654 Profiling will be disabled until you use the @samp{maint set profile}
35655 command to enable it. When you enable profiling, the system will begin
35656 collecting timing and execution count data; when you disable profiling or
35657 exit @value{GDBN}, the results will be written to a log file. Remember that
35658 if you use profiling, @value{GDBN} will overwrite the profiling log file
35659 (often called @file{gmon.out}). If you have a record of important profiling
35660 data in a @file{gmon.out} file, be sure to move it to a safe location.
35662 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35663 compiled with the @samp{-pg} compiler option.
35665 @kindex maint set show-debug-regs
35666 @kindex maint show show-debug-regs
35667 @cindex hardware debug registers
35668 @item maint set show-debug-regs
35669 @itemx maint show show-debug-regs
35670 Control whether to show variables that mirror the hardware debug
35671 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35672 enabled, the debug registers values are shown when @value{GDBN} inserts or
35673 removes a hardware breakpoint or watchpoint, and when the inferior
35674 triggers a hardware-assisted breakpoint or watchpoint.
35676 @kindex maint set show-all-tib
35677 @kindex maint show show-all-tib
35678 @item maint set show-all-tib
35679 @itemx maint show show-all-tib
35680 Control whether to show all non zero areas within a 1k block starting
35681 at thread local base, when using the @samp{info w32 thread-information-block}
35684 @kindex maint set per-command
35685 @kindex maint show per-command
35686 @item maint set per-command
35687 @itemx maint show per-command
35688 @cindex resources used by commands
35690 @value{GDBN} can display the resources used by each command.
35691 This is useful in debugging performance problems.
35694 @item maint set per-command space [on|off]
35695 @itemx maint show per-command space
35696 Enable or disable the printing of the memory used by GDB for each command.
35697 If enabled, @value{GDBN} will display how much memory each command
35698 took, following the command's own output.
35699 This can also be requested by invoking @value{GDBN} with the
35700 @option{--statistics} command-line switch (@pxref{Mode Options}).
35702 @item maint set per-command time [on|off]
35703 @itemx maint show per-command time
35704 Enable or disable the printing of the execution time of @value{GDBN}
35706 If enabled, @value{GDBN} will display how much time it
35707 took to execute each command, following the command's own output.
35708 Both CPU time and wallclock time are printed.
35709 Printing both is useful when trying to determine whether the cost is
35710 CPU or, e.g., disk/network latency.
35711 Note that the CPU time printed is for @value{GDBN} only, it does not include
35712 the execution time of the inferior because there's no mechanism currently
35713 to compute how much time was spent by @value{GDBN} and how much time was
35714 spent by the program been debugged.
35715 This can also be requested by invoking @value{GDBN} with the
35716 @option{--statistics} command-line switch (@pxref{Mode Options}).
35718 @item maint set per-command symtab [on|off]
35719 @itemx maint show per-command symtab
35720 Enable or disable the printing of basic symbol table statistics
35722 If enabled, @value{GDBN} will display the following information:
35726 number of symbol tables
35728 number of primary symbol tables
35730 number of blocks in the blockvector
35734 @kindex maint space
35735 @cindex memory used by commands
35736 @item maint space @var{value}
35737 An alias for @code{maint set per-command space}.
35738 A non-zero value enables it, zero disables it.
35741 @cindex time of command execution
35742 @item maint time @var{value}
35743 An alias for @code{maint set per-command time}.
35744 A non-zero value enables it, zero disables it.
35746 @kindex maint translate-address
35747 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35748 Find the symbol stored at the location specified by the address
35749 @var{addr} and an optional section name @var{section}. If found,
35750 @value{GDBN} prints the name of the closest symbol and an offset from
35751 the symbol's location to the specified address. This is similar to
35752 the @code{info address} command (@pxref{Symbols}), except that this
35753 command also allows to find symbols in other sections.
35755 If section was not specified, the section in which the symbol was found
35756 is also printed. For dynamically linked executables, the name of
35757 executable or shared library containing the symbol is printed as well.
35761 The following command is useful for non-interactive invocations of
35762 @value{GDBN}, such as in the test suite.
35765 @item set watchdog @var{nsec}
35766 @kindex set watchdog
35767 @cindex watchdog timer
35768 @cindex timeout for commands
35769 Set the maximum number of seconds @value{GDBN} will wait for the
35770 target operation to finish. If this time expires, @value{GDBN}
35771 reports and error and the command is aborted.
35773 @item show watchdog
35774 Show the current setting of the target wait timeout.
35777 @node Remote Protocol
35778 @appendix @value{GDBN} Remote Serial Protocol
35783 * Stop Reply Packets::
35784 * General Query Packets::
35785 * Architecture-Specific Protocol Details::
35786 * Tracepoint Packets::
35787 * Host I/O Packets::
35789 * Notification Packets::
35790 * Remote Non-Stop::
35791 * Packet Acknowledgment::
35793 * File-I/O Remote Protocol Extension::
35794 * Library List Format::
35795 * Library List Format for SVR4 Targets::
35796 * Memory Map Format::
35797 * Thread List Format::
35798 * Traceframe Info Format::
35799 * Branch Trace Format::
35805 There may be occasions when you need to know something about the
35806 protocol---for example, if there is only one serial port to your target
35807 machine, you might want your program to do something special if it
35808 recognizes a packet meant for @value{GDBN}.
35810 In the examples below, @samp{->} and @samp{<-} are used to indicate
35811 transmitted and received data, respectively.
35813 @cindex protocol, @value{GDBN} remote serial
35814 @cindex serial protocol, @value{GDBN} remote
35815 @cindex remote serial protocol
35816 All @value{GDBN} commands and responses (other than acknowledgments
35817 and notifications, see @ref{Notification Packets}) are sent as a
35818 @var{packet}. A @var{packet} is introduced with the character
35819 @samp{$}, the actual @var{packet-data}, and the terminating character
35820 @samp{#} followed by a two-digit @var{checksum}:
35823 @code{$}@var{packet-data}@code{#}@var{checksum}
35827 @cindex checksum, for @value{GDBN} remote
35829 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35830 characters between the leading @samp{$} and the trailing @samp{#} (an
35831 eight bit unsigned checksum).
35833 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35834 specification also included an optional two-digit @var{sequence-id}:
35837 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35840 @cindex sequence-id, for @value{GDBN} remote
35842 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35843 has never output @var{sequence-id}s. Stubs that handle packets added
35844 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35846 When either the host or the target machine receives a packet, the first
35847 response expected is an acknowledgment: either @samp{+} (to indicate
35848 the package was received correctly) or @samp{-} (to request
35852 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35857 The @samp{+}/@samp{-} acknowledgments can be disabled
35858 once a connection is established.
35859 @xref{Packet Acknowledgment}, for details.
35861 The host (@value{GDBN}) sends @var{command}s, and the target (the
35862 debugging stub incorporated in your program) sends a @var{response}. In
35863 the case of step and continue @var{command}s, the response is only sent
35864 when the operation has completed, and the target has again stopped all
35865 threads in all attached processes. This is the default all-stop mode
35866 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35867 execution mode; see @ref{Remote Non-Stop}, for details.
35869 @var{packet-data} consists of a sequence of characters with the
35870 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35873 @cindex remote protocol, field separator
35874 Fields within the packet should be separated using @samp{,} @samp{;} or
35875 @samp{:}. Except where otherwise noted all numbers are represented in
35876 @sc{hex} with leading zeros suppressed.
35878 Implementors should note that prior to @value{GDBN} 5.0, the character
35879 @samp{:} could not appear as the third character in a packet (as it
35880 would potentially conflict with the @var{sequence-id}).
35882 @cindex remote protocol, binary data
35883 @anchor{Binary Data}
35884 Binary data in most packets is encoded either as two hexadecimal
35885 digits per byte of binary data. This allowed the traditional remote
35886 protocol to work over connections which were only seven-bit clean.
35887 Some packets designed more recently assume an eight-bit clean
35888 connection, and use a more efficient encoding to send and receive
35891 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35892 as an escape character. Any escaped byte is transmitted as the escape
35893 character followed by the original character XORed with @code{0x20}.
35894 For example, the byte @code{0x7d} would be transmitted as the two
35895 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35896 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35897 @samp{@}}) must always be escaped. Responses sent by the stub
35898 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35899 is not interpreted as the start of a run-length encoded sequence
35902 Response @var{data} can be run-length encoded to save space.
35903 Run-length encoding replaces runs of identical characters with one
35904 instance of the repeated character, followed by a @samp{*} and a
35905 repeat count. The repeat count is itself sent encoded, to avoid
35906 binary characters in @var{data}: a value of @var{n} is sent as
35907 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35908 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35909 code 32) for a repeat count of 3. (This is because run-length
35910 encoding starts to win for counts 3 or more.) Thus, for example,
35911 @samp{0* } is a run-length encoding of ``0000'': the space character
35912 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35915 The printable characters @samp{#} and @samp{$} or with a numeric value
35916 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35917 seven repeats (@samp{$}) can be expanded using a repeat count of only
35918 five (@samp{"}). For example, @samp{00000000} can be encoded as
35921 The error response returned for some packets includes a two character
35922 error number. That number is not well defined.
35924 @cindex empty response, for unsupported packets
35925 For any @var{command} not supported by the stub, an empty response
35926 (@samp{$#00}) should be returned. That way it is possible to extend the
35927 protocol. A newer @value{GDBN} can tell if a packet is supported based
35930 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35931 commands for register access, and the @samp{m} and @samp{M} commands
35932 for memory access. Stubs that only control single-threaded targets
35933 can implement run control with the @samp{c} (continue), and @samp{s}
35934 (step) commands. Stubs that support multi-threading targets should
35935 support the @samp{vCont} command. All other commands are optional.
35940 The following table provides a complete list of all currently defined
35941 @var{command}s and their corresponding response @var{data}.
35942 @xref{File-I/O Remote Protocol Extension}, for details about the File
35943 I/O extension of the remote protocol.
35945 Each packet's description has a template showing the packet's overall
35946 syntax, followed by an explanation of the packet's meaning. We
35947 include spaces in some of the templates for clarity; these are not
35948 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35949 separate its components. For example, a template like @samp{foo
35950 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35951 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35952 @var{baz}. @value{GDBN} does not transmit a space character between the
35953 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35956 @cindex @var{thread-id}, in remote protocol
35957 @anchor{thread-id syntax}
35958 Several packets and replies include a @var{thread-id} field to identify
35959 a thread. Normally these are positive numbers with a target-specific
35960 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35961 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35964 In addition, the remote protocol supports a multiprocess feature in
35965 which the @var{thread-id} syntax is extended to optionally include both
35966 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35967 The @var{pid} (process) and @var{tid} (thread) components each have the
35968 format described above: a positive number with target-specific
35969 interpretation formatted as a big-endian hex string, literal @samp{-1}
35970 to indicate all processes or threads (respectively), or @samp{0} to
35971 indicate an arbitrary process or thread. Specifying just a process, as
35972 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35973 error to specify all processes but a specific thread, such as
35974 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35975 for those packets and replies explicitly documented to include a process
35976 ID, rather than a @var{thread-id}.
35978 The multiprocess @var{thread-id} syntax extensions are only used if both
35979 @value{GDBN} and the stub report support for the @samp{multiprocess}
35980 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35983 Note that all packet forms beginning with an upper- or lower-case
35984 letter, other than those described here, are reserved for future use.
35986 Here are the packet descriptions.
35991 @cindex @samp{!} packet
35992 @anchor{extended mode}
35993 Enable extended mode. In extended mode, the remote server is made
35994 persistent. The @samp{R} packet is used to restart the program being
36000 The remote target both supports and has enabled extended mode.
36004 @cindex @samp{?} packet
36005 Indicate the reason the target halted. The reply is the same as for
36006 step and continue. This packet has a special interpretation when the
36007 target is in non-stop mode; see @ref{Remote Non-Stop}.
36010 @xref{Stop Reply Packets}, for the reply specifications.
36012 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36013 @cindex @samp{A} packet
36014 Initialized @code{argv[]} array passed into program. @var{arglen}
36015 specifies the number of bytes in the hex encoded byte stream
36016 @var{arg}. See @code{gdbserver} for more details.
36021 The arguments were set.
36027 @cindex @samp{b} packet
36028 (Don't use this packet; its behavior is not well-defined.)
36029 Change the serial line speed to @var{baud}.
36031 JTC: @emph{When does the transport layer state change? When it's
36032 received, or after the ACK is transmitted. In either case, there are
36033 problems if the command or the acknowledgment packet is dropped.}
36035 Stan: @emph{If people really wanted to add something like this, and get
36036 it working for the first time, they ought to modify ser-unix.c to send
36037 some kind of out-of-band message to a specially-setup stub and have the
36038 switch happen "in between" packets, so that from remote protocol's point
36039 of view, nothing actually happened.}
36041 @item B @var{addr},@var{mode}
36042 @cindex @samp{B} packet
36043 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36044 breakpoint at @var{addr}.
36046 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36047 (@pxref{insert breakpoint or watchpoint packet}).
36049 @cindex @samp{bc} packet
36052 Backward continue. Execute the target system in reverse. No parameter.
36053 @xref{Reverse Execution}, for more information.
36056 @xref{Stop Reply Packets}, for the reply specifications.
36058 @cindex @samp{bs} packet
36061 Backward single step. Execute one instruction in reverse. No parameter.
36062 @xref{Reverse Execution}, for more information.
36065 @xref{Stop Reply Packets}, for the reply specifications.
36067 @item c @r{[}@var{addr}@r{]}
36068 @cindex @samp{c} packet
36069 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
36070 resume at current address.
36072 This packet is deprecated for multi-threading support. @xref{vCont
36076 @xref{Stop Reply Packets}, for the reply specifications.
36078 @item C @var{sig}@r{[};@var{addr}@r{]}
36079 @cindex @samp{C} packet
36080 Continue with signal @var{sig} (hex signal number). If
36081 @samp{;@var{addr}} is omitted, resume at same address.
36083 This packet is deprecated for multi-threading support. @xref{vCont
36087 @xref{Stop Reply Packets}, for the reply specifications.
36090 @cindex @samp{d} packet
36093 Don't use this packet; instead, define a general set packet
36094 (@pxref{General Query Packets}).
36098 @cindex @samp{D} packet
36099 The first form of the packet is used to detach @value{GDBN} from the
36100 remote system. It is sent to the remote target
36101 before @value{GDBN} disconnects via the @code{detach} command.
36103 The second form, including a process ID, is used when multiprocess
36104 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36105 detach only a specific process. The @var{pid} is specified as a
36106 big-endian hex string.
36116 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36117 @cindex @samp{F} packet
36118 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36119 This is part of the File-I/O protocol extension. @xref{File-I/O
36120 Remote Protocol Extension}, for the specification.
36123 @anchor{read registers packet}
36124 @cindex @samp{g} packet
36125 Read general registers.
36129 @item @var{XX@dots{}}
36130 Each byte of register data is described by two hex digits. The bytes
36131 with the register are transmitted in target byte order. The size of
36132 each register and their position within the @samp{g} packet are
36133 determined by the @value{GDBN} internal gdbarch functions
36134 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
36135 specification of several standard @samp{g} packets is specified below.
36137 When reading registers from a trace frame (@pxref{Analyze Collected
36138 Data,,Using the Collected Data}), the stub may also return a string of
36139 literal @samp{x}'s in place of the register data digits, to indicate
36140 that the corresponding register has not been collected, thus its value
36141 is unavailable. For example, for an architecture with 4 registers of
36142 4 bytes each, the following reply indicates to @value{GDBN} that
36143 registers 0 and 2 have not been collected, while registers 1 and 3
36144 have been collected, and both have zero value:
36148 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36155 @item G @var{XX@dots{}}
36156 @cindex @samp{G} packet
36157 Write general registers. @xref{read registers packet}, for a
36158 description of the @var{XX@dots{}} data.
36168 @item H @var{op} @var{thread-id}
36169 @cindex @samp{H} packet
36170 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36171 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
36172 it should be @samp{c} for step and continue operations (note that this
36173 is deprecated, supporting the @samp{vCont} command is a better
36174 option), @samp{g} for other operations. The thread designator
36175 @var{thread-id} has the format and interpretation described in
36176 @ref{thread-id syntax}.
36187 @c 'H': How restrictive (or permissive) is the thread model. If a
36188 @c thread is selected and stopped, are other threads allowed
36189 @c to continue to execute? As I mentioned above, I think the
36190 @c semantics of each command when a thread is selected must be
36191 @c described. For example:
36193 @c 'g': If the stub supports threads and a specific thread is
36194 @c selected, returns the register block from that thread;
36195 @c otherwise returns current registers.
36197 @c 'G' If the stub supports threads and a specific thread is
36198 @c selected, sets the registers of the register block of
36199 @c that thread; otherwise sets current registers.
36201 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36202 @anchor{cycle step packet}
36203 @cindex @samp{i} packet
36204 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36205 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36206 step starting at that address.
36209 @cindex @samp{I} packet
36210 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36214 @cindex @samp{k} packet
36217 FIXME: @emph{There is no description of how to operate when a specific
36218 thread context has been selected (i.e.@: does 'k' kill only that
36221 @item m @var{addr},@var{length}
36222 @cindex @samp{m} packet
36223 Read @var{length} bytes of memory starting at address @var{addr}.
36224 Note that @var{addr} may not be aligned to any particular boundary.
36226 The stub need not use any particular size or alignment when gathering
36227 data from memory for the response; even if @var{addr} is word-aligned
36228 and @var{length} is a multiple of the word size, the stub is free to
36229 use byte accesses, or not. For this reason, this packet may not be
36230 suitable for accessing memory-mapped I/O devices.
36231 @cindex alignment of remote memory accesses
36232 @cindex size of remote memory accesses
36233 @cindex memory, alignment and size of remote accesses
36237 @item @var{XX@dots{}}
36238 Memory contents; each byte is transmitted as a two-digit hexadecimal
36239 number. The reply may contain fewer bytes than requested if the
36240 server was able to read only part of the region of memory.
36245 @item M @var{addr},@var{length}:@var{XX@dots{}}
36246 @cindex @samp{M} packet
36247 Write @var{length} bytes of memory starting at address @var{addr}.
36248 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
36249 hexadecimal number.
36256 for an error (this includes the case where only part of the data was
36261 @cindex @samp{p} packet
36262 Read the value of register @var{n}; @var{n} is in hex.
36263 @xref{read registers packet}, for a description of how the returned
36264 register value is encoded.
36268 @item @var{XX@dots{}}
36269 the register's value
36273 Indicating an unrecognized @var{query}.
36276 @item P @var{n@dots{}}=@var{r@dots{}}
36277 @anchor{write register packet}
36278 @cindex @samp{P} packet
36279 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36280 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36281 digits for each byte in the register (target byte order).
36291 @item q @var{name} @var{params}@dots{}
36292 @itemx Q @var{name} @var{params}@dots{}
36293 @cindex @samp{q} packet
36294 @cindex @samp{Q} packet
36295 General query (@samp{q}) and set (@samp{Q}). These packets are
36296 described fully in @ref{General Query Packets}.
36299 @cindex @samp{r} packet
36300 Reset the entire system.
36302 Don't use this packet; use the @samp{R} packet instead.
36305 @cindex @samp{R} packet
36306 Restart the program being debugged. @var{XX}, while needed, is ignored.
36307 This packet is only available in extended mode (@pxref{extended mode}).
36309 The @samp{R} packet has no reply.
36311 @item s @r{[}@var{addr}@r{]}
36312 @cindex @samp{s} packet
36313 Single step. @var{addr} is the address at which to resume. If
36314 @var{addr} is omitted, resume at same address.
36316 This packet is deprecated for multi-threading support. @xref{vCont
36320 @xref{Stop Reply Packets}, for the reply specifications.
36322 @item S @var{sig}@r{[};@var{addr}@r{]}
36323 @anchor{step with signal packet}
36324 @cindex @samp{S} packet
36325 Step with signal. This is analogous to the @samp{C} packet, but
36326 requests a single-step, rather than a normal resumption of execution.
36328 This packet is deprecated for multi-threading support. @xref{vCont
36332 @xref{Stop Reply Packets}, for the reply specifications.
36334 @item t @var{addr}:@var{PP},@var{MM}
36335 @cindex @samp{t} packet
36336 Search backwards starting at address @var{addr} for a match with pattern
36337 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
36338 @var{addr} must be at least 3 digits.
36340 @item T @var{thread-id}
36341 @cindex @samp{T} packet
36342 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36347 thread is still alive
36353 Packets starting with @samp{v} are identified by a multi-letter name,
36354 up to the first @samp{;} or @samp{?} (or the end of the packet).
36356 @item vAttach;@var{pid}
36357 @cindex @samp{vAttach} packet
36358 Attach to a new process with the specified process ID @var{pid}.
36359 The process ID is a
36360 hexadecimal integer identifying the process. In all-stop mode, all
36361 threads in the attached process are stopped; in non-stop mode, it may be
36362 attached without being stopped if that is supported by the target.
36364 @c In non-stop mode, on a successful vAttach, the stub should set the
36365 @c current thread to a thread of the newly-attached process. After
36366 @c attaching, GDB queries for the attached process's thread ID with qC.
36367 @c Also note that, from a user perspective, whether or not the
36368 @c target is stopped on attach in non-stop mode depends on whether you
36369 @c use the foreground or background version of the attach command, not
36370 @c on what vAttach does; GDB does the right thing with respect to either
36371 @c stopping or restarting threads.
36373 This packet is only available in extended mode (@pxref{extended mode}).
36379 @item @r{Any stop packet}
36380 for success in all-stop mode (@pxref{Stop Reply Packets})
36382 for success in non-stop mode (@pxref{Remote Non-Stop})
36385 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36386 @cindex @samp{vCont} packet
36387 @anchor{vCont packet}
36388 Resume the inferior, specifying different actions for each thread.
36389 If an action is specified with no @var{thread-id}, then it is applied to any
36390 threads that don't have a specific action specified; if no default action is
36391 specified then other threads should remain stopped in all-stop mode and
36392 in their current state in non-stop mode.
36393 Specifying multiple
36394 default actions is an error; specifying no actions is also an error.
36395 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36397 Currently supported actions are:
36403 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36407 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36412 The optional argument @var{addr} normally associated with the
36413 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36414 not supported in @samp{vCont}.
36416 The @samp{t} action is only relevant in non-stop mode
36417 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36418 A stop reply should be generated for any affected thread not already stopped.
36419 When a thread is stopped by means of a @samp{t} action,
36420 the corresponding stop reply should indicate that the thread has stopped with
36421 signal @samp{0}, regardless of whether the target uses some other signal
36422 as an implementation detail.
36424 The stub must support @samp{vCont} if it reports support for
36425 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36426 this case @samp{vCont} actions can be specified to apply to all threads
36427 in a process by using the @samp{p@var{pid}.-1} form of the
36431 @xref{Stop Reply Packets}, for the reply specifications.
36434 @cindex @samp{vCont?} packet
36435 Request a list of actions supported by the @samp{vCont} packet.
36439 @item vCont@r{[};@var{action}@dots{}@r{]}
36440 The @samp{vCont} packet is supported. Each @var{action} is a supported
36441 command in the @samp{vCont} packet.
36443 The @samp{vCont} packet is not supported.
36446 @item vFile:@var{operation}:@var{parameter}@dots{}
36447 @cindex @samp{vFile} packet
36448 Perform a file operation on the target system. For details,
36449 see @ref{Host I/O Packets}.
36451 @item vFlashErase:@var{addr},@var{length}
36452 @cindex @samp{vFlashErase} packet
36453 Direct the stub to erase @var{length} bytes of flash starting at
36454 @var{addr}. The region may enclose any number of flash blocks, but
36455 its start and end must fall on block boundaries, as indicated by the
36456 flash block size appearing in the memory map (@pxref{Memory Map
36457 Format}). @value{GDBN} groups flash memory programming operations
36458 together, and sends a @samp{vFlashDone} request after each group; the
36459 stub is allowed to delay erase operation until the @samp{vFlashDone}
36460 packet is received.
36470 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36471 @cindex @samp{vFlashWrite} packet
36472 Direct the stub to write data to flash address @var{addr}. The data
36473 is passed in binary form using the same encoding as for the @samp{X}
36474 packet (@pxref{Binary Data}). The memory ranges specified by
36475 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36476 not overlap, and must appear in order of increasing addresses
36477 (although @samp{vFlashErase} packets for higher addresses may already
36478 have been received; the ordering is guaranteed only between
36479 @samp{vFlashWrite} packets). If a packet writes to an address that was
36480 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36481 target-specific method, the results are unpredictable.
36489 for vFlashWrite addressing non-flash memory
36495 @cindex @samp{vFlashDone} packet
36496 Indicate to the stub that flash programming operation is finished.
36497 The stub is permitted to delay or batch the effects of a group of
36498 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36499 @samp{vFlashDone} packet is received. The contents of the affected
36500 regions of flash memory are unpredictable until the @samp{vFlashDone}
36501 request is completed.
36503 @item vKill;@var{pid}
36504 @cindex @samp{vKill} packet
36505 Kill the process with the specified process ID. @var{pid} is a
36506 hexadecimal integer identifying the process. This packet is used in
36507 preference to @samp{k} when multiprocess protocol extensions are
36508 supported; see @ref{multiprocess extensions}.
36518 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36519 @cindex @samp{vRun} packet
36520 Run the program @var{filename}, passing it each @var{argument} on its
36521 command line. The file and arguments are hex-encoded strings. If
36522 @var{filename} is an empty string, the stub may use a default program
36523 (e.g.@: the last program run). The program is created in the stopped
36526 @c FIXME: What about non-stop mode?
36528 This packet is only available in extended mode (@pxref{extended mode}).
36534 @item @r{Any stop packet}
36535 for success (@pxref{Stop Reply Packets})
36539 @cindex @samp{vStopped} packet
36540 @xref{Notification Packets}.
36542 @item X @var{addr},@var{length}:@var{XX@dots{}}
36544 @cindex @samp{X} packet
36545 Write data to memory, where the data is transmitted in binary.
36546 @var{addr} is address, @var{length} is number of bytes,
36547 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36557 @item z @var{type},@var{addr},@var{kind}
36558 @itemx Z @var{type},@var{addr},@var{kind}
36559 @anchor{insert breakpoint or watchpoint packet}
36560 @cindex @samp{z} packet
36561 @cindex @samp{Z} packets
36562 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36563 watchpoint starting at address @var{address} of kind @var{kind}.
36565 Each breakpoint and watchpoint packet @var{type} is documented
36568 @emph{Implementation notes: A remote target shall return an empty string
36569 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36570 remote target shall support either both or neither of a given
36571 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36572 avoid potential problems with duplicate packets, the operations should
36573 be implemented in an idempotent way.}
36575 @item z0,@var{addr},@var{kind}
36576 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36577 @cindex @samp{z0} packet
36578 @cindex @samp{Z0} packet
36579 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36580 @var{addr} of type @var{kind}.
36582 A memory breakpoint is implemented by replacing the instruction at
36583 @var{addr} with a software breakpoint or trap instruction. The
36584 @var{kind} is target-specific and typically indicates the size of
36585 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36586 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36587 architectures have additional meanings for @var{kind};
36588 @var{cond_list} is an optional list of conditional expressions in bytecode
36589 form that should be evaluated on the target's side. These are the
36590 conditions that should be taken into consideration when deciding if
36591 the breakpoint trigger should be reported back to @var{GDBN}.
36593 The @var{cond_list} parameter is comprised of a series of expressions,
36594 concatenated without separators. Each expression has the following form:
36598 @item X @var{len},@var{expr}
36599 @var{len} is the length of the bytecode expression and @var{expr} is the
36600 actual conditional expression in bytecode form.
36604 The optional @var{cmd_list} parameter introduces commands that may be
36605 run on the target, rather than being reported back to @value{GDBN}.
36606 The parameter starts with a numeric flag @var{persist}; if the flag is
36607 nonzero, then the breakpoint may remain active and the commands
36608 continue to be run even when @value{GDBN} disconnects from the target.
36609 Following this flag is a series of expressions concatenated with no
36610 separators. Each expression has the following form:
36614 @item X @var{len},@var{expr}
36615 @var{len} is the length of the bytecode expression and @var{expr} is the
36616 actual conditional expression in bytecode form.
36620 see @ref{Architecture-Specific Protocol Details}.
36622 @emph{Implementation note: It is possible for a target to copy or move
36623 code that contains memory breakpoints (e.g., when implementing
36624 overlays). The behavior of this packet, in the presence of such a
36625 target, is not defined.}
36637 @item z1,@var{addr},@var{kind}
36638 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36639 @cindex @samp{z1} packet
36640 @cindex @samp{Z1} packet
36641 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36642 address @var{addr}.
36644 A hardware breakpoint is implemented using a mechanism that is not
36645 dependant on being able to modify the target's memory. @var{kind}
36646 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36648 @emph{Implementation note: A hardware breakpoint is not affected by code
36661 @item z2,@var{addr},@var{kind}
36662 @itemx Z2,@var{addr},@var{kind}
36663 @cindex @samp{z2} packet
36664 @cindex @samp{Z2} packet
36665 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36666 @var{kind} is interpreted as the number of bytes to watch.
36678 @item z3,@var{addr},@var{kind}
36679 @itemx Z3,@var{addr},@var{kind}
36680 @cindex @samp{z3} packet
36681 @cindex @samp{Z3} packet
36682 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36683 @var{kind} is interpreted as the number of bytes to watch.
36695 @item z4,@var{addr},@var{kind}
36696 @itemx Z4,@var{addr},@var{kind}
36697 @cindex @samp{z4} packet
36698 @cindex @samp{Z4} packet
36699 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36700 @var{kind} is interpreted as the number of bytes to watch.
36714 @node Stop Reply Packets
36715 @section Stop Reply Packets
36716 @cindex stop reply packets
36718 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36719 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36720 receive any of the below as a reply. Except for @samp{?}
36721 and @samp{vStopped}, that reply is only returned
36722 when the target halts. In the below the exact meaning of @dfn{signal
36723 number} is defined by the header @file{include/gdb/signals.h} in the
36724 @value{GDBN} source code.
36726 As in the description of request packets, we include spaces in the
36727 reply templates for clarity; these are not part of the reply packet's
36728 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36734 The program received signal number @var{AA} (a two-digit hexadecimal
36735 number). This is equivalent to a @samp{T} response with no
36736 @var{n}:@var{r} pairs.
36738 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36739 @cindex @samp{T} packet reply
36740 The program received signal number @var{AA} (a two-digit hexadecimal
36741 number). This is equivalent to an @samp{S} response, except that the
36742 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36743 and other information directly in the stop reply packet, reducing
36744 round-trip latency. Single-step and breakpoint traps are reported
36745 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36749 If @var{n} is a hexadecimal number, it is a register number, and the
36750 corresponding @var{r} gives that register's value. @var{r} is a
36751 series of bytes in target byte order, with each byte given by a
36752 two-digit hex number.
36755 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36756 the stopped thread, as specified in @ref{thread-id syntax}.
36759 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36760 the core on which the stop event was detected.
36763 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36764 specific event that stopped the target. The currently defined stop
36765 reasons are listed below. @var{aa} should be @samp{05}, the trap
36766 signal. At most one stop reason should be present.
36769 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36770 and go on to the next; this allows us to extend the protocol in the
36774 The currently defined stop reasons are:
36780 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36783 @cindex shared library events, remote reply
36785 The packet indicates that the loaded libraries have changed.
36786 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36787 list of loaded libraries. @var{r} is ignored.
36789 @cindex replay log events, remote reply
36791 The packet indicates that the target cannot continue replaying
36792 logged execution events, because it has reached the end (or the
36793 beginning when executing backward) of the log. The value of @var{r}
36794 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36795 for more information.
36799 @itemx W @var{AA} ; process:@var{pid}
36800 The process exited, and @var{AA} is the exit status. This is only
36801 applicable to certain targets.
36803 The second form of the response, including the process ID of the exited
36804 process, can be used only when @value{GDBN} has reported support for
36805 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36806 The @var{pid} is formatted as a big-endian hex string.
36809 @itemx X @var{AA} ; process:@var{pid}
36810 The process terminated with signal @var{AA}.
36812 The second form of the response, including the process ID of the
36813 terminated process, can be used only when @value{GDBN} has reported
36814 support for multiprocess protocol extensions; see @ref{multiprocess
36815 extensions}. The @var{pid} is formatted as a big-endian hex string.
36817 @item O @var{XX}@dots{}
36818 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36819 written as the program's console output. This can happen at any time
36820 while the program is running and the debugger should continue to wait
36821 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36823 @item F @var{call-id},@var{parameter}@dots{}
36824 @var{call-id} is the identifier which says which host system call should
36825 be called. This is just the name of the function. Translation into the
36826 correct system call is only applicable as it's defined in @value{GDBN}.
36827 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36830 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36831 this very system call.
36833 The target replies with this packet when it expects @value{GDBN} to
36834 call a host system call on behalf of the target. @value{GDBN} replies
36835 with an appropriate @samp{F} packet and keeps up waiting for the next
36836 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36837 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36838 Protocol Extension}, for more details.
36842 @node General Query Packets
36843 @section General Query Packets
36844 @cindex remote query requests
36846 Packets starting with @samp{q} are @dfn{general query packets};
36847 packets starting with @samp{Q} are @dfn{general set packets}. General
36848 query and set packets are a semi-unified form for retrieving and
36849 sending information to and from the stub.
36851 The initial letter of a query or set packet is followed by a name
36852 indicating what sort of thing the packet applies to. For example,
36853 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36854 definitions with the stub. These packet names follow some
36859 The name must not contain commas, colons or semicolons.
36861 Most @value{GDBN} query and set packets have a leading upper case
36864 The names of custom vendor packets should use a company prefix, in
36865 lower case, followed by a period. For example, packets designed at
36866 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36867 foos) or @samp{Qacme.bar} (for setting bars).
36870 The name of a query or set packet should be separated from any
36871 parameters by a @samp{:}; the parameters themselves should be
36872 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36873 full packet name, and check for a separator or the end of the packet,
36874 in case two packet names share a common prefix. New packets should not begin
36875 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36876 packets predate these conventions, and have arguments without any terminator
36877 for the packet name; we suspect they are in widespread use in places that
36878 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36879 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36882 Like the descriptions of the other packets, each description here
36883 has a template showing the packet's overall syntax, followed by an
36884 explanation of the packet's meaning. We include spaces in some of the
36885 templates for clarity; these are not part of the packet's syntax. No
36886 @value{GDBN} packet uses spaces to separate its components.
36888 Here are the currently defined query and set packets:
36894 Turn on or off the agent as a helper to perform some debugging operations
36895 delegated from @value{GDBN} (@pxref{Control Agent}).
36897 @item QAllow:@var{op}:@var{val}@dots{}
36898 @cindex @samp{QAllow} packet
36899 Specify which operations @value{GDBN} expects to request of the
36900 target, as a semicolon-separated list of operation name and value
36901 pairs. Possible values for @var{op} include @samp{WriteReg},
36902 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36903 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36904 indicating that @value{GDBN} will not request the operation, or 1,
36905 indicating that it may. (The target can then use this to set up its
36906 own internals optimally, for instance if the debugger never expects to
36907 insert breakpoints, it may not need to install its own trap handler.)
36910 @cindex current thread, remote request
36911 @cindex @samp{qC} packet
36912 Return the current thread ID.
36916 @item QC @var{thread-id}
36917 Where @var{thread-id} is a thread ID as documented in
36918 @ref{thread-id syntax}.
36919 @item @r{(anything else)}
36920 Any other reply implies the old thread ID.
36923 @item qCRC:@var{addr},@var{length}
36924 @cindex CRC of memory block, remote request
36925 @cindex @samp{qCRC} packet
36926 Compute the CRC checksum of a block of memory using CRC-32 defined in
36927 IEEE 802.3. The CRC is computed byte at a time, taking the most
36928 significant bit of each byte first. The initial pattern code
36929 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36931 @emph{Note:} This is the same CRC used in validating separate debug
36932 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36933 Files}). However the algorithm is slightly different. When validating
36934 separate debug files, the CRC is computed taking the @emph{least}
36935 significant bit of each byte first, and the final result is inverted to
36936 detect trailing zeros.
36941 An error (such as memory fault)
36942 @item C @var{crc32}
36943 The specified memory region's checksum is @var{crc32}.
36946 @item QDisableRandomization:@var{value}
36947 @cindex disable address space randomization, remote request
36948 @cindex @samp{QDisableRandomization} packet
36949 Some target operating systems will randomize the virtual address space
36950 of the inferior process as a security feature, but provide a feature
36951 to disable such randomization, e.g.@: to allow for a more deterministic
36952 debugging experience. On such systems, this packet with a @var{value}
36953 of 1 directs the target to disable address space randomization for
36954 processes subsequently started via @samp{vRun} packets, while a packet
36955 with a @var{value} of 0 tells the target to enable address space
36958 This packet is only available in extended mode (@pxref{extended mode}).
36963 The request succeeded.
36966 An error occurred. @var{nn} are hex digits.
36969 An empty reply indicates that @samp{QDisableRandomization} is not supported
36973 This packet is not probed by default; the remote stub must request it,
36974 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36975 This should only be done on targets that actually support disabling
36976 address space randomization.
36979 @itemx qsThreadInfo
36980 @cindex list active threads, remote request
36981 @cindex @samp{qfThreadInfo} packet
36982 @cindex @samp{qsThreadInfo} packet
36983 Obtain a list of all active thread IDs from the target (OS). Since there
36984 may be too many active threads to fit into one reply packet, this query
36985 works iteratively: it may require more than one query/reply sequence to
36986 obtain the entire list of threads. The first query of the sequence will
36987 be the @samp{qfThreadInfo} query; subsequent queries in the
36988 sequence will be the @samp{qsThreadInfo} query.
36990 NOTE: This packet replaces the @samp{qL} query (see below).
36994 @item m @var{thread-id}
36996 @item m @var{thread-id},@var{thread-id}@dots{}
36997 a comma-separated list of thread IDs
36999 (lower case letter @samp{L}) denotes end of list.
37002 In response to each query, the target will reply with a list of one or
37003 more thread IDs, separated by commas.
37004 @value{GDBN} will respond to each reply with a request for more thread
37005 ids (using the @samp{qs} form of the query), until the target responds
37006 with @samp{l} (lower-case ell, for @dfn{last}).
37007 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37010 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37011 @cindex get thread-local storage address, remote request
37012 @cindex @samp{qGetTLSAddr} packet
37013 Fetch the address associated with thread local storage specified
37014 by @var{thread-id}, @var{offset}, and @var{lm}.
37016 @var{thread-id} is the thread ID associated with the
37017 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37019 @var{offset} is the (big endian, hex encoded) offset associated with the
37020 thread local variable. (This offset is obtained from the debug
37021 information associated with the variable.)
37023 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37024 load module associated with the thread local storage. For example,
37025 a @sc{gnu}/Linux system will pass the link map address of the shared
37026 object associated with the thread local storage under consideration.
37027 Other operating environments may choose to represent the load module
37028 differently, so the precise meaning of this parameter will vary.
37032 @item @var{XX}@dots{}
37033 Hex encoded (big endian) bytes representing the address of the thread
37034 local storage requested.
37037 An error occurred. @var{nn} are hex digits.
37040 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37043 @item qGetTIBAddr:@var{thread-id}
37044 @cindex get thread information block address
37045 @cindex @samp{qGetTIBAddr} packet
37046 Fetch address of the Windows OS specific Thread Information Block.
37048 @var{thread-id} is the thread ID associated with the thread.
37052 @item @var{XX}@dots{}
37053 Hex encoded (big endian) bytes representing the linear address of the
37054 thread information block.
37057 An error occured. This means that either the thread was not found, or the
37058 address could not be retrieved.
37061 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37064 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37065 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37066 digit) is one to indicate the first query and zero to indicate a
37067 subsequent query; @var{threadcount} (two hex digits) is the maximum
37068 number of threads the response packet can contain; and @var{nextthread}
37069 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37070 returned in the response as @var{argthread}.
37072 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37076 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37077 Where: @var{count} (two hex digits) is the number of threads being
37078 returned; @var{done} (one hex digit) is zero to indicate more threads
37079 and one indicates no further threads; @var{argthreadid} (eight hex
37080 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37081 is a sequence of thread IDs from the target. @var{threadid} (eight hex
37082 digits). See @code{remote.c:parse_threadlist_response()}.
37086 @cindex section offsets, remote request
37087 @cindex @samp{qOffsets} packet
37088 Get section offsets that the target used when relocating the downloaded
37093 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37094 Relocate the @code{Text} section by @var{xxx} from its original address.
37095 Relocate the @code{Data} section by @var{yyy} from its original address.
37096 If the object file format provides segment information (e.g.@: @sc{elf}
37097 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37098 segments by the supplied offsets.
37100 @emph{Note: while a @code{Bss} offset may be included in the response,
37101 @value{GDBN} ignores this and instead applies the @code{Data} offset
37102 to the @code{Bss} section.}
37104 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37105 Relocate the first segment of the object file, which conventionally
37106 contains program code, to a starting address of @var{xxx}. If
37107 @samp{DataSeg} is specified, relocate the second segment, which
37108 conventionally contains modifiable data, to a starting address of
37109 @var{yyy}. @value{GDBN} will report an error if the object file
37110 does not contain segment information, or does not contain at least
37111 as many segments as mentioned in the reply. Extra segments are
37112 kept at fixed offsets relative to the last relocated segment.
37115 @item qP @var{mode} @var{thread-id}
37116 @cindex thread information, remote request
37117 @cindex @samp{qP} packet
37118 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37119 encoded 32 bit mode; @var{thread-id} is a thread ID
37120 (@pxref{thread-id syntax}).
37122 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37125 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37129 @cindex non-stop mode, remote request
37130 @cindex @samp{QNonStop} packet
37132 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37133 @xref{Remote Non-Stop}, for more information.
37138 The request succeeded.
37141 An error occurred. @var{nn} are hex digits.
37144 An empty reply indicates that @samp{QNonStop} is not supported by
37148 This packet is not probed by default; the remote stub must request it,
37149 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37150 Use of this packet is controlled by the @code{set non-stop} command;
37151 @pxref{Non-Stop Mode}.
37153 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37154 @cindex pass signals to inferior, remote request
37155 @cindex @samp{QPassSignals} packet
37156 @anchor{QPassSignals}
37157 Each listed @var{signal} should be passed directly to the inferior process.
37158 Signals are numbered identically to continue packets and stop replies
37159 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37160 strictly greater than the previous item. These signals do not need to stop
37161 the inferior, or be reported to @value{GDBN}. All other signals should be
37162 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37163 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37164 new list. This packet improves performance when using @samp{handle
37165 @var{signal} nostop noprint pass}.
37170 The request succeeded.
37173 An error occurred. @var{nn} are hex digits.
37176 An empty reply indicates that @samp{QPassSignals} is not supported by
37180 Use of this packet is controlled by the @code{set remote pass-signals}
37181 command (@pxref{Remote Configuration, set remote pass-signals}).
37182 This packet is not probed by default; the remote stub must request it,
37183 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37185 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37186 @cindex signals the inferior may see, remote request
37187 @cindex @samp{QProgramSignals} packet
37188 @anchor{QProgramSignals}
37189 Each listed @var{signal} may be delivered to the inferior process.
37190 Others should be silently discarded.
37192 In some cases, the remote stub may need to decide whether to deliver a
37193 signal to the program or not without @value{GDBN} involvement. One
37194 example of that is while detaching --- the program's threads may have
37195 stopped for signals that haven't yet had a chance of being reported to
37196 @value{GDBN}, and so the remote stub can use the signal list specified
37197 by this packet to know whether to deliver or ignore those pending
37200 This does not influence whether to deliver a signal as requested by a
37201 resumption packet (@pxref{vCont packet}).
37203 Signals are numbered identically to continue packets and stop replies
37204 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37205 strictly greater than the previous item. Multiple
37206 @samp{QProgramSignals} packets do not combine; any earlier
37207 @samp{QProgramSignals} list is completely replaced by the new list.
37212 The request succeeded.
37215 An error occurred. @var{nn} are hex digits.
37218 An empty reply indicates that @samp{QProgramSignals} is not supported
37222 Use of this packet is controlled by the @code{set remote program-signals}
37223 command (@pxref{Remote Configuration, set remote program-signals}).
37224 This packet is not probed by default; the remote stub must request it,
37225 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37227 @item qRcmd,@var{command}
37228 @cindex execute remote command, remote request
37229 @cindex @samp{qRcmd} packet
37230 @var{command} (hex encoded) is passed to the local interpreter for
37231 execution. Invalid commands should be reported using the output
37232 string. Before the final result packet, the target may also respond
37233 with a number of intermediate @samp{O@var{output}} console output
37234 packets. @emph{Implementors should note that providing access to a
37235 stubs's interpreter may have security implications}.
37240 A command response with no output.
37242 A command response with the hex encoded output string @var{OUTPUT}.
37244 Indicate a badly formed request.
37246 An empty reply indicates that @samp{qRcmd} is not recognized.
37249 (Note that the @code{qRcmd} packet's name is separated from the
37250 command by a @samp{,}, not a @samp{:}, contrary to the naming
37251 conventions above. Please don't use this packet as a model for new
37254 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37255 @cindex searching memory, in remote debugging
37257 @cindex @samp{qSearch:memory} packet
37259 @cindex @samp{qSearch memory} packet
37260 @anchor{qSearch memory}
37261 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37262 @var{address} and @var{length} are encoded in hex.
37263 @var{search-pattern} is a sequence of bytes, hex encoded.
37268 The pattern was not found.
37270 The pattern was found at @var{address}.
37272 A badly formed request or an error was encountered while searching memory.
37274 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37277 @item QStartNoAckMode
37278 @cindex @samp{QStartNoAckMode} packet
37279 @anchor{QStartNoAckMode}
37280 Request that the remote stub disable the normal @samp{+}/@samp{-}
37281 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37286 The stub has switched to no-acknowledgment mode.
37287 @value{GDBN} acknowledges this reponse,
37288 but neither the stub nor @value{GDBN} shall send or expect further
37289 @samp{+}/@samp{-} acknowledgments in the current connection.
37291 An empty reply indicates that the stub does not support no-acknowledgment mode.
37294 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37295 @cindex supported packets, remote query
37296 @cindex features of the remote protocol
37297 @cindex @samp{qSupported} packet
37298 @anchor{qSupported}
37299 Tell the remote stub about features supported by @value{GDBN}, and
37300 query the stub for features it supports. This packet allows
37301 @value{GDBN} and the remote stub to take advantage of each others'
37302 features. @samp{qSupported} also consolidates multiple feature probes
37303 at startup, to improve @value{GDBN} performance---a single larger
37304 packet performs better than multiple smaller probe packets on
37305 high-latency links. Some features may enable behavior which must not
37306 be on by default, e.g.@: because it would confuse older clients or
37307 stubs. Other features may describe packets which could be
37308 automatically probed for, but are not. These features must be
37309 reported before @value{GDBN} will use them. This ``default
37310 unsupported'' behavior is not appropriate for all packets, but it
37311 helps to keep the initial connection time under control with new
37312 versions of @value{GDBN} which support increasing numbers of packets.
37316 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37317 The stub supports or does not support each returned @var{stubfeature},
37318 depending on the form of each @var{stubfeature} (see below for the
37321 An empty reply indicates that @samp{qSupported} is not recognized,
37322 or that no features needed to be reported to @value{GDBN}.
37325 The allowed forms for each feature (either a @var{gdbfeature} in the
37326 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37330 @item @var{name}=@var{value}
37331 The remote protocol feature @var{name} is supported, and associated
37332 with the specified @var{value}. The format of @var{value} depends
37333 on the feature, but it must not include a semicolon.
37335 The remote protocol feature @var{name} is supported, and does not
37336 need an associated value.
37338 The remote protocol feature @var{name} is not supported.
37340 The remote protocol feature @var{name} may be supported, and
37341 @value{GDBN} should auto-detect support in some other way when it is
37342 needed. This form will not be used for @var{gdbfeature} notifications,
37343 but may be used for @var{stubfeature} responses.
37346 Whenever the stub receives a @samp{qSupported} request, the
37347 supplied set of @value{GDBN} features should override any previous
37348 request. This allows @value{GDBN} to put the stub in a known
37349 state, even if the stub had previously been communicating with
37350 a different version of @value{GDBN}.
37352 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37357 This feature indicates whether @value{GDBN} supports multiprocess
37358 extensions to the remote protocol. @value{GDBN} does not use such
37359 extensions unless the stub also reports that it supports them by
37360 including @samp{multiprocess+} in its @samp{qSupported} reply.
37361 @xref{multiprocess extensions}, for details.
37364 This feature indicates that @value{GDBN} supports the XML target
37365 description. If the stub sees @samp{xmlRegisters=} with target
37366 specific strings separated by a comma, it will report register
37370 This feature indicates whether @value{GDBN} supports the
37371 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37372 instruction reply packet}).
37375 Stubs should ignore any unknown values for
37376 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37377 packet supports receiving packets of unlimited length (earlier
37378 versions of @value{GDBN} may reject overly long responses). Additional values
37379 for @var{gdbfeature} may be defined in the future to let the stub take
37380 advantage of new features in @value{GDBN}, e.g.@: incompatible
37381 improvements in the remote protocol---the @samp{multiprocess} feature is
37382 an example of such a feature. The stub's reply should be independent
37383 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37384 describes all the features it supports, and then the stub replies with
37385 all the features it supports.
37387 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37388 responses, as long as each response uses one of the standard forms.
37390 Some features are flags. A stub which supports a flag feature
37391 should respond with a @samp{+} form response. Other features
37392 require values, and the stub should respond with an @samp{=}
37395 Each feature has a default value, which @value{GDBN} will use if
37396 @samp{qSupported} is not available or if the feature is not mentioned
37397 in the @samp{qSupported} response. The default values are fixed; a
37398 stub is free to omit any feature responses that match the defaults.
37400 Not all features can be probed, but for those which can, the probing
37401 mechanism is useful: in some cases, a stub's internal
37402 architecture may not allow the protocol layer to know some information
37403 about the underlying target in advance. This is especially common in
37404 stubs which may be configured for multiple targets.
37406 These are the currently defined stub features and their properties:
37408 @multitable @columnfractions 0.35 0.2 0.12 0.2
37409 @c NOTE: The first row should be @headitem, but we do not yet require
37410 @c a new enough version of Texinfo (4.7) to use @headitem.
37412 @tab Value Required
37416 @item @samp{PacketSize}
37421 @item @samp{qXfer:auxv:read}
37426 @item @samp{qXfer:btrace:read}
37431 @item @samp{qXfer:features:read}
37436 @item @samp{qXfer:libraries:read}
37441 @item @samp{qXfer:memory-map:read}
37446 @item @samp{qXfer:sdata:read}
37451 @item @samp{qXfer:spu:read}
37456 @item @samp{qXfer:spu:write}
37461 @item @samp{qXfer:siginfo:read}
37466 @item @samp{qXfer:siginfo:write}
37471 @item @samp{qXfer:threads:read}
37476 @item @samp{qXfer:traceframe-info:read}
37481 @item @samp{qXfer:uib:read}
37486 @item @samp{qXfer:fdpic:read}
37491 @item @samp{Qbtrace:off}
37496 @item @samp{Qbtrace:bts}
37501 @item @samp{QNonStop}
37506 @item @samp{QPassSignals}
37511 @item @samp{QStartNoAckMode}
37516 @item @samp{multiprocess}
37521 @item @samp{ConditionalBreakpoints}
37526 @item @samp{ConditionalTracepoints}
37531 @item @samp{ReverseContinue}
37536 @item @samp{ReverseStep}
37541 @item @samp{TracepointSource}
37546 @item @samp{QAgent}
37551 @item @samp{QAllow}
37556 @item @samp{QDisableRandomization}
37561 @item @samp{EnableDisableTracepoints}
37566 @item @samp{QTBuffer:size}
37571 @item @samp{tracenz}
37576 @item @samp{BreakpointCommands}
37583 These are the currently defined stub features, in more detail:
37586 @cindex packet size, remote protocol
37587 @item PacketSize=@var{bytes}
37588 The remote stub can accept packets up to at least @var{bytes} in
37589 length. @value{GDBN} will send packets up to this size for bulk
37590 transfers, and will never send larger packets. This is a limit on the
37591 data characters in the packet, including the frame and checksum.
37592 There is no trailing NUL byte in a remote protocol packet; if the stub
37593 stores packets in a NUL-terminated format, it should allow an extra
37594 byte in its buffer for the NUL. If this stub feature is not supported,
37595 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37597 @item qXfer:auxv:read
37598 The remote stub understands the @samp{qXfer:auxv:read} packet
37599 (@pxref{qXfer auxiliary vector read}).
37601 @item qXfer:btrace:read
37602 The remote stub understands the @samp{qXfer:btrace:read}
37603 packet (@pxref{qXfer btrace read}).
37605 @item qXfer:features:read
37606 The remote stub understands the @samp{qXfer:features:read} packet
37607 (@pxref{qXfer target description read}).
37609 @item qXfer:libraries:read
37610 The remote stub understands the @samp{qXfer:libraries:read} packet
37611 (@pxref{qXfer library list read}).
37613 @item qXfer:libraries-svr4:read
37614 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37615 (@pxref{qXfer svr4 library list read}).
37617 @item qXfer:memory-map:read
37618 The remote stub understands the @samp{qXfer:memory-map:read} packet
37619 (@pxref{qXfer memory map read}).
37621 @item qXfer:sdata:read
37622 The remote stub understands the @samp{qXfer:sdata:read} packet
37623 (@pxref{qXfer sdata read}).
37625 @item qXfer:spu:read
37626 The remote stub understands the @samp{qXfer:spu:read} packet
37627 (@pxref{qXfer spu read}).
37629 @item qXfer:spu:write
37630 The remote stub understands the @samp{qXfer:spu:write} packet
37631 (@pxref{qXfer spu write}).
37633 @item qXfer:siginfo:read
37634 The remote stub understands the @samp{qXfer:siginfo:read} packet
37635 (@pxref{qXfer siginfo read}).
37637 @item qXfer:siginfo:write
37638 The remote stub understands the @samp{qXfer:siginfo:write} packet
37639 (@pxref{qXfer siginfo write}).
37641 @item qXfer:threads:read
37642 The remote stub understands the @samp{qXfer:threads:read} packet
37643 (@pxref{qXfer threads read}).
37645 @item qXfer:traceframe-info:read
37646 The remote stub understands the @samp{qXfer:traceframe-info:read}
37647 packet (@pxref{qXfer traceframe info read}).
37649 @item qXfer:uib:read
37650 The remote stub understands the @samp{qXfer:uib:read}
37651 packet (@pxref{qXfer unwind info block}).
37653 @item qXfer:fdpic:read
37654 The remote stub understands the @samp{qXfer:fdpic:read}
37655 packet (@pxref{qXfer fdpic loadmap read}).
37658 The remote stub understands the @samp{QNonStop} packet
37659 (@pxref{QNonStop}).
37662 The remote stub understands the @samp{QPassSignals} packet
37663 (@pxref{QPassSignals}).
37665 @item QStartNoAckMode
37666 The remote stub understands the @samp{QStartNoAckMode} packet and
37667 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37670 @anchor{multiprocess extensions}
37671 @cindex multiprocess extensions, in remote protocol
37672 The remote stub understands the multiprocess extensions to the remote
37673 protocol syntax. The multiprocess extensions affect the syntax of
37674 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37675 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37676 replies. Note that reporting this feature indicates support for the
37677 syntactic extensions only, not that the stub necessarily supports
37678 debugging of more than one process at a time. The stub must not use
37679 multiprocess extensions in packet replies unless @value{GDBN} has also
37680 indicated it supports them in its @samp{qSupported} request.
37682 @item qXfer:osdata:read
37683 The remote stub understands the @samp{qXfer:osdata:read} packet
37684 ((@pxref{qXfer osdata read}).
37686 @item ConditionalBreakpoints
37687 The target accepts and implements evaluation of conditional expressions
37688 defined for breakpoints. The target will only report breakpoint triggers
37689 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37691 @item ConditionalTracepoints
37692 The remote stub accepts and implements conditional expressions defined
37693 for tracepoints (@pxref{Tracepoint Conditions}).
37695 @item ReverseContinue
37696 The remote stub accepts and implements the reverse continue packet
37700 The remote stub accepts and implements the reverse step packet
37703 @item TracepointSource
37704 The remote stub understands the @samp{QTDPsrc} packet that supplies
37705 the source form of tracepoint definitions.
37708 The remote stub understands the @samp{QAgent} packet.
37711 The remote stub understands the @samp{QAllow} packet.
37713 @item QDisableRandomization
37714 The remote stub understands the @samp{QDisableRandomization} packet.
37716 @item StaticTracepoint
37717 @cindex static tracepoints, in remote protocol
37718 The remote stub supports static tracepoints.
37720 @item InstallInTrace
37721 @anchor{install tracepoint in tracing}
37722 The remote stub supports installing tracepoint in tracing.
37724 @item EnableDisableTracepoints
37725 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37726 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37727 to be enabled and disabled while a trace experiment is running.
37729 @item QTBuffer:size
37730 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37731 packet that allows to change the size of the trace buffer.
37734 @cindex string tracing, in remote protocol
37735 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37736 See @ref{Bytecode Descriptions} for details about the bytecode.
37738 @item BreakpointCommands
37739 @cindex breakpoint commands, in remote protocol
37740 The remote stub supports running a breakpoint's command list itself,
37741 rather than reporting the hit to @value{GDBN}.
37744 The remote stub understands the @samp{Qbtrace:off} packet.
37747 The remote stub understands the @samp{Qbtrace:bts} packet.
37752 @cindex symbol lookup, remote request
37753 @cindex @samp{qSymbol} packet
37754 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37755 requests. Accept requests from the target for the values of symbols.
37760 The target does not need to look up any (more) symbols.
37761 @item qSymbol:@var{sym_name}
37762 The target requests the value of symbol @var{sym_name} (hex encoded).
37763 @value{GDBN} may provide the value by using the
37764 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37768 @item qSymbol:@var{sym_value}:@var{sym_name}
37769 Set the value of @var{sym_name} to @var{sym_value}.
37771 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37772 target has previously requested.
37774 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37775 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37781 The target does not need to look up any (more) symbols.
37782 @item qSymbol:@var{sym_name}
37783 The target requests the value of a new symbol @var{sym_name} (hex
37784 encoded). @value{GDBN} will continue to supply the values of symbols
37785 (if available), until the target ceases to request them.
37790 @itemx QTDisconnected
37797 @itemx qTMinFTPILen
37799 @xref{Tracepoint Packets}.
37801 @item qThreadExtraInfo,@var{thread-id}
37802 @cindex thread attributes info, remote request
37803 @cindex @samp{qThreadExtraInfo} packet
37804 Obtain a printable string description of a thread's attributes from
37805 the target OS. @var{thread-id} is a thread ID;
37806 see @ref{thread-id syntax}. This
37807 string may contain anything that the target OS thinks is interesting
37808 for @value{GDBN} to tell the user about the thread. The string is
37809 displayed in @value{GDBN}'s @code{info threads} display. Some
37810 examples of possible thread extra info strings are @samp{Runnable}, or
37811 @samp{Blocked on Mutex}.
37815 @item @var{XX}@dots{}
37816 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37817 comprising the printable string containing the extra information about
37818 the thread's attributes.
37821 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37822 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37823 conventions above. Please don't use this packet as a model for new
37842 @xref{Tracepoint Packets}.
37844 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37845 @cindex read special object, remote request
37846 @cindex @samp{qXfer} packet
37847 @anchor{qXfer read}
37848 Read uninterpreted bytes from the target's special data area
37849 identified by the keyword @var{object}. Request @var{length} bytes
37850 starting at @var{offset} bytes into the data. The content and
37851 encoding of @var{annex} is specific to @var{object}; it can supply
37852 additional details about what data to access.
37854 Here are the specific requests of this form defined so far. All
37855 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37856 formats, listed below.
37859 @item qXfer:auxv:read::@var{offset},@var{length}
37860 @anchor{qXfer auxiliary vector read}
37861 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37862 auxiliary vector}. Note @var{annex} must be empty.
37864 This packet is not probed by default; the remote stub must request it,
37865 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37867 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37868 @anchor{qXfer btrace read}
37870 Return a description of the current branch trace.
37871 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37872 packet may have one of the following values:
37876 Returns all available branch trace.
37879 Returns all available branch trace if the branch trace changed since
37880 the last read request.
37883 This packet is not probed by default; the remote stub must request it
37884 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37886 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37887 @anchor{qXfer target description read}
37888 Access the @dfn{target description}. @xref{Target Descriptions}. The
37889 annex specifies which XML document to access. The main description is
37890 always loaded from the @samp{target.xml} annex.
37892 This packet is not probed by default; the remote stub must request it,
37893 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37895 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37896 @anchor{qXfer library list read}
37897 Access the target's list of loaded libraries. @xref{Library List Format}.
37898 The annex part of the generic @samp{qXfer} packet must be empty
37899 (@pxref{qXfer read}).
37901 Targets which maintain a list of libraries in the program's memory do
37902 not need to implement this packet; it is designed for platforms where
37903 the operating system manages the list of loaded libraries.
37905 This packet is not probed by default; the remote stub must request it,
37906 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37908 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37909 @anchor{qXfer svr4 library list read}
37910 Access the target's list of loaded libraries when the target is an SVR4
37911 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37912 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37914 This packet is optional for better performance on SVR4 targets.
37915 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37917 This packet is not probed by default; the remote stub must request it,
37918 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37920 @item qXfer:memory-map:read::@var{offset},@var{length}
37921 @anchor{qXfer memory map read}
37922 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37923 annex part of the generic @samp{qXfer} packet must be empty
37924 (@pxref{qXfer read}).
37926 This packet is not probed by default; the remote stub must request it,
37927 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37929 @item qXfer:sdata:read::@var{offset},@var{length}
37930 @anchor{qXfer sdata read}
37932 Read contents of the extra collected static tracepoint marker
37933 information. The annex part of the generic @samp{qXfer} packet must
37934 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37937 This packet is not probed by default; the remote stub must request it,
37938 by supplying an appropriate @samp{qSupported} response
37939 (@pxref{qSupported}).
37941 @item qXfer:siginfo:read::@var{offset},@var{length}
37942 @anchor{qXfer siginfo read}
37943 Read contents of the extra signal information on the target
37944 system. The annex part of the generic @samp{qXfer} packet must be
37945 empty (@pxref{qXfer read}).
37947 This packet is not probed by default; the remote stub must request it,
37948 by supplying an appropriate @samp{qSupported} response
37949 (@pxref{qSupported}).
37951 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37952 @anchor{qXfer spu read}
37953 Read contents of an @code{spufs} file on the target system. The
37954 annex specifies which file to read; it must be of the form
37955 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37956 in the target process, and @var{name} identifes the @code{spufs} file
37957 in that context to be accessed.
37959 This packet is not probed by default; the remote stub must request it,
37960 by supplying an appropriate @samp{qSupported} response
37961 (@pxref{qSupported}).
37963 @item qXfer:threads:read::@var{offset},@var{length}
37964 @anchor{qXfer threads read}
37965 Access the list of threads on target. @xref{Thread List Format}. The
37966 annex part of the generic @samp{qXfer} packet must be empty
37967 (@pxref{qXfer read}).
37969 This packet is not probed by default; the remote stub must request it,
37970 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37972 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37973 @anchor{qXfer traceframe info read}
37975 Return a description of the current traceframe's contents.
37976 @xref{Traceframe Info Format}. The annex part of the generic
37977 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37979 This packet is not probed by default; the remote stub must request it,
37980 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37982 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37983 @anchor{qXfer unwind info block}
37985 Return the unwind information block for @var{pc}. This packet is used
37986 on OpenVMS/ia64 to ask the kernel unwind information.
37988 This packet is not probed by default.
37990 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37991 @anchor{qXfer fdpic loadmap read}
37992 Read contents of @code{loadmap}s on the target system. The
37993 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37994 executable @code{loadmap} or interpreter @code{loadmap} to read.
37996 This packet is not probed by default; the remote stub must request it,
37997 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37999 @item qXfer:osdata:read::@var{offset},@var{length}
38000 @anchor{qXfer osdata read}
38001 Access the target's @dfn{operating system information}.
38002 @xref{Operating System Information}.
38009 Data @var{data} (@pxref{Binary Data}) has been read from the
38010 target. There may be more data at a higher address (although
38011 it is permitted to return @samp{m} even for the last valid
38012 block of data, as long as at least one byte of data was read).
38013 @var{data} may have fewer bytes than the @var{length} in the
38017 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38018 There is no more data to be read. @var{data} may have fewer bytes
38019 than the @var{length} in the request.
38022 The @var{offset} in the request is at the end of the data.
38023 There is no more data to be read.
38026 The request was malformed, or @var{annex} was invalid.
38029 The offset was invalid, or there was an error encountered reading the data.
38030 @var{nn} is a hex-encoded @code{errno} value.
38033 An empty reply indicates the @var{object} string was not recognized by
38034 the stub, or that the object does not support reading.
38037 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38038 @cindex write data into object, remote request
38039 @anchor{qXfer write}
38040 Write uninterpreted bytes into the target's special data area
38041 identified by the keyword @var{object}, starting at @var{offset} bytes
38042 into the data. @var{data}@dots{} is the binary-encoded data
38043 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
38044 is specific to @var{object}; it can supply additional details about what data
38047 Here are the specific requests of this form defined so far. All
38048 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38049 formats, listed below.
38052 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38053 @anchor{qXfer siginfo write}
38054 Write @var{data} to the extra signal information on the target system.
38055 The annex part of the generic @samp{qXfer} packet must be
38056 empty (@pxref{qXfer write}).
38058 This packet is not probed by default; the remote stub must request it,
38059 by supplying an appropriate @samp{qSupported} response
38060 (@pxref{qSupported}).
38062 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38063 @anchor{qXfer spu write}
38064 Write @var{data} to an @code{spufs} file on the target system. The
38065 annex specifies which file to write; it must be of the form
38066 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38067 in the target process, and @var{name} identifes the @code{spufs} file
38068 in that context to be accessed.
38070 This packet is not probed by default; the remote stub must request it,
38071 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38077 @var{nn} (hex encoded) is the number of bytes written.
38078 This may be fewer bytes than supplied in the request.
38081 The request was malformed, or @var{annex} was invalid.
38084 The offset was invalid, or there was an error encountered writing the data.
38085 @var{nn} is a hex-encoded @code{errno} value.
38088 An empty reply indicates the @var{object} string was not
38089 recognized by the stub, or that the object does not support writing.
38092 @item qXfer:@var{object}:@var{operation}:@dots{}
38093 Requests of this form may be added in the future. When a stub does
38094 not recognize the @var{object} keyword, or its support for
38095 @var{object} does not recognize the @var{operation} keyword, the stub
38096 must respond with an empty packet.
38098 @item qAttached:@var{pid}
38099 @cindex query attached, remote request
38100 @cindex @samp{qAttached} packet
38101 Return an indication of whether the remote server attached to an
38102 existing process or created a new process. When the multiprocess
38103 protocol extensions are supported (@pxref{multiprocess extensions}),
38104 @var{pid} is an integer in hexadecimal format identifying the target
38105 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38106 the query packet will be simplified as @samp{qAttached}.
38108 This query is used, for example, to know whether the remote process
38109 should be detached or killed when a @value{GDBN} session is ended with
38110 the @code{quit} command.
38115 The remote server attached to an existing process.
38117 The remote server created a new process.
38119 A badly formed request or an error was encountered.
38123 Enable branch tracing for the current thread using bts tracing.
38128 Branch tracing has been enabled.
38130 A badly formed request or an error was encountered.
38134 Disable branch tracing for the current thread.
38139 Branch tracing has been disabled.
38141 A badly formed request or an error was encountered.
38146 @node Architecture-Specific Protocol Details
38147 @section Architecture-Specific Protocol Details
38149 This section describes how the remote protocol is applied to specific
38150 target architectures. Also see @ref{Standard Target Features}, for
38151 details of XML target descriptions for each architecture.
38154 * ARM-Specific Protocol Details::
38155 * MIPS-Specific Protocol Details::
38158 @node ARM-Specific Protocol Details
38159 @subsection @acronym{ARM}-specific Protocol Details
38162 * ARM Breakpoint Kinds::
38165 @node ARM Breakpoint Kinds
38166 @subsubsection @acronym{ARM} Breakpoint Kinds
38167 @cindex breakpoint kinds, @acronym{ARM}
38169 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38174 16-bit Thumb mode breakpoint.
38177 32-bit Thumb mode (Thumb-2) breakpoint.
38180 32-bit @acronym{ARM} mode breakpoint.
38184 @node MIPS-Specific Protocol Details
38185 @subsection @acronym{MIPS}-specific Protocol Details
38188 * MIPS Register packet Format::
38189 * MIPS Breakpoint Kinds::
38192 @node MIPS Register packet Format
38193 @subsubsection @acronym{MIPS} Register Packet Format
38194 @cindex register packet format, @acronym{MIPS}
38196 The following @code{g}/@code{G} packets have previously been defined.
38197 In the below, some thirty-two bit registers are transferred as
38198 sixty-four bits. Those registers should be zero/sign extended (which?)
38199 to fill the space allocated. Register bytes are transferred in target
38200 byte order. The two nibbles within a register byte are transferred
38201 most-significant -- least-significant.
38206 All registers are transferred as thirty-two bit quantities in the order:
38207 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38208 registers; fsr; fir; fp.
38211 All registers are transferred as sixty-four bit quantities (including
38212 thirty-two bit registers such as @code{sr}). The ordering is the same
38217 @node MIPS Breakpoint Kinds
38218 @subsubsection @acronym{MIPS} Breakpoint Kinds
38219 @cindex breakpoint kinds, @acronym{MIPS}
38221 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38226 16-bit @acronym{MIPS16} mode breakpoint.
38229 16-bit @acronym{microMIPS} mode breakpoint.
38232 32-bit standard @acronym{MIPS} mode breakpoint.
38235 32-bit @acronym{microMIPS} mode breakpoint.
38239 @node Tracepoint Packets
38240 @section Tracepoint Packets
38241 @cindex tracepoint packets
38242 @cindex packets, tracepoint
38244 Here we describe the packets @value{GDBN} uses to implement
38245 tracepoints (@pxref{Tracepoints}).
38249 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38250 @cindex @samp{QTDP} packet
38251 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38252 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38253 the tracepoint is disabled. @var{step} is the tracepoint's step
38254 count, and @var{pass} is its pass count. If an @samp{F} is present,
38255 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38256 the number of bytes that the target should copy elsewhere to make room
38257 for the tracepoint. If an @samp{X} is present, it introduces a
38258 tracepoint condition, which consists of a hexadecimal length, followed
38259 by a comma and hex-encoded bytes, in a manner similar to action
38260 encodings as described below. If the trailing @samp{-} is present,
38261 further @samp{QTDP} packets will follow to specify this tracepoint's
38267 The packet was understood and carried out.
38269 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38271 The packet was not recognized.
38274 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38275 Define actions to be taken when a tracepoint is hit. @var{n} and
38276 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38277 this tracepoint. This packet may only be sent immediately after
38278 another @samp{QTDP} packet that ended with a @samp{-}. If the
38279 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38280 specifying more actions for this tracepoint.
38282 In the series of action packets for a given tracepoint, at most one
38283 can have an @samp{S} before its first @var{action}. If such a packet
38284 is sent, it and the following packets define ``while-stepping''
38285 actions. Any prior packets define ordinary actions --- that is, those
38286 taken when the tracepoint is first hit. If no action packet has an
38287 @samp{S}, then all the packets in the series specify ordinary
38288 tracepoint actions.
38290 The @samp{@var{action}@dots{}} portion of the packet is a series of
38291 actions, concatenated without separators. Each action has one of the
38297 Collect the registers whose bits are set in @var{mask}. @var{mask} is
38298 a hexadecimal number whose @var{i}'th bit is set if register number
38299 @var{i} should be collected. (The least significant bit is numbered
38300 zero.) Note that @var{mask} may be any number of digits long; it may
38301 not fit in a 32-bit word.
38303 @item M @var{basereg},@var{offset},@var{len}
38304 Collect @var{len} bytes of memory starting at the address in register
38305 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38306 @samp{-1}, then the range has a fixed address: @var{offset} is the
38307 address of the lowest byte to collect. The @var{basereg},
38308 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38309 values (the @samp{-1} value for @var{basereg} is a special case).
38311 @item X @var{len},@var{expr}
38312 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38313 it directs. @var{expr} is an agent expression, as described in
38314 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38315 two-digit hex number in the packet; @var{len} is the number of bytes
38316 in the expression (and thus one-half the number of hex digits in the
38321 Any number of actions may be packed together in a single @samp{QTDP}
38322 packet, as long as the packet does not exceed the maximum packet
38323 length (400 bytes, for many stubs). There may be only one @samp{R}
38324 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38325 actions. Any registers referred to by @samp{M} and @samp{X} actions
38326 must be collected by a preceding @samp{R} action. (The
38327 ``while-stepping'' actions are treated as if they were attached to a
38328 separate tracepoint, as far as these restrictions are concerned.)
38333 The packet was understood and carried out.
38335 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38337 The packet was not recognized.
38340 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38341 @cindex @samp{QTDPsrc} packet
38342 Specify a source string of tracepoint @var{n} at address @var{addr}.
38343 This is useful to get accurate reproduction of the tracepoints
38344 originally downloaded at the beginning of the trace run. @var{type}
38345 is the name of the tracepoint part, such as @samp{cond} for the
38346 tracepoint's conditional expression (see below for a list of types), while
38347 @var{bytes} is the string, encoded in hexadecimal.
38349 @var{start} is the offset of the @var{bytes} within the overall source
38350 string, while @var{slen} is the total length of the source string.
38351 This is intended for handling source strings that are longer than will
38352 fit in a single packet.
38353 @c Add detailed example when this info is moved into a dedicated
38354 @c tracepoint descriptions section.
38356 The available string types are @samp{at} for the location,
38357 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38358 @value{GDBN} sends a separate packet for each command in the action
38359 list, in the same order in which the commands are stored in the list.
38361 The target does not need to do anything with source strings except
38362 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38365 Although this packet is optional, and @value{GDBN} will only send it
38366 if the target replies with @samp{TracepointSource} @xref{General
38367 Query Packets}, it makes both disconnected tracing and trace files
38368 much easier to use. Otherwise the user must be careful that the
38369 tracepoints in effect while looking at trace frames are identical to
38370 the ones in effect during the trace run; even a small discrepancy
38371 could cause @samp{tdump} not to work, or a particular trace frame not
38374 @item QTDV:@var{n}:@var{value}
38375 @cindex define trace state variable, remote request
38376 @cindex @samp{QTDV} packet
38377 Create a new trace state variable, number @var{n}, with an initial
38378 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38379 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38380 the option of not using this packet for initial values of zero; the
38381 target should simply create the trace state variables as they are
38382 mentioned in expressions.
38384 @item QTFrame:@var{n}
38385 @cindex @samp{QTFrame} packet
38386 Select the @var{n}'th tracepoint frame from the buffer, and use the
38387 register and memory contents recorded there to answer subsequent
38388 request packets from @value{GDBN}.
38390 A successful reply from the stub indicates that the stub has found the
38391 requested frame. The response is a series of parts, concatenated
38392 without separators, describing the frame we selected. Each part has
38393 one of the following forms:
38397 The selected frame is number @var{n} in the trace frame buffer;
38398 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38399 was no frame matching the criteria in the request packet.
38402 The selected trace frame records a hit of tracepoint number @var{t};
38403 @var{t} is a hexadecimal number.
38407 @item QTFrame:pc:@var{addr}
38408 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38409 currently selected frame whose PC is @var{addr};
38410 @var{addr} is a hexadecimal number.
38412 @item QTFrame:tdp:@var{t}
38413 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38414 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38415 is a hexadecimal number.
38417 @item QTFrame:range:@var{start}:@var{end}
38418 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38419 currently selected frame whose PC is between @var{start} (inclusive)
38420 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38423 @item QTFrame:outside:@var{start}:@var{end}
38424 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38425 frame @emph{outside} the given range of addresses (exclusive).
38428 @cindex @samp{qTMinFTPILen} packet
38429 This packet requests the minimum length of instruction at which a fast
38430 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38431 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38432 it depends on the target system being able to create trampolines in
38433 the first 64K of memory, which might or might not be possible for that
38434 system. So the reply to this packet will be 4 if it is able to
38441 The minimum instruction length is currently unknown.
38443 The minimum instruction length is @var{length}, where @var{length} is greater
38444 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
38445 that a fast tracepoint may be placed on any instruction regardless of size.
38447 An error has occurred.
38449 An empty reply indicates that the request is not supported by the stub.
38453 @cindex @samp{QTStart} packet
38454 Begin the tracepoint experiment. Begin collecting data from
38455 tracepoint hits in the trace frame buffer. This packet supports the
38456 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38457 instruction reply packet}).
38460 @cindex @samp{QTStop} packet
38461 End the tracepoint experiment. Stop collecting trace frames.
38463 @item QTEnable:@var{n}:@var{addr}
38465 @cindex @samp{QTEnable} packet
38466 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38467 experiment. If the tracepoint was previously disabled, then collection
38468 of data from it will resume.
38470 @item QTDisable:@var{n}:@var{addr}
38472 @cindex @samp{QTDisable} packet
38473 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38474 experiment. No more data will be collected from the tracepoint unless
38475 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38478 @cindex @samp{QTinit} packet
38479 Clear the table of tracepoints, and empty the trace frame buffer.
38481 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38482 @cindex @samp{QTro} packet
38483 Establish the given ranges of memory as ``transparent''. The stub
38484 will answer requests for these ranges from memory's current contents,
38485 if they were not collected as part of the tracepoint hit.
38487 @value{GDBN} uses this to mark read-only regions of memory, like those
38488 containing program code. Since these areas never change, they should
38489 still have the same contents they did when the tracepoint was hit, so
38490 there's no reason for the stub to refuse to provide their contents.
38492 @item QTDisconnected:@var{value}
38493 @cindex @samp{QTDisconnected} packet
38494 Set the choice to what to do with the tracing run when @value{GDBN}
38495 disconnects from the target. A @var{value} of 1 directs the target to
38496 continue the tracing run, while 0 tells the target to stop tracing if
38497 @value{GDBN} is no longer in the picture.
38500 @cindex @samp{qTStatus} packet
38501 Ask the stub if there is a trace experiment running right now.
38503 The reply has the form:
38507 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38508 @var{running} is a single digit @code{1} if the trace is presently
38509 running, or @code{0} if not. It is followed by semicolon-separated
38510 optional fields that an agent may use to report additional status.
38514 If the trace is not running, the agent may report any of several
38515 explanations as one of the optional fields:
38520 No trace has been run yet.
38522 @item tstop[:@var{text}]:0
38523 The trace was stopped by a user-originated stop command. The optional
38524 @var{text} field is a user-supplied string supplied as part of the
38525 stop command (for instance, an explanation of why the trace was
38526 stopped manually). It is hex-encoded.
38529 The trace stopped because the trace buffer filled up.
38531 @item tdisconnected:0
38532 The trace stopped because @value{GDBN} disconnected from the target.
38534 @item tpasscount:@var{tpnum}
38535 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38537 @item terror:@var{text}:@var{tpnum}
38538 The trace stopped because tracepoint @var{tpnum} had an error. The
38539 string @var{text} is available to describe the nature of the error
38540 (for instance, a divide by zero in the condition expression).
38541 @var{text} is hex encoded.
38544 The trace stopped for some other reason.
38548 Additional optional fields supply statistical and other information.
38549 Although not required, they are extremely useful for users monitoring
38550 the progress of a trace run. If a trace has stopped, and these
38551 numbers are reported, they must reflect the state of the just-stopped
38556 @item tframes:@var{n}
38557 The number of trace frames in the buffer.
38559 @item tcreated:@var{n}
38560 The total number of trace frames created during the run. This may
38561 be larger than the trace frame count, if the buffer is circular.
38563 @item tsize:@var{n}
38564 The total size of the trace buffer, in bytes.
38566 @item tfree:@var{n}
38567 The number of bytes still unused in the buffer.
38569 @item circular:@var{n}
38570 The value of the circular trace buffer flag. @code{1} means that the
38571 trace buffer is circular and old trace frames will be discarded if
38572 necessary to make room, @code{0} means that the trace buffer is linear
38575 @item disconn:@var{n}
38576 The value of the disconnected tracing flag. @code{1} means that
38577 tracing will continue after @value{GDBN} disconnects, @code{0} means
38578 that the trace run will stop.
38582 @item qTP:@var{tp}:@var{addr}
38583 @cindex tracepoint status, remote request
38584 @cindex @samp{qTP} packet
38585 Ask the stub for the current state of tracepoint number @var{tp} at
38586 address @var{addr}.
38590 @item V@var{hits}:@var{usage}
38591 The tracepoint has been hit @var{hits} times so far during the trace
38592 run, and accounts for @var{usage} in the trace buffer. Note that
38593 @code{while-stepping} steps are not counted as separate hits, but the
38594 steps' space consumption is added into the usage number.
38598 @item qTV:@var{var}
38599 @cindex trace state variable value, remote request
38600 @cindex @samp{qTV} packet
38601 Ask the stub for the value of the trace state variable number @var{var}.
38606 The value of the variable is @var{value}. This will be the current
38607 value of the variable if the user is examining a running target, or a
38608 saved value if the variable was collected in the trace frame that the
38609 user is looking at. Note that multiple requests may result in
38610 different reply values, such as when requesting values while the
38611 program is running.
38614 The value of the variable is unknown. This would occur, for example,
38615 if the user is examining a trace frame in which the requested variable
38620 @cindex @samp{qTfP} packet
38622 @cindex @samp{qTsP} packet
38623 These packets request data about tracepoints that are being used by
38624 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38625 of data, and multiple @code{qTsP} to get additional pieces. Replies
38626 to these packets generally take the form of the @code{QTDP} packets
38627 that define tracepoints. (FIXME add detailed syntax)
38630 @cindex @samp{qTfV} packet
38632 @cindex @samp{qTsV} packet
38633 These packets request data about trace state variables that are on the
38634 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38635 and multiple @code{qTsV} to get additional variables. Replies to
38636 these packets follow the syntax of the @code{QTDV} packets that define
38637 trace state variables.
38643 @cindex @samp{qTfSTM} packet
38644 @cindex @samp{qTsSTM} packet
38645 These packets request data about static tracepoint markers that exist
38646 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38647 first piece of data, and multiple @code{qTsSTM} to get additional
38648 pieces. Replies to these packets take the following form:
38652 @item m @var{address}:@var{id}:@var{extra}
38654 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38655 a comma-separated list of markers
38657 (lower case letter @samp{L}) denotes end of list.
38659 An error occurred. @var{nn} are hex digits.
38661 An empty reply indicates that the request is not supported by the
38665 @var{address} is encoded in hex.
38666 @var{id} and @var{extra} are strings encoded in hex.
38668 In response to each query, the target will reply with a list of one or
38669 more markers, separated by commas. @value{GDBN} will respond to each
38670 reply with a request for more markers (using the @samp{qs} form of the
38671 query), until the target responds with @samp{l} (lower-case ell, for
38674 @item qTSTMat:@var{address}
38676 @cindex @samp{qTSTMat} packet
38677 This packets requests data about static tracepoint markers in the
38678 target program at @var{address}. Replies to this packet follow the
38679 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38680 tracepoint markers.
38682 @item QTSave:@var{filename}
38683 @cindex @samp{QTSave} packet
38684 This packet directs the target to save trace data to the file name
38685 @var{filename} in the target's filesystem. @var{filename} is encoded
38686 as a hex string; the interpretation of the file name (relative vs
38687 absolute, wild cards, etc) is up to the target.
38689 @item qTBuffer:@var{offset},@var{len}
38690 @cindex @samp{qTBuffer} packet
38691 Return up to @var{len} bytes of the current contents of trace buffer,
38692 starting at @var{offset}. The trace buffer is treated as if it were
38693 a contiguous collection of traceframes, as per the trace file format.
38694 The reply consists as many hex-encoded bytes as the target can deliver
38695 in a packet; it is not an error to return fewer than were asked for.
38696 A reply consisting of just @code{l} indicates that no bytes are
38699 @item QTBuffer:circular:@var{value}
38700 This packet directs the target to use a circular trace buffer if
38701 @var{value} is 1, or a linear buffer if the value is 0.
38703 @item QTBuffer:size:@var{size}
38704 @anchor{QTBuffer-size}
38705 @cindex @samp{QTBuffer size} packet
38706 This packet directs the target to make the trace buffer be of size
38707 @var{size} if possible. A value of @code{-1} tells the target to
38708 use whatever size it prefers.
38710 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38711 @cindex @samp{QTNotes} packet
38712 This packet adds optional textual notes to the trace run. Allowable
38713 types include @code{user}, @code{notes}, and @code{tstop}, the
38714 @var{text} fields are arbitrary strings, hex-encoded.
38718 @subsection Relocate instruction reply packet
38719 When installing fast tracepoints in memory, the target may need to
38720 relocate the instruction currently at the tracepoint address to a
38721 different address in memory. For most instructions, a simple copy is
38722 enough, but, for example, call instructions that implicitly push the
38723 return address on the stack, and relative branches or other
38724 PC-relative instructions require offset adjustment, so that the effect
38725 of executing the instruction at a different address is the same as if
38726 it had executed in the original location.
38728 In response to several of the tracepoint packets, the target may also
38729 respond with a number of intermediate @samp{qRelocInsn} request
38730 packets before the final result packet, to have @value{GDBN} handle
38731 this relocation operation. If a packet supports this mechanism, its
38732 documentation will explicitly say so. See for example the above
38733 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38734 format of the request is:
38737 @item qRelocInsn:@var{from};@var{to}
38739 This requests @value{GDBN} to copy instruction at address @var{from}
38740 to address @var{to}, possibly adjusted so that executing the
38741 instruction at @var{to} has the same effect as executing it at
38742 @var{from}. @value{GDBN} writes the adjusted instruction to target
38743 memory starting at @var{to}.
38748 @item qRelocInsn:@var{adjusted_size}
38749 Informs the stub the relocation is complete. @var{adjusted_size} is
38750 the length in bytes of resulting relocated instruction sequence.
38752 A badly formed request was detected, or an error was encountered while
38753 relocating the instruction.
38756 @node Host I/O Packets
38757 @section Host I/O Packets
38758 @cindex Host I/O, remote protocol
38759 @cindex file transfer, remote protocol
38761 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38762 operations on the far side of a remote link. For example, Host I/O is
38763 used to upload and download files to a remote target with its own
38764 filesystem. Host I/O uses the same constant values and data structure
38765 layout as the target-initiated File-I/O protocol. However, the
38766 Host I/O packets are structured differently. The target-initiated
38767 protocol relies on target memory to store parameters and buffers.
38768 Host I/O requests are initiated by @value{GDBN}, and the
38769 target's memory is not involved. @xref{File-I/O Remote Protocol
38770 Extension}, for more details on the target-initiated protocol.
38772 The Host I/O request packets all encode a single operation along with
38773 its arguments. They have this format:
38777 @item vFile:@var{operation}: @var{parameter}@dots{}
38778 @var{operation} is the name of the particular request; the target
38779 should compare the entire packet name up to the second colon when checking
38780 for a supported operation. The format of @var{parameter} depends on
38781 the operation. Numbers are always passed in hexadecimal. Negative
38782 numbers have an explicit minus sign (i.e.@: two's complement is not
38783 used). Strings (e.g.@: filenames) are encoded as a series of
38784 hexadecimal bytes. The last argument to a system call may be a
38785 buffer of escaped binary data (@pxref{Binary Data}).
38789 The valid responses to Host I/O packets are:
38793 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38794 @var{result} is the integer value returned by this operation, usually
38795 non-negative for success and -1 for errors. If an error has occured,
38796 @var{errno} will be included in the result. @var{errno} will have a
38797 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38798 operations which return data, @var{attachment} supplies the data as a
38799 binary buffer. Binary buffers in response packets are escaped in the
38800 normal way (@pxref{Binary Data}). See the individual packet
38801 documentation for the interpretation of @var{result} and
38805 An empty response indicates that this operation is not recognized.
38809 These are the supported Host I/O operations:
38812 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38813 Open a file at @var{pathname} and return a file descriptor for it, or
38814 return -1 if an error occurs. @var{pathname} is a string,
38815 @var{flags} is an integer indicating a mask of open flags
38816 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38817 of mode bits to use if the file is created (@pxref{mode_t Values}).
38818 @xref{open}, for details of the open flags and mode values.
38820 @item vFile:close: @var{fd}
38821 Close the open file corresponding to @var{fd} and return 0, or
38822 -1 if an error occurs.
38824 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38825 Read data from the open file corresponding to @var{fd}. Up to
38826 @var{count} bytes will be read from the file, starting at @var{offset}
38827 relative to the start of the file. The target may read fewer bytes;
38828 common reasons include packet size limits and an end-of-file
38829 condition. The number of bytes read is returned. Zero should only be
38830 returned for a successful read at the end of the file, or if
38831 @var{count} was zero.
38833 The data read should be returned as a binary attachment on success.
38834 If zero bytes were read, the response should include an empty binary
38835 attachment (i.e.@: a trailing semicolon). The return value is the
38836 number of target bytes read; the binary attachment may be longer if
38837 some characters were escaped.
38839 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38840 Write @var{data} (a binary buffer) to the open file corresponding
38841 to @var{fd}. Start the write at @var{offset} from the start of the
38842 file. Unlike many @code{write} system calls, there is no
38843 separate @var{count} argument; the length of @var{data} in the
38844 packet is used. @samp{vFile:write} returns the number of bytes written,
38845 which may be shorter than the length of @var{data}, or -1 if an
38848 @item vFile:unlink: @var{pathname}
38849 Delete the file at @var{pathname} on the target. Return 0,
38850 or -1 if an error occurs. @var{pathname} is a string.
38852 @item vFile:readlink: @var{filename}
38853 Read value of symbolic link @var{filename} on the target. Return
38854 the number of bytes read, or -1 if an error occurs.
38856 The data read should be returned as a binary attachment on success.
38857 If zero bytes were read, the response should include an empty binary
38858 attachment (i.e.@: a trailing semicolon). The return value is the
38859 number of target bytes read; the binary attachment may be longer if
38860 some characters were escaped.
38865 @section Interrupts
38866 @cindex interrupts (remote protocol)
38868 When a program on the remote target is running, @value{GDBN} may
38869 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38870 a @code{BREAK} followed by @code{g},
38871 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38873 The precise meaning of @code{BREAK} is defined by the transport
38874 mechanism and may, in fact, be undefined. @value{GDBN} does not
38875 currently define a @code{BREAK} mechanism for any of the network
38876 interfaces except for TCP, in which case @value{GDBN} sends the
38877 @code{telnet} BREAK sequence.
38879 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38880 transport mechanisms. It is represented by sending the single byte
38881 @code{0x03} without any of the usual packet overhead described in
38882 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38883 transmitted as part of a packet, it is considered to be packet data
38884 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38885 (@pxref{X packet}), used for binary downloads, may include an unescaped
38886 @code{0x03} as part of its packet.
38888 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38889 When Linux kernel receives this sequence from serial port,
38890 it stops execution and connects to gdb.
38892 Stubs are not required to recognize these interrupt mechanisms and the
38893 precise meaning associated with receipt of the interrupt is
38894 implementation defined. If the target supports debugging of multiple
38895 threads and/or processes, it should attempt to interrupt all
38896 currently-executing threads and processes.
38897 If the stub is successful at interrupting the
38898 running program, it should send one of the stop
38899 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38900 of successfully stopping the program in all-stop mode, and a stop reply
38901 for each stopped thread in non-stop mode.
38902 Interrupts received while the
38903 program is stopped are discarded.
38905 @node Notification Packets
38906 @section Notification Packets
38907 @cindex notification packets
38908 @cindex packets, notification
38910 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38911 packets that require no acknowledgment. Both the GDB and the stub
38912 may send notifications (although the only notifications defined at
38913 present are sent by the stub). Notifications carry information
38914 without incurring the round-trip latency of an acknowledgment, and so
38915 are useful for low-impact communications where occasional packet loss
38918 A notification packet has the form @samp{% @var{data} #
38919 @var{checksum}}, where @var{data} is the content of the notification,
38920 and @var{checksum} is a checksum of @var{data}, computed and formatted
38921 as for ordinary @value{GDBN} packets. A notification's @var{data}
38922 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38923 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38924 to acknowledge the notification's receipt or to report its corruption.
38926 Every notification's @var{data} begins with a name, which contains no
38927 colon characters, followed by a colon character.
38929 Recipients should silently ignore corrupted notifications and
38930 notifications they do not understand. Recipients should restart
38931 timeout periods on receipt of a well-formed notification, whether or
38932 not they understand it.
38934 Senders should only send the notifications described here when this
38935 protocol description specifies that they are permitted. In the
38936 future, we may extend the protocol to permit existing notifications in
38937 new contexts; this rule helps older senders avoid confusing newer
38940 (Older versions of @value{GDBN} ignore bytes received until they see
38941 the @samp{$} byte that begins an ordinary packet, so new stubs may
38942 transmit notifications without fear of confusing older clients. There
38943 are no notifications defined for @value{GDBN} to send at the moment, but we
38944 assume that most older stubs would ignore them, as well.)
38946 Each notification is comprised of three parts:
38948 @item @var{name}:@var{event}
38949 The notification packet is sent by the side that initiates the
38950 exchange (currently, only the stub does that), with @var{event}
38951 carrying the specific information about the notification.
38952 @var{name} is the name of the notification.
38954 The acknowledge sent by the other side, usually @value{GDBN}, to
38955 acknowledge the exchange and request the event.
38958 The purpose of an asynchronous notification mechanism is to report to
38959 @value{GDBN} that something interesting happened in the remote stub.
38961 The remote stub may send notification @var{name}:@var{event}
38962 at any time, but @value{GDBN} acknowledges the notification when
38963 appropriate. The notification event is pending before @value{GDBN}
38964 acknowledges. Only one notification at a time may be pending; if
38965 additional events occur before @value{GDBN} has acknowledged the
38966 previous notification, they must be queued by the stub for later
38967 synchronous transmission in response to @var{ack} packets from
38968 @value{GDBN}. Because the notification mechanism is unreliable,
38969 the stub is permitted to resend a notification if it believes
38970 @value{GDBN} may not have received it.
38972 Specifically, notifications may appear when @value{GDBN} is not
38973 otherwise reading input from the stub, or when @value{GDBN} is
38974 expecting to read a normal synchronous response or a
38975 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38976 Notification packets are distinct from any other communication from
38977 the stub so there is no ambiguity.
38979 After receiving a notification, @value{GDBN} shall acknowledge it by
38980 sending a @var{ack} packet as a regular, synchronous request to the
38981 stub. Such acknowledgment is not required to happen immediately, as
38982 @value{GDBN} is permitted to send other, unrelated packets to the
38983 stub first, which the stub should process normally.
38985 Upon receiving a @var{ack} packet, if the stub has other queued
38986 events to report to @value{GDBN}, it shall respond by sending a
38987 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38988 packet to solicit further responses; again, it is permitted to send
38989 other, unrelated packets as well which the stub should process
38992 If the stub receives a @var{ack} packet and there are no additional
38993 @var{event} to report, the stub shall return an @samp{OK} response.
38994 At this point, @value{GDBN} has finished processing a notification
38995 and the stub has completed sending any queued events. @value{GDBN}
38996 won't accept any new notifications until the final @samp{OK} is
38997 received . If further notification events occur, the stub shall send
38998 a new notification, @value{GDBN} shall accept the notification, and
38999 the process shall be repeated.
39001 The process of asynchronous notification can be illustrated by the
39004 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39007 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39009 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39014 The following notifications are defined:
39015 @multitable @columnfractions 0.12 0.12 0.38 0.38
39024 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39025 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39026 for information on how these notifications are acknowledged by
39028 @tab Report an asynchronous stop event in non-stop mode.
39032 @node Remote Non-Stop
39033 @section Remote Protocol Support for Non-Stop Mode
39035 @value{GDBN}'s remote protocol supports non-stop debugging of
39036 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39037 supports non-stop mode, it should report that to @value{GDBN} by including
39038 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39040 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39041 establishing a new connection with the stub. Entering non-stop mode
39042 does not alter the state of any currently-running threads, but targets
39043 must stop all threads in any already-attached processes when entering
39044 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39045 probe the target state after a mode change.
39047 In non-stop mode, when an attached process encounters an event that
39048 would otherwise be reported with a stop reply, it uses the
39049 asynchronous notification mechanism (@pxref{Notification Packets}) to
39050 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39051 in all processes are stopped when a stop reply is sent, in non-stop
39052 mode only the thread reporting the stop event is stopped. That is,
39053 when reporting a @samp{S} or @samp{T} response to indicate completion
39054 of a step operation, hitting a breakpoint, or a fault, only the
39055 affected thread is stopped; any other still-running threads continue
39056 to run. When reporting a @samp{W} or @samp{X} response, all running
39057 threads belonging to other attached processes continue to run.
39059 In non-stop mode, the target shall respond to the @samp{?} packet as
39060 follows. First, any incomplete stop reply notification/@samp{vStopped}
39061 sequence in progress is abandoned. The target must begin a new
39062 sequence reporting stop events for all stopped threads, whether or not
39063 it has previously reported those events to @value{GDBN}. The first
39064 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39065 subsequent stop replies are sent as responses to @samp{vStopped} packets
39066 using the mechanism described above. The target must not send
39067 asynchronous stop reply notifications until the sequence is complete.
39068 If all threads are running when the target receives the @samp{?} packet,
39069 or if the target is not attached to any process, it shall respond
39072 @node Packet Acknowledgment
39073 @section Packet Acknowledgment
39075 @cindex acknowledgment, for @value{GDBN} remote
39076 @cindex packet acknowledgment, for @value{GDBN} remote
39077 By default, when either the host or the target machine receives a packet,
39078 the first response expected is an acknowledgment: either @samp{+} (to indicate
39079 the package was received correctly) or @samp{-} (to request retransmission).
39080 This mechanism allows the @value{GDBN} remote protocol to operate over
39081 unreliable transport mechanisms, such as a serial line.
39083 In cases where the transport mechanism is itself reliable (such as a pipe or
39084 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39085 It may be desirable to disable them in that case to reduce communication
39086 overhead, or for other reasons. This can be accomplished by means of the
39087 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39089 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39090 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39091 and response format still includes the normal checksum, as described in
39092 @ref{Overview}, but the checksum may be ignored by the receiver.
39094 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39095 no-acknowledgment mode, it should report that to @value{GDBN}
39096 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39097 @pxref{qSupported}.
39098 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39099 disabled via the @code{set remote noack-packet off} command
39100 (@pxref{Remote Configuration}),
39101 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39102 Only then may the stub actually turn off packet acknowledgments.
39103 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39104 response, which can be safely ignored by the stub.
39106 Note that @code{set remote noack-packet} command only affects negotiation
39107 between @value{GDBN} and the stub when subsequent connections are made;
39108 it does not affect the protocol acknowledgment state for any current
39110 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39111 new connection is established,
39112 there is also no protocol request to re-enable the acknowledgments
39113 for the current connection, once disabled.
39118 Example sequence of a target being re-started. Notice how the restart
39119 does not get any direct output:
39124 @emph{target restarts}
39127 <- @code{T001:1234123412341234}
39131 Example sequence of a target being stepped by a single instruction:
39134 -> @code{G1445@dots{}}
39139 <- @code{T001:1234123412341234}
39143 <- @code{1455@dots{}}
39147 @node File-I/O Remote Protocol Extension
39148 @section File-I/O Remote Protocol Extension
39149 @cindex File-I/O remote protocol extension
39152 * File-I/O Overview::
39153 * Protocol Basics::
39154 * The F Request Packet::
39155 * The F Reply Packet::
39156 * The Ctrl-C Message::
39158 * List of Supported Calls::
39159 * Protocol-specific Representation of Datatypes::
39161 * File-I/O Examples::
39164 @node File-I/O Overview
39165 @subsection File-I/O Overview
39166 @cindex file-i/o overview
39168 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39169 target to use the host's file system and console I/O to perform various
39170 system calls. System calls on the target system are translated into a
39171 remote protocol packet to the host system, which then performs the needed
39172 actions and returns a response packet to the target system.
39173 This simulates file system operations even on targets that lack file systems.
39175 The protocol is defined to be independent of both the host and target systems.
39176 It uses its own internal representation of datatypes and values. Both
39177 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39178 translating the system-dependent value representations into the internal
39179 protocol representations when data is transmitted.
39181 The communication is synchronous. A system call is possible only when
39182 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39183 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39184 the target is stopped to allow deterministic access to the target's
39185 memory. Therefore File-I/O is not interruptible by target signals. On
39186 the other hand, it is possible to interrupt File-I/O by a user interrupt
39187 (@samp{Ctrl-C}) within @value{GDBN}.
39189 The target's request to perform a host system call does not finish
39190 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39191 after finishing the system call, the target returns to continuing the
39192 previous activity (continue, step). No additional continue or step
39193 request from @value{GDBN} is required.
39196 (@value{GDBP}) continue
39197 <- target requests 'system call X'
39198 target is stopped, @value{GDBN} executes system call
39199 -> @value{GDBN} returns result
39200 ... target continues, @value{GDBN} returns to wait for the target
39201 <- target hits breakpoint and sends a Txx packet
39204 The protocol only supports I/O on the console and to regular files on
39205 the host file system. Character or block special devices, pipes,
39206 named pipes, sockets or any other communication method on the host
39207 system are not supported by this protocol.
39209 File I/O is not supported in non-stop mode.
39211 @node Protocol Basics
39212 @subsection Protocol Basics
39213 @cindex protocol basics, file-i/o
39215 The File-I/O protocol uses the @code{F} packet as the request as well
39216 as reply packet. Since a File-I/O system call can only occur when
39217 @value{GDBN} is waiting for a response from the continuing or stepping target,
39218 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39219 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39220 This @code{F} packet contains all information needed to allow @value{GDBN}
39221 to call the appropriate host system call:
39225 A unique identifier for the requested system call.
39228 All parameters to the system call. Pointers are given as addresses
39229 in the target memory address space. Pointers to strings are given as
39230 pointer/length pair. Numerical values are given as they are.
39231 Numerical control flags are given in a protocol-specific representation.
39235 At this point, @value{GDBN} has to perform the following actions.
39239 If the parameters include pointer values to data needed as input to a
39240 system call, @value{GDBN} requests this data from the target with a
39241 standard @code{m} packet request. This additional communication has to be
39242 expected by the target implementation and is handled as any other @code{m}
39246 @value{GDBN} translates all value from protocol representation to host
39247 representation as needed. Datatypes are coerced into the host types.
39250 @value{GDBN} calls the system call.
39253 It then coerces datatypes back to protocol representation.
39256 If the system call is expected to return data in buffer space specified
39257 by pointer parameters to the call, the data is transmitted to the
39258 target using a @code{M} or @code{X} packet. This packet has to be expected
39259 by the target implementation and is handled as any other @code{M} or @code{X}
39264 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39265 necessary information for the target to continue. This at least contains
39272 @code{errno}, if has been changed by the system call.
39279 After having done the needed type and value coercion, the target continues
39280 the latest continue or step action.
39282 @node The F Request Packet
39283 @subsection The @code{F} Request Packet
39284 @cindex file-i/o request packet
39285 @cindex @code{F} request packet
39287 The @code{F} request packet has the following format:
39290 @item F@var{call-id},@var{parameter@dots{}}
39292 @var{call-id} is the identifier to indicate the host system call to be called.
39293 This is just the name of the function.
39295 @var{parameter@dots{}} are the parameters to the system call.
39296 Parameters are hexadecimal integer values, either the actual values in case
39297 of scalar datatypes, pointers to target buffer space in case of compound
39298 datatypes and unspecified memory areas, or pointer/length pairs in case
39299 of string parameters. These are appended to the @var{call-id} as a
39300 comma-delimited list. All values are transmitted in ASCII
39301 string representation, pointer/length pairs separated by a slash.
39307 @node The F Reply Packet
39308 @subsection The @code{F} Reply Packet
39309 @cindex file-i/o reply packet
39310 @cindex @code{F} reply packet
39312 The @code{F} reply packet has the following format:
39316 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39318 @var{retcode} is the return code of the system call as hexadecimal value.
39320 @var{errno} is the @code{errno} set by the call, in protocol-specific
39322 This parameter can be omitted if the call was successful.
39324 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39325 case, @var{errno} must be sent as well, even if the call was successful.
39326 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39333 or, if the call was interrupted before the host call has been performed:
39340 assuming 4 is the protocol-specific representation of @code{EINTR}.
39345 @node The Ctrl-C Message
39346 @subsection The @samp{Ctrl-C} Message
39347 @cindex ctrl-c message, in file-i/o protocol
39349 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39350 reply packet (@pxref{The F Reply Packet}),
39351 the target should behave as if it had
39352 gotten a break message. The meaning for the target is ``system call
39353 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39354 (as with a break message) and return to @value{GDBN} with a @code{T02}
39357 It's important for the target to know in which
39358 state the system call was interrupted. There are two possible cases:
39362 The system call hasn't been performed on the host yet.
39365 The system call on the host has been finished.
39369 These two states can be distinguished by the target by the value of the
39370 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39371 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39372 on POSIX systems. In any other case, the target may presume that the
39373 system call has been finished --- successfully or not --- and should behave
39374 as if the break message arrived right after the system call.
39376 @value{GDBN} must behave reliably. If the system call has not been called
39377 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39378 @code{errno} in the packet. If the system call on the host has been finished
39379 before the user requests a break, the full action must be finished by
39380 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39381 The @code{F} packet may only be sent when either nothing has happened
39382 or the full action has been completed.
39385 @subsection Console I/O
39386 @cindex console i/o as part of file-i/o
39388 By default and if not explicitly closed by the target system, the file
39389 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39390 on the @value{GDBN} console is handled as any other file output operation
39391 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39392 by @value{GDBN} so that after the target read request from file descriptor
39393 0 all following typing is buffered until either one of the following
39398 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39400 system call is treated as finished.
39403 The user presses @key{RET}. This is treated as end of input with a trailing
39407 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39408 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39412 If the user has typed more characters than fit in the buffer given to
39413 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39414 either another @code{read(0, @dots{})} is requested by the target, or debugging
39415 is stopped at the user's request.
39418 @node List of Supported Calls
39419 @subsection List of Supported Calls
39420 @cindex list of supported file-i/o calls
39437 @unnumberedsubsubsec open
39438 @cindex open, file-i/o system call
39443 int open(const char *pathname, int flags);
39444 int open(const char *pathname, int flags, mode_t mode);
39448 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39451 @var{flags} is the bitwise @code{OR} of the following values:
39455 If the file does not exist it will be created. The host
39456 rules apply as far as file ownership and time stamps
39460 When used with @code{O_CREAT}, if the file already exists it is
39461 an error and open() fails.
39464 If the file already exists and the open mode allows
39465 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39466 truncated to zero length.
39469 The file is opened in append mode.
39472 The file is opened for reading only.
39475 The file is opened for writing only.
39478 The file is opened for reading and writing.
39482 Other bits are silently ignored.
39486 @var{mode} is the bitwise @code{OR} of the following values:
39490 User has read permission.
39493 User has write permission.
39496 Group has read permission.
39499 Group has write permission.
39502 Others have read permission.
39505 Others have write permission.
39509 Other bits are silently ignored.
39512 @item Return value:
39513 @code{open} returns the new file descriptor or -1 if an error
39520 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39523 @var{pathname} refers to a directory.
39526 The requested access is not allowed.
39529 @var{pathname} was too long.
39532 A directory component in @var{pathname} does not exist.
39535 @var{pathname} refers to a device, pipe, named pipe or socket.
39538 @var{pathname} refers to a file on a read-only filesystem and
39539 write access was requested.
39542 @var{pathname} is an invalid pointer value.
39545 No space on device to create the file.
39548 The process already has the maximum number of files open.
39551 The limit on the total number of files open on the system
39555 The call was interrupted by the user.
39561 @unnumberedsubsubsec close
39562 @cindex close, file-i/o system call
39571 @samp{Fclose,@var{fd}}
39573 @item Return value:
39574 @code{close} returns zero on success, or -1 if an error occurred.
39580 @var{fd} isn't a valid open file descriptor.
39583 The call was interrupted by the user.
39589 @unnumberedsubsubsec read
39590 @cindex read, file-i/o system call
39595 int read(int fd, void *buf, unsigned int count);
39599 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39601 @item Return value:
39602 On success, the number of bytes read is returned.
39603 Zero indicates end of file. If count is zero, read
39604 returns zero as well. On error, -1 is returned.
39610 @var{fd} is not a valid file descriptor or is not open for
39614 @var{bufptr} is an invalid pointer value.
39617 The call was interrupted by the user.
39623 @unnumberedsubsubsec write
39624 @cindex write, file-i/o system call
39629 int write(int fd, const void *buf, unsigned int count);
39633 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39635 @item Return value:
39636 On success, the number of bytes written are returned.
39637 Zero indicates nothing was written. On error, -1
39644 @var{fd} is not a valid file descriptor or is not open for
39648 @var{bufptr} is an invalid pointer value.
39651 An attempt was made to write a file that exceeds the
39652 host-specific maximum file size allowed.
39655 No space on device to write the data.
39658 The call was interrupted by the user.
39664 @unnumberedsubsubsec lseek
39665 @cindex lseek, file-i/o system call
39670 long lseek (int fd, long offset, int flag);
39674 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39676 @var{flag} is one of:
39680 The offset is set to @var{offset} bytes.
39683 The offset is set to its current location plus @var{offset}
39687 The offset is set to the size of the file plus @var{offset}
39691 @item Return value:
39692 On success, the resulting unsigned offset in bytes from
39693 the beginning of the file is returned. Otherwise, a
39694 value of -1 is returned.
39700 @var{fd} is not a valid open file descriptor.
39703 @var{fd} is associated with the @value{GDBN} console.
39706 @var{flag} is not a proper value.
39709 The call was interrupted by the user.
39715 @unnumberedsubsubsec rename
39716 @cindex rename, file-i/o system call
39721 int rename(const char *oldpath, const char *newpath);
39725 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39727 @item Return value:
39728 On success, zero is returned. On error, -1 is returned.
39734 @var{newpath} is an existing directory, but @var{oldpath} is not a
39738 @var{newpath} is a non-empty directory.
39741 @var{oldpath} or @var{newpath} is a directory that is in use by some
39745 An attempt was made to make a directory a subdirectory
39749 A component used as a directory in @var{oldpath} or new
39750 path is not a directory. Or @var{oldpath} is a directory
39751 and @var{newpath} exists but is not a directory.
39754 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39757 No access to the file or the path of the file.
39761 @var{oldpath} or @var{newpath} was too long.
39764 A directory component in @var{oldpath} or @var{newpath} does not exist.
39767 The file is on a read-only filesystem.
39770 The device containing the file has no room for the new
39774 The call was interrupted by the user.
39780 @unnumberedsubsubsec unlink
39781 @cindex unlink, file-i/o system call
39786 int unlink(const char *pathname);
39790 @samp{Funlink,@var{pathnameptr}/@var{len}}
39792 @item Return value:
39793 On success, zero is returned. On error, -1 is returned.
39799 No access to the file or the path of the file.
39802 The system does not allow unlinking of directories.
39805 The file @var{pathname} cannot be unlinked because it's
39806 being used by another process.
39809 @var{pathnameptr} is an invalid pointer value.
39812 @var{pathname} was too long.
39815 A directory component in @var{pathname} does not exist.
39818 A component of the path is not a directory.
39821 The file is on a read-only filesystem.
39824 The call was interrupted by the user.
39830 @unnumberedsubsubsec stat/fstat
39831 @cindex fstat, file-i/o system call
39832 @cindex stat, file-i/o system call
39837 int stat(const char *pathname, struct stat *buf);
39838 int fstat(int fd, struct stat *buf);
39842 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39843 @samp{Ffstat,@var{fd},@var{bufptr}}
39845 @item Return value:
39846 On success, zero is returned. On error, -1 is returned.
39852 @var{fd} is not a valid open file.
39855 A directory component in @var{pathname} does not exist or the
39856 path is an empty string.
39859 A component of the path is not a directory.
39862 @var{pathnameptr} is an invalid pointer value.
39865 No access to the file or the path of the file.
39868 @var{pathname} was too long.
39871 The call was interrupted by the user.
39877 @unnumberedsubsubsec gettimeofday
39878 @cindex gettimeofday, file-i/o system call
39883 int gettimeofday(struct timeval *tv, void *tz);
39887 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39889 @item Return value:
39890 On success, 0 is returned, -1 otherwise.
39896 @var{tz} is a non-NULL pointer.
39899 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39905 @unnumberedsubsubsec isatty
39906 @cindex isatty, file-i/o system call
39911 int isatty(int fd);
39915 @samp{Fisatty,@var{fd}}
39917 @item Return value:
39918 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39924 The call was interrupted by the user.
39929 Note that the @code{isatty} call is treated as a special case: it returns
39930 1 to the target if the file descriptor is attached
39931 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39932 would require implementing @code{ioctl} and would be more complex than
39937 @unnumberedsubsubsec system
39938 @cindex system, file-i/o system call
39943 int system(const char *command);
39947 @samp{Fsystem,@var{commandptr}/@var{len}}
39949 @item Return value:
39950 If @var{len} is zero, the return value indicates whether a shell is
39951 available. A zero return value indicates a shell is not available.
39952 For non-zero @var{len}, the value returned is -1 on error and the
39953 return status of the command otherwise. Only the exit status of the
39954 command is returned, which is extracted from the host's @code{system}
39955 return value by calling @code{WEXITSTATUS(retval)}. In case
39956 @file{/bin/sh} could not be executed, 127 is returned.
39962 The call was interrupted by the user.
39967 @value{GDBN} takes over the full task of calling the necessary host calls
39968 to perform the @code{system} call. The return value of @code{system} on
39969 the host is simplified before it's returned
39970 to the target. Any termination signal information from the child process
39971 is discarded, and the return value consists
39972 entirely of the exit status of the called command.
39974 Due to security concerns, the @code{system} call is by default refused
39975 by @value{GDBN}. The user has to allow this call explicitly with the
39976 @code{set remote system-call-allowed 1} command.
39979 @item set remote system-call-allowed
39980 @kindex set remote system-call-allowed
39981 Control whether to allow the @code{system} calls in the File I/O
39982 protocol for the remote target. The default is zero (disabled).
39984 @item show remote system-call-allowed
39985 @kindex show remote system-call-allowed
39986 Show whether the @code{system} calls are allowed in the File I/O
39990 @node Protocol-specific Representation of Datatypes
39991 @subsection Protocol-specific Representation of Datatypes
39992 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39995 * Integral Datatypes::
39997 * Memory Transfer::
40002 @node Integral Datatypes
40003 @unnumberedsubsubsec Integral Datatypes
40004 @cindex integral datatypes, in file-i/o protocol
40006 The integral datatypes used in the system calls are @code{int},
40007 @code{unsigned int}, @code{long}, @code{unsigned long},
40008 @code{mode_t}, and @code{time_t}.
40010 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40011 implemented as 32 bit values in this protocol.
40013 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40015 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40016 in @file{limits.h}) to allow range checking on host and target.
40018 @code{time_t} datatypes are defined as seconds since the Epoch.
40020 All integral datatypes transferred as part of a memory read or write of a
40021 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40024 @node Pointer Values
40025 @unnumberedsubsubsec Pointer Values
40026 @cindex pointer values, in file-i/o protocol
40028 Pointers to target data are transmitted as they are. An exception
40029 is made for pointers to buffers for which the length isn't
40030 transmitted as part of the function call, namely strings. Strings
40031 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40038 which is a pointer to data of length 18 bytes at position 0x1aaf.
40039 The length is defined as the full string length in bytes, including
40040 the trailing null byte. For example, the string @code{"hello world"}
40041 at address 0x123456 is transmitted as
40047 @node Memory Transfer
40048 @unnumberedsubsubsec Memory Transfer
40049 @cindex memory transfer, in file-i/o protocol
40051 Structured data which is transferred using a memory read or write (for
40052 example, a @code{struct stat}) is expected to be in a protocol-specific format
40053 with all scalar multibyte datatypes being big endian. Translation to
40054 this representation needs to be done both by the target before the @code{F}
40055 packet is sent, and by @value{GDBN} before
40056 it transfers memory to the target. Transferred pointers to structured
40057 data should point to the already-coerced data at any time.
40061 @unnumberedsubsubsec struct stat
40062 @cindex struct stat, in file-i/o protocol
40064 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40065 is defined as follows:
40069 unsigned int st_dev; /* device */
40070 unsigned int st_ino; /* inode */
40071 mode_t st_mode; /* protection */
40072 unsigned int st_nlink; /* number of hard links */
40073 unsigned int st_uid; /* user ID of owner */
40074 unsigned int st_gid; /* group ID of owner */
40075 unsigned int st_rdev; /* device type (if inode device) */
40076 unsigned long st_size; /* total size, in bytes */
40077 unsigned long st_blksize; /* blocksize for filesystem I/O */
40078 unsigned long st_blocks; /* number of blocks allocated */
40079 time_t st_atime; /* time of last access */
40080 time_t st_mtime; /* time of last modification */
40081 time_t st_ctime; /* time of last change */
40085 The integral datatypes conform to the definitions given in the
40086 appropriate section (see @ref{Integral Datatypes}, for details) so this
40087 structure is of size 64 bytes.
40089 The values of several fields have a restricted meaning and/or
40095 A value of 0 represents a file, 1 the console.
40098 No valid meaning for the target. Transmitted unchanged.
40101 Valid mode bits are described in @ref{Constants}. Any other
40102 bits have currently no meaning for the target.
40107 No valid meaning for the target. Transmitted unchanged.
40112 These values have a host and file system dependent
40113 accuracy. Especially on Windows hosts, the file system may not
40114 support exact timing values.
40117 The target gets a @code{struct stat} of the above representation and is
40118 responsible for coercing it to the target representation before
40121 Note that due to size differences between the host, target, and protocol
40122 representations of @code{struct stat} members, these members could eventually
40123 get truncated on the target.
40125 @node struct timeval
40126 @unnumberedsubsubsec struct timeval
40127 @cindex struct timeval, in file-i/o protocol
40129 The buffer of type @code{struct timeval} used by the File-I/O protocol
40130 is defined as follows:
40134 time_t tv_sec; /* second */
40135 long tv_usec; /* microsecond */
40139 The integral datatypes conform to the definitions given in the
40140 appropriate section (see @ref{Integral Datatypes}, for details) so this
40141 structure is of size 8 bytes.
40144 @subsection Constants
40145 @cindex constants, in file-i/o protocol
40147 The following values are used for the constants inside of the
40148 protocol. @value{GDBN} and target are responsible for translating these
40149 values before and after the call as needed.
40160 @unnumberedsubsubsec Open Flags
40161 @cindex open flags, in file-i/o protocol
40163 All values are given in hexadecimal representation.
40175 @node mode_t Values
40176 @unnumberedsubsubsec mode_t Values
40177 @cindex mode_t values, in file-i/o protocol
40179 All values are given in octal representation.
40196 @unnumberedsubsubsec Errno Values
40197 @cindex errno values, in file-i/o protocol
40199 All values are given in decimal representation.
40224 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40225 any error value not in the list of supported error numbers.
40228 @unnumberedsubsubsec Lseek Flags
40229 @cindex lseek flags, in file-i/o protocol
40238 @unnumberedsubsubsec Limits
40239 @cindex limits, in file-i/o protocol
40241 All values are given in decimal representation.
40244 INT_MIN -2147483648
40246 UINT_MAX 4294967295
40247 LONG_MIN -9223372036854775808
40248 LONG_MAX 9223372036854775807
40249 ULONG_MAX 18446744073709551615
40252 @node File-I/O Examples
40253 @subsection File-I/O Examples
40254 @cindex file-i/o examples
40256 Example sequence of a write call, file descriptor 3, buffer is at target
40257 address 0x1234, 6 bytes should be written:
40260 <- @code{Fwrite,3,1234,6}
40261 @emph{request memory read from target}
40264 @emph{return "6 bytes written"}
40268 Example sequence of a read call, file descriptor 3, buffer is at target
40269 address 0x1234, 6 bytes should be read:
40272 <- @code{Fread,3,1234,6}
40273 @emph{request memory write to target}
40274 -> @code{X1234,6:XXXXXX}
40275 @emph{return "6 bytes read"}
40279 Example sequence of a read call, call fails on the host due to invalid
40280 file descriptor (@code{EBADF}):
40283 <- @code{Fread,3,1234,6}
40287 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40291 <- @code{Fread,3,1234,6}
40296 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40300 <- @code{Fread,3,1234,6}
40301 -> @code{X1234,6:XXXXXX}
40305 @node Library List Format
40306 @section Library List Format
40307 @cindex library list format, remote protocol
40309 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40310 same process as your application to manage libraries. In this case,
40311 @value{GDBN} can use the loader's symbol table and normal memory
40312 operations to maintain a list of shared libraries. On other
40313 platforms, the operating system manages loaded libraries.
40314 @value{GDBN} can not retrieve the list of currently loaded libraries
40315 through memory operations, so it uses the @samp{qXfer:libraries:read}
40316 packet (@pxref{qXfer library list read}) instead. The remote stub
40317 queries the target's operating system and reports which libraries
40320 The @samp{qXfer:libraries:read} packet returns an XML document which
40321 lists loaded libraries and their offsets. Each library has an
40322 associated name and one or more segment or section base addresses,
40323 which report where the library was loaded in memory.
40325 For the common case of libraries that are fully linked binaries, the
40326 library should have a list of segments. If the target supports
40327 dynamic linking of a relocatable object file, its library XML element
40328 should instead include a list of allocated sections. The segment or
40329 section bases are start addresses, not relocation offsets; they do not
40330 depend on the library's link-time base addresses.
40332 @value{GDBN} must be linked with the Expat library to support XML
40333 library lists. @xref{Expat}.
40335 A simple memory map, with one loaded library relocated by a single
40336 offset, looks like this:
40340 <library name="/lib/libc.so.6">
40341 <segment address="0x10000000"/>
40346 Another simple memory map, with one loaded library with three
40347 allocated sections (.text, .data, .bss), looks like this:
40351 <library name="sharedlib.o">
40352 <section address="0x10000000"/>
40353 <section address="0x20000000"/>
40354 <section address="0x30000000"/>
40359 The format of a library list is described by this DTD:
40362 <!-- library-list: Root element with versioning -->
40363 <!ELEMENT library-list (library)*>
40364 <!ATTLIST library-list version CDATA #FIXED "1.0">
40365 <!ELEMENT library (segment*, section*)>
40366 <!ATTLIST library name CDATA #REQUIRED>
40367 <!ELEMENT segment EMPTY>
40368 <!ATTLIST segment address CDATA #REQUIRED>
40369 <!ELEMENT section EMPTY>
40370 <!ATTLIST section address CDATA #REQUIRED>
40373 In addition, segments and section descriptors cannot be mixed within a
40374 single library element, and you must supply at least one segment or
40375 section for each library.
40377 @node Library List Format for SVR4 Targets
40378 @section Library List Format for SVR4 Targets
40379 @cindex library list format, remote protocol
40381 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40382 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40383 shared libraries. Still a special library list provided by this packet is
40384 more efficient for the @value{GDBN} remote protocol.
40386 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40387 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40388 target, the following parameters are reported:
40392 @code{name}, the absolute file name from the @code{l_name} field of
40393 @code{struct link_map}.
40395 @code{lm} with address of @code{struct link_map} used for TLS
40396 (Thread Local Storage) access.
40398 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40399 @code{struct link_map}. For prelinked libraries this is not an absolute
40400 memory address. It is a displacement of absolute memory address against
40401 address the file was prelinked to during the library load.
40403 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40406 Additionally the single @code{main-lm} attribute specifies address of
40407 @code{struct link_map} used for the main executable. This parameter is used
40408 for TLS access and its presence is optional.
40410 @value{GDBN} must be linked with the Expat library to support XML
40411 SVR4 library lists. @xref{Expat}.
40413 A simple memory map, with two loaded libraries (which do not use prelink),
40417 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40418 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40420 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40422 </library-list-svr>
40425 The format of an SVR4 library list is described by this DTD:
40428 <!-- library-list-svr4: Root element with versioning -->
40429 <!ELEMENT library-list-svr4 (library)*>
40430 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40431 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40432 <!ELEMENT library EMPTY>
40433 <!ATTLIST library name CDATA #REQUIRED>
40434 <!ATTLIST library lm CDATA #REQUIRED>
40435 <!ATTLIST library l_addr CDATA #REQUIRED>
40436 <!ATTLIST library l_ld CDATA #REQUIRED>
40439 @node Memory Map Format
40440 @section Memory Map Format
40441 @cindex memory map format
40443 To be able to write into flash memory, @value{GDBN} needs to obtain a
40444 memory map from the target. This section describes the format of the
40447 The memory map is obtained using the @samp{qXfer:memory-map:read}
40448 (@pxref{qXfer memory map read}) packet and is an XML document that
40449 lists memory regions.
40451 @value{GDBN} must be linked with the Expat library to support XML
40452 memory maps. @xref{Expat}.
40454 The top-level structure of the document is shown below:
40457 <?xml version="1.0"?>
40458 <!DOCTYPE memory-map
40459 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40460 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40466 Each region can be either:
40471 A region of RAM starting at @var{addr} and extending for @var{length}
40475 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40480 A region of read-only memory:
40483 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40488 A region of flash memory, with erasure blocks @var{blocksize}
40492 <memory type="flash" start="@var{addr}" length="@var{length}">
40493 <property name="blocksize">@var{blocksize}</property>
40499 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40500 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40501 packets to write to addresses in such ranges.
40503 The formal DTD for memory map format is given below:
40506 <!-- ................................................... -->
40507 <!-- Memory Map XML DTD ................................ -->
40508 <!-- File: memory-map.dtd .............................. -->
40509 <!-- .................................... .............. -->
40510 <!-- memory-map.dtd -->
40511 <!-- memory-map: Root element with versioning -->
40512 <!ELEMENT memory-map (memory | property)>
40513 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40514 <!ELEMENT memory (property)>
40515 <!-- memory: Specifies a memory region,
40516 and its type, or device. -->
40517 <!ATTLIST memory type CDATA #REQUIRED
40518 start CDATA #REQUIRED
40519 length CDATA #REQUIRED
40520 device CDATA #IMPLIED>
40521 <!-- property: Generic attribute tag -->
40522 <!ELEMENT property (#PCDATA | property)*>
40523 <!ATTLIST property name CDATA #REQUIRED>
40526 @node Thread List Format
40527 @section Thread List Format
40528 @cindex thread list format
40530 To efficiently update the list of threads and their attributes,
40531 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40532 (@pxref{qXfer threads read}) and obtains the XML document with
40533 the following structure:
40536 <?xml version="1.0"?>
40538 <thread id="id" core="0">
40539 ... description ...
40544 Each @samp{thread} element must have the @samp{id} attribute that
40545 identifies the thread (@pxref{thread-id syntax}). The
40546 @samp{core} attribute, if present, specifies which processor core
40547 the thread was last executing on. The content of the of @samp{thread}
40548 element is interpreted as human-readable auxilliary information.
40550 @node Traceframe Info Format
40551 @section Traceframe Info Format
40552 @cindex traceframe info format
40554 To be able to know which objects in the inferior can be examined when
40555 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40556 memory ranges, registers and trace state variables that have been
40557 collected in a traceframe.
40559 This list is obtained using the @samp{qXfer:traceframe-info:read}
40560 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40562 @value{GDBN} must be linked with the Expat library to support XML
40563 traceframe info discovery. @xref{Expat}.
40565 The top-level structure of the document is shown below:
40568 <?xml version="1.0"?>
40569 <!DOCTYPE traceframe-info
40570 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40571 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40577 Each traceframe block can be either:
40582 A region of collected memory starting at @var{addr} and extending for
40583 @var{length} bytes from there:
40586 <memory start="@var{addr}" length="@var{length}"/>
40591 The formal DTD for the traceframe info format is given below:
40594 <!ELEMENT traceframe-info (memory)* >
40595 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40597 <!ELEMENT memory EMPTY>
40598 <!ATTLIST memory start CDATA #REQUIRED
40599 length CDATA #REQUIRED>
40602 @node Branch Trace Format
40603 @section Branch Trace Format
40604 @cindex branch trace format
40606 In order to display the branch trace of an inferior thread,
40607 @value{GDBN} needs to obtain the list of branches. This list is
40608 represented as list of sequential code blocks that are connected via
40609 branches. The code in each block has been executed sequentially.
40611 This list is obtained using the @samp{qXfer:btrace:read}
40612 (@pxref{qXfer btrace read}) packet and is an XML document.
40614 @value{GDBN} must be linked with the Expat library to support XML
40615 traceframe info discovery. @xref{Expat}.
40617 The top-level structure of the document is shown below:
40620 <?xml version="1.0"?>
40622 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40623 "http://sourceware.org/gdb/gdb-btrace.dtd">
40632 A block of sequentially executed instructions starting at @var{begin}
40633 and ending at @var{end}:
40636 <block begin="@var{begin}" end="@var{end}"/>
40641 The formal DTD for the branch trace format is given below:
40644 <!ELEMENT btrace (block)* >
40645 <!ATTLIST btrace version CDATA #FIXED "1.0">
40647 <!ELEMENT block EMPTY>
40648 <!ATTLIST block begin CDATA #REQUIRED
40649 end CDATA #REQUIRED>
40652 @include agentexpr.texi
40654 @node Target Descriptions
40655 @appendix Target Descriptions
40656 @cindex target descriptions
40658 One of the challenges of using @value{GDBN} to debug embedded systems
40659 is that there are so many minor variants of each processor
40660 architecture in use. It is common practice for vendors to start with
40661 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40662 and then make changes to adapt it to a particular market niche. Some
40663 architectures have hundreds of variants, available from dozens of
40664 vendors. This leads to a number of problems:
40668 With so many different customized processors, it is difficult for
40669 the @value{GDBN} maintainers to keep up with the changes.
40671 Since individual variants may have short lifetimes or limited
40672 audiences, it may not be worthwhile to carry information about every
40673 variant in the @value{GDBN} source tree.
40675 When @value{GDBN} does support the architecture of the embedded system
40676 at hand, the task of finding the correct architecture name to give the
40677 @command{set architecture} command can be error-prone.
40680 To address these problems, the @value{GDBN} remote protocol allows a
40681 target system to not only identify itself to @value{GDBN}, but to
40682 actually describe its own features. This lets @value{GDBN} support
40683 processor variants it has never seen before --- to the extent that the
40684 descriptions are accurate, and that @value{GDBN} understands them.
40686 @value{GDBN} must be linked with the Expat library to support XML
40687 target descriptions. @xref{Expat}.
40690 * Retrieving Descriptions:: How descriptions are fetched from a target.
40691 * Target Description Format:: The contents of a target description.
40692 * Predefined Target Types:: Standard types available for target
40694 * Standard Target Features:: Features @value{GDBN} knows about.
40697 @node Retrieving Descriptions
40698 @section Retrieving Descriptions
40700 Target descriptions can be read from the target automatically, or
40701 specified by the user manually. The default behavior is to read the
40702 description from the target. @value{GDBN} retrieves it via the remote
40703 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40704 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40705 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40706 XML document, of the form described in @ref{Target Description
40709 Alternatively, you can specify a file to read for the target description.
40710 If a file is set, the target will not be queried. The commands to
40711 specify a file are:
40714 @cindex set tdesc filename
40715 @item set tdesc filename @var{path}
40716 Read the target description from @var{path}.
40718 @cindex unset tdesc filename
40719 @item unset tdesc filename
40720 Do not read the XML target description from a file. @value{GDBN}
40721 will use the description supplied by the current target.
40723 @cindex show tdesc filename
40724 @item show tdesc filename
40725 Show the filename to read for a target description, if any.
40729 @node Target Description Format
40730 @section Target Description Format
40731 @cindex target descriptions, XML format
40733 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40734 document which complies with the Document Type Definition provided in
40735 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40736 means you can use generally available tools like @command{xmllint} to
40737 check that your feature descriptions are well-formed and valid.
40738 However, to help people unfamiliar with XML write descriptions for
40739 their targets, we also describe the grammar here.
40741 Target descriptions can identify the architecture of the remote target
40742 and (for some architectures) provide information about custom register
40743 sets. They can also identify the OS ABI of the remote target.
40744 @value{GDBN} can use this information to autoconfigure for your
40745 target, or to warn you if you connect to an unsupported target.
40747 Here is a simple target description:
40750 <target version="1.0">
40751 <architecture>i386:x86-64</architecture>
40756 This minimal description only says that the target uses
40757 the x86-64 architecture.
40759 A target description has the following overall form, with [ ] marking
40760 optional elements and @dots{} marking repeatable elements. The elements
40761 are explained further below.
40764 <?xml version="1.0"?>
40765 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40766 <target version="1.0">
40767 @r{[}@var{architecture}@r{]}
40768 @r{[}@var{osabi}@r{]}
40769 @r{[}@var{compatible}@r{]}
40770 @r{[}@var{feature}@dots{}@r{]}
40775 The description is generally insensitive to whitespace and line
40776 breaks, under the usual common-sense rules. The XML version
40777 declaration and document type declaration can generally be omitted
40778 (@value{GDBN} does not require them), but specifying them may be
40779 useful for XML validation tools. The @samp{version} attribute for
40780 @samp{<target>} may also be omitted, but we recommend
40781 including it; if future versions of @value{GDBN} use an incompatible
40782 revision of @file{gdb-target.dtd}, they will detect and report
40783 the version mismatch.
40785 @subsection Inclusion
40786 @cindex target descriptions, inclusion
40789 @cindex <xi:include>
40792 It can sometimes be valuable to split a target description up into
40793 several different annexes, either for organizational purposes, or to
40794 share files between different possible target descriptions. You can
40795 divide a description into multiple files by replacing any element of
40796 the target description with an inclusion directive of the form:
40799 <xi:include href="@var{document}"/>
40803 When @value{GDBN} encounters an element of this form, it will retrieve
40804 the named XML @var{document}, and replace the inclusion directive with
40805 the contents of that document. If the current description was read
40806 using @samp{qXfer}, then so will be the included document;
40807 @var{document} will be interpreted as the name of an annex. If the
40808 current description was read from a file, @value{GDBN} will look for
40809 @var{document} as a file in the same directory where it found the
40810 original description.
40812 @subsection Architecture
40813 @cindex <architecture>
40815 An @samp{<architecture>} element has this form:
40818 <architecture>@var{arch}</architecture>
40821 @var{arch} is one of the architectures from the set accepted by
40822 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40825 @cindex @code{<osabi>}
40827 This optional field was introduced in @value{GDBN} version 7.0.
40828 Previous versions of @value{GDBN} ignore it.
40830 An @samp{<osabi>} element has this form:
40833 <osabi>@var{abi-name}</osabi>
40836 @var{abi-name} is an OS ABI name from the same selection accepted by
40837 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40839 @subsection Compatible Architecture
40840 @cindex @code{<compatible>}
40842 This optional field was introduced in @value{GDBN} version 7.0.
40843 Previous versions of @value{GDBN} ignore it.
40845 A @samp{<compatible>} element has this form:
40848 <compatible>@var{arch}</compatible>
40851 @var{arch} is one of the architectures from the set accepted by
40852 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40854 A @samp{<compatible>} element is used to specify that the target
40855 is able to run binaries in some other than the main target architecture
40856 given by the @samp{<architecture>} element. For example, on the
40857 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40858 or @code{powerpc:common64}, but the system is able to run binaries
40859 in the @code{spu} architecture as well. The way to describe this
40860 capability with @samp{<compatible>} is as follows:
40863 <architecture>powerpc:common</architecture>
40864 <compatible>spu</compatible>
40867 @subsection Features
40870 Each @samp{<feature>} describes some logical portion of the target
40871 system. Features are currently used to describe available CPU
40872 registers and the types of their contents. A @samp{<feature>} element
40876 <feature name="@var{name}">
40877 @r{[}@var{type}@dots{}@r{]}
40883 Each feature's name should be unique within the description. The name
40884 of a feature does not matter unless @value{GDBN} has some special
40885 knowledge of the contents of that feature; if it does, the feature
40886 should have its standard name. @xref{Standard Target Features}.
40890 Any register's value is a collection of bits which @value{GDBN} must
40891 interpret. The default interpretation is a two's complement integer,
40892 but other types can be requested by name in the register description.
40893 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40894 Target Types}), and the description can define additional composite types.
40896 Each type element must have an @samp{id} attribute, which gives
40897 a unique (within the containing @samp{<feature>}) name to the type.
40898 Types must be defined before they are used.
40901 Some targets offer vector registers, which can be treated as arrays
40902 of scalar elements. These types are written as @samp{<vector>} elements,
40903 specifying the array element type, @var{type}, and the number of elements,
40907 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40911 If a register's value is usefully viewed in multiple ways, define it
40912 with a union type containing the useful representations. The
40913 @samp{<union>} element contains one or more @samp{<field>} elements,
40914 each of which has a @var{name} and a @var{type}:
40917 <union id="@var{id}">
40918 <field name="@var{name}" type="@var{type}"/>
40924 If a register's value is composed from several separate values, define
40925 it with a structure type. There are two forms of the @samp{<struct>}
40926 element; a @samp{<struct>} element must either contain only bitfields
40927 or contain no bitfields. If the structure contains only bitfields,
40928 its total size in bytes must be specified, each bitfield must have an
40929 explicit start and end, and bitfields are automatically assigned an
40930 integer type. The field's @var{start} should be less than or
40931 equal to its @var{end}, and zero represents the least significant bit.
40934 <struct id="@var{id}" size="@var{size}">
40935 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40940 If the structure contains no bitfields, then each field has an
40941 explicit type, and no implicit padding is added.
40944 <struct id="@var{id}">
40945 <field name="@var{name}" type="@var{type}"/>
40951 If a register's value is a series of single-bit flags, define it with
40952 a flags type. The @samp{<flags>} element has an explicit @var{size}
40953 and contains one or more @samp{<field>} elements. Each field has a
40954 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40958 <flags id="@var{id}" size="@var{size}">
40959 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40964 @subsection Registers
40967 Each register is represented as an element with this form:
40970 <reg name="@var{name}"
40971 bitsize="@var{size}"
40972 @r{[}regnum="@var{num}"@r{]}
40973 @r{[}save-restore="@var{save-restore}"@r{]}
40974 @r{[}type="@var{type}"@r{]}
40975 @r{[}group="@var{group}"@r{]}/>
40979 The components are as follows:
40984 The register's name; it must be unique within the target description.
40987 The register's size, in bits.
40990 The register's number. If omitted, a register's number is one greater
40991 than that of the previous register (either in the current feature or in
40992 a preceding feature); the first register in the target description
40993 defaults to zero. This register number is used to read or write
40994 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40995 packets, and registers appear in the @code{g} and @code{G} packets
40996 in order of increasing register number.
40999 Whether the register should be preserved across inferior function
41000 calls; this must be either @code{yes} or @code{no}. The default is
41001 @code{yes}, which is appropriate for most registers except for
41002 some system control registers; this is not related to the target's
41006 The type of the register. @var{type} may be a predefined type, a type
41007 defined in the current feature, or one of the special types @code{int}
41008 and @code{float}. @code{int} is an integer type of the correct size
41009 for @var{bitsize}, and @code{float} is a floating point type (in the
41010 architecture's normal floating point format) of the correct size for
41011 @var{bitsize}. The default is @code{int}.
41014 The register group to which this register belongs. @var{group} must
41015 be either @code{general}, @code{float}, or @code{vector}. If no
41016 @var{group} is specified, @value{GDBN} will not display the register
41017 in @code{info registers}.
41021 @node Predefined Target Types
41022 @section Predefined Target Types
41023 @cindex target descriptions, predefined types
41025 Type definitions in the self-description can build up composite types
41026 from basic building blocks, but can not define fundamental types. Instead,
41027 standard identifiers are provided by @value{GDBN} for the fundamental
41028 types. The currently supported types are:
41037 Signed integer types holding the specified number of bits.
41044 Unsigned integer types holding the specified number of bits.
41048 Pointers to unspecified code and data. The program counter and
41049 any dedicated return address register may be marked as code
41050 pointers; printing a code pointer converts it into a symbolic
41051 address. The stack pointer and any dedicated address registers
41052 may be marked as data pointers.
41055 Single precision IEEE floating point.
41058 Double precision IEEE floating point.
41061 The 12-byte extended precision format used by ARM FPA registers.
41064 The 10-byte extended precision format used by x87 registers.
41067 32bit @sc{eflags} register used by x86.
41070 32bit @sc{mxcsr} register used by x86.
41074 @node Standard Target Features
41075 @section Standard Target Features
41076 @cindex target descriptions, standard features
41078 A target description must contain either no registers or all the
41079 target's registers. If the description contains no registers, then
41080 @value{GDBN} will assume a default register layout, selected based on
41081 the architecture. If the description contains any registers, the
41082 default layout will not be used; the standard registers must be
41083 described in the target description, in such a way that @value{GDBN}
41084 can recognize them.
41086 This is accomplished by giving specific names to feature elements
41087 which contain standard registers. @value{GDBN} will look for features
41088 with those names and verify that they contain the expected registers;
41089 if any known feature is missing required registers, or if any required
41090 feature is missing, @value{GDBN} will reject the target
41091 description. You can add additional registers to any of the
41092 standard features --- @value{GDBN} will display them just as if
41093 they were added to an unrecognized feature.
41095 This section lists the known features and their expected contents.
41096 Sample XML documents for these features are included in the
41097 @value{GDBN} source tree, in the directory @file{gdb/features}.
41099 Names recognized by @value{GDBN} should include the name of the
41100 company or organization which selected the name, and the overall
41101 architecture to which the feature applies; so e.g.@: the feature
41102 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41104 The names of registers are not case sensitive for the purpose
41105 of recognizing standard features, but @value{GDBN} will only display
41106 registers using the capitalization used in the description.
41109 * AArch64 Features::
41114 * PowerPC Features::
41119 @node AArch64 Features
41120 @subsection AArch64 Features
41121 @cindex target descriptions, AArch64 features
41123 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41124 targets. It should contain registers @samp{x0} through @samp{x30},
41125 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41127 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41128 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41132 @subsection ARM Features
41133 @cindex target descriptions, ARM features
41135 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41137 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41138 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41140 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41141 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41142 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41145 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41146 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41148 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41149 it should contain at least registers @samp{wR0} through @samp{wR15} and
41150 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41151 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41153 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41154 should contain at least registers @samp{d0} through @samp{d15}. If
41155 they are present, @samp{d16} through @samp{d31} should also be included.
41156 @value{GDBN} will synthesize the single-precision registers from
41157 halves of the double-precision registers.
41159 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41160 need to contain registers; it instructs @value{GDBN} to display the
41161 VFP double-precision registers as vectors and to synthesize the
41162 quad-precision registers from pairs of double-precision registers.
41163 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41164 be present and include 32 double-precision registers.
41166 @node i386 Features
41167 @subsection i386 Features
41168 @cindex target descriptions, i386 features
41170 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41171 targets. It should describe the following registers:
41175 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41177 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41179 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41180 @samp{fs}, @samp{gs}
41182 @samp{st0} through @samp{st7}
41184 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41185 @samp{foseg}, @samp{fooff} and @samp{fop}
41188 The register sets may be different, depending on the target.
41190 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41191 describe registers:
41195 @samp{xmm0} through @samp{xmm7} for i386
41197 @samp{xmm0} through @samp{xmm15} for amd64
41202 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41203 @samp{org.gnu.gdb.i386.sse} feature. It should
41204 describe the upper 128 bits of @sc{ymm} registers:
41208 @samp{ymm0h} through @samp{ymm7h} for i386
41210 @samp{ymm0h} through @samp{ymm15h} for amd64
41213 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41214 describe a single register, @samp{orig_eax}.
41216 @node MIPS Features
41217 @subsection @acronym{MIPS} Features
41218 @cindex target descriptions, @acronym{MIPS} features
41220 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41221 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41222 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41225 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41226 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41227 registers. They may be 32-bit or 64-bit depending on the target.
41229 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41230 it may be optional in a future version of @value{GDBN}. It should
41231 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41232 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41234 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41235 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41236 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41237 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41239 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41240 contain a single register, @samp{restart}, which is used by the
41241 Linux kernel to control restartable syscalls.
41243 @node M68K Features
41244 @subsection M68K Features
41245 @cindex target descriptions, M68K features
41248 @item @samp{org.gnu.gdb.m68k.core}
41249 @itemx @samp{org.gnu.gdb.coldfire.core}
41250 @itemx @samp{org.gnu.gdb.fido.core}
41251 One of those features must be always present.
41252 The feature that is present determines which flavor of m68k is
41253 used. The feature that is present should contain registers
41254 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41255 @samp{sp}, @samp{ps} and @samp{pc}.
41257 @item @samp{org.gnu.gdb.coldfire.fp}
41258 This feature is optional. If present, it should contain registers
41259 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41263 @node PowerPC Features
41264 @subsection PowerPC Features
41265 @cindex target descriptions, PowerPC features
41267 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41268 targets. It should contain registers @samp{r0} through @samp{r31},
41269 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41270 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41272 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41273 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41275 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41276 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41279 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41280 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41281 will combine these registers with the floating point registers
41282 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41283 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41284 through @samp{vs63}, the set of vector registers for POWER7.
41286 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41287 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41288 @samp{spefscr}. SPE targets should provide 32-bit registers in
41289 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41290 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41291 these to present registers @samp{ev0} through @samp{ev31} to the
41294 @node TIC6x Features
41295 @subsection TMS320C6x Features
41296 @cindex target descriptions, TIC6x features
41297 @cindex target descriptions, TMS320C6x features
41298 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41299 targets. It should contain registers @samp{A0} through @samp{A15},
41300 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41302 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41303 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41304 through @samp{B31}.
41306 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41307 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41309 @node Operating System Information
41310 @appendix Operating System Information
41311 @cindex operating system information
41317 Users of @value{GDBN} often wish to obtain information about the state of
41318 the operating system running on the target---for example the list of
41319 processes, or the list of open files. This section describes the
41320 mechanism that makes it possible. This mechanism is similar to the
41321 target features mechanism (@pxref{Target Descriptions}), but focuses
41322 on a different aspect of target.
41324 Operating system information is retrived from the target via the
41325 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41326 read}). The object name in the request should be @samp{osdata}, and
41327 the @var{annex} identifies the data to be fetched.
41330 @appendixsection Process list
41331 @cindex operating system information, process list
41333 When requesting the process list, the @var{annex} field in the
41334 @samp{qXfer} request should be @samp{processes}. The returned data is
41335 an XML document. The formal syntax of this document is defined in
41336 @file{gdb/features/osdata.dtd}.
41338 An example document is:
41341 <?xml version="1.0"?>
41342 <!DOCTYPE target SYSTEM "osdata.dtd">
41343 <osdata type="processes">
41345 <column name="pid">1</column>
41346 <column name="user">root</column>
41347 <column name="command">/sbin/init</column>
41348 <column name="cores">1,2,3</column>
41353 Each item should include a column whose name is @samp{pid}. The value
41354 of that column should identify the process on the target. The
41355 @samp{user} and @samp{command} columns are optional, and will be
41356 displayed by @value{GDBN}. The @samp{cores} column, if present,
41357 should contain a comma-separated list of cores that this process
41358 is running on. Target may provide additional columns,
41359 which @value{GDBN} currently ignores.
41361 @node Trace File Format
41362 @appendix Trace File Format
41363 @cindex trace file format
41365 The trace file comes in three parts: a header, a textual description
41366 section, and a trace frame section with binary data.
41368 The header has the form @code{\x7fTRACE0\n}. The first byte is
41369 @code{0x7f} so as to indicate that the file contains binary data,
41370 while the @code{0} is a version number that may have different values
41373 The description section consists of multiple lines of @sc{ascii} text
41374 separated by newline characters (@code{0xa}). The lines may include a
41375 variety of optional descriptive or context-setting information, such
41376 as tracepoint definitions or register set size. @value{GDBN} will
41377 ignore any line that it does not recognize. An empty line marks the end
41380 @c FIXME add some specific types of data
41382 The trace frame section consists of a number of consecutive frames.
41383 Each frame begins with a two-byte tracepoint number, followed by a
41384 four-byte size giving the amount of data in the frame. The data in
41385 the frame consists of a number of blocks, each introduced by a
41386 character indicating its type (at least register, memory, and trace
41387 state variable). The data in this section is raw binary, not a
41388 hexadecimal or other encoding; its endianness matches the target's
41391 @c FIXME bi-arch may require endianness/arch info in description section
41394 @item R @var{bytes}
41395 Register block. The number and ordering of bytes matches that of a
41396 @code{g} packet in the remote protocol. Note that these are the
41397 actual bytes, in target order and @value{GDBN} register order, not a
41398 hexadecimal encoding.
41400 @item M @var{address} @var{length} @var{bytes}...
41401 Memory block. This is a contiguous block of memory, at the 8-byte
41402 address @var{address}, with a 2-byte length @var{length}, followed by
41403 @var{length} bytes.
41405 @item V @var{number} @var{value}
41406 Trace state variable block. This records the 8-byte signed value
41407 @var{value} of trace state variable numbered @var{number}.
41411 Future enhancements of the trace file format may include additional types
41414 @node Index Section Format
41415 @appendix @code{.gdb_index} section format
41416 @cindex .gdb_index section format
41417 @cindex index section format
41419 This section documents the index section that is created by @code{save
41420 gdb-index} (@pxref{Index Files}). The index section is
41421 DWARF-specific; some knowledge of DWARF is assumed in this
41424 The mapped index file format is designed to be directly
41425 @code{mmap}able on any architecture. In most cases, a datum is
41426 represented using a little-endian 32-bit integer value, called an
41427 @code{offset_type}. Big endian machines must byte-swap the values
41428 before using them. Exceptions to this rule are noted. The data is
41429 laid out such that alignment is always respected.
41431 A mapped index consists of several areas, laid out in order.
41435 The file header. This is a sequence of values, of @code{offset_type}
41436 unless otherwise noted:
41440 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41441 Version 4 uses a different hashing function from versions 5 and 6.
41442 Version 6 includes symbols for inlined functions, whereas versions 4
41443 and 5 do not. Version 7 adds attributes to the CU indices in the
41444 symbol table. Version 8 specifies that symbols from DWARF type units
41445 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41446 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41448 @value{GDBN} will only read version 4, 5, or 6 indices
41449 by specifying @code{set use-deprecated-index-sections on}.
41450 GDB has a workaround for potentially broken version 7 indices so it is
41451 currently not flagged as deprecated.
41454 The offset, from the start of the file, of the CU list.
41457 The offset, from the start of the file, of the types CU list. Note
41458 that this area can be empty, in which case this offset will be equal
41459 to the next offset.
41462 The offset, from the start of the file, of the address area.
41465 The offset, from the start of the file, of the symbol table.
41468 The offset, from the start of the file, of the constant pool.
41472 The CU list. This is a sequence of pairs of 64-bit little-endian
41473 values, sorted by the CU offset. The first element in each pair is
41474 the offset of a CU in the @code{.debug_info} section. The second
41475 element in each pair is the length of that CU. References to a CU
41476 elsewhere in the map are done using a CU index, which is just the
41477 0-based index into this table. Note that if there are type CUs, then
41478 conceptually CUs and type CUs form a single list for the purposes of
41482 The types CU list. This is a sequence of triplets of 64-bit
41483 little-endian values. In a triplet, the first value is the CU offset,
41484 the second value is the type offset in the CU, and the third value is
41485 the type signature. The types CU list is not sorted.
41488 The address area. The address area consists of a sequence of address
41489 entries. Each address entry has three elements:
41493 The low address. This is a 64-bit little-endian value.
41496 The high address. This is a 64-bit little-endian value. Like
41497 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41500 The CU index. This is an @code{offset_type} value.
41504 The symbol table. This is an open-addressed hash table. The size of
41505 the hash table is always a power of 2.
41507 Each slot in the hash table consists of a pair of @code{offset_type}
41508 values. The first value is the offset of the symbol's name in the
41509 constant pool. The second value is the offset of the CU vector in the
41512 If both values are 0, then this slot in the hash table is empty. This
41513 is ok because while 0 is a valid constant pool index, it cannot be a
41514 valid index for both a string and a CU vector.
41516 The hash value for a table entry is computed by applying an
41517 iterative hash function to the symbol's name. Starting with an
41518 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41519 the string is incorporated into the hash using the formula depending on the
41524 The formula is @code{r = r * 67 + c - 113}.
41526 @item Versions 5 to 7
41527 The formula is @code{r = r * 67 + tolower (c) - 113}.
41530 The terminating @samp{\0} is not incorporated into the hash.
41532 The step size used in the hash table is computed via
41533 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41534 value, and @samp{size} is the size of the hash table. The step size
41535 is used to find the next candidate slot when handling a hash
41538 The names of C@t{++} symbols in the hash table are canonicalized. We
41539 don't currently have a simple description of the canonicalization
41540 algorithm; if you intend to create new index sections, you must read
41544 The constant pool. This is simply a bunch of bytes. It is organized
41545 so that alignment is correct: CU vectors are stored first, followed by
41548 A CU vector in the constant pool is a sequence of @code{offset_type}
41549 values. The first value is the number of CU indices in the vector.
41550 Each subsequent value is the index and symbol attributes of a CU in
41551 the CU list. This element in the hash table is used to indicate which
41552 CUs define the symbol and how the symbol is used.
41553 See below for the format of each CU index+attributes entry.
41555 A string in the constant pool is zero-terminated.
41558 Attributes were added to CU index values in @code{.gdb_index} version 7.
41559 If a symbol has multiple uses within a CU then there is one
41560 CU index+attributes value for each use.
41562 The format of each CU index+attributes entry is as follows
41568 This is the index of the CU in the CU list.
41570 These bits are reserved for future purposes and must be zero.
41572 The kind of the symbol in the CU.
41576 This value is reserved and should not be used.
41577 By reserving zero the full @code{offset_type} value is backwards compatible
41578 with previous versions of the index.
41580 The symbol is a type.
41582 The symbol is a variable or an enum value.
41584 The symbol is a function.
41586 Any other kind of symbol.
41588 These values are reserved.
41592 This bit is zero if the value is global and one if it is static.
41594 The determination of whether a symbol is global or static is complicated.
41595 The authorative reference is the file @file{dwarf2read.c} in
41596 @value{GDBN} sources.
41600 This pseudo-code describes the computation of a symbol's kind and
41601 global/static attributes in the index.
41604 is_external = get_attribute (die, DW_AT_external);
41605 language = get_attribute (cu_die, DW_AT_language);
41608 case DW_TAG_typedef:
41609 case DW_TAG_base_type:
41610 case DW_TAG_subrange_type:
41614 case DW_TAG_enumerator:
41616 is_static = (language != CPLUS && language != JAVA);
41618 case DW_TAG_subprogram:
41620 is_static = ! (is_external || language == ADA);
41622 case DW_TAG_constant:
41624 is_static = ! is_external;
41626 case DW_TAG_variable:
41628 is_static = ! is_external;
41630 case DW_TAG_namespace:
41634 case DW_TAG_class_type:
41635 case DW_TAG_interface_type:
41636 case DW_TAG_structure_type:
41637 case DW_TAG_union_type:
41638 case DW_TAG_enumeration_type:
41640 is_static = (language != CPLUS && language != JAVA);
41648 @appendix Manual pages
41652 * gdb man:: The GNU Debugger man page
41653 * gdbserver man:: Remote Server for the GNU Debugger man page
41654 * gcore man:: Generate a core file of a running program
41655 * gdbinit man:: gdbinit scripts
41661 @c man title gdb The GNU Debugger
41663 @c man begin SYNOPSIS gdb
41664 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41665 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41666 [@option{-b}@w{ }@var{bps}]
41667 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41668 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41669 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41670 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41671 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41674 @c man begin DESCRIPTION gdb
41675 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41676 going on ``inside'' another program while it executes -- or what another
41677 program was doing at the moment it crashed.
41679 @value{GDBN} can do four main kinds of things (plus other things in support of
41680 these) to help you catch bugs in the act:
41684 Start your program, specifying anything that might affect its behavior.
41687 Make your program stop on specified conditions.
41690 Examine what has happened, when your program has stopped.
41693 Change things in your program, so you can experiment with correcting the
41694 effects of one bug and go on to learn about another.
41697 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41700 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41701 commands from the terminal until you tell it to exit with the @value{GDBN}
41702 command @code{quit}. You can get online help from @value{GDBN} itself
41703 by using the command @code{help}.
41705 You can run @code{gdb} with no arguments or options; but the most
41706 usual way to start @value{GDBN} is with one argument or two, specifying an
41707 executable program as the argument:
41713 You can also start with both an executable program and a core file specified:
41719 You can, instead, specify a process ID as a second argument, if you want
41720 to debug a running process:
41728 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41729 named @file{1234}; @value{GDBN} does check for a core file first).
41730 With option @option{-p} you can omit the @var{program} filename.
41732 Here are some of the most frequently needed @value{GDBN} commands:
41734 @c pod2man highlights the right hand side of the @item lines.
41736 @item break [@var{file}:]@var{functiop}
41737 Set a breakpoint at @var{function} (in @var{file}).
41739 @item run [@var{arglist}]
41740 Start your program (with @var{arglist}, if specified).
41743 Backtrace: display the program stack.
41745 @item print @var{expr}
41746 Display the value of an expression.
41749 Continue running your program (after stopping, e.g. at a breakpoint).
41752 Execute next program line (after stopping); step @emph{over} any
41753 function calls in the line.
41755 @item edit [@var{file}:]@var{function}
41756 look at the program line where it is presently stopped.
41758 @item list [@var{file}:]@var{function}
41759 type the text of the program in the vicinity of where it is presently stopped.
41762 Execute next program line (after stopping); step @emph{into} any
41763 function calls in the line.
41765 @item help [@var{name}]
41766 Show information about @value{GDBN} command @var{name}, or general information
41767 about using @value{GDBN}.
41770 Exit from @value{GDBN}.
41774 For full details on @value{GDBN},
41775 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41776 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41777 as the @code{gdb} entry in the @code{info} program.
41781 @c man begin OPTIONS gdb
41782 Any arguments other than options specify an executable
41783 file and core file (or process ID); that is, the first argument
41784 encountered with no
41785 associated option flag is equivalent to a @option{-se} option, and the second,
41786 if any, is equivalent to a @option{-c} option if it's the name of a file.
41788 both long and short forms; both are shown here. The long forms are also
41789 recognized if you truncate them, so long as enough of the option is
41790 present to be unambiguous. (If you prefer, you can flag option
41791 arguments with @option{+} rather than @option{-}, though we illustrate the
41792 more usual convention.)
41794 All the options and command line arguments you give are processed
41795 in sequential order. The order makes a difference when the @option{-x}
41801 List all options, with brief explanations.
41803 @item -symbols=@var{file}
41804 @itemx -s @var{file}
41805 Read symbol table from file @var{file}.
41808 Enable writing into executable and core files.
41810 @item -exec=@var{file}
41811 @itemx -e @var{file}
41812 Use file @var{file} as the executable file to execute when
41813 appropriate, and for examining pure data in conjunction with a core
41816 @item -se=@var{file}
41817 Read symbol table from file @var{file} and use it as the executable
41820 @item -core=@var{file}
41821 @itemx -c @var{file}
41822 Use file @var{file} as a core dump to examine.
41824 @item -command=@var{file}
41825 @itemx -x @var{file}
41826 Execute @value{GDBN} commands from file @var{file}.
41828 @item -ex @var{command}
41829 Execute given @value{GDBN} @var{command}.
41831 @item -directory=@var{directory}
41832 @itemx -d @var{directory}
41833 Add @var{directory} to the path to search for source files.
41836 Do not execute commands from @file{~/.gdbinit}.
41840 Do not execute commands from any @file{.gdbinit} initialization files.
41844 ``Quiet''. Do not print the introductory and copyright messages. These
41845 messages are also suppressed in batch mode.
41848 Run in batch mode. Exit with status @code{0} after processing all the command
41849 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41850 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41851 commands in the command files.
41853 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41854 download and run a program on another computer; in order to make this
41855 more useful, the message
41858 Program exited normally.
41862 (which is ordinarily issued whenever a program running under @value{GDBN} control
41863 terminates) is not issued when running in batch mode.
41865 @item -cd=@var{directory}
41866 Run @value{GDBN} using @var{directory} as its working directory,
41867 instead of the current directory.
41871 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41872 @value{GDBN} to output the full file name and line number in a standard,
41873 recognizable fashion each time a stack frame is displayed (which
41874 includes each time the program stops). This recognizable format looks
41875 like two @samp{\032} characters, followed by the file name, line number
41876 and character position separated by colons, and a newline. The
41877 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41878 characters as a signal to display the source code for the frame.
41881 Set the line speed (baud rate or bits per second) of any serial
41882 interface used by @value{GDBN} for remote debugging.
41884 @item -tty=@var{device}
41885 Run using @var{device} for your program's standard input and output.
41889 @c man begin SEEALSO gdb
41891 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41892 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41893 documentation are properly installed at your site, the command
41900 should give you access to the complete manual.
41902 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41903 Richard M. Stallman and Roland H. Pesch, July 1991.
41907 @node gdbserver man
41908 @heading gdbserver man
41910 @c man title gdbserver Remote Server for the GNU Debugger
41912 @c man begin SYNOPSIS gdbserver
41913 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41915 gdbserver --attach @var{comm} @var{pid}
41917 gdbserver --multi @var{comm}
41921 @c man begin DESCRIPTION gdbserver
41922 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41923 than the one which is running the program being debugged.
41926 @subheading Usage (server (target) side)
41929 Usage (server (target) side):
41932 First, you need to have a copy of the program you want to debug put onto
41933 the target system. The program can be stripped to save space if needed, as
41934 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41935 the @value{GDBN} running on the host system.
41937 To use the server, you log on to the target system, and run the @command{gdbserver}
41938 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41939 your program, and (c) its arguments. The general syntax is:
41942 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41945 For example, using a serial port, you might say:
41949 @c @file would wrap it as F</dev/com1>.
41950 target> gdbserver /dev/com1 emacs foo.txt
41953 target> gdbserver @file{/dev/com1} emacs foo.txt
41957 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41958 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41959 waits patiently for the host @value{GDBN} to communicate with it.
41961 To use a TCP connection, you could say:
41964 target> gdbserver host:2345 emacs foo.txt
41967 This says pretty much the same thing as the last example, except that we are
41968 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41969 that we are expecting to see a TCP connection from @code{host} to local TCP port
41970 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41971 want for the port number as long as it does not conflict with any existing TCP
41972 ports on the target system. This same port number must be used in the host
41973 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41974 you chose a port number that conflicts with another service, @command{gdbserver} will
41975 print an error message and exit.
41977 @command{gdbserver} can also attach to running programs.
41978 This is accomplished via the @option{--attach} argument. The syntax is:
41981 target> gdbserver --attach @var{comm} @var{pid}
41984 @var{pid} is the process ID of a currently running process. It isn't
41985 necessary to point @command{gdbserver} at a binary for the running process.
41987 To start @code{gdbserver} without supplying an initial command to run
41988 or process ID to attach, use the @option{--multi} command line option.
41989 In such case you should connect using @kbd{target extended-remote} to start
41990 the program you want to debug.
41993 target> gdbserver --multi @var{comm}
41997 @subheading Usage (host side)
42003 You need an unstripped copy of the target program on your host system, since
42004 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42005 would, with the target program as the first argument. (You may need to use the
42006 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42007 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42008 new command you need to know about is @code{target remote}
42009 (or @code{target extended-remote}). Its argument is either
42010 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42011 descriptor. For example:
42015 @c @file would wrap it as F</dev/ttyb>.
42016 (gdb) target remote /dev/ttyb
42019 (gdb) target remote @file{/dev/ttyb}
42024 communicates with the server via serial line @file{/dev/ttyb}, and:
42027 (gdb) target remote the-target:2345
42031 communicates via a TCP connection to port 2345 on host `the-target', where
42032 you previously started up @command{gdbserver} with the same port number. Note that for
42033 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42034 command, otherwise you may get an error that looks something like
42035 `Connection refused'.
42037 @command{gdbserver} can also debug multiple inferiors at once,
42040 the @value{GDBN} manual in node @code{Inferiors and Programs}
42041 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42044 @ref{Inferiors and Programs}.
42046 In such case use the @code{extended-remote} @value{GDBN} command variant:
42049 (gdb) target extended-remote the-target:2345
42052 The @command{gdbserver} option @option{--multi} may or may not be used in such
42056 @c man begin OPTIONS gdbserver
42057 There are three different modes for invoking @command{gdbserver}:
42062 Debug a specific program specified by its program name:
42065 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42068 The @var{comm} parameter specifies how should the server communicate
42069 with @value{GDBN}; it is either a device name (to use a serial line),
42070 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42071 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42072 debug in @var{prog}. Any remaining arguments will be passed to the
42073 program verbatim. When the program exits, @value{GDBN} will close the
42074 connection, and @code{gdbserver} will exit.
42077 Debug a specific program by specifying the process ID of a running
42081 gdbserver --attach @var{comm} @var{pid}
42084 The @var{comm} parameter is as described above. Supply the process ID
42085 of a running program in @var{pid}; @value{GDBN} will do everything
42086 else. Like with the previous mode, when the process @var{pid} exits,
42087 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42090 Multi-process mode -- debug more than one program/process:
42093 gdbserver --multi @var{comm}
42096 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42097 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42098 close the connection when a process being debugged exits, so you can
42099 debug several processes in the same session.
42102 In each of the modes you may specify these options:
42107 List all options, with brief explanations.
42110 This option causes @command{gdbserver} to print its version number and exit.
42113 @command{gdbserver} will attach to a running program. The syntax is:
42116 target> gdbserver --attach @var{comm} @var{pid}
42119 @var{pid} is the process ID of a currently running process. It isn't
42120 necessary to point @command{gdbserver} at a binary for the running process.
42123 To start @code{gdbserver} without supplying an initial command to run
42124 or process ID to attach, use this command line option.
42125 Then you can connect using @kbd{target extended-remote} and start
42126 the program you want to debug. The syntax is:
42129 target> gdbserver --multi @var{comm}
42133 Instruct @code{gdbserver} to display extra status information about the debugging
42135 This option is intended for @code{gdbserver} development and for bug reports to
42138 @item --remote-debug
42139 Instruct @code{gdbserver} to display remote protocol debug output.
42140 This option is intended for @code{gdbserver} development and for bug reports to
42144 Specify a wrapper to launch programs
42145 for debugging. The option should be followed by the name of the
42146 wrapper, then any command-line arguments to pass to the wrapper, then
42147 @kbd{--} indicating the end of the wrapper arguments.
42150 By default, @command{gdbserver} keeps the listening TCP port open, so that
42151 additional connections are possible. However, if you start @code{gdbserver}
42152 with the @option{--once} option, it will stop listening for any further
42153 connection attempts after connecting to the first @value{GDBN} session.
42155 @c --disable-packet is not documented for users.
42157 @c --disable-randomization and --no-disable-randomization are superseded by
42158 @c QDisableRandomization.
42163 @c man begin SEEALSO gdbserver
42165 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42166 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42167 documentation are properly installed at your site, the command
42173 should give you access to the complete manual.
42175 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42176 Richard M. Stallman and Roland H. Pesch, July 1991.
42183 @c man title gcore Generate a core file of a running program
42186 @c man begin SYNOPSIS gcore
42187 gcore [-o @var{filename}] @var{pid}
42191 @c man begin DESCRIPTION gcore
42192 Generate a core dump of a running program with process ID @var{pid}.
42193 Produced file is equivalent to a kernel produced core file as if the process
42194 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42195 limit). Unlike after a crash, after @command{gcore} the program remains
42196 running without any change.
42199 @c man begin OPTIONS gcore
42201 @item -o @var{filename}
42202 The optional argument
42203 @var{filename} specifies the file name where to put the core dump.
42204 If not specified, the file name defaults to @file{core.@var{pid}},
42205 where @var{pid} is the running program process ID.
42209 @c man begin SEEALSO gcore
42211 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42212 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42213 documentation are properly installed at your site, the command
42220 should give you access to the complete manual.
42222 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42223 Richard M. Stallman and Roland H. Pesch, July 1991.
42230 @c man title gdbinit GDB initialization scripts
42233 @c man begin SYNOPSIS gdbinit
42234 @ifset SYSTEM_GDBINIT
42235 @value{SYSTEM_GDBINIT}
42244 @c man begin DESCRIPTION gdbinit
42245 These files contain @value{GDBN} commands to automatically execute during
42246 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42249 the @value{GDBN} manual in node @code{Sequences}
42250 -- shell command @code{info -f gdb -n Sequences}.
42256 Please read more in
42258 the @value{GDBN} manual in node @code{Startup}
42259 -- shell command @code{info -f gdb -n Startup}.
42266 @ifset SYSTEM_GDBINIT
42267 @item @value{SYSTEM_GDBINIT}
42269 @ifclear SYSTEM_GDBINIT
42270 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42272 System-wide initialization file. It is executed unless user specified
42273 @value{GDBN} option @code{-nx} or @code{-n}.
42276 the @value{GDBN} manual in node @code{System-wide configuration}
42277 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42280 @ref{System-wide configuration}.
42284 User initialization file. It is executed unless user specified
42285 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42288 Initialization file for current directory. It may need to be enabled with
42289 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42292 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42293 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42296 @ref{Init File in the Current Directory}.
42301 @c man begin SEEALSO gdbinit
42303 gdb(1), @code{info -f gdb -n Startup}
42305 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42306 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42307 documentation are properly installed at your site, the command
42313 should give you access to the complete manual.
42315 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42316 Richard M. Stallman and Roland H. Pesch, July 1991.
42322 @node GNU Free Documentation License
42323 @appendix GNU Free Documentation License
42326 @node Concept Index
42327 @unnumbered Concept Index
42331 @node Command and Variable Index
42332 @unnumbered Command, Variable, and Function Index
42337 % I think something like @@colophon should be in texinfo. In the
42339 \long\def\colophon{\hbox to0pt{}\vfill
42340 \centerline{The body of this manual is set in}
42341 \centerline{\fontname\tenrm,}
42342 \centerline{with headings in {\bf\fontname\tenbf}}
42343 \centerline{and examples in {\tt\fontname\tentt}.}
42344 \centerline{{\it\fontname\tenit\/},}
42345 \centerline{{\bf\fontname\tenbf}, and}
42346 \centerline{{\sl\fontname\tensl\/}}
42347 \centerline{are used for emphasis.}\vfill}
42349 % Blame: doc@@cygnus.com, 1991.